Flexural Deflection Research Articles

Functionally graded IWP reinforced cementitious composites: Design, fabrication, and the enhanced ductility

The Schoen I-graph-wrapped package (IWP) structures have many promising applications for their high specific mechanical properties. In this work, functionally graded IWP (FG-IWP) architectures were developed and constructed to enhance the ductility of the produced cementitious composites. The FG-IWP architectures were designed using two grading strategies: relative-density-based and cell-size-based. The flexural test was used to investigate the mechanical behavior of the proposed composites, including flexural strength and deflections. The failure patterns and strain distributions of the specimens were measured using the Digital image correlation (DIC) approach. The results reveal that the designed IWP architectures noticeably improve the flexural strength and ductility of the composites. Comparing the FG-IWP to the uniformly configured IWP architectures, the grading strategies exhibit an increased ductility. Furthermore, the two grading strategies have different effects on ductility improvement. Cell size gradient strategy yields greater enhancement in flexural strength, whereas relative density strategy leads to better enhancement in ductility. The variations of cell size and relative density parameter ranges also result in distinct improvement on mechanical properties. Overall, the outcomes of this study present an FG-IWP-based novel approach for improving the ductility of cementitious materials.

Polypropylene Fiber Effect on Flexural Strength, Toughness, Deflection, Failure Mode and Microanalysis of Cementitious Backfills under Three-Point Bending Conditions

Cemented tailings backfill (CTB) is continually practiced in a large number of metallic mines for re-filling underground ore extraction areas. Re-filling these areas can boost the security of mining teams during construction. Hence, CTB’s durability/ductility is extremely vital to ensure the safety of the entire mine. In this study, layered-fiber-reinforced CTB (LFR-CTB) was manufactured using polypropylene fiber (PPF) to increase the strength and flexibility of backfilling. The strength and bending features of CTB and LFR-CTB specimens were explored through a three-point bending test and SEM microanalysis. Test findings pointed out that the flexural strength of 14-day-cured CTB specimens without fiber delamination and with cement showed that a tailings ratio of 1:4 was the largest among others. Residual flexural strength of LFR-CTB was greater than those of CTB without fiber delamination. Accumulating fiber delamination effectively improved CTB’s flexural features. CTBs without fiber delamination presented the largest average flexural modulus values. LFR-CTBs presented greater average toughness index values than ordinary CTB specimens. Adding fiber facilitated the progress of CTB’s post-peak rigidity. LFR-CTBs containing high-fiber delamination dimensional height have excellent bending properties. The damage mode of all backfill specimens is chiefly tensile damage. The overall bonding of LFR-CTB specimens in the presence of interlayer interfaces is outstanding, not affecting their bending performance. Ettringite and CSH gels were found to be key hydration materials. The addition of fiber to the filling has an inhibitory impact on the extension of the cracks occurring within specimens. Finally, this study’s key consequence is to deliver a technical guideline and reference in order to reveal LFR-CTB’s enhancement and delamination mechanism for industrial applications.

Comparative Study of and Voided Slab System and Conventional RCC Slab

This paper presents the flexural capacities of R.C.two-way hollow flat slabs with plastic voids. Recently, various types of slab systems which can reduce the self-weight of slabs have been studied as the height and span of building structures rapidly increase. To verify the flexural behaviour of this voided slab such as flexural stiffness, ultimate load, deflection, stresses and concrete compressive strain were studied.FEM model was created in ANSYS workbench 2022 for both conventional solid flat slab and voided slab. U-Boot beton from “daliform group building innovation Italy” was used as void former in this study. The dimensions of U-boot is 520×520mm and with 180mm and 160mm height. Dimension of FEM slab model is 8500×8500 mm with 500×500 column support at all four corners. Three different slab of 280mm, 300mm and 320mm was created. In addition, manual analysis of solid slab and voided slab was carried out using direct design method as per IS-456(2000). And further, design is checked to verify that it satisfies all design and serviceability criteria given as per IS-456(2000).Results obtain via theoretical calculation and FEM model simulation for both solid and voided slab were compared. The aim of this paper is to discuss and compare flexure behaviour of solid slab and voided slab and to study changes in inertia, stiffness and reduction in weight, of the slab by void formation.

