Cracked Beams Research Articles

Seismic behaviour of assembled monolithic concrete coupling beams through tests of two-story coupled shear walls

In the prefabricated concrete shear wall structure, in order to further improve the construction efficiency, the underwindow wall and the wall pier on both sides are often prefabricated as a whole. Therefore, the assemble integral coupling beam is composed of a prefabricated under-window wall, a cast-in-place strip and a prefabricated upper-window wall. The failure mode of this type assemble integral coupling beam under cyclic loading has not been reported. Because the wall under the window is also merged into the coupling beam, the length-to-depth ratio of the coupling beam is further reduced. However, the upper and lower walls are prefabricated standard walls with opening, which cannot be configured with inclined bars, which is a common way for cast-in-place coupling beams with relatively small length-depth ratio. In addition, how to connect the upper and lower prefabricated walls is also a key problem that affects the seismic performance. Six, two-story, full-scale assembled monolithic coupled concrete shear walls were tested to investigate the seismic behaviour of the new assemble integral coupling beam and the role of coupling beam aspect ratio (1.5, 1.85, 2.4) and connecting method (with and without grouted sleeves) between prefabricated panels on seismic performance. Two specimens were tested for each beam aspect ratio, one with a single row of grouted sleeves in the under-window panel used to splice reinforcement between the two precast panels and the other without sleeves. Test results indicate that damage in specimens with beam aspect ratios of 1.5 and 1.85 resulted from flexural yielding of beam reinforcement followed by diagonal cracking of the coupling beams, whereas damage in the specimen with larger aspect ratio (2.4) was primarily due to flexural hinging at the ends of the coupling beams. The connection details greatly affect the type and degree of damage, and more concentrated damage was observed in specimens without grouted sleeves along the interface between the precast under-window panel and cast-in-place strip. However, whether the grouted sleeve connection was used had little effect on the load capacity, deformation and stiffness of the specimens. Drift ratios at 15% drop in the peak strength ranged from 1.1% to 1.6%. The flexural capacity of the assembled integral coupling beam can be calculated as one beam according to the formula of the conventionally CIP concrete coupling beam.

Experimental study and analysis of RC beams shear strengthened with FRP/SMA composites

In practice, the prestressing is difficult to apply to achieve shear reinforcement of reinforced concrete (RC) beams due to the limited operating space used for installing mechanical tensioning equipment. So, how to efficiently introduce prestressing into RC beams is a practical problem. In this study, the authors utilized the recovery effect of shape memory alloys (SMA) wires to successfully introduce prestressing into RC beams and externally bonded with fiber reinforced polymer (FRP) sheets, forming a FRP/SMA composite shear reinforcement technology. After that, shear behavior of RC beams strengthened with FRP/SMA composites was investigated by a series of experiments. In order to further illustrate the effect of FRP/SMA composite shear reinforcement on RC beams, other reinforcement materials, such as SMA wires and FRP sheets, have also been separately applied in shear reinforcement experiments. Moreover, carbon fiber reinforced polymer (CFRP) and basalt fiber reinforced polymer (BFRP) are respectively applied to prepare FRP/SMA composites. For beams strengthened with FRP/SMA composites, the prestressing generated by the recovery effect of SMA wires can effectively suppress the formation of diagonal cracks in RC beams. The ultimate load and the corresponding displacement of strengthened beams significantly increased due to the constraint effect of FRP on the propagation of shear cracks. The shear capacity of CFRP/SMA composites strengthening beams was higher than that of BFRP/SMA composites strengthening beams, as CFRP/SMA composites better limited the propagation of cracks. Based on the test results, an analytical model has been proposed to predict the shear capacity of strengthened beams, and its effectiveness has been confirmed through comparison with experimental results.

