Strength Of Beams Research Articles

In-plane properties of an in-situ consolidated automated fiber placement thermoplastic composite

Automated fiber placement (AFP) has been employed to manufacture aerospace structures for decades, recently focusing on thermoplastic composites (TPC). The in-situ consolidation AFP of TPCs is pursued as an energy-efficient additive manufacturing (AM) approach for fabricating composite structures. This work compares the in-plane mechanical properties of in-situ consolidated coupons with those of compression molded counterparts to provide new insights into their failure mechanics and processing-structure relationships. Tensile and compressive properties along the fiber and transverse directions, in-plane shear properties, and short beam strength were measured for all samples. Failure modes and mechanics in tested coupons were related to AFP defects and processing, i.e., resultant crystallinities, fiber misalignment, matrix mechanical properties, porosity, and fiber–matrix interfacial strength. The findings of this study can be used to guide the manufacturing of future TPC structures and potentially open new avenues for applications where post-processing is not feasible or reduced mechanical performance is acceptable.

Lateral-Torsional Failure and DSM Design of CFS Lipped Channel Beams at Room and Elevated Temperatures

About a decade ago, in-depth investigations on the behaviour of cold-formed steel (CFS) single-span simply supported lipped channel beams failing in lateral-torsional modes at both room and elevated temperatures were reported at QUT (Queensland Technical University). They revealed a significant underestimation of the lateral-torsional (LT) failure moments by the Direct Strength Method (DSM) global design curve at room temperature, then codified in the Australian/New Zealand and North American specifications. In order to remedy this situation, these authors proposed two novel DSM-based beam strength curve sets, which were found to substantially improve the LT failure moment prediction quality, both at room and elevated temperatures. This work aims at extending the scope of the above investigations, by analysing a visibly larger set of CFS lipped channel beams at elevated temperatures (up to 800 °C), exhibiting (i) various cross-section dimensions and yield stresses, selected to cover wider LT slenderness ranges, (ii) two end support conditions, differing only in the end cross-section wall displacement/rotation and warping restraints (either fully free or fully prevented), and (iii) temperature-dependent steel material properties according with the model prescribed in Part 1-2 of Eurocode 3. The results presented and discussed consist of beam LT post-buckling equilibrium paths and failure moments, obtained through Abaqus shell finite element GMNIA that include critical-mode (LT) initial geometrical imperfections. Lastly, the numerical failure moment data obtained in this work and reported in the literature are used to develop and propose a new unified set of DSM-based strength curves capable of adequately handling beam LT failures at room or elevated temperatures. Since it is shown that the proposed strength curve set provides a quite good LT failure moment prediction quality, it is fair to argue that it constitutes a good starting point to search for an efficient general DSM-based design approach for CFS beams failing in LT modes at room and elevated temperatures.

Bending and shear strengthening of timber beams using prestressed steel and composite bars – experimental and numerical studies

The paper describes a program of experimental and numerical tests aimed at determining the mechanical properties of beams made of laminated timber (BSH) and laminated veneer lumber (LVL) reinforced with pre-stressed bars made of basalt, glass, natural and steel fibers, basalt mats with roving and composite, polyethylene and natural yarn. The paper presents various types of reinforcements, the purpose of which was to obtain higher load-bearing capacity and stiffness in bending with shear than for unreinforced beams. The effectiveness of different reinforcement schemes was compared for seventeen beams subjected to experimental tests on a test stand, the modes of destruction were described, as well as mechanical properties, deformations and deflections for reinforced and unreinforced beams under multiply variable and long-term loading. Based on the experimental studies, a significant increase in the load-bearing capacity and stiffness of the reinforced beams subjected to simultaneous bending and shear was confirmed, and it was indicated that the reinforcements by pre-stressed bars (steel, with polymer reinforcement or natural fibers) and composite mats eliminated local defects and discontinuities in the wood, without affecting the quality and strength of the FRP-wood connection. The numerical results of the analysis of the beam models using the finite element method showed compliance with the experimental studies in terms of deflections, linear and angular strains for the reinforced and unreinforced beams

