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Preforming process would change yarn angle and yarn orientation, its influence on the material properties and material orientations needs to be considered in the performance analysis. However, most current performance models fail to account for the preforming effect. An integrated performance model accounting for the impact of preforming has been developed in this research. In this integrated model, part geometry, yarn angle and orientation after preforming of multiple prepreg layers are predicted by Finite Element Analysis (FEA) using a non-orthogonal constitutive law. Experiments were conducted to validate the preforming simulation for a single dome composites structure made by two prepreg layers with different initial fiber orientations. Performance analysis until failure was then conducted for the single dome structure to validate the integrated performance model. Comparison between simulation and experiment shows that not only the failure mode and failure zone, but also the force-displacement curve during compression process are captured correctly by the performance model, demonstrating the effectiveness of the newly proposed model in accounting for the impact of preforming process.

This paper presents an experimental and numerical investigation on the local buckling behaviour of a new built-up Cold-Formed Steel (CFS) homogeneous and hybrid Double-I-Box Column sections (DIBCs and HDIBCs) under axial compression. In total, 24 experimental tests are conducted, out of those 12 tests are on stub columns and the remaining 12 are on short columns. The parameters considered are hybrid ratio (Φh), section’s breadth to depth ratio (B/D) and column height (H). The columns considered in this study are having an overall slenderness (λ) less than 0.20, and the flange plate slenderness (λpf) less than 1.85. Test specimens failed in either of the following three failure modes: local buckling, yielding or by the interaction of both. In all the tested specimens, typical Bottom Zone Local Buckling (BZLB) similar to the shape of Elephant’s Foot is identified. The deformation shape is recognized by expansion (outward buckling) along the major axis and contraction (inward buckling) along the minor axis at the bottom 1/4th height of the columns in opposite faces, followed by the collapse. This kind of failure mode is a clear representation of Poisson’s ratio effect at the ends causing a restraint which then creates a local imperfection under load which leads to a localized failure at bottom zones in the stub and short columns of DIBCs and HDIBCs. BZLB phenomenon is enhanced because of the tubular cross-section geometry, boundary conditions plate element slenderness, overall slenderness of these built-up sections. The ultimate capacities of both the stub and short columns are governed by their strength limits and slenderness. Nonlinear Finite Element Analysis (FEA) is performed on experimental FE models using ABAQUS software and verified against the test results and validated with the actual structural behaviour. Further FEA is performed on 96 ideal parametric FE models considering different material properties and slenderness values. Effect of the intermediate longitudinal stiffener and the influence of edge constraints on axial strengths are also reported. The axial strengths obtained from the experimental tests and FE parametric studies are compared with the predicted results using the Effective Width Method (EWM) as suggested in the Eurocode specifications to access the feasibility of the current design rules, which is found to produce reasonable predictions albeit slightly conservative. It is found that for stub columns with λ 0.1, the experimental values are found to be 1.25 times higher than the predicted values. It is also observed that for columns having λ ≥ 0.1 0.2 with λpf > 1.2 there is a reduction in local buckling resistance of around 2.5% for each increase of λpf by 10%. Hence, it is concluded that the concentric axial compression capacities of DIBCs and HDIBCs subjected to local buckling can be computed as the arithmetic summation of effective strengths of individual channel sections calculated by using the EWM design equations, as recommended in this study. The attained results prove that these sections have a considerable local inelastic reserve strength as specified in North American standards.

The complicated tunnelling conditions and variable engineering demands have made numerous challenges of mesh-reinforced lining structures. Thereafter, the steel fiber reinforced concrete (SFRC) is said to be a reliable alternative to mesh-reinforced linings. This paper reviews the constituent materials and typical properties of SFRC. The main causes of mesh-reinforced lining cracks or structure failures are summarized, and current challenges for mesh-reinforced linings are examined. Also, the advantages of using SFRC for the realization of the tunnel linings are highlighted. Furthermore, design considerations and some practical cases on application performance of SFRC in tunnel linings are summarized. This review confirmed the positive effect of SFRC lining on rock displacement control, lining pressure reduction, and global and local stability of the support structures. The research provides solid insights for promoting the development of SFRC in tunnel linings.

This paper presents a finite element analysis of cold-formed stainless steel channels with circular web holes, subjected to end-one-flange loading condition. The material properties of stainless steel types EN 1.4509 (Ferritic), EN 1.4462 (Duplex) and EN 1.4301 (Austenitic) were taken from the literature. To investigate the effect of web hole size, web hole location and bearing length on the web crippling strength of such sections, a parametric study involving a total of 1728 FE models was performed. The parametric study results were used to propose new web crippling strength equations and strength reduction factor equations which outperformed the equations of American Society of Civil Engineers Specification (ASCE 8–02), American Iron and Steel Institute Specification and Australia/New Zealand Standard (AISI&AS/NZS) and Lian et al (2016). A reliability analysis was then performed, which showed that the proposed design equations can closely predict the web crippling strength of cold-formed stainless steel channels with and without web holes under end-one-flange loading condition.

