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In this paper, an energy-conserving finite element method is developed and intensively analyzed for a class of nonlinear fourth-order wave equations in a general sense for the first time, where the two-level, Crank-Nicolson type of temporal discretization scheme is designed to cooperate with the Lagrange finite element approximation in space in order to achieve the conservation of discrete energy at each time step. The energy conservation is crucial in engineering field to preserve the total energy as constant for dynamic vibration problems of beams and thin plates that can be modeled by the presented wave equations. In addition, the optimal spatial convergence properties in both L 2 - and H 1 -norm and the second-order temporal approximation rate are obtained for finite element solutions of u (deflection), Δ u (bending moment) and/or u t (deflection speed) at the same time. Numerical experiments are carried out to validate all attained theoretical results. [ABSTRACT FROM AUTHOR]

This study investigates the load-carrying mechanism and proposes precise strength prediction methods for hole threads in Thread-fixed One-side Bolts bolted curved T-stubs to circular steel tube connections. A series of parametric analysis was performed with an advanced 3D finite element model considering critical parameters including tube wall thickness, bolt angle and bolt size. The axial load distribution along the hole threads and the shear stress distribution at the thread root were analyzed in detail. It was found that there were three typical load distribution patterns along hole threads, which were (1) linear pattern; (2) concave parabola pattern; and (3) convex parabola pattern, and the ratio of bolt stiffness to tube wall stiffness was identified as the pivotal factor affecting the axial load distribution. Meanwhile, the analysis results indicated that the bending moment on the TOBs did not affect the load distribution along hole threads, but led to a non-uniform stress distribution along the thread in the same turn. In the end, the prediction formulas for the carrying capacity of hole threads are presented by modifying Yamamoto's equation based on the analysis findings. The formulas are validated against the finite element analysis results and previous test results. The prediction can reach the highest accuracy when adopting the proposed failure criterion 2, with average errors of − 0.001 and − 0.002, respectively, demonstrating the accuracy and reliability. • An advanced 3D finite element model for bolted connections was developed. • The load distribution along hole threads were analyzed in detail. • Three typical load distribution patterns along hole threads were found. • Proposing methods to predict the load-carrying capacity of hole threads. [ABSTRACT FROM AUTHOR]

The seismic behaviour of hybrid coupled walls (HCWs) made of a single reinforced concrete (RC) wall connected to two steel side columns through steel links, named as single-pier HCWs (SP-HCWs), is studied through nonlinear finite element simulations. The design concept is that the steel links are intended to work as dissipative elements while the steel side columns and the RC wall should remain elastic. Given that previous studies highlighted difficulties in avoiding damage at the base of the RC wall due to the concentration of bending moment, this study focuses on a special configuration providing very limited damage at the base of the RC wall that could be rapidly and economically repaired. The original scheme of SP-HCW with fixed base is modified introducing a hinged connection combined with vertical steel elements, called corner components. A ductile design methodology is proposed and applied for proportioning 54 case studies with different building heights, coupling ratios, height-to-length ratios of the RC wall, in addition to different base conditions (fixed base, hinged base with corner components designed as non-dissipative elements, hinged base with corner components designed as dissipative elements). Results of nonlinear finite element analyses validate the design methodology and highlight the potentialities of the proposed solutions, showing the benefits of a hinged base with corner components. • The seismic performance of single-pier steel and concrete hybrid coupled walls is studied. • Focus is made on alternative hinged base solutions to protect the wall from damage. • A seismic ductile design procedure is proposed and applied to a wide set of case studies. • Results provide insights into the benefits of the developed base configurations. [ABSTRACT FROM AUTHOR]

Six T-shaped welded multi-partition composite members were tested under eccentric compression loading by considering the influence of eccentricity and eccentric angle. The test results showed that no weld tearing occurred when the specimen was damaged, indicating that the two vertical welds could ensure the overall working performance of the specimen. The specimens exhibited the smallest bearing capacity when failing along the asymmetric axis, which was the most dangerous situation. The parametric analysis is conducted by a verified finite element model considering the influence of the slenderness ratio, section height-to-width ratio, section depth-to-width ratio, concrete and steel grade, steel ratio, and eccentric angle. If concrete contributes a larger proportion to the bearing capacity, the interaction curve of axial force and bending moment tends to protrude. Conversely, the interaction curve of axial force and bending moment gradually shrinks as the slenderness ratio increases. Based on this observation, a calculation method of T-shaped welded multi-partition composite members under eccentric compressive loading along the asymmetric axis is proposed by considering the effect of the slenderness ratio. Formulas for bearing capacity under biaxial eccentric compression are proposed based on the results of the parametric analysis. • Eccentric compression of T-shaped welded multi-partition composite members was studied through experiments and FE analysis. • The measured torsion angle confirms the good torsional capacity of T-shaped composite members. • The effects of the slenderness ratio and biaxial eccentricity on the bearing capacity of the specimen are studied. • The N - M curve of T-shaped composite members under eccentric compression loading along the asymmetric axis is proposed. [ABSTRACT FROM AUTHOR]

This study examined the hysteretic behaviour of Square Hollow Section (SHS) T- and X-joints subjected to cyclic in-plane bending moments. A nonlinear finite element software, Abaqus, was used to investigate SHS T- and X-joint seismic performance. Prior to the parametric study, the numerical model was validated based on the available test results in the literature. A comprehensive parametric study employed validated finite element models to evaluate the influence of critical geometric parameters, including the brace-to-chord width ratio (β) and the chord width-to-thickness ratio (γ). The results of the finite element analyses regarding ductility, flexural strength, and energy dissipation behaviour of SHS T- and X-joints under quasi-static cyclic in-plane bending were evaluated. Based on the hysteretic curves, increasing β generally leaded to higher initial stiffness and moment capacity in SHS joints, considerably reducing joint rotation. Conversely, the joints with larger γ exhibited reduced initial stiffness and moment capacity. Besides, the Eurocode 3 EN1993-1-8 predictions for the ultimate flexural strength of the joints are found to be conservative compared to finite element results. The results also revealed that the SHS T- and X-joints showed satisfactory ductility levels under in-plane bending load. It was observed that the SHS T- and X-joints with high β and low γ are advantageous for absorbing energy under seismic loads. These findings offered valuable insights for the seismic-resistant design of structures incorporating SHS joints, aiding in selecting optimal configurations based on specific performance requirements. • This paper presents a numerical study of hysteretic behaviour of SHS T- and X-joints with IPBM. • An increase in β ratio generally corresponded to higher initial stiffness, moment capacity, ductility. • The joints with large γ ratio exhibited reduced initial stiffness, moment capacity and ductility. • Eurocode 3 predictions were conservative in estimating the ultimate flexural strength of the SHS T- and X-joints under IPBM. • SHS T- and X-joints with high β and low γ were advantageous for absorbing energy under seismic loads. [ABSTRACT FROM AUTHOR]

Single-point mooring (SPM) system has been used in offshore engineering for its superiority in overcoming severe sea conditions. However, researches focused on the interaction mechanism between the anchor pile and soil in SPM systems remains insufficient, especially regarding the calculation method for oblique pullout bearing capacity that considers padeye depth. Based on the p-y curve method and load transfer method, this paper presents a simple prediction method for the behavior of anchor piles embedded in sand under oblique pullout load. The theoretical predictions are validated through comparing with results from the three-dimensional finite element method and existing centrifuge model tests. The effect of the loading angle and the padeye depth are analyzed and discussed. A negative bending moment peak and axial force discontinuity phenomenon appear at the padeye depth. The optimal padeye depth for anchor piles in this study ranges from approximately 0.53 to 0.80 times the pile length. When the padeye depth is less than 0.33 times of the pile length, the ultimate bearing capacity of the anchor pile increases with increasing load angles. Conversely, when the padeye depth exceeds 0.33 times the pile length, the ultimate bearing capacity decreases with the increasing load angles. [ABSTRACT FROM AUTHOR]

