Journal of Bridge Engineering

This article describes the research work relating to the assessment and control of human-induced vibration of an unusual curved cable-stayed bridge with separate road and pedestrian decks. Dynamic simulations of human-induced vibration were performed with a mode-by-mode approach, and the results showed that a total of eight lateral and vertical modes of the bridge may suffer from excessive vibrations at the design crowd density. A hybrid control scheme was developed for control of human-induced vibration, which consists of steel braces fitted between the road bridge deck and the pedestrian deck to improve structural stiffness and eddy current tuned mass dampers to enhance damping ratios of lively modes. The modal properties of the bridge with steel braces were experimentally obtained by dynamic tests and used for parameter tuning of mass dampers. The performance of the hybrid control strategy was evaluated by group tests of up to 400 pedestrians. It is shown that the critical number of pedestrians triggering synchronous lateral excitation is generally in good agreement with the empirical model developed from measurements on the London Millennium Bridge, but the measured vertical acceleration amplitude is only about 40% of the prediction under the same pedestrian density. The damping ratios for both the vertical and lateral modes increase appreciably after installation of tuned mass dampers and no evidence of large-amplitude vibrations has been observed.

Advances in fiber-reinforced polymer (FRP) technology have led to the introduction of new basalt-fiber-reinforced-polymer (BFRP) bars. This paper presents a research project investigating the behavior of edge-restrained concrete bridge-deck slabs reinforced with BFRP bars. The tests included six full-scale edge-restrained concrete deck slabs simulating a slab-on-girder bridge deck commonly used in North America and one full-scale unrestrained concrete deck slab. The deck slabs measured 3,000 mm long × 2,500 mm wide × 200 mm thick. The test parameters investigated were (1) reinforcement type (BFRP and steel); (2) BFRP bar size (12 and 16 mm); (3) reinforcement ratio in each direction (0.4–1.2%); and (4) edge-restraining [restrained or unrestrained (free)].The slabs were tested up to failure over a center-to-center span of 2,000 mm under a single concentrated load acting on the center of each slab over a contact area of 600 × 250 mm to simulate the footprint of a sustained truck wheel load (87.5-kN CL-625 truck) as specified in Canadian standards. The observed mode of failure for the edge-restrained deck slabs was punching-shear, with carrying capacities exceeding the design factored load specified by Canadian standards.

An experimental study was conducted in which five identical, full-scale bulb-T bridge girders were constructed and tested to shear failure. Although the shear span was kept the same for all of the tests (a = 3d), the distance from the end of the specimen to the center of the support bearing (overhang length) was varied. Varying the overhang length controlled whether or not the critical section subject to shear fell within the transfer length, which affected whether the specimen failure was caused by a traditional shear mechanism (web crushing, flexure-shear, etc.) or a nontraditional shear mechanism (e.g., horizontal shear or shear failure induced by anchorage zone distress). The shear failure values were compared with each other to investigate whether nontraditional shear mechanisms result in a lower capacity than traditional mechanisms. These values were also compared with nominal design capacities related to each different failure mechanism.

Although several models are available for evaluating the structural performance of corroded reinforced concrete (RC) structures, seismic reliability assessments considering the effect of steel corrosion are currently scarce. Determining how long existing RC structures in an aggressive environment will be able to have a seismic safety level greater than the threshold remains difficult. Life-cycle reliability assessments of these structures under seismic hazards and hazards associated with airborne chloride are discussed in this paper. When predicting the seismic reliability of existing RC structures, observational data from inspection and/or nondestructive testing methods could be used to estimate the current material corrosion level. Considering the effect of steel corrosion in the plastic hinges of deteriorating structures on their seismic capacity is important. The displacement ductility capacity at the occurrence of longitudinal buckling of rebar in RC structures depends on the steel corrosion level in the plastic hinges. In this paper, the methodology to estimate the mean and variance of steel weight loss in the plastic hinge of corroded RC structures based on inspection results is presented. The number and space interval of inspection locations are considered when conducting the statistical estimation error process. The parameters to estimate the steel weight loss in the plastic hinges incorporating the spatial variability in steel corrosion are derived from experimental results to visualize the steel corrosion in RC members by X-ray technology. In addition, random variables associated with the prediction of time-variant steel weight loss are updated by sequential Monte Carlo simulations (SMCS) for consistency with the inspection results. The epistemic uncertainties can be reduced by SMCS. This process helps to conduct the reliability analysis more precisely. In this paper, a novel procedure for estimating the reliability-based life-cycle seismic reliability of existing RC structures in a marine environment by incorporating the spatial steel corrosion distribution is presented. In an illustrative example, the effects of the inspection results and frequency and the hazards associated with airborne chloride on the updated cumulative-time failure probability of a RC bridge pier in an earthquake-prone region are discussed.

