Normally, Laminated Rubber Bearing Pads (LRBPs) are directly placed between girders and piers and their role is to provide the bridge span with horizontal movement, and to transmit the gravity loads ...from the deck to the piers. Although not designed for seismic loads, they can act as a fuse, partially isolating the substructure from the superstructure and keeping the piers intact during earthquakes. However, recent investigations show that large relative displacement of superstructure against substructure caused by sliding at bearing (sliding between girders and LRBPs) can cause expansion joint failure or even bridge span collapse. Accordingly, proper restrainers should be selected to prevent large displacement. Among all types of restrainers, viscous dampers as passive energy dissipation devices have shown a great capacity in damping earthquake energy. This study investigates the effectiveness of a VD-LRBP system, a viscous damper in conjunction with LRBPs, in dissipating energy and reducing the displacement of the superstructure with reference to the substructure caused by sliding at bearing during a seismic event. A Finite Element (FE) model was first developed and validated using available experimental and numerical results. With the validated model, a 3D Nonlinear Time History Analysis (NTHA) was conducted on a reinforced concrete bridge model under various records of earthquakes using OpenSees, an open-source finite element software. The relative displacement histories were recorded for the bridge in two cases: 1- with only LRBPs and 2- with viscous dampers and LRBPs (VD-LRBP system). The results of this study show that applying viscous dampers can reduce the relative displacement of the superstructure with reference to the substructure for up to 60 percent. As importantly, it can also reduce the residual displacement after the earthquake to near zero.
The growing population and increasing demand for surface transportation have highlighted the importance of maintaining safe and reliable civil infrastructures for daily use. Among all civil ...infrastructures, bridges are one of the most important elements in the transportation system. As such, to prevent any failures caused by aging and environmental impacts, bridges require periodic inspections. This becomes even more critical due to climate change and its effect on bridges, especially in the coastal regions. Most of the inspections conducted incorporate the visual type of evaluation due to its simplicity. However, with the current developments in new technologies, there is a need for more advanced techniques of structural health monitoring (SHM) methods to be incorporated in the maintenance programs for more accurate and efficient surveys. In this paper, non-destructive testing (NDT) methods applicable to steel bridges are reviewed, with a focus on methods applicable to local damage detection. Moreover, the methodology, advantages and disadvantages, and up-to-date research on NDT methods are presented. Furthermore, the application of novel NDT techniques using innovative sensors, drones, and robots for the rapid and efficient assessment of damages on small and large scales is emphasized. This study is deemed necessary as it compiles in one place the available information regarding NDT methods for in-service steel bridges. Access to such information is critical for researchers who intend to work on new or improved NDT techniques.
The use of piles is a common method for establishing deep foundations for bridges where there is a top layer of weak soil. Among various types of pile and installation methods, driving ...prestressed-precast concrete piles (PPCP) is a durable and economical option compared with the alternatives. Also, since the method employs pile segments prefabricated in precast plants and delivered to the site for installation, it conforms to the principles of Accelerated Bridge Construction (ABC) and provides a rapid alternative to other methods. However, often because of limitations on shipping and transportation, the length of precast prestressed pile segments that can be delivered to the bridge site has to be reduced. Also, headroom limitations for pile driving may limit the length of pile segments such that establishing adequate resistance may not be achieved with one segment. Therefore, splicing of pile segments has to be performed at the site to produce longer lengths. A study carried out as part of research activities at the Accelerated Bridge Construction University Transportation Center (ABC-UTC) at Florida International University has reviewed various types of available pile splices and attempted to build on the experiences gathered for ABC connections to introduce an alternative configuration for splicing PPCP segments. Accordingly, a variation of grouted bar splice was introduced and designed to provide PPCPs with a time-effective, economical, and labor-friendly method of splicing. The proposed connection is completely new for connecting PPCP segments. Because many of PPCPs are driven in a marine environment, the application of corrosion-resistant material at the splice system is also emphasized. The paper summarizes these investigations. The results of this study show that the newly developed systems can provide the required strength in bending, tension, and compression with smaller sizes and numbers of bars. It also makes the installation faster and easier compared with the current methods.
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Fiber-reinforced polymer (FRP) composites have gained increasing recognition and application in the field of civil engineering in recent decades due to their notable mechanical properties and ...chemical resistance. However, FRP composites may also be affected by harsh environmental conditions (e.g., water, alkaline solutions, saline solutions, elevated temperature) and exhibit mechanical phenomena (e.g., creep rupture, fatigue, shrinkage) that could affect the performance of the FRP reinforced/strengthened concrete (FRP-RSC) elements. This paper presents the current state-of-the-art on the key environmental and mechanical conditions affecting the durability and mechanical properties of the main FRP composites used in reinforced concrete (RC) structures (i.e., Glass/vinyl-ester FRP bars and Carbon/epoxy FRP fabrics for internal and external application, respectively). The most likely sources and their effects on the physical/mechanical properties of FRP composites are highlighted herein. In general, no more than 20% tensile strength was reported in the literature for the different exposures without combined effects. Additionally, some provisions for the serviceability design of FRP-RSC elements (e.g., environmental factors, creep reduction factor) are examined and commented upon to understand the implications of the durability and mechanical properties. Furthermore, the differences in serviceability criteria for FRP and steel RC elements are highlighted. Through familiarity with their behavior and effects on enhancing the long-term performance of RSC elements, it is expected that the results of this study will help in the proper use of FRP materials for concrete structures.
