| Steel structures are becoming the preferred form of construction for large public buildings due to their excellent load-bearing performance and fast construction speed.However,steel structures can still collapse during the construction phase due to design or construction issues.Currently,research on structural anti-progressive collapse mainly focuses on the design and use stages,with less research on the construction phase.Therefore,studying how to reduce or avoid progressive collapse accidents during the construction process is of great significance.This thesis combines recent research on the anti-progressive collapse of building structures with the K8 single-layer spherical net shell structure as the research object.By using the APDL and LS-DYNA modules in ANSYS finite element software,the thesis analyzes the internal force changes,anti-progressive collapse,and impact performance of the structure during the use of the unsupported cantilever method in the installation process.The main contents of this thesis include:(1)Simulating the internal force changes of the net shell structure during the installation phase,performing nonlinear stability analysis,and obtaining the structure’s stability at each stage.The sensitivity index of the members at the 3rd to 6th rounds of installation is also calculated.The analysis shows that the maximum internal force of the net shell structure shows an upward trend followed by a downward trend during the installation process.The stability of the net shell during the installation phase is significantly smaller than during the usage phase,and any failure of a member during the installation process significantly affects the overall stability of the structure.(2)Conducting dynamic time history analysis of the anti-progressive collapse of the net shell structure during the roof panel installation phase.The dynamic response of the structure when critical members fail at each installation stage is obtained and compared with the same member failure situation during usage stage.The critical roof load for the net shell structure with three different span-depth ratios is also obtained.The analysis shows that the dynamic response and anti-progressive collapse performance of the structure during the roof panel installation phase are lower than those during the usage phase.The smaller the span-depth ratio,the lower the dynamic response and anti-progressive collapse performance of the net shell structure during both installation and usage phases.(3)Conducting dynamic time history analysis of the impact load on the net shell structure during the installation phase,obtaining the dynamic response of the structure at different positions when subjected to impact load.The effect of impact velocity and mass on the structure’s damage and acceleration changes when subjected to impact load is also analyzed.Finally,the thesis analyzes the effect of roof load on the structure’s resistance to impact.The analysis shows that an increase in the number of installation rounds significantly improves the structure’s ability to resist impact in its bottom area but has little effect on the edge area.When the impact velocity increases to a certain extent,it will change the structure’s failure mode.Moreover,external loads on the structure have a very unfavorable impact on its resistance to impact.The research conclusions drawn in this thesis have reference and guiding value for the safe construction and prevention of collapse accidents during the actual installation process of this type of net shell structure. |
