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Designing tunnels in urban areas necessitates an accurate estimation of their construction effects on adjacent structures. This study explores tunnelling impacts beneath raft foundations, focusing on settlement and bending moment variations due to different tunnel depths and soil densities. A verification model validated tunnel modelling with field data, employing a 2D finite element model to assess raft foundation performance above tunnels. It also examines the influence of tunnel depth, soil consistency, and spacing of two tunnels. Key results show raft settlement increasing by over 250% when tunnels are directly below at a 7.5 m depth, regardless of soil density. Soil cover thickness above the tunnel significantly affects the raft's bending moment, with an increase of up to 400% and 300% for 5 m and 7.5 m cover depths, respectively. Final tunnel construction stage settlements varied with soil density. The study also reveals that increasing the spacing between closely spaced tunnels beyond 1.2 diameters reduces both raft settlements and bending moments. These findings emphasize the importance of careful tunnel placement and soil cover management to minimize negative impacts on raft foundations. [ABSTRACT FROM AUTHOR]

The present study investigates the flexural failure properties of a hybrid laminate beam subjected to three-point bending. A symmetrically laminated hybrid beam is constructed using high-strain and inexpensive glass fibre on the top layers and low-strain and expensive carbon fiber on the middle layers. Classical lamination plate theory is used to find the stress and strain distribution that occurs due to the bending moment on the compressive side. The theoretical failure limits of the laminated hybrid beam are analyzed considering the targeted span-to-depth ratios, volume fractions of the fibers and hybrid ratios using the Tsai-Wu failure criterion and Matlab codes. Using the graph of failure index versus hybrid ratios, the minimum thickness of carbon fiber needed for the delay of failure and cost efficiency of the laminated hybrid beam is identified by applying the linear interpolation method. The numerical results indicate that the failure index increases with the increasing loading span and decreases when the volume fraction of fiber increases. In particular, the placement of glass fiber on the top layer of the laminated hybrid beam might have contributed to obtaining higher strains and curvatures before the catastrophic failure properties of carbon fiber. The flexural stiffness of the laminates is found to increase when the hybrid ratio increases. Overall, it is noted that the theoretical analysis is one method that is less time-consuming and cost-effective than other alternative approaches, such as finite element methods and experimental tests to estimate the minimum thickness of high-stiffness and the expensive material needed to maintain the strength and stiffness of the hybrid composite structures over long periods. [ABSTRACT FROM AUTHOR]

Compared with circular, arched, and pipe-arched soil–steel structures, box-type soil–steel structures (BTSSSs) have the advantages of high cross-section utilization and low cover depth. However, the degree of influence of the crown and haunch radii on the mechanical performance of BTSSSs is still unclear. Therefore, two full-scale BTSSS models with a span of 6.6 m and a rise of 3.7 m but with different crown and haunch radii were established, and the mechanical properties during backfilling and under live load were tested. Afterward, 2D finite element models (FEMs) were established using the ABAQUS 2020 software and verified using the test data. The influence of cross-section geometric parameters on mechanical performance was analyzed by using the FEM, and a more accurate formula for calculating the bending moment during backfilling was proposed. The results show that the BTSSS with a smaller crown radius has a stronger soil–steel interaction, which promotes more uniform stress on the structure and makes the structure have smaller relative deformations, bending moments, and earth pressure. The span and arch height greatly influence the bending moment and deformation of the structure. Based on the CHBDC, the crown and haunch radii were included in the revised calculation formula. [ABSTRACT FROM AUTHOR]

Distortion deformation usually imposes a potential threat to bridge safety. In order to comprehensively understand the distortion effect on thin-walled ultra-high performance concrete (UHPC) box girders, an innovative approach encompassing the governing distortion differential equation is introduced in this study based on the general definition of distortion angle within the cross-section plane. The analytical results obtained from the proposed method are in accordance with those obtained from the energy method, and exhibit favorable agreement with experimental findings documented in the existing literature. Furthermore, a finite element model is developed on the ANSYS 2021 R1 software platform with the employment of a Shell 63 element. Numerical outcomes are also in good agreement with the experimental data, affirming the validity and reliability of the findings. In addition, parameter analysis results indicate that the distortion angle remains approximately constant at a location approximately 1/10 of the span from the mid-span cross-section of the box girder, regardless of changes in the span-to-depth ratio. Increasing the web thickness yields a notable reduction in the distortion effects, and decreasing the wall thickness can effectively mitigate the distortion-induced transverse bending moment. Compared with normal-strength concrete box girders, UHPC box girders can reduce the distortion angle within the span range, which is beneficial for maintaining the overall stability of the box girders. The outcomes obtained from this study yield engineers an enhanced understanding of distortion effect on the UHPC girder performance. [ABSTRACT FROM AUTHOR]

The paper highlights the results of determining the strength of the brake pad of a freight wagon under uneven loading in operation. The main reasons for the uneven loading on the pad have been found. A mathematical tool for determining the strength of the pad unevenly loaded has been proposed. In the study, the pad is considered to be a rod system loaded with concentrated forces and bending moments. Sensors have been used in order to detect the load state of the brake pads. These sensors have been defined in the simulation software, and they have been placed on the working surface of the pad in the area of its interaction with the wheel. The operation of these sensors was simulated in the simulation software package. The results of the calculation have shown that the stresses in the pad are about 21.1 MPa; thus, they exceed the permissible values by 29%. Therefore, considering the uneven loading of the pad in operation, the strength of the pad is not ensured. To test the obtained results, the strength of the pad was determined using the finite element method. The Coulomb criterion was used for the calculation. It was found that the maximum stresses in the pad were about 19 MPa. These stresses were 21% higher than permissible values and occurred in the back of the pad. The study has proven that the uneven loading on the brake pad in operation can cause their destruction during braking. This may also cause traffic accidents with freight trains during their movement. The results of this study will contribute to the theoretical developments and recommendations aimed at improving the brake system of a freight wagon and rail traffic safety. It is considered that the tensometric sensors will be applied in future experimental tests for comparison and verification of the achieved results from the simulation computations. [ABSTRACT FROM AUTHOR]

The current design provisions for corrugated steel culverts in North America consider thrust at the springline to be the critical mechanism and location, respectively, when checking capacity. However, experiments have shown that, at shallow cover depths under vehicle loading, the response of these culverts involves both bending moments and thrust forces, and the critical location in terms of capacity is not at the springline. To address this, 3D finite element modeling of the culvert was undertaken using orthotropic shell elements for the corrugated steel structure and continuum elements for a discrete volume of the surrounding soil. The results of an extensive parametric study are used to develop equations for the critical thrust and bending moment under three different vehicle loading configurations. The proposed equations are then compared to the current design code equations in terms of how well they capture the behavior of the finite element model results. The proposed equations are then used to estimate the response of physical experiments conducted in the laboratory and the field and compared to the responses from distributed strain measurements. The equations were found to provide better estimates of thrust and allow the bending moments, which are currently not considered in North American design codes, to be estimated accurately. Limitations of the proposed equations are also discussed. [ABSTRACT FROM AUTHOR]