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Prestressed precast concrete pile (PPCP) is the most common type of pile currently practiced for establishing bridge foundations because it provides for a rapid, economical, and durable method of ...construction. For various reasons, including unpredictable soil conditions and shipping as well as transportation limitations, it is preferable or imperative to cast PPCPs with shorter lengths and connect them at the site to achieve longer lengths. Accordingly, various splice systems have been implemented over the decades for connecting PPCPs. However, current splice methods have shortcomings that have limited their applications. This study briefly reviews the limitations of the existing pile splices and introduces a novel method for splicing prestressed precast concrete piles. The proposed splice system utilizes Fiber Reinforced Polymer (FRP) sheets to provide the required strength. The performance of the proposed splice system in developing the required capacity has been investigated according to both ACI 318–14 and FDOT Standard Design Specifications. To demonstrate the effectiveness and constructability of the proposed system, the proposed splice has been designed for an 18-inch (457 mm) square PPCP according to a procedure consistent with ACI 440.2R-17. The results show that this system is effective and can meet all the requirements set forward by the design specifications. The major contribution of this study is the development of a new splicing method that is applicable to both unforeseen and preplanned situations, and offers an economical, corrosion-resistant, and rapid alternative advantageous to other available splicing methods. The new splice is especially valuable for unforeseen conditions where other splice systems fail to provide the required capacity. As important as its novelty, the proposed splice can be designed according to well-established and validated design codes making the need for experimental verification trivial.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
Fiber-reinforced polymer (FRP) composites are becoming increasingly popular as an alternative to conventional civil engineering materials in existing structures as externally applied systems ...for strengthening purposes, and in new structures as internal reinforcements in the form of bars, meshes, and strands. The next phase of development in the application of FRPs in concrete structures could culminate in elements possessing both internal and external FRP systems simultaneously. With these advancements in the application of FRP in civil engineering, it is conceivable that traditional steel reinforcements could become obsolete in certain aggressive and hostile environments, such as coastal areas. Although higher durability and performance are associated with FRP materials in some respects when compared to steel, concerns remain regarding the damage and defects in this material, many of them related to their unique features. Regardless, similarly to other structural materials, it is necessary to understand the damage and defects associated with the use of FRP composites, as well as to identify their sources. This knowledge will support the positive prospects for FRP technology, promoting its application in civil infrastructure. Accordingly, this study investigated the types, characteristics, and identification of the observed or expected damage and defects associated with using FRP in reinforced and strengthened concrete elements. The damage was classified according to location and time of initiation. In addition, the sources of these defects and damage were determined, and a damage etiology was established for preventing the occurrence of such damage in future use. The results of this study are intended to provide the background for the development of a guide and training material for the inspection of structures that use FRP materials. The ability to inspect and properly maintain structures containing FRP will result in the enhanced durability and service life of concrete structures reinforced or strengthened with FRP materials.
Practical Applications
With advancements in the application of fiber-reinforced polymer (FRP) in civil engineering and the development of practical means for its use in design and construction, it is conceivable that traditional steel reinforcements could become obsolete in certain aggressive and hostile environments, such as coastal areas. Although higher durability and performance is associated with FRP when compared to steel, concerns remain regarding the potential damage and defects that could be associated with its use. To help the owners of concrete structures feel comfortable with this relatively new application, guides and procedures are needed that will support the inspection and detection of potential damage in FRP. For this, it is necessary to understand the damage and defects that can occur in externally and internally applied FRP, and to be able to identify their sources. In this study, we investigated the types, characteristics, and identification of observed or expected damage and defects associated with using FRP in reinforced and strengthened concrete elements. In addition, the sources of these defects and damage were determined and a damage etiology established as a basis for developing a guide and training materials for the inspection of structures that use FRP materials. An accurate understanding of such damage and its sources could be used for maintenance and preventive measures for structures that were constructed using FRP materials.
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•Ultrasonic Testing is the most reliable method for damage detection in FRP bars.•Infrared Thermography is the most applicable method for detecting bond defects.•Ground Penetrating ...Radar is proposed for damage detection in FRP reinforced concrete elements.