Bridge weigh-in-motion (WIM) uses existing bridges to find the weights of vehicles that pass overhead. Contactless bridge weigh-in-motion (cBWIM) uses bridges to weigh vehicles without the need for any sensors to be attached to the bridge. A camera is mounted on the back of a telescope, which magnifies the image to the extent that submillimeter bridge deflections can be measured accurately. A second camera is used to monitor traffic and to determine axle spacings. The two cameras are synchronized using light-emitting diodes (LEDs) activated by an interval timer. The exact position of the test vehicle relative to the bridge influence line is determined by optimization at a postprocessing stage. The new WIM concept was tested on a bridge in the United Kingdom. In a modest test sample of eight statically weighed vehicles, cBWIM was shown to be a feasible alternative to other forms of WIM. Accuracy of gross weight is already reasonably good; accuracy of groups and individual axles will require greater magnification or additional cameras.

Sustainability of modern civil engineering structures is the broad objective of the present paper. Infrastructures should be designed and built to be used satisfactorily over longer life spans without collapse or deterioration requiring major repair. Progress in materials, analysis, and design makes it possible to achieve a life span for concrete infrastructures of 100–125 years. An appropriate life span can be a contractual requirement for all civil engineering infrastructures. For these objectives, provisions for lasting satisfactory serviceability are increasingly adopted in codes. Only deficient serviceability or strength, developing gradually over a number of years, is discussed. Lessons to be learned from collapse, excessive deflection and cracking of bridges, and intolerable sagging of slab floor are discussed. The paper presents limited means to control long-term deflection and cracking of bridges, including slab bridges and flat-plate floors; other recommendations that enhance sustainability of future infrastructures are put forward.

Lateral load-resisting structural members, such as piers, are often analyzed under one component base excitation. The influence of bidirectional shaking is accounted for by using a simplified 30% rule. During seismic shaking, piers are often subjected to bidirectional ground motion, which leads to a complex combination of biaxial moments. In this backdrop, a RC bridge pier has been analyzed under a set of bidirectionally applied near-field motions with forward directivity (FD) and fling-step characteristics. Bidirectional interaction under near-fault motion is observed to substantially amplify damage, particularly for a stiff system (30% and 45%–50% under FD and fling motions, respectively). A complex combination of bidirectional load paths may have also contributed to increased vulnerability. Additional studies have shown that pulses with fling-step characteristics may often be more detrimental than FD, at least for the first mode-dominated systems. The roles of important ground-motion parameters, such as Arias intensity, mean period, and significant duration, that regulate this interaction effect are discussed. Using energetic length and mean period as characteristic linear and time dimensions, a self-similar response scenario has emerged even when degradation, complex loading patterns under bidirectional shaking, and record-to-record variability coexisted. Geometric nonlinearity in the presence of an axial force may have intensified the interaction effect, as revealed through a sample code-designed pier.

Steel jacketing has been used extensively in the United States to retrofit seismically deficient bridge columns. This procedure, which consists of encasing a RC column in a steel jacket, is effective in providing a ductile seismic response but does not enhance the blast resistance of the column. This is because a gap is typically left at the top and bottom of the jacket to prevent increased flexural strength, such as to avoid undesirable overload of the footing or cap beam. Blast tests have demonstrated that direct shear failure can develop at these gap locations. A modification to steel-jacketed columns is proposed here to provide an added blast resistance. It consists of structural steel collars placed around the gaps and tied to the adjacent elements with postinstalled anchors. Blast tests were conducted to investigate the effectiveness of this simple proposed detail. Experimental results indicated that the concept was effective in preventing direct shear failure. Severe blast load demands were applied to investigate the behavior of the retrofitted column under extreme ductility demands. All specimens exhibited satisfactory ductile behavior, except one, which uncharacteristically failed due to fracture of the tube’s vertical weld seam.