Seismic fragility assessment is the probability of damage exceeding a certain design limit. The dynamic performance of a combined multiple tunnel complex is less explored and requires thorough study. This research is based on the numerical approach to evaluate the damage caused to the two new types of tunnel complexes, i.e. twin and triple tunnel complexes in a soft soil profile. A two-dimensional (2D) finite element analysis is performed to determine the induced bending moments for each of the tunnel complexes and develop the seismic fragility curves. A set of full acceleration-time histories are applied to the soil–tunnel complex system by varying embedment depths in different soft soil profiles. From the results, it is concluded that increasing the embedment ratio results in an increased probability of tunnel damage. The developed fragility curves are also inter-compared for both the tunnel complexes to evaluate the better performer during a seismic event. This study serves as an initial step toward the guidelines to determine the percentage of incurred damage and design the combined multiple tunnel complex in a seismic-prone area. [ABSTRACT FROM AUTHOR]

The complex distribution of synchronous grouting pressure results in excessive tunnel deformation and various structural diseases, especially for ultra-large-diameter shield tunnels. In this study, to reduce the risk of tunnel failure, a three-dimensional refined finite element model was established for the Wuhan Lianghu highway tunnel project, taking into account the non-uniform distribution of synchronous grouting pressure. This study focuses on investigating the development patterns of internal forces, deformations, and damages in segment structures under varying grouting pressure ratios. The results indicate that the primary failure mode of a segment is tensile failure occurring at the outer edge of the arch. Moreover, an increased ratio of grouting pressure between the arch bottom and top leads to a higher positive bending moment value and greater tensile damage at the arch waist. The tunnel ring gradually exhibits distinct "horizontal duck egg" shape deformation. When the grouting pressure ratio is 2.8, there is a risk of tensile cracking at the outer edge of the arch waist. At this time, the segment convergence deformation is 39.71 mm, and the overall floating amount reaches 43.12 mm. This research offers engineering reference for the prediction of internal forces and deformations in ultra-large-diameter shield tunnels during grouting construction, thereby facilitating their application in the development of resilient cities. [ABSTRACT FROM AUTHOR]

Segmental lining structures constructed by shields/tunnel boring machines are often subjected to uneven longitudinal cross-section torsion as a result of eccentric external loads, which is extremely adverse to tunnel safety but has not received sufficient attention for a long time. To figure out the torsional performance of segmental tunnels, it is essential to assess the longitudinal torsional stiffness and active-torsion-rejection capability of a segmented tunnel. The aim of the paper is to derive an analytical solution to the longitudinal torsional stiffness of a segmental tunnel with existing elliptical deformation. The longitudinal torsional stiffness under different internal force combinations is deduced considering the longitudinal axial force and bending moment based on the equivalent continuous model and force balance equation. The validity of the analytical solution is verified by comparing it with finite element method results. Then, a parametric analysis, using the new analytical solution, is included to investigate the effect of the key parameters on torsional behaviors, including the segment size, the bolt size and the transverse bending stiffness, etc. It is found that: (1) the longitudinal torsional stiffness efficiency (LTSE) of the segmental tunnel decreases with the rise of segment thickness to diameter ratio but increases with the ring width to diameter ratio; (2) the LTSE reduces with the increase of the effective shear length but rises with the diameter of bolts; (3) the LTSE increases rapidly with the ratio of compression-torsion or bending-torsion. Furthermore, the envelope curve of the critical load (N0, M0) for a tunnel to actively resist a certain internal torque is given. The proposed solution can be easily utilized to determine the longitudinal torsional stiffness of segmental tunnels and is an effective tool for tunnel design and maintenance. [ABSTRACT FROM AUTHOR]

Corroded transmission towers, whose load-bearing capacities are lowered, are suffering from wind-induced damage. By simulating the member corrosion through section thinning, the structural dynamic finite element model of an angle-steel transmission tower with a corrosion depth of 0 mm to 1.4 mm was established using ANSYS/LS-DYNA software. The incremental dynamic analysis method was used to study the collapse mode of the tower under different degrees of corrosion, as well as the effects of corrosion on structural self-vibration characteristics, wind-induced member stress, and tower-top displacement. The results show that with the corrosion deepening, the first three vibration frequencies decrease, and the torsional mode becomes the first mode. When the corrosion depth is smaller, the overall structure failure occurs under strong wind. The failure starts at the most unfavorable oblique rod between the upper and middle cross arm, then expands to the rods under the lower cross arm. When the corrosion depth is larger, the overall structure failure occurs restrictedly between the upper and middle cross arm. Internal axial force and bending moment redistribution happen when corrosion deepens. Under the critical failure state, the oblique rods are always at a high stress level, while the stresses of the main rods decrease. Corrosion has a stronger impact on component strength and stability than on structural stiffness. [ABSTRACT FROM AUTHOR]

Steel–concrete continuous composite beams are widely used in buildings and bridges and have many economic benefits. Slip has always existed in composite beams and will reduce the stiffness of composite beams. The effect of creep under a long-term load will also be harmful. Many scholars ignore the combined effects of slip and creep. In order to more accurately study the mechanical properties of steel–concrete continuous composite beams under long-term loads, this paper will consider the combined actions of slip and creep. By combining the elastic theory and the age-adjusted effective modulus method, the differential equation of the composite beam is derived via the energy variational method. The analytical solutions of axial force, deflection and slip under a uniform load are obtained by substituting the relevant boundary conditions. The creep equation is used to simulate the behavior of concrete with time in ANSYS. The analytical solution is verified by establishing a finite element model of continuous composite beams considering slip and creep. The results suggest the following: the analytical solution is consistent with the finite element simulation results, which verifies the correctness of the analytical solution. Considering the slip and creep effects will increase the deflection of the composite beam and the bending moment of the steel beam, reduce the bending moment of the concrete slab and have a significant impact on the structural performance of the continuous composite beam. The research results considering the coupling effect of slip and creep on continuous composite beams can provide a theoretical basis for related problems. [ABSTRACT FROM AUTHOR]

Vehicle-bridge collision accidents often result in significant economic losses and negative social effects, with heavy trucks being the most destructive to bridge structures. Therefore, this study uses a high-precision finite element method to investigate the impact resistance of concrete bridge piers when subjected to heavy truck impact. The main conclusions of this paper are as follows: (1) When heavy trucks collide with bridge piers, two peak impact forces are generated due to engine and cargo collisions. The peak collision force generated by engine impact is 17.7% greater than that generated by cargo impact. (2) The damage to the bridge, when impacted by heavy trucks, is mainly concentrated on the affected pier. The primary damage characteristics of the bridge piers include punching shear damage at the impact point, tensile damage at the backside, and shear damage at the pier top. (3) The peak values of shear force and bending moment both appear at the bottom of the pier, and the combination of the two causes serious flexural-shear failure damage at the bottom of the pier. (4) The axial force is fluted along the pier height, and the axial force at the top and bottom of the pier is the largest, while the axial force at the middle section is relatively small. The instantaneous axial force of bridge pier will reach more than 2 times the axial force during operational period, seriously threatening the safety of bridge. Overall, this study provides valuable insights into the impact resistance of concrete bridge piers when subjected to heavy truck impact, which can help engineers and policymakers in designing more robust and safer bridges. [ABSTRACT FROM AUTHOR]

