Development of Design Criteria for Simply Supported Skew Slab-and-Girder Bridges (Distribution, Load, Truck, Live, Wheel)
Marx, Hendrik Jacobus
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https://hdl.handle.net/2142/69956
Description
Title
Development of Design Criteria for Simply Supported Skew Slab-and-Girder Bridges (Distribution, Load, Truck, Live, Wheel)
Author(s)
Marx, Hendrik Jacobus
Issue Date
1985
Department of Study
Civil Engineering
Discipline
Civil Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Civil
Abstract
A parametric study is done in which the behavior of simply supported, right and skew slab-and-girder bridges is determined by varying the properties of the structural members and the bridge geometry. The results obtained from linear elastic finite element analyses are used to develop a simplified analysis procedure for the bending moments in the girders. This analysis procedure is an improvement on the AASHTO wheel load fractions which do not include the effects of skew. The precast prestressed concrete and steel I-beam girders are modeled as eccentric stiffeners which cause shear lag in the slab. The effect of skew on the solution accuracy is demonstrated.
The effect of skew is a reduction in the girder bending moments. The reduction in the maximum interior girder bending moment is less than 5% for angles of skew up to 30 degrees. As the angle of skew reaches 60 degrees the reduction can be as much as 38%. The maximum moment in the exterior girder is less affected by skew. The reduction is less than 8% for angles of skew up to 45 degrees. At 60-degree skew the reduction can be as much as 25%. For all girders, the reduction in bending moment due to skew is most pronounced for angles of skew larger than 45 degrees.
The AASHTO wheel load fraction S/5.5 for interior girders gives girder bending moments which are between 12% on the unsafe side and 32% too large. The AASHTO method to determine the maximum exterior girder bending moment by assuming that the slab acts as if simply supported between girders, underestimates the actual exterior girder bending moments in most of the bridges considered. It gives bending moments which are up to 23% too small. The AASHTO exterior girder wheel load fraction S/(4 + S/4) for steel I-beams yields results which are between 30 and 60% too large. The simplified analysis procedure proposed gives girder bending moments which are within 7% of the values obtained from the finite element analyses.
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