Steel H-piles (HP shapes) are most commonly available as ASTM A572 Grade 50 material, having a nominal yield strength of F_y = 50 ksi (345 MPa). However, until fairly recently, HP shapes were typically available as ASTM A36 shapes, for which F_y = 36 ksi (248 MPa). Many state DOT provisions for driven piles continue to base design structural capacity calculations on the lower yield stress. In this paper, a parametric study investigating the impact of increasing the yield capacity from F_y = 36 ksi to F_y = 50 ksi on design structural capacity and driving analysis of steel H-piles is presented. Results of the parametric study indicate that the AASHTO-permitted pile capacity of 0.5 A_gF_y is not achievable without a reduction in the required overstrength factor of 2 (based on assessing driveability by wave analysis only), and even then, this capacity may only be achievable for smaller pile sections. Driving piles to the maximum permitted driving stress of 0.90 F_y = 45 ksi (310 MPa) resulted in pile capacities at refusal ranging from 0.64 to 0.76 A_gF_y, with smaller pile sections having marginally higher achievable capacities. A representative cost analysis led to the conclusion that increasing the design capacity of a pile results in a decrease in cost per driven pile capacity, although, because of the need for larger hammers and cranes, permitting design capacities greater than 16.5 ksi (114 MPa) results in only marginal additional savings.

This paper presents an improved softened membrane model for the analysis of reinforced concrete (RC) circular bridge columns under torsion loading. Concrete exhibits higher tensile strength and stiffness due to the strain-gradient effect under torsional loading. Results of previous studies suggest that the inclusion of strain-gradient and bidirectional stress effects improves prediction of the torsional behavior of concrete members. However, the influence of strain-gradient and bidirectional effect stresses on the torsional response of circular columns has never been investigated. With this paper, the authors aim to fill the existing knowledge gap in this important area of research by proposing a modified softened membrane model for torsion (SMMT) for circular columns. The authors also recommend a new tension–stiffening relationship of concrete for improved predictions. The estimated analytical response is compared with experimental data, and a good correlation can be seen. Predictions from the proposed model are also compared with the classical rotating-angle softened truss model (RA-STM) to illustrate the efficacy of the proposed model. Parameters such as postcracking stiffness, peak torque, and twist at peak torque are captured by the improved SMMT better than with the existing RA-STM. The improved model can be used also for developing simplified design equations.

Steel and concrete bridge structures that serve as the backbone of U.S. transportation and navigational infrastructure systems have been exhibiting moderate to severe deterioration within a few years of service. The focus of this paper is on the rehabilitation of water-submerged bridge steel piles using precured glass-fiber-reinforced polymer (GFRP) shells wrapped with water-curable GFRP prepreg fabrics. The GFRP shells were placed around the corroded steel piles of the East Lynn Lake Campground Bridge in Wayne County, West Virginia, and wrapped with GFRP fabrics. The space between GFRP shells and steel piles was filled with self-consolidating concrete to strengthen and protect the piles from further deterioration. Prior to field implementation, experiments were conducted on concrete cylinders embedded with steel I-sections that were encased by a polymeric shell and FRP wrap system to evaluate the load transfer mechanisms and increase in concrete strength as a result of confinement. To increase the load transfer between embedded steel and concrete, steel rods and angles were welded to the steel I-sections, which resulted in a 92% or higher degree of compositeness. Using the GFRP shell and wrap system, the bridge was restored to its design capacity at approximately 10–15% of its replacement cost.

An innovative lightweight composite deck (LWCD) is proposed for steel bridges to avoid premature fatigue cracking. The composite deck is composed of an open-ribbed orthotropic steel deck (OSD) and a thin ultrahigh-performance concrete (UHPC) layer. This study is based on a suspension steel bridge in China, namely, the Second Dongting Lake Bridge. The following investigations were performed: (1) preliminary finite-element analysis (FEA) was carried out to evaluate the vehicle-induced stress ranges (i.e., Δσ = σ_max − σ_min) of six typical fatigue-prone details; (2) parameter analyses were performed to investigate the effects of the shape of cutouts and the thickness of the floor beams; and (3) two fatigue tests, one that used a full-scale LWCD panel and another that used a LWCD beam specimen, were conducted to reveal fatigue performance of the OSD and the stud shear connectors, respectively. Results of the preliminary FEA show that, with the contribution of the UHPC layer, the vehicle-induced stress ranges at some fatigue details of the LWCD, such as the rib–deck plate welded joints and the splice welds of the longitudinal ribs, were reduced to be less than their constant-amplitude fatigue limits, which indicates theoretically infinite fatigue lives of these details. The parameter analyses reveal that the apple-shaped cutout had relative good fatigue properties among the four cutout schemes and that the thickness of the floor beams is recommended to be 14–18 mm. According to the fatigue tests on the composite panel specimen and on the composite beam specimen, both the open-ribbed OSD and the stud shear connectors exhibited satisfactory fatigue endurances, which were much greater than 2 million cycles. The current theoretical and experimental investigations reveal that the proposed open-ribbed LWCD has favorable fatigue performances.

