Journal of Bridge Engineering

This paper presents the cyclic behavior of four self-centering bridge bents with different construction details, including external energy dissipaters and neoprene isolation. The columns of these bents consisted of precast posttensioned concrete-filled fiber tubes (PPT-CFFT). A fifth monolithic moment resisting concrete bent was also tested as a reference specimen. The tests showed that PPT-CFFT bents can be used in bridge construction as a lateral load resistance system. The PPT-CFFT bents without external energy dissipaters displayed a lateral drift of approximately 9.2% without experiencing significant damage or residual displacement. The PPT-CFFT specimen with external energy dissipaters reached a drift angle of 9.2% with some damage. The reinforced concrete specimen failed at a drift angle of approximately 6.9% with substantial damage and residual displacement.

Pipe-pin rotational two-way column hinges were developed by bridge designers at the California Department of Transportation. An extensive experimental and analytical study was undertaken to understand the behavior of pipe-pin hinges and develop design guidelines. As part of the study, six 1:3.5 scale push-off tests were carried out to assess the bearing capacity of the concrete against the pipe. The tests showed that the bearing strength of concrete is as high as twice the concrete compressive strength because of the confining effect of the concrete and reinforcement. In addition, to determine the shear capacity of the concrete-filled steel pipe, six concrete-filled pipe specimens were tested in pure shear, and an empirical design equation was developed to assess their shear strength. In the analytical studies, ABAQUS finite-element (FE) package was used to perform a series of detailed nonlinear analyses. The results showed that the FE models accurately simulated the behavior of the push-off specimens and the observed modes of failure.

Bidirectional cyclic testing was performed on four half-scale reinforced-concrete rectangular bridge column specimens to examine the need to account for bidirectional seismic loading in design for earthquakes expected in eastern and western regions of North America. The prototype structures are common two-span, skewed bridge structures designed according to the seismic provisions of Canadian Standards Association (CSA)-S6-06. The column specimens are $1.2\times 0.6\mathrm{m}$ in cross section and 3.0 m tall and assumed to carry a gravity load of 6% $A_g{f}_c^{\prime }$. Two specimens were designed for Montreal, Quebec, Canada (east site), using 0 and 30% combination rules, resulting in longitudinal steel ratios of 0.41 and 0.57%. Two specimens represented the column part of bridges located in Vancouver, British Columbia, Canada (west site), with longitudinal steel ratios of 0.97 and 1.72% resulting from the application of 0 and 40% combination rules. Site-specific cyclic displacement test protocols were developed from time-history analysis of the bridges. For both sites, the tests showed that the combination rules used in design had no significant influence on the inelastic cyclic response of the columns. The columns designed for the Montreal site exhibited satisfactory inelastic cyclic performance even if they had a longitudinal reinforcement ratio less than the current CSA S6 limit of 0.8%. All columns were subjected to biaxial shear forces corresponding to their biaxial flexural strength envelope. For all specimens, the height of the plastic hinge region was approximately equal to the smaller column dimension, rather than the larger one as currently specified in CSA S6.

This paper investigates the implications of ground motion spatial variability on the seismic response of an extended highway bridge. An existing 59-span, 2,164-meter bridge with several bearing types and irregularity features was selected as a reference structure. The bridge is located in the New Madrid Seismic Zone and supported on thick layers of soil deposits. Site-specific bedrock input ground motions were selected based on a refined probabilistic seismic hazard analysis of the bridge site. Wave passage and ground motion incoherency effects were accounted for after propagating the bedrock records to the ground surface. The results obtained from inelastic response-history analyses confirm the significant impact of wave passage and ground motion incoherency on the seismic behavior of the bridge. The amplification in seismic demands exceeds 150%, whereas the maximum suppression of these demands is less than 50%. The irregular and unpredictable changes in structural response owing to asynchronous earthquake records necessitate in-depth seismic assessment of major highway bridges with advanced modeling techniques to realistically capture their complex seismic response.

