Linear Elastic Finite Element Analysis Research Articles

Numerical analysis of fixed-end hollow rectangular beam under uniformly distributed load

The purpose of using opening in the reinforced concrete (RC) rectangular beam is the reduction of self-weight, cost, displacement, and strain. Therefore, this research performs linear elastic finite element analysis by using ETABS for fixed-ended RC hollow and solid rectangular beams under uniformly distributed loadings with variable beam lengths, compressive strengths, and opening sizes.The solid and hollow beams are considered to be a 2-nodded line element for the numerical analysis. The maximum range of validation result in case of hollow beam is found to be (3.9 to 7.9) %, which may indicate good accuracy of numerical analysis. The 50 × 50 mm opening size is suitable for 300 × 300 mm RC rectangular beam because of showing the positive normalized deflection of (0–1.45) % and lower strain rates (i.e. 0.13 % and 0.17 %) to compare the solid beam. This research may help professional engineers to use suitable opening size for design and construction works. Although, there is a scope to enhance this research in future by performing nonlinear analysis.

Finite element analysis of macro-crack behavior in the cortical bone of a human tibia

The bone is a biological tissue that possesses a highly complicated hierarchical structure; hence, the tissue components of the bone exhibit variable mechanical proper-ties and a complex bone geometry. This is why the creation of a three-dimensional mod-el through CAD software facilitates the study of the mechanical behavior of bones. Com-bining the concepts of linear elastic fracture mechanics and finite element analysis pro-vides a practical solution to study the fracture behavior of the tibial bone. The objective of this study is to analyze the behavior of cracks in the cortical bone of the human tibia us-ing stress intensity factors in mode I, II, and III as rupture criteria to assess the bone damage response. The tibial bone is one of the most common sites for lower limb stress fractures, which pose problematic injuries. The results investigating the effect of the crack position in the bone demonstrate that the risk of crack propagation is mainly due to mode I opening and is highly favored in the distal zone compared to the middle and proximal regions, regardless of bone density. For the second case study, it is observed that regardless of the crack size, the maximum values of stress intensity factors KI are obtained in the distal zone. Regarding the effect of crack orientation, the results indicate the dominance of mode II for angles α = – 45°, 30°, 45°, leading to high values of stress intensity factors KII.

Parametric Analysis of Moment-Resisting Timber Frames Combined with Cross Laminated Timber Walls and Prediction Models Using Nonlinear Regression and Artificial Neural Networks

The light weight and moderate stiffness of multistorey timber buildings make them susceptible to increased lateral displacements and accelerations under service-level wind loading. Therefore, the fulfilment of serviceability requirements is a major challenge. In this study, linear elastic finite element analysis was used to perform a parametric study of moment-resisting timber frames combined with cross laminated timber walls. In the parametric study, various mechanical and geometrical parameters were varied within practical ranges. The results of the parametric study were used to derive simplified analytical expressions and to train artificial neural networks which can be used to estimate fundamental frequency, mode shape, top floor displacement, maximum inter-storey drift, and wind-induced acceleration. The analytical expressions and the artificial neural networks can be used for the preliminary assessment of serviceability performance of moment-resisting timber frames with and without cross laminated timber walls, under service-level wind loading.

Study on the applicability of a modified strain approach to predict the fatigue life of HFMI-treated transverse stiffeners under variable amplitude loading

AbstractThis paper analyses the applicability of a modified strain approach to predict the fatigue life of HFMI-treated transverse stiffeners under variable amplitude loading (VAL) with random load sequences of a p(1/3) and linear shaped spectrum. Local stresses are determined using linear-elastic finite element analyses. The measured weld geometry and component imperfections are considered. From the hardness of the HFMI-treated zone and the base material, the elastic–plastic material behaviour and Coffin-Manson parameters to describe the damage parameter Woehler curve are estimated. Based on a hysteresis counting method (HCM), the damage for each closed hysteresis is calculated. The applied notch strain approach includes the impact of residual stresses and the influence of surface roughness. Thus far, the application of similar approaches has only been validated for welded components with comparatively low residual stresses and HFMI-treated welds subjected to constant amplitude loading. To validate the accuracy of the approach for HFMI-treated welds under variable amplitude loading, the approximated fatigue life is compared to the number of cycles derived from experimental investigations. In this study, it is shown in conjunction with experimental results that it is essential to consider the strength of the base material near the weld when assessing the service life. This area can be more critical than the HFMI-treated weld toe.

