Fiber Reinforced Polymer Retrofit Research Articles

Developing a Sprayed-Glass Fiber-Reinforced Polymer Retrofitting System for Decommissioned Wooden Utility Poles

Wooden utility poles are vulnerable to degradation and decay, which requires maintenance or replacement. The strengthening and retrofitting techniques for wooden poles are either prone to corrosion or encountering installation difficulties. However, the use of sprayed fiber-reinforced polymer (FRP) composites seems to be a viable solution as it has proven its efficiency and applicability for reinforced concrete members and connections. This study includes a comprehensive experimental program where the mechanical properties of the sprayed-glass FRP (GFRP) composite was evaluated in terms of tensile, compressive and shear strength, in addition to its bond strength to wood and confinement efficiency. Afterwards, the results of the material testing phase were implemented on full-scale old utility poles to evaluate their structural performance with varying composite thicknesses and sprayed zone lengths. The behavior of the retrofitted poles reflected remarkable effectiveness for the sprayed-GFRP composite and highlighted the need for a design model for the optimum length for the sprayed zone. Two simplified analytical models were introduced which predicted the failure loads and locations for the tested poles and estimated the required length for the retrofitted zone, which all agreed well with the experimental results of the tested poles.

FRP retrofit for RC frame substructures against progressive collapse: Scheme optimisation and resistance calculation

Fibre-reinforced polymer (FRP) strips have been widely used to retrofit existing reinforced concrete (RC) frame structures to improve their progressive collapse resistance. However, existing FRP retrofitting schemes improve structural collapse resistance by simultaneously enhancing the tensile and flexural strengths of horizontal structural members. The enhancement in flexural strength may lead to an unfavourable strong-beam weak-column mechanism in the seismic scenario. Hence, existing FRP retrofitting schemes were optimised in this study by numerical investigation using LS-DYNA, and effective schemes against both progressive collapse and earthquake were identified for RC beam-column and beam-slab-column substructures. The identified schemes remarkably improved the structural performance against progressive collapse at large deformations whilst marginally affecting the progressive collapse resistance at small deformations to guarantee the strong-column weak-beam mechanism in the seismic scenario. Furthermore, based on the parametric analyses for 81 full-scale substructures, analytical methods were proposed to calculate the strength of RC frame substructures retrofitted with the identified schemes under catenary mechanism, which can be further used to design the FRP retrofitted RC frames.

Shear strengthening of reinforced concrete T-beams with anchored fiber-reinforced polymer composites

T-shaped beams are widely used in reinforced concrete (RC) structures, both buildings and bridges. Under-designed shear reinforcement and long-term aging make these structural elements susceptible to shear failure during earthquakes. The currenlty availalbe experimental work investigating the retrofit of these beams against shear failure is very limited. In this work, the external strengthening of RC T-beams with splay anchored strips of fiber reinforced polymer (FRP) composites under cyclic shear loading for the cases of normal and high strength concrete was studied. Six beams with 3.05 m length and 0.46 m that were conservatively reinforced against flexural failure were designed. The shear reinforcement of the beams was sufficiently high to ensure the dominance of shear failure. Three of the beams were built using a normal strength concrete and the other three were built using a high strength concrete with 28-day strengths of 30.5 MPa and 44.0 MPa, respectively. From each group of normal and high strength RC beams, one beam served as the reference. The other two beams were retrofitted with external strips of FRP composites that were bonded on the web and anchored under the flange of the beams. The beams were tested under cyclic four-point loading to evaluate the performance of the FRP retrofitting system against shear failure under simulated seismic loading. The deflection and the strain in the FRP composites were recorded while monitoring the strain of the longitudinal reinforcement to ensure an elastic response in flexure. The reference beams failed by shear cracking and the retrofitted beams failed by shear cracking and FRP delamination. The retrofitting technique increased the shear capacity of the beams by up to 37% and 20% for the normal and high strength beams, respectively, and promoted the beam ductility prior to failure.

