Journal of Bridge Engineering

This study investigates the distortion behavior of steel plate girders under the cumulative influence of welding and hot-dip galvanizing processes and is presented in two papers. This paper presents the results of a parametric study on the effects of girder geometry (length, depth, flange and web thickness, and stiffener placement) on distortions during hot-dip galvanizing. Nonlinear simulations were carried out using the commercial software Abaqus. It was found that girder length did not strongly affect girder distortion trends, but changes in girder depth and flange-to-web-thickness ratio did. Including stiffeners was found to offer some benefit to controlling distortion during galvanizing; however, the results also indicated that more stiffeners were not necessarily better. The results supported industry recommendations. The results of this study provide guidance to engineers, galvanizers, and fabricators to minimize steel plate girder distortion so that they can more confidently use hot-dip galvanizing to protect their bridges, and it presents a novel modeling framework that will enable significant future work in this field of study.

This paper, the second of a two-part series, presents a parametric study investigating the influence of welding and galvanizing practices on the susceptibility of welded plate girders to distortion during and after galvanizing. Three methods of welded fabrication were studied: welding in lay-down position, welding in the trough, and welding in the vertical position. In addition, galvanizing dipping and extraction speed, dwell time in the zinc bath, and dipping angle were examined as parameters. It was found that welding in the vertical position corresponded to the least distortion during galvanizing, especially for unstiffened plate girders. Dipping speed was also identified as an important parameter for reducing distortion, and faster dipping and extraction speeds resulted in less distortion during and after galvanizing. The results of this study provide guidance to engineers, galvanizers, and fabricators to minimize steel plate girder distortion so that they can more confidently use hot-dip galvanizing to protect their bridges, and the paper describes a modeling methodology that will enable future research in this field.

The architectural potential of tensegrity structures is proven. Yet, paradoxically, very few real construction projects have been built around the world. The main reasons are complex construction processes, lack of design and optimization guidelines, and excessive self-weight due to the prestress needed to guarantee stiffness and dynamic behavior. Hence, optimizing the stiffness and self-weight is a key aspect when designing a tensegrity footbridge. Previous research has demonstrated the validity of a design and optimization methodology, based on morphological indicators, that identifies geometry with a maximum stiffness and/or a minimum self-weight for a family of structures. In this paper, that methodology is applied to footbridges composed of tensegrity modules comprising simplex, quadruplex, pentaplex, and hexaplex types. A comparison of the stiffest and lightest structures is provided, a practical case study is developed, and the relevance and feasibility of such tensegrity footbridges are discussed. As a result, the study provides advice on optimum footbridge topologies with the following characteristics: excellent stiffness and dynamic behavior; efficient structures composed of simplex modules; and self-weight that is still rather high but similar to that of bended structures, although with potential to be reduced thanks to optimization of the prestress scenario.

A comprehensive condition assessment of long-span prestressed concrete (PSC) continuous box-girder bridges in service is the foundation of bridge maintenance and management. In this paper, first, the original interval evidence theory is improved through the conflict test of original evidence and the correction of conflict evidence based on credibility. Second, a new comprehensive condition assessment method considering the interval uncertainty of measured data and the impact of measured conflict data is proposed for long-span PSC continuous box-girder bridges through the natural integration of the improved interval evidence theory (IIET) and the fuzzy analytic hierarchy process (AHP). Third, to illustrate the implementation process of the proposed method, a three-span PSC continuous box-girder bridge is assessed considering the effect of spatial variability of materials and structural dimensions. The advantages of the proposed method over the existing AHP assessment method and the traditional combination method are verified by comparing the condition assessment results with the actual status of components or the whole bridge.

Adjacent concrete box beam bridges constitute more than 15% of bridges built or replaced each year and have been in service for many decades. A recurring problem with this type of bridge is cracking in the longitudinal joints between adjacent beams, which allows water and salt leakage through the joint and reflective cracks in the wearing surface. In this paper, a comprehensive review of the past literature is presented to identify potential reasons joint cracking is induced. An innovative connection was then designed with a wide joint, shrinkage-compensated concrete, a rough interface between the joint and box girder, and reinforcing steel that crosses the interface between the joint and box beam, to overcome the problems mentioned in the literature review. The design was evaluated on four small-scale specimens designed with different amounts of transverse reinforcement. The specimens were monitored for early-age joint behavior and then tested for ultimate capacity. A three-dimensional (3D) finite-element model (FEM) was developed to simulate early-age joint behavior and determine the stress distribution in the joint and at the interface between the joint and the box beam concrete. The shrinkage, temperature, and strain data collected during the early-age monitoring were used to validate the FEM. Both experimental and finite-element analysis results indicate that the innovative joint showed good performance in resisting joint cracking when subjected to joint material expansion and the heat of hydration. The results also indicate that the expansion of the joint material formed a compression-dominated joint, which would naturally inhibit crack formulation. The transverse reinforcing steel across the interface resisted the expansion of the joint material and resulted in some additional transverse compression in the joint.