Aeroelastic flutter of actively controlled nanocomposite beams with an open edge crack

Active control of aeroelastic flutter in composite structures is vital for improving the performance and safety of aerospace systems. Understanding the impact of cracks on flutter behavior of active controlled structures is of importance for early crack detection and accident prevention. The present work investigates the aeroelastic flutter of functionally graded (FG) graphene nanoplatelet (GNP)-reinforced nanocomposite (GNPRC) beams containing an edge crack under active control with an attached piezoelectric patch. The governing differential equations are derived using Hamilton's principle together with the Ritz method, based on the first order shear deformation theory (FSDT) and a rotational spring model. The flutter velocities of the system are determined by numerically solving the eigenvalue problem. Through a comprehensive parametric study, the effects of crack length and location, GNP parameters, and different control actions on the flutter velocities of the FG-GNPRC beams with different end supports are discussed. The results reveal that the presence of a crack reduces the flutter velocities of GNPRC beams, with the extent of reduction depending on the GNP distribution pattern, crack location and support ends. Additionally, the cracked GNPRC beams can be enhanced by attaching piezoelectric actuators with feedback gains at appropriate locations on the beam's surface.

Dynamic Analysis of Coupled Train and Cracked Bridge Systems Using Multiscale Finite Element Modeling

Cracking frequently encountered in railway bridges can lead to significant changes in bridge dynamic characteristics and further dynamic performance of train–bridge interaction (TBI) system. It is desirable to develop an effective method to understand the dynamic behavior of coupled train and cracked bridge systems. This paper proposes a framework for coupled vibration analysis of train and cracked bridge systems using multiscale finite element modeling. A multiscale bridge model adopting frictional surface–surface contact to characterize nonlinear breathing phenomenon of the crack is incorporated into the three-dimensional coupled TBI model. Subsequently, a multiloop numerical solution strategy is formulated to solve the established dynamic equation of coupled train and cracked bridge systems. The proposed framework is used to analyze the cracked beams presented in the literature, and the obtained and literature data are compared. Moreover, an actual heavy-haul railway bridge is taken as an illustrative example, in which vehicle dynamic response, bridge vibration, and train running safety index are calculated considering various crack types, train speeds, and track conditions. The results show that apart from the bridge displacement and acceleration, the presence of crack can have a large influence on the vehicle acceleration response, derailment factor, and offload factor. Differences larger than ±10% in the maximum dynamic indices associated with the intact and cracked bridges are observed, indicating the necessity of considering the crack damage in train–bridge coupled dynamic analysis.

Calculation Method for the Cracking Resistance and Bearing Performance of SFRAC Beams.

The utilization of recycled aggregate (RCA) in preparing recycled concrete (RAC) is an effective measure to solve the increase in construction waste. Furthermore, applying RAC to flexural members is a viable practice. The addition of steel fiber to RAC to prepare steel fiber recycled concrete (SFRAC) solves the performance deterioration caused by the recycled aggregate, so it is necessary to study the effects of the recycled aggregate replacement rate and fiber-volume ratio on the crack resistance and bending performance of SFRAC beams. In this study, 13 beams were designed and manufactured, with the water-cement ratio, recycled aggregate replacement rate, and fiber-volume ratio as the primary variables, and the cracking moment and ultimate moment of the SFRAC beams were systematically studied. The results show that the cracking and ultimate moments of the SFRAC beams increased with decreases in the water-cement ratio or with increases in the fiber-volume ratio and were unaffected by the replacement rate of recycled aggregates. Based on the experimental results and theoretical analysis, a calculation model and formula for the cracking moment were established. The ultimate bearing capacity of SFRAC beams can be accurately determined using the ACI 318 and ACI 544 standards. The research results serve as a valuable reference for the design of SFRAC beams, effectively address the issue of performance degradation in RAC structural members, and promote the use of green building materials.

