Search

A novel concept of hybrid reinforcement in the form of glass fiber‒reinforced polymer (GFRP) longitudinal column bars combined with steel longitudinal column bars and high-strength post-tensioning all-threaded rods is investigated in this research to construct bridge columns for seismic regions. Two half-scale specimens were constructed using grouted ducts to connect the columns to the footings as an accelerated bridge construction method. The first column was reinforced with a combination of mild steel and GFRP longitudinal bars (hybrid column) and the second with all-mild steel longitudinal bars, and both columns were confined with a double layer of GFRP spirals; this arrangement improves column longevity since GFRP materials do not corrode. Both specimens utilized high-strength all-threaded rods for post-tensioning. Carbon fiber‒reinforced polymer jackets were externally wrapped at the column bottom to confine the concrete in the plastic hinge region. The seismic behavior of both precast concrete specimens was assessed through quasi-static cyclic tests. Both columns exhibited satisfactory strength and deformability. The combination of post-tensioning bars with GFRP longitudinal bars improved the self-centering capability. The residual displacement of the hybrid column was decreased by 46% compared with the all-steel-reinforced column at 6.0% drift ratio. The elastic nature of the GFRP longitudinal bars provided substantial self-centering by reducing the residual displacement of the hybrid specimen thereby enhancing seismic resilience. [ABSTRACT FROM AUTHOR]

The fatigue provisions for bridge design in North America and Europe are highly simplified for the sake of practical implementation, in comparison with the state of the art in understanding of the true fatigue behavior. Historically, one significant simplification in the calibration of damage equivalence factors has been to assume that trucks cross the bridge one at a time, when in reality trucks are known to platoon, and multiple truck presence is not uncommon on longer span structures with higher traffic volumes. While code writers have taken steps more recently to consider multiple presence effects, these efforts have been limited, and a clear understanding of the influence of key design parameters on multiple presence effects has not yet been fully established. Against this background, the present work considers real-time multilane weigh-in-motion (WIM) data and compares fatigue damage from recorded loading events over years to the damage resulting from the same vehicles crossing the bridge individually, to better understand the significance of multiple vehicle presence effects on fatigue damage. For both finite and infinite life fatigue design, the results show that multiple vehicle presence effects can be significant, depending on traffic volume, road configuration, and influence line characteristics. Multiple presence factors are therefore defined, allowing practitioners to consider multiple presence effects appropriately when designing bridges where they may be relevant. [ABSTRACT FROM AUTHOR]

Precast slab bridges are an attractive option for short- to medium-span bridges; however, the presence of longitudinal joints and concrete overlays adds great complexity to the transverse load distribution (TLD) analysis. Currently, one of the most commonly used methods for simplified analysis relies on the semiempirical formulas provided in AASHTO LRFD Bridge Design Specifications; yet, these formulas have certain limitations in their applicability. This study presents an algorithm based on the transfer matrix method (TMM) to determine the TLD of precast slab bridges. A connection model utilizing shear-and-torsion spring hinges (STSHs) is proposed to simulate the structural behavior of shear keys and the overlay of precast slab bridges in TLD calculations. The transfer matrices and transfer equations between slabs and between joints are established. The TLD for slabs is then computed by introducing boundary conditions and solving transfer equations. In addition, the finite-element method (FEM), along with the existing field tests of two different bridges, is used to verify the accuracy and validity of the proposed method. The study concludes that the TMM shows high algorithmic efficiency compared to the FEM modeling procedure and better precision and applicability than the semiempirical equations provided in AASHTO LRFD. Moreover, extended parametric studies are conducted on the effects of the thickness of concrete overlay and the relative flexibility coefficients of slabs on the TLD of bridges. [ABSTRACT FROM AUTHOR]

To investigate the performance of in-service skewed bridges, two continuous two-span steel I-girder bridges, one skewed 45° with integral abutments and the other skewed 41° with stub abutments, were instrumented during construction for long-term field monitoring. The bridges are located near each other and experience similar traffic volume and thermal variation, from roughly −18°C to 38°C (0°F to 100°F). Critical girders and cross-frames were instrumented with strain gauges and/or tiltmeters, and temperature was recorded at each sensor. Superstructure response over more than 2 years of data collection was recorded and studied, including for the in-service first-stage half bridges (temporarily for 6 months) and the full bridges. Girder cross-sections and cross-frames were within the elastic range during field monitoring, so stress directly relates to measured strain. The bridge superstructures experienced cyclic stress variation under thermal loading—there was clear linear correlation between bridge response and seasonal temperature variation, especially for decomposed girder axial stress and strong-axis bending stress. Deviation from the correlation was observed due to changes in abutment restraint during seasonal temperature variation and thermal gradient under daily temperature changes. Exterior girders were frequently unevenly heated by direct sunlight, which induced a diverging daily stress–temperature relationship compared to long-term observations. Thermal response of exterior girders is more complex than interior girders regarding both strong-axis and lateral bending, which is often not incorporated in standard bridge design procedures. Several girder bottom flanges and cross-frame members exhibited atypical increasing stress that started during the first cold-weather period; some of the stress development continued over time, regardless of long-term thermal cycles. [ABSTRACT FROM AUTHOR]

The provisions for avoidance of brittle fracture in various bridge design codes vary in complexity, from the simple tables in North American codes, which present impact energy requirements as a function of steel grade, climate zone, and member type, to the more involved methods presented in the Eurocodes, which allow factors such as plate thickness, demand-to-capacity ratio, and strain rate to be considered. While these provisions generally appear to be meeting the needs of the code users, two issues are noteworthy. The first is that the North American provisions offer less flexibility and guidance for handling unusual situations than the Eurocode methods. The second is that very few studies can be found in the literature attempting to assess the level of reliability against brittle fracture provided by any of the existing design provisions. The current paper presents a study that attempts to make a first step in addressing both issues, using the Canadian design provisions as an example. Specifically, this paper describes a time-dependent Monte Carlo simulation (MCS)-based probabilistic model and then uses it to assess the extent to which the Canadian provisions provide consistent and adequate levels of reliability against brittle fracture over a range of steel grades, plate thicknesses, and climates. Based on the analysis results, areas of potential improvement of these requirements are identified. [ABSTRACT FROM AUTHOR]

Fiber-reinforced polymer (FRP) composites are promising materials already being used in bridge construction. Lightweight deck panels, mainly used in the rehabilitation or replacement of existing bridges, are the most commonly used FRP bridge components. However, FRP decks are prone to damage due to delamination, matrix cracking, interlaminar cracking, and debonding. In addition, due to their microstructure, FRP materials tend to deteriorate in ways that are not easily detected by visual inspection. Therefore, nondestructive methods should often complement visual inspections aimed at assessing the technical condition of the structure. New measurement techniques are constantly being researched and developed to assist in the evaluation of FRP structures. Distributed fiber optic sensing (DFOS) has been chosen as the main measurement technique of the newly developed FRP bridge deck panel because this technique provides extended advantages compared to the conventional spot gauges. The concept of a component with an integrated DFOS-based system capable of structural control and detection of overloaded vehicles has been developed and verified both in laboratory conditions. The novelty of the presented approach is that sensors (strain-sensing fibers) are precisely embedded in FRP laminates for simultaneous internal strain and vertical displacement (shape change) measurements and delamination detection. The experimental verification of a full-scale deck under static and dynamic loading is described in the paper. The performance of the DFOS system was verified using reference techniques. The results proved the system to be a reliable tool for diagnosing FRP bridge decks. [ABSTRACT FROM AUTHOR]

Owing to undesired hydraulic effects, bridge collapse accidents have become increasingly frequent during the flooding season. Considering hydraulic effects in bridge design is paramount to controlling and mitigating hydrological damage. Despite the efforts in previous studies on bridges under floods, a proper partial factor of hydraulic effects considering foundation scour is still lacking for bridge design against floods. To bridge the gap, this study proposed an inverse reliability analysis framework to generate a proper partial factor of hydraulic effects and a corresponding partial factor of resistance. First, failure modes of typical short- to medium-span bridges were summarized to construct limit state functions. Then, an inverse reliability analysis framework considering hydraulic effects was proposed. The optimum partial factors of hydraulic effects and corresponding partial factors of resistance were calculated for various design specifications. Finally, a classification early warning system of foundation scour was built to forecast hydraulic failure accurately. This paper reveals the necessity of considering the hydraulic effects of floods in bridge design. The proposed framework and warning system can effectively enhance bridge safety against floods. [ABSTRACT FROM AUTHOR]

