Study On The Temperature Effect And Vertical Crack On The Concrete Rectangular Hollow Pier

In the current highway bridge design specification, the provisions about the uniform temperature effect of concrete bridge aren’t detailed, which exists certain contradiction with the greatly different climatic conditions across the country. At present, there are relatively less systemic research achievements for the non-uniform temperature effect of rectangular concrete hollow pier domestically, which is convenient to be referenced and used by design analyst. In addition, the vertical crack occurred in a lot of rectangular concrete hollow pier, and there are relatively insufficient researches of systematic mechanism analysis and crack control. By the combination of experiments and numerical simulation, an in-depth study on the temperature effect as well as the key calculation parameters and the crack mechanism and prevention measures of the concrete rectangular hollow piers has been launched, and the main research work and results are as follows:Based on the long-term observation data of temperature, the relationship between the average temperature of the concrete hollow pier and the air temperature was studied, and two methods used for predicting the average temperature range of the hollow pier by the air temperature were proposed. Through the prediction of the average temperature range of the trial pier in the observation period, it has been found that temperature range obtained when 2oC is increased on the basis of the highest and lowest daily mean temperature is basically consistent with the predicted range. With reference to the European structural design standard, it was recommended to take the highest and lowest daily mean temperature as the basic air temperature in return periods of 50 years and the standard value of effective temperature of concrete bridge could be got when 2oC is increased on the basic air temperature. Through statistical analysis, the recommended value of effective temperature of concrete bridge in 194 weather stations was given, and a co MParative analysis with the current highway bridge design specification was made, and it shortcomings was pointed out, and the suggestions for uniform temperature effect of concrete bridge was proposed.Based on the long-term observation data of temperature, the relationship between the positive, negative temperature effect of concrete hollow pier and the meteorological condition was systematically studied. Based on actual measurement of temperature field of sunshine and cold wave with temperature decreasing in rectangular concrete hollow pier and finite element simulation, the two-dimensional temperature distribution pattern of non-uniform temperature function of rectangular concrete hollow pier and power function temperature distribution curve along the path of wall thickness were proposed. Such data as coefficient of atmospheric transparency, diurnal temperature variation, maximum decline of daily mean air temperature in 24 hours, daily average wind speed etc in 20 representative locations of the country were collected, and the biggest standard value of positive and negative temperature difference on the wall in 20 representative observation stations were calculated by the the method of finite element simulation. Through the fitting calculation and comprehensive analysis, the suggest value of a in the power-function and b, the influence depth of temperature were presented.A series of key parameters for the calculation of concrete bridges temperature effects were studied experimentally. A concrete specimen heating device was designed, and the synchronization of concrete deformation with temperature change was proved by direct heating. Through embedment of steel string strain gauge in concrete block without outside constraint and actual measurement of internal strain distribution of the block under solar radiation, the assumption of plne cross-section for calculation of temperature self-stress was verified. A simple method to test linear expansion coefficient of concrete using buried concrete strain gauge was put forward. Using this method the influence of negative temperature conditions on the linear expansion coefficient was studied, and it was found that the coefficient of linear expansion would soar dramatically under negative temperature.Using heating equipment combined with hydraulic- servo dynamic fatigue testing machine, temperature stress of concrete and the short-term stress relaxation coefficient were measured, and suggestions for the reduction factor and combination problem of temperature stress were proposed.Combining the method of finite element analysis with field measurement, the i MPact on the vertical crack of concrete hollow pier by such factors as cement hydration heat effect, differential shrinkage of concrete, negative temperature difference on the wall and vertical load were systematically analyzed, and the results show that the different types joint effect of these four factors was the direct cause of vertical crack of concrete hollow pier. As the vertical crack of rectangular concrete hollow pier mainly belongs to deformation-caused crack, and we should give priority to the precautionary measures and control measures of reinforcement in the prevention and take crack treatment measures when necessary.