R Lessons from Stadium Structures in Seismic Zones · Raker Diagonal beam supporting seating tiers. ... in the design of the column connections so that gravity support is not lost

2017 SEAOC CONVENTION PROCEEDINGS

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Lessons from Stadium Structures in Seismic Zones

Rafael Sabelli, Director of Seismic Design Walter P Moore

San Francisco, California Laura Whitehurst, Senior Project Engineer

Holmes Consulting Wellington, New Zealand

Abstract Stadium structures are a special category of structures with

many conditions not addressed in building codes or published

design examples. Drawing on recent projects (by the authors

and others), design approaches to such special conditions as

multi-story transfer trusses, sloped raker girders, thermal

jointing, switch-back ramp systems, and curved, sloped seating

bowls are discussed. These lessons highlight the importance of

addressing seismic response by accommodating large

displacements.

Introduction

Stadium structures are a special category of structures with

many conditions not addressed in building codes or published

design examples. The special configurations required for this

type of structure pose special challenges in seismic design

related to providing ductility and accommodating inelastic

drift.

Terminology Concourse Large floor areas outside of the seating bowl

used for circulation, concessions, and services.

Event level Field level, typically the lowest level of the

stadium.

Moat Space separating stadium structure from the

retained earth.

Raker Diagonal beam supporting seating tiers.

Seating bowl Multi-story assembly of seating tiers and

rakers.

Seating tier L-shaped or Z-shaped beam that spans

between rakers and forms the seating area of a

stadium.

SLRS Seismic load resisting system

Vomitory Opening in a seating bowl to allow spectators

to enter

Figure 1 shows several typical components of a stadium

structure.

Fig. 1. Typical stadium components

Sloped Construction One of the distinctive characteristics of stadium construction

is the sloped construction due to seating configuration. While

sloped roof construction is not uncommon, in stadia this sloped

construction occurs at multiple levels and complicates the load

path. In seismic design, sloped construction requires special

consideration of sloped raker beams and short columns, and

should be considered in determining the structural height.

Seating tiers typically span horizontally between sloped

“raker” beams that follow the form of the seating bowl along

radial lines. These rakers in some ways are similar to stairs:

they may connect two adjacent floor levels, and thus act as an

implicit load path for lateral loads. In areas of low seismicity,

this load path may be acceptable and provide an efficient

means of resisting lateral loads. In areas of high seismicity,

consideration of the ductility of the lateral-load resisting

system is required, and rakers cannot provide much ductility,

as these are gravity beams that would be axially loaded under

seismic loading and would need to exhibit axial ductility.


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These rakers are typically sized to prevent objectionable

vibrations. They may have substantial area, and ductility

demands may occur in connections. To avoid such ductility

demands, slip connections similar to those used for stairs may

be employed. As these connections are typically subject to

high gravity forces, low-friction connections may be

considered to make the behavior more predictable.

In some cases, the lower support of the sloped raker occurs

significantly above the floor level below, typically on a column

that may be short compared to those supporting the upper end

of the raker and the flat concourse. The sloped, curved

construction of the raker and seating tiers will move essentially

as a rigid body. Thus the drift at the top of the short column

will be the same as the drift at the concourse, but the effective

drift ratio of this column is amplified by the ratio of the story

height to the column height. Figure 2 shows a schematic of this

movement.

Fig. 2. Schematic of amplified drift in short columns

While ASCE 7 drift limits do not apply to this condition, it is

recommended that if this movement imposes large inelastic

rotation of the column, compact column sections should be

used. Additionally, the required rotation should be considered

in the design of the column connections so that gravity support

is not lost. Further, the analysis model should consider these

columns as pin-pin members to avoid “stealing” load from the

designated SLRS.

The sloped construction of the upper level of an open-air

stadium may be considered to be the roof of the structure for

purposes of determining structural height. ASCE 7 has

clarified that structural height is measured from the base to the

mean roof height. In the case of open-air stadia, the latter point

can be taken as the center of mass of the upper seating level.

Temperature changes Stadium structures can be quite large. Often the length exceeds

700 feet. Even in moderate climates such lengths result in very

large thermal expansion, and it is necessary to analyze thermal

effects. The greatest differential thermal expansion typically is

between the ground floor (which is restrained by the

foundation and is also less likely to reach peak temperatures)

and the second floor, which is only restrained form thermal

expansion or contraction by the SLRS and bending of columns.

ASCE 7 does not specify a temperature range to consider, nor

the appropriate load combinations, but does require

consideration of self-straining loads. Examples abound of

poorly configured structures that have sustained damage

through a combination of temperature swings and concrete

shrinkage.

