The Structural Design of Tall and Special Buildings (Wiley)

8102019 The Structural Design of Tall and Special Buildings (Wiley)

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Comparison of nonlinear behavior of steel moment framesaccompanied with RC shear walls or steel bracings

Hamed Esmaeili1dagger Ali Kheyroddin1 Mohammad Ali Ka 10472971 and Hamed Nikbakht 2

1Faculty of Civil Engineering Semnan University Semnan Iran2 Department of Civil Engineering Sharif University of Technology Tehran Iran

SUMMARY

In this paper the seismic behavior of dual structural systems in forms of steel moment-resisting frames accom-panied with reinforced concrete shear walls and steel moment-resisting frames accompanied with concentricallybraced frames have been studied The nonlinear behavior of the mentioned structural systems has been evaluatedas in earthquakes structures usually enter into an inelastic behavior stage and hence the applied energy to thestructures will be dissipated As a result some parameters such as ductility factor of structure (m) over-strength

factor ( Rs) and response modi1047297cation factor ( R) for the mentioned structures have been under assessment Toachieve these objectives 30-story buildings containing such structural systems were used to perform thepushover analyses having different load patterns Analytical results show that the steel moment-resisting framesaccompanied with reinforced concrete shear walls system has higher ductility and response modi1047297cation factor than the other one and so it is observed to achieve suitable seismic performance using the 1047297rst system can havemore advantages than the second one Copyright copy 2011 John Wiley amp Sons Ltd

Received 2 August 2011 Accepted 3 November 2011

KEYWORDS dual system steel moment-resisting frame shear wall steel bracing reinforced concrete seismic behavior

1 INTRODUCTION

As extensive areas in Iran especially the populated cities are located on the critical seismic zones and

they have high vulnerability to destruction the study of seismic behavior of structural systems is of great

importance Today reinforced concrete (RC) shear walls or steel bracings are used widespread as a main

load-carrying system in tall buildings for different reasons such as increase of energy dissipation and its

ability to resist lateral displacements of tall buildings that have moment-resisting frames Therefore the

recognition of the seismic behavior of the dual structural systems and 1047297guring out their advantages can

be helpful to structural engineers in selecting a proper system for structures that are being designed

Studying the behavior of building structures as subjected to severe earthquake ground motions

reveals that this type of structures can exhibit enough strength due to the nonlinear behavior of materials

and possibility of suf 1047297cient deformations of the structures These structures absorb the applied energy and

will dissipate it via tolerating great displacements in nonlinear seismic behavior

Nonlinear time history analysis of a detailed analytical model is perhaps the best option for theestimation of deformation demands However because of many uncertainties associated with the

site-speci1047297c excitation as well as uncertainties in the parameters of analytical models in many cases

the effort associated with detailed modeling and analysis may not be justi1047297ed and feasible (Hajirasouliha

and Doostan 2010)

In current years nonlinear static analyses have earned a great deal of research attention within the

earthquake engineering community Their main purpose is to demonstrate the nonlinear capacity of

a structure when subjected to horizontal loading with a reduced computational attempt with respect

Correspondence to Hamed Esmaeili Faculty of Civil Engineering Semnan University Semnan IrandaggerE-mail H_Esmaeilisunsemnanacir

THE STRUCTURAL DESIGN OF TALL AND SPECIAL BUILDINGSStruct Design Tall Spec Build (2011)Published online in Wiley Online Library (wileyonlinelibrarycom) DOI 101002tal751

Copyright copy 2011 John Wiley amp Sons Ltd



to nonlinear dynamic analyses Pushover methods are particularly shown for assessing existing structures

(frequently not originally designed with seismic criteria in mind) when the employment of linear elastic

methods typical in new design situations tends to be unsuitable For these goals many codes and guidelines

(eg Eurocode 8 2005 ATC-40 1996 FEMA-356 2000) propose the use of nonlinear static methodolo-

gies to evaluate structural behavior under seismic movement (Ferracuti et al 2009) To assess the seismic

performance of the structures three various nonlinear static analyses are used each of which contains a

constant load pattern These approaches are pushover analyses with load patterns proportionate to uniform and reverse triangular displacements of structures and modal pushover analysis (MPA)

2 REVIEW OF THE LATEST RESEARCHES

In general numerous studies in forms of analytical and experimental works have been implemented on

the mentioned structural systems Most important results of which are as follows

A series of experimental programs including two-story specimens was developed to recognize the

cyclic behavior of the composite structural systems This study shows that the lateral shear force tolerate

via compressive strut of wall and shear studs (Tong 2001)

Tong et al (2005) presented an experimental study on the cyclic behavior of a composite structural

system consisting of partially restrained steel frames with RC in1047297

ll walls The one-bay two-story test specimen was built at one-third scale The study shows that this system has the potential to offer

strength appropriate for resisting the forces from earthquakes and stiffness adequate for controlling

drift for low-rise to moderate-rise buildings located in earthquake-prone regions

As a basis of many studies structural frames with in1047297ll panels are typically providing an ef 1047297cient

method for bracing buildings (Jung and Aref 2005) The presence of in1047297lls can also have a signi1047297cant

effect on the energy dissipation capacity (Decanini et al 2002)

