Research Of The Shock Response Spectrum After The Steel Strand Cable Failure

With the rapid development of society,more and more pre-stressed technology has been applied to steel structure engineering.The steel frame pre-stressed cable bracing structure is one of the innovative achievements of this technology.The pre-stressed cables are introduced into the steel frame to make them participate in the structural and enhance the lateral resistance of the structure effectively.But there is a huge strain energy inside the cable after the structure loaded and it will be released in an instant,which results from a variety of contingency factors,it may have a certain impact on the remaining structure after the cable broken and even induce the dynamic response.It is time-consuming and arduous with the traditional finite element software to calculate of the dynamic response of the broken cable structure,and the results are difficult to verify.This paper first combines the dynamic tensile test of the pre-stressed steel strand,the whole process phenomenon and the necessary cable force parameters of the cable failure are recorded.Then shock response spectrum is calculated by Matlab,and the impact response spectrums which under different cable break paths and different failure time are plotted.At last,selecting the pre-stressed cable bracing single-story steel frame as the calculated model,and the dynamic time history method and response spectrum method are used to calculate the broken cable response of the model,and the feasibility of this method is verified.Obtaining a reliable response spectrum of the broken cable is the key to the calculation of the response of this type of structure.Therefore,this paper follows the broken cable test,and then to the calculation of the impact response spectrum.Then the shock response spectrum is applied to the broken cable project and compared with the finite element.Finally,the concept of vulnerability is introduced at the end of the paper,and the structural damage boundary curves under three different impact loads are drawn.It can clearly see the impact resistance of structures under different loads.The conclusions are divided into the following three parts:(1)The fracture shape of undamaged steel strand generally presents two kinds.One is the destruction along the 45 degree direction,the other is the 90 degree cross section failure,and the central steel wire generally produces slippage.There is only one failure form of steel strand with initial damage,that is,the fracture shape is 90 degrees.There is the most unfavorable load rate of undamaged steel strand.After failure,the stress in the cable is redistributed,and finally reaches a new balance.However,the yield platform gradually decreases with the increase of loading rate.The failure time of the steel strand does not change with the change of the loading rate and the notch depth.(2)The impact response spectra of different failure paths are different.When the ratio of impact duration to natural cycle ratio is small,the dynamic magnification coefficient hardly changes with the impact duration.But when the impact duration approaches the natural cycle of the structure,the impact duration has a certain effect on the dynamic amplification factor.The response spectrum is different under different cable unloading paths,but the response spectrum is almost the same under the same unloading path.The impact of damping on shock response spectrum is more obvious.(3)When the failure time is relatively short,the results obtained by the finite element method and the response spectrum method are quite error,but with the increase of failure time,the error of the two calculation results is about 10%.For structures with short impact duration,most of the loads acting on structures are resistant to structural inertia,so the maximum dynamic responses generated by them will be much smaller than those generated by long duration loads.