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Exploring fire resistance of high strength steel end-plate connections is one of the key technical bases for fire resistance design and fire safety assessment of high strength steel structures. Numerical simulation and parameter analyses of high strength Q690 steel flush end-plates will contribute to a reasonable design of high strength flush end-plate connections. In this paper, a finite element model of high strength steel flush end-plate connection considering thermal creep effect was established and validated by experimental results. The thermal creep finite element model can simulate accurately heat performance, failure modes and deformations of high strength flush end-plate connections at elevated temperatures. The increase of axial compression ratio has little effect on rotation, deflection, failure time, critical temperature, and critical rotation with elevated temperatures. The increase of bending moment ratio has little effect on the development trend of rotation and deflection. Proper increase of thickness of the end-plate can improve failure time and critical rotation, and the increase range is within 7% and 36% respectively. Proper increase of diameter of bolt can improve failure time, critical temperature, and critical rotation to a certain extent, and the increase range is within 10%, 6% and 27% respectively. Proper increases of thickness of the end-plate and diameter of bolt will improve the fire resistance of flush end-plate connection. [ABSTRACT FROM AUTHOR]

The collapsible tubular mast (CTM) can be compactly folded for transport and deployed in orbit to serve as a key structural element. Once deployed, the CTM is vulnerable to buckling under axial load and bending moments, compromising its load-bearing capacity. The intricate relationship between the CTM's cross-section and its buckling behavior poses a significant challenge for designers. This is due to the ultra-thin nature of the CTM, which gives rise to highly localized buckling modes rather than global ones. To overcome this challenge, we developed surrogate models using a neural network (NN) trained with data from finite element analysis (FEA). These NN-based surrogate models provide high computational accuracy in predicting nonlinear buckling loads under axial force and bending moments around the two principal axes of the CTM's cross-section, achieving R 2 values of 0.9906 , 0.9987 , and 0.9628 , respectively. These models also significantly improve computational efficiency, reducing prediction time to a fraction of a second compared to several minutes with FEA. Furthermore, the NN-based surrogate models enable the usage of the non-dominated sorting genetic algorithm (NSGA-II) for multi-objective optimization (MOO) of the CTMs. These models can be integrated in the NSGA-II algorithm to evaluate the objective function of existing and new individuals until a set of 1000 non-dominated solutions, i.e., cross-sectional configurations optimizing buckling performance, is identified. The proposed approach enables the design of ultra-thin CTMs with optimized stability and structural integrity by promoting design decisions based on the quantitative information provided by the NN-based surrogate models. [ABSTRACT FROM AUTHOR]

The present design guidelines for rigid-faced (RF) geosynthetic reinforced soil (GRS) walls recommend a minimum toe embedment depth as a geometric requirement. The toe condition effect is ignored in these designs. Development of tools for serviceability design and refinement of present design methods require a complete understanding of the toe condition's role. Finite element analysis of RF-GRS walls is carried out in this study for different toe conditions, such as fixed, rotating and frictional toe, representing different construction methods. The analysis of fixed toe conditions shows 3–5 times lesser deformations and 10–20 times lesser loads in bottom reinforcements compared to other toe conditions. Reduced reinforcement stiffness at the bottom of the wall for a fixed toe condition has a negligible effect on deformations. The fascia experiences high bending moments at the bottom of the wall with fixed toe conditions. Frictional toe condition mobilizes both sliding and rotation modes of wall deformations. It also shows toe force increasing by 5–20% for embedment depth increase by 6 times. The results for rotating toe with restrained sliding show higher top displacements than other toe conditions. The use of stiffer reinforcements at the wall top reduces such rotations. Possible design concepts to impart toe fixity in the field are also discussed. [ABSTRACT FROM AUTHOR]