Comparative Study in Design of Fiber-Reinforced Concrete at Elevated Temperatures by Numerical Evaluation through Developed Hybrid Metaheuristic Algorithms

Fibrous concrete has good properties such as high ductility, high strength, suitable energy absorption and cracking resistance, which can be useful in many applications. This type of concrete is one of the best materials used in the construction of impact-resistant masonries, such as burial masonry structures, and explosive masonry warehouses. In this study, an artificial intelligence assessment based on the experimental test data from a laboratory has been performed on the fibrous concrete to evaluate the behavior of the samples at elevated temperatures and determine the most governing parameter on the mechanical properties of the fibrous concrete at elevated temperatures. For the first time, a hybrid intelligence algorithm has been developed based on the neural network structure using both genetic and swarm optimization algorithms. The ANFIS-PSO-GA (APG) algorithm was trained with experimental data and evaluated the flexural load and deflection of the samples. In order to detect the most prominent feature in the fire resistance of the fibrous concrete, five different subdatasets were designed. The results of the APG algorithm have been challenged with the ANFIS-PSO algorithm, which is a well-known hybrid numerical evaluation algorithm. As per the results, the newly designed APG algorithm has been successfully performed on both deflection and flexural prediction phases. Based on the numerical achievements, fiber features such as the fiber content and fiber mechanical properties are governing factors on the fibrous concrete resistance at elevated temperatures.

Mechanical properties of geopolymer-based ultra-high performance concrete with ceramic ball coarse aggregates

This research reported the mechanical properties of geopolymer-based ultra-high performance concrete containing ceramic ball coarse aggregates. 10 mm straight steel fibres with various contents (0, 0.6 vol-%, 1.2 vol-% and 1.8 vol-%), medium-aluminium ceramic balls with various sizes (3 mm, 6 mm and 10 mm) and contents (0, 10 vol-%, 20 vol-% and 30 vol-%) were utilised. Mechanical properties, including the slump flow, uniaxial compressive, splitting tensile and flexural strengths, were investigated via a series of material tests. Fundamental contributions arisen from the steel fibre content, ceramic ball size and content towards the mechanical properties were analysed and discussed. In the light of the flexural load-midspan deflection curves, a constitutive flexural model was established, and the flexural toughness characteristics were quantitatively assessed using two indexes. Also, empirical equations to evaluate the strength relationships were proposed. Scanning electron microscope observation was carried out on the steel fibre-matrix interface to further explain the influencing mechanism of ceramic balls on the fibre reinforcement efficiency.

Flexural strengthening of reinforced concrete beams using textile-reinforced mortar improved with short PVA fibers

Textile-reinforced mortar (TRM) composites were developed to avoid the problems caused by fiber-reinforced polymer (FRP) composites. Furthermore, short and dispersible polyvinyl alcohol (PVA) fibers were applied in TRM matrix to improve the brittle behavior and limit the crack width of TRM composites. In this study, eight reinforced concrete (RC) beams, including two reference beams and six strengthened beams, were designed to investigate the flexural behaviors of RC beams strengthened with PVA fibers-improved TRM composites. The investigation variables were (i) the longitudinal steel bar ratio, (ii) the carbon textile reinforcement ratio, and (iii) the sustaining load level. The test results indicated that (1) TRM composites could effectively limit the crack width of RC beams, and multi-crack behavior was observed in the strengthening overlay. (2) The flexural capacity of strengthened beams was enhanced as the number of textile layers increased. This enhancement came with a decrease in deformation, energy absorption, and ductility to some extent depending on the failure modes. (3) For strengthened RC beams with the sustaining load of 60kN and 96kN, the yield load was decreased by 8% and 16% respectively compared with the strengthened beam without the sustaining load. The enhancement efficiency in yield load was reduced as the sustaining load level increased. However, an acceptable reduction in ductility was obtained. Finally, based on the plane section assumption, an analytical mode was proposed to calculate the flexural capacity and deflection of RC beams strengthened with TRM composites.

