Accurate acquisition of the lithological composition of a tunnel face is crucial for efficient tunneling and hazard prevention in large-diameter slurry shield tunnels.While widely applied,current data-driven methods o...Accurate acquisition of the lithological composition of a tunnel face is crucial for efficient tunneling and hazard prevention in large-diameter slurry shield tunnels.While widely applied,current data-driven methods often face challenges such as indirect prediction,data sparsity,and data drift,which limit their accuracy and generalizability.This study develops an integrated method that combines a knowledge-driven method to directly compute distribution patterns of lithological components,which are used as a priori knowledge to guide the development of a data-driven method.Coupled Markov chain(CMC)and deep neural networks(DNNs)serve as the knowledge-driven and data-driven components,respectively.Additionally,a dynamic prediction strategy is proposed,where the model is continuously optimized as construction progresses and training samples accumulate,rather than being statically trained on post-construction data,as is common in data-driven methods.Finally,the proposed method is evaluated using a real-world project.The evaluation results show that the integrated method outperforms both individual data-and knowledge-driven methods,demonstrating higher predictive performance,greater stability,and greater robustness to data scarcity and data drift.Furthermore,the dynamic prediction strategy better captures the effects of gradual data accumulation and lithological spatial variability on prediction performance during construction,providing new insights for real-time prediction in practical tunneling applications.展开更多
This study addresses the increasing demand for large-diameter production timber,and considers the time and space variability of half-sib families of Pinus massoniana.Height,diameter at breast height(DBH)and timber vol...This study addresses the increasing demand for large-diameter production timber,and considers the time and space variability of half-sib families of Pinus massoniana.Height,diameter at breast height(DBH)and timber volume of 440 open-pollinated half-sib progeny families were investigated in 14 progeny trials in different years and production regions.An evaluation of the genetic variation of all half-sib families was carried out during the sustainable rapid growth period and individual volumes were characterized as a major index.ANOVA analysis showed that there was considerable variance in the growth traits of most families in different years and on different sites.The variations caused by temporal and spatial changes of the mating system required three selection methods for analysis.The results show that there were differences among the heritabilities of different growth traits by different halfsib progenies.Average heritability values of height,DBH and volume were 0.33,0.34 and 0.36,respectively.Fortyfive superior families were selected in every progeny test,12 were selected in progeny trials by different years and five in different habitat progeny trials.Three superior families(Gui GC553A,Gui GC414A and Gui GC431A)were selected,although in different years and production regions.The genetic gains of timber volume of these selected r families ranged from 1.20 to 47.00%,which could provide a foundation for superior wood property selection and serve as material for seed improvement and extension in surrounding areas.展开更多
A rigorous analytical model is developed for simulating the vibration behaviors of large-diameter openended pipe piles(OEPPs)and surrounding soil undergoing high-strain impact loading.To describe the soil behavior,the...A rigorous analytical model is developed for simulating the vibration behaviors of large-diameter openended pipe piles(OEPPs)and surrounding soil undergoing high-strain impact loading.To describe the soil behavior,the soil along pile shaft is divided into slip and nonslip zones and the base soil is modeled as a fictitious-soil pile(FSP)to account for the wave propagation in the soil.True soil properties are adopted and slippage at the pile-soil interface is considered,allowing realistic representation of largediameter OEPP mechanics.The developed model is validated by comparing with conventional models and finite element method(FEM).It is further used to successfully simulate and interpret the behaviors of a steel OEPP during the offshore field test.It is found that the variation in the vertical vibrations of shaft soil along radial direction is significant for large-diameter OEPPs,and the velocity amplitudes of the internal and external soil attenuate following different patterns.The shaft soil motion may not attenuate with depth due to the soil slippage,while the wave attenuation at base soil indicates an influence depth,with a faster attenuation rate than that in the pile.The findings from the current study should aid in simulating the vibration behaviors of large-diameter OEPP-soil system under high-strain dynamic loading.展开更多
The application of mass timber elements in different structures has gained publicity over the last few years,pri-marily due to climate change adaptation policies and net zero carbon targets.Timber is a renewable const...The application of mass timber elements in different structures has gained publicity over the last few years,pri-marily due to climate change adaptation policies and net zero carbon targets.Timber is a renewable construction material that can outperform other building materials regarding environmental impact.However,when used in seismically active regions,its application has been limited due to the uncertainties on their seismic behaviour in respect with different design standards and limited ductility in conventional connections.Conventional timber connections typically suffer from stiffness and strength degradation under cyclic loads.Their repairability is also low due to permanent damage in the fasteners and the associated crushing in the wood fibres.The