This study investigates the seismic behavior of long-span prestressed concrete box-girder bridges subjected to long-duration (LD) ground motions and spectrally equivalent near-fault (NF) and far-fault (FF) short-duration ground motions. For this purpose, the Kömürhan and Gülburnu Highway Bridges built with the balanced cantilever method using prestressed concrete box-girder were selected. This paper consists of two main sections. First, ambient vibration tests were conducted to identify the modal parameters of the bridges and calibrate the finite element models. Second, using three ground motion sets consisting of 42 acceleration records applied to the orthogonal and vertical directions of the bridges, the structural responses were evaluated and compared. In order to determine the type of ground motion that is critical for this type of bridge, these sets consist of 14 long-duration ground motions, 14 spectrally equivalent near-fault short-duration ground records, and 14 spectrally equivalent far-fault short-duration records. The comparison parameters considered for this study were displacements and internal forces in the piers and decks. The results strive to highlight the extent to which the duration and characteristics of the ground motion sets affect the structural behavior. Results indicate that the mean deck displacements of selected bridges obtained from FF short-duration records were nearly 10.70% and 7.44% less than those obtained from the LD and NF short-duration ground motions. These trends were also observed in the bridge piers. Moreover, increases of up to 17.54% and 26.65% in the mean shear forces of the piers under LD and NF short-duration ground motions were observed compared to those determined from the FF short-duration counterparts. Similar trends were observed in the bending moment values. It was also observed that far-fault short-duration records may have substantial consequences on such structures. [ABSTRACT FROM AUTHOR]

This paper presents a multibody model of the post-derailment dynamics of a railway vehicle and its impact with a derailment containment wall (DCW) built aside the line and demonstrates the use of the model in the context of the structural sizing of devices intended to mitigate derailment effects. With respect to existing multibody models of railway vehicle dynamics, the innovative features of this model are a new contact model capable to provide a plausible prediction of the derailment process despite a simple and computationally efficient formulation, and the model of the interaction between the derailed vehicle and the impacted derailment containment structure, the latter being described by a Finite Element Model. Results from the model are compared to an established multibody software for a non-derailment case, and then a comparison is performed with a measurement from a derailment experiment published in the scientific literature, finding in both cases satisfactory agreement. The model is then applied to analyse a derailment scenario caused by the sudden failure of an axle for a locomotive vehicle travelling at 300 km/h in a HS curve, deriving the peak values of the impact force and bending moment at the base of the derailment containment wall. [ABSTRACT FROM AUTHOR]

Recent experimental evidence has shown that wood–steel–wood dowel-type connections exhibit a semi-rigid behaviour even after 90 min of fire exposure. Because a semi-rigid behaviour influences the bending moment distribution among structural members, considering the moment–rotation relationships within frame analyses in which structural members are modelled as beam elements can enable a realistic fire response analysis that is significantly simpler than the three-dimensional finite element method. This study proposes an analytical methodology that accounts for the thermo-mechanical behaviour of timber and dowels, enabling the simulation of the non-linear moment–rotation relationships under fire conditions. The proposed analytical model divides dowels into a series of elements on an elastoplastic foundation and performs a direct stiffness method in a time-incremental procedure using an element stiffness matrix derived from beam-on-elastic-foundation theory. This study also presents the results of load-carrying tests on timber frames with dowel-type connections performed under ambient and fire conditions. The analytical results were consistent with the fire test results. Additionally, the analyses were also performed under three conditions in which the dowels were rigid, linear elastic, and elastoplastic bodies. These three results converged to the same value after 65 min of heating, which suggests that the ultimate states of beams with dowel-type connections exposed to fire can be modelled by assuming that dowels are rigid bodies. [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]

