Book Description

In the design of highway bridges, structural engineers are faced with the determination of realistic lateral load distribution on steel girders. AASHTO Bridge Specifications contains a simple procedure used in the analysis and design of steel girder bridges. This procedure consists of calculating the maximum bending moment in an isolated individual girder under the application of a wheel line load (from a design truck load), and then multiplying the corresponding moment by an empirically derived distribution factor. In a previous study conducted by Mabsoul et al. (1996). a typical one-span two-lane composite steel girder bridge was analyzed using the finite clement method. Four finite element meshes were tested, of which two were selected for further analyses. A parametric study was performed for a wide variety of span lengths and girder spacings. which were thought to primarily affect the wheel load distribution (Tarhini et al. 1992). This study, which served to assess current design procedures (AASHTO 1992 and 1994). was limited to single-span two-lane bridges only. In the proposed research, the finite element analysis is extended to simple and continuous multi-lane steel girder bridges. The analysis will consider simple (one-span) and two-span bridges with two. three, and four lanes. This study will focus on the determination of the lateral wheel load distribution factor on the girders. Typical steel girder bridges will be discretized and analyzed by the finite element method for a variety of span lengths and girder spacings. Bridges will be loaded by AASHTO design trucks. The position of the truck will be varied along both the longitudinal and lateral directions to produce maximum positive and negative moments in the girders. The finite clement structural program SAP90 (1992) will be used. The proposed research will present a comprehensive study of straight steel girder bridges. It will therefore assist structural engineers in the analysis of simple and continuous multi-lane bridges. The finite element analysis will present an accurate approach for the evaluation of the load-earn ing capacity of existing or new bridges, and will serve to assess approximate methods currently used in bridge design practice.