Performance Of Concrete Beams Research Articles

Bending damage and fractal characteristics of steel fiber-reinforced concrete under three-point bending test

Steel fiber-reinforced concrete (SFRC) has outstanding mechanical properties and is widely used in the construction industry. To investigate the damage characteristics of SFRC beams with different steel fiber (SF) contents (0, 15, 30, 45, and 60 kg/m3) accurately, this study analyzed the bending damage (including the load-crack mouth opening displacement curve, flexural–tensile strength, fracture toughness, and microstructure and macrostructure) and fractal characteristics of SFRC beams under three-point bending tests. The crack propagation process in the SFRC beams was monitored by the digital image correlation technique. Information on microcrack evolution and macrocrack development during the loading process was collected using acoustic emission techniques. Furthermore, the correlation dimension reflecting the development state of the cracks was obtained based on the Grassberger–Procaccia algorithm. Test results showed that the performance of concrete beams in terms of deformation and cracking significantly improved by adding SFs. The beam with an SF content of 45 kg/m3 had the highest flexural–tensile strength of 6.979 MPa, which was 1.668 times higher than that of a plain concrete beam. The beam with a 60 kg/m3 SF content had the highest fracture toughness of 1.691 MPam1/2, which was 53.87% higher than that of the plain concrete beam. The fractal analysis results showed that when the correlation dimension increased, numerous small-sized, low-evolution microcracks accumulated in the fracture process zone. When the correlation dimension decreased, the microcracks converged and formed macrocracks. The peak value of the correlation dimension can be used as precursor information for SFRC beam fracture prediction.

Effects of treated corrosion reinforcement on structural behavior of concrete beams

Structural degradation phenomena like reinforcement corrosion in concrete structures imply a consequent reduction in time of the safety level. Corrosion causes a reduction of the sectional area, ductility and strength of rebars, bond strength between steel and concrete. The subsequent redistribution of internal stresses induces a reduction in ductility at ultimate limit state and a variation of the deformational behavior in serviceability conditions. In this paper, an experimental investigation was carried out to study the effect of treated corrosion reinforcement on structural behavior of concrete beams. In this investigation, phosphoric acid and vinegar solution are used to treat the corroded steel bars and compared the bending strength of concrete beams with treated and untreated corrosion reinforcement. A finite element computer software (ANSYS) has been used to compare the experimental results. From the experimental and analytical results, it was observed that performance of concrete beams with treated corrosion reinforcement is better than the concrete beams with corrosion reinforcement,

Experimental Study on the Shear Strength of Reinforced Concrete Beams with Various Integrated Shear Reinforcements

The purpose of this study was to evaluate the shear performance of concrete beams with integrated shear reinforcements made of steel plates and rebar bent in an N shape (N-type rebar), and to evaluate the applicability of the current relevant design standards. For this purpose, four concrete beam specimens were manufactured. Four-point loading tests were performed with all the specimens. The experiments confirmed that both types of shear reinforcements had a shear-reinforcing effect (an about 60% increase in shear strength), but the N-type rebar did not exceed the nominal shear strength, probably because the rebar did not yield sufficiently. A sufficient number of steel-plate-type shear reinforcements yielded in the shear crack. When evaluating the shear performance of a new shear reinforcement, it is necessary to calculate the design strength by actually reflecting whether the shear reinforcements’ yields are due to the angle of the diagonal crack. Calculating the shear contribution based on the strain of the shear reinforcements and comparing this shear strength with those five design standards, the shear strength of the shear reinforcements were evaluated conservatively. It is considered that there will be no problem in structural safety even if the shear design is carried out according to the current design standards.

Prestressed ultra-high performance concrete (UHPC) beams for reusable structural systems: design and testing

With the aim to reduce the environmental footprint of buildings, this paper presents an original structural system concept for two-way slabs in residential and office buildings. The proposed system extends the best practice in terms of modularity, versatility, demountability, reusability, and durability. A finite set of elements can be used to form the main load-bearing system of multiple successively constructed buildings having different and unpredicted layouts and static systems. Ultra-High Performance Concrete (UHPC) was identified as one of the most promising materials for this application because of its high strength, extreme durability and the opportunities it opens for shape optimization and material consumption reduction. In the first part of this contribution, the main features of the new structural system and preliminary design assumptions for UHPC modules are briefly outlined. Then, the authors present and discuss the results of an experimental campaign on prestressed UHPC beams that were tested in bending and shear, under service and ultimate load conditions. Beams with transversal openings in the web were also tested to assess the influence of these openings on the cracking behavior and shear strength of the beams. Experimental results provide useful information for the subsequent modeling of the structural system. Thanks to the presence of fibers, transversal openings in the web only have a limited influence on the response of the beams, thus allowing horizontal technical shafts to pass through the structural thickness of the slab.