This paper proposes a finite element method (FEM) for the free vibration analysis of sandwich nanoplates with an auxetic honeycomb core. The proposed method uses a third-order shear deformation theory accounting for both shear deformation and stretching effects without any need for shear correction factors. The size-dependent effect is solved using the nonlocal elasticity theory. The auxetic sandwich nanoplate with negative Poisson’s ratio is applied to achieve ultra-light features and high strength. The obtained numerical results by the proposed method are compared with other published works to demonstrate the accuracy and reliability. Moreover, the influence of the nonlocal factor, geometrics parameters, and material properties (especially the auxetic honeycomb parameters) on the free vibration behavior of sandwich nanoplates is also examined in the numerical examples.

Textile-reinforced concrete has emerged in recent years as a new and valuable construction material. The design of textile-reinforced concrete requires knowledge on the mechanical properties of different textile types as well as their reinforcing behaviour under different loading conditions. Conventional load-bearing tests tend to be complex, time-consuming, costly and can even lack consistent specifications. To mitigate such drawbacks, a standardised tensile test for fibre strands was used to characterise the material properties needed for the design of a textile-reinforced concrete member. The standardised tensile test uses a fibre strand with 160 mm length, which is cut out of a textile grid. For the sake of this study, an epoxy resin-soaked AR-glass reinforcement was considered. The results show that the textile reinforcement has a linear-elastic behaviour, and the ultimate tensile strength can be statistically modelled by a Gumbel distribution. Furthermore, the results indicate that the modulus of elasticity is not influenced by the length or the number of fibre strands. Therefore, the mean value attained from the standardised test can be used for design purposes. These findings are essential to derive an appropriate partial safety factor for the calculation of the design values of the tensile strength and can be used to determine the failure probability of textile-reinforced concrete members.

The probability of failure estimation of composite structures under applied loads is an inevitable requirement given the uncertainties related to the material properties, loads, and boundary conditions. The properties of composite materials have more scatter due to non-homogeneity and anisotropic characteristics, and manufacturing defects. In this paper, the reliability of S2-Glass/Epoxy laminate composite materials containing a central circular hole under static tensile load is presented. Failure in fiber-reinforced plastic structures, since individual faults in each ply cannot be traced, is a random process due to the scatter caused by the behavior of the material. According to the continuum damage mechanics (CDM) approach, a damage model proposed by Ladeveze is used to model the matrix cracking and fiber/matrix debonding and then, the material constitutive relationships are implemented in the ABAQUS software by the subroutine. The first-order reliability method (FORM) and second-order reliability method (SORM) have been used to analyze the system failure probability of the composite plates, and the failure functions and random variables have been obtained according to the CDM approach. Scatter in random parameters have been displayed to have a significant effect on damage development. Finally, using sensitivity analysis, sensitive and effective parameters in the reliability of laminate composite were introduced.

The surface/subsurface-initiated pitting is one of the most common failure modes in a gear. Although models for predicting the initiation of pitting are available, a model for predicting the growth of an existing pitting is not yet available. The present work proposes a hybrid prognosis approach for estimating the growth of pitting on the gear tooth surface, utilizing both empirical model (i.e., modified Paris law) and measured pitting area. The proposed approach is generic as the pitting growth rate is modelled as a function of gear material properties (such as Poisson’s ratio and modulus of elasticity), oil property (such as dynamic viscosity), gear geometrical parameters (such as pitch circle diameter, module, pressure angle and face width) and operating conditions (such as applied load and speed). The pitting evolution process is likely to be different for similar gear pairs due to inherent variations in material properties, manufacturing process, etc. Hence for a more accurate life prediction, the pit growth model parameters need to be updated, which is done using Bayesian inference.

This paper has completed the three-dimensional reconstruction of normal young people’s L4–L5 lumbar spine integration model and the integrated model of different degree of disk herniation. On the b...

PurposeThis paper presents the details of a research study on developing composite masonry blocks using two types of mixes, conventional and lightweight mix, to enhance their fire/bushfire resistance and residual compressive strength.Design/methodology/approachComposite masonry blocks (390 × 190 × 90 mm) were fabricated using conventional cement–sand mix as the outer layer and lightweight cement–sand–diatomite mix as the inner layer. Material properties were determined, and all the mixes were proportioned by the absolute volume method. After 28 days of curing, density tests, compression tests before and after fire exposure and fire resistance tests of the developed blocks were conducted, and the results were compared with those of conventional cement–sand and cement–sand–diatomite blocks.FindingsDeveloped composite blocks satisfy density and compressive strength requirements for loadbearing lightweight solid masonry units. Fire resistance of the composite block is –/120/120, and no cracks appeared on the ambient side surface of the block after 3 h of fire exposure. Residual strength of the composite block is higher compared to cement–sand and cement–sand–diatomite blocks and satisfies the loadbearing solid masonry unit strength requirements.Practical implicationsComposite block developed in this research can be suggested as a suitable loadbearing lightweight solid masonry block for several applications in buildings in bushfire prone areas.Originality/valueLimited studies are available for composite masonry blocks in relation to their fire resistance and residual strength.

