86-s60Confinement of Reinforced Concrete Columns With Welded Wire Fabric

7/28/2019 86-s60Confinement of Reinforced Concrete Columns With Welded Wire Fabric

1/9

ACI STRUCTURAL JOURNAL TECHNICAL PAPERTitle no. 86-S60

Confinement of Reinforced Concrete Columns withWelded Wire Fabric

by Salim R. Razvi and Murat SaatciogluThe behavior of reinforced concrete columns confined with weldedwire fabric was investigated. Thirty-four small-scale column specimens with different reinforcement arrangements, including four corner bars as longitudinal reinforcement and various combinations ofwelded-wire fabric and tie steel as lateral reinforcement, were testedunder concentric loading.

The results indicate that welded-wire fabric can be effective in confining the core concrete, resulting in significant improvements instrength and ductility o f columns. This improvement, which isachieved with 11 relatively small percentage of steel, is equivalent tothat achieved with closely spaced tie and longitudinal reinforcementwith a considerably larger steel percentage. Although some practicalproblems remain, welded-wire fabric can potentially be used inearthquake-resistant structures as confinement reinforcement.Keywords: columns (supports); confined concrete; earthquake resistant structures; reinforced concrete; reinforcing steels; structural design; tests; weldedwire fabric.

Tests of reinforced concrete columns have indicatedthat strength and ductility of concrete in compressionare improved very significantly when confined by reinforcement. Concrete under high axial compression develops transverse strains due to internal cracking, but inthe presence of reinforcement, the core concrete applies pressure on the steel, which in turn applies reactive pressure on the concrete. This limits further cracking in the concrete and improves its ability to sustainhigher stresses and strains.Experimental and analytical research has been conducted in the past to investigate confinement ofconcrete by rectilinear ties.'.{j The main variables considered in that research were the size, amount, andspacing of lateral reinforcement. Other variables considered included concrete strength and type, cross section shape and dimensions, characteristics of lateral reinforcement (yield strength and heat treatment), andrate and type of loading (eccentric and cyclic).Prior to 1975, researchers ignored the effect of longitudinal reinforcement on concrete confinement. Theeffect of longitudinal reinforcement was discussed byPark and Paulay7 in 1975 and Vallenas Bertero andPopov8 in 1977. However, it was not until 1978 thatACI Structural Journal I September-October 1989

Sheikh and Uzumeri demonstrated the substantial improvement achieved in column strength and ductility bydistributing the longitudinal steel around the core perimeter and providing a support for each bar by meansof cross ties and/or hoops.' This observation was laterconfirmed by large-scale column tests by Scott, Park,and Priestley9 in 1982 and Ozcebe and Saatcioglu 10 in1987.

It has become clear that both transverse and longitudinal bar spacings play important roles in confiningthe core concrete; therefore, it is reasonable to expectthat concrete confinement will be increased if the concrete is placed in a cage that consists of closely spacedreinforcement in both longitudinal and transverse directions. Welded-wire fabric (WWF) appears to satisfythis requirement; however, no attempt has been madein the past to investigate the effect of WWF on concrete confinement.The current research at the University of Ottawa includes investigation of WWF as confinement reinforcement. Thirty-four small-scale column specimens havebeen tested as part of this investigation. Various combinations of WWF and tie reinforcement have beenused as confinement steel. It is the objective of this paper to present the results of the experimental program.

RESEARCH SIGNIFICANCEThe importance of ductility in earthquake-resistantstructures has long been recognized. However, due tothe brittle nature of plain concrete, the required ductility is difficult to achieve, especially in members subjected to high compressive stresses. The research project reported in this paper deals with a new application

AC I Structural Journal, V. 86, No.5, September-October 1989.Received June 27, 1988, and reviewed under Inst itute publication policies.Copyright 1989, American Concrete Institute. All rights reserved, includingthe making of copies unless permission is obtained from the copyright proprietors. Pertinent discussion will be published in the July-August 1990 ACIStructural Journal if received by Mar. I, 1990.615


