Dynamic Response of Highway Bridges Subjected to Moving Load

摘要

Over the past couple decades there have been significant developments in availability ofnew materials and technologies suitable for civil infrastructure such as highway bridges. Highperformance steel (HPS) is one such a material that offers higher yield strength, enhancedweldability, and improved toughness. As a result of higher strength it can result in lighter andmuch more economical designs. However, live-load deflection limitations of bridge designspecifications negate the economical implementation of HPS.AASHTO Standard Specifications limit live load service deflection to L/800 for generalbridges and to L/1000 for bridges that are used by pedestrians. These limits were originallyfounded to control undesirable structural or psychological effects due to bridge vibration.However the results of prior studies indicate that deflection and L/D limits do not necessarilyaddress these objectives; and undesirable bridge vibration can be better controlled by otherparameters of vibration such as acceleration, velocity, and frequency. Although AASHTO LRFDBridge Specifications has made these limitations optional, there is not yet any method suggestedby AASHTO to limit vibration.There are a few alternate design methods which have been developed to better addressthe serviceability and durability issues. However, these methods have not been adopted in partdue to the practical limitations in their application but mostly due to the lack of consensuses.Therefore, there is a need to develop a more rational serviceability requirement in whichvibration is limited by the use of other parameters of vibration beside deflection.To develop such a requirement, bridge vibrational behavior should be completelyinvestigated considering different bridge characteristics and types of loading. This paper presentsa summary of the previous studies on human response to the vibration and the structuralperformance due to vibration; and the effect of parameters such as span continuity and theexcitation of higher modes due to different types of loading on bridge dynamic response. Theanalytical study employs 2-D Finite Element (FE) models to evaluate dynamic response ofbridges under moving truck load.