Buckling-restrained braces offer a unique advantage over other

braced frames in the design for thermal loads. Most elements

that attract high forces due to temperature changes offer very

little ductility. These elements must be designed to resist the

forces corresponding to the maximum temperature swing that

is deemed appropriate to consider. (This temperature swing is

typically with respect to an unknown but moderate

construction temperature, and is combined with concrete

shrinkage.) Buckling-restrained braces, however, offer very

high ductility, and the ductility demands corresponding to

temperature effects is typically a small percentage of both the

maximum and cumulative ductility capacity of the brace. It is

reasonable to allow some yielding of these braces under the

maximum thermal loads, providing that yielding does not

occur regularly. (That is, a frequent temperature range —

perhaps 25 years—may be considered for evaluating the

braces.) Such yielding has no effect on the lateral strength of

the braces, and effectively releases the shrinkage-induced

stresses.

Jointing Stadium configuration takes into account the immense entry

and exiting requirements. One result of this is that it is

generally beneficial to have the event level (the playing field)

well below ground level, which allows people to enter at the

mid-height of the structure and disperse more quickly. In this

case, a substantial retention system is required. The below

grade structure may be integrated with that retention system—

requiring analysis of complex soil-structure interactions—or it

may be separate, resulting in a seismic base at event level and

a structure that is effectively much taller. With the latter

approach a substantial seismic separation is required at the

ground level (a “moat”). This separation must be sized for

movements of both the retention system and the stadium, and

joint covers used for exiting must remain operational under the

design event. Consideration of the consequences under other

events, such as a more frequent event or the maximum

considered event, should be discussed with the owner.

Typically temperature-induced effects may be reduced by

placing frames near the midpoint of the building along the

frame line. Such an approach is insufficient for stadia due to

the large dimensions and the large transverse thermal

movement, as well as ring-effects of a circular plan creating no

“midpoint”. Instead, the typical approach is to introduce

thermal joints along radial lines such that the building is

divided into a number of wedges that can expand and contract


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with respect to their individual centers of rigidity, thus greatly

reducing the maximum thermal movement. Such joints also

divide the lateral system, such that each wedge requires a

separate system and a separate analysis. Relative movements

at upper stories can become quite large, and the joint sizes

follow suit. Double columns (one on each side of the joint) are

often employed at these seismic joints instead of slip

connections to preclude the possibility of loss of gravity

support of a beam subject to such large displacements. Figure

3 shows a schematic of a stadium plan with such jointing.

Fig. 3. Stadium plan with thermal joints.

The individual wedge shapes that result from thermal jointing

are not well configured for efficient seismic resistance. They

may approach a triangular form, with the center of mass offset

at every level due to the seating configuration. These

characteristics can lead to a high torsional response, and the

need for much additional strengthening and stiffening.

Lock-up devices One alternative to having seismically independent wedges is

to interconnect the wedges across the thermal joints with

“lock-up devices” (LUDs) that provide negligible restraint for

slow loading (such as thermal) but provide a high degree of

restraint for faster loads (such as seismic). LUDs are typically

viscous dampers proportioned to provide these force-velocity

characteristics. This allows the relative movement under

temperature swings necessary to prevent overloading of the

structure, while providing an efficient seismic system that can

reduce the torsional response of the structure. Each wedge still

requires a complete lateral-load-resisting system for gravity

stability, but the SLRS as a whole will be more efficient.

Using such an approach, joints are sized for the relatively small

thermal movement (which do not increase with height), rather

than the large seismic movements (which generally approach

the drift limits for taller structures).

A structure interconnected by such LUDs act as a single

structure with respect to seismic loads. Thus the torsional

resistance corresponds that of the entire system of

circumferential frames, rather than that of the unusual,

triangular configuration of radial and circumferential frames

within a wedge. This configuration tends to have a much lower

torsional response.

These LUDs may be located across thermal joints at every

level. Complete connection of the two diaphragm segments

requires three connections. Two connections at or near the

boundaries along circumferential lines provide constraint in

one translational direction and in rotation. A shear connection

on the radial line provides constraint in the orthogonal

translation direction. This last constraint does not require

accommodation of large thermal movement in the direction of

force and may be done using more conventional methods such

as slotted holes (not loaded in shear under gravity); transverse

movement under temperature swings must be accommodated.

Figure 4 shows a schematic of LUDs at a thermal joint.