Composite steel bridges in the United Sates are typically constructed using 22 mm-diameter (7/8 in.-diameter) shear studs. The number of shear studs on a girder can be significantly reduced by using larger-diameter studs. This study employed 11 push-out tests to investigate the static performance of 29 mm-diameter (1-1/8 in.-diameter) shear studs. An extensive welding investigation was conducted to develop the optimum welding parameters for 29 mm-diameter studs. Results from experiments showed the static strength of 29 mm-diameter studs satisfied stud strength equations in the AASHTO LRFD Bridge Design Specifications and Eurocode 4. The ductility of the 29 mm studs was comparable or better than that of 22 mm-diameter shear studs. Concrete cracking under service level loading was similar between specimens with 22 and 29 mm studs. Observations indicate that the minimum allowable stud penetration into the concrete deck may need to increase in order for the 29 mm-diameter studs to have good static performance. Using partial-depth precast concrete panels in the bridge deck reduced the static strength of both 22 and 29 mm-diameter shear studs in push-out specimens. Efficient steel bridge girder design makes use of a composite action between the concrete deck and the steel girders. Composite action is achieved by welding shear studs to the top flange of the steel girder during fabrication or erection. The number of shear studs needed is directly related to the individual stud strength, which is controlled by the stud diameter. The shear stud diameter most commonly used in steel bridge construction throughout most of the United States is 22 mm. This paper presents laboratory experiments evaluating the static strength of 29 mm-diameter shear studs. The test results showed that 29 mm-diameter shear studs have a static strength that satisfies US bridge design standards. Compared with 22 mm-diameter shear studs, the use of 29 mm-diameter shear studs is estimated to reduce the number of studs needed on a steel bridge girder by 40%. This reduction in the number of shear studs can enhance construction safety, reduce the cost of fabrication, and facilitate the use of partial-depth precast concrete deck panels, which in turn can increase the speed of construction. [ABSTRACT FROM AUTHOR]

In countries similar to Austria, bridges fail due to debris-flow impact on a regular basis. As there is a large uncertainty in terms of the acting forces during these events, this study examines debris-flow impact forces on bridge superstructures. We first set up an idealized load pattern for the load case of debris-flow impact on a bridge superstructure. Second, we conducted 60 experiments in a small-scale physical model (scale 1:30), where we measured debris-flow impact forces on six different bridge profiles in the presence and absence of a bridge pier with two 3-axis force sensors installed at the bridge abutments. Our findings indicate that there is an influence of the superstructure profiles on the magnitude of the effective frontal debris-flow impact force while the presence or absence of a bridge pier affects the direction of the effective frontal impact force, but not necessarily its magnitude. Our results also indicate that the effective frontal impact force acts mainly in the horizontal direction as the vertical proportion is mostly <10%. We found that the forces that act on bridge superstructures are on average between one- and three-fifths of the peak debris-flow force. Our findings can contribute to a better design of bridges against debris-flow impact in the future. A debris flow is a mixture of stones, plant parts, soil and other solids, and water that often causes great damage in mountainous regions, as it can transfer very large forces. When debris flows hit bridges, they are often destroyed. Because debris flows are expected to become more frequent due to climate change and therefore more damage to bridges can be expected in the future, it is necessary to gain a better understanding of the impact process of a debris flow on a bridge. Here, we looked at the forces acting on the deck of the bridge. To this end, we have carried out small-scale experiments and systematically investigated the magnitude of occurring forces and how they are influenced by different shapes of the bridge. We found that it makes a difference which bridge profile is impacted and that usually less than half of the total force of the debris flow acts on the deck of the bridge. Our discoveries can help to better construct bridges against debris-flow impact in the future. [ABSTRACT FROM AUTHOR]

The objective of this research is to evaluate numerically and experimentally the cyclic performance of corroded columns constructed with accelerated bridge construction (ABC) methods. Three column-to-footing specimens were built and tested under quasi-static cyclic loads; one specimen was subjected to corrosion with a target 10% mass loss (moderate corrosion), one was subjected to a target 25% mass loss corrosion (severe corrosion), and one served as the control. For the moderately corroded specimen, the accelerated corrosion method resulted in an actual mass loss of 10.5% in the longitudinal steel bars and 18.4% in the steel spiral; for the severely corroded specimen there was an actual mass loss of 24.1% in the longitudinal steel bars and 39.9% in the steel spiral. Increased corrosion caused reduction in column lateral displacement capacity in the cyclic load experiments; the control, moderately corroded, and severely corroded specimens reached a drift ratio of 9.0%, 7.0%, and 6.0%, respectively. Computational models were developed for the control and corroded specimens. Corrosion effects were considered by reducing the cross-sectional area, yield strength, and modulus of elasticity of steel bars; reduction in concrete compressive strength was included due to concrete cracking and reduction of bond. The computational models include bond-slip, intentional debonding, low-cycle fatigue, and buckling. Global and local response comparisons of the numerical models with experiments are carried out. The numerical models show good agreement with the experimental results regarding load and displacement capacity and hysteretic energy dissipation; they are able to capture the main effect of corrosion, which was a reduction in lateral displacement capacity. The computational models were used in parametric studies to examine the lateral force and displacement capacity for a range of corrosion levels. [ABSTRACT FROM AUTHOR]

The present study focuses on the seismic response of bridges with rocking piers of nonconventional shape, combining the inherent benefits of rocking isolation and accelerated bridge construction. The governing equations of motion of bridge structures with different configurations of piers are derived, including the basic kinematics of the rocking motion, the equation of motion during rocking, as well as the intrinsic energy dissipation mechanisms of impact at the rocking interfaces and on the abutment backwalls. This analytical framework is based on dimensionless parameters that are related to the shape of the piers, and it is shown that the reduction of mass that is achieved with the nonconventional pier configurations leads to: (1) lower restoring effects compared to conventional piers that are rectangular in elevation; and (2) higher rocking stability based on rocking principles. The efficiency of the proposed pier configurations in a bridge with rocking pier isolation is examined for different levels of seismic action, also including earthquakes much stronger than the design earthquake in the area. It is demonstrated that the proposed nonconventional pier configurations can improve the seismic performance of rocking bridges, and at the same time bring benefits related to economic and sustainability aspects associated with a reduction in the use of construction materials. [ABSTRACT FROM AUTHOR]

Assembly of precast elements is a widely adopted technology for achieving accelerated bridge construction (ABC) owing to the increased construction speed and quality. Connection methods between precast structural members, if designed properly, can facilitate a convenient postearthquake replacement of damaged members and hence enable rapid function recovery of bridges. This study proposes a new precast bridge pier–footing connection using external sockets. The external sockets are prefabricated on the top of bridge footings and the precast piers can be directly inserted into the sockets with postgrouting. Quasi-static cyclic loading tests were conducted on four 1/4-scale pier–footing specimens, including three external socket pier specimens and a cast-in-place (CIP) specimen for comparison purposes. The experimental results show that the external sockets with normal design sizes are effective precast pier–footing connection methods, ensuring that plastic hinges are formed in the piers without damaging the external sockets and footings. Because of the shortened effective pier height, the socket piers show increased lateral stiffness and strength but decreased displacement capacity compared with the CIP pier. The measured peak horizontal forces for the precast socket pier specimens PCS-1, PCS-2, and PCS-3 are increased by 7.5%, 34.5%, and 51.4%, respectively. However, the ultimate displacements are reduced by 11.1%–22.0% compared with the CIP pier. The hysteretic energy dissipation of the socket piers is compared with that of the CIP pier, with a difference less than 20%. Postexperiment replacement of a tested precast pier was carried out, which demonstrates the feasibility of rapidly replacing damaged bridge piers when using the proposed external socket connections. A subsequent experiment reveals that the newly replaced pier specimen could show an equivalent seismic performance to the previous specimen. The maximum differences of the peak force and initial stiffness between the two piers are within 6.7%, and the difference of the dissipated energy is only 3.8%. The experimental results verified the effectiveness of the rapid replacement. [ABSTRACT FROM AUTHOR]