Flexural Strength and Modulus of Elasticity of Concrete Beam Cast with Binary Blending of Recycled Concrete Aggregate and Marble Dust

This research paper presents the combined effect of recycled coarse aggregates and marble dust on the flexural strength and modulus of elasticity of concrete. Use of the waste materials in concrete leads to sustainable development; and is the need of the day. Recycled aggregates were processed from demolishing waste and ensured by sieve analysis for well-graded concrete. Marble dust was used as cement replacement from 2.5% to 10% in increments of 2.5%. Recycled aggregates were used in equal dosage with conventional aggregates. A total of five batches of beams and cubes were cast using normal mix concrete. The curing of the specimens was done for 28 days. Ultrasonic pulse velocity testing was done to evaluate the modulus of elasticity. The same was also evaluated using an empirical equation of ACI and from the literature. A comparison of the results shows that both UPV testing and numerical equation by ACI can comfortably be used for evaluation of the modulus of elasticity of recycled aggregate concrete. Beams were tested under central point load for flexure. Comparison of flexural strength and deflection with control concrete shows that a 5% dosage of marble dust as cement replacement along with 50% replacement of conventional coarse aggregates with coarse aggregates from demolishing waste is optimum as with this replacement level residual flexural strength is 88% and the deflection is only 5% more than control concrete and less compared to the maximum approximate deflection allowed by ACI-31.

Mechanics and properties of fish fin rays in nonlinear regimes of large deformations

Fins from ray-finned fishes do not contain muscles, yet fish can change the shape of their fins with high precision and speed, while producing large hydrodynamic forces without collapsing. This remarkable performance has been intriguing researchers for decades, but experiments have so far focused on homogenized properties, and models were developed only for small deformations and small rotations. Here we present fully instrumented micromechanical tests on individual rays from Rainbow trout in both morphing and flexural deflection mode and at large deflections. We then present a nonlinear mechanical model of the ray that captures the key structural elements controlling the mechanical behavior of rays under large deformations, which we successfully fit onto the experiments for property identification. We found that the flexural stiffness of the mineralized layers in the rays (hemitrichs) is 5-6 times lower than their axial stiffness, an advantageous combination to produce stiff morphing. In addition, the collagenous core region can be modeled with spring elements which are 3-4 orders of magnitude more compliant than the hemitrichs. This fibrillar structure provides negligible resistance to shearing from the initial position, but it prevents buckling and collapse of the structure at large deformations. These insights from the experiments and nonlinear models can serve as new guidelines for the design of efficient bioinspired stiff morphing materials and structures at large deformations. Statement of significanceFins from ray-finned fishes do not contain muscles, yet fish can change the shape of their fins with high precision and speed, while producing large hydrodynamic forces without collapsing. Experiments have so far focused on homogenized properties, and models were developed only for small deformations and small rotations providing limited insight into the rich nonlinear mechanics of natural rays. We present micromechanical tests in both morphing and flexural deflection mode on individual rays, a nonlinear model of the ray that captures the mechanical behavior of rays under large deformations and combine microCT measurements to generate new insights into the nonlinear mechanics of rays. These insights can serve as new guidelines for the design of efficient bioinspired stiff morphing materials and structures at large deformations.