Fig. 4. Schematic of lock-up-device at thermal joint

Because the thermal effects are greatest at the first floor it is

possible to discontinue them at some point above the second

floor. This location is likely not the third level. Careful thermal

analyses must be performed to ensure that the differential

movement between the jointed level and the adjacent

continuous level does not induce excessive force in any

element. The combination of jointless upper levels and lower

levels interconnected by LUDs minimizes the intrusiveness of

joints by reducing their number and size, and provides for an

efficient seismic system.

SLRS Complexity A complex and large structure such as a stadium requires well-

distributed seismic resistance. The number of bays of lateral

load-resisting elements (braces, walls) can easily exceed a

thousand for a large stadium. Due to the different functions at

each level (e.g., locker rooms, suites, concourses), the

architectural programming can also lead to highly inefficient

systems, including in-plane and out-of-plane discontinuities in

the lateral load path. The structure can also react in ways that

might seem counterintuitive to the engineer experienced in

normal building design (such as highly torsional response that

is not easily controlled). All of these factors can lead to a

SLRS system that is not easy to proportion based on hand

methods and requires a three –dimensional analysis.


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The authors recommend an iterative approach, in which initial

sizes are chosen at each level of the stadium using back-of-the-

envelope calculation to determine the rough area of SLRS

needed to resist the base shear, providing that area in the

available bays at the base level, and then incrementally

decreasing that area at each level going up the building. Once

these rough sizes have been implemented, an initial analysis

can be completed and the behavior of the building assessed.

Some elements will be overstressed and some will be

understressed. The overstressed elements should be upsized

relative to their demand-capacity ratio (e.g., a brace that has a

DCR of 1.30 should have its area increased by 30%). The

understressed elements should only be downsized by a

predetermined ratio (such as ¾ or 2/3). This incremental

downsizing avoids a feedback loop wherein the understressed

element gets drastically smaller and less stiff, and therefore

attracts less load, which triggers it being downsized further,

becoming less stiff, etc.

After all the elements are resized, the model should be re-

analyzed and the sizing process repeated until all elements

have DCR’s less than one. This iteration can be done

manually, but it may be more convenient to program an

algorithm to run the process without constant input from the

engineer.

Accidental Eccentricity ASCE 7’s approach to accidental eccentricity is intended to

capture mislocated mass and building torsional sensitivity.

The approach applies a torsional moment corresponding to the

diaphragm mass placed at an eccentricity of 5% of the building

dimension. This method is targeted at structures without large

diaphragm discontinuities. Stadia inherently have large

openings or re-entrant corners in the diaphragm at every level

(possibly excluding the event level and the roof, if there is

one). By taking the full out-to-out dimension of a stadium

bowl, the ASCE 7 method therefore implies a very large

misplacement of mass, disregarding the fact that there is no

mass in the “donut hole” in the middle of the diaphragm

opening. Conservatively, this large accidental torsion could be

considered to place a strong emphasis on preventing torsional

response, but the authors feel that further investigation may be

desired to avoid this perhaps unwarranted penalty on the

structure.

Conventional structural analysis software is not capable of

capturing the ASCE 7-mandated accidental eccentricity in a

complicated sloping structure such as a stadium bowl. The

authors suggest summing up the seismic mass tributary to each

diaphragm, multiplying that mass by the prescribed

dimensions, and amplifying as necessary per ASCE 7 to find

the total accidental torsion on each level. The accidental

eccentricity torsion can be distributed as point-moments

applied to the main diaphragms at suitably small intervals

(such as every grid intersection) so that the local effects near

the application point are moderate.

Non-Orthogonality A stadium bowl is typically curved to allow optimal views to

the playing area, which inherently requires a non-orthogonal

structure. This non-orthogonality constitutes a Type 5

horizontal irregularity per ASCE 7, and also requires special

consideration of application of seismic loads.

For analysis and design of lateral load-resisting elements such

as collectors or braces, a square-root-sum-of-the-squares

(SRSS) method should be used to capture load coming from

any angle. This method can be applied in most sophisticated

analysis software (such as ETABS or SAP2000). In an SRSS

combination, X and Y directional forces are applied, and for

each element, the demand corresponding to each directional

application is combined using SRSS, simulating the load being

applied at the worst-case angle for that element. This method

is preferable to the more conventional approach of combining

100% one direction’s demands with 30% of the other

direction’s demands, which would underestimate demand in

the 35-55° range and overestimate demand in the 0-35° and the

55-90° range. The use of 100%+40% always exceeds the

SRSS, and is substantially conservative in many cases. See

Figure 5.