In offshore jacket structures, the stress within the chord thickness of tubular joints arises from both membrane and bending stresses. The Degree of Bending (DoB)—the ratio of bending stress to the total stress—is key to evaluating these joints' fatigue resistance. This study delves into the DoB in tubular X-joints reinforced with fiber-reinforced polymer (FRP) subjected to in-plane bending moment. It begins by validating finite element (FE) analysis accuracy through comparison with existing theoretical and experimental evidence. Following this, the analysis of 166 joints was conducted to examine how variations in FRP characteristics (such as type, layer count, and layout) and the joints' dimensionless geometric factors influence the DoB and its ratio in reinforced joints compared to their unreinforced counterparts. Findings indicate that FRP layers enhance fatigue resistance by lowering hot spot stresses on the chord's inner and outer surfaces and elevating the DoB value by up to 26.16%. Consequently, the study introduces a parametric formula for calculating the DoB in FRP-reinforced tubular X-joints under an in-plane bending moment. This development is significant, as there was no existing parametric formula for determining DoB in FRP-reinforced joints. The proposed formula stands out for its high determination coefficient and minimal error, effectively addressing a notable gap in the field. • The Degree of Bending (DoB) evaluation in FRP-reinforced tubular X-joints under in-plane bending (IPB) is conducted. • 166 finite element models are analyzed for parametric investigation. • The influence of FRP characteristics and geometric factors on the DoB is investigated. • A parametric formula is introduced to calculate the DoB in FRP-reinforced tubular X-joints subjected to IPB moment. [ABSTRACT FROM AUTHOR]

This paper presents the results from two full-scale transversally stiffened plate girder's load tests in shear and bending. The plate girder's internal stiffener forces and shear buckling resistance are estimated using the web and stiffener measured strains. These results show that the reported axial compression and bending moment of the intermediate transverse stiffeners for the tested plate girder are 70% of the FprEN 1993–1-5: 2022 [1] design force. The two full-scale plate girders fail due to buckling shear. Nonlinear FEM analyses based on the test girder geometry, measured initial geometric imperfections, and the material properties from the tensile tests, show excellent agreement with the test results, with less than 5% on the maximum applied forces and related displacements. The principal membrane stresses path that triggers the failure of the web plate are investigated based on numerical results and compared with the test measurements. Contrary to the assumption of a rotated stress field model, the principal compression stress obtained in the experimental test was higher than shear buckling stress in the vicinity of the intermediate transverse stiffener. • Experimental shear behaviour of full-scale thin-walled plate girders in what concerns shear loading past ultimate loading. • Focus on intermediate transverse stiffener behaviour and shear load path. • Data acquisition techniques are resumed regarding measurements using optical extensometer and laser scanning. • Finite Element Model and Analysis were performed for the simulation of the experimental tests reported. • Obtained experimental and numerical outcomes are compared to current recommendations provided by EN1993-1-5. [ABSTRACT FROM AUTHOR]

• V-H-M failure envelopes and failure mechanisms of tripod pile foundations are identified considering a bunch of practical factors. • The direction of loading plane affects both the size and the location of the failure envelope in loading space for the tripod pile configuration. • An empirical design approach is proposed to predict the failure envelopes of tripod pile foundations in the 3D V-H-M space which will be helpful for engineering practice. The problem considered in this computational study is for the bearing capacity determination of three-dimensional (3D) rigid tripod-pile groups subjected to combined vertical (V), horizontal (H), and bending moment (M) loads. Using the adaptive 3D finite element limit analysis (FELA) coupled with lower bound, upper bound and mixed Gauss element formulations, numerical results are compared with those of the previous study under a single-component loading (V , or H, or M). The failure envelope in the 3D V – H – M loading space is then constructed, and several failure mechanisms presented to complement the discussions on the complex 3D responses. This is followed by a parametric study for the various factors such as the pile length, pile spacing, pile-soil adhesion factors as well as the loading direction angle. Finally, a closed-form design expression of failure envelopes considering the abovementioned influential parameters and the combined load are derived. Noting that the current industry-based design procedures for tripod-pile groups are rarely found, the outcome of the present study can be used with great confidence in design practice. [ABSTRACT FROM AUTHOR]

[Display omitted] • Coupled CFD-FEM thermo-mechanical analysis method was proposed. • Elaborate numerical model was established based on a large shield tunnel. • Structural fire safety of composite lining shield tunnel was investigated. • Effects of the timing of secondary lining and the tunnel depth were discussed. The composite lining has been extensively used in shield tunnels. In this study, the thermos-mechanical behaviors of composite lining shield tunnel structures under fire conditions were investigated. A method combined by computational fluid dynamics (CFD) and finite element method (FEM) is proposed to simulate the temperature distribution within the tunnel, the initial stress state of the structure, and the thermo-mechanical coupling process. The elaborate numerical model was established based on a large composite lining shield tunnel. The influence of the timing of secondary lining application and tunnel burial depth on the deformation, internal forces, and structural damage of the composite tunnel structure under fire conditions was investigated. According to the results, the composite lining experiences a significant increase in temperature on the fire-exposed side, which results in significant changes in bending moments and axial forces of the lining during fire. The timing of secondary lining application and burial depth have a significant impact on tunnel deformation during the fire. In comparison to other locations in the tunnel, the application of the secondary lining has the most significant impact on the internal forces at the tunnel arch position. And the burial depth has a considerable influence on the internal forces at both the tunnel top and arch positions. The post-fire damage to the secondary lining is more severe with the post casting and shallow depth. These results provide structural fire safety support for large shield tunnels with composite linings. [ABSTRACT FROM AUTHOR]

Composite shear walls are usually employed at the bottom of super high-rise structures to resist large axial forces, bending moments, and shear forces. A lot of investigations have been carried out on composite shear walls, but there are fewer comparative studies on composite shear walls with different steel layouts. In this paper, low cyclic horizontal loading tests were carried out on conventional reinforcement concrete shear walls and composite shear walls with different steel layouts (H-section steel in boundary members and the steel plate in the shear wall web, H-section steel in boundary members and the slotted steel plate in the shear wall web, evenly arranged H-shaped steel in the wall). Comparative analyses of load-carrying capacity, failure modes, and seismic performance were conducted. The effects of different steel layouts on the seismic performance of composite shear walls were investigated. Based on the tests, the finite element method is used to further analyze the influence of the shear span ratio of the shear wall and the opening rate of the built-in slotted steel plate. • Low cyclic horizontal loading tests were carried out on conventional reinforcement concrete shear walls and composite shear walls with different steel layouts. • The effects of different steel layouts on the seismic performance of composite shear walls were investigated. • The parametric analysis of the composite shear walls with different steel layouts was conducted based on numerical simulation. [ABSTRACT FROM AUTHOR]

This research developed a robust Bayesian framework for evaluating geomaterials and soil-structure interactions involving deep excavation, utilizing Bayesian Regression and Bayesian Network methods that combined data training, validation, and updating into a cohesive framework. A methodology based on Bayesian Generalized Linear Model (a variant of Bayesian Regression) was applied to a laboratory-based case study on sustainable cementitious blends. The framework effectively used past research data to estimate design parameters even though the studies involved different mix design requirements. Then, a framework based on Gaussian Bayesian Network (a variant of Bayesian Network) incorporating Bayesian updating was applied to an established case history for deep excavation in clay. Two-dimensional finite element analysis was used to generate data for model training and updating. The GBN models accurately estimated responses such as wall deflections, wall bending moments, and ground surface settlements through a sequential updating process. The research was conducted using R programming language, with a custom R script designed to follow the process flow of the proposed framework. The successful application and validation of this framework demonstrated its potential for characterizing geomaterials and evaluating complex soil-structure interactions in deep excavation, leveraging on the availability of existing data and a reliable sequential updating process. [ABSTRACT FROM AUTHOR]

