Behavior Of Beam Structures Research Articles

Моделирование процессов в изгибаемых балках с дисперсным армированием при знакопеременных воздействиях

The results of studies of the effect of dispersed reinforcement on the behavior of structures under static load of one sign or alternating static load under reinforcement with relatively long fibers are considered. The developed mathematical models and methods of experimental investigation of the behavior of beam elements with dispersed and combined reinforcement under alternating static effects, based on mathematical planning using a specially manufactured frame, are presented. The behavior of fibro-reinforced concrete and reinforced concrete beam elements under similar influences is compared. The results of experimental studies of cubes and prisms for static and compression are considered. The presented results of experimental studies allow us to conclude about the influence of dispersed reinforcement with relatively short fibers on the behavior of beam structures under alternating low-cycle static effects and the feasibility of combined reinforcement of structures operating under such influences. The results of the full-scale experiment are compared with the results of numerical modeling of processes in the studied structural elements. It is revealed that the use of dispersed reinforcement with relatively short fibers in combined reinforced beam structures operating under alternating influences will increase the crack resistance, and with a certain percentage of reinforcement, the strength of such structures. At the same time, the use of relatively short fibers will significantly reduce the complexity of manufacturing such structures.

Effect of partial cement replacement with sugarcane bagasse ash

Research into mixing and replacing the component ingredients of concrete has become necessary since there is a widespread need in most parts of the globe for more affordable housing and the discovery of an alternative to standard Portland cement. Despite the fact that a great number of investigations have been carried out to evaluate the viability of combining cement with sugarcane bagasse ash and sand with laterite soil, no research has been conducted on the influence that combining the two materials has on the characteristics of concrete. This study presents the findings on the strengths, permeability, and structural behaviour of concrete beams containing sugarcane bagasse ash and laterite soil. The goal of the research was to combine traditional concrete with sugarcane bagasse ash to produce sugarcane bagasse ash laterised concrete, which could be used for the construction of low-cost housing. Ash from sugarcane bagasse and lateritic soil were used as blenders and blended with regular concrete materials. Cement was largely replaced with sugarcane bagasse ash in the following proportions by mass: 0%, 5%, 10%, and 15%. The impact of different degrees of material substitution on the workability and compressive strength of concrete was investigated using a concrete mixture with the proportions 1:2:4 and a water-to-cement ratio of 0.55. The same mixture was utilised, but this time with a continuous slump of 30mm+3mm. This was done in order to assess the influence of different degrees of combination material replacement on the characteristics of concrete and the behaviour of structural beams.

Behavior of Reinforced Concrete Beams Containing Waste Crushed Concrete and Bricks

Abstract Recycling demolition waste materials as construction materials offers environmental as well as economic benefits by protecting virgin materials and reducing overall costs of project. This paper presents an experimental investigation on flexural behavior of reinforced concrete beams made with coarse aggregate fully 100 % or partially 50 % replaced by crushed concrete or crushed bricks as waste materials in full or half depth of beams. Nine beams are tested over a simply supported span, one with full natural aggregate as reference and the others with waste aggregate in different ratios and depths (four with crushed concrete and four with crushed bricks). Results show that the structural behavior of beams with waste aggregates is similar to the reference beam with strength reduction of 3 – 20 %. Crushed concrete beams show higher strength and stiffer behavior (in general) than crushed bricks. Also, increasing replacement ratio from 50 % to 100 % or replacement depth from half to full reduced strength by about 10 % only which encourage utilizing maximum quantity of waste construction materials in concrete structures.