use of friction connections can be an efficient way to mitigate these issues.They offer many advantages as they are economical and yet provide a high level of reliable and continuous energy dissipation.In recent years,a new generation of friction connections has been developed that can provide self-centring behaviour(i.e.,the ability of the structure to return to its original position at the end of an earthquake).However,how these connections perform compared to a mass timber system with conventional timber connections is still unknown.Several studies in the literature have suggested that these connections can enhance the performance of mass timber structures.However,the seismic performance of such systems specifically in terms of base shear,response drifts and response accelerations-has not been thoroughly investigated.This paper examines various design aspects of conventional friction connections and self-centring friction connections,providing insights into their differences concerning key seismic performance indicators.It compares the seismic performance of mass timber buildings equipped with both solutions,highlighting their advantages and limitations and drawing conclusions based on the results.The key findings are that friction connections can provides a superior seismic performance for timber structures.However,that may need to be combined with a parallel system avoid residual displacements.展开更多
Platform-style construction is a widely recognized and well-established approach among engineers and developers for multi-story mass timber buildings.This construction method offers many advantages,such as rapid assem...Platform-style construction is a widely recognized and well-established approach among engineers and developers for multi-story mass timber buildings.This construction method offers many advantages,such as rapid assembly,an excellent strength-to-weight ratio,and appealing aesthetic features.In a platform-type construction,each story is constructed by placing the floor panels on top of the load-bearing wall,creating a platform for the level above.Although this method offers numerous advantages,recent research findings have revealed that cross-laminated(CLT)platform buildings with conventional connections,such as wall-to-floor hold-down brackets and shear connectors with nails and screws,are prone to experience a high degree of damage under design-level earthquakes.Consequently,conventional connections in platform-type construction are vulnerable to more damage under aftershocks and do not meet the damage avoidance requirements of seismic design.This paper introduces an innovative floor-to-wall connection for a platform-type low-rise mass timber building that mitigates the limitations of conventional connections.The effectiveness of the proposed connection has been investigated,and the seismic performance of the system,which incorporates the proposed connection,has been outlined in this paper.A numerical model with an innovative inter-story isolation system is developed in ETABS,and the seismic performance of the isolated structure was evaluated using Response Spectrum Analysis(RSA)and Nonlinear Time History Analysis(NLTHA).This study revealed that inter-story isolation systems significantly reduced the seismic demands on the mass timber components,demonstrating the system’s ability to dissipate seismic energy.Additionally,the system displayed effective energy dissipation while exhibiting self-centering behaviour.展开更多
Tube thinning control without wrinkling occurring is a key problem urgently to be solved for improving the forming qualities in numerical control （NC） bending processes of large-diameter Al-alloy thin-walled tubes ...Tube thinning control without wrinkling occurring is a key problem urgently to be solved for improving the forming qualities in numerical control （NC） bending processes of large-diameter Al-alloy thin-walled tubes （AATTs）. It may be a way solving this problem to exert axial compression loads （ACL） on the tube end in the bending. Thus, this article establishes a three-dimensional （3D） elastic-plastic explicit finite element （FE） model for the bending under ACL and has its reliability verified. Through a multi-index orthogonal experiment design, a combination of process parameters, each expressed by a proper range, for this FE model is derived to overcome the compression instability on tube ends. By combining the FE model with a wrinkling energy prediction model, an in-depth study is conducted on the forming characteristics of large-diameter AATTs with small bending radii and it can be concluded that （1） The larger the tube diameters and the smaller the bending radii, the larger the induced tangent tension stress zones on tube intrados, by which the tube maximum tangent compression stress zones will be partitioned in the bending processes; thus, the smaller the ACL roles in decreasing thinning degrees and the larger the compression instability possibilities on tube ends. （2） The tube wrinkling possibilities under ACL are larger than without ACL acting in the earlier forming periods, and smaller in the later ones. （3） For the tubes with a size factor less than 80, the ACL roles in decreasing thinning degrees are stronger than in increasing wrinkling possibilities.展开更多
