Two-point Loading Research Articles

Structural Shear Behavior of Composite Box Beams Using Advanced Innovated Materials

This paper presents a new conception of shear behaviour of box concrete beams reinforced by composite fabrics. For this purpose, stirrups, wire meshes as shear reinforcement were used. Seven box section concrete beams were tested using two-point loading system. Beams with tensar wire mesh exhibited increasing in ultimate failure load, shear capacity and deflection with respect to beams used fiber-glass wire mesh instead of stirrups. Nonlinear finite element analysis was conducted using finite element program of ANSYS 14.5 to verify the experimental test program. An acceptable acceptance found between the experimental and numerical results.

Neural-network-based approach to predict the deflection of plain, steel-reinforced, and bamboo-reinforced concrete beams from experimental data

The necessity of providing low-cost housing to economically weaker sections of society has been recognised by the national government of India. In mountainous areas, the use of locally available construction material, such as bamboo, as concrete reinforcement has increased due its easy availability and economic benefit. However, due to the inadequate codal provisions for the design and detailing of bamboo-reinforced structures, evaluating the serviceability criteria for their deflection behaviour under different loads is difficult. Furthermore, factors such as bond failure between reinforcement and concrete, shrinkage and corrosion of reinforcing material, and uncertainty in material strength make the prediction of deflection even more cumbersome. This study presents an artificial neural network (ANN)-based method modelled using MATLAB for predicting the deflection behaviour of three types of beams, namely plain, steel-reinforced, and bamboo-reinforced beams. Experimental investigation is conducted to record data at regular load increments for the aforementioned three beam typologies fabricated in the laboratory under two-point loading for 28 days. A total of 122 laboratory test data are recorded for modelling the ANN. The used approach involves predicting the relationship among the applied load, tensile strength of the reinforcement, percentage (amount) of reinforcement (taken as input), and deflection of the beam (obtained as output). The present ANN approach exhibits gives satisfactory performance (coefficient of determination $$(R^2) = 0.9983$$ and mean square error = 0.00049) in predicting the deflection behaviour of beams. Hence, the ANN approach can be used as an efficient and robust tool in predicting serviceability behavior of different types of reinforced concrete beams.

Shear Behaviour of Reinforced Self-Compacting Concrete Beams Made with Treated Recycled Aggregate

In this paper, an experimental work was conducted to investigate the possibility of improving the structural performance of reinforced self-compacting concrete (SCC) beams cast with 100% treated and untreated recycled aggregate (RA). RA was first exposed to a simple treatment method to reduce the amount of its adhered mortar and to improve its performance by the impregnation in polyvinyl alcohol (PVA) polymer solution. After completing RA treatments, rectangular simply supported reinforced SCC beams cast with RA, treated recycled aggregate (TRA) as well as normal aggregate (NA), were prepared and tested under two-point loading up to failure. Half of the prepared beams were tested to evaluate the shear behaviour of normal strength (NS) SCC mixes, while the other half was tested for high strength (HS) SCC mixes. The results were evaluated with regards to load deflection response, ultimate failure load, first crack load, and cracking pattern. The main experimental results demonstrated that using treated RA considerably improved the shear capacity of reinforced SCC beams in comparison with that of untreated RA. Based on the ACI 318-14 and Euro codes, the shear strength values showed that the treated RA beams were considered more conservative compared to the RA beams in both strength grades.

Experimental Study on Flexural Behavior of RC Beams Strengthened by External Prestressing

The efficient external prestressing reinforcement technology has the characteristics of simple construction, clear force transmission and convenient changing of cables, and has become a hot spot in the research of concrete structure reinforcement. In this paper, the external prestressed steel members are taken as the research object, and the two test beams are subjected to two-point loading test. The load-deflection curve is drawn. The ultimate bearing capacity, crack morphology and deflection of bending reinforced RC beams adopted external prestressing technology were compared and evaluated based on the experimental and theory analyzation. The experimental results show that the efficient external prestressing reinforcement technology can significantly improve the performance of concrete members and can be applied to structural reinforcement.

