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The use of permeable piles as an effective drainage method in liquefiable sites has become widely accepted. In this study, the seismic response of both the liquefiable soil and the pile was simulated using FLAC3D software to validate the anti-liquefaction performance of the permeable pile. A group of permeable piles designed according to the China foundation code were numerically modeled with various opening ratios (i.e. area of openings/total surficial area). The numerical results showed that the permeable pile is able to enhance liquefaction resistance by dissipating excess pore water through the drainage holes. The bending moments and axial force of the permeable pile decrease but the ultimate bearing capacity increases in the process of drainage. It is found that the excess pore water pressure ratio (EPWPR) of soil around permeable pile under seismic loading reduces rapidly with increasing opening ratio, but the excess pore water pressure tends to keep nearly a stable level once the opening ratio is beyond a critical value of 0.5%. As a result, the critical value of the opening ratio may be considered as the optimum parameter to design the permeable pile against liquefaction. [ABSTRACT FROM AUTHOR]

The construction of concrete-filled steel tube tied-arch bridges typically employs the "beam first and arch later" methodology. In this approach, tie beams are initially constructed on temporary supports, followed by the erection of the arch ribs. When post-construction loads—such as those from arch-rib supports and concrete-filled steel tubes—are applied, a synergistic force phenomenon occurs between the tie beam and temporary supports, which collectively bear these loads. To investigate the collaborative-force mechanism of the tie beam during construction, we developed a collaborative-force model based on Winkler's double-layer elastic foundation beam theory. We derived equations for displacement, rotation angle, bending moment, and shear force of the tie beam under concentrated loads. Using a 72-m concrete-filled steel tube arch bridge as our research subject, we conducted a comparative analysis utilizing finite element methods. The results indicated that our derived formulas were consistent with those obtained through finite element meta-computing techniques. Under concentrated loading conditions, it was observed that the load increment at the location of the steel pipe column in the Bailey beam was significantly larger than what traditional averaging methods would predict. Conversely, load increments at both mid-span and pier locations of the Bailey beam were relatively small. Furthermore, it was found that variations in concrete strength grade had minimal impact on displacement, bending moment, and bearing ratio for both tie beams and Bailey beams. However, factors such as cross-sectional height of the tie beam and arrangement of sandwich buckle frames exerted considerable influence on both displacement and load-bearing ratios for these structural elements. Additionally, while arrangements within Bailey beams significantly affected displacements in both types of beams (tie beam and Bailey beam), their impact on bending moments and bearing ratios was comparatively less pronounced. [ABSTRACT FROM AUTHOR]

The issues of numerous steel beam components and the tendency for deck cracking under negative bending moment zones have long been challenges faced by traditional composite I-beams with flat steel webs. This study introduces an optimized approach by modifying the structural design and material selection, specifically substituting flat steel webs with corrugated steel webs and using ultra-high-performance concrete for the deck in the negative bending moment zone. Three sets of model tests were conducted to compare and investigate the influence of deck material and web forms on the bending and crack resistance of steel–concrete composite I-beams under a negative bending moment zone. The findings indicate that, compared to a conventional steel–normal concrete composite I-beam, incorporating ultra-high performance concrete into the negative bending zone enhances the cracking load by 98%, resulting in finer and denser cracks, and improves the ultimate bearing capacity by approximately 10%. In comparison to the composite I-beam with flat steel webs, the longitudinal stiffness of the composite I-beam with corrugated steel webs is smaller, which can further enhance the bridge deck's resistance to cracking in the negative bending moment zone, and maximize the steel-strengthening effect of the lower flange of the steel I-beam. Based on the findings of this study, it is recommended to use steel ultra-high-performance concrete composite I-beams with corrugated steel webs due to their superior crack resistance, bending strength, and efficient material utilization. [ABSTRACT FROM AUTHOR]

The article in the Journal of Experimental Botany explores the complex mechanisms involved in the resupination of a lady's slipper orchid, highlighting both active and passive processes at play. The study delves into the biomechanics and developmental timing of the flower, emphasizing the importance of mass, timing, and functional traits in achieving the 180° inversion necessary for pollination. The research sheds light on the intricate interplay of active growth processes and passive structural traits in plant movements, offering insights into bio-inspired technologies and the potential applications of understanding living machines in nature. [Extracted from the article]

In order to study the factors that affect the crack width, cracking mechanism, and development laws of the U‐shaped steel concrete composite (USCC) beam, and to propose a crack width calculation formula suitable for this new type of composite beam, cracking tests were conducted on four simply supported beam specimens. These specimens, which featured different steel beam forms, shear connectors, and longitudinal reinforcement arrangements, were all subjected to negative bending moments. Research has shown that USCC beams and H‐shaped steel concrete composite (HSCC) beams exhibited basically consistent crack width‐load relationships. In the early stage of the experiment, the crack width of the specimen exhibits an approximately linear relationship with the load, while in the late stage of the experiment, the crack width rapidly increases. In addition, the crack width of the USCC beam specimen developed faster than that of the HSCC beam. The experimental phenomenon shows that whether it is an USCC beam or a HSCC beam, the distribution of crack width along the concrete slab width is uneven, and this non‐uniformity is more obvious outside the beam width range. The centralized arrangement of longitudinal bars will exacerbate the non‐uniformity of crack width distribution, and the overall crack width is greater than that of specimens with uniformly arranged longitudinal bars. In addition, the effectiveness of channel shear connectors in controlling crack propagation is better than that of shear studs, and the slip at the interface between the concrete slab and the steel beam of the specimen using shear studs is greater than that of the specimen using channel shear connectors when the load is large. Based on the experimental results and formulas in the “Design Standards for Steel Structures” and the “Design Specifications for Concrete Structures,” a formula for calculating the crack width of USCC beams is proposed, and the coefficients in the current specifications have been corrected. The calculated crack width is in good agreement with the experimental value, which can provide a reference for calculating the crack width of this type of composite beam. [ABSTRACT FROM AUTHOR]

AbstractDamping plays an important role in the design of offshore wind turbine structures. The hysteretic damping of the seabed soil represents the energy dissipation caused by the soil-particle interaction and the nonlinear behavior of the soil under cyclic loading. However, the effect of sand damping on the lateral response of the monopile foundation of an offshore wind turbine is still unclear. In this paper, the effect of soil hysteretic damping on the lateral dynamic response of a monopile foundation in a sandy seabed is investigated using a subplastic soil constitutive model. The constitutive model response at the foundation level is verified by comparing the monotonic and cyclic responses of the monopile with the results of the 1g model test. The results show that when soil hysteretic damping is present in the monopile-soil system, the energy dissipation in the soil reduces the stress accumulation in the soil, resulting in a reduction in the bending moment and horizontal displacement of the monopile, compared with the case without soil hysteretic damping. The results are crucial for optimizing the monolithic design of offshore wind turbine structures. [ABSTRACT FROM AUTHOR]

