Search results for: openings in deep beams

Authors: Mannal Tariq

Abstract:

Construction industry is making progress at a high pace. The trend of the world is getting more biased towards the high rise buildings. Deep beams are one of the most common elements in modern construction having small span to depth ratio. Deep beams are mostly used as transfer girders. This experimental study consists of 16 reinforced concrete (RC) deep beams. These beams were divided into two groups; A and B. Groups A and B consist of eight beams each, having 381 mm (15 in) and 457 mm (18 in) depth respectively. Each group was further subdivided into four sub groups each consisting of two identical beams. Each subgroup was comprised of solid/control beam (without opening), opening above neutral axis (NA), at NA and below NA. Except for control beams, all beams with openings were strengthened with carbon fibre reinforced polymer (CFRP) vertical strips. These eight groups differ from each other based on depth and location of openings. For testing sake, all beams have been loaded with two symmetrical point loads. All beams have been designed based on strut and tie model concept. The outcome of experimental investigation elaborates the difference in the shear behaviour of deep beams based on depth and location of circular openings variation. 457 mm (18 in) deep beam with openings above NA show the highest strength and 381 mm (15 in) deep beam with openings below NA show the least strength. CFRP sheets played a vital role in increasing the shear capacity of beams.

Keywords: CFRP, deep beams, openings in deep beams, strut and tie modal, shear behaviour

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Authors: Y. Heyrani Birak, R. Hizaji, J. Shahkarami

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Reinforced Concrete (RC) deep beams are special structural elements because of their geometry and behavior under loads. For example, assumption of strain- stress distribution is not linear in the cross section. These types of beams may have simple supports or fixed supports. A lot of research works have been conducted on simply supported deep beams, but little study has been done in the fixed-end RC deep beams behavior. Recently, using of fixed-ended deep beams has been widely increased in structures. In this study, the behavior of fixed-ended deep beams is investigated, and the important parameters in capacity of this type of beams are mentioned.

Keywords: deep beam, capacity, reinforced concrete, fixed-ended

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Authors: A. Aarabzadeh, R. Hizaji

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Reinforced Concrete (RC) deep beams are a special type of beams due to their geometry, boundary conditions, and behavior compared to ordinary shallow beams. For example, assumption of a linear strain-stress distribution in the cross section is not valid. Little study has been dedicated to fixed-end RC deep beams. Also, most experimental studies are carried out on simply supported deep beams. Regarding recent tendency for application of deep beams, possibility of using fixed-ended deep beams has been widely increased in structures. Therefore, it seems necessary to investigate the aforementioned structural element in more details. In addition to experimental investigation of a concrete deep beam under cyclic load, different failure mechanisms of fixed-ended deep beams under this type of loading have been evaluated in the present study. The results show that failure mechanisms of deep beams under cyclic loads are quite different from monotonic loads.

Keywords: deep beam, cyclic load, reinforced concrete, fixed-ended

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Authors: Ali Shubbar, Hasanain Alwan, Ee Yu Phur, John McLoughlin, Ameer Al-khaykan

Abstract:

This paper aims to investigate the structural behaviour of RC beams with circular openings of different sizes and locations modelled using ABAQUS FEM software. Seven RC beams with the dimensions of 1200 mm×150 mm×150 mm were tested under three-point loading. Group A consists of three RC beams incorporating circular openings with diameters of 40 mm, 55 mm and 65 mm in the shear zone. However, Group B consists of three RC beams incorporating circular openings with diameters of 40 mm, 55 mm and 65 mm in the flexural zone. The final RC beam did not have any openings, to provide a control beam for comparison. The results show that increasing the diameter of the openings increases the maximum deflection and the ultimate failure load decreases relative to the control beam. In the shear zone, the presence of the openings caused an increase in the maximum deflection ranging between 4% and 22% and a decrease in the ultimate failure load of between 26% and 36% compared to the control beam. However, the presence of the openings in the flexural zone caused an increase in the maximum deflection of between 1.5% and 19.7% and a decrease in the ultimate failure load of between 6% and 13% relative to the control beam. In this study, the optimum location for placing circular openings was found to be in the flexural zone of the beam with a diameter of less than 30% of the depth of the beam.