The paper describes a study to characterize intentional human dynamic loads (vandal loads) and their induced effects on a footbridge. A numerical model to characterize the dynamic behavior of the footbridge has been developed, is experimentally validated, and is used to numerically simulate the response induced by groups of pedestrians synchronized at critical bridge frequencies. The vandal load associated with a single pedestrian is characterized and compared with definitions in the literature. The response is then calculated considering the measured load and compared with the measured response to the excitation induced by a single pedestrian or a group with varying dimensions. The definition of a general load model for vandal excitation, including a tentative definition for synchronization is discussed.

Computation of the dynamic stress of long suspension bridges under multiloadings is essential for either the strength or fatigue assessment of the bridge. This paper presents a framework for dynamic stress analysis of long suspension bridges under wind, railway, and highway loadings. The bridge, trains, and road vehicles are respectively modeled using the finite-element method (FEM). The connections between the bridge and trains and between the bridge and road vehicles are respectively considered in terms of wheel-rail and tire-road surface contact conditions. The spatial distributions of both buffeting forces and self-excited forces over the bridge deck surface are considered. The Tsing Ma suspension bridge and the field measurement data recorded by a wind and structural health monitoring system (WASHMS) installed in the bridge are utilized as a case study to examine the proposed framework. The information on the concerned loadings measured by the WASHMS is taken as inputs for the computation simulation, and the computed stress responses are compared with the measured ones. The results show that running trains play a predominant role in bridge stress responses compared with running road vehicles and fluctuating wind loading.

The use of continuous welded rail (CWR) with direct fixation of track on concrete deck is typical of most modern light-rail aerial structures. The interaction between the CWR and the elevated structure takes place through direct-fixation rail fasteners, which have a nonlinear force-displacement relationship. Factors that have significant influence on this interaction include the following: the bearing arrangement at the substructure units, trackwork terminating on the aerial structure, type of deck construction, and type of rail fasteners. To better understand the interaction mechanism, a nonlinear three-dimensional (3D) finite-element analysis of a straight, skewed, elevated steel guideway was carried out using the commercially available software GT STRUDL. The load cases considered in this study are temperature change, temperature change with rail breaking, and train braking. Results are presented in the form of rail axial stresses along the length of the bridge and normal bearing forces at both abutments and at all pier locations. The study shows that nonlinear 3D modeling can give a comprehensive insight into the rail-structure interaction (RSI) forces.

When studying the vibration of a bridge-vehicle coupled system, most researchers focus on the vertical vibration of bridges under moving vehicular loads. In reality, the moving vehicular loads can also induce significant lateral vibrations of high-pier bridges. This study is focused on establishing a new methodology considering the bridge’s lateral vibration induced by moving vehicles. The vehicle tire is modeled as a three-dimensional elementary spring model, and the contact patch is assumed to be a rectangle. Three significant factors that affect the lateral forces, including the slip angle, camber angle, and vehicle tires moving with an “S” shape, are introduced in studying the effect of the lateral forces on the lateral vibration of bridges. The bridge-vehicle coupled equations are established by combining the equations of motion of both the bridge and vehicles using the displacement relationship and interaction force relationship at the contact patch. The accuracy and efficiency of the present method are verified by comparing the simulations and the field test results of a typical high-pier bridge, showing that the proposed method can rationally simulate the lateral vibration of the bridge under moving vehicular loads.

New designs of precast bridge parapets made with fiber-reinforced concrete (FRC) were developed using nonlinear finite-element calculations. Specific properties of high- and ultrahigh-performance FRC were exploited in these designs. The conventional reinforcement required in the FRC precast parapets varied from 0 to 50% when compared with a reference built-on-site parapet. An extensive experimental program was carried out to verify the performance of the FRC precast parapets. The parapet mechanical behavior was established under quasi-static tests and under dynamic loading replicating a vehicle impact. The results of the quasi-static tests indicate that precast FRC parapets possess the required strength and have ductility comparable to reference parapets. Quasi-static tests carried out after the dynamic tests indicate that the residual strength of the parapets corresponds to 75 to 100% of their original capacity. The finite-element model adopted in the project satisfactorily reproduced the strength, stiffness, and failure mode of the parapets. Finally, the system efficiency of precast FRC parapets was established for their application in a typical urban bridge project, considering the mechanical performance, the fabrication costs, and the required installation time.