Recent research has shown that full mobilization of foundation bearing capacity may be beneficial in terms of structural integrity—especially in the case of seismic motions that exceed the design limits. Full mobilization of foundation bearing capacity may serve as seismic isolation because it limits the inertia loading transmitted to the superstructure. Although most research has focused on rocking shallow or embedded foundations, a rocking pile group has attracted much less attention. A potential reason is the probability of structural damage below the ground level (at the piles), which may be difficult to repair or even detect. To shed more light on the problem, the present study investigates the seismic performance of a rocking pile group in clay, aiming to assess its efficiency as a seismic isolation alternative. Employing the finite-element (FE) method, an idealized yet realistic example of a single bridge pier supported by a pile group foundation is analyzed. A carefully calibrated and thoroughly validated kinematic hardening constitutive model is employed for the soil, and the concrete damage plasticity model is applied for the structural members. Using a suite of records as seismic excitation, the response of an intentionally underdesigned rocking pile group is compared with that of a conventionally (capacity) designed system. Similarly to what has been shown for shallow foundations, the comparison reveals that the rocking pile group can be beneficial for the seismic performance of the bridge, reducing the flexural demand on the pier at the expense of increased settlement. Interestingly, the rocking pile group exhibits a genuinely ductile response, such that none of the studied ground motions could lead to full mobilization of the bending moment capacity of the piles. Thus, pile structural damage is avoided. The findings of the present study reveal the advantages of exploiting nonlinear soil–foundation response and indicate that there is a great potential to optimize the contemporary seismic foundation design, which conventionally culminates in massive pile group foundations. The rocking pile group concept may be of particular interest for the retrofit of existing bridges that do not meet the requirements of the current seismic design provision because it can reduce or even completely avoid strengthening the foundation. Ultimately the presented findings call for a shift toward performance-based design, with due consideration of geotechnical failure modes. [ABSTRACT FROM AUTHOR]

In contemporary sheet metal forming processes such as electromagnetic forming, the sheet is subjected to significant out-of-plane compression stress. This study focuses on predicting springback in isotropic sheet metal bending under through-thickness compressive normal stress. An analytical approach was employed to calculate the longitudinal stress distribution across the sheet thickness by utilizing equilibrium equations and applying the flow rule in incremental plasticity based on a power law hardening model. The reverse bending moment was then obtained from these calculations. During unloading, the springback was estimated by assuming linear elastic behavior and neglecting the Bauschinger effect through a superposition method. A case study was conducted on an aluminum alloy sheet with varying compressive stresses and bend curvatures. The comparison of springback angles with finite element modeling revealed that increasing compressive normal stress to 75% and 100% of yield stress resulted in a reduction in springback by 17.4% and 32%, respectively. At 75% yield stress, the numerical model exhibited only a 4.4% difference from the analytical model. Validation of the analytical model included a four-point bending test with varying initial bend curvatures and angles, demonstrating substantial agreement between experimental, numerical, and analytical outcomes. [ABSTRACT FROM AUTHOR]

The prediction of the design parameters of short to medium-span supported bridges in critical locations (such as canal/road crossings) under the action of high-speed trains has been investigated in this article. An artificial neural network (ANN)-based MIMO (multiple-input multiple-output) metamodels is proposed in conjunction with the semi-analytical framework of simply-supported bridges. Three cases, namely single moving load, series of moving loads at equal spacing (HSLM-B), and as per conventional train configuration (HSLM-A) recommended in Eurocode1: EN 1991-2 (2003), are considered. The prime novelty of the article is to develop a dimensionless semi-analytical framework to train and validate a MIMO metamodel implementing ANN for predicting the multiple dynamic responses of bridges under high-speed loads. The dependency of the maximum dynamic responses, that is, displacement, shear force, and bending moment, on the governing parameters (structural and loading) have been elucidated using Pearson's correlation matrix for the three different train configurations. Further, the robustness and efficiency of the best-fitted metamodels have been compared, and a user interface has been developed for ease of implementation. This platform evaluates the responses such as displacement, shear force, bending moment, and structural safety confirming the standards of Eurocode EN 1990:2002 + A1:2005 (E). [ABSTRACT FROM AUTHOR]

This paper presents a streamlined methodology to assess the horizontal response of an embedded pile subjected to combined horizontal dynamic and axial static loads in a nonhomogeneous Pasternak medium. The stiffness matrix equations for the pile elements are formulated using the modified finite beam element method (FBEM), enabling a comprehensive consideration of factors such as the axial second-order effect of the pile (P-Δ effect), soil shear effect, and side friction on the pile. Utilizing the FBEM, the solutions for the pile's lateral displacements and bending moments are derived while accounting for continuous pile–soil system boundary conditions. The accuracy of the FBEM is verified against existing solutions. Subsequently, a thorough parametric analysis is performed to investigate the influences of various properties of the pile, soil, and applied load on the pile's horizontal vibration response. This study underscores the significant role of the shear effect exerted by the surrounding soil in restraining the lateral deformations and internal forces of the pile. In stratified soils, the horizontal performance of the pile is notably impacted by the properties of the surface soil. Reducing the strength of the surface soil results in a substantial increase in the pile's bending moments and lateral displacements. Additionally, an increase in axial load at the pile head significantly affects the bending moments and lateral displacements due to the P-Δ effect. Moreover, the study reveals that the lateral displacements and bending moments of the pile exhibit an increase with the increases of the horizontal harmonic load amplitude H0 and a decrease with the increases in the dimensionless frequency a0 of the applied load. Practical Applications: The research work presented in this paper suggests a simplified approach to investigate the horizontal dynamic performance of an embedded pile subjected to combined horizontal dynamic and axial static loads in a nonhomogeneous Pasternak soil. The results of the parametric analysis indicate that the soil shear effect typically constrains the pile's internal forces and deformations, and ignoring the soil shear effect leads to overestimated lateral deformations and bending moments. This finding highlights the importance of accurately considering the soil shear effect during the design and analysis of a pile. Additionally, the study demonstrates that the Pasternak foundation model effectively simulates the continuity and stratification of the soil medium and provides high computational accuracy. The findings suggest the need to prioritize the effects of the surface soil's nature and high-amplitude horizontal harmonic load environments, as well as low-frequency vibration environments, on the pile's horizontal dynamic response during engineering design calculations. These practical implications of the study are beneficial to engineers and practitioners involved in the design and analysis of a pile in a nonhomogeneous soil environment. [ABSTRACT FROM AUTHOR]

