Carbon Fiber Reinforced Polymer Sheets Research Articles

Compression behavior of RC wall-like columns strengthened using NSM/CFRP system without shape modification

The wall-like columns are commonly employed in high-rise buildings for carrying heavy loads without affecting the usable space. However, the retrofitting of these columns often becomes essential under some circumstances. Thus, the designers are looking for strengthening schemes that do not cause changes in the column section for which a combination of near-surface mounted (NSM) bars and carbon fiber reinforced polymer (CFRP) confinement can be adopted. This study was undertaken with the objective of developing such a scheme and studying the confinement provided by CFRP wrapping on wall-like columns. In this study, besides testing two control columns, four columns strengthened using different schemes were tested in axial compression. The performance of the schemes was assessed in terms of the failure modes, load-carrying capacity, and different characteristics of the load-displacement plots. The best scheme was found to be the one wherein the column was strengthened using NSM steel bars connected to the column heads, along with the wrapping of three CFRP sheets covering the NSM rebars. Two analytical models were proposed to estimate the peak load. The first model used the approach of both the ACI 318-19 code and ACI 440.2R-17 guidelines, whereas, the second model utilized the formulas of both Eurocode 2 and the ACI 440.2R-17. The second model predicted the peak load of retrofitted columns more accurately than the first one with prediction errors for the second model varying from 2% to 9%.

Flexural Performance of Cracked Reinforced Concrete Beams Strengthened with Prestressed CFRP Sheets under Repeated Loads

Because researchers are aiming to restore the deformation and minimize the crack width of existing concrete structures, the strengthening technology of prestressed carbon-fiber-reinforced plastic (CFRP) is currently the focus of many studies and applications. In terms of the strengthening of a prestressed CFRP sheet on the flexural performance of cracked reinforced concrete beams under repeated loads, a four-point bending test of 12 beams was conducted considering the prestress degree reflected by the amount and the prestress force of the CFRP sheet. The longitudinal strengthened CFRP sheet was bonded on the bottom surface of the test beam and fixed by U-jacket CFRP sheets at the ends after tensioning. The strains of concrete, longitudinal tensile steel bars and CFRP sheets were measured at the pure bending segment of test beams, while the cracks, midspan deflection and failure pattern were recorded. The results show that the normal strain on the mid-span section of the strengthened beams by the prestress CFRP sheets was fitted for the assumption of plane section, the cracks and mid-span deflection decreased with the prestress degree of the CFRP sheets to provide better serviceability for the strengthened beams, the load capacity could be increased by 41.0–88.8% at the yield of longitudinal tensile steel bars and increased by 41.9–74.8% at the ultimate state and the ductility at the failure state was sharply reduced by 54.9–186%. The peeling off of broken CFRP sheets played a role in controlling the failure pattern of the strengthened beams under repeated loads. Finally, methods for predicting the bending performance of reinforced concrete beams strengthened by prestressed CFRP sheets were proposed. This study enriches the knowledge about damaged reinforced concrete beams that were strengthened with prestressed CFRP sheets.

Efficiency of rapid repairing for composites and structural fibre-reinforced plastic waste aggregate concrete members

In underdeveloped countries, improperly disposed of electronic waste material (E-waste) causes environmental deterioration and health hazards. The previous related work focused on the axial performance of concrete compressive members reinforced with glass fibre reinforced polymer (GFRP), rather than the efficacy of repairing them after minor damage. The present work has endeavored to deliberate the structural performance of partially damaged E-waste aggregate concrete (EAC) compressive members reinforced with structural synthetic fibres reinforced with GFRP bars and GFRP spirals. Carbon fibre-reinforced polymer (CFRP) sheets were utilized to quickly restore the damaged samples. Twelve circular samples with diameters of 250 mm and heights of 1000 mm were constructed. Six samples were reinforced with GFRP bars and spirals (SSEAC compressive members) while the others had steel reinforcement. Following concentric and eccentric compression, which caused a 30% reduction in axial load-carrying capacity in the stage following peak loading, the samples were repaired using CFRP sheets. Before and after their rapid repair, samples' axial load-carrying capacity, load-shortening response, stiffness index, axial shortening, strength index, ductility index, and failure modes were assessed. These factors included spiral pitch, CFRP wrapping, structural synthetic fibres, E-waste concrete, and reinforcement type. The findings showed that as compared to the original compressive members, both restored SSEAC and GSEAC compressive members had good structural behavior in terms of studied parameters due to the efficiency of CFRP wraps. A new theoretical model is also suggested to predict the axial load-carrying capacity of CFRP-repaired members.

