NUMERICAL ANALYSIS OF BRIDGE GIRDERS DURING DECK CONSTRUCTION USING 7-DOF FRAME ELEMENT

Abstract

During bridge deck construction, the use of deck finishing machine and the fresh concrete often produces vertical loads and torsional moments acting on the bridge girder system. Sometimes, these loads can cause excessive deflection and twisting in the bridge girders, leading to many problems such as instability and non-uniform deck thickness during construction, as well as potential maintenance issues over the life of the bridge. Therefore, a detailed analysis is often required to evaluate the response of bridge girders under construction loads. In this study, an additional degree of freedom which represents the warping effects was added to the classic 6-DOF frame element to evaluate the torsional response of the bridge girder accurately. A finite element computer program was created in Matlab using the new 7-DOF frame element developed in this study. To evaluate the 7-DOF frame element, two Finite Element models using shell element and classic 6-DOF frame element were built in SAP2000 and compared with the model using 7-DOF frame element in term of accuracy and time consumption. The construction loads were considered moving along the bridge to simulate the whole procedure of the deck construction. The result shows that the finite element model using classic 6-DOF frame element failed to give reliable rotation values in the transverse direction since it allowed the structure members to warp freely, and the applied torque was entirely resisted by the torsional shear stress. Although both the shell element and 7-DOF frame element were able to provide accurate and reliable stress and defection results, the model using shell element was considerably time- consuming in both modeling and computing. The findings of this study will provide designers and contractors a more efficient way to analyze the bridge girders during construction and can also be used in the future research to evaluate the lateral torsional response of bridges in the service stage.