In common practice steel bracing system is used to increase the lateral load resistance of steel struc-

tures Steel moment-resisting frame structures possess high strength and signi1047297cant ductility thus are

effective structural forms for earthquake-resistant designs However the load-carrying ef 1047297ciency of

such designs is limited when an earthquake induces large story drift because of the lower structural

stiffness of the steel frames (Hsu et al 2011)

Over-strength ductility and response modi1047297cation factors of buckling-restrained braced frames

were evaluated by Asgarian and Shokrgozar (2009) To do so buildings with various stories and

different bracing con1047297gurations including diagonal split X and chevron (V and inverted V) bracings

were considered In this article seismic response modi1047297cation factor for each of bracing systems has

been determined separately and tentative values of 835 and 12 has been suggested for ultimate limit

state and allowable stress design methods respectively

The over-strength ductility and response modi1047297cation factors of special concentric braced frames

and ordinary concentric braced frames were evaluated by performing pushover analysis of model

structures with various stories and span lengths (Kim and Choi 2005) The results were compared with

those from nonlinear incremental dynamic analyses The results of incremental dynamic analysis

generally matched well with those obtained from pushover analysis

A signi1047297cant aspect in the design of steel braced RC frames is the level of interaction between the

strength capacities of the RC frame and the bracing system Maheri and Ghaffarzadeh (2008)

conducted an experimental and numerical investigation to evaluate the level of capacity interactionbetween the two systems It was found that the capacity interaction is primarily due to the connections

over-strength and also the number of braced bays and the number of frame stories recognized

3 SEISMIC BEHAVIOR OF STRUCTURES

31 The ductility of structures

As a general rule it is possible to replace the ideal bilinear elasto-plastic diagrams with the base

shear ndashdisplacement curves of structures (Figure 1) The ductility factor in single degree-of-freedom

H ESMAEILI ET AL

Copyright copy 2011 John Wiley amp Sons Ltd Struct Design Tall Spec Build (2011)

DOI 101002tal



(SDOF) systems is a proportion of maximum lateral displacement to the yielding lateral displacement

of structures

m frac14Δmax

Δy

(1)

In fact the ductility factor explains to what extent the structure enters when in nonlinear state There is

no accurate de1047297nition for the ductility factor of multiple degrees-of-freedom structures In some provi-sions yielding is assumed to have been simultaneous although not precise (Wakabayashi 1986) Mean-

while the relation between the base shear and displacement is not an elasticndashperfectly plastic equation

With consideration to Figure 1 an idealization in de1047297nition of the ductility factor is accepted

32 Response modi 1047297cation factor

Seismic codes consider a reduction in design loads taking advantage of the fact that the structures

possess signi1047297cant reserve strength (over-strength) and capacity to dissipate energy (ductility) The

over-strength and the ductility are incorporated in structural design through a force reduction or a

response modi1047297cation factor This factor represents ratio of maximum seismic force on a structure

during speci1047297ed ground motion if it was to remain elastic to the design seismic force Thus actual

seismic forces are reduced by the factor lsquo Rrsquo to obtain design forces The basic 1047298aw in code procedures

is that they use linear methods but rely on nonlinear behavior (Kim and Choi 2005)As it is shown in Figure 1 usually real nonlinear behavior is idealized by a bilinear elasto ndashperfectly

plastic relation The yield force of structure is shown by V y and the yield displacement is Δy In this

1047297gure V e or V max correspond to the elastic response strength of the structure The maximum base shear

in an elasto perfectly behavior is V y (Uang 1991) The ratio of maximum base shear considering elastic

behavior V e to maximum base shear in elasto perfectly behavior Vy is called force reduction factor

Rm frac14V e

V y(2)

The over-strength factor is de1047297ned as the ratio of maximum base shear in actual behavior V y to the 1047297rst

signi1047297cant yield strength in structure V s

RS frac14

V y

V s (3)

To design for allowable stress method the design codes decrease design loads from V s to V w This

decrease is done by allowable stress factor which is de1047297ned as (Asgarian and Shokrgozar 2009)

Figure 1 General structure response (Uang 1991)

COMPARISON OF NONLINEAR BEHAVIOR OF STEEL MOMENT FRAMES


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Y frac14V S

V W(4)

The response modi1047297cation factor therefore accounts for the ductility and over-strength of the structure

and for the difference in the level of stresses considered in its design It is generally expressed in the

following form taking into accounts the aforementioned conceptions (Asgarian and Shokrgozar 2009)

R frac14V e

V Wfrac14

V e

V y

V y

V S

V S

V Wfrac14 Rm RS Y (5)

33 The relation between the force reduction factor the ductility factor and the period of structure

The force reduction factor ( Rm) is related to many parameters of which many are correlated to character-

istics of the structural system and some of them are independent from the structure and are related to the

other parameters such as respected loading (the time history of earthquake) Rm will be correlated to a set

of factors especially the ductility factor of structure and its performance characteristics in the nonlinear

state if we consider a speci1047297c earthquake for a particular place Therefore the 1047297rst step in determining

force reduction factor is specifying the relation between it and the capacity of the ductility of structure

Multiple factors are known that af 1047298uence on the relation between Rm and m such as materials period of

system damping PΔ effects the loadndashdeformation model in the hysteresis loops and type of the soil

that exists in the site If we consider this assumption that the ductility in the structures with short period is

the same as those that have longer periods then smaller Rm is obtained Also New Mark and Hall (1982)

suggested the following equations for calculation of the force reduction factor of structures

