The Seismic Vulnerability Analysis Of Steel Framework Composite Structure Based On The Maximum Entropy Method

Earthquake,tsunami,landslides and other natural disasters brought bigl impact to people's life.And strong earthquake is one of the most severe,devastating natural disasters.Previous quake caused casualties and property losses,and most of the loss was caused by the destruction of buildings.So building designers are trying to find out some ways to improve the seismic resistance of structures.And there are also many researchers are exploring how to more effectively analysis of structure response under the seismic action before earthquake.Therefore more and more get people's attention to structural seismic vulnerability research.Structural earthquake vulnerability research can get the damage state of structure in the quake zone before the quake;It also can offer help to earthquake disaster assessment and the post-disaster relief organization after the quake.The other kind of earthquake disaster prevention is making disaster assessment about the possibility of failure form and quantity in the disaster area before the quake.Structural vulnerability analysis can not only reducing earthquake losses by optimizing structural design before quake,but also can provide an explicit rescue train of thought and reasonable distribution of resources when quake happened.So,structural seismic vulnerability analysis has positive significance to structural seismic design,disaster prevention and mitigation.Steel become the indispensable material in building structure products due to its superior tensile compressive performance,and steel frame structure can make full use of the performance of steel.Steel became the darling of the construction industry with its superior seismic performance and smaller self-respect.Steel structure become the preferred structure with large space span and good seismic performance.But some steel frame structure showed the phenomenon of vulnerability in some earthquake,which makes people thought further understanding on seismic performance of steel frame structure is needed.Structure vulnerability curve can be obtained through the finite element analysis based on incremental dynamic method.First,setting a series of ground motion intensity and then simulating the structure' response in different intensity levels of earthquake.Second,solving the probability distribution of structure's response,and then calculating the probability of the structure under specified seismic action to meet or exceed the state,according to a predefined level of structure performance.Third,matching the probability point which is the structure reached the same condition under the action of the different strength grade of earthquake.So the seismic vulnerability analysis of steel frame structure can predict the structure's probability of damage under the effect of different intensity levels of earthquake.When determining the probability density distribution function in structural vulnerability analysis,researchers were mostly assumes that distribution patterns as some prior assumes,which will increase the subjective factors in the results and brought certain influence in the authenticity and accuracy of the results.In order to get more accurate and accord the actual distribution of probability density function with analysing the typical small sample data.This article bring in the maximum entropy method of the information theory apply to solving the probability density function and bring in genetic algorithm to optimize the parameters in the probability density function.Maximum entropy method is widely used in probability and statistics and it's an effective tool to solve the uncertainty problem,which mixed subjective factors in the measurement data and can't accurately reflect the objective fact problems.Maximum entropy method is mainly to extract information of the measurement data to solve the probability density function,rather than suppose the measured data form as a classical probability distribution form.So it can greatly reduces the influence of subjective factor on the result.The maximum entropy method can find the probability density distribution function that contain the most information,in order to get more accord with actual probability distribution function.Therefore,the maximum entropy method is the most effective method to solve the uncertainty problem.However,when using the maximum entropy method to solve the probability density function,there are multiple and complex function relation between the unknown variables and it is a multiple of multimodal extremum problems.Mathematics method of general value is difficult to quickly get the requirements.So this paper bring in the genetic algorithm for solving the problem of multiple unknown parameters.Finally,getting the requirements of the variable parameters of approximate values by using the algorithm's iterative calculation step by step.This article makes seismic vulnerability analysis of the steel frame structure,making structural maximum displacement of the vertices and the maximum displacement between layers as the structure of the quantitative indicators.By using structural dynamic time history analysis method to obtain the data of structure response in different intensity levels of earthquake through the calculating of analysis software.And then,determine the probability density distribution function that the structural response obeyed.Drawing the vulnerability curve of the structure.Provide a reference for seismic design based on displacement and also provide certain information to aid after disasters.