In this paper, based on the centrifuge test of liquefied soil-pile foundation system, a numerical model of liquefied soil-pile foundation-structure system is modelled by using OpenSees platform. In the simulation model, the friction effect between liquefied ground and low pile cap is considered, and the method of establishing virtual nodes is used to deal with the non-linear contact between liquefiable soil and low pile cap. The rationality and effectiveness of the numerical simulation method adopted in this paper has been verified and evaluated by comparing with the results of centrifuge experiments. A typical liquefaction soil-pile integrated finite element model is modelled using validated numerical simulation methods. The law of seismic response of the pile foundation system with different embedding depths of pile cap, different contact modes between the pile cap and saturated sand, and the thickness of the overlying saturated loose sand layer are discussed. The results show that the pile cap and pile foundation in the high pile cap system show higher seismic response characteristics than the other three low pile cap system conditions; Under the condition of different contact modes between the pile cap and the surrounding saturated sand, the peak bending moment and residual displacement of the pile foundation calculated by the bond contact are larger than calculated by the friction contact, and the deformation of pile is more significant. By comparing the working conditions of different thicknesses of overlying saturated loose sand layer, it is found that the degree of liquefaction in shallow soils is less affected by thickness of the saturated loose sand. As the thickness of saturated loose sand layer increases, the peak bending moment and residual displacement at the top of the pile also gradually increase. The change of peak bending moment at the soil interface is more obvious. • A numerical model of liquefied soil-pile group-superstructure system is established. • The friction effect between liquefied soil and low pile cap is considered. • The non-linear contact between soil and pile cap is simulated by establishing virtual nodes. • The effects on seismic response of the contact of liquefaction soil-pile cap and are discussed. [ABSTRACT FROM AUTHOR]

Nuclear power plant piping systems frequently encounter complex loads due to factors like internal pressure, self-weight, structural supports, and operational conditions. Within these systems, pipe bends play a crucial role in releasing energy through deformation. Cracks pose a risk to the integrity of the system, necessitating the calculation of the plastic collapse load for cracked pipe bends. This study presents estimations for the plastic collapse load of cracked pipe bends under pure out-of-plane bending moments and simultaneous in-plane and out-of-plane bending moments. Cracks located in the intrados, extrados, and crown of pipe bends were considered. The estimations for plastic collapse load are proposed based on the observed similarity between plastic collapse load and plastic deformation under both in-plane and out-of-plane bending conditions. For combined in-plane and out-of-plane bending moment conditions, circular and parabolic relationships have been proposed for a straightforward plastic collapse load prediction. Additionally, the estimations for plastic collapse loads were derived from the results of finite element analysis conducted on crack-free pipe bends, demonstrating its applicability to cracked pipe bends as well. • Plastic collapse load estimates for cracked pipe bends under combined loads, including out-of-plane bending, were studied. • Yield loci were compared with plastic collapse loads of cracked pipe bends under combined in-plane and out-of-plane bending. • Plastic collapse load estimates for crack-free and cracked pipe bends under combined in-plane and out-of-plane bending are proposed. [ABSTRACT FROM AUTHOR]

In this study, a Finite Element (FE) model of locally strengthened high-strength stainless-steel tube subjected to lateral impact loads is established using LS-DYNA to investigate its dynamic behaviours. The accuracy of the FE results is verified by comparing with the test results. The impact force, bending moment, stress and strain responses as well as the internal energy dissipation histories of the strengthened tube are analysed during the entire impact process. The results indicate that the impact resistance of the strengthened tube is obviously enhanced as compared to hollow stainless-steel tube. Furthermore, parametric studies are conducted to reveal the influence of axial compressive force, impact position, impact velocity and material strength on the impact behaviour of the strengthened tube. The results show that the application of axial compressive force reduced the impact force and increased the deformations of the strengthened tube. The impact resistance of the strengthened tube performed an increasing trend when moving the impact position towards the support and increasing the material strength. In addition, the increase of impact velocity significantly reduced the impact duration. Finally, design recommendations and process were proposed to facilitate the application of locally strengthened tube. • The impact response of locally strengthened stainless-steel tube was numerically studied. • The impact force, bending moment, stress and strain response and energy dissipation were analysed. • Concrete was found to dissipate more impact energy than the other parts. • The effects of variant parameters on impact performances of the strengthened tubes were investigated. [ABSTRACT FROM AUTHOR]

• The dynamic response of thin-walled cylindrical shells subjected to lateral shock loading via foam projectile impact was systematically studied. • Structural deformation evolution, deformation/failure modes, and mid-point deflections of thin-walled cylindrical shells under lateral shock loading were experimentally measured. • The sensitivity of the dynamic response of thin-walled cylindrical shells to the impact momentum level and geometric parameters under lateral shock loading was numerically explored. • It is found that the deformation on the rear side exhibits two patterns: indentation and bulge, which are dictated by the combined effect of circumferential membrane forces and bending moments. A combined experimental and numerical study was carried out to explore the dynamic response of Q235 thin-walled cylindrical shells under lateral shock loading. The machined Q235 specimens were clamped on both sides and subjected to centered lateral simulated shock loading via foam projectile impact tests, with their dynamic deformation evolution, mid-point deflections, and final deformation modes experimentally measured. The mid-point deflections of the impact side are all positive (the direction of deformation is the same as the impact direction) while those of the rear side all exhibit negative values (the direction of deformation is opposite to the impact direction). To further explore this phenomenon, the method of finite element (FE) was employed to simulate the foam projectile impact, with good agreement against experimental measurements achieved. Using the validated numerical model, the effects of impact velocity, length-to-diameter ratio, and thickness-to-diameter ratio on the dynamic response of the thin-walled cylindrical shell were further analyzed. The direction of both side deflections and deformation modes are significantly affected by the impact level and the shell geometries. For the rear side, within the given range of impact momentum and geometric parameters, the numerically predicted deflection varies from −1.775 mm to 2.45 mm. Thereupon, the coupling of indentation and bulge deformation patterns are indicated, and their corresponding contribution changes are considered the main mechanism for determining the final deformation of the thin-walled cylindrical shell's rear side. [ABSTRACT FROM AUTHOR]

• Experimental research on the out-of-plane ultimate bearing capacity of high strength steel (HSS) arches with thin-walled I-section. • Examined the out-of-plane ultimate bearing capacity of 14 HSS arch specimens, considering variations in yield strength, cross-sectional dimensions, slenderness, rise-span ratios, and span. • The finite element analysis of HSS arch, accounting for residual stress and initial defects, demonstrated a high degree of alignment with experimental results. • Investigated the effects of yield strength, rise-span ratio, and slenderness on the ultimate bearing capacity of HSS arches. • Established axial force-bending moment (N-M) design formulas for the out-of-plane ultimate bearing capacity of HSS arches. This study presents an experimental investigation on the out-of-plane ultimate strength of high-strength-steel (HSS) I-section arches, which has not been reported previously. Fourteen I-section HSS arches having different yield strengths, cross-sectional dimensions, slendernesses, and rise to span ratios were tested under three-point symmetrical vertical loading. The corresponding out-of-plane deformation modes and strengths are identified. Subsequently, in order to predict the out-of-plane capacities of HSS arches, a finite element analyses is carried out, which takes into consideration residual stresses and initial geometrical imperfections. This analysis demonstrates a strong alignment with the experimental results, confirming the accuracy of finite element model and experimental results. Furthermore, the study comprehensively analyzes the influence of yield strength of steel, rise-span ratio, and slenderness on the ultimate bearing capacity of HSS arches. Through a parametric analysis, design formulas for the out-of-plane bearing capacity of HSS arches subjected to arbitrary compression forces combined with arbitrary bending moments are formulated. It is found that the out-of-plane ultimate strength of HSS arches is significantly influenced by the yield strength of the steel. Compared to a low strength steel (LSS) arch, the out-of-plane ultimate bearing capacity of the HSS arch increases with an increase in yield strength in the plastic stage, and the ultimate lateral displacement of the HSS arch decreases with an increase in yield steel strength due to the lower ductility of HSS. In addition, after reaching the out-of-plane ultimate bearing load of arch, the load-displacement curve of the HSS arch drops faster than the LSS arch. It is also found that the proposed design formulas can effectively predict the out-of-plane bearing capacity of HSS arches. [ABSTRACT FROM AUTHOR]