The kinematic interaction between piles under seismic loading has been extensively studied from analytical, experimental, and numerical perspectives. Of note, within numerical modeling, the majority of the existing literature relies on simplified approaches for characterizing the soil–pile interaction, which leads to the requirement for more reliable and comprehensive research. In this paper, using FLAC3D, the seismic response of the soil–pile system was investigated with a set of fully nonlinear three-dimensional (3D) numerical analyses in the time domain. This model simulated the soil strength and stiffness dependency on the stress level and soil nonlinear behavior under cyclic loading. The Mohr–Coulomb (M–C) constitutive model described the soil's mechanical behavior, which was used with additional hysteretic damping to suit the dynamic behavior. In the framework of a parametric study, the effects of loading frequency on the response of a soil–pile system that was subjected to seismic loading were studied. The results showed that the pile response and soil characteristics, as well as the natural frequency mode of the system's dynamic behavior, are strongly affected by the frequency of the seismic loading. Therefore, the bending moment and lateral displacement along the length of a pile increase as the loading frequency approaches the natural frequency of the system. In addition, when the loading frequency reaches a threshold value far from the fundamental frequency of the system, the effect of loading frequency on the soil–pile system response becomes negligible. In addition, the relationship between the pile diameter and maximum pile bending moment at different loading frequencies is affected by the soil properties. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study puts forward a reliability analysis for the bearing performance of piles subjected to the coupled action of chloride corrosion and scouring. A chloride diffusion model was constructed based on the stiffness degradation factor and Fick's law. The Monte Carlo simulation method, along with the consideration of the scouring effect of water flow on the pile foundation, was employed to assess the impact of key factors on the failure probability, considering both the bending moment and lateral displacement damage criteria. The results show that for the same exposure period, the failure probability increases as the bending moment, lateral and vertical loads, and seawater velocity increase; furthermore for the same conditions, the failure probability increases with longer exposure times. According to a particular case study, the mean bending moment, mean lateral and vertical loads, and seawater velocity all have an impact on the lateral displacement failure criterion, making it more sensitive than the bending moment failure criterion. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Architecture & Civil Engineering is the property of Chang'an Daxue Zazhishe and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Elliptical deep beams have a peculiarity: the compression paths (struts) are neither straight nor symmetrical within the same span. The asymmetrical horizontal curvature in one span leads to the formation of asymmetrical torsional moments. The strut-and-tie method (STM), approved by ACI 318-19 and most international codes, does not take into consideration the curvature of the strut and the consequent bending and torsional moments. Therefore, eight deep elliptical specimens were cast and reinforced with variable amounts of web and flexural reinforcement to study the role and importance of each one experimentally and theoretically from the STM point of view. Only the stress paths were cast and reinforced in two other specimens to study the STM in detail and to present alternative specimens to the reference ones with less weight and cost, in addition to providing openings for services. The STM has proven its effectiveness with asymmetrical, horizontally curved deep beams due to its ease and the high safety it provides. STM development has also been presented here by adding the effect of the horizontal curvature. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the moment redistribution in continuous glass fiber reinforced polymer (GFRP)-concrete composite slabs caused by concrete cracking and steel bar yielding in the negative bending moment zone. An experimental bending moment redistribution test was conducted on continuous GFRP-concrete composite slabs, and a calculation method based on the conjugate beam method was proposed. The composite slabs were formed by combining GFRP profiles with a concrete layer and supported on steel beams to create two-span continuous composite slab specimens. Two methods, epoxy resin bonding, and stud connection, were used to connect the composite slabs with the steel beams. The experimental findings showed that the specimen connected with epoxy resin exhibited two moments redistribution phenomena during the loading process: concrete cracking and steel bar yielding at the internal support. In contrast, the composite slab connected with steel beams by studs exhibited only one-moment redistribution phenomenon throughout the loading process. As the concrete at the internal support cracked, the bending moment decreased in the internal support section and increased in the mid-span section. When the steel bars yielded, the bending moment further decreased in the internal support section and increased in the mid-span section. Since GFRP profiles do not experience cracking, there was no significant decrease in the bending moment of the mid-span section. All test specimens experienced compressive failure of concrete at the mid-span section. Calculation results showed good agreement between the calculated and experimental values of bending moments in the mid-span section and internal support section. The proposed model can effectively predict the moment redistribution behavior of continuous GFRP-concrete composite slabs. [ABSTRACT FROM AUTHOR]

The force responses of thin-walled beams under three-point bending can be divided into an elastic–plastic stage and a subsequent buckling stage. An accurate theoretical analysis of the elastic–plastic responses of the beams is the first step to predict their bending responses and help design the beams with better performances. However, the linear small deformation theory is still widely applied in the analysis of beams under three-point bending, leading to significant errors in the elastic–plastic force or bending moment responses of the beams. In this work, the elastic–plastic responses of honeycomb beams are analyzed theoretically with the consideration of the influence of large deformation. A theoretical solution for the bending moment distribution along beams is first derived based on a large deformation bending model. The elastic–plastic responses of the beam are obtained based on the bending moment distribution. Some problems on the large deformation bending theory are then discussed. Finally, the accuracy of the proposed theory is demonstrated. The newly proposed large deformation bending theory predicts the elastic–plastic responses of honeycomb beams with much better accuracy than the small deformation bending theory. The maximum difference in the average bending moment between the theory and simulation drops from 11.2 % to 4.5 %. [ABSTRACT FROM AUTHOR]

The repaired sandwich specimens were fabricated with an upper facesheet, a Nomex core, and a lower facesheet, which were then tested to characterize the failure behavior. At first, the specimens were tested under static loading to the maximum load of 7.75 to 10.17 kN. Then, the maximum fatigue amplitude was selected at 90% of 10.17 kN and gradually reduced until the fatigue cycles greater than 60,000 reached. This was defined as an endurance limit. During static testing, four strain gauges were attached to the repaired section and the strain values were used to analyze the failure behavior. The S1 strain and the applied load were used to estimate the elastic modulus with a mean of 53.74 MPa of the upper facesheet. By analyzing the failure behavior, two critical failure points (A and B) were observed where the maximum bending moment was applied to the repaired section under static and fatigue loadings. The progressive failure analysis under static loading confirmed that the failure occurred due to weft tow splitting, matrix cracking, and warp tow rupturing. A similar analysis was carried out to characterize the fatigue failure behavior. The excessive matrix cracking was observed at critical points A and B before the failure of the facing sheet occurred. At the mesoscale, matrix cracking and intra-tow splitting were observed before facing sheet failure. SEM images show rough and cusp-like failure features due to fatigue loading, which is different from the smoother failure surfaces by static loading. [ABSTRACT FROM AUTHOR]

Wind and wave loads are crucial factors affecting the structural safety of offshore wind turbines. With the trend towards larger wind turbines, the DTU 10 MW wind turbines have become mainstream models. The jacket-type foundation has been widely used due to its high rigidity and suitability for a wide range of water depths. Therefore, a scaled experiment was conducted on a DTU 10 MW jacket-type offshore wind turbine to reveal the dynamic characteristics of the structure. The experimental results showed that the wind loads dominated the mean of the structural response. Under the coupling action of wind and wave, the wind load suppresses the response at the structure's first-order frequency and the wave frequency. Both the wind and wave loads influence the amplitude of the structural response. The response amplitudes of the tower top displacement and foundation bending moment were smaller than the square root of the sum of the squares (SRSS) obtained from the separate wind and wave actions. Under extreme wind speed, the tower top displacement's amplitude is 75 % of the SRSS value, and the amplitude of the foundation bending moment is only 67 % of the SRSS value. • The dynamic characteristics of an offshore wind turbine were experimentally studied. • The structural responses under the coupling action of wind and wave were analysed. • The characteristics of wind, wave, and wake fields were explored. • Based on mass and stiffness matrices, the model's scaling relationship was corrected. [ABSTRACT FROM AUTHOR]

• Collapse tests on modular steel substructures are conducted. • Corner column loss and side column loss are considered. • Comparisons of collapse behavior of the substructures are made. With the increasing adoption of modular construction technology, understanding the modular steel buildings' collapse mechanisms has become crucial. This study presents comparative collapse tests on two modular steel substructures: specimen in corner column loss (S-CCL) and specimen in side column loss (S-SCL). The failure modes, load-bearing capacities, lateral displacements of modules, relative slips of double-layer beams, and deformation mechanisms of the components were compared. The findings reveal significant buckling at the ends of module beams far from the column loss area in both specimens, with minor buckling near the column loss area. No bolt hole fracture is observed in S-CCL, while S-SCL exhibits clear fractures. S-SCL demonstrates approximately double the load-bearing capacity of S-CCL during the elastic stage, and this increases further in the elastoplastic stage due to catenary action, ultimately reaching three times that of S-CCL. Significant lateral displacement occurs only in the double-span beam direction of S-SCL, towards the column loss area, while in other directions, displacement is minor and directed away. Digital image correlation (DIC) measurements indicate that relative slip in double-layer beams is significantly smaller in S-SCL compared to S-CCL. Strain gauge readings show that both module columns remain within the elastic range, but columns in S-SCL continue to deform in the plastic stage due to tensile forces in the connected beams, with beam ends away from the column loss area experiencing negative bending moments. [ABSTRACT FROM AUTHOR]