Sbno1 mediates cell–cell communication between neural stem cells and microglia through small extracellular vesicles

BackgroundNeural stem cells (NSCs) play a crucial role in the progress of ischemic stroke. Research on zebrafish embryonic demonstrates an association between Strawberry Notch 1 (Sbno1) and central nervous system development. However, the regulation and underlying mechanism of Sbno1 in NSCs have not been studied yet. Here, we investigated the role and the mechanism of Sbno1 in NSCs development and the potential therapeutic value of Sbno1 in ischemic stroke.MethodsAdeno-associated virus (AAV) was used for overexpression or knockdown of Sbno1 in vitro or in vivo. A mouse model of MCAO was established to evaluate the neuroprotective effects of AAV-Sbno1, including balance beam test, rotarod test, and strength evaluation. H&E and immunofluorescence assessed neuronal impairment. Western blot and RT-qPCR were used to detect the expression of Sbno1 and its downstream target genes. RNA-seq and western blot were performed to explore further molecular mechanisms by which Sbno1 promoted endogenous repair of NSCs and macrophages M2 polarization. CCK8 was conducted to assess the effects of Sbno1 on NSCs proliferation. The impact of Sbno1 on NSCs apoptosis was evaluated by flow cytometry. NSCs derived from small extracellular vesicles (sEV) were obtained using ultracentrifugation and identified through nanoparticle tracking analysis (NTA) and western blot analysis.ResultsOur results showed that Sbno1 is highly expressed in the central nervous system, which plays a crucial role in regulating the proliferation of NSCs through the PI3k-Akt-GSK3β-Wnt/β-catenin signaling pathway. In addition, with overexpression of Sbno1 in the hippocampus, post-stroke behavioral scores were superior to the wild-type mice, and immunofluorescence staining revealed an increased number of newly generated neurons.sEV released by NSCs overexpressing Sbno1 inhibited neuroinflammation, which mechanistically impaired the activation of the microglial NF-κB and MAPK signaling pathways.ConclusionsOur studies indicate that sbno1 promotes the proliferation of NSCs and enhances endogenous repairing through the PI3k-Akt-GSK3β-Wnt/β-catenin signaling pathway. Additionally, NSCs overexpressing sbno1 improve ischemic stroke recovery and inhibit neuroinflammation after ischemia by sEV through the MAPK and NF-κB signaling pathways.

Design of lattice metamaterials under the equal strength concept and research on the mechanical properties of their sandwich structures

This study proposes a novel lattice metamaterial with equal strength struts based on the concept of equal strength of beams, which has been designated the strut-enhanced body-centered cubic lattice structure (EBCC). The structure is capable of effectively reducing the stress concentration of the lattice structure at the nodes and increasing the structural energy absorption. The effective elastic properties of EBCC unit cells are investigated in detail under periodic boundary conditions (PBC), and the results show that the deformation response of the unit cell under compressive loading is dominated by bending. A novel sandwich structure, designated S-EBCC, was developed utilizing EBCC as the core material. The effects of geometrical parameters and relative density on the deformation mechanism and mechanical properties of the sandwich structure were analyzed through experiments, numerical simulations and theoretical predictions. The results show that under compressive loading, the stress concentration at the nodes of the EBCC structure is effectively improved and the peak stress is reduced while the energy absorption is increased compared with the traditional S-BCC structure. Under three-point bending load, the larger the strut angle of the S-EBCC structure, the higher the load capacity. Comparison of experimental and theoretical results shows that the failure modes of the S-EBCC structure under both compressive and three-point bending loads are plastic yield.

