Experimental characterization and diagnostics of the early‐age behavior of a semi‐integral abutment FRP deck bridge

Abstract

Purpose -The purpose of this paper is to further validate a wireless sensor system developed at Clarkson University for structural monitoring of highway bridges. The particular bridge monitored employs a fiber reinforced polymer (FRP) panel system which is fairly innovative in the field of civil engineering design. The superstructure was monitored on two separate occasions to determine a change in structural response and see how the structural system performs over time. Design/methodology/approach -A series of wireless sensor units was deployed at various locations of the steel superstructure, to measure both the modal response from acceleration measurements as well as quasi-static and dynamic strain response. Ambient and forced loading conditions were applied to measure the response. Data results were compared over two separate periods approximately nine months apart. Findings -The first eight mode shapes were produced from output-only system identification providing natural frequencies ranging from approximately 6 to 42 Hz. The strain response was monitored over two different testing periods to measure various performance characteristics. Neutral axis, distribution factor, impact factor and end fixity were determined. Results appeared to be different over the two testing periods. They indicate that the load rating of the superstructure decreased over the nine month period, possibly due to deterioration of the materials or composite action. Research limitations/implications -The results from the two testing periods indicate that further testing needs to be completed to validate the change in response. It is difficult to say with certainty that the significant change in response is due to bridge deterioration and not other factors such as temperature effects on load rating. The sensor system, however, proved to provide high quality data and responses indicating its successful deployment for load testing and monitoring of highway infrastructure. Originality/value -The paper provides a depiction of the change in structural behavior of a bridge superstructure using a wireless sensor system. The wireless system provided high-rate data transmission in real time. Load testing at two different points in time, eight months apart, showed a significant change in bridge behavior. The paper provides a practical and actual physical load test and rating during these two periods for quantifiable change in response. It is shown that the wireless system is capable of infrastructure monitoring and that possible deterioration is expected with this particular bridge design. Additionally, the load testing occurred during different seasons, which could create cause for temperature effects in load rating. This can provide a basis for future performance monitoring techniques and structural health monitoring.

Detecting minute damage in beam-like structures using the neutral axis location

“…The location of the neutral axis varies under loading, even in a healthy cross-section (Elhelbawey et al 1999, Chakraborty and DeWolf 2006, Cardini and DeWolf 2009, Gangone et al 2012, Sigurdardottir and Glisic 2013. Thus, choosing one point as representative for the neutral axis location does not provide accurate information on the true behavior.…”

“…In the laboratory, under controlled environmental conditions and severe loading, the neutral axis can be evaluated using deterministic analysis. However, in on-site conditions, the neutral axis location varies, even in healthy (non-damaged) cross-sections (Elhelbawey et al 1999, Cardini and DeWolf 2009, Gangone et al 2012, requiring statistical approaches for accurate evaluations (Chakraborty andDeWolf 2006, Sigurdardottir andGlisic 2013). The neutral axis location has been evaluated on real structures during controlled testing, and it has been used to detect severe damage (Gangone et al 2014), as well as small cracks (Sigurdardottir and Glisic 2013).…”

The neutral axis location for structural health monitoring: an overview

“…The same researchers conducted a similar test on a single-span semi-integral abutment bridge in North Lawrence, NY [15]. Strain transducers (7.62 cm gauge-length) were installed in the center spans of the five steel girders and close to the abutments of one girder in a similar fashion as described earlier.…”

“…Artificial damage was introduced into the concrete deck with plastic sheets. Three cross-sections were studied, Modified from Gangone et al [15] J Civil Struct Health Monit one with horizontal delamination, one with a vertical crack reaching the surface, and one healthy. Each monitored cross-section was equipped with four sensors, two embedded in the concrete and two surface mounted on the steel flanges.…”

Condition Evaluation of an Existing T-Beam Bridge Based on Neutral Axis Variation Monitored with Ultrasonic Coda Waves in a Network of Sensors

“…On the other hand, the general idea of gauge measurements is to install gauge arrays along the vertical direction of structural cross-section to collect the strain profiles at positions where they are exactly placed. Then the neutral axis is located at the height corresponding to the zero deformation through the intercept of the strain diagram [ 5 , 6 , 7 ]. However, gauge measurements do not carry any information about the areas among their installation positions.…”