Fatigue performance of cracked diaphragm cutouts in steel bridge reinforced employing CFRP/SMA

Under long-term service conditions, fatigue cracking occurs at the diaphragm arc-shape cutouts in the orthotropic steel deck (OSD) bridges subjected to vehicle-induced vibration and cyclical wheel load. To repair cracks of the diaphragm cutouts, this study proposes two repair methods of the carbon fiber reinforced polymer (CFRP) sheets and shape memory alloys (SMA)/CFRP composite patches on the basis of crack-stop holes. The crack-stop hole eliminates the obvious source of fatigue propagation at the crack tip, but it weakens the section and harms the entirety of the diaphragm. The edge of the crack-stop hole in the cracked section becomes a new stress concentration site and the potential crack initiation point. The CFRP sheets can effectively improve the stiffness and reduce the stress amplitude of the cracked part. Moreover, the SMA/CFRP composite patches can further introduce precompression by activating SMA to reduce the stress level. Relative to the reinforcement by the crack-stop hole only, the fatigue notch factor is reduced by 12.28% and 30.76% after bonding CFRP sheets and SMA/CFRP composite patches, respectively. The fatigue tests show that the bonding of CFRP sheets and SMA/CFRP composite patches can effectively postpone the initiation of fatigue cracks and inhibit crack propagation, so they are ideal repair methods for strengthening fatigue cracks of the diaphragm cutouts in the OSD bridges.

Structural Strengthening of Insufficiently Designed Reinforced Concrete T-Beams using CFRP Composites

This study aims to compare the response of reinforced concrete (RC) T-beams strengthened with carbon fibre-reinforced polymer (CFRP) composite with that of non-strengthened control beams when subjected to monotonic two-point loading until failure for flexural once and shear again. The experimental programme tested eight RC T-beams, which included two reference beams without strengthening and six strengthened beams. The eight beams were divided into two main groups according to strengthening (flexural and shear). Experimental analysis was performed to study the effect of the CFRP laminate width in the flexural group and the spacing of CFRP U-wrap sheets in the shear group on the ultimate load capacity, load-strain relationship, and load-deflection relationship. Results show that increasing the width of the CFRP laminate in the flexural group improves the ultimate strengths to approximately 9.5%, 35%, and 41% for beams with CFRP laminate widths of 50, 100, and 150 mm, respectively, compared with the reference non-strengthened beam. The stiffness of the beams increases in direct proportion to the width of the CFRP laminate. In the meantime, decreasing the spacing of the CFRP laminate in the shear group increases the ultimate strengths to approximately 13.2%, 17.7%, and 23.5% for beams with CFRP U-wrap sheet spacings of 166, 125, and 100 mm, respectively, compared with the reference non-strengthened beam. Therefore, the spacing of the CFRP sheet is inversely proportional to the stiffness of the beam. Doi: 10.28991/CEJ-2023-09-08-05 Full Text: PDF

Fatigue performance improvement of U-rib butt-welded connections of steel bridge decks using externally bonded CFRP strips

