Search

Digital Twins (DT) provide a critical approach to connecting physical structures and corresponding virtual representations through constant observations-to-decision flows, enabling near real-time analysis and assessment of structural health. A critical component of DTs of reinforced concrete structures lies in the definition of prognostic capabilities to predict/infer the system response. This is achieved by devising efficient computational methods for the simulation of the mechanical behavior of the system. This study presents the first step in devising a Multiscale Lattice Discrete Particle Model (M-LDPM) approach to be embedded in a DT framework to allow for forward prediction of damage evolution in the structural system. In the DT framework, a modification of the M-LDPM is proposed to address well-known issues associated with linking the macroscopic mesh configuration and the corresponding representative volume elements, significantly reducing the total computational cost. The effectiveness of the proposed multiscale model is validated by comparing numerical results with the full-order solutions for plain concrete members under 3-point bending, and further investigated by comparison with experimental results on three reinforced concrete beams. [ABSTRACT FROM AUTHOR]

This study employed an enhanced social force model to investigate the impact of bidirectional crowd load on the vertical vibration characteristics of pedestrian bridges. The research incorporated a two-step prejudgment approach to optimize agents' transcendental behavior and introduced a fan-shaped pedestrian perception area for bidirectional crowd movement simulation based on the social force model. The structural vibration response resulting from the evolution of these behaviors was numerically simulated and analyzed. Vertical crowd–structure coupling models were established using a pedestrian moving dynamics model with spring, mass, and damping. A real-time solution method for the structural acceleration response, varying with the moving pedestrian load entering the footbridge deck, was implemented in a numerical environment. Subsequently, the structural response under crowd load, considering multiple behavioral factors, was investigated on an interior steel footbridge. The results demonstrated that bidirectional crowd load generates a higher vertical acceleration response than unidirectional crowd load under the same pedestrian density conditions. The vertical peak acceleration reached its maximum when the number of left- and right-oriented pedestrians was the same, while the peak acceleration of the structure decreased as the difference between the left- and right-oriented pedestrian numbers increased, both in steady-state and transient-state conditions. Bidirectional crowd load poses a higher risk of inducing severe potential vertical resonance of the structure due to synchronization issues, highlighting its significance in the operation of the footbridge. [ABSTRACT FROM AUTHOR]

In this study, numerical models were developed with three different core widths and heights, and numerical analyses were performed to investigate the coupled effects of design parameters on stress and structural weight under gravitational prestress. In addition, the design parameters were optimized using the Response Surface Methodology (RSM), and thus core width and height were determined, providing minimum weight and maximum strength. The numerical findings were validated by comparing them to the statistical-based optimization results. On the other hand, thermal pre-stressed structural analyses were performed to assess the effect of the elasticity modulus and thermal expansion coefficients of the adhesives on the structural responses. The current study demonstrated that core width was more effective than core height on stress and deformation responses, and also that ascending core width had an adverse impact on bending stiffness. Furthermore, the optimum core width and height were determined as 5.0042 and 14.844 mm, respectively, using RSM. The maximum stress and weight responses of the sandwich structure with optimal design parameters were also found as 83.455 kPa and 2.2667 g. It was revealed that impacts of core height become more noticeable with larger core widths, and they should not be considered separately. [ABSTRACT FROM AUTHOR]

Maximum drift ratio (MDR), one of the engineering demand parameters (EDPs), provides fundamental physical value for predicting building damage. Existing machine learning based prediction models mainly rely on numerical simulation data or structural experiments and are not appropriate for prediction of seismic response of real structures. The New Earthquake Data (NDE1.0) is the most comprehensive publicly available dataset of actual structural seismic response observations. Currently the prediction models using NDE1.0 are mainly based on linear or log-linear regression. In this study, based on the NDE1.0 flatfile, we develop a full-feature support vector regression (SVR) based MDR prediction model (SVR-MDR), treating all the available 41 characteristic parameters including structural information as input feature. To improve the model’s efficiency and practical applicability, we also establish a reduced-feature SVR model (RSVR-MDR) by selecting 10 fundamental parameters based on SHapley Additive exPlanations (SHAP) values and the accessibility of features. Our results demonstrate that SVR-MDR model outperform other machine learning models such as kernel ridge regression and decision tree models, and SVR-MDR and RSVR-MDR models outperform conventional loglinear regression and multinomial models, because SVR can map the complex nonlinear function of multiple variables and consider the available information of buildings especially the fundamental frequency. The proposed RSVR-MDR model have promising potential application for post-event seismic damage assessment and post-event emergency response in near real time. [ABSTRACT FROM AUTHOR]

