Seismic Analysis And Damage Prediction Of Gantry Crane

With the development of modern logistics system,gantry crane,known as an important part of the system,is widely used in port,dock and other freight distribution center,and continues to develop with larger span and larger lifting capacity,which will make the steel structure more vulnerable under the earthquakes.The traditional design of gantry crane mainly utilizes the equivalent static method based on the linear elastic theory,which cannot well consider the particularity of gantry crane structure,the complexity of the wheel-rail boundary conditions and the randomness of ground motions,and therefore,cannot meet the seismic design needs of modern gantry cranes.At present,there is a lack of research related to the elastic-plastic dynamic response and structural damage prediction of gantry cranes under earthquakes.This thesis takes gantry cranes as the research object,takes the seismic nonlinear response and damage prediction of gantry cranes as the research objective,uses theoretical analysis and numerical simulation and other methods to study the seismic response of gantry cranes under different seismic excitations and different working conditions,mainly carried out the following research work:(1)Firstly,a nonlinear finite element model of a typical gantry crane based on plastic hinge theory is established,and the incremental dynamic analysis method is utilized to study the seismic response of the gantry crane under different working conditions.Then,considering the long span and lifting height of the gantry crane,gantry-crane-specified damage indexes,local displacement ratio,is proposed and the calculations of these indexes based on static pushover analysis is established.Finally,the fragility curves of the gantry crane are analyzed to assess the probability and degree of crane damage under different intensity earthquakes.(2)The endurance time analysis is optimized based on the China’s crane design code and a proved trinomial fitting method is proposed to conform to the seismic response characteristics of the gantry crane.Firstly,the correlation between incremental dynamic analysis and endurance time analysis is carried out to verify the accuracy of the endurance time method.Then,the effect of seismic incidence angle on the seismic response of gantry cranes is discussed.And then,based on the principle of seismic isolation,a special seismic device for gantry cranes is designed,and its characteristic parameters are optimized by means of numerical simulation to improve the seismic performance of gantry cranes.Finally,the effect of gantry crane’s size on the seismic response pattern of the structure is investigated.(3)The incremental dynamic analysis method is introduced to firstly solve the problem of lack of data sets faced in engineering practice,and the damage prediction model of gantry cranes is constructed using nine machine learning algorithms.Meanwhile,a new solution to solve the classification imbalance problem,dimensionality incorporation and reduction method,is proposed to effectively improve the prediction accuracy of minority classes.Then,the predicted fragility curves of crane structures are developed,and a rapid damage assessment process based on machine learning algorithms is proposed to efficiently assess the seismic damage probability of gantry cranes.Finally,the random forest and decision tree methods are used to study the performance of the prediction model with different sample capacities.(4)The wheel-rail friction contact model of gantry cranes is proposed to establish a torsional uplift-available crane model that is more in line with the actual situation,and to study the occurrence mechanism and response law of torsional uplift under different working conditions during strong earthquakes.Then the probabilities of uplift events under different seismic incidence angles are studied to analyze coupling effect of plastic damage and uplift behavior on the seismic response of gantry cranes.Finally,a comparison is carried out between fixed and friction contact boundary conditions to explore the relationship between the uplift behavior and the seismic demand of gantry cranes.(5)A variable permanent displacement baseline correction method based on the Iwan method is proposed to obtain the time history curves with required permanent displacement.And the coupling effect of traveling wave and earthquake induced permanent displacement on the seismic response of gantry crane structure is studied.This thesis systematically analyses the plastic seismic response of gantry cranes and optimizes the incremental dynamic analysis method and endurance time analysis method to make them applicable to the seismic design of gantry cranes.The proposed seismic damage assessment model for gantry cranes based on machine learning methods provides a new method for seismic analysis of gantry cranes.The basic data and revision ideas are provided to supplement and improve the content related to seismic performance analysis of gantry crane in China’s crane design specifications.