Load Distribution and Shear Strength Evaluation of an Old Concrete T-Beam Bridge

Abstract

There are about 330 T-beam bridges in the Australian state of Victoria that were built before 1950. Australia-wide there are nearly 1,000 of these early T-beam bridges. The shear capacity of these bridges, when assessed in accordance with current codes of practice, is in some cases not adequate for the current design loading. In 1996, VicRoads, the Victorian state road authority, initiated a project to enable a more accurate assessment of the shear capacity of these bridges to be made so that decisions on load rating or replacement could be made. An analysis of an existing reinforced concrete T-beam bridge that had been identified for a load test to failure was commissioned. The purpose of the analysis was to predict the load distribution behavior and the ultimate strength and to advise on the testing and monitoring program. After successful load testing of the bridge, a comprehensive analysis of the observed behavior was carried out and compared with the theoretical models. The pre-and posttesting analysis, which was undertaken with linear and nonlinear finite element analysis and with the modified compression field theory, are described and the analysis results are compared with the real behavior of the tested bridge. In particular, the load distribution in the elastic range and the ultimate shear strength of the reinforced concrete T-beams are discussed. The consequences of these findings on the load rating procedures are discussed, and a strategy for rating old reinforced concrete T-beam bridges is outlined.

Strategies for load rating of infrastructure populations: a case study on T-beam bridges

“…The actual modes of failure observed during laboratory testing of beam-slab systems have been through a flexural collapse mechanism typically after significant overloads and excessive deformations are reached following the formation of yield lines (Park and Gamble 2000). In addition, the shear capacity of Tbeam bridges are significantly greater than code values as observed from destructive testing of T-beam bridges due to the redundancy provided by beam flexural-shear and slab punching-shear mechanisms that are both present (Al-Mahaidi et al 2000, Song et al 2002.…”

“…Most of the bridges were constructed using standard set of drawings (Standards 1983). As most of these T-beam bridges share geometry and design details, materials and similar cast-inplace construction, and since recent field experiments on monolithic cast-in-place RC beam-slab behavior demonstrated excellent reserve capacity (Al-Mahaidi et al 2000, Song et al 2002, this bridge population was an excellent candidate for implementing statistical evaluation approaches. A statistical study was conducted on 1651 bridges with complete information in the NBI out of the entire population of 1899 single span RC T-beam bridges in Pennsylvania.…”

State-of-the-art on load testing of concrete bridges

“…When comparing the transverse flexural distribution from the AASHTO LRFD code [9] to field measurements of the flexural distribution from diagnostic load tests, differences of over 500% in the resulting rating factor are found [10,11]. The use of diagnostic load tests for the determination of the transverse flexural distribution has been reported in Florida [12,13], Delaware [14] and Ohio [15] on concrete slab bridges, in Australia [16] on girder bridges, in Texas on reinforced concrete pan girder bridges [17], in Pennsylvania on concrete T-beam bridges [18], and in Poland on prestressed concrete bridges [19].…”

“…This information can then be translated into stop criteria for proof load tests. Both bridges [5,16,[91][92][93][94][95][96][97][98][99][100][101][102][103][104] and buildings [105][106][107] have been subjected to collapse tests in the past.…”

Impacts of Epistemic (Bias) Uncertainty on Structural Identification of Constructed (Civil) Systems

“…In addition, despite the 1960-era, pre-seismic design, details, the bridge bents exhibited ductile behavior, which was attributed to the rotational flexibility of the soil. To assess shear capacity of reinforced concrete T-beam bridges, a decommissioned bridge was loaded to failure by Al-Mahaidi et al (2000). Finally, Halling et al (2001) performed several forced vibration tests on a single-span of a freeway overpass in conjunction with a series of intentionally induced damage states and repairs.…”