Braces with intentional eccentricity (BIE) are recently proposed to improve the seismic behaviour of conventional buckling braces (CBBs) by inserting intentional eccentricity along the brace length. Due to this eccentricity and the resultant bending moment, the BIE bends uniformly from small storey drifts and moves smoothly into the postbuckling behaviour under compression and sustains trilinear behaviour under tension. This behaviour delays the appearance of midlength local buckling which causes unstable energy dissipation. BIEs have a desirable postyielding stiffness which results in stable energy dissipation during cyclic loading and are capable of dissipating energy during low-intensity earthquakes. The seismic behaviour of structures with BIEs for use in buildings has not yet been investigated, specifically in tall buildings. Therefore, this study concentrates on investigating the seismic behaviour of tall buildings equipped with BIEs that uses a 3-dimensional (3D) finite element model in ETABS. In the first step, a 20-storey structure is designed using both eccentric brace frame (EBF) and BIE system and their seismic performance under the TABAS earthquake record is compared. In the second step, the seismic performance of a 25-storey irregular structure is assessed to evaluate the efficiency of the BIE system in irregular structures. Results show the desirable performance and energy dissipation capacity of the BIE system but it also shows large out-of-plane deformation in some cases. [ABSTRACT FROM AUTHOR]

In this study, the seismic behavior of a recycled aggregate concrete-filled square steel tube (S-RACFST) frame under different design conditions was investigated. Based on previous studies, a finite element model for the seismic behavior of the S-RACFST frame was developed. Moreover, the axial compression ratio, beam–column line stiffness ratio, and yield bending moment ratio of the beam–column were regarded as the variation parameters. It was through these parameters that the seismic behavior of eight S-RACFST frame finite element specimens was discussed. The seismic behavior indexes, such as the hysteretic curve, ductility coefficient, energy dissipation coefficient, and stiffness degradation were obtained—which, in turn, revealed the influence law and the degree of the design parameters regarding seismic behavior. Moreover, the sensitivity of the various parameters with respect to the seismic behavior of the S-RACFST frame was evaluated via grey correlation analysis. The results show that the hysteretic curves of the specimens were fusiform and full with respect to the different parameters. Firstly, with the axial compression ratio increasing from 0.2 to 0.4, the ductility coefficient increased by 28.5%. In addition, the equivalent viscous damping coefficient of the specimen with the axial compression ratio of 0.4 was 17.9% higher than that of the specimen with the axial compression ratio of 0.2, which was 11.5% as well as that with an axial compression ratio of 0.3. Second, when the line stiffness ratio rises from 0.31 to 0.41, the specimens' bearing capacity and displacement ductility coefficient both get better. However, the displacement ductility coefficient gradually decreases when the line stiffness ratio is greater than 0.41. As a result, an optimal line stiffness ratio (0.41) thus exhibits good energy dissipation capacity. Thirdly, with the increase in the yield bending moment ratio from 0.10 to 0.31, the bearing capacity of the specimens improves. In addition, the positive and negative peak loads increased by 16.4% and 22.8%, respectively. Moreover, the ductility coefficients were all close to three, thus demonstrating good seismic behavior. The stiffness curve of the specimen with a large yield bending moment ratio with respect to the beam–column, is higher than those that possess a small beam–column yield moment ratio. In addition, the yield bending moment ratio of the beam–column possesses a significant influence on the seismic behavior of the S-RACFST frame. Furthermore, the yield bending moment ratio of the beam–column should be considered first in order to ensure the seismic behavior of the S-RACFST frame. [ABSTRACT FROM AUTHOR]

This article presents a study of the behavior of hybrid steel beams of I-profile cross section subjected to bending. Numerical models of finite elements were developed and validated in the ABAQUS software. In the models, lateral buckling with torsion was disregarded, since the beam will be laterally restrained, so that only local instabilities are present and thus evaluated. Analyses were divided into two stages: first, the elastic buckling analysis was carried out to obtain the critical buckling loads and the buckling modes of the beams; subsequently, analysis of the ultimate strength capacity of the beams was carried out considering residual stresses and initial imperfections. The numerical model was defined and a sensitivity study of the yield strength of the flange steel was carried out. The obtained results from the developed numerical model were satisfactory and, as expected, showed that the hybrid beams resist a greater bending moment effort when compared to their corresponding homogeneous beams. [ABSTRACT FROM AUTHOR]

In order to investigate the stress characteristics of ballastless track under high latitude, and multi-source and multi-field extreme temperature conditions. Based on the finite element theory and the elastic foundation beam–plate principle, a finite element model of the ballastless track considering the limit convex abutment, gel resin, and interlayer bonding is established. The mechanical characteristics of the ballastless track under the slab–CAM layer bonding state, mortar separation, freeze–thaw degradation and forced deformation of the foundation are studied. Considering the deterioration of materials, the bending moment and reinforcement of track structures in cold regions are checked and calculated. The studies show that under the action of negative temperature gradient load, the edge of the track slab is subjected to tension, and structural separation occurs at the edge of the slab. When the interface between the track slab–CAM layer is poorly bonded, the bearing capacity can be improved, and the amount of separation can be reduced by increasing the structural stiffness of the CAM layer. Under the action of freeze–thaw cycles, the material performance deteriorates seriously, the separation between the track structures intensifies, the baseplate is seriously powdered and cracked, and the maximum tensile stress exceeds 6 MPa. The CAM layer and the baseplate are weak structures, and the foundation frost heave occurs at the expansion joint of the baseplate, which is the frost heave condition. Under freeze–thaw deterioration, the original reinforcement design of the substructure structure does not meet the requirements of structural cracks and reinforcement yield stress. In severely cold areas, the structural reinforcement scheme should be reasonably determined. [ABSTRACT FROM AUTHOR]

A problem of stability of cylindrical shells made of a composite material is solved, taking into account the momentum and nonlinearity of their subcritical stress–strain state. In geometric terms, the nonlinear stability problem is solved by finite element methods and the Newton–Kantorovich linearization. Critical loads are determined in the process of solving a nonlinear problem using the Sylvester criterion. The study is carried out using the finite elements of composite cylindrical shells of natural curvature developed on the basis of the Timoshenko hypothesis, with rigid displacements being explicitly distinguished within their displacement approximation, which significantly affects the convergence of the solution. The stability of a circular cylindrical shell made of a polymer composite material under combined loading by torque, bending moment, and internal pressure is investigated. This study also touches upon the influence of the stacking method of monolayers, deformation nonlinearity, and internal pressure on critical loads at which shell buckling is observed. [ABSTRACT FROM AUTHOR]

The main aim of the study is an assessment of models suitability for steel beams made of thin-walled cold-formed sigma profiles with respect to different numerical descriptions used in buckling analysis. The analyses are carried out for the sigma profile beam with the height of 140 mm and the span of 2.20 m. The Finite Element (FE) numerical models are developed in the Abaqus program. The boundary conditions are introduced in the formof the so-called fork support with the use of displacement limitations. The beams are discretized using S4R shell finite elements with S4R linear and S8R quadratic shape functions. Local and global instability behaviour is investigated using linear buckling analysis and the models are verified by the comparison with theoretical critical bending moment obtained from the analytical formulae based on the Vlasow beam theory of the thin-walled elements. In addition, the engineering analysis of buckling is carried out for a simple shell (plate) model of the separated cross-section flange wall using the Boundary Element Method (BEM). Special attention was paid to critical bending moment calculated on the basis of the Vlasov beam theory, which does not take into account the loss of local stability or contour deformation. Numerical shell FE models are investigated, which enable a multimodal buckling analysis taking into account interactive buckling. The eigenvalues and shape of first three buckling modes for selected numerical models are calculated but the values of critical bending moments are identified basing on the eigenvalue obtained for the first buckling mode. [ABSTRACT FROM AUTHOR]

