Theoretical And Experimental Study On Existing Stress Measurement Of The Concrete Beam By New Grooving Method

Prestressed concrete structures are widely used in modern engineering construction, in the process of the construction and operation, due to the influence of factors such as the prestressed construction technology, material shrinkage and creep, prestress loss occurs inevitably, the size of the loss of prestress is about 10% to 20%. As the growth of operating time, under the influence of the natural environment and the loads, prestressed concrete structure will inevitably produce diseases and in need of repairing reinforcement. Also with the increasing load, some prestressed concrete structures often need structural reinforcement. To maintain and enhance the prestressed concrete structure, the first thing is to determine the status of existing structures, and the existing prestressed state is an important indicator. Due to the complexity of prestressed concrete structures’ stress state itself, it’s very difficult to measure the existing prestressed stress. So the existing stress measurement of prestressed concrete structure has been a hotspot problem but also the difficulty of research.In the measurement of the existing stress of prestressed concrete structures, the most widely used method currently is still the stress release method. The new grooving method studied in this paper is on the basis of the stress release method. In this paper, the main research contents are as follows:(1) On the basis of summarizing the existing stress release method, puts forward the new grooving method of stress measurement, which combines the technology of the flat jack with the stress release method measurement to eliminate the uncertainty of the elastic modulus of concrete in stress release method. Then this paper studied the measuring theory of the new grooving method, deduced the relevant formula, and developed the corresponding testing system.(2) Conducting the experiment on concrete beam, carving a dumbbell slots on the beam body, then using the new grooving method to measure the existing stress value of the beam, by comparison the experimental value with the theoretical analysis, validate the feasibility of this new grooving method, and gives a detailed analysis of measurement process.(3) The stress release method of stress measurement is a measurement bases on points, but the structures in engineering are the continuous structures. Using the stresses of points to describe the stress state of the entity structure, we need a reasonable choice of measuring points, and to study the impact of stress state around points in the non-uniformity media on the measurement results. In this paper using the finite element software ANSYS to establish a prestressed concrete box girder model, use the finite element method to analyze the influence factors of the new grooving method, like the measuring points arrangement and selection, the size of the slot, the layout and arrangement of reinforcement of prestressed tendons, to improve the accuracy of the measurement method. The purpose is to improve the accuracy of the measurement method, making it become more effective.