Ship structures may collapse or be severely deformed during a fire. To precisely assess the post-fire structural integrity of ships, in this study, a thermal–mechanical coupling data interface was created, employing a significant eddy simulation algorithm for fire dynamics and a technique to analyze the structural thermal–mechanical coupling reaction. PyroSim was utilized to build a fire scenario, exporting 3D data through the device's own program, and then the ANSYS thermal–mechanical coupling model was employed to study the spatial temperature distribution under fire-induced conditions. Data from the three-dimensional spatial temperature field served as the boundary condition for the determination of the structural temperature burden. Building on this, an analysis was conducted on the structural response of the intricate two-story interior compartment under fire conditions. The results showed that the location of the fire source and the structural distribution of the mechanical equipment inside the cabin had a great influence on the temperature and combustion heat, followed by the ventilation conditions, while the temperature variations in the parallel dual fuel tanks were greatly influenced by the stack effect. By comparing the stress and strain of the two-layer cabin under normal and fire conditions, the damage and mechanisms associated with important positions in the cabin under fire conditions were revealed. [ABSTRACT FROM AUTHOR]

This study uses a time-domain simulation to investigate the effect of aerodynamic damping on a freestanding bridge tower under the joint action of wind and wave loads. The physical model of the bridge tower, which has been tested in laboratory, is numerically reconstituted considering structural nonlinearities obtained from free oscillation tests. Random wind fields are generated using the harmonic superposition method, and the wind flow characteristics, such as mean wind velocity and turbulence intensity, are identified based on the data collected in the laboratory. The wave loads measured at the bottom of the foundation during the experimental model tests are used for the simulation. The dynamic responses of the tower under the joints action of wind and wave loads are successfully simulated. A clear reduction in structural vibration in the wave-controlled region is confirmed by simulation results. Further numerical investigation indicates that an increase in the mean wave velocity produces additional aerodynamic damping in the structural motion system, which significantly dampens the responses of the wave-induced vibration. A simple method for determining the dynamic responses of a bridge tower under the joint action of wind and wave loads, using the data obtained from wind- and wave-only cases, is proposed. [ABSTRACT FROM AUTHOR]

Before reassessing the reliability condition of an offshore jacket platform, it is essential to understand the behaviours that the offshore platform exhibits while it is at sea. This paper presents the response of the offshore jacket platform as its ultimate strength under operating and extreme loads. Malaysian waters' metocean data from a 1-year return period (operating condition) and a 100-year return period (storm condition) are used to predict the four-legs jacket platform's behaviour by evaluating its ultimate strength. Also, two values of minimum design water depth (WD) of 105.9 m and maximum design WD of 115.4 m are chosen. The SACS software, a nonlinear finite element analysis software, is used to calculate the jacket platform's ultimate strength, called pushover analysis. For instance, the pushover analysis result will determine the Reserve Strength Ratio (RSR) as an approach to examining the offshore jacket platform's ultimate strength. Responses to the offshore jacket platform are base shear design, base shear ultimate, rotation, displacement, and moment, which illustrate the behaviour of the offshore jacket platform. There are eight combinations of environmental load directions are applied, to obtain the structure's weakest part. It is found that 45° is the critical direction for maximum design WD, while 90° is the critical direction for minimum design WD. The study's findings indicate that the response of the offshore jacket platform is very important for the safe design and operation of offshore jacket platforms. [ABSTRACT FROM AUTHOR]

This study investigates the impact of soil–structure interaction (SSI) and foundation–soil–foundation interaction (FSFI) on the dynamic behaviour of jacket substructures founded on buckets for offshore wind turbines. A parametric analysis was conducted, focusing on critical load cases for conservative foundation design. Different load configurations were examined: collinear wind and wave (fluid–structure interaction) loads, along with misaligned configurations at 45° and 90°, to assess the impact of different loading directions. The dynamic response was evaluated through key structural parameters, including axial forces, shear forces, bending moments, and stresses on the jacket. Simulations employed the National Renewable Energy Laboratory (NREL) 5MW offshore wind turbine mounted on the OC4 project jacket founded on suction buckets. An additional optimised jacket design was also studied for comparison. An OpenFAST model incorporating SSI and FSFI considering a homogeneous soil profile was employed for the dynamic analysis. The results highlight the significant role of the FSFI on the dynamic behaviour of multi-supported jacket substructure, affecting the natural frequency, acceleration responses, and internal forces. [ABSTRACT FROM AUTHOR]

This study investigates the structural response of in-service tunnels during excavation to provide an accurate evaluation of their service status. Existing theoretical analytical models typically simplify tunnels as continuous long beams, overlooking the reduction in stiffness at segment joints; this fails to reflect real-world conditions. To address this, a discontinuous beam-Pasternak model is established which accounts for joint stiffness weakening, and a theoretical solution for the tunnel’s structural response under excavation unloading is derived using the finite difference method. The model’s rationality and accuracy are validated through comparison against two sets of measurement data and calculation results from existing models. The results show that the displacement curve calculated by the proposed model shows discontinuity in the abrupt change at joints, which is advanced. In certain cases, the parameters of the proposed model can be aligned with those of existing models by using specific values. The influence of the critical parameters of the proposed model on the structural response of the in-service joined tunnel is further analyzed. The findings of this study may offer a practical method for swiftly assessing the structural response characteristics of in-service tunnels during excavation unloading.