• Field experiment was conducted based on China's largest sectional JPCCP. • Strain of prestressed steel wires analyzed in three sections over various periods. • JPCCP numerical model with multiple interlayer relationships was developed. • Failure risk of key JPCCP areas under ultimate compression jacking was analyzed. • Inner concrete at the spigot end is more prone to crack and damage. Jacking prestressed concrete cylinder pipe (JPCCP) represents an innovative composite structure for pipe jacking applications. As a critical component of the JPCCP, the stress levels and stress loss of the prestressed steel wires significantly influence the axial bearing capacity during the jacking process, subsequently impacting the long-term safety and durability of the pipeline. This study presents a field loading experiment conducted with China's largest JPCCP project. The results reveal tension and relaxation phenomena in the prestressed wires at various positions throughout the jacking process, and the wires' deformation in the pipe's central section was greater than that at the bell-spigot end. Following the initial jacking, the stress loss of the prestressed wires was the highest, with significantly reduced deformation in subsequent jacking stages, culminating in a maximum stress loss of 29.0 MPa. Utilizing ABAQUS, a numerical model of the JPCCP incorporating multiple interlayer relationships was developed and validated against experiment data. The study further analyzes the effects of steel wire spacing, prestress level, and prestress loss across different concrete layers, and examines the damage to key areas of the pipe under ultimate compression jacking. The findings indicate that the inner concrete at the spigot end is more prone to damage and yielding, predominantly due to cross-sectional mutations, additional bending moments, and tensile stresses. Based on these findings, specific design and construction proposals are proposed. This study provides an in-depth analysis of the impact of prestressed steel wires on the axial bearing capacity of ultra-large section JPCCP, offering valuable insights into its design and construction. [ABSTRACT FROM AUTHOR]

Bridges with high piers and long spans crossing valley sites are often located in near-fault regions. The seismic analysis of these bridges should comprehensively consider both site effects and near-fault effects. This paper develops a comprehensive seismic analysis method for valley-crossing bridges that accounts for near-fault source parameters, propagation paths, valley terrain, and bridge structures. This method fully leverages the advantages of the frequency-wavenumber method for semi-analytically solving the Green's function of a semi-infinite crustal space, and the finite element method for finely simulating the valley terrain and bridge structure. Consequently, it comprehensively considers near-fault effects, terrain effects, soil layer effects, and pile-soil interaction effects. First, the correctness of the proposed method is verified through an analysis example. Subsequently, focusing on the Longtan River Bridge, a valley-crossing bridge, this study examines the impacts of terrain effects, soil layer effects, and pile-soil interaction effects on the seismic response of the bridge. The results show that terrain effects increase the relative displacement of piers while reducing the shear force and bending moment at the bottom of the piers compared to uniform excitation. The influence of the soil layer primarily increases the relative displacement of shorter piers and increases the shear and axial forces at the pier bottoms by 8 %, while decreasing the bending moment by 3 %, compared to the bridge directly situated on bedrock. Furthermore, accounting for pile-soil interaction reduces the seismic response of the bridge. • A hybrid method for seismic analysis from a near-fault source to the bridge. • Global and local parameters of faults based on finite fault source model. • Valley terrain effects amplify the relative displacement of the bridge. • Pile-soil interaction effects reduce the seismic response of the bridge. [ABSTRACT FROM AUTHOR]

An experimental investigation to assess the major-axis flexural behaviour of 10 hot-rolled steel I-section beams, strengthened by the addition of material through wire arc additive manufacturing (WAAM) and tested under either four-point or three-point bending conditions, is presented in this study. The ability of WAAM to pre-camber hot-rolled steel I-section beams, as well as to enhance their bending moment resistance and initial elastic stiffness, has been demonstrated. The geometry of the strengthened beam specimens, including the initial imperfections and pre-camber, were obtained by means of 3D laser scanning. Complementary material testing was conducted to obtain the mechanical properties of both the hot-rolled and WAAM steel under monotonic tensile loading. The experimental results showed that significant pre-cambers of approximately 1/200 of the span of the beam could be achieved with only a 2.6% increase in mass. Moreover, increases of between 11.5% and 33.2% in the ultimate bending moment resistance, and increases of between 8.7% and 35.9% in the initial stiffness, were achieved for increases in mass of between just 2.6% and 12.3%. The presented WAAM-strengthening approach can be employed for the strengthening, repair and retrofitting of steel beams in service, as well as for the fabrication of hybrid steel members with improved flexural behaviour in new structures. [Display omitted] • The concept, design and testing of WAAM-strengthened steel I-section beams are demonstrated. • 3D laser scanning is used to determine the specimen geometries. • Influence of material arrangements on the structural behaviour of the beam specimens is investigated. • Increases of between 11.5% and 33.2% in the ultimate bending moment resistance were achieved for increases in mass of between just 2.6% and 12.3%. [ABSTRACT FROM AUTHOR]

A series of numerical simulations are performed to investigate the dynamic response of J-tube submarine cable around monopile foundation. The variations of maximum curvature, maximum effective tension and motion amplitude with incident angle, significant wave height, current velocity and suspended length are analyzed. The results show that as the significant wave height and current velocity increase, the maximum curvatures at both ends of submarine cable increase. Moreover, the maximum curvature and effective tension significantly increase with the increase of suspended length. Different protection methods for the J-tube submarine cable are investigated to reduce the risks of curvature and bending failures. It is found that the riprap-concrete mattress combined protection can effectively reduce the maximum curvature and motion amplitude of J-tube submarine cable. [ABSTRACT FROM AUTHOR]

• 14 RCFCST specimens tested under combined bending-torsion and compression-bending-torsion loads. • Failure modes, key curves, and strain developments addressed comparatively. • Working mechanism under combined loads discussed carefully. • Design methods of RCFCSTs under complex combined loads. Reinforced concrete-filled thin-walled galvanized corrugated steel tube (RCFCST) is a novel composite member that has application potential in extremely corrosive environments and seismic activity regions. A series of preliminary works have been conducted on its compressive, flexural, shear, and torsional behaviour. However, the combined loading condition is almost inevitable in practice. The correlations between the flexural and torsional behaviour of RCFCSTs are unique due to the special spiral corrugated profile, which is unclear and needs to be addressed. This paper, therefore, presents an experimental investigation of the RCFCST under combined bending-torsion and compression-bending-torsion loads, encompassing the main test variables of torsion-to-bending ratios, torsional directions, and axial compression ratios. The loading set-up and instruments have been introduced in detail. The failure modes, lateral load versus lateral displacement curves, bending moment versus flexural lateral displacement curves, torsion moment versus torsional angle curves, and strain distributions are carefully addressed. The working mechanisms of the RCFCST under monotonic combined loads are discussed, with a particular explanation of the dependent behaviour on the torsion-to-bending ratios and torsional directions. The applicability of the existing design methods for the bearing capacity of RCFCST specimens under combined loads is examined carefully, with specific design suggestions proposed. [ABSTRACT FROM AUTHOR]

Real-time prediction of the mechanical behaviors based on prototype monitoring data is crucial for ensuring the integrity and safety of deep-water jacket platforms. As complex nonlinear systems, these platforms' response exhibit varying temporal trends, dynamic spatial correlations, and load dependencies. This makes accurate prediction of future axial force and bending moment responses a significant challenge. In this paper, a novel deep learning method called Adaptive Spatio-Temporal Load Network (Ada-STLNet) is proposed aiming to address the issue of multi-node axial force and bending moment response prediction of deep-water jacket platform. Our model utilizes an enhanced graph convolution (EGCN) and self-attention mechanism for efficient spatial correlation modeling in multi-node response, LSTM for long sequence temporal feature capture. It integrates spatial and temporal, along with load-aware modules to capture intricate patterns in structural responses. Additionally, a multi-gated coupling mechanism with two independent gating modules is designed to adaptively represent the complex dependencies of structural responses, ensuring model stability and robustness. Extensive experiments conducted on prototype structural monitoring data from a deep-water jacket platform in the South China Sea demonstrate that Ada-STLNet outperforms six traditional models, including HA, SVR, KNN, MLP, LSTM, and GRU, across various prediction steps. The proposed model exhibits superior accuracy, particularly in short-term predictions, achieving up to 62.80% improvement in MAE and 48.11% in RMSE for axial force predictions compared to the second-best model. Ablation studies confirm the effectiveness of each component within Ada-STLNet. This research highlights the potential of Ada-STLNet for reliable and accurate prediction of structural responses, contributing significantly to the field of marine engineering. • Ada-STLNet is developed based on prototype monitoring data, making it highly applicable to real-world engineering. • Ada-STLNet considers the interaction of time, space, and load factors, achieving more accurate and robust predictions. • Spatial-Aware Module integrates the attention and enhanced graph convolution, enriching the model's representation. [ABSTRACT FROM AUTHOR]

