Number Of Fiber-reinforced Polymer Layers Research Articles

Factors affecting axial and lateral load transfer of hollow fibre-reinforced polymer piles in soft clay

ABSTRACT The growing interest in the long-term performance of pile foundations and their ability to resist the negative effects of water exposure and aggressive environmental conditions has led to considering non-corrosive materials such as fibre-reinforced polymer (FRP). The most common applications are light-bearing structures in waterfront environments, while applications for larger structures have not been widely accepted in industry due to the lack of long-term records and design guidelines available. In this study, a numerical model using the finite element method was developed to simulate small-scale load tests of hollow carbon-fibre reinforced polymer (CFRP) and glass-fibre reinforced polymer (GFRP) piles in soft clay. The findings of this research indicate that the number of FRP layers impacts loading behaviour significantly, while inner tube soil height has a reasonable influence on axial load response and fibre orientation has a minor effect under lateral load conditions.

Structural Behaviour of FRP-Reinforced Tubular T-Joint Subjected to Combined In-Plane Bending and Axial Load

In this study, 90 finite-element models are used to explore the behaviour of fibre-reinforced polymer (FRP) reinforced joints under combined in-plane bending (IPB) and axial load (AX). The effects of joint geometry, FRP layer count, and AX levels of the chord or brace are considered. Three typical failure modes are observed: chord plastic failure, brace plastic failure, and brace buckling failure. Increasing the number of FRP layers can ensure that failure is chord-related failure in a ductility manner rather than the unexpectedly brace-related brittle failure. Depending on the stress distribution of fibres, FRP reinforcement can restrict the deformation of joints subjected to complex loading patterns. Moreover, added FRP layers efficiently reduce the effect of brace AX on the IPB resistance. Finally, a modified strength equation is established, including the influence of FRP reinforcement, chord AX, and brace AX.

Behavior of grouted splice sleeve connection using FRP sheet

Most existing studies on grouted splice connections have focused on the bond behavior between connected steel rebars and conventional steel or iron sleeves. These research findings cannot properly predict the bond behavior and performance of the grouted splice connections, particularly when a new splice device, such as fiber reinforced polymer (FRP) materials, are adopted. The main purpose of this study is to investigate the feasibility of the proposed grouted splice sleeve connection (GSSC) using sheet materials of carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP). A total of 45 GSSC specimens with various rebar embedded lengths and different polymer sleeve materials were tested to failure under incremental axial pull-out load to evaluate the bond performance of the connected steel rebars in confined grout provided by the FRP sleeves. To evaluate the confinement effect of FRP sleeves on the tensile strength of the grouted connection, an analytical model was developed. The pull-out test results showed that the rebar embedded length was the major parameter affecting the average tensile strength of the GSSC. Also, the effects of mechanical properties of FRP sheets, such as the number of FRP layers and type of FRP sheets, contributed to the tensile strength of the GSSC sleeves that allow the transmission of tensile load between rebars through the medium of grout, aluminum tube, and FRP sheets. The analytical model that incorporates the confinement effects predicted well the experimental ultimate tensile strength of GSSC connections.

Influence of GFRP Confining Tube Parameters in Double-Skin Tubular Short Columns under Axial Loading

Abstract Composite construction with steel and concrete has become a widespread solution in modern construction practices because of its inherent properties such as high strength-to-weight ratio, good corrosion resistance, and high stiffness. Concrete-filled fiber-reinforced polymer (FRP) steel double-skin tubular compression members as vertical load–carrying members in buildings helps in optimizing the advantages of three materials: steel, concrete, and FRP. This study investigates the axial compressive behavior of short, concrete-filled glass fiber–reinforced polymer (GFRP) steel double-skin tubular (GSDST) columns and concrete-filled GFRP tubular (CFFT) columns. Parameters such as the number of FRP layers, hollow section ratio (HSR), variation of diameter of the inner steel tube, and the angle of orientation of the fibers have been examined in this investigation. The experimental study was carried out by performing a monotonic axial compressive loading condition. Three different angles of fiber orientation, 0° along the hoop direction, 45°, and 0°/90° with respect to the axis of the column, were adopted in this study. The ultimate load-carrying capacity, axial displacement, axial and horizontal strains, and failure modes were observed. The experimental results indicate that the structural performance of GSDST columns is significantly influenced by GFRP tube thickness, inner steel-tube diameter, and fiber-orientation angle. Maximum displacement was observed in the specimens with high HSR, thus showing a ductile characteristic in the axial load-displacement behavior. The load-carrying ability of the specimens decreased as the HSR increased. The load-carrying capacity of the specimens increased with the increase in outer GFRP tube thickness. This study demonstrates that GFRP tubes can be used efficiently in the construction field as vertical load–carrying components by enhancing the axial behavior of FRP steel double-skin tubular columns.