Keywords: ultimate failure load, maximum deflection, shear zone and flexural zone

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Authors: Hana' Al-Ghanim, Mu'tasim Abdel-Jaber, Maha Alqam

Abstract:

This experimental investigation deals with shear strengthening of reinforced concrete (RC) deep beams using the externally bonded carbon fiber-reinforced polymer (CFRP) composites. The current study, therefore, evaluates the effectiveness of four various configurations for shear strengthening of deep beams with two different types of CFRP materials including sheets and laminates. For this purpose, a total of 10 specimens of deep beams were cast and tested. The shear performance of the strengthened beams is assessed with respect to the cracks’ formation, modes of failure, ultimate strength and the overall stiffness. The obtained results demonstrate the effectiveness of using the CFRP technique on enhancing the shear capacity of deep beams; however, the efficiency varies depending on the material used and the strengthening scheme adopted. Among the four investigated schemes, the highest increase in the ultimate strength is recorded by using the continuous wrap of two layers of CFRP sheets, exceeding a value of 86%, whereas an enhancement of about 36% is achieved by the inclined CFRP laminates.

Keywords: deep beams, laminates, shear strengthening, sheets

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Authors: Jakub Bartus, Jaroslav Odrobinak

Abstract:

In general, composite steel and concrete structures present an effective structural solution utilizing the full potential of both materials. As they have numerous advantages on the construction side, they can greatly reduce the overall cost of construction, which has been the main objective of the last decade, highlighted by the current economic and social crisis. The study represents not only an analysis of composite beams’ behavior having web openings but emphasizes the influence of these openings on the total strain distribution at the level of the steel bottom flange as well. The major investigation was focused on a change in structural performance with respect to various layouts of openings. Examining this structural modification, an improvement of load carrying capacity of composite beams was a prime objective. The study is divided into analytical and numerical parts. The analytical part served as an initial step into the design process of composite beam samples, in which optimal dimensions and specific levels of utilization in individual stress states were taken into account. The numerical part covered the discretization of the preset structural issue in the form of a finite element (FE) model using beam and shell elements accounting for material non–linearities. As an outcome, several conclusions were drawn describing and explaining the effect of web opening presence on the structural performance of composite beams.

Keywords: beam, steel flange, total strain, web opening

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Authors: Felix Eyben, Simon Schaffrath, Markus Feldmann

Abstract:

A building should maximize the potential for use through its design. Therefore, flexible use is always important when designing a steel structure. To create flexibility, steel beams with web openings are increasingly used, because these offer the advantage that cables, pipes and other technical equipment can easily be routed through without detours, allowing for more space-saving and aesthetically pleasing construction. This can also significantly reduce the height of ceiling systems. Until now, beams with web openings were not explicitly considered in the European standard. However, this is to be done with the new EN 1993-1-13, in which design rules for different opening forms are defined. In order to further develop the design concepts, beams with web openings under bending are therefore to be investigated in terms of damage mechanics as part of a German national research project aiming to optimize the verifications for steel structures based on a wider database and a validated damage prediction. For this purpose, first, fundamental factors influencing the load-bearing behavior of girders with web openings under bending load were investigated numerically without taking material damage into account. Various parameter studies were carried out for this purpose. For example, the factors under study were the opening shape, size and position as well as structural aspects as the span length, arrangement of stiffeners and loading situation. The load-bearing behavior is evaluated using resulting load-deformation curves. These results are compared with the design rules and critically analyzed. Experimental tests are also planned based on these results. Moreover, the implementation of damage mechanics in the form of the modified Bai-Wierzbicki model was examined. After the experimental tests will have been carried out, the numerical models are validated and further influencing factors will be investigated on the basis of parametric studies.