Aerodynamic modelling affects the prediction of wind loads if they are derived from wind tunnel tests. Depending on the structural type, difference in applied loads may induce larger or smaller differences in the predicted structural response. For low rise buildings, the roof roughness is a crucial parameter that affects the wind action distribution and magnitude, and its impact on the structural response. This paper discusses the results from wind tunnel pressure measurements on eight geometries of hyperbolic paraboloid roofs, coming from experimental campaigns in three different wind tunnels and using different models. The pressure distributions are then used to evaluate vertical displacements of cable nets tensile structures, which are also compared with each other. Results show that significant differences in the measured pressures are only slightly reduced when vertical displacements are compared, that is inaccuracy of the load is only slightly mitigated when propagated to the response. [ABSTRACT FROM AUTHOR]

There exist so many approaches to extract the time-varying mean (TVM) of nonstationary wind speeds under the nonstationary wind speed model, such as the wavelet transform and empirical model decomposition. These approaches yield different fluctuating wind components, resulting in significant differences in related wind parameters of fluctuating wind speeds (e.g., turbulence intensity, turbulence integral length scale, and wind spectrum). Meanwhile, compared to the stationary wind speed model, the nonstationary wind speed model would lead to different predictions of wind loads and wind-induced responses of a tall building even under the same wind field. This paper first derives the theoretical relationships of statistical parameters between stationary and nonstationary wind speed models, including turbulence intensity, turbulence integral length scale, and turbulence wind spectrum across different models. Wind speed data recorded during Typhoon Mangkhut from September 15 to September 18, 2018, are analyzed to validate the derived relationships. The analysis results confirm that the turbulence intensities and turbulence integral length scales of fluctuating wind speed components under the nonstationary wind speed model are generally smaller than those under the stationary wind speed model. The response analyses of an actual tall building were conducted under Typhoon Mangkhut utilizing various wind speed models. Significant disparities in structural responses are observed between the simulated stationary and nonstationary wind conditions. This result indicates that for typhoon wind fields with noticeable nonstationary properties, the conventional stationary wind speed models may not adequately capture the full dynamic wind effects on tall buildings. Besides, improper extraction of the TVM and subsequent simulation of the nonstationary wind velocity field can lead to substantial discrepancies between the calculated structural responses and the true values. It is thus necessary to establish a nonstationary wind speed model with a proper TVM for the wind-resistant design of tall buildings under typhoons or other nonsynoptic wind environments. [ABSTRACT FROM AUTHOR]

ObjectivesAs wheel loading on the vehicle decks of ro-ro ships may introduce difficulties for structural analysis due to the uncertainty of their quantities, ranges, and positions, it is necessary to study the equivalence and simplification of such loads. MethodsUsing a multi-span beam model as an idealized vehicle deck secondary member, wheel loading is simulated by distributed load and concentrated force respectively, and several structural responses are compared and analyzed. Furthermore, an analysis is made of the change in structural response after multiple wheel loadings have been simultaneously transformed into concentrated force. ResultsThe calculation results suggest that for vehicle decks with an ordinary arrangement, such equivalence and simplification tends to be safer and will not bring significant changes to the structural response. ConclusionsBased on the above conclusions, a reasonable equivalent multi-wheel loading method is provided for engineering application, thus contributing to the design simplification and strength verification of vehicle decks.

• A novel composite parallel machining machine platform based on the structure of parallel robots is proposed. • A dynamic model method of the parallel machine platform based on geometric relationships is proposed. • The dynamic stress modelling approach of the parallel machine platform is given. In order to accurately analyze the structural characteristics of a composite parallel machine tool, a new structural response modelling approach is proposed in this paper. A system dynamics model of the novel composite parallel machining machine platform is established by using the generality of the Jacobian matrix. Based on the mechanical characteristics, a structural stress identification index is presented to reflect the structural response of the composite parallel machining machine platform. Based on the prototype of the parallel robot platform, numerical examples are presented and some performances of the structural response characteristics have been fully discussed. The proposed mathematical model and structural identification index can provide a convenient method for structural optimization of composite parallel machining platforms. [ABSTRACT FROM AUTHOR]

Copyright of Railway Construction Technology is the property of Railway Construction Technology Editorial Office 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.)