Built-up radially battened columns (RBCs), comprising several identical circular steel tubes interconnected by multiple radial-shaped battens, represent an innovative column design that combines aesthetic appeal with exceptional load-bearing capacity. This makes them well-suited for architectural applications in large public buildings such as stations and airports. The axial compressive strength design methods for the built-up RBC have been extensively explored in the authors' prior studies. However, in real-world engineering applications, built-up RBCs may experience simultaneous axial compression and varying directional bending moments, particularly when considering potential eccentric compression or wind and earthquake loads in public buildings. Currently, strength design methods for this loading condition are still lacking. To address this deficiency, this paper primarily delves into the failure mechanism and strength design methods for built-up RBCs experiencing combined axial compression and arbitrary directional bending moments. Initially, the sectional strength of the built-up RBC is investigated by using a shell finite element model (FEM) for the built-up RBC. It is revealed that the compression-bending sectional strength of the built-up RBC exhibits significant differences with varying bending directions and tube numbers. Moreover, in some bending directions, the M - N sectional strength curve of the built-up RBC exhibits convexity. By integrating theoretically derived equations grounded in the principles of materials mechanics with FEM numerical calculations, concise and practical design equations are proposed for accurately predicting the sectional strength of the built-up RBC under combined axial compression and arbitrary directional bending moments. Subsequently, The buckling strength of the built-up RBC is studied using the FEM, considering initial geometrical imperfections consistent with first-order flexural buckling and accounting for geometric nonlinearity. It is noted that the bending direction of the built-up RBC may deviate during loading. Besides, the M - N buckling strength curve of the built-up RBC is not as convex as its M - N sectional strength curve. Based on calculations from numerous examples, practical design equations for predicting the buckling strength for the built-up RBC under axial compression and any directional bending moments are introduced. The key findings of this paper contribute to the compression-bending strength design of RBCs, enriching RBC design theory and promoting the widespread application of built-up RBCs in actual engineering projects. [Display omitted] • The M - N strength of RBCs varies with different bending directions and tube numbers. • The M - N sectional strength curve of the built-up RBC is convex. • The built-up RBC's bending direction may deviate during loading. • The M - N buckling strength curve of RBCs is less convex compared to its M - N sectional strength. • The M - N strength of RBCs can be predicted by a quadratic function. [ABSTRACT FROM AUTHOR]

In deep-sea mining operations, the mining riser is the most fragile and technologically demanding segment of the entire system. It is crucial to investigate the dynamic response and fatigue characteristics of mining risers to elucidate their motion patterns and fatigue mechanisms. In this study, we examine the vibration behavior of the deep-sea mining riser using the time-domain finite element method under various sea conditions and estimate the fatigue life of the mining riser based on the Miner-Palmgren damage rule. Results indicate that the significant wave height and peak period of irregular waves significantly influence the dynamic response characteristics and fatigue damage properties of the riser. The axial displacement, rotation angle, bending moment, effective tension, and von Mises stress of the riser are maximized and minimized at the top and bottom, respectively, whereas the lateral displacement shows the opposite trend. In general, the axial displacement exhibits a more complex pattern than the lateral displacement, and the maximum fatigue damage is predominantly concentrated in the middle and upper sections of the riser. • Dynamic behaviors of a deep-sea mining riser under various sea conditions are investigated. • The axial compared with lateral displacements of the riser demonstrate a more intricate pattern of behavior. • The motion trajectory and frequency of the buffer station of the mining riser are ascertained. • The dynamic stress levels and fatigue distribution along the mining riser affected by the irregular waves are given. [ABSTRACT FROM AUTHOR]

• An analytical method for evaluating stability of network arch bridges is derived. • A parametric finite element model is employed to validate the proposed method. • The effects of various design parameters on the stability are explored. • A practical expression for calculating the buckling length factor is developed. Network arch bridges typically feature inclined cables with a net configuration to support the bridge deck, therefore, improving the bridge's stiffness and reducing bending moments along the arch elements. Given their relatively slender cross-sections and large compression stresses, properly evaluating stability safety is crucial to the integrity of network arch bridges. However, because of the unique design of cable configuration, current design specifications mostly do not provide specific methods for such stability assessments. To address this gap, the study proposes a new analytical methodology that elucidates the mechanical relationship between basic design parameters and the stability performance of network arch bridges. A numerical example is conducted using finite element analysis to validate the performance of the proposed method. In addition, the influence of several design parameters on the stability factor and buckling length factor is investigated. This research further proposes a practical expression for the buckling length factor of arch ribs with nonlinear regression analysis. The results exhibit that the proposed method can efficiently and accurately evaluate the buckling stability performance of network arch bridges, and the established practical expression can facilitate designers in easily estimating the critical buckling load during the design process. [ABSTRACT FROM AUTHOR]

The bending mechanical properties of FRP-confined square concrete-filled steel tubes (CFST) reinforced with internal latticed steel angles, including the failure modes, characteristic curves and characteristic mechanical parameters of tested specimens, were investigated through experiments in this paper. The bending mechanisms were also analyzed using an established finite element model, including the analysis of the bending moment borne by each component, the distributions of contact pressure between different components at the mid-span section, and the distributions of the neutral axis under the bending capacity. The key influential parameters, including the tensile strength and thickness of the FRP, were also examined. The results indicate that the FRP has almost no influence on bending stiffness, however, it enhances the yield bending moment and bending capacity to a certain extent. It was also found that the enhancement decreases as the width of steel tube increases, and the influence of FRP is more profound before reaching the peak load. The calculation formulas for the bending capacity were developed using the superposition method and numerical fitting method. Analysis of their accuracy shows that the formulation using the superposition method yields relatively accurate and safe prediction results, with the prediction errors of less than 20 %. • The bending behavior of FRP-confined square CFST reinforced with internal latticed steel angles is investigated through experiment; • A method for characterizing the yield bending moment and bending capacity of the tested specimens is proposed; • The bending mechanisms are analyzed using an established finite element model; • The calculation formulas for the bending capacity are proposed based on the superposition method and numerical fitting method. [ABSTRACT FROM AUTHOR]

The present paper reports results of a numerical investigation of the mechanical behavior of a column base plate connection subjected to an axial compression force and a bending moment. A three-dimensional nonlinear model was developed, using the Cast3M software, and validated against experimental data. In addition, the material nonlinearity as well as contact conditions between the different components of the connection were thoughtfully considered. Based on the validated model, an extensive parametric analysis was conducted to investigate the effect of stiffeners on the forces in the anchor rods. The results clearly indicate that the design approaches that consider only the tensile strength of anchor rods while neglecting the bending moments can lead to a poor estimation of the forces applied to these rods. They also suggest that adding stiffeners provides additional strength and reduces the anchor rod bending in one direction. However, it is important to note that the stiffeners also induce an additional moment in the opposite direction. This could make the anchor rod more susceptible to biaxial bending with tension. Furthermore, this study proposes a new specific shape of stiffener is suggested (c bp5). It was concluded that the proposed shape of stiffeners allows a more uniform distribution of forces and avoids excessive stress concentrations, effectively prevents the biaxial bending in the anchor rod. [Display omitted] • 3D FE model is developed to analyze column base plate connection behavior. • Eurocode 3 overestimated anchor rod strength by neglecting bending moment. • Stiffeners induced biaxial bending on anchor bolts in stiffened connections. • Proposed stiffener shape prevented biaxial bending of anchor rods. • Compression center position influenced by the stiffeners and their shapes. [ABSTRACT FROM AUTHOR]

• Peeling forces in friction stir composite joints are not enough to overcome the binding forces. • Higher stiffness of composite joints resulted in a rigid body rotation due to secondary bending. • The failure mechanism exhibited a brittle behaviour with crack nucleation at the highly strained region. • A relationship between tension, bending and mechanical performance of the joint was obtained. • The development of secondary bending moment acts as main catalyst of the failure mechanism. Friction stir composite joints between an aluminum alloy (AA6082-T6) and reinforced polymer (NorylTM GFN2) were studied regarding their failure characteristics. A comprehensive analysis on the mechanical behaviour of the joints was carried out, assessing the resulting deformed shape, the associated strain field and the observed failure modes using a digital image correlation (DIC) system and comparing with a finite elements method (FEM) model. The numerical model evidenced a good fitness to the experimental results since both the displacements and strain fields were found to be very similar. Both numerical and experimental strain fields in the longitudinal direction exhibited a localized spot of highly strained material, clearly indicating the nucleation site. Since secondary bending occurs in structural elements under tension due to geometrical and stiffness asymmetries, as is the case of overlap composite joints, a bending stress is induced, increasing the local stress compared to the nominal tension stress values. The ultimate tensile stress of the joints was found to range between 60.2 and 70.4 MPa, leading to an average joint efficiency of 82.6 %. The bending factor (k b) at the failure region was found to be 2.0, which means that the bending stress accounts for 2/3 of the total stress, acting as main failure catalyst. [ABSTRACT FROM AUTHOR]