Seismic behavior of RC square columns strengthened with LRS FRP under high axial load ratio

A new type of fiber-reinforced polymer (FRP) with a tensile rupture strain of more than 5% was used for the seismic retrofitting of reinforced concrete (RC) square columns in this paper. A control column and 9 FRP-wrapped RC square columns were prepared with different number of FRP layers and FRP types. The seismic performance was comprehensively discussed and analyzed in terms of the failure modes, hysteretic behaviors, cumulative energy dissipation and FRP strain evolution. Experimental results showed that the ductility of specimens had a remarkable improvement as the confinement stiffness increased. Moreover, the buckling of longitudinal bars was restricted and postponed. Numerical analysis was conducted in OpenSees to further research the seismic performance of specimens based on an LRS FRP-confined concrete model and a reinforcing bar buckling model considering FRP confining effect. The simulated results were in close agreement with the experimental results. Parametric analysis was also conducted to investigate the influence of the FRP wrapping thickness, axial compression ratio and longitudinal reinforcement ratio on the seismic performance.

Cyclically loaded elliptical FRP-confined concrete: Behavioral characteristics and modeling

The previous studies on elliptical concrete confined with fiber-reinforced polymer (FRP) are mainly concerned with their monotonic compressive responses. By contrast, no research has been focused on their performance under cyclic axial loading. Motivated by this research gap, the behavioral characteristics of cyclically compressed elliptical FRP-confined concrete (FCC) were investigated in this research. The experimental parameters included the aspect ratio varying between 1.0 (circular section), 1.3, 1.7 and 2.0, the number of FRP layers, and the loading pattern (monotonic loading or two schemes of cyclic loading). The results revealed that plastic strains and stress degradation in elliptical FCC were confinement-independent parameters, regardless of confinement efficiency (affected by sectional geometry) and confinement level (governed by FRP thickness). This was similar to the case of cyclically loaded rectangular FCC (characterized by depth-to-width ratio). Moreover, the mechanism of non-uniform hoop strain distribution was dominated by two aspects, namely curvature radius-induced varying confinement stiffness and concrete cracking-induced strain localization. In contrast, the cyclic loading had a marginal effect on this distribution. Based on the monotonic model (considered as envelope curve) for elliptical FCC and the hysteretic rules originally for circular FCC, the complete compressive behavior of cyclically loaded elliptical FCC could be modeled with favorable accuracy.

Nano filler incorporated epoxy based natural hybrid fiber confinement of concrete systems: Effect of fiber layers and nano filler addition

The utilization of environment friendly materials in the construction industry is essential for sustainable development. For the purpose of strengthening and retrofitting concrete structures, fiber reinforced polymer (FRP) composites have been predominantly used. In the area of structural strengthening, as an alternative to synthetic fiber reinforced composites, the application of natural fiber reinforced composites is of immense interest. This study discusses the mechanical properties of externally strengthened concrete cylinders using a natural hybrid fiber system with two layers of sisal fiber sheets followed by 1 to 3 layers of basalt fiber sheets. In addition, the effect of multi walled carbon nanotubes (MWCNT) incorporation in the epoxy matrix from 0.5 to 1.5 wt%, on the various properties are analyzed. The inclusion of MWCNT in the epoxy matrix improved the overall performance of the FRP significantly. The results show that there is substantial improvement in mechanical properties up to 1 wt% MWCNT content in composites, beyond which it is reduced due to agglomeration of nanofiller. The MWCNT incorporated epoxy based five layered hybrid sisal basalt FRP confined specimens showed an improvement of 114% and 427% in peak strength and strain values under axial compressive strength tests. Moreover, the axial compressive behavior, stress–strain response, energy absorption and ductility characteristics of the confined column specimens were evaluated. The major focus of the study is to assess the influence of basalt FRP layers on the ultimate load carrying capacity and performance of hybrid sisal basalt FRP (HSBFRP) confined specimens. Statistical analysis of variance (ANOVA) was carried out and revealed that the number of FRP layers and addition of MWCNT in epoxy significantly affect the overall performance. The addition of basalt fiber layers in hybrid sisal basalt FRP systems is found to improve the load carrying capacity and energy absorption characteristics of confined specimens. Therefore, HSBFRP confinement can be used in areas where moderate strength and greater ductility is commanded.