Development of sustainable concrete using recycled polyethylene terephthalate (PET) granules as fine aggregate

Solid waste management has become a significant environmental challenge globally. This study aims to examine the performance of sustainable concrete incorporating polyethylene terephthalate (PET) granules as partial (0%, 10%, 30%, and 50%) volumetric replacement of sand. The mechanical properties including compressive strength, tensile strength and elastic modulus were examined. The flexural and cracking performance of the reinforced concrete (RC) beams, as well as bond behaviour of concrete mixes with steel reinforcement were investigated. Incorporating 10% PET granules demonstrated positive impact on the mechanical properties, flexural strength and cracking behaviour of RC beam, as well as bond strength. A theoretical model was proposed for predicting bond strength of concrete containing PET granules and the results corresponded well with both experimental and previous research findings. The American and Australian standards conservatively predicted cracking and flexural moments of the RC beams. Finite element modelling was conducted on the RC beams and the results corresponded well with the experimental findings.

Contactless and Vibration-Based Damage Detection in Rectangular Cement Beams Using Magnetoelastic Ribbon Sensors

This study investigated the innovative use of magnetoelastic sensors to detect the formation of single cracks in cement beams under bending vibrations. The detection method involved monitoring changes in the bending mode spectrum when a crack was introduced. The sensors, functioning as strain sensors, were placed on the beams, and their signals were detected non-invasively using a nearby detection coil. The beams were simply supported, and mechanical impulse excitation was applied. The recorded spectra displayed three distinct peaks representing different bending modes. The sensitivity for crack detection was determined to be a 24% change in the sensing signal for every 1% decrease in beam volume due to the crack. Factors influencing the spectra were investigated, including pre-annealing of the sensors, which improved the detection signal. The choice of beam support material was also explored, revealing that steel yielded better results than wood. Overall, the experiments demonstrated that magnetoelastic sensors enabled the detection of small cracks and provided qualitative information about their location.

Failure Mode of GFRP Bar RC Beams Using GFRP Sheet as Shear Reinforcement

The objectives of this study are to analyze the pattern crack and failure mode of the GFRP concrete beam by using GFRP sheet as shear reinforcement (GFB) compared with the two types of the conventional reinforced concrete beam (CB and GB). One of the conventional reinforced concrete beams is reinforced with the steel bar (CB) and the other is the GFRP bar (GB) as longitudinal reinforcement. The nine beams were cast from one concrete batch with dimensions of 150 mm width, 250 mm depth and 3300 mm length. This study focuses on a simply-supported beam using a roller and pinned supports at the end of the beam. Control beam (CB) that using steel reinforcement shows three phases of deformation based on the deflection load curve, ie before crack, after crack, and after yield, while GB and GFB beams that use GFRP bar reinforcement only show two phases of linear deformation namely the deformation phase before cracking and after cracking. From the crack pattern, CB beams experience the flexural cracks which starting from the mid-span on the tensile side of the constant moment region and propagated to the compression region along with the increase in load. All GB beams show the crack starts from the mid-span and then propagates towards the support. Whereas GFB beam show the flexural cracks that occur in the constant moment region and in the shear span, also diagonal cracks that divide the GFRP sheet occurred. From the failure mode, CB experienced flexural failure, while GB experienced compression failure and shear failure in all GFB beams.

Shear behaviour of seawater sea-sand coral aggregate concrete beams reinforced with FRP strip stirrups

The preparation of concrete for remote islands or reefs using locally available seawater, sea sand, and coral aggregate can greatly shorten the construction period and mitigate the shortage of river sand and natural gravel resources. This study is the first to experimentally investigate the shear behaviour of seawater sea-sand coral aggregate concrete (SSCAC) beams reinforced with non-corrosive carbon fibre-reinforced polymer (CFRP) strip stirrups. The test parameters included concrete strength, concrete type, and stirrup configuration. The experimental results suggested that CFRP-reinforced SSCAC beams exhibited a brittle shear failure mode because of the sudden CFRP rupture at the bend portions. The ratio of the measured maximum strain to the ultimate tensile strain of the CFRP strip stirrups varied from 36.6% to 47.8%. The critical diagonal shear cracks of SSCAC beams directly penetrated through the coral aggregates and split the aggregates, whereas those in the natural aggregate concrete (NAC) beams bypassed the natural gravel. In this regard, the SSCAC beams exhibited approximately 10% lower shear strength than their NAC counterparts owing to the loss of the aggregate interlocking effect after the occurrence of smooth diagonal shear cracks. The higher the strength grade of SSCAC, the greater the shear strength and service load.