Study on Nanomaterials Coated Natural Coir Fibers as Crack Arrestor in Cement Composite

The process of inclusion of carbon nanotubes as fibers in cement paste has been proved to have optimistic effect as it enhances the tensile property of cement paste composite. Coir fibers have exceptional mechanical qualities and are thus employed as reinforcement in cement composites. Epoxy resin, which has a high Young’s modulus, is an ideal component for bonding carbon nanotubes (CNTs) to coir fiber. This paper describes a novel kind of nanocomposite made of L-12 epoxy resin and CNTs at the nanolevel, along with coir fibers at the microlevel which operate as crack arrestors. To remove surface contaminants, coir fibers are first treated with sodium hydroxide (NaOH). Epoxy/CNTs polymer coatings were developed at varying CNTs fractions (0.05, 0.1, 0.15, and 0.2 wt.% of cement). Multiwalled CNTs were combined in distilled water, followed by epoxy resin and hardener (9 : 1 v/v) polymer in an ultrasonic sonicator for 90 min to ensure full dispersion of CNTs within the epoxy polymer. This blend is now coated on the treated clustered coir fiber (length 10 cm, 10 strands) and reinforced along the length of a cement composite beam 20 mm × 20 mm × 80 mm in size. Tensile and three-point tests were performed to evaluate the mechanical characteristics of the hybrid composite. The linear elastic finite element analysis is employed to distinguish their failure phenomena via fatigue or fracture behavior. The microstructure behavior and the effect of coating material on the coir fibers were investigated using scanning electron microscope and EDX analysis. The reinforcing impact of nanopolymer coated coir fiber in cement composite diminished the tensile and flexural strength after 0.1 wt.% of CNT fraction but increased the composite’s durability and Young’s modulus. Fourier transform infrared spectroscopy analysis was carried out to assess the chemical interaction between the epoxy/CNTs and the coir fibers. The simulation was performed using ANSYS workbench, and the modeling results were within an acceptable 10% range of the experimental data. Nevertheless, it can be concluded that the hybrid composite is capable of enhancing the composite’s stress and strain capacity by regulating the fracture propagation process at the crack’s end.

Structural Performance of Large-Scale 3D-Printed Walls Subjected to Axial Compression Load

Despite the growing incorporation of additive manufacturing in the construction industry, a significant gap persists in the availability of design guidelines and comprehensive structural assessments for 3D-printed components. This research employs experimental methods to evaluate the performance of large-scale hollow unreinforced 3D-printed masonry walls under axial compressive load. Furthermore, a design methodology tailored for 3D-printed masonry walls under compressive loads is proposed in compliance with both American and Canadian masonry standards. This methodology is supported by the application of linear elastic 3D finite element analysis. Moreover, supplementary insights into material behavior are garnered through the examination of small specimens extracted from an additional 3D-printed wall. The results reveal that 3D printing reduces stiffness and compressive strength. The 3D-printed infills played an important role in redistributing stress after cracking. All full-scale 3D-printed masonry walls examined in this research exceeded the performance criteria set by the American masonry standard for load-bearing walls.

Using the Point Method to estimate failure loads in 3D printed graphene-reinforced PLA notched plates

This work estimates failure loads in Fused Filament Fabrication (FFF) printed graphene-reinforced PLA (polylactic acid) plates containing different types of stress risers. With this aim, firstly, several notched plates are tested and conducted to fracture. Then, linear elastic Finite Element (FE) analyses are completed to define the corresponding stress profiles and, finally, the Point Method (PM) is applied to establish the failure criterion. This approach asserts that fracture conditions are achieved when the stress level equates the inherent strength (σ0) at a distance from the notch tip equal to L/2, so both parameters (related to each other through the material fracture toughness, Kmat) have been defined beforehand. The estimations of fracture loads obtained following this approach agree with the experimental results. Thus, the present work demonstrates the accuracy of the PM to estimate failure loads in this 3D printed material.