Experimental study on the seismic behavior of RC columns with high axial compression ratios retrofitted by large rupture strain fiber-reinforced polymer

Fiber-reinforced polymer (FRP) composites being utilized to retrofit reinforced concrete (RC) columns has been well documented. However, the axial compression load of the FRP retrofitting RC columns was relatively limited. Aiming to analyze the applicability of FRP retrofitting RC columns with higher axial compression loads, this paper presents an experimental study on the seismic performance of RC columns retrofitted by the Polyethylene Terephthalate (PET) FRP composites. A total of twelve 1/3 scale RC columns were fabricated, including four control specimens and eight PET FRP retrofitting columns with two retrofit schemes. All the columns were tested under combined high axial compression load and cyclic lateral displacement excursions, and the maximum axial compression ratio reaches 1.1. The seismic performance of RC columns retrofitted by PET FRP was analyzed detailedly from the failure mode, shear force and deformation capacity, energy dissipation and ductility. The test results showed that PET FRP retrofitting changed the failure mode of RC columns from brittle to more ductile. The post-peak strength degradation of the columns was more rapid with the increase of axial compression ratio, but the strength degradation of the PET FRP retrofitting columns was more gradual. PET FRP retrofitting significantly improved the ductility and lateral deformation capacity of the columns even under the high axial compression ratio. PET FRP retrofitting can be applied for the RC columns with serous demand of deformation capacity due to the lighter change of shear-loading capacity and stiffness. Contrastively, the improvement of the seismic capacity of the RC columns retrofitted by the laterally wrapped scheme is higher than that of the striped wrapped scheme. Conclusions from this study provide useful references for the seismic retrofitting of RC structures.

Experimental behavior of fire-exposed reinforced concrete slabs without and with FRP retrofitting

In this study, experiments were conducted on nine reinforced concrete slabs which were divided into three groups, namely S0, S45, and S75. Group S0 included one slab which was not exposed to fire to use as the control specimen. Each of groups S45 and S75 included four slabs which were subjected to 45 min and 75 min of fire, respectively. After exposure to fire, two fire-exposed slabs of each group were retrofitted using fiber reinforced polymer (FRP). These slabs were monotonically or cyclically loaded to failure. The test results showed that the control and fire-exposed slabs exhibited flexural failure while the FRP-retrofitted fire-exposed slabs failed in the form of FRP debonding. Fire slightly decreased the ductility but it was still much larger than 4, classifying the specimens to be highly ductile. Fire marginally reduced the yield and ultimate strengths while it significantly reduced the stiffness by about 30%. Retrofits with 1/2 and 1 FRP layer for fire-exposed slabs increased the yield strength by 30% and 45% and increased the ultimate strength by 46% and 65%, respectively. The effect of cyclic loading caused negligible strength degradation, but it caused considerable stiffness degradation of 20% and 35% for the 1/2 and 1 FRP retrofitted fire-exposed slabs, respectively. Finally, a theoretical model was developed to compute the capacity of FRP retrofitted fire-exposed slabs. The model can be useful for engineers to estimate the capacity of FRP retrofitted fire-exposed slabs in practice.

Development of P-I model for FRP composite retrofitted RC columns subjected to high strain rate loads using LBE function

The efficiency of fibre reinforced polymer (FRP) in strengthening the concrete structure against blast loads is investigated for RC columns exposed to blast loads. It should be mentioned that no systematic investigations derived pressure and impulse (P-I) models for FRP retrofitting RC columns in the literature. Thus, the primary goal of this project is to construct a finite element model that will offer data for the development of a P-I diagram that can be utilized to mitigate blast threats and predict damage in RC columns retrofitted with FRP. Another aspect of the present work is to propose a new technique to determine the damage index to identify the capacity degradation of the RC columns when exposed to extreme loads in the current research various strengthening schemes are quantitatively tested against blast loads by doing LS-DYNA software. Numerical simulation of blast load is implemented by using Load-Blast-Enhanced (LBE) technique. The models are validated through experimental work to assess the correctness of model simulations in order to illustrate the models behavior. The structural behavior of un-strengthened RC columns was compared to the structural behavior of various columns retrofitted with varying FRP wrap thickness, strength, and arrangement. The simulations revealed that strengthening columns with FRP is a viable strategy to improve their explosion resistance capability, and that retrofit procedures are useful in minimizing the building's hazard. Engineers can utilize the P–I curves obtained to assess the damage levels of new columns and to estimate the damage levels of existing columns subjected todifferent extreme load scenarios.

