Rationality Of Partial Coefficient In Design Expression And System Reliability Analysis Of Transmission Tower

In order to meet the requirements of the power transmission, transmission tower was a special featured, unique structure, and it had characters of definite load conditions. It survived form tested and optimized. Transmission tower was a kind of high altitude, long and thin shape, light weight and large flexibility of high-rise structure, and its response under wind load was sensitive. The sections of tower structure were often controlled by wind load.At present, the design codes of the structures of transmission tower was basically reference form architectural structure code. When the wind load effect significantly, the level of reliability of the transmission tower structure was low. It couldn't meeting the demand of the reality of engineering.Therefore, this paper continuing to use the partial coefficient design expression of building structure code, calibrated the code of transmission tower structure based on the predecessors and studied the rationality of the design expression of each factors in existing design code. In this paper, main research work is as follows:(1)Considered the mean wind pressure and randomness of fluctuating wind pressure of the equivalent static wind load model for accurately calculating the statistical parameters of wind load. Mainly studyed the influence regularity of load effect ratio under commonly load combination. It also considered design code measures such as wind load adjustment coefficient impact on the reliability level. In general, it was found that the reliability level of code(DL/T 5154-2012) was lower than the requirements of target reliability, and it has a certain distance between them.(2)On the condition of analyzed the statistical parameters of wind load, resistance and design expression of code systematically. According to principle of the consistent with the target reliability, optimized partial load factors when the dead load and wind load producing the same effect. The recommended values for partial load factors were G? =1.2 and Q? =1.7 respectively; while the effects opposite, the suggested values were G? =0.8 and Q? =1.7 respectively; Recommended structure importance coefficient value 0? for temporary line is 0.9, for important line is 1.15; For the transmission tower structure in ice area, it was suggested that the combination value is 0.9 while the wind load?ice load are multiplied by combination value. Draw a set of reasonable values of partial coefficient in design expression of the transmission tower structure, as a reference for code;(3)Established equivalent performance function based on the theory of equivalent extreme value event, and used the response values of finite element analysis of transmission tower to calculate reliability of the structure with main load conditions in code DL/T 5154-2012. In the combination of dead load and wind load, the reliability for criteria of material yield stress and the displacement limit were higher than the target; With the ice load in combination, the working condition of non-uniform ice basically could reach the target reliability requirements, and working condition of wire break lower than target reliability, some measures should be taken when it is applied in the actually project to improve its reliability.