To comprehensively understand the explosion risk in underground energy transportation tunnels, this study employed computational fluid dynamics technology and finite element simulation to numerically analyze the potential impact of an accidental explosion for a specific oil and gas pipeline in China and the potential damage risk to nearby buildings. Furthermore, the study investigated the effects of tunnel inner diameter (d = 4.25 m, 6.5 m), tunnel length (L = 4 km, 8 km, 16 km), and soil depth (primarily Lsoil = 20 m, 30 m, 40 m) on explosion dynamics and on structural response characteristics. The findings indicated that as the tunnel length and inner diameter increased, the maximum explosion overpressure gradually rose and the peak arrival time was delayed, especially when d = 4.25 m; with the increase in L, the maximum explosion overpressure rapidly increased from 1.03 MPa to 2.12 MPa. However, when d = 6.5 m, the maximum explosion overpressure increased significantly by 72.8% from 1.25 MPa. Evidently, compared to the change in tunnel inner diameter, tunnel length has a more significant effect on the increase in explosion risk. According to the principle of maximum explosion risk, based on the peak explosion overpressure of 2.16 MPa under various conditions and the TNT equivalent calculation formula, the TNT explosion equivalent of a single section of the tunnel was determined to be 1.52 kg. This theoretical result is further supported by the AUTODYN 15.0 software simulation result of 2.39 MPa (error < 10%). As the soil depth increased, the distance between the building and the explosion source also increased. Consequently, the vibration peak acceleration and velocity gradually decreased, and the peak arrival time was delayed. In comparison to a soil depth of 10 m, the vibration acceleration at soil depths of 20 m and 30 m decreased by 81.3% and 91.7%, respectively. When the soil depth was 10 m, the building was at critical risk of vibration damage. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Shenzhen University Science & Engineering is the property of Editorial Department of Journal of Shenzhen University Science & Engineering 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.)

The folding/unfolding mechanism and collision recovery effect of the beetle's hind wings can provide biomimetic inspiration for the optimization of wing deplorability and the investigation of collision prevention recovery mechanism of new amphibious morphing vehicle. In this study, a method is described to investigate the structural response and mechanical properties of the hind wings of the beetle Protetia brevitarsis under natural conditions. The specially processed test samples were conducted to tensile testing, which facilitates the evaluation of the mechanical properties of specific areas of the hind wing. The micro geometric morphological characteristics of the cross‐section of the specimen after tensile fracture were observed by scanning electron microscopy. The three‐dimensional morphology of the ventral and dorsal sides of the hind wing was characterized using three‐dimensional scanning and reverse modeling methods. The finite element model of the hind wing is developed to investigate the structural deformation and modal response characteristics of its flapping. The uniformly distributed load on the hind wing surface is derived from the lift characteristics obtained from the computational fluid dynamics simulation of flapping wing motion. Research Highlights: Scanning electron microscope is used to observe the cross‐sectional characteristics of the veins and membranes.The material properties of the wing membranes and veins of the hind wings were measured using the tensile testing system.The three‐dimensional morphology of the hind wing was characterized using 3D scanning and reverse modeling methods.The finite element model of the hind wing is developed to investigate the structural deformation and modal response characteristics of its flapping. [ABSTRACT FROM AUTHOR]

Material optimization was one of the challenges for achieving cost-competitive solutions when concrete was introduced in construction, leading to new structural shapes for both civil works and buildings. As concrete construction became dominant, saving material was given less significance, and the selection of the structural typology was mostly influenced by construction or architectural considerations. Simple and non-time-consuming methods for building thus arose as the dominant criteria for design, and this led to the construction of less efficient structures. Currently, the awareness of the environmental footprint in concrete construction has brought the focus again to the topic of structural efficiency and material optimization. In addition, knowledge of material technology is pushing the use of cements and binders with lower environmental impact. Within this framework, Fiber-Reinforced Concrete (FRC) has been identified as a promising evolution of ordinary concrete construction. In this paper, a discussion is presented on the structural properties required for efficient design, focusing on the toughness and deformation capacity of the material. By means of several examples, the benefits and potential application of limit analysis to design at the Ultimate Limit State with FRC are shown. On this basis, the environmental impact of a tailored mix design and structural typology is investigated for the case of slabs in buildings, showing the significant impact that might be expected (potentially reducing CO2-eq emissions to half or even less in slabs when compared to ordinary solutions). [ABSTRACT FROM AUTHOR]

Studies on cable-stayed bridges exposed to blast loads encounter significant challenges arising from the complex interaction among different structural elements. Despite extensive investigation into how buildings respond to explosive loads, there is limited literature on the dynamic response of prestressed concrete bridge decks to blast loads. Single plane cable stayed bridges are very sensitive to cable loss or degradation. This study investigates the response of a prestressed concrete cable-stayed bridge with a single plane under blast loads, utilizing a comprehensive Finite Element (FE) model that incorporates nonlinear effects. The investigation considers blast weights of 230 kg, 680 kg, and 2270 kg of TNT. The analysis reveals that even small explosions cause damage to the deck, with more significant effects observed under higher blast loads, resulting in a damaged region measuring 12 m x 10 m with a 2270 kg TNT weight. Forces in cables near the detonation point increase by 19% during a 2270 kg TNT explosion. Notable changes are observed in pylon moments under different explosion charges. Maximum Bending Moment (BM) values are observed at the base under dead loads, while BMs at mid-height increase under various blast weights, with no discernible change at the base. This study provides valuable insights for designers, emphasizing the importance of incorporating explosion-resistant design principles into cable-stayed bridges.