Staged construction is often used for bridges, in which a portion of a bridge remains open to traffic while another portion is closed for construction. Although staged construction reduces delays and the need for detours, subjecting the partially constructed bridge to dead and vehicular live loading can lead to damage and subsequent deterioration, including compromised longitudinal construction joints and transverse deck cracking. Despite past studies and best practices, transverse cracking persists and is often observed more on one side of the deck during construction, and no definitive explanation has been provided. As such, the objective of this study is to present a mechanics-based method for assessing transverse deck cracking in bridges during staged construction. Demonstrated on two bridges that underwent staged construction, the assessment method provides insights into the persistence of the issue and provides a mechanics-based explanation for observations of transverse cracking sometimes being observed only on one side of the bridge. The method, based on the superposition of strains, considers the sequence of steps in the construction process and estimates strain demands in the concrete decks at each stage, considering variations of the structural configuration, applied loads, and time-dependent behaviors. The results of the assessment agree with finite-element analysis results while requiring less model development and computational effort. The estimated strain history is then used to assess whether transverse cracking occurs by comparing the demand to the concrete's tensile strength in time. The method is demonstrated on a new bridge constructed in stages and an existing bridge that underwent rehabilitation via staged construction. The results of the demonstrations suggest the importance of evaluating both the open and closed portions of bridge decks at each stage, as each portion has different structural and mechanical properties and loading demands. The assessment results are qualitatively validated based upon information from postconstruction bridge inspections. Furthermore, the method can be used to gain insight into mitigating transverse deck cracking and support decision-making for bridge construction practices. [ABSTRACT FROM AUTHOR]

Bridge design specifications include design provisions for ductile diaphragms to resist seismic excitations perpendicular to a bridge's axis. Buckling restrained braces (BRBs) can conveniently be used for this purpose. Bidirectional ductile diaphragms expand the concept to resist all-direction seismic forces, and nonlinear inelastic response history analyses (NL-RHAs) can be used to show that satisfactory seismic performance objectives can be obtained using this concept. However, a simple design procedure is needed to address the design of the BRBs in the bridge longitudinal direction. As a first step, to fill that need for common multispan simply-supported bridges, a relatively simple-to-use equivalent lateral force (ELF) procedure has been developed on the basis of results from "optimal designs" obtained using NL-RHAs. Findings indicate that the proposed ELF design procedure leads to design that meet the target design objectives. [ABSTRACT FROM AUTHOR]

The failure of the support system is one of the primary reasons for bridge failures during construction. Existing research on support system failures primarily focused on falsework, with less attention given to other components such as Bailey beams, transverse beams, and steel pipe piles. This study focused on an incident where the support system of a cast-in-situ box girder bridge experienced settlement due to the failure of Bailey beams, transverse beams, and steel pipe piles. To thoroughly analyze the accident's causes, a multiscale elastic–plastic finite-element model of the support system was developed based on the actual on-site layout. By combining the results of the finite-element model with comprehensive on-site data, it was found that the support system settlement accident was caused by a series of construction errors, including the incorrect placement of the Bailey beams, excessive vulnerability in the steel pipe piles' support positions, and inadequate welding strength between the transverse beams. To prevent similar accidents from recurring, the design, construction, and supervisory parties should collectively ensure the consistency between design and construction and increase their attention to potential stress concentrations in certain components of the support system. When the possibility of stress concentration exists, Bailey beams should be reinforced with vertical or diagonal struts depending on their actual support positions, while steel pipe piles should be reinforced with annular steel plates higher than 500 mm. This study focuses on an incident where the support system of a cast-in-situ box girder bridge experienced settlement due to the failure of Bailey beams, transverse beams, and steel pipe piles. These failures were primarily caused by inconsistencies between design and construction and a lack of attention to potential stress concentrations in certain components of the support system. In fact, the differences between design and construction are widespread and are one of the primary reasons for the failure of support systems during bridge construction. Therefore, the design, construction, and supervisory parties should work together to reduce the occurrence of such situations. Designers need to identify the most critical assumptions made during calculation and communicate these assumptions clearly to the construction team through a checklist. Construction and supervisory parties should implement these assumptions as much as possible and promptly report when they cannot be met. Furthermore, more attention should be given to potential stress concentrations in the support system. This requires designers to be aware of the limitations of beam element models when analyzing stresses at connection points. When stress concentrations are inevitable, the methods proposed in this study can be used to reinforce Bailey beams and steel pipe piles. [ABSTRACT FROM AUTHOR]

Hot-dip galvanized steel structures are well-established and state of the art for public and industrial buildings. They can achieve a corrosion protection period in the magnitude of the lifetime of the structures (≥100 years). The application of this corrosion protection system would also have great potential in bridge construction. Economic efficiency and sustainability in bridge construction are, in addition to the cost of new building, determined by the incurred maintenance costs. A prior research project had demonstrated hardly any losses on the fatigue strength compared with the nongalvanized steel components. Large bridge structures must be designed with assembly joints. Welded field joints of hot-dip galvanized components require a complex pretreatment and posttreatment of the corrosion protection. Nevertheless, onsite applied corrosion protection cannot reach the protection durability of a hot-dip galvanizing. This technological restriction can be avoided by the use of hot-dip galvanized bolted connections. Slip-resistant pretensioned connections with pretensioned bolts have been proven successful in steel bridge construction. Major scientific investigations are not yet available for the use of slip-resistant connections for hot-dip galvanized joints. Technical and scientific foundations for the application of hot-dip galvanized bolted connections in cyclically loaded steel and composite bridge constructions, based on the European standard for steel constructions are investigated within the scope of this research project. Construction and design recommendations are provided. [ABSTRACT FROM AUTHOR]

Bridges are among the key elements of the transportation network. Many bridges are severely damaged or destroyed when subjected to earthquakes. One of the effective methods to reduction of a bridge's seismic damage is to upgrade the seismic codes. Equivalent static analysis (ESA) is the most conventional method for the seismic design of bridges. Bridges can be classified into two groups based on the connection system between the superstructure and substructure, namely isolated bridges and integrated bridges. In this paper, the adequacy of the ESA method is investigated to estimate the seismic base shear force (BSF) of controlled (isolated) bridges and integrated bridges according to AASHTO, Caltrans, and ATC-32 provisions. For this purpose, three bridges are modeled in three dimensions. The effects of lead rubber bearings, friction pendulum bearings, and viscous dampers on the response of bridges are evaluated using eigenvector analysis, ESA, and nonlinear dynamic analysis. The results indicate that there are significant differences between the BSF estimated by the ESA method and in different provisions. The results of nonlinear dynamic analysis indicate that energy dissipation equipments can decrease the seismic response of structures. Also, the use of the ESA method can only be employed for an initial estimate of the BSF of vibration-controlled bridges. For the detailed study and design of bridges, the ESA method does not provide an accurate estimate of the BSF. This is why the use of the ESA method is not recommended. [ABSTRACT FROM AUTHOR]

The Allegheny Aqueduct (1845–1861) in Pittsburgh was the first suspension bridge designed and constructed by John A. Roebling (1806–1869), who would go on to design some of the most prominent and longest-spanning suspension bridges of the 19th century. The Allegheny Aqueduct was a seven-span suspension bridge built on the existing unreinforced masonry piers of the prior wooden-covered aqueduct. To evaluate the progression of Roebling's innovations throughout his career, it is important to document his expertise and experience in suspension bridge design and construction at the onset of his career. This research used the published writings of Roebling and other contemporary engineers, archival documents, and modern nonlinear structural analyses to evaluate the design and performance of the Allegheny Aqueduct as built, as well as several possible design alternatives. The structural design of the multispan bridge required Roebling to accommodate unbalanced loading conditions from water within the aqueduct and from repair or removal of any single span, all while maintaining the stability of the masonry piers. Roebling developed a unique design, analysis, and construction approach to safely meet these criteria, and modern structural analyses demonstrated the soundness of Roebling's approach. Roebling patented and constructed a new style of anchorage that was simpler to build, prevented ingress of moisture and corrosion of the iron bars, and allowed for straightforward rigid-body stability analysis. Roebling also patented, developed the mechanical equipment for, and implemented a new wire-by-wire cable fabrication (spinning) technique that resulted in a nearly uniform stress state amongst all wires of the cable and prevented ingress of moisture and corrosion of the wires. Roebling's developments in anchorages and cables represented significant advancements over existing European techniques, and fundamental aspects of his techniques remain in use to this day. [ABSTRACT FROM AUTHOR]