Residual Strength of Concrete Beams Reinforced with GFRP Bars Exposed to Elevated Temperatures

Residual Strength of Concrete Beams Reinforced with GFRP Bars Exposed to Elevated Temperatures

Residual Strengths of RC Beams Strengthened with Basalt and Carbon Textile Reinforced Mortars After Exposure to Elevated Temperatures

Residual Strengths of RC Beams Strengthened with Basalt and Carbon Textile Reinforced Mortars After Exposure to Elevated Temperatures

Numerical investigation on flexural performance of dowel laminated timber with laminas made of laminated veneer lumber

Horizontal dowel laminated timber (H-DLT) is a doweled engineered wood product with laminas made of solid timber. H-DLT has excellent bending resistance. However, the height of cross-section of H-DLT as a beam is limited by the width of solid wood laminas. Laminated veneer lumber (LVL) is an engineered wood product formed by hot-pressed gluing thin veneers, which is flexible in cross-section size compared to solid timber. Horizontal dowel laminated veneer lumber (H-DLVL) was developed by utilizing the H-DLT production methods and LVL material characteristics. H-DLVL has flexible size and good mechanical properties, and it can be made into beams and panels with large cross-sections. In this paper, the flexural performance of H-DLVL beams was investigated. A predictive finite element model of H-DLVL beams was created by the extended finite element method (XFEM) with cohesive zone model (CZM). The numerical models using solid-beam elements without fictitious cracks were verified and calibrated by experimental results. The influence of five variables, including lamina width, thickness, and quantity, dowel spacing along the grain, and dowel row (edge distance), on the flexural performance of H-DLVL beams was analyzed, and the flexural strength of H-DLVL beams was parameterized. The results showed that the failure mode of H-DLVL beams could be well predicted by XFEM without considering fictitious cracks combined with CZM, and the error range of simulated flexural strength of H-DLVL beams was within ±10 %. The flexural strength of H-DLVL beams was directly affected by lamina thickness and dowel spacing along the grain. The flexural strength of H-DLVL beams increased with the increase of those two variables. Lamina width and dowel row (edge distance) affected the flexural strength of H-DLVL beams indirectly by influencing the failure mode of H-DLVL beams. Based on this research, the recommended dowel spacing along the grain of H-DLVL beams was 6.25–12.5 times the wood dowel diameter, and the recommended edge distance of H-DLVL beams was 5–7 times.

Experimental study on the shear behaviors of inverted castellated T-steel reinforced UHPC (ICTSRU) beams with hollow section

To reduce the production costs of steel reinforced UHPC composite beams and fully utilize the material strength of steel, this paper introduced an innovative prefabricated composite beam comprising a reinforced ultra-high performance concrete beam and an internal castellated inverted T-steel, forming an inverted castellated T-steel reinforced UHPC (ICTSRU) composite beam. Investigating the shear behavior of ICTSRU beams is the primary objective of this research. Seven composite beams were loaded under simply supported four-point loading conditions, and the effects of key parameters such as the shear span-depth ratio, steel fiber volume fraction, and stirrup ratio were studied. The findings from the test indicated that the ICTSRU beams demonstrated superior deformation ability and significant residual shear strength after the peak load. The shear span-to-depth ratio significantly influenced the failure modes and carrying capacity of the ITSRU beams. As the span-to-depth ratio increased from 1.1 to 1.6 and 2.1, the failure mode developed from shear failure to flexural failure and the shear resistance decreased by 19 % and 48 %, respectively. Enhancing the steel fiber volume fraction and the stirrup ratio can mitigate the initiation and propagation of diagonal cracks, thereby augmenting the shear strength and ductility of ICTSRU beams. Following a comprehensive analysis of the experimental results, a predictive model for the shear strength of the ICTSRU beam is proposed. This model posits that the shear capacity of the ICTSRU beam comprises the shear resistance contributions from the UHPC matrix, stirrups, steel web, and steel fibers. A comparative analysis of the computed values and the test results showed that the proposed calculation method has a high accuracy in predicting the ultimate shear strength of ICTSRU beams.