Feasibility of outrigger structural system for tall timber buildings: A numerical study

Tall timber buildings are prone to serviceability problems (e.g. lateral displacements and wind-induced accelerations). This article investigates the feasibility of timber outrigger system to build up to 20 storeys using linear elastic finite element analysis and relevant European and international standards such as EN 1990, EN 1991-1-1, EN 1991-1-4, EN 1995-1-1 and ISO 10137. The location of up to two outriggers was optimised based on different serviceability criteria. Various outrigger layouts were investigated, and their stiffness demands were discussed. The efficiency of outrigger structures in reducing lateral displacements and wind-induced accelerations is highlighted. A feasibility study considering serviceability requirements was performed using different basic wind velocities, number of storeys and gravity loads. Although the focus of the article is on serviceability requirements, some ultimate limit state considerations (forces and stresses) were briefly discussed. The results demonstrate the feasibility of building up to 16 storeys under medium to high wind velocities.

Assessment of residual stresses in welded T-joints using contour method

Welded T-joints are commonly used in manufacturing of stiffened panels or crossbeams. However, welding of web-to-flange joint induces residual stresses and distortions resulting in significant challenges during both manufacturing and service. These issues can ultimately impact the structural performance, including fatigue and stability, and lifetime of the weldment. The purpose of current paper is determining the distribution and magnitude of manufacturing-induced longitudinal residual stresses in welded T-joints. Influence of hot rolling, thermal cutting, prestressing, welding, etc. are all included using the so-called contour method. Deformed surfaces are measured using coordinate measuring machine after wire electrical discharge machining of specimens. An inverse linear elastic finite element analysis is carried out for assessing residual stresses after data smoothing. Two-dimensional longitudinal residual stress patterns are evaluated in representative cross-sections clearly indicating high stress peaks near the welds, even exceeding yield strength of the base material. In addition, longitudinal membrane residual stresses are determined based on through-thickness stresses. In addition, a simplified residual stress model, satisfying the requirement for equilibrium of internal forces and bending moments, is developed for welded T-joints with double-sided fillet welds based on contour method results.

Investigation of anchorage plate opening on bursting force

Three-dimensional (3D) Finite Element analyses were performed to investigate transverse stresses and bursting forces at the anchorage zone in post-tensioned concrete beams. The behavior of the concrete beam was investigated through linear elastic Finite Element analyses. To validate the Numerical modeling results, an experimental study was performed on a beam and results are compared in terms of ultimate strength. The effect of duct hole and eccentricity are investigated by varying diameter and eccentric distances on the concrete beam. Furthermore, the results are validated for bursting stress and bursting force. Altogether, the equation of bursting force in IS 1343:2012 hasn’t considered the effect of duct hole and eccentricity, the results are compared with IS 1343:2012, and an equation is presented considering the effect of duct and eccentricity.

A linear elastic finite element approach to fatigue life estimation for defect laden materials

This work assumed that the stress-life behaviors of defect-laden materials converge at a certain low life cycle and attempted to estimate fatigue life by applying relative knock-downs to the endurance limit of a reference stress-life data. Linear elastic finite element analysis on small cracks initiated from defects was performed to evaluate the effect of defect size, aspect ratio, and location on endurance limit. While for internal defects size and shape are both influential, size and depth were found to be more important for surface defects. These findings were validated against the fatigue lives of laser powder bed fused Ti-6Al-4V specimens.

STRESS ANALYSIS OF TEETH, PERIODONTAL TISSUES, AND MAXILLA BONES DUE TO BRUXISM

This paper investigates the stress distribution on the teeth and jaw during bruxism that may provide additional insights to the consequences of bruxism, splint design considerations, a basis for possible therapy protocols, and a baseline for future bruxism studies. A three-dimensional (3D) solid model of a complete jaw comprised of teeth, periodontal ligaments, and maxilla bone is reconstructed based on a Cone Beam Computed Tomography (CBCT) scan of a patient. A finite element model of the jaw is then constructed using the geometry imported from the solid model that has been reworked to remove imperfections during reconstruction and to allow proper contact between teeth. A linear elastic finite element analyses were then performed to simulate the bruxism phenomenon which includes biting and grinding. Numerical analysis is conducted only to the maxilla, with forces are placed on the teeth’s surface where contact occurs. The analysis is conducted for all stages of bruxism and possible movements patterns. Results suggest that high stresses occur during grinding, indicating a strong correlation between bruxism and dental issues such as tooth wear and alveolar resorption.