Machine learning prediction of structural response for FRP retrofitted RC slabs subjected to blast loading

Explosive and impact events, which in recent years have inflicted colossal human and economic losses, are dire warnings that civil infrastructure is not immune to blast and explosion scenarios. Thus, designing resilient new civil infrastructure and retrofitting the existing one to enhance its blast resistance is paramount. Retrofitting reinforced concrete (RC) slabs using external fiber-reinforced polymer (FRP) is known to enhance blast resistance, mitigate displacements and cracking, and contain debris. However, existing approaches to simulate the structural response to blast loading require competent knowledge, substantial modeling efforts, and high computational cost. Therefore, this study investigates the practicality of deploying machine learning to predict the maximum displacement of FRP strengthened RC slabs under blast loading as a novel approach to achieve simplified and accurate predictions. A Gaussian process regression algorithm was implemented for model development considering several influential features of the application. Due to the limited pertinent data in the open literature, a novel approach based on Tabular Generative Adversarial Network (TGAN) was used to generate 200 additional synthetic data used for model training. A design parameter prediction model was also proposed to predict the cross-section of FRP retrofitting considering blast parameters and the displacement specified by the design code. Statistical performance metrics including MAE, MAPE, and R2 indicate that the developed model achieved predictions with superior accuracy. Feature importance analyses were also conducted and corroborated by existing experimental and numerical studies. Based on the proposed model and its validation and feature importance analyses, the implementation of ML was proven to be a viable approach for structural response predictions under blast loading. Thus, the proposed model can potentially provide designers with accurate results for FRP retrofitting of RC slabs against blast loading through a highly simplified approach at low computational cost.

New Model Of Enhanced Plasticity For Reinforced Concrete Structural Elements That Take Into Account The Effects Of Lateral Loading And Gravity

Reinforced concrete structures are exposed to a progression of activities all through their life expectancy which may be the purpose behind damage. Subsequently, rehabilitation of existing structures is typically performed either to restore structural limit because of decay or damage or to broaden existing structural limit due to expanded loads. To fortify existing structures, numerous new creative materials like progressed fiber-reinforced polymers (FRPs) are discovered to be acceptable substitute for reinforcing materials like steel. They are actualized to fortify the presentation of structural components in flexure, pivotal, shear, and twist. In a RC outline, migrating plastic pivots in the beam off from the column face is normally prescribed to broaden pliability of the edge. This could be accomplished through rib reinforced FRP retrofit of the joint. Furthermore, to it, thus we execute an expanded pliancy for the concrete structural components like column, beam, chunk, dividers then on. The primary motivation behind a wide range of structural frameworks utilized in the structure type of structures is to transfer gravity and horizontal loads effectively.

Buckling Behavior of Non-Retrofitted and FRP-Retrofitted Steel CHS T-Joints

This paper aims to investigate the buckling behavior of circular hollow section (CHS) T-joints in retrofitted and non-retrofitted states under axial brace compressive loading. For this purpose, two types of analysis are carried out. The first one is evaluating the critical buckling load in various tubular joints, and the other one is investigating the post-buckling behavior after each buckling mode. More than 180 CHS T-joints with various normalized geometric properties were numerically modeled in non-retrofitted state to compute their governing buckling mode, i.e., chord ovalization, brace local, or global buckling. Then three joints with different buckling modes were selected to be retrofitted by fiber-reinforced polymer (FRP) patches to illustrate the improving effect of the FRP wrapping on the post-buckling performance of the retrofitted joints. In addition, FRP composite failures were investigated. The results indicate that the FRP retrofitting is able to prevent the brace local buckling, and that matrix failure is the most common composite failure in the retrofitted joints.

3D Finite Element Pseudodynamic Analysis of Deficient RC Rectangular Columns Confined with Fiber Reinforced Polymers under Axial Compression.

This paper utilizes the advanced potential of pseudodynamic three-dimensional finite-element modeling to study the axial mechanical behavior of square and rectangular reinforced concrete columns, confined with fiber reinforced polymer (FRP) jackets and continuous composite ropes in seismic applications. The rigorous and versatile Riedel-Hiermaier-Thoma (RHT) material model for concrete is suitably calibrated/modified to reproduce the variable behavior of characteristic retrofitted columns with deficient internal steel reinforcement detailing, suffering nonuniform local concrete cracking and crushing or bulging and bar buckling. Similarly, the 3D FRP jacket or rope confinement models may account for damage distribution, local fracture initiation and different interfacial bonding conditions. The satisfactory accuracy of the reproduced experimental stress-strain envelope behavior enables the analytical investigation of several critical design parameters that are difficult to measure reliably during experiments. Additional parametric analyses are conducted to assess the effects of steel quality. The significant variation of the field of developed strains on the FRP jacket at the ultimate and of the developed strains and deformations on steel cages among different columns are thoroughly investigated. This advanced analytical insight may be directly utilized to address missing critical parameters and allow for more reliable FRP retrofit design of seismic resistant reinforced concrete (RC) columns. Further, it allows for arbitrary 3D seismic analysis of columns (loading, unloading, cyclic or loading rate effects or preloading) or addresses predamages.