Unreinforced masonry (URM) walls, found in most historical buildings in Indonesia, are relatively brittle with wide variety of material properties. The behaviour of URM walls is very complex, especially when subjected to seismic excitation. In this research, a finite element modelling was set up in order to analyse the seismic performance of URM wall experimental test units, with and without strengthening material. The analysis was conducted using SAP2000 computer program. Three dimensional solids and springs as link connectors were assigned to represent the masonry behaviour. This research aims to compare results obtained from the computer analysis and the previously conducted laboratory experiments. The effectiveness of Kevlar fibre material, which was installed on both wall surfaces and modelled as truss element was also investigated. It was found that the failure mechanisms shown by the SAP2000 model was similar to the laboratory test results. The use of Kevlar Fibre as strengthening material was found able to significantly increase the stiffness and shear capacity of the URM wall.

The continuous-supported modules using light steel multi-column wall systems have excessively been used in low-rise modular steel buildings (MSBs). In order to account for high-rise MSBs, the current research first developed continuous-supported load-bearing wall systems using hot-rolled structural hollow sections (SHS). Then a 3D nonlinear finite element model (NFEM) was generated and validated using five full-scale axial compression tests carried out in reference to simulate the actual structural behaviours of walls subjected to axial compression. The main parameters in the reported tests were varying cross-section sizes (D/B) and slendernesses (D/t), and material properties. The validated NFEM accounted for complex interactions among walls components and their material and geometrical nonlinearities. They accurately predicted ultimate strength and failure behaviour. Following that, parametric studies were conducted to understand the effects of various parameters on the compressive behaviours of walls and columns. These parameters included material strength, columns D/B and D/t ratios, columns spacings, column number and stiffener thickness. Through NFE analysis results, prediction equations in EC3, AISC360, and GB50017 were used to predict the ultimate compressive resistance of columns in these walls. Due to elastic buckling, the nominal capacity of SHS columns in multi-column walls declines, making the EC3 compressive resistance design non-conservative and necessitating the calculation of member capacity with global buckling. Reducing D/B or D/t and increasing stiffener size increases the strength and stiffness of columns and walls. Although the walls were ductile, elastic buckling and mutual restraints reduced the individual column bearing capacity, ductility, and stiffness. The external columns increase the constraint effect on corners due to more rigid constraints while weakening other columns, inducing system instability. The predictions on ultimate strengths of columns showed that GB50017 was safer than the other two codes, while EC3 predictions with or without accumulating buckling length were the least secure. Based on these numerical and analytical findings, the study tended to evaluate the axial compression behaviour of continuous-supported multi-column wall systems with SHS columns in high-rise MSBs.

The Cold-formed steel (CFS) light frame shear wall is the most important lateral force-resisting element in CFS building systems. Extensive researches have been completed on the shear performance of CFS shear walls with various kinds of panels. It’s found that the shear capacity of the CFS shear walls is affected by many aspects. Therefore, this paper consolidates a large number of test results world-wide and establishes a database on the lateral strength of CFS light frame shear walls. The influencing factors of the shear wall’s shear capacity are analyzed systematically, which includes material properties, stud sections and spacing, framing thickness, sheathing thickness, aspect ratios, openings, screw types and spacing, loading methods, etc. The logic behind these factors is found out through the analyses of the test data and design suggestions are made accordingly.

In the present study, an analytical model was proposed to predict the fatigue response of damaged beams strengthened with ground granulated blast-furnace slag (GGBS) based ultra-high performance concrete (UHPC) strips. The proposed analytical fatigue prediction model (FPM) incorporated with fatigue properties of constituent materials and cross-sectional stress analysis of composite reinforced concrete (RC) beams subjected to fatigue loading condition. The critical parameter controlling the fatigue behaviour of damaged beams strengthened with UHPC strips were a degree of damage in the reinforcing bars and thickness of GGBS based UHPC strips (5, 10 and 15 mm). The damage incorporated in the FPM was categorised as mild, severe and very severe based on the degree of damage level (0.2, 0.3 and 0.7, respectively). In the FPM, fatigue response of strengthened RC beams was captured at the end of each stage of fatigue cycle and updating the material properties iteratively until the threshold of constituent material was attained. From the FPM results, strengthening with a thin UHPC strip (5 mm) was effectively restored the fatigue performance of RC beams induced with a very severe degree of damage level. The analytical studies carried out in the present study were validated with the author’s previous experimental investigation. The maximum deviation in predicted results between the experiments and the FPM was 16, 28 and 12% for mild, severe and very severely damaged beams, respectively.