Rm frac14 1 T lt 0125 s(6)

Rm frac14 ffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2m 1

p 0

125 s lt

T lt

0

5 s (7)

Rm frac14 m 05 s lt T (8)

34 The conversion coef 1047297cient of linear to nonlinear displacement (C d)

It rsquos clear that the structural damages are normally originated from excessive deformations of the

structure Therefore with regard to the effective parameters on seismic design of a structure the

discussion about assessment and accurate prediction of displacement and monitoring of them are the

most important aims in seismic design of a structure The C d coef 1047297cient can be calculated as follows

C d frac14Δmax

ΔS

frac14Δmax

Δy

Δy

Δs

frac14 m Rs (9)

4 DESIGN OF THE STRUCTURAL MODELS IN THIS STUDY

In this study two structural models are used for specifying the trend of this research de1047297nes

as follows

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(1) Model A A 30-story building in the form of special steel moment-resisting frame accompanied

with special RC shear wall

(2) Model B A 30-story building in the form of special steel moment-resisting frame accompanied

with concentrically steel braced frames (X-braces)

The height of the all stories is 35 m Both of them have a residential application Therefore a 1047298oor

dead load an equivalent partition load and a live load for each story of values 200 kgm 2 650 kgm 2

and 150 kgm 2 (1961 Nm 2 6374 Nm 2 and 1471 Nm 2) respectively are applied Also the structural

system of the 1047298oor is composite of RC slabs and steel secondary beams The steel material used in the

sections of the structural members is of ST37 type with yielding strength of 2400 kgcm 2

(235 359 600 Nm 2) and ultimate strength of 3700 kgcm 2 (362 846 050 Nm 2) The compressive

strength of concrete material f primec used in the shear walls is 300 kgcm 2 (29419 950 Nm 2) American

Institute of Steel Construction Speci1047297cation (AISC 2005) and American Concrete Institute Requirements

(ACI Committee 318 2008) were used to design steel members and shear wall respectively Also in

order to calculate earthquake load the spectrum dynamic method was used The equation suggested by

Kheyroddin (2006) was used to determine the thickness and the number of required shear walls

rmin frac14

hw

l w

2

835thorn 205 hw

l w

(10)

In which rmin is the minimum wall-area-to-story-area ratio hW is the total wall height and l W is the wall

length (average shear wall lengths present in building plan)

The plans of the structures the direction of the girders and secondary beams and the location of

shear walls and bracings are shown in Figures 2 and 3 In the design process of these structures it

has been tried that moment frame members tolerate 25 of earthquake forces in addition to bearing

gravity load The thicknesses of the shear walls for each story are shown in Table 1 and the sizes

of the steel braces for each story are shown in Table 2 With regard to the design of the structures

box-shaped and I-shaped sections are obtained for section area of columns and beams respectively

5 NONLINEAR ANALYSIS

51 Existing pushover analysis methods

During a pushover analysis a frame structure is subjected to gravitational loads and horizontal loads

applied at each story with the latter being incremented up to failure Ideally the distribution of horizon-

tal loads should approximate the inertia forces that are generated in the structure during an earthquake

Conventional pushover procedures adopt an invariant load pattern during the analysis and according to

a number of codes and guidelines at least two different force distributions must be considered uniform

and proportional to the 1047297rst modal shape The invariant load pattern is one of the most signi1047297cant

limitations of traditional methods because the actual inertia force distribution changes continuously

during seismic events as a result of higher mode contribution and structural degradation which modi1047297es

the stiffness of individual structural elements and consequently of the structure as a whole

A procedure that proposed by Chopra and Goel (2003) is MPA whereby a series of independent

pushover analyses are carried out considering different horizontal load patterns for each modal shapeAccording to the authors it is suf 1047297cient to consider the 1047297rst two or three modal shapes Results in terms

of capacity curves for various modal shapes are transformed in capacity curves for equivalent SDOFs

one for each mode Seismic demands are separately evaluated for each SDOF and 1047297nally combined by

the square-root-of-the-sum-of-the-squares method A common drawback of this method is the mode

superposition of results obtained from nonlinear pushover analyses carried out separately for various

modes The method neglects the interaction amongst the modes with modal superposition being

performed just as in elastic modal analysis Accordingly capacity curves typically overestimate base

shear values (Hernandez-Montes et al 2004)

On the basis of an analytical work that is conducted by Mortezaei et al (2009) it is shown that non-

linear static procedures based on invariant load vectors using elastic modal properties cannot capture



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Figure 2 The structural plan of the model A

Figure 3 The structural plan of the model B

Table 1 The thickness of the shear walls in the Model A

Story 1ndash2 3ndash6 7ndash9 10ndash12 13ndash15 16ndash18 19ndash21 22ndash24 25ndash27 28ndash30

Thickness (mm) 650 600 500 500 450 400 350 300 250 200

Table 2 The sizes of the steel braces in the Model B

Story 1ndash2 3ndash6 7ndash9 10ndash12 13ndash15 16ndash21 22ndash24 25ndash27 28ndash30