Hydrothermal co-liquefaction (HTCL) is the prominent process for producing bio-products with a higher conversion rate. It is performed at high temperatures and pressure in the presence of water. Earlier, it was mostly conducted in batch reactors, but it has major limitations including operating volume, back mixing, and tedious process for high productivity. With that, the present investigation is performed on designing the screw shaft for the high-pressure HTCL process. The dimensional factors including flight length, pitch, helix angle, and depth were considered to design the optimal screw shaft. Likewise, principal stresses, shear stress, bending stress, bending moment, and total deformation were regarded as inevitable response variables to analyze the internal strength of the shaft. In this regard, the Taguchi approach provides the L9 (34) orthogonal array as an experimental design. Then, the numerical results from the transient structural analysis were analyzed with the assistance of statistical methods such as Grey Relational Grade (GRG), Grey Fuzzy Reasoning Grade, Analysis of Variance (ANOVA), and Taguchi method to find the most influential dimensions for minimizing the response variable. Consequently, the results from both GRG and Taguchi optimization were compared, and selected the most optimum parameters. [ABSTRACT FROM AUTHOR]

The interspersed railway track is an enhanced timber railway track, spot-replacing damaged wooden sleepers with new concrete sleepers to improve the bearing capacity of existing railway lines. Although this interspersed solution is characterised by low cost and short maintenance time, the interspersed tracks have worse stability than concrete tracks and can deteriorate quickly when exposed to extreme weather conditions such as heavy rains and floods. In many cases, heavy rains and floods are accompanied by strong winds. Ballast washaway can often be observed under flood conditions while the mass of trains is unevenly distributed on two rails due to the effect of lateral wind load and rail irregularities. The current work is the first in the world to investigate the collective multi-hazard effects of ballast washway and uneven axle loads on the vulnerability of conventional and interspersed railway tracks using nonlinear FEM software, STRAND 7. The train bogie is modelled by two sets of point loads. The maximum displacement, bending moment and twists have been studied to evaluate the worst condition. The novel insights will help the railway industry develop proper operations of interspersed railway tracks against naturally hazardous conditions. [ABSTRACT FROM AUTHOR]

This paper focuses on investigating the structural behavior of members and connections that are part of moment frames under the combined effect of bending moment and thermally induced axial force during a compartment-fire event. The finite-element analysis method was employed to conduct this study using models benchmarked against experimental data from several past studies while utilizing temperature-dependent material models. A numerical parametric study on typical floor beams with slender elements for compression were conducted under combined bending and axial loading to develop interaction-capacity curves at temperatures representing fire events. The results were compared against the member-strength equations provided in the AISC Specification. The analysis results demonstrated that the AISC beam-column strength equations including the combined effects of axial-load and bending moment provided reasonable estimates for member-slenderness ratios greater than 60, but overestimated the strength of beams with slender elements for low member-slenderness ratios. Combined-load-strength studies were also conducted on a typical connection used in moment frames. The moment-connection behavior was governed by failure modes exhibited at the ends of floor beams. Therefore, the interaction equations available for beam columns resulted in conservative estimates and are recommended for calculating moment-connection capacity during compartment-fire scenarios. [ABSTRACT FROM AUTHOR]

The material constants of wood required for finite element analysis (FEA) are usually calculated using small clear specimens. However, defects, such as knots and slope of grain affect the strength reduction in the fullsize specimens. Consequently, an error occurs if only the material constant calculated from the small clear specimens is used to predict modulus of rupture (MOR). Therefore, in this study, the MOR reduction coefficient according to defect was obtained through the bending test of the full-size specimens and applied to the FEA, in addition to the material constant from the small clear specimens. The maximum bending moment section was measured for a 3-section four-point load, and defects in the outermost tension layer were measured for laminated timber and glulam. The result of the bending test confirmed that MOR also decreased as the size of the defect increased. Therefore, when predicting MOR, a strength reduction ratio according to visual grade was applied. The MOR predicted FEA was twice as large as the actual MOR before defect correction, but the prediction error after defect correction was greatly reduced to 8%, thus increasing the prediction accuracy. [ABSTRACT FROM AUTHOR]

Modern solid wood armchairs are developing in the direction of simplicity and lightness, and favored by the market. However, the low mechanical strength of the connecting joint of cantilevered handrails is an issue that needs to be improved. In this study, the armrest joints of a cantilever armchair made by beech (Fagus orientalis Lipsky) were examined. To improve the mechanical strength of handrail joints, three novel joints were proposed including dovetail tenon, cross-stepped tenon, and rear plug corner tenon. The finite element analysis (FEA) was used to compare and analyze the five joints to obtain the optimal joint. Finally, experimental tests were conducted to verify the results of the FEA. The novel cross-stepped tenon had better mechanical performance, i.e., bending moment capacity and stiffness, than other joints evaluated. The maximum load of the novel cross-stepped tenon was greater than that of the commonly used tenon. In conclusion, the cross-stepped tenon was most suitable for cantilevered handrail joint of chair. This study will contribute to the structural design of modern solid wooden chairs. [ABSTRACT FROM AUTHOR]

Hot stretch bending (HSB) was an advanced manufacturing process for fuselage structure of aircraft. In this work, U shaped titanium extrusion hot stretch bending was investigated by applying numerical and experimental approaches. Hot uniaxial tension was tested to investigate the deformation behavior. Sequential coupling finite element model setup between electro-thermal coupling and thermalmechanical coupling was established to optimize U shaped extrusion stretch bending process parameters for electro-thermal-mechanical coupling. The optimal process parameters for hot stretch bending of U shaped extrusion were determined and the springback after hot stretch bended was evaluated. In the bending experimental verification, under the condition of the strain neutral layer Rn of mold was equal to 829.5μm, the angular springback rate was 0.56%, which is in a reasonable agreement with simulated result of 0.44%. [ABSTRACT FROM AUTHOR]

Diagnostic load testing refers to the use of the measured historical responses of the structure in the field data to better understand its dynamic and static structural behaviours. It is important and necessary to predict the health state, load capacity, and aging of the structure by updating the finite element (FE) model, which can give useful information to aid the design of retrofits and the maintenance of the existing bridge in the future. The paper presents an update of the full-scale FE model for the reinforced concrete (RC) bridge structure over the seawater river based on the experimental strains under the static load testing in which the representative FE model of the actual structure is determined from the optimisation procedures. The optimisation variables are applied, including the cross-sectional properties and concrete material calibrated through the genetic algorithm (GA) optimisation in the MATLAB software, which interfaces with the FE modelling in the scripting of the SOFISTIK TEDDY software automatically. The bending moments at the mid-span of the RC girders are determined in the FE modelling to compute stresses, which are compared with the measured stresses through optimisation scenarios with a percentage error of the objective function less than 10%. The measured data of concrete strains are recorded from reusable strain transducers installed on the mid-span girders for every bridge span, which are used to calibrate the bridge model in static load testing. The novelty of the solution is to implement innovative techniques using field data as an improved approach for calibrating automatically the analytical FE model parameters of all RC spans of the bridge until its static behaviours are very similar to those of the actual bridge. The final updated FE modelling is used to apply truck load configurations according to bridge design standards such as the AASHTO specifications, which can predict the load limits of the existing bridge structure more accurately and reliably. These proposed approaches can be applied to large bridges as well as complex structures with supporting FE analysis software and data processing software. [ABSTRACT FROM AUTHOR]