К вопросу о допустимости дефектов в нижнем поясе подкрановых балок

Crane beams are among the most damaged structures in the buildings with heavy, and very heavy-duty overhead cranes. Their destruction can lead to the death of people working in the workshop, and to significant material losses. The durability of crane structures is determined by the intensity of work of the overhead cranes. The main defects and damages of metal crane beams are regulated by the standard STO-22-05—04, according to which all the cracks in the crane beams are divided into groups according to the risk of destruction. It is believed that the presence of cracks in the lower (stretched) chord of crane beams is unacceptable. Modern methods of non-destructive testing allow to detect defects with a minimum size from 2 mm (ultrasound) to 1 µm (capillary method). These cracks may be due to the inhomogeneity of the chemical composition of the alloy, or be of a structural nature, manifesting itself, in contrast to fatigue cracks that grow in the most loaded areas of the structure, in any part of the lower chord of the beam. If any crack is found in the lower chord of the crane beams, it is required to stop the operation of the crane and carry out a major overhaul of the crane runways. However, following these formal rules is not always economically and logically justified. The paper considers an example of rationing by the criterion of non-straining through cracks in the lower stretched chord (cracks of the first group). Based on the criteria of linear fracture mechanics, coefficients are proposed for all steels from which the crane beams are made, allowing for their technical inspection to give an express assessment of the admissibility of the detected through cracks. It is also shown that it is necessary to normalize the permissibility of the parameters of semi-elliptical cracks in the stretched zone (in the lower shelf of the I-beam crane beam), since these cracks can eventually develop into through defects.

Dynamic response of damaged rigid-frame bridges subjected to moving loads using analytical based formulations

PurposeThis study aims to perform dynamic response analysis of damaged rigid-frame bridges under multiple moving loads using analytical based transfer matrix method (TMM). The effects of crack depth, moving load velocity and damping on the dynamic response of the model are discussed. The dynamic amplifications are investigated for various damage scenarios in addition to displacement time-histories.Design/methodology/approachTimoshenko beam theory (TBT) and Rayleigh-Love bar theory (RLBT) are used for bending and axial vibrations, respectively. The cracks are modeled using rotational and extensional springs. The structure is simplified into an equivalent single degree of freedom (SDOF) system using exact mode shapes to perform forced vibration analysis according to moving load convoy.FindingsThe results are compared to experimental data from literature for different damaged beam under moving load scenarios where a good agreement is observed. The proposed approach is also verified using the results from previous studies for free vibration analysis of cracked frames as well as dynamic response of cracked beams subjected to moving load. The importance of using TBT and RLBT instead of Euler–Bernoulli beam theory (EBT) and classical bar theory (CBT) is revealed. The results show that peak dynamic response at mid-span of the beam is more sensitive to crack length when compared to moving load velocity and damping properties.Originality/valueThe combination of TMM and modal superposition is presented for dynamic response analysis of damaged rigid-frame bridges subjected to moving convoy loading. The effectiveness of transfer matrix formulations for the free vibration analysis of this model shows that proposed approach may be extended to free and forced vibration analysis of more complicated structures such as rigid-frame bridges supported by piles and having multiple cracks.