• Dynamic response of double-layer rectangular sandwich plate with graded foam cores under blast loading is studied theoretically and numerically. • Analytical model for dynamic response of a double-layer rectangular sandwich plate with graded foam cores is established under blast loading. • Numerical results are in good agreement with the analytical results. • The double-layer rectangular sandwich plates with positive upper and negative lower graded foam cores have better impact resistance. In this paper, dynamic response of a fully clamped double-layer (DL) rectangular sandwich plate with graded foam cores (GFC) under blast loading is studied theoretically and numerically. Based on the yield criterion, an analytical model for dynamic response of a DL rectangular sandwich plate with GFC is established under blast loading. With the use of the inscribing and circumscribing squares of the exact yield locus, the bound of the analytical solution of the dynamic response of a double-layer rectangular sandwich plate with GFC is obtained. By neglecting the effect of bending moments, the membrane mode solution of a DL rectangular sandwich plate with GFC in large deflection is obtained. Finite element analysis (FEA) is performed using ABAQUS/Explicit software. The effects of interlayer factor, average yield strength of graded foams, and gradient properties of graded foams on the dynamic response of DL rectangular sandwich plate with GFC are considered. The analytical predictions are in excellent accord with the numerical ones. It is demonstrated that the proposed analytical model is effective to predict the blast response of a DL rectangular sandwich plate with GFC. [ABSTRACT FROM AUTHOR]

The authors have been developing a new composite foundation composed of soilbags, piles and footing, hereafter called as proposed composite foundation (PCF). PCF is characterized by laying soilbags between the pile heads and the footing. The expected effects of PCF are to reduce the bending moment of the piles and the response acceleration of the pier during earthquakes by cutting off the fixed connection between the piles and the footing. To apply PCF to practical use, it is necessary to confirm the validity of the numerical analysis model of PCF through comparison with the seismic behavior of the entire system of PCF confirmed by the previous in-situ loading tests. In this study, therefore, FEM analysis based on rational elastoplastic model was conducted to reproduce the in-situ loading tests, and the numerical model was verified by comparing the calculation results to the test results. Furthermore, since it is not always easy to conduct sophisticated elastoplastic FEM analysis in practical engineering, a simplified numerical method is proposed, and its applicability was examined by comparing to the test results and the elastoplastic FEM analysis results. The results showed that, although not all the results of the in-situ loading tests could be explained, the proposed simplified method could generally explain the test results and was useful for the practical engineering of the newly proposed PCF. • A new foundation composed of piles and soilbags (PCF) is developed and studied. • Validity of the simulation was confirmed by comparing with the previous loading tests. • The seismic response of foundation with soilbags were successfully reproduced. • A simplified numerical method that is useful for practical engineering was developed. [ABSTRACT FROM AUTHOR]

This paper presents a method to obtain the exact closed-form solution for the static analysis of Timoshenko beams and frames on elastic Winkler foundation, subjected to arbitrary external loads and bending moments. The solution is derived using the Green's Functions Stiffness Method (GFSM), a novel mesh reduction method that combines the strengths of the Stiffness Method (SM) and Green's Functions (GFs). By incorporating the core concepts of the SM, the GFSM exhibits similarities to the Finite Element Method (FEM), including the use of shape functions, stiffness matrices, and fixed-end forces. The application of GFs facilitates the derivation of analytical expressions for displacement and internal force fields for arbitrary external loads and bending moments. Three examples are presented: a single-span beam, a two-span beam, and a one-bay, one-story plane frame on elastic Winkler foundations; which demonstrate applicability and efficacy of the method. • Closed-form solution of Timoshenko frames on elastic Winkler foundation. • Mesh reduction method closely related to the Finite Element Method. • Decomposition of the structural response as a homogeneous and a fixed one. • The fixed response is obtained using Green's functions of fixed elements. • New method closely related with the Transcendental Finite Element Method to obtain closed-form solutions. [ABSTRACT FROM AUTHOR]

As early as the mid-18th century, Euler proposed a critical load formula for compression rods with multiple half-sine wave modes. However, a critical load formula for compression rods constrained by cylinders with multi-helix buckling modes has not yet been proposed. In this paper, a mechanical model of multi-helix buckling of a slender compression constrained by a cylinder is established. Utilizing the dynamic relaxation method, a finite element solution strategy is presented. Its notable advantage lies in its capability to compute stable configurations of multiple helical buckling, effectively addressing challenges such as contact identification and convergence issues during computation. Furthermore, parameter analysis quantifies the influence of length, diameter, and annular gap on the critical load, while also analyzes the shear force, bending moment, and contact force after buckling. This paper presents formulas for the critical load of multi-helix buckling and the length of the multi-helix buckling modes, which is suitable for various length, diameter, and annular space gap conditions, and partially validates these results against finite element analysis. • Stable multi-helix buckling configurations can be obtained by using the dynamic relaxation method. • Quantified the dimensionless lengths of various sections in multi-helix buckling. • Formula for the critical load of multi-helix buckling and the length of the multi-helix buckling modes. [ABSTRACT FROM AUTHOR]

• AK-MCMC was employed for extreme nonlinear vertical bending moment prediction. • Karhunen–Loève expansion was employed to expedite AK-MCMC. • Superior efficiency and accuracy of AK-MCMC compared to FORM was demonstrated. • Methods for mean-out-crossing rate estimation using AK-MCMC were validated. An efficient extreme ship response prediction approach in a given short-term sea state is devised in the paper. The present approach employs an active learning reliability method, named as the active learning Kriging + Markov Chain Monte Carlo (AK-MCMC), to predict the exceedance probability of extreme ship response. Apart from that, the Karhunen-Loève (KL) expansion of stochastic ocean wave is adopted to reduce the number of stochastic variables and to expedite the AK-MCMC computations. Weakly and strongly nonlinear vertical bending moments (VBMs) in a container ship, where the former only accounts for the nonlinearities in the hydrostatic and Froude-Krylov forces, while the latter also accounts for the nonlinearities in the radiation and diffraction forces together with slamming and hydroelastic effects, are studied to demonstrate the efficiency and accuracy of the present approach. The nonlinear strip theory is used for time domain VBM computations. Validation and comparison against the crude Monte Carlo Simulation (MCS) and the First Order Reliability Method (FORM) are made. The present approach demonstrates superior efficiency and accuracy compared to FORM. Moreover, methods for estimating the Mean-out-crossing rate of VBM based on reliability indices derived from the present approach are proposed and are validated against long-time numerical simulations. [ABSTRACT FROM AUTHOR]