Experimental and Finite Element Analysis of Continuous RC Slab Panels with Steel Fiber Reinforced Concrete (SFRC) as an Alternative to Negative Reinforcement

This paper presents experimental and finite element analysis of RC slab panels with steel fiber reinforced concrete (SFRC). For this purpose, four SFRC slab panels with (2000×250×50mm) dimensions are poured using a concrete class of ( f' c =22MPa) with (15kg/m 3 ) dosage of steel fibers and steel class ( f y =410MPa) without shear stirrups. Two of the slab panels were modeled by using nonlinear material properties adopted from experimental study and analyzed till the ultimate failure by ANSYS (Version-15) software. The tested slab panels are subjected to bending by two-point loading, exactly after having been moist-cured for (28 days). The slab panels were tested up to the failure with control of loads. The applied loads and mid-span deflections are carefully recorded at every (5kN) load increment from the beginning till the ultimate failure. The results obtained from the finite element and experimental analyses are compared to each other. It is seen from the results that the finite element failure behavior indicates a good agreement with the experimental failure behavior. The paper concludes that the traditional negative steel reinforcement (steel bars) can be replaced (partially or totally) by using the adopted technique and the contribution of SFRC in manufacturing of thin slabs panels was enhanced. Keywords: Finite Element, Steel fiber, Continuous Slab, Concrete, NSC, Ansys. DOI : 10.7176/CER/11-3-01 Publication date : April 30 th 2019

Effect of Shear Span to Effective Depth Ratio on the Behavior of Self-Compacting Reinforced Concrete Deep Beams Containing Openings Strengthened with CFRP

Results of test on seven simply supported self-compacting reinforced concrete deep beams, including six of these beams containing circular openings in center of load path are reported in this paper. The objective of the tests was determined the influence of, changing shear span to effective depth ratio a/d, the existence of circular openings in shear span and using inclined strips of carbon fiber polymer (CFRP) on behavior of deep beams. The general trend in crack pattern, the load-deflection response, and the mode of failure of reinforced SCC deep beams were also investigated. All specimens had the same geometry, details of the flexure and shear reinforcement in both vertical and horizontal directions and they were tested under symmetrical two-point loads up to failure. The experimental results revealed that the web openings within shear spans caused an important reduction in the deep beam capacity by 50% when compared with the corresponding solid beam. The increase a/d ratio from 0.8 to 1.2 decreases the ultimate load by 21.7% and 22.5 % for the reference unstrengthened beam and strengthened beam, respectively, also it was found that the externally inclined CFRP strips in deep beams increased the ultimate strength up to 39.5%, and enhanced the stiffness of deep beams with openings.

Experimental study and theoretical prediction of flexural behaviors of reinforced SFRELC beams

Abstract To promote the structural application of a new high-performance steel fiber-reinforced expanded-shale lightweight concrete (SFRELC), the experimental study on flexural behaviors of reinforced SFRELC beams was conducted in this paper. Compared to two reinforced beams without steel fiber, eight reinforced SFRELC beams with steel fiber in volume fraction ranged from 0.4% to 1.6% were fabricated and tested under two-point concentrated loads. Results showed that the cracking moment, the flexural stiffness, the flexural capacity and the flexural ductility of reinforced SFRELC beams were effectively promoted due to the addition of steel fibers. The crack growth was restrained with decreased space and width. Concrete strains at normal-section of mid-span fitted the assumption of plain cross-section in flexure. Based on the experimental and theoretical researches, methods for predicting cracking moment, crack width, flexural stiffness and flexural capacity of reinforced SFRELC beam were proposed.

