Rectangular Beam Research Articles

Epoxy-Printed Circuit Board Interfacial Fracture Reliability Under Three-Point and Four-Point Bend Loading After Sustained Elevated Temperature Exposure

Abstract The survivability and reliability of commercial electronic components under very high thermo-mechanical loads are improved using underfilling and potting methods. Potting protects from operating conditions such as moisture, water, or corrosive agents. Furthermore, potting offers damping against shock and vibrations, heat dissipation, and structural support. Being one of the most cost-efficient methods, potting greatly increases reliability and therefore reduces costs for replacements and repairs. It also addresses trapped hot air issues better than other restraint technologies. In potted electronic assemblies, interfacial delamination at the epoxy and printed circuit board (PCB) interface has been one of the major failure modes. Interfacial delamination happens at the epoxy/PCB interface under dynamic shock loads, which leads to failures at the solder interconnects of the electronic components. Sustained operation and storage at elevated temperatures change the interfacial characteristics at the epoxy/PCB interface. This research is focused on interfacial failure mechanics at epoxy/PCB interfaces with high-temperature isothermal aging. In the selection of the epoxy potting material and the reliability assessments of the supplemental restraint systems, fracture parameters such as steady-state strain energy release rate stress and fracture toughness are critical. Rectangular beam specimens of the epoxy/PCB interface are fabricated for different potting compounds, and the fracture behavior is studied under quasi-static monotonic three-point and four-point bend loads. One of the main differences between three-point and four-point bend loading is that the maximum bending stress occurs at the midpoint under the point of loading of the specimen in three-point bending, whereas the peak stress is distributed over the section of the specimen between the loading points in four-point bending. Four different potting compounds with diverse properties have been studied. The recommended curing schedule from the manufacturer has been chosen and followed for all the potting compounds. The epoxy/PCB interfacial samples are aged at a high temperature of 100 °C for 30–180 days. Damage has been assumed to happen at the epoxy/PCB interface under dynamic loads. The critical load of crack initiation for the epoxy/PCB interface has been determined from the experimental findings, and it is used in the computation of fracture toughness values. The fracture toughness values are compared for the various epoxy/PCB systems based on the number of days of thermal aging and the method of flexure testing. A cohesive zone model has been constructed for predominantly mode-I delamination with four-point bend stress to predict the interfacial delamination behavior at the epoxy/PCB interfaces. It has been assumed that the bulk material is linear elastic during the bending load. The cohesive zone has been modeled at the interface, where the interfacial fracture has been assumed to occur. The fracture behavior in the simulation is predicted based on the fracture parameters determined through the experiment. The computed cohesive zone parameters are unique to the interfaces, and they can be used across various applications with the same epoxy/PCB interface to predict interfacial delamination and to select a more suitable potting material.

MODELING OF STRESS-STRAIN STATE AND STRENGTH OF DAMAGED CONCRETE BEAMS REINFORCED WITH CARBON FIBER FABRIC IN PC "LIRA-SAPR"

The study examines the problem of preserving and improving the architectural heritage in Ukraine. Many buildings and structures have a long service life or are already deteriorating due to their age and other factors. This is particularly true for reinforced concrete structures, which often have various defects and damage. Unfortunately, there are no clear methods for assessing the residual load-bearing capacity of such structures. However, the research indicates that the residual potential of damaged elements may be significantly underestimated. Therefore, it is crucial to explore and apply effective innovative solutions for strengthening these constructions. One such solution involves using composite materials (fiber-reinforced polymers, FRP) for external reinforcement of structures. Composite materials offer numerous advantages, including high strength, low weight, resistance to aggressive environments, and durability. The article presents the results of a numerical experiment aimed at investigating the influence of damage and reinforcement with carbon fiber-reinforced polymer (CFRP) on the stress-strain state and residual load-bearing capacity of concrete beams with basalt-plastic reinforcement (BFRP). For the experiment, 15 rectangular beams with dimensions of 2000×200×100 mm were prepared and nonlinearly analyzed using the "LIRA-SAPR" software, which employs the finite element method. The data obtained for each beam were compared with the results of laboratory tests, revealing that CFRP reinforcement increases the residual load-bearing capacity of the beams without significantly affecting their working deformation. Additionally, a comparative analysis was conducted on the residual load-bearing capacity and stress-strain state of the beam components: CFRP fabric, concrete, and reinforcement. The authors assert that modeling the complex stress-strain state of experimental basalt-concrete beams using nonlinear finite element calculations through the "LIRA-SAPR" software accurately reproduces experimental results, provides insight into the most likely failure mode, and reliably predicts their load-bearing capacity.

