Research On The Temperature Loading Method Of Concrete Specimen

Most of the structures are subjected to temperature load in practical projects. Thermal stress is an importmant structural load and sometimes becomes the critical cause of structural cracking or damage. Calculation theory of thermal stress and temperature field is quite mature, but the thermal stress of the indoor testing method and field testing technology is still the technical problem which has not been solved. Thermal stress analysis of the practical engineering structures is mostly applied by the theoretical calculation method, rarely using special instrument to directly determine the thermal stress of the structures or measuring the thermal stress of the specimens in the laboratory.Engineering practice generally considered that vibrating-wire concrete strain gauge can not be used to measure concrete thermal stress, but based on the working principle of concrete strain gauge, it is through theoretical analysis that vibrating-wire concrete strain gauge can measure concrete thermal stress. In order to verify the theoretical feasibility, this paper especially proposes a thermal stress testing method and makes a lot of experimental studies, the basic principle of this method is that the temperature load is applied by the electric heater cable wrapped on the lateral surface of the concrete specimen, using the embedded concrete strain gauge and peripheral dial gauges measuring the specimen deformation under the temperature load, using the ordinary testing machine to exert the constraints, and using the load cell to detect the thermal stress.This paper focuses on the temperature loading method and makes analysis of the temperature loading effect and heating rule. Test results show that a relative uniform temperature distribution was obtained by this method to meet the thermal stress testing requirements, through making reasonable heating system, it can exert temperature load by classification and each grade of temperature ranges 9℃to 11℃. Taking certain measures of thermal insulation can produce a strain and temperature reading at the same steady state period after exerting the temperature load to collect the measuring data. On the basis, according to the testing strain changes measured by the concrete strain gauge and the deformation measured by the dial gauges to calculate the coefficient of linear expansion with the concrete specimen, the results of these two different methods are similar with the recommended standard reference values.The temperature loading method is not only simple in structure, even in heating effect, but also make it possible to measure thermal stress with normal testing machine, it proposes a new technical idea for the experimental study of thermal stress.