Accelerated bridge construction (ABC) has been widely used in the United States since the late 1990s following a national ABC initiative by the Transportation Research Board (TRB) in 1996. The press-brake-formed tub girder (PBFTG) system is one of the innovative bridge systems that has been developed recently for the accelerated construction of simple and short span bridges. The PBFTG shape is optimized to achieve the maximum structural capacity and torsional stiffness due to the distribution of the steel around the centroid of the shape, a major limitation in conventional W-shape and plate I-girders. Despite the promising advantages of PBFTG systems, it received less attention than conventional superstructure systems, especially when dealing with their live load distribution factors (LLDFs). Stemmed from these limitations, LLDFs for moment and shear of one and multiple design-loaded lanes for exterior and interior beams in PBFTG bridges are computationally investigated. More than 190 bridges are modeled using a validated finite-element (FE) approach to cover a wide range of geometric parameters of PBFTG bridges, including spacing between beams (S), bridge span (L), skew angle (θ), and number of lanes (NL). Detailed FE models show that LLDFs of PBFTG bridges are highly dependent on the selected geometric parameters. A regression analysis is performed leading to a new proposed set of equations for studies showing that the LLDFs of PBFTG bridges are highly dependent on the selected geometric different types of LLDFs for fascia and interior beams in PBFTG bridges. The results of the parametric study suggest that the current AASHTO equations are unconservative for both single lane and multilane moment and shear LLDFs for fascia and interior PBFTGs compared with proposed equations (except for single lane moment LLDFs of interior beams). [ABSTRACT FROM AUTHOR]

Steel I-girder bridges are subjected to unique loading conditions when they are under construction, and, in particular, lateral bending of skewed bridges during deck placement is of interest. Proper evaluation of skew effects on girder lateral bending stress in precomposite steel superstructures under concrete dead load is necessary for ensuring safety and economy in design for construction-stage loading. To provide new data on bridge response during deck placement, strains at selected cross sections were monitored for two steel I-girder bridges skewed around 45°, with variation in support conditions at the abutments. Girder stress components associated with strong-axis bending and lateral bending were calculated from field strain measurements, and complementary three-dimensional (3D) finite-element numerical simulations were conducted. Modeling methods that properly incorporate field girder boundary conditions and deck overhang loading for precomposite bridges were validated using field data from the two instrumented bridges, and parametric studies were then conducted on 33 bridges to evaluate skew effects on flange lateral bending stress. A staggered cross-frame layout provided additional load paths that transferred lateral load internally from an exterior girder, which was observed to be most significant near the midspan of a skewed bridge. Development of flange lateral bending near supports of a skewed bridge was found to be primarily caused by superstructure stiffness along the skewed bearing lines; large flange lateral bending stress occurred when the lateral movement induced from girder rotation along the skew is restrained at the support. For a skewed bridge with a staggered cross-frame layout along its length, standard design recommendations from the AASHTO LRFD Bridge Design Specification regarding skew-related lateral bending stress were observed to be effective for interior girders, except near ends of some bridges with skew over 45°, but inadequate for exterior girders. [ABSTRACT FROM AUTHOR]

As an essential sector of the construction industry, bridge construction produces a large amount of carbon dioxide and other greenhouse gases, greatly intensifying the global greenhouse effect. Prefabricated reinforced concrete (RC) T-beams are a vital type of structural element widely used in bridge construction projects such as river-spanning bridges, high-speed railways, and urban expressways. This study proposes a bridge structural optimization framework using building information modeling (BIM) and two-stage metaheuristic searching (MS) in order to minimize the carbon emission of prefabricated RC T-beams. Under the constraints of corresponding design specifications, the first stage of the proposed MS is utilized to optimize the longitudinal steel section size and area of the T-beam, with carbon emission as the optimization objective. The optimal combination of rebar diameters is then obtained in the second stage of the proposed MS. An illustrative example is also provided to demonstrate the performance of the proposed framework. Moreover, the proposed framework is compared with conventional approaches as well as other metaheuristic algorithms to validate the developed optimization approach. [ABSTRACT FROM AUTHOR]

There has been a growing interest in using large-diameter strands to alleviate congestion by using fewer strands, reduce the total number of girders by increasing girder spacing, increase the span length, and allow shallower girders. While the 2020 AASHTO LRFD Bridge Design Specifications included 17.8-mm (0.7-in.) strands by reference to AASHTO M203, these larger-diameter strands were not used in bridge construction primarily because AASHTO LRFD was silent about the design aspects of members reinforced with 17.8-mm (0.7-in.) strands. The presented multifaceted, multiyear research involved an extensive parametric design case study, nonlinear finite-element analyses, material characterization, component tests, and full-scale girder experiments. This paper focuses on the full-scale girder tests, which were used to examine development length, detailing requirements, and flexural and shear behavior and strength. Experimentally determined development lengths were found to be shorter than those prescribed by the AASHTO LRFD Specification. Flexural and shear strength could be determined using established procedures. The current minimum required amount of confinement reinforcement was found to be sufficient to confine 17.8-mm (0.7-in.) strands. The extension of bottom flange confinement reinforcement was found to be inadequate for cases with partially debonded 17.8-mm (0.7-in.) strands, but extension of bottom flange confinement reinforcement to 1.5d beyond the end of the girder was adequate for cases with no debonded strands. The minimum bottom flange confinement reinforcement required by the AASHTO LRFD Specification must be extended to at least 1.5d beyond the termination of the longest debonded length of 17.8-mm (0.7-in.) strands. [ABSTRACT FROM AUTHOR]

A diaphragm is an essential component of a T-girder bridge. Evaluating the influence of various truss diaphragms (TDs) on the structural behavior and load distribution factor of T-girder bridges assists in bridge design and strengthening. In this study, a series of experiments and simulations were conducted to investigate the strengthening effect of two types of TDs (i.e., triangle-TDs and K-TDs) based on a small-scale T-girder bridge model. Formulas for the flexural rigidity of the two types of TDs were proposed and verified by using rigid-joint girder methods, experiments, and simulations. Then, taking the K-TD as an example, the calculation method for the stiffness of the truss was analyzed and derived based on rigid-joint girder and graphic multiplication methods. The results showed that K-TDs had a better strengthening effect than triangle-TDs. The deflection and strain of the K-TD-strengthened T-girder bridge were reduced by 21% and 16%, respectively, compared with those of the triangle-TD-strengthened bridge. The formulas for flexural rigidity were proposed and used to calculate the load distribution factor. The maximum error of the calculated load distribution factor was 16% compared with the simulation and experimental results. Moreover, the calculation method for the stiffness of the K-TDs was analyzed and obtained. Deterioration of multigirder bridges is getting worse due to the increasing traffic load and insufficient maintenance. Adding diaphragms to the existing bridges can improve the load distribution of multigirder bridges and reduce the maximum load of the girders. This work evaluated the influence of two types of truss diaphragms (triangle truss diaphragm and K truss diaphragm) on the load distribution of a T-girder bridge, and the results showed that the two types of truss diaphragms can reduce the maximum deflection and strain in the T-girder bridge effectively. The flexural rigidity formulas for the two types of truss diaphragm were proposed and proved to be accurate by comparing with experiments and finite-element methods. Moreover, the truss stiffness of the K truss diaphragm was derived by a graphic multiplication method. These formulas can be used by bridge engineers for new bridge designing or existing bridge strengthening in practical engineering. [ABSTRACT FROM AUTHOR]

Many of the procedures used in bridge design are force-based and may be considered reasonable design approaches that will lead to safe structures. But they do not directly address performance criteria at the initial stage of the design. On the other hand, the previously presented displacement-based design procedures of isolated bridges only considered the displacement of the deck, which means the pier's seismic performance and the substructure mass effects are ignored. This paper presents a new performance-based design method for isolated RC bridges considering the contribution of substructure mass. This method allows the designer that selects the performance level of the superstructure and substructure at the beginning of the design procedure. In this respect, the two degrees of freedom analytical model of the isolated bridge containing substructure mass is presented to quantify its effect on the performance of the seismically isolated bridge. The proposed design method is applied to two continuous-span bridges with regular and irregular substructures, and different target performance levels, including elastic and yielded substructures. The results of the proposed design method have been compared with nonlinear time history analyses, AASHTO, and National Cooperative Highway Research Program simplified methods. The results showed that the seismic performances are close to the results of the nonlinear time history analyses. However, the other design approaches, which ignore the substructure mass, underestimate the responses of the substructure. [ABSTRACT FROM AUTHOR]

