Carbon Fiber Composite Cable Research Articles

Flexural loading test of a tunnel lining concrete model strengthened with carbon-fiber composite cables

In general, incorporating fiber-reinforced polymer reinforcements into arch-shaped tunnel lining concrete (TLC) is challenging. To overcome this, the TLC can be strengthened by combining a flexible carbon-fiber composite cable (CFCC) with the near-surface mounted (NSM) technique. Thus, this study evaluated the load-carrying capacity of arched concrete members strengthened by NSM–CFCC and investigated the effectiveness of the strengthening system for TLC. To measure the load-carrying capacity of arched concrete members, a specialized loading system was fabricated to conduct flexural loading tests on TLC models. The primary test models were the reference TLC models without reinforcement. TLC models bonded with a carbon-fiber sheet (CFS), and NSM–CFCC-strengthened TLC models, and two types of NSM–CFCC TLC models were tested. Eight TLC models were constructed using the conventional NSM technique in which the CFCC was embedded into a cementitious material-filled groove. The results revealed that the TLC member was not perforated by a flexural crack, even in non-strengthened concrete, owing to the arch effect. The load-carrying capacity of the NSM–CFCC TLC was remarkably higher than that of the reference and CFS strengthening models. The ultimate failure of all TLC members was caused by the crushing of the upper concrete. A finite difference analysis (FDA) for the loading test was also performed using commercial software FLAC3D. The numerical simulation results were found to be in good agreement with the cracking behavior of the strengthened TLC members observed in the experiment. These results suggest that the strengthening system using NSM–CFCC is effective for the TLC.

COMPARATIVE STUDY ON TUNNEL LINING CONCRETE STRENGTHENED WITH CARBON-FIBER COMPOSITE CABLES AND SHEETS

Most lining concretes of road tunnels in Japan have been gradually deteriorated by aging and various environmental effects. The study focuses on a strengthening system for tunnel lining concrete (TLC) subjected to external forces. Carbon fiber (CF) sheets are often used in TLC for preventing concrete exfoliation. The strengthening effect of CF sheet for TLC was not sufficiently known. The experimental study conducted a mock-up loading test to examine failure mode and load-capacity of the TLC model bonding CF sheet. In addition, the study prepared TLC models strengthened with near-surface mounted (NSM) technique using carbon-fiber composite cables (CFCC). The strengthening effects of CF sheet and NSM-CFCC were quantified and compared via the mock-up loading test. The experimental study revealed that the TLC model bonding CF sheet failed by intermediate-crack-induced debonding at around 100 kN, and the load carrying capacity was almost equivalent to the capacity of non-strengthened TLC model. On the other hand, the NSM-CFCC strengthened TLC model indicated higher ductility after concrete cracking and superior load capacity. The experimental study confirmed the NSM-CFCC as an effective strengthening system for TLC members.

Experimental Study on the Flexural Behavior of Connected Precast Concrete Square Piles

Part of deep foundation pit support engineering needs to select connected precast concrete square piles (CPCSPs). Under the premise that the quality of precast concrete square piles (PCSPs) meets engineering requirements, the quality of CPCSPs becomes the key factor to ensure the safety of foundation pit support structures. This paper puts forward a new connection technology of CPCSPs and carries out the flexural behavior experiment of unconnected precast concrete square piles (UPCSPs) and CPCSPs. The distribution of crack and strain on different surfaces of UPCSPs and CPCSPs are measured by carbon fiber composite strain sense optical cables, glass fiber composite strain sense optical cables, and fixed-point polyurethane strain sense optical cables. The anti-crack load, ultimate load, bending moment, and flexural deformation of UPCSPs and CPCSPs are measured. The experimental results of UPCSPs and CPCSPs are compared. The results show that the anti-crack strength of CPCSPs is greatly increased while the flexural deformation of CPCSPs is decreased before the occurrence of crack. With the development of crack (failure stage), the outside areas of hoop steel plate exhibit cracks. At this moment, the strength of CPCSPs is no longer controlled by the strength of middle areas. The ultimate strength of CPCSPs is basically equivalent to that of UPCSPs. The ultimate bending moment of CPCSPs is higher than its design value (about 66%∼76%). The selection of CPCSPs in the design of foundation pit support has good reliability.

