Experimental Study On Concrete Formwork Lateral Pressure

In recent years, the concrete formwork accidents occurred frequently. It is not only caused by improper construction operations, but also has relation with the unreasonable calculated values of concrete formwork lateral pressure in current related specifications. In recent years, on the one hand, design of concrete formwork is more and more conservative in China, on the other hand, the concrete formwork accidents occurred frequently. It not only caused concrete formwork waste, even may lead to formwork accident.The following problems are existed in the current formwork lateral pressure specification: 1) Factors being considered of different specification is different. 2) The calculated values computed by specification of different countries have a big difference, and the calculated values existed significant differences in the same country but in different industry standards. 3) Experiment data which is the basis of the specification have been very long time. 4) Compared with the traditional concrete, the working performance of concrete has changed a lot. And rate of placement and method of pouring have changed much too. All in all, it is not clear whether the specification formula apply to today’s engineering.Firstly, this paper based on specifications of Ministry of Construction, Ministry of Communications and Ministry of Railways, make a summing up of relevant formwork lateral pressure specifications, trace back to the source of formwork lateral pressure. And then, find out the problem of formwork lateral pressure calculation from the course of formula modification. With an engineering project as the background, comparative studying of different standards on the domestic and international mainly from the ambient temperature, concrete slump, initial setting time and pouring speed on the impact of lateral pressure of concrete formwork,which reveals the problems involve calculation of lateral pressure of concrete formwork.To improve the accuracy and reliability of the lateral pressure calculation of concrete formwork, a series of concrete formwork lateral pressure test was done. The different influence factors of lateral pressure were systematic studied by experiment. The test data and the calculated value of different specifications are analyzed in comparison. And then, the impact of concrete slump, pouring speed, the ambient temperature and vibrating mode on concrete formwork lateral pressure were discussed. The study shows that there was a great difference between calculated values according to various specifications and test values. Concrete slump, casting speed and vibration mode has great influence on formwork lateral pressure. But the influence of ambient temperature on the lateral pressure is slightly. On this basis, concrete formwork lateral pressure formula modification suggestions are put forward through regression analysis of experimental data. The relevant construction measures are proposed to ensure the safety and economy of formwork engineering.