In this study, OBC joint is improved by incorporating one web, two flanges, and two additional bolts, putting forward a novel semi-rigid joint referred to as IBC joint. Finite element models of both OBC and IBC joints are established and the former is validated based on previous research. Subsequently, a total of 84 numerical models is utilized to investigate and compare the mechanical behaviors of OBC and IBC joints, taking into account different thicknesses of side plate and flange as wll as various loading conditions. The numerical results indicate that: (I) in comparison to OBC joints, the IBC joints exhibit significant enhancements in strong axis bending performance and axial tensile performance, including average enhancement ratios of 48%, 67%, 44%, and 19% in initial strong axis bending stiffness, ultimate strong axis bending moment, initial tensile stiffness and ultimate tension, respectively; (II) compared to OBC joints, the IBC joints demonstrate reduced capacity in axial torsional resistance and axial compressive performance, with mean decline ratios of 54%, 39%, 14%, and 7% in initial torsional stiffness, ultimate torque, initial compressive stiffness and ultimate compression, respectively; (III) OBC joints have better weak axis bending performance compared to IBC joints, but this gap decreases remarkably with increasing thicknesses of side plate and flange; (IV) the initial out-of-plane shear stiffness and ultimate out-of-plane shear of the IBC joint exhibit average enhancement of approximately 20% and 10%, respectively, when compared to those of the OBC joint; (V) regarding in-plane shear performance, the initial stiffness of IBC joints exceeds that of OBC joints by an average ratio of 61%, while IBC joints with flange thickness over 10 mm demonstrate significant improvement in ultimate capacity; (VI) The mechanical performance of OBC and IBC joints shows varying degrees of improvement with an increase in the thicknesses of side plate and flange. [ABSTRACT FROM AUTHOR]

Axial forces are generated in the plates of ADAS-yielding dampers when subjected to lateral loading due to their boundary conditions. This on one hand can lead to an increase in strain level of the plates and accelerate the damage process, while on the other hand, the interaction of the bending moment with the tensile axial force leads to increasing strength, which is undesirable in the performance of ductile members. In this paper, a modified ADAS device (MADAS) is introduced to prevent undesirable interaction of axial forces, and its cyclic behavior is evaluated both experimentally and numerically. To this end, in the first step, two test specimens with different number of connection pins were prepared and subjected to cyclic loading in a rigid frame. Experimental and numerical results have shown that due to the removal of the constraint in the vertical direction, the level of forces produced by the damper is almost constant and the X-shaped plates have been able to tolerate significant number of cycles before crack initiation. Afterwards, the cyclic performance of ADAS and MADAS dampers was numerically compared individually and also when placed in the frame. Furthermore, in the frame equipped with ADAS damper, the increase in the level of forces produced by the damper led to the buckling of the braces, while the level of generated forces was totally in the expected range in the frame equipped with MADAS damper. [ABSTRACT FROM AUTHOR]

In this paper, a new beam Euler–Bernoulli finite element for the transverse static bending analysis of cracked slender strip tapered footings on an elastic two-parameter soil is presented. Standard Hermitian cubic interpolation functions are selected to derive the closed-form expressions of complete stiffness matrix and the load vector. The efficiency of the proposed finite element is verified on an example with several width tapering variations of a simple cracked footing with the results of governing differential equation. Another novelty of this study is improved bending moment functions with included discontinuity conditions at the crack location. These functions now accurately describe the bending moments in the vicinity of the crack of the finite element. [ABSTRACT FROM AUTHOR]

The monopile-friction wheel hybrid foundation withstands various loads in the marine environment, such as the vertical load (V) transmitted from the superstructure, horizontal loads (H) caused by wind or wave, torsional loads (T) caused by rotating structures. In this article, 1 g model tests are used to investigate the behavior of the monopile-friction wheel hybrid foundation under independent horizontal load (H) or torsional load (T), and combined loads (H-T) in sand soil, respectively. The failure envelopes of H-T loading plane are obtained from the measured load-displacement data with the simplified calculation equations presented as well. Finally, we also discuss quantitatively the influences of the pre-vertical loads, foundation geometry and loading eccentricity on the bearing capacity of the hybrid foundation via the three-dimensional finite element method. The results indicate that the displacement response of the hybrid foundation under independent loading is significantly different from that subjected to combined loads (H-T). The torsional bearing capacity of the hybrid foundation can be significantly improved by 6.6-33.34% under pre-horizontal load. The horizontal bearing capacity of the hybrid foundation decreases sharply after the pre-torsional load reaches a certain value, which decreases by about 20%. The presence of a friction wheel improves the torsional/bending moment distribution of pile shaft. [ABSTRACT FROM AUTHOR]

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]