Keywords: damage mechanics, finite element, steel structures, web openings

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Authors: Ferhat Erdal, Osman Tunca, Serkan Tas, Serdar Carbas

Abstract:

Web-expanded steel beams provide an easy and economical solution for the systems having longer structural members. The main goal of manufacturing these beams is to increase the moment of inertia and section modulus, which results in greater strength and rigidity. Until recently, there were two common types of open web-expanded beams: with hexagonal openings, also called castellated beams, and beams with circular openings referred to as cellular beams, until the generation of sinusoidal web-expanded beams. In the present research, the optimum design of a new generation beams, namely sinusoidal web-expanded beams, will be carried out and the design results will be compared with castellated and cellular beam solutions. Thanks to a reduced fabrication process and substantial material savings, the web-expanded beam with sinusoidal holes (Angelina™ Beam) meets the economic requirements of steel design problems while ensuring optimum safety. The objective of this research is to carry out non-linear finite element analysis (FEA) of the web-expanded beam with sinusoidal holes. The FE method has been used to predict their entire response to increasing values of external loading until they lose their load carrying capacity. FE model of each specimen that is utilized in the experimental studies is carried out. These models are used to simulate the experimental work to verify of test results and to investigate the non-linear behavior of failure modes such as web-post buckling, shear buckling and vierendeel bending of beams.

Keywords: steel structures, web-expanded beams, angelina beam, optimum design, failure modes, finite element analysis

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Authors: Jakub Bartus

Abstract:

In general, composite steel and concrete structures present an effective structural solution utilizing full potential of both materials. As they have a numerous advantages on the construction side, they can reduce greatly the overall cost of construction, which is the main objective of the last decade, highlighted by the current economic and social crisis. The study represents not only an analysis of composite beams’ behaviour having web openings but emphasizes the influence of these openings on the total strain distribution at the level of steel bottom flange as well. The major investigation was focused on a change of structural performance with respect to various layouts of openings. Examining this structural modification, an improvement of load carrying capacity of composite beams was a prime object. The study is devided into analytical and numerical part. The analytical part served as an initial step into the design process of composite beam samples, in which optimal dimensions and specific levels of utilization in individual stress states were taken into account. The numerical part covered description of imposed structural issue in a form of a finite element model (FEM) using strut and shell elements accounting for material non-linearities. As an outcome, a number of conclusions were drawn describing and explaining an effect of web opening presence on the structural performance of composite beams.

Keywords: composite beam, web opening, steel flange, totalstrain, finite element analysis

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Authors: Atef Ahmad Bleibel

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Most codes of practice, like ACI 318-14, require the use of strut-and-tie modeling to analyze and design reinforced concrete deep beams. Though, investigations that conducted on deep beams do not include ring deep beams of influential parameters. This work presents an analytical parametric study using strut-and-tie modeling stated by ACI 318-14 to predict load capacity of 20 reinforced concrete ring deep beam specimens with different parameters. The parameters that were under consideration in the current work are ring diameter (Dc), number of supports (NS), width of ring beam (bw), concrete compressive strength (f'c) and width of bearing plate (Bp). It is found that the load capacity decreases by about 14-36% when ring diameter increases by about 25-75%. It is also found that load capacity increases by about 62-189% when number of supports increases by about 33-100%, while the load capacity increases by about 25-75% when the beam ring width increases by about 25-75%. Finally, it is found that load capacity increases by about 24-76% when compressive strength increases by about 24-76%, while the load capacity increases by about 5-16% when Bp increases by about 25-75%.

Keywords: load parameters, reinforced concrete, ring deep beam, strut and tie

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Authors: Ruqaya H. Aljabery

Abstract:

Reinforced Concrete (RC) deep beams are one of the main critical structural elements in terms of safety since significant loads are carried in a short span. The shear capacity of these sections cannot be predicted accurately by the current design codes like ACI and EC2; thus, they must be investigated. In this research, non-linear behavior of RC deep beams strengthened in shear with Fiber Reinforced Polymer (FRP) strips, and the efficiency of FRP in terms of enhancing the shear capacity in RC deep beams are examined using Finite Element Analysis (FEA), which is conducted using the software ABAQUS. The effect of several parameters on the shear capacity of the RC deep beam are studied in this paper as well including the effect of the cross-sectional area of the FRP strip and the shear reinforcement area to the spacing ratio (As/S), and it was found that FRP enhances the shear capacity significantly and can be a substitution of steel stirrups resulting in a more economical design.

