Load Carrying Capacity Of Beams Research Articles

Flexural strengthening of RC beams using sisal fibre reinforced polymer (SFRP) composite with anchorage systems

This research paper presents a study on the use of sisal fibre reinforced polymer (SFRP) composite as a sustainable alternative to artificial fibre reinforced polymers (FRPs) for strengthening reinforced concrete (RC) beams. Three anchorage systems, namely SE, SEM, and EE, were developed to prevent delamination of the SFRP composite from the RC beams, and their effectiveness was evaluated. The effects of SFRP composite layers, configuration, and main reinforcement ratio on the flexural capacity of RC beams were investigated. Experimental results from four-point loading tests on 15 simply supported RC beams showed that the SFRP composite improved the ductility and load-carrying capacity of the beams. Numerical analysis supported the experimental findings and successfully simulated the load-displacement curve, failure load, and failure modes of the RC beams. The research contributes to sustainable and environmentally friendly methods of strengthening RC beams and concludes that the SEM anchorage system was the most efficient in avoiding SFRP delamination, and strengthening configuration B (U-shaped) resulted in a significantly higher increase in the ultimate load-carrying capacity of RC beams due to improved bonding at the side faces of the beams.

Behaviour of Steel I Beams with Web Openings

This paper aims to study the behavior of steel I beams with web openings. However, web openings might lead to a noteworthy reduction in the load-carrying capacity of beams, but can also be so supportive and essential from an economic point of view. An experimental investigation and nonlinear three-dimensional finite element analysis using the ABAQUS computer program were planned and conducted on six steel I-beams having the same dimensions, different diameter ratio spacing, and opening shapes such as circular, rectangular, and hexagonal. Experimental results showed that the ultimate load of a steel beam with web openings reduced with an increase in the area of the opening. A circular opening has a stronger shape than a rectangular opening because a rectangle has fast deflection and torsion angles, so it resists an applied load less than a circular opening. Also, the beam with hexagonal openings is better than that with rectangular openings because hexagonal openings are more resistant to deflection and deformation than rectangular openings. The finite element results, which are validated against the experimental results, show good accuracy with the experiment. Besides, a parametric study is presented here to study the influence of varying the shape of openings on the value of the failure load and midspan deflection. It can be noticed that the steel beam with a circular opening, which had been tested experimentally and modeled by the Abaqus program, is the best case and gives a higher failure load as compared to the diamond, octagonal, trapezoidal, transverse, and longitudinal ellipses. Thus, providing web openings reduces the weight and increases structural efficiency. Doi: 10.28991/CEJ-2023-09-03-08 Full Text: PDF

An experimental study on behaviour of ferrocement

Ferrocement (FC) is a composite material of cement matrix and reinforcement having multiple layers of mesh. It has been proved as a cheap, reliable method in construction industry and can be successfully applicable for low load bearing structures. This paper deals with the experimental study on different sections such as (channel sections, box sections, slab and plate) of ferrocement elements by using different diameter of wire mesh with different shear span to depth ratio. The shear capacity of ferrocement (FC) plates can be calculated. In this paper the volumetric fraction of wire as well as the area of reinforcement will be calculated. This paper gives an emphasis on the comparison of load carrying capacity of beams and plates by using different proportion of materials. The tests are conducted to find the load carrying capacity of beams and plates by using the mix composition of 1:2.5 (cement: sand) and 0.9:0.1:2.5 (cement: slag powder:sand) and the results are compared. The load testing of the beams as well as plates was done after 28 days of curing and conducted up to failure to determine the actual load carrying capacity of those elements. From this experiment it has been found that the load carrying capacity of ferrocement elements can be increased by increasing the number of layer of wire mesh. It is also found that up to a shear span to depth ratio 3, the shear behavior is predominant and beyond shear span to depth ratio 3, the flexural behavior is predominant.

