The Free Vibration Characteristics And Seismic Response Analysis Of Curved Box Girder With Corrugated Steel Webs

With the development of the city,the curved bridges are used in traffic lines increasingly.The composite box girder with corrugated steel web regard as a novel and efficient composite girder,which are gradually applied in curved bridge.The mechanical properties of composite box girder with corrugated steel webs and ordinary concrete box girder are quite different.What’s more,during the situation of earthquake,the dynamic response of curved bridge is more complex than the straight bridge.According to previous earthquakes,bridges as a key node have a powerful influence in the rescue during a disaster and the post-disaster reconstruction.There are few studies on the dynamic characteristics of curved composite box girder with corrugated steel web.So the natural vibration characteristics and the dynamic response under earthquake about composite box girder with corrugated steel webs are studied in this paper.The main contents are as follows:(1)At first,the formula of natural frequency of curved concrete beams and straight composite girder with corrugated steel web is summarized.Then the expression of natural frequency is deduced according to the characteristics of composite box girder with corrugated steel webs.(2)The influence of curvature radius,width span ratio and diaphragm number on the natural vibration characteristics of the bridge were analyzed.The natural vibration characteristics of composite box girder with corrugated steel webs and curved ordinary concrete box girders are compared.(3)In order to analyze the dynamic response of this bridge under the effect of seismic action,the method of response spectrum was adopted,and the influence of curve radius was analyzed by changing the curve radius.The input direction of the most unfavorable earthquake effect of this bridge is determined by changing the seismic excitation direction.In this paper,the formula of vertical bending natural frequency of simply supported box girder with corrugated steel web was derived.With the elevation of the curvature radius of the box girder,the natural frequency of the vertical bending of the composite box girder with corrugated steel webs increases gradually,but the increasing speed gradually slows down.According to analysis,it is found that the number of diaphragm increase can effectively increase the torsion stiffness of the beam within a certain range,and the frequency of each order the curved steel web composite box beam is smaller than those of the equivalent concrete box beam,especially when the vibration type of torsion occurs,there have the great difference on the corresponding vibration frequencies With the increase of radius of curvature,the tangential displacement raise and the radial displacement decreases gradually.What’s more,the more obvious the change of the curvature radius the more obvious phenomenon will be,at the top of the middle span and the fixed pier during an action of earthquake.The results of the response spectrum should be checked with the time history analysis results to ensure the design safety of curved composite box girder with corrugated steel web during an seismic design.