Damage monitoring of glass/epoxy-curved laminates with different stacking sequences using acoustic emission

Delamination is a major concern in the curvature area of a composite laminate due to the flexural stresses occurring between the laminates. This research focuses on the respective merits of different stacking sequences obtained by layering the glass fiber reinforcement at various orientations in an epoxy resin to manufacture a curved laminate. In particular, laminates with stacking sequences, such as Unidirectional [0°]24, Cross-ply [0°/90°]6S, Angle ply [±45°]6S, and Quasi-isotropic laminates [0°/±45°/90°]3S, were tested by performing four-point bending tests. Acoustic emission (AE) monitoring and experimental analysis characterized damage modes, including delamination. AE parameters, such as amplitude, energy, duration, cumulative count, and peak frequency, were utilized to characterize the damage mechanisms of the various stacking sequences. Experimental AE data confirmed that fiber orientation influences delamination resistance and failure mechanisms. Furthermore, compared to other layup sequences, the peak load of cross-ply (Layup B) was found to be greater by 48.7%, 32.87%, and 50.14%. Cross-ply curved laminates also have higher interlaminar tensile strength and curved beam strength than other sequences. They also failed less often due to delamination than other sequences. Finally, scanning electron microscope characterization verified and validated all damage processes found in the AE data collection. As a result, these findings play a significant role in predicting the lifetime, delamination failure, and strength of curved composite laminates.

Influence of fine aggregates replaced ratio on shear strength of oyster shell concrete beam using GFRP rebars

The recycle of oyster shell as a component of concrete is a considerable solution around the world, not only ameliorate environment quality due to waste pollution but also decelerate the depletion of traditional aggregates. In this study, the oyster concrete is elaborated and performed in the order to determine many mechanic properties such as compressive strength, tensile strength or modulus of elasticity. These parameters are an important information, allowing to predict the shear strength of concrete in the structure using Glass Fiber Reinforced Polymer (GFRP) rebar, where a part of fine aggregate is replaced by oyster shell. Besides, many 3-points bending test were realized in several beams with different ratios of replacement. The presence of oyster shell crushed replacing the natural sand reduced many mechanic characteristics of concrete, including the shear behaviour. However, compared to theoretical predictions, the results given by experiment seems betters, although there is a diminution of shear strength in almost specimens. This argument leads to the possibility of using this kind of concrete with GFRP rebar in the design of manufacturing precast members, mainly under the load introducing the shear force

Experimental and Numerical Study of Steel-Concrete Composite Beams Strengthened under Load.

This study analysed the strengthening process of a classical steel-concrete composite beam. The beam consisted of a reinforced concrete slab connected by shear studs to an IPE steel profile. The key idea was that the composite beam was strengthened under load. This process simulated an actual reinforced structure that is always subjected to dead loads, with possible service loads. This study assumed that strengthening was implemented to increase the load-carrying capacity and stiffness, not as a way for simulation a repair. The strengthening consisted of expanding the steel part of the beam by welding an additional plate to the bottom flange of the IPE profile. This study included the results of numerical analyses conducted in Abaqus software and lab results. A three-dimensional numerical model was created, taking into account the non-linear behaviour of concrete and steel, the susceptibility of the composite at the joint plane, and the residual stresses created during welding. A full-scale strengthening of the composite beams under load was carried out. Comparison of the results obtained in the experimental tests and numerical analyses showed a very high convergence of the results, as well as in terms of the non-linear operation of steel and concrete. This confirmed the validity of the created numerical model, which can be the basis for further research into the process of optimal strengthening of composite elements.

Experimental and Analytical Evaluation to Strengthened R.C Beams Using Ferrocement Under Torsion

The safety of structures around the globe represents a significant and pressing concern, underscoring the urgent need for the development and implementation of effective rehabilitation methods to ensure their continued functionality. Ferrocement has emerged as a durable method for the restoration of reinforced concrete (RC) structures, demonstrating resilience and versatility in addressing structural damage. A substantial body of research has been conducted to examine the mechanical properties of ferrocement, with a particular focus on its efficacy in reinforcing beams against a range of forces. In light of the limited understanding of the factors affecting the torsional strength of ferrocement-wrapped beams, it is imperative to conduct experimental investigations. The objective of this study is to evaluate and compare the torsional strength, angle of twist and crack development of different wrapping types using both analytical analysis and experimental data. The findings indicate that three-sided wrapping is an effective method for enhancing torsional behaviour, as evidenced by both experimental and analytical results. Furthermore, the utilization of styrene-butadiene rubber (SBR) as a connecting material has been demonstrated to be an effective method for maintaining cohesion across reinforced beams.

