A new recommended load cycle for dynamic wind-resistant test of roof system based on the principle of damage equivalence

At present, the load cycle recommended in the dynamic wind-resistant test standards of metal roof system has some problems, such as unreasonable load sequence combination and too conservative selection of the number of cycles corresponding to each load sequence. This leads to the excessively long period of dynamic wind-resistant test of roof system, and further restricts the systematic research of the dynamic numerical simulation of wind-resistant performance of roof system. To this end, this study is carried out from two aspects: the optimization of load sequence combination and the selection of the number of cycles corresponding to each load sequence. First, ABAQUS is used to analyze the damage of the finite element model of aluminum alloy standard specimens under the action of 8 load sequences in the existing test standards. The calculation results show that the aluminum alloy standard specimens are damaged only under the action of the 3rd, 4th and 7th load sequences, and the damage factor SDEG are 1, 1 and 0.197 respectively. Taking into account the large differences in the ranges of load sequence N3, N4 and N7, the effects of 8 detailed load sequences on the damage of specimens are further studied, and the optimized load sequence combination is proposed according to the obtained 7 kinds of load sequences which can cause the damage of specimens. Referring to the load sequence combination recommended in the test standard, simplified load sequence combination and optimized load sequence combination, the wind pressure time history of 18 measurement points is counted by rain flow counting method to obtain the corresponding three load cycles respectively, and the above 18 groups of four forms of load are applied to the aluminum alloy standard specimens respectively. The numerical results show that the damage factor of the specimen under the optimized load cycle is the closest to that under the wind pressure time history of measurement point, with an average error of 0.05, while the average error is 0.14 and 0.21 under the load cycle recommended by the test standard and the simplified load cycle, respectively. Therefore, the effectiveness of the optimized load sequence combination is verified based on the principle of damage equivalence. Finally, with reference to the optimized load sequence combination, the wind pressure time history of 48,748 measurement points obtained from the wind tunnel test of large-span flat roof is counted by the rain flow counting method, and the probability distribution of the number of cycles corresponding to each load sequence was obtained. Taking the exceedance probability of 1% as the standard, combined with the probability distribution of the number of cycles, the number of cycles corresponding to the 7 load sequences are determined as 60, 50, 20, 10, 25, 10 and 5 respectively, and then the recommended load cycles are proposed.