2/9

Salim R. R a ~ v i is a doctoral student in the Department of Civil Engineering,University ofOttawa, Canada. He received his MASc from the same universityin /988.ACJ member Murat Saatcioglu is an associate professor of civil engineering atthe University of Ottawa, Canada. He received his graduate degrees from theUniversity of Toronto, Canada, and Northwestern University, Evanston, l/1.Dr. Saatcioglu was previously on staff at the Portland Cement Association,Skokie, l/1., and was on the faculty at the University of Toronto. He is a member of joint ACJ-ASCE Committees 44/, Reinforced Concrete Columns; and442, Response of Concrete Columns to Lateral Forces; and ACJ Committee340, Design Aids for Building Codes.

120 nun

CROSS-SEcnON

Fig. ]-Specimen geometry

1-:. : : : : : : : : : : : : : : . : ..I I I I1 I I I: : ! !:=1:::::::::::::::1'1

f:!: ::::::::::: : : f :! ! l it= !:::::::::::::::t:1

I

rr=============n

1'!:::::::::::::::1'1i .............. .J: ---------- r - ~j j j 1

~ : ~ : : : : :::::: :: :160 nunEl.IYATION

Table 1 - Summary of specimen properties

of welded-wire fabric, i.e., to improve ductility of concrete in reinforced concrete members. Therefore, it hasa potential application to earthquake-resistant structures.

EXPERIMENTAL PROGRAMTest specimensFig. 1 illustrates the geometry of a typical columnspecimen. A total of 34 small-scale columns were prepared in three sets, each cast from the same batch ofconcrete, then tested under concentric axial compression. Two identical specimens were prepared for eachreinforcement configuration, with the exception ofColumns 17(a) and 18(a). Letters (a) and (b) were usedto differentiate columns in a given pair and columnpairs were numbered in the sequence in which they wereprepared. Column pairs No. 1 through 5 and 6 through11 formed the first and second sets, respectively. Column pairs No. 12 through 16 and Columns 17(a) and18(a) formed the third set.All columns contained four longitudinal bars, one ateach corner. The longitudinal bars were either 16 or11.3 mm (0.63 or 0.44 in.) diameter deformed bars. Theties were 6.53 mm (0.25 in.) diameter plain bars withhooks extending I 0 times the bar diameter. The lengthof each WWF piece used in a column was 600 mm (23 .4in.) in the transverse direction. A summary of all testspecimens and their properties is provided in Table 1.

Column Longitudinal reinforcement Lateral ties Welded-wire fabricpair /,', f .. Prrws' f.,. d, s, P., Hook Spacing, /. . . p:. Reinforcementno. MPa Bars MPa percent MPa mm mm percent angle mm Gage MPa percent configuration1 32 4 No. 15 470 3.13 373 6.53 70 1.34 90 12.7 X 12.7 16 300 0.35 32 32 4 No. 15 470 3.13 373 6.53 70 1.34 90 25.4 X 25.4 14 375 0.30 33 32 4 No. 15 470 3.13 373 6.53 35 2.68 135 - N/A - - 14 32 4 No. 15 470 3.13 373 6.53 70 1.34 135 - N/A - - I5 32 4 No. 15 470 3.13 373 6.53 70 1.34 90 - N/A - - 26 39 4 No. 10 480 1.56 373 6.53 35 2.78 135 - N/A - - I7 39 4 No. 10 480 1.56 373 6.53 70 1.39 135 - N/A - - I8 39 4 No. 10 480 1.56 - - N/A - - 25.4 X 50.8 10 500 1.07 69 39 4 No. 10 480 1.56 - - N/A - - 25.4 X 50.8 10 500 1.07 6