Identification of crack location in metallic biomaterial cantilever beam subjected to moving load base on central difference approximation

Abstract If not detected early, the cracks in structural components may ultimately result in the failure of the structure. This issue becomes even more critical when the component under investigation is a prosthesis placed in the human body. This study presents a crack location identification method based on the time domain in a cantilever beam of metallic biomaterials (CBMB). The absolute difference between the central difference approximation of the root mean square (RMS) of displacement of points on the cracked and uncracked beams was applied as a cracked location indicator. Captured time-domain data (displacement) at each node of the cracked and uncracked beams were processed into a central difference approximation of the RMS of displacement. Then, the crack could be detected by a sudden change of the cracked location indicator. The feasibility and effectiveness of the proposed method were validated by numerical simulations. The finite-element simulation of a CBMB with a transverse notch was analyzed in the numerical study. The notch or crack was detected along the beam under a moving load at various locations. A set of simulation experiments and numerical calculations was performed to determine whether the proposed identification method would accurately detect the location of a crack in a cantilever beam under a moving load compared to the location found by an exact solution method. The results showed that the proposed method was not only as able as the analytical method but also robust against noise: it was able to detect a crack precisely under 5% noise.

Free vibration disturbance and local mesh refinement induced by microcrack damage in circularly curved beams

PurposeThis study aimed to solve the engineering problem of free vibration disturbance and local mesh refinement induced by microcrack damage in circularly curved beams. The accurate identification of the crack damage depth, number and location depends on high-precision frequency and vibration mode solutions; therefore, it is critical to obtain these reliable solutions. The high-precision finite element method for the free vibration of cracked beams needs to be developed to grasp and control error information in the conventional solutions and the non-uniform mesh generation near the cracks. Moreover, the influence of multi-crack damage on the natural frequency and vibration mode of a circularly curved beam needs to be detected.Design/methodology/approachA scheme for cross-sectional damage defects in a circularly curved beam was established to simulate the depth, location and the number of multiple cracks by implementing cross-section reduction induced by microcrack damage. In addition, the h-version finite element mesh adaptive analysis method of the Timoshenko beam was developed. The superconvergent solution of the vibration mode of the cracked curved beam was obtained using the superconvergent patch recovery displacement method to determine the finite element solution. The superconvergent solution of the frequency was obtained by computing the Rayleigh quotient. The superconvergent solution of the eigenfunction was used to estimate the error of the finite element solution in the energy norm. The mesh was then subdivided to generate an improved mesh based on the error. Accordingly, the final optimised meshes and high-precision solution of natural frequency and mode shape satisfying the preset error tolerance can be obtained. Lastly, the disturbance behaviour of multi-crack damage on the vibration mode of a circularly curved beam was also studied.FindingsNumerical results of the free vibration and damage disturbance of cracked curved beams with cracks were obtained. The influences of crack damage depth, crack damage number and crack damage distribution on the natural frequency and mode of vibration of a circularly curved beam were quantitatively analysed. Numerical examples indicate that the vibration mode and frequency of the beam would be disturbed in the region close to the crack damage, and a greater crack depth translates to a larger frequency change. For multi-crack beams, the number and distribution of cracks also affect the vibration mode and natural frequency. The adaptive method can use a relatively dense mesh near the crack to adapt to the change in the vibration mode near the crack, thus verifying the efficacy, accuracy and reliability of the method.Originality/valueThe proposed combination of methodologies provides an extremely robust approach for free vibration of beams with cracks. The non-uniform mesh refinement in the adaptive method can adapt to changes in the vibration mode caused by crack damage. Moreover, the proposed method can adaptively divide a relatively fine mesh at the crack, which is applied to investigating free vibration under various curved beam angles and crack damage distribution conditions. The proposed method can be extended to crack damage detection of 2D plate and shell structures and three-dimensional structures with cracks.

