Response Analysis of Multi-Storey RC Buildings under Equivalent Static and Dynamic Loads According to Egyptian Code

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1 nternatonal Journal of Cvl and tructural Engneerng Research N (Onlne) Vol. 2, ssue 1, pp: (79-88), Month: Aprl eptember 2014, Avalable at: Response Analyss of Mult-torey RC Buldngs under Equvalent tatc and Dynamc Loads Accordng to Egyptan Code ayed Mahmoud 1, Waleed Abdallah 2 1 Department of Constructon Engneerng, College of Engneerng, Dammam Unversty Dammam, aud Araba 2 Faculty of Engneerng at Matara, Helwan Unversty Caro, Egypt Abstract: The frequent occurrence of earthquakes around the world has heghtened the need for studyng the sesmc performance of exstng structures accordng to code of practce. Ths concept has become an urgent ssue n Egypt especally after httng a dramatc earthquake to Caro n The objectve of ths research s to assess the sesmc performance of an exstng shear wall resdental buldng located n Caro. Both dynamc response spectrum (R) and equvalent statc force (EF) methods are used n the sesmc analyss. The desgn R curve suggested by the Egyptan Code (EC) for sesmc desgn s utlzed to perform the dynamc analyss. The response analyss of the buldng under the actng sesmc loads has been performed usng ETAB, unversal fnte element analyss software for dynamc analyss. The entre work has been carred out n two stages n order to rescale the dynamc base shear. n the frst stage, the bult three dmensonal buldng model has been subjected to the statc and dynamc earthquake loadng followng Egyptan code gudelnes and hence the obtaned statc and dynamc base shear are compared. The second stage s concerned wth scalng the obtaned dynamc base shear and reloadng the model as the frst stage. The consdered responses are expressed n terms of floor dsplacements, shear forces at each floor level, base shear and base moment. Moreover, results from numercal smulatons, for storey torsonal rregularty ratos are presented for the consdered statc and dynamc analyss methods. The results of the study show sgnfcant dfferences n buldng's responses obtaned usng EF and R analyss methods. t has been found that the applcaton of statc method n a specfed drecton results n responses n the same drecton. However, the applcatons of dynamc R method nduces response n both drectons regardless the drecton of loadng. Keywords: Equvalent statc force, response spectrum, base shear, Egyptan code.. NTRODUCTON After the devastatng 1992 earthquake n Egypt, the Housng and Buldng Natonal Research Center started modfyng the exstng EC for loads n order to effcently smulate expected ground motons and provde the sesmc loads requred for earthquake resstant desgn of structures [1-4]. Reconsderng the exstng structure desgn requrements was also one of the man roles of the establshed commttees at that tme. The EC for loads ssued n 1993 only consdered the EF method as suffcent to represent lateral sesmc loads. n fact, ths method has been permtted n most of the desgn codes for loads all over the world and often proves to be suffcent for regular buldngs wth heghts range from low to medum. For hgh-rse structures, where more modes have to be consdered, as well as structures havng rregulartes whether n plan or n elevaton, where torsonal effects may be sgnfcant, dynamc analyss rather than statc one can be used for more accurate analyss. Two types of dynamc analyss namely; tme-hstory (TH) analyss and R analyss methods can be used to make the structures sound aganst sesmc actvty. everal major modfcatons were ntroduced to edton of Research Publsh Journals Page 79

2 nternatonal Journal of Cvl and tructural Engneerng Research N (Onlne) Vol. 2, ssue 1, pp: (79-88), Month: Aprl eptember 2014, Avalable at: Egyptan code for loads through mprovng the EF method and the ncluson of the dynamc R analyss n order to accurately determne the lateral earthquake force at base and consequently the dstrbuton of such dynamc base shear at the storey levels. Analyss of structures usng statc and dynamc analyss methods has been carred out usng several authors accordng to the Canadan code and other codes [5-10]. Based on the Natonal Buldng Code of Canada (NBCC), Patrck P. et al. [11] ntroduced a spread sheet for the purpose of computng the sesmc desgn forces usng the equvalent statc force procedure. aleh M. et al. [12] conducted two-dmensonal analyss