A new type of UHPC‐NC (normal concrete) structure in the negative moment zone was proposed to improve the bearing capacity of the connection structure in the negative moment zone of prefabricated prestressed concrete (PC) beam bridges. First, the distribution characteristics of the crack, cracking load, ultimate moment, and ductility coefficient of the new structure were obtained by the 1:4 scale model tests. The feasibility of the connection structure is verified. Then, the value ranges of critical structural parameters affecting the bearing capacity of the connection structure based on the plane section assumption analysis, including the reasonable thickness of the UHPC layer, the reinforcement ratio of the longitudinal tensile reinforcement, and the diameter of the reinforcement, are obtained. At the same time, based on the verification of the finite element model, the influence of crucial research parameters on the bending capacity of the connection structure is obtained by using the finite element method. Finally, a theoretical method for the bending moment capacity of the connection structure of the UHPC‐NC structure is proposed, considering the high ductility characteristics of UHPC materials. The average relative error between the calculation results and the finite element method is within 7.2%, which verifies the reliability of the calculation method in this paper and provides a reference for its design and engineering application. [ABSTRACT FROM AUTHOR]

The hydrocarbon transportation industry uses extensive pipeline networks subject to complex loading conditions. The finite element analysis (FEA) has proven to be effective in simulating the deformation behavior in these pipelines, which assists in the assessment of their integrity and risks. In this work, a model developed using finite elements is proposed to analyze the behavior of API 5L Gr B carbon steel pipes, subject to internal pressure and lateral loads. The model is validated through uniaxial tensile and four-point bending tests. In addition, parametric analysis is carried out considering variables such as diameter, lateral load, and distance between supports. The objective is to identify which one of these variables has the most influence in the unit strain. The results indicate that the unit strain obtained from the numerical model agrees with the experimental tests. Furthermore, it is concluded that the diameter is the influential parameter. [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]

During pipeline construction and operation, the occurrence of surface dents presents a critical concern, primarily arising from factors such as pipeline installation and geological forces exerted upon the pipeline, particularly in the form of rock protrusion. These dents pose a significant threat to the pipeline's safe functionality and have the potential to diminish its load-bearing capacity. Presently, China's oil and gas pipelines predominantly employ X80 high-grade steel. It is noteworthy that prior research into the ultimate load capacity of dented pipelines has largely centered on medium and low-grade steels. The implications of these findings for the suitability of the X80 pipeline remain inconclusive. Consequently, it is imperative to undertake a comprehensive investigation into the load-bearing capacity of high-grade steel pipelines with dent defects. In addition to internal pressure, variations in the pipeline's transported medium, ambient temperature fluctuations, soil displacement, and other factors introduce additional loading effects, including bending moments and axial loads. These supplementary loads introduce latent hazards to the pipeline's operational safety. Hence, this research endeavors to investigate the ultimate load-bearing capacity of X80-grade dented pipelines under the influence of typical loading conditions and to identify pertinent factors that affect this capacity. Finite element analysis (FEA) is deployed to study the behavior of the dented pipelines under typical loads. Failure criterion for ascertaining the ultimate load is proposed and verified by the comparison to test results. Furthermore, the impact of varying dent sizes on the ultimate load capacity of X80-grade dented pipelines is examined. These findings serve as a robust foundation for the safety assessment of dented pipelines, ensuring the sustained safe operation of these vital infrastructures. [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]

Typical concentrically braced frames (CBFs), such as cross-braced (X-braced) frames, are commonly used to provide resistance against lateral loads. These systems are prone to buckling under compression, resulting in instability before reaching the yield strength. In other words, this bracing system exhibits an asymmetric behavior in tension and compression that undermines its energy dissipation capacity during excitation and leads to substantial damage to the structural and non-structural members. In an attempt to improve these shortcomings, this study introduces the novel quasi-X-braced frames. The stiffness and stability of the quasi-X-braced steel moment frames were evaluated by novel analytical and numerical methods. Drawing on strain energy concepts and Castigliano's theorem, this study presents an accurate analytical formulation for the lateral elastic stiffness of two-dimensional single-span and one-story quasi-X-braced steel moment frames (QXB-MFs). In this regard, all effective parameters, including the axial and shear loads and bending moments of all members, were taken into account. The proposed relation was validated with results from different cases using OpenSees. The error between the elastic stiffness results of the developed relation and the finite element numerical analysis was found to be negligible. Also, the seismic performance of QXB-MF systems was investigated according to the FEMA P695 methodology for near-field and far-field ground motion records compared with the intermediate moment frame. The results showed that using quasi-X braces in the intermediate moment frame improves the seismic performance of this system. [ABSTRACT FROM AUTHOR]

