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Mining shallow coal seams and deep coal seams is obviously different. In the deep environment of a coal mine, the stress concentration degree is high, and the dynamic load with impact tendency is prominent. In the practice of underground mining engineering in coal mines, the common coal–concrete combination structure has different degrees of damage and failure under the continuous action of dynamic load at different impact rates, which in turn affects the overall stability of the engineering structure. Therefore, it is of great significance to study the mechanical failure characteristics and energy dissipation law of coal–concrete combinations under the influence of impact rate. In this paper, the split Hopkinson pressure bar (SHPB) dynamic load test system is selected, and coal–concrete combination samples are taken as the impact compression test object. Comparative tests under different impact rates are carried out, and the experimental results of the mechanical parameters of the sample change with the impact rate are obtained. Fractal theory and energy dissipation theory are introduced to study the macroscopic failure characteristics of the combination sample after impact dynamic load and the energy dissipation law during the impact process. The results show that the sample has a strong strain rate correlation, and its dynamic compressive strength, dynamic elastic modulus, and impact rate also have a strong positive correlation. The dynamic stress–strain curve conforms to the four typical stages of the dynamic stress–strain curve. The degree of fragmentation of the sample is proportional to the impact rate. The larger the impact rate, the smaller the proportion of large particle size to small particle size; the fractal dimension of particle size also increases with the impact rate. The transmitted energy, reflected energy, dissipated energy, and incident energy increase with the impact rate, but the increase amplitude is different. The overall energy value is reflected energy > transmission energy > dissipated energy. The energy ratio of different forms fluctuates with the impact rate, the reflected energy ratio is positively correlated with a certain impact rate, the transmission energy ratio is basically symmetric and fluctuates between 30% and 40%, and the dissipated energy ratio increases with the impact rate. [ABSTRACT FROM AUTHOR]

To simulate the nonlinear stress-strain curve of rocks under static loads and contribute to the design and construction of rock engineering structures, a constitutive model has been proposed based on the elastic modulus E decreasing with the increase in longitudinal cracks. This constitutive equation offers numerous advantages, with the most noteworthy being that the simulation of stress-strain curves for rocks necessitates only three equations (Eqs 1–3) and four parameters (A, k0, C and εs). Following this, we employ the constitutive equation to analyze the stress distribution around a thick-walled cylinder and explore the impact of its four parameters on the stress distribution surrounding the thick-walled cylinder. Parameter A primarily affects the range of the plastic zone and the magnitude of the maximum tangential stress; parameter C mainly influences the magnitude of the maximum tangential stress; parameter εs mainly affects the range of the plastic zone and the magnitude of the maximum tangential stress; parameter k0 primarily influences the magnitude of the maximum tangential stress. We got the similar results with Bray model, but distribution of stress around the tunnel are different present that the shape of stress-strain curves are different. [ABSTRACT FROM AUTHOR]

Accurate estimation of the effects of dynamic disturbances on stress concentration is crucial for the stability of rock engineering and the corresponding analytical approaches are needed. This study presents an analytical approach to calculate the relative stress distribution with a point source inside and outside a hole using the linear theory of elasticity. The Helmholtz potentials and Sommerfeld integral are employed to describe the displacement and stress components, and then formulate the equilibrium equations to solve the equivalent stress distribution around the hole. Numerical examples demonstrate the impact of model parameters on the equivalent stress, such as frequency, hole radius, source location, etc. It is found that sometimes high frequencies can make the equivalent stress greater far from the source than that close to the source. Additionally, when the ratio of the distance between the source and the hole axis to the hole radius exceeds ten, the equivalent stress distribution around the hole remains nearly constant. This approach can be used for the design and assessment of underground engineering structures' stability under dynamic disturbances. [ABSTRACT FROM AUTHOR]

Based on a soft rock tunnel in a mountainous area of northwest Yunnan Province, a refined numerical model of different support forms considering structural interaction is established to comprehensively evaluate the structural failure mechanisms and mechanical responses of different support forms. Research shows that compared to steel rib structures, the axial force and bending moment of sprayed concrete structures is larger under different combinations of support structures. Compared with a single-layer support structure, the stress distribution at each position of the double-layer I-shaped steel structure is more uniform, and the sprayed concrete structure only experiences compression damage at the corner of the side wall. As the strength of sprayed concrete increases, the stress distribution of sprayed concrete at the arch waist becomes more uniform. The stress concentration state of sprayed concrete at the corner of the tunnel wall and the plastic yield state of the steel rib structure have also been improved. The higher the concrete strength, the lower the stress ratio on the steel rib's inner and outer sides. [ABSTRACT FROM AUTHOR]

This study investigates the mechanical properties of tiled laminates, frequently used in FRP bridges, and a completely new class of composites for which currently no experimental literature is available. In this paper, first a microscopic examination of laminates extracted from bridge deck flanges is performed, revealing complex multi-ply structures and tiled laminates in the transverse direction of the bridge deck. The subsequent fabrication of tiled laminates in the transverse (i.e., weak) and longitudinal (i.e., strong) span direction explores stiffness and strength characteristics depending on the stacking angle. It is observed that the stiffness in both directions is only slightly reduced with increasing stacking angles, reaching a maximum decrease of 10%, while the failure strength is significantly reduced, particularly with longitudinal tiling, dropping by approximately 70% for a 2° stacking angle. Transverse tiling demonstrates a more moderate 45% strength reduction due to the presence of some 90° plies. Given the small reduction in the stiffness and the fact that in many applications the design is mainly governed by serviceability (i.e., stiffness) requirements than strength, this strength reduction may be acceptable, considering other advantages of the concept. Additionally, this research sheds light on failure mechanisms, emphasizing the role of ply assembly in stress distribution and highlighting the importance of gradual ply ends in reducing strain concentrations. These findings provide valuable insights for optimizing tiled laminates in structural applications, ensuring their effective and reliable use. [ABSTRACT FROM AUTHOR]

The flat-roof and four-slope folded plate structure is a space thin-walled structure composed of four trapezoidal plates and a rectangular plate parallel to the bottom surface, which is widely used in various engineering applications. In order to clarify the force transmission path and stress distribution law under the action of this structural load, the folded plate structures were made by utilizing the plexiglass with the thicknesses of 3 and 4 mm, respectively, and had the simple support on opposite sides and fixed support on another opposite side. Then, the static load tests and ANSYS finite element analysis were implemented, and the results were compared. It shows that the test results are basically consistent with the finite element calculation results, the maximum stress values of the folded plate structure along the X and Y directions appear in the same position, and the maximum stress value of a 3 mm thick folded plate structure is greater than that of 4 mm. The junction position of the roof and the slope plate is the dangerous section, and the special treatment should be made for this section to prevent the damage of folded plate structure in the practical engineering. Moreover, some reasonable measures also should be taken to meet the design requirements of the plate–plate junction position. [ABSTRACT FROM AUTHOR]

