President's Message

A New Beginning: C.O.Q.

The prestressed concrete industry has come a long way since its auspicious beginningwith the construction of the Walnut Lane Bridge in Philadelphia over 35 years ago.Those who worked in the industry in the early days were entrepreneurs with greatenthusiasm, ingenuity and pride of accomplishment. In a short period of time, thesepioneers led the industry from zero volume to a significant factor in the constructionmarketplace.

We are now in a changed world with a new generation of equally talented people whohave a harder job ahead because of the increased capabilities and construction methodsof competitive materials. The novelty of prestressed concrete is gone and today it mustbe merchandised on its merits. Unfortunately, in the past few years, we have not beenincreasing our market share. Obviously, this situation must be reversed.

Recently, the PCI commissioned a study to investigate how it can increase its marketshare and a Strategy Implementation Committee is currently working on ways andmeans of implementing some of the recommended strategies. We are coming to amilestone decision where we will have to critically review who we are, what we do, howwe operate, where do we go from here and how do we get there. This applies both to ourindustry and our Institute.

The precast and prestressed concrete industry is approaching an identity crisis relativeto our competitors. We must develop and implement a market strategy that will positionitself in the minds of our clients that we have the ideal products and expertise for theirprojects.

To instigate a dynamic NEW BEGINNING, we should:Have the CONFIDENCE that we can put together and implement an industry

program that will drive our industry to new and increased markets through better use ofexisting products, new products and fresh applications.

Be OPTIMISTIC that we can create a higher basic enthusiasm and pride ofaccomplishment than we have ever experienced in the past.

Whatever avenues we choose to accomplish our goals, we must continually improveon the high QUALITY of our products, our people, and the operation and image of ourInstitute.

I urge everyone to increase their involvement in our industry's affairs and especially inthe activities of the market study Strategy Implementation Committee. Heighten yourexpectations but remember, you usually get no more than what you expect!

Presents the major design and construction features ofthe East Huntington Bridge over the Ohio River in WestVirginia. The author discusses the conceptual plan,component design and erection method used to buildonly the second, long span prestressed concretecable stayed bridge completed in North America.

Design and Construction ofthe East Huntington Bridge

Arvid GrantPrincipal EngineerArvid Grant & Associates, Inc.Olympia, Washington

The East Huntington Bridge (Fig. 1)over the Ohio River in West Virginiais the second, long span, precast pre-st essed concrete cable stayed bridgecompleted in North America. The proj-ect is an extension of the successfulfeatures incorporated in our firm's firstcable stayed bridge built over the Col-umbia River at Pasco-Kennewick. E4This paper will describe the new designelements of the East Huntington Bridgeand discuss some of the key features in-volved in the design and construction ofcable stayed bridges.

In order to promote engineering de-velopment, the United States govern-ment requires two different competingdesigns for all major bridges. When analternate concrete design was au-thorized tor the East Huntington Bridge,a steel girder system had already beencompleted. Also, the main river piers forthe designed steel system had alreadybeen built.

In competitive construction contractbidding for both designs, steel and con-crete, the concrete alternate received a$1.0,000,000 lower bid ($23,500,000 ver-

20

Fig. 1, Scale model of the East Huntington Bridge.

sus $33,500,000) and was accepted. Thebridge was opened to traffic in August1985.

The East Huntington Bridge is a pre-cast prestressed concrete cable stayedbridge with one tower only and mainspans of 900 and 608 ft (274 and 184 m).The structure is built using 250 ton (227t) prefabricated high strength pre-stressed concrete elements and incor-porates steel floor beams in a hybrid ar-rangement.

The bridge's dynamically insensitivestructural system is lighter than concretecable stayed bridges built earlier, and isespecially suitable for spans longer than1650 ft (500 m) without modification.

The southern 640 ft (195 m) of the2000 ft (610 m) long bridge girder wasbuilt using the cast-in-place segmentalcantilever method and travelling form-work; the remainder of the girder wasassembled segmentally using 45 ft (13.7m) long, 250 ton (227 t) precast concreteelements. The main section of thebridge (Fig. 2) is supported from a 420 ft(128 m) high stay cable tower and 62

stay cables. The two stay cable sup-ported spans 900 and 608 ft (274 and185 m) long are of a constant 5 ft (1.52m) depth and incorporate steel cross-beams in the precast elements.

Only two expansion joints accommo-date longitudinal movements in the2000 ft (610 m) girder. At the bridgetower, the girder is permitted to moveonly vertically. This structural con-figuration comprises one-half of a tradi-tional, symmetrical two tower cablestayed bridge with an equivalent mainspan of 1650 ft (500 m), proving thatsegmental concrete cable stayed bridgescan be built to accommodate very longspans.

The plan, elevation and typical crosssection of the bridge are shown in Fig. 2.

Special Design ConsiderationsThe presence of the previously con-

structed piers, which were designed tosupport the originally intended steelcable stayed bridge, required that theconcrete alternate not exceed the load

PCI JOURNALJanuary-February 1987 21

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Fig. 2. Plan, elevation and typical cross section of East Huntington Bridge.

Fig. 3. A 250 ton (227 t) precast girder segment being transported to project site.

carrying capacities of the existing piersand foundations.

All major bridges built earlier in theEast Huntington area are steel and useof concrete as a primary structural mate-rial was not well established. The ob-jective for the concrete design was todevelop a system that was not too heavy,yet could accept all loads and forcesnecessary for satisfactory service anddurability.

A research program was initiated priorto design to develop applicable data onlocal production and availability of highstrength concrete. As a result of thesepreparations, a 28 (lay concrete designstrength of 8000 psi (55 MPa) wasadopted.

Reasons for SelectingVery High Strength Concrete

Long term durability is the uppermostpriority of any new bridge. For concrete,the density of the material, wear resis-tance, and residual tensile stress capac-ity are the features which fulfill thisquality. Although high strength con-cretes have been found to be less ductilethan conventional concretes at the ulti-mate load state, very high strength con-cretes can assume a broader spectrum ofstresses at normal loading ranges. Thisis due primarily to the fact that they are

more dense and have a higher tensilestress capacity than ordinary con-cretes.

Perhaps the most important propertyis the residual tensile stress capacity ofvery high strength concrete to resist themany small, cumulative and incidentalservice load effects which may lead tothe structure's slow deterioration. TheEast Huntington Bridge incorporatedprecasting techniques for low water-cement ratio, densely consolidated con-cretes.

Hybridization ofSteel and Concrete

Reinforced concrete by its very con-stitution is a hybrid material. When thedesigner extends this technique evenfurther, via hybridization of major steelmembers with concrete elements, notonly can member size and structuralweight be reduced, but so can overallunit cost.

In order to achieve these benefits, thedesigner must also adequately providefor temperature changes and distribu-tion forces. In the East HuntingtonBridge, the successful interactive ar-rangement of the steel and concretemembers reduced the bridge's size,weight and cost, as well as the complex-ity of the required workmanship.

PCI JOURNALIJanuary-February 1987 23

Fig. 4, The southern portion of the bridge was built using cast-in-place segmentalcantilever construction and traveling formwork.

Concrete GirderThe 640 ft (195 m) long bridge girder

on the south approach is of the tradi-tional, varying depth, continuous boxgirder design. The high concretestrength permitted a girder with a veryslender shape, only 13 ft (4 in) deep overthe piers, varying to less than 7 ft (2 m)elsewhere.

The cable stayed part of the concretegirder is made tip of precast concreteelements, 45 ft (13.6 m) long, 40 ft (12.2m) wide, 5 ft (1.5 m) deep and weighing250 tons (227 t) each. Each precast con-crete girder element has anchorages fortwo stay cables, one in each side of thegirder.

The girder cross section is simple itconsists of reinforced concrete edgebeams, 5 ft (1.5 m) deep by 3.5 ft (1 m)wide, and an 8 in. (200 mm) thick road-way slab. This slab is supported by 33in. (840 mm) deep rolled steel beams,framed into the concrete edge beams

and spaced 9 ft (2.75 m) apart.The girder face is hlunt. The stream-

lined, aerodynamic shape of the girderused earlier has been omitted as unnec-essary. The standard size, rolled steelcross beams are modified for the re-quired camber, with attachments to de-velop fixity at the concrete edge beams.Simplicity in arrangement for prefabri-cation of the precast elements was in-tended and achieved.

TowerThe hollow, sloping tower legs con-

tain an electric elevator for access to thecable anchorages. These legs terminateat the towerhead. The concrete tower-head is I-shaped and features a centralcore 6 ft (1.83 m) thick for receiving the62 cable anchorages and their compres-sion forces,

The cable anchorage part of the tow-erhead is 89 ft (27 m) high. The anchor-

24

age area is protected from weather con-ditions with dark colored precast con-crete panels 3 1 in. (90 mm) thick.

Cable SystemBBR type cables with Hi-Am anchor-

ages were specified and used. These ca-bles consist of straight 6 mm wires en-cased in forged steel anchorage as-semhlies, covered with polyethylenepipes and filled with grout for corrosionprotection.

The cable sizes vary from 83 to 307wires each; their length varies from 200to 769 ft (61 to 233 in). The cables wereprefabricated to their prescribed Iengthand installed from top to bottom withforce adjustments at the bottom anchor-ages.

Both upper and lower stay cable an-chorages contain rigid steel pipes sur-rounding the part of the cable end inwhich neoprene dampers were installedto control potential cable vibrations.The use of these neoprene dampers hasproven to be very successful. For exam-ple, the stay cables used in the Pasco-Kennewick Bridge have the dampers atthe lower end only and the cables oc-casionally experience slight, barely per-ceptible oscillations. At East Hun-tington, cable oscillations seldom occurand are not easily perceptible.

