Rapid impact testing for quantitative assessment of large populations of bridges

Abstract

Although the widely acknowledged shortcomings of visual inspection have fueled significant advances in the areas of non-destructive evaluation and structural health monitoring (SHM) over the last several decades, the actual practice of bridge assessment has remained largely unchanged. The authors believe the lack of adoption, especially of SHM technologies, is related to the 'single structure' scenarios that drive most research. To overcome this, the authors have developed a concept for a rapid single-input, multiple-output (SIMO) impact testing device that will be capable of capturing modal parameters and estimating flexibility/deflection basins of common highway bridges during routine inspections. The device is composed of a trailer-mounted impact source (capable of delivering a 50 kip impact) and retractable sensor arms, and will be controlled by an automated data acquisition, processing and modal parameter estimation software. The research presented in this paper covers (a) the theoretical basis for SISO, SIMO and MIMO impact testing to estimate flexibility, (b) proof of concept numerical studies using a finite element model, and (c) a pilot implementation on an operating highway bridge. Results indicate that the proposed approach can estimate modal flexibility within a few percent of static flexibility; however, the estimated modal flexibility matrix is only reliable for the substructures associated with the various SIMO tests. To overcome this shortcoming, a modal 'stitching' approach for substructure integration to estimate the full Eigen vector matrix is developed, and preliminary results of these methods are also presented.

A new impact testing method for efficient structural flexibility identification

“…The proposed method also offers a solution for the signal processing of the experiment data from mobile testing, which is a novel and promising experimental area developed recently [18]. The mobile testing system integrates the impact device, limited numbers of sensors and data acquisition into a mobile vehicle, which automatically moves on the bridge under investigation to sequentially perform impact tests on localized portions of the large structure.…”

Multiple Reference Impact Testing for Bridge Assessment with Drop Hammer

“…A Rebound Controlled Drop Hammer is designed to provide large sufficient robust impact force for the bridge test. An adjustable heavy moving mass drops from an adjustable height and a PCB 200C50 load cell (0.10mv/lb, <50000lb) with a medium polyurethane impact tip (Model 084A32) provides an impact on the surface of the deck [3]. Since the impact carriage bounces off the bridge deck, several impacts occur.…”

“…National Instruments CompactRIO (cRIO) model line was selected for the basis of the distributed data acquisition system. A program written in Lab View has been deployed to run on any NI hardware as well as on a PC to provide intuitive, real-time visualization of the data during the test, including spatial variation [3]. Signal quality check and modal analysis.…”

“…It is hypothesized that the GSA system will execute a series of independent SIMO tests as it traverses a bridge, each test delivering an impact and capturing the responses of the structure through an array of sensors in the vicinity of the impact. While each SIMO test may be processed independently to obtain local flexibility coefficients as well as the deflection basins along the measurement points, it may also be possible to artificially stitch multiple SIMO tests together and process them in an integrated manner to obtain more complete flexibility information [3].…”

“…6). Three additional sensors were roved around with the impact device to capture the acceleration at the driving point by using various averaging techniques [5].…”