Assessing the structural behavior of steel beams strengthening with additional plates

In this study, two I-steel beams were tested under the application of vertical concentrated load. These beams can be distinguished as one without strengthening bottom plate and the second one is with an additional strengthening bottom plate. The tested beams have the same physical properties, i.e. clear span length and sectional area. To ensure the failure will happen in the bottom flange of beams, a cover plate and intermediate stiffeners were used at the top flange of beams. The main aim of this test is to assess the use of an additional plate in the bottom flange on the structural behavior of these beams in relation to the load and moment versus deflection, load and moment versus strain, and yielding with ultimate loadings. It is concluded that the strengthened beam has better results in terms of deflection and tensile strain than the unstrengthen specimen. Also, the structural behavior in terms of the yielding and ultimate capacities for the strengthened specimen was significantly improved in comparison with the referenced specimen by 100% and 60.9%, respectively.

Reactive Powder Concrete Beam's Behavior in Flexural : Review

Reactive Powder Concrete can be considered as a special type of concrete in which the coarse aggregate will be eliminated to get a homogenous microstructure with a maximum density for final result. Many researchers presented a state of the art review on reactive powder's production, mechanical properties, durability, development and applications. But the review about structural behavior is hardly to found. Because of importance of this type of concrete and its structural applications. This paper focused on review the researchers that deals with structural behavior of reactive powder concrete beams under bending load. Also review the proposed design equations related with reactive concrete behavior. Before starting a review of strength , stress-strain relation and ductility are presented because of their importance and effect on structure behavior of beams under bending. According to review of previous studies the type of fibers and its content as volumetric ratio, type of pozalanic materials and its content , amount of longitudinal steel reinforcement are main factors that affected the flexural behavior of reinforced Reactive Powder Concrete

Structural behaviour of novel composite beams consisting of geopolymer concrete and high-performance concrete

Over the past few years, geopolymer concrete (GPC) has experienced increasing demands in construction technology thanks to its numerous advantages, such as being eco-friendly and highly resistant to elevated temperatures and chemical attacks in aggressive environments. However, similar to normal concrete, GPC has limited tensile strength and deformation capacity. High-performance concrete (HPC) exhibits high flexural strength and enhanced mechanical properties, such as tensile strength. In this study, novel hybrid beams consisting of GPC at the compression zone and HPC at the tension zone are explored and investigated. The mechanical properties of GPC and HPC as well as the structural behaviour of hybrid beams consisting of two different layers of GPC and HPC with different ratios (50% to 50%, 75% to 25%) are also investigated. Moreover, full-depth beams consisting of single layer of either GPC or HPC are cast and tested as the control specimens. In addition, the structural behaviour of beams with and without shear reinforcement in terms of shear strength, crack patterns, failure modes, ductility, and energy absorption is investigated. As shown by the results, compared to full-depth GPC and HPC beams, hybrid composite beams without shear reinforcement exhibit low ultimate strength mainly because of the large debonding between the GPC and HPC layers. However, hybrid beams with shear reinforcement exhibit high stiffness, shear strength, and ductility, especially hybrid beams with a GPC-to-HPC ratio of 50% to 50%, which demonstrate full composite actions between the GPC and HPC and as a result exhibit high ductility and deformation capacity.

Influence of Minimum Tension Steel Reinforcement on the Behavior of Singly Reinforced Concrete Beams in Flexure

The requirements of minimum flexural reinforcement in the last decades have been a reason for controversy. The structural behavior of beams in bending is the best way of investigating and evaluating the minimum reinforcement in flexure. For this purpose, twelve singly reinforced concrete beams with a rectangular cross-section of (125 mm) width by (250 mm) height and (1800 mm) length were cast and tested under two-point loads up to failure. These beams were divided into three groups with different compressive strengths (25, 50, and 80 MPa). Each group consists of four beams with different amounts of tension steel reinforcement approximately equal to (0% Asmin, 50% Asmin, 100% Asmin and 150% Asmin), two bar diameters (Ø6 mm and Ø8 mm) were used as the longitudinal tension reinforcement with different yield and ultimate strengths, the minimum amount of reinforcement required is calculated based on ACI 318M-2014 code. The results show that for the reinforced concrete beams, the flexural reinforcement in NSC beams increases the first cracking load and the increment increased with an increasing amount of reinforcement, while for HSC beams the increasing in first cracking load are very little when the quantity of reinforcement less than the minimum flexural reinforcement and increased with the increasing amount above the minimum flexural reinforcement. The equation of ACI 318M-14 code gives adequate minimum flexural reinforcement for NSC and overestimate value for HSC up to (83 MPa), A new formula is proposed for HSC rectangular beams up to (90 MPa) concrete compressive strength by reducing the equation of ACI 318M-14 code for minimum flexural reinforcement by a factor depending on concrete compressive strength.