Flexural performance of concrete composite metal decking with different base-metal-thickness new smart system

Industrial Revolution 4.0 has led to the age of automation and industrialized building systems. Composite slabs gain its popularity in the modern construction industry due to its speed of construction and cost saving features with lightweight structure. However, from time to time the manufacturer will introduce new corrugated roll forming cold formed steel metal decking systems, which cause the end user to ponder if the product is up to desired performances. The aim of this research is to study the structural performance of SMARTDEK composite slab composed of 0.75 mm and 1.0 mm thickness compared to the conventional reinforced concrete slab under flexural strength, deflection, and failure mode. Concrete slab with thickness of 130 mm was constructed to uncover the ultimate load capacity of the slabs. The novelty of this research is the discovery of longitudinal shear resistance constant through derived equations and the new SMARTDEK profiled composite slab performs better than the conventional slab. Four-point flexural tests were conducted according to ASTM C293 standards to determine the performance of the slabs, and three linear variable displacement transducers (LVDTs) were used to determine the deflection of the slabs. Load-Deflection graphs were plotted for the specimens to determine the yielding point and ultimate point of the slabs. The composite slab with 1.0 mm Base-Metal-Thickness (BMT) had the highest ultimate strength at 75 kN, followed by the composite slab with 0.75 mm BMT at 65 kN, and finally the conventional slab at 39 kN. The failure mode of the conventional slab was pure flexural; while the composite slab first failed in flexural, followed by longitudinal slip failure due to flexural and flexural-shear cracks, which disabled the composite action between the concrete slab and metal decking. The finding showed that the increasing thickness of the metal decking improves the slab strength which results in higher ultimate strength and reduces the overall deflection of the slab. Moreover, the breakthrough of this research is that increasing the overall thickness of the slabs increases the performance in loading’s capacity which could result in higher ultimate strength.

Flexural strength and drift ratio of reinforced concrete beams with longitudinal square hole

The main aim of this investigation was to study the flexural strength and drift ratio of simply supported rectangular RC hollow beams (with a longitudinal square hole) subjected to gradually increased and symmetrically applied one-point load. Each hollow beam had a 300 mm2 and 900 mm2-area of a square, and the position of the center of the hole was 80 mm from the top. The cross-section of the beam, the amount of longitudinal steel, and the stirrups of the beam was kept constant. The flexural strength and deflection of these hollow beams were compared with that of a solid RC beam that had the same outer dimensions and steel reinforcements. A comparison of experimental results shows that specimens with square holes 10 x 30 achieve higher peak load, MOE, and MOR. On other hands, solid beam specimens achieve a larger drift ratio.

Effects of inertia on the time-averaged propulsive performance of a pitching and heaving foil

The inertia may play an important role in the unsteady behavior of a flapping foil. Of particular relevance in forward flapping locomotion is how the foil inertia may affect its time-averaged propulsive performance. This is the question addressed by the present study from a general, nonlinear formulation of the unsteady interaction with the surrounding fluid of a thin, flexible, two-dimensional and non-uniform foil undergoing prescribed pitching and heaving motion of any amplitude about an arbitrary pivot axis. For a rigid foil it is shown that, although the unsteady inertial forces and moments may be much larger than the unsteady aerodynamic forces and moments if the fluid density is much smaller than the foil density, the inertia does not affect the cycle-averaged propulsive performance for harmonic pitching and heaving motion, independently of their amplitude. Inertia may affect only the cycle-averaged moment if the mean angle of attack is not zero, but without affecting the cycle-averaged power input, and therefore the propulsive efficiency. When a small flexural deflection of the foil is considered, although the cycle-averaged inertial thrust and lift also vanish for any amplitude of the pitching and heaving harmonic motion, the cycle-averaged power input does not. Thus, the foil inertia contributes through the moment and power to the time-averaged propulsive performance for any flexural deflection of the foil, obtained her e analytically in terms of the trailing edge location for general pitching and heaving motion of any amplitude and phase and small flexural deflection amplitude. Simple analytical results are also provided for inertia dominated deflection, characterizing the conditions that minimize the power consumption. The results are valid for arbitrary chord-wise distribution of mass, thickness and (sufficiently large) stiffness of the foil.