Analytical study and design approach of the axial and flexural response of reinforced masonry columns confined with FRP jackets

Using fiber-reinforced polymer (FRP) wraps has proven to be an effective and optimized confinement technique to upgrade the axial and flexural capacity of reinforced concrete (RC) and reinforced masonry (RM) columns. The axial capacity of FRP-confined masonry depends on both the compressive strength of masonry before strengthening and the confinement pressure provided by the FRP jacket. This study proposes a simplified methodology to design and analyze prismatic fully grouted reinforced masonry columns (RMCs) strengthened with FRP Jackets. The proposed design methodology included an analytical confinement model to predict the compressive strength gain in RMCs due to the effective confinement pressure provided by FRP jackets. The proposed procedure was also designed to predict the nominal capacity of RMCs for practical design applications, with columns subjected to both axial loading and bending moment. The essential parameters to perform detailed section analysis were established, and suggested expressions were proposed to obtain the parameter values. Practical values for the equivalent rectangular stress block parameters were proposed. The theoretical axial force-moment interaction diagrams obtained by the proposed procedure were compared with available experimental data. The experimental test results were in good agreement with the analytical predictions by a reasonable marginal error. Furthermore, the effect of five design variables on the axial-flexural interaction of FRP-wrapped RMCs was investigated. The variables considered in the parametric study were the number of FRP layers, radius of the corners, stiffness of the FRP composite, cross-sectional aspect ratio, and masonry compressive strength. The results showed that increasing the FRP layers, corner radius, and FRP jacket stiffness significantly enhanced the axial capacity of the FRP-confined RMCs. However, the increase in the masonry compressive strength and cross-sectional aspect ratio negatively affected the axial capacity gain ratio of FRP-strengthened RMCs.

An experimental research on reinforced concrete deep beams fully wrapped with fiber reinforced polymers against shear

This paper presents a comprehensive experimental study to investigate the shear behavior of reinforced concrete (RC) deep beams fully wrapped with fiber reinforced polymer (FRP) strips. A total of eighteen deep beams were tested and the test results were evaluated. The test parameters were the shear span-to-effective depth ratio, the number of FRP layers, the clear spacing of FRP strips and the type of FRP. According to the experimental results, as the shear span-to-effective depth ratio increased, the rate of increase in the shear capacity decreased. On the other hand, the rate of increase in the deflection capacity increased with the shear span-to-effective depth ratio. It was observed that the steel plates used at the supports and loading point affected the contribution of FRP strips and the shear behavior of beams. Moreover, increasing the number of FRP layers, reducing the clear spacing of FRP strips or using glass FRP strips enhanced the shear and deflection capacities of beams. A comparative study was also conducted based on the experimental results. Comparisons between the experimental results of this study and the predictions obtained from a total of twelve models consisting of those given by the codes and those proposed by various researchers. The model superior to the others statistically is the one proposed by the German code.

Hybrid confinement mechanism of large-small rupture strain FRP on concrete cylinder

This study aims to investigate the hybrid mechanism of concrete cylinders confined with different types of fiber reinforced polymer (FRP). The adoptive FRP sheets include three types of low rupture strain FRPs (carbon fiber polymer (CFRP), glass fiber polymer (GFRP) and basalt fiber polymer (BFRP)) and two types of high rupture strain FRPs (polyethylene terephthalate fiber polymer (PET-FRP) and polyethylene naphthalate fiber polymer (PEN-FRP)). More hybrid gradients are designed to exposit the hybrid mechanism of large-small rupture strain FRPs. A total of 39 FRP-confined concrete cylinders are conducted under axial compression. The tested parameters are FRP types and the number of FRP layers. The failure modes, stress-strain responses, lateral confined pressures under different axial stresses, the apparent Poisson's ratio variation and energy-dissipating capacities are analyzed to reveal the mechanical mechanism of the specimens. The results show that the hybridization of the FRP sheets with rather different elongation capacities brings a pseudo ductility behaviour of concrete cylinders. That definitely improves the strain capacity, but the strength improvement relies on the adequate axial stiffness discrepancy between higher elongation FRP and lower elongation FRP sheets. By the hybridization, the utilization of lower elongation FRP sheets is markedly improved. The concrete cylinders confined by hybrid FRP sheets with similar elongation capacities behave like to the single FRP confined ones. Moreover, the predicted formulas are proposed and capture well the ultimate state of hybrid FRP confined concrete cylinders.

