Papers in This Issue

This January 2013 issue of the Journal features six technical papers, one case study, one technical note, one discussion with a closure, and an erratum. All these manuscripts address different areas of bridge engineering. In the paper “Experimental Evaluation of the Scale of Fluctuation for Spatial Variability Modeling of Chloride-Induced Reinforced Concrete Corrosion,” O’Connor and Kenshel experimentally investigated the scale of fluctuation of the surface chloride content (Cs) and diffusion coefficient (Dapp) in modeling chloride-induced corrosion of RC based on the analysis of experimental data recorded on a bridge in southeast Ireland. They used maximum likelihood and autocorrelation curve fitting methods for the analysis. The introduction of the kriging statistical interpolation method is demonstrated to improve the reliability of the estimates of the scale of fluctuation. In the paper “Analysis of Eccentrically Loaded Adjacent Box Girders,” Kasan and Harries investigated the effect of rotation of the neutral axis of a box girder on impact damages. Common structural rating practices analyze the member about its horizontal axis, neglecting the effects of neutral axis rotation and thus overestimating the actual capacity of the member. The authors conducted a parametric study to analyze the effects of varying levels of damage to eight prototype adjacent box girders. Based on 106 analytical simulations, they proposed a relationship to determine the capacity of adjacent box girders subject to asymmetric loading, which includes the composite behavior of the barrier wall assembly and the effect of prestressing strands lost as a result of damage to the girder. This relationship is based on easily obtained capacity predictions and is shown to result in predictions of capacity, with an average absolute error of less than 6%. This study also examined, in the context of complete adjacent box girder bridges, the potential for in-service loading to exceed assumed design loads. In the paper “Bilinear $S\text{-}N$ Curves and Equivalent Stress Ranges for Fatigue Life Estimation,” Yen et al. provided information regarding the development of the new equivalent constant amplitude stress ranges for the bilinear $S\text{-}N$ curves produced analytically for estimating fatigue life of existing structures subjected to variable live load stresses. Results from a few examples are presented. The paper “Effect of Pier Section Reinforcement on Inelastic Behavior of Steel I-Girder Bridges” by Vasseghi presented the results of an analytical study on inelastic behavior of a four-span continuous composite bridge girder. The objective of this work was to evaluate the effect of pier section reinforcement on strength and ductility of the girder. The reinforcement consisted of two pairs of longitudinal ribs bolted to the web of steel sections adjacent to interior piers. Nonlinear finite-element analyses were carried out to determine the moment curvature characteristic of the pier sections. The results indicated that unreinforced sections fail because of local buckling on yielding of the compression flange, whereas the reinforced sections reach their plastic moment capacity with good ductility. Idealized moment-curvature curves were developed based on the nonlinear analyses of the sections. The idealized curves were then used to evaluate the behavior of the girder. The results indicated that strength and ductility of the girder improves substantially when the pier sections are reinforced. At failure, the maximum vertical deflection of the reinforced girder was approximately twice the deflection of the unreinforced girder. The ultimate load-carrying capacity of the reinforced girder was also significantly larger than that of the unreinforced girder. In the paper “Numerical Simulation of Vortex-Induced Vibrations of Inclined Cables under Different Wind Profiles,” Chen et al. investigated vortex-induced vibration of an inclined cable under wind with varying velocity profiles through computational fluid dynamics numerical simulation. As a complicated fluid-structure interaction issue, the flow field around the freely oscillating cable was simulated. The shear stress transport (SST) turbulent model based on the Reynolds-averaged Navier-Stokes (RANS) method was used to simulate the behavior of turbulent flow in the computational fluid dynamics (CFD) numerical simulation. This computational method and turbulent model was validated through comparison of the computational results with the wind tunnel test results of a rigid circular cylinder. Two inclination angles, 30 and 90°, were chosen for the inclined cable; wind with a uniform velocity profile (velocity profile U) and four types of velocity profiles were used as the inlet velocity conditions. On the basis of the cable vibration and flow field obtained under wind with varying velocity profiles, characteristics of the cable vibrations and aerodynamic coefficients in both time and frequency domains, as well as the wake patterns, were analyzed. The results indicated that the cable vibration exhibits both single-mode and multimode vibrations. The single-mode vibration of the cable exhibited a standing wave response, whereas the multimode vibration exhibited a traveling wave motion. The single-mode vibration had large lock-in regions (the entire cable length or the upper segments of the cable). Vortex shedding was found to be in-phase or synchronous over these regions. However, for a multimode vibration (wind with large velocity changes), the vortex shedding was irregular and complicated along the cable axis. The paper “Monitoring and Analysis of Abutment-Soil Interaction of Two Integral Bridges” by Pétursson and Kerokoski presented field tests of two jointless bridges, focusing on the magnitude and significance of earth pressure behind the abutments. Instrumentation was used to measure the horizontal displacement of an abutment, abutment rotation, abutment pile strains, earth pressures behind the abutments, superstructure displacements, frost depth, and air temperature for the 56-m-long, continuous three-span Haavistonjoki bridge. The measured earth pressures were compared with pressures that had been calculated on the basis of Nordic codes of practice and Eurocodes pertaining to bridges. The bridge over the Leduån is a single-span composite bridge with a cast-in-place concrete deck on top of two steel beams. This bridge, spanning 40 m, is slender, with a 1.7-m-high superstructure. The bridge was fitted with strain and displacement gauges, and short-term measurements were made using a loaded truck. The field test results for this bridge were verified with calculations based on a developed abutment rotation stiffness calculation model.