10 39 4 No. 10 480 1.56 - - N/A - - 25.4 X 50.8 10 500 1.07 6I I 39 4 No. 10 480 1.56 - - N/A - - 12.7 X 12.7 16 300 0.39 612 29 4 No. 15 470 3.13 373 6.53 70 1.34 90(W) 25.4 X 25.4 14 375 0.30 413 29 4No. 15 470 3.13 373 6.53 70 1.34 90(W) 12.7 X 12.7 16 300 0.35 414 29 4 No. 15 470 3.13 373 6.53 70 1.34 90(W) 12.7 X 12.7 16 300 0.35 315 29 4 No. 15 470 3.13 373 6.53 70 1.34 135 - N/A - - I16 29 4 No. 15 470 3.13 373 6.53 35 2.68 135 - N/A - - I17(a) 29 4 No. 15 470 3.13 373 6.53 70 1.34 135 12.7 X 12.7 16 300 0.35 518(a) 29 4 No. 15 470 3.13 373 6.53 70 1.34 135 25.4 X 25.4 14 375 0.30 5

I mm = 0.0394 in; I MPa = 0.145 ksi.Notes: (W) indicates ties welded at overlaps; for details of reinforcement configurations, see Fig. 2; No. 10 bar has a nominal diameter of I I 3 mm (0.44 in.); No.I5 bar has a nominal diameter of I6.0 mm (0.63 in.).616 ACI Structural Journal I September-October 1989


3/9

(1 )

(4 )

Fig. 2-Reinforcement configurationsReinforcement configurations used in the specimensare illustrated in Fig. 2. Configurations 1 and 2 did notinclude WWF. Configuration 3 consisted of WWFplaced between the longitudinal and tie reinforcementwith a 90-deg overlap at the opposite corner of the tiehooks. Configuration 4 consisted of ties with 90-deghooks welded at overlaps and WWF placed in a circular manner inside the core so as to barely touch the tiesteel. Configuration 5 also included WWF placed in thecore; however, this time the ties had 135-deg hooks anddid not permit the placement of WWF in a circularmanner. The WWF was placed arbitrarily inside thecore so as to enclose as much core concrete as possible.Configuration 6 consisted of WWF placed around thelongitudinal bars without the tie reinforcement.The material properties, as determined from standard concrete cylinder tests and reinforcement coupontests, are shown in Fig. 3 and 4. The stress-strain relationships for WWF also were obtained experimentally.The yield strength for the WWF was assumed to be

equal to 67 percent of the ultimate strength since noclear yield point was observed in the test results.InstrumentationAxial deformations of columns were measured bylinear variable differential transformers (LVDTs). OneLVDT with a gage length of 240 mm (9.45 in.) wasplaced on each column face. Strains in ties were measured using electric strain gages. The data were recorded using a computerized data acquisition system.Test setup and procedureThe columns were tested using a compression testingmachine with a 1335-kN (300-kip) load capacity. Thecolumns were externally confined in the top and bottom regions, where the load was applied, by means o(steel brackets. Upon fixing the LVDTs, each columnACI Structural Journal I September-October 1989

(2 ) (3 )

(5 )

454035

'0 ' 30!l...2......., 25(f )(f ) 20wa:: 15-(f )

105

(6 )

, '

BATCH ONEBATCH TWOBATCH THREE

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35STRAIN (%)

Fig. 3-Concrete stress-strain relationshipsBOO70 060 0'0 '

!l... 50 02.......,(f ) 40 0(f )wa:: 30 01-(f )

20 0100

0

---

0

---------------------16 mm ba r11.3 mm ba r6. 5 mm ba r

2 3 4 5 6 7 8 9 10STRAIN (%)

Fig. 4-Stress-strain relationships for reinforcing barswas placed in the center of the testing machine. Anini-tial load of 90 to 180 kN (20 to 40 kips) was applied,and the L VDTs were monitored to insure concentricloading. Shims were used when necessary to minimizeaccidental eccentricity.

617


4/9

1.2

1.0 -z60 0.6 ~(g 0.4

0.2 I ~ COL.5 (a) ICOL.5 (b)0.00. 0 0. 5 1.0 1.5 2.0 2.5 3.0 3.5 4.0(a) STRAIN (%)

(b)Fig. 5-Response of column pair No. 5: a) axial force-axial strain relationships and b) Column 5(a) after test-ing

The specimens were loaded slowly and the data wererecorded at selected load and/or strain increments. Theloading continued until a significant drop in load capacity was observed.

