Report - PEER - University of California, Berkeley

To evaluate some performance and damage criteria one may need advanced,experimentally verified analytical models and computational tools, in particular if theinvestigated system implies special, less-investigated and/or limited ductile structuraldetails. The paper addresses a number of such specific systems recently investigatedby Slovenian researchers, both experimentally and analytically — lightly reinforcedstructural walls (Chapter 3), steel frames with partial strength connections (Chapter4), timber-frame buildings (Chapter 5) and masonry structures (Chapter 6).There has been general impression that much more research effort in PBSE hasbeen employed on the demand side than on the capacity side. Consequently relativelycrude and loosely defined damage criteria (like 2% drift) are frequently used inconjunction with sophisticated and detailed demand evaluations. Some researchresults related to the capacity evaluation of the addressed structural systems isincluded in the paper.In short, there are two main objectives of the presented paper — to identify somepotential pitfalls related to specific applications of general PBA procedures as well asto make an overview of the related experimental and analytical research in Slovenia.2. RC VIADUCTS WITH CONTINUOUS DECKExtrapolation of the standard push-over procedures from buildings to bridges shouldbe done with care, as it will be demonstrated in the case of the analysis of singlecolumnbent RC viaduct in the transverse direction. There are several differences instructural system of such bridges compared to buildings: (a) The superstructure of theviaduct is often quite flexible in its own plane. Consequently, many modes can beexcited during the response, depending on the instantaneous stiffness of the piers. (b)In bridges the structural elements resisting lateral load are usually situated in oneplane only. Therefore, quite complex torsional (in the case of the roller supports at theabutments) and distorsional (in the case of the pinned supports at the abutments)response modes can be excited. (c) It is not straightforward to define characteristicforce and deformation as well as deformation shape of viaduct structure for push-overanalysis. All these may preclude the use of the inelastic static analysis. Thus, theobjective of the reported research has been to identify the cases where the pushoveranalysis (either single mode or multi mode) is acceptable and the cases where morerigorous inelastic time-history analysis is required for typical European viaductstructures. Only one, irregular, torsionally sensitive viaduct (Fig. 1), which wasexperimentally tested in ELSA (Pinto 1996) and addressed by many researchers, ispresented here as the main example. More complete results are available in (Isakovićet al. 2003).Many codes (i.e., EC8/2) would classify this viaduct as regular since (due to thevery stiff central column) the eccentricity is 0.6%, which is less than 5%.Consequently simple single mode push-over procedure would be allowed and evenencouraged by the code for this viaduct.294