The need for smooth, gapless mechanisms that offer superior aerodynamic performance has been the prime mover for a wide range of studies on the morphing concepts from the early years of the twenty-first century. In light of the importance of novel analytic means for inspecting such structures, this article describes a comprehensive dynamic model for the flexural vibration of a special type of morphing structure known as fish bone active camber (FishBAC). In view of the shortcomings of previous models, the developed procedure considers the variable thickness of the central spine of FishBAC as well as the possibility of arbitrary truncations in its numerous partitions to offer more accurate results. A general idea is first proposed based on the assumptions of classical plate theory for such partitioned structures. The equations are derived using the energy method and the assumption of artificial springs to satisfy the continuity of shear force and bending moment along the connecting lines between partitions. A robust Rayleigh-Ritz method along with a set of fast-converging admissible functions is presented to solve the governing equations of motion. Combined with the power of Mathematica and validated by other analytic models and finite element codes, this technique can be used to deal with a plethora of similar systems while paving the path for the dynamic analysis of FishBAC built around various airfoils. [ABSTRACT FROM AUTHOR]

Present work deals with the design and finite element analysis (FEA) of a three-wheeled foldable electric vehicle. The vehicle is intended for use of inhouse purposes. The design phase includes evaluation of stress and deflection using classical approach. Use of shear force and bending moment diagram for calculating stresses and deflections are shown. Section properties of individual members of the vehicle structure are also calculated. The theoretical values of stresses and deflection fall within the acceptable limits of yield stresses of the material. FEA of the vehicle has been carried out using Ansys software. Values of stress and deflection from FEA are in close correlation with those available in literature. From model analysis, six different modes of vibrations and corresponding frequencies are evaluated. Crash analysis of the vehicle is also carried for three types of impacts viz., front, rear and side. The velocity considered for analysis is 25kmph. Ergonomics aspect of the vehicle is also assessed. From the RULA and REBA analysis the ergonomic aspect of the vehicle is found to be in acceptable limits. [ABSTRACT FROM AUTHOR]

Curved panels are structural elements that form the skin of wings, fuselages and tail booms in aircraft. Buckling of these structures would adversely affect aircraft performance. Due to this, the problem of buckling has been extensively researched in the past. Most of the research has been restricted to the analysis of flat composite panels and analysis of curved panels through simplifications involving geometry, material properties and boundary conditions. The present study aims to develop an analytical solution that can predict the critical buckling load for a wider range of problems. An analytical solution was developed in order to obtain the critical buckling load for a doubly-curved composite laminate under compression, shear, moment or any combination of the three loads. The assumptions of the classical laminate plate theory were used in order to obtain the displacement fields as well as strains of the laminate. The energy method was employed in order to obtain the critical buckling load for various load cases. The values obtained through the analytical solution are compared to the critical buckling loads obtained through finite element analysis (FEA). The highest deviation of critical buckling load from FEA was calculated to be 16.55%. Variation of the critical buckling load with respect to the radius of curvature, boundary conditions and stacking sequence was analyzed. The developed solution was also found to be valid for cases when radii of curvatures are unequal as well as when the length and breadth of laminate are unequal. [ABSTRACT FROM AUTHOR]

Ring origami has emerged as a robust strategy for designing foldable and deployable structures due to its impressive packing abilities achieved from snap-folding. In general, polygonal rings with rationally designed geometric parameters can fold into compact three-loop configurations with curved segments which result from the internal bending moment in the folded state. Inspired by the internal bending moment-induced curvature in the folded state, we explore how this curvature can be tuned by introducing initial natural curvature to the segments of the polygonal rings in their deployed stress-free state, and study how this initial curvature affects the folded configurations of the rings. Taking a clue from straight-segmented polygonal rings that fold into overlapping curved loops, we find that this behavior can be reversed by introducing curvature into the ring segments in the stress-free initial state such that the rings fold into a looped straight-line configuration with "zero" area. This strategy realizes extreme packing of the rings. In this work, by a combination of experimental observation, finite element analysis, and theoretical modeling, we systematically study the effect of segment curvature on folding behaviors, folded configurations, and packing abilities of curved ring origami with different geometries. It is anticipated that curved ring origami can open a new avenue for the design of foldable and deployable structures with simple folded configurations and high packing efficiency. [ABSTRACT FROM AUTHOR]