Lug is one of the most important lap joints in many engineering structures, especially airframes. Through‐thickness and part‐through cracks emanating from pin‐loaded lug hole are frequently encountered due to stress concentration. Stress intensity factors for various crack geometries are the prerequisite for damage tolerance design of attachment lug. In this paper, analytical 2D weight functions for through‐thickness crack in lug are derived considering the contact condition between the pin and lug. With the derived 2D weight function, a highly efficient 3D slice synthesis weight function method (SSWFM) is then developed to determine 3D SIFs of hole‐edge corner/surface crack in straight and tapered lugs under various pin loadings. The resulting 3D SIFs are verified by comparisons with the numerical FEM/Franc3D solutions and literature data. The SSWFM is about 1800 times faster than the numerical FEM/Franc3D and therefore will significantly enhance damage tolerance analysis capability for attachment lugs. Highlights: Accurate and wide‐range weight functions of pin‐loaded cracked lug are derived considering the contact constraint.A 3D weight function method for corner and surface cracks of lug is established.It is accurate and much faster than FEM for SIF calculation. [ABSTRACT FROM AUTHOR]

To investigate the influence of the crack dip angle on the strength of rock specimens, uniaxial compression tests were conducted on granite specimens containing pre-existing cracks. The strain energy evolution during the loading process was analyzed, and the loading-induced cracking process was simulated using the cohesive element method. Both the experimental and numerical results indicate that cracks significantly impact the plastic-yielding stage of the stress–strain curve more than the initial and elastic deformation stages. When the crack dip angle is less than 45°, the stress concentration near the crack is significant, which is an important factor affecting the strength and elastic strain energy distribution of rock specimens. When the crack dip angle is greater than 45°, the degree of stress concentration decreases, and the uniformity of the elastic strain energy distribution and the possibility of crack bifurcation increase. Combining the energy theory with the cohesive element method helps comprehensively understand the initiation, propagation, and coalescence of microcracks near pre-existing crack tips. These research results can provide a reference for geotechnical engineering design and structural stability assessment. [ABSTRACT FROM AUTHOR]

The primary focus of this paper is to investigate the application of ANSYS Workbench 19.2 software's advanced feature, known as Separating Morphing and Adaptive Remeshing Technology (SMART), in simulating the growth of cracks within structures that incorporate holes. Holes are strategically utilized as crack arrestors in engineering structures to prevent catastrophic failures. This technique redistributes stress concentrations and alters crack propagation paths, enhancing structural integrity and preventing crack propagation. This paper explores the concept of using holes as crack arrestors, highlighting their significance in increasing structural resilience and mitigating the risks associated with crack propagation. The crack growth path is estimated by applying the maximum circumferential stress criterion, while the calculation of the associated stress intensity factors is performed by applying the interaction integral technique. To analyze the impact of holes on the crack growth path and evaluate their effectiveness as crack arrestors, additional specimens with identical external dimensions but without any internal holes were tested. This comparison was conducted to provide a basis for assessing the role of holes in altering crack propagation behavior and their potential as effective crack arrestors. The results of this study demonstrated that the presence of a hole had a significant influence on the crack growth behavior. The crack was observed to be attracted towards the hole, leading to a deviation in its trajectory either towards the hole or deflecting around it. Conversely, in the absence of a hole, the crack propagated without any alteration in its path. To validate these findings, the computed crack growth paths and associated stress intensity factors were compared with experimental and numerical data available in the open literature. The remarkable consistency between the computational study results for crack growth path, stress intensity factors, and von Mises stress distribution, and the corresponding experimental and numerical data, is a testament to the accuracy and reliability of the computational simulations. [ABSTRACT FROM AUTHOR]

Pultruded GFRP (glass fiber-reinforced polymer) materials are widely used in structural engineering because of their lightweight, corrosion immunity, and electromagnetic transparency. However, the design of load-bearing components facing substantial compressive stresses, e.g., columns, must be more stringent than steel structures due to excessive deformability, material heterogeneity, and vulnerability to stress concentration. This manuscript investigates the failure performance of locally produced GFRP materials, focusing on the material heterogeneity effect on the mechanical resistance of a support joint of a pultruded tubular GFRP column. This experimental campaign employs relatively short rectangular profile fragments to isolate the support behavior and verify a simplified numerical finite element model, which neglects the nonlinearity of GFRP material. This work determines the material failure mechanisms behind the mechanical performance of pultruded profiles subjected to longitudinal compression for various column lengths. [ABSTRACT FROM AUTHOR]

The γ‐procedure for calculation of partially composite beams consisting of flexibly jointed cross‐section with any number of sub‐elements: double‐symmetric cross‐sections Partially composite beam cross‐sections consisting of any number of sub‐elements with a double‐symmetric structure exhibit antimetric normal stress distribution and symmetric shear stress distribution. The symmetry properties are exploited to develop simple formulas for determining the individual γ‐values in this paper. Formulas are given for double‐symmetric partially composite beam cross‐sections with up to nine sub‐elements. [ABSTRACT FROM AUTHOR]

High-strength steel (HSS) has been increasingly applied in structural engineering, while the work on residual stress of HSS sections is still insufficient. Limited research is available for welded H-sections above 690 MPa while with a plate thickness of more than 10 mm. This paper deals with the residual stress distributions of welded H-sections with flame-cut edges, which are fabricated from HSS plates with yield strength of 690 MPa and 960 MPa and thickness of 10 mm–20 mm, using both experimental and numerical method. The experiments showed that the welded tensile residual stresses in the weld region are not significantly affected by sectional dimensions and steel grade. Verified by comparing with the experimental results, three-dimensional (3D) finite element (FE) models using sequentially coupled thermal-stress analysis was adopted for parametric study of compressive residual stress of welded H-sections made of 690 MPa HSS. The results showed that the compressive tensile stress is negatively correlated with plate thickness as well as width-thickness ratio. Through regression analysis, formulae were proposed for estimation of compressive residual stress in the flange and web, respectively. Finally, residual stress distribution model was developed, which was proved effective by comparing with the experimental and FE results. [ABSTRACT FROM AUTHOR]

The presented work focuses on the spatially distributed actuation behavior of flexoelectric actuators on a parabolic cylindrical shell panel with simply supported boundary conditions. A flexoelectric actuator with significant electric field gradients could generate actuation forces and control moments to drive or control system oscillations. For an engineering structure with initial excitations, flexoelectric actuators could be employed to achieve vibration control with designed electric inputs. The dynamic equations of the parabolic cylindrical panel laminated with an arbitrary flexoelectric actuator are defined first. The transverse displacement excited by an external mechanical loading and flexoelectric actuators is calculated. Actuation effects and vibration control efficiency contributed by various design parameters including flexoelectric patch thickness and atomic force microscopy (AFM) probe radius are studied. As the purpose of this study is to accelerate the vibration attenuation, the open-loop control usually causes insufficient control or over-actuation effects. Using displacement feedback, velocity feedback, and acceleration feedback, the effectiveness of these three closed-loop control methods is analyzed and evaluated by the modal response. Analyses suggest that the velocity feedback could effectively attenuate oscillations with the lowest voltage input than in the other two cases. Specifically, the system damping ratio can be adjusted with velocity feedback. Lower voltage input could benefit system design and release stress concentrations caused by high electric field gradients. This research provides a basis for vibration control based on flexoelectric parabolic shell structures and provides an optimal choice for the design of flexoelectric drive closed-loop control for parabolic shell structures. [ABSTRACT FROM AUTHOR]