Pola Kegagalan Balok Beton Bertulang Spiral Tanpa Beton Pada Penampang Tarik

Abstract The exploration of natural materials to produce concrete has an impact on environmental conditions and global warming that can cause natural disasters. Therefore, the use of concrete materials must be as efficient as possible. One solution to overcome this problem is to reduce the concrete in the tensile area and strengthen the beam using steel reinforcement in the support area. This study aims to determine the effect of tensile reinforcement on the behavior of beams without concrete in the tension area using a spiral system on crack patterns and beam patterns. The method used was an experimental method by making 2(two)specimens, a normal concrete beam (BN) as a control beam, and a spiral concrete beam without reinforcement in the tensile section with the addition of experimental reinforcement at the support section (BTRS 60D) where D is the diameter of the main reinforcement. The beams were designed as normal quality concrete beams with concrete quality of 45.07 MPa at the testing age of 28 days. The beam's dimension was 150 mm x 200 mm x 3100 mm. This study obtained the ultimate load on the BTRS specimen of 35.1 kN. While on the BN specimen, the ultimate load reached 47.65 kN. There was a decrease in BTRS service load by 27.57%. It is observed that the BN specimen experienced flexural cracks. The beam failure of the 2 test objects experienced beam failure that resembled under-reinforced where the reinforcing steel melted before the concrete was crushed. Keywords: spiral reinforcement, failure pattern, crack pattern.

Automated detection of propagating cracks in RC beams without shear reinforcement based on DIC-controlled modeling of damage localization

In spite of an extensive research in the past few decades, design of beams without shear reinforcement is still considered to be a challenging task. With the goal of developing realistic and simple engineering models, many researchers have contributed to the development of analytical and numerical approaches that have improved the understanding of the mechanical background of shear fracture. Still, some assumptions in these approaches, such as the rigid body kinematics which relies on the assumption of a uniquely identifiable center of rotation, have raised critical questions in the scientific community that need further consideration. In this paper, an automated crack detection scheme based on DIC-controlled modeling of damage localization is developed and presented. This scheme enables an automatic evaluation of opening and sliding profiles along the crack ligament, the center of rotation between two neighboring concrete teeth, and the moment–rotation curve directly from the DIC measurements of the surface displacement. To demonstrate the feasibility and the features of the developed scheme, verification studies are performed using tests performed on longitudinally reinforced concrete beams. The description of the mathematical concepts behind the developed crack detection scheme is accompanied with the explanation of the implementation method using modern Python packages for scientific computing, providing code snippets that show a straightforward translation of the mathematics into an executable code. Furthermore, a publicly available implementation of the developed scheme is provided in the form of an interactive Jupyter notebook.

A novel DISTINCT method for characterizing breathing features of nonlinear damage in structures

The detection of breathing cracks in in-service structures is an intractable issue due to the distinctive dynamic behavior, typically the opening and closing of the crack subjected to cyclic loading. The existing methods to identify breathing cracks generally rely on the hypothesis of the crack-induced nonlinear features, mostly represented by super-harmonics. Nevertheless, an in-service structure even free of cracking somehow has nonlinear components in material, geometry, boundary etc., such that it tends to present inherent nonlinear features, i.e., nonlinearities prior to cracking, which could impair the effectiveness of super harmonics-like methods to depict breathing cracks. In such a circumstance, a sophisticated method that can characterize breathing cracks-induced nonlinearity by accommodating inherent nonlinear of the structure is desired. Herein, a novel method, termed DISTINCT (Difference in Split Temporal signal with Inherent Nonlinear Components Tolerated) method, is proposed. This method is formulated by splitting a whole response of a structure bearing breathing cracks into positive and negative response components. Each response component largely reflects structural dynamic behavior with regard to the crack-opening state or crack-closing state. From positive or negative response components, the dynamic property such as the frequency spectrum arising from the Fast Fourier Transform, corresponding to crack-opening state or crack-closing state, can be derived. To this end, the differences between the two frequency spectra relatively purely manifests the characteristic of breathing cracks including their presence and severity. The feasibility of the DISTINCT method is numerically verified via the identification of breathing crack in a cantilever beam and a shell, with emphasis on its stronger noise resistance than the traditional super-harmonics-based method. Furthermore, the method’s effectiveness is experimentally validated via the inspection of breathing cracks in a scaled arch dam model subject to excitations induced by artificial seismic accelerations. The results show that the proposed DISTINCT method can quantify the severities of four levels of damage comprising breathing cracks by tolerating inherent nonlinearity of the structure. The advantages of the DISTINCT lie in its tolerance to structural inherent nonlinearities and requiring no numerical or physical benchmarks nor any prior knowledge of the material properties and boundary conditions in assessing breathing cracks of structures.

