EVALUATION OF STRUCTURAL PERFORMANCE IN DECHATIWONG BRIDGE

Abstract

Dechatiwong Bridge crossing Chao Phraya River is located at Nakhon Sawan province. It has been in service since 1950, reaching over 74 years. Visual inspection results revealed that main structural components were deteriorated, igniting concern for its safety. The assessment found that the structural capacity of the bridge’s substructures was still sufficient. Thus, the bridge restoration for superstructure was proceeded using AASHTO-LRFD.

Strengthening plans were separated into 2 main approaches: 1) arch spans and 2) approaching spans. For the arch spans, the strengthening included: enlarge cross section of arch girders and cover with steel plates; strengthen joints on arch girders with gusset plates; add a vertical steel rod between two inclined hanger rods; enlarge cross section of tie girders, install post-tension bars along the longitudinal direction and cover with steel plates; brace two tie girders on both sides (left-right) with transverse rods installing turnbuckles; replace old bearings with new spherical bearings.  For the approach spans, the strengthening included: enlarge cross section of tie girders and cover with steel plates; brace two tie girders on both sides (left-right) with transverse rods installing turnbuckle; strengthen with a diagonal PT bar at the section near support to increase shear capacity. In addition, decks in arch spans and approach spans were reinforced by attaching steel plate at the bottom. Despite several strengthening measures will be applied to enhance structural capacity, the analysis of safety index that considered variation of deteriorated material strength did not allow full trailers and semi-trailers on bridge to increase safety and prolong bridge life.