Self-tapping screws (STS) are used in wood-to-wood and wood-to-steel connections in timber structures. Premature failure of STS during the construction phase has been reported by structural engineers and contractors in relation to a few North American mass-timber projects. This STS failure type is suspected of having been precipitated by additional axial stress exerted on STS from swelling of the wood resulting from prolonged wetting. This study investigates the axial stress distribution of STS installed in two mass timber products, cross-laminated timber (CLT) and glulam, under axial loading and changing moisture conditions in the linear elastic regime. The focus is on modelling the stress distribution of STS during wood-wetting. Properties of self-tapping screws under axial loads, such as tensile and withdrawal properties, along with swelling properties of CLT and glulam, have been investigated. A numerical method to predict the axial stress distribution of the screw from these material property tests has been developed. The numerical model has been calibrated with test results. The method developed in this research helps in understanding the premature failure of self-tapping screw connections under the moisture content variation of wood. The next step will be developing an analytical model to predict the axial stress distribution of STS. [ABSTRACT FROM AUTHOR]

Unequal distribution of stresses in soil underneath the foundations of adjacent buildings represents a great challenge in structural engineering, especially for buildings prone to earthquakes. Another serious problem facing earthquakeprone adjacent buildings is collision, which severely affects the behaviour of the buildings and changes the distribution of the soil stresses under the foundations of the buildings. This research investigates seismic responses of adjacent High-Rise Buildings (HRBs) exposed to seismic-induced pounding and impose irregular soil stress distribution considering the Soil-Structure Interaction (SSI) effect. For this purpose, numerical nonlinear dynamic analysis of three-dimensional models of adjacent four HRBs is conducted. To mitigate the exaggerated effect of seismic-induced collision and soil stress irregularity on the seismic response of the adjacent HRBs, three approaches are proposed; improving soil bearing capacity in the highly stressed zone, joining the adjacent HRBs by means of Fluid Viscous Links (FVLs), and combining the two previous approaches. Three-dimensional models of the adjacent 4HRBs group are studied under different earthquakes to examine the abovementioned three approaches. The combination approach shows promising results in moderating the collision effects; it considerably mitigates the pounding effects between the adjacent HRBs in terms of reducing straining actions and displacements of buildings as well as controlling stresses irregularity in soil under the foundations of such buildings. [ABSTRACT FROM AUTHOR]

Carbon fibre-reinforced polymer (CFRP) plates are promising materials for cables and prestress tendons in structural engineering for the excellent tensile performance, light in weight and anti-corrosion character. Anchoring has always been the main challenge of this high-performance material due to its anisotropy and brittleness. Corrugated anchors are high-efficiency clamping-type anchorage devices. Nevertheless, premature failure of the CFRP plates can still be observed with this type of anchors, and the anchor efficiency for the corrugated anchors needs further improvement. This paper proposes a novel configuration of corrugated anchors. Experimental tests are then carried out to investigate the influence of the pre-tensioning bolt load and adhesive layer. Consequently, numerical analysis is conducted to reveal the anchoring mechanism. The results indicate the traditional corrugated anchors lead to non-uniform stress distribution in the CFRP plate, and with the proposed configuration the anchor efficiency can be increased up to 100 %. • Novel configuration of corrugated anchors for CFRP plates. • Mechanism and stress distribution of corrugated anchors. • Achieving anchor efficiency up to 100 %. [ABSTRACT FROM AUTHOR]

To address the challenges of difficult extrusion for super-large cross-section aluminium alloy members, pairs of T-shaped sections were proposed to be longitudinally friction stir welded (FSW) to form the H-shaped sections widely used in structural engineering. It was significantly different from the previous member forming method that one web plate and two flange plates were welded at the flange-web junctions. To understand the novel FSW-induced residual stress distributions and magnitudes in the H-shaped sections, six specimens made of 6061-T6 and 6013-T6 normal-strength aluminium alloys, including various width-to-thickness ratio and plate thickness, were tested using the sectioning method, leading to over 4000 original readings of compressive and tensile residual stresses. The analysis results showed that great tensile residual stresses were clearly concentrated within the web weld, and then rapidly descended to lower compressive stresses near the weld region, followed by approximately linear regression to zero state from the weld edge to the flange-web junction, while the flange data points were relatively scattered. The compressive and tensile residual stresses in each flange and web plate were observed to be slightly associated with the width-to-thickness ratio and plate thickness. A simplified multi-linear residual stress distribution model, including the magnitudes and ranges of constant and linear variation curves, was proposed for the FSW aluminium alloy H-shaped sections, and good accuracy and consistency were observed between the test and predicted results. • The residual stress of friction stir welded aluminium alloy H-shaped sections was tested. • The bending deformation correction and interaction effect of cross-section parameters were evaluated. • The simplified residual stress distribution model and specific calculation formulas were proposed. [ABSTRACT FROM AUTHOR]

• Extended phase-field models with high accuracy are developed. • Thermal-induced fracture of functionally graded composites is investigated. • The temporal evolution of strain energy and fracture energy are examined. • The crack propagation and stress distribution are comprehensively examined. • Composites of different geometries are investigated. A phase-field modeling is presented to study the complex thermal mismatch fracture behavior in functionally graded materials. The fracture resistance in functionally graded materials is homogenized by the rule of mixtures of the energy release rate. For validation, the bi-material plates and rectangular plates coated with functionally graded materials under thermal load are examined and the obtained results are compared with existing theoretical and experimental data. In the bi-material plates, the model captures commonly experimentally observed crack patterns such as the perpendicular crack, benching, and the formation of two pairs of parallel cracks. Additionally, a detailed comparison of the correlation between crack depth and film thickness is conducted among theoretical, experimental, and phase-field model data. Notably, the results of the phase-field model exhibit good agreement with experiments compared to the theoretical model. Subsequently, the model is applied to examine the thermal mismatch fracture behavior in plates of different shapes. The analysis emphasizes three key aspects: (i) examining the damage field to understand crack initiation and propagation, (ii) analyzing the major principal stress field in the coatings to identify fracture-critical regions, and (iii) tracking the evolution of elastic/fracture/total energies to investigate the fracture/deformation behavior. This analysis enhances a fundamental understanding of thermal fracture mechanisms in functionally graded materials and provides a foundation for optimizing materials and structures in various engineering applications. [ABSTRACT FROM AUTHOR]