Exceptional mechanical properties of ultra-high performance concretes (UHPC) offer strong strengthening capacities in bending and shear when used as overlay on normal strength concrete (NSC) structures. Nonetheless, lack of simple and intuitive design models for hybrid elements in design guidelines refrain designers from using UHPC overlays for structural applications. Thereby, a simplified sectional analysis model for NSC-UHPC hybrid elements was developed based on the philosophy of the Canadian Bridge Design Code CSA-S6. By using a new average stress distribution for NSC in hybrid elements that considers the strain at the extreme compressed fiber, equilibrium of forces can be solved by a second-degree equation with direct computation. The simplified model provides the complete moment–curvature behavior of hybrid elements for design purposes, thus allowing verifications in service and ultimate state conditions. An empiric equation is also proposed to evaluate the maximum bending capacity of hybrid elements for predesign. It only uses an approximation of a lever arm between forces in the hybrid cross section and thus offers a quick and easy way to evaluate the bending capacity. Both tools were validated on a detailed and iterative sectional analysis program and with results of four international experimental campaigns. The simplified sectional analysis model and empirical equation showed very good accuracy at reproducing the behavior of a wide range of NSC-UHPC hybrid elements configurations. [ABSTRACT FROM AUTHOR]

The perceived and observed differences in the dynamic behavior between wheeled and tracked military vehicles should be considered when applying appropriate dynamic load effect values for bridge design and assessment. Based on available test data, tracked military vehicles appear to impose less severe dynamic load effects when compared with wheeled vehicles under similar crossing conditions. In exploring a range of crossing conditions, a review of test data was used to make a general comparison of the dynamic loading amplification between tracked and wheeled military vehicles. To expand the range of crossing conditions tested for an instrumented bridge, additional data were collected for an artificially induced roughness of the bridge surface. By combining the test results from previous studies with the results from this testing program, the relative dynamic loading amplification between tracked and wheeled military vehicles can be quantified for situations with similar crossing conditions. Given this comparison, it may be appropriate to use a dynamic load allowance (DLA) of as low as 70% of the code-specified DLA for wheeled vehicles when evaluating the capacity of bridges subjected to military tracked traffic. This is especially relevant when considering maneuver options for main battle tanks during military combat operations. [ABSTRACT FROM AUTHOR]

The stiffness of suspension bridges, which are flexible systems composed of main cables and stiffening beams, is frequently increased by adding one or more pairs of central buckles in the midspan. This study examined a suspension bridge with flexible central buckles, proposing a set of analytical calculation methods for the shape-finding of the main cable under dead load and the structural deformation and internal forces under any uniform live loads. The proposed method is based on the known bridge design parameters. First, the suspender and central buckle tension of each hanging point of the stiffening beam was determined by the multipoint rigid support continuous beam method. After assigning these tensions to the suspenders and the central buckles, the multisegment catenary theory was used to derive the equation for each main cable segment in turn. The constraint equation was established through the closure condition of the height difference within the span. The equation was then transformed into an objective function to be programmatically solved, determining the completed bridge state. To determine the live load response of the bridge, the deformation and position relationships of the main cable, main beam, and bridge towers were analyzed in sequence, with known live load parameters. Five types of constraint equations were established through the conservation of the unstrained length of each main cable segment, the coordination of the force and deformation of each suspender, the coordination of the force and deformation of each central buckle, the closure of span length and height difference in each span, and the force balance of the main beam. Then, they were converted into an objective function to be programmatically solved, leading to the live load response of the structure. Finally, a case study of a suspension bridge with a main span of 1,050 m was used to verify the feasibility and effectiveness of the proposed method. The structural deformation and internal forces provided by the analytical solution for the live load action had good accuracy, which is in good agreement with the finite-element method results. Long-span suspension bridges, compared with traditional small- and medium-span bridges, have greater flexibility, and they are more prone to large deflection and deformation under live loads such as vehicles. To improve the structural stiffness of suspension bridges, engineers often set central buckles connecting the cable and stiffening beam in the middle of the span. The current method of calculating the live load response of suspension bridges depends on finite-element modeling. However, when purchasing and using finite-element software, it is often expensive. At the same time, the finite-element method (FEM) modeling process is relatively complex and exhibits low efficiency. In addition, Link10 element in the current commercial finite-element software ANSYS (version 16.0) cannot consider its geometric nonlinearity, which will produce deviation to the results. Therefore, this paper proposes a set of accurate live load analytical algorithms for suspension bridges with central buckles, which are solved by the same number of basic unknowns and constraint equations. It is helpful to reduce the dependence of practitioners on finite-element software and can also be used as the verification and supplement of finite-element results. [ABSTRACT FROM AUTHOR]

The stability of stiffened plates has always been an important research issue in bridge engineering. The application of stiffened curved plates (SCPs) in the field of bridge engineering is gradually increasing, but the corresponding research needs to be more comprehensive. Guidelines have yet to be established in bridge design codes for the stability design of SCPs. To study the failure mode and ultimate resistance of SCPs with trapezoidal longitudinal stiffeners under uniaxial compression, six test specimens with a scale ratio of 1:2 were designed in this work, and static loading tests were conducted on three kinds of SCPs with different curvatures. The influence of curvature on the ultimate resistance and failure mode of SCPs was analyzed, and a calculation method for the ultimate resistance of SCPs was discussed. Results showed that the SCPs with trapezoidal longitudinal stiffeners have sufficient overall and local stability. The failure of the SCPs occurred locally in the subpanels between stiffeners, and the ultimate resistance of specimens with different bending radii was insignificantly different. The ultimate compressive resistance calculated following the effective section of the main plate was close to the test results. When the subpanels are locally buckled, the stiffened flat plate calculation method can be used to analyze the ultimate resistance of SCPs, and the calculated results deviate conservatively. [ABSTRACT FROM AUTHOR]

As the demands on the country's aging infrastructure continue to grow, new methods of construction that prioritize speed of construction, reliability, and environmental impact will have an outsized impact on how the country rebuilds and rehabilitates its infrastructure. Accelerated bridge construction or ABC for short, is one such method that is already being implemented in many states in the United States, such as Idaho. Precast concrete offers many advantages for ABC. The use of precast concrete for bridge substructures in seismic regions is of great interest but the required detailing of connections needed to sustain the forces and displacements generated by earthquakes is a challenge. In addition, having adequate construction tolerance between precast elements is important. As such, this research proposes a new fully precast pier system that employs ABC methods for applications in seismic regions. The system offers many advantages, in addition to better construction tolerances compared with some previously investigated connections between precast elements. The seismic performance of the system is experimentally investigated using large-scale structural testing and subsequently compared to the benchmark cast-in-place (CIP) specimens. The proposed precast system uses structural steel tubes (pipes) filled with concrete in the plastic hinge zones that are meant to serve as seismic energy dissipaters enhancing the structural performance of the pier. In this type of connection, the concrete filled steel pipe provides shear/flexural resistance as well as confinement to the concrete at the plastic hinge. Results from the large-scale structural testing of the proposed ABC precast pier and benchmark CIP pier showed that the former outperformed the latter in various aspects. Given the superior performance of the precast system investigated in this research, it has been implemented in a bridge in Idaho located in an area of high seismicity. [ABSTRACT FROM AUTHOR]

Scoured pile-group foundations (SPGFs) are susceptible to inelastic deformation during earthquakes. Hence, the ductile behavior of SPGFs has become a rising concern in academic and industrial communities. Traditionally, pushover analyses with single-point load patterns have been adopted to obtain the ductile characteristics of bridge pile-group foundations. However, this practice cannot properly account for the inertial effects from both the superstructure and the pile-cap. Accordingly, in this study, the well-known incremental dynamic analysis (IDA) was adopted to rigorously and comprehensively investigate the ductile behavior of SPGFs for the seismic design of bridges in flood-prone regions. To this end, a shake-table test on an SPGF-supported RC bridge bent model was firstly employed to validate the adopted numerical modeling technique. An in-depth parametric study was then conducted on the bridge bent with the damage potential of the SPGF embedded in cohesionless soil, considering various structural and geotechnical parameters. Based on the IDA results, the seismic failure process, structural limit states, and ductile performance indices of SPGFs were systematically investigated. It was found that the failure process of SPGFs obtained from IDA was consistent with that reported in a previous quasistatic test. Scoured pile-group foundations have a considerable displacement ductility capacity (quantified as 2.48 and 3.47, on average, for the easy-to-repair and ultimate states, respectively), as well as lateral strength enhancement capacity (i.e., the lateral strength values for the easy-to-repair and ultimate states were, on average, 1.40 and 1.46 times that of the first-yield state, respectively). The displacement ductility capacity of SPGFs can be improved by using more rows of piles, a larger pile diameter, a higher transverse confinement of the pile section, a lower longitudinal reinforcement ratio of the pile section, or a larger pile spacing. Those with a shorter aboveground pile height (scour depth), or supporting a shorter pier, exhibited a larger displacement ductility capacity. [ABSTRACT FROM AUTHOR]