• A novel software-in-the-loop system for real-time hybrid model (RTHM) test has been developed. • A design theory for a multi-degree-of-freedom (MDF) loading device has been introduced. • A hardware-in-the-loop system has been proposed to verify the loading performance of the device. • The RTHM test method, utilizing an MDF loading device, effectively reduces the scaling effects. To address the challenges encountered in reproducing turbulent wind loads and scaling conflicts between the turbine and platform in traditional model tests for floating offshore wind turbines. This paper proposes a new real-time hybrid model test strategy with a multi-degree-of-freedom loading device. The design theories of the multi-degree-of-freedom loading device are thoroughly presented. Following this, a software-in-the-loop simulation system was constructed in MATLAB to develop simulation validation on the feasibility and load reproduction capability of the multi-degree-of-freedom loading device. This study addresses the challenges of scale conflicts and turbulent wind load reproduction in traditional model tests, providing a reference for the further development of real-time hybrid model testing techniques for floating offshore wind turbine. The results indicate that the thrust force error in the Fx direction is within 2 %, while the torque and bending moment errors in the Mx, My, and Mz directions are within 8 %. Finally, a hardware-in-the-loop testing system was established to conduct performance tests on the static and dynamic load reproduction capabilities of the multi-degree-of-freedom loading device. The dynamic load variation rate of the multi-degree-of-freedom loading device is 45 N/s, ensuring its capability for dynamic force changes at the scaled-down level. The reproducibility of aerodynamic loads on floating offshore wind turbine under steady wind and turbulent wind conditions by the multi-degree-of-freedom loading device is investigated. The maximum error in reproducing steady wind loads using the multi-degree-of-freedom loading device was found to be 3.7 %. In comparison, the maximum error in reproducing the average values of thrust force and torques in different directions under turbulent wind loads was 9.05 %. Within the 0–5 Hz frequency range, the aerodynamic loads in various directions achieved an energy recurrence rate of at least 99.2 %. It has been demonstrated that the thrust force, torque and bending moment of the floating offshore wind turbine can be effectively reproduced by the device, thereby mitigating the impact of scale effects on floating offshore wind turbine model testing. [ABSTRACT FROM AUTHOR]

• Higher-order springing phenomenon is investigated through experimental and numerical measures, examining harmonics up to 14th order. • A segmented barge model was chosen, with careful observations to capture springing vibrations only. • A direct coupled method between CFD-FEM is developed and used to reproduce the springing phenomenon numerically. • The performance of the numerical model is discussed in comparison with experimental results by dissecting individual harmonics. In this paper, the higher-order springing phenomenon is addressed for a segmented barge ship model through experimental and numerical measures. An efficient in-house two-way coupled numerical solver between Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) is developed and validated against experimental results. The coupling method is based on a domain-separated approach and necessitates the resolution of individual boundary value problems in distinct domains. To ensure convergence within these individual domains, an implicit numerical scheme is employed and further facilitated exchange of variables for coupling. The current approach emphasizes the overall convergence between two solvers, maintaining a strongly coupled setup to comprehensively address fluid-structure interaction phenomena, including added mass and damping effects. A series of tank tests were conducted first to measure the wave-induced sectional loads and motions, during which the springing responses to very high-order harmonics of wave load were observed. By comparing the numerical prediction with the tank test results for rigid body motion and flexible vertical bending moment (VBM), the proposed numerical method demonstrated agreement with experimental results, affirming its validity and robustness. Finally, the springing response up to 14th order harmonics is discussed and investigated. [ABSTRACT FROM AUTHOR]

• The coupled equations of wake oscillator model and dynamic beam model to predict Cross-Flow vortex-induced vibration of deepwater drilling riser with internal flow are solved by central difference method. • The vortex-induced vibration of the riser exhibits multiple modes and a mixed behavior of traveling waves and standing waves. • Parameter sensitivity analysis is carried out on the factors affecting the vortex-induced vibration response and fatigue life of the riser. • The In-Line and Cross-Flow coupled vortex-induced vibration of the riser is analyzed and the calculated fatigue life of the riser is in good agreement with the published experimental data. Coupled equations of the dynamic model and the Van der Pol wake oscillator model are solved by the central finite difference method for the deepwater drilling riser. The vortex-induced vibration (VIV) response and fatigue life of the riser are calculated and the model validation is performed by comparing with the published experimental and simulation results. The effects of the top tension, current flow velocity, flow velocity profile, internal flow velocity as well as the installation of buoyancy modules on the VIV are discussed. Dynamic response and fatigue life of the riser under In-Line (IL) and Cross-Flow (CF) VIV are preliminarily analyzed. The results show that the VIV of the riser has multiple modes and exhibits a mixed behavior of standing waves and traveling waves. With the increase of top tension and flow velocity profile coefficient, the order of the VIV dominant mode and the peak values of the root mean square (RMS) of VIV displacement decrease, and the fatigue life of the riser is extended. With the increase of current flow velocity, the order of the VIV dominant mode increases and the riser fatigue life decreases. The effect of internal flow velocity on the riser VIV is neglectable. The installation of buoyancy modules can improve the riser stress state and extend the fatigue life. Compared with the CF VIV model, the calculated minimum fatigue life of the riser is extended under the IL and CF coupled VIV model due to the decrease of bending moment and the changing position of fatigue weak point. [ABSTRACT FROM AUTHOR]

Dynamic power cable acts as both electricity current channel and information channel between offshore floating wind turbine and substation. Key role as it plays, the mechanical behaviors of dynamic power cable in operation is complicated, owing to the multiple internal loads involved in the cross section and the drastic stress distribution along the cable. In this paper, a multi-task integrated model based on LSTM is proposed to realize both the tension and the bending moment prediction at several fatigue-prone locations. Regarding the parameter combination in high dimension and time-consuming search for the optimum, halving grid search algorithm is applied to conduct hyper-parameters optimization with higher efficiency over wider range. Additionally, due to the motion effects brought by the buoyancy section, the prediction accuracy of the model at locations other than the hang-off point is lower, which is resolved by introducing an subsea sensor at the hog bend to provide additional 3-DOF motion inputs. The improvement brought by the additional inputs at the other points than the hang-off point can be up to 10%. The reliability of the multi-task integrated model is evaluated in a stochastic irregular wave generated by a different random seed as well as wave parameters scaled at different ratios, and a satisfying consistency is observed. Furthermore, the proposed model is applied in extreme sea state, in which the model exhibits comparable performance with its performance in operational sea state. The desirable performance in both the operational and extreme sea states demonstrates the robustness of the model, and implies its potential in more various sea states. • A multi-task integrated LSTM model is proposed to predict mechanical behaviors along dynamic cable. • Halving grid search algorithm is applied in the parameter optimization of the multi-task integrated model. • A subsea motion sensor is introduced to enhance performance of the machine learning model. • A comprehensive review of development status of digital twin approach is conducted. [ABSTRACT FROM AUTHOR]

The issue of ship structural fatigue strength caused by springing is receiving increasing attention from designers. To investigate nonlinear springing more precisely on ultralarge container ships that have large-opening structural characteristics, a new segmented ship model with a U-shaped backbone was designed and fabricated in this paper. The novel U-shaped backbone can simultaneously simulate the vertical, horizontal, and torsional stiffnesses as well as the shear center of a full-scale container ship. Measurements of the vertical and horizontal bending moments of the ship model were achieved by assessing the corresponding bending strains of the U-shaped backbone. Integration of the shear flow method was developed for direct measurements of torsional moments. This method was validated through the calibration of the U-shaped backbone. On the basis of the new segmented ship model, vertical, horizontal, and torsional nonlinear springing tests were conducted successfully for the 20000 TEU container ship in the seakeeping basin of the CSSRC, and their characteristics and mechanisms were investigated. The test results reveal that nonlinear springing is a special case of high-frequency vibration that is induced by the harmonic excitation force. The resonance frequency component of the vertical bending moment of the midship is almost 2.5–4.5 times the corresponding wave frequency component when the ship experiences double-frequency vertical nonlinear springing at high speed under different wave headings. The severity of torsional nonlinear springing is not as pronounced as that of vertical nonlinear springing. • The integration of shear flow method which is applicable for U-shaped backbone was developed to measure the torsional moments. • The characteristics and mechanisms of vertical, horizontal and torsional nonlinear springing were investigated. • The resonance frequency components of torsional moment are almost 0.6–1 times their corresponding wave frequency components when the ship experience double-frequency torsional nonlinear springing. [ABSTRACT FROM AUTHOR]

