悬索桥英文词汇.docx

2 Description and modeling of the bridgeBeing a type of multi-tower suspension bridge, the TaizhouYangtze River Bridge is longest in the world with the dualmain spans reaching 1080m. As shown in Fig.1, the bridgeconsists of three towers, making two main spans (1080m) andtwo side spans (390m). The sag-span ratio of cable is 1/10, andthe transverse spacing between the two main cables is 35.6m.The streamlined steel box girder is 3.6m high and 36.9m wide.Of the three towers, two side-towers are made of concrete witha height of 178m. The tower located in the middle is 192m inheight and constructed with steel. All the towers are doorshapedin the transverse direction. But in the elevation view,the middle tower differs from the two side-towers with aninverted Y-type.Fig. 1. Taizhou Yangtze River BridgeThe computer program SAP2000 is used to establish a 3Dfinite element analytical model of the bridge. The steel girder,as well as the towers, is idealized as 3D beam elements, and thehangers and the cables are modeled using 3D bar elements. Inconsidering the nonlinear behaviors, effects of axial forceunder dead load on structural components geometricalstiffness are incorporated in the model. The girder is connectedby an elastic spring to the mid-tower but remains relatively freeat the side-towers in the longitudinal direction. In thetransverse direction, however, the girder is constrained to all the three towers. The 3D finite element analytical model ofTaizhou Yangtze River Bridge is shown in Fig.2.1/2/of the bridge site is carried outby Jiangsu Earthquake Bureau. According to the analysis, theseismic fortification intensity of the bridge site is assessed tobe 7 degree and the peak ground acceleration is 1.65m/s2：地震设防烈度为7度Fig.3presents one of these three pieces of horizontal groundaccelerations.3/4.1 Seismic demands on structure componentsFor Taizhou Yangtze River Bridge, a multi-tower suspensionbridge with large spans, nonlinear time history analysis methodcould be most proper in determining the seismic demand forthe bridge structure.This study presents an analytical methodology fordeveloping seismic fragility assessments for a long-span multi-towersuspension bridge, i.e. Taizhou Yangtze River Bridge.Based on the results of this comprehensive analytical study, thefollowing main conclusions can be made.For Taizhou Yangtze River Bridge, the smallestC/D ratio values are found to be at the bottom of the tower, ataround 1/4 height of the tower-column from the top of thetower, at some places of the pile foundations and at the saddleswhere the slip of the main cables may happen under the Ex+Ezearthquake input：地震输入DESCRIPTION OF THE BRIDGEA bridge has been approved to build by the government of Xining City, QinghaiProvince to connect the two sides of Huangshuihe River. As an important project ofXining city, the project owners determined to build a self-anchored suspensionbridge for aesthetic considerations. The bridge is a two-tower self-anchoredsuspension bridge with a span layout of 24m+65m + 158m+65m + 24 m, Figure 1shows the architectural effect figure of the bridge.The sag of the main cable is 26.333m and the span:sag ration is 6:1. The maingirder is a concrete box girder with a height of 2.2m and a width of 27.3m.There are 41 couples of vertical hangers with 25supporting the main span and 8 supporting each side spans. The hangers are evenlyspaced with a distance of 6m at the deck level on the side as well as main spansThe two towers have same height of 45.4m from the top of their pile capsA three-dimensional model (Figure 2, Figure 3) of the bridge was built inSAP2000 to perform the dynamic analysis. The coordinates system of the model wasset as x-axis along the longitudinal direction of the bridge, y-axis along thetransverse direction and z-axis in the vertical direction. Frame type elements havebeen used to model the girder, towers, piers, piles, main cables and hangers. Bearings and dampers were modeled with link type elements.Compression limit was set as zero for the main cables and hangers：主缆和吊杆不能压缩Seismic excitations were exerted on the bridge model in horizontal and verticaldirections simultaneously during the analysis process.For loading cases of time history analysis (THA), Rayleigh damping was used tomodel the damping of the bridge. To calculate the proportional coefficients of globalmass and stiffness matrix, 5% was chosen as the damping ratio of two dominantvibration modes which contributed most modal participating mass in the considereddirection of earthquake input.DYNAMIC CHARACTERISTICS OF THE BRIDGEThe boundary conditions of the deck were assumed as type A in Table 1. In orderto have a good understanding of the modal characteristics of the bridge, the modalanalysis was performed on the bridge model and the first 10 vibration modes ofwhich are listed in Table 2. As no constraints were applied in the