Fig. 5. Directional loading combination diagram

For analysis and design of vertical elements in the lateral load-

resisting system, consideration should be given to the

requirements of the material codes. For steel buildings in high-

seismic areas, AISC 341 requires capacity-based design of

columns in ductile braced frames (such as Special

Concentrically Braced Frames, Eccentrically Braced Frames,

and Buckling-restrained Braced Frames). Given the above-

stated non-orthogonality and the likely complexity of the

structure, the authors recommend a stress-based approach to


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simulating the applied load equivalent to the capacity of the

horizontal lateral load-resisting elements, which takes

advantage of the capabilities of analysis programs to evaluate

complex configurations.

A method that the authors have used is the application of

fictitious temperature load that corresponds to the tension or

compression capacity of an element. This approach requires

greatly decreasing the modulus of elasticity so that the stresses

induced in each brace element are due only to this imposed

temperature self-straining load, combined with restraint at the

diaphragm levels (which are not allowed to translate). The

element capacities should be combined in a way to impose the

worst case loading on a column from all braces connecting to

it simultaneously. In a regular, orthogonal building, this would

be simple enough to combine (±Assumed Force in X ±

Assumed Force in Y). However, in an irregular, non-

orthogonal building such as a stadium, this approach would

miss the full capacities for elements not oriented with X or Y.

Therefore another strategy must be used.

Assuming a non-jointed structure (see above for discussion of

the relative merits of diaphragm jointing), the authors have

used the concept of four virtual loadings to inform the

application of loads: a force sucking the entire structure

towards the center, a force repelling the entire structure away

from the center, a force twisting the structure clockwise, and a

force twisting the structure counter-clockwise. See Figure 6.

Fig. 6. Four virtual loading directions for column analysis

These forces do not correspond to the actual structural

response, but they do create the relevant loading conditions

locally, and thus can be used to determine the worst case

loading on any individual column. A column receives seismic

axial loading, only from the braces that connect to it directly;

the fact that a radial or circumferential loading case is

unrealistic is not relevant to determining column demands.

Therefore, the toward/away from center effects can be

combined with the clockwise/counter-clockwise effects to get

the worst-case demand on a single column.

It should be noted that a typical collector analysis, where one

end of the building is set to zero and the capacity-based

demands are tracked through the collector lines, will not be

possible in a circular building. Using the system overstrength

factor may be required, rather than a capacity-based analysis.

Gravity systems

Due to the scale of stadium structures certain configurations

are commonly employed to provide efficient load paths for

gravity load. Many stadia include such features as sloped

columns, story-deep kickers, and story-deep transfer trusses.

Each of these conditions has an effect on the lateral-load-

resisting system, and requires special attention when used in

an area of high seismicity.

Because of the sloped stadium bowl, there is often more space

under the upper concourses than the program requires. There

are programmatic reasons, therefore, to extend the upper levels

beyond the footprint of the building. For this reason, sloped

columns are sometimes employed. These have a permanent

lateral thrust on the structure, which should be included in the

analysis, and in the evaluation of P-Delta limits in AISC 360

(2016) and ASCE 7 (2016). The effect of sustained lateral

forces on structure has not been thoroughly examined.

However, at least one study indicates sustained thrust less than

10% of the story shear strength does not have a measurable

effect on response (Yi et al., 2012). Figure 7 shows a schematic

of a frame with a sloped column.

Fig. 7. Schematic of a frame with a sloped column

For similar reasons, extending the concourses via cantilever

may be considered. In some stadiums the cantilever can take

the form of a story-deep truss. Such a truss joins two adjacent

levels. However, it does not form a braced frame, as the

diagonal cannot impart overturning forces to a column at its

outer end. It nevertheless interacts with the seismic system,


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being essentially a highly-sloped column, imposing similar

sustained thrust on the lateral system. Additionally, the vertical

movement of the cantilever is coupled with the lateral drift,

and the geometry may be such that the vertical movements are

an amplification of the horizontal. While this is not inherently

a performance issue, it may be disconcerting to experience.

Figure 8 shows a story-deep kicker.

Fig. 8. Schematic of a frame with a story-deep kicker

Because of special programming requirements at event level

such as loading docks, transfer trusses are often used to allow

closer column spacing at upper levels. Such trusses often

support several levels of structure and must be quite deep to

provide sufficient strength for the loading and stiffness for

erection. These trusses may be a full story deep. If both the top

and bottom chord are engaged into their respective levels, only

very small inelastic drift is possible unless the gravity-carrying

truss webs are subject to axial ductility (which would

compromise the gravity system). This can be avoided by

detaching one of the two chords from the diaphragm. Such

detachment needs to be preserved even as the chord is braced

laterally. Figure 9 shows a story-deep transfer truss.