Design codes and recommended practices for geotechnical structures generally include some conservatism to take into account any possible source of uncertainty, with conservative design being generally accepted as safe. Such approaches are not appropriate for offshore wind turbines where both over-and-under designs would result in a sub-optimal performance in terms of structural dynamics. The soil surrounding wind turbines is a main contributor to their stiffness, it is also one of the major sources of uncertainty, which makes an accurate prediction of the structural dynamics a rather difficult task. Monitoring data on wind turbines can provide useful insight into their real in-situ behaviour, allowing designers to examine the validity of design assumptions further. In this paper, the bending moments of five monitored wind turbine monopiles are back analysed, using 3D FEM and 1D beam–column models in which the soil is modelled according to API RP2 GEO recommendations, and the rule-based PISA reaction curves. It is found that despite the efforts to get an as accurate soil response as possible, the monitored bending moments are overestimated by the 3D FEM models at some locations, reflecting a mismatch between the simulated and monitored wind turbine monopiles. The possible effect of scour protection is highlighted. The API-based 1D beam–column models overestimate bending moments, rotations, and displacements and underestimate the wind turbine stiffness, while the PISA models are able to give satisfactory results. • Five site-specific wind turbine models are established. The calibration of advanced soil constitutive models is presented. • Bending moments on five wind turbines are computed using both 3D and 1D models and are compared to the monitoring data. • A clear mismatch is shown between the simulated and the monitored bending moments. • One of the possible reasons for this mismatch is the missing contribution of the scour protection in the simulations. • The API RP2 GEO recommendations overpredict the wind turbine's bending moments, rotations and displacements. [ABSTRACT FROM AUTHOR]

The assessment of the ultimate strength of hull girders constitutes a critical safeguard for the structural integrity and safety of maritime vessels. Beyond the traditional approach of assessing the static ultimate strength of hull girders in a one-time analysis, incorporating an evaluation of the ultimate strength under cyclic bending moments provides a more precise representation of the operational realities faced by vessels in service. This approach accounts for the repetitive loading cycles that ships encounter, thereby offering a more accurate reflection of their structural integrity under actual loading conditions. When subjected to cyclic bending moments of varying amplitudes, the hull girder may either achieve an elastic shakedown condition or experience progressive plastic accumulation. The nonlinear finite element approach is employed to evaluate the ultimate strength of a bulk carrier girder subjected to monotonic/cyclic bending moments. Initial deformations and residual stresses, intrinsic to the welding manufacturing process, are fundamental parameters incorporated into the finite element analysis framework. Building upon this foundation, the study conducts a detailed investigation into the elastic shakedown and plastic accumulation behaviors of the hull girder under various cyclic loading amplitudes. The findings reveals that the bulk carrier hull girder's ultimate strength will be weakened by the welding residual stress, and the extent of this weakening is most noticeable while the hull girder is sagging. At its maximum, the bulk carrier hull girder's ultimate strength is 8.22% less. When considering both of the initial deformation and welding residual stresses, the bulk carrier hull girder exhibits the widest elastic shakedown interval. Under the influence of extreme cyclic bending moments, the bulk carrier hull girder ultimately fractures as a result of the ongoing accumulation of plastic deformation. • The effects of varying levels of welding initial deformation and residual stress on ultimate strength of a bulk carrier hull girder was studied. • The static one-time analysis, the characteristics of elastic shakedown and plastic accumulation under cyclic bending moments was considered. • The fracture failure location of a bulk carrier hull girder was identified under extreme cyclic bending moments. [ABSTRACT FROM AUTHOR]

Concrete-filled tubular flange (CFTF) girders offer superior torsional stiffness compared to traditional I-shaped plate girders, providing enhanced flexural performance. To accurately assess the flexural capacity of CFTF girders, both flexural tests and theoretical analyses were conducted on specimens with and without concrete decks. The experimental data were meticulously analyzed to understand the flexural mechanism, yielding sequence, interface slip, strain distribution, and confinement effect of CFTF girders. Subsequently, finite element models were then utilized to analyze the influence of cross-section dimensions and material optimization on the flexural behavior of CFTF girders. Comparative analyses with I-shaped girders were also performed to highlight the structural advantages of CFTF girders. The proposed flexural calculation formulas were validated against both experimental and analytical results, demonstrating a fitting accuracy between 95 % and 98 % for the yield moment and between 96 % and 98 % for the ultimate moment. The method proposed in this paper provides a reliable and accurate approach for evaluating the flexural capacity of CFTF girders, significantly contributing to the advancement of design and analysis practices in structural engineering. • The flexural tests and theoretical analyses on concrete-filled tubular flange (CFTF) girders were conducted. • The flexural mechanism, interface slip, strain distribution, and the confinement effect are analyzed. • Finite element models are utilized to analyze the influence of cross-section dimensions and material optimization. • A calculation method for the elastic and plastic flexural behavior of CFTF girders is proposed. [ABSTRACT FROM AUTHOR]

• A novel Bayesian inference method was proposed to study deep excavations. • Machine learning with Bayesian Network could predict soil-structure interactions. • The Bayesian Network model could predict ground/wall responses accurately. • The sequential updating process could improve model performance effectively. • The Bayesian framework could be applied to various geological settings reasonably. The demand for deep excavations to construct underground infrastructure has been growing in metropolitan cities due to rapid urban development and limited land space. In this original research, a machine learning technique based on Bayesian Network is proposed to evaluate and predict soil-structure interactions caused by braced excavations. A novel framework based on Bayesian Network incorporating the Bayesian updating process was proposed to study the ground and wall responses induced by deep excavations. Three established case studies collected from the literature were used to implement and showcase the novel concept. Besides, original two-dimensional finite element models were developed to simulate the first two case studies involving deep excavations in clay in order to generate sufficient ground and wall response data for the training and updating phases of the proposed Bayesian model. The third deep excavation case study carried out in a totally different geology (predominantly sand) was then used to assess and verify the robustness of the Bayesian framework in predicting the soil-structure responses. It was eventually established that the developed novel Bayesian Network model managed to successfully predict the wall deflections and bending moments as well as the ground surface settlements of the third case study with good accuracy through using only two case studies as priors via the versatile sequential updating processes, albeit having totally different geological settings. [ABSTRACT FROM AUTHOR]

• Previous studies have lacked comparative research on tunnel failure analysis under oblique-slip fault conditions. • Under the action of fault displacement, tunnels undergo shear and bending failures. • Oblique-slip faults cause more severe damage to tunnels, with more cracks and a wider range of damage. • The displacement mode of active faults is the key factor determining the final failure mode of tunnels. To deeply study and compare the failure characteristics of tunnels under strike-slip and oblique-slip active faults, with the engineering background of a railway tunnel in western China crossing both strike-slip and oblique-slip active faults, two sets of large-scale indoor model tests with a geometric similarity ratio of 1:35 were conducted. The fissure development patterns and strain trends of the tunnel under the movement of both types of faults were monitored and analyzed. Meanwhile, a three-dimensional model of tunnel-rock-fault interaction was established using ABAQUS finite element analysis software to determine the variation patterns of bending moments and shear forces of the tunnel under the movement of both types of faults. The results showed that under the movement of strike-slip and oblique-slip active faults, circumferential bending fissures appear at the right waist of the hanging wall and the left waist of the footwall of the tunnel, and shear oblique fissures appear at the vault of the fault fracture zone. Among them, the number of cracks, the range of tunnel cracking and the degree of crack damage under the condition of the oblique-slip fault are obviously more serious than those under the condition of the strike-slip fault. Under the dislocation of the oblique-slip fault, a large area of broken zone appears in the vault of the fault fracture zone, the lining falls off, the steel bar is exposed, and there is an obvious uplift phenomenon. The right waist of the tunnel's hanging wall mainly experiences tension while the left waist experiences compression, whereas on the hanging wall, the right waist experiences compression while the left waist experiences tension. Under the fault movement, the maximum bending moment value mainly occurs at a distance of 10 m from the fault fracture zone on both the hanging wall and the footwall, with the bending moment values at the fault fracture zone nearly approaching zero. The maximum shear force value occurs at the fault fracture zone. Under the movement of both types of faults, the failure mode of the tunnel is mainly characterized by bending failure of the hanging wall and the footwall and shear failure at the fault fracture zone. Compared to strike-slip active faults, the development of fissures in tunnels under oblique-slip active faults is more severe, with larger bending moment and shear force values, and a wider range of tunnel failure. These results can provide theoretical and technical experience for future similar projects. [ABSTRACT FROM AUTHOR]