Keywords: Abaqus, concrete, deep beam, finite element analysis, FRP, shear strengthening, strut-and-tie

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Authors: K. S. Sivakumaran, Bo Chen

Abstract:

The floor beams of steel buildings, cold-formed steel floor joists, in particular, often require large web openings, which may affect their shear capacities. A cost effective way to mitigate the detrimental effects of such openings is to weld/fasten reinforcements. A difficulty associated with an experimental investigation to establish suitable reinforcement schemes for openings in shear zone is that moment always coexists with the shear, and thus, it is impossible to create pure shear state in experiments, resulting in moment influenced results. However, finite element analysis can be conveniently used to investigate the pure shear behaviour of webs including webs with reinforced opening. This paper presents that the details associated with the finite element analysis of thick/thin-plates (representing the web of hot-rolled steel beam, and the web of a cold-formed steel member) having a large reinforced openings. The study considered thin simply supported rectangular plates subjected to inplane shear loadings until failure (including post-buckling behaviour). The plate was modelled using geometrically non-linear quadrilateral shell elements, and non-linear stress-strain relationship based on experiments. Total Lagrangian (TL) with large displacement/small strain formulation was used for such analysis. The model also considered the initial geometric imperfections. This study considered three reinforcement schemes, namely, flat, lip, and angle reinforcements. This paper discusses the modelling considerations and presents the results associated with the various reinforcement schemes under consideration. The paper briefly compares the analysis results with the experimental results.

Keywords: cold-formed steel, finite element analysis, opening, reinforcement, shear resistance

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Authors: Rifat Sezer, Abdulhamid Aryan

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The purpose of this study is to research both the ductility of the reinforced concrete beams without fiber and the ductility of the reinforced concrete beams with fiber. For this purpose, the analytical load - displacement curves of the beams were formed and the areas under these curves were compared. According to the results of this comparison, it is concluded that the reinforced concrete beams with polypropylene fiber are more ductile. The dimension of the used beam-samples for analytical model in this study is 20x30 cm, their length is 200 cm and their scale is ½. The reinforced concrete reference-beams are produced as one item and the reinforced concrete beams with P-0.60 kg/m3 polypropylene fiber are produced as one item. The modeling of reinforced concrete beams was utilized with Abaqus software.

Keywords: polypropylene, fiber-reinforced beams, strengthening of the beams, abaqus program

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Authors: P. Chantarawitoon, H. Askarinejad

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The steel beams with web opening including the cellular and castellated I-beams are fabricated from a solid web I-beam through a double cutting method to a specific shape and size along the beam. The two halves of the beams are then welded together, increasing the overall depth of the web section. In this paper, the deflection of the cellular and castellated beams subject to uniform vertical loads are investigated using Finite Element Autodesk simulation package. The structural response of the beams with web opening are compared with regular solid beams. Additionally, parametric studies are carried out to study the influence of the geometric properties of a cellular beam to its structural responses.

Keywords: beams with web opening, cellular and castellated beams, finite element analysis, vertical deflection

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Authors: Ghusen al-Kafri, Mohammed Ali Abdallah Elsageer, Ahmed Mohamed Hadya Alsdaai, Abdeimanam Salhien Salih Khalifa

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In this paper, external reinforcement to enhance a reinforced concrete structure performance has been done using externally bonded steel plate. This technique has been reported effective in enhancing the strength of reinforced concrete beam, a study to determine the effectiveness of steel plate as an external reinforcement was carried out. A total of two groups of beams and one group content five beams, each 750 mm long, 150 mm wide, and 150 mm deep were cast, strengthened and tested till failure under two point loads. One beam was act as a control beam without strengthening and other four beams were strengthened with steel plate at a different arrangement. Other group beams were strengthened with steel plate in shear zone and also strengthened at bottom as first group. The behaviours of the strengthened beams were studied through their load-deflection characteristic upon bending, cracking and mode of failure. The results confirmed that all steel plate arrangements enhanced the strength of the reinforced concrete beam, the positioning of the steel plate affect the moment carrying capacity of the beam.

Keywords: beams, bending, beflection, steel plates

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Authors: Mohamed M. El-heweity, Ahmed Shamel Fahmy, Mostafa Shawky, Ahmed Sherif

Abstract:

Cold-formed steel (CFS) lipped channel sections are popular as load-bearing members in building structures. These sections are used in the construction industry because of their high strength-to-weight ratio, lightweight, quick production, and ease of construction, fabrication, transportation, and handling. When those cold formed sections with high slenderness ratios are subjected to compression bending, they do not reach failure when reaching their ultimate bending stress, however, they sustain much higher loads due stress re-distribution. Hence, there is a need to study the sectional nominal capacity of CFS lipped channel beams with different web openings subjected to pure bending and uniformly distributed loads. By using finite element (FE) simulations using ANSYS APDL for numerical analysis. The results were verified and compared to previous experimental results. Then a parametric study was conducted and validated FE model to investigate the effect of different openings shapes on their nominal capacities. The results have revealed that CFS sections with hexagonal openings and intermediate notch can resist higher nominal capacities when compared to other sectional openings.