Aerodynamic StabilitySuspended girder response to wind

has been studied extensively and theknowledge gained from such studies hasbeen beneficial for the proper design ofsuspension bridges. Lacking compar-able knowledge about cable stayedbridge girder behavior in wind, the sus-pension bridge criteria were used forthe cable stayed bridge girder design.

The presence of many cable stays,high longitudinal forces in the girder,and the effects of girder mass in con-crete bridges measurably enhance the

concrete cable stayed girder's dynamicstability. The Pasco-Kennewick Bridge,being the first of its kind, receivedstringent suspension bridge treatment.The Pasco-Kennewick girder has astreamlined, aerodynamic shape andsubsequent motion studies have re-vealed that the expected motions do notoccur or are not measurable.s

Conventional wind tunnel sectionmodel studies were carried out in ac-cordance with FHWA policy. 6 The testsection exhibited vortex induced oscil-lations of less than 2,5 percent of gravityfor 12 to 15 miles per hour (5.4 to 6.7rn/sec) wind speeds. Actual bridge mo-tion noted to date has been impercept-ible.

The girder is also safe against flutterinstability in an extremely strong wind.Aided by the stiff A-frame tower, the tor-sional to vertical oscillation frequencyratio is 3.0 at 2 percent critical damping.The potential flutter producing windspeed has been estimated at the 230miles per hour (103 rnlsec) level orhigher.

Other Design ParametersCritical elements for structural organ-

ization were:1, Steel cross beam framing into the

concrete edge beams, and managementof differential temperature stresses inthe region where the steel girders frameinto the edge beams, both during castingof the girder elements and in service.

2. Stress array distribution in thetower head core would have to with-stand all forces generated from the en-tire cable system. Critical were theupper cables because their forces arethe highest.

3. The areas where the girder stiffnessand tower stiffness change rapidly, forexample, at the cable stayed girder endsand at the ends of the tower legs.

To avoid concrete transitions withundue rapid stress rises or stress con-

PCI JOURNALJanuary-February 1987 25

Fig. 5. Aerial view of tower. Fig. 6. Closeup of towerhead beforeinstallation of cables.

centrations, local prestressing and lib-eral distribution of local mild steel re-inforcement have been provided at re-gions where large force and stiffnesstransitions Occur.

Construction

In order for the bridge constructionprocess (Figs. 3 to 12) to conclude withall design objectives accomplished, it isimperative that a high level of work-manship and quality control disciplinebe maintained. All operations must bethoroughly planned in advance and con-structors must adhere to such planswithout improvisation. The design en-gineer should guide the work sequenceand quality control procedures to ensurecompliance.

These principles were adhered toduring construction of the East Hun-tington Bridge. The concrete operationsprogram was developed beforehand andstrictly implemented. Due to the own-er's rigid guidelines pertaining to theminimum strength requirements of the

concrete, all concrete was made to10,000 psi (69 MPa) 28 day strength. Theconcrete mix had a water-cement ratio of0.30 and was produced in a speciallybuilt floating concrete plant equippedwith electronic moisture monitoring andbatching controls.

The cable stayed girder elementswere match cast in a specially built, longline casting yard near the bridge site,then barged and lifted by a 600 ton (544t) floating crane into position. Match castsurfaces were coated with epoxy andprestressed onto the previously erectedgirder parts. To control the stability ofthe tall tower on the narrow foundation,and to resist the effects of imbalance onthe long girder, temporary stability ca-bles were used during erection of thegirder.

AestheticsThe purpose of engineering design is

to organize the least complicated systempossible that will fully serve all objec-tives. If correctly done, an observer of

26

Fig. 7. Towerhead with cables in place. Fig. 8. Closeup of towerhead afterinstallation of cables.

the East Huntington Bridge will per-ceive the purpose of the visible order,will accept its simplicity, and will sensethe latent power and strength of thestructure.

All three of the above are positive,gratifying perceptions that are easilymade. And, when positive feelings doresult, the work is termed aestheticallyacceptable, aesthetically correct orpleasing, and satisfying.

With regard to the overall organi-zation of the East Huntington Bridge,the observer notes that the river is wide,the tower is tall, the girder is slender,and the cables are white and thin. Thesystem is simple and graceful andstrong, all at the same time. This per-ception communicates a message and afeeling that great strength can be ob-tained, and much service received, froma simple arrangement. This emotionalacceptance of the whole structure is ac-claimed freely by the users of the com-pleted bridge; and this is the essence ofaesthetics in the work of a bridge en-gineer.

Concluding Remarks

The completed work, built on piersoriginally meant for a steel bridge, re-duced the expected project costs consi-derably. The main span material con-crete was made in the field to veryhigh strength requirements. The resultwas an overall reduction of the struc-ture's weight, increased durability, andthe availability of residual tensile stresscapability for accommodating incidentalstresses. In addition, the low water-cement ratio in the concrete markedlyreduced concerns about concrete creepand shrinkage.

Incorporation of structural steelmembers in the concrete girder resultedin simple workmanship, low girderweight and low project costs. It alsoproved that the hybridization of con-crete and steel components can be usedsuccessfully in concrete bridges. Fur-thermore, the concrete bridge systemincreased the original steel bridge'sfoundation loads by less than 20 per-cent, making foundation changes un-

PCI JOURNAL/January-February 1987 27

Fig. 9. Nearly completed East Huntington Bridge.

the East Huntington Bridge is capableof supporting a 1650 ft (500 m) or longermain span when used in a two tower,symmetrical configuration. This is pos-sible without altering member size.

The East Huntington Bridge was awinner in the 1985 PCI ProfessionalDesign Awards Program.

CreditsOwner: West Virginia Department of

Highways, sponsored by the FederalHighway Administration.

General Contractor: Melbourne Bros.,Inc., North Canton, Ohio. Stay cablesmanufactured by Shinko Wire, Japan.

Engineer for Project Design and Con-struction Control Guidance: ArvidGrant & Associates, Inc., ConsultingEngineers, Olympia, Washington.Arvid Grant, project concept and sys-tem; Conrad Bridges, detaileddesign;David Goodyear, construction control.

References

1. Grant, Arvid, "The Pasco-Kennewick In-tercity Bridge," PCI JOURNAL, V. 24, No.3, May-June 1979, pp. 90-109.

2. Bridges, Conrad P., and Coulter, CliffordS., "Geometry Control for IntercityBridge," PCI JOURNAL, V. 24, No. 3,May-June 1979, pp. 112-1225.

3. Grant, Arvid, "Pasco-Kennewick Bridge,The Longest Cable-Stayed Bridge inNorth America," Civil Engineering, V. 47,No. 8, August 1977.

4. Bridges, Conrad P., "Erection Control ofPasco-Kennewick Intercity Bridge,"Cable-Stayed Bridges, Structural Engi-neering Series, No, 4, Bridge Division,Federal Highway Administration,Washington, D.C.

5. Bampton, M. C. C., and Ramsdell, J. V.,"Dynamic Characteristics of the Pasco-Kennewick Cable-Stayed Bridges,"Fourth U.S. National Conference on WindEngineering and Research, BattellePacific Northeast Laboratories, Seattle,Washington, July, 1981.

Fig. 11. Roadway view of the EastHuntington Bridge.

Fig. 12. Finished view of East HuntingtonBridge at twilight.

6. Cermak, J. E., Bienkiewicz, B., andPeterka., J. A., "Wind Tunnel Study of theEast Huntington Bridge Concrete Alter-native," Colorado State University, FortCollins, Colorado, 1980.

PCI JOURNAUJanuary-February 1987 29

Concepts for the Developmentof Earthquake Resistant

Ductile Frames ofPrecast Concrete

Robert E. Englekirk*PresidentRobert Englekirk Consulting Engineers Inc.Chief Executive OfficerEnglekirk & Hari Consulting Engineers, Inc.and Adjunct ProfessorCivil Engineering DepartmentUniversity of CaliforniaLos Angeles, California

P recast concrete ductile moment re-sisting frames have traditionallybeen permitted by building codest pro-vided that they comply with the provi-sions contained in a building code de-

*Dr. Englekirk serves on PCI's Board of Directorsand Technical Activities Committee and is amember of the PCI Seismic Committee.

t"Precast concrete frame members may he used ifthe resulting construction complies with all of theprovisions of this section." The section referencedis the section describing ductile moment resistingspace frames of cast-in-place reinforced concrete.Uniform Building Code, 1983 Edition.'

CA reinforced concrete structural system notsatisfying the requirements of this Appendix' maybe used if it is demonstrated by experimental evi-dence and analysis that the proposed system willhave strength an t i toughness equal to or exceedingthose provided by a comparable monolithic rein-forced concrete structure satisfying this seedon.'Uniform BuiI lir g Code,1985 Edition.-'

veloped for the design of cast-in-placeconcrete ductile frames.'

Prescriptive provisions for concreteductile frames are contained in Appen-dix At of the ACI Building Code (ACI318-83). 2

Unfortunately, these provi-sions severely restrict the developmentof precast concrete ductile frame con-struction and, indeed, if strict compli-ance were required, a ductile frame ofprecast concrete would be impossible toattain,

More recent codes permit the de-signer considerably more latitude in thedevelopment of a precast ductile mo-ment resisting frame. Therefore, tocomply with the intent of recent codeprovisions, there must be a return tobasic concepts. This paper will discussthese fundamental principles and showhow they might reasonably be applied

30

to the development of a precast ductileframe.

The PCI Seismic Committee is in theprocess of developing a recommendedpractice for the design and constructionof precast and prestressed concretestructures to resist earthquake forces. Amajor part of this report is to focus onconceptual aspects.