Occurrence of progressive collapse events invariably leads to significant economic and human-life losses. Progressive collapse analysis and design of building structures have become a research hotspot worldwide. Existing studies have proved that development of extra load-carrying mechanisms could significantly improve the resistance of structures to progressive collapse. However, limited research has been conducted to quantitatively analyze these mechanisms. This study proposed a new and unified division method for mechanisms for resisting progressive collapse; furthermore, it provides a basis for their quantitative analysis. In addition, the progressive collapse behavior of a 1/3-scaled two-story, one-bay-by-two-bay reinforced concrete (beam–slab–column) frame with an edge column lost was experimentally investigated. Additionally, a 3 D solid finite element model was established and validated based on the test results. The effects of different extensive parameters, including ideal lateral constraints, slab thickness, and beam–slab interaction, on each resisting mechanism were quantitatively investigated. Finally, a new simple method for predicting the first peak load was proposed based on the contribution of each mechanism. The results from the simple method were in agreement with the simulation results of beam–slab–column structures. [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]

To explore the supporting performance of oblique piles (OPs) used in pit excavation, a field test was performed at a foundation excavation using OPs with various inclination angles. Then, numerical models using the finite-element method were established and validated on the basis of the field test result. A novel arrangement of oblique‒vertical alternating piles (OVAPs) was proposed as the retaining structure for excavation. The displacements of the pile top, internal forces of the pile body, earth pressures on the pile body, and soil deformation were observed and studied. The results indicated that both pile inclinations and arrangements had an effect on the supporting performance of oblique piles. Furthermore, four effects were summarized to explain the advantages and working mechanisms of OP and OVAP arrangements used in retaining structures. Finally, a force analysis of oblique supporting piles in the foundation pit was conducted and a simplified formula was derived and applied to calculate the bending moments of pile bodies under different working conditions. [ABSTRACT FROM AUTHOR]

The large underground structure in saturated stratum is vulnerable to float during an earthquake. This results in a plethora of problems, such as uneven settlement, large internal force and structure damage. In this study, the seismic behavior of a three-story, two-span subway station in complex saturated stratum was investigated through water-soil fully coupled 3D finite element method. In the analysis, the nonlinear soil behavior was described by a cyclic mobility model and the structure was calculated using a nonlinear constitutive model which can consider the influence of axial force on its bending moment. Joints elements were used to model the contact surface between soil and structure. The development of the soil displacement and internal force of the station structure at different times during a huge earthquake was examined. The bearing capacity of the station structure members was analyzed. The results indicated that the vertical displacement was spatially distributed. The larger additional seismic stresses appeared in the bottom slab and side wall. Failed elements were observed in both the walls and slabs, and the walls were more easily damaged than the slab. The results provide useful reference for the large underground structure seismic design in the construction of urban underground space. [ABSTRACT FROM AUTHOR]

Buried pipelines are critical infrastructure components which employed for delivering and distributing vital products such as water, gas and oil. Such energy transmission lines might cross fault lines on their routes, undergo tension and compression strains due to crossing angle under permanent ground deformations and severely damaged. Steel pipe failures are expected to be due to tensile loads in terms of design issues. However, in cases where reverse or some strike-slip faults have to be crossed due to forced routing, premature failures may occur under net axial compressive loads. According to the current code, the design principles for pipelines are specified due to maximum axial tension and compression deformation values correspond to uninterrupted and controlled damage cases. In this study, limit states due to axial deformations under axial compressive and bending load conditions, which mainly cause loss of pressure integrity and pipe damages, are investigated. For this purpose, corresponding D/t ratios and material properties are considered to characterize the existing pipelines in Turkey such as, Kullar water transmission, Trans-Anatolian-Natural Gas (TANAP) and Baku-Tbilisi-Ceyhan Crude Oil (BTC) pipelines by using three-dimensional finite element model under combined loading conditions. In this way, limit states due to displacements and rotation demands are specified. The results of this study are expected to be used in the performance-based design of steel pipes in Turkey. [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]

