Journal of Bridge Engineering

The simple for dead load and continuous for live load (SDCL) steel bridge system has proven to be economical for nonseismic application. Although the system has been used in different methods of construction, this paper concentrates on accelerated bridge construction (ABC) application. The application of the SDCL steel bridge system in high seismic areas has been nonexistent, mainly due to lack of appropriate details. The extension of the SDCL system to high seismic areas was initiated by conducting a detailed numerical analysis to comprehend the types of forces that the connection must resist. The results of the numerical study led to the development of connection details over the middle pier. In this research, a component testing of the proposed SDCL connection was conducted to find the ultimate limit states, verification of numerical results, and merits of the proposed detail in light of established seismic design provisions. The developed connection behaved as designed and prevented damage to capacity-protected elements. The column showed sufficient ductility during cyclic tests, which indicated the connection should perform well under high levels of displacement.

A study of the dynamic response of a circular bridge pier forced simultaneously by earthquake and wave–current actions is presented. On the basis of diffraction wave theory, the analytic solution for the diffraction of incident waves with uniform current on a circular pier is given. On the basis of the radiation wave theory, the analytic solution for the hydrodynamic pressures on a circular pier induced by combined earthquake and wave–current action is obtained. Further, the solution for the dynamic responses of the pier under combined earthquake and wave–current action is obtained by treating the pier as a cantilever beam governed by beam theory. Last, the effects of hydrodynamic force, wave force, wave–current interaction, and surface wave condition on the dynamic responses of the pier are investigated. The results may be used for engineering practice and further research.

Girder unseating in skewed bridges with seat-type abutments has been frequently observed in past earthquakes. This has been attributed to excessive in-plane rotation of the superstructure, and a handful of numerical studies have been conducted to investigate the cause of this rotation. The most common explanation has been pounding between the superstructure and abutment back wall, but this phenomenon has not been verified by experimental testing. Accordingly, this paper describes an experimental investigation into the behavior of skewed bridges, with special attention being given to the interaction between the superstructure and abutment. Shake table experiments are described on a family of four single-span simply supported bridge models with skew angles of 0°, 30°, 45°, and 60° and five different expansion gaps. These models were subjected to a suite of ground motions that varied by type (near field and far field), intensity, and input direction. In total, 876 experiments were conducted. Data collected included superstructure displacements and accelerations, and impact forces at the abutments. The results confirm that a skew bridge experiences large in-plane rotation when the obtuse corner of the span impacts the adjacent back wall with or without slippage along the face of the wall. As a consequence, these bridges can experience large in-plane displacements normal to the back wall at their acute corners, and larger support lengths are required to prevent unseating than for straight bridges. The comprehensive data set obtained in these experiments may be used in future studies to validate numerical models for skew bridges and improve the empirically based minimum support length requirements that are specified for skew bridges in many bridge design codes.

This paper investigates the seismic response of skewed bridges using the comprehensive data set obtained from a family of shake table experiments. To begin, the influence of friction along the abutment on the in-plane rotation of skewed bridges is evaluated. Then the influence of expansion gap size, type of ground motion (near field and far field), and input direction on seismic response is described. It is shown that once impact occurs between the bridge and abutment back wall, significant forces can be generated normal to the back wall due to impact and in the plane of the back wall through friction. These forces cause in-plane rotation of otherwise symmetrical skewed bridges. Both impact and friction should therefore be included in numerical models used to compute in-plane displacements of the superstructure. Moreover, it is shown that bridges with very small or very large gaps experience lower response. It is also shown that numerical models that do not include the gap could give nonconservative results, especially for moderate-sized gaps. Furthermore, skew bridges are more vulnerable to near-field ground motions than far-field motions. Finally, if the major component of the ground motion is applied in the transverse direction alone, comparable maximum displacements and in-plane rotations are obtained for biaxial excitations, but it produces significantly smaller impact forces than for biaxial input due to the contribution of the minor component in the longitudinal direction.

When an existing bridge is being considered for replacement due to a deteriorated or obsolete superstructure, the foundation may still have significant functional value. Reuse of these foundations during bridge replacement or widening can present significant cost and time savings over constructing new elements. The potential time savings associated with foundation reuse can reduce mobility impacts, a key goal of accelerated bridge construction (ABC), and the cost savings can increase the economic viability and sustainability of an ABC bridge replacement project. However, existing foundations may have uncertain material properties, geometry, or details that impact the risks associated with reuse. Unlike a new foundation, an existing foundation may have been damaged, may not have sufficient capacity, and may have limited remaining service life due to deterioration. Assessment of these issues, possible foundation-strengthening measures, and innovative approaches to optimize loading are discussed in this paper. An analysis of an ABC database is performed to examine the current role of foundation reuse in ABC projects. This paper presents some key findings identified through various research projects related to foundation reuse. Six case examples are presented in which foundations were reused or considered for reuse during a bridge replacement project.

Vertical displacements are one of the crucial parameters defining, for example, the load-carrying capacity of a bridge deck in short- and long-term monitoring. Bridge managers are always looking for an easy way to measure vertical displacements of bridges. However, such measurements are difficult to perform. With the advancement of fiber-optic technologies, fiber Bragg grating (FBG) sensors are more commonly used in structural health monitoring due to their outstanding advantages, including multiplexing capability over long distances as well as high resolution and accuracy. In this study, a set of FBG-differential settlement measurement (DSM) sensors, connected by a hydrostatic leveling system of communicating vessels, and previously adopted for displacement monitoring along a steel member, were used for displacement measurements along a large-scale prestressed concrete I (PCI) beam. Specifically, the PCI beam was subjected to a set of three-point bending tests in the laboratory. The measured displacements matched well with the corresponding experimental values recorded by LVDTs. In addition, in situ experiments on Bridge No. 24 of Highway No. 86 in Taiwan indicated that the FBG-DSM system can be effectively employed to measure vertical displacements along span bridges. In conclusion, the proposed FBG-DSM system can be used for field bridge applications referring to an absolute reference and without any external physical reference or a requirement for accessibility or particular environmental conditions.

In steel truss bridges, some truss members are exposed to solar radiation, while others are shaded by steel decks, which may result in large temperature gradients between truss members and further induce significant horizontal rotation angles (HRAs) at beam ends of steel truss bridges. Therefore, using the long-term monitoring data from a railway steel truss bridge with a 2-layer deck, the effect of temperature gradients on HRA was studied. Several analytic methods related to this topic are proposed, including a method for identifying large temperature gradients in steel truss bridges, a method for identifying whether the thermal load is the dominant load affecting HRA, and a method for identifying what kinds of temperature gradients have significant impacts on HRA. The results show that there are significant vertical temperature gradients between the top and bottom truss members in the side trusses and significant transverse temperature gradients between the bottom truss members, the thermal load is the dominant load affecting HRA compared with the other dynamic loads, and the temperature gradient between the bottom truss members in the side trusses has the greatest effect on HRA.