The paper reports on the computation of the hydrodynamic loads on a full-scale caisson at high Reynolds number in the presence of vortex shedding. The objective was to obtain reliable predictions of the resulting mean and fluctuating forces to guide the design of an actual caisson in the absence of relevant experimental data. A further objective was to investigate the effectiveness of alternative methods for the control of vortex shedding that can be implemented in practice. Two such methods were evaluated: (1) by rounding the corners of the rectangular-sectioned caisson, and (2) by the placement of a splitter plate in the separated wake region. The computations, which were performed using the OpenFOAM open-source software, were for a fixed caisson and hence did not account for motions due to vortex-induced vibrations. The effects of turbulence were accounted for by performing large-eddy simulations, and by using two-equation eddy-viscosity closures, one of which was specifically adapted to account for the interactions between the periodic vortex shedding and the random turbulence. The numerical accuracy was checked using the grid convergence index method, and the computations were extensively validated against data from relevant benchmark flows. The recommendations of this research were implemented in the design of a full-scale caisson that has since been deployed in a bridge construction project. [ABSTRACT FROM AUTHOR]

In the 1950s and 1960s, some Louisiana's bridges were constructed using steel twin-girder or truss systems, in which floorbeams are carried by the main members and continuous (spliced) stringers are supported by the floorbeams. The main members are either two-edge (fascia) girders or trusses. One of the byproducts of this type of design is that stringer bottom flanges are in compression in the negative moment region over the floorbeams, which could result in lateral torsional buckling (LTB) should inadequate lateral bracing be provided. When the continuous stringers are load-rated using AASHTOWare Bridge Rating analysis software (BrR 7.1), their LTB resistance is calculated in accordance with American Association of State Highway Officials (AASHTO) LRFD Bridge Design Specifications, which do not account for potential bracing provided by a noncomposite deck and could underestimate flexural strength. As a result, the rating may be low enough to require restrictive load posting or even bridge closure. This paper summarizes extensive experimental and numerical studies investigating the behavior of this type of floor system by testing two-span, continuous, steel stringers in a grillage that included three stringer lines, an interior transverse support (floorbeam), and transverse diaphragms at the end supports. The tests and finite-element analysis studies encompassed a variety of unbraced lengths and support conditions with steel diaphragms or timber ties acting as bracing members. The findings demonstrated that, for the systems examined, minimal bracing could substantially enhance LTB resistance and supported the use of higher flexural strengths than those currently predicted using AASHTO Specifications. This paper illustrates the use, challenges, and successes in LTB modeling beams with various support and bracing conditions. The most flexible cases were the most difficult to achieve close agreement with experimental results. [ABSTRACT FROM AUTHOR]

Design methods for corrugated steel culverts in current design standards consider the circumferential force in culvert walls (i.e., hoop thrust) to be the dominant load-carrying mechanism in these structures. However, recent studies have shown that bending moment, rather than thrust, is often the more dominant response for corrugated steel culverts under shallow burial conditions and vehicle loading. In addition, 2D finite element analyses have historically been unable to effectively capture the effects of discrete surface loads, such as wheel loads, on the response of buried metal culverts. To investigate these issues, the bending moment and thrust responses from an experiment involving an elliptical corrugated steel culvert under shallow burial conditions and simulated vehicle loading are compared with the bending moment and thrust estimates from the Canadian bridge design code and CANDE-2019 (a commonly used public domain finite element software package) and the thrust estimates from the American AASHTO LRFD bridge design code (which does not consider moment directly). The comparisons show that the Canadian code and CANDE-2019 models with a fine mesh and the continuous load scaling elasticity-based method appear to be the most effective for the investigated culvert and loading, while there is a need to modify the American AASHTO LRFD code to consider moment more directly. In addition, the results suggest that, under these conditions, the current approaches for estimating the peak bending moment response are more effective compared with the approaches for estimating the peak thrust response. [ABSTRACT FROM AUTHOR]

To promote accelerated bridge construction (ABC), precast bridge columns are now being more widely used in engineering applications. Researchers have often studied the seismic performance of precast bridge columns, but the study of shear performance is quite limited. The main purpose of this study is to investigate shear behavior of low-aspect-ratio precast columns with grouted sleeve connections considering the effect of axial load ratios. Cyclic quasistatic tests of four 1/4-scaled reinforced concrete precast column specimens were conducted to investigate their seismic performance. The experimental results showed that large axial load reduced ductility factor of columns, but increased lateral force capacity. A predicting method for lateral force capacity of precast bridge columns based on a strut-and-tie model in the sleeve region was developed. The method can realistically predict the lateral force capacity and take into the influence of axial load on lateral force capacity of precast columns with grouted sleeve connection. Grouted sleeve connections have been one of the most effective connections for precast columns in prefabricated bridge construction. For urban expressway bridge engineering, there are many columns with low aspect ratio. Lack of corresponding performance evaluation methods of the short columns with grouted sleeve connection restricts its application in medium- and high-intensity earthquake zones. This study revealed damage mechanisms of precast column under cyclic load, such as shear crack, shear slip of joint, and failure modes of joint connection. In addition, a strut-and-tie model was proposed to accurately predict lateral bearing force for precast columns with grouted sleeves under various axial load ratios. The achievement of this study can provide theoretical support for seismic design of short columns (aspect ratio less than 2.5), and the related research results have been applied to the engineering construction of urban bridges in medium- to high-intensity areas such as Jingxiong Expressway, Zunqin Expressway, and Shanghai S26 Expressway. [ABSTRACT FROM AUTHOR]

The grouted splice sleeve (GSS) connection is considered to be an effective bending moment–resisting connection between precast RC members. This connection type has been used extensively in nonseismic regions. The application of such a connection type in moderate or high seismic regions has been investigated and considered for multistory moment frame buildings and highway bridges. A computational modeling strategy is proposed at local and global levels for developing an appropriate computational model for such a connection type using a recessed GSS connection with intentional debonding. A computational model capable of predicting the structural response under cyclic loading was developed using established material models and a forced-based beam-column element considering low-cycle fatigue of reinforcing bars, bar-slip, intentional debonding of reinforcing bars, and plastic hinge length. The proposed model for recessed GSS connections with intentional debonding was experimentally validated. The proposed model was subsequently used to obtain the seismic response of a three-column bridge bent to near- and far-field earthquakes in terms of the overall maximum drift ratio and the drift ratio at the maximum seismic force. [ABSTRACT FROM AUTHOR]

The use of lightweight self-consolidating concrete (LWSCC) has significantly increased due to enhanced mix designs and its projected lower overall costs than normal-weight concrete. Accelerated bridge construction (ABC) has become a common alternative to conventional construction techniques. The use of LWSCC in ABC will reduce structural loads and expedite transportation and installation of precast bridge elements. Limited research, however, has investigated LWSCC bridge elements reinforced with glass fiber–reinforced polymer (GFRP) bars. This paper reports on the performance of full-scale edge-restrained bridge deck slabs (simulating slab-on-girder bridges) fabricated with LWSCC reinforced with GFRP bars. The test specimens included three edge-restrained slabs and one unrestrained slab for comparison. The test specimens were 3,000 mm long × 2,500 mm wide × 200 mm thick and were tested up to failure under a concentrated load simulating the footprint of a standard CL-625 truck wheel load (87.5 kN) defined in current design codes. The investigated parameters were (1) reinforcement ratio; (2) top reinforcement; and (3) effect of edge-restraining. The cracking behavior, ultimate capacity, deflection, and concrete and reinforcement strains of the specimens were presented and discussed. In addition, the punching-shear capacity of the tested specimens was assessed with the currently recommended design equations. The test results indicate that the overall performance of LWSCC deck slabs reinforced with GFRP bars is similar to such structures made with normal-weight concrete. [ABSTRACT FROM AUTHOR]