Pull-out test of carbon-fiber composite cable (CFCC) tendon for an internal anchorage

An internal strengthening system involving the embedding of a post-tensioned prestressing tendon in a wedge-shaped anchorage of an existing concrete member was developed previously. The previous study confirmed the adequate load capacity of the prestressing tendon for the internal strengthening technique. The tendons used in the previous investigation were steel-rigid bar and steel-wire cables. These steel tendons are prone to corrosion under severe environmental conditions, such as bridge deck slabs sprayed with deicers. Carbon fiber composite cables (CFCC) are occasionally employed as tendons in prestressed concrete bridges. This study focused on the non-metallic material and examined the load capacity of CFCC tendon in internal strengthening systems to achieve the feasibility of the technique under corrosive environment. The main concern of the novel strengthening system was the anchoring system of the CFCC in the internal wedge. In general, both ends of the CFCC tendon can be gripped with external fasteners and be provided a tensile force using a hydraulic jack. In an internal prestressing system, a CFCC end must be anchored without any external fastener. It is preferable to simply fix the CFCC in a small wedge anchor made of existing concrete. This study focused on developing a CFCC anchoring method in a wedge-shaped hole and examined the tensile load capacity of the CFCC tendon fixed in the anchorage. The end of the CFCC tendon was reversely twisted to improve the pullout resistance by increasing the diameter of the cable. To examine the load-bearing capacity of the developed CFCC tendon, a mock-up reinforced concrete (RC) block with an internal wedge-shaped anchorage was used. A CFCC tendon equipped with a reverse-twisted tip was inserted into a wedge-shaped hole filled with high-strength grout. A pull-out test of the CFCC tendon was conducted to examine its load-bearing capacity. The test results revealed that the CFCC tendon with a reverse-twisted tip embedded in the anchorage exhibited adequate load-bearing capacity. This study confirmed that the post-tensioned prestressing system using the CFCC tendon is appropriate for strengthening RC members having the thickness of at least 200 mm, such as bridge deck slabs.

Transfer Length vs. Slip of Prestressed Fiber-Reinforced Polymer Reinforcement.

A comprehensive analysis of the relationship between transfer length and slip of different types of prestressed fiber reinforced polymer (FRP) reinforcement is provided. The results of the transfer length and slip together with the main influencing parameters of approximately 170 specimens prestressed with different FRP reinforcement were collected. After the analysis of a larger database of transfer length versus slip, new bond shape factors were proposed for carbon fiber composite cable (CFCC) strands (α = 3.5) and carbon fiber reinforced polymer (CFRP) bars (α = 2.5). It was also determined that the type of prestressed reinforcement has an influence on the transfer length of the aramid fiber reinforced polymer (AFRP) bars. Therefore, α = 4.0 and α = 2.1 were proposed for AFRP Arapree bars and AFRP FiBRA and Technora bars, respectively. Moreover, the main theoretical models are discussed together with the comparison of theoretical and experimental transfer length results based on the slip of reinforcement. Additionally, the analysis of the relationship between transfer length and slip and the proposed new values of the bond shape factor α have the potential to be introduced in the production and quality control processes of precast prestressed concrete members and to stimulate additional research that increases the understanding of the transfer length of FRP reinforcement.