Dual-band terahertz metamaterial sensor and its sensing capacity enhanced with a central-relief design.

In this paper, a dual-band terahertz metamaterial sensor based on aluminum and silicon is proposed and simulated. The aluminum surface, which is deposited on a silicon substrate, is made of a C-shaped frame resonator, a rectangular beam, and a cross. The device is insensitive to the change of incident angle in the range of 0°-30°, which shows the great transmission stability of the sensor. By examining the resonance frequency shift, it is shown that 98.3 and 237.5GHz/RIU refractive index sensitivity can be obtained near 1.76 and 2.404THz transmission dips of the proposed structure, respectively. The two dips can be used to sense analytes in different refractive index ranges, respectively. For Dip 1 at 1.76THz, the range is 1.0-1.6. For Dip 2 at 2.404THz, the range is 1.6-2.0. Different from traditional multi-band metamaterial sensors, two dips generated by the proposed device can measure continuous and non-multiplexed refractive index ranges, respectively. Because the resonance frequencies of matters are different, such a characteristic enables the device to measure different types of analyte using the appropriate resonant peak. A central-relief design is then proposed based on perturbation theory to further improve its sensing performance. The aluminum cross is covered by polyimide, which can interfere with the scattering field on the metal surface and affect the transmission results. For both transmission dips, the optimized structure realizes higher sensitivities of 111.7GHz/RIU and 262.5GHz/RIU, respectively. More significantly, the optimized structure also has the characteristic of a wide and non-multiplexed refractive index range. In addition, the effects of analyte thickness and polyimide layer thickness on sensor performance are also discussed. The proposed structure opens up new prospects in the design of multiple-band terahertz metamaterial sensors. It can also meet the sensing needs of biomedical, environmental monitoring, and industrial manufacturing.

Mechanical properties of conventional versus microwave-polymerized denture base acrylic resins

New denture base acrylic resins have been introduced that are specifically formulated for microwave polymerization. Microwave polymerization is a time-efficient procedure, but few studies have evaluated how these new acrylic resin formulations compare with conventionally processed acrylic resins. The purpose of this in vitro study was to compare the stiffness and strength of denture base acrylic resins formulated for microwave polymerization with conventionally processed acrylic resin. Rectangular beams were fabricated from 2 microwave-polymerized denture base acrylic resins, microwave-specific resin (Nature-Cryl MC), resin with the option of microwave polymerization (Diamond D), and a conventionally processed resin as a control (Lucitone 199). Specimens (n=10) were stored in water for 1 week and subjected to a 3-point bend test to determine the flexural modulus (stiffness) and flexural strength before (initial properties) or after 120 000 load cycles. The load cycles, conducted between 5 and 25N at 2Hz, simulated 6 months of mastication. Data were analyzed by using 2-way ANOVA, followed by pairwise comparisons (α=.05). The initial flexural modulus (mean ±standard deviation) was conventionally processed resin, 2.65 ±0.33GPa; microwave-specific resin, 3.01 ±0.20GPa; and microwave-option resin, 2.63 ±0.04GPa. After load cycling, the mean flexural modulus was conventionally processed resin, 2.34 ±0.32GPa; microwave-specific resin, 2.69 ±0.20GPa; and microwave-option resin, 1.96 ±0.11GPa. The initial flexural strength was conventionally processed resin, 77.6 ±11.0MPa; microwave-specific resin, 83.6 ±3.5MPa; and microwave-option resin, 78.9 ±2.6MPa. After load cycling, the mean flexural strength was conventionally processed resin, 68.7 ±9.0MPa; microwave-specific resin, 73.3 ±3.3MPa; and microwave-option resin, 65.5 ±3.5MPa. Resin and loading state significantly affected the stiffness and strength (P<.01); the interaction resin×state was not significant (P≥.558). Microwave-polymerized denture base acrylic resins were comparable in stiffness and strength with conventionally processed acrylic resin. All acrylic resins decreased in stiffness and strength after load cycling. The microwave-specific resin was significantly stiffer and stronger than the other denture base acrylic resins, initially and after 120 000 load cycles.