Influence of the Cross-Sectional Shape and Corner Radius on the Compressive Behaviour of Concrete Columns Confined by FRP and Stirrups.

Axial compression tests were carried out on 72 FRP (fiber reinforced polymer)–stirrup composite-confined concrete columns. Stirrups ensure the residual bearing capacity and ductility after the FRP fractures. To reduce the effect of stress concentration at the corners of the confined square-section concrete columns and improve the restraint effect, an FRP–stirrup composite-confined concrete structure with rounded corners is proposed. Different corner radii of the stirrup and outer FRP were designed, and the corner radius of the stirrup was adjusted accurately to meet the designed corner radius of the outer FRP. The cross-section of the specimens gradually changed from square to circular as the corner radius increased. The influence of the cross-sectional shape and corner radius on the compressive behaviour of FRP–stirrup composite-confined concrete was analysed. An increase in the corner radius can cause the strain distribution of the FRP to be more uniform and strengthen the restraint effect. The larger the corner radius of the specimen, the better the improvement of mechanical properties. The strength of the circular section specimen was greatly improved. In addition, the test parameters also included the FRP layers, FRP types and stirrup spacing. With the same corner radius, increasing the number of FRP layers or densifying the stirrup spacing effectively improved the mechanical properties of the specimens. Finally, a database of FRP–stirrup composite-confined concrete column test results with different corner radii was established. The general calculation models were proposed, respectively, for the peak points, ultimate points and stress–strain models that are applicable to FRP-, stirrup- and FRP–stirrup-confined concrete columns with different cross-sectional shapes under axial compression.

Compressive behavior of rectangular concrete-filled fiber-reinforced polymer and steel composite tube columns with stress-release grooves

To investigate the behavior of rectangular concrete-filled fiber-reinforced polymer (FRP) and steel composite tube (CFCT) columns with stress-release grooves under axial compression, sixty specimens were fabricated and divided into five groups for axial compression testing. The main variables were the corner radius, the number of FRP layers, the steel tube thickness and the presence of stress-release grooves. The test results indicate that steel tubes and FRPs can complement each other and discontinuous steel tubes can provide an effective confinement force on in-filled concrete. The stress–strain responses of CFCT columns with stress-release grooves consist of a linear elastic stage, a nonlinear transition stage, a linear hardening stage and a residual stage. The ultimate strength of a CFCT column is in direct proportion to the number of FRP layers, the thickness of the steel tube and the value of the corner radius. Stress-release grooves only play a positive role in specimens with relatively large values of the corner radii (r ≥ 30 mm). A new model was suggested for calculating the ultimate stress of CFCT columns with stress-release grooves. The model is applicable for CFCT and concrete-filled steel tube (CFT) specimens with stress-release grooves; the predicted results agree well with the experimental statistics.

Life-cycle analysis of FRP-strengthened offshore CFST columns suffering from steel corrosion

When a concrete-filled steel tube (CFST) is used in offshore construction such as electricity towers, bridges or platforms, it is subjected to continuous degradation during its service life due to the long-term in-service actions and the ocean corrosive environment. Fibre reinforced polymer (FRP) strengthening makes an effective solution to extending the service life of corroded CFST columns in existing offshore structures. For the rational design and tactful application of this corrosion strengthening technique, it is crucially important to understand the life-cycle performance of the strengthened column after experiencing the combination of multiple deterioration factors. In this study, an advanced finite element analysis (FEA) model, which is stage-by-stage verified against collected test data on 104 columns, is established to capture the nonlinear structural performance of FRP-strengthened CFST columns under coupled progressive degradation factors, i.e., initial imperfections, construction preload, sustained service load and corrosion. Corrosion of the steel results in less confinement on concrete and thus affects the loading capacity of the columns, while increasing the number of FRP layers can weaken the negative influence brought by multiple degradation factors. Based on parametric studies, a simplified design method is proposed for the ultimate strength prediction of corroded CFST columns strengthened by FRP.

