Research On Failure Modes Of High-rise Steel Structures Considering The Influence Of Ground Motion And The Control Methods

The failure of high-rise steel structures is closely related to the characteristics of ground motions.To date,there are limited studies on the identification method of the correlation between the failure mode of high-rise steel structures and the ground motion characteristics and control methods of the failure mode.In this paper,a high-rise steel structure model considering the cumulative effect of beam end damage is established and verified.Based on this,the failure mode classification and identification methods of high-rise steel structures considering the influence of seismic characteristics are studied,and the failure mode control method of high-rise steel structures based on viscous dampers is further developed.The main research contents and conclusions are as follows:(1)A method for determining the damage parameters of steel beams is proposed,which can be used to simulate the fatigue damage of steel beam and improve the modeling accuracy of beam elements of beam-to-column connections.The results show that both the steel beam model and the structure model with recalibrated steel damage parameters can reproduce the fatigue damage effect of the beam end,and they still have good applicability under different loading systems.(2)A method to identify the failure mode of high-rise steel frame structures is proposed.The distribution law of storey drift under 20 groups of ground motions is analyzed,and the statistical analysis of acceleration response spectrum values of the ground motions is carried out.The criterion of failure mode is determined and verified by numerical examples.The results show that the failure modes of high-rise steel frame structures can be classified into three types according to the location of the failure,which are related to the ratio of acceleration response spectrum corresponding to the first and second-order modal periods.In this paper,when the value is larger than 0.36,the failure within the height of the lower 1/3 structure is easy to occur;when it is less than 0.23,the damage within the height of the upper 1/3 structure is likely to occure;the above two kinds of damage may occur simultaneously when the value is between 0.23 and0.36.The example analysis shows that the prediction accuracy of this method for the three failure modes is up to 89%.(3)A method for evaluating the damage uniformity of high-rise steel frame structures is proposed.Based on the dispersion degree of storey drift distribution,the uniformity degree of storey damage is divided into three categories,and its quantitative index is determined.The statistical law of 20 groups of storey drift curves and the index is analyzed.The results show that the larger the index value is,the more discrete the distribution of storey drift is.In this paper,when the index value is less than 0.12,the storey damage is uniform;in the range of 0.12 ～ 0.21,the damage is concentrated within2/3 of the structure height;when it exceeds 0.21,the damage is concentrated within the upper or lower 1/3 of the structure height.(4)A failure mode control method for high-rise steel frame structures based on viscous dampers is proposed.The dampers layout plan takes the damage uniformity as the control index,determines the number of layout floors based on the principle of effective inter-story displacement,and uses the average inter-story shear ratio to determine the ratio of damping coefficients between different floors.In the analysis of this paper,after using this method to control the failure mode of high-rise steel frame structure,the difference between the maximum and minimum storey drift with dampers can be reduced from 0.024 rad to 0.002 rad,and the damage uniformity index of the whole story can be reduced from 0.37 to 0.11.The damage of the strcutre tends to distribut uniformly.