Accurate and reliable prediction of the maximum pile bending moment of soil-pile-superstructure system (SPSS) in liquefiable soils is essential for the seismic design. The maximum pile bending moment can be obtained using experiments that consider only a limited number of factors or time-consuming finite element simulations. The study aims to develop a machine learning-based model for predicting the maximum pile bending moment of SPSS in liquefiable soils. To train the model, a large number of three-dimensional finite element models considering soil and structural uncertainties are dynamically analyzed under different ground motions. In addition, six machine learning regression algorithms are used to develop the predictive model: multiple linear regression (MLR), lasso regression (Lasso), decision tree (DT), random forest (RF), gradient boosting decision tree (GBDT), and extreme gradient boosting (XGBoost). The results show that the XGBoost prediction model has the highest prediction accuracy. The ground motion features (especially peak ground velocity, PGV) have the greatest effect than soil- and structure-related features on the maximum pile bending moment of SPSS in liquefiable soils. • A finite element model verified is used to establish the database. • Six ML methods are developed to predict the maximum pile bending moment. • XGBoost is found to perform the best in both accuracy and overfitting. • Ground motion features are more important than soil and structure-related features. [ABSTRACT FROM AUTHOR]

The monopile-wheel composite foundation is an innovative type of offshore wind turbine (OWT) foundation with good bearing capacity. The foundation is subjected to cyclic loads from wind, waves, and tides, so it is necessary to study its horizontal cyclic characteristics. By introducing cyclic degradation constitutive and Rayleigh damping parameters, numerical models are generated and validated by comparing with laboratory experiment results. The laws of horizontal accumulated displacement of the composite foundation are then explored through changes in the cycle amplitude, number, wheel diameter, height of loading point and pre-vertical load. The main findings are that the composite foundation is more likely to reach a stable displacement under constant amplitude cyclic loading compared to that of monopile. Under transient dynamic response (74 % of the horizontal ultimate bearing capacity), accumulated displacement will increase rapidly regardless of the foundation form. The composite foundation has smaller hysteresis loop area and slower accumulation rate of bending moment. The soil pressure weakening of the monopile mainly occurs in front of the pile, while that of the composite foundation mainly occurs under the wheel. After cyclic loading, the V–H envelopes for the composite foundation contract unevenly inwards. Above these, prediction methods for the cumulative displacement, maximum bending moment and V–H envelopes for composite foundation considering cyclic degradation are proposed. • This paper incorporates the cyclic weakening constitutive model of pile-soil interaction and Rayleigh damping. • The study obtains the variation patterns of cumulative displacement, soil pressure around the pile, and bending moment along the pile under different factors. • The V–H envelopes for composite foundation considering cyclic degradation are proposed. • A set of calculation formulas for predicting the accumulated displacement and maximum bending moment along the pile body are proposed. [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 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 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]

• Perform three-point bending tests on high strength grouted tube-sleeve connection. • Investigate load transfer mechanism of grouted tube-sleeve connection. • Perform FE simulation of grouted tube-sleeve connection under lateral load. • Perform moment-shear interaction analysis of grouted tube-sleeve connection. Prefabricated prefinished volumetric construction divides traditional buildings into room-sized modules that are manufactured off-site and assembled on-site. This construction method offers improved construction speed, superior quality control, and reduced environmental impact compared to traditional construction. In high-rise modular construction, the connections between modules may experience significant bending moments due to wind loads or earthquakes. Therefore, the flexural performance of these connections becomes a critical factor that affects the overall stability and robustness of the modular structures. The present study combines the advantages of high strength grout and square hollow section tube sleeves to develop a robust grouted connection for prefabricated structures without compromising assembly efficiency. Firstly, the study conducts three-point bending tests on eight full-scale specimens to investigate the flexural behavior of the connection. The load transfer mechanism, failure modes, moment-curvature relationship, and strain development of the tube-sleeve connection under lateral load are analyzed in detail. The study also quantifies and discusses the effects of different shear key spacing, grout length, inner tube width, and steel fiber content on the strength and stiffness of the connection. In addition, the study utilizes ABAQUS to simulate the bending responses of the connection, including inner tube fracture, grout crack development, and internal complex strain state. The finite element analysis results demonstrate good agreement with the experimental results, with an average ratio of 1.04 between numerical results and test results for flexural resistance, and a standard deviation of 0.04. Furthermore, based on elasto-plastic mechanics and the actual cross-sectional stress distribution of the connection, three analytical models are proposed to predict the flexural resistance of the connection. Finally, the moment-shear interaction relation is verified against the finite element and test results using the elastic-plastic analytical model and the ultimate state shear model. [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]

• 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]

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]

Frequent and intense internal solitary waves (ISWs) and ISW packets pose serious threats to the in-service safety of deep-water risers in the South China Sea. In this study, a deep-water steel catenary riser (SCR) under multiple ISWs was investigated along with the dynamic characteristics of the touchdown zone (TDZ), including displacements, pipe-soil interactions, tensions, and bending moments. A nonlinear numerical model was developed with a novel vector form intrinsic finite element method and improved pipe-soil interaction model that considers soil stiffness degradation and trench formation. The ISW flow velocity field was solved using the mixed Korteweg-de Vries (mKdV) equation and the hydrodynamic forces were determined using Morison's equation. The effects of the ISW amplitudes, riser configurations, seabed stiffnesses, and pipe-soil models on the structural dynamic responses were investigated. The results showed that the ISW packets rapidly increased the penetration depth of the TDZ. Trench formation changes the bending moment response of the TDZ in subsequent ISWs, increasing the response of the front section and decreasing the response of the latter section. However, its effect on the riser tension is limited. The steel lazy wave riser (SLWR) has significantly larger displacement and bending moment responses in the TDZ than SCR because of the different riser tension and configuration. Different pipe-soil interaction models exert a significant influence on the penetration depth and the variation of the bending moment in the TDZ. • Dynamic analysis of SCRs under multiple ISWs considering soil stiffness degradation and trench formation. • A nonlinear numerical model based on Vector form intrinsic finite elements and an improved pipe-soil interaction model. • Quantitative analysis of displacements, pipe-soil interactions, tensions, and bending moments of the touchdown zone. • Impact analysis of ISW amplitudes, seabed stiffnesses, pipe-soil models, and riser configurations. [ABSTRACT FROM AUTHOR]

The current Eurocode 3 rules for buckling of welded I-section members are based on the assumption of hot-rolled flanges. However, flame-cut flanges are widely used in practice and induce significantly different residual stress distributions, affecting the lateral-torsional buckling resistance. Experimental tests and finite element analyses considering residual stress distributions clearly highlighted the beneficial effect of flame-cut flanges compared with hot-rolled flanges on the lateral-torsional buckling resistance of welded I-beams. To complete these preliminary results, a large number of non-linear finite element analyses are performed considering welded beams made of hot-rolled or flame-cut flanges. The beams are composed of steel grades S275 and S355. Numerical results confirm the influence of the flange fabrication process on the buckling behaviour. Eurocode 3 rules are found to be overly conservative for welded beams made of flame-cut flanges. Consequently, proposals are made that are more suitable for estimates of the lateral-torsional buckling resistance of welded beams made of flame-cut flanges. The code rules are also very conservative for welded beams made of hot-rolled flanges with a medium-to-high slenderness. A design method is thus proposed to improve the prediction accuracy of the lateral-torsional buckling resistance of slender welded beams made of hot-rolled flanges. The novel design method from prEurocode 3 provides acceptable values of the buckling resistance for welded beams made of flame-cut flanges but is restricted to uniform doubly symmetric beams. An extension of its scope to mono-symmetric uniform beams as well as tapered beams is thus suggested. An enhanced imperfection factor is proposed, adapted to welded beams made of flame-cut flanges. • Design method to compute the LTB resistance of welded beams with flame-cut flanges using the Eurocode 3 buckling curves. • Design method to compute the LTB resistance of welded beams depending on their geometry, flange fabrication process and bending moment distribution. • Adaptation of the new verification format of prEN 1993–1-1 for lateral-torsional buckling to tapered and/or mono-symmetric beams. [ABSTRACT FROM AUTHOR]