Sizes of braces 2UNP300 2UNP280 2UNP260 2UNP240 2UNP220 2UNP200 2UNP180 2UNP160 2UNP140

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the changes to the dynamic modes resulting from inelastic action The variation of inertial forces must

be considered in static procedures that attempt to reproduce inelastic dynamic response

52 Nonlinear modeling of the structures

In order to assess the seismic behavior of selected buildings we have conducted a series of nonlinear

static analysis The designed structures have been used by importing into PERFORM-3D (Computers and

Structures Inc 2006a) software to create a nonlinear model After a preliminary design of the struc-tures the nonlinear model of the following elements forcendashdeformation relationship and deformation

capacities in PERFORM-3D has been developed There are a number of different ways to model inelastic

beams and columns in PERFORM At one extreme are 1047297nite element models using 1047297ber sections At the

other extreme are chord rotation models that consider the member as a whole and essentially requires

one to specify only the relationship between end moment and end rotation In between these extremes

are a number of other models In this study the chord rotation model for beams and columns has been

selected The basic model is shown in Figure 4 This is a symmetrical beam with equal and opposite

end moments and no loads along the beam length To use this model one has to specify the nonlinear

relationship between the end moment and end rotation An advantage of this model is that FEMA-356

gives speci1047297c properties including end rotation capacities (Mohammadjafari and Jalali 2009)

Figure 5 shows a PERFORM frame compound component for the chord rotation model The key parts of

this model are the FEMA beam components These are 1047297nite length components with nonlinear proper-ties The model has two of these components for cases where the strengths are different at the two ends of

element PERFORM allows user to specify different strength for two components and also different lengths

to consider cases where the in1047298ection point is not at mid-span (Mohammadjafari and Jalali 2009)

For modeling the braces the Simplr Bar element is used and parameters in Tab 5ndash6 of FEMA-356 are

implemented to model this element in the software An example of the FndashD relationship of Simplr Bar

element is shown in Figure 6

To make the RC shear wall sections de1047297ning the linear and nonlinear characteristics of its materials

(concrete and steel bar) are necessary

As it is shown in Figure 7 the stressndashstrain curve of concrete is selected in the form of trilinear with

strain hardening and its tension strength is ignored The modulus of elasticity E C is assumed to be

Figure 4 Chord rotation model

Figure 5 Basic components for chord rotation FEMA Federal Emergency Management Agency

Figure 6 Modeling of the behavior of bracing in PERFORM



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261 540 kgcm 2 (2561010 Nm 2) The strain of ultimate strength of concrete eL is taken 0003

(Kheyroddin 2008) and the strain of crushing limit of concrete eCU is taken 0005 As it is seen in

Figure 7 the strain of yielding strength of concrete eY is taken 0002 then the ratio of initial modulus

of elasticity to secondary modulus of elasticity is speci1047297ed to 0402

The stressndashstrain relationship of steel bar is supposed to be bilinear (elasticndashperfectly plastic) The

modulus of elasticity E S is taken 2 100 000 kgcm 2 (2061011Nm 2) and the ultimate strain eSU

is taken 005 (Kheyroddin 2008) Also its yielding strength F Y is 4000 kgcm 2 (392 266 000 Nm 2)

53 Nonlinear analysis of the models

In this study three nonlinear static analysis approaches are used for each model which are described in

the following So six pushover analyses have been performed The center of mass at the roof level is

selected as a control point of the displacement of structure in all analysis Thus the relative lateral

displacement (drift) of the roof is used as a reference relative to lateral displacement for plotting the

capacity curves of the structures and for interpretation of the results obtained from these analyses

During application of these analyses two approaches have been used to regulate the drift of structure

The 1047297rst criterion is the limitation of reference drift and inter-story drift for the structure which is 2 on

the basis of Tab C1-3 of FEMA-356 and Standard No2800 (2007) (Table 3) Consequently the analysis

will be stopped when these drifts exceed from the mentioned limit The second criterion for 1047297nishing the

analysis is when the deformation capacity of each element is reached

531 Uniform nonlinear static procedure

To perform a static pushover analysis you must specify the distribution of horizontal loads over the

structure height The current version of PERFORM-3D (Computers and Structures Inc 2006b) allows

1047297xed distributions only (ie you cannot consider lsquoadaptiversquo load distributions that depend on the

de1047298ected shape) As will be explained later you can specify load distributions using nodal load

patterns or you can specify loads on the basis of the structure mass and a de1047298ected shape

One of the most dif 1047297cult issues for pushover analysis is choosing the pushover load distribution

During an actual earthquake the effective loads on a structure change continuously in magnitude

distribution and direction The distribution of story shears over the height of a building can thus change

substantially with time especially for taller buildings where higher modes of vibration can have

signi1047297cant effects In a static pushover analysis the distribution and direction of the loads are 1047297xed

and only the magnitude varies Hence the distribution of story shears stays constant To account for

Figure 7 Nonlinear properties of concrete

Table 3 The structural properties of model A and model B in linear design stage

Type of model T 1 (s) R V (kN) ∆ x (mm) ∆ y (mm) Max drift X Max drift Y

Model A 284 11 11 576 200 1931 00027 00026Model B 3066 9 10 791 2296 2126 0003 00028