The finite element analysis model is developed to investigate the bending capacity of the concrete-filled micro-steel-tube (CFMST) piles. First, the classical elastic-plastic model is employed to describe the constitutive relation of the steel material, while the plastic damage model is applied to portray the concrete material. Then, the three dimensional (3D) finite element numerical model for analyzing the flexural bearing capacity of the CFMST pile is established by virtue of the ABAQUS software. The reliability and accuracy of the present numerical model is carefully validated by comparing with the experimental data. The influence of the concrete strength grade, wall thickness of the steel tube, external diameter of the steel tube, and yield strength of the steel are analyzed in detail. It is shown that increasing the wall thickness/external diameter of the steel tube and the yield strength of the steel can greatly improve the flexural bearing capacity of the CFMST pile. Finally, a concise formula for the ultimate bending moment of the CFMST pile is proposed, which could be directly applied into the future engineering design. [ABSTRACT FROM AUTHOR]

Trapezoidal corrugated web girder (TCWG) is widely used in many fields. The elastic transverse bending moment which exists in the flange influences the mechanical properties of TCWG. For the simply supported TCWG, the equivalent load method is proposed in this paper. And the transverse bending moment calculation model is established. The calculation formula of the elastic maximum transverse bending moment under the most unfavorable geometrical situation is deduced. The formula is consistent with the existing literature. ANSYS finite element method is used to calculate the elastic transverse bending moment of the flange. The calculation results of formula are in good agreement with the finite element analysis. The existence of transverse bending moment is verified by the experimental data. The physical significance of the transverse bending moment as the integral bearing performance index of the TCWG is revealed in this paper. This paper provides a reference for further analysis of transverse bending moment of simply supported TCWG. [ABSTRACT FROM AUTHOR]

Detailed three-dimensional numerical models considering concrete indentation, bolts, elastic gasket (EG) and sealing gasket (SG) are established for the segmental joint with gaskets, and the load tests of the joints with EG and without EG are simulated and compared. The results reveal that the bearing performance of the joint with EG is very complex. In sagging moment scenarios, it can be divided into four stages by three key points "EG starts to open", "joint external edge starts to contact" and "EG fully opened". In hogging moment scenarios, it can be divided into three stages by two key points "SG opened" and "EG starts to open". The EG has a significant effect on the joint bearing performance. It can soften the joint, which leads to the result that the average bending stiffness and ultimate bearing capacity of the joint with EG are evidently smaller and weaker than those of the joint without EG. With decreasing the joint axial force, this softening effect tends to be more obvious. Besides, for the two joints, the ultimate states of the joints subject to the bending moments are both that the concrete at the joint edges yields firstly, and it is necessary to protect or strengthen the corresponding concrete. [ABSTRACT FROM AUTHOR]

This paper presents the derivation and validation of a mechanics-based finite element for the analysis of shear-critical slender reinforced concrete beams and columns. The element can capture the load-deformation behavior associated with axial loads, bending moments, and shear in uncracked or cracked reinforced concrete using only a small number of degrees of freedom and easily measurable input parameters: the gross cross-section dimensions and steel and concrete material stress/strain curves. The element is specifically derived to represent the full reinforced concrete cross section (i.e., one element is required over the depth of a member) and consists of four nodes, with two translational degrees of freedom (DOFs) per node. This formulation facilitates modeling the interface regions between walls or joint regions, beams, or columns and lowers the numerical complexity and number of decisions that the user must make. The element shows improvements to results from design codes when validated against experimental results for 782 beams without shear reinforcement and 167 beams with shear reinforcement taken from the literature. By reducing the number of degrees of freedom, the element will allow relatively rapid two-dimensional (2D) nonlinear analyses of full reinforced concrete buildings. [ABSTRACT FROM AUTHOR]

This paper examines the effects of different loading patterns on the static characteristics of continuous concrete beams reinforced with external prestressed carbon fiber-reinforced polymer tendons (EPCFRPT) and qualitatively analyzes the results for two continuous concrete beams: SB-1 under symmetrical loading, and SB-2 under asymmetrical loading. Then, a finite element analysis model is introduced and calibrated by tests conducted at Southeast University and data collected from a literature review. Based on the FEA model, the initial prestress, cross-section area, and eccentricity of CFRP tendons as well as the steel reinforcement configuration were selected by a parametric study. The results indicated that the initial prestress and tendon cross-section area had the most influence on the tendon stress increment and the secondary bending moment of the middle support, while the reinforcement distribution and eccentricity of the tendons had little effect. The secondary bending moment had a linear positive correlation with the stress increment of tendons. These results allow a simplified equation for calculating the external load bending moment amplitude coefficient at ultimate to be proposed. [ABSTRACT FROM AUTHOR]

In recent years, the construction of a CFST arch bridge has developed rapidly; however, as a kind of structural system dominated by compression, with the increase of material strength and span, the stability of the main arch of the CFST arch bridge has become more and more important. In this paper, the finite element method is used to analyze the hanger force and the main arch stability of the long-span CFST arch bridge. Combined with the Shenzhen Rainbow Bridge project, the axial force of the hanger, the internal force, and stability of the main arch of the arch bridge are studied. In the establishment of the finite element model, considering the actual operation of the arch bridge, the model simulates the interaction between steel pipe and concrete, it studies the large deformation of CFST arch bridges, and the stress distribution and overall stability of the arch bridge are analyzed. The results show that the main deformation of the CFST arch bridge is the vertical displacement of the deck, and the axial force of most members of the upper arch ribs is greater than that of the lower arch ribs. The axial force and bending moment of the lower arch rib near the arch foot are larger, and the compressive stress of the arch foot is greater than that of other positions. The axial force of the suspender of the arch bridge is the largest at both ends of the hanger and the middle hanger, and the axial force of the other hanger is close to each other, and the axial force changes little under the same case. The buckling modes of the arch are mainly the lateral buckling or flexural buckling of the arch rib outside the plane, which indicates that the vertical stiffness of the arch bridge structure is larger than that of the transverse stiffness. The research results make the load-bearing mechanism of the CFST arch bridge more clear and also provide a certain reference for the design and construction of the CFST arch bridge. [ABSTRACT FROM AUTHOR]

Rotary ultrasonic machining is a cost-effective and precise machining method for hard and brittle materials. Aiming at processing SiCp/Al composites, a rotary ultrasonic grinding spindle is proposed in the present study. Expressions were established to calculate the displacement, rotation angle, bending moment, and shear force of the vibrating elements based on the Mindlin moderately thick plate theory. Combining continuous and boundary conditions of vibrating elements with the proposed expressions, the vibration model and frequency equation of a longitudinal-flexural resonating transformer with a large load were established. Then two transformers were designed according to the frequency equation. The resonant characteristics of the transformers were studied using finite element analysis, impedance analysis, and ultrasonic resonance experiments. The obtained results show that the maximum deviation between the resonant frequency and the design frequency of the transformers was 4.95%. Moreover, the maximum deviation of the positions of the pitch circles was 6.51%. It is concluded that the proposed designs have high accuracy. Finally, the orthogonal single-factor experiments of SiCp/Al composites were performed with and without ultrasound. The obtained results show that introducing ultrasonic vibrations significantly reduces the grinding force and the surface roughness while improving the surface quality of the SiCp/Al workpiece. The present study is expected to provide experimental fundamentals to further improve the structure of the grinding spindle, optimize process variables of ultrasound-assisted grinding, and improve the processing efficiency. [ABSTRACT FROM AUTHOR]