Open hole structures are common in ship and marine structural engineering design. Geometric discontinuity can lead to local stress concentration during loading, reducing the structure's service life. In this paper, cold expansion experiments were conducted on titanium alloy open hole structures with different lubrication conditions, and the tensile and fatigue properties were evaluated. The cold expansion resistance under different lubrication conditions was measured and compared during these studies. The tensile properties were compared, and the strain state during the tensile process was analyzed using two-dimensional digital image correlation (DIC). The fatigue performance of specimens and their stiffness degradation characteristics were analyzed. The results showed that lubricants could effectively reduce strengthening resistance and improve the uneven strengthening situation. For tensile properties, the tensile strain of the strengthened groups that used lubricants decreased significantly. Among all the experimental groups, except for the silicone oil group, the fatigue life of the other experimental groups was significantly improved compared to the un-strengthened group. Therefore, it can be inferred that appropriately lubricating to adjust expansion resistance is beneficial for enhancing fatigue performance and improving fatigue life, while excessively reducing interfacial resistance is not conducive to increasing fatigue life. • The optimization design analysis was conducted for cold expansion strengthening under different lubrication conditions. • The tensile fracture process of the open-hole structure was analyzed using two-dimensional digital image correlation. • Proper lubrication could contribute to the enhancement of fatigue life under high cyclic loads. • The microscopic mechanism of fatigue fracture was studied and clarified using the scanning electron microscope. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mechanical property of T riply P eriodic M inimal S urface structure is studied. • The mechanism of residual stress generation in TPMS structure is analyzed. • An optimized process scheme is proposed to reduce the residual stress. • How residual stress affects mechanical property of TPMS structure is checked. • Effects of cell type, volume fraction and compression direction are explored. Due to its special porous structure with smooth continuous surface and high specific surface area, the triply periodic minimal surface (TPMS) lattice structure exhibits excellent properties such as strong bearing capacity, high energy absorption rate and good fatigue performance. The residual stresses generated during the additive manufacturing (AM) process can have a significant impact on the mechanical properties of the TPMS structure. In this paper, the AM process of four typical TPMS structures are investigated by the thermal–mechanical coupling model. The mechanism of residual stress generation is analyzed, and an optimized preparation process scheme is proposed to reduce the residual stress. Furthermore, the effects of residual stresses on the mechanical properties of TPMS structures are investigated for different types, volume fractions and compression directions. Results show that the influences of scanning speed and hatch spacing on the residual stress are not significant with constant laser power, but the deposition thickness should be adjusted according to the characteristics of the structure. The residual stress will reduce the elastic modulus and yield strength, while no obvious effect on the plastic behavior is observed. Importantly, the residual stress has the greatest influence on the mechanical properties of I-WP-type among the four investigated types, which becomes more pronounced with the increase of volume fraction. Moreover, the influence of residual stress on the mechanical properties of TPMS structures depends on the compression direction. Our results give a comprehensive understanding of the residual stress distribution and impact on the mechanical properties of TPMS structures, providing guidance to the rational design and optimization of TPMS structures in engineering applications. [ABSTRACT FROM AUTHOR]

In the field of engineering structures, the adoption of concrete-filled double-skin steel tubular members has emerged as a promising solution to address problems related to excessive structural weight or susceptibility to local buckling. To enhance the performance of these members, lightweight concrete is used instead of normal concrete, and the steel tubes are designed to be tapered with the addition of longitudinal stiffeners. This innovative approach has led to the development of tapered lightweight concrete-filled double-skin stiffened steel tubular members with large hollow ratio, offering significant advantages in terms of strength-to-weight ratio and spatial efficiency. This study investigated the torsional performance of tapered lightweight concrete-filled double-skin stiffened steel tubular members to develop a predictive model for their torsional capacity. Torsion tests on eleven specimens demonstrated that reducing the diameter-to-thickness ratio of the outer tube from 166 to 121 and 80 increased the torsional capacity of unstiffened specimens by 8.5% and 37.9%, and for stiffened specimens by 11.7% and 44.8%, respectively. Similarly, adjustments to the inner tube from 115 to 84 and 56 enhanced the capacity of unstiffened specimens by 6.2% and 23.8%. Stiffened specimens showed greater ductility but had slightly reduced torsional capacity due to the segmenting effect of stiffeners. Numerical analysis explored stress distribution under torsional loads, leading to a highly accurate new method for predicting torsional capacity in such members. • Torsion tests on LHRTL-CFDSST members were conducted. • The torsional behavior of LHRTL-CFDSST members was investigated using experimental and numerical methods. • A novel theoretical method for predicting the torsional capacity of concrete-filled double-skin steel tubular (CFDST) members was proposed. [ABSTRACT FROM AUTHOR]

After millions of years of natural evolution, bamboo stems have formed exquisite variable cross-section hollow multi-node structures that are lightweight, tough, and stable. Bamboo is difficult to break and damage from the roots under dynamic loads, providing an important reference for te biomimetic design of lightweight components. This paper investigates the structural characteristics and variation patterns of bamboo stems and subsequently proposes an imitation bamboo stem structure design strategy for engineering structural members, namely, imitation bamboo double-jointed columns (IDJC). We establish a macro scale finite element model to predict the mechanical properties and failure modes of the IDJC under cyclic bending loads, and validate the model using experimental and analytical methods. The simulation and experimental results show that compared with traditional double-jointed columns (DJC), the weight of the IDJC is reduced by 41.7 %. Under bending load, the compressive stress of each section is approximately equal, reducing stress concentration, and increasing bending resistance. The strength to weight ratio of IDJC is 1.96 times that of DJC, indicating lightweight and high-strength characteristics. The stiffness degradation, energy dissipation, and damping and vibration reduction performance of the IDJC were also evaluated. The results showed that compared with the DJC, the stiffness degradation rate of the IDJC decreased by 6.87 times, the energy dissipation rate increased by 1.07 times, and the damping and vibration reduction performance improved by 48.40 %, reflecting a high stability and robust vibration reduction performance. The results demonstrate the potential application of biomimetic structures for the development and design of resource-rich, low-carbon, and sustainable bamboo for bamboo engineering members with excellent performance and functionality. Biomimetic structures have great potential in replacing nonrenewable structural materials in the fields of civil engineering and transportation. ● Quantitative study on the characteristics and patterns of bamboo stem structure. ● A bamboo like structural component was prepared using the concept of biomimetics. ● The prepared structural components have excellent stability and damping performance [ABSTRACT FROM AUTHOR]

