Torsional Effects on Load Tests to Quantify Shear Distribution in Prestressed Concrete Girder Bridges

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Title: Torsional Effects on Load Tests to Quantify Shear Distribution in Prestressed Concrete Girder Bridges

Author(s): Benjamin Z. Dymond, Catherine E. W. French, Carol K. Shield

Publication: Special Publication

Volume: 323

Issue:

Appears on pages(s): 10.1-10.18

Keywords: concrete bridge, load testing, prestressed concrete, vertical shear strain, torsional shear strain, finite element model

Date: 5/1/2018

Abstract:
Torsion due to superimposed loads is often ignored in prestressed concrete bridge girders because it is considered negligible compared to other forces that control the structural design. However, during load testing of prestressed concrete girder bridges, shear strains due to torsion can be on the same order of magnitude as shear strains due to the vertical shear force resultant for superimposed loads. The inability to differentiate between the two types of shear strains may lead to inaccuracy when determining the vertical shear force distribution in statically indeterminate bridge structures. Rosette strain gages need to be placed on both sides of the girder web to differentiate between torsion and vertical shear to characterize the shear distribution. The need for this instrumentation configuration likely applies to other studies in the literature that have calculated shear force through the use of rosette strain gages on only one side of prestressed concrete girder webs in bridges. This paper discusses best practices to quantify shear distribution data. The study included tests and finite element modeling of laboratory and field bridges.