OBSERVED BEHAVIOR AND TEST RESULTSThe columns showed similar response up to theirpeak loads. The peak load and corresponding axialstrain varied somewhat depending on the confinementcharacteristics of the core concrete. The first set ofcracks appeared on column faces at a strain of approximately 0.2 percent. These cracks propagated vertically

and increased in width before the peak load wasreached.At ultimate load, concrete cover was spalled off inmost of the specimens. It was noted that columns withclosely spaced ties and those reinforced with WWF andties continued resisting the peak load even after thecover concrete had completely spalled off. Well-confined columns developed significant inelastic deformations at approximately the peak load level. The load resistance started dropping when bending and buckling oflongitudinal reinforcement was observed. At this load618

1.21.0z 0.86

0 0. 6< (g 0. 40.2 COL.14 (a)COL.14 (b)0. 0

0. 0 0. 5 1.0 1.5 2.0 2.5 3. 0 3.5 4.0(a) STRAIN (%)

(b)Fig. 6-Response of column pair No. 14: a) axial force-axial strain relationships and b) Column 14(a) aftertesting

stage, LVDT readings started deviating sustantiallyfrom each other, indicating redistribution of the loadresulting from eccentricity in columns.The eccentricity in columns could be attributed touneven spalling and buckling of longitudinal bars atdifferent times. Once all the longitudinal bars hadbuckled, the load was observed to be nearly concentric.The reduction in load resistance continued at differentrates, depending on the confinement characteristics ofspecimens.Typical results of column tests are shown in Fig. 5and 6 for poorly confined and well-confined columns.A summary of test results is presented in Table 2. Thetable contains average values for the two columns withidentical test parameters within each pair. When complete results were not available for both columns in apair, the results for a single column were tabulated. Insuch cases, the column is identified by its proper labelas (a) or (b). The table includes computed and measured values determined as

Poconc = af: (Ag - As - Aww1) (2)ACI Structural Journal I September-October 1989


5/9

Table 2 - Summary of test resultsPo, pocooc> POCO'" plnl' P,m=Column kN kN kN kN kN

l(b) 1191 791 622 1217 8172 1193 791 622 1161 7603 1170 794 625 1141 7654(a) 1170 794 625 1023 6475(b) 1170 794 625 968 5926 1175 983 722 1148 9567 1175 983 722 1042 8508 1225 978 721 1032 7859 1225 978 721 1099 852

10 1225 978 721 1138 891I I 1195 980 681 1170 95412 1119 717 564 1201 79913 1117 717 564 Jl04 70414 1117 717 564 1124 72415 1095 719 566 1028 65216 1095 719 566 1117 74117(a) 1117 717 564 1203 80318(a) 1119 717 564 1181 780

I kN = 0.225 kip.

P,es, = maximum column load applied in test (4)

where a is the ratio of unconfined concrete strength tocylinder strength. The value of a was taken as 1.0 incomputing the values given in Table 2 because of thesimilarities in size and shape of the column specimensand the standard cylinder. However, a varies between0.85 and 0.90 in large-size members. Strength enhancement of core concrete due to confinement is indicatedin the table by the ratio Pcma;/ Poco,. Ductility of concrete is indicated in the same table by the ratio E85 / E1Detailed descriptions of observed response for eachspecimen are presented in Reference 11. The significance of test variables and related test results are presented and discussed in the following section.ANALYSIS OF TEST DATAThe test data were analyzed to investigate the significance of the variables considered. The main variablesstudied in the research program included: l) tie spacing

and amount of lateral reinforcement, 2) tie hooks, 3)WWF as confinement steel between the longitudinaland tie reinforcement, 4) WWF as confinement steel incore concrete, and 5) WWF as lateral reinforcementwithout ties.ACI Structural Journal I September-October 1989

P,m!P. P,m,/Poco"1.022 1.3130.973 1.2220.975 1.2240.870 1.0360.827 0.9480.977 1.3240.887 1.1770.842 1.0890.895 1.1820.928 1.2350.978 1.4001.073 1.4160.988 1.2481.007 1.2820.940 1.1501.020 1.3101.076 1.4201.056 1.380

1.2 ,--I1.0 III..........z 0. 8::::E.._..