Tissue engineered scaffolds need to possess various functionalities, including biocompatibility, mechanical support, bioactivity, and vascularization. The design and fabrication of bioscaffolds to attain mutual coordination among these functionalities with minimal processing complexity are a highly challenging but rewarding task. In this study, a simple, effective one-step electrospinning method was developed to fabricate hierarchical spiderweb-like bioscaffolds that achieve both superior biological and mechanical functionalities. By incorporating ionic drugs of deferoxamine mesylate and lithium chloride, the spiderweb-inspired structures with adjustable coverages (up to 100 %) were successfully created, imparting the fibrous bioscaffolds with remarkable tensile strengths (∼88.28 MPa). The strengthening mechanisms endowed by the spiderweb structure in optimizing stress distribution to delay damage and enhance load-bearing ability were elucidated through finite element simulations. Furthermore, this hierarchical spiderweb-like bioscaffold demonstrated favorable biological characteristics, including biocompatibility, osteogenesis, angiogenesis, and hemostasis. The presence of the nano-spiderweb structures significantly improved cell adhesion and differentiation on the scaffold and increased the spreading area of cells by 2–3 times. The dual-drug loaded bioscaffolds with full coverages of the spiderweb structure exhibited the least amount of bleeding (45.33 ± 27.47 mg) and the fastest hemostasis speed (82 ± 8.19 s) in the hemostasis test, compared to the control group. Overall, the outstanding performance makes the developed bioscaffolds a promising alternative for tissue repair and regeneration in the field of tissue engineering. [ABSTRACT FROM AUTHOR]

Finite-element analysis (FEA) for structures has been broadly used to conduct stress analysis of various civil and mechanical engineering structures. Conventional methods, such as FEA, provide high fidelity results but require the solution of large linear systems that can be computationally intensive. Instead, Deep Learning (DL) techniques can generate results significantly faster than conventional run-time analysis. This can prove extremely valuable in real-time structural assessment applications. Our proposed method uses deep neural networks in the form of convolutional neural networks (CNN) to bypass the FEA and predict high-resolution stress distributions on loaded steel plates with variable loading and boundary conditions. The CNN was designed and trained to use the geometry, boundary conditions, and load as input to predict the stress contours. The proposed technique's performance was compared to finite-element simulations using a partial differential equation (PDE) solver. The trained DL model can predict the stress distributions with a mean absolute error of 0.9% and an absolute peak error of 0.46% for the von Mises stress distribution. This study shows the feasibility and potential of using DL techniques to bypass FEA for stress analysis applications. [ABSTRACT FROM AUTHOR]

The common damage in engineering structures, especially in functionally graded materials, such as failure resulting from fiber breaking or cracking in the matrix or deboning between fibers and matrix, as well as the delamination between the composite material plies and between its layers, may be due to thermal effects, vibration, load concentration as a result of stress and strain for provides information's about structural health monitoring. Virtual energy method such as Hamilton's was used to investigate the effect of the design parameters such as side to thickness and modular as well as material graduation index ratio on the stress-strain relationships, displacement, resultants of stresses, and resultants of mid plane strain. The analysis and simulation of the FGM shells is done in this paper utilizing MATLAB19 code and ABAQUS20 programs. The distribution of characteristics across shell thickness had also been determined using a power law. Normal stress was varied gradually from 5.74 MPa to 9.55 MPa with material index (n) from 0 to 10 respectively, while shear stress varied from 4.2 to 8.23 MPa for the same value of (n). The strain percent increased slightly from 0.00059 to 0.0012 with displacement 0.22 and 1.2 respectively for the same value of (n). [ABSTRACT FROM AUTHOR]

In order to ensure high weld qualities and structural integrity of engineering structures, it is crucial to detect areas of high stress concentrations along weld seams. Traditional inspection methods rely on visual inspection and manual weld geometry measurements. Recent advances in the field of automated measurement techniques allow virtually unrestricted numbers of inspections by laser measurements of weld profiles; however, in order to compare weld qualities of different welding processes and manufacturers, a deeper understanding of statistical distributions of stress concentrations along weld seams is required. Hence, this study presents an approach to statistically characterize different types of butt joint weld seams. For this purpose, an artificial neural network is created from 945 finite element simulations to determine stress concentration factors at butt joints. Besides higher quality of predictions compared to empirical estimation functions, the new approach can directly be applied to all types welded structures, including arc- and laser-welded butt joints, and coupled with all types of 3D-measurement devices. Furthermore, sheet thickness ranging from 1 mm to 100 mm can be assessed. [ABSTRACT FROM AUTHOR]

• An ESFI approach was proposed for notch fatigue life prediction. • The fatigue failure region was improved to consider actual stress distribution. • A novel weight function was proposed to consider all points relative stress gradient. • The impact of combining notch and size effect was characterized in the ESFI approach. The notch characteristics of engineering components significantly impact their fatigue lives. Accurately analyzing the notch effect and size effect is of great significance for structural integrity evaluation, which provides insights into the extent of fatigue failure in engineering structures. In this paper, a new method is proposed for determining the fatigue failure region based on actual elastic–plastic stress distribution under various notch geometries and applied loads. It considers the complex mechanical behavior of the plastic effect and stress relaxation near the notch root. Furthermore, a novel weight function is employed to consider the relative stress gradient at all points within the fatigue failure region. Finally, an enhanced stress field intensity approach is developed to predict notch specimens fatigue lives utilizing experimental lives of smooth specimens. Additionally, the effectiveness of the proposed method is analyzed by predicting the fatigue lives of three distinct materials notched specimens with varying geometries and applied loads. The prediction absolute errors of the proposed approach are compared with those of the other traditional notched fatigue analysis methods. The comparative results indicated that the performance of the proposed method outperforms the other methods. [ABSTRACT FROM AUTHOR]

Due to the complex geometric structure of screw thread, it is difficult to mesh the internal and external screw surfaces of screw thread parts in the finite element analysis of screw thread parts, which often leads to difficulties in finite element modeling of screw thread structure and poor convergence of numerical calculation. In this paper, based on the fact that the geometry of any cross section of the thread perpendicular to its axis is the same, the standard helix formula formulated by the International Organization for Standardization (ISO) is selected, and the three-dimensional eight node element is used to accurately establish the finite element model of the threaded connector. The model not only considers the influence of screw thread elevation angle on itself, but also arranges the element layers of each pitch in order, the node numbers on each layer are orderly distributed, and the nodes on the internal and external screw thread surfaces are close to each other. These characteristics enable the model to accurately map the mechanical properties of threaded connection structures in engineering, optimize the convergence state of numerical calculation of the model, and facilitate the mechanical profile analysis of the calculated results. To verify the validity of the established finite element modeling method of threaded connection structure, the relationship between tightening angle and preload force in screw structure, the distribution of axial force in screw structure are deduced and theoretically analyzed, and the axial force distribution of M12 standard bolt is calculated as an example. The results of numerical experiments show that the relationship between the tightening angle and the preload of the screw connection structure is consistent with the theoretical analysis results, the axial force distribution of M12 bolt is consistent with the theoretical calculation results, the stress concentration coefficient at the root of the thread is consistent with the experimental results, the stress distribution and plastic strain distribution are consistent with the actual engineering measurement. A parametric modeling software for bolt and nut is developed base on proposed the finite element modeling scheme of threaded connection structures. The software can quickly view and generate three-dimensional finite element models of different types of bolts and nuts according to the input thread diameter, pitch number and other parameters. In the engineering analysis and optimization design, it not only avoids the tedious repetitive work of designers, but also improves the design accuracy and work efficiency, which can better meet the actual engineering needs. [ABSTRACT FROM AUTHOR]