The application of Fiber Reinforced Polymer (FRP) materials in concrete structures has been rising due to their several advantages, including lightweight, high tensile strength, ease of installation, and corrosion resistance. They have been mostly implemented for strengthening and repairing existing structures in the form of an externally bonded system, i.e., sheet, jacket, near surface mounted. Furthermore, they have been recently utilized as internal reinforcement of concrete elements in the form of bars, meshes and tendons. Although higher durability and performance are associated with the FRP as compared to steel, this fact does not exclude the possibility of damages and defects, many of which are related to their unique features. For example, debonding of FRP materials from a concrete surface or within a concrete element has occurred and needs to be corrected to avoid the premature failure of a structure. To this end, concrete elements reinforced or strengthened with FRP materials (FRP-RSC) should be inspected periodically to detect potential problems and hence prevent premature failures. This study first determines possible or potential damages and anomalies attributed to FRP-RSC elements. It then investigates Non-Destructive Testing (NDT) methods that can be applicable to the inspection of FRP reinforced/strengthened concrete elements from a literature survey of past studies, applications, and research projects. Finally, it proposes the most promising methods for detecting FRP and their damage/defects in FRP-RSC elements. By providing the inspection community with more clarity in the application of NDT to FRP, the results of this study offer means for verifying the performance and, therefore, help the proliferation of FRP materials in concrete structures.
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AbstractThe use of prestressed precast concrete pile (PPCP) has been increasing because of the advantages provided including accelerating and facilitating the construction operation at a site and ...increasing the durability of foundation systems. For various reasons including the shipping and transportation limitations and variable soil conditions, casting PPCPs with shorter lengths and splicing them at the site to achieve the required length becomes unavoidable or advantageous. As such, various techniques have been implemented to splice PPCPs at the site in preplanned and unforeseen situations. However, the current systems have shortfalls limiting their applications. These shortcomings are vulnerability to corrosion, inability to develop the required strength capacities in unforeseen situations, and on occasion requiring time-consuming and costly procedures. This study introduces a new method for splicing PPCPs to overcome the limitations that exist in current pile splices. As such, a near-surface-mounted fiber-reinforced polymer (NSM FRP) pile-splice system is introduced as an alternative to current splice systems. The effectiveness and feasibility of the suggested splice system are investigated according to national building code requirements and state standard design specifications. Accordingly, to demonstrate the capability to develop the required capacity in tension, compression, and flexure, as well as constructability, a splice system was designed in this study for an 457-mm (18-in.)-square PPCP. The results indicate the effectiveness of the proposed splice in satisfying the requirements set by both design references. Furthermore, details developed for the splice system have demonstrated their constructability. The NSM FRP splice offers an economical, labor-friendly method of splicing, and provides an advantageous option especially for unforeseen situations where other techniques are either impractical or fail to develop the required capacity. It is expected that the results of this study will pave the way for the implementation of this system in future construction.
Establishing a bridge foundation when there is a top layer of weak soils normally requires the application of deep foundations such as piles. Driving prestressed-precast concrete piles (PPCP) is one ...of the options among various types of piles and installation methods. However, it often happens that shipping and transportation constraints limit the length of precast prestressed pile segments that can be delivered to the bridge site. Therefore, the length of pile segments may be smaller than the length required to establish adequate resistance, and splicing of pile segments becomes necessary. The review reported in this paper aims at identifying and analyzing the available splice systems to be able to build upon the existing experiences when considering the development of new alternatives. The existing splice systems were compared based on capacity, ductility, durability, and ease of installation. As importantly, a thorough investigation was also conducted on the existing filler or bonding materials used for PPCP splicing to help the selection of the most applicable material. The review identified a set of filler/bonding material with rapid strength gain, workability and setting time suitable for establishing splices. This research was deemed necessary since there has been little or no recent innovation related to the PPCP splices. This paper combines in one place all available information on this subject and will help the researchers to understand the existing systems as well as the types of materials used for splicing. The results of this study are expected to motivate new ideas on more effective, durable, and economic systems for establishing PPCPs splices.
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Fiber-Reinforced Polymer (FRP) composites have emerged as a promising alternative to conventional steel reinforcements in concrete structures owing to their benefits of corrosion resistance, higher ...strength-to-weight ratio, reduced maintenance cost, extended service life, and superior durability. However, there has been limited research on non-destructive testing (NDT) methods applicable for identifying damage in FRP-reinforced concrete (FRP-RC) elements. This knowledge gap has often limited its application in the construction industry. Engineers and owners often lack confidence in utilizing this relatively new construction material due to the challenge of assessing its condition. Thus, the main objective of this study is to determine the applicability of two of the most common NDT methods: the Ground-Penetrating Radar (GPR) and Phased Array Ultrasonic (PAU) methods for the detection of damage in FRP-RC elements. Three slab specimens with variations in FRP type (glass-, carbon- and basalt-FRP, i.e., GFRP, CFRP, and BFRP, respectively), bar diameter, bar depths, and defect types were investigated to determine the limitations and detection capabilities of these two NDT methods. The results show that GPR could detect damage in GFRP bars and CFRP strands, but PAU was limited to damage detection in CFRP strands. The findings of this study show the applicability of conventional NDT methods to FRP-RC and at the same time identify the areas with a need for further research.
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