Precast deck panels are increasingly being utilized to reduce construction times and traffic delays as many departments of transportation (DOTs) emphasize accelerated bridge construction. Despite the short-term benefits, the connections between panels have a history of service failure. This research focused on the evaluation of the service and ultimate capacities of five precast deck panel connections. Full-scale tests were developed to determine the cracking and ultimate flexural strengths of two welded connections, a conventionally posttensioned connection, and two newly proposed, posttensioned, curved bolt connections. The conventionally posttensioned specimens were shown to perform well with the highest cracking loads and 0.42 times the theoretical capacity of a continuously reinforced concrete deck panel. The proposed curved bolt connections were shown to be a promising connection detail with approximately 0.5 times the theoretical capacity of a continuously reinforced panel. Data from the welded specimens showed that some welded connection types perform significantly better than others. The experimental results also compared closely with values calculated on the basis of finite-element modeling, which can be used for future analytical studies.

The flexural capacity rating of prestressed girders having severed or corroded strands often progresses by simply neglecting the contribution of the affected strands from the girder section and assessing the capacity. While this is an adequate approach at the affected section, it is conservative elsewhere along the span, assuming that fully bonded strands are used. Once it reenters sound concrete, the severed or corroded strand continues to be bonded to the concrete; thus stress transfer between the concrete and strand is possible and the strand prestress force may be “redeveloped” (in the sense of transfer length) by bond transfer at a distance from the damage location. This paper reports an experimental study that clearly shows that prestress force is redeveloped at a distance from the location at which a strand is severed. Furthermore, American Association of State Highway and Transportation Officials (AASHTO) and American Concrete Institute (ACI) code-prescribed transfer-length calculations appear to remain valid for this redevelopment behavior.

Vertical prestress is widely used in the webs of large-span concrete box girder bridges but has lost efficacy since it was first applied. To solve this widespread problem, a dynamic model for the exposed segment of the vertical prestress system is built to help detect effective tension retained in the bar. Results of laboratory experiments show that the flexural rigidity of the exposed segment in the anchorage zone increases as effective tension gets larger. Both approximate and exact solutions of the dynamic model are proposed to identify the flexural rigidity. On this basis, some field experiments have been conducted to fit the flexural rigidity-tension relationship curves, which can be used to identify the effective tension indirectly when the inherent frequency of the exposed segment is obtained. The aforementioned principle is easy to implement and can be used to find a practical quantitative testing method to detect the effective tension retained in vertical prestressing bars. Thus, it will be significant to ensuring construction quality and preventing the webs of concrete box girder bridges from cracking.

This paper investigates retrofitting precast, nonprestressed, channel beams (PCB) used in short-span bridges to improve beam shear strength and, consequently, beam ductility. Three retrofit approaches were investigated: applying carbon-fiber-reinforced polymer (CFRP) strips, applying an epoxy spray-on, and retrofitting by installing shear bars within the stems of the precast channel beam. Implanting shear bars into each precast channel beam stem was found to be the optimal retrofit based on improved beam strength, installation ease, and economics. The suitability of the shear bar retrofit was further explored by implementing the shear bar retrofit at a short-span precast channel beam bridge. Precast channel beam sections cast without shear reinforcement were used to construct Arkansas Bridge #02992 over the Flat Hollow Branch Creek. The bridge was constructed in 1955, but several of the beams used in the original construction have since been replaced with better-condition similar-style beams. The bridge is made up of four simple spans. Each span consists of 5.79-m (19-ft) precast channel beams cast without shear reinforcement. Five interior beams along with two exterior beams were placed side-by-side to develop the 7.62-m (25-ft) overall bridge cross section. Each interior beam has a width of 1.07 m (3 ft-6 in.), and each exterior beam has a width of 1.14 m (3 ft-9 in.). The exterior beams are slightly wider than the interior beams to incorporate the roadway curb within the cross section. During the implementation study, live-load distribution and dynamic-load amplification for a precast channel beam bridge were investigated.