To reduce the mass of mechanical elastic wheels, the lightweight analysis was conducted by the finite element analysis software of Abaqus. Considering the bending moment load and radial load conditions of the wheels at all times, the finite element model of mechanical elastic wheels was established, and the finite element simulation analysis was carried out. The force data of the nodes were extracted from the simulation results to determine the load of wheel hub and hinge group. The weighted variable density method was used to optimize the topology of the hub and hinge group of mechanical elastic wheel, and the 3D model was reconstructed after optimization. The results show that the mass values of the optimized mechanical elastic wheel, wheel hub and hinge assembly are reduced by 15.1%, 27.9% and 22.6%, respectively. [ABSTRACT FROM AUTHOR]

A systematic study into the behavior of reinforced semi-rigid piles in response to lateral monotonic and cyclic loading in clay was performed with centrifuge modeling tests (100×g). The aim was to investigate the pile–soil interaction mechanism of reinforced semi-rigid piles and to give some generally applicable design advice for reinforcing semi-rigid piles with cement-improved soil. For monotonic loading, the overall load–deflection behavior, profile of bending moment, net soil pressure and pile deflection have been fully studied, in addition to the p–y curves and excess pore pressure response of reinforced and unreinforced piles. It is found that shallow cement-improved soil reinforcement can greatly improve the lateral capacity of piles. In addition, a hyperbolic tangent model was proposed to fit the p–y curves obtained from monotonic tests for reinforced and unreinforced piles. For cyclic loading, it was found that compared with unreinforced piles, reinforced semi-rigid piles reduce the accumulation of pile deflection and the degradation of stiffness. The trends of the cyclic bending moment and cyclic p–y curves are also revealed. A series of supplementary finite element analyses were conducted to study the effects of reinforcement parameters (reinforced width, reinforced depth and strength of cement-improved soil) on lateral pile capacity. It is suggested that shallow reinforcement with a reinforced width of 5D and a reinforced depth above the rotation point of a semi-rigid pile is both economical and practical. [ABSTRACT FROM AUTHOR]

Tunneling in urban environments is challenging due to the number of pipelines to cross, which may adversely impact the pipelines due to tunneling-induced ground settlement. An adequate vertical separation distance between the bottom of the pipeline and tunnel crown is not always possible, and a minimum volume loss may be difficult to achieve due to subsurface conditions encountered and tunneling methods available. Therefore, the impact to the existing pipelines from tunneling needs to be assessed to mitigate the risk. Considering gap formation beneath the existing pipeline explicitly and a limiting overburden loading acting on the pipeline, this study proposes a design-oriented analytical approach to estimate the upper bound of the maximum bending moment of the pipeline induced by tunneling. A dimensionless quantity, namely, the overburden loading factor defined as the ratio of overburden loading and the minimum required loading to eliminate the gap, is introduced to evaluate the extent of gapping, by which gap formation can be predicted. The effect of pipe-soil interaction, which reduces the maximum bending moment in the pipeline, is considered by conducting nonlinear Winkler-based finite element analyses with varying stiffness factors. The design chart and table are presented to provide a more accurate estimation of the maximum bending moment, especially for greater stiffness factors. It is demonstrated for small overburden loading and stiffness factors, i.e., wider gaps, a perpendicular crossing may not always be the worst-case scenario. As illustrated by the partially supported beam model, the effect of the increase in the unsupported span is greater than the effect of the reduction of the curvature of the settlement trough for these cases. Design examples are provided to demonstrate the analytical procedure step-by-step, and a comparison with previous studies is made. It is demonstrated with reasonable conservatism for small to moderate stiffness factors, the proposed design-oriented analytical approach can straightforwardly predict the maximum bending moment in pipelines. It is common to cross beneath an existing buried pipeline in the proximity for any tunneling project in urban areas due to the restrictions of underground space, soil conditions, right-of-way, and construction costs, etc. Considering gap formation beneath and an ultimate overburden loading on the existing pipeline, this study can be used to estimate the maximum bending moment in the existing pipeline due to ground settlement induced by tunneling, especially in the preliminary stage when the soil information is unavailable. The analytical procedure can be easily implemented by hand calculation or a spreadsheet, and more accurate results can be found with the aid of a chart and table provided when the soil information is available. The results obtained can assist the tunnel practitioners to determine an adequate separation distance, intersection angle, and an appropriate tunneling method to minimize the impact to the existing pipeline. Three detailed design examples are provided in the Appendix to illustrate the procedure step-by-step. [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]