Performance of concrete beams partially/fully reinforced with glass fiber polymer bars

One of the major advantages of using glass fiber-reinforced polymer bars as a replacement to the traditional steel-reinforced bars is its lightweight and high-resistant to corrosion. This research focuses on the performance of concrete beams partially/fully reinforced with glass fiber-reinforced polymer bars with 50% of GFRP bars were used to reinforce partially concrete beams at flexural zone. While 100% of GFRP bars were used to reinforce fully concrete beams at flexural and compression zones with different concrete compressive strength.This study reported the test results of 6 reinforced concrete beams with dimensions 150 × 200mm and a 1700-mm clear span length subjected to a four-point loading system. The tested beams were divided into three groups; the first one refers to the glass fiber-reinforced polymer bar effect. The second group is referring to the effect of concrete compressive strength, while the third group is referring to the effect of the GFRP bar volume ratio.Using longitudinal GFRP bars as a full or partial replacement of longitudinal steel bar reinforcement led to an increase in the failure load capacity and the average crack width, while a decrease in ductility was reported with a lower number of cracks. Increasing the concrete compressive strength is more compatible with GFRP bar reinforcement and enhanced the failure performance of beams compared with normal compressive strength concrete.

Flexural behavior of PVA‐FRC GFRP reinforced concrete beams

AbstractFiber reinforced concrete beams are a popular research topic because of the improvement in the performance of concrete beams with fibers. PVA‐FRC GFRP reinforced concrete beams have better mechanical properties than those of ordinary reinforced concrete beams when considering the combination of multidirectional material properties. This article presents the results of an experimental study on the flexural behavior of PVA‐FRC GFRP reinforced concrete beams. Seven GFRP concrete beams were tested. The test variables included the PVA fiber content and GFRP diameter. The test results indicated that the existence of GFRP bars is effective for enhancing the load‐carrying capacity of RC beams and that PVA fibers can substantially inhibit the development of cracks in PVA‐FRC GFRP reinforced concrete beams and increase the midspan deflection. The experimental midspan deflection and maximum crack widths are also compared with theoretical predictions using new guidelines from the American Concrete Institute. Finally, the maximum crack correction formula for PVA‐FRC GFRP reinforced concrete beams is proposed.

Deflection of GFRP-reinforced concrete beams

This paper presents an investigation of the performance of concrete beams reinforced with glass fiber-reinforced polymers (GFRP) under short-term loading. A total of six specimens with rectangular cross-sections (75 mm in height and 150 mm in width) were tested under a four-point bending test to failure. Each specimen was reinforced with two GFRP bars with diameters of 8 mm. The results of this study demonstrated the behavior of GFRP-reinforced concrete members and a validation of the available calculation methods for the deflection of these members and assumed possibilities of the use of a GFRP reinforcement over the long term. The results of the study presented show a very good agreement of an experimentally measured and theoretically calculated instantaneous deflection when using the approaches in the European and American standards. In calculations of long-term deflections, the results are highly inconsistent and seem to be quite overestimated in some cases. The study shows the necessity of real-time long-term measurements to demonstrate the real deformations to be assumed during design of structures reinforced with GFRP reinforcement.