Observation of maxon-like ultrasound in elastic metabeam

We observe maxon-like dispersion of ultrasonic guided waves in elastic metamaterials consisting of a rectangular beam and an array of cylindrical resonators. The pillars act as asymmetric resonators that induce a strong modal hybridization. We experimentally observe the strongly localized maxon mode with zero group velocity. Our study also demonstrates a unique feature of the maxon with a down-shifting peak frequency in space. To reveal the fundamental mechanism, we conduct comprehensive numerical studies on all frieze group symmetries and key geometric parameters.

Fracture toughness determination for epoxy-based polymer concrete mixtures: Applicability of different rectangular beam and circular disc specimens

The purpose of this study was to examine the potential impact of the testing procedure, the shape of the test sample, loading method and sample size on the KIc value of polymer concrete (PC) materials. The research involved experimental investigations using five different testing techniques and specimen types, namely the single edge notched beam (SENB), short bend beam (SBB), semi-circular bend (SCB), edge notch disc bend (ENDB), and center cracked Brazilian disc (CCBD). A typical PC mixture made of mineral silicious aggregate, ML506 epoxy resin, chopped E-glass, and foundry sand filler. Despite the difference in the shape and loading type of the tested samples, the KIc data obtained from all groups of specimens are in good agreement with together and with the SENB proposed by RILEM. Depending on the test type, the KIc value varied from 1.43 to 1.74 MPa.m0.5 and the discrepancy between the data was mainly attributed to the type of loading (compression or bending) and the crack type (center crack or edge crack). The T-stress affects the fracture toughness for different testing samples and configurations. The lowest fracture toughness corresponds to the CCBD specimen (the center cracked disc loaded diametrically). The other test samples with edge cracks and loaded by a three-point bend setup showed KIc = 1.7 - 1.74 MPa.m0.5. Moreover, the fracture toughness data for PC mixtures can be achieved by utilizing sub-sized samples like SBB (for smaller amounts of PC material) instead of larger beam samples (i.e., SENB).

Seismic flexural behavior of CFRP strengthened reinforced concrete beams secured with fiber anchors

An experimental program was conducted to examine the seismic performance of flexural beam members strengthened with carbon fiber-reinforced polymer (CFRP) sheet and anchored using carbon fiber splay anchors. This research study extends the use of carbon fiber anchors to secure the top and bottom CFRP flexural sheets under cyclic loading. In this study, low strength concrete is examined, with lightly reinforced steel ratio (0.0034) to test full-scale rectangular beams. Five reinforced concrete beams were cast, strengthened, and tested under reversed cycles of four-point bending to failure. The beams were categorized into a control specimen, strengthened specimens with thin sheets with and without fiber anchors, and strengthened specimens with thick sheets with and without fiber anchors. They were tested cyclically under displacement control according to the AC 125 loading protocol. The failure modes ranged from classical ultimate failure for the control beam to rupture and intermediate crack (IC) debonding for the beam with unanchored thin CFRP sheets. On the other hand, debonding took place for the thicker sheets with no anchors, while the thicker sheets with fiber anchors underwent cover delamination failure mode despite the fact that the sheets were extended very close to the simple supports. The hysteresis response loops were compared for the different specimens and the analytical envelop curves were predicted resulting in a close agreement to the experimental finding.