U-rib butt-welded connections in steel bridge decks are known to be highly susceptible to fatigue cracking, which can pose a direct threat to the safety and durability of bridge structures. Carbon fiber-reinforced polymer (CFRP) materials have shown promising potential for fatigue strengthening. This study investigated the effectiveness of CFRP application on the fatigue performance of U-rib butt-welded connections by employing full-scale fatigue tests and finite element analysis. Two single U-rib specimens with welded splice joints were initially tested to initiate real fatigue cracks under cyclic loading. Different techniques of CFRP installation were then proposed to promote the fatigue performance of cracked butt-welded connections. The failure modes and fatigue strength of the tested specimens were evaluated before and after strengthening. Research results showed that fatigue cracks were observed at the arc transition of butt welds, where remarkable incomplete penetration was also discovered. The fatigue strength grade of the tested U-rib butt-welded details was less than 71 MPa stipulated by Eurocode 3. However, after being repaired by CFRP sheet bonding, the equivalent fatigue life of U-rib butt welds with different damage degrees can be extended by 0.5–16.6 times that of the original ones. These findings suggest that CFRP strengthening should be applied instantly on U-rib butt-welded connections once fatigue cracks are found.

Fire endurance tests of CFRP-strengthened RC beams with different insulation schemes

The fire performance of externally bonded (EB) carbon fiber-reinforced polymer (CFRP)-strengthened reinforced concrete (RC) beams is an important issue in practical strengthening design. The cable mechanism of CFRP sheets in a fire can improve the fire endurance of the strengthened beams. This paper presents a feasible method to activate the cable mechanism of EB CFRP sheets in the strengthened beams by using appropriate insulation schemes and a mechanical anchorage system. Seven beams were constructed: three were tested at room temperature, while the remaining four were subjected to the ISO 834 standard fire. The experimental results showed that the three insulation schemes could provide reasonably good protection for the specimens, and thus all of them achieved a fire endurance of 2.5 h. The combined use of fire insulation and a mechanical anchorage system could reduce the deflection responses, mainly due to the active cable mechanism of the EB CFRP sheets during fire exposure. A finite element (FE) model was then proposed to predict the thermal and structural responses of insulated CFRP-strengthened RC beams. The FE parametric results further indicated that different insulation schemes with various thicknesses and thermal conductivities had significant effects on the fire performance of the strengthened beams.

Analytical and experimental investigation on axial compression capacity of carbon fiber-reinforced plastic-confined concrete-filled double-skin steel tube stub columns

Concrete-filled double-skin steel tubes (CFDSTs) are widely used in civil engineering. During the service life of CFDSTs, their bearing capacity can be easily weakened by the corrosion of outer steel tubes. This study investigated the interaction mechanism and reinforcement effects of carbon fiber-reinforced plastic (CFRP)-confined CFDSTs under axial compression. Typical failure modes, axial load-shortening curves, and axial load-strain behaviors of CFDST and CFRP-confined CFDST (CFRP-CFDST) specimens were obtained. The test results showed that the ultimate bearing capacity of stub columns with concrete strength of C40 and C60 increased by 19.78% and 15.12%, respectively, when wrapped with two layers of CFRP sheets, and by 41.60% and 37.99%, respectively, when wrapped with four layers of CFRP sheets. In addition, the FE modeling of CFRP-CFDSTs was established and validated by experimental results. On this basis, the parametric analysis was conducted. To avoid local buckling and yield failure of the inner steel tubes before the outer steel tubes, a calculation formula was proposed for predicting the minimum wall thickness of the inner tube. Furthermore, the prediction formulas for the bearing capacity of CFDSTs and CFRP-CFDSTs were proposed.

Bond performance of spliced GFRP bars in pre-damaged concrete beams retrofitted with CFRP and UHPC