Nonlinear analysis of steel-concrete composite beams with flexible shear connectors

Steel-concrete composite beam is a typical construction which is made up of two dissimilar materials such as steel and concrete. It is used mainly for construction of commercial/residential high-rise buildings and bridges. From last few decades steel-concrete composite structure has been utilised in construction industry due to several advantages such as reduced time and cost of major construction and the avoidance of one of the major issues in present era, space scarcity. Shear connector is a basic component through which steel and concrete components are mechanically connected to transfer the load from concrete slab to steel beam in a conventional type of steel-concrete composite beam. Three dimensional numerical models are created using finite element analysis commercial software package ANSYS15 to study the flexural capacity of beam specimens. Earlier, validation has been done with the test results available in the literature and the proposed model is found to be capable of analysing the specimens with acceptable accuracy. Further numerical models are made to understand the behaviour of steel-concrete composite beam which is made up of two different flexible shear connectors such as stud and channel connector under four-point bending. Degree of shear connection, geometry and layout of shear connectors are taken into account as key parameters for this present numerical study. Normal strength of concrete is considered. The associated results such as ultimate load, mid-span deformation, interfacial slip capacity are presented. Diameter along with length of stud connector is found to influence the load carrying capacity of beams. Ultimate load capacity as well as stiffness of beams is found to enhance when channel section is considered with minimal spacing of connector. Thus finding the required degree of shear connection was also proved to be vital for assessing the performance of steel-concrete composite beams.

Structural Behaviour of Green Geopolymer Concrete Beams and Columns Made with Waste Wood Ash a Partial Substitution Binder

On the demand of reducing the global warming due to cement production which is used as main constituent in the production of concrete and minimizing the environmental impact caused by the waste and its disposal methods, this study was aimed. This study looked in to detail insight view on effective utilization of waste wood ash in the production of geopolymer concrete beams and columns to alternate the conventional reinforced concrete elements in construction industry. Waste wood ash is a waste by product produced in the nearby hotel and factories by burning the waste wood collected from timber industries and the ash are thrown in to land which creates a major environmental pollution. Geopolymer is a novel inorganic eco-friendly binding agent derived from alkaline solution that stimulates aluminosilicate source material (such as metakaolin, fly ash and GGBS). In this research, behaviour of beams in deflection, ductility factor, flexural strength and toughness index and columns in load carrying ability, stress strain behaviour and load-deflection behaviours were examined for three types of concretes (30% WWA – 70% Fly ash Geo-polymer concrete, Fly ash Geo-polymer concrete and Reinforced Cement Concrete). The results showed that inclusion of waste wood ash in geopolymer concrete helped in enhancing the load carrying capacity of beam and column by 42% and 28%. Further, the behaviour of structural elements in stiffness, ductility and toughness were also improved with the replacement of waste wood ash.

Flexural behavior of reinforced concrete beams strengthened by carbon fiber reinforced polymer using different strengthening techniques

The externally bonded reinforcement on grooves (EBROG) method is increasingly recognized as an alternative strengthening method that can overcome the debonding problem. This study aims to experimentally investigate the effectiveness of EBROG as compared to the conventional externally bonded reinforcement (EBR) method in strengthening reinforced concrete (RC) beams. Twelve RC beams have been tested under four point load bending. One of these beams has been designated as a reference beam, seven beams have been strengthened with carbon fiber reinforced polymer (CFRP) sheets, and four beams have been strengthened with CFRP laminates using EBROG or EBR methods. The effect of CFRP type, number of layers, as well as the type of strengthening methods on the flexural performance have been also investigated. The load, deflection, stiffness, and failure modes were recorded and discussed intensively. Overall, test results indicated that the flexural strength and stiffness of the strengthened specimens using EBR or EBROG methods increased compared to the control beam, where the increase in the load carrying capacity of beams strengthened using the EBR method ranged between 24.8 and 48.2% and by the EBROG method ranged between 31.7 and 76.7% of the control beam. The most interesting result obtained is that the failure mode of beams has been changed from debonding of CFRP material to rupture of CFRP in some samples strengthened by EBROG, which demonstrates the superior behavior of this strengthening technique as compared to the traditional strengthening using EBR.