To accurately predict the peen forming effectiveness under different parameters, coverage and paths, a regional averaging method is proposed in this paper. The realistic peening stress is estimated based on the average stress of all nodes in a specific area and introduced into the peening area as the initial stress to obtain the resultant shape of the sheet. On the basis of the saturated peening field, an analytical expression is proposed for calculating the average stress considering the interaction between projectiles. And the bending moment is acquired by integrating the stresses on the cross-sectional indentation. Moreover, a series of finite element models are adopted to obtain the accurate average stress. Using a Python script, the finite element models are divided into several regions and the average stress of each region is calculated separately. Through single- and four-shot models, the average stress field around a single shot and the interaction between shots are investigated. And with random peening models, the quantitative relationship of the average stress with respect to the peening intensity and coverage is revealed. In addition, the averaged stresses are introduced to sheet forming models to predict the peen forming effectiveness. Narrow strip experiments are designed under the same peening conditions as that of the sheet forming models, and the simulated values are in good agreement with experimentally measured resultant curvatures. [ABSTRACT FROM AUTHOR]

The cantilevered leg joint commonly used in modern wood furniture was studied by numerical and experimental methods. A novel joint was proposed and compared with the typical joint commonly used in the cantilevered leg. Both of them were made of beech wood (Fagus orientalis. Lipsky). The experimental results showed that the bending moment capacity of the novel joint was remarkably higher than the typical joints, which confirmed that the novel structure had a better mechanical performance. The numerical analysis was conducted according to GB/T 10357.3 standard, the results showed that the stresses of the typical joint were mainly concentrated on the wooden components, while the stresses of the novel joint were concentrated on the metal connectors. The stress concentration obtained by the finite element method (FEM) was consistent with the failure modes of the experimental tests, which provides a reliable method for evaluating and optimizing the novel furniture structure. [ABSTRACT FROM AUTHOR]

This study aims at investigating the effects of local wall thinning on the cyclic plasticity behaviours of 90° back-to-back pipe bends, which are commonly utilised in flexible piping systems within plant facilities. Over time, the prolonged operation of these pipe bends may lead to wall thinning and a deterioration of their structural integrity. To understand the effects of such wall thinning, a 3D finite element analysis is conducted. Load interaction diagrams are generated using the Linear Matching Method, which considers the cyclic plasticity behaviours of shakedown and ratcheting. The investigation includes pipe bends with three different locations of local wall thinning: intrados, extrados, and crown. The pipe bends are subjected to steady internal pressure and various cyclic bending moments, including in-plane closing, in-plane opening, and out-of-plane bending. Moreover, comprehensive parametric studies are carried out for the pipe bend structures, varying the wall thinning rates. Semi-empirical formulas are derived based on the study results, enabling the prediction of limit load, shakedown limit, and ratchet limit concerning the position of the local wall thinning. Results and discussions have demonstrated the most detrimental combination of wall thinning type and loading on the structural integrity of the pipe bends and have provided valuable insights into the problems associated with deteriorated pipe bends. • The effects of local wall thinning on the cyclic plasticity behaviours of 90° back-to-back pipe bends are investigated. • The pipe bends with three different locations of local wall thinning is considered: intrados, extrados, and crown. • Shakedown and ratchet limit boundaries are analysed using the Linear Matching Method. • Critical loading combinations and the specific wall thinning locations that may lead to adverse effects are identified. [ABSTRACT FROM AUTHOR]

This paper presents the Green's Functions Stiffness Method (GFSM) for solving linear elastic static problems in arbitrary axially non-uniform Timoshenko beams and frames subjected to general external loads and bending moments. The GFSM is a mesh reduction method that seamlessly integrates elements from the Stiffness Method (SM), Finite Element Method (FEM), and Green's Functions (GFs), resulting in a highly versatile methodology for structural analysis. It incorporates fundamental concepts such as stiffness matrices, shape functions, and fixed-end forces, in line with SM and FEM frameworks. Leveraging the capabilities of GFs, the method facilitates the derivation of closed-form solutions, addressing a gap in existing methods for analyzing non-uniform reticular structures which are typically limited to simple cases like single-span beams with specific axial variations and loading scenarios. The effectiveness of the GFSM is demonstrated through three practical examples, showcasing its applicability in analyzing non-uniform beams and plane frames, thereby broadening the scope of closed-form solutions for axially non-uniform Timoshenko structures. [ABSTRACT FROM AUTHOR]

This study presents enhancements made to traditional aluminum alloy gusset (AAG) joints, including the integration of a central stiffening (CS) system, an inter-panel stiffening (IS) system, and a peripheral stiffening (PS) system. Three sets of tests on a full-scale specimen are conducted to investigate the improved AAG joint's axial stiffness, in-plane and out-of-plane bending stiffness, as well as ultimate load-bearing capacity. Nonlinear refined finite element models (FEMs) are established and validated through experimental results. Theoretical mechanical models are developed by integrating experiments and FEMs. These models elucidate the contribution of the stiffening systems to the joint's mechanical performance. The CS system is proven to significantly assist in load transfer, particularly in out-of-plane bending conditions. The IS system enhances overall inter-panel integrity, especially during the plastic deformation phase under out-of-plane bending moments. The PS system improves joint stiffness by participating in load transmission under both axial load and in-plane bending moments. Compared to traditional AAG joints, the combined effects of the three stiffening systems enhance overall structural integrity, stiffness, and load-bearing capacity. This enables the full utilization of component material properties and provides excellent ductility before failure occurs. • A theoretical model of an improved aluminum alloy gusset joint was developed. • FEM and mechanical model alignment were achieved, validated by full-scale tests. • Three loading phases in directions confirmed joint enhancements in mechanical model. • Stiffening systems optimized load transfer, increasing joint stiffness and capacity. [ABSTRACT FROM AUTHOR]

• The wooden drum-tower exhibits poor ductility, and the premature withdrawal of tenon-mortise joints in components adjacent to the failure zone is a triggering factor for the collapse of the structure. • After component failure, the structure undergoes internal force redistribution. The beam in the failure zone is forced to bear tension, bending, and torsion simultaneously, leading to the failure of the tenon-mortise joints. At the moment of mortise-tenon joints failure, the columns within the failure zone gradually tilt under the influence of gravity, eventually leading to progressive collapse. • The failure of mortise-tenon joints in the failure zone is characterized by compression deformation of the tenon in the transverse direction and splitting of the mortise edges. Non-collapsed structure tilts as a whole, with slight detachment of tenon heads and uplift of column bases. The drum-tower belongs to the category of towering structures, and the overall collapse is a common accident in such structures. In order to study the anti-collapse performance of drum-towers, this research used the bottom floor of a wooden drum-tower in the southwest China as a prototype, designing and producing a 1/3 scale structural model. The sudden-column-removal (SCR) method was employed to simulate the structural collapse process, observe collapse characteristics, and analyze the dynamic response of the structure. A finite element model was established, and on the basis of verifying its accuracy, a parameter expansion analysis was conducted. The study indicates that the ductility of wooden drum-towers is relatively poor, and the pulling out of mortise- tenon joints in adjacent components in the failure area is a primary factor for the progressive collapse of the structure. Due to the redistribution of internal forces, the load-bearing status of beams in the failure area changes, experiencing tension, bending moment, and torsion simultaneously, leading to the pulling out, compression, and splitting of mortise-tenon joints. After the failure of these joints, the structure undergoes progressive collapse under the influence of gravity. The dimensions of mortise-tenon joints and the friction coefficient have a significant impact on the anti-collapse performance of the structure. Larger dimensions and friction coefficients result in slower structural damage and more stable structural response. Among these factors, increasing the depth of mortise-tenon joints has the most significant effect. [ABSTRACT FROM AUTHOR]

