Studies About Safety Of Highway Flyovers Under The Action Of Billboard

The users of the flyover bridges usually set large area of billboards in pursuit of more benefits.However,as the wind load will produce a lateral force to the bridge,and the designers mostly do not take this factor into account in the bridge design,thus improper use will lead harm or hidden trouble to the bridge,which have been reported frequently.In this paper,we acquaintance and analyse the basic types of billboards which are commonly used in highways through investigation of many highways in Hubei province.At the same time,according to static calculation and dynamic analysis,we carry on the calculation and contrast analysis to several main bridges by studying the effect on billboards wind load characteristics,which uses MATLAB and Midas Civil to set up its finite element analysis model.And we get many useful results by this.In this paper,main work and conclusions are as follows:(1)Studies the characteristics of wind load on the billboards by two aspects of static calculation and dynamic analysis and summarizes the numerical calculation and simulation method of two kinds of wind load.(2)Based on related data,chooses three common types of flyover bridges to calculate and compare by field investigation of many highways in Hubei province.(3)Sets up finite element analysis model by Midas/Civil to calculate and compare the mechanical properties of the three common types of flyover bridges which are set the same billboard.And analyzes their mechanical characteristics and stability of the under lateral load,which can provide a reference in the selection of the highway flyover bridges.According to the comparative result,the continuous steel box girder is the most sensitive bridge to the billboard.On the other hand,rigid frame arch bridge is the most stable type of flyover bridge.(4)In the case of continuous steel box girder,which is the most sensitive bridge to the billboard,it is calculated under different schemes and directions of the wind from the aspect of static calculation.The results show that the size of the billboard set on the continuous steel box girder should be controlled in the range of 50m× 3m to keep the bridge safe.And the continuous steel box girder is more sensitive to the herght of the billboard than its length.These conclusions can provide references for engineering.(5)Dynamic analysis is applied to the continuous steel box girder with billboard on the basis of static calculation.Based on the method of harmonic synthesis,the paper uses MATLAB to simulate fluctuating wind field.The fluctuating wind field is accurate and effective by the validation of power spectrum and correlation with PSD function.The fluctuating wind load is imported to Midas/Civil as external data.And the results show that billboard makes the bridge’s lateral displacement,as well as torsional displacement and torsional acceleration,increase very much with the effect of fluctuating wind load.The dynamic response is relative to wind speed.