Strengthing of Beams and Columns using GFRP Bars

Nowadays infrastructure development is raising its pace. Many reinforced high concrete and masonry buildings are constructed annually around the globe. There are large numbers of structures which deteriorate or become unsafe to use because of changes in use, changes in loading condition, change in the design configuration, inferior building material used or natural calamities. Thus repairing and retrofitting of these structures for safe usage of has a great market. There are several situations in which a civil structure would require strengthening due to lack of strength, stiffness, ductility and durability. Beams, columns may be strengthened in flexure by using GFRP in tension zone. In this present work comparative study will be made with and without GFRP circular bars in a beam and column. An experiment study will be carried out to study the change in the structural behavior of beams & columns with GFRP circular bars of different thickness, varying span to depth ratio.

Structural Behaviour of Beam with HDPE Plastic Balls Subjected to Flexural Load

This paper presents the structural behaviour of reinforced concrete beam embedded with high density polyethylene balls (HDPE) subjected to flexural load. The HDPE balls with 180 mm diameter were embedded to create the spherical voids in the beam which lead to reduction in its self-weight. Two beam specimens with HDPE balls (RC-HDPE) and one solid beam (RC-S) with dimension 250 mm x 300 mm x 1100 mm were cast and tested until failure. The results were analysed in the context of its ultimate load, load-deflection profile, and crack pattern and failure mode. It was found that the ultimate load of RC-HDPE was reduced by 32% compared to RC-S beam while the maximum deflection at its mid span was increased by 4%. However, RC-HDPE is noticed to be more ductile compared to RC-S beam. Both types of beams experienced flexure cracks and diagonal tension cracks before failure.

An extended finite element model for structural analysis of cracked beam-columns with arbitrary cross-section

In this paper, an efficient finite element model for the structural analysis of cracked beam-columns with arbitrary cross-sections is presented. For this propose the combination of a planar beam element with only displacement degrees of freedom and extended finite element method (XFEM) is used. This element is highly capable in modeling the effect of edge cracks on the structural behavior of beams under various loading and boundary conditions. The method is able to solve the problem related to cracked beams with non-rectangular cross-sections with much less computational efforts compared to the available extended finite element models. Numerical examples are given to demonstrate the accuracy and the efficiency of the present method. There is a good agreement between the results obtained by the proposed method and those obtained by ABAQUS XFEM.

Analytical study of slant end-plate connection subjected to elevated temperatures

Due to thermal expansion, the structural behaviour of beams in steel structures subjected to temperature increase will be affected. This may result in the failure of the structural members or connection due to extra internal force in the beam induced by the thermal increase. A method to release some of the thermally generated internal force in the members is to allow for some movements at the end supports of the member. This can be achieved by making the plane of the end-plate of the connection slanted instead of vertical as in conventional design. The present paper discusses the mechanical behaviour of beams with bolted slant end-plate connection under symmetrical gravity loads, subjected to temperature increase. Analyses have been carried out to investigate the reduction in internal force with various angles of slanting, friction factor at the surface of the connection, and allowable temperature increase in the beam. The main conclusion is that higher thermal increase is tolerable when slanting connection is used, which means the risk of failure of structures can be reduced.

