Distributed displacement estimation of pre-stressed concrete beams with random cracks using long-gauge strain sensing

Large pre-stressed concrete structures are usually confronted with random cracks and down-warping. Aiming to these structure diseases, a strategy for estimating distributed displacement of pre-stressed concrete beams with random cracks based on long-gauge strain sensing is presented in this article. First, an indirect method of calculating displacement of beams considering the presence of random cracks and pre-stress effect is derived. The method only relies on the collected strain responses and material parameters, and is irrelevant to external load. Then, a pre-stressed beam subjected to static load is designed for prove the effectiveness of the strategy. In the experiment, variable neutral axis position, curvature, concrete stress and vertical displacement are extracted under different load steps. Experiment results indicate that the estimated displacement has large relative error if random cracks are neglected. When the influence of random cracks is taken into account, the identified displacement agrees well with the directly monitored one by displacement sensors. Meanwhile, the results using different sensor arrangement are also compared. The presented strategy without the necessity of reference point could be an alternative for displacement monitoring of pre-stressed structures.