LOAD CAPACITY OF TUNNEL LINING CONCRETE STRENGTHENED WITH CARBON-FIBER COMPOSITE CABLE (CFCC)

Efficient strengthening systems for tunnel lining concrete (TLC) have not been sufficiently discussed while various systems are available for other structures. The study aims at development of a strengthening system applicable for TLC. In particular, the present study focused on an NSM-FRP strengthening system which is often employed in deck-slabs and girders of bridge. Most of FRP materials used in such supra-structures are laminates and rods. It may be hard to embed FRP materials into inner surface of arched tunnels. Flexible FRP must be a favorable material for strengthening of TLC. The study focused on a carbon-fiber composite cable (CFCC) which is often used in prestressed concrete structures. The CFCC is embedded in inner surface of TLC by using a polymer cementitious mortar and epoxy resin. Fundamental loading test using mock-up TLC models was conducted to examine the strengthening effect of the proposed system. The paper reports the load-carrying capacity of the strengthened TLC models.

An Analysis of the Transfer Lengths of Different Types of Prestressed Fiber-Reinforced Polymer Reinforcement.

The main aim of this paper is to provide a broader analysis of the transfer lengths of different types of fiber-reinforced polymers (FRPs) and to provide corrections to the existing theoretical models. Therefore, this paper presents a description of the main factors that influence the transfer lengths of different types of FRPs based on experimental results found in the literature. A database of more than 300 specimens was compiled with the results of the transfer lengths of different FRPs and the main influencing parameters. The analysis of the database results showed that the transfer length of the carbon fiber composite cable (CFCC) strands depends on the type of prestressed reinforcement release. Therefore, in this article, the new coefficient αt = 2.4 is proposed for the transfer length of suddenly released CFCC strands. Additionally, the transfer length of the aramid fiber reinforced polymer (AFRP) depends on its surface conditions. Therefore, new coefficients αt = 1.5 and αt = 4.0 are also proposed for the transfer lengths of smooth braided and sanded and rough AFRP bars, respectively. Furthermore, the proposed coefficients αt = 2.6, αt = 1.9, and αt = 4.8 found in the literature were validated with the analysis of a larger database of the transfer lengths of glass fiber-reinforced polymer (GFRP) bars, carbon fiber-reinforced polymer (CFRP) bars, and gradually released CFCC strands, respectively. Moreover, the main existing theoretical models are presented, and the comparison of theoretical and experimental transfer length results is discussed. However, the low number of specimens prestressed with basalt fiber-reinforced polymer (BFRP) bars prevented the deeper analysis of the results. the analysis of the transfer length and the proposed new values of the coefficient αt provides possibilities for adapting it to design codes for engineering applications and performing additional research that fills the missing gaps in the field.

Experimental and numerical studies on buckling restrained braces with posttensioned carbon fiber composite cables

SummaryThere has been an increasing interest in using residual deformation as a seismic performance indicator for earthquake resistant building design. Self‐centering braced structural systems are viable candidates for minimizing residual deformations following a major earthquake. Hence, this study proposes an alternative type of buckling restrained brace (BRB) with externally attached posttensioned (PT‐BRB) carbon fiber composite cables (CFCCs). The steel core of the brace is used as an energy dissipator, whereas the CFCCs provide the self‐centering force for minimizing residual story drifts. Three proof‐of‐concept specimens are designed, fabricated, and cyclically tested at different posttensioning force levels. The CFCC behavior to obtain cyclic response, including the anchorage system, is examined closely. A parametric study is also conducted to show the effect of the different configurations of PT‐BRBs on the inelastic response. Furthermore, optimal brace parameters are discussed to realize design recommendations. The results indicated that the implementation of partially self‐centering BRBs in building frames can lead to the target residual displacements. A stable behavior is obtained for the proposed PT‐BRBs when subjected to the loading protocol specified in the American Institute of Steel Construction (AISC) 2016 Seismic Provisions.