Hydrodynamic function and spring constant calibration of FluidFM micropipette cantilevers

Fluidic force microscopy (FluidFM) fuses the force sensitivity of atomic force microscopy with the manipulation capabilities of microfluidics by using microfabricated cantilevers with embedded fluidic channels. This innovation initiated new research and development directions in biology, biophysics, and material science. To acquire reliable and reproducible data, the calibration of the force sensor is crucial. Importantly, the hollow FluidFM cantilevers contain a row of parallel pillars inside a rectangular beam. The precise spring constant calibration of the internally structured cantilever is far from trivial, and existing methods generally assume simplifications that are not applicable to these special types of cantilevers. In addition, the Sader method, which is currently implemented by the FluidFM community, relies on the precise measurement of the quality factor, which renders the calibration of the spring constant sensitive to noise. In this study, the hydrodynamic function of these special types of hollow cantilevers was experimentally determined with different instruments. Based on the hydrodynamic function, a novel spring constant calibration method was adapted, which relied only on the two resonance frequencies of the cantilever, measured in air and in a liquid. Based on these results, our proposed method can be successfully used for the reliable, noise-free calibration of hollow FluidFM cantilevers.

FE Analysis on Size Effect in Torsional Behavior of Rectangular RC Beams with and Without FRP Strengthening

Although torsion is usually considered a secondary consideration in structural design, it can lead to failures, especially in structures with irregular geometry exposed to seismic forces or in unique situations. While some studies have explored the size effect on the torsional behavior of RC beams, none have addressed the impact of reinforcement. This paper investigates the size effect on the torsional behavior of RC beams with varying reinforcement ratios, including both FRP sheets and steel rebars. In this study, the torsional behavior of reinforced concrete (RC) beams with and without FRP strengthening was investigated numerically. Modeling was carried out by Finite element (FE) software ABAQUS and validated using experimental data from literature. The torsional behavior of 24 models with differences in cross-section size and reinforcement ratio were investigated. Concrete damage plasticity, Hashin damage criteria, and von Mises stress were used to investigate the damage in concrete, FRP, and steel, respectively. The cracking torsional moment, ultimate torsional moment, and torque-twist curve of the beams were evaluated and presented. The results indicated the presence of a significant size effect in the torsional strength of beams. After reinforcing the beams with FRP fabrics, the average cracking moment increased by a range of 1.72% to 36% across different groups of beams. An 8.2% increase in ultimate strength is observed with just a 0.4% rise in the FRP strengthening ratio. Post-cracking behavior was seen in 8 models with adequate steel and FRP reinforcement ratio.

The behavior of strengthened RC beams under pure torsion using NSM-CFRP rope

PurposeThe paper aims to introduces an experimental work to investigate the torsional behavior of reinforced concrete (RC) beams strengthened by near-surface mounted (NSM) carbon fiber-reinforced polymer (CFRP) ropes.Design/methodology/approachIn this research, nine rectangular RC beams of 250 mm × 300 mm cross-section and 1,600 mm in length were constructed and tested considering the studied parameters. These parameters include the length of the CFRP rope, the orientation of the CFRP rope, the arrangement of longitudinal and the scheme of NSM-CFRP ropes.FindingsIn comparison to control specimens, the results demonstrate a considerable improvement in the torsional response of RC beams strengthened with the CFRP rope. Additionally, specimens strengthened with 90° vertical ropes increase torsional moment capacity more efficiently than specimens strengthened with 45° inclined ropes since the stress concentration leads to premature debonding of the CFRP rope. Whereas RC beams' ability to withstand torsional moments is reduced as the distance between reinforcing CFRP ropes is increased. According to test results, adding CFRP ropes to RC beams' bottoms had a slightly positive impact on torsional response.Originality/valueThis paper fulfills an identified need to study how the using of the CFRP rope is effective in strengthening RC beam subjected to torsion moment.