Structural Performance of Concrete Beams with Micro-reinforcement Strengthened with GFRP Laminates under Monotonic Loading

Abstract The behavior of structural elements under different loading conditions decides the performance of the built structures. Fiber-reinforced concrete and fiber-reinforced polymers (FRPs) have received increasing attention in recent years for many structural applications. Steel fibers, when added into concrete as micro-reinforcement, impart a bridging effect, resulting in enhanced mechanical properties. FRPs are most commonly composed of glass, aramid, or carbon fibers in a polymeric matrix and can be tailor-made to provide a large variety of material properties to suit the prerequisites of the engineer. This article presents an experimental investigation of steel fiber reinforced concrete beams externally strengthened with glass fiber reinforced polymer (GFRP) laminates to study their static flexural behavior and failure modes. The experimental program consisted of six concrete beams strengthened with GFRP laminates, and one concrete beam was left unstrengthened to serve as the control beam. The beams were designed for under-reinforced conditions and cast with different fiber volume fractions (Vf) and GFRP laminate thickness (tf). The beams were tested under monotonic loading until failure. The experimental results showed that the strengthened beams exhibit significantly improved performance compared with the control beams in terms of strength, deformation, ductility, and crack resistance under monotonic loads.

GLASS FIBRE REINFORCE POLYMER STRUCTURAL SELECTION AS CONCRETE BEAM REINFORCEMENT

Fibre Reinforced Polymer (FRP) made of a combination of continuous fibre embedded in resin matrix is an advanced composite material that has been identified as a potential new construction material. Some of the advantages of FRP are high tensile strength, lightweight, non-magnetic and durable. Since it is a non-corrodible material it may be used as reinforcement in concrete member. This paper presents the performance of concrete beams reinforced with different types of glass Fibre Reinforced Polymer (GFRP) sections. Two concrete beams, 125x200x2400 mm, reinforced with GFRP I-section and GFRP plate were cast and tested to study their flexural behaviour. Comparison was made with a control beam on the aspect of ultimate load, load-deflection behaviour, load-reinforcement strain behaviour, and mode of failure. The experimental results show that beams reinforced with GFRP sections experienced lower load carrying capacity, lower stiffness, larger deflection and less number of cracks. The failure of the GFRP reinforced concrete beams was either by crushing of concrete at the compression zone or rupture of the GFRP reinforcement.

FEM performance of concrete beams reinforced by carbon fiber bars

Concrete structures may be vulnerable to harsh environment, reinforcement with Fiber Reinforced Polymer (FRP) bars have an increasing acceptance than normal steel. The nature of (FRP) bar is (non-corrosive) which is very beneficial for increased durability as well as the reinforcement of FRP bar has higher strength than steel bar. FRP usage are being specified more and more by public structural engineers and individual companies as main reinforcement and as strengthening of structures. Steel reinforcement as compared to (FRP) reinforcement are decreasingly acceptable for structural concrete reinforcement including precast concrete, cast in place concrete, columns, beams and other components. Carbon Fiber Reinforcement Polymer (CFRP) have a very high modulus of elasticity “high modulus” and very high tensile strength. In aerospace industry, CFRP with high modulus are popular among all FRPs because it has a high strength to weight ratio. In this research, a finite element models will be used to represent beams with Carbon Fiber Reinforcement and beams with steel reinforcement. The primary objective of the research is the evaluation of the effect of (CFR) on beam reinforcement.

Mechanical performances of concrete beams with hybrid usage of steel and FRP tension reinforcement

Fiber reinforced polymer (FRP) bars have been recently used to reinforce concrete members in flexure due to their high tensile strength and especially in corrosive environments to improve the durability of concrete structures. However, FRPs have a low modulus of elasticity and a linear elastic behavior up to rupture, thus reinforced concrete (RC) components with such materials would exhibit a less ductility in comparison with steel reinforcement at the similar members. There were several studies showed the behavior of concrete beams with the hybrid combination of steel and FRP longitudinal reinforcement by adopting the experimental and numerical programs. The current study presents a numerical and analytical investigation based on the data of previous researches. Three-dimensional (3D) finite element (FE) models of beams by using ANSYS are built and investigated. In addition, this study also discusses on the design methods for hybrid FRP-steel beams in terms of ultimate moment capacity, load-deflection response, crack width, and ductility. The effects of the reinforcement ratio, concrete compressive strength, arrangement of reinforcement, and the length of FRP bars on the mechanical performance of hybrid beams are considered as a parametric study by means of FE method. The results obtained from this study are compared and verified with the experimental and numerical data of the literature. This study provides insight into the mechanical performances of hybrid FRP-steel RC beams, builds the reliable FE models which can be used to predict the structural behavior of hybrid RC beams, offers a rational design method together with an useful database to evaluate the ductility for concrete beams with the combination of FRP and steel reinforcement, and motivates the further development in the future research by applying parametric study.

