Journal of Bridge Engineering

Current analysis procedures for seismically isolated bridges frequently use an equivalent (approximate) linearization approach to represent the response of nonlinear isolation/energy dissipation devices. Linearization allows standard linear elastic analysis methods, e.g., the response spectrum method, to be conveniently used for design purposes. The linearization approach is by nature an iterative method implying the need to repeatedly correct and analyze a numerical finite-element model. A further simplification could be achieved using closed form equations to represent (1) the structure displacement patterns and (2) the restoring forces from structural elements. The paper explores such a possibility with reference to partially isolated continuous bridges, i.e., bridges with isolation devices at piers and pinned supports at abutments. The role and effect of higher modes of vibration on the system response are discussed, and an approximate method is proposed to account for such effects. An improvement of the classical Jacobsen’s approximation for the effective viscous damping ratio is also proposed using the results of response history analyses. The latter are carried out on two-dimensional numerical models of five case studies, generated from a real existing bridge supposed to be isolated with friction pendulum devices. Comparison of approximate predictions with response history analysis results is presented and discussed. Nonlinear dynamic analyses of a three-dimensional numerical model of the existing bridge were also carried out for comparison purposes.

The seismic vulnerability of the Chemin des Dalles Bridge over Highway 55 located in Trois-Rivières (Quebec, Canada) was evaluated through fragility analysis using field- and laboratory-validated models. This approach offers an effective means to capture the uncertainties in ground-motion realizations, the demands placed on key structural components, and the capacity of the components to resist various levels of seismic excitation. A series of 180 synthetic ground-motion time histories (GMTHs) compatible with eastern Canada was used to capture the uncertainties related to the hazard. Nonlinear time history analyses were performed with these GMTHs and statistically analyzed to define the probabilistic seismic demand model for the abutments, bearings, and columns, which are the critical components. Data from the literature, coupled with sectional and damage mechanics analyses, were used to define the limit states (LSs) for these components. Bridge component and system fragility curves were used to evaluate the likely failure modes of the bridge and potential targets for retrofit, while accounting for key sources of uncertainty in the performance assessment. The results reveal the seismic vulnerability of this specific bridge and even offer insight into the seismic vulnerability of a typical multispan girder-type concrete bridge in Quebec.

Accidental collisions between overheight trucks and bridge superstructures have occurred frequently in recent years. These collisions dramatically affect the safety of bridge structures and traffic systems in metropolitan areas. Frequent collision-induced bridge damages have highlighted the importance of scientific research in this field. In this study, considering the inherent difficulties of full-scale laboratory testing, the FEM is used to simulate the collision procedure. The finite-element (FE) results indicate that collisions between overheight trucks and bridge superstructures induce two types of failure modes, global damage and local damage, which need to be incorporated into bridge design guidelines. The numerical results also reveal that the collision forces are mainly influenced by the parameters associated with overheight trucks. To reduce computational costs and facilitate engineering application, a simplified model for calculating the collision forces is also proposed. The predictions of the simplified model, although slightly conservative, are in good agreement with the FE results.

Recently, increasing terrorist threats on bridges have illustrated the vulnerabilities of this type of transportation infrastructure. Because of cost and safety constraints, it is impractical to obtain the complete structural response by testing a real bridge, so in recent years, a fully coupled fluid-structure interaction model, which still has several assumptions, was developed to simulate the blast wave propagation process and its interaction with the structure; this has become an advanced method to better analyze blast loading effects. However, because of the complicated computational algorithm and desktop computer resource limitations involved in using this model, it is not practical to simulate large structural responses, especially for long-span bridges. The purpose of this paper is to develop a multi-Euler domain method to solve the problems listed earlier. Both the verification of the method and its application for a RC composite slab-on-girder bridge proved its accuracy and efficiency. The blast-resistant capacity of three different detonation scenarios was investigated, including one above-deck detonation and two under-deck detonations, with different trinitrotoluene (TNT)-equivalent charge weights. This study established the dynamic performance and the damage mechanisms of the whole bridge and identified the critical blast event for this typical slab-on-girder bridge. The results and observations of this study provide a global understanding of protection strategies for highway bridges.

A large number of railway structures in Europe are metallic bridges. The increasing volume of traffic and axle weight of trains mean that, for many structures, the loads today are much higher than those envisaged when they were designed. This paper presents a summary of the different recommendations and advice proposed in European guidelines for assessing load and resistance of railway bridges issued from a research project. The knowledge of the material properties of existing metallic bridges is essential for the resistance assessment and the determination of the remaining lifetime of old metallic bridges. Furthermore, old bridges require more exact and efficient assessment methods that call for a precise description of the material. Among the problems met in metallic structures and material properties estimation, fatigue is the most common cause of failure. To be able to make accurate assessments of existing bridges, it is important to know the behavior of bridges exposed to fatigue and how the old materials behave owing to cyclic exposure. The main question answered in this paper is how to make a safe estimation concerning the remaining life in service. The possible traffic load on steel rail bridges is usually limited by the fatigue resistance, but for certain situations the static resistance also has to be checked. Most design rules for steel structures are applicable also to riveted structures. However, some information is missing on how to deal with the special case when elements are intermittently connected in contrast to welded structures that are connected continuously. Because the traditional methods for assessing the resistance of steel bridges are based on elastic analysis, a method for utilizing a limited redistribution of bending moments based on beam theory is proposed.