Shear behavior of web huge rectangular opening RC beams

Abstract Opening in the web of reinforced concrete (RC) beams will destroy the integrity of the beam and weaken the mechanical properties of the RC beam, such as the bearing capacity and stiffness. The three-point loading test and finite element analysis were carried out on 10 RC beams with a huge rectangular opening in the web. The effects of stirrups around the holes on the shear properties of RC opening beams, such as bearing capacity, deformation capacity, and stirrup strain, were studied, and the shear transfer mechanism of RC beams at the openings was explained by using the strut-and-tie model. The finite element test results are consistent with the actual test results, as shown by the results. When the hole width is small, the reinforcement of stirrups at the hole side can significantly improve the shear capacity of the specimen, but it can also cause chord shear failure. When the hole height is small, with the strengthening of the chord stirrup, the ultimate bearing capacity of the specimen increases, but it can still result in hole-side shear failure. The curve of stiffness degradation is approximately logarithmic. Moreover, according to the finite element stress vector diagram, the shear transfer mechanism of the perforated beam based on the strut-and-tie model has been proved.

A Key Contribution for Concrete Durability: Harnessing Force‐Magnetic Coupling for Stress State Detection in Reinforced Concrete Beams

Over the past 20 years, more than 200 major bridge‐collapsed accidents have occurred during their service life. The durability of reinforced concrete (RC) beams is a serious threat to the safety performance of the structures. To accurately grasp the service performance of RC beams, a four‐point bending loading experiment was conducted on RC rectangular beams, and magnetic field data were detected. The results show that during four‐point bending loading, the damage modes of RC beams can be categorized into the elastic stress stage, stage of work with cracks, and yield stage. The change rule of the rebar tangential magnetic induction intensity (Bx) curves varies from overlapping each other to rotating counterclockwise, finally generating abrupt changes. The force‐magnetic coupling model is optimized based on the magnetization angle. The “force‐magnetic area parameter” Kσx is proposed to quantitatively analyze the rebar stress. Finally, the stress state assessment model of RC beam rebars is established. The relative error of the assessment results is near 6.61%. The nondestructive testing and assessment of the rebar stress state inside the RC beams are realized through the comparison and verification of the experimental phenomenon analysis and the force‐magnetic coupling model. It lays a theoretical foundation for ensuring the safe operation of bridge structures and building structures during the service life.

Shear behavior of prestressed UHPC rectangular beams: experimental investigation and limit equilibrium state-based prediction method

Shear behavior of prestressed UHPC rectangular beams: experimental investigation and limit equilibrium state-based prediction method

The Effect of Concrete Cover Thickness on the Torsional Resistance of Fibrous, High-strength, Under-reinforced Concrete Beams

This study focuses on the role of concrete cover in enhancing the torsional resistance of peak load in under-reinforced fibrous high-strength concrete beams. In this study, the primary variable that varied from 17 mm to 53 mm was the concrete cover thickness. Four rectangular solid beams were cast and tested to determine the effect of concrete cover thickness on the behaviour of under-reinforced fibrous, high strength concrete beams subjected to pure torsional loading. The test results revealed an 80.6% improvement in the torsional resistance at peak load. In addition, at maximal loads, the twisting angle, shear strain in concrete, transverse reinforcement strain, and longitudinal reinforcement strain were reduced by 70.2%, 90%, 50.6%, and 34.5%, respectively. It is therefore possible to draw the conclusion that the concrete cover has a new function, which is an improvement in torsional resistance at ultimate load that is in addition to protecting the reinforcement from corrosion.