Size Effect on FRP External Reinforcement and Retrofit of Concrete Structures

The size effect on the strength of reinforced concrete (RC) beams flexurally strengthened by surface bonded sheets of fiber-reinforced polymer (FRP) is studied. As the failure is neither ductile nor brittle, but quasibrittle, occurring after stable growth of large cracks with large damage zones, the transitional size effect governed by the energetic size effect law (SEL) must be expected, which the present analysis confirms. Owing to scarcity of size effect experimental data, finite element (FE) analysis is used. A powerful microplane damage constitutive model M7 for concrete, coupled with the crack band model to suppress spurious mesh sensitivity, is calibrated by fitting the existing test data to FRP-strengthened RC specimens of diverse types, and consequently is trusted to simulate the size effect. The analysis captures the debonding near the concrete–FRP interface starting at midspan or at the end of the FRP sheet. It also captures the debonding between adjacent concrete shear cracks, and the delamination of concrete cover. The causes of these different delamination modes are explained. Simple beam-type formulas, in which the size characteristic is not the beam depth but the length of the shear span, are proposed and validated by FE results. The use of single-lap shear tests to determine the bond strength is critically discussed. Finally, a good fit of a few existing limited test data on the size effect of FRP-strengthened specimens is demonstrated.

Effectiveness of hybrid fibre-reinforced polymer retrofitting on behaviour of fire damaged RC columns under axial compression

Reinforced concrete (RC) members when subjected to elevated temperatures due to fire undergo a significant reduction in material strength, concrete cover damage, and loss of bond of reinforcing steel with concrete. In such cases, to ensure the safety of the structure and to allow its future use, it is essential to assess the performance of the fire-affected RC elements and strengthen them appropriately. The objective of this study is to understand the effectiveness of hybrid fibre reinforced polymer (FRP) retrofitting technique on the emergency repair of the severely damaged RC columns under combined fire and axial compression loads. The hybrid FRP retrofitting technique uses the combination of near-surface mounted (NSM) carbon fibre reinforced polymer (CFRP) reinforcement and externally bonded (EB) CFRP wrapping for lateral confinement. In total, eleven short RC columns were damaged under a combination of thermal and axial compression loading conditions. The damaged columns were then retrofitted using an innovative hybrid FRP retrofitting technique. Experimental results reveal that the hybrid FRP retrofitting technique restored 71%–116% of the original capacity of columns before the fire damage.

Numerical Evaluation of Reinforced Concrete Columns Retrofitted with FRP for Blast Mitigation

Fiber reinforced polymer (FRP) material is commonly applied in retrofitting structures due to the advantages of high strength and well corrosion resistance. Previous studies indicated that retrofitting with FRP sheet was an effective way for protecting the existing structures to resist the blast loads, but little research made comprehensive comparison study on the blast response of RC columns with different retrofitting strategies. This paper proposed a series of FRP retrofitting strategies and evaluated their effect on blast mitigation using numerical analysis approach. Comparison studies were conducted on the effect of FRP type, FRP thickness, and retrofitting mode on blast mitigation. A finite element model of RC columns retrofitted with FRP under blast loading was developed. The model considered the strain rate effect of steel and concrete and the orthotropic property of FRP composites. The reliability of the proposed model was validated against the data from a field blast test. Based on the verified model, the blast responses of RC columns with different retrofitting strategies were numerically investigated. According to the result analysis, appropriate FRP type, FRP thickness, retrofitting mode, and retrofitting length were recommended.

Effect of FRP stitching anchors on ductile performance of shear-deficient RC beams retrofitted using FRP U-wraps

Premature debonding failure of fiber-reinforced polymer (FRP) composites has remained a problem hindering the efficient utilization of FRP U-wraps. While implementation of end anchorage systems is recommended to overcome this issue, its influence on enhancing the flexural performance of shear-strengthened reinforced concrete (RC) beams has not yet been fully explored. In an attempt to address this, a novel end anchorage system is developed and its efficiency in improving the behavior of shear-strengthened RC beams is evaluated using experiments. The proposed anchorage technique involves an FRP stitching anchor embedded in holes drilled at the end of a groove that is carved out at the terminal point of a U-wrap FRP retrofit along the shear span of the beam. The experimental program is performed using six RC beams, five of which are strengthened with FRP U-wrap shear retrofits. The as-built test specimens are intentionally designed to be shear-deficient prior to the application of FRP composites sheets and that undergo a flexural failure if the FRP shear retrofits used are successful. All the beams are tested monotonically under four-point bending. The results are discussed in terms of load–displacement behavior, ultimate strength, displacement capacity, and ductility factor to show that the proposed anchorage technique is capable of converting the failure mode of the retrofitted specimens from a brittle shear to a ductile flexure-shear one. Finally, the efficiency of the adopted end anchorage system in improving ductility in shear-retrofitted RC beams is explored in detail.

