Live-Load Testing Application Using a Wireless Sensor System and Finite-Element Model Analysis of an Integral Abutment Concrete Girder Bridge

As part of an investigation on the performance of integral abutment bridges, a single-span, integral abutment, prestressed concrete girder bridge near Perry, Utah was instrumented for live-load testing. The live-load test included driving trucks at 2.24 m/s (5 mph) along predetermined load paths and measuring the corresponding strain and deflection. The measured data was used to validate a finite-element model (FEM) of the bridge. The model showed that the integral abutments were behaving as 94% of a fixed-fixed support. Live-load distribution factors were obtained using this validated model and compared to those calculated in accordance to recommended procedures provided in the AASHTO LRFD Bridge Design Specifications (2010). The results indicated that if the bridge was considered simply supported, the AASHTO LRFD Specification distribution factors were conservative (in comparison to the FEM results). These conservative distribution factors, along with the initial simply supported design assumption resulted in a very conservative bridge design. In addition, a parametric study was conducted by modifying various bridge properties of the validated bridge model, one at a time, in order to investigate the influence that individual changes in span length, deck thickness, edge distance, skew, and fixity had on live-load distribution. The results showed that the bridge properties with the largest influence on bridge live-load distribution were fixity, skew, and changes in edge distance.

Recent Experience with High-Performance Concrete Jointless Bridges in Tennessee

Experimental and analytical studies of two high-performance concrete (HPC) jointless bridges with integral abutments built in Tennessee as part of the FHWA’s nationwide initiative to implement HPC in bridge structures are presented. Performance of the two bridges is observed through all stages of construction and service to date, via material testing, bridge instrumentation for both short- and long-term performance monitoring, and live-load testing. The up-to-date observed performance of the bridges reveals the success of such bridge construction. Local contractors were found to be capable of producing concrete to meet increased requirements in strength and durability parameters. In addition, new insights were derived about HPC behavior in such applications, identifying the areas requiring updating of current practice. Load test data revealed that load distribution among the girders is in marked difference from codes of practice. Thermal response of the bridges indicated longitudinal flexibility offered by the jointless construction.