Local wall-thinning of pipe is a common volume defect in application, which would cause pipeline leakage or rupture under complicated pipeline loads. The finite element analysis method was used to analyze the limit load of Pipe Bend with Local Wall-Thinning defect (PB LWT) under internal pressure, bending moment, torsion moment, axial force, and their combinations. The limit load empirical equations of PB LWT under single load and complex loads were fitted. According to the allowable pipeline load on equipment nozzles, the influences of torsion moment and axial force on the load bearing capacity of PB LWT were quantitatively analyzed. It is found that the load bearing capacity is reduced by an average of 1 % for medium and low-pressure equipment. For high-pressure equipment, the load bearing capacity is reduced by 10.07 %∼20.90 % under the influence of torsion moment. Under the effect of axial force, the load bearing capacity is reduced by 2.01 %∼12.40 %. • The limit loads of bends with extrados local wall-thinning defect are analyzed under internal pressure, bending moment, torsion moment, axial force, and their combinations. • Empirical equations for limit load of bend with defects are worked out for complex loads. • Torsion and tension can decrease the load-bearing capacity of bends by up to 10 %∼20 %. [ABSTRACT FROM AUTHOR]

• The impact test results of the scaled model corresponding to the finite element model were used to verify the accuracy of the adopted material models and contact relationships. • Based on the spatial complexity of urban overpasses, the dynamic responses and failure mode of the full-bridge model under non-bottom impact were numerically simulated. • Four comparative models were established to study the effect of the bridge model parameters on impact responses. Urban viaducts are likely to be subjected to non-ground-level vehicle collisions during their service life period. However, current research primarily focus on vehicle impacts on the bottom of bridge piers. In this research, a full-bridge scale model impact test was conducted to validate the accuracy of the finite element (FE) model. Then, LS-DYNA is used to establish refined vehicle-bridge collision FE models. The dynamic responses and failure mode of the pier impacted by the non-bottom vehicle are investigated. Besides, the effects of bridge structure spatial stiffness, superstructure mass, and double-column structure on the impact responses of bridges are analyzed. The results show that vehicle collisions are characterized by a continuous impact action involving multiple components. The damage to the full bridge model is concentrated in the directly impacted double-column pier, where the head-on column sustains three-point bending damage, the indirectly impacted column sustains bending damage at the top and bottom, and the cover beam sustains tensile shear damage. The non-bottom impact significantly increases displacements and bending moments of the pier while causing a substantial decrease in bottom shear. The impact responses of the pier are greatly influenced by the superstructure mass and double-column structure, while the spatial stiffness of the bridge has minimal affection. [ABSTRACT FROM AUTHOR]

Aluminum alloy tubes are widely used in various industries because of their excellent performance. Up to now, when the tube is bent, the elastoplastic deformation evolution mechanism of the cross-section has not been clear, and no direct analytical proof has been found. In this paper, based on the bilinear material model assumption, a new mechanical model of tube plane bending deformation is constructed. The analytical model can describe in detail the evolution mechanism of elastic–plastic deformation on the cross-section of the tube after bending deformation, the position of the elastic–plastic boundary, the position of the radius of the strain neutral layer, and the relationship between the bending moment over the section and the bending radius. According to this model, the deformation law of the tube cross-section during bending is elucidated. The results are as follows: (1) the deformation evolution of the cross-section of the bending deformed tube calculated by the analytical model is in good agreement with the finite element model (FEM) of pure bending. (2) By comparing the results of the analytical model with FEM results, and the processing test of the self-designed four-axis free bending forming tube bender, the bending moments are in good agreement. (3) Compared with the bending moments calculated by several other analytical models of tube bending, this model has a relatively small deviation value. [ABSTRACT FROM AUTHOR]

The vertical and horizontal bending of micro-beams subjected to axial compressive and transverse concentrated loadings is a common lateral deformation in micro-/nano-engineering that plays a significant role in the design and optimization of micro-/nano-devices. The present study aims to investigate it using the nonlocal theory. For this purpose, the simplified mathematical model is developed, and the nonlocal differential constitutive equation is applied. Since the mechanical properties of micro-beams are different from those of macro-beams, the non-classical nonlocal bending moment is introduced to improve the classical bending formulation in order to adapt to the vertical and horizontal bending of micro-beams. The effects of the external load, external size, structural stiffness, and internal characteristic scale on the vertical and horizontal bending deformation including the midpoint deflection and critical compression are presented. The present analytical model and results are validated by the finite element method. It is shown that the critical compression decreases with increasing the internal characteristic scale. Moreover, the midpoint deflection varies remarkably with respect to the axial and transverse loadings, structural stiffness, internal characteristic scale, and external size. An obvious nonlocal scale effect is found, in which the internal characteristic scale cannot be neglected compared with the external size. Besides, a threshold value of the structural stiffness is determined, and the connotation of the nonlocal interaction requires that the structural stiffness shall not be lower than that threshold. A mutual restriction between structural stiffness and external loadings is observed in the vertical and horizontal bending. In particular, it is further proved that the classical continuum mechanics can not be used in micro-/nano-scaled mechanics through a strange phenomenon that is contrary to mechanical common sense in the calculation example. The study is expected to be beneficial to the design and application of micro-beams subjected to the vertical and horizontal bending. [ABSTRACT FROM AUTHOR]

Intermediate diaphragms (ID) in bridges with precast girders are intended to improve load distribution among girders. Despite this, their efficacy has been doubted recently due to the complex construction tasks needed to join them to the girders. Accordingly, this work aimed to determine the effect of the number of IDs on the distribution of vertical loads and girders response of a simply supported bridge. Four bridge layouts (0, 1, 2, and 3 IDs) were analyzed using 3D computational grillage models. The load distribution factors from the models were compared to those calculated using the Engesser-Courbon and Fauchart methods to determine the latter's accuracy in capturing the effect of the number of IDs. Moreover, the girders responses under the live loads in the current Colombian and Brazilian bridge design codes were assessed. The results show that the IDs have a more significant effect on the load distribution and deflection of interior girders than the exterior girders. Additionally, increasing the number of IDs reduced the maximum shear and torque while the bending moment and deflections remained nearly constant. [ABSTRACT FROM AUTHOR]

