HOW TO ACHIEVE REGULAR SEISMIC BEHAVIOR OF IRREGULAR BRIDGES WITH UNEQUAL HEIGHT PIERS?

Abstract eng:
EuroCode 8 simplistically addresses the seismic behavior of irregular bridges. The proposed criterion for regularizing the response depends on the ratio between the moment demand and moment capacity on each pier aiming to regularize the distribution of seismic design demand among, and ultimately guarantee synchronized failure of, all piers irrespective of their different heights. This criterion may not be effective in addressing some pier height ratios within the same bridge, hence results may not be as expected by code developers. The present paper scrutinizes and evaluates the validity of the criterion proposed by EC8, where the seismic response of four types (featuring a permutation of elastomeric and/or pot bearings along with monolithic pier-to-deck connections) of three-span continuous bridges with one short and one long pier designed to satisfy EC8 regularity condition are compared. Each bridge type has been investigated for four different pier height ratios. Several nonlinear static and dynamic analyses have been performed on each of the total sixteen schemes (namely, four pier height ratios for each of the four bridge types). Nonlinear analysis has resulted in different bridge behavior from that mentioned (and expected) by EC8. The study has led to evidence of realizing somehow regular seismic behavior by altering EC8design obtained steel reinforcement ratios in either piers of each bridge scheme. It has been also noted that bridge regularity is achieved more efficiently in bridges with elastomeric bearings on shorter piers rather than bridges without elastomeric bearings.

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