This paper deals with the modal analysis of optimized trapezoidal stiffened plates with simple supported conditions on the four edges of the base plate. The main objective of the finite element analysis is to investigate the natural frequencies and mode shapes of some stiffened structures subjected to lateral pressure and uniaxial compression in order to identify any potentially dangerous frequencies and eliminate the failure possibilities. The natural frequencies and mode shapes are important parameters in the design of stiffened plates for dynamic loading conditions. In this study, the numerical analysis is performed for such a design of this kind of welded plates which have already been optimized for lateral pressure and uniaxial compression. The objective function of the optimization to be minimized performed with the Excel Solver program is the cost function which contains material and fabrication costs for Gas Metal Arc Welding (GMAW) welding technology. In this study, the eigenvalue extraction used to calculate the natural frequencies and mode shapes is based on the Lanczos iteration methods using the Abaqus software. The structure is made of two grades of steel, which are described with different yield stress while all other material properties of the steels in the isotropic elastic model remain the same. Drawing the conclusion from finite element analysis, this circumstance greatly affects the result.

Structural safety evaluation is a critical issue in the realm of civil engineering. It involves factors such as uncertainties, external loads, and structural damage after long-term service. Presently, real-time safety evaluation of structural resistance remains challenging for real-world structures. This study proposes a resistance updating model for reinforced concrete beams based on Bayesian inference. The measured static loads of six experimental beams were taken as the proof loads for assessing real-time safety, and a stiffness degradation coefficient (SDC) was developed to embody resistance reduction. The SDC was continuously updated based on the deflection monitoring data of the beams under the proof loads. Specifically, the beam resistances were defined as the random distributions, and their initial distributions were calculated according to the material properties of the beams. Then, the corresponding SDCs of each proof load were estimated. Based on the initial resistance distributions and the real-time SDCs, the iterative updating of the resistance distributions was carried out using Bayesian inference. Subsequently, the future reliability indices of these beams were inferred using the JC method, which utilized the updated resistance distributions and the assumed future load distributions. Finally, a reliability index evolution model was established to evaluate the safety of the experimental beams. The analysis results showed that the proposed method can effectively estimate the resistance to provide an upper limit of future loading. The proposed method is sensitive to the proposed SDC but insensitive to the initial distributions of the resistance.

In this paper, the three-dimensional post-buckling analysis of functionally graded materials plate (FGM) with temperature independent (TID) and dependent (TD) material properties under different types of thermal loads is examined. The analysis is performed by a modified first-order enhanced solid-shell element. The formulation is based on the first-order shear deformation theory (FSDT) with a special representation of the transverse shear strains imposed in the compatible strain part. To subdue locking problems, two methods are employed the assumed natural strain (ANS) method and the enhanced assumed strain (EAS) method with a minimal number of internal parameters. Numerical results of the present research are compared and validated with the existing studies on the thermal post-buckling of FGM plates. Numerical results are also provided to explore the effects of power-law index and different geometrical parameters of the FGM plates subjected to different types of thermal loads.

Post-earthquake observations have outlined the poor seismic performance of substandard reinforced concrete (RC) beam-column joints in existing buildings. They often exhibit significant cracking even under moderate intensity earthquakes, compromising the seismic performance of the entire building. This makes the quantification of their residual capacity and the definition of reliable repairability thresholds critical. Different approaches are available in the literature to establish the repairability of RC joints. However, a simple crack width-based criterion is required for practitioners during in-situ inspections. This study deals with the definition of crack width-based fragility curves relying on numerical analyses. Those are carried out by using the validated finite element (FE) models, being capable of reproducing the initiation and development of cracks in RC joints. To this end, the uncertainties in material properties, influencing the seismic performance of structural components, are accounted for different joints. In particular, experimentally validated FE models are evolved to stochastic level by generating random variables of material properties with the stratified sampling scheme. Fragility curves representing a certain level of probability of exceeding the defined crack width at the joint back, joint core, and beam-to-joint interface are developed. An application of the proposed methodology for in-situ inspections is also presented, and the results of in-situ measurements of residual crack width from real buildings damaged by recent earthquakes are used for the validation.

Unreinforced masonry buildings undergoing seismic actions often exhibit local failure mechanisms which represent a serious life-safety hazard, as recent strong earthquakes have shown. Compared to new buildings, older unreinforced masonry buildings are more vulnerable, not only because they have been designed without or with limited seismic loading requirements, but also because horizontal structures and connections amid the walls are not always effective. Also, Out-Of-Plane (OOP) mechanisms can be caused by significant slenderness of the walls even if connections are effective. The purpose of this paper is to derive typological fragility functions for unreinforced masonry walls considering OOP local failure mechanisms. In the case of slender walls with good material properties, the OOP response can be modeled with reference to an assembly of rigid bodies undergoing rocking motion. In particular, depending on its configuration, a wall is assumed either as a single rigid body undergoing simple one-sided rocking or a system of two coupled rigid bodies rocking along their common edge. A set of 44 ground motions from earthquake events occurred from 1972 to 2017 in Italy is used in this study. The likelihood of collapse is calculated via Multiple Stripe Analysis (MSA) from a given wall undergoing a specific ground motion. Then, the single fragility functions are suitably combined to define a typological fragility function for a class of buildings. The procedure is applied to a historical aggregate in the city center of Ferrara (Italy) as a case study. The fragility functions developed in this research can be a helpful tool for assessing seismic damage and economic losses in unreinforced masonry buildings on a regional scale.