Thirty Years Researches on Development for Sustainable Concrete Technology

The enormous amount of concrete production has a serious impact on energy, resources, environment and ecosystem. Therefore, the issue of development of sustainable concrete technology with little impact on the environment is becoming a major issue. In this paper, researches related with sustainable development of concrete are presented in last three decades. FRP has high corrosion resistance and lightweight, thus it can be potential solution for sustainable development of concrete structures as strengthening material or reinforcement instead of steel. Researches and techniques are presented on performance of concrete beam with FRP rebar and enhancing performance of existing concrete structure using FRP strengthening methods. The application of recycled concrete aggregate (RCA) has sometimes been limited in the practice and remained in the low-valued purposes only such as road base materials. In past 10 years, a great improvement in the recycling technique to produce RCA of which quality is close to natural aggregate, hence the applicability and evaluation of RCA are presented in this paper. This paper includes experimental studies for application of waste glass which could decrease CO 2 emission from cement producing. The achievements of these studies are presented in this paper to contribute for sustainable development of concrete infrastructures.

Flexural behavior of concrete beams reinforced with different types of fibers

Enhanced tensile properties of fiber reinforced concrete make it suitable for strengthening of reinforced concrete elements due to their superior corrosion resistance and high tensile strength properties. Recently, the use of fibers as strengthening material has increased motivating the development of numerical tools for the design of this type of intervention technique. This paper presents numerical analysis results carried out on a set of concrete beams reinforced with short fibers. To this purpose, a database of experimental results was collected from an available literature. A reliable and simple three-dimensional Finite Element (FE) model was defined. The linear and nonlinear behavior of all materials was adequately modeled by employing appropriate constitutive laws in the numerical simulations. To simulate the fiber reinforced concrete cracking tensile behavior an approach grounded on the solid basis of micromechanics was used. The results reveal that the developed models can accurately capture the performance and predict the load-carrying capacity of such reinforced concrete members. Furthermore, a parametric study is conducted using the validated models to investigate the effect of fiber material type, fiber volume fraction, and concrete compressive strength on the performance of concrete beams.

Prestressing Effects on the Performance of Concrete Beams with Near-surface-mounted Carbon-fiber-reinforced Polymer Bars

The effects of various prestressing levels on the flexural behavior of concrete beams strengthened with prestressed near-surface-mounted (NSM) carbon-fiber-reinforced polymer (CFRP) bars were investigated in this study. Four-point flexural tests up to failure were performed using a total of six strengthened prestressed and nonprestressed concrete beams. The nonprestressed strengthened beam failed by premature debonding at the interface of concrete and the epoxy adhesive, but the prestressed one failed owing due to rupture of the CFRP bar. As the prestressing level of the CFRP bar increased, the cracking and yield loads of the prestressed beams increased, but its effect on their deflections was insignificant. The ultimate load was constant regardless of prestressing level, but the ultimate deflection was almost inversely proportional to the level.

Numerical simulation of concrete beams reinforced with composite GFRP-Steel bars under three points bending

Fiber reinforced polymer (FRP) applications in the structural engineering field include concrete- FRP composite systems, where FRP components are either attached to or embedded into concrete structures to improve their structural performance. This paper presents the results of an analytical study conducted using finite element model (FEM) to simulate the behavior of three-points load beam reinforced with GFRP and/or steel bars. To calibrate the FEM, a small-scale experimental program was carried out using six reinforced concrete beams with 200x200 mm cross section and 1000 mm length cast and tested under three point bending load. The six beams were divided into three groups, each group contained two beams. The first group was a reference beams which was cast without any reinforcement, the second group concrete beams was reinforced using GFRP, and the third group concrete beams was reinforced with steel bars. Nonlinear finite element simulations were executed using ANSYS software package. The difference between the theoretical and experimental results of beams vertical deflection and beams crack shapes were within acceptable degree of accuracy. Parametric study using the calibrated model was carried out to evaluate two parameters (1) effect of number and position of longitudinal main bars on beam behavior; (2) performance of concrete beam with composite longitudinal reinforcement steel and GFRP bars.