To provide such input, a workshopwas held in conjunction with the PCIConvention in Los Angeles in October1986 on the Effective Use of PrecastConcrete for Seismic Resistance. Theworkshop was structured from theviewpoint of the constructor, design en-gineer, researcher and building official.Papers dealing with basic issues suchas building systems, ductile frames andsegmental shear walls were presented.Highlights of the workshop were pub-lished in the November-December PCIJOURNAL.4

Precast concrete offers a wide varietyof fabrication and assembly processes. Itis only through the innovative use ofthese fabricated components thateconomical and functional buildings ofprecast concrete can be developed.Ductile frames are the best way to pro-vide the flexible open spaces requiredof many building functions. Precast con-crete is most effectively applied as abuilding system only when all its com-ponents are precast including the brac-ing system.

This required design flexibility makesprescriptive codification difficult. Un-fortunately, without some form of pre-scriptive guidelines the engineeringprofession will not readily accept pre-cast concrete ductile frames as a viableconstruction alternative.

The key to prescriptive codificationlies in the relationship between the lo-cation of the joint between precast com-ponents and the point at which the duc-tile hinge will form. The criterion forconnecting precast elements at pointswhere the ductile behavior is typifiedby strain reversals in the post yield

SynopsisPresents the basic concepts in de-

veloping a precast concrete ductilemoment resisting frame for a buildingsituated in a region of high seismicity.

Describes the design considera-tions concerning hinged connectors,ductile energy dissipating connectorsand strong nonyielding connectors.

Discusses the various connectortype assemblages including a precastshell with cast-in-place core, coldjoints reinforced with mild steel,grouted post-tensioned assemblageof precast components and unbondedpost-tensioned assembly of precastcomponents.

range must be different from the criter-ion for connectors located in regionswhere the structure is expected or de-signed to remain elastic.

Connector types are crucial not onlyto the behavior of the completed struc-ture but also to the economical de-velopment of the building system.Cast-in-place or grouted connections arereadily accepted as design solutionswhen they closely emulate cast-in-placeconstruction. Welded and post-ten-sioned connectors are usually avoidedbecause of the brittle behavior whichhas historically been associated withthis type of connector. A generic codifi-cation such as this is not reasonablesince connecting precast components bypost-tensioning or welding does notnecessarily reduce system ductility.System economics require that accept-able connectors be identified in such amanner that maximum design freedomis preserved.

Clearly, understanding the basic be-havior of a ductile moment resistingframe is essential. Therefore, a brief re-view of the key elements involved willbe given.

PCI JOURNAUJanuary-February 1987 31

E f P E ^PE

JLh

(a) FORCES

Mu MuE

E/2 E/2^Mu nih/2

(b) DEFORMED SHAPE

Fig. 1. Ductile frame showing forces (left) and deformed shape (right).

BASIC CONCEPTS OFDUCTILE FRAMES

Post-elastic behavior is anticipated inall ductile frames. The system is de-signed so as to cause this post-elasticbehavior to occur in the part of the sys-tem which can best provide for post-elastic rotations. Post-elastic behavior isusually promoted in flexural members(beams or girders) as opposed to col-umns. Axial compressive loads tend toreduce available ductility. When hingesare allowed to form in columns, the po-tential for mechanism failures or "softstories" is increased.

Codes and spectral procedures de-velop a first yield criterion which pro-poses an elastic limit for ductile sys-tems. The development of ductileframes requires that the yield strength ofthe ductile hinge be then used as anelastic criterion for the design of allcomponents of the system. Thus, a hingelocation is created, post-elastic behaviorlocalized and elastic strength require-ments for all elastic components of thesystem identified.

Consider, for example, the ductileframe shown in Fig. 1. Ductile frameconcepts require that the design of thesystem conform to the following steps:

1. The lateral seismic force E is usedto establish the yield criterion for thebearn : *

M = (E/2) (h/2) (1)

in which,, is the ultimate moment de-

mand on the column which in this caseis the same as for the beam.

2. The shear strength of the beammust exceed the shear generated in thebeam when a plastic hinge (yielding)forms at each end of the beam:

V. _ 2Mp /1,1ear +Vp +Vy (2)where

lctear = clear span of the beam, face ofcolumn to face of column

M, = actual yield moment whichcan he developed in a beamdesigned to an ultimate mo-ment of M. It is usually as-surned that M, = 125M5.

M = nominal moment capacity ofthe beam

3. The strength of the column mustexceed that which is required to resistloads imposed on it when yielding oc-curs in the beam:

M,,, > M,, when P, = P P&(3)

whereP = unfactored dead and live

loadsPE = 2 for all levels above

column in questionPe = ultimate axial design load on

column= ultimate design moment for

column

'Note that the lateral seismic force E in this caseis the ultimate base shear as prescribed by the Uni-form Building Code: E = 1.4 V = 1.4 ZICSKIV. See,for example, Ref. ! or3.

32

(I)

h/2(II}

^^s^^tS Cr+r^^h/2

(III)

(IV) 1/2

PRECAST UNIT CAST SOAS TO LOCATEPRECAST JOINT AT POINTS OF LEASTMOMENT DEMAND. THIS SYSTEM ISOFTEN REFERRED TO AS A TREECOLUMN FOR T-$E BEAM AND COLUMNARE USUALLY CAST AS ONE PIECE.

PRECAST JOINTS (MOMENT RESISTANT)TO BE LOCATED AT POINTS OF MAXIMUMMOMENT BUT HINGING WILL NOT OCCURAT THE PRECAST JOINT.

PRECAST JOINTS LOCATED AT POINT OFMAXIMUM MOMENT AND POINT AT WHICHA HINGE IS EXPECTED TO FORM.

PRECAST HINGE OCCURS IN MEMBER ATPOINT OF MAXIMUM MOMENT BUT HINGELOCATION IS NOTANTICIPATED AT THEPRECAST JOINT.

Fig. 2. Classification of precast frames according to component connector location.

The design of a ductile frame requiresthat the designer know where thestructure will yield and what forces thisyielding will impose on the componentsof the system.

CLASSIFICATION OFPRECAST SYSTEMSAND CONNECTORS

For the purpose of identifying genericproblems, precast systems can be iden-tified in terms of (a) component con-nector location and (b) connector type.

(a) Precast frames may be classifiedaccording to the precast connector loca-tion and the anticipated location ofyielding or ductile hinge location. Fourbasic types are identified in Fig. 2.

The following symbols are used toidentify behavior and construction char-acteristics:

A Strong, nonyielding connection

joining precast members.o Ductile, energy dissipating con-

nection joining precast members.q Hinged, free but guided connec-

tion joining precast members. Plastic hinge location (first yield).(b) Connector type1. Precast shell with cast-in-place

core.2. Cold joint reinforced with mild

reinforcing steel.3. Cold joint partially prestressed

(grouted).4. Cold joint partially prestressed

(ungrouted).5. Mechanical connection.

DESIGN CONSIDERATIONSThe precast systems previously de-

scribed require that the treatment ofprecast ductile frame design deal withseveral basic issues, for example, hinged

PCI JOURNAL/January- February 1987 33

JOINT INPRECASTMEMBER

ELASTICCOLUMN

PLASTIC HINGEiN THE BEAM

DUCTILE BEAM

Fig. 3. Deformation of a subassembly.

FACE OF BEAM

MID HEIGHT OF COLUMN

COLUMN VARIATION INCOLUMN FACE MOMENTS BEAM MOMENTS

(a)

(b)

Fig. 4. Variations in moment demand on precast components.

connectors, ductile energy dissipatingconnectors and strong nonyielding con-nectors.

Hinged ConnectorsConsider first the case where the con-

nector location is at a point of minimalmoment. The design must either allowfor the accidental moments that mayoccur or it must permit shear transfers tooccur in conjunction with the cyclic ro-tations the precast joint might be ex-pected to undergo during an earth-quake.

To illustrate the difference, considerthe members of the subassembly shownin Fig. 3. [see also Fig. 2(i)].

If the precast members are connectedby connections capable of resisting mo-ments, the design must consider the

member moment gradients to which thejoints will be subjected. Beam momentdemands will usually be larger than thatwhich will be imposed on the joint inthe column (see Fig. 4).

Observe that the moment in the col-umn at the joining point is not subjectedto the variations imposed on the joint inthe beam for the dead load, live loadmoments on successive floor beams areusually the same. The influence ofhigher modes of vibration and the asso-ciated variations in moment demandmust, of course, be considered. If, on theother hand, the joint between the pre-cast elements is free to rotate, the rota-tional demands imposed on the joint inthe beam and the joint in the column area function of geometry, elastic joint ro-tation, and post yield hinge rotation.

34

Recall that elastic rotation is a func-tion of MiIEI. Since M and E are thesame (or vary by a factor of two), jointrotation depends on the ratio of length toinertia. Observe, however, that theamount of rotation which occurs at theplastic hinge will have no effect on therotational demand on the joint whichoccurs between precast elements. As aconsequence, rotational demands onfree connectors will probably be quitesmall.

Ductile Energy DissipatingConnectors

Where connector locations occur at thepoint in which a plastic hinge will form,Fig. 2(iii), the connector must be capa-ble of undergoing cycles of post yieldrotation without reducing the momentor shear capacity of the joint. This is acomplex analytical problem and little ifany effort has been expended on con-firming analytical procedures with testprograms. Designers tend to avoid theissue by making sure that hinge loca-tions and connector locations are notcoincident, Fig. 2(u),

Unfortunately, locating the hinge andprecast connector at the same point, Fig.2(iii), probably produces the most eco-nomical construction type provided theconnector cost is not prohibitive. Theeconomics are derived principally fromthe fact that members are rectangular(beam extensions are not cast with col-umns) and hence are easy to transportand handle. Further, single columnpieces may be erected for several levelsthereby reducing the number of pieces[see Fig. 2(iii) ]. Clearly, an economicalconnector and an analytical procedurefor insuring adequate performanceshould be a major research objective.