Flexural strength and serviceability evaluation of concrete beams reinforced with deformed GFRP bars

This paper presents a study to investigate serviceability, strength, and deformability of normal- and high-strength concrete beams reinforced with deformed glass-fiber-reinforced-polymer (GFRP) bars under flexural loading. Understanding the flexural behavior of concrete beams reinforced with deformed GFRPbars with normal- and high-strength concrete would contribute to the existing literature and would provide information critical to the further use of deformed GFRP bars as internal reinforcement for concrete structures. Eight beams with a cross-sectional width and height of 200 mm and 300 mm, respectively, and a clear span of 2700 mm were tested under two-point flexural loading until failure. Four beams were made with 35 MPa normal-strength concrete (NSC); the other four with 65 MPa high-strength concrete (HSC). The bottom/tensile reinforcement of each beam consisted of two GFRP bars. Four different GFRP bar sizes (12 mm, 16 mm, 20 mm, and 25 mm in diameter) were used with reinforcement ratios ranging from 0.38% to 1.63%. Seven beams failed in concrete compression and the eighth beam failed in tension when the FRP ruptured. The test results showed that increasing the FRP reinforcement ratio had a greater effect on the service moment than the resistance moment. The effects of bar spacing on the behavior of wide beams were also investigated, revealing that the service moment increased when the bar spacing decreased, while the resistance moment increased when the concrete strength increased. In addition, the deformability concept produced significantly higher ductility indices than the energy-based concept. Neither method evidenced a clear trend in the ductility indices of the tested beams. A new approach was proposed to determine the ductility index of concrete beams with FRP bars based on beam curvature. This approach demonstrated a clear trend with the tested beams: the high-strength concrete beams had higher ductility indices than the normal-strength concrete beams.

Structural behavior of concrete beams and columns reinforced with Waste Plastic incorporated GFRP (WPGFRP) rebars

Experimental investigations were carried out on novel Waste Plastic incorporated GFRP (WPGFRP) rebars and concrete specimens reinforced with the novel WPGFRP rebars. The WPGFRP rebars were manufactured through pultrusion, using waste plastic (PET powder) as a strength additive filler and various engineering properties are assessed. Tests results indicate that use of PET powder in GFRP rebars which leads to the WPGFRP rebars, increases tensile and compressive strengths of rebars by 17.2% and 19.3% respectively, hence proving to be a strength additive material. Three types of beams and columns were tested for flexure capacity (two-point loading) and axial compression, respectively. First type (Conventional) consists of beams and columns reinforced with Fe500 Steel rebars and stirrups/ties. While both second (Total-FRP) and third (Hybrid) types of beams and columns were reinforced with novel WPGFRP rebars, however differ in the material of their stirrups/ties. WPGFRP stirrups/ties were used in second type of members while Fe500 Steel stirrups/ties were provided in third type. Results indicate that the performance of Hybrid members is superior to that of Conventional and Total-FRP members, in terms of first crack load and failure load. However, large flexural deformations and compressive strains were also observed in case of Hybrid beams and columns, respectively.

The flexural behavior model of bamboo reinforced concrete beams using a hose clamp

Bamboo can use at the simple concrete construction because of the tensile strength of its mechanical property. Meanwhile, a slippery surface of the bamboo caused cracks in the bamboo reinforced concrete beam (BRC) not to spread and yield slip failure between a bamboo bar and concrete. Load test at the BRC beam yield humble load capacity. This study aims to improve the capacity and behavior of BRC beam bending by giving waterproof coating, sand, and hose clamp installation. The beam test specimen with the size of 75x150x1100mm made as many as 26 pieces with the variety of reinforcement. The hose clamp used on the bamboo reinforcement varies with a distance of 0 cm, 15 cm, 20 cm, and 25 cm. The testing using a simple beam with two-point loading. The test results show that BRC beams have different bending behavior compared to the steel reinforced concrete beam (SRC).

