Determination of rebar forces based on the exterior crack opening displacement measurement of reinforced concrete
This paper presents the determination of rebar forces based on the exterior crack opening displacement measurement of a reinforced concrete beam. The problem formulation of the forward and inverse analysis of reinforced concrete fracture is briefly mentioned. The forward problem is to solve for the crack opening displacement profile with externally applied load and rebar forces given, while the inverse problem is to solve for rebar forces with the crack opening displacement measured and the externally applied load given. The inverse problem is ill posed; therefor it is regularized with Tikhonov regularization method. Numarical solution of the inverse estimated rebar forces is compared with the experimental measurement. A four point flexural loading experiment of a reinforced concrete beam is conducted, and, with the usage of a digital microscope, the crack opening displacement profile is captured. The measured profile is input into the inverse analysis scheme, leading to the rebar forces as output. The comparison of the estimated rebar forces with the guage measurements shows a reasonable agreement, and also the location of rebars is identified correctly. Finally, the error and the influencing factors are discussed.