Notched components are commonly used in engineering structures, where stress concentration may easily lead to crack initiation and development. The main goal of this work is to develop a simple numerical method to predict the strength and crack‐growth‐path of U‐notched specimens made of brittle materials. For this purpose, the Fragile Points Method (FPM), as previously proposed by the authors, has been augmented by an interface debonding model at the interfaces of the FPM domains, to simulate crack initiation and development. The formulations of FPM are based on a discontinuous Galerkin weak form where point‐based piece‐wise‐continuous polynomial test and trial functions are used instead of element‐based basis functions. In this work, the numerical fluxes introduced across interior interfaces between subdomains are postulated as the tractions acting on the interface derived from an interface debonding model. The interface damage is triggered when the numerical flux reaches the interface strength, and the process of crack‐surface separation is governed by the fracture energy. In this way, arbitrary crack initiation and propagation can be naturally simulated without the need for knowing the fracture‐patch before‐hand. Additionally, a small penalty parameter is sufficient to enforce the weak‐form continuity condition before damage initiation, without causing problems such as artificial compliance and numerical ill‐conditioning. As validations, the proposed FPM method with the interface debonding model is used to predict fracture strength and crack‐growth trajectories of U‐notched structures made of brittle materials, which is useful but challenging in engineering structural design practices. [ABSTRACT FROM AUTHOR]

Welded steel box sections are applied in various fields like in bridges as well as in structural engineering and industrial constructions. Apart from square‐shaped sections, these sections have the tendency to warp under torsion. Therefore – in case of torsional loading – restraints of the member's longitudinal displacements always result in additional stress components, the so‐called warping normal stresses and warping shear stresses. Due to the complex distributions of this warping stress components, frequently simplifications are done in practice within the design for ULS. It means, that only the St Venant shear stresses are considered, without taking into account the warping stresses. The neglect of these locally restricted warping stress fields seems accurate according to the ductile material behaviour of steel, as long as no part of the member is susceptible for local buckling. Within this paper a comprehensive study for slender box sections is presented, whether a buckling analysis with only the St Venant shear stresses, provides sufficient safety against buckling. The investigation included members under pure torsion as well as combined loading – consisting of axial force and torsion or bending and torsion. The ultimate load carrying capacity of the box section member was compared with the isolated buckling capacity of the individual plates with all‐round hinged supports, under only St. Venant shear stresses, while neglecting all additional occurring warping effects. [ABSTRACT FROM AUTHOR]

This paper presents three-dimensional planar crack and non-planar defects analysis of piezoelectric materials by the finite element method (FEM). Based on practical engineering, a series of reasonable three-dimensional defects models are established. Different from the usual two-dimensional plane as a three-dimensional defect form, the present paper takes into account the different causes, concrete position, and various shapes of typically three-dimensional non-planar defects in practical engineering. By changing the geometric size of the defect and the electro-mechanical boundary conditions, the effects of three-dimensional defect geometry and different electro-mechanical coupling boundary conditions on the distribution of stress, electric field strength, and electric displacement around the defect are investigated. The calculation results show that the electro-mechanical parameters are strongly affected by the geometry of defect and boundary conditions. Furthermore, the distribution of electro-mechanical parameters in the detailed position of the different three-dimensional defect model is also studied, which can accurately assess the location where the defect is prone to fracture. It is concluded that this paper can be used as a reference of three-dimensional defects and the service life of piezoelectric materials in practical engineering structures. [ABSTRACT FROM AUTHOR]

The Bayueshan (BYS) tunnels are adjacent tunnels which comprise key engineering structures important for Yurong highway from Chongqing to Sichuan, China. The tunnels were established crossing over the old goafs of a coal mine. The tunnels have been damaged three times between 2014 and 2016. To evaluate the reasons for the damage, fast Lagrangian analysis of continua in three dimensions ( FLAC 3 D ) was used to simulate the underground coal-mine excavation yearly from 2012 to 2015. The simulation results show that the subsidence of the ground surface increased annually. The maximum subsidence of the left tunnel was 505 mm and that of the right tunnel was 512 mm. The excavation led to increase in the tunnels' stress concentration. The simulations further show that uneven horizontal displacement and subsidence were the major factors in inducing tunnel construction defects. Poor geological conditions, water, and vehicle dynamic loads were also important factors that induced damage. Several engineering suggestions for ways to maintain the tunnels are given in this paper, and the research provides a reference for safety evaluation for tunnels crossing over an old goaf. [ABSTRACT FROM AUTHOR]

Structural components with arbitrary cross sections play a key role in several engineering fields. Many engineering structures are subjected to torsional moments, so it is important to design and analyze these type of crucial engineering issues. First, this study offers a novel analytical solution for Prandtl's stress distribution of arbitrary annular wedge-shaped bars under uniform torsion moment based on eigenfunction expansion. Next, warping function is derived by integration of Cauchy-Riemann type relations in polar coordinate system. The solution encompasses existing solutions for standard wedge-shaped bars as subsets. Finally, accuracy of the proposed analytical method is fully demonstrated through some benchmarks which are available in the literature. [ABSTRACT FROM AUTHOR]

Suncun coal mine in Xinwen mining area is a typical deep rockburst mine. And the main mining seams are the No.2 and No.4 coal seams. The No.2 coal seam is with the weak bursting liability, and its roof and floor with the strong bursting liability; the No.4 coal seam and its roof and floor are with the weak bursting liability. In order to ensure the safe production of mine, the No.4 coal seam should be chosen as the liberating seam and firstly mined. Therefore, first of all, the upward mining feasibility of coal seam group is studied by theoretical analysis method, and then the structural evolution, fracture development and stress distribution characteristics of overlying strata in stope after mining of No.4 coal seam are studied by numerical simulation method. The research results show that the mining of No.4 coal seam do not destroy the mining condition of No.2 coal seam, instead, it can effectively reduce or even eliminate the bursting risk in the process of No.2 coal seam mining. Based on the above research results, the No.4 coal seam was mined by the following prevention and control rockburst measures, namely: the large-diameter borehole for pressure relief of coal mass, and the drilling cutting method for effect test and evaluation. Besides, the borehole stress sensors are used to monitor and analyze the pressure relief effect of No.2 coal seam after mining of No.4 coal seam. The in-situ monitoring results show that the implementation of large-diameter pressure relief borehole in the front of working face can effectively ensure the safe production in coal seam with weak bursting liability; and the mining of liberating seam is an effective measure for safe production in coal seam with strong bursting liability. [ABSTRACT FROM AUTHOR]