T 1 is the natural period of the structure R is the response modi1047297cation factor of the structureV is the base shear of the structure∆ x and ∆ y are the displacements at roof level of the structure in the X and Y directions respectivelyMax drift X and max drift Y are the maximum drifts of the structure in the X and Y directions respectively

H ESMAEILI ET AL


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different story shear distributions to consider a number of different pushover load distributions is

necessary One option in FEMA-356 is to use uniform and triangular distributions over the building

height Note that a uniform distribution usually corresponds to a uniform acceleration over the building

height so that the load at any 1047298oor level is proportional to the mass at the 1047298oor

In fact to access this load pattern in the software a procedure is performed for loading on the basis

of uniform displacement pattern over the building height Then in loading step the software calculates

the necessary force proportioned to the created displacement

532 Triangular nonlinear static procedure

The difference between this procedure and the previous one is in their load pattern in this procedure

the inverted triangular pro1047297le is used for displacement-based load pattern of story masses based on

FEMA-356 Therefore the imposed displacement and hence the acceleration will not be uniform over

the building height

533 Modal pushover analysis

Load distributions can be based on the structure mode shapes For a low-rise structure that is

dominated by its 1047297rst mode response a load distribution based on the 1047297rst mode may be reasonable

Also considering the higher modes is important for a structure with signi1047297cant higher mode responses

(medium-rise and high-rise buildings)

In this study the three 1047297rst mode shapes in the X -direction of structural plan (see Figures 2 and 3)

are selected to perform of modal pushover analyses

The capacity curves of models A and B which are acquired from the aforementioned pushover

procedures are converted to the ideal bilinear diagrams which are shown in Figures 8 and 9 respectively

Also the values of V S V Y V U ΔY and ΔU which are obtained from the analyses and the value of V W

Figure 8 The ideal bilinear diagrams of the pushover analyses for model A UNSP uniform nonlinear

static procedure TNSP triangular nonlinear static procedure MPA modal pushover analysis

Figure 9 The ideal bilinear diagrams of the pushover analyses for model B UNSP uniform nonlinear




DOI 101002tal



which is speci1047297ed in preliminary design stage are represented in Table 4 Therefore seismic parameters

have been calculated by using the equations which are de1047297ned in Section 3 as indicated in Table 5 Also

the averages of the aforementioned values are determined that are shown in following tables At the end

the mean of capacity curves of models A and B are shown in Figure 10

As it observed from analytical results the parameters obtained from MPA such as ductility factor

(m) force reduction factor ( Rm) and response modi1047297cation factor ( R) for the mentioned structures will

be larger than the same parameters gained from other pushover approaches This behavior can revealthe importance and hence the effect of higher mode shapes of the structure in tall buildings

Considering the capacity curves in Figure 10 it is clear that the energy dissipation of the structural

system in model A is greater than that of model B Also the mean value of response modi 1047297cation

factor ( R) for model A is bigger than the same parameter of model B Therefore structures with shear

walls have better seismic behavior rather than structures with steel X-bracings

To evaluate combined behavior and interaction of RC shear wall with steel moment-resisting frame

and comparison of that with concentrically braced frame system the percent of shear absorption of

Table 4 The structural properties of models A and B in nonlinear analysis stage

Type of model Type of analysis V W (kN) V S (kN) V Y (kN) V U (kN) ∆Y ∆U

Model A UNSP 11 576 27 125 44 047 47 628 000463 001768TNSP 18 080 31 294 35 551 000468 001678MPA 30 784 49 737 52 660 000430 001757Mean 25 329 41 692 45 283 000454 001734

Model B UNSP 10 791 26 301 37 719 38 416 000486 001759TNSP 19 443 26 291 29 734 000513 001800MPA 27 939 40 417 42 585 000426 001540Mean 24 564 35 385 36 915 000475 001700

UNSP uniform nonlinear static procedure TNSP triangular nonlinear static procedure MPA modal pushover analysis

Table 5 The seismic parameters of models A and B

Type of model Type of analysis m Rm RS Y R C d

Model A UNSP 382 162 234 1453 620TNSP 358 173 156 968 620MPA 408 162 266 1758 660Mean 382 165 219 1378 629

Model B UNSP 362 143 244 1265 519TNSP 350 144 180 910 505MPA 361 145 259 1352 522Mean 358 144 228 1174 515


Figure 10 The mean of capacity curves of the Model A and Model B

H ESMAEILI ET AL


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these models has been studied in this paper The meaning of the percent of shear absorption is the ratio

of shear quantity that is endured by the columns of frame or brace in each story to the total shear

absorbed in that story Figures 11 and 12 indicate the quantity of shear absorbed by moment-resisting

frames and RC shear walls in model A and quantity of shear absorbed by moment-resisting frames

with steel bracing in model B in terms of the average of various analytical methods applied in this

study in levels of yield and ultimate strength of structure

As it is observed in these 1047297gures in system with shear wall major part of transferring lateral force inthe middle and lower stories is tolerated by RC shear wall and contribution of shear absorbed by