Fiber-reinforced polymer (FRP) reinforced concrete structures are inevitably subjected to extreme loads. The retrofitting of damaged FRP-reinforced concrete structures will become an important issue, especially with the gradual application of FRP bars in concrete structures. For structures that can be retrofitted, the structural performance is significantly affected by the bond of FRP bars in pre-damaged concrete. For this reason, this paper investigated the effectiveness of retrofit methods of carbon FRP (CFRP) sheet and/or ultra-high performance concrete (UHPC) at restoring the bond strength of glass FRP (GFRP) bars in pre-damaged concrete, and twenty spliced GFRP-reinforced concrete beams were tested under four-point loading. The beams were pre-loaded until bond failure occurred, and then retrofitted and reloaded to assess the restoration of the bond strength. The effects of retrofit methods, spacing of confining stirrups, GFRP bar diameter, and pre-loading type were investigated. The bond strength of the 20 mm and 28 mm diameter GFRP bars was increased by 4~138% and 4~234% after retrofitting with CFRP sheet and/or UHPC, respectively. The modified flexural strength model and modified effective moment of inertia addressing the adverse effect of partial fracture of glass fibers and concrete cracks predicted well the load-carrying capacity and deflection of the retrofitted specimens showing flexural failure, respectively.

Practical Investigation on the Strengthening of the Built-Up Steel Main Girder of a Metro Station with Carbon-Fiber-Reinforced Polymer on the Inside Part of the Tensioned Flange

This study investigates the effectiveness of a carbon-fiber-reinforced polymer (CFRP) in enhancing the load-carrying capacity of a steel main girder in a metro station. The objective is to evaluate the applicability of CFRPs in sustaining increases in applied loads and assessing their effectiveness on curved surfaces. Finite element analysis (FEA) identified the most stressed areas of the girder under design loads. Based on the FEA results, a targeted strengthening procedure using CFRP sheets was proposed. Various arrangements of CFRP sheets were tested, including different orientations and thicknesses up to 60% of the girder’s flange thickness. To validate the FEA accuracy, two small-scale specimen beams were prepared and tested in the laboratory. One beam was strengthened with CFRP sheets on the tension part of the inner flange side, similar to the suggested strengthening method for the girder. The FEA results show that the CFRP increases stresses by an average of 8% to 10% for the steel main girder, with strengthening effects up to 19% at the center of the CFRP strengthening positions, differing from a regular straight flange shape. Significantly reducing stresses required a total CFRP layer thickness of at least 50% of the flange’s total thickness. Applying a CFRP on the inner face of the girder preserves its usability without the need for openings in finishes or the metal deck surface. The findings highlight CFRP’s potential to enhance load-carrying capacity on curved surfaces and sustain increased applied loads, offering a promising solution for strengthening infrastructure and similar applications.

Shear Behavior of Reinforced Concrete Beams with Different Arrangements of Externally Bonded Carbon Fiber-Reinforced Polymer

Carbonfiber-reinforced polymer (CFRP) composites are frequently utilized in the repair and reinforcement of reinforced concrete members because they are more corrosion-resistant, durable, and flexible than commonly used materials like steel plates. Many studies have demonstrated that the use of CFRP as an internal strengthening material has a substantial impact on the shear capacity of RC beams. This research looks into the possibility of using FRP material as an externally bonded reinforcement to increase the shear strength of RC beams. Because shear improvement and mode of failure are based on the right configuration of the CFRP sheets, the experimental work consisted of eight RC beams with various types, orientations, and configurations of CFRP sheets. All beams were examined under two-point bending. The test results show that the CFRP sheet significantly improved the beam’s shear strength and ductility and that it is advantageous to orient the FRP at 45 degrees to the beam’s longitudinal axis.

Structural Performance of Strengthening of High-Performance Geopolymer Concrete Columns Utilizing Different Confinement Materials: Experimental and Numerical Study

