Accuracy of nonlinear static procedures for the seismic assessment of shear critical structures

Abstract

Summary The nonlinear behavior of reinforced concrete (RC) members represents a key issue in the seismic performance assessment of structures. Many structures constructed in the 1980s or earlier were designed based on force limits; thus they often exhibit brittle failure modes, strength and stiffness degradation, and severe pinching effects. Field surveys and experimental evidence have demonstrated that such inelastic responses affect the global behavior of RC structural systems. Efforts have been made to consider the degrading stiffness and strength in the simplified nonlinear static procedures commonly adopted by practitioners. This paper investigates the accuracy of such procedures for the seismic performance assessment of RC structural systems. Refined finite element models of a shear critical bridge bent and a flexure‐critical bridge pier are used as reference models. The numerical models are validated against experimental results and used to evaluate the inelastic dynamic response of the structures subjected to earthquake ground motions with increasing amplitude. The maximum response from the refined numerical models is compared against the results from the simplified static procedures, namely modified capacity spectrum method and coefficient method in FEMA‐440. The accuracy of the static procedures in estimating the displacement demand of a flexure‐critical system and shear‐critical system is discussed in detail. Copyright © 2015 John Wiley & Sons, Ltd.

Numerical Seismic Assessment of an Existing Bridge With Different Support Configurations

“…Thus, a complete characterization of the specimen behavior with particular care of the seismic relevant response characteristics and failure mode is needed. This aspect has been found to be very sensitive for the seismic assessment of RC structural systems [8], [9]. The low amount of transverse reinforcements strongly reduce the lateral capacity of the piers, resulting in low ductility capacity and potential shear failure.…”

“…In fact, the behavior of a circular cross section can be accurately reproduced in a 2D model by linearizing the curve shape and preserve the area and the inertia [9], [15], the reduced confinement pressure of the hollow cross section is difficult to be accounted in a 2D model. This phenomena was investigated by Ranzo and Priestley [16] that suggested for practical purpose to reduce the confinement pressure calculated for a circular cross section of the 30% to account of the hollow core.…”

“…VecTor2 can use a piecewise linear bond slip model in terms of -slip to account for the effective slip between concrete and reinforcements at each node of the 2D mesh. The adopted numerical model was validated against experimental results on a shear critical frame tested by Paolacci and Giannini (2012) (Del Vecchio et al 2015). However, a more specific validation at the column level is required to evaluate the accuracy of the model predicting the strong nonlinear behavior at high level of ductility characterized by marked rocking mechanism.…”

“…The latter requirement is due to the large computational demand associated with VecTor2 software [8], [9]. In compliance with consolidated modelling procedures for RC columns [8]- [10], an OpenSees non-linear fiber model has been created including the foundation block and the pier cap.…”

Validation of Refined Numerical Modeling for Existing Rc Buildings: Comparison Between Predicted and Observed Earthquake Damage

“…This makes the modeling of such components of paramount importance to have reliable estimation of the earthquake damage, of the seismic capacity and to design proper retrofit solutions. The advanced numerical models proposed in the recent years improved accuracy in reproducing the nonlinear behavior of RC structural systems [8,9] and the contribution of infill walls. New mechanical models and solution algorithms have been developed, and a great effort has been made to combine them with the state-of-the-art knowledge in refined tools (e.g., [10,11]) suitable for the use in the practical applications.…”