Figure 11 The interaction curves of the Model A and Model B for mean state of different analysis

methods in level of yield strength of structure


methods in level of ultimate strength of structure



DOI 101002tal



moment-resisting frames gradually has increased in higher stories In addition in both levels of yield

and ultimate strength negative shear has been created in the last story indicating that shear wall relies

to the steel moment-resisting frame but in braced systems a main part of this process in lower stories

is carried by steel bracings and in the middle and higher stories contribution of shear absorbed by

moment-resisting frames has increased considerably as levels of yield and ultimate strength of the

structure has generated negative shear in the top two and 1047297ve stories This issue has demonstrated high

lateral stiffness for structures with shear wall system than that with braced system

6 CONCLUSIONS

Some of the key results obtained from the present analytical work are as follows

bull In the studied structures the capacity curves have larger values of lateral strength in the uniform

nonlinear static procedure than that in the triangular nonlinear static procedure However the peak

value is in the MPA The difference can show the effect of load pattern and importance of considering

the higher mode shapes in pushover analysis

bull The mean value of m and Rm factors for special steel moment-resisting frame accompanied with

special RC shear wall system (model A) is 382 whereas the value of mentioned factors is 358 for

special steel moment-resisting frame accompanied with concentrically steel braced frames (X-braces)system (model B)

bull The mean value of the over-strength factor RS for model A and model B are 165 and 144

respectively

bull The mean value of the response modi1047297cation factor R for model A and model B in allowable stress

design method are evaluated as 1378 and 1174 respectively

bull The mean value of the increasing coef 1047297cient of linear to nonlinear displacement C d for model A

and model B are evaluated as 629 and 515 respectively

bull The ductility and response modi1047297cation factors are larger for model A than model B Therefore it

seems that the use of special steel moment-resisting frame accompanied with special RC shear wall

system is more effective than the use of special steel moment-resisting frame accompanied with

concentrically steel braced frames (X-brace) system

bull

In regard to the results it seems that the C d factor for the mentioned structural systems is less thanthe values that are in Standard No 2800 (2007) The C d factor is suggested as 07 times of the

response modi1047297cation factor R in this code

REFERENCES

ACI Committee 318 2008 Building Code Requirements for Structural Concrete (ACI 318-08) and Commentary American

Concrete Institute Farmington Hills Michigan

AISC 2005 Speci 1047297cation for Structural Steel Buildings American Institute of Steel Construction Chicago

Applied Technology Council (ATC-40) 1996 Seismic Evaluation and Retro 1047297t of Concrete Buildings ATC Redwood City USA

Asgarian B Shokrgozar HR 2009 BRBF response modi1047297cation factor Journal of Constructional Steel Research 65 290ndash298

BHRC (Building and Housing Research Center) 2007 Iranian Code of Practice for Seismic Resistant Design of Buildings

Standard No 2800 ndash 07 BHRC Tehran

Chopra AK Goel RK 2003 A modal pushover analysis procedure for estimating seismic demands for buildings Earthquake

Engineering and Structural Dynamics 31

561ndash

582Comiteacute Europeen de Normalization 2005 Eurocode 8 mdash Design of Structures for Earthquake Resistance Part 3 Assessment

and Retro 1047297tting of Buildings EN 1998-3 CEN Brussels Belgium

Computers and Structures Inc 2006a Perform Components and Elements for PERFORM-3D and PERFORM-COLLAPSE CSI

Berkeley CA

Computers and Structures Inc 2006b PERFORM-3D nonlinear analysis and performance assessment for 3D structures

components and elements version4 CSI Berkeley CA

Decanini LD Liberatore L Mollaioli F 2002 Response of bare and in1047297lled RC frames under the effect of horizontal and vertical

seismic excitation In 12th European Conference on Earthquake Engineering

Federal Emergency Management Agency (FEMA) 2000 Prestandard and Commentary for the Seismic Rehabilitation of Buildings

Report No FEMA 356 Washington USA

Ferracuti B Pinho R Savoia M Francia R 2009 Veri1047297cation of displacement-based adaptive pushover through multi-ground

motion incremental dynamic analyses Engineering Structures 31 1789ndash1799

H ESMAEILI ET AL


DOI 101002tal



Hajirasouliha I Doostan A 2010 A simpli1047297ed model for seismic response prediction of concentrically braced frames Advances

in Engineering Software 41 497ndash505

Hernandez-Montes E Kwon OS Aschheim MA 2004 An energy-based formulation for 1047297rst- and multiple-mode nonlinear

static (pushover) analyses Journal of Earthquake Engineering 8(1) 69ndash88

Hsu HL Juang JL Chou CH 2011 Experimental evaluation on the seismic performance of steel knee braced frame structures

with energy dissipation mechanism Steel and Composite Structures 11(1) 77ndash91

Jung WY Aref AJ 2005 Analytical and numerical studies of polymer matrix composite sandwich in1047297ll panels Journal of

Composite Structures 68 359ndash370

Kheyroddin A 2006 Analyses and Design of Shear Walls Semnan University Press Iran

Kheyroddin A 2008 Investigation of nonlinear behavior of RC frames strengthened with steel bracing International Journal of

Engineering Sciences Iran University of Science and Technology 2(19) 25ndash35

Kim J Choi H 2005 Response modi1047297cation factors of chevron-braced frames Engineering Structures 27 285ndash300

Maheri MR Ghaffarzadeh H 2008 Connection overstrength in steel-braced RC frames Engineering Structures 30 1938ndash1948