The split-Hopkinson pressure bar (SHPB) is a widely used experimental technique for studying the mechanical properties of materials at high strain rates. There are two kinds of loading methods applied in the SHPB technique, namely one-side loading and symmetric loading. However, the experimental accuracy of the two loading methods is affected by the interface contact. The present study focused on the inadequate contact caused by the misalignment of the pressure bars. The commercial software ABAQUS was used for simulations. The result shows that the inadequate contact caused by the alignment of the bars has a non-negligible effect on the calculated results. Compared with the one-side loading Hopkinson pressure bar, the symmetric loading Hopkinson pressure bar has a more relaxed requirement for the alignment of the bars. The conclusion arrived at in this paper can help researchers to make a reasonable choice between one-side and symmetric loading Hopkinson pressure bars according to actual requirements.

This paper presents a methodology that integrates the semi-empirical corrosion models with probabilistic analysis to study steel structural failure behavior considering material and parametric uncertainties. The semi-empirical models are used to assess the asset’s susceptibility, system degradation rate, and defect growth over time under harsh corrosive environment. The developed model is translated into a limit state function in a probabilistic framework to define the asset’s safe operating envelope. The probabilistic framework is simulated considering the variations in the material properties of steel grades, corrosion response parameters, and types of susceptibility models. The variabilities in the ultimate tensile strength, operating pressure, and wall thickness exhibit the highest contributions to pipeline failure behavior in a harsh offshore environment. It is also observed that the failure probability of the pipeline increases with an increase in the coefficient of variation at the lower bound of failure, while it decreases at the upper bound of failure. The coefficient of variation for the tensile strength shows a 32.2% (the highest) impact on the limit state function performance as the year of exposure progresses. The proposed approach offers a systematic framework for an appropriate material selection and risk-based integrity management strategy for offshore structures, including pipelines.

Modeling the mechanical behavior of soft tissue probe insertion remains a challenging endeavor due to involved interdependent phenomena comprising tissue nonlinear deformation, contact between the probe and the tissue, crack propagation, and viscoelastic effects. To that matter, cohesive elements allow simulating crack formation and propagation, which provides a promising path to modeling the mechanical behavior of probe insertion in soft tissues. As such, the aim of the present study was to investigate the feasibility of devising and integrating an algorithm in a finite element (FE) case study in efforts of reverse engineering the material properties of non-homogeneous soft tissues. A layered nonlinear tissue model with a cohesive zone was created in the commercial software ABAQUS. Material properties were iteratively modified via a hybrid gradient descent optimization algorithm: minimizing the resultant error to first find optimum Ogden’s hyperelastic parameters, followed by obtaining the damage parameters. Perceived material properties were then compared to those obtained via experimental human cadaver testing. Under the investigated four-layered muscle model, numerical results overlapped, to a great extent, with six different force-insertion experimental profiles with an average error of $$\pm$$ 15%. The best profile fit was realized when the highest sudden force drop was less than 60% of the peak force. Lastly, the FE analysis revealed an increase in stiffness as the probe advanced inside the tissue. The optimization algorithm demonstrated its capability to reverse engineer the material parameters required for the FE analysis of real, non-homogeneous, soft tissues. The significance of this procedure lies within its ability to extract tissue material parameters, in real time, with little to no intervention or invasive experimental tests. This could potentially further serve as a database for different muscle layers and force-insertion profiles, used for surgeon and physician clinical training purposes.

Purpose Mechanical anisotropy associated with material extrusion additive manufacturing (AM) complicates the design of complex structures. This study aims to focus on investigating the effects of design choices offered by material extrusion AM – namely, the choice of infill pattern – on the structural performance and optimality of a given optimized topology. Elucidation of these effects provides evidence that using design tools that incorporate anisotropic behavior is necessary for designing truly optimal structures for manufacturing via AM. Design/methodology/approach A benchmark topology optimization (TO) problem was solved for compliance minimization of a thick beam in three-point bending and the resulting geometry was printed using fused filament fabrication. The optimized geometry was printed using a variety of infill patterns and the strength, stiffness and failure behavior were analyzed and compared. The bending tests were accompanied by corresponding elastic finite element analyzes (FEA) in ABAQUS. The FEA used the material properties obtained during tensile and shear testing to define orthotropic composite plies and simulate individual printed layers in the physical specimens. Findings Experiments showed that stiffness varied by as much as 22% and failure load varied by as much as 426% between structures printed with different infill patterns. The observed failure modes were also highly dependent on infill patterns with failure propagating along with printed interfaces for all infill patterns that were consistent between layers. Elastic FEA using orthotropic composite plies was found to accurately predict the stiffness of printed structures, but a simple maximum stress failure criterion was not sufficient to predict strength. Despite this, FE stress contours proved beneficial in identifying the locations of failure in printed structures. Originality/value This study quantifies the effects of infill patterns in printed structures using a classic TO geometry. The results presented to establish a benchmark that can be used to guide the development of emerging manufacturing-oriented TO protocols that incorporate directionally-dependent, process-specific material properties.