The objective of this study was to investigate the effectiveness of different confinement materials in strengthening geopolymer concrete (GP) columns subjected to axial compression loading. This research encompassed both experimental and numerical analyses. The experimental phase involved testing seven circular GP columns, while the numerical phase involved developing 3D finite element (FE) models using ABAQUS software. The primary focus of this study was to assess the impact of using outer and inner steel tubes, as well as an outer polyvinyl chloride (PVC) tube and a carbon-fiber-reinforced polymer (CFRP) sheet. To validate the FE models, the experimental results were utilized for comparison. The findings of this study revealed that the outer steel tube provided superior confinement effects on the GP column’s concrete core compared to the PVC tube and CFRP sheet. The axial capacities of the columns confined with steel, PVC, and CFRP materials were observed to increase by 254.7%, 43.2%, and 186%, respectively, in comparison to the control specimens. Furthermore, the utilization of all confinement materials significantly enhanced the absorbed energy and ductility of the columns. The FE models demonstrated a reasonably close match to the experimental results in terms of load–displacement curves and deformation patterns. This correspondence between the numerical predictions and experimental data confirmed the reliability of the FE models and their suitability for generating further predictions. In summary, this study contributes to the field by exploring the efficacy of various confinement materials in strengthening GP columns. The results highlight the superior performance of the outer steel tube and demonstrate the positive influence of PVC and CFRP materials on enhancing the structural behavior of the columns. The validation of the FE models further supports their reliability and their potential for future predictions in similar scenarios.

Ferrocement, Carbon, and Polypropylene Fibers for Strengthening Masonry Shear Walls.

This paper describes an experimental investigation into the feasibility of using ferrocement jacketing, polypropylene fibers, and carbon fiber reinforced polymer sheets (CFRP) to enhance the shear resistance of unreinforced brick masonry. The study involved testing 12 wall panels in diagonal compression, three of which were strengthened using each of the above-mentioned techniques. The results showed that all three strengthening techniques led to a significant improvement in the shear resistance and deformation capacity of the unreinforced walls. Furthermore, the results showed that the strengthened walls exhibited a significant improvement in shear resistance and deformation capacity by a factor of 3.3-4.7 and 3.7-6.8, respectively. These findings suggest that ferrocement jacketing is a viable and highly effective method for strengthening masonry structures. Test results can assist in the decision-making process to identify the most suitable design and retrofitting solution, which could indicate that not only new materials, but also traditional methods and materials (ferrocement) could be interesting and effective, also considering their lower initial cost.

The shear strength of existing non-seismic RC beam-column joints strengthened with CFRP Sheets: Numerical and analytical study

A key part of RC structure seismic performance is the effective distribution of earthquake forces across all resistance elements through reinforced concrete (RC) beam-column (B-C) joints. By virtue of their ease of implementation and convenient material properties, Carbon-Fiber-Reinforced Polymers (CFRP) are highly utilized for strengthening existing structures with inadequate reinforcement or insufficient confinement. Previous experimental research revealed that debonding failure widely occurs on CFRP shear-strengthened B-C joints. The experimental research as well showed the value of column axial load makes a great contribution to such joint’s failure mode. Using CFRP U-jacketing to strengthen non-seismically B-C joints, this article presents a non-linear, two-dimensional FE model for investigating shear behavior. The developed FE model considered the adhesive layer between CFRP sheets and concrete to capture the debonding and a bond-slip model was implemented between concrete-to-CFRP sheets using connector elements. The FE results were verified versus experimental works from literature to prove the proposed FE model's accuracy with appreciate to load-deformation relation and failure modes. Depending on the verified FE model, a parametric study on shear-strengthened RC B-C joints with CFRP U-jacketing with free and fixed ends was performed below monotonic loading. In the existing study, several parameters, including column-to-beam flexural strength ratio (over strength ratio), concrete strength, and value of column axial load, were investigated on the structure's strength and ductility. Using the developed strut-and-tie model (STM), new design equations were proposed to calculate strengthened RC B-C joint's shear strength using CFRP. The proposed equations incorporate the interfacial bond among concrete and CFRP effect, as well CFRP sheet end boundary (free or fixed). The developed design equation’s ability to estimate shear strengths of strengthened B-C joints with CFRP was verified through experimental works and FE results. It was evident from verification results that the produced design equations were compatible with experimental and FE model results.