Highly-skewed steel I-girder bridges are commonly used across the US, especially in congested areas, despite complications in their analysis and design. The American Association of State Highway and Transportation Officials (AASHTO) LRFD Bridge Design Specification provides suggestions for design values of flange lateral bending stress in addition to line girder analysis when bridge skew exceeds 20° for certain cross-frame layouts. For bridges with skew exceeding 60°, a higher level of analysis is often required, with cross-frames considered primary members in design. Neither the magnitude of additional lateral stress nor the associated skew limits are particularly well understood, so more study is needed to refine and support this analysis and design approach. In addition to short-term response and load distribution, long-term bridge behavior for thermally induced stresses and deformations also needs to be more thoroughly studied. In support of an ongoing research initiative in Illinois, an agency survey was formulated and distributed across the US to understand practices used and challenges faced by state transportation agencies when designing and constructing skewed steel I-girder bridges. Findings from the responses of 23 state agencies illuminate issues, concerns, and current practice related to design, construction, and service life of those bridges. The agency survey informed selection of two bridges in Champaign, Illinois, for field monitoring, in order to provide new understanding of skew effects on bridge superstructure behavior. Three-dimensional finite-element analysis was conducted to guide field instrumentation planning, and initial measurements from the monitored bridges under traffic load confirmed good predictions compared to the planning-stage numerical study. This paper presents the initial stages of a long-term project that employs field monitoring and three-dimensional finite-element analysis of skewed steel I-girder bridges. Findings from a survey of state transportation agencies describe issues, concerns, and current practice related to design, construction, and service life of these bridges, which can be of interest to practicing engineers and contractors. This paper illustrates the integration of data from current practice and targeted numerical simulations to establish a rigorous basis for planning a bridge superstructure field monitoring campaign. The information and experiences summarized can be helpful to both practicing engineers and researchers. [ABSTRACT FROM AUTHOR]

Socket connections are suggested to connect a precast column with adjacent members in accelerated bridge construction owing to their large construction tolerance. However, a typical socket-embedded connection always causes a heavy footing or pile cap due to the required embedment length, which is not preferable in the seismic design of a bridge system. In this paper, a new type of socket connection, namely, the partially embedded connection between a precast rectangular column and a stepped pile cap, is proposed to overcome this defect. Three half-scale specimens, that is, a cast-in-place specimen and two such designed socketed specimens with different step heights, were fabricated and tested to verify the new socket connection design concept. Experimental results showed that all specimens formed the approximate plastic hinges at the column bases and only minor damage occurred in the pile caps and the connecting regions; the hysteretic curves of the socketed specimens were approximately the same as that of the cast-in-place specimen, which proves that this new socket partially embedded connection is reliable to transfer the horizontal bending moment from columns to pile caps in a column–pile cap system and, meanwhile, can not only reduce the pile cap volume but also achieve the expected seismic performance. [ABSTRACT FROM AUTHOR]

Segmental posttensioned precast concrete (SPPC) is a promising approach to accelerated bridge construction (ABC). However, an impediment to the performance-based design of SPPC piers lies in the challenge of defining appropriate damage states and corresponding engineering demand parameter (EDP) limits. To address this, in this study, genetic programming (GP), a form of artificial intelligence, is used to develop drift ratio–based EDP limit models in order to identify the onset of four damage levels that are particularly introduced herein for SPPC piers. In this respect, a finite-element model using ABAQUS is developed and experimentally validated to simulate the response of SPPC piers under seismic loading. The model is then utilized to generate a data set of 316 cases, all within the feasible design space of SPPC piers. This data set is subsequently used to develop GP-based predictive equations that map the relationship between different SPPC pier design parameters (e.g., posttensioning strand ratio, concrete compressive strength, and gravity load level) and EDP (i.e., drift ratio) limits. The performance of the developed equations is evaluated through different measures, including fitness function and performance index. Ultimately, parametric and sensitivity analyses are conducted to demonstrate that the GP-based equations are robust enough to characterize the four damage states for SPPC piers. [ABSTRACT FROM AUTHOR]

The structural deterioration knowledge in existing mathematical physics models offers a unique opportunity to develop data-driven, physics-informed machine learning (ML) for enhanced bridge deterioration prediction. However, existing physics models typically represent deterioration knowledge using mathematical symbols and are limited in capturing the semantic meanings and relationships of the symbols, making the models not understandable and operable by machines. As a result, it is challenging to automatically instantiate mathematical physics models to deduce knowledge-driven deterioration facts to inform the learning. To address this challenge, this paper proposes a new structural deterioration knowledge ontology (DT-KL-Onto). The ontology represents structural deterioration knowledge in mathematical physics models as related to structure deficiency, deficiency property, and deficiency contributing factor in a formal, explicit, and semantic way to allow for automated model instantiation. To evaluate the performance of the ontology, the DT-KL-Onto was implemented in automatically instantiating structural deterioration-related mathematical physics models using bridge design, construction, and inspection data. The evaluation results show that the ontology was able to accurately instantiate the models in an automated way: the coefficient of determination and mean squared error between the deterioration facts deduced from the automated instantiation and those from the manual instantiation are 1.0000 and 0.0000, respectively. Two bridge deterioration prediction models were also developed to further demonstrate the benefits of using the deterioration knowledge captured by the ontology to inform the learning. Compared to the purely ML-based prediction model, the physics-informed ML-based prediction model improved the performance of predicting the condition ratings of concrete decks by 10.0%. This research contributes to the body of knowledge by offering an ontology that can semantically represent structural deterioration knowledge in mathematical physics models to enable automated model instantiation. This research thus has the potential to fully unleash the power of the large amount of bridge data and deterioration knowledge that exist to develop next-generation learning machines for data-driven, physics-informed ML-based deterioration prediction and maintenance decision making. [ABSTRACT FROM AUTHOR]

Currently, the published methods used to optimize the number of beam pedestals in a precasting yard for bridge beams or segments do not consider all relevant constraints. Therefore, an optimal calculation method based on multiobjective constraints is proposed. The constraints used are the demand plan for erecting beams, the minimum beam storage time, and the actual beam storage time. Two cases were considered based on the relationship between the minimum and actual storage times. When the minimum storage time of the finished beams was equal to the actual storage time, the minimum number of pedestals could be determined through the stage of maximum demand. When the actual storage time of the finished beams exceeded the minimum storage time, multiobjective constraint equations for the production and demand plans of each stage were established, and a logic algorithm is proposed to calculate the minimum number of pedestals. In addition, to identify the appropriate production plan, an optimization method is proposed based on three evaluation indexes: vacancy rate, dispersion, and core area. Taking one project as an example, the minimum number of platforms and optimized production plans were obtained using the proposed method. A complete set of planning processes, including calculation analysis and scheme comparison, is presented in this paper. The results demonstrate that the proposed methods are applicable and can provide a theoretical reference for the optimization of precast yards for bridge construction projects. [ABSTRACT FROM AUTHOR]

This case study focuses on excessive and undesired deformations that occurred during construction of newly rehabilitated steel bridges. The case study responds to problems with elevation control and subsequent ride quality problems exhibited in newly constructed or newly rehabilitated steel girder bridges made composite with concrete decks cast atop steel girders. Forensic investigations were performed on three bridges that had been in service for only a few years. These investigations discovered strong evidence that cantilevered portions of concrete decks were not supported adequately during construction loadings. The purpose of the case study is to identify causes for undesirable elevation profiles, and to recommend design and construction practices to help mitigate problems created for the highway users and extend the useful life of bridges. [ABSTRACT FROM AUTHOR]

Force–deformation relationships of waterway vessels play an important role in the impact-resistant design of bridge structures. Characterizations of barge bow force–deformation (i.e., crushing) behaviors found in design provisions and previous research are reviewed as part of the present study. Results obtained from use of the relationships in impact analyses are then compared with computed responses from high-resolution finite-element barge–bridge collision simulations. As motivated by the comparisons, new relationships are proposed to further enhance designer capabilities for head-on barge impact design. In developing the proposed relationships, a parametric study of nonlinear dynamic collision simulations is performed to account for impacted pier surface geometry and barge bow versus impacted surface widths. Considerations are also made for impact velocities and peaks in force magnitudes that can occur for deformations near to the onset of nonlinear bow crushing. Merits of the proposed force–deformation relationships are then assessed via the shock spectrum approximation method. Key characteristics of barge bow force–deformation relationships (e.g., initial stiffness, maximum force, residual force plateau, impulse) are identified across typical ranges of bridge vibration periods and also in relation to propensities of empirical curve components for bringing about severities in computed structural demands. [ABSTRACT FROM AUTHOR]