Experimental Assessment on the Flexural Bonding Performance of Concrete Beam with GFRP Reinforcing Bar under Repeated Loading

This study intends to investigate the flexural bond performance of glass fiber-reinforced polymer (GFRP) reinforcing bar under repeated loading. The flexural bond tests reinforced with GFRP reinforcing bars were carried out according to the BS EN 12269-1 (2000) specification. The bond test consisted of three loading schemes: static, monotonic, and variable-amplitude loading to simulate ambient loading conditions. The empirical bond length based on the static test was 225 mm, whereas it was 317 mm according to ACI 440 1R-03. Each bond stress on the rib is released and bonding force is enhanced as the bond length is increased. Appropriate level of bond length may be recommended with this energy-based analysis. For the monotonic loading test, the bond strengths at pullout failure after 2,000,000 cycles were 10.4 MPa and 6.5 MPa, respectively: 63–70% of the values from the static loading test. The variable loading test indicated that the linear cumulative damage theory on GFRP bonding may not be appropriate for estimating the fatigue limit when subjected to variable-amplitude loading.

Performance in Fire of Fibre Reinforced Polymer Strengthened Concrete Beams and Columns: Recent Research and Implications for Design

This paper considers the fire performance of concrete beams and columns that have been strengthened with fibre reinforced polymers (FRPs). Results from four recent full-scale tests are presented. A newly developed type of insulation was employed and the thickness of the insulation (15 to 20 mm) was approximately half that provided in earlier tests. All of the members survived four hours of the fire exposure. A conceptual model for design to determine when insulation is required is also presented. Further research needed to fully develop the conceptual model to a more practical design tool is outlined.

Design Method of Shear Resistance of Hybrid Fiber Reinforced High Performance Concrete Deep Beams

In order to study the shear resistance and design method of hybrid fiber (steel fiber and polypropylene fiber) reinforced high performance concrete deep beams, the shear tests were conducted according to the orthogonal experimental design. The contributory factors such as the characteristic parameters of steel fiber (types, volume fraction, aspect ratio), the volume fraction of polypropylene fiber, the ratio of web horizontal reinforcement and the ratio of web vertical reinforcement were analyzed. Results illuminate that shear failure mode of hybrid fiber reinforced HPC deep beams are splitting failure and diagonal compression failure. Hybrid fiber can notably increase the diagonal cracking strength and shear strength of HPC deep beams. The diagonal cracking strength is increased by 5.6%~83.8% while the shear strength is increased by15.6%~35.2%. A formula to calculate the shear resistance of hybrid fiber reinforced HPC deep beams is put forward based on spatial strut-and-tie mode and splitting failure. Meantime test verification is carried out and the calculated results are satisfied.

Experimental Research on Bending Performance of Concrete Beams Reinforced with CFRP-PCPs Composite Rebars

The flexural behavior of concrete beams reinforced with CFRP-PCPs composite rebars was studied. Experimental results showed that the deflection of beams reinforced with highly prestressed prisms is at service loads coMParable to deflection of steel reinforced beam. Flexural cracks of CFRP-PCPs composite rebars reinforced beams are hairline before prism cracking, and widened after the prism cracking. When the concrete beam was reinforced with the prestressed concrete prisms, the crack width decreased as the prestress in the prism increased.

A Study of Effectiveness of Fiber Reinforced Polymer (FRP) System on the Performance of Concrete Beams and Columns

The durability of marine concrete structures has long been a concern of many countries, especially in the island country of Singapore, where many structures are constructed along coastal areas. Currently, the durability of concrete under marine conditions can be enhanced by the addition of admixtures, and using high grade concrete. The FRP system can also be used to increase the durability of the concrete structures under marine conditions, by preventing the ingress of chloride ions into the structures, thereby preventing the corrosion of the steel reinforcements. In addition, the FRP system has the additional function of increasing the strength of the structure. The FRP system, which composed of the epoxy developed and carbon fiber selected in our previous paper [7], was evaluated according to various standard testing methods to get the basic technical information of the FRP system. Concrete beams and columns were wrapped with the FRP system in different design and tested to verify the effectiveness of FPR wrapping. The results showed that the performance of concrete specimens wrapped with FRP system developed could be increased up to 6 times compared to control specimens without wrapping.