The Ilsun Bridge is the world’s longest (801 m in total length) and widest (30.9 m in maximum width) prestressed concrete box girder bridge incorporating a corrugated steel web. This bridge has fourteen spans, twelve of which were erected using an incremental launching method, a method that is rarely applied in this type of bridge. To verify the construction safety of the Ilsun Bridge, this investigation focuses on the span-to-depth ratio, buckling shear stress of the corrugated steel webs, optimization of the length of the steel launching nose, detailed construction stage analysis, and the stress level endured by the corrugated steel webs during the launching process. The span-to-depth ratio of the Ilsun Bridge was found to be well-designed, using a conservative corrugated steel web design. Further, our investigation revealed that the conventional nose-deck interaction equation was not suitable for corrugated steel web bridges. As a result, a detailed construction stage analysis and measurements of this bridge was performed to examine stress levels and ensure safety during the erection process. The results revealed that there are essential design issues that should be considered when designing prestressed concrete box girder bridges with corrugated steel webs and that, when constructing them, the incremental launching method should be used.

The conventional design process of a launching nose of an incrementally launched bridge is based on trial-and-error methods to reduce bending moment of prestressed concrete deck at the foremost support during launch. With this method, there is no guarantee that the obtained solution is the best among all the possible solutions, since they all depend on the experience and intuition of a designer, and they are also restricted by a limited number of possible iterations. Given that launched bridges constitute an important constructive typology, all the available capacities of design innovation should be incorporated, including numerical optimization. This research work proposes an objective and rigorous formulation to optimize the launching nose of a launched bridge under real constraints that a bridge designer can encounter in practice. Comparing the results obtained by conventional process and those obtained by optimization techniques allows us to verify that some of the assumptions considered in classical design methods of a launching nose are not based on any theoretical foundation. This fact demonstrates the utility of numerical optimization to improve a design.

Recent innovation in the engineered wood industry has produced structural composite lumber (SCL) that achieves excellent strength, stiffness, and efficient use of wood. Product variations of SCL, such as laminated veneer lumber (LVL) and parallel strand lumber (PSL), are currently being used in transportation to produce bridge girders and decks for rural and other low traffic volume roads. Although the elastic and shear properties of SCL are available, no attempt has been made to estimate the fatigue performance of bridge girders. This study tested 12 new and 2 old, weathered SCL T-beam bridge girders with material and preservative variations for AASHTO-specified flexural fatigue under a stress-controlled test setup simulating 60 years of service. Transverse posttension was applied to the girders simulating a real-life situation. Results from the study indicate that the girders are capable of withstanding the repetitive loads without much physical damage. A few of the LVL girders had severe delamination at the SCL-epoxy interface. The fatigued girders were loaded statically up to failure and compared with the ultimate flexural strength of fresh girders. The girders did not show any appreciable strength loss because of one million cycles of fatigue loading. There was no effect of SCL type and preservative treatment on fatigue strength.

Posttensioning is an effective method for the construction of different types of bridge girders such as those used in segmentally erected bridges. Available nonlinear analysis programs for bridge girders under severe loading conditions are computationally expensive though. In addition, they neglect important phenomena such as bond-slip, friction, and anchorage losses. The objective of the proposed work is to develop a new nonlinear finite-element program for analysis of posttensioned bridge girders. The new model overcomes most of the difficulties associated with existing models. The model is based on the computationally efficient mixed formulation and considers bond, friction, and anchorage loss effects. The mixed formulation is characterized by its fast convergence, usually with very few finite elements and its robustness even under severe loading conditions. The posttensioning operation is accurately simulated using a phased-analysis technique, in which each stage of the posttensioning operation is simulated through a complete nonlinear analysis procedure. Correlation studies of the proposed model with experimental results of posttensioned specimens are conducted. These studies confirmed the accuracy and efficiency of the newly developed software program, which represents an advancement over existing commercial software packages for evaluating posttensioned bridge girders, in particular those subjected to severe loading conditions.