Research On Wind Load Characteristics And Wind-induced Vulnerability Of Tower Cranes

Tower cranes are widely used in the construction process of civil engineering and belong to a typical towering structural system.Wind load is one of the controlling loads in the structural design of tower cranes.Wind-induced collapse and damage accidents of tower cranes often occur.Therefore,research on the wind load characteristics and wind-induced vulnerability of tower cranes has important scientific significance and engineering practical value for guiding the wind resistance design and disaster prevention and mitigation of tower cranes.At present,the wind resistance design of tower cranes is mainly based on the vertical wind drag coefficient given in the "Code for Design of Tower Cranes"(GB/T 13752-2017)and "Code for Loading of Building Structures"(GB 50009-2012).The research results mainly focus on the dynamic response assessment under the action of wind load,and the research on the probabilistic resistance and wind-induced vulnerability assessment of tower cranes is not perfect.In this paper,the wind load characteristics and wind-induced vulnerability of tower cranes are studied through wind tunnel tests,finite element and probability statistics methods.The research work mainly focuses on the following two aspects:(1)This article selects a tower crane as the research object,the wind tunnel tests for head of the tower crane jib,working arm and balance arm are carried out on section model tests by force balance method,the effects of length of section model,turbulence intensity and Reynolds number on the wind loads characteristics of tower crane are studied.It is shown that the Reynolds number and turbulent intensity,as well as the length of segment has little effect on the drag coefficients.But the interference between the adjacent segments of the balance arm and the boom will reduce the drag coefficient of the test segment.The measured drag coefficients or standardization drag coefficients of the balance arm,crane boom and tower from current wind tunnel tests are close to the values from national standard for normal wind direction,and the drag coefficients for each section of tower crane on typical wind direction are given in this paper.Finally,based on the wind tunnel test results,the calculation formula of oblique wind load of tower crane is proposed,which can be recommended to the related engineering application,or provide some suggestions for the modification of related specifications..(2)The finite element model of the tower crane is established by the finite element software ANSYS,and the time history of the wind load at different heights of the tower crane is calculated by combining the fluctuating wind time history simulated by the harmonic synthesis method and the drag coefficient obtained from the wind tunnel test.The base shear force and top displacement response time history obtained based on the IDA method are used to establish the capacity curve of the tower crane.The results show that the structural capacity obtained by the NSPA method is greater than the structural capacity curve based on the IDA method.The maximum base shear-maximum displacement results are the closest;the IDA capacity analysis under multiple simulated samples shows that the simulation randomness and uncertainty of the fluctuating wind have little effect on the structural capacity based on the IDA method;Loaded IDA capacity analysis showed no significant difference in IDA capacity curves obtained using 1-minute and 5-minute wind load time histories.Using the IDA method to study the vulnerability of tower cranes in different wind directions,by comparing the vulnerability curves of different wind directions,it is found that the most unfavorable wind direction of tower cranes is 0° wind direction,and the maximum wind direction of structural resistance is 90° wind direction.