Studies on cable-stayed bridges exposed to blast loads encounter significant challenges arising from the complex interaction among different structural elements. Despite extensive investigation into how buildings respond to explosive loads, there is limited literature on the dynamic response of prestressed concrete bridge decks to blast loads. Single plane cable stayed bridges are very sensitive to cable loss or degradation. This study investigates the response of a prestressed concrete cable-stayed bridge with a single plane under blast loads, utilizing a comprehensive Finite Element (FE) model that incorporates nonlinear effects. The investigation considers blast weights of 230 kg, 680 kg, and 2270 kg of TNT. The analysis reveals that even small explosions cause damage to the deck, with more significant effects observed under higher blast loads, resulting in a damaged region measuring 12 m x 10 m with a 2270 kg TNT weight. Forces in cables near the detonation point increase by 19% during a 2270 kg TNT explosion. Notable changes are observed in pylon moments under different explosion charges. Maximum Bending Moment (BM) values are observed at the base under dead loads, while BMs at mid-height increase under various blast weights, with no discernible change at the base. This study provides valuable insights for designers, emphasizing the importance of incorporating explosion-resistant design principles into cable-stayed bridges. [ABSTRACT FROM AUTHOR]

The explosion venting experiments of hydrogen‐air premixed gas were carried out in a 1‐m3 cuboid container. The effects of the obstacles parallel to the vent on the structural response of the container during the explosion venting were investigated. The internal overpressure and acceleration of the vessel wall were captured by acceleration and pressure sensors, respectively. The time–frequency distributions of pressure and acceleration were obtained by a Short‐Time Fast Fourier Transform. The effects of obstacles on the dynamic structure response were studied by analyzing the internal overpressure, vibration acceleration, and high‐speed videos. With the increase of obstacles, the maximum overpressure and vessel vibration increased, and the maximum overpressure and maximum vibration acceleration appeared earlier. The vibration signals had two dominant frequencies, 300‐600 Hz and 900‐1200 Hz. The low‐frequency vibration (300–600 Hz) was induced by acoustic oscillation of the internal pressure. The high‐frequency vibration (900–1200 Hz) was a container resonance triggered by the coupling of the flame and the acoustic wave. As VBR increased, the duration of high‐frequency oscillations decreased gradually; the increase of obstacles would weaken the high‐frequency structural response of the container. The results can guide the design of hydrogen explosion protection and mitigation measures. [ABSTRACT FROM AUTHOR]

The arrangement of eccentric bracing has a significant impact on the seismic performance of structures. However, there is no further stipulation on different forms of eccentric bracing in the current Chinese code. At the same time, there is a lack of research on the seismic loss of eccentrically braced structures by Chinese domestic scholars. Therefore, this paper designs different forms of eccentrically braced frames and analyzes them according to the concept of seismic engineering based on performance, which provides some reference for the selection of the eccentrically braced steel frame structure layout in future engineering practice. In this paper, K-shaped, V-shaped, and D-shaped eccentrically braced steel frame structures with 3, 5, and 8 floors are designed, and the finite element analysis model is used for static napping and dynamic time history analysis. The results show that the K-shaped eccentrically braced structure has the best performance in bearing capacity and stiffness and has good seismic and collapse resistance performance. In the FEMA P-58 seismic assessment and vulnerability assessment, it is found that the V-shaped eccentrically braced structure has the smallest loss. However, it is necessary to fully consider the acceleration sensitivity of the non-structural components in the design. In general, the seismic performance of the eccentrically braced structure is improved by the energy dissipation beam yielding to consume energy, which provides a useful reference for structural design. [ABSTRACT FROM AUTHOR]

Fast calculations are widely required in the traditional applications and the emerging digital twin fields. For those considerations, a novel physics-based fast algorithm, namely generalized rotation-superposition method, is proposed for fast calculating linear elastic responses of generalized rotationally axisymmetric structures under arbitrary mechanical loads. This improved method breaks through the limitations of the previous basic rotationsuperposition method in rotational similarity of load and structural axisymmetry, and greatly expands its application scope. In this paper, firstly, the basic theory of the rotation-superposition algorithm is introduced; secondly, the theoretical model of the generalized rotation-superposition method is established; thirdly, the effectiveness and accuracy are verified by using finite element simulations; finally, through a complex case study, the applicability of the generalized rotation-superposition method for complex engineering problems and its advantages in efficiently obtaining massive amounts of data are further illustrated. [ABSTRACT FROM AUTHOR]

The potential collapsible deformation of loess surrounding rock is not conducive to the safety and stability of the tunnel, especially under rainfall conditions, which may induce severe engineering disasters. This paper analyzes the regularity of water infiltration in loess and failure response of tunnel structure under rainfall conditions. Rainfall infiltration in loess strata includes unsaturated infiltration and dominant channel infiltration. The dominant channels enhance soil permeability, leading to the overall downward movement of the wetting front, which provides conditions for the instability and failure of surrounding rock of loess tunnel. Through case statistics, the loess tunnel engineering disasters caused by rainfall are analyzed, elucidating the mechanism of tunnel instability and failure. Finally, according to the characteristics of loess surrounding rock and the response regularity of rainfall to tunnel structure, a series of engineering measures to prevent the deformation of surrounding rock and the specific construction method of loess tunnel structure safety warning system under the condition of rainfall are proposed. [ABSTRACT FROM AUTHOR]

Copyright of Tunnel Construction / Suidao Jianshe (Zhong-Yingwen Ban) is the property of Tunnel Construction Editorial Office 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.)