The behavior of cast-in-place flexuralmembers subjected to post-elastic rota-tions has been studied in the testinglaboratory and their performance hasbeen emulated analytically. The proce-dures used in predicting post yield

+P

FIXED

1 p

END

^^ lyE

Fig. 5. Displacement-curvature relations ina hinge region.

hinge behavior start by estimating ahinge length. Curvatures and strains inthe hinge region are then estimated andcompared with test data so as to evaluatethe design procedure. The analyticalprocess follows from mechanics. Eq. (4)relates curvature, 0, to tip deflection fora component of the seismic resistingsubassembly.A = 4 (1/3) + (0u 0, )1 [1 -(1/2)] (4)where

A = tip deflectionI, = length of plastic hinge

= curvature at yield= ultimate curvature

Fig. 5 shows the displacement curva-ture relations graphically in the hingeregion of a flexural member.

If a connector is introduced in this re-gion, the validity of the mathematicalmodel must be either established or ap-propriately modified. Suppose that thebeam and column were to be simplyconnected with a mechanical connectorproducing a joint similar to that shownin Fig. 6.

Before the beam reaches its yieldmoment, a crack will undoubtedly format the face of the column. Post-elasticrotation will to a large extent be con-fined to the joint and any post yield de-flection of the member must produce anassociated opening of the joint. Cycleworking of a joint in this manner will

PCI JOURNAL`January-February 1987 35

REINFORCINGMECHANICALLYCONNECTED ^^^

J

GROUTEDJOINT ep=pp/,e

.L^

Fig. 6. Cold joint located at face of column.

/

CONVENTIONALREINFORCING

SHEARAT DUCTS CASTELLATIONS

Fig. 7. Post-tensioning is used to clamp beam column connection.

undoubtedly reduce its capacity totransfer shear forces. Repeated highstrains and subsequent strain reversalsin the reinforcement have been shownto lead to severe moment degradation ifnot controlled. Reinforcing bars strainedin tension when recompressed producehigh lateral pressure on surroundingconcrete which usually reduces thecapacity of the concrete to take sub-sequent compressive cycles of load.

In cast-in-place concrete this degra-dation is mitigated by confining ties.The effectiveness of confining tiesplaced near a cold joint has not, how-ever, been proven. Both the steel andconcrete industry groups have dealtwith the development of joints in re-gions subjected to post yield behavior.Based on extensive test programs, ac-ceptable joints were developed.

Precast concrete affords the designerconsiderable flexibility and imaginativealternative solutions exist to the post

yield connector problem. Post-tensioning provides one such alterna-tive.

Fig. 7 shows how post-tensioningtendons can be used to clamp the beamcolumn connection and yet permit ahinge to form close to the column.Grouted tendons have been successfullytested in New Zealand without supple-mental mild steel reinforcement. Teststo (late have been limited to straighttendon configurations. This type of con-nector is not economical principally be-cause shoring is required until tendonshave been placed, stressed and grouted.Alternatives such as that shown in Fig. 8need to be considered.

Strong Nonyielding ConnectorsA logical alternative to the problems

created when the joint between precastmembers is coincident with the plastichinge location is to force the hinge away

36

STRESS POINT

--SHEAR TRANSFER(UP AND DOWN)

A

B TEMPORARYSUPPORT

CONVENTIONALREINFORCING

A A

STRESSEDo 6 RODS

o 0BB

Fig. 8. Alternative beam column connection using mild steel reinforcementand stressed bars.

TENSIONEDTENDONS

CONVENTIONALM p REINFORCING

COLUMN

HP1REGION

0u

Fig. 9. Beam column connection with plastic hinge located awayfrom joint.

from the joint as shown in Fig. 2(11).Now the elastic capacity at the face ofthe column must exceed that generatedby hinging at the plastic hinge locationwhich has been created in the beam.The details of this scheme are shown inFig. 9.

The elastic moment capacity at theface of the column Mf must be largerthan the plastic moment capacity at thehinge location:

M (5)

PCI JOURNALIJanuary-February 1987 37

PLASTIC HINGESHEAR TRANSFERLOCATION

PRECASTBEAM

REINFORCING

PRECASTCOLUMN

Fig. 10. Beam column connection with plastic hinge located atpoint of maximum moment.

Higher strains and shears will he im-posed on this member if the yield anddeformation criterion is the same as thatused for the same member were theplastic hinge to coincide with the jointbetween the precast members. Rota-tions which occur in the plastic hinge forthe beam shown in Fig. 9 will clearly begreater than those generated on thesystem described in Fig. 5. Variations onthis design approach are numerous andall that the designer need do is satisfyhimself that adequate elastic capacityexists at the joint between precast mem-bers and that rotations and strains at theplastic hinge can be sustained.

Placing the precast joint at the point ofmaximum moment on the column butyet outside the plastic hinge location,Fig. 2(iv), presents an interesting alter-native (for connection details, see Fig.10). Problems posed by the two previ-ous alternatives are avoided, since theprecast beam elements are continuousacross the column support locations andplastic hinges occur in monolithic con-crete sections, The only penalty is a lossof erection speed (single lift columns).In order to effect this alternative themoment capacity of the column at thejoint should be larger than that whichwould he generated when plastic hingesform in the beam.

Connectors can now be designed to anelastic criterion providing the designerwith a wide variety of alternatives in-cluding welding, post-tensioning orgrouted splices.

CONNECTOR CONCEPTSThe connector types previously iden-

tified must be designed to satisfy the re-quirements of the systems in which theywill be used. Three basic use categoriesidentified were:

Strong (nonyielding).Ductile (energy dissipating).Hinged (free to rotate but guided).Connector types often adapt more

readily to a particular use category. Thedesigner must accordingly select theconnector type which best matchesfunction and intended construction pro-cedure.

CONNECTOR TYPES ANDSUGGESTED APPLICATIONS

This section will consider the fol-lowing connector type assemblages:

Precast shell with cast-in-placecore.

Cold joints reinforced with mildsteel.

38

Grouted post-tensioned assemblageof precast components,

Unbonded post-tensioned assemblyof precast components.

Precast Shell WithCast-in-Place Core

Cast-in-place cores of precast shellelements have been a popular means ofemulating cast-in-place concrete frameconstruction. In this system the "shell"unit is used to support other precastelements. Shell units essentially takethe place of beam forms, usually re-quiring shoring to support wet concreteplaced on top of the precast system.Supplemental reinforcement, usually allof the seismic reinforcement, is placedwithin the shell to create the desiredstrength.

Column shells are often used in con-junction with beam shells, in effect pro-ducing cast-in-place construction. Thedesign of this type of system is well cov-ered elsewhere' and the process willonly be discussed from the perspectiveof shell behavior. Where either thebeam or the column is a shell and theother component is solid, the joint be-tween the shell elements and the coldjoint produced requires special atten-tion.

Continuity is inherent in this system.Connector uses which require hinges,which are free to rotate, are not wellsuited to this construction process.Strong nonyielding joints designed to anelastic criterion require the effectivetransfer of shear across the natural coldjoint. The shear transfer at the joint mustexceed the shear demand which is cre-ated when plastic hinges form in thesystem. It is not necessary to developthe strength of the member being con-nected. For example, the shear transferin the column [Fig. 2(iv) ] is a function ofthe plastic moment capacity of thebeam. The plastic moment capacity ofthe column need not be developed.

Shear transfers across cold joints can

be accomplished in a variety of ways.When strong nonyielding behavior canhe ensured, shear transfer should presentno special design problem. Shear ismost economically transferred throughshear keys (or castellations) cast in theprecast element. Shear friction is notpopular because of the number ofevenly spaced bars which must cross thecold joint making precast element erec-tion considerably more complex. A typi-cal joint is shown in Fig. 11.

If, on the other hand, the beam of Fig.11 is to be subjected to post yield de-formations, special provisions must bemade to insure that the joint does notopen up and that shear transfer is in-sured through cycles of reverse curva-ture. An early crack at the weakenedplane near the column face would placelarge strain demands on tension steel inthis area and recycling to compressionstrains would produce large dilatationalforces on the shell. Shell constructionsimilar to that described herein hasbeen tested in New Zealand." The be-havior of the unit from the standpoint ofenergy dissipation and shape of thehysteresis loop is quite comparable tocast-in-place concrete construction.

Since bonding of the shell to the con-crete core can only achieve a nominalshear transfer, large compressive strainsshould not be introduced into shellcomponents. The New Zealand tests re-vealed that when the beam shell and theconcrete column were in contact and didtransfer compressive stresses, the col-umn shell spalled after several cycles ofload. The best behavior was achievedwhen a gap was maintained between thebeam and column. The New Zealandtests were performed on full size proto-type assemblies. The column was castbefore the beam core, thereby produc-ing a cold joint at the top of the column.Where a cold joint exists in the beam atthe column interface, cracking at theinterface will probably occur unlessspecial reinforcement is provided.

In the absence of test data to support

PCI JOURNALJJanuary-February 1987 39

GROUTEDSLEEVEIN PRECASTCOLUMN

POUREDCONCRETE

8EAM SHELL L: .PRECAST COLUMN PRECASTSOLID

SHELL

PLAIN GROOVED CASTELLATED

Fig, 11. Beam column connection with elastic behavior in beam.

