Study On The Extant Pre-stressed Force Of The Concrete Structure In Service Based On The Stress Release Method

The extant pre-stressed force of the pre-stressed concrete is a very important parameter which affects the structural—load—carrying capacity, and takes on an uncertain property as the development of pre-stressed force loss. It controls the formation and development of the fracture and the displacement magnitude even the load—carrying capacity of the structural element. Serious loss in pre-stressed force will affects the performance and life-span, even result in structural safety accidents. Therefor, it is necessary to get the extant pre-stressed force of the concrete structure in service, which can provide the directest data and has important significance for the maintenance, the assessment in the structural-load-carrying capacity and the reinforcement of the concrete structure in service.In this paper, we make numerical calculation using the ANSYS software with the stress-releasing method in concrete due to two rectangle section pre-stressed concrete beams with simply supported ends—beeline bar and curve bar. We incise a ring-slot with some diameter and width around the center point in the bottom of the mid span, simulate the stress release of the test point in the incising process, discuss the influence factors on the incision depth which the stress can be released to zero and its formula approximately, and then estimate the extant pre-stressed force according to the differential value resulted from the stress-releasing.This paper concludes several aspects as follows:1) Put forward a compute method in the extant pre-stressed force of the concrete structure in service based on the stress-releasing method, and prove that it is feasible from two aspects—the theory and the numerical calculation;2) Establish the numerical calculation model with this method, and has studied the pre-stressed force, the cutting inside diameter as well as the cutting width separately which have influence on the stress release rate, and the result indicates the cutting inside diameter affects it directly;3) Establish the estimate formula for the cutting depth with which the stress can be released to zero in the cutting process, and when the cutting depth is 0.31-0.32 times than cutting inside diameter approximately, the stress can be released to zero;...