usng four dfferent resdental steel structures wth dfferent heghts and desgned usng the standard equvalent statc procedure per the ranan esmc Code of practce. Qaser Z.K. [13] performed a detaled comparson between R and EF analyss methods consderng a 20 story buldng of 200 ft ncreased up to 400 ft heght wth about 40 story n order to determne the heght above whch R analyss sgnfcantly affects the structure desgn. The lateral sesmc forces and the nduced deformatons obtaned from the EF procedure and the dynamc R analyss method accordng to the 2005 NBCC are compared for buldngs wth dfferent storey heghts and havng structural mass rregularty [14]. An analytcal study for nvestgatng the dynamc behavor of ndustral buldngs modelled respectvely as regular crane-supportng steel structure and rregular buldng housng a vertcal mechancal process has been carred out by Rchard J. et al. [15]. The dynamc R analyss and EF analyss method have been used to evaluate the sesmc response of both structures. Moreover, the elastc tme-hstory dynamc analyss was employed for comparson purposes wth the other two methods of analyss as well as valdatng the predcted results for both structures.. A. Raheem [16] performed a research study n order to evaluate the Egyptan code for sesmc desgn utlzng a RC mult-story buldng desgned as moment-resstant frame employng the TH analyss procedure together wth the dynamc R analyss procedure and the EF procedure. Analyss of the obtaned results under the applcaton of the three dfferent approaches has been used to evaluate the advantages, lmtatons, and ease of applcaton of each approach for sesmc analyss accordng to EC for sesmc desgn. A revew of the above cted papers ndcates that among the conducted works to evaluate the performance of the dynamc R analyss and the EF analyss n sesmc desgn only the work done by. A. Raheem evaluates the recommended two methods of analyss by the Egyptan code for sesmc desgn. However, n hs work, the base shear determned by the EF analyss method has not been used as a benchmark to scale the desgn base shear obtaned by the dynamc R analyss and hence affects both the dstrbuton of the lateral sesmc forces over the heght of the structure and the analysed results. The objectve of the present paper s to provde a comparatve study between the two sesmc desgn analyss methods recommended by the 2012 edton of the EC for loads namely; EF analyss and the dynamc R analyss. The two methods of analyss are appled to a resdental mult-storey renforced concrete buldng of fourteen storey and desgned accordng to the EC provson. The results under both the statc and dynamc analyss are analysed and presented n the form of storey shear forces before and after scalng. The storey deflectons and drfts n the drecton of both X and Y drectons are also presented. Further, the nduced storey moments as well as the storey torsonal rregularty ratos are computed and presented under the consdered methods of loadng n both drectons of loadng. A. Buldng Descrpton. MODELLNG AND DEALZATON Ths research studes renforced concrete buldng as a typcal fourteen storey flat slab-column system located n Caro. The buldng s near to be square n plan wth dmensons 18.6m x 19.3m. The buldng s desgned for resdental use. Typcal floors plan and sometrc vew are presented n Fg. 1 and Fg. 2. Typcal floor heght s 3m. The floors are made of concrete flat slabs supported by columns. The thckness of the floor slab s 25 cm for all storeys. The cross-secton of the columns used to support the structure s determned as 30cm x 50cm for smallest column dmensons n the structure and as 30x140 for the largest ones. The desgned system to resst the sesmc forces conssts of two elevator cores n both X and Y drecton. Addtonal shear wall n X drecton s also desgned for sesmc resstance purpose. The consdered heren buldng structure has been desgned accordng to the EC wth specfed characterstc compressve strength f cu = 25 MPa and steel renforcement wth yeld strength f y = 360 MPa. Research Publsh Journals Page 80

