Journal of Engineering and Technology

ARTICLE
Year
: 2011  |  Volume : 1  |  Issue : 1  |  Page : 43--46

Effect of Height on Seismic Response of Reinforced Cement Concrete Framed Buildings with Curtailed Shear Wall


RS Malik, SK Madan, VK Sehgal 
 Department of Civil Engineering, NIT, Kurukshetra, India

Correspondence Address:
R S Malik
Department of Civil Engineering, NIT, Kurukshetra
India

Abstract

Reinforced cement concrete (RCC) framed structures combined with shear walls have been widely used to resist lateral forces during earthquakes in tall buildings. Shear walls are generally provided for full height of the frames. Lateral forces are carried mostly by frames in the upper portion of the building and shear walls contribute the least in this region. This concept has been extended to 10, 20, and 30 storeyed symmetric RCC buildings with curtailment of shear walls at various heights. Efforts have been made to study the effect of height on the curtailment of shear wall. Three-dimensional models of RC special moment resisting frames have been analyzed using STAAD-Pro (Research Engineers, USA, 2005) software. The results show that curtailment of shear wall up to 50% height of the building, has a marginal effect on the distribution of horizontal storey shear among the shear wall frames and interior frames. But height of the building has a significant role in storey shear distribution.



How to cite this article:
Malik R S, Madan S K, Sehgal V K. Effect of Height on Seismic Response of Reinforced Cement Concrete Framed Buildings with Curtailed Shear Wall.J Eng Technol 2011;1:43-46


How to cite this URL:
Malik R S, Madan S K, Sehgal V K. Effect of Height on Seismic Response of Reinforced Cement Concrete Framed Buildings with Curtailed Shear Wall. J Eng Technol [serial online] 2011 [cited 2020 Sep 23 ];1:43-46
Available from: http://www.onlinejet.net/text.asp?2011/1/1/43/74549


Full Text

 1. Introduction



RC Special Moment Resisting Frames (SMRF) are especially detailed to provide ductile behavior and comply with the requirements of IS codes [1],[2] . According to ACI committee 442 [3] , SMRFs are generally efficient up to 10-15 storeys only. Taller moment resisting frames are undesirable for earthquake resistance as large interstorey displacements can cause severe damage to nonstructural components. SMRF with shear walls are the structural systems frequently used in reinforced cement concrete (RCC) buildings to resist earthquake forces. In areas of high seismic risk, RC shear walls have been widely used as the main lateral load resisting system in medium and high-rise buildings because of their high lateral stiffness. Shear walls have considerable stiffness in their own plane, but very little stiffness in the perpendicular direction and their satisfactory performance depends on the stiffening effect of floor diaphragms, which prevent buckling of walls. Recent earthquakes have shown that only properly designed shear walls can withstand strong earthquake forces with no or minor damages. Yoshimura and Inoue [4] analyzed shear wall frames and concluded that the manner of arrangement of shear walls remarkably affected the maximum base shear caused by earthquakes. Ashraf et al [5] carried out a study to determine the optimum configuration in location of shear walls (lift core) in multistorey buildings and concluded that shear walls should be placed at a point by coinciding the center of mass and center of rigidity of the building.

Ishac and Heidebrecht [6] concluded that the dynamic analysis of high-rise buildings should be a prime essential because dynamic coupling amplifies the torsional response, and static analysis would not adequately determine stresses and deformations. Frank et al [7] carried out experiments on wood shear walls and found that walls with oversized large panels resisted more load. Wen and Song [8] investigated the redundancies of SMRF and dual systems. The factors considered were structural configuration (number of bays and shear walls), ductility capacity, uncertainty in demand and capacity, interaction between walls and moment frames, and three-dimensional (3-D) motions. They concluded that in a dual system the number of shear walls had a small effect.

Zhao and Abolhassan [9] discussed the advantages and disadvantages of traditional RC Shear walls and steel shear walls. They found that composite shear walls, that is, steel plate shear wall with RC wall attached to one side of it using bolts can mitigate most of the disadvantages of both RC and steel shear walls and take advantage of the best characteristics of the 2 construction materials of steel and concrete. Nollet and Smith [10] investigated deflection of tall wall-frame structures using two-dimensional models, in which shear walls were reduced in size or terminated entirely at intermediate heights. It was shown that curtailment of walls was not necessarily detrimental to the performance of the structures.

 2. Objective of the Study



Safety and minimum damage level of a structure could be the prime requirement of tall buildings. To meet these requirements, the structure should have adequate lateral strength, lateral stiffness, and sufficient ductility. Among the various structural systems, shear wall-concrete frame could be a point of choice for the designer. It is common in high-rise wall-frame structures to reduce in size and number or to eliminate entirely, the shear walls in the upper part of the building. Hence, the objective of this study is to compute the seismic response of reinforced concrete framed structures with curtailed shear walls and the effect of height of a building on such curtailments.