The existing researches of the magnetic liquid rotation seal have been mainly oriented to the seal at normal temperature and the seal with the smaller shaft diameter less than 100 mm. However, the large-diameter magne...The existing researches of the magnetic liquid rotation seal have been mainly oriented to the seal at normal temperature and the seal with the smaller shaft diameter less than 100 mm. However, the large-diameter magnetic liquid rotation seal at low temperature has not been reported both in theory and in application up to now. A key factor restricting the application of the large-diameter magnetic liquid rotation seal at low temperature is the high breakaway torque. In this paper, the factors that influence the breakaway torque including the number of seal stages, the injected quantity of magnetic liquid and the standing time at normal temperature are studied. Two kinds of magnetic liquid with variable content of large particles are prepared first, and a seal feedthrough with 140 mm shaft diameter is used in the experiments. All experiments are carried out in a low temperature chamber with a temperature range from 200℃ to -100℃. Different numbers of seal stages are tested under the same condition to study the relation between the breakaway torque and the number of seal stages. Variable quantity of magnetic liquid is injected in the seal gap to get the relation curve of the breakaway torque and the injecting quantity of magnetic liquid. In the experiment for studying the relation between the breakaway torque and the standing time at the normal temperature, the seal feedtrough is laid at normal temperature for different period of time before it is put in the low temperature chamber. The experimental results show that the breakaway torque is proportional to the number of seal stages, the injected quantity of magnetic liquid and the standing time at the normal temperature. Meanwhile, the experimental results are analyzed and the torque formula of magnetic liquid rotation seal at low temperature is deduced from the Navier-Stokes equation on the base of the model of magnetic liquid rotation seal. The presented research can make wider application of the magnetic liquid seal in general. And the large-diameter magnetic liquid rotation seal at low temperature designed by using present research results are to be used in some special fields, such as the military field, etc.展开更多
The large-diameter cylinder structure, which is made of large successive bottomless cylinders placed on foundation bed or partly driven into soil, is a recently developed retaining structure in China. It can be used i...The large-diameter cylinder structure, which is made of large successive bottomless cylinders placed on foundation bed or partly driven into soil, is a recently developed retaining structure in China. It can be used in port, coastal and offshore works. The method for stability analysis of the large-diameter cylinder structure, especially for stability analysis of the embedded large-diameter cylinder structure, is an important issue. In this paper, an idea is presented that is, embedded large-diameter cylinder quays can be divided into two types, i.e. the gravity wall type and the cylinder pile wall type. A method for stability analysis of the large-diameter cylinder quay of the cylinder pile wall type is developed and a method for stability analysis of the large-diameter cylinder quay of the gravity wall type is also proposed. The effect of significant parameters on the stability of the large-diameter cylinder quay of the cylinder pile wall type is investigated through numerical calculation.展开更多
Considering the viscous damping of the soil and soil-pile vertical coupled vibration,a computational model of large-diameter pipe pile in layered soil was established.The analytical solution in frequency domain was de...Considering the viscous damping of the soil and soil-pile vertical coupled vibration,a computational model of large-diameter pipe pile in layered soil was established.The analytical solution in frequency domain was derived by Laplace transformation method.The responses in time domain were obtained by inverse Fourier transformation.The results of the analytical solution proposed agree well with the solutions in homogenous soil.The effects of the shear modulus and damping coefficients of the soil at both outer and inner sides of the pipe pile were researched.The results indicate that the shear modulus of the outer soil has more influence on velocity admittance than the inner soil.The smaller the shear modulus,the larger the amplitude of velocity admittance.The velocity admittance weakened by the damping of the outer soil is more obvious than that weakened by the damping of the inner soil.The displacements of the piles with the same damping coefficients of the outer soil have less difference.Moreover,the effects of the distribution of soil layers are analyzed.The results indicate that the effect of the upper soil layer on dynamic response of the pipe pile is more obvious than that of the bottom soil layer.A larger damping coefficient of the upper layer results in a smaller velocity admittance.The dynamic response of the pipe pile in layered soil is close to that of the pipe pile in homogenous soil when the properties of the upper soil layer are the same.展开更多
A method of coupled BEM-FEM analysis for the elastic spatial structure system is presented. It can be applied to the calculation of the stress and deformation of the large-diamater cylinder structure system and it is ...A method of coupled BEM-FEM analysis for the elastic spatial structure system is presented. It can be applied to the calculation of the stress and deformation of the large-diamater cylinder structure system and it is suitable for symmetric or non-symmetric structures under the distributed or concentrated load. Numerical examples show that the proposed method and computer program BEFEM are quite efficient in the analysis of the large-diameter cylinder structure problems in ocean engineering.展开更多