Development of Approaches for Strengthening and Retrofitting of Concrete Beams Using Structural Steel

In structural analysis, the term 'frame' typically refers to a robust structure comprising various elements such as slabs, beams, columns, and footings. These components are cast together to create a monolithic construction, effectively functioning as a single integral unit. The frame is subject to various forces, which are transferred through its different components. Additionally, changes in facility usage or the introduction of additional live loads can exert further stresses on the structure. Consequently, it is imperative that the elements of the frame possess sufficient strength to withstand these loads. In this study, we focus on the development of approaches for strengthening and retrofitting concrete beams using structural steel elements. Specifically, our investigation involves the analysis of beams under different load combinations to enhance their integrity performance. To achieve this, angles and steel plates are utilized for reinforcement. We conduct numerical analysis through finite element modeling using ANSYS Workbench. Multiple beam models are created within the ANSYS platform, allowing us to study and compare various outcomes, including total deformation. This comprehensive approach aims to contribute to the advancement of methods for enhancing the structural resilience of concrete beams in real-world applications.

Shear behavior of reinforced concrete beams with high-strength reinforcements after high temperatures

This paper investigates the effect of steel reinforcement configured with different strengths after different high temperatures on the shear performance of the test beams, a total of 20 reinforced concrete (RC) beams, through experiments, numerical analyses and theoretical studies, in order to understand the key factors affecting the shear performance of the beams. The test revealed that the mechanical properties of concrete and steel reinforcement showed a trend of increasing and then decreasing after high temperatures. Increasing the stirrup ratio and stirrup strength can significantly improve the crack resistance and shear capacity of the beams, as well as the deformation performance of the beams. The residual shear strengths of test beams with high-strength stirrups after exposure to high temperatures are significantly greater than those of ordinary reinforced concrete beams. Specifically, the shear capacity of beams with high-strength stirrups after exposure to 800°C increased by 23.7 % compared to ordinary beams, and the mid-span deflection performance increased by 28.7 %. The stresses in the shear span region of the test beams after high temperature were more concentrated at the diagonal and the number of cracks was significantly reduced. In this paper, a simplified formula for calculating the residual shear capacity of RC beams after room and high temperatures is proposed, which can well predict the test results.

Strengthening of RC Beam with GFRP Composites in Shear N. B. Bhopale

The rehabilitation, repair and strengthening of existing reinforced concrete (RC) structures is essential due to factors such as aging, steel reinforcement corrosion, construction/design defects, increased service loads demand, seismic events, and advancements in design guidelines. Fiber-reinforced polymers (FRP) are now being recognized as a promising material for the rehabilitation of such structures, through strengthening or repairing. In buildings and bridges, RC sections are commonly found in the form of beams and girders. Shear failure of RC beams is particularly due to its sudden occurrence without warning. Therefore, the utilization of externally bonded (EB) FRP composites for shear strengthening of RC beams has gathered popularity as a structural enhancement technique, primarily due to advantages of FRP composites, such as high strength-to- weight ratio and exceptional corrosion resistance. In addition, FRP repair systems give a cost-saving choice to traditional repair methods and materials. A study was performed to analyse the shear characteristics of RC beams enhanced with continuous glass fiber-reinforced polymer (GFRP) sheets. Reinforced concrete beams externally bonded GFRP sheets subjected to failure using a symmetrical two-point concentrated static loading system. The experimental data obtained included load, deflection, and failure modes of each beam, along with the effect of the number of GFRP layers on the beams The failures observed in strengthened beams typically commence with the debonding of the FRP sheets, followed by brittle shear failure. The shear capacities of these beams were higher than that of the control beam.