Experimental and analytical investigations of a novel end anchorage for CFRP flexural retrofits

Flexural strengthening of reinforced concrete (RC) structures using fiber-reinforced polymer (FRP) composites has gained ground as a technique preferred over its rival ones. However, premature failure of FRP retrofitting systems in the form of debonding or delamination still remains to be an element of concern when using this technique. Despite many studies devoted to this phenomenon, no consensus has as of yet been gained on a universal anchorage system that is capable of preventing different premature debonding failures. In an attempt to address this issue, a novel end anchorage method is developed in this study and its efficiency evaluated through experimental tests. The proposed method involves squeezing carbon FRP (CFRP) sheets at their ends into a groove and stitching them with CFRP anchors. To evaluate their combined action in precluding different types of debonding, the end anchors are combined with different types of middle ones. The experimental program was comprised of uses six large scale RC beams, five of which are retrofitted with CFRP composite sheets. All the beams are then tested monotonically under a four-point bending setup. The results are reported in terms of loading capacity, ultimate displacement, flexural stiffness, ductility factor, and failure modes. The proposed anchorage technique is found capable of preventing different debonding scenarios that might occur in flexural retrofitting with CFRP composites. Finally, an analytical procedure is implemented to predict the experimental load-displacement curves of the retrofitted specimens.

Reversible techniques for FRP-confinement of masonry columns

Heritage buildings worldwide are primarily masonry construction. Over the centuries, these structures have demonstrated a high vulnerability in seismic events. The seismic protection and retrofitting of these historical structures require an effective structural solution, without compromise, cover or loss of architectural and artistic value. For these scenarios, the use of Fiber Reinforced Polymers (FRPs) is discouraged since removability of the intervention is often a mandatory requirement, and the polymeric adhesives bond the fiber to the masonry substrate, eliminating the possibility of preserving the underlying material during a replacement operation.In FRP-strengthening, the force transfer from the substrate to the FRP occurs by means of bond stresses. However, in the case of column confinement, while full bond is nevertheless developed through the adhesive, it is not necessary for the effectiveness of the confinement. Instead, the confining pressure is applied by the FRP when transversal dilatation of the column is mobilized. Thus, with the exception of the overlapping regions, an FRP retrofit for column confinement works due to a contact phenomenon instead of bond. In this context, new FRP-confinement techniques, based on contact rather than adhesion, can be developed.This paper presents research on fully-reversible contact-based techniques for FRP-confinement. Three different techniques were developed and demonstrated by the authors. Each technique was experimentally evaluated through compression tests of small-scale limestone cylinders. The reversibility of each technique was verified through comparison of the substrates before the FRP-confinement and after the testing. The effectiveness of each technique was evaluated by comparing the compressive strength and the deformability with those obtained for unconfined specimens. The concepts show promise as effective and reversible strengthening techniques.

Plastic hinge relocation in reinforced concrete beam–column joint using carbon fiber–reinforced polymer

Reinforced concrete buildings with moment-resisting frames comprising beam–column joints (without joint shear reinforcement) designed prior to introduction of seismic codes are shear deficient when subjected to seismic loading, thereby mostly fail in shear at the core of the beam–column joint. However, those designed to the new seismic codes may fail by flexural hinging at the interface of the beam–column joint due to the yielding of the beam reinforcement at the location of highest stress demand (usually the beam–column joint interface). The shear failure has been precluded through the provision of transverse reinforcement at the joint in new design and the use of carbon fiber–reinforced polymer retrofitting in old buildings. Plastic hinge formation at the interface of the beam–column joint is critical because of its penetration into the joint and its effect on bond deterioration. In this study, eight corner-external beam–column joint specimens of 1/3 scale of a typical moment-resisting frame, made without transverse reinforcement, were tested for monotonic and reversed cyclic test under displacement-controlled regime. The control specimens failed by flexural hinging at the beam–column joint interface. The experimental results have been validated using the finite element model. The specimens were retrofitted with unidirectional carbon fiber–reinforced polymer of different layers and different length. After retrofitting, the plastic hinge was relocated to the curtailment end of the carbon fiber–reinforced polymer. The relocation of the plastic hinge resulted in higher load capacity and ductility.