Experimental study and numerical analysis on seismic performance of FRP confined high-strength rectangular concrete-filled steel tube columns

The fiber reinforced polymer (FRP) has attracted increasing attention as a strengthening method for concrete-filled steel tube (CFT) columns because of its lightweight and high strength. Nevertheless, related investigations on seismic performance of FRP confined high-strength rectangular CFT columns are rarely reported. Herein, a series of experimental and numerical analysis on the seismic performance of FRP confined rectangular CFT columns using high-strength thin-walled steel tubes and high-strength concrete are presented considering the following parameters: aspect ratio, axial compression ratio, number of FRP layers and fiber direction. The seismic performance of specimens under reversed cyclic lateral loading was evaluated by discussing the failure modes, hysteretic behaviors, capacity degradation, stiffness degradation, ductility, and strains. The numerical models were developed and verified by the test results, which could accurately simulate the mechanical behaviors and the failure of specimens. The observations drawn from this research might provide a good basis for the application of high-strength material and FRP-strengthened CFT structures.

Behavior and modeling of double-skin tubular columns filled by ultra-lightweight cement composites (ULCCs)

Double skin tubular columns (DSTCs) filled by ultra-lightweight cement composites (ULCCs), as primary load-bearing elements, are a practical and reasonable structural asset in lightweight civil infrastructure. This DSTC-ULCC system combines the advantages of three materials, 1) outer fiber-reinforced polymer (FRP) 1–3 ply jackets, 2) filled ULCCs, and 3) inner steel tubes to achieve lightweight, high strength and superior ductility. This article presents an experimental study on the mechanical behavior of DSTCs with FRP and ULCCs under axial compressive loading. The experiment designed a total of 26 DSTCs that were all filled with ULCCs. The key parameters were the number of FRP layers and the inner steel tube properties, (i.e., thickness and diameter of the steel tube). The test results indicate that the properties of the inner steel tube not only influences the effective FRP rupture strain ratio but also the ultimate axial strain of confined ULCCs. This calls attention to the inward buckling behavior for larger void ratios; moreover, thinner steel tubes result in more axial deformation of ULCC-filled DSTCs. In addition, ULCCs showed a much lower elastic modulus compared with normal concrete, which helped cause the change of transition stress of ULCCs in DSTCs, and FRP confinement can effectively increase the elastic length of the stress–strain curves for ULCCs. The experimental results are subsequently compared with predictions from an FRP-confined ULCC model, which led to a new ultimate strain model proposed herein for ULCC-filled DSTCs. The comparison demonstrates that the model can provide reasonably accurate predictions of the stress–strain curves of ULCCs in hollow DSTCs.

U-type mechanical clamping to anchor the CFRP composites in strengthening of RC beams subjected to bending

The present study investigates the performance of U-type clamp anchorage on external strengthening of reinforced concrete beams using carbon fibre-reinforced polymer composites. Unidirectional carbon fibre was used to strengthen the beam having a cross-section of 150 × 200 mm2 and the fabricated U-type clamp was used as a clamping device to enhance the fibre-reinforced polymer (FRP) bonding. To test the beam, four-point bending system was adopted and the experimental parameters were the number of FRP layers. The failure mode of strengthened beams with U-type clamp was very similar (rupture of FRP composites) to the beams without U-type clamp. However, the delamination of FRP was evaded by counteracting the peeling stress development at the edge of fibre. Since the beams strengthened with U-type clamp exhibited more linear behaviour than that of the beams strengthened without U-type clamp, there may be a higher possibility for abrupt/rapid/brittle mode of failure and the ductility index of the beam with U-type clamp confirmed the above behaviour. However, the introduction of U-type clamp enhanced the flexural stiffness and ultimate strength by counteracting the debonding, and the beam with U-type clamp exhibited a maximum of 58.33% and 20.37% enhancement in flexural stiffness and ultimate strength than that of the beam without U-type clamp, respectively. The theoretical strength value of all strengthened beams was evaluated using models proposed in the previous research and compared with experimental results. It is inferred that the use of U-type clamp in FRP strengthening provides economic and structural benefits compared to a beam without U-type clamp.