The present study aims to examine the suitability of two commonly used assumptions that simplify modelling metocean conditions for designing offshore wind turbines in the South China Sea (SCS). The first assumption assumes that joint N-year extreme wind and wave events can be independently estimated and subsequently combined. The second one assumes peak wind and waves can be modelled as occurring simultaneously during a tropical cyclone (TC) event. To better understand the potential TC activity, a set of 10000 years synthetic TC events are generated. The wind field model and the Mike 21 spectral wave model are employed to model the TC-induced hazards. Subsequently, the effect of the assumptions is evaluated by analyzing the peak structural response of both monopile and semisubmersible offshore wind turbines during TC events. The results demonstrate that the examined assumptions are generally accurate. By assessing the implications of these assumptions, valuable insights are obtained, which can inform and improve the modelling of TC-induced hazards in the SCS region. [ABSTRACT FROM AUTHOR]

Asymmetric base-isolated structures subjected to severe torsion may suffer further aggravation of their torsional and translational responses under pulse-type earthquakes. To counteract these detrimental impacts, this study introduces a two-stage optimal design method. The first stage involved the application of the NSGA-II algorithm for determining an optimal isolator arrangement—namely, position and category—with the objective of reducing both the maximum interstory rotation of the superstructure and the isolation layer. In the second stage, the inclusion of viscous dampers served to minimize the excessive translational response triggered by pulse-type earthquakes. The influence of these dampers' positions on the structural response was carefully evaluated. The final application of this optimal design method was demonstrated on an asymmetric base-isolated structure. The results indicated a significant reduction in the translational and torsional responses of the asymmetric base-isolated structure when the two-stage optimal design method was utilized, compared to those of structures designed using traditional conceptual methods. It was found that by installing viscous dampers in the isolation layer along both the x and the y directions—specifically, underneath the mass center of the superstructure (CMS)—the effectiveness of the torsional resistance from the first stage could be effectively maintained. [ABSTRACT FROM AUTHOR]

The environment and structure of the tanks used in aquaculture vessels are remarkably different from those of ordinary ships, and the resulting problem of structural strength is related to breeding safety. In this study, a model of aquaculture tank corrosion was constructed by using the multiphysical field coupling analysis software COMSOL Multiphysics, and wave and sloshing loads were calculated on the basis of potential flow theory and computational fluid dynamics. The influence of different calculation methods for corrosion allowance and sloshing load on the structural responses of aquaculture tanks was analyzed. Through our calculations, we found that the corrosion of aquaculture tanks is different from that of ordinary ships. The corrosion allowance in Rules for the Classification of Sea-going Steel Ships is small, and the influence of the aquaculture environment on corrosion can be ignored. Compared with the method set in the relevant rules, our proposed coupling direct calculation method for the structural response calculation of aquaculture tanks can better combine the specific environment of aquaculture tanks and provide more accurate calculations. [ABSTRACT FROM AUTHOR]

The post-fire assessment of concrete structures is a complex task that requires the integration of multiple measurements from different techniques. The current approach to integrate information from different sources relies mainly on expert judgement, meaning that no explicit consideration is given to the precision of different techniques. This paper presents a Bayesian updating methodology that integrates information from different sources about the maximum temperature the concrete experienced during fire exposure at a certain depth, such as discoloration and rebound hammer measurements, by considering the uncertainties and errors associated with measurements. The data is then used to update the prior information on the uncertain parameters of interest, here the fire load density and opening factor. These updated distributions provide a better estimate of the fire exposure, thermal and damage gradient and the residual condition of the structure. The proof-of-concept and effectiveness of the proposed methodology are demonstrated through a case study. The results show that the proposed methodology is able to effectively incorporate the uncertainties and errors associated with the assessment techniques, producing more reliable estimates of the fire severity. This method has the potential to improve the post-fire assessment process and provide more accurate information for the rehabilitation of concrete structures. [ABSTRACT FROM AUTHOR]

The Bouc--Wen model and subsequent improvements are widely used to simulate the hysteretic behaviour of mechanical elements subjected to load reversals. Within such class of analytical models, an enhanced version is proposed. Elaboration is simple, nevertheless it features: (i) convenient parameters to govern deteriorating stiffness and strength, (ii) asymmetry, and (iii) versatile pinching. The latter capability is necessary for variously pinched loops observed in the experimental tests on reinforcedconcrete elements. Relevant parameters have physical meaning, consistent with phenomenological application of the model at the member scale. Depending on such parameters, the reloading branch can be made initially concave, convex, or almost linear. The proposed model is validated by simulation of cyclic and pseudo-dynamic experimental test results available in the literature. An asymmetric Tbeam, and code-conforming and substandard columns failing under either flexure or shear, are considered. The error on force is normally distributed with mean value less than 4% and standard deviation less than 9% of the experimental strength. The greatest errors on final energy and residual displacement are on the order of 20% with severe damage. The proposed model proves to be effective to simulate the hysteretic response for engineering performance assessment of building and bridge elements. [ABSTRACT FROM AUTHOR]