Fig. 9. Story-deep transfer truss

It is typically much more efficient to locate braced frames at

upper levels away from columns supported by transfer trusses.

The large overturning forces associated with ductile braced

frames would require substantial increases in truss-member

size, constituting a much larger penalty than coping with

inefficiencies in braced-frame layout.

Seating Stadium bowls typically consist of flat concourses with seating

bowls sloping down and away, cantilevering toward the

playing area. The main diaphragm is typically the flat cast-in-

place concrete or flat slab on metal deck, similar to more

typical buildings. The seating bowl is necessarily a stepped

structure which cantilevers laterally and vertically off the main

diaphragm. Careful attention must be paid to the seismic load

path in tracing these loads back to the main SLRS.

Currently, two predominant options are available to provide

the structure for the seating bowls: precast concrete seating

units and proprietary systems such as the Sandwich Plate

System (SPS). The precast option is the more traditional

method, and consists of planks of precast concrete formed into

“Z” shapes one or two rows high (see Figure 10). These then

span from raker to raker, typically with a horizontal slip

connection at one end to prevent cracking under thermal loads.

The individual seating units are connected together and can

span laterally over their own length in the transverse direction,

but do not act as a full diaphragm over multiple bays.

Therefore, a supplementary diaphragm must be provided to

carry these forces back to the main diaphragm. See further

discussion of this “under-bowl” diaphragm below.

Fig. 10. Precast seating unit schematic cross section

SPS seating consists of two steel plates with an elastomer core

sandwiched between them, again formed into Z-shaped

sections. The two plates act as flanges resisting bending, while

the core transmits shear. See Figure 11. The plates also

transmit in-plane shear, allowing them to act as a diaphragm.

SPS seating is much lighter than equivalent concrete systems

(as little as 20% of the concrete weight, according to the

manufacturer), which can reduce the seismic mass of the

structure. However, in stadia with wide expanses of flat slabs

driving the bulk of the seismic mass (e.g., extensive

concourses or box seating), the potential mass savings may be

outweighed by the higher cost of the SPS units.


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Fig. 11. Sandwich Plate System schematic cross section

Under-bowl diaphragms

For systems that do not inherently have diaphragm capacity, a

supplementary diaphragm must be provided. This diaphragm

is typically accomplished by using a steel truss underneath the

seating units. Several complications arise in using this

configuration that must be carefully considered by the design

engineer.

• The diaphragm is vertically eccentric to the mass.

The truss diaphragm will need to be located below the

deepest stems of the seating units above. It may be

convenient to locate the truss members at the

centerline of the rakers, but the lower the truss is

located relative to the seating units, the more bending

will need to be taken by the rakers and other axially-

loaded collector members.

• The seating units are typically axially released on one

end to prevent the build-up of thermal stresses. This

release means that longitudinal seismic loads have to

track back to the fixed end. The connection from the

seating unit to the raker should be checked for this

full load. This configuration can also result in minor-

axis bending and torsion in the rakers. Rakers

typically have fixed-end units framing from one side

and free-end units framing from the other side. The

fixed-end units will induce bending which would not

be resisted by the free-end units.

• The entire under-bowl diaphragm may not line up

with the main diaphragm. Some bowls may be

stepped down from the main diaphragm, requiring

careful detailing to transfer the bowl forces into the

main diaphragm. Examples include kickers, braces,

or short “shear walls” that span from the top of the

bowl diaphragm up to the main diaphragm.

Rigid-body translation of precast walls

Where precast walls are used in sloped construction, careful

attention must be paid to jointing to avoid the walls acting as

unintentional shear walls. Not only would this load path be

undesirable and undesigned, it could cause major damage to

the walls in minor seismic events. This damage would be

unappealing aesthetically and from a public perception-of-

safety perspective.

The most common application of precast walls in sloped

construction is vomitory walls, where spectators can enter the

seating bowl from a small opening in the bowl. The walls must

not have hard connections to both the bowl above and the level

below, as this would provide an unintentional load path

between the levels. Therefore a horizontal joint should be

provided, but if the joint is along the sloped end of the wall, it

will bind up in one direction of relative movement. The joint

must be completely horizontal, which will necessitate hanging

at least part of the wall from above. The joint does not

necessarily need to be at the bottom of the wall, but this may

be the most convenient place for it. See Figure 12.