CONFININGREINFORCING

SHELL GAPUNIT

SLEEVES

CASTELLATIONS

FLEXURALREINFORCING

SHEAR REINFORCING(SHEAR FRICTION)

Fig. 12. Modified reinforcement details for beam column connectionshown in Fig. 11.

the behavior of joints of this type, thetendency would be to provide uniformlydistributed horizontal reinforcementacross the joint. This reinforcementwould he intended to keep the jointclosed, improve the sheartransfer acrossthe castelIations and provide a shearfriction type shear transfer. Shear fric-tion has been shown to be effective in

transferring shear across joints subjectedto cyclic strain reversals especiallywhere cold joints or cracks occur. Shearkeys and aggregate interlock, which canbe counted on to transfer significantshears when strains are low, deterioraterapidly under cyclic loads when strainsare high. The connection in Fig. 11should he modified as shown in Fig. 12.

40

CONFINING HOOPSCAST-IN-PLACECONCRETE

Hwm

PRECAST BEAM

Fig. 13. Wet splice (beam elevation) with confinement reinforcement.

Providing evenly distributed rein-forcement across a joint affects con-structihility and, for that matter, columnstrength. The number of column pene-trations should, therefore, beminimized. A uniform spacing of barsdoes not seem to be as important as try-ing to control the crack width. Barsshould then be placed close to theflexural face (top and bottom). Quantifi-cation by shear friction needs study butat least at this writing the method seemsreasonable.

Horizontal reinforcement should ex-tend through the length of anticipatedhinging to control cracking. Confine-ment in the hinge region ensures betterbehavior of the concrete because it in-creases the ultimate stress and strainvalues in the concrete and controls dila-tional stresses.

Cold Joints Reinforced WithMild Steel

This type of joint is typically placed inregions of low moment demand. Themost common use type is hinged, free torotate because they are usually installedin regions where analytical hinges occur(see Fig. 3 for example.)

Beams are most often connected bywet splices (Fig. 13). The design criter-ion for this connector requires thequantification of moment demand as de-scribed in Fig. 4 and the shear imposedon the beam when plastic hinges form.From the perspective of designing theprecast interface, the objective is to

create a strong, nonyielding connection.Minimizing joint length is advantage-

ous from a constructibility perspectiveand also to reduce the moment demand.Bond transfer of stress from tensionreinforcement is usually preferred be-cause it eliminates tolerance problemsassociated with the installation of me-chanical splices. Stress transfer is con-siderably improved by providing con-finement reinforcement as shown inFig. 13.

Wet splices are not practical for col-umn splices. Dowel splices and me-chanical splices as shown in Fig. 14 arethe most common connectors whenmoment demands are low. Moment de-mand at the midheight of a column istypically low as described in Fig. 4.Tension transfer through dowel splicescan be quite high especially if epoxygrouts are used. As a consequence, ten-sion stresses induced by overturningmoments and accidental column Tno-ments can be transferred.

Shear transfer must also occur acrossthe joint. Analytically it would be dif-ficult to establish much shear transferthrough the joints shown in Fig. 14.Even castellation or shear keys are notcapable of transferring shears over theIimited area available for shear transfer.This often forces the designer to usecastellated shear plates (Fig. 15). Me-chanical splice sleeves such as the oneshown in Fig. 16 are becoming morepopular as their price becomes morecompetitive.

Cold joints which are truly free to ro-

PCI JOURNALIJanuary-February 1987 41

A 11 ^r

RI

II IIII IIIIII IIo II

f I ^'II

II 4 IILJ I I iJ

(a) DOWEL SPLICE{ b) MECHANICAL SPLICE

Fig. 14. Column connections showing dowel splice (left) and mechanicalsplice (right).

tate are seldom used in ductile frameconstruction. Seat type connections forbeams must be significantly modified totransfer large shears acting in either di-rection while shear, compression andtension transmission through a columnconnector which is free to rotate wouldundoubtedly cost more than the con-nectors previously described and wouldnot offer a performance advantage.

Current construction economics seemto dictate that where splicing of precastsubassemblies in columns is en-visioned, joints such as those shown inFigs. 14 and 15 are most practical. Forbeam splices, the wet splice shown inFig. 13 is most popular.

Grouted Post-TensionedAssemblage of PrecastComponents

Grouted post-tensioning as a means ofconnecting precast elements has beenstudied in New Zealand and Japan. In-

vestigators have concluded that, if prop-erly used, it is an effective and oftensuperior way of assembling precast ele-ments. A variety of tests have been con-ducted in New Zealand on precast duc-tile frames incorporating post-tensioning as a ductile energy absorbingconnector.' Lateral load resisting sys-tems joined by post-tensioning are per-mitted by the New Zealand Code andseveral buildings of this type have beenbuilt including one three-story struc-ture.

Two basic alternative systems exist,the continuous column system (Fig. 17)and the continuous beam system (Fig.18). The New Zealand tests7 involvedonly the continuous column systemshown in Fig. 17. Concerns that thelength of the plastic hinge might be sig-nificantly reduced did not materialize.Large cracks did not form at the beamcolumn interface.

Both systems must be considered forconstruction benefits and constraints

42

Fig. 15. Column splice with grouted joint.

NONSHRINK

__1'

GROUT

SPLICECj SLEEVE

Fig. 16. NMB column splice sleeve system.

exist with each. The erection of multi-story columns is clearly an advantage butthe horizontal post-tensioning of this as-sembly is probably considerably more

costly than for the continuous beamsystem. From a design perspective, thecontinuous column system of Fig. 17 re-quires that the plastic hinge form at a

PCI JOURNAL/January-February 1987 43

PRETENSIONED TENDONSAND/OR NONPRESTRESSEDREINFORCEMENT

MORTAR DUCTILE ENERGYMORTAR JOINT ABSORBING JOINT.JOINT

POST TENSIONED MIDSPANTENDONS

NOTE; ONLY LONGITUDINAL STEEL IN MEMBERS SHOWN

Fig. 17. Precast concrete units connected by post-tensioning(continuous column).

joint between precast members. As aconsequence, the yield moment must besupplied by grouted post-tensioning.Shear transfer across a cold joint must beaccomplished. Post-tensioning must herelied upon to make a castellated jointperform well in a region where yieldlevel strains will occur.

Alternatives do exist which forceplastic hinges away from the connector(Fig. 19). However, more reinforcementand a higher moment and shear demandat the precast interface result if the sameyield criterion is used to design bothsystems. The continuous beam system(Fig. 18), though more expensive toerect, has significant advantages in thatthe beam element may be reinforcedwith mild steel, post-tensioning or acombination of the two. The column ismore easily post-tensioned and subjectonly to an elastic design criterion.

The continuous beam system adheresto the basic philosophy of ductile framedesign when conventionally reinforced.A post-tensioned column section can bedeveloped which would remain elasticwhen subjected to a mechanism in-duced by moments and shears. Castel-

lations or shear keys can be incorporatedinto the beam column joint which com-ply with accepted theories for sheartransfer. In effect, the only current rea-son for not permitting this type of con-struction is the rather arbitrary exclusionof post-tensioning from ductile frames.

The continuous column system clearlyrequires an in-depth investigation ofseveral issues. Not only must it beshown to he equivalent to concrete duc-tile frames as described by currentpractice but major construction con-straints must also be dealt with. Col-umns will be several stories high. Whenbeams are erected they must be quicklyreceived by the system. A simple shearconnection is required and ideally boththe beam and the column should rapidlybecome a part of the erection bracingsystem. Quick vertical load transfer isusually accomplished by corbels.

Corbels are not effective in frame as-semblies where load reversal is ex-pected. Shear transfer for reverse load-ing is most easily incorporated in theinterface, thereby making the corbel re-dundant. In post and beam precast sys-tems temporary bracing is usually ac-

COUPLED POST-TENSIONED TENDONSAND/OR

COUPLED NONPRESTRESSED REINFORCEMENT

MORTAR II I I ^P-O T TENSIONED MIDSPANJOINT

STRONG MORTAR/

NON -YIELDINGJOINT PRETENSIONED TENDONS

JOINTAND/OR

T NONPRESTRESSED REINFORCEMENT

NOTE: ONLY LONGITUDINAL STEEL IN MEMBERS SHOWN.

NOTE : OTHER PRESTRESSING TENDONS AND/OR NONPRESTRESSEDREINFORCEMENT IS AS SHOWN IN FIGURE 17.

Fig. 18. Precast units connected by post-tensioning (continuous beam).

complished by tieing the precast systemto the previously constructed shearwalls, Temporary support systems suchas that shown in Fig. 20 are probably thebest solution to both problems. Thesetemporary supports should he installedin such a way that erection stability canbe attained.

Complex ducts such as those shown inFig. 18 are not easily connected nor isthe post-tensioning easily installed.

Stressing losses will prevent long con-tinuous stressing operations. Ideallystraight ducts should be used. If thecommitment to a precast interface at thepoint of plastic hinging is accepted andthe construction constraints are under-stood, reliable joining details must bedeveloped.

Beam column joints with mortarplaced in the gap which are subse-quently post-tensioned have been

PCI JOURNALiJanuary-February 1987 45

COLUMN BEAM

IjIL

MILDPOST REINFORCINGTENSIONING

Fig. 19. Strong nonyielding precast connection.

EGHRENGTHLTS

SLEEVECAST IN BEAMAND COLUMN

Fig. 20. Temporary beam column connection erectionassembly.

shown to behave favorably when sub-jected to cyclic loads." Plastic curvatureextends throughout the hinge region asopposed to being concentrated in themortar joint. Subassembly tests did re-veal a somewhat lower hystereticenergy dissipation when compared toconventionally reinforced concrete sub-assemblies of the same size. Park s

con-cludes that higher deflections will occurwhen the system is subjected to earth-quake loading and as a result a baseshear coefficient which is 25 percentlarger than that used for conventionallyreinforced concrete ductile frames ap-pears warranted.