In this study, the cumulative buckling deformation process is evaluated for a stiffened panel subjected to two different uniaxial cyclic loading conditions, namely compressive loading only and alternating tensile-compressive loading. The impact of the cyclic load on the ultimate strength of the panel is then estimated. It should be noted that the occurrence of permanent deformations could be simulated by finite element analysis using a suitable model capable of correctly capturing the deformation components. The results show that the structure accumulates a deformation that appears to grow almost linearly therefore, consequently, it is realistic to expect that if a large number of load cycles of this magnitude are imposed, the accumulated plastic deformation can be quite severe. Furthermore, it is found that these residual deformations, caused by an entity of the cyclic load lower than the design limit, affect the tensile strength of the stiffened panel. Finally, the effects on the numerical evaluation of the ultimate strength of the structure are shown. [ABSTRACT FROM AUTHOR]

This study presents the adaptive flexible controller frequency optimization method (AFCFOM) as a means of minimizing dynamic loads and structural response in large-scale floating wind turbines, with the goal of enhancing reliability and reducing the frequency of failures. AFCFOM employs a flexible proportional integral (PI) controller frequency, allowing the wind turbine to autonomously adapt to different wind and wave conditions while minimizing structural response. The AFCFOM framework utilizes Latin hypercube sampling for spatial compression, two Bayesian neural networks (BNN) for training and mapping, and particle swarm optimization (PSO) for controller frequency seeking, along with the extreme response surface method for processing the response dataset. OpenFSAT was used for raw data collection and method effect validation. The simulation results demonstrate that the application of AFCFOM effectively reduces the extreme values and variance of the axial displacement at the blade top of the floating offshore wind turbine blade and enhances the robustness of the floating platform. The study provides an overview of the potential effects of adaptive flexible controller frequency on wind turbines, serving as a reference for future wind turbine control optimization research. [ABSTRACT FROM AUTHOR]

The emerging floating vertical axis wind turbines (VAWTs) are regarded as a preferred solution to overcome the challenges faced by the traditional horizontal type in open-sea environments. Numerous numerical models have been advanced for assessing this novel object. However, current fully coupled models predominantly rely on simplified theories, assuming a linear fluid load and a one-dimensional slender beam structure. Despite computational fluid dynamic and finite element (CFD-FEA) coupling being qualified for high precision, this technology remains limited to the fixed VAWT field. To predict the load and structural response accurately and comprehensively, this study aims to extend CFD-FEA technology to floating VAWTs. First, an aero-hydro-moor-elastic fully coupled model is developed, and this model is validated by comparing it with several model experiments. Subsequently, a full-scale floating straight-bladed VAWT is simulated with the geometry and numerical models introduced. Furthermore, load and structural responses in a typical case are analyzed in both time and frequency domains. Finally, the sensitivity analysis of each structure part in floating VAWTs to environmental parameters is conducted and discussed. The discovery highlights the intricate nature of tower structural response, which incorporates 2-node, 3-node, wind frequency, and wave frequency components. Distinct from blades or floating foundations, which are primarily influenced by a single environmental parameter, the tower response is significantly amplified by the combined effects of wind and waves. [ABSTRACT FROM AUTHOR]

Featured Application: (1) A gas explosion simulation combining the chemical reaction mechanism and tunnel structure is described; (2) the shock wave flow fields in tunnels with uneven walls and smooth walls are compared; and (3) the dynamic responses in tunnels with uneven walls and smooth walls are analyzed. A numerical simulation method combining the detailed chemical reaction mechanism of methane deflagration with an approximate real tunnel structure was proposed to confirm whether the unevenness of the tunnel wall during a coal mine gas explosion can be ignored. The approximate real tunnel model and smooth wall tunnel model were developed using 3D modeling methods. The propagation and attenuation processes of shock waves in the two tunnel models, as well as the different dynamic responses of the two tunnel walls, were compared and analyzed. Research results show that the non-uniformity of the tunnel wall decreases the shock wave overpressure and propagation velocity. The peak overpressure reduction value of the shock wave reaches 81.91 kPa, and the shock wave overpressure reaches its peak at an extended maximum time of 7.4 ms. The stress distribution on the approximate real tunnel wall is discontinuous, the propagation speed of stress waves in the bend tunnel is slower, and the duration of high load is relatively low. The displacement of the approximate real tunnel after gas explosion is lower than that of tunnels with smooth walls, and the displacement of most measuring points on the tunnel on the right is only 1/3–1/2 that of the smooth tunnel. [ABSTRACT FROM AUTHOR]