Directions of high cycle fatigue cracks emanating from circular notches studied by optical profilometry

Current models for predicting the fatigue endurance of notched solids use the stresses along a straight line, beginning at the notch root, as a simplification of the real crack propagation path. In this work, the experimental crack paths for hollow notched samples were analysed through different microscopy techniques, with the objective of establishing high cycle fatigue crack growth directions in a mild steel. Fully reversed tension–compression fatigue tests (R=−1) of thin-walled tube specimens with a passing-through hole were carried out. The crack paths observed in the outer cylindrical surface were studied in each case, with special attention to the crack initiation point and the crack direction along the first grains. Moreover, the analysis of the fracture surfaces allowed the same analysis to be performed to determine the internal crack paths. It was observed that the crack initiation point was close to the maximum principal stress point at the hole contour as obtained from linear elastic finite element analysis, and the crack direction in its initiation was generally close to Mode I direction, contrary to the conventionally accepted 45∘ crack growth direction.

Parametric optimization of corner radius in hexagonal honeycombs under in-plane compression

What is the optimum corner radius for a regular hexagonal honeycomb in the context of in-plane, quasistatic compression loading? Drawing inspiration from social insect hexagonal cell nests, where a non-zero corner radius appears to be a design feature, a 400-point design of experiments study is conducted using 2D plane strain Finite Element Analysis (FEA) to study the influence of cell size, beam thickness and corner radius on effective modulus and maximum corner stress in the honeycomb cells. An experimental study is conducted to examine these relationships beyond the bounds of the small deformation, linear elastic FEA analysis. The study finds that corner radii always increase the effective modulus of the honeycomb, even after accounting for the additional mass associated with the corner fillet. A key finding of this work is that while corner radii also reduces the maximum corner stress, there exists a clear optimum, beyond which stresses rise again as the corner radius increases in magnitude. This optimum corner radius is shown to be a function of the beam thickness (t) to beam length (l) ratio (t/l), with the optimum value increasing with increasing t/l. The experimental study shows that the presence of a corner radius shifts the failure mechanism from nodal fracture to plastic hinging for honeycombs with thick beams, and may have benefits for energy absorption applications. This work makes the case for the treatment of the corner radius as an independent design feature for optimization in the wider context of cellular materials, as well as has implications for the study of the geometry of insect nests.

Estimation of Raft Settlement Based on Linear Elastic Finite Element Analysis

Estimation of Raft Settlement Based on Linear Elastic Finite Element Analysis

Determination of notch factors for transverse non-load carrying stiffeners based on numerical analysis and metamodeling

Stress concentration factors (SCFs) at weld toes and weld roots as required for the effective notch stress concept (see [1, 2]) are usually computed using finite element analysis (FEA) which requires a certain amount of effort for model generation, the solving process, and postprocessing. Regression functions of many FEAs within given parameter bounds provide the possibility of a fast prediction of SCFs. This paper provides new and accurate regression formulae for the estimation of notch stresses at idealized weld geometries on the basis of multiple linear-elastic FEAs for the transverse stiffener (non-load carrying T-joint) under tension and bending of the load carrying slab. Regression of sampled finite element results has been performed using (a) second-order polynomial regression with coupling terms (PRC) and (b) artificial neural networks (ANN). The presented formulae are compared with several existing estimations of stress concentration factors. The new methods appear to show a higher quality of prognosis as well as apply to significant larger ranges of the geometrical parameters of the weld joint. The formulae presented here for the transverse stiffener add another welded joint to a series of similar surrogate models presented from Munich University of Applied Sciences in earlier publications and made available for use by the web-based tool SCF-Predictor.

