Irregularity Effects on the Seismic Performance of L-Shaped Multi-Story Buildings

Abstract

Past and recent earthquakes events demonstrate that buildings with configuration irregularity are more vulnerable to earthquake damages. So it's essential to investigate the seismic response of these structures in active seismic zones to reduce the potential seismic damages. The configuration irregularities introduce major challenges in the seismic design of building structures. One such form of irregularity is the presence of re-entrant corners that causes stress concentration due to sudden changes in stiffness and torsion amplification in the buildings; hence causes early collapse. This, the conventional design codes have not recommendations for proper evaluation of these buildings yet. Thus, a constructive research into re-entrant corner irregularity problems is essentially needed greater than ever. The objective of this study is to grasp the seismic behavior of the buildings with irregular plan of L-shape floor plan through the evaluation of the configuration irregularity of reentrant corners effects on measured seismic response demands. The measured responses include inter-story drift; story shear force; overturning moment; torsion moment at the base and along the building height; top floor displacement; and torsional Irregularity Ratio. Three dimensional finite element model of nine stories moment resisting frame buildings as reference model is developed; six L-shaped models are formulated with gradual reduction in the plan of the reference model. The models are analyzed with ETABS using Equivalent Static Load (ESL) and Response Spectrum (RS) Methods. The results prove that buildings with severe irregularity are more vulnerable than those with regular configuration resulting from torsion behavior, and the additional shear force produced in the perpendicular direction to the earthquake input. Also, in the codal empirical equation for the calculation of fundamental period of vibration could not grasp significant higher vibration modes such as torsional vibration of irregular buildings that could significantly affect seismic demands.

Plane shape impact to non-bearing masonry walls in a high rise reinforced concrete walls building

“…These stresses are compared to the masonry design strengths [18]: horizontal compression fdh, vertical compression fd, shear strength for horizontal direction fvd,0, shear for diagonal direction fvd,i, horizontal and vertical strengths perpendicular to the wall fxd1 and fxd2. The design strengths are calculated using the characteristic values: fkh, fk, fvk,0, fvk,i, fxd1 and fxd2, in formulas (1) to (5) The masonry strengths insurance factor is γM=1.9 [18]. The concrete compression design strength fcd, is determined using the characteristic strength fck.…”

“…The behavior of buildings during earthquakes depends on many conditions like stiffness, strength, ductility and most probably on structure's configuration [4]. L-shaped floor buildings are significantly influenced by the lateral forces at its level because of the different lateral deformations [5]. Literature does contain nonlinear studies of 3D plan irregular buildings [6] and buildings with structural irregularities may show different drifts of adjacent stories or excessive torsion [7].…”

Effect of position of steel bracing in L-shape reinforced concrete buildings under lateral loading

“…Normally to calculate the FTP of the buildings, the code provided the empirical formula is used but in this study program based natural period of building is considered. However the formula is only for regular structures, the code-provided formula does not give accurate FTP for structures when the buildings are irregular and braced [13], [15]. Fig 4 shows the variation of the fundamental time period of the structures on both the x and yaxis.…”

“…Researchers have mainly focused on the seismic behaviors of the L shape building based on the displacements, drift, by using the response spectrum analysis (RSA) and static linear analysis. They focused on the observation of comparative study on the regular and L shape buildings and torsional irregularity ratio (B. Khanal and H. Chaulagain [13], Shehata E. Abdel Raheem et al [14], Momen M. M. Ahmed et al [15]). Some other researchers such as S.S. Tezcan, C. Alhan [16], Özmen et al [17], Ali Koçak et al [18] were focused on the study of the torsional effect of shear wall buildings.…”

Damage Detection in Different Types of 3D Asymmetric Buildings Using Vibration Characteristics

“…Studies on asymmetric buildings were mainly focused on seismic performance [23][24][25][26][27], modal identification [28,29], and the effect of torsional coupling during an earthquake [30].…”