Durability performance of RC beams strengthened with CFRP laminates and galvanized steel mesh bonded with epoxy and mortar systems

The galvanized steel mesh (GSM) systems are novel strengthening materials for the concrete structural elements, but their mechanical and long-term durability properties are needed to be investigated to enhance understanding and reliability in their use. This study investigates the behavior of reinforced concrete (RC) beams strengthened with carbon fiber reinforced polymers (CFRP) and GSM sheets under harsh climatic conditions of saline water and direct sunlight. The main focus was to recommend two important reduction factors, the bond reduction factor and the overall flexural reduction actor, when concrete beams are subjected to two said environments for a long period. These factors were compared to the ones recommended by different codes. The CFRP sheets were attached to the beams’ soffit with epoxy adhesive, whereas the GSM sheets were bonded either with epoxy (SME) or epoxy-based mortar (SMM). The specimens were weathered under saline water and direct sunlight for a period of 6, 12, and 24 months. The load-carrying capacity of CFRP, SMM, and SME strengthened specimens increased by 47%, 55%, and 55%, respectively, when compared to the unstrengthened specimens at 28 days. The bond capacity reduction factors (Rb) for CFRP, SMM, and SME strengthening systems were 0.75, 0.85, and 0.95 for saline water exposure, and 0.95, 0.85, and 0.85 for sun exposure, respectively, over a period of two years. On the other hand, the recommended overall flexure strength reduction factors (Rn) for CFRP, SMM, and SME strengthening systems were 0.85, 0.85, and 0.90 for saline water exposure, and 0.95, 0.90, and 0.90 for sun exposure, respectively. The results suggest that epoxy-based strengthening systems are more durable compared to the mortar-based systems under harsh climatic conditions.

Flexural Behavior of Corroded Concrete Beams Strengthened with Carbon Fiber-Reinforced Polymer.

The present study investigates the flexural behavior of reinforced concrete (RC) beams; the longitudinal reinforcing rebars of the beams were corroded and then strengthened with carbon fiber-reinforced polymer (CFRP). The corrosion of the longitudinal tension reinforcing rebars in eleven beam specimens was accelerated in order to obtain different corrosion levels. Afterwards, the beam specimens were strengthened by bonding one layer of CFRP sheets to the tension side to restore the strength loss due to the corrosion. The failure modes, flexural capacity, and midspan deflection of the specimens with different corrosion levels of the longitudinal tension reinforcing rebars were obtained by the four-point bending test. It was found that the flexural capacity of the beam specimens decreased with the increase in the corrosion level of the longitudinal tension reinforcing rebars and that the relative flexural strength was only 52.5% when the corrosion level was 25.6%. The stiffness of the beam specimens decreased significantly when the corrosion level was higher than 20%. Through a regression analysis of the test results, a model for the flexural bearing capacity of the corroded RC beams strengthened with CFRP was proposed in the study.

Effect of bond length on bond behavior between basalt fiber-reinforced polymer sheet and concrete

Many reinforced concrete structures are always damaged due to material aging during service life. Reinforced concrete structures can be retrofitted by fiber-reinforced polymer (FRP) sheets to improve load carrying capacity and extend the service life. The bond behavior between the FRP sheet and concrete is important for assessing the load carrying capacity of reinforced concrete structures retrofitted with FRP sheets, and the effective bond length is often used in determining the bond behavior. Basalt FRP (BFRP) has excellent properties, such as light weight and high tensile strength. Although the effective bond length between carbon FRP sheets and concrete has been studied, study on the effective bond length between BFRP sheets and concrete remains lacking. The effect of bond lengths on the bond behavior between BFRP sheets and concrete was investigated in the present study. The results revealed that: (1) the failure load between the BFRP sheets and concrete increased with the increase of the bond length when the bond length was not beyond the effective bond length; (2) the effective bond length of the interface between BFRP sheet and concrete was not beyond 80 mm obtained from the failure load; (3) the effective bond length of the interface between BFRP sheet and concrete was obtained from the bond stress; and (4) models for the failure load and the effective bond length were established.

