Prestress-Force Estimation in PSC Girder Using Modal Parameters and System Identification

Abstract

In this paper, a vibration-based method to estimate prestress-forces in a prestressed concrete (PSC) girder by using vibration characteristics and system identification (SID) approaches is presented. Firstly, a prestress-force monitoring method is formulated to estimate the change in prestress forces by measuring the change in modal parameters of a PSC beam. Secondly, a multi-phase SID scheme is designed on the basis of eigenvalue sensitivity concept to identify a baseline model that represents the target structure. Thirdly, the proposed prestress-force monitoring method and the multi-phase SID scheme are evaluated from controlled experiments on a lab-scaled PSC girder. On the PSC girder, a few natural frequencies and mode shapes are experimentally measured for various prestress forces. System parameters of a baseline finite element (FE) model are identified by the proposed multi-phase SID scheme for various prestress forces. The corresponding modal parameters are estimated for the model-update procedure. As a result, prestress-losses are predicted by using the measured natural frequencies and the identified zero-prestress state model.

The effect of prestress force magnitude and eccentricity on the natural bending frequencies of uncracked prestressed concrete beams

“…Recently the interest on variability of dynamic properties of bridges (i.e. natural frequency, mode shape, damping ratio) caused by environmental effects such as temperature, humidity, wind and other factors is increasing [22].…”

Advances in Smart Technologies for Structural Health Monitoring of Cable-stayed Bridges

“…Those indications are unexpected from numerical modal analysis, which is described in the later part. It has been reported that these noisy peaks can be caused by power supply issue of SHM-H sensor board [13]. Further studies should be made to resolve the problem related to the performance of the SHM-H sensor board.…”

“…For vibration monitoring, SHM-A, SHM-AS and SHM-H sensor boards were selected. The SHM-A and SHM-H sensor boards were developed for acceleration measurement by University of Illinois at Urbana-Champaign (UIUC) [7,13,14]. The SHM-AS sensor board was modified from SHM-A sensor board in order to measure PZT's dynamic strain signal [15].…”

Effect of Temperature Variation on Vibration Monitoring of Prestressed Concrete Girders

“…Two simple supports were modeled by steel rods between the girder and the rigid frame. As detailed in existing publications [21], the PSC girder model has the T-section reinforced in both longitudinal and transverse direction with 10 mm diameter reinforcing bars. As the prestressing tendon, a seven-wire monostrand with 15 diameter was embedded in a 25 mm diameter duct.…”