In this study, the buckling behavior of cold-formed beam-column members with sigma and lipped channel sections under the combined effect of axial load and biaxial bending moment (P-M x -M y) was compared. A total of 30 specimens (15 with sigma sections and 15 with lipped channel sections), each measuring 1500 mm in length, were tested under monotonic loading. The performances of the specimens under eccentric loading such as strength and energy absorption capacity were investigated experimentally and numerically. The local, distortional and global buckling modes that determine the bearing capacity of the section and the length of the sigma and lipped channel member where all these buckling modes can be seen were determined. Finite element analysis (FEA) was performed with Abaqus software, and the numerical results were verified against experimental results. Using the validated finite element model, a comprehensive parametric study was carried out by performing 2894 FEA on sigma and lipped channel section members with various cross-sectional dimensions and lengths. Experimental results show that there are significant differences in load bearing capacity, energy absorption capacity and buckling modes of sigma and lipped channel section members. In the FEA/ AISI-S100 code comparison made at the end of the parametric study, it was determined that differences occurred according to the lengths, cross-sectional properties and loading points of the members. It was determined that the error rate was safer when the lips were subjected to tensile stresses than when they were subjected to compressive stresses. Finally, it was determined that the FEA/AISI-S100 error rate decreased as the length of the sigma-section members increased. • The experimental behavior of sigma and lipped channel sections was investigated under the combined actions of axial load and biaxial bending. • The buckling behavior of sections was determined through a comprehensive parametric study. • The experimental and numerical results were discussed. • Results were compared with AISI-S100 standard. [ABSTRACT FROM AUTHOR]

Reported studies on T-head Square-neck One-side Bolts (TSOBs) bolted I-beam to Hollow Section Square Column (HSSC) connections demonstrated the potential of TSOB applications in terms of mechanical properties, installation construction, and cost savings [11–14]. However, existing research was limited to the connection tests and lack a systematic and complete design approach. In this paper, the method for predicting the bending moment capacities and failure modes of the connections was proposed based on the existing test researches. Besides, the Finite Element Model (FEM) of the connections was established and validated by the reported test results. A sensitive analysis on the geometric parameters of the plastic hinge line pattern for calculating the bending moment capacity of the HSSC connecting face was carried out by the validated FEM. The proposed method was compared with the numerical simulation method in terms of the predicted results of the connection structural behavior. The results show that the prediction method proposed in this paper for the connection bending moment capacities and failure modes is accurate and reliable. Moreover, the mixed patterns of Type-H bolt holes and Type-V bolt holes are recommended for the TSOBC design because of the higher bending moment capacity than the unitary bolt hole patterns. • Method for predicting the bending moment capacity of TSOBC was proposed. • Failure mode of TSOBC was predicted based on design information. • Mixed patterns of Type-H and Type-V bolt holes are recommended for TSOBC. [ABSTRACT FROM AUTHOR]

• SHG deflection and local deflection correlate with cumulative underwater explosion damage. • SHGs deform at 10 impact factors; increased explosive mass causes plastic bending deformation. • SHG's residual strength decreases with explosions, primarily due to altered load distribution. The dynamic response and cumulative damage mechanism of simplified hull girders (SHGs) subjected to repeated underwater explosions were investigated in this research. Experimental and numerical investigations were conducted to gain a comprehensive understanding of the relationship between cumulative damage and explosive charge. Three series of experiments were carried out on SHGs, subjecting them to both single and repeated loading (up to five times). The analysis focused on the overall deflection values of the SHG and the local bottom plate deflection values, revealing a linear relationship with the cumulative number of occurrences. A validated finite element simulation model was employed to examine the response of the SHGs under repeated blast loading, utilizing experimental results for validation. An impact factor was established to quantify the magnitude of the explosive force, considering both the power of the explosive and the distance of detonation. The SHGs showed localized deformation at 10 impact factors, but experience pronounced cumulative effects at 14.4 and 20 impact factors. Furthermore, a consistent decline in the residual strength of the SHGs as the number of explosions increased. Following the first underwater explosion, the damaged SHG displayed an ultimate plastic bending moment of 3696.5 N m, reflecting a 16.3 % reduction compared to the unloaded SHGs. This reduction can primarily be attributed to the altered load distribution on the deformed SHGs. These findings contributed to the understanding of the cumulative damage behavior and response of SHGs exposed to repeated underwater explosions, providing valuable insights for the design and structural integrity assessment of naval vessels. [ABSTRACT FROM AUTHOR]

• Proper quantification of joint rotational stiffness (JRS) of a flight intersection joint (FIJ) influences the dynamic characteristics of a flight vehicle. • JRS of an FIJ is often determined experimentally due to the lack of a right predictive model. • An analytical model is proposed to evaluate the JRS of a radial-type FIJ when subjected to an external bending moment. • Numerical analyses and experiments are performed on six different FIJ configurations. • JRS and moment-rotation behavior predicted by the proposed model are correlated with both experimental and numerical analyses. • Further, the effect of joint clearances on the behavior of FIJ is investigated through the present model. Joint rotational stiffness (JRS) of a flight intersection joint (FIJ) and its accurate quantification play an essential role in studying the dynamic modal characteristics of a flight vehicle. This JRS of a FIJ is mostly determined through elaborate experiments due to the non-availability of a reliable predictive model. Therefore, in this paper, an analytical model is proposed to evaluate JRS of a radial type FIJ when subjected to external bending moment. In this model, at first, the tensile and compressive part of the FIJ section is identified by determining the neutral axis position. The respective part's contributing stiffness is then estimated by employing a spring-mass model. Later, the JRS expression is derived from the moment equilibrium condition and expressed as a function of the stiffness of the tensile and compressive part and neutral axis position. Subsequently, finite element analysis (FEA) is conducted with different numbers of screws, followed by detailed experimental investigations. The proposed analytical model is validated with the results from FEA and experiments for different screw configurations of FIJ. Further, the proposed model is extended to account for the effect of joint clearances on the JRS and the corresponding moment-rotation characteristics of the FIJ. [Display omitted] [ABSTRACT FROM AUTHOR]

Round-ended concrete-filled steel tubular (RECFST) columns are gaining increasing usage in bridge structures. During their service life, RECFST columns under eccentric compression may suffer from impact loading. This study conducted test and numerical investigations to assess the performance of RECFST columns under the coupled actions of compression, bending and lateral impact loads. Fourteen columns were fabricated and tested, considering the influences of axial-load ratio, bending moment and impact energy. The damage mode and the time histories of impact force and displacement were accessed and analyzed. The experimental findings revealed that the initial bending moment negatively affected the impact resistance of RECFSTs. In addition, finite element model was established in ABAQUS and calibrated against the test results. The calibrated model was then employed to conduct the failure mechanism analysis and parametric study. Finally, a single-degree-of-freedom (SDOF) analysis was conducted to predict the mid-height deflection of RECFST columns under combined action of compression, bending and lateral impact loads, by incorporating the influences of pre-axial load and initial bending moment. • Drop-hammer impact tests on RECFST columns with varying eccentric compression. • Coupling influence of compression, bending and lateral impact loads. • Prediction of mid-height deflection response using the SDOF method. [ABSTRACT FROM AUTHOR]