Optimization of reinforced concrete beam using hybrid algorithms with multi-objective function as CO2 emission and cost

In this study, algorithms with two objective functions are defined considering the TS500 (2000) (Reinforced concrete structures design and construction rules) and TBDY (2018) (Turkey Building Earthquake Regulation) standards for rectangular beam design. These objective functions were determined as CO2 emission and cost. Optimizations were performed in MATLAB program using the Hybrid Algorithm of Teaching-Learning Based Optimization and Jaya Algorithm. In the case of using two objective functions, cases were created by multiplying the coefficient values found in the objective function according to the formula with the cost and CO2 emission values at different rates in order to prevent CO2 emission which is one of the biggest problems for the world. In the objective function, each rate used for CO2 and cost is implemented in a manner that increases or diminishes the impact of these values. In this way, comparisons were made between the cross-section dimensions to be formed according to not only impact rates but also the reinforcement area to be used, the CO2 emission and cost values that will arise as a result of these. Impact rates are related to cost and CO2 rate in the objective function, and the total rate is chosen as 1. Impact rates for cost are chosen as 0.1, 0.3 along with 0.5, and comparisons between the results are checked. In addition, recyclable and non-recyclable steel with different properties were used in separate analyses and the values were compared. Since the CO2 rate released by the non-recyclable steel is very high compared to the recyclable steel, the results show that the CO2 emission value is higher and this causes the objective function value to increase.

Free vibration of three-layered piezoelectric semiconductor rectangular beam

In this paper, the free vibration of a three-layered piezoelectric semiconductor (PS) rectangular beam is studied within the framework of the theory of Timoshenko beam and the theory of piezoelectric semiconductor. The perturbations of displacement, electric potential and electron concentration are given according to the theory of Timoshenko beam. By introducing the assumption of plane stress, the governing equations are integrated along the beam thickness direction, and the governing equations including motion equation, Gauss law and current continuity condition are obtained. The vibration of a simply supported three-layered piezoelectric semiconductor rectangular beam is realized by solving the governing equations. The effects of the ratio of layer thickness, length to thickness ratio, width to thickness ratio and length on the vibration of three-layered piezoelectric semiconductor rectangular beam are shown by numerical examples. The results show that there is an initial electron concentration range where the natural frequency of PS beam decreases sharply with the increase of the initial electron concentration. The damping characteristic of PS beams increases with the increase of the layer thickness ratio. For different length dimensions and length to thickness ratios, the damping characteristics of PS beams decrease with the increase of length and length to thickness ratio.

Predicting strength of non-prestressed concrete I-beams repaired/strengthened in flexure and shear using Ultra-High-Performance Concrete (UHPC)

The applications of Ultra-High-Performance Concrete (UHPC) have been growing significantly in the past two decades because of its superior mechanical and durability properties compared to those of conventional concrete (CC). Using UHPC as a repair and/or strengthening material for beams can offer several advantages, such as: ease of construction, protection against severe environment, high ductility, reduced encasement dimensions, and economy compared to existing repair materials. Limited repair cases were reported in the literature and a few experimental investigations were conducted on rectangular non-prestressed concrete beams repaired with UHPC in flexure and shear. In this paper, these cases and investigations are reviewed and new prediction models for the flexural and shear strength of composite CC-UHPC beams are developed. The paper also presents the testing of three non-prestressed I-beams in flexure: one control beam, and two beams strengthened with reinforced UHPC layer at the beam soffit. Three additional non-prestressed beams tested in shear are also presented: one control beam, and two beams strengthened with unreinforced UHPC layers at the two sides of the web. The construction procedure and structural behavior of the composite CC-UHPC beams up to failure are discussed. Test results showed that the strengthened I-beams achieved significantly higher strength in flexure and shear compared to those of the control beams. The average measured-to-predicted flexural and shear strength using the developed models were 1.08 and 1.32 respectively. In addition, no delamination or cracking was observed between the two materials up to failure indicating the adequacy of the interface shear resistance and design.