Mohammadjafari A Jalali A 2009 Assessment of performance based parameters in near fault tall buildings Journal of Applied

Sciences 9(22) 4044ndash4049

Mortezaei A Ronagh HR Kheyroddin A Ghodrati Amiri G 2009 Effectiveness of modi1047297ed pushover analysis procedure for

the estimation of seismic demands of buildings subjected to near-fault earthquakes having forward directivity Structural

Design of Tall and Special Buildings DOI 101002tal553

New Mark NM Hall WJ 1982 Earthquake Spectra and Design Engineering Monograph Earthquake Engineering Research

Institute Berkeley CA

Tong X 2001 Seismic behavior of composite steel frame-reinforced concrete in1047297ll wall structural system PhD Thesis Department

of Civil Engineering University of Minnesota

Tong X Hajjar JF Schultz AE Shield CK 2005 Cyclic behavior of steel frame structures with composite reinforced concretein1047297ll walls and partially-restrained connections Journal of Constructional Steel Research 61 531ndash552

Uang C 1991 Establishing R (or Rw) and C d factors for building seismic provisions Jornal of Structural Engineering ASCE

117(1) 19ndash28

Wakabayashi M 1986 Design of Earthquake-resistant Buildings Mc Graw-Hill New York



DOI 101002tal



to nonlinear dynamic analyses Pushover methods are particularly shown for assessing existing structures

(frequently not originally designed with seismic criteria in mind) when the employment of linear elastic

methods typical in new design situations tends to be unsuitable For these goals many codes and guidelines

(eg Eurocode 8 2005 ATC-40 1996 FEMA-356 2000) propose the use of nonlinear static methodolo-

gies to evaluate structural behavior under seismic movement (Ferracuti et al 2009) To assess the seismic

performance of the structures three various nonlinear static analyses are used each of which contains a

constant load pattern These approaches are pushover analyses with load patterns proportionate to uniform and reverse triangular displacements of structures and modal pushover analysis (MPA)

2 REVIEW OF THE LATEST RESEARCHES

In general numerous studies in forms of analytical and experimental works have been implemented on

the mentioned structural systems Most important results of which are as follows

A series of experimental programs including two-story specimens was developed to recognize the

cyclic behavior of the composite structural systems This study shows that the lateral shear force tolerate

via compressive strut of wall and shear studs (Tong 2001)

Tong et al (2005) presented an experimental study on the cyclic behavior of a composite structural

system consisting of partially restrained steel frames with RC in1047297

ll walls The one-bay two-story test specimen was built at one-third scale The study shows that this system has the potential to offer

strength appropriate for resisting the forces from earthquakes and stiffness adequate for controlling

drift for low-rise to moderate-rise buildings located in earthquake-prone regions

As a basis of many studies structural frames with in1047297ll panels are typically providing an ef 1047297cient

method for bracing buildings (Jung and Aref 2005) The presence of in1047297lls can also have a signi1047297cant

effect on the energy dissipation capacity (Decanini et al 2002)

In common practice steel bracing system is used to increase the lateral load resistance of steel struc-

tures Steel moment-resisting frame structures possess high strength and signi1047297cant ductility thus are

effective structural forms for earthquake-resistant designs However the load-carrying ef 1047297ciency of

such designs is limited when an earthquake induces large story drift because of the lower structural

stiffness of the steel frames (Hsu et al 2011)

Over-strength ductility and response modi1047297cation factors of buckling-restrained braced frames

were evaluated by Asgarian and Shokrgozar (2009) To do so buildings with various stories and

different bracing con1047297gurations including diagonal split X and chevron (V and inverted V) bracings

were considered In this article seismic response modi1047297cation factor for each of bracing systems has

been determined separately and tentative values of 835 and 12 has been suggested for ultimate limit

state and allowable stress design methods respectively

The over-strength ductility and response modi1047297cation factors of special concentric braced frames

and ordinary concentric braced frames were evaluated by performing pushover analysis of model

structures with various stories and span lengths (Kim and Choi 2005) The results were compared with

those from nonlinear incremental dynamic analyses The results of incremental dynamic analysis

generally matched well with those obtained from pushover analysis

A signi1047297cant aspect in the design of steel braced RC frames is the level of interaction between the

strength capacities of the RC frame and the bracing system Maheri and Ghaffarzadeh (2008)

conducted an experimental and numerical investigation to evaluate the level of capacity interactionbetween the two systems It was found that the capacity interaction is primarily due to the connections

over-strength and also the number of braced bays and the number of frame stories recognized

3 SEISMIC BEHAVIOR OF STRUCTURES

31 The ductility of structures

As a general rule it is possible to replace the ideal bilinear elasto-plastic diagrams with the base

shear ndashdisplacement curves of structures (Figure 1) The ductility factor in single degree-of-freedom

H ESMAEILI ET AL


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of structures

m frac14Δmax

Δy

(1)

















Rm frac14V e

V y(2)



RS frac14

V y

V s (3)






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Y frac14V S

V W(4)




R frac14V e

V Wfrac14

V e

V y

V y

V S

V S














Rm frac14 1 T lt 0125 s(6)


p 0

125 s lt

T lt

0

5 s (7)