Effect of Fire on Reinforced Concrete Beams with FRP and Conventional Steel at Limited Time of Fire

Abstract The aim of this study is to investigate the behavior of RC concrete beams reinforced with basalt, carbon, glass fiber reinforced polymer bars and conventional steel. A comparison between the results has been performed to investigate and study the effect of fire on reinforced concrete beams considering the following items: (flexural capacity, deflection behavior and crack pattern). It is noticeable that the use of FRP bars significantly increased the ultimate load of the specimens, where the percentage of increase ranged between 34 - 73 % of the ultimate load of the specimen C-S under static load. The greatest ultimate load was reached the beam that was reinforced with carbon bars (CFRP). It was also noticed able that the use of FRP rods significantly increases the deflection of the beams. The percentage of increase was between 45 - 170 % of the final deflection of the C-S specimen under static load. It was noted that the effect of the fire on the beams reinforced with fiber bars (FRP), where the efficiency of bearing capacity of beams after fire decreases by 11 to 18 % of the actual efficiency of bearing capacity of beams control. As for the beam reinforced with conventional steel bars, its efficiency was reduced by 15 % from the actual capacity.

Multi-Objective Optimization of Epoxy Resin Adhesive for Pavement Toughened by Self-Made Toughening Agent.

Epoxy resin adhesive for pavement is often insufficient in flexibility and toughness. Therefore, a new type of toughening agent was prepared to overcome this shortcoming. To achieve the best toughening effect of a self-made toughening agent on an epoxy resin adhesive, its ratio to the epoxy resin needs to be optimally selected. A curing agent, a toughening agent, and an accelerator dosage were chosen as independent variables. The epoxy resin's adhesive tensile strength, elongation at break, flexural strength, and flexural deflection were used as response values to establish a single-objective prediction model of epoxy resin mechanical property indexes. Response surface methodology (RSM) was used to determine the single-objective optimal ratio and analyze the effect of factor interaction on epoxy resin adhesive's performance indexes. Based on principal component analysis (PCA), multi-objective optimization was performed using gray relational analysis (GRA) to construct a second-order regression prediction model between the ratio and gray relational grade (GRG) to determine the optimal ratio and to validate it. The results showed that the multi-objective optimization using response surface methodology and gray relational analysis (RSM-GRA) was more effective than the single-objective optimization model. The optimal ratio of epoxy resin adhesive was 100 parts of epoxy resin, 160.7 parts curing agent, 16.1 parts toughening agent, and 3.0 parts accelerator. The measured tensile strength was 10.75 MPa, elongation at break was 23.54%, the bending strength was 6.16 MPa, and the bending deflection was 7.15 mm. RSM-GRA has excellent accuracy for epoxy resin adhesive ratio optimization and can provide a reference for the epoxy resin system ratio optimization design of complex components.

Use of high ductile mortar mixing method for the enhancement of flexural fracture behaviour of steel filler mortar

The use of steel fillers enhances the flexural behaviour of mortar and concrete. However, it makes it more difficult to disperse them uniformly and coat them firmly in the mortar/concrete with the conventional mixing method while using them at higher content. In this method, steel fillers are generally mixed after the mixing of mortar with a full part of water. In the high ductile mortar mixing method, the viscous mortar was first prepared with the first part of the water and then the steel fillers were mixed. Its workability was increased in the final stage of mixing with the second part of the water. The mixture proportion of the base mortar was similar to that used for the production of the permanent formwork (W/C = 30% and W = 206 kg/m3). The content of steel filler (0, 1.5%, and 2.5%) was by volume of the mortar and it was used as part of the sand. The distribution and coating condition of steel filler was better in the second mixing method. It was made possible due to the strong kneading and lapping action within the viscous mortar. The flexural strength was increased by 28.7% with less variation. It was a 241% increase from that of plain mortar and only a 165% increase was with the conventional mixing method. The high ductile mortar mixing method enhanced the flexural strength, deflection, rigidity, flexural performance, and fracture energy of steel filler mortar more than that of the conventional mixing method. This result contributes to reducing the thickness of permanent steel filler mortar formwork as well as of other structures enabling easier transportation and erection work. Moreover, it also helps to reduce the overall cost of the steel filler mortar structures.