An investigation of the dynamic behavior of a footbridge located at Jordan University of Science and Technology, Irbid, Jordan, is presented in this paper. The work includes the evaluation of vibrations serviceability and comfort criteria of the footbridge structure for which several pedestrians felt a level of discomfort when passing through. The authors conducted an experimental investigation in which they investigated various dynamic excitations (walking, jogging, and running with varying numbers of pedestrians). Nine different dynamic excitations were applied to the structure with one, two, five, eight, and nine pedestrians. It is recognized that the pedestrians exert both vertical and lateral dynamic forces on the footbridge structure; the maximum vertical and lateral accelerations as a result of various pedestrian excitations are compared to extensively used international vibration serviceability codes/guidelines. These guidelines are HIVOSS, British Standards 5400, Sétra, Ontario Highway Bridge Design Code, ISO-1992, Hong Kong Structures Design Manual for Highways and Railways, and Japanese Footbridge Design Code. Concerning vertical accelerations, for everyday walking, the structure is found acceptable for most of the codes and almost all dynamic excitations used in the study, whether there is only a single pedestrian or a group of pedestrians walking on the footbridge. There are a few dynamic excitations where the vertical accelerations exceed the comfort limits specified in the codes. Still, those are extreme excitations that would not occur during the daily use of the footbridge. Maximum accelerations (i.e., vertical and lateral) exceed the limiting criteria for the majority of relatively older codes, but for relatively recent standards (HIVOSS and Sétra), excitations are found to be acceptable with medium or minimum comfort classes. However, some dynamic excitations (running and synchronous walking excitations) are deemed unacceptable, although these are considered extreme excitations that would not occur during everyday footbridge use. The old or early used codes in the design of lightweight footbridges are concerned to study the serviceability of bridges under human-induced vibration and are used until nowadays, and the new codes are concerned to study the comfort criteria of bridges under human-induced vibration. [ABSTRACT FROM AUTHOR]

Design factors in load and resistance factor design (LRFD) codes are determined using structural reliability theory to account for the uncertainties in loads and resistance. The calibration of load factors for strength limit states has been investigated during the development of AASHTO LRFD bridge design specifications (BDS). In comparison, sparse efforts can be found for calibrating service limit state load factors. Temperature variations affect all types of bridges and cause additional stresses, deformations, and moments in different bridge components. Calibration of load factors for vertical temperature gradients appear to be lacking for both strength and service limit states. This paper focuses on calibrating positive vertical temperature gradient load factors for the Service III limit state. A design space consisting of 70 two-span continuous bridges with different bridge configurations is established and designed for severe corrosive exposure conditions. Design stresses for various load cases are first calculated. Using the first-order reliability method (FORM) and considering the sources of uncertainties due to materials, fabrication, and load effects, temperature gradient load factors were then calibrated for different risk levels. The results show that vertical temperature gradient load factors between 1.00 and 1.40 should be used for the Service III limit state. [ABSTRACT FROM AUTHOR]

This paper presents the formulation of a comprehensive risk-targeted performance-based seismic design (PBSD) framework involving the seismic design of bridge piers for California Ordinary Standard Bridges (OSBs), facilitating risk-informed design and decision making in the face of uncertainty. A full-fledged implementation of this all-inclusive design method formulated by retaining the inherent rigor of the underlying seismic performance assessment methodology might impose a seemingly prohibitive computational cost for the available resources in the current scenario of seismic bridge design practice. For reasons of practicability, the findings of the full-fledged design framework are inventively utilized to distill out a simplified and computationally more economical PBSD procedure. Its efficacy is validated using four already-built California testbed OSBs as cases in point. The proposed simplified design methodology is able to (1) find a design point in the primary design parameter space of a bridge to be designed for multiple risk-targeted performance objectives; and (2) delineate an approximate, yet sufficiently accurate, feasible design domain and identify the limit states controlling its boundary in the primary design parameter space of the bridge, at a computational cost significantly lower than that of the original method. [ABSTRACT FROM AUTHOR]

In this study, seven one-third-scale bridge column specimens are tested via a quasi-static cyclic test to understand seismic performance differences between cast-in-place (CIP) and precast bridge columns with various shear span-to-depth ratios and connection design details. The columns are designed based on practical engineering application, which aims to provide design reference for the seismic behavior of real-world bridge structures with varying column heights, such as bridge ramps. Based on the test results, it was found that column height exceeding the plastic hinge region is of combined bending and shear failure and that the full development of the plastic hinge region of these columns yields the same damage progression. However, short columns that are lower than the height of the plastic hinge are subjected to pure shear failure, and they are also of the same level of seismic performance except for displacement-related indices. Though the strengthening effect of the grouted splice sleeve connections is observed and damage is more concentrated at the joint for precast bridge columns, the difference of overall seismic performance between CIP and precast bridge columns is less than 5% in terms of ductility and energy dissipation. The addition of shear keys or change of bond material help improve the structural integrity, while the increase of seismic performance is still limited. [ABSTRACT FROM AUTHOR]

With the development trend of accelerated bridge construction, the precast ultra-high-performance concrete (UHPC) segmental bridge might be increasingly used due to the advantages of lightweight superstructure and advanced structural performance. However, there is still lack of study on the UHPC keyed epoxy joint, especially in terms of theoretical aspects. In this study, a theoretical model was developed to predict the shear capacity of UHPC large-keyed epoxy joints. In the proposed model, the shear capacity of joint was determined as the superposition of the shear contributions of the flat part and the keyed part. For the flat part, the shear strength mainly depends on the bond shear performance at the joint interface, which could be determined though test results of flat epoxy joints. To obtain the shear strength of the keyed part, the failure envelopes for UHPC were determined based on Mohr–Coulomb shear failure criterion, and the theory of Mohr's circle was adopted. Then, the direct shear test was performed on 15 UHPC large-keyed epoxy joint specimens and four flat epoxy joint specimens to obtain their failure modes and shear resistance for verification. In addition to the test data in this study, test results of related existing studies were also utilized to validate the proposed theoretical model. Furthermore, the AASHTO equation and the existing formulas for epoxy joint were also used for comparison. Results indicated that the proposed model performed well in both the accuracy and the variation degree. With the development trend of accelerated bridge construction (ABC), the precast ultra-high-performance concrete (UHPC) segmental bridge might be increasingly used due to the advantages of lightweight superstructure and advanced structural performance. The shear performance of joint between precast segments is of great importance since fibers and reinforcements are discontinuous at the joint. This paper presents a theoretical model for predicting the shear capacity of UHPC large-keyed epoxy joints in precast UHPC segmental bridges. In this model, the shear capacity of UHPC large-keyed epoxy joints is assumed to be contributed by the flat part and the keyed part, and the shear strength of the keyed part is determined based on Mohr–Coulomb shear failure criterion and the theory of Mohr's circle. This theoretical model has been validated by the test data of UHPC keyed epoxy joint specimens obtained from this study and other existing studies, indicating that it performs well in both accuracy and variation degree. It should be noted that this model is limited to the UHPC large-keyed or single-keyed epoxy joint while it is not applicable to the multikeyed joint. This study will contribute to establish the equation for determining the shear capacity of UHPC precast segmental bridges in the design. [ABSTRACT FROM AUTHOR]

Many bridges would be washed away due to giant tsunamis caused by the anticipated Nankai Trough earthquake. The accelerated bridge construction (ABC) concept should be applied to temporary bridge construction to save on-site construction time and help roads reopen immediately after the event. In this paper, a temporary bridge using precast reinforced concrete (RC) blocks with connections composed of steel shear keys and carbon fiber–reinforced polymer (CFRP) sheets is proposed. The proposed bridge facilitates rapid recovery from natural disasters and accordingly enhances disaster resilience. Bending and shear tests are conducted to investigate the effects of the proposed connection on the structural performance of beams. The experimental results indicate that the connection with an adequate CFRP sheet length provides sufficient flexural capacity for temporary bridges and does not negatively affect the shear capacity. Moreover, a 3D finite-element (FE) model is applied to simulate the bending tests. The FE model provides good agreement with the experimental results and can be applied to design the structural details of full-scale RC blocks. [ABSTRACT FROM AUTHOR]