Assessment of multistory RC buildings suffering inter-story pounding

Abstract

The pounding of adjacent RC frames with different heights is studied. The main issue behind this investigation is the influence of the local behaviour of the columns that suffer the hit from the slabs of the adjacent building during the seismic excitation. This column's requirements for ductility and shear capacity have been proven to be the critical parameters for the behaviour and final performance of the whole structure. These parameters can be designed in order the obtained performances to satisfy the seismic demands of the Eurocodes. In this study the critical column's requirements for ductility and shear capacity are evaluated for three seismic demands based on Eurocode 8-part3: (a) demand for Damage Limitation limit state that corresponds to ground motions with return periods of 225 years (b) demand for Significant Damage limit state that corresponds to ground motions with return periods of 475 years and (c) demand for Near Collapse limit state that corresponds to ground motions with return periods of 2475 years. The evaluated requirements are for seven different seismic excitations that have been properly scaled to fit the Eurocode's three seismic demands of low zone of seismic hazard. Afterwards, the minimum required gap distances between the adjacent structures are evaluated taking into account the local capacities of the columns that suffer the inter-story pounding effect. These results are compared with the corresponding limitations for adequate gap distances that are provided by the Eurocode 8. The results show that even in the case of Damage limitation seismic demand special measures have to be taken for the column of the multistory RC frame that suffers the hit. The seismic performance of the columns at a specific limit state of the assessment should be considered for the estimation of an adequate gap distance between the adjacent structures. Thus, the minimum gap distance that is required in order to eliminate the possibility for interaction between adjacent structures depends on the limit state of the assessment. Eurocode's provisions for adequate gap separation do not depend on the seismic demand (limit state) but in any case based on the results of this study these provisions seem to be conservative.