Flexural toughness and its evaluation method of ultra-high performance concrete cured at room temperature

This study investigates the effects of water-binder ratio and steel fiber content on the flexural response characteristics of UHPC cured at room temperature by four-point bending tests. These flexural properties include load-deflection curve, flexural strength, initial cracking strength and flexural toughness. Based on the review of existing evaluation methods about flexural toughness, a deflection offset method that can quantitatively determine the initial crack point of UHPC in bending tests is proposed, and the optimized evaluation indicators of UHPC flexural toughness are further established from the perspective of equivalent strength. The proposed method with clear physical meaning and strong applicability can be used to evaluate the flexural toughness of UHPC cured at room temperature during the whole loading process. The results indicate that: (1) The flexural strength and deflection decrease as the water-binder ratio increases from 0.14 to 0.20, in which the decrease of peak deflection is the most significant (56.95%). (2) Although the flexural strength increases linearly with the increase of steel fiber content, the peak deflection increases slowly when the fiber content exceeds 1.0%. (3) The strength and deflection corresponding to the initial cracking point are about 2/3 of the flexural strength and 1/3 of the peak deflection respectively. (4) The flexural toughness decreases with the increasing water-binder ratio, especially when the water-binder ratio exceeds 0.18. (5) The flexural toughness of UHPC increases and the toughening effect of fiber first increases and then decreases with the increase of steel fiber content, and UHPC mixed with 1.5% steel fiber achieves the most remarkable toughening effect. Therefore, the superior flexural toughness and load-bearing capacity of UHPC cured at room temperature are highlighted when the water-binder ratio is less than 0.18 and the steel fiber content exceeds 1.0%.

Pattern and filament optimization for 3D-printed reinforcements to enhance the flexural behavior of cement-based composites

Cement-based materials are the world's most widely utilized construction materials due to their high compressive strength. However, they need reinforcement to withstand direct or indirect tensile forces. This study evaluated the potential use of 3D-printed polymers as an alternative reinforcement in cement-based composites. Polyethylene terephthalate glycol (PETG), Polyamide (PA), and Acrylonitrile butadiene styrene (ABS) based triangular and honeycomb-patterned 3D-printed reinforcements were incorporated into cement-based composites, and their mechanical performances were compared under three-point flexural tests by considering both polymer and pattern type. Both triangular and honeycomb patterns enhanced flexural behavior. Considering all filaments, the honeycomb pattern was found more effective than the triangular one for increasing flexural strength, deflection capacity, and toughness up to 46.80%, 251.85%, and 77.66%, respectively. In the case of filament type, 3D-printed PA-type filament in a honeycomb pattern preserved flexural strength, enhanced deflection capacity, and increased flexural toughness with pseudo-deflection hardening behavior. 3D-printed honeycomb patterned reinforcements produced by PA have the opportunity to be used in the manufacture of cement-based composites.

Serviceability behaviour of FRP-reinforced slatted slabs made of high-content recycled aggregate concrete

At service load levels, shear-induced deflections of reinforced concrete (RC) slabs are small and therefore they are usually ignored in deflection calculations. However, shear-induced deflections can be large in RC slabs reinforced with Fibre Reinforced Polymer (FRP) bars, especially after the development of diagonal cracks. This article investigates the serviceability behaviour (deflections and crack widths) of FRP-reinforced slatted slabs cast with recycled aggregate concrete (RAC). Fifteen slabs were tested in flexure, including five slabs cast with normal concrete (NC), five slabs cast with RAC made with 50% recycled concrete aggregate, and five slabs cast with RAC made with 100% recycled concrete aggregate. The test results are compared to crack widths and deflection predictions given by current guidelines and Nonlinear Finite Element Analysis (FEA). The results show that, for the tested slabs with 100% recycled concrete aggregates, the predictions given by ACI 440.1R underestimate the experimental deflections by up to 30% at maximum load levels. Conversely, the sum of the flexural deflections given by Eurocode 2 and of the shear crack-induced deflections (calculated using a model proposed recently by the authors) match better the experimental deflections at both the onset of diagonal shear cracking load, and at the maximum load. The Concrete Damage Plasticity (CDP) model adopted in the FEA was found suitable to predict accurately the deformations of FRP RAC slabs. This study contributes towards the development of new more sustainable structural solutions for FRP RAC elements, as well as towards more accurate models to calculate their deflections.