Track loading on Russian Railways under modern maintenance conditions

Rail fasteners loading and its influence on the track deformability under modern maintenance conditions with increased cars axle loads is observed. The difference between oneand two-point wheelrail contact loading scheme is shown. The authors present the analysis of domestic and foreign methods of pads bench tests and show the necessity of carrying out tests imitating real (two-point contact) loading of pads. The bench test method for researching fastener loading and pad strain characteristics in a wide range of vertical and lateral loads under two-point contact scheme based on a number of field tests is presented. The results of static tests and following dynamic ones with cycling loading, which were carried out on a two-sleepers bench, are observed. Bench tests carried out by VNIIZHT and the analysis of the cyclic test methods showed the importance of fasteners tests with a real loading simulation making it possible to explain the causes of track gauge widening and decrease of track inclination, which considerably influences track stability and wear of the track and rolling stock.

Experimental Study for Ability to Use Plaster of Pairs Instead of Normal Concrete

This research investigated the possibility of using plaster of Paris instead of cement in some internal structural parts and non-exposed to moisture by casting (nine) samples divided in three group. First group was normal concrete, second was plaster of pairs concrete group and finally plaster of Paris with aggregate concrete. All of them have the same dimension (1000×150×200) mm and the same reinforcement ratio. Group one was cured with water while the rest were isolated in a place far away from the moisture. All sample designed to be failed in flexural. The process of testing was divided in two methods; for properties of material used as explain above and for samples tested under two-point load at several curing time (7,28 and 90) days. Each period consists of three samples one from each group. The result showed that the third group (plaster of Paris with aggregate concrete) approximately closer to normal concrete in applying a load by the ratio of (98%) in 7 days, (87%) in 28 days and (94%) in 90 days. While the second group (plaster of pairs concrete) was acceptable when compared with normal concrete because of missing aggregate.

Effect of the Rib Depth to the Overall Beam Depth Ratio in the Lightweight One-Way Ribbed Slabs

The ribbed slabs provide a lighter and stiffer slab than an equivalent traditional slab with minimizing the total volume of the materials. Four one-way lightweight concrete panels, including one flat and three ribbed panels were cast and tested under two-point load as simply supported up to the failure. The main investigated variable is a ratio of the rib depth (d) to the overall beam depth (h). All the panels have the same concrete volume and the same steel reinforcement ratio. Also, the width of the rib is equal to the slab thickness as a constraint condition in all the panels. Data were recorded at the loading stages to determine the load capacity and the deflection. A nonlinear finite element analysis carried out by using ANSYS-15 software program to analyze the panels and to verify the results. Increase the (d/h) ratio improved the structural behavior by increase the carrying load capacity and reduces the deflection to a certain limit. Compatibility results have been obtained between the numerical and experimental work.

Behaviours of hybrid deep beams with RPC Layers in the tension region

This paper presents an experimental study that included casting and testing six reinforced concrete simply supported deep beams under two-point loads. Two of these, with homogenous cross-sections, were made using normal strength concrete (NSC) only. The other four deep beams of hybrid cross-sections were cast using reactive powder concrete (RPC) in the tension layer and normal strength concrete (NSC) in the compression layer. Experimental results showed that the partial use of RPC noticeably increased both the first cracking load and ultimate load. The ultimate load was found to be increased further as the thickness of the RPC layer increased. The behaviours in terms of load-deflection also became stiffer as the shear span to overall depth ratio (a/h) decreased.

Shear behaviours of hybrid continuous deep beams strengthened with carbon fibre reinforced polymer

This paper investigates the shear strength characteristics of reinforced concrete continuous deep beams (RCCDB) consisting of homogenous versus hybrid concrete, and further looks at the effect of Carbon Fibre Reinforced Polymer (CFRP) on the shear strength of hybrid RCCDBs. The experimental work included testing ten specimens of RCCDB under two-point loads. The effects of high strength concrete (HSC) layer thickness and CFRP on the strength of RCCDB were thus studied. The experimental results showed that the strengthening of RCCDB by an HSC layer at the top is better than that from one at the bottom, as the increments in ultimate load strength were 17 and 34% for top strengthening and 8 and 26% for bottom strengthening for 25 and 50% thickness of total depth of beam, respectively. The optimal strengthening of RCCDB using an HSC layer at the top was at 50%. Shear strengthening using 5 cm width CFRP strips for hybrid RCCDBs increased the ultimate shear strength by 69% and 49% for strengthening with inclined and straight shapes, respectively, where such strengthening was applied near to the centre of the specimens.