3 nternatonal Journal of Cvl and tructural Engneerng Research N (Onlne) Vol. 2, ssue 1, pp: (79-88), Month: Aprl eptember 2014, Avalable at: B. Buldng Model Fg. 1.Typcal floors plan of the fourteen storey resdental buldng The three dmensonal RCmult-storey buldng used n ths study was modelled as flat slab-column system wth shear walls. For the purpose of modellng the real behavour of the slabs, they were modelled usng shell elements to ensure provdng stffness n all drectons and transfer mass of slab to columns and beams. A rgd daphragm was assumed at all floor levels. n order to account for the modal dampng effect, the complete quadratc combnaton (CQC) technque, whch takes nto account the statstcal couplng between closely spaced modes caused by modal dampng, s used for modal combnaton. The frst modellng step wth ETAB nvolves defnng the physcal propertes of the used materals. ectons for horzontal and vertcal elements of the consdered buldng are defned n terms of dmensons and materal propertes. Consequently the defned sectons are assgned to the correspondng plane elements such as slabs and beams and the correspondng vertcal elements such as columns and shear walls. Choosng the correct boundary condtons through assgnng supports and connectons wth approprate restrants s one of the mportant aspects n structural modellng. Three-dmensonal analyss s carred out under statc and dynamc sesmc analyss n both X and Y drectons, whch are known to be orthogonal drectons. Fg. 2.Three-dmensonal buldng model Research Publsh Journals Page 81

4 nternatonal Journal of Cvl and tructural Engneerng Research N (Onlne) Vol. 2, ssue 1, pp: (79-88), Month: Aprl eptember 2014, Avalable at: EARTHQUAKE ANALY METHOD Most of the used desgn codes provde the mnmum standards requred lfe safety but not to nsure preventng damage.there are two commonly used procedures for specfyng sesmc desgn forces namely: the lnear dynamc R analyss and the EF analyss. A. Equvalent tatc Force Method n ths method the nerta forces are determned as statc force wth the use of emprcal formulas. To adequately represent the dynamc behavour of the structures, the method s hghly recommended for regular structures wth unform dstrbuton of mass and stffness as well as unform shape and statcal system,. However, t can be appled to rregular ones wth some lmtatons. The desgn base shear can be calculated as: F b ( T) W d g (1) Where, T represents the fundamental tme perod of the structure, s a correcton factor, dependent on the fundamental perod of the structure wth respect to the value of T, W s the structure s weght. Addtonally, the sesmc zone C factoraffects thevalue of the nduced base shear. The formulas used to calculate the prevously defned terms can be found n the desgn codes for loads. The use of the method requres defnng parameters such as sesmc zone factor, sol profle and sesmc source type whch can be calculated n accordance wth the prncpals of the regulatons used n ths study. The base shearf, as determned from Eq. (1) s dstrbuted over the heght of the structure as a force F at each level n addton to a force b Ft at the top of the structure accordng to the formula: F b F t n 1 F (2) The extra force F 0. 07TF and no more than 0.25 F b only when T 0. 7 sec t The remanng porton of the total base shear F ) Where, w and b ( b t F s dstrbuted over the heght, ncludng the top, by the formula: ( Fb F F )( w h ) n 1 t w h h respectvely refer tothe floor's weght and floor's heghtat the th level above thebuldng's base. The pont of acton of the calculated storey force s actng at the storey centre of mass. The overturnng moment M at a partcular storey level s the sum of the moments of the story forces above, about that level. Hence: M F ( h h ) t n n j F j (3) h h j (4) The accdental torsonal moment shall be determned through dvdng the maxmum dsplacement max at level by the average dsplacement avg and torsonal rregularty exsts f the obtaned rato exceeds 1.2. The effect of torsonal rregularty at a specfed storey shall be accounted for by ncreasng the accdental torson at the specfed level by an amplfcaton factor, A determned from the followng formula: x A x max 1.2 avg 3 Research Publsh Journals 2 (5) Page 82