A STM-based analytical model for predicting load capacity of deep RC beams with openings

Deep reinforced concrete beams constitute one of the most important structural members carrying large loads in long span structures that have been less investigated than ordinary beams due to their unconventional behavior. Due to their excessive height, deep beams often pose problems for the proper housing of mechanical and electrical installations that occupy rather large spaces or plumbing systems that pass through structural elements. As a remedy, openings are often needed in such beams that not only serve as a practical provision to house installations but also offer architectural advantages in the structure. Despite these advantages, the openings have serious adverse repercussion on the load-carrying capacity of the beams which, if not properly addressed, might cause grave damages to the structure. The present study introduces an analytical model based on the strut-and-tie method for estimating load-carrying capacity in simply-supported deep RC beams with rectangular or circular openings. The proposed model is capable of independently considering each of the different failure modes including that due to web crippling under load-bearing support sheets as well as flexural and shear failures to identify the dominant failure before it determines the failure mode of the specimen and to estimate, subsequently, the pertinent load-carrying capacity. Being based on the strut-and-tie method, the model relies for its accuracy on the accurate analysis of the strut model. Comparison of the model results and experimental measurements reported elsewhere reveals the accuracy of the proposed model in estimating the load-carrying capacity of deep RC beams. Verification of the model using measured results reported in the literature indicates mean predicted to measured load-carrying capacity ratios of 0.91 and 0.97 for beams with and without openings, respectively.

Failure mode and strength prediction of laterally braced Litzka-type castellated beams

The present paper aims to investigate the failure modes of laterally braced non-composite Litzka-type castellated beams using finite element simulations, evaluating aspects such as mutual influence of the constituent parts to the behavior, interaction of individual modes and post-buckling reserve of strength. For a comprehensive analysis, a parametric study is carried out and the behavior is depicted in a plot (‘map’) in terms of the bending moment-to-shear force ratio, the flange and web geometries and the generalized non-dimensional slenderness depending on the plastic and buckling loads. It is shown that the failure mode of a certain beam can be roughly predicted according to the region of the ‘map’ it belongs. The results confirm the occurrence of interaction between individual modes and reveal that the normalized strength decays more quickly with slenderness for shear-dominated failure, although some post-critical reserve of strength can be observed. Finally, inspired by the Direct Strength Method, a design approach is proposed to assess the load carrying capacity of beams with usual geometries.

Basalt Fibre Reinforcement of Bent Heterogeneous Glued Laminated Beams

The purpose of this paper is to demonstrate the properties of glued laminated beams made in diverse configurations of timber quality classes, reinforced using a new technique that is cheaper and easy to apply. The aim of the experimental investigations was to enhance reinforcement effectiveness and rigidity of glued laminated beams. The tests consisted of four-point bending of large-scale specimens reinforced with basalt fibres (BFRP). The tests were meant to obtain images of failure, the load–displacement relation and load carrying capacity of basalt fibres depending on the reinforcement ratio. The tests, which concerned low and average quality timber beams, were conducted in a few stages. The aim of the study was to popularize and increase the use of low-quality timber harvested from reafforested areas for structural applications. In the study, theoretical and numerical analysis was carried out for reinforced and unreinforced elements in various configurations of wood quality classes. The aim was to compare the results with the findings of experimental tests. Based on the tests, it was found that the load carrying capacity of beams reinforced with basalt fibre was higher by, respectively, 13% and 20% than that of reference beams, while their rigidity improved by, respectively, 9.99% and 17.13%. The experimental tests confirmed that basalt fibres are an effective structural reinforcement of structural timber with reduced mechanical properties.

