Analysis Of Bearing Capacity And Stability Of Asymmetric Special-shaped Steel Arch Bridge

The asymmetrical special-shaped steel arch bridge has a peculiar shape,and the arch ribs are linear and graceful,which makes great use of the space effect.The large and small arch ribs are supported by three points.Near the middle pier,the arch ribs are combined into one and pass through the main girder,the arch ribs and main girder are separated,the arch ribs and piers are combined.Its unique structural form makes the structural force more complex,strong in particularity,outstanding stability problems,uneven internal force distribution,and higher requirements for bearing capacity.Therefore,it is of great significance to analyze the bearing capacity and stability of such structures.In this thesis,the Midas/civil finite element model of the whole bridge is established based on the research background of a two-span asymmetric special-shaped steel arch bridge to analyze the bearing capacity and stability of the landscape steel arch bridge.The main contents of this thesis are as follows:(1)Using the finite element analysis model to analyze the bearing capacity of the landscape steel arch bridge,discussing the influence of rise-span ratio and suspender spacing on bearing capacity.The maximum stress occurs at the middle arch toe section of the large arch side,and the maximum stress is-206.1MPa,the maximum vertical displacement occurs at the joint arch of the large arch,and the maximum vertical displacement is-122.6mm,indicating that the strength and stiffness of the bridge structure meet the requirements.With the decrease of the rise-span ratio,the axial force of the large arch increases,the bending moment decreases,the internal force of the dome section changes the most,the stress of the arch toe and the dome of the large arch decreases,and the stress of the other sections increases.The maximum vertical displacement of large arch and girder decreases with the decrease of rise-span ratio.When the suspender spacing increases from 5m to 7m,the internal force of the arch rib from the combined arch to the middle arch toe section has the greatest impact,in this section,the axial force of the large arch decreases and the bending moment increases.(2)The stability of the special-shaped steel arch bridge is analyzed based on the stability theory,discussing the influence of rise-span ratio,suspender spacing and the number of transverse braces on stability.The stability safety factor of the structure is 22.869,which is far greater than the limit requirement of 4～5,indicating that the stability of the structure is good.The lateral wind load has little effect on the stability.The vertical stiffness of this kind of structure is greater than the lateral stiffness,and the stability is controlled by the large arch and the main girder.When the rise-span ratio is reduced from 1/2.4 to 1/3.4,the stability of the structure is obviously increased in all directions,but the rise-span ratio is further reduced,the stability of the structure decreases.When the suspender spacing is increased from 5m to7 m,the vertical stability of the structure decreases,and the lateral stability first increases and then decreases.When the number of transverse braces increases from 0 to 6,the stability safety factor of the structure increases significantly,the number of transverse braces continues to increase,and the increase in stability tends to be flat.The overall stability of the landscape bridge can be effectively improved by selecting 1/3.4 rise-span ratio,6m suspender spacing and 6 transverse braces.(3)The local model of the arch abutment at the middle arch toe is established by using Ansys,the temperature field and stress field of T-shaped welded joint of steel box are simulated by indirect method.The welding residual stress field is loaded in the form of the initial stress of the element,and the load obtained from the overall model analysis is added to the local model.Only under the action of external load,the stress concentration phenomenon at the consolidation point of the arch rib is more obvious.The maximum equivalent stress of the steel box is 192.55 MPa,and the stress caused by dead load accounts for 76%.In addition to the consolidation point,the stress distribution of steel box and concrete is relatively uniform,which meets the strength requirements.Under the combined action of residual stress and combined load,the stress of the steel box weld element has a significant increase.The maximum equivalent stress of the weld joint is 223.29 MPa,an increase of 52.27%.The residual stress leads to redistribution of stress in the steel box,which reduces the concentrated stress of the steel box at the consolidation point.