5 d (T ) nternatonal Journal of Cvl and tructural Engneerng Research N (Onlne) Vol. 2, ssue 1, pp: (79-88), Month: Aprl eptember 2014, Avalable at: B. Response pectrum Analyss Method Response spectrum analyss s used for analysng the performance of structures under earthquake motons. The method assumes a sngle degree of freedom system to be excted by a ground moton n order to obtan the response spectrum curves for peak dsplacement, peak velocty or peak acceleraton. Thus once the natural perod of the structure s known then the response spectrum curves helps n estmatng the peak responses of such structure. These estmated values are consdered as the bass for calculatng the earthquake forces to be ressted through earthquake resstant desgn stages. n order to perform R analyss, mportant parameters n terms of expected earthquake ntensty n the consdered zone and the supportng base sol behavour have to be consdered. One of the other parameters related to the computaton process s the modal analyss n whch the R analyss computes the structure s response through consderng the sgnfcant modes. Mode contrbuton to the structure s response and flexural deformaton s manly dependent on the structure s heght. For low to md-rse structures, the frst three modes are suffcent to capture accurate results where the hgher modes contrbutons dmnsh very quckly. However, more than three modes have to be consdered for hgh-rse structures. These numbers of requested modes can be selected such that ther combned partcpatng mass s at least of 90% of the total effectve mass n the structure. Once the number of sgnfcant modes s establshed, several methods are used for the purpose of estmatng the peak response values. The quare Root of ome of quares (R) of the maxmum modal values s one of the popular methods. Another two methods namely: sum of the absolute of the modal response values (AB) and the CQC are also used for peak response computaton. calng the response spectrum curve to consder the over strength and global ductlty capacty of lateral force-resstng systems s another mportant parameter durng dynamc R analyss. Rescalng the desgn base shear n accordance wth the ones obtaned wth the EF analyss s another mportant parameter. The regularty and rregularty of structures manly govern the scalng factor of the desgn base shear. The desgn buldng codes n sesmc regons uses the obtaned pseudo acceleraton values (T ) as bass for calculatng the forces that a structure must be desgned to resst. The Egyptan desgn code for loads defnes specfc equatons for each range of the spectrum curve for four dfferent sol types and dampng rato as: d d 2 d ( T) ag ( T) ag R d d T T 2.5 T ( T) a R T B R 3 C g T T ( T) a 2 R T 0. a g C D g 2 0. a g 0 < T < T B T B < T < T C T C < T < T D T D < T < 4 2.5a g a g 0 T T T 4 B C D T( sec) Fg. 3. Typcal response spectrum curve Page 83 Research Publsh Journals

6 nternatonal Journal of Cvl and tructural Engneerng Research N (Onlne) Vol. 2, ssue 1, pp: (79-88), Month: Aprl eptember 2014, Avalable at: Where a g,, and respectvely represent the desgned peak ground acceleraton, the mportant factor for the structure, and sol factor. R s a factor accounts for the ductlty and over strength of the structural system. T, are values for the perods descrbng the shape of the elastc response spectrum and depend on the ground type. B T C, T D V. TATC AND DYNAMC ANALY REULT The nonlnear fnte element analyss software ETAB s employed to create the buldng model and run analyss. The consdered software package enables the user to defne the earthquake load actng on the structure as statc and/or dynamc loads. Moreover, the software allows the user to perform the analyss accordng to several predefned codes. The adopted model for analyss s resdental fourteen stores buldng wth floor slabs as flat slabs of thckness 25 cm. hear wall and cores of thckness 30 cm are used to resst the lateral forces. The buldng conssts of rectangular columns wth dfferent dmensons vary from 30cmx50cm to 30cmx140cm. The foundaton s desgned as a raft of 1.50 m. The stores of the buldng are of 3.00 m heght. tatc and dynamc R analyss methods whch are equvalent to the sesmc forces actng on the consdered buldng structure wll be calculated accordng to the EC for loads. esmc zone 3 wll be selected snce the buldng s located n Caro. The consdered sesmc zone s of peak ground acceleraton of 0.15 g. Caro s characterzed wth stff ol profle type and hence the sol at the ste that wll be used n the analyss s assumed to be of type C. The numercal coeffcent R, whch s a representatve of the over strength and global ductlty capacty of lateral force-resstng systems, s equvalent to 5 as the buldng s desgned wth shear walls to resst lateral forces. The sesmc mportance factor = 1. The results of the performed analyss are presented n the form of fgures and tables. The nduced nonscaled and scaled storey shear forces n X and Y drectons under dynamc and statc loads actng n X drectons