The dislocation of concrete pipe joints, caused by factors such as uneven settlement and surface loads, can lead to structural deterioration and even failure of the pipeline. Addressing how to repair such pipelines to enhance their disaster resistance and resilience is a critical issue. This study focuses on Bell & Spigot dislocated concrete pipes, conducting a full-scale model box experiment on the bending moment responses of dislocated pipes before and after Cured-In-Place Pipe (CIPP) rehabilitation under various burial depths. Additionally, a 3D finite element model was constructed to analyze the interaction between the dislocated concrete pipes and the surrounding soil, considering burial depth, load position, dislocated forms, flexural modulus of CIPP liner, and the liner thickness. A comparison of finite element (FE) model predictions and experimental measurements was made for CIPP liners at different burial depths, validating the reliability of the simulation results. Building on this, the study explores the influence of various factors on the longitudinal and circumferential bending moment responses of the dislocated concrete pipes before and after CIPP rehabilitation. Key findings indicate that at a burial depth of 0.5 m, the pipe experiences a deformation tendency with tension on the upper side and compression on the lower side. At burial depths of 1.0 m and 1.5 m, the pipe exhibits a deformation tendency with compression on the upper side and tension on the lower side. When the traffic load is positioned directly above the dislocated joint, the peak values of the longitudinal bending moments for the left pipe (P2) and right pipe (P3) adjacent to the dislocated joint increase by approximately 64 % and 137 %, and 74 % and 234 %, respectively, compared to when the traffic load is applied at the spigot and bell. The longitudinal bending moment of the pipe is significantly affected by both burial depth and dislocated forms, while the circumferential bending moment is primarily influenced by burial depth. At a burial depth of 0.5 m, the repair rates of the circumferential bending moments for the spigot and bell are higher than those at a depth of 1.0 m. When the dislocated form is BL, the circumferential bending moment repair rate for the spigot is the highest, approximately 0.52. When the flexural modulus of CIPP increases from 7000 MPa to 9000 MPa, the peak longitudinal bending moments in the midsections of P2 and P3 pipes decrease by about 15 %, while the longitudinal bending moment at the spigot of P2 pipe increases by approximately 22 %. Additionally, when the CIPP liner thickness is increased from 6.0 mm to 18 mm, the peak longitudinal bending moments in the midsections of P2 and P3 pipes decrease by 48 %, and the peak circumferential moments at the spigot and bell decrease by approximately 46 % and 17 %, respectively. [ABSTRACT FROM AUTHOR]

In urban area tunnelling projects, preventing the adverse effects of tunnel construction on nearby structures often involves the use of embedded walls or piles. Designing the key parameters of these embedded structures is challenging due to the complex interaction between the soil and the structure. This paper presents a numerical investigation into the effects of embedded wall bending stiffness and soil-wall interface roughness on tunnel-wall interaction in sandy ground. Three dimensional numerical models were developed to simulate tunnel construction near an embedded wall with varying parameters, with sand behaviour simulated using a hypoplastic constitutive model calibrated by element tests and centrifuge models. The findings reveal that a decrease in interface roughness enhances the wall's effectiveness in reducing tunnelling-induced settlements, while a decrease in wall bending stiffness reduces its performance in mitigating surface settlements and increases the wall bending moment. Based on the results, an improved design chart was developed by introducing correction coefficients for wall depth, taking into account the effects of wall stiffness and interface roughness on the wall's efficiency in reducing tunnelling-induced settlements. This chart aims to assist engineers in quickly determining the preliminary horizontal locations and depths of embedded walls, ensuring both safety and effectiveness in selecting the depth and horizontal position of the embedded wall relative to the tunnel. These findings provide valuable guidance for the practical design and implementation of protective measures in urban excavation projects. [ABSTRACT FROM AUTHOR]

Single shell segmental lining can withstand a maximum water head of about 50 m. If the water pressure exceeds this value, it is necessary to partially reduce groundwater pressure acting behind the tunnel lining.This paper presents a novel TBM tunnel drainage technology that employs adjustable pressure valves to regulate the volume of incoming water. This method not only reduces the impact of tunnel drainage on the surrounding groundwater environment but also effectively decreases the water pressure behind the lining, lowering the risk of structural damage and enhancing the load-bearing capacity of the lining. This represents an integration of prevention and drainage in the engineering concept of groundwater control.The study commenced with field experiments in the Daxiang Mountain Tunnel of the Fuzhou Intercity Railway, focusing on the effects of different drainage hole spacings and pressure valve settings on tunnel water inflow, pressure behind segmental linings, and strain on the linings' inner surfaces. A numerical model was subsequently constructed to compare and validate these field monitoring results, which demonstrated a high level of agreement. Finally, a parametric analysis was conducted, and the results indicate: (1) Although increasing the spacing between drainage holes effectively controls groundwater discharge, the resulting higher water gradient near these holes significantly increases bending moments at the foot of the side wall and invert of the lining, thus elevating the risk of structural disorders in the lining. (2) At segmental linings with drainage holes spaced at 3.6 m, the installation of pressure valves set to 400 kPa reduced the drainage volume from 2.18 m3/(D·m) to 1.56 m3/(D·m) compared to the full drainage scenario. This reduction satisfies the groundwater conservation requirements of the Daxiang Mountain area and significantly lowers the risk of structural damage to the lining caused by high water gradients near the drainage holes. Consequently, the load-bearing capacity of the segmental tunnel structure is effectively utilized. The research outcomes of this paper can offer guidance for the drainage countermeasure design in similar TBM tunnel projects. [ABSTRACT FROM AUTHOR]

In designing reinforced concrete frame structures under seismic and static gravity loads, the ductility is as important as the strength. Plastic analysis, taking advantage from the redistribution of the bending moment, allows the ultimate load to increase, leading to a more efficient use of the material. Regions designed to undergo plastic deformations, need to provide the required ductility, exploiting their post-elastic capacity. The plastic rotation depends on the physical plastic hinge length, which is deeply investigated here. The definitions and the literature equations proposed for its estimation are explained highlighting their use and abuse. Referring to a reinforced concrete beam, partially restrained at both ends and under a concentrated load at the mid-span, a reliable closed-form equation to predict the length of plastification, as impacted by the failure mechanism, is provided. The accuracy of the analytical equation is checked through a comparison with both literature results and existing formulas. The proposed equation well reproduces the influence on the length of plastification of those parameters neglected by current equations, such as the steel hardening behavior and the steel yielding strength, which cannot be ignored for an accurate prediction of the nonlinear capacity of reinforced concrete beams. • An equation for the length of plastification of RC beams is provided. • A partially restrained RC beam under a force at the mid-span is investigated. • The proposed equation is verified through a comparison with literature results. • The influence of parameters affecting the length of plastification is assessed. • The closed-form equation provides results more accurate than existing formulas. [ABSTRACT FROM AUTHOR]