Seismic Retrofit of Diagonal Tension Members in Steel Deck-Truss Bridges Using CFRP Sheets

This study entailed axial cyclic loading tests conducted on full-scale diagonal tension members of steel deck-truss bridges to evaluate the effects of seismic retrofitting methods using carbon fiber–reinforced polymer (CFRP) sheets. The loading tests were performed on CFRP-retrofitted specimens with varying anchoring lengths of the CFRP sheets. The results indicated that the proposed retrofitting methods, which employed the intermediate-modulus CFRP type (390–450 GPa) and polyurea putty (a ductile adhesive), delayed the plastic buckling of the flanges and substantially increased the load-carrying capacities, stiffnesses, and ductility capacities of the retrofitted diagonal tension members. Additionally, the polyurea putty effectively suppressed the peeling failure of the CFRP sheets. It maintained the cross-sectional integrity between the steel members and CFRP sheets even after the plastic buckling of the flanges and rupture failure of the CFRP sheets. Further, finite-element analyses accurately reproduced the loading test results by considering the nonlinear bond-slip performance of polyurea putty, anisotropic characteristics of the CFRP sheets, and cyclic plasticity properties of steel.

Synergistic use of ultra‐high‐performance fiber‐reinforced concrete (UHPFRC) and carbon fiber‐reinforced polymer (CFRP) for improving the impact resistance of concrete‐filled steel tubes

SummaryConcrete‐filled steel tubes (CFSTs) have received growing attention, owing to their rapid construction, reduced labor requirement, and reasonable material cost. While in service, the CFSTs can be subjected to unexpected impact loads, originating from vehicle and vessel collision, as well as water‐ and wind‐borne debris impact. Such extreme loading events often cause a partial or complete failure of conventional CFSTs, risking the safety and performance of the entire structural systems that rely on them. To address this issue, the current study explores how two advanced composite materials, including ultra‐high‐performance fiber‐reinforced concrete (UHPFRC) and carbon fiber‐reinforced polymer (CFRP), can be utilized to provide superior mechanical properties and minimize the vulnerability of CFSTs to impact loads. The composite materials under consideration are appropriate for both new and existing structures, in which normal‐strength concrete can be replaced with UHPFRC, while CFRP sheets can further strengthen the CFSTs. For obtaining in‐depth insights, a computational framework validated with the experimental tests was developed in the current study. Using a set of representative impact scenarios, various response measures, such as internal forces and deflections, as well as the energy absorbed by the CFSTs, were recorded during impact simulations. The investigations were then further extended to capture the influence of the main design parameters related to concrete, CFRP, and steel tube. From the conducted investigations, an energy absorption index was introduced, as a measure to evaluate the performance of CFSTs under impact loads.

Effect of Soil Creep on the Bearing Characteristics of Soil Slope Reinforced with CFRP and Anti-Slide Piles

In order to research the displacement characteristics and stability of a soil slope reinforced with carbon-fiber-reinforced plastic (CFRP) and anti-slide piles, the displacement composition, aging deformation and failure mode of a soil mass were analyzed. According to the Mohr–Coulomb strength criterion, a new nonlinear, accelerated creep model of soil mass was founded with the addition of a self-building M-C plastic element. Furthermore, a viscoplastic strain analytical formula of an M-C plastic element was obtained, and the tensile deformation characteristics of a CFRP sheet were also discovered under a landslide thrust creep load. According to the environmental conditions of the anti-slide pile, the CFRP was arranged along the load-bearing side of the pile to control deformation. Combining the calculation example, it is shown that the horizontal displacement of the soil slope’s composite structure decreases by approximately 40% with CFRP reinforcement. Furthermore, for the first two calculation conditions, after one year, the maximum horizontal displacement decreased by 50% and increased by 10%, respectively. Simultaneously, the overall safety factor increased by 31.3% without soil creep properties. On the contrary, the overall safety factor was reduced, and the slope has a tendency toward unstable failure. Moreover, there is no through plastic zone in the slope. The stability of the reinforced slope and the bearing capacity of the pile are related to the CFRP method. Simultaneously, the structure can reduce the costs and construction difficulty of anti-slide piles in a complex environment surrounded by the soil creep effect.