Experimental study on flexural performance of reinforced concrete beams strengthened by PET

AbstractPolyethylene terephthalate (PET) is a new type of fiber‐reinforced polymer (FRP) composite material, which has the characteristics of high performance, high toughness, high tensile fracture load, low elongation, low creep, no rust, and safety in use. The good performance of PET can significantly improve the mechanical properties of its components. A total of six reinforced concrete (RC) beams were produced in the test, one of which was a comparison beam, and the other five were reinforced with PET. In the test, the PET reinforcement spacing, number of reinforcement layers, and laying method were used as control variables, and an experimental study on the normal section bending performance of the specimen was performed. The test analyses the failure characteristics, crack width, bearing capacity, and deflection of the specimens under different reinforcement conditions. The test results showed that PET reinforcement can effectively inhibit the occurrence and development of cracks in RC beams and improve the ultimate bearing capacity and ductility of the components. The smaller the PET reinforcement spacing, the higher the ultimate bearing capacity; the greater the number of PET layers, the better the ductility of the specimen. Additionally, the economy, environmental protection, and portability of PET are of great significance for its application in practical engineering reinforcement.

Experimental investigation on ultra high-performance concrete beams without shear reinforcement

Seven ultra high-performance concrete (UHPC) beams without shear reinforcement are tested in this work to examine their structural behavior as shear failure is a major concern in such members. Coarse aggregate was not used in two of the beams while the other five are made with coarse aggregate as 50% replacement of fine sand. Three longitudinal steel reinforcement ratios (1.14%, 1.64% and 2.46%) and three steel fiber ratios (0, 1% and 2%) are used. Results show that UHPC beams with coarse aggregate show higher ultimate loads (4.7% − 11.5%) than UHPC beams without coarse aggregate and incorporating 1% and 2% steel fiber raises ultimate loads by 60% and 131%, respectively for beams with coarse aggregate. Also, using 2% steel fiber changes failure mode from brittle shear failure by diagonal crack in beams of 0 or 1% steel fiber to ductile flexural failure by yielding of longitudinal reinforcement. Higher stiffness and toughness and lower deflections are observed with the increase of longitudinal reinforcement, steel fiber or coarse aggregate. Using 2% steel fiber highly improved toughness by more than 17 times. Lower rates of improvement are recorded for longitudinal reinforcement and coarse aggregate. However, it is recommended to perform more research to examine more parameters such as fiber types.

Experimental Study on Flexural Cracking and Deformation of Reinforced-Concrete Beams Strengthened with NSM FRP Reinforcement

Experimental Study on Flexural Cracking and Deformation of Reinforced-Concrete Beams Strengthened with NSM FRP Reinforcement

An experimental behaviour of RCC rectangular beams with U-shaped encased welded wire mesh under torsion phenomena

Concrete is one form of composite material composed of fine and coarse aggregate bonded together with cementitious paste that is durable in its hardened state over time. Although it is robust in compression, it has a brittle material property in tension. Axial and shear forces, bending moments, and torsion moments may arise in the concrete body in a reinforced concrete design depending on the loading conditions. In this sequel, the encased welded wire mesh with high yield strength is used in order to improve composite material characteristics and reduce abrupt cracking with an increase in torque carrying capacity of concrete specimens. A total of 18 beam specimens were casted and tested under pure torsion, in that six numbers were control specimens and the remaining twelve numbers were specimens with encased welded wire mesh. U-shaped wrapped WWM, both in the form of transverse strips and continuous U-shaped sheets are used to observe enhancement in the cracking and ultimate torsional strength of plain and RCC rectangular beams respectively. The curves of tested specimens containing WWM wrapping patterns showed the specimens containing WWM resist more torsional loads as compared to control specimens. The ultimate torque get increased effectively due to the introduction of U-shaped WWM wrap in fully reinforcement type means longitudinal reinforcement with closed stirrups beam specimens.