Keywords: cold-formed steel, nominal capacity, finite element, lipped channel beam, numerical study, web opening

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Authors: Hadi Barghlame, M. A. Lotfollahi-Yaghin, Mehdi Mohammad Rezaei, Saeed Eskanderzadeh

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In this paper, the capacity of cracking torsion on rectangular and cylindrical beams with spiral and normal stirrups in similar properties are investigated. Also, in the beams with spiral stirrups, stirrups are not wrapping and spiral stirrups similar to normal stirrups in ACI code. Therefore, models of above-mentioned beams have been numerically analyzed under various loads using ANSYS software. In this research, the behavior of rectangular reinforced concrete beams is compared with the cylindrical reinforced concrete beams. The capacity of cracking torsion of rectangular and cylindrical RC beams with spiral and normal stirrups are same. In the other words, the behavior of rectangular RC beams is similar to cylindrical beams.

Keywords: cracking torsion, RC beams, spiral stirrups, normal stirrups

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Authors: J. Bartus, J. Odrobinak

Abstract:

The paper presents a nonlinear analysis 3D model of composite steel and concrete beams with web openings using the Finite Element Method (FEM). The core of the study is the introduction of basic modeling techniques comprehending the description of material behavior, appropriate elements selection, and recommendations for overcoming problems with convergence. Results from various finite element models are compared in the study. The main objective is to observe the concrete failure mechanism and its influence on the structural performance of numerical models of the beams at particular load stages. The bearing capacity of beams, corresponding deformations, stresses, strains, and fracture patterns were determined. The results show how load-bearing elements consisting of concrete parts can be analyzed using FEM software with various options to create the most suitable numerical model. The paper demonstrates the versatility of Ansys software usage for structural simulations.

Keywords: Ansys, concrete, modeling, steel

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Authors: Asal Pournaghshband

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This paper presents the development of a finite element model to study the large deflection behavior of restrained stainless steel cellular beams at elevated temperature. Cellular beams are widely used for efficient utilization of raw materials to facilitate long spans with faster construction resulting sustainable design solution that can enhance the performance and merit of any construction project. However, their load carrying capacity is less than the equivalent beams without opening due to developing shear-moment interaction at the openings. In structural frames due to elements continuity, such beams are restrained by their adjoining members which has a substantial effect on beams behavior in fire. Stainless steel has also become integral part of the build environment due to its excellent corrosion resistance, whole life-cycle costs, and sustainability. This paper reports the numerical investigations into the effect of structural continuity on the thermo-mechanical performance of restrained steel beams with circle and elongated circle shapes of web opening in fire. The numerical model is firstly validated using existing numerical results from the literature, and then employed to perform a parametric study. The structural continuity is evaluated through the application of different levels of axial restraints on the response of carbon steel and stainless steel cellular beam in fire. The transit temperature for stainless steel cellular beam is shown to be less affected by the level of axial stiffness than the equivalent carbon steel cellular beam. Overall, it was established that whereas stainless steel cellular beams show similar stages of behavior of carbon steel cellular beams in fire, they are capable of withstanding higher temperatures prior to the onset of catenary action in large deflection, despite the higher thermal expansion of stainless steel material.