0 0.6


6/9

1.2

1.0z 0.860 0.6


7/9

1.21.0z 0.82

'- "

0 0.6< (3 0.40.2

0. 00. 0 0.5

COL.14 (a), s=70 mm, with wwfCOL.15(o), s=70mm, without wwf

1.0 1.5 2.0 2.5 3.0 3.5 4.0STRAIN (%)

Fig. 11-Effect of WWF as confinement reinforcementwhen placed between welded ties and longitudinal reinforcementhooks welded at the overlaps. These hooks were used assubstitutes for 135-deg hooks, which could not be useddue to the presence of WWF. One of the columns in thepair was compared with another column that had tieswith 135-deg hooks without the WWF. The comparison is shown in Fig. 11.

The results indicate improvements no t only instrength but also in ductility with the use of WWFcombined with welded ties. Furthermore, the improvedresponse obtained in this case is comparable to that obtained with a reduced tie spacing of d/4, but withoutthe WWF. Since the latter represents the current designpractice based on ACI 318-83, 12 this may be regarded asa favorable indication of possible use of WWF as confinement steel.WWF as confinement steel in concrete coreThe failure mechanism of columns with WWF placedbetween the longitudinal and tie reinforcement indicated that the pressure exerted on the WWF by the longitudinal bars would rupture the WWF and limit itsusefulness as confinement steel. Therefore, another reinforcement arrangement was used in some columnswhere the WWF was placed inside the longitudinal reinforcement. This would enable the WWF to confinethe core concrete while the ties provide lateral supportto the longitudinal bars.WWF was placed inside the core in column pairs No.12 and 13. Ties with 90-deg welded hooks were placedat d/2 spacing. Responses of columns from each pairare compared with that of Column 15(a), which did nothave WWF. This is shown in Fig. 12. The results indicate a significant improvement in strength and ductilitywith the use of WWF. The improvement in responsewas about the same as that for Column 16(b), whichhad a reduced tie spacing of d/4, as shown in Fig. 13.

A similar WWF arrangement was used in preparingColumns 17(a) and 18(a). However, the tie hooks had135-deg hooks instead of the 90-deg hooks used in theprevious case. Extension of the hooks into the coreconcrete reduced the clear core area enclosed by WWF;however, the same improvements observed in columnACI Structural Journal I September-October 1989

1.21.0z 0. 82

'- "

0 0. 6< (g 0.40. 2

0. 0 o.o 0. 5

---COL.12(o), s=70mm, with wwfCOL.13(o), s=70mm, with wwfCOL.15(o), s=70mm, without wwf

1.0 1.5 2.0 2.5 3.0 3.5 4.0STRAIN (%)

Fig. 12-Effect of WWF as confinement reinforcementwhen placed in the core, and inside welded ties andlongitudinal reinforcement

z2'- "

0< (30. 8

0.6

0. 4

0.2

0.0 0. 0 0. 5

COL.12(o), s=?Omm, with wwfCOL13(o), s=70mm, with wwfCOL 16 (b), s=35mm, without wwf

1.0 1.5 2.0 2.5 3. 0 3.5 4.0STRAIN (%)

Fig. 13-Comparisons of columns confined with WWFor closely spaced ties

1.21.0z 0. 86

0< (30.6

0. 4

0.2

~ - - - - - - ~ . > . . . . . . . . - - - - = - - = - - - - - - ~ ---------------

COL 15(o), s=70mm, without wwfCOL 17(o), s=70mm, with wwfCOL.18(o), s=70mm, with wwf

0.0 0.5 1.0 1.5 2.0 2.5 3. 0 3.5 4.0STRAIN (%)

Fig. 14-Effect of WWF as confinement reinforcementwhen placed in the core, inside ties with 135-degreehooks and longitudinal reinforcementpair No. 12 and 13 also were observed in Columns 17(a)and 18(a). Fig. 14 shows the comparisons of the forcedeformation relationships of these columns with Column l5(a). The results indicate that columns withWWF show as good a response as columns withoutWWF but with half the tie spacing and approximatelytwice the volumetric ratio of transverse steel.