C d frac14Δmax

ΔS

frac14Δmax

Δy

Δy

Δs

frac14 m Rs (9)



as follows

H ESMAEILI ET AL


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rmin frac14

hw

l w

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835thorn 205 hw

l w

(10)

































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Thickness (mm) 650 600 500 500 450 400 350 300 250 200




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Model A 284 11 11 576 200 1931 00027 00026Model B 3066 9 10 791 2296 2126 0003 00028


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the building height

















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H ESMAEILI ET AL


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6 CONCLUSIONS










respectively









bull



REFERENCES










561ndash




Berkeley CA









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DOI 101002tal



























117(1) 19ndash28




DOI 101002tal




of structures

m frac14Δmax

Δy

(1)

















Rm frac14V e

V y(2)



RS frac14

V y

V s (3)






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Y frac14V S

V W(4)




R frac14V e

V Wfrac14

V e

V y

V y

V S

V S














Rm frac14 1 T lt 0125 s(6)


p 0

125 s lt

T lt

0

5 s (7)







C d frac14Δmax

ΔS

frac14Δmax

Δy

Δy

Δs

frac14 m Rs (9)



as follows

H ESMAEILI ET AL


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rmin frac14

hw

l w

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835thorn 205 hw

l w

(10)

































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Thickness (mm) 650 600 500 500 450 400 350 300 250 200




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Model A 284 11 11 576 200 1931 00027 00026Model B 3066 9 10 791 2296 2126 0003 00028


H ESMAEILI ET AL


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the building height

















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6 CONCLUSIONS










respectively









bull



REFERENCES










561ndash




Berkeley CA









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117(1) 19ndash28




DOI 101002tal



Y frac14V S

V W(4)




R frac14V e

V Wfrac14

V e

V y

V y

V S

V S














Rm frac14 1 T lt 0125 s(6)


p 0

125 s lt

T lt

0

5 s (7)







C d frac14Δmax

ΔS

frac14Δmax

Δy

Δy

Δs

frac14 m Rs (9)



as follows

H ESMAEILI ET AL


DOI 101002tal


















rmin frac14

hw

l w

2

835thorn 205 hw

l w

(10)

































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Thickness (mm) 650 600 500 500 450 400 350 300 250 200




H ESMAEILI ET AL


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Model A 284 11 11 576 200 1931 00027 00026Model B 3066 9 10 791 2296 2126 0003 00028


H ESMAEILI ET AL


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the building height

















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H ESMAEILI ET AL


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6 CONCLUSIONS










respectively









bull



REFERENCES










561ndash




Berkeley CA









H ESMAEILI ET AL


DOI 101002tal



























117(1) 19ndash28




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rmin frac14

hw

l w

2

835thorn 205 hw

l w

(10)

































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Thickness (mm) 650 600 500 500 450 400 350 300 250 200




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Model A 284 11 11 576 200 1931 00027 00026Model B 3066 9 10 791 2296 2126 0003 00028


H ESMAEILI ET AL


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the building height

















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H ESMAEILI ET AL


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6 CONCLUSIONS










respectively









bull



REFERENCES










561ndash




Berkeley CA









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117(1) 19ndash28




DOI 101002tal







Thickness (mm) 650 600 500 500 450 400 350 300 250 200




H ESMAEILI ET AL


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DOI 101002tal




































Model A 284 11 11 576 200 1931 00027 00026Model B 3066 9 10 791 2296 2126 0003 00028


H ESMAEILI ET AL


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the building height

















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H ESMAEILI ET AL


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DOI 101002tal










6 CONCLUSIONS










respectively









bull



REFERENCES










561ndash




Berkeley CA









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117(1) 19ndash28




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Model A 284 11 11 576 200 1931 00027 00026Model B 3066 9 10 791 2296 2126 0003 00028


H ESMAEILI ET AL


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the building height

















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H ESMAEILI ET AL


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DOI 101002tal










6 CONCLUSIONS










respectively









bull



REFERENCES










561ndash




Berkeley CA









H ESMAEILI ET AL


DOI 101002tal



























117(1) 19ndash28




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Model A 284 11 11 576 200 1931 00027 00026Model B 3066 9 10 791 2296 2126 0003 00028


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the building height

















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H ESMAEILI ET AL


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6 CONCLUSIONS










respectively









bull



REFERENCES










561ndash




Berkeley CA









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117(1) 19ndash28




DOI 101002tal














the building height

















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H ESMAEILI ET AL


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6 CONCLUSIONS










respectively









bull



REFERENCES










561ndash




Berkeley CA









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117(1) 19ndash28




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H ESMAEILI ET AL


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6 CONCLUSIONS










respectively









bull



REFERENCES










561ndash




Berkeley CA









H ESMAEILI ET AL


DOI 101002tal



























117(1) 19ndash28




DOI 101002tal
















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6 CONCLUSIONS










respectively









bull



REFERENCES










561ndash




Berkeley CA









H ESMAEILI ET AL


DOI 101002tal



























117(1) 19ndash28




DOI 101002tal










6 CONCLUSIONS










respectively









bull



REFERENCES










561ndash




Berkeley CA









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117(1) 19ndash28




DOI 101002tal



























117(1) 19ndash28




DOI 101002tal

The Structural Design of Tall and Special Buildings (Wiley)

Documents

Transcript of The Structural Design of Tall and Special Buildings (Wiley)