Journal of Bridge Engineering

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.

Bridge codes tend to provide general guidance on the thermal gradients acting on bridge decks based on data from historical extreme events that have occurred within a country, without considering the location of the bridge itself. However, the thermal gradient is a function of the climate conditions that occur locally, in the vicinity of the bridge. Thus, a significant number of bridge decks are designed for climate conditions that might not be representative of their locations. The aim of this research is to optimize current guidelines to ensure that thermal gradients are derived based on bridge location. This objective is achieved through the investigation of the relationship that occurs between climate parameters and the resulting thermal extremes. An advanced finite-element platform was used to model the thermal performance of a concrete box girder. Several sets of meteorological data from 18 locations across Canada (representative of different Canadian climate types) were used as input in the thermal models to simulate the temperature distribution within the bridge deck. Upon analysis of the results, it was determined that a correlation exists between the direct normal irradiance (DNI) at a certain location and the resulting thermal differential that occurs between the top and the interior of the cross section. Four categories were defined, with each category representing a range of DNI values and a resulting range of thermal differentials between the top and the interior. To demonstrate the applicability of the established relationship, a case study was performed in which the maximum limit provided by the Canadian Highway Bridge Design Code was investigated across several provinces in Canada.

The aim in this study is to experimentally and numerically evaluate the effectiveness of the fiber-reinforced polymer (FRP) rehabilitation technique on postblast piers. Firstly, contact explosion, carbon FRP (CFRP) rehabilitation, and axial compression tests were successively conducted on half-scale RC pier specimens. The incident overpressure time histories and damage profiles of specimens in the explosion test, as well as the axial force–displacement curves, strain time histories of FRP, and specimen damage modes in the axial compression test were recorded. Secondly, a finite-element (FE) analysis approach was proposed and experimentally validated to reproduce the blast wave–pier interactions and dynamic behaviors of RC piers under explosions, as well as the axial compressive performance of the intact, unrehabilitated, and FRP-rehabilitated RC piers. Furthermore, three typical explosion threats specified by the Federal Emergency Management Agency were selected, and the damage profiles and residual axial capacities of the seismically designed prototype bridge piers were further examined. An FRP rehabilitation scheme, covering FRP type, rehabilitation height, and number of rehabilitation layers, for restoring the axial capacities of postblast prototype piers is recommended. It indicates the following. (1) FRP rehabilitation effectively improves the axial capacity and ductility of postblast piers, but slightly affects the axial stiffness. (2) The residual axial capacities of the presented prototype piers reduced to 92% and 58% of the intact value under contact explosion from a suicide belt or suicide vest, and increased to 99% and 84% after two-layer CFRP rehabilitation. (3) Compared with glass FRP and aramid FRP, CFRP rehabilitation along the overall pier height is more strongly recommended. (4) Increasing the number of rehabilitation layers to four could prominently improve the axial capacity. This work could provide a supportive reference on the FRP rehabilitation of a RC bridge pier after explosions.

Metallic dampers with plastic energy dissipation are often used in the seismic protection of civil structures. However, conventional metallic dampers cannot provide adequate energy dissipation capacity due to the small displacement vibrations. This paper proposed a torsional metallic damper to improve energy dissipation performance. The proposed damper utilized ball screw devices to amplify plastic deformation, which can excessively enhance its damping capacity. First, the axial tension and pure torsion experiments were conducted to evaluate the energy dissipation capacity of solid aluminum round rods under different loads. The torsional tests of three different sections of aluminum rods were carried out to explore the optimal section of torsional energy consumption. The results showed that aluminum 1060 exhibits good plastic properties under pure torsion and the solid aluminum rod had the best energy dissipation capacity among the three test specimens. Second, the dynamic theoretical model of the proposed damper was established and verified by experiment results. The influence of the diameter and length of the aluminum rod and the lead of the ball screw on the energy dissipation performance of the damper was also analyzed. Finally, a cable-stayed bridge was numerically modeled to verify the damping performance of the proposed damper for longitudinal seismic control, which indicates that the displacement of the bridge at the girder end and tower top is significantly reduced with the proposed damper compared to that without the damper. In general, the displacement amplification mechanism of the proposed damper can increase the damping capacity, and the optimal parameters of the damper designed from one certain earthquake wave are also effective for response reduction under other waves.

This study aims to investigate the influence of turbulent three-dimensional (3D) and distortion effects on the unsteady lateral buffeting force of trains on a streamlined deck and propose a closed form equation for the 3D aerodynamic admittance function (AAF). Six fluctuating wind fields were simulated to analyze the influences of different turbulence characteristics on the lateral force of trains through pressure measurement tests. In addition to a train on a bridge, a plain ground scenario was simulated as a reference. The results show that the lateral force correlation of the train is always greater than that of the fluctuating wind. As L_u/D increases, the lateral force coefficient and spanwise correlation of the lateral force increase, and the 3D effect weakens. The AAF is sensitive to L_u/D at high frequencies, and the wind exhibits a clear distortion effect during turbulence flow on the train. A difference exists between the aerodynamic characteristics of trains on the ground and on a bridge. The turbulence intensity has little influence on the lateral aerodynamic characteristics of a train. To correct the uncertainty caused by the 3D and distortion effects, a generalized AAF model was proposed to accurately estimate the gust loading on a train.