621


8/9

1.21.0z 0.8::::E.._..

Cl< ( 0.6g 0.40.2

- - - , : ~' , , ::-....--- - - - - - - ~ - , : ~COL7(b), s=70mm, wllhollt-wwf -

COL.8(b), welded meshCOL.9(b), mechanical connectionCOL10 (b), wire connection

0. 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0STRAIN (%)

Fig. 15-Effect of WWF as confinement reinforcementwithout tiesWWF as lateral reinforcement without tiesThe possibility of using WWF without ties was considered in Set 2. To be consistent with ACI 318-83,which requires the diameter of lateral ties to be at least30 percent of that of the longitudinal bars, 11.3 mm(0.44 in.) diameter bars were used as longitudinal reinforcement. Three pairs of columns were prepared withthe same size WWF without any ties. The only difference between the column pairs was the way WWF wasconnected at the overlaps. Column pair No. 8 hadWWF welded at the overlaps, whereas column pair No.9 had mechanical connecters. Column pair No. 10 hadWWF connected by 1.5 mm (0.059 in.) diameter wires.Responses of one column from each pair are compared with that of Column 7(b), which had ties with135-deg hooks at d/2 spacing. The comparison isshown in Fig. 15. The results indicate that WWF cannot replace ties as lateral reinforcement if any ductilityis to be expected from the column. Fig. 15 indicates abrittle response immediately after reaching the peakload. It was observed during the tests that WWF couldnot provide sufficient lateral support for the longitudinal bars. The pressure applied by bending and bucklinglongitudinal bars caused WWF to rupture suddenly.The three types of connections used at WWF overlaps did not have much significance since the responsewas not governed by opening of WWF at the overlaps.However, the column with WWF welded at the overlapshowed the least strength, possibly because of the reduction in steel strength due to the exposure to heatduring welding.The same reinforcement arrangement with anothersize WWF was used in column pair No. 11. These columns had 60 percent less total lateral steel area as compared to the previous pair. The comparison of results,shown in Fig. 16, indicates that while both sizes ofWWF produce brittle response the one with less arearesults in a higher rate of strength drop after the peakload.

CONCLUSIONSThe following conclusions can be made based on theexperimental investigation reported in this paper:622

1.21.0z 0.86

Cl< (g 0.60.4

0.2

''

COL.10(b), 25.4X50.8mmX10gageCOL.11(b), 12.7X12.7mmX16gageo.o ............. . . ~ . . ~ . . ....... .............................. .............. ..._ ...... ............0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4. 0

STRAIN (%)Fig. 16-Effect of WWF size when used without ties

1. The use of WWF as confinement reinforcementimproves concrete strength and ductility very significantly. Concrete strength confined with WWF was observed to increase by as much as 40 percent. The improvement in response resulting from the use of WWFwas equivalent to that obtained by closely spaced tieswith twice as much steel area.2. WWF is effective in improving concrete ductilityonly if buckling of longitudinal reinforcement is prevented by ties. Ties placed at a spacing of d/2 appearto satisfy this requirement; however, the ties must be inthe form of closed hoops to prevent them from opening under lateral pressure.

3. Columns confined with WWF without lateral tiesshow brittle response with a sudden strength drop immediately after the peak load. WWF is not capable ofproviding the necessary lateral support to longitudinalreinforcement.4. WWF can be used as confinement reinforcementeither between the longitudinal and lateral tie reinforcement or in the core, inside the reinforcement cage.

5. For approximately the same area of steel, finermesh produces better confinement than coarser mesh.6. Practical difficulties exist in placing WWF, especially when ties with 135-deg hooks are used.

ACKNOWLEDGMENTSThe research program reported in this paper was sponsored by theNatural Sciences and Engineering Research Council of Canada underGrant No. A6851. The experimental program was conducted at theStructures Laboratory of the University of Ottawa.

