Seismic Forces in Ancillary Components Supported on Piers and Wharves

This paper presents a simple procedure to estimate seismic forces in ancillary components (secondary systems) supported on marine structures such as piers, wharves, and marine oil terminals (primary systems). Since many such marine structures can be idealized as single-degree-of-freedom (SDOF) systems, this study uses a simple linear-elastic model with two DOF, one representing the marine structure and the other representing the ancillary component. This study shows that acceleration at the base of the secondary system is approximately equal to spectral acceleration at the fundamental period of the primary system. It also proposes a formula, which is an improvement over current ASCE 7-10 recommendations, to estimate acceleration amplification in the secondary system due to its flexibility when mass and period ratios of the secondary and primary systems are known. The procedure in this paper is strictly applicable to marine structures for which primarily a single mode contributes to seismic response

Experimental Evaluation of In-Span Hinge Details in Reinforced Concrete Box Girder Bridges

During the past three decades, considerable research efforts have sought to improve the seismic design of California highway bridges. However, the in-span hinge (ISH) regions of concrete box girders have not been studied adequately. ISHs are classified as disturbed regions caused by the concentrated bearing loads and the possible existence of utility and maintenance openings, which induce a complicated three-dimensional stress state. Nevertheless, ISHs are commonly designed as two-dimensional short cantilevers following standard procedures. These designs typically lead to congested reinforcement causing constructability concerns from practical and economical aspects. The behavior and the strength of ISHs were assessed with five one-third scale specimens that were tested at the University of California, Berkeley. The first two specimens represent the as-built conditions of typical ISHs of California box girder bridges. These specimens were detailed identically, hut with one, utility openings were considered to study their influence on the behavior and strength of ISHs. The typical ISH characteristics were obtained from a survey of eight projects in California. The other three specimens represent new ISH designs, aimed at reducing the steel congestion and improving the structural performance of ISHs. Findings from the experimental results revealed that as-built ISHs fail with a combination of three failure modes: (a) beam shear, (b) two-dimensional strut and tie, and (c) punching shear. On the basis of the observed failure modes, it was concluded that the current ISH design could he optimized to reduce steel congestion and improve constructability.California Department of Transportation (Caltrans