Model Identification and Seismic Analysis of Meloland Road Overcrossing

摘要

This report presents the results of research directed toward model identification andudseismic analysis of the MRO. This research has been implemented to meet the requirements ofudTasks 4 and 5 of the UNR-D&M research program (Sec. 1.1.3) and also to provide a basis foruddeveloping improved bridge modeling procedures as required under the D & M research programudon SBOs (Sec. 1.1.4).udThe scope of this research effort consisted of our development of a finite element modeludof the MRO whose parameters were estimated through the application of state-of-the-art systemudidentification methods to the MRO's recorded motions from the Imperial Valley Earthquake.udThese estimated model parameters were also checked for consistency with an overall range ofudmodel parameter values computed using established engineering procedures. This model wasudthen used in a series of parametric dynamic analyses of the seismic response of the MRO whichudenabled us to evaluate the effects of uncertainties in the various model parameters on the demandudforces and moments in the structural members and the foundation springs. Maximum foundationudspring forces and moments obtained from these analyses were used as input to nonlinear staticudanalyses of the MRO's pile foundations in order to compute the demand forces and momentsudwithin the piles. The demand forces and moments within the MRO's structural and pile elementsudwere then compared against the capacities of these elements. These analysis results have beenudinterpreted to assess the seismic performance and design of the MRO, and also to provide anudimportant basis for our development of improved modeling and seismic evaluation proceduresudfor short bridge overcrossing structures.udThe above efforts have focused on the modeling and analysis of the MRO's translationaludand rotational response to transverse horizontal input motions; i.e., the bridge's response toudvertical and longitudinal input motions was not included in this research. This focus on theudMRO's response to transverse horizontal input motions was adopted because: (a) this responseudwill lead to more severe earthquake-induced internal forces and moments, particularly in theudcentral pier which is the element of an SBO that is typically most vulnerable to seismic excitation; and (b) our past evaluations of the MRO's recorded motions have shown that itsudresponse to transverse horizontal input motions is strongly affected by SSI, whereas SSI has onlyuda negligible effect of the MRO's response to vertical and longitudinal input motions (Werner, et.udal., 1987).