are presented n Fg. 4 and Fg. 5. The obtaned maxmum deflecton at each storey level n the orthogonal drectons X and Y for the consdered two methods of analyss s presented n Fg. 6. n addton the varaton storey moments n both X and Y drectons due to appled statc and dynamc load n X drecton can be shown n Fg. 7. The values for torsonal rregulartes at each storey due to tatc force and dynamc R analyss n both drectons of loadngs are presented n Table 1. Fg. 4. Nonscaled storey shear forces under (a) EF X-dr and (b) dynamc R X-dr For the purpose of comparsons and accordng to the EC for loads requrements, f the shear at base determned by dynamc R analyss s less than that specfed by the EF procedure, t has to be scaled to the statc base shear determned by the lateral force procedure. mlarly, f the dynamc base shear obtaned from a dynamc R analyss s of hgher value compared to the statc base shear, t may be scaled down.fg.4, shows the obtaned base shear usng both EF and R procedures before scalng. From the fgure, t can be seen that the dynamc R analyss produces shear at base lower than the one obtaned applyng the statc force procedure. Followng the code requrements, rescalng the dynamc base shear through a magnfcaton factor nduces same base as the one obtaned employng the statc analyss Research Publsh Journals Page 84

7 nternatonal Journal of Cvl and tructural Engneerng Research N (Onlne) Vol. 2, ssue 1, pp: (79-88), Month: Aprl eptember 2014, Avalable at: (see n Fg. 5). t has to be noted that mantanng the code level of base force to be same for the statc and dynamc analyss does not necessarly lead to smlar dstrbuton of storey shear forces usng the EF and the dynamc R procedures. Fg. 5. caled storey shear forces under under (a) EF X-dr and (b) dynamc R X-dr tory shear s an mportant parameter from the structural desgner's pont of vew. Varaton of change n scaled story shear under the equvalent statc earthquake load and dynamc R load s presented n Fg. 5. Although the drecton of loadng s n X-drecton, the dynamc R nduced storey shear forces n both X and Y-drectons. However, the EF only nduces storey shear n the drecton of loadng. torey base shear n both X and Y-drectons under EF analyss as compared to the same dynamc storey base shear obtaned consderng R analyss shows sgnfcant changes especally n the nduced storey shear n Y-drecton (V y ). calng the dynamc shear at base to be the same as the statc shear at base does not necessarly lead to smlar statc and dynamc shear forces at the correspondng floor levels. As t can be seen from the fgure, the use of R procedure predcts sgnfcantly more story shear n X-drecton (V x ) at hgher stores as compared to those predcted due to loadng the structure wth EF method. The ncrease n dynamc storey shear at the top storey wth respect to statc storey shear s of 41%. However, at lower storeys the dynamc storey shear are slghtly less than the story shear of structure obtaned under statc force analyss wth about 7%. Fg. 6. torey deflectons under EF and dynamc R loadngs n (a) X-dr and (b) Y-dr Research Publsh Journals Page 85

8 nternatonal Journal of Cvl and tructural Engneerng Research N (Onlne) Vol. 2, ssue 1, pp: (79-88), Month: Aprl eptember 2014, Avalable at: Fg. 6 shows the max story deflecton under EF analyss and dynamc R analyss n both X and Y drectons. As t s shown, the nduced max story dsplacement due to statc loadng n X drecton are of hgher values as compared wth those obtaned under dynamc R loadngs n X drecton, (see Fg. 1 (a) and (b)). mlar results have been obtaned when loadng the buldng n Y drecton. As t s expected the hgher the storey levels the hgher the nduced storey deflecton. Moreover, the varance n the obtaned maxmum storey deflectons under statc and dynamc earthquake loadng are more pronounced at the top stores regardless the drecton of loadng consdered. t can be seen from the fgure that the nduced storey dsplacements n X drecton due to EF and R show sgnfcant ncrease n comparson wth the correspondng values n Y drecton. Ths ncrease n the story dsplacement n X drecton comparable to Y drecton s occurrng due to the overall global stffness n X are of lower values to the overall global stffness n Y drecton. Based on the calculated storey deformatons under the two methods of analyss, t has been found that the computed percentage varatons n storey deflecton under statc loadng and the correspondng storey