Moment redistribution and flexural performance of RC continuous T-beams strengthened with NSM FRP or steel bars

This paper discusses the flexural strengthening of continuously reinforced concrete (RC) beam constructions in hogging or sagging regions using near-surface mounted (NSM) technique. The main difficulties in strengthening RC continuous beams in hogging are the vertical middle column which prevents continuity of the NSM reinforcement bars and end anchorage of the NSM reinforcement. A test program consisted of seven two-span T-beams was used; one control beam, which was used for comparison, four beams were strengthened at the hogging region, and two beams were strengthened at the sagging regions. Two types of strengthening material were adopted in this study, carbon fiber reinforced polymers (CFRP) rebars, and high tensile steel bars. An RC column loaded with a constant load (120 kN) was used as the middle support. The main test parameters were the type of the reinforcement bars, continuous NSM bars beside the middle column, or NSM bars anchored inside the middle column, as well as the strengthened region. Besides, the impact of using embedded through-section (ETS) end anchorage of NSM CFRP bars was investigated as well. The experimental results were evaluated for the effects of strengthening technique and materials on the load-carrying capacity of beams, deformation, ductility index, and moment redistribution. The experimental results showed that strengthening with NSM steel bars could improve the service load carrying capacity by 23–40%, whereas the NSM CFRP rebars improved the service loads by 33–36%. The ETS end anchorage at the hogging region and the NSM steel bars at the sagging region helped to achieve the flexural rigidity by a very significant amount relative to the other strengthened beams and control beam by 270%. The moment redistribution achieved after the beam cracking load until the failure load varies in accordance with the strengthening region and the strengthening material type.

Influence of Recycled High-Performance Aggregate on Deformation and Load-Carrying Capacity of Reinforced Concrete Beams

The use of recycled concrete aggregates (RCA) in high performance concrete (HPC) was analyzed. The paper presents the experimental studies of model reinforced concrete beams with a rectangular section using high-performance recycled aggregates. Two variable contents of recycled aggregate concrete were used in this study: 50% and 100%. The experimental analyses conducted as immediate studies concerned the following issues: short time loads-deflection, load-carrying capacity of beams, deformation of concrete, cracks, and long-term loads-deflection. The comparative analysis involves the behavior of beams made of high performance concrete-high strength concrete (HPC-HSC) recycled aggregates with model control elements made of regular concrete based on natural aggregates. The deflection values for the recycled aggregate beams were 20% higher than in the case of the control beams made of HPC-HSC exclusively. Replacement of aggregate with recycled concrete aggregate resulted in a large decrease in the value of these two parameters, i.e., compression strength by about 42% and modulus of elasticity by about 33%.

Flexural Behavior of Polypropylene Fiber Reinforced Concrete Beams

This paper portrays an experimental research conducted to determine the strength and flexural behavior of the polypropylene fiber reinforced beams. Polypropylene fibers were being added in concrete with different dosages viz., 0.6, 0.8, 1.0, 1.2, 1.4, and 1.6% to the total volume of concrete and Ordinary Portland Cement (OPC) and Portland Slag Cements (PSC) were added in the ratio of 60:40 with the overall cement content. Cubes were cast for compressive strength test and cylinder were cast for tensile strength test and beams were cast for flexural strength test. Seven beams were tested; one normal beam without polypropylene fiber and six beams with polypropylene fiber were cast and flexural strength test was conducted. Polypropylene fiber and slag cements were used in mass concrete structures to reduce heat of hydration and shrinkage cracks. Flexural strength and the cracking pattern were monitored during the test. The results indicated that the addition of polypropylene fibers and slag cements in concrete significantly increased the compressive strength, tensile strength, flexural strength and load carrying capacity of beams with different cracking patterns

Experimental Investigation on OSB Webbed Laminated Bamboo Lumber Box Shaped Joists

A novel bamboo-wood box beam was introduced in this paper, which consisted of laminated bamboo lumber flanges and OSB webs. Four-point bending tests were conducted on composite beams to investigate the effects of shear span ratio and stiffeners on failure mode and strength. The results showed that the composite beams with shear span ratio less than two failed in web shear failure, but for the others, the beams failed in twist and delamination of OSB in flanges. The load carrying capacity of beams decreased with the increase of shear span ratio. However, the mechanical performance of beams can be improved moderately by the presence of stiffeners, and theultimate bearing capacity and initial stiffness was increased by 16.5% and 13.1% respectively.