Stochastic Perturbation Analysis of Deteriorated Structures

The paper addresses a generalized perturbation method for the uncertainty analysis of concrete structures subject to reinforcement corrosion. The initiation phase is modelled by the well known Ficks 2ndlaw of diffusion. Deterioration models derived from experimental studies and a non-linear finite element (FE) model are used to simulate the structural behaviour of beams from the serviceability to the ultimate conditions. The time of corrosion initiation and the failure load are expressed by a Taylor series expansion about the origin of the space of independent standard normal random variables.

Discrete crack sectional analysis for shear evaluation of RC beams

The use of spiral links for preventing diagonal failures in beams will enable designers to utilise transverse reinforcement geometry for a better confinement effect. However, to develop such model it is essential that better understanding of the actual structural behaviour of beams with different transverse shear reinforcement configuration is reached. This can be achieved by looking further into the concepts of shear transfer mechanisms and by investigating the influence of the spiral geometry on the level of shear contribution. This paper provides an analytical method based on equilibrium of sectional analysis for predicting the shear load capacity and the mode of failure for beams reinforced with spiral links under different spiral configurations.

Optimization of the Natural Frequencies of Beams Via Dimpling Technique

In this paper, the natural frequencies of a beam, with different boundary conditions, are enhanced by creating cylindrical dimples on its surface. These dimples alter the local stiffness in the beam while keeping its mass the same. This method is cost-effective in comparison with other structural dynamics modification methods (SDM) because it is a one-step manufacturing method and because it enhances the dynamic behaviour of beam structures without additional weight or additional joints.The natural frequencies of dimpled beam are calculated by finite element method. In particular, ANSYS package is used in building the dimpled beam models for modal analysis. The effect of dimple location and size on the beam fundamental frequency is investigated. The simulation results indicated that creating dimples on simply supported and free–free beams decreases their fundamental frequencies, while creating dimples on clamped beams may increase their fundamental frequency.The optimal designs of dimpled beams are presented. The proposed method couples the finite element method for the modal analysis with an optimization technique based on genetic algorithm (GA). The optimization results show that dimpling technique is an effective technique to optimize the natural frequencies. The proposed technique is experimentally validated. The experimental results show a good agreement with the simulation results.

Influências de fibra de aço no comportamento estrutural de vigotas reforçadas com PRFC

Neste trabalho, apresenta-se a metodologia utilizada e os resultados da análise do comportamento de vigotas armadas e reforçadas externamente à flexão com manta de PRFC (polímeros reforçados com fibras de carbono). Avalia-se o comportamento do reforço de vigotas de concreto comum e compara-o com o do reforço de vigotas moldadas com um compósito cimentício à base de argamassa e fibras curtas de aço. O objetivo principal foi investigar a influência do compósito cimentício (escolhido sem maiores critérios) sobre o comportamento e o modo de ruína das vigotas reforçadas. Para tanto, uma série de ensaios de flexão em três pontos em seis vigotas foi conduzida, além dos ensaios de caracterização dos materiais: ensaios de flexão em três pontos em corpos-de-prova prismáticos entalhados, ensaios de tração em barras de aço e ensaios de compressão axial em corpos-de-prova cilíndricos. Adicionalmente, uma análise de elementos finitos foi desenvolvida com objetivo de comparar os resultados obtidos com os experimentais. O ganho de tenacidade e de resistência à fissuração provocou mudanças significativas no desempenho da vigota moldada com fibras e reforçada quando comparada com a vigota reforçada de concreto comum.

CALCULATING THE CARRYING CAPACITY OF FLEXURAL PRESTRESSED CONCRETE BEAMS WITH NON-METALLIC REINFORCEMENT

The article reviews moment resistance design methods of prestressed concrete beams with fibre-reinforced polymer (FRP) reinforcement. FRP tendons exhibit linear elastic response to rupture without yielding and thus failure is expected to be brittle. The structural behaviour of beams prestressed with FRP tendons is different from beams with traditional steel reinforcement. Depending on the reinforcement ratio, the flexural behaviour of the beam can be divided into several groups. The numerical results show that depending on the nature of the element failure, moment resistance calculation results are different by using reviewed methods. It was found, that the use of non-metallic reinforcement in prestressed concrete structures is effective: moment capacity is about 5% higher than that of the beams with conventional steel reinforcement.