deflecton under the dynamc analyss show nearly smlar values for X and Y drectons. Consderng the top storey as an example, the percentage varaton of the maxmum deflecton usng the two methods of analyss s 17.98% when loadng s appled n X drecton and about 18.85% when loadng s appled n Y drecton whch clearly seems to be dentcal. Computatons of the percentage varaton for the other stores under statc and dynamc loadng n X and Y drectons show nearly dentcal values. The varaton n moments versus storey number s plotted n Fg. 7. For the graphs representng statc loadng case can be seen n Fg. (1a) and the graphs for the dynamc R case can be seen n Fg. (1b). As t can be observed and rrespectve of the type of loadng, the lower the storey the hgher moment obtaned under the earthquake load. Regardng the type of load, loadng the buldng wth EF method as a representatve to the earthquake load produces hgher moment as compared to the correspondng values when representng the earthquake load by the dynamc R analyss method. Although, the buldng s loaded n Y drecton, the dynamc equvalent load nduces double moments around X and Y (see Fg. (1b)). On the other hand, the EF method only nduces moment around X (see Fg. (1a)). mlar results has been found when loadng the buldng n X drecton where the EF method only produced overturnng moment around Y drecton whle the R dynamc loadng produces overturnng moments around both X and Y drectons. Fg. 7. torey deflectons under EF and dynamc R loadngs n (a) X-dr and (b) Y-dr Research Publsh Journals Page 86

9 nternatonal Journal of Cvl and tructural Engneerng Research N (Onlne) Vol. 2, ssue 1, pp: (79-88), Month: Aprl eptember 2014, Avalable at: TABLE : TORONAL RREGULARTY UNDER EF AND R ANALY N BOTH X AND Y-RECTON torey Earthquake Loadng (X-dr) torey torsonal rregularty ratos Earthquake Loadng (Y-dr) EF R EF R Numerous studes nvestgated the structural damage durng earthquakes concluded that torson s one of the crtcal factors leadng to major damage or complete collapse of buldngs. ETAB software package enables the structural engneers to calculate the center of rgdty and hence the desgners can perform torsonal analyss. The results of the accdental torson analyss under EF and R analyss are shown n Table 2. For loadng n X-drecton and Y-drecton, both EF and R analyss produce torsonal rregularty where all the ratos (max. deformaton/avg. deformaton) are more than 1.2. However for applyng R loadng n the Y-drecton, shows no torsonal rregularty because all the computed ratos are less than 1.2. On the other hand, applyng EF loadng n the Y-drecton produces torsonal rregularty from level 1 to level 8 of the buldng where the rato of maxmum to average story drft s varyng from at level 8 to at level 1. Accordng to the Egyptan Code for loads and based on the calculated results presented n Table 1 for loadng n X drecton, torsonal amplfcaton factors has to be determned for all the storeys of ths buldng regardless the type of loadng whether EF or R analyss. For loadng the consdered buldng n Y drecton, specfed storeys requre such amplfcaton factor under the equvalent statc procedure. However, dynamc R analyss shows none torsonal rregularty n torson and hence no torsonal amplfcaton factors are need for the buldng s storeys. V. CONCLUON Analyses of 14-storey flat slab-column buldng wth shear walls system, desgned n accordance wth the EC for loads and subjected to two dfferent approaches equvalent to earthquake loadng, has been studed n both X and Y drectons. The consdered two approaches are the dynamc R and statc force analyss. The dynamc and statc base shear n both drectons of loadng are computed and compared. An amplfcaton factor has been used to scale the dynamc base shear wth respect to the statc one. The buldng's responses n terms of scaled base shear, storey deflectons, storey moments, storey drfts, and torsonal rregularty ratos have been calculated under the consdered two methods of analyss. t s clear from the analyss that the statc analyss gves hgher values for maxmum dsplacement of the stores n both X and Y drectons rather than the dynamc R analyss method, especally n hgher stores. Although scalng the base shear due to R analyss to be of equal value to the one due to EF, t has been found that a sgnfcant ncrease n the dynamc shear at hgher stores. However at lower stores a slght ncrease n the dynamc shear compared wth statc shear regardless the drecton of loadng. The dynamc R analyss produces storey shear n both drectons regardless the loadng drecton whle the statc analyss only produces storey shear n the drecton of loadng. Contrary to the storey shear forces, the nduced storey moments under EF and R analyss methods are of hgher values at lower stores Research Publsh Journals Page 87

