Fiber-reinforced polymers (FRP) reinforcements have become one of the most used construction materials during the last decade. ACI Committee 440 is leading the writing of design standards and guidelines and is sponsoring these full sessions. Four 2-hour sessions will highlight and collect the most recent research, development, and application of FRP reinforcement in the concrete industry. Numerous important topics related to external and internal FRP reinforcement will be presented.
(1) Discuss the influence of the infill FRP-strengthening and column’s shear reinforcement on the seismic performance, using nonlinear numerical modeling;
(2) Review previous studies and applications of carbon FRP-External reinforcements for bridges (Case-Study: Original Champlain Bridge, Montreal, Canada);
(3) List the design properties that drive a more specific and detailed design guideline for CFRP-external anchors, using full-scale testing;
(4) Describe non-destructive evaluation of reinforced-concrete slabs rehabilitated with Glass Fiber-Reinforced Polymers (GFRP) sheets;
(5) To learn about numerical modeling of bond behavior and anchors of FRP external reinforcement with concrete.
This session has been approved by AIA and ICC for 2 PDHs (0.2 CEUs). Please note: You must attend the live session for the entire duration to receive credit. On-demand sessions do not qualify for PDH/CEU credit.
Effects of Infill Retrofit with FRP Materials on the Seismic Behavior of RC Frames
Presented By: Gianni Blasi
Affiliation: University of Salento
Description: The damage on infill walls caused by earthquakes often represents a major safety issue in reinforced concrete buildings. For this reason, the infill FRP-retrofit is increasingly adopted in high seismic hazard countries to increase the in-plane capacity of the walls and to avoid out-of-plane failure modes. On the other hand, the infill strengthening might significantly modify the seismic performance of the buildings, influencing the failure modes and the global ductility. Recent studies assessed that the enhancement of the in-plane strength of the infill can cause brittle failure in lightly shear reinforced columns. In this study, non-linear analyses are performed on reinforced concrete framed buildings to investigate the influence of the infill FRP-strengthening and column’s shear reinforcement on the seismic performance. A three-dimensional numerical model is developed to assess the seismic capacity and the failure modes depending on the frames and infill’s details. The proposed study aims to encourage a smart design of the infill FRP-retrofit, geared to a global performance enhancement rather than the mere strengthening of the single infill wall.
Literature-Review on External Carbon Fiber-Reinforced Polymers (CFRPs) Reinforcements for Concrete Bridges
Presented By: Mohamed Ahmed
Affiliation: Universite de Sherbrooke
Description: Development of strategies to enhance or rehabilitate reinforced concrete bridges is one of the major concerns of civil engineers. Bridges located in harsh environmental condition region and exposed daily to fatigue loading are vulnerable to corrosion and accelerated deterioration of its components. Previous studies and field applications have shown that bonding carbon fiber reinforced polymer (CFRP) to the bridge element surface is an attractive solution for bridge strengthening. To date, there have been many experimental results and field testing. This paper aims to review and evaluate the use of external bonded CFRP for bridge rehabilitations. The paper is organized to be in two main parts as follow: First, experimental and field survey on the use of CFRP as external reinforcement for concrete bridges. The second part is focused on the evaluation of the performance of the Original Champlain Bridge (OCB) edge girder strengthened with external bonded CFRP under live load tests, which were performed by the owner, the Jacques-Cartier and Champlain Bridges Inc., (JCCBI) and its partners. The results of truckload tests on edge girder of the bridge show that the rehabilitation-technique using external-CFRP sheets bonded on edge girder of the bridge was able to keep the shear strains constant; and extend its service life for up to 10 years until deconstruction of the whole bridge. In addition, the effect of the temperature variations with time on the shear strains was recorded.
Full-scale Testing of CFRP Anchors to Determine Design Properties
Presented By: Scott Arnold
Affiliation: Fyfe Co
Description: Fiber-reinforced polymers (FRP) are widely recognized as versatile materials for the retrofit and repair of structural members. Over the last 30-years there have been a variety of anchorage details used to improve the performance of these externally bonded FRP systems. Although conventional materials can be used in some applications, the use of embedded FRP anchors has been proven to be more beneficial. These FRP anchors are currently beyond the scope of any specific ASTM standard. However, they are essentially an adhesive anchor and, as such, can be characterized by using existing test standards such as ACI 355.4 (Qualification of Post-Installed Adhesive Anchors in Concrete) and ASTM E488 (Standard Test Methods for Strength of Anchors in Concrete Elements). Since there is limited design guidance for FRP anchors, acceptance within the engineering community has been challenging. This paper will concentrate on full-scale testing performed on CFRP anchors, which has been critical in defining their design values. A critical review of the design properties will drive a more specific and detailed design guideline for CFRP anchors. In addition, there will be discussions on the specific detailing required for FRP anchors to ensure an overall safe and durable CFRP strengthening system.