Keywords: axial restraint, catenary action, cellular beam, fire, numerical modeling, stainless steel, transit temperature

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Authors: Erkan Polat, Barlas Ozden Caglayan

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By day-to-day developed techniques, it is possible to pass through larger openings by using smaller beam-column sections. Parallel to this trend, it is aimed to produce not only smaller but also economical and architecturally more attractive beams. This study aims to explain the structural behavior of arch steel beam reinforced by using post-tension cable. Due to the effect of post-stressed cable, the arch beam load carrying capacity increases and an optimized section in a smaller size can be obtained with a better architectural view. It also allows better mechanical and applicational solutions for buildings. For better understanding the behavior of the reinforced beam, steel beam and arch steel beam with post-tensioned cable are all modeled and analyzed by using SAP2000 Finite element computer program and compared with each other. Also, full scale test specimens were prepared to test for figuring out the structural behavior and compare the results with the computer model results. Test results are very promising. The similarity of the results between the test and computer analysis shows us that there are no extra knowledge and effort of engineer is needed to calculate such beams. The predicted (and proved by tests) beam carrying capacity is 35% higher than the unreinforced beam carrying capacity. Even just three full scale tests were completed, it is seen that the ratio (%35) may be increased ahead by adjusting the cable post-tension force of beams in much smaller sizes.

Keywords: arch steel beams, pre-stressed cables, finite element, specimen Test

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Authors: Alireza Mirzaee, Soosan Abdollahi, Mohammad Abdollahi

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Unreinforced Masonry (URM) wall is vulnerable in resisting horizontal load such as wind and seismic loading. It is due to the low tensile strength of masonry, the mortar connection between the brick units. URM structures are still widely used in the world as an infill wall and commonly constructed with door and window openings. This research aimed to investigate the behavior of URM wall with openings when horizontal load acting on it and developed load-drift relationship of the wall. The finite element (FE) method was chosen to numerically simulate the behavior of URM with openings. In this research, ABAQUS, commercially available FE software with explicit solver was employed. In order to ensure the numerical model can accurately represent the behavior of an URM wall, the model was validated for URM wall without openings using available experimental results. Load-displacement relationship of numerical model is well agreed with experimental results. Evidence shows the same load displacement curve shape obtained from the FE model. After validating the model, parametric study conducted on URM wall with openings to investigate the influence of area of openings and pre-compressive load on the horizontal load capacity of the wall. The result showed that the increasing of area of openings decreases the capacity of the wall in resisting horizontal loading. It is also well observed from the result that capacity of the wall increased with the increasing of pre-compressive load applied on the top of the walls.

Keywords: masonry constructions, performance at earthquake, MSJC-08 (ASD), bearing wall, tie-column

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Authors: Jazlah Majeed Sulaiman, Lakshmi P.

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Concrete slabs are considered to be very ductile structural members. Openings in reinforced slabs are necessary so as to install the mechanical, electrical and pumping (MEP) conduits and ducts. However, these openings reduce the load-carrying capacity, stiffness, energy, and ductility of the slabs. To resolve the undesirable effects of openings in the slab behavior, it is significant to achieve the desired strength against the loads acting on it. The use of Basalt Fiber Reinforcement Polymers (BFRP) as reinforcement has become a valid sustainable option as they produce less greenhouse gases, resist corrosion and have higher tensile strength. In this paper, five slab models are analyzed using non-linear static analysis in ANSYS Workbench to study the effect of openings on slabs reinforced with basalt bars. A parametric numerical study on the loading condition and the shape and size of the opening is conducted, and their load and displacement values are compared. One of the models is validated experimentally.

Keywords: concrete slabs, openings, BFRP, sustainable, corrosion resistant, non-linear static analysis, ANSYS

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Authors: Yonas Masresha Aymeku

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The purpose of capacity modelling at U-turns is to develop a relationship between capacity and its geometric characteristics. In fact, the few models available for the estimation of capacity at different transportation facilities do not provide specific guidelines for median openings. For this reason, an effort is made to estimate the capacity by collecting the data sets from median openings at different lane roads in Hyderabad City, India. Wide difference (43% -59%) among the capacity values estimated by the existing models shows the limitation to consider for mixed traffic situations. Thus, a distinct model is proposed for the estimation of the capacity of U-turn vehicles at median openings considering mixed traffic conditions, which would further prompt to investigate the effect of different factors that might affect the capacity.