Energy absorption would appear to bea better way of evaluating structural

systems than deflections. Clearly, moretesting must be done before suitablecriteria can be developed. The most en-couraging aspect of this test program isthat a mortar joint (presumably withoutspecial castellations) was able to transfershear through repeated cyclic excur-sions well into the plastic range. Fur-ther, finite hinge lengths developed andlarge strains or rotations did not occur inthe mortar joint.

This type of construction appears tohe a viable means of constructing duc-tile moment resisting frames from pre-cast concrete components. Input fromprecasters as to the constructibility ofgrouted post-tensioned precast framesystems is required.

46

Unbonded Post-TensionedAssembly of Precast Components

The use of unbonded post-tensioningin a concrete ductile moment resistingframe has not been accepted- The basicconcern focuses on the ability of theanchorage to perform adequately whileundergoing seismic deformations. Par-tial post-tensioning should improve theperformance of a ductile frame by pro-viding a compression over the section. Itis hard to imagine that a continuous un-grouted tendon which passes throughmany strain reversals along the length ofthe member could be elongated to thepoint that the anchorage would fail. Un-grouted strands cannot provide anyyield moment strength in a plastic bingeregion and must, therefore, be used incombination with the same amount ofmild reinforcing steel which would berequired of an unpost-tensioned section.

Reservations as to the ability of post-tensioning to withstand seismic stressreversal should not prevent its use inthose portions of ductile frames inwhich yielding will not occur. The per-formance of the system shown in Fig. 18should not be lessened if unbondedpost-tensioning is used in the columns.If the beam were reinforced with non-stressed reinforcement in the hinge re-

gion (top and bottom) and ungroutedpost-tensioning placed as shown in Fig,18, the performance of the systemshould be comparable to a system whichis not stressed.

Test programs for grouted post-ten-sioning of precast ductile frames shouldalso include ungrouted assemblies. Theassembly of precast components by un-bonded post-tensioning would seem tooffer significant economic advantages.

CONCLUDING REMARKSThe purpose of this paper has been to

present basic concepts for developing aprecast concrete ductile moment re-sisting frame suitable for buildings lo-cated in severe earthquake regions.These ideas have been extracted frompublished articles, s- e accepted practiceand the author's experience. Inevitably,some of the frame systems, connectionsand post-tensioning schemes need fur-ther development work and testing be-fore they can be applied in actual pre-cast buildings. Nonetheless, it is theauthor's hope that this paper will sparksome new ideas thereby making precastand prestressed concrete a more viableand competitive building material in re-gions of high seismicity.

NOTE: Discussion of this paper is invited. Please submityour comments to PCI Headquarters by September 1, 1987.

PCI JOURNAUJanuary-February 19B7 47

REFERENCES1. Uniform Building Code (1983 Edition),

International Conference of Building Of-ficials (ICBO), Whittier, California.

2. ACI Committee 318, "Building Code Re-quirements for Reinforced Concrete (ACI318-83)," American Concrete Institute,Detroit, Michigan.

3. Uniform Building Code (1985 Edition),International Conference of Building Of-ficials (ICBO), Whittier, California,

4. Englekirk, Robert E., "Overview of PCIWorkshop on Effective Use of PrecastConcrete for Seismic Resistance," PCIJOURNAL, V. 31, No. 6, November-De-cember 1986, pp. 48-58.

5. Park, Robert, and Bull, D. K., "SeismicResistance of Frames Incorporating Pre-cast Prestressed Concrete Beam Shells,"PCI JOURNAL, V. 31, No. 4, July-August1986, pp. 54-93.

6. Park, Robert, "New Trends in the Designof Buildings and Bridge Structures for

Earthquake Resistance," Fourth Interna-tional Seminar on Seismic Engineering,Universidad de Los Andes, Bogota, Col-ombia, September 1985.

7. Park, Robert, "Design Concepts for Pre-stressed and Partially PrestressedlPrecastConcrete Frames," Proceedings of theApplied Technology Conference, ATC-8,Los Angeles, California, April 27-29, 1981,pp. 145-182.

8. Sorensen, Svend A. K., "Precast ConcreteFrame Construction in Zones 3 and 4,"Proceedings of the Applied TechnologyConference, ATC-8, Los Angeles, Califor-nia, April 27-29, 1981, pp. 183-201.

9. Andrews A. L., "Design of Partially Pre-stressed Precast Concrete Ductile Mo-ment Resisting Frames," Proceedings ofthe Applied Technology Conference,ATC-8, Los Angeles, California, April27-29, 1981, pp. 225-249.

APPENDIX-NOTATIONE = lateral seismic forceM = moment

= ultimate design moment for col-umn

^i^f^ = moment at joint between precastmembers

= nominal moment capacity ofbeam

M = actual yield moment (plasticmoment capacity)

= actual yield moment for beamMw = ultimate moment demand on

memberP unfactored dead and ] ive loadsP' = ultimate axial design load on

columnP^ = maximum possible earthquake

induced axial load on columnVr, = shear created by imposing dead

loadsVL = shear created by imposing live

loadsV = ultimate shearh = story heightl = lengthhua,. = clear span of beam, face of col-

umn to face of columnl = length of plastic hinge0 = curvatureC,u = ultimate curvature4,y = curvature at yieldA = strong, nonyielding connection

joining precast memberso = ductile, energy dissipating con-

nection joining precast membersq = hinged, free but guided connec-

tion joining precast members = plastic hinge location (first yield)

48

Based on a survey questionnaire aimed at PCIproducer members and computer consultants,conclusions are drawn regarding the status ofcomputer software within the precast andprestressed concrete industry.Computer programs available from consultantsand PCI Headquarters are listed.

Survey on Availability ofComputer Software Within

the Precast and PrestressedConcrete Industry

Today, the computer plays an integralrole in engineering practice and inthe design and development of engi-neering products. The most significantadvance in the last decade has been thegeneral availability of microcomputersand the current proliferation of com-puter software.

Although many engineering firms andproducer companies have developedtheir own in-house computer programs,there is a general consensus that full ad-vantage of the potential of computershas not been taken by the precast andprestressed concrete industry. Thisview is reinforced by the large numberof requests and inquiries concerning

Note: This report was prepared by George D.Nasser, Editor-in-Chief, PC! JOURNAL, underthe direction of PCI's Technical Activities Com-mittee. Reader comments are welcomed.

computer software received at PCIHeadquarters not only from producercompanies but also from engineeringfirms.

Despite the fact that substantial ben-efits have been derived from the easyaccess of computer software, severalmajor problems have arisen from therapid growth of computer technology.Most of these problems have been as-sociated with the purchase of computerprograms. For example:

1. Reliability of purchased computerprograms.

2. Problems in converting programsto in-house computer system.

3. Little or no support assistance fromfirms marketing programs.

4. Problems in updating programs,5. Cost factors involved in purchasing

the proper computer hardware in arapidly changing technology.

50

6. Occasional legal problems.7. Marketing/purchasing problems.One possible solution to the above

problems would be for the PCI, as thecentral organization of the industry, toact as the administrator or clearinghousein the dissemination and disposition ofcomputer software for precast and pre-stressed concrete. The functions and re-sponsibilities of such a role could, ofcourse, vary greatly. Inasmuch as thisservice would need a budget plus man-power (in addition to possible legalcounsel), the benefit-cost ratio wouldhave to he carefully evaluated.

INDUSTRY SURVEYIn order to assess the extent of the use

of computers within the precast and pre-stressed concrete industry and to eval-

uate the possible role the PCI couldplay in administering the proliferationof computer software, two question-naires were sent out to:

1. PCI producer members.2. Firms marketing computer soft-

ware.

(1) Summary of response fromPCI producer members(see Appendix A)

out of a mailing to 360 PCI producermembers, 73 responses were received.This represents a response of 20 percentwhich statistically speaking is con-sidered very reliable.

The detailed responses to the ques-tionnaire are included in this report (seeAppendix A). Only the highlights aregiven here:

1. Computer software is in fact being

PCI JOURNALIJanuary-February 1987 51

used by many PCI producer membersfor quality control, design of products,analysis and design of structural sys-tems, detailing of shop drawings, pro-duction scheduling, and several otheruses such as accounting, billing andpayrolls.

2. Producers rely on both in-housedeveloped software plus purchased pro-grams.

3. The microcomputer has taken overas the dominant computer system.

4. Almost all programs use "BASIC"software language.

5. The vast majority of producershave developed their own computerprograms for in-house use.

6. Only one surveyed producer com-pany is in the business of actively mar-keting its programs.

7. By a two-to-one ratio, the surveyedproducers believe the PCI should be-come involved in computer programevaluation or certification.

S. On the question of whether theproducers would be willing to pay forsuch a service, the responses were 32yes and 36 no.

9. There were numerous individualcomments as to what PCI's role shouldbe. These responses are summarized inAppendix A.

10. The general consensus seems tobe that the PCI should be doing morefor the industry than what it currentlydoes.

grams on precast and prestressed con-crete.

Summarized below are the highlightsof the responses to the questionnairesent to computer consultants:

1. A surprisingly small number ofconsultants are involved in the market-ing of computer software for the precastand prestressed concrete industry.

2. The number of commercial corn-puter programs dealing directly withprecast and prestressed concrete is rela-tively small.

3. By a two-to-one ratio, the surveyedconsultants believe that the PCI shouldbecome a clearinghouse for computersoftware.

4. The responding consultants areabout evenly divided as to whether thePCI should become involved in theevaluation and certification of computersoftware.

5. Most of the consultants have verystrong reservations regarding:

(a) Legal pitfalls concerning liabil-ity.

(b) PCI becoming entwined incommercialism.

(c) Financial involvement.(d) Standardization.(e) Obstacle to future progress.