Non-Destructive Evaluation of Reinforced-Concrete Slabs Rehabilitated with Glass Fiber-Reinforced Polymers
Presented By: Wael Zatar
Affiliation: Marshall University
Description: Fiber-reinforced polymer (FRP) materials provide an excellent alternative for shear, flexure, and confinement retrofitting of deteriorated infrastructure. Despite the advanced technology employed in fabricating FRP materials, the monitoring and quality control of the FRP installation still present a challenge. For externally bonded FRP-rehabilitated structures, the existence of undesirable defects, including surface voids and debonding, on the concrete surface should be evaluated, as these defects would adversely affect the durability and capacity of the FRP-rehabilitated structures. Non-destructive testing has the potential to provide a fast and precise mean to assess these FRP rehabilitated structures. This paper presents an experimental and theoretical investigation on the use of ground-penetrating radar (GPR) and infrared tomography (IRT) methods to evaluate reinforced-concrete (RC) slabs externally bonded with glass Fiber-reinforced polymer (GFRP). Four externally bonded GFRP RC slab specimens were fabricated. Surface voids, interfacial debondings, and vertical cracks were artificially created on the concrete surface of the RC slabs. Test variables include location and size of surface voids, interfacial debonding, and diameter of steel reinforcement. Improved two-dimensional and three-dimensional image reconstruction method, using the synthetic aperture focusing technique (SAFT), was established to effectively interpret the GPR test data. The results showed that an in-house developed software, that played the enhanced image reconstruction technique, provided sharp and high-resolution images of the GFRP-retrofitted RC slabs in comparison to those images obtained from the device’s original software. The data suggests that the GPR testing could effectively be employed to accurately determine the size and location of the artificial voids, as well as spacing of the steel reinforcement.
Parametric Study of Bond Behavior of FRP-to-Concrete Joint with Epoxy Interlocking
Presented By: Baolin Wan
Affiliation: Marquette University
Description: External bonding of FRP composite with epoxy interlocking enhancement (EB-FRP-EI), in which epoxy fills pre-cut transverse grooves on concrete surface to form epoxy ribs to provide the interlocking resistance of debonding, has been proved to have potential of improving the bond behavior of externally bonded FRP strengthened concrete. This study developed a 3D nonlinear finite element (FE) model to investigate the key parameters that affect the bond behavior of FRP-to-concrete joint with epoxy interlocking enhancement. By comparing the load vs. slip relationships and cracking patterns with experimental results, the developed FE models were validated. The validated FE models were used to study the effects of the groove depth, the number of grooves, and the compressive strength of concrete on the bond strength of FRP-to-concrete joint with epoxy interlocking, respectively. The parametric study showed that increasing the number of grooves, depth of groove and compressive strength of concrete could significantly improve the performance of epoxy interlocking enhancement.
2-D Finite Element Modeling of the Bond-Slip Behavior of CFRP Anchors
Presented By: Jose Luis Jimenez
Affiliation: Pontifica Universidad Catolica De Chile
Description: CFRP reinforcement has become a consolidated technology in the retrofit of existing structures. Extensive experiments have shown that delamination of externally bonded CFRP plies governs their failure mode. To delay delamination, CFRP anchors have been found to be particularly attractive due to their wide range applicability and large increases in strength and deformability. This paper presents a 2D finite element model for single-lap push-pull tests of concrete blocks reinforced with CFRP subject to monotonic loading. A numerical model is implemented to simulate the bond between CFRP anchors and concrete. CFRP anchors present a complex geometry and a combined tensional state of tangential and normal stresses. For these reasons it is difficult to determine a bond-slip law for CFRP anchors; however, with the proposed procedure the necessary parameters are obtained in a numerical way, at low computational cost. Experiments taken from literature with a single CFRP anchor are replicated and used to capture the parameters of the bond-slip curve for a particular anchor. The procedure is then validated with experiments with two and three anchors. The proposed procedure achieves reasonable results when comparing the obtained maximum strength achieved, the strains along the CFRP reinforcement and the anchor stress behavior with the experiments.