FINITE ELEMENT ANALYSIS OF DEEP BEAM UNDER DIRECT AND INDIRECT LOAD

This research study the effect of exist of opening in web of deep beam loaded directly and indirectly and the behavior of reinforced concrete deep beams without with and without web reinforcement, the opening size and shear span ratio (a/d) was constant. Nonlinear analysis using the finite element method with ANSYS software release 12.0 program was used to predict the ultimate load capacity and crack propagation for reinforced concrete deep beams with openings. The adopted beam models depend on experimental test program of reinforced concrete deep beam with and without openings and the finite element analysis result showed a good agreement with small amount of deference in ultimate beam capacity with (ANSYS) analysis and it was completely efficient to simulate the behavior of reinforced concrete deep beams. The mid-span deflection at ultimate applied load and inclined cracked were highly compatible with experimental results. The model with opening in the shear span shows a reduction in the load-carrying capacity of beam and adding the vertical stirrup has improve the capacity of ultimate beam load.

Seismic performance of reinforce concrete buildings designed according to codes in Bangladesh, India and U.S.

This paper focuses on the comparison of seismic design provisions in Bangladesh (BNBC-1993), India (IS-1893), and the U.S. (ASCE 7-10) in relation to analysis, design, and seismic performance of reinforced concrete buildings on the basis of the type of allowable analysis procedures, zoning system, site classification, fundamental vibration period of the structure, response reduction factor, importance factor, minimum design lateral force, allowable story drifts, and design response spectra.Three geometrically similar commercial reinforced concrete buildings in high seismic regions of Bangladesh, India, and U.S. were designed and detailed per the respective codes. Three-dimensional nonlinear dynamic analyses of the designed structures were conducted. Each structure was subjected to a pair of orthogonally applied artificial ground motions compatible with the design response spectrum for each building code. The structural performance of each building was compared in terms of roof displacements, inter-story drifts, load-carrying capacity of beams and columns, and overall energy dissipation characteristics. The comparisons allowed an in-depth evaluation of the differences in the seismic performance of buildings designed according to ASCE 7-10, BNBC-1993, and IS-1893 codes. The Indian code performed better when subjected to the ground motion that is intended to represent the Indian design response spectrum.

Influence of the deformation mode nature on the 1st order post-yielding strength of thin-walled beams

This paper presents a study on the influence of the deformation mode nature (global, local, distortional) on the load carrying capacity of beams beyond the yield load. Following recent investigations on the decomposition of elastic buckling modes into combinations of structurally meaningful deformation modes, this work applies the same concept to the 1st order failure modes (elastic-plastic collapse mechanisms). To achieve this goal, a GBT-based code that performs first-order elastic-plastic analyses of thin-walled members is employed. In order to study the influence of the mode nature on the post-yielding strength, five beams with different cross-sections, lengths, supports and loadings are analysed, and the results displayed by means of load-deflection curves, failure mode configurations and modal participation diagrams. On the basis of the limited study performed, it is concluded that larger contributions of local and distortional modes to the beam failure mode lead to a higher post-yielding strength reserve, which implies a higher beam load carrying capacity beyond the yield load. The opposite occurs for the contributions of global modes. Therefore, the member strength reserve obtained in geometrically non-linear analysis should not be credited only to the elastic post-buckling effects, but also to the plastic post-yielding effects.

