No abstract

This paper presents a study that investigated the effect of substructure stiffness on the performance of short- and medium-length steel integral abutment bridges (IABs) built on clay under thermal load effects. Various parameters, such as pile size and orientation, pile type, and foundation soil stiffness, were considered in the study. Detailed, three-dimensional (3-D), finite element (FE) models were developed to capture the behavior of IABs. Field measurements from a IAB were used to validate the 3-D FE model developed with LUSAS software. With the use of validated models, a parametric study was carried out to study the effect of these parameters on the performance of IABs under thermal loading with AASHTO load and resistance factor design temperature ranges. The study showed that the substructure stiffness had a significant effect on the stress level induced by thermal loads in various components of the substructure and superstructure. The results also showed significant variations in displacement and stress between interior and exterior locations in relatively wide IABs. The study showed that prestressed concrete piles could form a viable alternative to steel H-piles for short-span bridges. The stress level from thermal loading in the various components of the bridge could be reduced significantly if the top part of the pile were placed in an enclosure filled with crushed stone or loose sand.

In recent decades, orthotropic steel decks (OSDs) have been routinely incorporated into long-span bridges. The most widely used method to reduce stress concentration, improve fatigue performance, and control crack propagation is to cut out the diaphragms (or subfloor beams) into which the OSDs frame. However, the capital cost of cutout fabrication in the United States is high and may not be economically feasible. Study is required of cost-effective modified design details without cutouts as well as comparisons with their corresponding flexural and fatigue performance against current design details that use cutouts. Alternative design details (e.g., deck ribs welded directly to the transverse diaphragms using full-penetration welds) with thicker deck plates, but without cutouts, were investigated for potential improvements in fatigue resistance and capital cost. A parametric study was conducted with calibrated finite element models of a portion of the Bronx–Whitestone Bridge in New York City to study the effects of cutouts, deck plate thickness, and other important parameters on fatigue performance. Various traffic load combinations and truck types were considered with the use of an elaborate weigh-in-motion database. Results detail the equivalent stress ranges at critical locations in the OSDs that were calculated to quantitatively estimate fatigue lives for two OSD models: one with cutouts and one without. On the basis of these comparisons, recommendations related to overall structural performance were made to ensure a safe and rational design for various OSD options in long-span bridges.

Deflection and vibration play an important role in the serviceability of bridges. Their limits are specified in design codes either for consideration or as requirements. To promote understanding of the role of deflection and vibration limits, a comprehensive literature review is presented and comparison is made to propose the rational method to control bridge vibration for human comfort. To investigate the vibration and deflection criteria and applicability for bridges, actual bridges to represent typical bridge types are selected for experimental tests and theoretical study. Comparisons of the experimental results of deflection, acceleration, and frequency with the theoretical results are performed to verify the validity of the theoretical models. To ensure the applicability of the design code, bridges are redesigned so that they have minimum capacities as required by the design code. Finally, the vibration parameters of actual bridges and bridges using minimum sections are compared with current design limits and proposed criteria.

<p>This paper deals with the development of live load model for long span bridges. New live load model reflects truck traffic in Korea using Weigh-In-Motion system that was installed on the road with the heaviest truck traffic volume. By using collected WIM data, various truck traffic scenarios are assumed. To analyze the load effect, typical long span bridge such as a suspension bridge and a cable stayed bridge are modelled. Based on traffic scenarios, equivalent uniformly distributed load are calculated and loaded to the selected bridge. The results of load effects are compared with other load model in internationally renowned design code such as AASHTO LRFD, Honshu-Shikoku bridge design code and existing Korea Bridge Design Code. Based on the results of analyses, new live load model for long span bridges is proposed.</p>