Advanced Materials Research Vols. 255-260

Abstract: For continuous girder bridges, each bearing has different function requirements under normal traffic conditions and under earthquakes of different intensity levels. To meet the requirements of the three-level seismic design for continuous girder bridges presented in this paper, a new kind of multi-defense seismic spherical bearing is developed and its configuration and working mechanism are introduced in this paper. Then the results of mechanical properties test of the bearing are presented and it’s shown that the design requirements are all satisfied and the seismic performance of the bearing is effective and reliable.

Abstract: FRP rubber bearing was developed just almost 10 years ago, and it is characterized by less weight, lower cost, and better damping capacity. In this paper, the concept of the FRP rubber bearing is introduced first, and a finite element simulation of the bearing is presented then. At last the effects of dimension parameters on the compression performance of FRP rubber bearing are investigated, including the tensile stresses of the FRP plates and the vertical stiffness of the bearing. The influence laws of the dimension parameters are preliminarily concluded, and which can be taken as a reference for the design of FRP rubber bearings.

Abstract: Earthquake ground motions were reasonally selected for the nonlinear dynamic time-history analysis conducted for a two-tower long-span cable-stayed bridge. The correlation between frequency content of earthquake ground motions and probabilistic seismic demands reveals that the geometric mean and dispersion of response spectra from earthquake ground motions have significant effects on probabilistic seismic demand assessment of long-span bridge stuctures and these effects are related to the difference of the shape of geometric mean spectra in the important period ranges where cumulative modal mass participation is significant. Response spectra of selected earthquake ground motions should match well with target spectra in the important period ranges. If input ground motions are reasonally selected, analytic results can be obtained more precisely and effectively and more amplitude parameters can be selected as intensity measures.

Abstract: A dynamic unstressed length link element and a catenary element are developed based on classical link element and catenary element, and a dynamic unstressed finite element method is proposed which takes unstressed length as input of the finite element and adjusts cable force by modifying unstressed length of element in finite element calculation. Only a finite element model for initial stage of rotation needs to be set in simulating bridge construction of vertical rotation from above to below, and the whole rotation process could be simulated only by adjusting unstressed length of buckle cable and tractive cable, the internal force of buckle, tractive cable and structure in each construction stage can be accurately calculated. This method can also be applied to tension process for cable-stayed bridge, suspension bridges and other cable structure bridges. This paper takes case study to show the correctness of this method and its practical engineering value in application.

Abstract: The existing Komurhan Bridge was built over the dam reservoir prior to water storage. The aging segmental post-tensioned concrete bridge with two lanes had an active sagging problem at its mid-span. As the traffic demand increased over the years, the authorities decided to add two more lanes to have a twin two-lane road for this part of highway network. Therefore, a need was developed to build a new bridge. Unlike the existing one, the suggested crossing needed to pass 300 meters wide water body with a depth of 45 meters to avoid piers at water body. Couple of alternatives was considered to cross the deep water at conceptual design phase. The focus of this study is given to the conceptual design of a cable-stayed bridge with two towers crossing the water at the narrowest location. This option results in a curved back span at one side of the water. A three-dimensional computer model was developed to assess challenges in design. Special care is given to the design details of the cables and the superstructure. Even if one of the back spans is curved, the proposed conceptual cable-stay bridge design is satisfactory under service and earthquake loads.

Abstract: Damping coefficient and damping exponent play a dominant role on the displacement constraint effect and the damping force of the fluid viscous damper. In this paper, parametric sensitivity study of the fluid viscous damper is carried out by using nonlinear dynamic time history method based on a long suspension bridge. Acceptable damping force and reasonable displacement between stiffening girder and tower are set as the optimization objectives of the damping parameters. It is shown that: as to long suspension bridge, bigger damping coefficient can lower the displacement but increase the force of the dampers, and the smaller damping exponent can aggravate the trend. Fluid viscous damper can play the biggest role of displacement constraint effect while with little additional seismic force is introduced in the whole structure with suitable damping parameters.

Abstract: Although located in the very low intensity area, the superstructure of Daxinglu Ramp Bridge sustained huge damage in Wenchuan earthquake. The longitudinal displacement of superstructure at the joint was about 400mm, which outdistanced the average displacement of all the other bridges in this area. In this paper, finite element model of the ramp bridge is made by general FEA software and the damage of the ramp bridge is analyzed by using nonlinear dynamic time history method. The results are obtained as follow: (1) the displacements restriction capacity of bearing system is reduced greatly by setting too many movable pot rubber bearings in the bridge. (2) The earthquake record near the bridge site is a typical long period ground motion. The extended natural period of the damaged bridge absorbed more but not less energy from the long period ground motion, which aggravated the damage.

Abstract: Compared to the traditional testing technology, the fiber bragg grating(FBG) test technology has many unique advantages and is suitable for the long-term structure health monitoring. By testing the stress and strain conditions of the corrugated steel pipe culverts under different fill heights with FBG sensors set in the inner and outer of the culverts, the mechanical properties of the steel pipe culverts could be obtained. The field fiber optic test results show that the FBG sensors can be used in the structures under complex engineering conditions. When the fill height is added, the FBG test results will change significantly in real-time, and the strain values of all test points on the culvert will change with the increase of the fill height, particularly in the top and bottom test points of the culvert. So the Fiber optic test technology can adapt to the testing requirements of the corrugated steel structure, and can provide a basis for the design of the corrugated steel pipe.

Abstract: In this paper, taken a steel box arch bridge as background, a FEA model is built and the stability is analyzed, including buckle stability and extreme stability. The results show that there are significant differences between buckle stability factor and extreme stability factor. It is a must to pay more attention to arch bridge stability.

Abstract: The shear bearing capacity of pretensioning prestressed concrete beam bridge mainly depends on the stirrup and concrete of the beam, but the longitudinal pre-pressure plays a certain role for the shear bearing of the structure. Under the carbonization corrosion condition, the shear-bearing capacity of the pretensioning prestressed concrete beam will attenuate gradually with the stirrup corrosion and concrete deteriorate. And the risk of brittle shear failure will be increased with the enhanced reinforcement corrosion amount. The paper presents an anti-shear calculation model of the pretensioning prestressed concrete beam bridge, and discusses the time-variation model of the corrosion stirrup considering the effective prestress attenuation under the carbonization corrosion condition. The analysis method on the anti-shear reliability of existing pretensioning bridges under the corrosion condition is proposed then. The method will be used in the durability and safety evaluation of the shear-bearing capacity of the existing pretensioning prestressed concrete bridges.