Predicting shear strength of fiber-reinforced concrete beams reinforced with longitudinal FRP bars with machine learning techniques

ABSTRACT This study investigates the shear strength prediction of Fibre-Reinforced Concrete (FRC) beams reinforced with Fibre-Reinforced Polymer (FRP) bars and without stirrups through the application of Machine Learning (ML) techniques. The utilisation of FRP bars, particularly Glass Fibre-Reinforced Polymer (GFRP) and Basalt Fibre-Reinforced Polymer (BFRP) bars, has emerged as a promising alternative to traditional steel reinforcement due to their superior mechanical properties and corrosion resistance. Moreover, the incorporation of macro- and micro-discrete fibres into concrete compositions enhances both shear and flexural behaviour while reducing crack propagation induced by tensile stresses. The primary objective of this research is to develop accurate predictive models for the shear capacity of FRP-reinforced concrete beams, considering various influential parameters. Six different ML techniques, namely Multiple Linear Regression (MLR), Gaussian Process Regression (GPR), k-Nearest Neighbors (KNN), Support Vector Machines (SVMs), Artificial Neural Networks (ANNs) and Random Forest Regression (RFR), are employed to analyse the complex interactions between input variables, such as fibre type, bar diameter, concrete compressive strength, beam dimensions and the resulting shear strength. By leveraging these computational approaches, we aim to overcome the limitations of conventional analytical methods and provide robust predictions for structural design and optimisation.

Experimental Study on Shear Strengthening of Reinforced Concrete Beams by Fabric-Reinforced Cementitious Matrix.

In this study, an experiment was conducted to investigate the shear performance of reinforced concrete (RC) beams strengthened using fabric-reinforced cementitious matrices (FRCM). Four reinforced concrete beams, including a control specimen, were fabricated, and the shear strengthening effect of the FRCM was investigated on eight shear specimens, with the strengthening type and shear reinforcement as key variables. In particular, the digital image correlation (DIC) technique was applied to closely analyze the deformation of reinforced concrete beams subjected to shear forces. The average shear strain-shear stress curve of each specimen was derived, and the contributions of shear and bending to the vertical deflection and the change in the principal strain angle with increasing shear force were analyzed. The experiment results showed that all specimens failed with diagonal cracks within the shear span. In the specimens without shear reinforcement, the shear strength increased by up to 65% according to the FRCM strengthening, while in the specimens with shear reinforcement, only the sided bond strengthened specimen showed a strength increase of 16% compared to the control specimen. Based on displacement data of the DIC, it was confirmed that FRCM strengthening can control the deformation of the RC beam. To evaluate the shear strength of the FRCM-strengthened RC beams, a shear strength model was proposed by considering the contributions of the concrete section, shear reinforcement, and FRCM. The proposed model was capable of reasonably evaluating the shear strength of RC beams strengthened with FRCM, considering the shear contribution of FRCM and bond capacity between FRCM and concrete substrate, in which the shear strength of specimens was underestimated by 28% to 35%.

Flexural Behavior of Reinforced Concrete Beams with Steel-Plate Reinforced Vertical Opening

The structural response of simply supported Reinforced Concrete (RC) beams with square vertical openings is investigated in this work. Studies were conducted using seven specimens of RC beams, with the aim of comparing beams with vertical openings to those without. Meanwhile, the other beams featured carefully positioned square openings. Note that one of these beams served as the control and had no openings. Each beam was the same length (1400 mm) with a 180×120 mm cross-section. Two-point loads were applied over a span of 1200 mm throughout the testing method, with a central load placed 300 mm from the ends. The openings were positioned in the middle of the span and came in three different widths: 20, 40, and 60 mm. Openings were made using either 1.5 mm thick square steel tubing or none at all. The major goal of this study was to determine whether the steel tube could compensate for the decrease in beam strength and the impact of decreasing beam cross-section (producing opening). Correspondingly, the beam ultimate load was found to decrease by 15.75%, 24.2%, and 32.5% for opening widths of 20 mm, 40 mm, and 60 mm, respectively, as the opening width increased. On the other hand, the performance gain for beams strengthened with steel plates when steel tubes were used was 11.78%, 12.14%, and 13.28% for the respective opening widths. Doi: 10.28991/CEJ-2024-010-09-04 Full Text: PDF

Flexural Strength and Deformations Capacity of Structural Beams Reinforced with Steel Bars Milled from Recycled Metals in Ghana

Flexural Strength and Deformations Capacity of Structural Beams Reinforced with Steel Bars Milled from Recycled Metals in Ghana