10 nternatonal Journal of Cvl and tructural Engneerng Research N (Onlne) Vol. 2, ssue 1, pp: (79-88), Month: Aprl eptember 2014, Avalable at: compared to the hgher ones. Moreover, sgnfcant ncrease n the obtaned storey moments at lower storeys under R compared to the correspondng low levels under EF analyss. n addton, R analyss produces Moments n both drectons regardless the drecton of loadng and the EF s not. The results obtaned from the structure presented heren have shown that the torsonal rregularty n a structure subjected to sesmc loadng may be nfluenced by the drecton of sesmc loadng as well the loadng approach and strongly lead to analyzng rregular buldngs for torson. Even though the dynamc R analyss method of sesmc desgn s the prefered method due to the computonal advantage n predctng response of structural systems where t nvolves the calculaton of only the maxmum values of the nduced response n each mode. However, The EF analyss method s used as a benchmark to scale the desgn base shear obtaned by the dynamc R analyss before the dstrbuton of the lateral sesmc forces over the heght of the structure under the dynamc R base shear. REFERENCE [1] ECP (1993) - ECP-201, "Egyptan code for calculatng loads and forces n structural work and masonry", Housng and Buldng Natonal Research Centre. Mnstry of Housng, Utltes and Urban Plannng, Caro, [2] ECP (2004a) - ECP-201, "Egyptan code for calculatng loads and forces n structural work and masonry", Housng and Buldng Natonal Research Centre. Mnstry of Housng, Utltes and Urban Plannng, Caro, [3] ECP (2008) - ECP-201, "Egyptan code for calculatng loads and forces n structural work and masonry", Housng and Buldng Natonal Research Centre. Mnstry of Housng, Utltes and Urban Plannng, Caro, [4] ECP (2012) - ECP-201, "Egyptan code for calculatng loads and forces n structural work and masonry", Housng and Buldng Natonal Research Centre. Mnstry of Housng, Utltes and Urban Plannng, Caro, [5] Bahador,. F.Ehsan, and Y. Mohammadreza, Comparatve tudy of the tatc and Dynamc Analyss of Mult- torey rregular Buldng, Engneerng Technology, vol. 6, pp , [6] T. Fnley, and R. A. Crbbs, "Equvalent tatc vs. Response pectrum A Comparson of Two Methods" Proceedngs of the PE, Vol. 5495, pp , [7] J. M. Humar and M. A. Mahgoub, "Determnaton of sesmc desgn forces by equvalent statc load method" Canadan Journal of Cvl Engneerng, Vol. 30, pp , [8] Q.. Nguyen,. Erlcher and F. Martn, "Comparson of several varants of the response spectrum method and defnton of equvalent statc loads from the peak response envelopes"paper no 4269, 15WCEE, Lsbon, Portugal, [9] B.J. Davdson "Base hear calng" NZEE Conference, Paper no. 58, [10] A.R. Touqan and. H. Helou,"A crutny of the Equvalent tatc Lateral Load Method of Desgn for Multstory Masonry tructures" AP Conference Proceedngs, Vol. 1020, pp , [11] P.Paultre, É.Laponte,.Mousseau, and Y.Bovn, "On calculatng equvalent statc sesmc forces n the 2005 Natonal Buldng Code of Canada" Canadan Journal of Cvl Engneerng, Vol. 38, pp [12].Malekpour F.Dasht and A. Kan, "Assessment of Equvalent tatc Earthquake Analyss Procedure for tructures wth Mass rregularty n Heght" 6th Natonal Congress on Cvl Engneerng,emnan Unversty, emnan, ran, Aprl 26-27, [13] Q. Z. Khan, "Evaluaton on effects of response spectrum analyss on heght of buldng" nternatonal Conference on ustanable Bult Envronment (CBE) Kandy, December, [14] R. Tremblay,. Merzouq, C.zvernar, and K.Alexeva."Applcaton of the equvalent statc force procedure for the sesmc desgn of multstorey buldngs wth vertcal mass rregularty" Canadan Journal of Cvl Engneerng, Vol. 32,pp , [15] J. Rchard,. Koboevc and R. Tremblay, "esmc Desgn and Response of Crane-upportng and Heavy ndustral teel tructures" Engneerng Journal, Amercan nsttute of teel Constructon (AC), 3rd quarter 2011 [16]. E. Abdel Raheem, "Evaluaton of Egyptan code provsons for sesmc desgn of moment-resstng-frame multstory buldngs" nternatonal Journal of Advanced tructural Engneerng, Vol. 5, pp. 1-18, Research Publsh Journals Page 88