The research on the dynamic response and influencing factors of shield tunnel lining under earthquake demonstrates significant engineering value in guiding the design of antiseismic tunnels. In this paper, a nonlinear finite element model of soil-tunnel interaction is established based on FLAC finite difference software, and then Mohr–Coulomb elastoplastic model and dynamic plastic damage model are used to simulate the dynamic characteristics of soil and lining damage of tunnel, and the seismic waves of South Iceland are selected to analyze the residual internal force, dynamic internal force distribution, and the relative deformation of the top and bottom of the arch of the shield tunnel under the earthquake load. Meanwhile, the effects of depth tunnel, lining thickness, and tunnel diameter on the dynamic response of the tunnel are discussed. In addition, the interaction law of horizontal parallel tunnel and the amplification effect on the surface acceleration are also studied. The results show that under the action of a strong earthquake, the bearing capacity of the tunnel decreases sharply, the lining is destroyed, and a large residual internal force appears. When the buried depth of the tunnel is small, the nonlinear effect is more significant, and the R value increases at first and then decreases with the increase in the seismic acceleration. The maximum dynamic bending moment and maximum dynamic axial force of the tunnel lining aggrandize obviously with the increase in tunnel diameter and lining thickness. In particular, the dynamic bending moment has internal force redistribution and deflection under the condition of large tunnel diameter and small lining thickness. Moreover, the interaction of parallel tunnels affects the distribution of internal force and the magnitude of adjacent surface acceleration. [ABSTRACT FROM AUTHOR]

Peen forming is a die-less forming method that has been applied to aircraft wings and rocket tanks; the surface of a metal plate is deformed convexly by plastic strain when it is peened with multiple steel balls at less than 100% coverage. To introduce uniform compressive residual stress over the entire surface of the plate, additional saturation peening may be performed at 100% or more coverage, unlike peen forming. Changes in deformation and residual stress distribution owing to saturation peening after peen forming were investigated by dynamic explicit and static implicit finite element method (FEM). The FEM results were validated experimentally. The plastic strain introduced during saturation peening was affected by the plastic strain and compressive residual stress after peen forming on the peen-forming surface and by the compressive residual stress generated by the bending moment after peen forming on the back surface. The application of double-sided saturation peening had no effect on curvature and improved the compressive residual stress near the surface. [ABSTRACT FROM AUTHOR]

Buried pipelines are commonly damaged when laid across strike-slip faults, always leading to some level of destruction with fault movement. The moment of the neutral axis of a pipe section was obtained by integration, and the equations for the bending moment and the bending strain on a pipeline's section were presented here, based on a trilinear stress-strain model. The calculation method for the lateral soil pressure and pipeline's bending strain near the fault-crossing point was improved. Lateral soil pressure was regarded as being related to lateral pipeline movement and, for accurate calculation, this part of the pipeline was divided into finite element segments. An iterative process for solving for pipe bending strain was derived, and the algorithm and program for calculating bending strain and the potential damage position of the pipeline's sections was compiled based on Matlab software. Compared with finite element method (FEM) results and the current standard method, in the situation of a pipeline being in tension under the action of a strike-slip fault (intersection angle < 90°), the result of the proposed method is in good agreement with FEM results. This shows that the proposed analytical method possessed a good reference value for the strain response analysis of tensile steel pipelines under strike-slip faulting. [ABSTRACT FROM AUTHOR]

This study aimed to design and evaluate the detachable corner joints used in wooden furniture frames, including a commonly used detachable joint (control) form using mortise and tenon with plug reinforcement and three novel proposed joints, i.e., novel joint I ~ III, which adopted in-line doublehole nuts, metal sheet connector, and embedded nuts and screws respectively, via numerical and experimental methods. The numerical analysis results indicated that the optimal proposed joint (novel joint І) had good mechanical performance when subjected to bending load with proper stress distributions and relatively low maximum stress compared with the other two proposed joints. The experimental results showed that the bending load resistance of the control and the optimal proposed joints were 1920 N (0.14) and 4390 N (0.05), respectively. The bending moment capacity and bending stiffness of the optimal joints were remarkably higher than the bending moment capacity and bending stiffness of the control joint. In addition, the combination of the numerical and experimental methods could effectively simplify the steps of furniture connection design and development and save costs in terms of time and materials. [ABSTRACT FROM AUTHOR]

In order to ease consequences of spudcan-footprint interactions during jack-up rigs reinstalling in the vicinity of an existing seabed footprint, three new types of spudcan shapes, that is, a lotus-shaped spudcan with six circular holes, a flat-bottomed spudcan, and a concave-shaped spudcan, were proposed to perform an optimizing study of the spudcan structures, and the effectiveness of them were analyzed comparatively with other different measures. Firstly, 3D Large Deformation Finite Element (LDFE) analyses were carried out using the Coupled Eulerian-Lagrangian (CEL) method in the commercial finite element package ABAQUS. After calibrating the validity of the numerical calculation model against existing centrifuge test data and LDFE results, the differences in interaction mechanism between the novel spudcans and the generic spindle-shaped spudcan were studied when penetrating near an existing footprint with an eccentric distance of 0.5D, and the horizontal range of plastic deformation of the disturbed soils, the inclination angle of the spudcan and the offset distance of the pile legs were analyzed comparatively as well. The results show that the proposed novel spudcans can mitigate the maximum horizontal sliding force and the maximum bending moment at the top of the pile leg obviously, compared with those of the generic one, which were reduced by 32.59%, 22.47%, 28.18%, and 26.32%, 12.88%, 18.02%, respectively. It also can be seen that all novel structures can ease the adverse consequences of spudcan-footprint interactions effectively, and can improve the in -place stability of the spudcan as well. Finally, three possible measures in mitigating interactions of the spudcan-footprint were contrasted, that is, the novel spudcan (represented by the lotus-shaped spudcan with six holes), stomping method, and perforation drilling method. The results show that all of them can reduce adverse impacts induced by interactions of the spudcan-footprint, and also can improve the in-place stability of the spudcan during reinstallation. In addition, among them, according to the effect of reducing the additional stress of the spudcan, the effectiveness of them can be listed as follows: perforation drilling near an existing footprint > the lotus-shaped spudcan with six holes > stomping method. In terms of the vertical bearing capacity of the spudcan, the lotus-shaped spudcan with six holes can improve it as much as 16.33% compared with the spindle-shaped structure due to the particularity of the structure. While reducing the continuity and strength of soil foundations, the perforation drilling measure leads to the decrease of the vertical bearing capacity of the spudcan by 13.07%. It can be concluded that all the three measures have merits and demerits, so the relevant construction environment conditions and engineering practice should be fully considered when selecting measures to deal with interactions of the spudcan-footprint. [ABSTRACT FROM AUTHOR]

Kriging-based finite element method (K-FEM) is an enhancement of the conventional finite element method using a Kriging interpolation as the trial solution in place of a polynomial function. In the application of the K-FEM to the Timoshenko beam model, the discrete shear gap (DSG) technique has been employed to overcome the shear locking difficulty. However, the applied DSG was only effective for the Kriging-based beam element with a cubic basis and three elementlayer domain of influencing nodes. Therefore, this research examines a modified implementation of the DSG by changing the substitute DSG field from the Kriging-based interpolation to linear interpolation of the shear gaps at the element nodes. The results show that the improved elements of any polynomial degree are free from shear locking. Furthermore, the results of beam deflection, cross-section rotation, and bending moment are very accurate, while the shear force field is piecewise constant. [ABSTRACT FROM AUTHOR]