Keywords: geometric, guiddelines, median, vehicles

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Authors: Salah A. Aly, Mohammed A. Ibrahim, Mostafa M. khttab

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The amount of construction and demolition (C&D) waste has increased considerably over the last few decades. From the viewpoint of environmental preservation and effective utilization of resources, crushing C&D concrete waste to produce coarse aggregate (CA) with different replacement percentage for the production of new concrete is one common means for achieving a more environment-friendly concrete. In the study presented herein, the investigation was conducted in two phases. In the first phase, the selection of the materials was carried out and the physical, mechanical and chemical characteristics of these materials were evaluated. Different concrete mixes were designed. The investigation parameter was Recycled Concrete Aggregate (RCA) ratios. The mechanical properties of all mixes were evaluated based on compressive strength and workability results. Accordingly, two mixes have been chosen to be used in the next phase. In the second phase, the study of the structural behavior of the concrete beams was developed. Sixteen beams were casted to investigate the effect of RCA ratios, the shear span to depth ratios and the effect of different locations and reinforcement of openings on the shear behavior of the tested specimens. All these beams were designed to fail in shear. Test results of the compressive strength of concrete indicated that, replacement of natural aggregate by up to 50% recycled concrete aggregates in mixtures with 350 Kg/m3 cement content led to increase of concrete compressive strength. Moreover, the tensile strength and the modulus of elasticity of the specimens with RCA have very close values to those with natural aggregates. The ultimate shear strength of beams with RCA is very close to those with natural aggregates indicating the possibility of using RCA as partial replacement to produce structural concrete elements. The validity of both the Egyptian Code for the design and implementation of Concrete Structures (ECCS) 203-2007 and American Concrete Institute (ACI) 318-2011Codes for estimating the shear strength of the tested RCA beams was investigated. It was found that the codes procedures gives conservative estimates for shear strength.

Keywords: construction and demolition (C&D) waste, coarse aggregate (CA), recycled coarse aggregates (RCA), opening

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Authors: Ilker Kalkan, Saruhan Kartal

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Reinforced concrete (RC) beams rarely undergo lateral-torsional buckling (LTB), since these beams possess large lateral bending and torsional rigidities owing to their stocky cross-sections, unlike steel beams. However, the problem of LTB is becoming more and more pronounced in the last decades as the span lengths of concrete beams increase and the cross-sections become more slender with the use of pre-stressed concrete. The buckling moment of a beam mainly depends on its lateral bending rigidity and torsional rigidity. The nonhomogeneous and elastic-inelastic nature of RC complicates estimation of the buckling moments of concrete beams. Furthermore, the lateral bending and torsional rigidities of RC beams and the buckling moments are affected from different forms of concrete cracking, including flexural, torsional and restrained shrinkage cracking. The present study pertains to the effects of concrete cracking on the torsional rigidities of RC beams prone to elastic LTB. A series of tests on rather slender RC beams indicated that torsional cracking does not initiate until buckling in elastic LTB, while flexural cracking associated with lateral bending takes place even at the initial stages of loading. Hence, the present study clearly indicated that the un-cracked torsional rigidity needs to be used for estimating the buckling moments of RC beams liable to elastic LTB.

Keywords: lateral stability, post-cracking torsional rigidity, uncracked torsional rigidity, critical moment

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Authors: Mohammad R. Irshidat, Rami H. Haddad, Hanadi Al-Mahmoud

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Reinforced concrete (RC) is the most common used material for construction in the world. In the past decades, fiber reinforced polymer (FRP) bars had been widely used to substitute the steel bars due to their high resistance to corrosion, high tensile capacity, and low weight in comparison with steel. Experimental studies on the behavior of FRP bar reinforced concrete beams had been carried out worldwide for a few decades. While the research on such structural members under elevated temperatures is still very limited. In this research, the flexural behavior of heat-damaged concrete beams reinforced with FRP bars is studied. Two types of FRP rebar namely, carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP), are used. The beams are subjected to four levels of temperature before tested to monitor their flexural behavior. The results are compared with other concrete beams reinforced with regular steel bars. The results show that the beams reinforced with CFRP bars and GFRP bars had higher flexural capacity than the beams reinforced with steel bars even if heated up to 400°C and 300°C, respectively. After that the beams reinforced with steel bars had the superiority.