The paper presents the stress distribution along the plate thickness in a bimetallic steel -- titanium circular perforated plate produced in the technological process of explosion welding. The steel layer is the layer that transfers the load in the plate, while the titanium layer is used to improve the properties of the plate, e.g. corrosion resistance, thermal transmittance, etc. in the plate. Two cases of fastening were considered, i.e. a freely supported and fixed plate. Such plates are used in various engineering structures, e.g. simply supported plates can be used in loose material screens, while plates are fixed in heat exchangers. The load was assumed as a concentrated force applied perpendicularly to the plate surface. The results obtained numerically using the finite element method were compared with the results calculated according to the analytical equations. It has been shown that the difference in the results of equivalent von Mises stress calculations does not exceed 13%. The research results presented in the paper can be used by engineers to design bimetallic perforated plates perpendicularly loaded to their surface. [ABSTRACT FROM AUTHOR]

The creases and wrinkles that form on soft matter have been comprehensively analyzed and engineered to utilize their topological advantages in various research fields. Although the principle for the formation of such structures is found to be the inhomogeneous distribution of mechanical stress, simultaneous and omnidirectional propagation of surface patterns makes it difficult to engineer these structures. A design strategy for the reversible formation of highly uniform crease patterns on hydrogel films is proposed by driving the stepwise evolution of creases. A hydrogel film with a smooth‐ and submicron‐scale surface topology, so‐called hill and valley structures, is prepared by engineering the reaction‐diffusion‐mediated photopolymerization and viscoelastic deformation of hydrogels. As the hydrogel film undergoes a morphological change in response to pH, creases are selectively nucleated from the hill and valley structures and propagate directionally, resulting in the formation of long‐range ordered crease patterns. Different interactions are observed via the investigation of three colloidal systems, demonstrating the capacity to control colloidal particles with the highly uniform surface topology of hydrogels. Finally, the pattern‐guided alignment and reproduction of yeast cells are demonstrated, providing an opportunity for producing an artificial environment for the guided growth and analysis of biomaterials. [ABSTRACT FROM AUTHOR]

The authors present the results of computer simulation of the stress-strain state of a thin-walled spherical shell with an elliptical opening and the surrounding reinforcing inclusion of another material. The effect of geometric and mechanical parameters of inclusions on the stress distribution around the opening and deformation of the shell under uniform internal pressure are investigated. The issue of stress concentration in modern leading fields of technology and industry, namely, in mechanical engineering, rocket, and space, is quite topical since it is associated with the reliability and durability of the designed structures or their elements. Stress concentrators can occur due to imperfections in the materials' structure (cavities, cracks, foreign inclusions, etc.) or technological and structural necessity (openings, cutouts, leaks). Shell structures are used as load-carrying structures in many fields of engineering. They combine high strength with low weight, which contributes to their reliability and safety during operation. In most cases, shells in real structures have simple geometric surfaces (shells of rotation). Complex structures are usually a combination of such shells. It is important to investigate the effect of local stress concentrators as openings (considering inclusions) on the stress-strain state of shells. The methods of stress concentration reduction should be outlined. The authors performed a finite element analysis of the effect of reinforcements modeled by inclusions made of the different materials as compared with the shell material having an opening on the parameters of its stress-strain state. Such investigations are crucial for the design and optimization of the structures in many engineering fields. [ABSTRACT FROM AUTHOR]

Increasing the bending capacity of reinforced concrete (RC) elements is one of important topics in structure engineering. The goal of this study is to develop a transferred stress system (TSS) on longitudinal reinforcement bars for increasing the bending capacity of RC frames. The study is divided into two parts, i.e., experimental tests and nonlinear FE analysis. The experiments were carried out to determine the load-deflection curves and crack patterns of the ordinary and TSS fixed frame. The FE models were developed for simulating the fixed frames. The obtained load-deflection results and the observed cracks from the FE analysis and experimental tests are compared to evaluate the validation of the FE nonlinear models. Based on the validated FE models, the stress distribution on the ordinary and TSS bars were evaluated. We found the load carrying capacity and ductility of TSS fixed beam are 29.39% and 23.69% higher compared to those of the ordinary fixed beams. The crack expansion occurs on the ordinary fixed beam, although there are several crack openings at mid-span of the TSS fixed beam. The crack distribution was changed in the TSS fixed frame. The TSS fixed beam is proposed to employ in RC frame instead of ordinary RC beam for improving the performance of RC frame. [ABSTRACT FROM AUTHOR]

Challenges associated with local stress concentration on layers in stretchable devices under mechanical deformation by bodily motions, which causes strain‐induced signal interference and generates cracks, constitute one of the remaining issues for realization of skin‐attachable stretchable electronics. Herein, a new structural engineering approach is introduced for an elastomeric substrate, a microtrench‐patterned stretchable substrate, in which microtrenches are formed on the substrate backside, effectively mitigating local stress on the surface layers under stretching. Combining the microtrench pattern on the backside and 3D stress‐absorbing microstructured surface on the frontside of the elastomeric substrate for stress engineering results in effective suppression of stress concentration on the crack‐prone carbon paste electrode and piezoresistive pressure sensing layer on the frontside surface due to stress‐concentration on microtrench pattern and, in turn, minimal change in their resistance with deformation. This approach using a simple and facile method to minimize stress in device layers under motion‐induced deformation has great potential for applications of diverse materials for body‐attachable stretchable electronics with minimal strain‐responsiveness. [ABSTRACT FROM AUTHOR]

This Special Issue presents the latest advances in the field of fatigue and fracture performances of additively manufactured mechanical components, including components made of traditional materials (metals, sintered steels, etc.) but undergoing complex loading conditions (multiaxial fatigue and mixed mode fracture). This Special Issue is composed of seven papers covering new insights in structural and material engineering. The advent of additive manufacturing (AM) processes applied to the fabrication of structural components creates the need for design methodologies and structural optimization approaches that take into account the specific characteristics of the process. While AM processes give unprecedented geometrical design freedom, which can result in significant reductions of component weight (e.g., through part count reduction), they have implications in the fatigue and fracture strength due to residual stresses and microstructural features. This is due to stress concentration effects and anisotropy that still need research. The papers of this Special Issue report on numerical simulation and experimental work, or a combination of both. The application of damage and fracture mechanics concepts, the appraisal of stress concentration effects, and the consideration of residual stresses and anisotropic behaviour are tackled for a range of structural applications from biomedical engineering to aerospace components. [ABSTRACT FROM AUTHOR]