Design-Oriented Stress-Strain Model for FRP-Confined Lightweight Aggregate Concrete

Despite the advantages of lightweight aggregate concrete (LWAC), its brittleness in compression has limited its vast application. Jacketing by fiber-reinforced polymer (FRP) tends to be one method to overcome this negative point. The current study attempted to recognize the FRP confinement impact on the LWAC compressive monotonic behavior. Both fine and coarse aggregates were Scoria aggregate. The variables include the type and number of FRP layers; 150 × 300 mm cylindrical specimens were wrapped with 1, 2, 3, and 4 layers of glass FRP (GFRP) and carbon FRP (CFRP) strips. An investigation was performed on the monotonic stress-strain curve belonging to LWAC confined with FRP, and key points, including ultimate stress and strain on the curve, were explored. The results revealed that the key points would significantly improve by increasing FRP layers. Although the influence of GFRP confinement on enhancing the ultimate strain appears to be more considerable than the CFRP confinement, CFRP jacketing of LWAC upgrades the ultimate strength to the higher level compared to wrapping with GFRP. Based on the interpretation of experimental results, a design-oriented stress-strain model was established to predict the monotonic compressive response of Scoria-LWAC circular specimens confined with CFRP and GFRP. The validity of the model was examined. The predicted output was appropriately in line with the experimental findings.

Experimental and numerical investigation on the deflection behavior of pre-cracked and repaired reinforced concrete beams with fiber-reinforced polymer

This paper presents an experimental and numerical study on the effect of fiber-reinforced polymer (FRP) sheets/laminates on the flexural deflection of pre-cracked and repaired reinforced concrete (RC) beams. The experimental program was aimed at studying the carrying capacity of repaired beams through load-deflection curves along with failure modes which can occur in unrepaired and repaired RC beams. The types of FRP reinforcement (CFRP sheet, GFRP sheet and CFRP laminate) and the number of FRP layers were selected as two main parameters in the test program. The major code models, namely Eurocode 2, the ACI-318 and the BS-8110 are used for evaluation of ultimate moment, and the results are also compared with experiments ones. Finite element analysis (FEA) using ANSYS software is presented to predict the load-deflection behavior of the RC beams, and completed with a numerical analysis to assess the interfacial shear stresses, focusing on debonding failure. The experimental results show an improvement in the ultimate load capacity of repaired RC beams with FRP ranging from 13% to 100%, with lower mid-span deflections ranging from 15% to 35% as compared to the control beam (without FRP). On the other hand, the major code models could not accurately predict the moment capacity of RC beams strengthened with FRP sheets/laminates, with a gap closer to 1.40. Moreover, the numerical FEA predictions show a good agreement in the load-deflection response for all tested beams. Also, the numerical analysis results indicate that the shear stresses rise with the number of FRP sheets layers.

Study on the flexural strengthening effect of RC beams reinforced by FRP grid with PCM shotcrete

Recently a new repair and retrofit method of reinforced concrete (RC) members that uses fibre-reinforced-polymer (FRP) grid with polymer-cement-mortar (PCM) shotcrete has been proposed. Four RC beams externally strengthened with CFRP grid-PCM at the bottom and one non-reinforced RC beam were tested to reveal their flexural behaviour and strengthening effect. The number of FRP layers and reinforcement amount per unit length of the CFRP grid were selected as the two main parameters in the test programme. The test results indicated that the flexural strengthening effect of the CFRP grid-PCM was sufficient; moreover, two-layer reinforcements were effective as one-layer ones under similar unit-reinforcement values. Furthermore, a new analytical model was proposed to evaluate the flexural capacities of RC beams strengthened with CFRP grid, and the predicted values were well matched to the test results and collected data.

Optimal FRP Jacket Placement in RC Frame Structures Towards a Resilient Seismic Design

This paper proposes an optimal plan for seismically retrofitting reinforced concrete (RC) frame structures. In this method, the columns are wrapped by fiber-reinforced polymer (FRP) layers along their plastic hinges. This technique enhances their ductility and increases the resiliency of the structure. Two meta-heuristic algorithms (i.e., genetic algorithm and particle swarm optimization) are adopted for this purpose. The number of FRP layers is assumed to be the design variable. The objective of the optimization procedure was to provide a uniform usage of plastic hinge rotation capacity for all the columns, while minimizing the consumption of the FRP materials. Toward this aim, a single objective function containing penalty terms is introduced. The seismic performance of the case study RC frame was assessed by means of nonlinear pushover analyses, and the capacity of the plastic hinge rotation for FRP-confined columns was evaluated at the life safety performance level. The proposed framework was then applied to a non-ductile low-rise RC frame structure. The optimal retrofit scheme for the frame was determined, and the capacity curve, inter-story drift ratios, and fragility functions were computed and compared with alternative retrofit schemes. The proposed algorithm offers a unique technique for the design of more resilient structures.