This study presents the results of spaceborne monitoring of two posttensioned bridges in Virginia. Routine safety inspections revealed extensive cracking in the concrete girders. Problems were traced to the inadequate quality of tendon grouting, resulting in the partially bonded condition. The TerraSAR-X radar satellite, operated by the German Aerospace Center, was used to acquire radar imagery in the Staring SpotLight mode from the ascending and descending orbits at 11-day intervals. The data were processed with the SqueeSAR algorithm, resulting in millimeter-range precision of the time-displacement series. No permanent deformations were detected at the posttensioned segments during the monitoring period of 1.3 years. The high density of the measurement points allowed adequate characterization of bridge displacements. The results of the interferometric analysis attest to the feasibility of implementing satellite-based performance monitoring of bridges, offering an innovative asset management tool that can complement and augment current inspection methods.

This study proposes an approach for developing seismic fragility models based on elastic net regularized logistic regression and applies it to two railway bridge classes typical to the central and southeastern United States (CSUS). Railway bridge class fragilities are not available in the literature despite recorded evidence of earthquake damage to railway bridges. The introduction of elastic net regularization helps in selecting the best set of predictor variables for fragility modeling even if they are mutually correlated. The proposed fragility models are compared to their corresponding highway bridge counterparts, given that current practice in regional risk assessment recommends adopting these as proxies for railway bridge fragility. The analysis reveals that multispan simply supported steel girder railway bridges, the most common bridge class, show lower fragility than their corresponding highway bridge counterparts. However, multispan simply supported steel through plate girder railway bridges, the other common bridge class, show comparatively higher seismic fragility. The proposed fragility models serve as key inputs in a broader framework of quantifying seismic resilience of railway networks, as well as providing a practical baseline for seismic loss assessment and retrofit prioritization.

A numerical parametric study was conducted with two primary objectives: (1) to investigate the accuracy of existing AASHTO shear distribution factors for prestressed concrete girder bridges in the United States; and (2) to provide recommendations to more accurately rate bridges for shear and permitting. Results from the parametric study indicated that the longitudinal stiffness (girder composite longitudinal moment of inertia divided by cube of span length) to transverse stiffness (transverse deck strip moment of inertia divided by cube of beam spacing) provided an indication of the elastic shear distribution in nonskewed bridges. Shear distributed more broadly to adjacent girders when the ratio of longitudinal to transverse bending stiffness was lower. The stiffness ratio can be used as a screening tool to delineate cases for which AASHTO shear distribution factors are conservative or unconservative relative to results of detailed finite-element or grillage analyses. Because grillage analyses can account for the distribution of shear associated with truck axle position, they can be used to better determine permit truck demand.

In the last six decades, closed-box orthotropic steel girders have been widely used in cable-supported bridges. Several parametric studies were previously carried out to reduce inherent fatigue stress problems and to generally improve bridge girder designs. However, in most cases, only one or two parameters were studied simultaneously; hence, the full potential of orthotropic girders is not achieved. In the present work, a multiscale finite-element (FE) model of a suspension bridge is established with sophisticated boundary conditions applied to a local parametric submodel of a bridge girder. With this local model an automated gradient-based parametric optimization is carried out with the goal of minimizing the weight and price of the girder. It is possible to simultaneously optimize several design variables and fulfill constraint functions on fatigue stresses, deformation, and buckling. The results show potential weight savings of 6%–14% and price savings of 9%–17%, mainly found by using thinner plates and narrower troughs. Besides the explicit savings, the results indicate the potential for applying gradient-based optimization in civil engineering designs.