• Bond behavior between SFCB and ECC is comprehensively investigated by tests. • A local bond-slip model of SFCB in ECC is developed to predict the bond behavior. • The embedment lengths of SFCB in ECC applicable to different cases are investigated. Steel-FRP composite bar (SFCB) reinforced engineered cementitious composites (ECC) members are promising to apply in structural engineering due to their excellent mechanical properties and durability. The bond behavior between SFCB and ECC was investigated by direct pullout tests. The experimental variables included the diameter of SFCB, bond length, type of matrix, compressive and tensile strengths of ECC, and type of reinforcement. All ECC specimens failed in a ductile manner with ECC keys being crushed and sheared off. The bond strength and bond toughness of ECC specimens were higher than those of concrete specimens possessing similar compressive strengths. An interfacial bond-slip model was proposed to predict the bond behavior of SFCB embedded in ECC. An iteration procedure was performed utilizing the developed bond-slip model to analyze the distributions of bond stresses and slips. Notably, an increase in bond length and the yielding of SFCB led to heightened non-uniformity in bond stress and slip distributions. Furthermore, equations were derived to predict the embedment lengths of SFCB applicable to various scenarios. [ABSTRACT FROM AUTHOR]

• The zero-point characteristic structural stress parameter can identify the influence of undercut notch effect on stress concentration. • The concept of strain is used instead of stress to consider the mixed effect of plastic effect and notch effect. • The Modified EIFS method is proposed to calculate the equivalent initial crack size and the undercut fatigue life. • This method is also suitable for large engineering welding structure by combining sub-model technology. Undercut, as a typical surface imperfection at the weld toe, significantly impacts the weld fatigue life. Neither the ISO5817 standard for imperfection level definition nor the traditional fatigue life prediction methods for welds can accurately identify the undercut effect on weld fatigue life. To solve this problem, a new stress concept and life prediction method are proposed, which can predict the fatigue life of undercut welds in both linear elastic and elastic–plastic conditions. Its prediction accuracy is verified by test data and engineering examples. [ABSTRACT FROM AUTHOR]

• An analytical formulation to design blunt notched specimens to be tested in an ultrasonic machine is developed. • The analytical formulation is numerically verified and experimentally validated. • An experimental fatigue campaign of S690 steel with smooth and notched specimens is performed. • The fatigue behaviour of S690 steel in VHCF regime is assessed. • The mechanisms of fatigue failure are investigated. The presence of a notch or a detail which leads to stress concentration due to complex geometries has a considerable impact on the fatigue life of engineering structures. Therefore, on the one hand, the notch effect must be investigated and considered in the fatigue assessment of these structures. On the other hand, in the last decades, an interest in studying the very high-cycle fatigue regime (VHCF) has been perceived, due to the extension of the service life of engineering components beyond the 10 million cycles. Thus, the notch effect in the VHCF regime was analysed for the S690 structural steel. Therefore, an analytical approach to design notch specimens was developed and a numerical simulation was performed to assess it. Then, an experimental campaign with smooth and notched specimens with two different stress concentration factors was performed in an ultrasonic fatigue machine to assess the VHCF behaviour. The mechanisms of failure and fracture surfaces were also investigated. It was observed a fully notch sensitivity as well as the dominance of surface crack initiation for the S690 steel in the VHCF regime. [ABSTRACT FROM AUTHOR]

• Bond behavior between SFCB and ECC is comprehensively investigated by spliced beam tests. • A bond-slip constitutive model of SFCB in ECC is devised to estimate the bond-slip behavior. • The bond stress distribution of splicing SFCB in the splice region of ECC beams is discussed through FE analysis. The collaborative utilization of steel-FRP composite bar (SFCB) and engineered cementitious composites (ECC) represents a favorable choice for engineering structures exposed to aggressive environments, offering benefits involving both mechanical behavior and durability. This paper primarily studies the bond performance of SFCB embedded in ECC through spliced beam tests coupled with finite element analysis. The findings demonstrate that with an appropriate cover thickness or transverse confinement, spliced ECC beams exhibit failure modes characterized by splitting and pull-out. Under such conditions, the bond-slip response demonstrates limited sensitivity to changes in cover thickness and transverse confinement. Conversely, increasing the cover thickness or introducing transverse confinement in spliced concrete beams, which exhibit splitting failure, significantly enhances the bond strength. Furthermore, in contrast to spliced concrete beams, spliced ECC beams are observed to demonstrate a bond toughness that is 3.85–12.10 times greater. The discrepancy in bond toughness between ECC and concrete diminishes as the cover thickness and transverse confinement increase. Notably, the uniform distribution of bond stress in the splice region of ECC beams remains unaffected by variations in splice length. To incorporate the impact of bond stress distribution when calculating the splice length of SFCB in ECC beams, a coefficient of 0.85 is introduced. [ABSTRACT FROM AUTHOR]

This paper presents a test and numerical investigation into the monotonic behavior of three different complex steel trusses to concrete-filled tubular (CFT) column joints. Based on an engineering structure, 1 : 4 reduced-scale specimens are manufactured and the three-dimensional subassembly testing system is designed to apply the monotonic load. Test phenomena and load-stress curves show that all three types of joints have a considerable load-carrying capacity and joint rigidity. Finite element (FE) analysis is adopted, and the stress distribution shows good agreement with test data. Both test and FE results show that local buckling and yielding in the root region of steel truss are the main failure modes of test joints and the core area of the CFT column remains intact which are in accordance with the design conception of "strong column and weak beam." Design conception of proposed overlap joint form is then investigated based on the FE model, and results show that the optimized overlap joint can effectively reduce the stress concentration in the adjacent steel tube and beam member when compared to the traditional N-type overlap joint. Finally, the influence of the outer diaphragm on the stiffness of joint is analyzed. By comparing the end-displacement of the beam member, conclusion can be obtained that the beam flange thickness is suggested to be chosen as the outer diaphragm thickness. The forms of three different proposed joints and their design conceptions can provide good guidance for designers and engineers. [ABSTRACT FROM AUTHOR]

The advantages of different types of elements are synthesized in the multi-scale finite element analysis, which can improve the calculation accuracy of the engineering structures. The connection between different types of elements is a key issue that determines the accuracy of the simulation. Based on the quasi-static test of two typical substructures of single-layer spatial grid structures, the multi-scale finite element analysis method was thoroughly discussed in anti-progressive collapse analysis of spatial grid structures. The connection with the principle displacement of identical displacement between different scale elements was established and verified through experiment. Then, this method was employed in the anti-collapse analysis of the Kiewitt and Geodesic domes. The study results show that the optimal approximate solution of the simulation can be obtained by using the principle of identical displacement, when the distance between the connection interface and the micro critical area is appropriate. The multi-scale model can obtain the correct and reasonable calculation results with reduced computational resources. The rigid body assumption for joints can further reduce the number of elements. The detail local stress distribution obtained through multi-scale numerical analysis can facilitate the analysis to identify the initial failure position. Additionally, due to the real modeled hollow spherical joints in the multi-scale model, the simulation is more close to the actual situation and results in more accurate structural response. [ABSTRACT FROM AUTHOR]