Theory-based approaches and microstructural analysis to evaluate the service life-retention of stressed carbon fiber composite strands for concrete bridge applications

Prestressed concrete girders and piles with steel strands are used in construction of bridges in North America, due to their economy of design, fabrication, and installation. However, they are often exposed to harsh environments, which results in rapid degradation. Therefore, carbon fiber reinforced polymer (CFRP) tendons have successfully been introduced as prestressing reinforcement for pile applications. This paper presents a study on the physical characterization, microstructural analysis, and durability performance of unstressed and stressed carbon-fiber composite cables (CFCCs) for prestressing applications. This is achieved through testing 120 CFCC specimens, subjected to stress levels of about 40% and 65% of their guaranteed strength, and 51 specimens without sustained load under tension. Moreover, prediction models were introduced to assess the long-term performance and retentions of CFCC strands. The models included Arrhenius model, Fick's law, Fib Bulletin (40) model, and a developed approach that incorporates the effects of temperature, design life, and relative humidity of exposure into the environmental reduction factor. Based on the predication model, the tensile strength retention (CE) for CFCC strands, is predicted to retain over 0.95 and 0.84 of ultimate tensile strength for a relative humidity (RH) < 90% and a moisture saturated environment (RH = 100%), respectively, after 100 years of service life with elevated temperature and sustained load.

Effect of applied sustained load and severe environments on durability performance of carbon-fiber composite cables

The research work reported in this paper involves investigation of the mechanical and durability performance of unstressed and stressed Tokyo Rope carbon-fiber composite cables for prestressing applications. This research is critical in order to establish the critical (allowable) stress and safety factors for the use of carbon-fiber composite cable tendons for prestressed precast-concrete members. The carbon-fiber composite cable specimens were exposed to simultaneous high alkali environment and sustained loading at different elevated exposure temperatures (22℃ and 60℃) for 3000, 5000, and 7000 h. The high alkali environment (12.8 pH) simulated the concrete pore solution and the elevated temperature was used to accelerate the aging process. The applied sustained stress on the carbon-fiber composite cable strands was equivalent to 40% and 65% of their guaranteed tensile strength. This was achieved through testing 171 carbon-fiber composite cable specimens subjected to stress levels of 0%, 40%, and 65% of their guaranteed strength, under tensile load. Also, 136 carbon-fiber composite cable specimens were tested to investigate the transverse shear strength. In addition, the durability characteristics of the constituent materials of the carbon-fiber composite cable strands were assessed to understand the long-term behavior of these materials. The results showed the effect of sustained stress on the degradation of carbon-fiber composite cable strands. Under sustained stress of 40% and 65%, the reductions in tensile strength were 10.6% and 12.3%, respectively. Scanning electron microscope results on epoxy resin indicated that no degradation is detected since the surface remains smooth without any pitting or loose material.

Experimental and numerical investigation of splicing of concrete-filled fiber-reinforced polymer tubes

The structural performance of spliced, concrete-filled FRP tubes was evaluated. The splices consisted of an internal FRP collar adhesively bonded to the tube segments and a concrete reinforcing cage of carbon fiber composite cable (CFCC). Spliced beams were tested to determine the splice flexural capacity. Adhesive bond strength and CFCC development lengths were experimentally determined. Splice behavior was investigated with 3D finite-element models employing a modified concrete damage plasticity model and cohesive interfaces. Model predictions were in good agreement with the experiments; the predicted capacity was 13.8% greater than the 113.1 kN average failure load of the splice.

Long-term Application of Carbon Fiber Composite Cable Tendon in the Prestressed Concrete Bridge-Shinmiya Bridge in Japan

Carbon fiber reinforced plastic (Carbon Fiber Composite Cable, CFCC) has the outstanding features in comparison with regular steel. In October 1988, CFCC was applied as the tensioning material in main girders of new Shinmiya Bridge in Ishikawa, Japan. This was the first bridge in Japan and in the world, which CFCC tendons were used in the prestressed concrete bridge to counter salt damage. To investigate the serviceability and durability of the main girders and CFCC, three full-scale test girders were fabricated in 1988. At the same time, a bending experiment was conducted on one girder to investigate the ultimate behavior, load carrying capacity of the PC girder, as well the strain behavior of the CFCC. Besides, two PC girders were placed next to the main girders of the bridge in the same conditions. One of them was used for a destructive test after six years of the construction time (1994). In this study, another test specimen that was exposed to the actual corrosive environment after nearly 30 years was subjected to a destructive test by bending load. The load carrying capacity of the girder was clarified, and the durability of the PC girders using CFCC tendon was confirmed.