In order to reduce the self-weight of conventional steel-concrete composite girders and to improve the crack-resisting behavior of normal strength concrete (NC) bridge decks for long-span cable-stayed bridges, an innovative steel–ultrahigh performance concrete (UHPC) composite girder was proposed. Coarse aggregates (CA) were added to UHPC to control shrinkage and cost. On the basis of the Fifth Nanjing Yangtze River Bridge (FNYRB), a 2 × 600 m cable-stayed bridge in China, a series of experimental tests was conducted. The studies aimed to reveal the material properties of UHPC with and without CA and the static and fatigue flexural performances of the reinforced UHPC deck with CA. The test results implied that the UHPC with CA had compressive strength and flexural strength comparable to UHPC without CA, but the former exhibited much lower shrinkage strains under the natural curing condition. The static bending test results showed that the steel fibers and steel reinforcement bars could effectively control the propagation of cracks in UHPC. The average nominal cracking strength of the UHPC bridge deck specimens was 13.8 MPa, about 1.97 times the maximum tensile stress in the design requirement of the FNYRB under serviceable design loads. Further, the fatigue bending test results demonstrated that the cracks in UHPC propagated very slowly under cyclic tensile stresses, and the residual flexural loads were only 7.2% and 10.9% lower than the ultimate loads obtained for specimens free from the fatigue loading processes. Thus, the current study verified the safety of applying UHPC with CA to long-span cable-stayed bridges.

In bridge tower designs, the cross beam provides the connection for a special lean-on bracing, which effectively enhances the lateral load transfer mechanism of the bridge tower. This study investigated the adequately rigid cross beam for a bridge tower based on elastic buckling and second-order analyses of a symmetrical portal frame. To obtain exact closed-form solutions, a classical matrix structural analysis approach considering a second-order effect was applied. First, the global structural stiffness matrix was formulated by combining the element stability stiffness matrices after coordinate transformation. Then the buckling axial load was formulated in the elastic buckling analysis. The lateral stiffness and bending moment of the bridge tower were formulated in the second-order analysis. These structural behaviors were then plotted in relationships with the cross-beam rigidity for given column inclinations. The tower lateral stiffness and the column base bending moment owing to the increase in the cross-beam rigidity had an asymptotic trend approaching the behaviors associated with an infinitely rigid cross beam. Considering this asymptotic trend, the adequately rigid cross beam requirements for the stiffness and strength behaviors were formulated and recommended for bridge tower designs. A detailed design procedure and an elementary design example are presented. Design implications for multiple-cross-beam bridge towers and bridge piers are also noted.

The National Bridge Inventory reports indicate that a noticeable portion of the United States bridge infrastructure is drastically approaching the end of its intended design life, mainly due to environmental effects such as corrosion. This necessitates developing new techniques and materials for the rehabilitation of these deficient structures in a timely manner. To address this issue, a repair method has been developed at Florida International University (FIU) using ultrahigh-performance concrete (UHPC). This paper investigates the performance of the proposed retrofit method through experimental studies. A total of 11 1/4-scale columns with equal height-to-diameter ratios (H/D = 5) were cast and intentionally damaged to simulate a deficient column. Three columns with different transverse reinforcement ratios were considered as the baseline, seven of the columns were repaired using UHPC, and one was repaired with normal strength concrete (NSC) to compare. The retrofitted columns were subjected to combined constant vertical axial and cyclic lateral loads. The obtained experimental results revealed that the UHPC shell increased the strength of the damaged elements without increasing their size.

Integral abutment bridge (IAB) length is limited by the lateral displacement capacity of the piles supporting the bridge. This paper presents a numerical study calibrated to experimental tests to investigate the lateral displacement capacity of H-piles (HPs) in integral abutment bridges subjected to combined axial load and cyclic displacement amplitude. Eleven steel HP sections with two axis orientations (weak and strong) commonly used in IAB construction practice were investigated. Several soil types surrounding the piles were examined to investigate the effect of soil stiffness on displacement capacity. Buckling displacement capacity was found to be an average of 3 and 1.5 times the plastic moment capacity for weak and strong axis bending, respectively. It was revealed that soil stiffness has a significant impact on the onset of local buckling of the piles. Based on computed pile displacement capacities, the maximum length of integral abutment bridges was estimated and compared with the current practice of US departments of transportation.

Orthotropic steel decks have been applied after World War II to long-span bridges due to several advantages, such as light weight, high strength, rapid construction, durability, and life-cycle economy. However, depending on the relative slenderness of their components these decks may be quite susceptible to traffic-induced fatigue cracks. Therefore, fatigue problems in orthotropic steel bridge decks and predicting the remaining fatigue life of their welded details are nowadays a challenging problem for bridge engineers and researchers. The recommendations for the estimation of the remaining fatigue life of steel bridges recently prepared by the European Convention of Constructional Steelwork (ECCS) were applied to predict the remaining fatigue life of an existing orthotropic deck bridge built in 1981. This approach follows the principles and application rules in the Eurocodes. Detailed fatigue calculation and supplementary testing were performed for two details, which were estimated to be the most critical for fatigue according to preliminary evaluation. The prediction showed that the remaining fatigue life of the details is practically unlimited despite nearly 40 years of service.