Bending Reinforcement of Full-Scale Timber Beams with Mechanically Attached GFRP Composite Plates

This paper presents the results of an experimental campaign aimed to evaluate the performance of timber beams strengthened in bending using GFRP (Glass Fiber Reinforced Polymer) plates mechanically attached with high-strength metal screws. Modest ratios of GFRP composite reinforcement can increase beam load-carrying capacity and manipulate failure mode from the brittle tensile in the unreinforced beams to a more extensible failure in the strengthened timber beams. Application of mechanical reinforcement presents a solution of reversibility, compatibility and durability for reinforced timber. The experimental campaign focused on load-deflection relationship and failure modes in order to increase the bending capacity and stiffness of the timber beam. Oak beams with dimensions 145 x 145 x 2450 mm were reinforced with un-bonded pultruded GFRP plates. Hexagon head coach screws 16 mm diameter, 130 mm length, grade 8.8, were used to mechanically attach the reinforcement along with 34 mm outer diameter fender washers, distributing the fastening load away from the screw’s position. All beams were tested until failure under the four-point bending configuration. Experimental results demonstrate the effectiveness of the reinforcement method and ability to reversibly repair the timber, representing a capability to be utilised in the new constructions or restoration of timber structures.

Uncertainty analysis of FRP reinforced timber beams

Abstract Timber has been a popular building material for centuries and offers significant sustainable credentials, high mechanical and durability properties. Availability, ease to use, convenience and economy have made timber the most used construction material in history but, as it is a natural material, uncertainty in its mechanical characteristics is considerably higher than man-made structural materials. National codes and engineers usually employ high factor of safety to incorporate timber strength uncertainty in design of new structures and reinforcement of existing ones. This paper presents the results of 221 bending tests carried out on unreinforced and reinforced soft- and hardwood beams (fir and oakwood) and illustrates the reinforcement effect on timber capacity and strength uncertainty. Both firwood and oakwood beams have been tested in flexure before and after the application of a composite reinforcement made of FRP (Fiber Reinforced Polymer) unidirectional sheet. The uncertainty in the strength of reinforced timber is also quantified and modelled. Test results show that the FRP reinforcement is effective for both enhancing the beam load-carrying capacity and for reducing strength uncertainties.

An experimental study on the effectiveness of externally bonded corrugated GFRP laminates for flexural cracks of RC beams

In recent years, the most important challenges in the field of structural engineering are the repair and rehabilitation of structural members of existing buildings and bridges. Strengthening of existing structures may become necessary to cater for the latest codal provisions and to meet the expected life span. Many researches have carried out on shear and flexural strengthening of reinforced concrete beams using plain Glass Fibre Reinforced Polymer (GFRP) sheets. Usage of plain GFRP composites is a traditional method for strengthening reinforced concrete (RC) beams. So in the present work, the author is intended to check the possibility/suitability of using GFRP corrugated laminates for the purpose of strengthening the RC beams. With GFRP chopped strand mat, corrugated profile was fabricated in the industry and used as a new technique of strengthening system with a view to improve sectional properties and hence flexural strength of RC beams. It is observed that cracks are formed in existing structural members due to excessive deflections as a result of uncertainty in loading conditions. To simulate this condition, the test beams were pre-cracked up to 0.3mm width at tension zone. Fourteen beams were tested to study the load carrying capacity of beams strengthened with plain sheets and corrugated laminates and those results were compared with control specimens. The novelty of using GFRP rectangular corrugated laminates to enhance the load carrying capacity of pre-cracked beams has been carefully studied experimentally. Also mathematical models were developed for the prediction of load carrying capacity of pre-cracked strengthened beams. Furthermore theoretical analysis for control and beams strengthened with plain sheets and corrugated laminates were done and the results were compared with experimental results. The experimental results indicate that RC beams strengthened with GFRP corrugated laminates may provide an attractive rehabilitation technique for repair as well as strengthening.

Delamination of carbon-fiber strengthening layer from concrete beam during deformation (infrared thermography)

Technology of strengthening reinforced concrete structures with composite materials has found wide application. The effectiveness of strengthening of concrete structures with externally bonded reinforcement is supported by a great deal of experimental evidence. However, the problem of serviceability of such structures has not been adequately explored. The present work describes the results of experimental studies on the loadcarrying capacity of concrete beams strengthened with carbon fiber reinforced plastic (CFRP). Special emphasis is placed on studying the debonding of the strengthening layer from the concrete surface and analyzing its influence on the load-carrying capacity of beams. Infrared thermography is used to detect the first signs of debonding and to assess the debond growth rate.