Reliability Analysis And Safety Evaluation Of High Falsework

Many disastrous collapses of high falsework happened frequently, which caused vast economic loss and personnel casualties. The safety of high falsework has become a growing concern during construction currently. Since the high falsework has a higher of construction hight and a larger of bearing load, it causes easily collapses to the overall system if several members lose stability. Therefore, study on the reliability analysis and safety evaluation of high falsework that to make sure its safety which has important theoretic and practice meanings. The major contents of this work can be summarized as follows:(1) According to the accident cause of part of collapses of falsework in the recently ten years, the major factors of collapses are obtained, which can provide a direction for the later reliability analysis of high falsework.(2) Parts of erection parameters of falsework are acquired from on-site measurements and then the probability distribution and statistical parameters of those are obtained, which can provide calculation tool for the reliability. analysis of the high falsework.(3) Through on-site investigation and other analysis of valuable literatures, the current safety standard of falsework are analysed which is used the methods of safety factor and safety margin. Meanwhile, the influences of the factors of erection quality to the safety of falsework are discussed, based on the influences the redundant safety reserves is presentetd and it is necessary for the safety of the falsework.(4) Based on the results of on-site measurements, the wall thickness of steel tubes, the lengths of vertical tubes extending form the top horizontal tubes, the tightening torques of bolts of couplers and the settings of diagonal bracing are regarded as the main experimental factors. According to the statistical parameters of on-site measurements and mainly considering the influences of the main experimental factors, the ultimate bearing capacity of high falsework under different operating conditions are calculated. The probabilistic model of resistances of high falsework is obtained by fitting the calculated ultimate bearing capacities using Response Surface Method, while the probabilistic model of loads are sured through literatures about construction loads. Then on the basis of the limit state equation of the falsework, the reliability analysis of high falsework is conducted to use the Monte Carlo Method. According to the analytical results, it is shows that the setting of diagonal bracing is great important to the construction progress of high falsework. Meanwhile, the lengths of vertical tubes extending form the top horizontal tubes and the tightening torque of coupler must strictly control in a certain range that to make sure the reliability of high falsework.(5) The inspection contents of human error of falsework in erection processes are obtained through surveying in construction sites, and DER evaluation method is presented to evaluate the safety of falsework. Moreover, the progress of using DER evaluation method to evaluate the safety of falsework is discussed. According to the application of an engineering project, it provides references for the evaluation of high falsework.