Study of Damping of Bare and Encased Steel I-Beams Using the Thermoelastic Model

Steel I-beams are a fundamental structural component in civil construction. They are one of the main load-bearing components in a building that must withstand both the structure and any incoming external perturbations, such as seismic events. To avoid damage to the structure, the building must be designed to dissipate the maximum amount of energy possible. One way energy can be dissipated is through internal or structural damping, of which thermoelasticity is one of the causes, especially in low-frequency harmonic excitations. The main goal of this study is to analyze the amount of damping in an I-beam generated by thermoelasticity and when encased in a Portland cement concrete layer, using a Finite Element model. It was found that, due to the geometry of the I-Beam, the damping coefficient as a function of frequency has two local maxima, as opposed to the traditional single maximum in rectangular beams. Encasing an I-beam in a concrete layer decreases the overall damping. While the extra coating protects the beam, the reduction in damping leads to a lower energy dissipation rate and higher vibration amplitudes.

Flexural performance of rectangular CFST composite T-beams: Experimental, numerical, and theoretical investigation

Steel-concrete composite beams find extensive application in bridge construction, offering adaptability to complex terrains and structural advantages. Nevertheless, a persistent challenge lies in local instability, especially in steel beams with large aspect ratios. This study proposes stirrup-confined concrete-filled steel tube (CFST) composite beams as a solution to enhance structural performance by mitigating local instability. The research comprises comparative tests, numerical simulations, and theoretical examinations of rectangular CFST composite beams. Results demonstrate a significant improvement, with a 40% increase in flexural stiffness and a 10% increase in ultimate bearing capacity compared to traditional composite beams. Stirrup confinement effectively limits cross-section slip between the steel tube and infilled concrete, resulting in slip measurements of 0.72 mm at the end of loading. Examination of aspect ratios reveals substantial enhancements, showing a 65.6% increase in flexural stiffness and a 54.7% increase in ultimate bearing capacity as aspect ratios increase. Concrete strength grade exhibits minor effects, with slight improvements as the grade increases. Steel yield strength significantly influences ultimate bearing capacity, with a maximum 24.4% increase in higher-strength steel. Moreover, the steel content ratio enhances both flexural stiffness (up to 40.2%) and ultimate bearing capacity (up to 34.6%) with an increased steel ratio. Increased concrete slab thickness leads to improvements of up to 18.3% in flexural stiffness and up to 10.1% in ultimate bearing capacity. Formulas for predicting the flexural stiffness and bearing capacity of rectangular CFST composite T-beams are developed, offering practical guidance for optimizing their performance in structural engineering applications.

Advancing Shear Capacity Estimation in Rectangular RC Beams: A Cutting-Edge Artificial Intelligence Approach for Assessing the Contribution of FRP

Shear strength prediction in FRP-bonded reinforced concrete beams is crucial for ensuring structural integrity and safety. In this extensive investigation, advanced machine learning algorithms are harnessed to achieve precise shear strength predictions for rectangular RC beams reinforced with FRP sheets. The aim of this research is to enhance the accuracy and reliability of shear strength estimation, providing valuable insights for the design and assessment of FRP-strengthened structures. The primary contributions of this study lie in the meticulous comparison of various machine learning algorithms, including Xgboost, Gradient Boosting, Random Forest, AdaBoost, K-nearest neighbors, and ElasticNet. Through comprehensive evaluation based on predictive performance, the most suitable model for accurately estimating the shear strength of FRP-reinforced rectangular RC beams is identified. Notably, Xgboost emerges as the superior performer, boasting an impressive R2 value of 0.901. It outperforms other algorithms and demonstrates the lowest RMSE, MAE, and MAPE values, establishing itself as the most accurate and reliable predictor. Furthermore, a sensitivity analysis is conducted using artificial neural networks to assess the influence of input variables. This additional research facet sheds light on the critical factors shaping shear strength outcomes. The study, as a whole, represents a substantial contribution to advancing the development of accurate and dependable prediction models. The practical implications of this work are far-reaching, particularly for engineering applications in the realm of structures reinforced with FRP. The findings have the potential to transform the approach to the design and assessment of such structures, elevating safety, efficiency, and performance to new heights.