 3. Parametric Details of Models Studied



Ten, 20, and 30 storeyed regular buildings consisting of symmetric RC frames with different arrangements of shear walls have been considered. They are assumed to be located in seismic zone IV. The shear walls have been provided in the outermost frame panels with a thickness of 250 mm up to different storey heights. Depending on the height of shear walls, various models of the buildings have been designated as shown in [Table 1]. The dynamic analysis has been done using 3-D modeling in STAAD-Pro (Research Engineers, USA, 2005). These models consist of 7 bays of 5 m each in global X-direction (7 Χ 5 = 35 m) and 3 bays of 5 m each in global Z-direction (3 Χ 5 = 15 m). The plan area of the buildings is 35 Χ 15 m with 3 m as height of each storey. The size of the columns taken is shown in [Table 2]. All beams are of 0.35 Χ 0.65 m sections. The supports of the columns are assumed to be fixed. The plan of the building is shown in the [Figure 1]. {Figure 1}{Table 1}{Table 2}

 4. Method of Analysis



The analysis of the buildings has been done using 3-D modeling in STAAD-Pro. 2005 and as per IS - 1893: 2002 (Part-I). The effect of infill walls in resisting the earthquake forces has been ignored. Shear wall is modeled using the 4-noded surface elements. Floors are assumed to act as rigid diaphragms. For distribution of earthquake forces, the contribution of 6 interior frames without shear walls has been grouped together and the remaining forces are assumed to be taken by the 2 exterior frames with shear walls. Related factors taken are seismic Zone factor 0.24, Response reduction factor 5, Importance factor 1.5, Damping 0.05, and Foundation Soil type medium. The dead load intensity at all floor levels is taken as 6 kN/m 2 and live load as 3 kN/m 2 for floors. For calculation of seismic weight no live load is considered at the roof level.

 5. Analysis and Discussion on Results



The results of the analysis are presented in Apendix-1 and [Figure 2] and [Figure 3]. {Figure 2}{Figure 3}

5.1 Storey Shear

The 2 exterior frames with shear walls bear 45%-46% of base shear (Vb) in all the models studied for 30-storey building, 48%-49% for 20-storey building, and 36%-38% for 10-storey building. The storey shear (Vi) taken by these frames in the top storey in building S-100 with 30, 20, and 10 storeys is 23%, 21%, and 21%, respectively, whereas 6 interior frames take the remaining shear. The percentage share in the top storey reduces to 17%, 18%, and 18% with curtailment of shear wall up to 50% of the building height. It is observed that at curtailment level in models S-90 to S-50, the decrease in storey shear for all heights is 1%-5%, which is marginal.

5.2 Lateral Displacement

For S-50 model, the lateral displacement in the shear wall frames at the top storey levels increases by 5%, 8%, and 31% for 30, 20, and 10 storeys, respectively, when compared with S-100 model. The stiffening effect of shear wall on the lateral displacement is evident as a decrease in the displacement at other storey levels.

5.3 Interstorey Drift

Interstorey drift at each storey level is worked out and the values for each case are within the permissible limit of 0.004 h. The drift reduced in the top storey with a curtailment of 50% in the shear walls is 26%, 40%, and 4%, respectively.

 6. Conclusions



Dynamic analysis of reinforced concrete frames with shear walls was carried out for various arrangements of curtailed shear walls. The results can be summarized as follows:

In the dual system the exterior frames with shear walls attract more storey shear caused due to earthquake because of higher lateral stiffness. The share in storey shear for these frames is more for buildings with medium height of about 20 storeys. This share is reduced significantly with decrease in the frame height (10-storey) and slightly reduced with increase in the frame height (30-storey).

By curtailing the shear wall, the storey shear taken by shear wall frames also reduces. It is marginally reduced for medium and low height frames (about 3% in 10- and 20-storey buildings) and considerably reduced for higher frames (about 6% in 30-storey building) in top storey for 50% curtailment of shear wall.

It is seen that curtailment of shear walls can be effected at 60% height from base of the building of almost all heights, without much scarifying the lateral load resisting capacity of the frames, because the lateral displacement at the top storey level is marginally increased.

References

1IS 1893-2002 (Part I), "Indian Standard Criteria For Earthquake Resistant Design of Structures," New Delhi: Bureau of Indian Standards; 2002.
2IS 13920, "Indian Standard Ductile Detailing of Reinforced Concrete Structures subjected to Seismic Forces-Code of Practice," New Delhi: Bureau of Indian Standards; 1993.
3ACI committee 442, "Response of Buildings to Lateral forces," Journal of American Concrete Institute, Vol. 68, pp. 81-106, 1971.
4K. Yoshimura, and M. Inoue, "Dynamic Analysis of Reinforced Concrete Frames with Shear walls", 7 th World Conference Proceedings Earthquake Engineering. Symposium London, vol. 2, pp. 1178-1184, 1977,
5M. Ashraf, Z. A. Siddiqui, and M. A. Javed, "Configuration of a multistorey building subjected to Lateral Forces," Asian Journal of Civil Engineering (Building and Housing), vol. 9, No.5, pp. 525-537, 2008.
6M. Ishac, and A. Heidebrecht, "Dynamic Response of Asymmetric Shear wall Frame Building Structure," 7 th World Conference Proceedings Earthquake Engg. Symposium London, vol. 2, pp. 1363-1368, 1977.
7F. Lam, H. G. Prion, and M. He," Lateral Resistance of Wood Shear Walls with Large Sheathing Panels," Journal of Structural Engineering, Pp. 1656-1672, Dec, 1997.
8Y. K. Wen, and S. H. Song, "Structural Reliability/Redundancy under Earthquakes," Journal of Structural Engineering, pp. 56-67, Jan, 2003.
9Q. Zhao, and A. Abolhassan, "Cyclic Behaviour of Traditional and Innovative Composite Shear Walls," Journal of Structural Engineering, pp. 271-284, Feb, 2004.
10M. J. Nollet, and B. S. Smith, "Behavior of curtailed wall-frame Structures," Journal of Structural Engineering, Vol. 119, No. 10, pp 2835-2854, 1993.