Steel-concrete structures are widely applied in bridge engineering due to their superior mechanical performance and cost-effectiveness. However, normal concrete (NC) decks often suffer cracking problems, adversely affecting their serviceability. Ultra-high performance concrete (UHPC) can be used to partially replace the top of NC decks to enhance their post-cracking behavior because UHPC shows high tensile strength, strain-hardening characteristics in tension, and strong bond strength with NC. To this end, this paper focused on the flexural behavior of steel-NC-UHPC composite beams regarding their failure mode, stiffness, strain development, cracking behavior, crack width, etc. Test results indicated that the test specimens mainly exhibited two types of failure modes: shear failure of the NC layer and local buckling of the compressive flange at the steel girder, which were mainly determined by the reinforcement ratio. Flexural stiffness was controlled by the steel girder, and the reinforcement ratio had a notable effect on the reinforcement strain and crack propagation. Additionally, cracks can be categorized into three types: through cracks, connecting cracks, and separate cracks. These cracks in the UHPC layer and NC layer would affect each other, especially those near the roughening interface. The sectional nonlinear analysis was employed to calculate the strain of reinforcement and the steel girder accurately. Finally, the prediction methods of crack width for the NC layer and UHPC layer were discussed. Formulas in NF P18–710 were verified to be feasible for the prediction of UHPC crack width. The UHPC influence factor was introduced to modify the calculation results of the NC crack width by the Chinese NC code. • The flexural post-cracking behavior, of steel-NC-UHPC composite structures was investigated. • Experimental variables included the reinforcement of general concrete layer and the thickness of the UHPC layer. • Cracks in specimens can be divided into through, connecting, and separate cracks. • The maximum crack width of the entire deck was controlled by the crack on the side surface of the NC layer. • The UHPC influence factor was proposed to consider the effect of the UHPC layer on the NC crack width. [ABSTRACT FROM AUTHOR]

For a composite box girder bridge with cantilever deck slabs, its welded connection between external inclined strut and gusset plate is subject to combined axial force and bending moment. Considering heavy vehicles on the outside lane, the connection is the most unfavorable fatigue detail and of critical concern. Thus, one full-scale and two reduced-scale specimens to model the welded connection with 24 mm thick gusset plate and 20 mm thick strut wall were fabricated and tested, and the evolution of strain and fatigue crack was recorded. The specimens' fatigue lives were compared with existing experimental data and the design fatigue curve in the codes. The results showed that on the higher-loaded side of the connection, the welded detail suffering compressive stress cycles exhibited fatigue cracking, and the FAT45 curve in Eurocode 3 and IIW is generally conservative for fatigue life prediction. Specimens with steel plate thickness less than 10 mm in the literature and reduced-scale specimens in this study have a higher fatigue strength than the full-scale one, and thus, provide an overestimation of the actual connection's fatigue life, which confirmed the necessity of full-scale fatigue testing. Moreover, the residual tensile stress was found to be an important cause of fatigue crack propagation. • Welded connection with 24 mm thick gusset plate and 20 mm thick tube wall was studied. • Fatigue life and crack propagation mechanism under eccentric compression was revealed. • Reduced-scale tests provide an overestimation of the connection's fatigue life. [ABSTRACT FROM AUTHOR]

Design of frame corners in presence of opening moments is a task that has concentrated many research and engineering efforts in the past. It deals with the response of discontinuity regions, where beam theory does not hold valid and the use of equilibrium-based models (such as strut-and-tie models or stress fields) could be a suitable manner to understand the transfer of forces and to lead to consistent reinforcement detailing. However, the assessment of efficiency factors for equilibrium-based models is not straightforward for such details as their response has been observed to be governed in many cases by the tensile resistance of concrete and crack propagation. Furthermore, most efforts so far have been devoted to determining only the resistance of the region as a function of its reinforcement detailing, but limited works have been dedicated to their post-peak response. The post-peak response is nevertheless instrumental for redundant structures, as it governs the level of potential redistributions of internal forces in order to develop the full structural resistance of the system. Such aspect has become even more significant in present days, where the assessment of existing structures with potentially poor nodal detailing has become a need to avoid unnecessary retrofitting or replacement, in an effort to reduce carbon footprint of construction. In this paper, comprehensive research on this topic is presented. It is based on the results of a large database compiled by the authors comprising 126 tests. After filtering of the database, conclusions on the expected response of several details are obtained. Also, a general procedure grounded on an equilibrium-based model is proposed, providing tailored efficiency factors as a function of the mechanical reinforcement ratio and detailing type, but also providing a complete description of the post-peak response. This latter model is based on a kinematically-compatible displacement field for the post-peak phase, allowing to evaluate the opening of the cracks in the nodal region and the associated softening of resistance. • Database with tests on nodal regions of RC frames subjected to opening bending moments consisting on 126 tests. • Failures of nodal regions depend on the detail, mechanical reinforcement ratio and the presence of secondary reinforcement. • In brittle failures, toughness of nodal regions growths with secondary reinforcement; in ductile ones, it is always achieved. • Models for calculation of the resistance and the post-peak response of nodal regions are proposed. [ABSTRACT FROM AUTHOR]

The results presented in this paper are based on a set of centrifuge model tests (50 g) exploring the lateral behavior of single piles in dense Fujian standard sand subjected to different levels of scouring. The hypoplastic model used to capture the stress–strain response of Fujian sand was calibrated and validated via experimental data, which was subsequently integrated into the ABAQUS finite element software package using the UMAT subroutine facility. A comprehensive numerical investigation was conducted to explore the effect of key pile/soil parameters on the pile load–displacement relationship, bending moment distribution, soil resistance distribution, and resulting p-y curves for different scour hole geometries and sand relative densities. The findings demonstrate that scour changed the pile–soil interaction mode and significantly reduced the lateral bearing capacity of the pile. The effect of scour depth on the lateral bearing capacity of the piles is also shown to be more significant than that of other geometries such as the scour slope angle and the scour hole base width. A novel p-y model appropriate for laterally loaded piles vulnerable to scour conditions is developed by the numerical output from the parametric analysis. [ABSTRACT FROM AUTHOR]

Very limited studies have been conducted to investigate the influences of different internal configurations and the size effect on the impact responses of SRCFST members. In this study, numerical simulations are conducted by using ABAQUS. The numerical model of SRCFST members under lateral impact directly incorporates material damage, strain rate effect and steel fracture, and the model is verified against available impact testing data. Following model verification, the impact behaviors of SRCFST members with four commonly used internal configurations of steel sections are compared and discussed. It is found that the damage modes of SRCFST members are largely unaffected by internal configurations. These internal configurations minimally affect energy absorption capacity, with a maximum difference of only 2.04 %. SRCFST specimen with inner steel tube (SRCFST-T1) exhibits the best impact resistance performance among four types by showing its ability to sustain the highest impact force plateau, the least mid-span deformation and the largest bending moment. Moreover, the size effects on dynamic responses are also investigated. The results show that the key indicators (e.g., the peak impact force, plateau impact force, impact duration, maximum mid-span displacement, and energy absorption) closely align with the standard lines, displaying a maximum deviation of less than 10 %. The traditional similarity law is verified in predicting the impact responses using the scaling factor. Finally, an improved single-degree-of-freedom (SDOF) analytical model is formulated for predicting the displacement responses of SRCFST members under drop weight impact, and it gives an accurate prediction of the displacement response. • Impact response of SRCFST members is numerically studied. • The effect of different internal steel section configurations on the impact responses of SRCFST members is revealed. • The size effect on the impact responses of SRCFST members is also investigated. • An improved SDOF analytical model is formulated to predict the responses of SRCFST members under lateral impact. [ABSTRACT FROM AUTHOR]

• General exact closed-form solution for rectangular FG beams are derived. • Application of closed-form solutions does not require reconsideration of load conditions. • Retaining the first few terms of the exact solution also achieves high accuracy. • A novel three-parameter power-law modulus is presented. • Explicit special solutions for four cases with quadratic loads are obtained. This paper derives the exact general elasticity solution for functionally graded rectangular beams subjected to arbitrary normal and tangential loads and with arbitrary end constraints. The general solution consists of bending moments and their integrals and derivatives, along with load-independent function sequences of the longitudinal coordinate. The method for determining function sequences has been established based on the stress function method. General solution formulas for stresses, strains and displacements have been derived and used to solve explicit special solutions for six cases involving concentrated forces, uniformly loads, and quadratically distributed loads with different displacement constraints scenarios. The results obtained are compared with existing exact solutions and those of Euler–Bernoulli and Timoshenko beams, and the errors of the latter two are analysed. [ABSTRACT FROM AUTHOR]