Higher order composite beam theory built on Saint-Venant’s solution. Part-II: Built-in effects influence on the behavior of end-loaded cantilever beams

The higher order composite beam theory (HOCBT), established in Part-I, is a refinement of the one-dimensional beam-like theory related to 3D Saint-Venant’s solution. HOCBT is based on a displacement model including in/out-of plane warpings and is devoted to symmetric and orthotropic composite beams. In the present Part-II, HOCBT is applied to analyze the built-in effects influence on the structural behavior of end-loaded cantilever beams (torsion, tension and shear-bending). In the critical region, close to the built-in section, the 3D (axial and shear) stresses calculated by the proposed theory are relevant and quite comparable to those obtained by 3D-FEM computations. These results, obtained for a representative set of cross-sections, show that HOCBT is able to describe the built-in effects, and hence their influence on the structural behavior of the beam. As expected, moving from the built-in section, the results (displacements and stresses) tend towards Saint-Venant’s solution in the interior part of the beam. It is shown that the extents of the built-in effects are related to dimensionless constants that take into account the whole nature of the composite section and the loading case. Practically, regarding to Saint-Venant results, these constants allow to predict the built-in effects expansion.

Probability of Fault Location in a Beam Structure Using the Spectral Element Method and the Spatial Wavelet Analysis

The aim of the work is to develop a procedure allowing the test engineer to determine the probability of finding a crack in a beam structure. The procedure is based on the use of wavelet analysis and the simulation is performed by taking advantage of spectral elements to represent accurately the dynamic behaviour of beam structures in the high frequency range. In this context, numerical analyses are performed with the final scope of simulating a real testing environment: measurement error is considered and spectral elements are used so as to avoid influencing the capacity of the procedure with regard to solving the inverse problem. In this article the relation between the excitation frequency and the probability of locating the fault is shown. In particular, it is demonstrated by simulation that the probability of correctly determining the fault location increases with the excitation frequency.

An experimental study on the flexural behaviour of RC beams strengthened with high-strength bars

External unbonded strengthening offers advantages in speed and simplicity of installation over other strengthening techniques. Unlike externally bonded steel plate or carbon fibre sheet, surface preparation of the concrete for installation of a high-tension bar is not required and installation is not affected by environmental conditions. An anchoring pin or anchoring plate is installed at the end of the beam to connect the high-tension bar to the concrete beam. The deviators are used so that supplementary external bars follow the curvature of the tested beam. The main test parameters are the section area of strengthening bar, the depth of deviator and the number of deviators. The current paper provides a general description of the structural behaviour of beams strengthened using the technique. The test results of a strengthened beam are compared with those from a reference specimen. It is shown that the reinforcing technique can provide greater strength enhancements to an unstrengthened beam and that the provision of deviator enhances efficiency. The ultimate moment of the specimen with two deviators was higher than that of specimens with one deviator.

Shear Strengthening of Reinforced Concrete Beams Using GFRP Wraps

The objective of the experimental work described in this paper was to investigate the efficiency of GFRP composites in strengthening simply supported reinforced concrete beams designed with insufficient shear capacity. Using the hand lay-up technique, successive layers of a woven fiberglass fabric were bonded along the shear span to increase the shear capacity and to avoid catastrophic premature failure modes. The strengthened beams were fabricated with no web reinforcement to explore the efficiency of the proposed strengthening technique using the results of control beams with closed stirrups as a web reinforcement. The test results of 18 beams are reported, addressing the influence of different shear strengthening schemes and variable longitudinal reinforcement ratios on the structural behavior. The results indicated that significant increases in the shear strength and improvements in the overall structural behavior of beams with insufficient shear capacity could be achieved by proper application of GFRP wraps.