The objective of this research has been to design, develop, and evaluate experimentally a modified type of construction joint of limited length between concrete slab segments. The design concept is based on an anchorage hook of reduced development length stiffened by transverse reinforcement bars. The purpose of this paper is to investigate the mechanical behavior of the joint in terms of stiffness and strength for an application that requires high durability, which often leads to serviceability problems such as cracking and water leakage at transverse joints. This can regularly appear in bridges. Additionally, bridge decks are structures that are subjected to repeated loading such as traffic loads, making it necessary to evaluate the behavior of joints under fatigue load. Therefore, studies focusing on the strength, stiffness, and serviceability of the joints must be carried out. This paper investigates experimentally the fatigue behavior and strength of loop joints with regard to the loop bar diameter, loop joint width, and applied load ranges. These results were compared with the behavior of RC slabs without joints. A total of eight slabs were fabricated for fatigue loading tests, and the failures of the different specimens (with loop joints and without) were obtained. From the test results, the mechanical behavior of the slabs with loop joints was confirmed to be similar to that of the slabs without joints. The experimental loop joint design was found to perform correctly under fatigue loads.

This paper discusses the crashworthiness of prototype steel post-and-beam barriers [Ministry of Transportation of Québec (MTQ) Type 210] whose concrete curb-to-bridge deck connection is reinforced with corrosion-resistant glass fiber-reinforced polymer (GFRP). Experimental evidence is obtained from proof tests on five full-scale barrier and overhang subassemblies. The text matrix includes three GFRP RC and two steel RC specimens. The steel RC benchmark system is currently used as specified in the Canadian Highway Bridge Design Code (CHBDC). The objective is to verify whether (1) the resistance to out-of-plane quasi-static loads and the associated transverse deflection of the GFRP RC curb and steel barrier system are comparable to those of the steel RC counterparts; (2) the transverse strength exceeds the CHBDC equivalent static load demand; and (3) failure at the curb-deck connection is attained at safe transverse loads, and premature failure at the curb-deck connection is prevented. The GFRP and steel RC systems exhibit comparable strength, with the former undergoing greater deformations. For both systems, premature brittle failure of the curb-deck connection is prevented, and the equivalent static load requirements are satisfied. A larger capacity is attained when closed GFRP stirrup connectors are used at the curb-deck connection in lieu of C-shaped stirrups. An analytical model is used to predict the lower-bound strength of the GFRP RC curb-deck connection, and relevant design implications are discussed. It is recommended that the adoption of the proposed GFRP RC design relies on conclusive evidence from crash testing to verify safety against vehicle rollover because of the greater deformations compared with steel RC systems having the same amount of reinforcement.

Fiber-reinforced polymer (FRP) composite materials can be used for the fabrication of lightweight, corrosion-resistant honeycomb sandwich panels, representing a convenient and economical alternative to traditional steel RC for bridge decks. Composite panels are particularly advantageous for the construction of temporary bridge structures in terms of both ease of construction and reusability of panels. Although FRP sandwich panels have been considered for the construction of bridge decks, no barrier system has been developed and crash tested for use with this specific type of deck. The objective of this research project was to develop a crashworthy concrete barrier system for use with temporary FRP composite bridge decks. Upon failure of a full-scale crash test with a New Jersey concrete safety shape barrier, an accurate analysis of the potential problems led to a series of design modifications to the barrier as well as to the attachment between the composite deck and both the bridge structure and the barrier. The second design, which used a vertical-faced barrier, was successfully crash tested according to Test-Level 3 impact safety standards set forth in the AASHTO Manual for Assessing Safety Hardware (MASH).

Self-consolidating concrete (SCC) is a highly workable concrete with tremendous potential to reduce the production time and cost of precast members. Institutions in Japan, Europe, and the United States have successfully utilized SCC in large-scale applications, particularly in bridges. However, lack of experimental data has hindered SCC’s implementation in prestressed design. This paper reports the findings of a study investigating the development length of steel strands in SCC full-scale prestressed bridge girders. Flexural tests are conducted on two 8.5-m-long box girders and two 14.6-m-long I-girders cast with SCC to determine the development length of their 12.7-mm-diameter prestressing steel strands. Experimental results are compared with requirements of the American Concrete Institute and AASHTO. Results are also compared with analytical expressions for development length proposed in the literature.

The calculation of minimum required prestressing levels in prestressed bridge deck girders is usually governed by serviceability requirements in terms of allowable stress levels. In the case of continuous structures, different quantities of prestressing steels have to be quantified for different critical locations and, owing to the structure hyperstaticity, the prestressing force required for a given critical cross section depends on the quantities of prestressing steels adopted in the remainder of the structure. This paper presents a feasible methodology for quantification of the minimum required prestress forces for different critical cross sections, avoiding the use of iterative procedures. A methodology for taking into account the variability of the structure response, owing to the uncertainty associated with the quantification of creep, shrinkage, and construction timings is also presented. Monte Carlo simulations, based on the Latin Hypercube sampling method, are used in the calculation of the statistical distribution of the long-term structure response. Two case studies are presented to show the relevance of the aforementioned variability and its consequences in terms of minimum required prestressing levels.

This paper describes a field validation of a second-generation, statistical-based damage-detection algorithm and its ability to detect actual damage in bridges accurately. The algorithm had been theoretically validated previously. For the field tests, in lieu of introducing damage to a public bridge, two sacrificial specimens that simulated damage-sensitive locations of the bridge were mounted on the bridge, and different types and levels of damage in the form of cracks and simulated corrosion were induced in the specimens. Using strain data collected from sensors on the sacrificial specimens and on the bridge, the algorithm correctly identified the damage. Analysis of data from sensors far away from the damaged area revealed a relatively high false-positive rate.