Laminated rubber bearing pad (LRBP) is widely used in small to medium-span highway bridges. They are directly placed between piers and girders to allow the bridge span to have horizontal movement and to transfer the gravity loads from decks to piers. Although LRBPs are not designed for seismic loads, their application can partially isolate the superstructure from the substructure keeping the piers intact during earthquake events. However, recent investigations indicate that large relative displacement between superstructure and substructure caused by sliding between girders and LRBPs can cause expansion joint or bridge span failure. As such, suitable restrainers should be implemented to control the potential large displacement. Among all types of restrainers, passive energy devices such as viscous dampers have shown a remarkable capacity in dissipating the earthquakes energy. This study aims at investigating the effectiveness of VD-LRBPs system, viscous dampers in conjunction with LRBPs, in controlling the large displacement between decks and piers. Accordingly, a 3D Nonlinear Time History Analysis (NTHA) was conducted on a case study RC bridge model under several earthquakes. OpenSees, an open sources finite element software, was used for the analysis. The relative displacements between decks and piers as well as the force in the piers, were recorded for two cases: 1- with only LRBPs and 2- with viscous dampers and LRBPs (VD-LRBP system). The results indicate that adding viscous dampers can reduce the relative displacement up to 60 percent. Also, it can reduce the potential residual displacement post-earthquakes to near zero.
With the increase in population, surface transportation has significantly increased, highlighting the need to maintain reliable and safe civil infrastructures. Bridges can be considered the most critical element in transportation infrastructure. Accordingly, they require periodic inspection to prevent any failure caused by aging and environmental impacts. Over the years, visual inspection has been practiced the most due to its simplicity. However, detection of small and internal cracks and defects requires more advanced techniques. To address this, various non-destructive testing (NDT) methods have been developed and implemented in recent decades. With the advance of technology, opportunities for developing more advanced and effective NDT methods have been created. To achieve the development of such advanced techniques, the knowledge of available methods and their future trends becomes necessary. This paper gathers in one place all the relevant information regarding existing non-destructive testing for steel bridges. Furthermore, the future direction and recent innovations in this field, including the application of robots, sensors, and drones for fast and efficient evaluation of steel bridges are discussed. The parameters for selecting the most appropriate NDT method for specific cases are explored. The methodology, and pros and cons of each technique are also presented. It is expected that the results of this study pave the way for development of new methods and improvement of currently practiced NDT techniques for steel bridges.
The use of fiber reinforced polymer (FRP) materials has been on the rise in bridge construction industry. They have been mostly utilized for strengthening purposes, especially as externally bonded reinforcement for columns, slabs, and beams. Their lightweight, flexibility and ease of installation, and higher strength offer an ideal solution for increasing the axial, bending, and shear resistance of existing concrete elements, as well as restoration and retrofitting of damaged members. FRP bars have also been used as internal reinforcement for concrete structural elements, providing corrosion-resistant alternatives to conventional steel reinforcements. Although the application of FRP for concrete members has offered many advantages, there have been issues and concerns associated with their long-term performance including their debonding from a concrete surface or within a concrete element. Accordingly, despite their durability, concrete elements strengthened/reinforced with FRP materials need to be inspected periodically to detect potential issues and hence prevent any premature failures. This study investigates Non-Destructive Testing (NDT) methods applicable to inspection of in-service FRP reinforced/strengthened concrete (FRP-RSC) bridge elements. Accordingly, this study first introduces damages and anomalies attributed to FRP reinforced/strengthened concrete bridge elements, and causes are discussed. The study includes a review of some promising NDT methods for the detection of these damages. The results of this study are expected to provide the inspection community more clarity in the application of NDT to FRP reinforced/strengthened concrete.
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