Operational Performance Seismic Design of Highway Bridges for 2500-Year Earthquake Using Proposed NCHRP Provisions

Abstract

The Applied Technology Council (ATC), in ajoint venture with the Multidisciplinary Center for Earthquake Engineering Research (MCEER), has recently developed Comprehensive Specifications for the Seismic Design of Highway Bridges (National Cooperative Highway Research Program, NCHRP Project 12–49). The American Association of State Highway and Transportation Officials (AASHTO) is considering these recommended specifications for possible incorporation into the future AASHTO Load and Resistance Factor Design specifications. The primary objective of the NCHRP Project 12–49 was to develop seismic design provisions that reflect the latest research findings, design philosophies, and design approaches. Henceforth, implementation of the newly developed provisions will ensure enhanced seismic performance of highway bridges. In this study, the highway bridge seismic design procedures of the current AASHTO and proposed NCHRP provisions are compared for the substructure and superstructure of the bridge remain the same for both provisions. An existing bridge located in a high seismic zone of Missouri with Seismic Performance Category D is redesigned according to the proposed NCHRP provisions. In this project, this bridge has been redesigned using the NCHRP provisions by Operational Performance Level for the Maximum Considered Earthquake (MCE) with a 3% of probability of exceedance in 75 years (with an approximate return period of 2500 years). By the new design the bridge will remain functional after the MCE as a critical bridge with lifeline performance. This research indicates that changing from the current AASHTO Standard to the new provisions requires 49% increase of reinforcing steel for this bridge. Transverse reinforcement of the piles increases significantly for the requirements of the new provisions (2500% increase). By using the new provisions, concrete increases 72% at wing-walls and the piles.