This paper aims to present a theoretical method to study the bearing performance of vertically loaded large-diameter pipe pile groups.The interactions between group piles result in different bearing performance of bot...This paper aims to present a theoretical method to study the bearing performance of vertically loaded large-diameter pipe pile groups.The interactions between group piles result in different bearing performance of both a single pile and pile groups.Considering the pile group effect and the skin friction from both outer and inner soils,an analytical solution is developed to calculate the settlement and axial force in large-diameter pipe pile groups.The analytical solution was verified by centrifuge and field testing results.An extensive parametric analysis was performed to study the bearing performance of the pipe pile groups.The results reveal that the axial forces in group piles are not the same.The larger the distance from central pile,the larger the axial force.The axial force in the central pile is the smallest,while that in corner piles is the largest.The axial force on the top of the corner piles decreases while that in the central pile increases with increasing of pile spacing and decreasing of pile length.The axial force in side piles varies little with the variations of pile spacing,pile length,and shear modulus of the soil and is approximately equal to the average load shared by one pile.For a pile group,the larger the pile length is,the larger the influence radius is.As a result,the pile group effect is more apparent for a larger pile length.The settlement of pile groups decreases with increasing of the pile number in the group and the shear modulus of the underlying soil.展开更多
A new technique for the analysis of the three-dimensional collapse failure mechanism and the ground surface settlements for the large-diameter shield tunnels were presented.The technique is based on a velocity field m...A new technique for the analysis of the three-dimensional collapse failure mechanism and the ground surface settlements for the large-diameter shield tunnels were presented.The technique is based on a velocity field model using more different truncated solid conical blocks to clarify the multiblock failure mechanism.Furthermore,the shape of blocks between the failure surface and the tunnel face was considered as an entire circle,and the supporting pressure was assumed as non-uniform distribution on the tunnel face and increased with the tunnel embedded depth.The ground surface settlements and failure mechanism above large-diameter shield tunnels were also investigated under different supporting pressures by the finite difference method.展开更多
Cooling strength is one of the important factors affecting microstructure and properties of gas cylinders during quenching process,and reasonable water spray volume can effectively improve the quality of gas cylinders...Cooling strength is one of the important factors affecting microstructure and properties of gas cylinders during quenching process,and reasonable water spray volume can effectively improve the quality of gas cylinders and reduce production costs.To find the optimal water spray parameters,a fluid-solid coupling model with three-phase flow was established in consideration of water-vapor conversion.The inner and outer walls of gas cylinder with the dimensions of d914 mm×38 mm×12000 mm were quenched using multi-nozzle water spray system.The internal pressure,average heat transfer coefficient(have)and stress of the gas cylinder under different water spray volumes during quenching process were studied.Finally,the mathematical model was experimentally verified.The results show that both the internal pressure and have increase along with the increase of spray volume.The internal pressure increases slowly first and then rapidly,but have increases rapidly first and then slowly.To satisfy hardenability of gas cylinders,the minimum spray volume should not be less than 40 m^3/(h·m).The results of stress indicate that water spray quenching will not cause deformation of bottle body in the range of water volume from 40 to 290 m^3/(h·m).展开更多
Light-framed timber structure(LTS)buildings have been highly valued in recent years due to their low-carbon characteristics.However,the applicability of the building envelope is closely related to indoor and outdoor c...Light-framed timber structure(LTS)buildings have been highly valued in recent years due to their low-carbon characteristics.However,the applicability of the building envelope is closely related to indoor and outdoor conditions.The hot summer and cold winter(HSCW)climate zone in China has high humidity and great temperature variation throughout the year,resulting in distinct outdoor environments in different seasons.The indoor environment is greatly affected by energy-consumption patterns and window-opening habits,which largely depend upon the regulation operations of occupants.All these interrelated factors lead to extremely complex boundary conditions on each side of the building envelope.Whether the structures of LTS buildings are applicable in this climate zone,therefore,needs to be carefully considered.In this study,two LTS buildings with different envelopes were established in Haining,China,situated in the HSCW climate zone,and selected as the study objects.Different operation modes were adopted to create a variety of indoor environments.Under each condition,the processes of heat and moisture transfer within the building envelopes and the indoor environment were monitored and compared.The comparison indicated that the building envelope with high moisture storage and insulation ability maintained a relatively stable indoor environment,especially when the environment changed abruptly.Conversely,if the outdoor environment was equable(e.g.,relative humidity within the range of 30%–60%)or intermittent energy consumption modes were adopted,the building envelope with a low thermal inertia index and weak moisture-buffering ability performed better because it enabled a faster response of the indoor environment to air conditioning.Moreover,a high risk of moisture accumulation between the thermal insulation layer and other materials with a large water vapour transfer resistance factor was also identified,suggesting a higher requirement for the vapour insulation of the envelopes of LTS buildings.展开更多
