新世纪台湾桥梁的技术发展与远景

本拟介绍台湾桥梁的技术发展现况及近年来的代表作，也将探讨台湾桥梁所面临的问题及永续发展的远景。     

Behavior of Cyclically Loaded Squat Reinforced Concrete Bridge Columns Upgraded with Advanced Composite-Material Jackets

This paper summarizes comprehensive experimental studies on scaled models of squat bridge columns repaired and retrofitted with advanced composite-material jackets. In the experimental program, a total of 14 half-scale squat circular and rectangular reinforced concrete columns were tested under fully reversed cyclic shear in a double bending configuration. In order to provide a basis for comparison, a total of three as-built columns were tested. Another 10 column samples were tested after being retrofitted with different composite jacket systems. One circular as-built column was repaired after failure. The repair process involved both crack injection as well as addition of carbon/epoxy composite jacket. The repaired column was then retested and evaluated. Experimental results showed that all as-built columns developed an unstable behavior and failed in brittle shear mode. The common failure mode for all retrofitted samples was due to flexure with significant improvement in the column ductility. The repaired column demonstrated ductility enhancement over the as-built sample.     

Flexural Response of Steel Beams Strengthened with Partial-Length CFRP Plates

This paper presents the flexural behavior of rolled steel beams that were strengthened with partial-length, adhesive-bonded carbon fiber-reinforced polymer (CFRP) plates. The hybrid beams had two types of failure mode, depending on the length of the plate: (1) plate debonding in beams with short plates;?and (2) plate rupture at midspan in beams with long plates. The flexural behavior that was investigated includes the development of tensile stresses in the plate, the moment-curvature of the strengthened section, and the load-deflection of the strengthened beam. The analytical methods used include shear lag analysis, section analysis, and application of the virtual work principle. Agreement between the experimental results and the analytical predictions is discussed.     

Ultimate strength reliability analysis of corroded steel-box girder bridges

Structural reliability theory is a useful tool for estimating the risks associated with deteriorating structures. The aim of this study is to develop and demonstrate a procedure for the assessment of box girder bridge ultimate strength reliability with the degradation of plate members due to general corrosion taken into account. A probabilistic model for ultimate steel-box girder strength is established on the basis of an analytic formula that considers corrosion-related, time-dependent strength degradation. The study involves the selection of representative structures, formulation of limit state functions, development of resistance models for corroded steel-box girders, development of load models, development of a reliability analysis method, reliability analysis of the selected bridges and development of the time-dependant reliability profiles, including deterioration due to corrosion. The results of this study can be used for the better prediction of the service life of deteriorating steel-box girder bridges and the development of optimal reliability-based maintenance strategies.     

Dynamic and Impact Behavior of Half-Through Arch Bridges

The objective of this paper is to present the results of an investigation of the dynamic and impact characteristics of half-through arch bridges with rough decks caused by vehicles moving across them. Seven arch bridges modeled as three-dimensional structures with overall span lengths ranging from 20?to?200?m (65.5?to?656.2?ft) are analyzed. The American Association of State Highway and Transportation Officials Specifications HS20-44 truck is the applied vehicle loading used in the analysis and is simulated as a three-dimensional, nonlinear vehicle model with 11 degrees of freedom. Truck components include the body, suspension, and tires. The bridge deck surface is assumed to have a “good” surface roughness and is simulated using a stochastic process (power spectral density function). The effect on impact factors of span length, rise-to-span ratio, and vehicle speed is discussed. The results of the analyses show that the impact factors of bending moment and axial force will not exceed 0.4 and 0.25, respectively. The proposed impact equations are simple and conservative and can be used in the design of half-through arch bridges.     

Effect of Friction on Unbonded Elastomeric Bearings

This paper describes a theoretical analysis of a type of thermal expansion bridge bearing which could be used as a lightweight low-cost elastomeric seismic isolator for application to housing, schools, and other public buildings in earthquake-prone areas of the developing world. The analysis covers the effect of the frictional resistance of the supports on the vertical stiffness of this type of isolator. The most important aspect of these bearings is that they do not have end plates, which reduces their weight, but also means that they are not bonded to the upper and lower support surfaces and are held in place only by friction. This at first sight might seem to be a deficiency of this design, but it has the advantage that it eliminates the presence of tensile stresses in the bearings. It is these tensile stresses and the bonding requirements that arise from them that lead to the high costs of conventional isolation bearings. A theoretical analysis of the response of these bearings to vertical load shows that slip between the unbonded surfaces and rigid supports above and below can have a significant influence on the vertical stiffness and the internal pressure distribution.     

Theoretical Studies of the XY-FP Seismic Isolation Bearing for Bridges

The XY-friction pendulum (XY-FP) bearing is a modified friction pendulum that consists of two perpendicular steel rails with opposing concave surfaces and a connector. The connector resists tensile forces, allows independent sliding in the two orthogonal directions and enables small relative rotation of the rails about a vertical axis. Theoretical analyses were undertaken to study applications of XY-FP bearings to bridges. Two of the key features of the XY-FP bearing for the seismic isolation of bridges are: (1) resistance to tensile axial loads and (2) opportunity to provide a different period of isolation in each principal direction of the isolated structure. Numerical analyses on an XY-FP isolated bridge with different isolation periods in the principal directions subjected to near-field ground motions demonstrated the effectiveness of XY-FP bearings. Furthermore, numerical analyses that investigated the sensitivity of XY-FP isolation system response to differences in the coefficients of friction of the bearings demonstrated that bounding analysis using upper and lower estimates of the coefficients of friction will generally provide conservative estimates of displacements and shear forces for isolation systems with nonuniform isolator properties.     

Damage Analysis of Hanshin Expressway Viaducts during 1995 Kobe Earthquake. III: Three-Span Continuous Girder Bridges

Almost all the single reinforced concrete (RC) piers from P35 to P350 received consistently severe damage, considering the large residual inclination of piers included in earthquake-induced severe damage. However, some of the piers in the section from P35 to P350 remained lightly damaged, and this phenomenon is observed especially in many piers under fixed bearings in continuous girder bridges. In this study, using experimentally based models for metal bearings and installing them to an existing FEM code, a nonlinear dynamic response analysis of a continuous girder bridge system is conducted. It is shown that the results depend on the ground motion, but the fuse effect of the breaking of the bearings could have been a reason for the phenomenon.     

Differences between Calculated and Measured Long-Term Deflections in a Prestressed Concrete Girder Bridge

The monitoring of five precast, prestressed bridge girders during fabrication and service provided the opportunity to observe changes in camber over time. These camber variations were compared with corresponding strain and temperature measurements. Each of the girders was cast outside during the winter. As a result, the cold ground acted as a heat sink, and a significant temperature gradient existed during curing of each of the instrumented girders. These temperature gradients are believed to have caused the wide range in the short- and long-term cambers. A procedure to calculate the effect that curing temperatures have on girder camber is presented. In addition, the measured camber values are compared with predicted values using the multiplier method, improved multiplier method, and a detailed time-step method. It was found for the long-span girders that the measured camber values were on average within 10% of the predicted values using the detailed time-step method, but ranged from 22% lower to 27% higher for the simpler methods.