Keywords: concrete beams, FRP rebar, flexural behavior, heat-damaged

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Authors: Yasmin Z. Murad, Haneen M. Abdl-Jabbar

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An experimental program is conducted in this research to investigate the influence of basalt fibers and steel fibers on the flexural behavior of RC beams. Reinforced concrete beams are constructed using steel fiber concrete and basalt fiber concrete. Steel and basalt fibers are included in a percentage of 15% and 2.5% of the total cement weight, respectively. Test results have shown that basalt fibers have increased the load carrying capacity of the beams up to 30% and the maximum deflection to almost 2.4 times that measured in the control specimen. It has also shown that steel fibers have increased the load carrying capacity of the beams up to 47% and the ultimate deflection is almost duplicated compared to the control beam. Steel and basalt fibers have increased the ductility of the reinforced concrete beams.

Keywords: basalt fiber, steel fiber, reinforced concrete beams, flexural behavior

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Authors: Salem Alsanusi, Abdulla Alakad

Abstract:

An experimental investigation to study the behaviour of under flexure reinforced concrete T-Beams. Those Beams were loaded to pre-designated stress levels as percentage of calculated collapse loads. Repairing these beans by either reinforced concrete jacket, or by externally bolted steel plates were utilized. Twelve full scale beams were tested in this experimental program scheme. Eight out of the twelve beams were loaded under different loading levels. Tests were performed for the beams before and after repair with Reinforced Concrete Jacket (RCJ). The applied Load levels were 60%, 77% and 100% of the calculated collapse loads. The remaining four beams were tested before and after repair with Bolted Steel Plate (BSP). Furthermore, out previously mentioned four beams two beams were loaded to the calculated failure load 100% and the remaining two beams were not subjected to any load. The eight beams recorded for the RCJ test were repaired using reinforced concrete jacket. The four beams recorded for the BSP test were all repaired using steel plate at the bottom. All the strengthened beams were gradually loaded until failure occurs. However, in each loading case, the beams behaviour, before and after strengthening, were studied through close inspection of the cracking propagation, and by carrying out an extensive measurement of deformations and strength. The stress-strain curve for reinforcing steel and the failure strains measured in the tests were utilized in the calculation of failure load for the beams before and after strengthening. As a result, the calculated failure loads were close to the actual failure tests in case of beams before repair, ranging from 85% to 90% and also in case of beams repaired by reinforced concrete jacket ranging from 70% to 85%. The results were in case of beams repaired by bolted steel plates ranging from (50% to 85%). It was observed that both jacketing and bolted steel plate methods could effectively restore the full flexure capacity of the damaged beams. However, the reinforced jacket has increased the failure load by about 67%, whereas the bolted steel plates recovered the failure load.

Keywords: rehabilitation, strengthening, reinforced concrete, beams deflection, bending stresses

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Authors: Yassir M. Abbas, Mohammad Iqbal Khan, Galal Fare

Abstract:

In the present work, the structural responses of 12 ultrahigh-performance concrete (UHPC) beams to four-point loading conditions were experimentally and analytically studied. The inclusion of a fibrous system in the UHPC material increased its compressive and flexural strengths by 31.5% and 237.8%, respectively. Based on the analysis of the load-deflection curves of UHPC beams, it was found that UHPC beams with a low reinforcement ratio are prone to sudden brittle failure. This failure behavior was changed, however, to a ductile one in beams with medium to high ratios. The implication is that improving UHPC beam tensile reinforcement could result in a higher level of safety. More reinforcement bars also enabled the load-deflection behavior to be improved, particularly after yielding.

Keywords: ultrahigh-performance concrete, moment capacity, RC beams, hybrid fiber, ductility

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Authors: Wojciech Gilewski, Anna Al Sabouni-Zawadzka, Jan Pelczynski

Abstract:

This paper focuses on the analysis of tensile stresses perpendicular to the grain in simply supported beams with different geometry made of glued laminated timber. Two types of beams are considered: standard double-tapered beams described in Eurocode 5 and non-standard glulam beams with a flattened apex. The beams are analyzed using two methodology approaches: a code design verification method and a finite element method (FEM) in terms of the linear theory of elasticity with plane stress assumption. The performed analyses proved that both methodologies lead to consistent results in case of standard glulam beams and therefore, the FEM can be used in case of non-standard structures, which are not included in Eurocode 5. Moreover, the FE analysis of the glulam beam with a flattened apex showed that it can be treated as a structure with two apex zones.

Keywords: double-tapered beams, finite element analysis, glued laminated timber, perpendicular to grain stress

Procedia PDF Downloads 235