Flexural strength and toughness of self-leveling UHPFRC

Acquiring higher performance at both fresh and hardened states is critical in the practical design of ultra-high performance concrete (UHPC)/ultra-high performance fiber reinforced concrete (UHPFRC). Herein, a total of 12 self-leveling UHPC and UHPFRC mixtures were developed and evaluated for their flexural performance by three-point bending tests, together with their workability and mechanical properties. From load-deflection curves, the first cracking flexural strength, post cracking flexural strength, flexural deflection capacity, and flexural toughness were determined. By corelating the flexural responses to fiber factor and matrix strength, the flexural strengths were found to be positively affected by fiber factor and matrix strength, while the flexural deflection capacity and toughness indices were less influenced by matrix strength but can be substantially enhanced by increasing steel fiber volume. Design equations were derived by physics-informed data-fitting for flexural strengths and toughness with high accuracy, allowing for quantification of synergistic effect between fiber factor and matrix strength in resilient design.

A parametric study on shear deflection performance of open web steel joist

This paper focuses on doing a parametric analysis to ascertain the shear deflection of an open web steel joist under non-uniform bending utilizing theoretical and numerical studies. The goal of this work is to determine the significance of taking shear deflection into account when dealing with open web steel joists as well as how it interacts with changes in beam parameter variations. Using ABAQUS software, a total of forty finite element models were created. The differences between these models may be seen in the flange and web slenderness ratios, which are derived from the three standard steel design codes. Theoretical shear deflection was calculated using Timoshenko and Gere's equations, and flexural deflection for the point load case was calculated using conventional formulae. Since theoretical equations up to the elastic limit are known, the elastic behaviour of the joists is the focus of the whole research. The result compares the load to the maximum elastic deflection obtained by theoretical and finite element analysis and demonstrates strong collaboration, validating the numerical investigation. Additionally, a plot of load versus deflections was made for fewer models, with and without taking into account shear deflection, demonstrating the significance of this factor. Finally, the variance in shear deflection was shown by plotting the total elastic deflections versus the load for all the models with various values. The study's findings suggest that it is significant to take the impact of shear and determine the shear deflection in the case of structural components such open web steel joists. The analysis further reveals that an open web steel joist's shear deflection is greatly impacted by the parametric variation.

A statistical approach to predict fatigue failure of leaf springs manufactured with nanotube incorporated epoxy‐woven glass fiber composites

AbstractIn this study, a statistical approach was developed to predict fatigue failure of laminated composite leaf springs prepared with carbon nanotube (CNT) filled epoxy/woven glass fibers. Electrical resistance change method and the Weibull analysis were adopted to develop a statistical approach. The electrical conductivity for successful application of health monitoring of leaf springs was achieved by dispersing 0.4 wt% of CNTs into epoxy resin. In‐situ monitoring of damage in composite leaf springs during fatigue tests applied as cyclic flexural deflection was carried out at nine different displacement ratios. The critical fatigue cycle and the corresponding change in electrical resistance were determined at each displacement ratio. Then, the critical electrical resistance change to cyclic fatigue was found 0.15% with 95% reliability by the Weibull analysis. The average fatigue life and the average strength loss corresponding to the 0.15% resistance change ratio were found to be 48.33% and 9.88%, respectively. The reported statistical concept based on the monitoring of change in electrical resistance during deflection can be successfully employed as a useful tool to predict safety limits of composite structures subjected to fatigue loading, especially in aerospace industry.