Fig. 12. Vomitory wall joint

Vertical transportation

In addition to more traditional vertical transportation, such as

stairs, escalators, and elevators, most large stadia also include

ramps. These ramps can be one long run (such as from grade

to concourses a level above or below grade), or service many

levels with several switchbacks. The former is easily designed

and can be treated like a typical stair with a single horizontal

joint at the top or bottom. The latter requires more thoughtful

analysis to keep the ramp from acting as an unintentional

seismic load path between floors and creating “short” columns.

The authors have found that the cleanest way to achieve this is

by assigning the runs of ramp branching off each level (one

going up and one going down) to that level’s diaphragm.

When two adjacent levels’ assigned ramp diaphragms intersect

mid-ramp, a seismic joint equal to the interstory drift must be

provided. See Figure 13. This joint does not necessarily need

to be at one of the ends of the ramp – one level’s run could turn

the switchback and continue, as long as the ramp diaphragm

has been designed for this load path.

In order to provide a robust gap (i.e., without relying on

corbels, which can cause collapse if the seismic movement

even slightly exceeds their bearing ledge’s dimension), the

authors recommend a double column at the outside of the joint

and a triple column at the inside of the joint (to avoid a short


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column). Providing double columns does mean that the

seismic joint must occur in the same place in every run of

ramp. This could pose problems if the story heights are

drastically different (e.g., double-height stories), resulting in

runs of ramp that are not tied to any level’s diaphragm.

However, supplemental ramp-only bracing can be provided to

brace those runs to a level above or below.

Figure 13. Switchback ramp schematic.

As with switchback ramps, switchback stairs also present

issues with providing joints between levels. Typically

switchback stairs have a landing which is either posted up from

the floor below or hung from the floor above. If the landing is

attached to the floor below, there must be a horizontal joint in

the stair above that landing (typically at the top). Similarly, if

the landing is hung from the floor above, the joint must occur

below the landing (typically at the floor level). See Figure 14.

For a joint at elevation (either at the top or at the landing),

consideration should be given to the bearing length to prevent

loss of support in large movement. The authors recommend

designing the stair stringers assuming a bearing support for

typical loading and designing the stringers to cantilever from

below if they lose their support (without the full live load

applied).

Figure 14. Stair joint diagram

For switchback stairs that to do not have standalone landings

(such as a stairwell between four building columns), the

jointing needs to carefully located and detailed to avoid

connecting floors together or creating short columns. This

jointing could be achieved with two-way bearing sliders, but

that will require larger gaps between the stairs and the shaft

walls that may not be palatable to the architect. Another

method would be to hang landings from above, or post up from

below, similar to what is discussed above. Typically this

supplemental structure would need to be buried in the shaft

walls for fire rating reasons.

Façades Façades in stadium structures may be quite tall due to the large

heights between concourses. This results in the need for a

substantial system to resist out-of-plane loading. In plane, the

façade structure can either span laterally between floor levels,

or it can travel with one level and allow slip at the other. In

either case a substantial in-plane structural system is required

and must be accommodated in the architecture of the façade.

Although these façades may form an ellipse around the

structure, the curvature is gradual enough that the façade may

be treated as planar.

Summary Stadium structures present special challenges in seismic

design. Many of the issues encountered in stadium design are

illustrative of broader themes and issues in seismic design and

can be instrumental in elucidating and communicating basic

principles of seismic design. Among these are clearly

delineating a load path that can provide significant inelastic

drift capacity; considering the effects of large inelastic drifts

on other elements of the structure; providing good torsional

resistance; and avoiding nonductile load paths.


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References

AISC (2016). Specification for Structural Steel Buildings,

ANSI/AISC 360-16, American Institute of Steel

Construction, Chicago, IL.

AISC (2016), Seismic Provisions for Structural Steel

Buildings, ANSI/AISC 341-16, American Institute of Steel

Construction, Chicago, IL.

ASCE (2016). Minimum Design Loads and Associated

Criteria for Buildings and Other Structures, ANSI/ASCE/SEI

7-16, American Society of Civil Engineers, Reston, VA.

Yi, Tianyi; Sabelli, Rafael; and Patel, Viral (2012). “Nonlinear

Seismic Response of Structural System with Gravity Bias,”

SEI Congress Proceedings, ASCE,

Documents

R Lessons from Stadium Structures in Seismic Zones · Raker Diagonal beam supporting seating tiers. ... in the design of the column connections so that gravity support is not lost