[Display omitted] • An innovative corrugated tube-rubber-concrete flexible joint (CTRCFJ) was proposed. • CTRCFJ without adding complexity to the structure and can bend and stretch/compress. • Buckling is reduced by 85.1% compared to the straight steel tube under reverse fault. • CTRCFJ is an effective mitigation method for permanent ground displacement. When water conveyance tunnels cross seismic fault fracture zones, significant deformation may occur, threatening the structural integrity of the tunnel. To resolve this problem, a novel corrugated tube–rubber–concrete flexible joint (CTRCFJ) for improving fault resistance is proposed for the first time. The effectiveness of the CTRCFJ was evaluated using advanced three-dimensional non-linear finite element analysis. The design parameters of the CTRCFJ, including rubber width, corrugated tube interval, and corrugated tube width, were selected based on the distribution of the axial bending moment of the lining structure. An orthogonal test was performed to determine the optimal combination of parameters. The effects of the number of crests, different steel grades, and wall thickness of the corrugated tube on the fracture resistance of the CTRCFJ are investigated. Results show that the CTRCFJ can effectively improve the dislocation resistance performance of composite lining water conveyance tunnels crossing reverse faults by reducing axial compression and bending strain. This study provides a reference for the structural design of composite lining structures that can cross reverse faults. [ABSTRACT FROM AUTHOR]

Based on the zig-zag theoretical model of corrugated steel web beam (CSW), the governing equations in the form of state equations are derived and their analytical solutions are obtained for different loads, variable cross-sections and boundary conditions. Through numerical examples, it is verified that the bending moment, deflection and stresses predicted by the present analytical method have a good agreement with the results of the three-dimensional finite element model. The applicability of the present method for non-prismatic continuous beams with CSWs under different loads is also demonstrated. Meanwhile, it is found that the quasi-plane assumption is still valid in non-prismatic continuous beams with CSWs. Through quantitative analysis of the flexural stresses in the top and bottom slabs, it is confirmed that the zig-zag theory in this study can well reflect the accordion effect of CSWs. Because of the inclined bottom slabs in the non-prismatic beams with CSWs, the Resal effect on the shear stresses in the CSWs and bottom slabs, which is caused by the vertical component of the axial force in the bottom slab, is discussed. A refined shear formulation is developed for more accurate shear stresses in the CSWs and bottom slabs, which provides fundamental theoretical support for the strength prediction of the non-prismatic beam with CSWs. • The zig-zag theory is developed for the non-prismatic beams with CSWs based on the state space method. • The quasi-plane assumption is still valid in non-prismatic continuous beams with CSWs. • The refined shear formula considering Resal effects is derived for the CSW beam with inclined bottom slab. [ABSTRACT FROM AUTHOR]

This paper presented a series of tests to investigate the behaviour of the extended end-plate connection utilizing high strength Q960 steel. A total of 8 specimens were tested, including two under ambient temperature and three under high temperature. The results of the tests indicated that increasing the end-plate thickness from 8 mm to 12 mm significantly enhances the flexural capacity and initial rotational stiffness of the connections but reduces the critical temperature and ultimate rotation. In addition, a higher beam bending moment ratio was found to increase the ultimate rotation of the connections while having minimal impact on the critical temperature. Then, the finite element model of the connections was established to investigate the parametric effect, including column axial pressure ratio, beam bending moment ratio, and end-plate thickness on fire resistance. The numerical analysis indicated that increased column axial pressure ratio and end-plate thickness decreased fire endurance, critical temperature, and ultimate rotation of the connections. On the other hand, increasing the beam-bending moment ratio enhanced the ultimate rotation of the connections. Lastly, a rotation-temperature relationship model was proposed to accurately predict the temperature-rotation curve of high-strength steel Q960 end-plate connections, which was validated with experimental data. • Fire tests on response of high strength Q960 steel connections were carried out. • Numerical models were developed to simulate the behaviour of Q960 teel connections at elevated temperatures. • Parametric studies were performed to investigate the effect of key factors on fire resistance of the connections. • A rotation-temperature relationship model was proposed to predict the fire behaviour of Q960 steel connections. [ABSTRACT FROM AUTHOR]

In this paper, a pinned scaffolding node is proposed and studied with Q355 steel and sorbite stainless steel. Twelve sets of forward and reverse bending tests were designed to study the bi-directional bending performance at temperatures of +20 °C, −20 °C, and − 40 °C. The test results show that as the temperature decreases, the initial rotational stiffness and bearing capacity of the QSJ and the SSSJ both increase. Under the same temperature conditions, the yield bearing capacity and maximum bearing capacity of the SSSJ are greater than those of the QSJ. However, the SSSJ is susceptible to cracking in the weak zone of the C-shaped member subjected to forward bending moments in low-temperature environments, which requires attention in design and use. A finite element model can accurately simulate the bi-directional bending performance of the joint. The results show that increasing the thickness of the U-shaped members by 1–1.5 mm significantly increases the maximum load capacity of the joint. The wall thickness of the pipe has no influence on the bending properties of the joint, but the initial stiffness of the joint can be increased by the depth of wedging, a wall thickness of 6 mm is recommended for C-members. The form of damage to the SSSJ can be improved by increasing the curvature of the upper edge of the C-member at the wedge. The results of this paper can provide methods and references for the engineering design of scaffolding as well as for testing in low-temperature environments. • This paper adopts the separated low temperature loading device, which is convenient for the installation and disassembly. • This study presents a low-temperature loading test device and method. It can provide a test environment of −70 °C ∼ 150 °C. • It's innovative to study the material properties of cable body stainless steel and Q355 at −40 °C, −20 °C and room temperature. • The mechanical properties of the pin-type scaffolding nodes using sorbite stainless steel and Q355 at low temperature were investigated. [ABSTRACT FROM AUTHOR]

This paper investigates experimentally and numerically the behaviour of a balcony-to-slab connection made by an H-profile embedded in the concrete slab. A large-scale test was performed on a specimen of the connection system in order to determine the moment-bearing capacity, the deformation behaviour, the cracking patterns, the distribution of the bending moment along the axis of the embedded steel H-profile as well as the failure mode of the connection system. The test results showed that the failure mode was governed by the concrete shear of the slab. In addition, a 3D finite element model of the experimental test was also carried out and successfully validated against the experimental results. For a practical design of the connection system, a model based on Timoshenko beam on elastic foundation (BEF) was investigated and verified against the results obtained from the validated FE model. The Winkler modulus of the BEF model was determined by considering the local deformation of the concrete based on a strut-and-tie model. The results demonstrate that the BEF model with this value of the Winkler modulus provides a conservative estimation of the shear and bending forces applied to both the embedded H-profile and the concrete cross-sections. This method is a first tentative design basis using linear elastic theory for such a system. • Experimental and numerical investigation on the behaviour of embedded H-profile balcony-to-slab connection • A BEF model is proposed to determine the distribution of shear and bending forces on embedded steel profile and concrete. • Winkler modulus is determined by considering the local deformation of the concrete based on a strut-and-tie model. [ABSTRACT FROM AUTHOR]

With the increasing demand for underground transport infrastructures in urban areas, and associated hazards during the construction of these complex structures characterized with a number of uncertainties, there is an acute need for the development of methods and tools that enable efficient and accurate exploration of the design options to minimize risks induced to the environment. Mechanized tunneling, although it requires high initial investments compared to other tunneling methods, offers a safe and productive way to construct urban tunnels. In the mechanized tunneling process, the lining plays a critical role to provide the support for internal structures, i.e roads, facilities. At the same time, it helps stabilize the ground condition. Together with the jacking system, the lining provides the mean to thrust the tunnel shield (TBM) during excavation. In this work, we address the problem of effective modeling and simulation of the tunnel lining segment. The objective is to demonstrate a systematic and versatile approach to analyze the tunnel lining in different practical scenarios. In terms of modeling, a BIM-based approach is used, which connects the user-friendly software interface used in daily engineering practice with effective simulation tools. The proposed approach utilizes high-order definition of geometry in the design model as well as parametric model definitions to reconstruct the corresponding high-order numerical models. This results in a high-accuracy and computationally low-cost model to analyze a complex structure including an interaction with the soil based on a nonlinear surface springs model. In addition, it allows to analyze the stress and bending moment in the lining segment with high accuracy. The numerical results show that negligible modeling efforts and a reduced computational time up to ten times for given accuracy are achieved. • Isogeometric Analysis is used for tunnel lining deformation and bending moment analysis. • The geometry of the lining is reconstructed from the BIM-based design software. • The time-to-accuracy analysis is superior to traditional finite element analysis. [ABSTRACT FROM AUTHOR]