The full damping treatments have been widely used in many fields for structural vibration and noise reduction. Compared to the partial damping treatments, the full damping treatments have not significantly enhanced the effect of vibration reductions. It is essential to find the optimal damping treatments in lightweight designs. Moreover, the solution methods should be beneficial to engineering applications. In this work, a layerwise finite element (FE) model of plates with constrain layer damping (CLD) treatments is proposed, based on Kerwin’s hypothesis. The dynamic characteristics of CLD system are analyzed by the modal strain energy (MSE) method. Based on the variable density method and the rational approximation of material properties (RAMP) interpolation scheme, a topology optimization model of the CLD system is built, and the optimal layouts are determined by the proposed modified guide-weight (MGW) method. The results are compared with optimal layouts using other common methods. The layerwise FE model, the topology optimization model and the MGW method are validated by numerical examples. The proposed layerwise FEM-MSE solutions converge to the analytical or semi-analytical solutions more accurately than the NASTRAN/MSE solutions. The optimization results indicate that the added weight of viscoelastic material (VEM) layer decreases by 50 percent, and meanwhile the modal loss factors can just decrease by 5.18 percent compared to plates with VEM full coverage in some cases. The results of this work are beneficial to the vibration and sound radiation suppression of plates with CLD treatments in engineering applications.

In this paper, an integrated procedure is proposed to identify cracks in a portal framed structure made of functionally graded material (FGM) using stationary wavelet transform (SWT) and neural network (NN). Material properties of the structure vary along the thickness of beam elements by the power law of volumn distribution. Cracks are assumed to be open and are modeled by double massless springs with stiffness calculated from their depth. The dynamic stiffness method (DSM) is developed to calculate the mode shapes of a cracked frame structure based on shape functions obtained as a general solution of vibration in multiple cracked FGM Timoshenko beams. The SWT of mode shapes is examined for localization of potential cracks in the frame structure and utilized as the input data of NN for crack depth identification. The integrated procedure proposed is shown to be very effective for accurately assessing crack locations and depths in FGM structures, even with noisy measured mode shapes and a limited amount of measured data.

Link slabs have been introduced for many years for the construction of jointless bridges. However, conventional concrete as a main material for link slabs construction has demonstrated insufficient strength and ductility. Hence, new high performance material like engineered cementitious composite (ECC) with superior performances in both strength and ductility may able to replace conventional concrete and enhance the performance of link slabs. This research provided a derivation of some required material properties’ ranges needed for link slab fabrication by translating the requirements of link slab’s performance into material properties requirements. Firstly, according to a set of commonly used design parameters, the required ranges of material properties were determined. A graphical approach was then employed to determine the required material properties at different reinforcement ratios. Three mix designs for polyethylene and steel fibre ECC (PE-ST-ECC) which could meet the requirements were then proposed. Their material properties were validated by a series of standard mechanical tests and the best mix design among the three proposed was identified.

In this research study three dimensional (3D) finite element analysis are performed on a flexible pavement section for different material properties, temperature and loading conditions. The main objective of this study is to predict the rut depth under different conditions of temperature, loadings and material properties. Three dimensional finite element model of flexible pavement is developed using ABAQUS to predict rut depth. The pavement system is assumed to be an elastic multi-layers system with each layer being isotropic, homogeneous with specified Resilient Modulus (Mr) and Poisson ratio (µ). With the exception of the bottom subgrade layer, each layer is extending to an unlimited horizontal extent and has a finite thickness. The pavement system analyze in this study for a cyclic load of 10000 cycles taken as 0.01sec per cycle. Standard Axle Load (ESAL) of 18 kips (80 kN) loading on an axle with a dual set of tires, the wheel spacing is 13.78 in (350 mm) with a tire contact pressure of 100 psi (0.69 MPa) is used. After performing a series of analysis the results showed that rut depth increases with increase in temperature and loading and decreases by using base stabilizer. Doi: 10.28991/cej-2021-03091727 Full Text: PDF

Damper is frequently used to suppress panel vibration and related vehicle interior noise. Unlike an unconstrained damper, a method to find material properties of a constrained damper is more complicated. This study presents a verified method for obtaining material properties of a constrained asymmetrical damper. The most important material parameters of this constrained damper are shear modulus, shear factor, and of course damping loss factor. The paper provides newly corrected equations to give proper numerical values of these parameters. The difference of natural frequencies between the test and the simulation using the estimated values is about 2 %, which shows that the estimation method is correctly presented. Important characteristics such as shear motion and wavelength of a composite beam constrained by a damper are also investigated. Finally, vibration response of a vehicle roof with a constrained damper is measured and is compared to the simulation. It is noticed that the correlation is much improved, comparing with the simulation based on old material properties.

