Bidirectional Pseudodynamic Tests of Bridge Piers Designed to Different Standards

Abstract

Circular reinforced concrete highway bridge piers, designed in accordance with the requirements of Caltrans, New Zealand and Japanese specifications, are experimentally investigated to assess their seismic performance. Pseudodynamic test procedures are developed to perform experiments on 30% scaled models of the three prototype bridge piers. Each specimen is subjected to a sequence of three different earthquake ground motions scaled appropriately to represent: (i) the Design Basis Earthquake (DBE) with a 90 percent non-exceedance probability; (ii) the Maximum Considered Earthquake (MCE) with a 50 percent non-exceedance probability; and (iii) the MCE with a 90 percent non-exceedance probability. Damage states after the earthquakes are assessed and mapped for seismic risk assessment. The damage outcomes and the corresponding seismic risks validate the objectives of the performance based design codes of the three countries. The results show that when bridge piers are designed to the specifications of each of the three countries, satisfactory performance with only slight to moderate damage can be expected for DBE. For the MCE, severe damage without collapse is likely for the Caltrans and Japanese piers. However, the NZ pier may not be able to survive MCE motions with sufficient reliability to ensure the preservation of life-safety. IntroductionRecent major earthquakes such as the 1994 Northridge and the 1995 Hyogoken-Nanbu (Kobe) events had a severe impact on the serviceability of bridges. Consequently, there has been a growing interest in comparing the seismic performance of bridges designed according to the codes and standards of different countries. This is because both the loading requirements and structural detailing procedures vary considerably, even though the magnitude of hazard exposure may be similar. As part of a cooperative four-country international project, Tanabe [1999] designed four bridge piers, in accordance with Caltrans, New Zealand, Japanese and European design standards. The main purpose of this international project was to identify differences in the cross-section dimensions and reinforcing details, to clarify the reasons for these differences, and to assess the likely seismic performance by computational means. This previous comparative research was restricted to uni-directional earthquake motions. Given that simultaneous bidirectional earthquake motions occur in reality, and computational predictions may differ from real response due to modelling simplifications, it is considered desirable to conduct an experimental investigation of the seismic response of bridge piers including bi-directional effects.Although simplified test procedures such as quasi-static and high-speed cyclic tests [Dhakal and Pan 2003] exist for general experimental studies of structural behaviour, more advanced test procedures such as pseudo-dynamic tests (referred to as PD tests hereafter) or shaking table tests are needed to experimentally assess the expected seismic performance of structures. PD tests offe...

An overview of seismic hybrid testing of engineering structures

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Improved seismic hazard model with application to probabilistic seismic demand analysis

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Seismic Performance of Reinforced Concrete Rectangular Hollow Bridge Piers

“…However, little experimental study of the structure and components under the seismic ground motion has been conducted over a long period of time due to the limitation of experimental techniques and conditions. Experimental study of reinforced concrete piers has rarely been performed on hollow piers subjected to combined axial load and biaxial bending [1][2][3][4][5][6] and thus there is a lack of information about seismic damages and design experience of hollow piers. Taking into account the multidimensional nature of earthquake ground motion and the advantages of the hollow cross-section bridge piers, it is close to the engineering practice and thus it plays an important role as engineering reference to study the seismic performance of widely used reinforced concrete piers with different axial compression ratio subjected to combined axial load and biaxial bending.…”