The material properties of high-strength steels deteriorate under fire conditions and depends on the temperature and fire duration. As a time-dependent inelastic strain behavior, the thermal creep effect becomes significant at elevated temperatures and influences the fire resistance of connections. This paper presents numerical studies on the fire response of unprotected extended end-plate connections made of high-strength steels (Q460, Q690 and Q960), explicitly considering the creep effect. Transient state finite element models including or excluding creep were developed using ABAQUS and validated against the experimental results under the restrained sub-framework. The numerical analysis results exhibit a better agreement with the experimental results regarding the deformation ability and failure mode if the creep effect is considered. Thus, creep is a non-negligible effect in investigating the fire performance of end-plate joints. Parametric studies were carried out to quantitatively assess the influence of moment ratio of connection, axial pressure ratio of column, end-plate thickness and heating rates on rotation–time–temperature characteristics and stress distribution. The numerical results show that the magnitudes of bending moment applied on the connection and axial load on the column play crucial roles in evaluating the fire endurance and critical temperatures. However, the effect of end-plate thickness on the fire-structural behavior of extended end-plate connections is negligible. The heating rate has little effect on the critical temperatures of connections. The rotation capacity of high-strength steel extended end-plate connections depends on the failure mode to a large extent. Finally, fire resistance design suggestions for high-strength steel end-plate connections were put forward according to the observations on the parametric studies. [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]

Piles in soft soil supporting bridge abutments are often exposed to passive loading induced by adjacent bridge approach embankment. Several methods for analysis of passive piles have been developed, but the international design specifications do not recommend a specific method for the analysis of passive piles. Therefore, the applicability of existing empirical and analytical analysis (conventional) methods is examined by comparing their outputs with those of a validated finite element model (FEM) at various adjacent embankment stress levels, and construction times, soft clay thicknesses, and pile spacing to diameter ratios. Outputs of both conventional methods and FEM show that increasing the embankment stress, thickness of soft clay layer, and pile spacing to diameter ratio results in an increase in the lateral pile displacement, maximum bending moment, and lateral pressure, and vice-versa on increasing embankment construction time. The outputs of the conventional analysis methods are compared to the FEM outputs and are underestimated except for few cases. The conventional analysis methods may yield better predictions at pile diameter-to-spacing ratio equals 3–4 for a soil preloaded prior to pile construction to a degree of consolidation greater than 50%. [ABSTRACT FROM AUTHOR]

The injury conditions of the sitting position occupant inside the military equipment are highly related to the vertical impact environments. In this study, a detailed three-dimensional finite element (FE) model of pelvis-lumbar spine of seated human with nonlinear material property and strain failure criterion was developed and validated. A series of sinusoidal accelerations with a constant peak speed of 8 m/s and frequencies ranging from 10 Hz to 90 Hz were loaded on the FE model to investigate the injury conditions under different high loading rates. The results indicated that the injury patterns mainly include wedge fracture of the junction between lumbar spine and pelvis, and comminuted fracture of ischial tuberosity. The bending moment caused by the large angle deflection of pelvis under 10 Hz case (low rate) and the acting force caused by the excessive curvature of lumbar spine under 30 Hz–70 Hz cases (medium and high rate) cause the junction wedge fractured, while the high impact force under 30 Hz–50 Hz cases (medium rate) leads to comminuted fracture of the ischial tuberosity. The associated mechanism that the shorter the time interval between the peak of seat loading speed and the peak of hip muscle compression, the more serious dynamic responses of pelvis-lumbar spine is revealed for the first time. [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]