Post-tensioned timber structures: New perspectives

The structural behaviour of both glued laminated timber (GL) and laminated veneer lumber (LVL) is well described by the strength effectiveness ratio f/ρ (resistance over unit weight) and the deformation effectiveness ratio E/ρ (elastic modulus over unit weight). They are comparable to those provided by steel, together with the buckling effectiveness ratio E0.5/ρ which is higher than that provided by other structural materials. Current GL and LVL technologies, which give their best in covering wide spans, have probably reached their maximum capabilities and new ideas are growing up in order to improve this field of application. In the present paper, a new technology, which uses post-tensioning of timber beams, based on an Italian patent, is described. The structural behaviour, here analysed, shows a considerable improvement respect to the traditional technology, in terms of both strength and deformation. In particular, after the theoretical considerations that lie at the base of the idea, a case study is presented in which the behaviour of a post tensioned GL main girder of a footbridge is compared with a traditional timber and steel ones. The prestress is applied by means of a set of tendons made of carbon fiber composite cable (CFCC).

An Experimental Study on Non-Compression X-Bracing Systems Using Carbon Fiber Composite Cable for Seismic Strengthening of RC Buildings

Cross-bracing (X-bracing) is one of the most popular methods of seismic retrofitting, and has been shown to significantly increase the structural stiffness and strength of buildings. Conventional steel X-bracing methods typically exhibit brittle failure at the connection between the brace and the building, or buckling failure of the braces. This study investigated the structural properties of a new type of non-compression X-bracing system using carbon fiber composite cable (CFCC). This non-compression X-bracing system uses CFCC bracing and bolt connections between structural members and the terminal fixer of the CFCC, instead of conventional steel bracing. The aim is to overcome the brittle and buckling failures that can occur at the connection and bracings with conventional steel X-bracing methods. We carried out cyclic loading tests, and the maximum load carrying capacity and deformation were investigated, as well as hysteresis in the lateral load–drift relations. The test results revealed that the CFCC X-bracing system installed in reinforced concrete frames enhanced the strength markedly, and buckling failure of the bracing was not observed.

Durability Performance and Service Life of CFCC Tendons Exposed to Elevated Temperature and Alkaline Environment

AbstractThis paper presents the physical, mechanical, and durability characterization of Tokyo Rope carbon fiber composite cables (CFCCs). Specimens were exposed to and alkaline solution (12.8 pH) for 1,000, 3,000, 5,000, and 7,000 h at different elevated exposure temperatures (22, 40, 50, and 60°C) to yield a simulated acceleration of the effect of a concrete environment. The durability performance of the Tokyo Rope CFCC tendons was assessed by conducting tensile tests on the specimens after different exposure periods. In addition, the microstructure of the CFCCs—both conditioned and unconditioned specimens—was investigated with scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) to assess any changes or degradation. The preexposure and postexposure tensile strengths of the conditioned and unconditioned specimens were used for long-term behavior/performance predictions based on the Arrhenius theory. The test results revealed that the average tensile strength retentions o...

Performance of Carbon-Fiber-Reinforced Polymer Stirrups in Prestressed-Decked Bulb T-Beams

AbstractEleven decked bulb T beams were constructed, instrumented, and tested under shear loading to failure. Nine beams were reinforced and prestressed with carbon-fiber composite cable (CFCC) strands, whereas one beam was prestressed with conventional low-relaxation steel strands and one beam was reinforced with non-prestressed CFCC strands. Half the span of each beam was reinforced with CFCC stirrups, whereas the other half was reinforced with conventional steel stirrups. Both ends of each beam were tested to evaluate the performance of CFCC stirrups versus that of steel stirrups. The investigation addressed the shear performance with respect to several shear parameters, including shear-span-to-depth ratio, stirrup spacing, prestressing force, and type of longitudinal and transverse reinforcement. All test beams failed by crushing of concrete in either the web or the top flange. No rupture of CFCC stirrups was experienced in any of the test beams. The performance of CFCC stirrups was analogous to that ...