NOTATIONA ~ area of core concrete enclosed by center-to-center of exte-rior hoop reinforcementA, gross area of column cross sectionA, area of longitudinal reinforcementA area of welded wire fabric (WWF)d effective depth of column section measured from extremecompression fiber to the centroid of tension steel1: concrete cylinder strength/ , yield strength of longitudinal reinforcementJ:, yield strength of transverse hoop reinforcementACI Structural Journal I September-October 1989


9/9

sCi

yield strength of welded wire fabric (WWF)maximum axial load carried by concrete during a columntestcomputed capacity of column under concentric loadingcomputed concrete contribution to column strength underpure concentric loadingcomputed core concrete contribution to column strengthunder pure concentric loadingmaximum axial load recorded during a column testtie spacingratio of plain (unconfined) concrete strength in a memberto concrete cyclinder strengthminimum axial strain corresponding to the maximum loadresistance

t, axial strain corresponding to 85 percent of the maximumload resistance on the falling branch of the load-strain relationship

p,= ratio of longitudinal steel area to gross column areap, ratio of volume of tie steel to volume of concrete core

measured center-to-center of outer tiep; ratio of volume of lateral wires in WWF to volume of con

crete core measured center-to-center of outer tie

REFERENCESI. Sheikh, S. A., "Effectiveness of Rectangular Ties as Confinement Steel in Reinforced Concrete Columns," PhD dissertation, Department of Civil Engineering, University of Toronto, 1978, 256 pp.

2. Chan, W. W. L., "Ultimate Strength and Deformation of Plastic Hinges in Reinforced Concrete Frameworks," Magazine of Con-crete Research (London), V. 7, No. 21, Nov. 1955, pp. 121-132.

3. Roy, H. E. M., and Sozen, M.A., "Model to Simulate theRe-sponse of Concrete to Multi-Axial Loading," Civil Engineering

Studies, Structural Research Series No. 268, University of Illinois,Urbana, 1963, 227 pp.

4. Soliman, M. T. M., and Yu, C. W., "Flexural Stress-Strain Relationship of Concrete Confined by Rectangular Transverse Reinforcement," Magazine of Concrete Research (London), V. 19, No.61, Dec. 1967, pp. 223-238.

5. Sargin, M.; Ghosh, S. K.; and Handa, V. K., "Effect of Lateral Reinforcement Upon the Strength and Deformation Properties ofConcrete," Magazine of Concrete Research (London), V. 23, No. 76,June-Sept. 1971, pp. 99-110.

6. Kent, Dudley Charles, and Park, Robert, "Flexural Memberswith Confined Concrete," Proceedings, ASCE, V. 97, ST7, July1971, pp. 1969-1990.

7. Park, Robert, and Paulay, Thomas, Reinforced Concrete Struc-tures, John Wiley & Sons, New York, 1975, 769 pp.

8. Vallenas, J. ; Bertero, V. V.; and Popov, E. P. , "Concrete Confined by Rectangular Hoops and Subjected to Axial Loads," ReportNo. UCB/EER C-77 /13, Earthquake Engineering Research Center,University of California, Berkeley, 1977, 114 pp.

9. Scott, B. D.; Park, R.; and Priestley, M. J. N., "Stress-StrainBehavior of Concrete Confined by Overlapping Hoops at Low andHigh Strain Rates," ACI JoURNAL, Proceedings V. 79, No. I, Jan.Feb. 1982, pp. 13-27.

10. Ozcebe, Guney, and Saatcioglu, Murat, "Confinement ofConcrete Columns for Seismic Loading," ACI Structural Journal, V.84, No.4, July-Aug. 1987, pp. 308-315.

II . Razvi, S. R., and Saatcioglu, M., "Behavior of ReinforcedConcrete Columns Confined with Welded Wire Fabric and/or Rectilinear Ties," Research Report No. 8902, Department of Civil Engineering, University of Ottawa, 1989, 103 pp.

12. ACI Committee 318, "Building Code Requirements for Reinforced Concrete (ACI 318-83)," American Concrete Institute, Detroit, 1983, Ill pp.

Documents

86-s60Confinement of Reinforced Concrete Columns With Welded Wire Fabric