Lessons learned from six different structural health monitoring systems on highway bridges

Structural health monitoring has been utilized in numerous ways to investigate the performance and integrity of highway bridges. This paper highlights the use of six structural health monitoring systems, which were deployed to monitor distinct behaviors on six bridges in Kentucky. The structural health monitoring systems are as follows: (1) Over-height truck impact detection and monitoring on the I-64 over US 60 bridge, (2) Barge impact detection and monitoring on northbound US 41 over the Ohio River, (3) effectiveness of carbon fiber-reinforced polymer retrofit evaluation based on prestressed concrete I-girder crack movement on the I-65 elevated expressway in Louisville, (4) effect of thermal loads on bridge substructure evaluation on KY 100 over Trammel Creek, (5) thermal movement of expansion joints evaluation on eastbound I-24 over the Tennessee River, and (6) crack growth monitoring on steel floor beam on I-275 over the Ohio River. The deployment of the different structural health monitoring systems on Kentucky bridges has provided valuable insights on their planning, implementation, and maintenance, which can be applied on future structural health monitoring projects. While several of the projects have proved immensely successful, with some still being continuously monitored, others, due to numerous complications, have met with only limited success. The best return on investment was realized from structural health monitoring instrumentation that was focused and limited in scope. The successful structural health monitoring systems had continuous communication between all stakeholders during planning, implementation, and monitoring phases of the projects. Following implementation, the availability of contingency funds through the funding source, to replace/upgrade sensors and networking equipment and costs for reprogramming and reinstallation outside of regular maintenance costs, was also important for the structural health monitoring to be successful.

On the design of shear-strengthened RC members through the use of textile reinforced mortar overlays

Abstract Textile reinforced mortar (TRM) is a promising alternative to the FRP retrofitting solution for shear strengthening of reinforced concrete (RC) beams, based on the experimental results presented so far in the literature. Thus, the development of reliable and accurate design models for shear strengthening of concrete members with TRM is required for enabling their wider use in real applications. The available experimental data in the literature are limited and in most cases, a detailed description of the failure modes observed in the TRM jackets and information related to the characteristics of the textile material and the mortar strength are missing, complicating the development of design guidelines. In this paper, a design model to calculate the contribution of the TRM jacket to the total shear resistance was developed using all the well reported available data that were grouped based on the observed failure modes. Specifically, local damage of the jacket including slippage of the fibres through the mortar constitutes a recurring failure mode in concrete beams strengthened in shear with TRM jackets, apart from debonding of the jacket from the concrete substrate including peeling-off of the concrete cover or fracture of TRM jacketing that are also observed in case of fibre reinforced polymer (FRP) jacketing. The key parameters affecting each failure mode were defined and design formulations to calculate the contribution of the TRM jacket to the total shear resistance of RC beams for each failure mode were suggested, whereas a criterion indicating when each failure mode is possible to be observed was also set for using the proper formulation for each TRM system.

Numerical modeling and seismic evaluation of masonry-infilled reinforced concrete frames retrofitted with carbon fiber–reinforced polymer wraps

This article investigates the efficiency of various retrofitting schemes using carbon fiber–reinforced polymers in improving the seismic performance of a substandard masonry-infilled reinforced concrete frame. One virtual five-story reinforced concrete frame was designed according to out-of-date Chinese codes. In total, 15 carbon fiber–reinforced polymers retrofitting schemes were adopted before earthquakes, and three sets of earthquakes representing low, medium, and high frequency contents were selected to conduct the incremental dynamic analysis. The influence of infills’ collapse due to out-of-plane effect was discussed detailedly, and then, the effectiveness of different retrofitting schemes was evaluated. It was found that the collapse of infills obviously reduced the seismic capacity and finally resulted in a soft-story failure mechanism for the reinforced concrete frame. For earthquakes with low frequency content, the enhancement efficiency of retrofitting infills or both columns and infills was increased with the increase in the number of retrofitted stories; however, for medium and high earthquake frequency contents, retrofitting infills or both columns and infills were inefficient when less than half of the structure height was retrofitted. Among the adopted 15 schemes, carbon fiber–reinforced polymers retrofit of both columns and infills along the full building height was found to be the most efficient. Improper selection of a retrofitting scheme could lead to the change of soft-story location. The inter-story drift ratio capacity of effectively retrofitted frames can meet the requirements of current seismic code.