X-가새형 탄소섬유케이블을 이용한 중·저층 철근콘크리트 건물의 내진보강법 개발

Improving the earthquake resistance of buildings through seismic retrofitting using steel braces can result in brittle failure at the connection between the brace and the building, as well as buckling failure of the braces. In this study, a non-compression cross-bracing system using the Carbon Fiber Composite Cable (CFCC), which consists of CFCC bracing and bolt connection was proposed to replace the conventional steel bracing. This paper presented the seismic resistance of a reinforced concrete frame strengthened using CFCC X-bracing. Cyclic loading tests were carried out, and the maximum load carrying capacity and ductility were investigated, together with hysteresis of the lateral load-drift relations. Test results revealed that the CFCC X-bracing system installed RC frames enhanced markedly the strength capacity and no buckling failure of the bracing was observed.

Flexural Behavior of a Carbon Fiber–Reinforced Polymer Prestressed Decked Bulb T-Beam Bridge System

AbstractExperimental and numerical investigations were conducted to evaluate the performance of a newly developed bridge system. Through the investigation, a decked bulb T-beam bridge model was constructed, instrumented, and tested under service and ultimate loads. The bridge model had a width of 2.59 m (8.5 ft), an effective span of 9.45 m (31 ft), a depth of 356 mm (14 in.), and was composed of five adjacent decked bulb T-beams. The T-beams were interconnected at their top flanges using 76-mm (3-in.)-wide ultra-high-performance concrete (UHPC) shear key joints and five full-depth equally spaced transverse diaphragms along the span. Each diaphragm was posttensioned with two nonbonded transverse carbon fiber composite cable (CFCC) strands. The investigation revealed that the developed decked bulb T-beam bridge system maintained its structural integrity under service loads with signs of distress in neither the shear key joints nor top flanges. UHPC shear keys with the transverse diaphragms were adequate to...

PS16 炭素繊維複合材料ケーブルの疲労試験

In this study, The relationship of between the load stress and number of cycles (S-N curve) about Carbon Fiber Composite Cable (CFCC) are obtained by fatigue testing of repeated tensile cycles. The strain in 4 edges points of thimbles of both ends, that are assessed with strain gauges. In S-N curve behavior, CFCC is fixed in number of cycles to failure of load amplitude about 65 kN. Breaking point of CFCC is edge of thimble in both ends.

Flexural Behavior of CFRP Precast Prestressed Decked Bulb T -Beams

This study introduces an innovative scheme of bridge superstructure for expedited construction, improved serviceability, and extended life span. The new bridge superstructure is assembled from precast prestressed decked bulb T-beams reinforced and prestressed with corrosion-free fiber-reinforced polymer (FRP) materials. An experimental investigation accompanied by analytical and numerical simulations was developed to evaluate the performance of the newly developed beams. Through the experimental investigation, three single decked bulb T-beams were constructed and tested to failure. The first beam, served as a control beam, and was prestressed and reinforced with conventional steel strands and reinforcing bars. The second and third beams were prestressed and reinforced with carbon-fiber composite cable (CFCC) strands and carbon-fiber-reinforced polymer (CFRP) tendons, respectively. The investigation revealed that the performance of beams reinforced with CFRP tendons or CFCC strands was comparable with the performance of the control beam at both service and ultimate limit states. All three beams exhibited high load-carrying capacity with large corresponding deflection and fair amount of absorbed energy before failure. The study showed that the corrosion-free FRP-reinforced decked bulb T-beams can be safely deployed in construction to enhance the performance and extend the life span of bridge superstructures.