6. The general consensus, though,appears to be that the PCI should be-come involved in some form of servicingcomputer software.

(2) Summary of response fromcomputer consultants(see Appendix B)

A separate questionnaire was sent toabout 100 selected structural engineer-ing consultants specializing in computersoftware. Only ten firms responded.The detailed responses are given in Ap-pendix B1. Appendix B2 gives thenames and addresses (with phone num-bers) of the consultants supplying com-puter software. Appendix B3 lists thecommercially available computer pro-

SUPPLEMENTALINFORMATION

As a service to PCI JOURNAL readersthis report contains a listing of computerprograms (Appendix C1) available fromPCI Headquarters. These programs arerelated to papers published in the PCIJOURNAL. In addition, a listing is fur-nished of PCI JOURNAL articles (Ap-pendix C2) which are based upon com-puter methods but for which no com-puter programs are available from thePCI,

52

CONCLUSIONS ANDRECOMMENDATIONS

Based on the surveys to producercompanies and computer consultants,the following conclusions can be made:

1. It is apparent from both surveysthat computer software is being utilizedby precast and prestressed concreteproducers to a greater extent than origi-nally realized.

2. Producer companies believe thePCI should be involved in the dissemi-nation and evaluation of computer soft-ware.

3. The number of consultants in-volved in the marketing of Computersoftware and the number of programsavailable for sale are relatively low.

4. The PCI should be extremely cau-tious in entering program certification orsoftware commercialization.

The following recommendations areoffered:

1. The PCI should pursue a muchgreater role than it presently does in thearea of computer software. This task istoo involved and time consuming for thecurrent PCI staff to carry out effectively.

2. Appoint a highly qualified com-mittee with a mission to develop andadminister a PCI-centered computersoftware activity.

3. Propose a reasonable budget itemfor execution of this assignment (other-wise little work can be expected in thisarea).

4. Suggest that a seminar/workshop orsession on computer software (includingcomputer graphics) be planned for a fu-ture PCI Convention.

5. Continue to encourage articles inthe PCI JOURNAL which have accom-panying computer programs.

* * w

NOTE: Discussion of this report is invited. Please submityour comments to PCI Headquarters by September 1, 1987.

PCI JOURNAL^January-February 1987 53

APPENDIX A - RESPONSE TO QUESTIONNAIREON USE OF COMPUTER PROGRAMSFOR DESIGN AND PRODUCTION BY

PRECAST PRESTRESSED CONCRETE PRODUCERS

The following is a compilation of re-Quality Control

sponses to the Questionnaire sent toPSCOMP

PCI producer members. Prestress

A total of 73 responses out of 360 Beams

questionnaires were received. Tees E xeu PIan

Question 1 In what areas does Memorizeyour company use computer Frame Design

STRUDLsoftware?

IngressResponse

PIS Member Design25 Quality control, proportioning Elog

mixes, curing, etc. Dynaframe Design

58 Design of productCOP

36 Design of structural systems, e.g., Microsoft-Word

floors, walls, frames, etc. Skiko-Milic-20

21 Detailing of shop drawings Microtrak

23 Production scheduling Profile 4 Plus

28 Accounting, billing and payroll Visicaic

Super CMC IQuestion 2 List the computer Frame Analysisprograms your company is using: Precast Programs

Financial IBM AASHTO

Mix DesignACIBM

Fast Draft Continuous Beam

Abutment Section Properties

Engineering Products Autocad

SAP 80LOTUS 123

SAPLOT PSANAL

FA-3 Gensec

PSFLEX Accounting

Hollow-Core Slabs Concrete Curing

SPAN A-CAD

Bridge Geometry PREST$

HOLCOR WALL$

PFRAME Prestressing Beam

Versacad General Frame

Estimate Design

QC Column

MANHOUR Multi Made

Time Sheets Prestress Design

COLUMN Elongations

DAPBEAM

54

Symphony Reinforced Concrete Beam Frame Design Prestress TableGradeConnectP/C Column Design

Question 3 Have you developedyour own software or purchasedprograms?Response18 Developed own 13 Purchased37 Both

Question 4 Name the computerhardware system the programs aresuited for:

Ultimate Strength ConcreteColumns......................$100

Question 9 Should the PCIbecome involved in computerprogram evaluation orcertification?Response48 Yes 25 No

Question 10 If the answer was"yes" to Question 9, would yourcompany be willing to pay theadded cost of a certified program(including service and maintenancecosts)?Response32 Yes 36 No

Response5 Time Sharing 57 Microcomputer9 Main Frame 4 Other

Question 5 What is the computersoftware language?Response61 BASIC 6FORTRAN 9 Other

Question 6 Are the computerprograms your company developedfor in-house use only?Response57 Yes 6 No

Question 7 Is your company inthe business of selling any of itsprograms?Responsel Yes 62 No

Question 8 If so, what is thename and approximate cost of eachprogram?ResponseSimpleBeams ...................$156Ultimate Strength Concrete Beams $100

Question 11 If PCI gets involvedin computer related activities,would you or someone from yourfirm be willing to serve oncommittees, review teams, etc.?Response35 Yes 39 No

Question 12 What do you thinkthe PCI should be doing in the areaof computer software?Various Responses

Precast prestressed concrete designis still in a stage of innovative engi-neering development. Much of this de-velopment is assisted by computermethods. PCI as the industry standardbearer has a unique opportunity to act asa control clearinghouse for informationand discussion in this area. PCI shouldfulfill this role.

Educate members and set guide-lines.

Computer programs are needed todesign precast products, particularlyhighway girders, double tees, columns,beams and hollow-core slabs.

PCI JQURNAL.IJanuary-February 1987 55

Offer PCI produced program:similar to other organizations.

Programs are needed for theflexural design and analysis of pre-stressed members, columns, stringersand other members. Also, there is a needto analyze secondary effects in pre-stressed concrete frames.

Advertise the source and capabilityof programs which may be of interest toPCI members. (The capability would hethe description offered by the author ofthe program.)

Engineers must understand andevaluate the design programs they areusing. They must know program limita-tions. The final design responsibilitystill rests on the engineer, not the pro-gram source. Certified programs mightbe used by unqualified people in un-usual circumstances without realizingthe danger involved.

Programs that aid in bridge designare needed.

Of course, the PCI should be in-volved in computer software. There is atremendous cost advantage to all pro-ducers over developing each programindependently.

PCI should be developing com-puter programs for torsion design, con-tinuous prestressed beams, frame analy-sis and prestress losses.

Do not adopt, promote or marketany software. There are too many liabil-ity problems involved.

Review available software, developnew software, update programs period-ically to stay abreast with state of the artwith the following priority: (1) Drafting.(2) Design. (3) Cost control. (4) Produc-tion scheduling.

(1) Evaluate and report on availablesoftware and its usefulness. (2) Push forindustry standards for software. (3)Serve as a clearinghouse for free soft-ware to be shared between members.

(1) Certify that the program is ac-ceptable; satisfy latest codes and statewhich items PCI does not agree on, (2)Write or hire someone to write or con-

vert standard programs that will stan-dardize the design procedures. (3) Writenew programs for torsion design. (4)Prepare examples to show how a pro-gram can be used by computers. (5) Sellnew programs for PC. Many plantscould afford this. (6) Recommend com-puters such as IBM PC. Standardizehardware at many plants.

Catalog available software; evaluateCAD hardware and software and provideconsumer reports.

Not sure since we do not have acomputer system. However, it seemsthat an evaluation of existing programsalong with their interchange of hard-ware would have value. Perhaps retain acomputer expert who would: Evaluateexisting programs; build some newsoftware programs not readily available.Obviously, these would have to appealto a total cross section of PCI. Screensome computer type experts and makethem available to PCI members.

A comprehensive standardizationaccounting program would be beneficialto some precasters and add muscle tothe industry's business survey. Stan-dardization on product design would behelpful. Quality control reporting,scheduling, etc., would he a worthwhilefunction for the industry.

Share information on who has com-puter software available for sale.

Survey what is available in com-puter software and give some guidanceto producer members as to the value ofthese programs.

(1) Drafting. (2) Design. One possible idea could be for the

PCI to act as a clearinghouse or distri-bution center. If IBM PC compatibleprograms are obtained, smaller firmswith sporadic needs could rent/borrowthe programs.

Computer programs could quicklyreview, evaluate and check designs forconformity to codes.

Programs on prestress losses andprestressed slender columns would beof value to the industry at this time.

56

Make producers' in-house com-puter programs available to all mem-bers, Educate Associate Members onusefulness of design programs.

-- Act as a clearinghouse for softwarereview/certification with special em-phasis on meeting PCI standards andAC1 Code.

Furnish any data better than main-frames: graphs, spread sheets, etc.

Develop programs for weld design. Market software for companies that

do not write their own programs.Provide information to members on

available programs, costs, etc.-- Setup education, seminars and ex-

change of information. Direct researchand development in cooperation withcompanies currently writing programs.

PCI should compile listings ofavailable software for distribution to itsmembership.

PCI should get a list of softwarefirms that are supplying progams to pre-stress designers from names sent in byproducers and publish the list for PCImembers. The members themselves cancontact the software f rms and users forevaluation,

The use of computer design inconjunction with computer drafting of-fers a great potential for plant engi-neering productivity improvement. Thispotential needs to be defined and theindustry needs to begin to take advan-tage of available new hardware andsoftware to be able to compete better.

PCI should act as a clearinghouseand certify programs.

PCI should investigate hardwareand software evaluation and recommendpackages to large, medium and smallusers for specific areas such as bidding,design, drawing, etc.

Set standards/guidelines for struc-tural programs.

PCI could render a valuable ser-vice by evaluating and certifying soft-ware which is pertinent to our industry.I see no point in reviewing general pur-pose software.

