Research On The Reasonable Completion State Of Cable-stayed Bridge Based On Optimization Of Safety Factor

Cable-stayed bridges have become one of the most widely used bridge types in the field of long-span bridges due to their mechanical characteristics and good spanning capabilities,and the study of reasonable cable-stayed bridge completion state is the core link in the design process of cable-stayed bridges.In order to continue to make breakthroughs on the basis of existing research,the current research direction of cable-stayed bridge completion state should not only focus on structural forces,but also expand the scope of objects and target depths.It is not only necessary to take into account the effects of constant and live load,but also to consider deeper pursuit goals such as the optimization of the safety performance of the cable-stayed bridge structure in the optimization goals,so as to determine a more reasonable cable-stayed bridge completion state that considers multi-dimensional goals.Combined with the supporting project,the following researches were specifically carried out and the research results were as follows:1.On the basis of existing research,it breaks the inherent concept of "validation is reasonable" in the design of cable-stayed bridges and the limitations of using the "bending moment feasible region" to determine the reasonable completion state of the cable-stayed bridge under the combined action of constant and live loads.The optimization goal of the reasonable completion state of the bridge is extended to the goal of the safety factor of each component of the cable-stayed bridge under the most unfavorable load combination that takes into account the combined effects of constant and live loads.The results of comparison and analysis with existing studies show that this optimization principle can ensure the reasonable completion state of the cable-stayed bridge and improve the overall safety reserve capacity of the bridge based on the reasonableness of the force.2.Taking into account the safety factor goal,this comprehensive optimization method of reasonable bridge status is proposed to combine the relative stiffness method to calculate the initial cable force,substitute this initial cable force to solve the unknown load factor,and then use the influence line method and the influence matrix method to optimize the minimum safety factor of each component under the most unfavorable load combination.The optimization process verified the rationality of the relative stiffness method to determine the initial cable force and the defects of the solution results on the structural displacement;It is verified that the input of the initial cable force value in the solution process of the unknown load factor method has a great influence on the rationality of the final bridge state result,and it is confirmed that using the initial cable force obtained by the relative stiffness method as the input value of the cable force to solve the unknown load factor is more reasonable;It is verified that the influence line method and the influence matrix method can effectively adjust the minimum safety factor of each member of the cable-stayed bridge under the most unfavorable load combination;The final optimization results show that the comprehensive method proposed in this paper is effective in optimizing the minimum safety factor of each member under the most unfavorable load combination.Under the premise of ensuring reasonable force in the completed state of the bridge,the safety reserve level of the cable-stayed bridge under the combined action of constant and live loads is improved.3.Implement the idea of taking into account the goal of safety factor into the study of reasonable construction status,determine the reasonable construction cable force of the supporting project through the stress-free state method,and analyze the rationality of the result of the formal installation and the reasons for non-closure.It is verified that this method is superior and reliable in the calculation of the reasonable construction cable force of steel box girder cable-stayed bridges;the optimization control study of the construction process has been carried out,and the results show that the components are safe and have good stress reserves during the construction process.Based on the reasonable safety factor range of the stay cable and the maximum cable force under the most unfavorable load combination determined in the article,the original cable plan is optimized.The results show that the cable cost is effectively reduced under the premise of ensuring the cable has a reasonable safety reserve.