Fatigue assessment of weld seams considering elastic\u2013plastic material behavior using the local strain approach

In this contribution, the notch strain approach is applied to seam welds including butt welds and filet welds. This allows the fatigue assessment for all regimes of fatigue life, including the low cycle fatigue regime (N > 10). Linear-elastic finite element analyses are used to determine the local stresses. The modeling of the geometry to be assessed is similar to that of the effective notch stress concept. Necessary input values besides linear-elastic stresses are estimated from the hardness of the heat-affected zone. Subsequently, the elastic–plastic stresses and strains are estimated, and a service life calculation is carried out. The used algorithm for the notch strain approach is based on the German FKM-guideline “nonlinear” and includes the influence of stress gradients, highly stressed surfaces, and the influence of surface roughness. Up to now, this FKM-guideline has only been approved for non-welded components. However, this article shows that, with a few modifications, it can also be applied to welds.

Shear strength of plain concrete made of recycled low-strength concrete aggregates and natural aggregates

This paper reports the results of an experimental study of the shear strength of plain concrete made using recycled low-strength concrete coarse aggregates (RCA) and natural coarse aggregates (NCA). Ninety push-off specimens were cast and tested. Three types of coarse aggregates were used: recycled low-strength waste concrete, limestone, and gabbro. The other variable in the concrete was the water to cementitious materials ratio (w/cm), which varied from 0.31 to 0.72. The push-off shear strength (vpo), the cube compressive strength (fcu), and the shear failure surfaces were investigated. The results showed that recycled aggregates concrete (RAC) had lower push-off shear and compressive strengths relative to the natural aggregates concrete (NAC) of similar w/cm ratios. However, the relationship between vpo and fcu was similar for the NAC and the RAC. This indicates that the effects of using RCA on the shear strength can be accounted for indirectly by consideration of their effects on fcu. The tests also showed that failure surfaces were more smooth in the concrete with lower w/cm ratios. In addition, the use of RCA affected the failure surfaces slightly. Based on a linear-elastic finite element analysis, a relationship between the tensile cracking strength σcr and vpo for the push-off specimen was established. Consequently, the experimental results suggest that the equation σcr=0.43fcu can be used to relate the tensile strength to the compressive strength of concrete.

A novel approach to modelling the bond characteristics between CFRP fabrics and steel plate joints under quasi-static tensile loads

Carbon fiber-reinforced polymer (CFRP) materials have been effectively used as externally bonded sheets to repair damaged steel structures such as airplanes and ships. In this study, a series of double strap joints with different bonding lengths are considered and examined to experimentally and theoretically assess the effective bond length. Various models exist in the literature which are used to predict the strength of steel and CFRP joints under various loading conditions. Non-linear Lagrange stress method (NLS) which is a novel stress-based method for predicting the failure load values is presented for the first time. This approach is based on 2D and 3D linear elastic finite element analysis. Relying only on two experimental tests, the new approach proposed here can quickly and easily predict the failure load in steel/CFRP samples. In this methodology, it is assumed that the adhesive joint will fail as the normal stress along the adhesive mid-line reaches a predetermined value at a critical distance. In addition, experimental data on steel/CFRP joints gathered from the literature are compared to predictions using the NLS method. It was found that results from the theoretical predictions (NLS) were in good agreement with experimental tests conducted on double strap joints. It was also revealed that the average accuracy of the NLS method is superior to other methods such as cohesive zone model and Hart-Smith. The results revealed that under the best conditions, the NLS model is 5 times more accurate than existing models.

Stress concentration factors for multi-planar DKT tubular truss joints under axially balanced loads

This paper presents a set of empirical equations to predict stress concentration factors (SCFs) in multiplanar right-angle DKT-joints. The SCFs were obtained from linear elastic finite element analyses, wherein the weld profiles were carefully modelled. The modelling techniques were first verified against previous experiments on steel and acrylic test specimens and were found to yield accurate predictions. Parametric studies encompassing a total of 54 DKT-joint models, including two different loading conditions, were performed. The SCFs from 8 locations around the perimeters of the middle and outer braces on the chord side were extracted from the models. The carry-over effect in the unloaded braces was carefully included in the investigation. The resulting SCF database was used to derive empirical parametric equations for the SCFs in DKT-joints using non-linear regression analysis.