Publish the names of firms that de-velop andlor supply software.

Review software and uses. (1) Compile lists of available soft-

ware and keep it current. (2) Makeevaluation of useability of software. Thiscould be a survey of users.

PCI should review and providelists of computer software. Full evalua-tion should be by purchaser.

(1) May set up a "self supporting"department within PCI. (2) May contractit outliability carried by vendor simi-lar to "LOTUS," etc.

I do not think the PCI should bedeveloping software but should be act-ing as a coordinator and review partybetween computer hardware and soft-ware suppliers and producer members;especially small and midsize producers.

PCI should become involved in theevaluation of software only. Certifica-tion may be dangerous from a liabilityviewpoint.

Prepare a summary of suitable pro-grams. Evaluate CAD systems for use inprestress plants.

Provide members with a source listto help reduce their search time and ef-forts.

Stay up-to-date on what is avail-able.

Develop design and analysis pro-grams suited to standard products suchas beams, columns, frames, double tees,hollow-core slabs, and bridge girders.

Create procedures and standardsfor the industry. Develop computer pro-grams for sale to member companies,using above standards. Act as a clear-inghouse.

Prepare programs compatible withPCI literature (i.e., Design Handbook,Connections Manual); keep programscurrent; updates for code changes, newresearch and development.

Develop design and drafting pro-grains for PCI members.

Purchase or develop programs foruse by producers and PCI professionalmembers.

PCI JOURNALJ January-February 1987 57

Encourage the development of re-liable software and cataloging it so thatusers may know where and how to ob-tain it.

Question 13 Other CommentsVarious Responses

Computerization goes hand in handwith standardization. This fact shouldbe considered in the development ofany computer related service.

We at this point in time are workingon our own in-house programs. How-ever, the full potential of computers isstill in the future.

Not up-to-date with projects in-volved with computer use.

IBM microcomputers should bestandard computer for software to bedeveloped because of their broad base,support and maintenance.

Computer system designed for pre-cast concrete industry for detailing ofshop drawings. Design and drawingscontinue to be the industry's AchillesHeel.

-- Now is the time for action.

Quality control reporting,scheduling, etc., would be a fine func-tion for the industry.

Do more extensive research ofCAD capabilities. Make research anddevelopment project out of CAD.

We utilize an IBM System 38. It is difficult for a small manufac-

turer to keep abreast of new develop-ments in CAD/CAM. I have heard rum-ors of people spending large sums ofmoney for systems that later sat idle orare doing minimal work. User evalua-tion would be helpful to avoid others'mistakes. This would benefit industry asa whole.

I feel the personal computers jus-tify PCI evaluating design applications;I also feel CAD on small computers jus-tifies PCI's efforts toward economicalapplications to our industry,

Which hardware would be thestandard: IBM, WANG, APPLE? Noneis fully IBM compatible)

The Masonry Institute and otherorganizations have programs availablefor engineers, so it is "easy" to use ordesign their products.

58

APPENDIX B1 - RESPONSE TOQUESTIONNAIRE ON THE AVAILABILITY OFCOMPUTER PROGRAMS FOR PRECAST AND

PRESTRESSED CONCRETE

1. List the computer programs onprecast and prestressed concreteavailable from your firm. Provide:(1) title, (2) summary of program'scapability, and (3) cost. SeeAppendix B3.

2. Name the computer hardwaresystem the programs are suited forResponse2 Time Sharing9 Microcomputer (PC)I Other

3. What is the computer softwarelanguage?Response7 BASIC4 FORTRAN2 Other

4. Does your firm provide supportservices to buyers, e.g., in programinterpretation or other possibleproblems?Response9 Yes0 No

5. Should the PCI become aclearinghouse for computersoftware related to precast andprestressed concrete?Response6 Yes3 NoComments to Question 5:

1. Brings in elements of liability and

favoritism to PC 1.2. If they can do it objectively.3.1 do not think it would be effective.4. A single authority on such programs

would help those who are interested butdo not know where to look.

5. PCI should provide a list of avail-able sources.

6. There are two problems: (1) as-sessing the quality of the programs and(2) legal. Since the PCI is perceived ashaving "deep pockets," it will be sued ifany program is used in designing astructure which collapses.

6. Should the PCI become involvedin program evaluation orcertification of programs?Response3 Yes2 No

Comments to Question 6:1. Yes, only if the PCI has the person-

nel qualified to certify or evaluate pro-grams from both a technical and com-puter operational procedures viewpoint.

2. Keep away from endorsements.3. Some standardization is needed to

establish a degree of professionalismand program certification capability.

4. Many programs available may notmeet PCI standards. Evaluation is re-quired to ensure consistency with thePCI Design Handbook.

5. This would tend to limit develop-ment of software since it would be onemore hurdle the developer would be re-quired to do to reach the market.

6. This is a tremendously difficult taskwith little financial reward.

7. It could be helpful if done properly.

PCI JOURNAL/January-February 1987 59

7. What do you think the PCI shouldbe doing in the area of computersoftware?

1. Aquaint members with the use ofcomputers and the many ways they canhelp to increase efficiency and savetime.

2. Publish, periodically, a list of soft-ware for the engineering profession andthe construction industry.

3. Provide clear, concise design pro-cedures that lend themselves to com-puter methods.

4. Nothing. Let the marketplace takecare of this.

5. The two questions above (Ques-tions 5 and 6) would be good starts.Maybe later, perhaps try to promotefurther programming and bettersoftware.

6. PCI should market evaluated and

certified software; also, program listingsshould be solicited for publication. Thiswould allow user customization. Theprogram author(s) would get by-linerecognition.

7. Provide information on where pro-grams may be obtained.

8. Other comments:1. Provided PCI is not ultimately in-

terested in entering software publishingand development business, PCI's in-volvement in Items 5 and 6 above is ac-ceptable.

2. Since we have a very comprehen-sive package of software particularlysuited to the needs of PCI members, wewould welcome the opportunity to helpin any way possible to advance knowl-edge and computer usage among PCImeml rs.

APPENDIX B2 - CONSULTANTS SUPPLYINGCOMPUTER SOFTWARE

Listed below are the names and ad-dresses of consulting firms supplyingcomputer programs to the precast andprestressed concrete industry.

Allen Engineering Technologies, Inc.3300 Arapahoe Avenue, Suite 201Boulder, Colorado 803033031444-}726

Automated Structural Designs, Inc.6731 South Marion Circle WestLittleton, Colorado 80122303/798-2868

The Consulting Engineers Group1701 East Lake AvenueGlenview, Illinois 600253121729-0646

ECOM Associates, Inc.8634 W. Brown Deer Road

Milwaukee, Wisconsin 53224414/354-0243

LEAP Software Inc.P.O. Box 290414Tampa, Florida 33617Toll-free: 800/624-2232, ext. 128Tampa area: 813/985-9170

James J. Mallett, PE, PA416 N, Baylen StreetPensacola, Florida 32501904/438-7794

POSTEN Design Systems610 Sixteenth StreetOakland, California 946124151832-3592

B. C. Schend & Associates4706 Harrison RoadKenosha, Wisconsin 53142414/694-7070

60

The Software Engineering Company Zeiler-Pennock, Inc.P.O. Box 836 2727 Bryant StreetSeattle, Washington, 98111 Denver, Colorado 80211206/874-4121 303/455-3322

APPENDIX B3 - COMMERCIALLY AVAILABLECOMPUTER PROGRAMS ON PRECAST AND

PRESTRESSED CONCRETE

Listed below are the titles and shortdescriptions of computer programs onprecast and prestressed concrete avail-able from consulting firms.

Allen Engineering Technologies,Inc.

PSBM (Prestressed Beam) will design oranalyze the prestressing and shear re-inforcement for a composite or noncom-posite prestressed beam in accordancewith either ACI 318-83 or AASHTO. Program handles I girders, double

tees, slabs, box sections and box gird-ers.

All input saved for easy retrieval andedit.

Handles composite sections. Increments prestressed concrete

strength. Designs both stirrups and horizontal

shear ties. Checks ultimate strength. Computes approximate creep detlec-

tions. Loads may he retrieved from a load

file, generated by the program orinput manually.

Automated Structural Designs,Inc.

Bearing Plate Design. Rebar Corbel Design. Beam Seat Design. Beam Dap Design. Beam Ledge Design. Section Properties.

Headed Anchor Design. Fillet Weld Analysis. Panel CG, Wt, CuYds. Design Strength. Torsion Analysis. Column Load Rundown. Wall Panel P/M Loads.---- Shear Wall Connection.

The Consulting EngineersGroup, Inc.

GENSEC (General Section Prop-erties).

PRES (Prestressed Beam Analysis). JNTRCURV (Prestressed Panel and

Column Analysis). PCFRAME (Plane Frame Analysis

Program). ACADSEC (GENSEC to AUTOCAD

Link). SYMLIB (Precaster's Symbol Li-

brary).PRECAST DOUBLE TEE DE-

TAILER (Links with AUTOCAD).

ECOM Associates Inc.PD-1 (Prestressed Beam Design) com-putes composite or noncomposite, con-stant cross section or slabs with slippedstrands up to two depression points. Re-sults include stresses, moment capacity,web reinforcement and deflections.

LEAP Software, Inc. CONSYS: Continuous beam analysis.

Variable moment of inertia withinspans, moving loads, static loads, in-

PCI JOURNALJanuary- February 1987 61

fluence lines. PC-HELP: Precast connection de-

sign. Dapped ends, corbels, weldgroups, welded headed stud groups,ledges, pads, etc.

PRESTO: General prestressed beamdesign (ACI). Cantilevers, openings,straight or draped patterns, debond-ing, etc.

RC-HELP: Reinfor