Effect of irregular structural configuration on floor acceleration demand in hill‐side buildings

Abstract

Summary A suite of reinforced‐concrete frame buildings located on hill sides, with 2 different structural configurations, viz step‐back and split‐foundation, are analyzed to study their floor response. Both step‐back and split‐foundation structural configurations lead to torsional effects in the direction across the slope due to the presence of shorter columns on the uphill side. Peak floor acceleration and floor response spectra are obtained at each storey's center of rigidity and at both its stiff and flexible edges. As reported in previous studies as well, it is observed that the floor response spectra are better correlated with the ground response spectrum. Therefore, the floor spectral amplification functions are obtained as the ratio of spectral ordinates at different floor levels to the one at the ground level. Peaks are observed in the spectral amplification functions corresponding to the first 2 modes in the upper portion of the hill‐side buildings, whereas a single peak corresponding to a specific kth mode of vibration is observed on the floors below the uppermost foundation level. Based on the numerical study for the step‐back and split‐foundation hill‐side buildings, simple floor spectral amplification functions are proposed and validated. The proposed spectral amplification functions take into account both the buildings' plan and elevation irregularities and can be used for seismic design of acceleration‐sensitive nonstructural components, given that the supporting structure's dynamic characteristics, torsional rotation, ground‐motion response spectrum, and location of the nonstructural components within the supporting structure are known, because current code models are actually not applicable to hill‐side buildings.

Seismic performance and improvements of split-foundation buildings in across-slope direction

“…The torsion angle of the upper ground floor is always the maximum. The similar conclusion was also drawn from the previous research (Surana et al, 2016, 2018a, 2018b). The normalized floor eccentricity of the upper ground floor is the largest, which indicates that there is significant torsional effect in the upper ground floor.…”

Effect of the Damping Ratio of the Non-Structural Components on Floor Acceleration Demands in Torsionally Irregular Buildings

“…In the present study, CR is obtained considering the definition of the single floor eccentricity. The additional details about estimation of CR in the investigated step-back building is available elsewhere [21]. Based on the obtained estimates of the eccentricity between CM and CR, it is observed that in the investigated irregular step-back building, the maximum torsional effects exist at the base floor (Fig.…”

“…As highlighted in the past research [2][3][4][5][6][7][8], the floor response is significantly affected by the dynamic characteristics of the building, therefore, the dynamic characteristics of the investigated buildings are summarized in Table 1. Past investigations [21] on irregular step-back buildings suggest that in such buildings, the period corresponding to the fundamental mode of vibration is usually controlled by the number of storeys measured on the uphill side (Fig. 1(d)), irrespective of the direction under consideration.…”

Peak floor acceleration demands in torsionally irregular buildings

“…They observed that with the increase in building inelasticity, the participation of higher modes of vibration increases, and PFA/PGA are reduced in most cases, though some exceptions also exist. Surana et al 25 . showed PFA/PGA increases at the flexible edge (FE) compared to the CR in the elastic step‐back and split‐foundation buildings.…”