Structural steel members are subjected to corrosion due to environmental condition. As a result, there is decreasing in the cross-section properties of the member. This causes different stability problems and reduction in the load carrying capacity of members. Then, the probability of failure, Pf increases due to corrosion. The need arises to determine expected level of safety for such members and systems. Besides, reliability of the steel structure is also effected by the structural stability problems that result decreasing in the resistance. Lateral torsional buckling is one of the most encountered problems in steel members and affected by the critical moment which is a function of lateral and torsional stiffness. Critical moment depends on the material properties, boundary conditions, unbraced length, load pattern, and the member’s cross section. Under the corrosion, it is inevitable to observe changing in some of properties. In this study, a damage model to determine the reliability of a corroded I-shape steel member under linear moment gradient is developed considering corrosion exposure time. Uniform and varying thickness loss models are considered to show the corrosion effect. Influence of environmental condition on the load carrying capacity of the members is considered and their effects on member design is evaluated. As a result, it is concluded that load carrying capacity of steel members degrades and safety of them adversely effected. With presented formulas, it is ensured that the load carrying capacity and reliability indices of the steel members can be calculated practically under the examined situations

In the 21st century, with the increasingly urgent requirements for lightweight in the fields of aviation, aerospace, and electronics, especially automobiles, many properties of magnesium alloy materials, especially the low-density performance characteristics, have been widely valued. In order to better use magnesium metal materials, it is very important to evaluate its mechanical properties. This article is based on 196 sets of mechanical performance experimental results and related data of AZ31 and AZ91 2 magnesium alloys. Based on data analysis and sorting, take deformation temperature, deformation rate, deformation coefficient, solid solution temperature, and solid solution time as input and take ultimate tensile strength (UTS), yield strength (YS), and elongation (ELO) as output. The 5-8-1 three-layer BP neural network forecast model optimized by the genetic algorithm is used for data training. The training results show that the prediction model can accurately predict the tensile strength, yield strength, and elongation. Compared with the general BP neural network prediction model, the BP neural network based on the genetic algorithm has small discreteness and high fitness: the average error of UTS and YS of AZ31 magnesium alloy is reduced to 0.88% and 3.3%, respectively. The most obvious is that the elongation of AZ31 ELO is reduced, and the error is reduced to 8.1%.

Impact dampers (ID) are one of the passive dampers for controlling undesirable vibration and are suitable to operate in harsh environments and effective over a wide range of frequencies. These dampers can be classified as single-unit or multi-unit. The multiple-unit impact damper where is composed of one cavity and some impact mass can be used in various engineering applications. The disadvantage of single-mass impact dampers is high noise level after repeated impacts, because of high contact forces during the impact process. This noise causes discomfort in humans. The contact forces relatively reduced in multiple-mass impact dampers, so the noise generated during the damper’s impact process is reduced in multiple-unit impact damper. The effect of multiple-unit impact damper in vibration and noise reducing is related to the configurations of impact masses. These configurations can be classified as uniform, linear, eight, and diamond. A way for studying the effect of various layouts of masses is using balls with different material properties together. In this paper, three various materials are selected to perform multiple-mass impact damper, the stainless steel, glass and the pearl balls. All of these balls have the same diameter. The results show that the effect of diamond mass configuration in impact damper performance is better than the other configurations. The major innovation of this paper is to investigate the effect of different mass layouts on the performance of multi-mass impact damper experimentally.

This paper presents an analytical-based approach to simulate fatigue growth of surface cracks in round bars subjected to cyclic tension and/or bending. The proposed approach assumes a part-elliptical crack front shape, and it is capable to incorporate plasticity-induced crack closure models. In addition, it is mesh-insensitive, easy to implement, and much faster than the numerical methods which are currently utilised for the same purpose. In the beginning, it is developed, in orthogonal elliptical coordinates, a governing equation describing the crack shape evolution. Then, the governing equation is extended to incorporate plasticity-induced crack closure effects. Further, it is investigated the main parameters affecting fatigue crack growth in round bars, in particular, the initial crack length, the loading conditions and, the material properties. Finally, the outcomes of fatigue crack growth simulations based on the proposed approach are compared with published experimental and theoretical studies. Overall, an excellent agreement can be observed.

Currently, a great deal of controversy exists regarding the real forces generated in drawbeads during sheet metal forming processes. The present work focuses on the analysis of the uplift force. First, a detailed literature review is carried out to analyse previous experimental procedures used to measure uplift forces. It is found that previous setups do not perfectly replicate the real geometry of industrial drawbeads. In order to obtain reliable forces, an experimental drawbead tester capable of adequately replicating industrial drawbeads is developed. Later, a variety of steels ranging from mild steels to 3rd-generation ultra-high-strength steels are tested and reliable uplift and also restraining force values are obtained. The main purpose of the work is to share with the research community reliable experimental data that allows precise evaluation of the accuracy of current drawbead models and that supports the generation of new numerical and equivalent drawbead models. In parallel to the experimental procedure, a step forward in the understanding of the drawbead closing phenomena is also achieved through a 2D numerical model. The main purpose of the model is to identify the variables that greatly affect uplift force. Going beyond previous studies, in which some variables were analysed, the present work covers, in a holistic manner, the impact that material properties, the geometry of drawbeads and contact behaviour between sheet and drawbead have on the uplift force. It is determined that surprisingly minor geometrical deviations in the drawbead nominal geometry have a large impact on the uplift force.