Original and Repair Bulk Fracture Resistance of Particle Filler and Short Fiber-Reinforced Composites.

This study aimed to evaluate the original (OR) and repair (RR) fracture resistance of a semi-interpenetrating polymer network (semi-IPN)-based short fiber-reinforced composite compared to dimethacrylate-based composite materials by means of the V-notch test. Circular specimens (5×2 mm) with a centrally machined 90° V-shaped notch were prepared. Four bulk fill (Filtek Bulk Fill, Venus Bulk Fill, TetricEvo Ceram Bulk Fill, SDR), three microfilled hybrid (GC-Anterior, GC-Posterior, Z250), one nanofilled (SupremeXTE), and two short fiber-reinforced (Alert, everX Posterior) composites were selected. EverX Posterior was the semi-IPN material. Specimens (n=12/group) were either dry or water stored for 7 and 30 days, respectively, at 37°C and then loaded in two-point load until fracture. One-half of each tested specimen was used for the repair procedure. Repairing surfaces were diamond-bur ground, etched, and treated with silane containing universal adhesive (Scotchbond Universal) before repair. Three-way analysis of variance revealed a significant statistical difference between the groups ( p<0.05). The fracture resistance of dry-stored groups was greater than that of water-stored groups. The highest OR was observed for dry-stored Alert (23.4 N/mm), which significantly deteriorated in water (17.4 N/mm) ( p<0.05). The highest RR was observed for everX Posterior (20.0 N/mm), which did not deteriorate in water significantly (19.0 N/mm) ( p>0.05). The everX Posterior preserved the specimens' integrity at the final fracture load (ductile fracture), whereas all other materials fractured into two halves at the interface (adhesive failure). The only material that provided enhanced repair strength that was close to the original cohesive strength of the material was everX Posterior. The endurance of repaired restorations can be improved by using semi-IPN-based filling material.

Repairing steel beams with different notch levels using composite materials

Three notch levels were used to simulate fatigue crack propagation in the steel beams. The three levels are a complete loss of the tension flange of the simply supported beam adding 10.9% web loss; notch level #1, a complete loss of the flange adding 21.74% web loss; notch level #2 and a complete loss of flange adding 32.26% web loss; notch level #3. Nineteen beams were tested under two-point bending static loading up to failure. An intact beam and three notched beams with the three notch levels at the mid-span are the control specimens. Five specimens from each notch levels were repaired with different configurations. These configurations include attaching CFRP to the tension flange, covering 18 and 28 mm heights of the beam webs plus the flange, bonding CFRP to the flange and applying GFRP strips around the beam section and increasing the number of CFRP layers from two to three layers. A finite element (FE) program was used to simulate the beams. By wrapping CFRP to cover 18 mm web height, the difference between the peak load values of the repaired beams with notch level #1 and 2 was not increased than 1.8% while this difference reached 7.7% between repaired beams with notch level #1 and 3. Additionally, clear differences in mid-span deflection and energy absorption values between repaired beams with CFRP attached on the tension flange only and repaired beams with CFRP bonded on the flange and wrapping GFRP strips around the section of the beam were appeared in the cases of the three notch levels.

Flexural strengthening of RC beams with externally bonded (EB) techniques using prestressed and non-prestressed CFRP laminate

This paper presents a detailed study on flexural strengthening of RC beams with externally bonded technique using carbon fiber-reinforced polymer laminate. The different strengthening methods used in this work are externally bonded laminate (EBL), externally bonded laminate with anchorage (EBLA), and externally bonded prestressed laminate with anchorage (EBPLA). All the beams were designed for under-reinforced condition. Totally, eight beams were cast; out of this, two beams were control beams. Strengthened beams were divided into three sets (EBL, EBLA, and EBPLA) of two beams each. The work was mainly concentrated on the improvement of ultimate load carrying capacity by delaying the debonding failure. The experimentation was done using two-point loading condition. The result shows that the ultimate load for all the strengthened beams was improved when compared to control beams. The beams strengthened with EBPLA technique show maximum increase in ultimate load, i.e., 73.91% with reference to control beams. All the control and strengthened beams satisfy the serviceability requirement. The comparative study was done on the theoretical and experimental results to check the efficiency of different strengthening codes.