The transverse joint between full-depth precast concrete panels in accelerated bridge construction (ABC) is a critical element for satisfactory performance of bridge decks. Live loads on bridge decks are caused by concentrated loads from truck tires. The shear capacity of new female-to-female grouted transverse joints constructed with precast concrete panels under concentrated loads was investigated and compared to experimental results. The experiments were carried out on transverse joints posttensioned with carbon-fiber-reinforced polymer (CFRP) rods and on non-posttensioned joints. A finite-element model was developed to determine stress transfer of concentrated loads at transverse joints. Two different design distribution widths were investigated based on (1) AASHTO recommendations and (2) finite-element analysis. Four methods were considered for calculating transverse joint capacity: shear friction, strut-and-tie model, principal tension stress, and a beam shear equation under axial compression. The shear friction method predicts the capacity with satisfactory accuracy for non-posttensioned joints and is conservative for posttensioned joints; the strut-and-tie model predicts the capacity of posttensioned joints with satisfactory accuracy.

Reinforced concrete (RC) highway bridges are essential lifeline structures, especially in California, which has numerous active faults at which earthquakes are common occurrences. Accurate seismic structural analysis is important to ensure their safety. The most suitable analytical simulation method for this purpose is nonlinear time-history analysis (NTHA). However, one of the main challenges for NTHA is related to the convergence of the numerical solution, which usually arises at high levels of nonlinearity. Inherent lack of high degrees of redundancy of the bridge systems and the need for their continuous functioning in the aftermath of an earthquake require accurate modeling and robust numerical solutions for the response investigation of these important structures. This paper presents solutions to the problems of convergence encountered in NTHA of RC highway bridges during the use of direct integration algorithms. The considered numerical integration algorithms include two that are explicit, namely, the Newmark and operator-splitting algorithms, and one that is implicit, namely, the TRBDF2 algorithm. Applicability of these integration algorithms, instead of the commonly used implicit Newmark, is explored for three representative RC highway bridges in California. Furthermore, the suitability of an adaptive switching among these integration algorithms during the NTHA is investigated. Finally, the efficacy of the solutions is demonstrated for a challenging performance-based earthquake engineering-related subject that involves a large number of NTHAs to identify the predominantly first-mode engineering demand parameters.

This study investigates the seismic behavior of the connection between concrete-filled steel tube piles and concrete pile caps. This connection is an important component of an accelerated bridge construction technique, which involves driving steel piles to a finished elevation just below the design deck level, forming a pile cap around the ends of the driven piles, reinforcing this cap, and then filling both the piles and formwork with concrete. This cap will then serve as the deck support system. In this research, a total of six connection specimens with various details were tested under lateral loads until failure while monitoring applied loads and lateral displacements. All of the specimens achieved the desired moment capacity, and all but one experienced a typical progression of damage in the concrete cap. This progression initiated with crushing of the concrete (interior and exterior), was followed by yielding of the longitudinal reinforcement, and concluded with yielding of the transverse reinforcement and the formation of diagonal cracks extending from the embedded pile to the edge of the cap. Based on the results of this and a previous investigation, an initial design methodology is proposed.

The precast segmental construction is advantageous for rapid erection, high quality of concrete segments, and minimal disturbance to traffic. This paper compares two different tendon layouts of a segmental bridge erected by the span-by-span method. These comparisons include the stress analysis based on the 14-degrees of freedom (DOF) spatial beam model that considers warping, construction speed, and constructability. A simplified two-dimensional (2D) planar model for the reinforcement design of a rib deviator was proposed. The tensile stress region method (TSRM) was applied in the reinforcement design of the diaphragm in this type of bridge; thus the original reinforcement design was optimized, which can be useful in the design for structures of the same type.

In seismic design, bridges are typically designed to undergo inelastic deformations during a severe earthquake. In those instances, most of the seismic energy is dissipated through hysteretic behavior of the critical load-resisting components, which results in permanent system deformations and damage and could make repairs expensive or, in some cases, impossible. Thus, concentrating earthquake damage in structural fuses inserted in bridge bents is desirable; the performance objective is for the main gravity load-bearing members (the columns, in this case) to be intact after an earthquake, limiting repairs to fuses that can be removed and replaced easily. This paper presents results from case studies that considered the use of buckling-restrained braces (BRBs) as hysteretic energy-dissipation devices inserted in bridge bents to dissipate earthquake energy and improve structural performance by minimizing inelastic demands on the columns. A typical California bridge was used for this purpose. For structural fuse application only in the transverse direction (along the bent), results indicate that BRBs are implementable. Alternative bent configurations were also considered to provide the benefit of structural fuses for seismic excitations in the bridge’s longitudinal and transverse directions. Findings are presented along with observations from a comparison of seismic responses between bridges with and those without structural fuses in their bents.