SIGNIFICANCE OF U-WRAP FRP SHEAR STRENGTHENING ON FLEXURAL BEHAVIOR OF RC BEAMS STRENGTHENED USING NEAR SURFACE MOUNTED FRP BARS

The aim of this study is to investigate the significance of U-wrap shear strengthening on the flexural behavior of Near Surface Mounted (NSM) Fiber Reinforced Polymers (FRP) strengthened Reinforced Concrete (RC) beams. It is well-known that the performance of NSM-FRP technique is strongly dependent on bond performance between adhesive-concrete and adhesive-FRP interface. Although a full development length is provided for the NSM FRP bar, rupture of the FRP bar is highly unlikely. This is attributed to the fact that the NSM FRP bar typically observes a stress level lower than 60% of its ultimate capacity at RC beam failure by debonding of NSM-FRP from the surrounding adhesive. Here, a typical three-side FRP U-wrap using wet layup was employed to improve the shear strength of the RC beam. A test matrix of 25 beams was tested under static load to failure. Four sets were considered including conventional RC beams, RC-beams with U-wrap only, RC-beams with NSM-FRP strengthening only without U-wrap FRP shear strengthening, RC beams with NSM-FRP flexural strengthening and U-wrap FRP shear strengthening, RC beams with NSM-FRP flexural strengthening and U-wrap FRP shear strengthening in shear zone only. The experimental results showed that incorporating FRP U-wrap has a significant effect of the performance of NSM-FRP strengthened RC beams. While a limited improvement of flexural strength of 20% was observed, NSM-FRP strengthened beams with FRP U-wrap experienced a significant reduction in ductility causing sudden failure. The change in the NSM-FRP strengthening system behavior might be attributed to the confinement provided by the U-wrap FRP which resulted in improving the bond strength of the NSM-FRP to the adhesive. This in its turn lead to NSM-FRP bar picking significantly high load level up to rupture with abrupt RC beam failure. The experimental results shed light on the need to consider design limitations when NSM-FRP flexural strengthening is combined with U-wrap FRP shear strengthening in RC beams

Fit-in GFRP Liner for Retrofitting Corroded Metal Culverts

Corrugated metal pipes (CMPs) have been used as culverts in North America since the 1950s. Today, corrosion of CMPs is a major problem that requires an urgent and efficient solution to retrofit thousands of corroded CMPs across the country. One potential solution gaining wide acceptance is to use a fit-in Glass Fiber Reinforced Polymer (GFRP) liner inside the old CMPs and to connect them using polymer grout. In this paper, a methodology to retrofit corrugated metal culvert using a fit-in GFRP profile liner was developed and implemented. First, material characterization of the GFRP material and the epoxy grout were carried out for proper design of the retrofit system. Second, full-scale CMP-GFRP composite section was tested under three-point bending configuration to observe the retrofitted culvert behavior to failure. The new CMP-GFRP section develops full composite action and shows failure capacity of 75 kip with a deflection of 3.52 in at the end of the test. Post failure of the polymeric grout, GFRP pipe failure was observed at mid-span location starting on the tension side. A finite element model was developed to understand the behavior of the CMP-GFRP composite pipe and to allow for the efficient design of the proposed retrofitting system

Fit-in GFRP Liner for Retrofitting Corroded Metal Culverts

Corrugated metal pipes (CMPs) have been used as culverts in North America since the 1950s. Today, corrosion of CMPs is a major problem that requires an urgent and efficient solution to retrofit thousands of corroded CMPs across the country. One potential solution gaining wide acceptance is to use a fit-in Glass Fiber Reinforced Polymer (GFRP) liner inside the old CMPs and to connect them using polymer grout. In this paper, a methodology to retrofit corrugated metal culvert using a fit-in GFRP profile liner was developed and implemented. First, material characterization of the GFRP material and the epoxy grout were carried out for proper design of the retrofit system. Second, full-scale CMP-GFRP composite section was tested under three-point bending configuration to observe the retrofitted culvert behavior to failure. The new CMP-GFRP section develops full composite action and shows failure capacity of 75 kip with a deflection of 3.52 in at the end of the test. Post failure of the polymeric grout, GFRP pipe failure was observed at mid-span location starting on the tension side. A finite element model was developed to understand the behavior of the CMP-GFRP composite pipe and to allow for the efficient design of the proposed retrofitting system