Behavior of High Strength Hybrid Reinforced Concrete Deep Beams under Monotonic and Repeated Loading

Introduction:This study presents the experimental and analytical investigation of the behavior of high strength hybrid reinforced concrete deep beams under monotonic and repeated two-point load. The idea of hybrid in this work is different. Two types of concrete were used in beam but not in cross-section. The first type was the Fibrous High Strength Concrete (FHSC) at shear spans for enhancing shear capacity against cracking due to diagonal strut failure (by adding Steel Fiber (SF) in that regions), while the second type was the Conventional High Strength Concrete (CHSC) at the mid-portion between the two strengthened shear spans.Methods:The experimental work included the casting and testing of ten deep beams. Five among the beams were tested under monotonic loading (control beams) and other beams were tested under repeated loading at the level of 75% of ultimate load of control beams. The effect of some selected parameters as the type of load, the hybrid and non-hybrid beams, the compressive strength of concrete (fʹc) (normal and high) and the amount of web reinforcement (ρw) were studied in terms of crack patterns, ultimate load and load versus midspan deflection.Results and Conclusion:From the experimental test results, when beam cast with fibrous with SF of 1% concrete along entire length, the ultimate load of 10.96% increased as compared with hybrid beam. And it was observed to increase as much as 32.78% as compared with beam cast from conventional high strength concrete under monotonic loading. Under repeated loading of 75% control ultimate load, the ultimate load for beam cast with fibrous concrete along entire length increased as much as 15.32% as compared with hybrid beam. And it was seen to increase 36.17% as compared with the beam cast from conventional high strength concrete. The percentage increase in ultimate load of hybrid (SF ratio 1%) deep beam cast with high strength concrete became 97.3% as compared with the identical beam cast with normal strength concrete under monotonic loading and (98.21%) under repeated loading (load 75% control beam load). The percentage increase as ultimate load for hybrid beam cast with SF ratio 1% was 9.62% as compared with hybrid beam with SF ratio 0%. As the web reinforcement increased from 0 to 0.004 and from 0 to 0.006, the percentage increased in the ultimate load as 28.07% and 57.89%, under monotonic loading as 26.14% and 59.09%, under repeated loading.Then, Strut and Tie model (STM) procedures were used to analyze the experimentally tested hybrid deep beams under monotonic loading of the present investigation. Comparison of experimental results was made with corresponding predicted values using the STM procedure presented of ACI 318R-14 Code and with other procedures

Efficiency of Steel Fiber on Carrying Capacity of Short Square Columns

An experimental investigation is carried out to find the beneficial effect of adding steel fiber to reinforced concrete square columns. Hooked end steel fiber type is used in this investigation. The aspect ratio is 60 and the percentages of the steel fiber that added to the concrete are 0.5%, 1.0% and 1.5%. The experimental work consists of fabricated twenty columns to observe the effect of steel fibers on the axial and bending moment capacity. The specimens are classified into five groups according to the applied load on it. Each of these groups is consisted of four columns having different steel fiber ratios (0, 0.5, 1.0 and 1.5) %. The columns are tested under concentric, eccentric with variable eccentricities and two-point loading. All tested columns in a one group having the same dimensions, same interior reinforcement and were tested under one applying–load and they have a square cross-section with a dimension of (100 × 100) mm. Specimens with steel fiber results are compared with the control specimen of their own (columns mad of plain concrete). The results showed that increasing steel fiber ratio is caused an increasing in the first cracking load and an increase in the ultimate load for all tested columns.