The case study “Strengthening of Slab Action in Transverse Direction of Damaged Deck of Prestressed Box Girder Bridge” by Rai et al. discussed a case study of a prestressed concrete (PSC) box girder that developed early damage to the deck because of poor placement of concrete at the time of construction, as established by the in situ nondestructive and core tests. The possibility of total replacement of the top deck was ruled out because of the disruptive and tedious nature of the process, which could endanger the overall stability of the box girder. Strengthening of the deck was performed by installing a series of steel joists at the underside of the deck slab and adding a thin overlay of concrete at the top to restore it to the requisite strength. This approach was best suited, for it not only improved the stress distribution in the deck but also maintained the original load resistance mechanism provided by the prestressing arrangement in the girder. The presented scheme was easy to implement and can be used for similar damages occurring to the deck of PSC box girder bridges.

The technical note “Performance Evaluation of RC Beams Strengthened with an Externally Bonded FRP System under Simulated Vehicle Loads” by Wang et al. investigated the effect of transient vehicle loads present during the installation of carbon fiber-reinforced polymer (CFRP) on the bond performance between the CFRP and the concrete substrate. A total of eight RC beams were tested. Two were unstrengthened reference beams; five were strengthened with CFRP sheets and subjected to transient loads; the final beam was strengthened with CFRP sheets and subjected to only a sustained static load. The test parameters included the amplitude of the transient load, the anchorage length of CFRP sheets, and the reinforcing/strengthening ratio. The transient loads were continued for 2 days (during CFRP cure) before all five CFRP-strengthened RC beams were tested to failure in four-point flexure. The test results were compared with those of the reference beams and the one strengthened under a sustained load. It was shown that a 1-Hz sinusoidal transient load varying between 30 and 50% of the ultimate capacity of the unstrengthened beam during the installation and curing of CFRP sheets does not affect the structural performance of CFRP-strengthened RC beams. Results presented in this paper demonstrated the applicability of the fiber-reinforced polymer strengthening technique for bridge girders that are subjected to continuous vehicle loads.

This issue has a discussion on “Experimental Study on the Performance of Approach Slabs under Deteriorating Soil Washout Conditions” by Zanuy and Albajar. The authors Chen and Chai presented their closure. The issue also has an erratum on “Calibration of Live-Load Factor in LRFD Bridge Design Specifications Based on State-Specific Traffic Environments” by Kwon et al.