This paper presents a statistical analysis of the actual mean material properties for typical grades of concrete and reinforcement available in Australia. The analysis was performed using a database of 3,447 concrete cylinder test results and 15,201 reinforcement tensile test results. The test results were taken over a period from 2009 to 2021. The paper provides a summary of the mean values and respective coefficient of variation values for the different grades of concrete and reinforcement that make up the database. Distinctive manufacturing trends and variability between suppliers were observed for reinforcement samples and appropriate recommendations have been proposed. Researchers or designers can adopt these values to undertake probabilistic assessments of RC structures. The paper also provides recommendations for mean material properties for the purpose of undertaking non-linear analysis of RC structures. The database of test results also includes early age strength data for concrete, which have been used to provide recommendations for predicting the early age strength of various standard grades of concrete available in Australia. The paper also presents an assessment of the theoretical characteristic values from the database for the various grades of reinforcement and concrete and how they compare to respective specified code requirements.

Displacement-based methods, such as a non-linear static pushover analysis (e.g. the capacity spectrum method), have many advantages compared to traditional force-based design methods. However, implementing a non-linear analysis and design method in accordance with the Australian Standard for concrete structures (AS 3600) introduces many difficult technical issues into the design, of which the standard provides little guidance. The aim of this study is to provide a framework and general guidance for designers who wish to perform non-linear displacement-based analysis methods for RC wall buildings. The paper will present how these methods can be used in accordance with the Australian Standard for earthquake actions (AS 1170.4) to assess seismic compliance and then provide recommendations for the requirements stipulated by AS 3600, which includes an experimentally validated tension stiffening model, nonlinear stress-strain material curves, mean material properties and material strain limits. The paper is concluded with a case study example of how a displacement-based seismic assessment can be performed using a typical case study building.

An effective computational approach that can simultaneously deal with several complexities in geometries, material properties, and size effects is of non-trivial yet important tasks for the design and optimization of device components in micro- and nano-electromechanical systems. This study is devoted to the development of such an effective computational approach, which is formed by integrating the modified couple stress theory into isogeometric analysis framework. The proposed approach is applied to mechanical problems of laminated Timoshenko curved microbeams, i.e., anazlying static bending, natural frequency and transient response. The developed method enables to describe and examine nontrivial features in both material and geometrical properties of laminated curved microbeams. Geometries of curved microbeams and displacement approximation are accurately described by the non-uniform rational B-spline basis functions. For laminated composites, the material coupling is taken into account with the use of equivalent elastic modulus; and the deepness term is properly included in laminate stiffness parameters. In addition, the small-scale size effects are captured with the use of modified couple stress theory. The accuracy and performance of proposed method are demonstrated through several numerical examples, in which the static bending, free vibration and transient response of laminated curved microbeams are considered under effects of some factors such as aspect ratios, lay-ups, boundary conditions and size dependence.

The nonlinear behavior of reinforced fly ash concrete (RFAC) beams until the ultimate failure is highly a multifaceted phenomenon due to the contention of heterogeneous material properties and the cracking behavior of concrete. This paper represents an exploration of nonlinear finite element analysis of reinforced concrete beams with the inclusion of fly ash under flexural loading. Finite element modelling of RFAC beams is carried out using a distinct reinforcement modelling method. The capability of the model to capture the critical crack regions, loads and deflections for various loadings in RFAC beams has been evaluated. Comparison is made between experimental results and finite element modelling with respect to crack formation and the ultimate capacity for flexural loading and mid-span deflection. The achieved results in the present study indicate acceptable approximation with those in the previous investigations.

The paper presents a method for assessing the probability of fracture of structural components of technical systems subjected to monotonic and cyclic loading, which permits taking into account the scatter of mechanical properties of materials and the size of macrodefects passed into operation by means of nondestructive testing. The presented method can be used in the implementation of probabilistic and risk-based approaches to ensuring strength, service life and safety of technical systems in real operating conditions and in adjusting standard operating programs in terms of selecting the frequency and scope of non-destructive testing.

The aim of this paper is to estimate the damage of railway carriage wheels caused by lock-up braking. First, we investigate the typical characteristics of wheel-rail contact including the parameters of contact patch, longitudinal creep and coefficient of adhesion. Then we show the current requirements concerning the wheel-slide protection systems and determine the points which should be reviewed. To predict the effect of the sliding phenomenon, material properties are needed, as well. Afterwards, a simplified thermal simulation is built to estimate where martensite formation may occur.