Polymer Concrete for Bridge Deck Closure Joints in Accelerated Bridge Construction

Prefabricated concrete bridge deck panels are utilized in Accelerated Bridge Construction (ABC) to simplify bridge deck construction. Concrete with good bond and shear strength as well as excellent flowability is required to fill bridge deck closure joints. This paper discusses the use of polymer concrete (PC) for bridge deck closure joints in ABC. PC produced using poly methyl methacrylate and standard aggregate was tested. Test results of PC are compared to Ultra-High Performance Concrete (UHPC). Development length, lap splice length and shear strength of unreinforced PC were tested. It is shown that PC has a development length of 3.6 to 4.1 times the reinforcing bar diameter that is close to one-half the development length of 6 to 8 times the bar diameter required with UHPC. PC also showed a shorter splice length compared with that reported for UHPC. Finally, unreinforced PC showed shear strength that is twice that of UHPC. It is evident that using PC in bridge deck closure joints in ABC can improve constructability and provide cost-savings and eliminate reinforcing bar congestion

Flexural behavior of polymer-based textile-reinforced concrete using basalt fibers

7th International Conference on Structural Engineering, Mechanics and Computation (SEMC) -- SEP 02-04, 2019 -- Cape Town, SOUTH AFRICAWOS: 000504648100256Textile reinforced concrete (TRC) is a class of cementitous composites that entails several advantages compared to traditional reinforced concrete such as lightweight, high tensile strength, design flexibility, and potentially corrosion free. As a result, TRC is suggested in a variety of structural applications including facades, protection panels, bridges, and waterproofing systems. A typical TRC element consists of multiple fiber fabrics embedded in thin cementitous concrete plate. Previous research reported a high potential for debonding between the fiber fabrics and the surrounding cementitous matrix due to poor impregnation and relatively high voids content. Recently, a new class of TRC is introduced by replacing the cementitious matrix by a polymer matrix to overcome the debonding problem. In this paper, textile-reinforced polymer concrete (TRPC) is produced using basalt fiber textile mesh and fine-grained Methyl Methacrylate (MMA) polymer concrete. Four different specimen configurations were produced by incorporating 0, 1, 2, and 3 textile layers in polymer concrete. Three-point bending test was carried out to examine the flexural performance of the TRPC specimens and the flexural strength of the different configurations was compared. In addition, the crack pattern intensity was determined via image processing technique to assess the ductility of TRPC. Comparison between different TRPC configurations reveals that increasing the number of fabric layers significantly improves the flexural behavior of TRPC.Natl Res Fdn S Africa, S African Natl Roads Agcy Ltd, ADINA R & D IncUniversity of New Mexico; Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [BIDEB-2219]The financial support of University of New Mexico to conduct the experimental study is greatly appreciated. The financial support from the Scientific and Technological Research Council of Turkey (TUBITAK) BIDEB-2219 Postdoctoral Research program to the first author is greatly appreciated

UV-Resistant GFRP Composite using Carbon Nanotubes

Degradation due to exposure to ultraviolet (UV) radiation is an important durability challenge with glass fiber reinforced polymer (GFRP) composite. Design and construction guidelines of GFRP suggest using UV protection paint to prevent GFRP degradation. In this study we examine the possible use of multi-walled carbon nanotubes (MWCNTs) dispersed in epoxy matrix to produce UV-resistant GFRP composite. We suggest that MWCNTs can result in a significant improvement to UV degradation resistance in the GFRP. Direct tension tests of GFRP coupons incorporating 0.25 wt%, 0.50 wt%, and 1.0 wt% of MWCNTs show inherent stability and good resistance to UV degradation. Microstructural analysis shows the ability of MWCNTs to resist polymer backbone disassociation caused by UV radiation thus preventing UV degradation in GFRP. Scanning electron microscopy (SEM) images show MWCNTs can resist microcracking caused by UV radiation and thus improve UV degradation resistance of GFRP