The main issues associated with cement concrete pavements are cracks and broken plates that affect driving comfort and road service life. To ensure sustainable use of the cement concrete, a buffer layer (AC-10) can be introduced between the base and the cement concrete panel. In this study, the interlayer shear test was performed, and the interlayer bonding coefficient under different temperature conditions was determined. The creep test of the buffer layer was also conducted, and the four parameters (E1, E2, η1, and η2) of the Burgers model of the buffer layer were analyzed using regression. According to the parameters obtained from the test, the finite-element model was established, and the moving load was applied to analyze the structural model response under high-, medium-, and low-temperature conditions. The results show that the (1) temperature stress is mainly concentrated in the buffer layer and regions above the structural layer. At low temperatures, the maximum stress at the top of the surface layer is 2.16 MPa, and the vertical strain decreases as a function of depth. (2) Under the combined action of temperature and moving load, the variation ranges of tensile and compressive stresses at the top of the surface layer are the largest; the variation range of the buffer layer and the subsequent structure is small; the maximum warpage deformation of the surface layer is 0.453 mm under high-temperature conditions; and the maximum compression deformation is 0.219 mm under low-temperature conditions. (3) The comprehensive coefficient k c of the fatigue equation was modified, and the comprehensive coefficient k c of the fatigue equation under different vehicle speeds was proposed. This study provides a reference for the sustainable development of cement concrete pavements with buffer layers. [ABSTRACT FROM AUTHOR]

The performance of High-rise Reinforced Concrete (R.C.) design buildings with the shear wall is targeted to provide stability, simplicity of maintenance, and durability of the framed structure. The impacts of lateral loads, axial forces, shear forces, base shear, maximum story drift, and tensile forces are common in high-rise structural systems. The present paper analyses G+20 story R.C. framed buildings for base shear, maximum story displacement and bending moment behaviour of structures with and without shear walls under seismic loading. The building is located in Dehradun, and the load has been considered as per I.S. code 1893:2016. Framed has been analysed using E-tabs to identify maximum base shear for the concern load conditions. The result shows that the frame designed with an appropriate shear wall absorbs more lateral forces, and minimum displacement values are induced and resist maximum moments throughout the height of the building when a structure is appropriately configured with a shear wall. The structure configured with the shear walls has high resistance to absorb earthquake forces compared to structures without shear walls.

ObjectiveAs polar exploration develops, hull structure designs for ice routes are no longer limited to the traditional empirical formula method as more attention is paid to the actual ice load and structural response acting on the structure. The study of structural response calculation under ice load is crucial for the structural design of polar ships. MethodsFirst, the finite element method is used to numerically simulate the ice load cases of a polar navigation ship, such as crushed ice, floating ice and layered ice. Considering the influence of the material strain rate, the dynamic response of the structure under ice load is calculated. Second, based on the structural response equivalence, the static transformation of the dynamic response is completed, and the concept of the dynamic static transformation coefficient is proposed. Finally, the range of the dynamic static conversion coefficient under different ice load cases is obtained.ResultThe results show that the conversion coefficient of the dynamic-static equivalent conversion of the bow structure under different ice load cases is between 1.0 and 1.4.ConclusionThe quasi-static equivalent method of the ice-induced dynamic response of a bow structure is verified as reasonable and feasible.

Wind turbine blade pitch fault is easy to cause unstable ultra-high load, which can lead to structural failure and damage. Firstly, the aerodynamic characteristics of NREL 5 MW wind turbine blades with pitch fault/success were analyzed based on the computational fluid dynamics method. Then, the two-way strong fluid-structure coupling and bending analysis were used to study the state of blades with pitch fault under typical azimuths. The results show that average flapwise torque of the blade with pitch fault under the cut-out wind speed is 13. 8 times that of the blade with successful pitch, and the flow field wake of the former is more obvious. The fluctuation range of blade flapwise torque under two-way strong fluid-structure coupling is significantly wider than that without fluid-structure coupling, and the maximum tip displacement of the blade with pitch fault is 14. 1 times that of the blade with successful pitch. For the four typical azimuth angles of 0°, 60°, 120°, and 180°, the bending moment, tip displacement, bending degree, end effect, wake range and strength of the blade with pitch fault gradually decrease with the increase of the angle. Buckling analysis reveals that the buckling factor increases with the enlargement of azimuth angle, and the first-order buckling factor of 180°azimuth is 20.2% higher than that of 0° azimuth.

Sandwich structures are widely used in many industries such as marine& submarine, aerospace, automobiles and etc due to its lightweight nature, high bending stiffness, high fatigue resistance and ability to absorb energy. However, the investigations into sandwich structures with 3D printed core are limited in number. These structures can create a meta material behavior with the change of geometry which leads to negative poison ratio of core. Hence, in this article, investigations into sandwich structures with 3D printed core under various loading for comparing their structural responses have been reviewed in detail. Different shapes of 3D printed cores have been reviewed and their specifications are discussed. [ABSTRACT FROM AUTHOR]