The synchronous construction of the secondary lining during the boring of large-diameter shield faces challenges such as the design of the lining jumbo,the high requirements on the performance for the lining jumbo,the...The synchronous construction of the secondary lining during the boring of large-diameter shield faces challenges such as the design of the lining jumbo,the high requirements on the performance for the lining jumbo,the organization of the construction activities in the small and confined area,the horizontal transportation for shield boring and high safety management requirements.A super-long invert lining construction jumbo,as well as the matching California switch,is developed,which provides solution for the confliction between the invert lining construction and the horizontal transportation.The procedure and method for the synchronous operation of the shield boring and the secondary lining are developed by referring to the synchronous construction of the secondary lining during the boring of the TBMs in hard rocks.Due to the adoption of the synchronous operation of the shield boring and the secondary lining,the construction period is shortened and the construction cost is reduced.The paper can provide reference for the synchronous construction of the secondary lining in similar projects in the future.展开更多
This paper conducts a comprehensive analysis of the export dynamics within the Ukrainian timber industry, emphasizing its pivotal role in the national economy. The study begins by outlining the research objectives, co...This paper conducts a comprehensive analysis of the export dynamics within the Ukrainian timber industry, emphasizing its pivotal role in the national economy. The study begins by outlining the research objectives, context, and innovative methodologies, setting the stage for a deep dive into the theoretical underpinnings of sustainable and competitive trade. It explores Ukraine’s rich forest biodiversity across varied vegetation zones and its geopolitical significance. Detailed evaluations of forest resource management, policy frameworks, and institutional support form the core of the analysis. Challenges such as imbalanced export structures and legal inconsistencies are critically examined. The research employs trade gravity models and competitive indicators like the Revealed Comparative Advantage (RCA) and Market Share (MS) to assess factors influencing exports and to forecast potential growth areas. The findings inform strategic recommendations aimed at enhancing export capacity through market diversification, brand development, and legal stability. The conclusion highlights the need for strategic interventions to harness Ukraine’s timber resources sustainably, balancing economic gains with environmental stewardship.展开更多
Objective To discuss the postoperative curative effects of two surgical techniques of minimally invasive total hip arthroplasty (THA) using metal-on-metal largediameter and conventional diameter femoral head for the e...Objective To discuss the postoperative curative effects of two surgical techniques of minimally invasive total hip arthroplasty (THA) using metal-on-metal largediameter and conventional diameter femoral head for the elderly patients展开更多
基金supported by the Beijing Natural Science Foundation(Grant No.8252012)the National Natural Science Foundation of China(Grant No.52378475).
文摘Accurate acquisition of the lithological composition of a tunnel face is crucial for efficient tunneling and hazard prevention in large-diameter slurry shield tunnels.While widely applied,current data-driven methods often face challenges such as indirect prediction,data sparsity,and data drift,which limit their accuracy and generalizability.This study develops an integrated method that combines a knowledge-driven method to directly compute distribution patterns of lithological components,which are used as a priori knowledge to guide the development of a data-driven method.Coupled Markov chain(CMC)and deep neural networks(DNNs)serve as the knowledge-driven and data-driven components,respectively.Additionally,a dynamic prediction strategy is proposed,where the model is continuously optimized as construction progresses and training samples accumulate,rather than being statically trained on post-construction data,as is common in data-driven methods.Finally,the proposed method is evaluated using a real-world project.The evaluation results show that the integrated method outperforms both individual data-and knowledge-driven methods,demonstrating higher predictive performance,greater stability,and greater robustness to data scarcity and data drift.Furthermore,the dynamic prediction strategy better captures the effects of gradual data accumulation and lithological spatial variability on prediction performance during construction,providing new insights for real-time prediction in practical tunneling applications.
文摘This study addresses the increasing demand for large-diameter production timber,and considers the time and space variability of half-sib families of Pinus massoniana.Height,diameter at breast height(DBH)and timber volume of 440 open-pollinated half-sib progeny families were investigated in 14 progeny trials in different years and production regions.An evaluation of the genetic variation of all half-sib families was carried out during the sustainable rapid growth period and individual volumes were characterized as a major index.ANOVA analysis showed that there was considerable variance in the growth traits of most families in different years and on different sites.The variations caused by temporal and spatial changes of the mating system required three selection methods for analysis.The results show that there were differences among the heritabilities of different growth traits by different halfsib progenies.Average heritability values of height,DBH and volume were 0.33,0.34 and 0.36,respectively.Fortyfive superior families were selected in every progeny test,12 were selected in progeny trials by different years and five in different habitat progeny trials.Three superior families(Gui GC553A,Gui GC414A and Gui GC431A)were selected,although in different years and production regions.The genetic gains of timber volume of these selected r families ranged from 1.20 to 47.00%,which could provide a foundation for superior wood property selection and serve as material for seed improvement and extension in surrounding areas.
基金support from the Exploring Youth Project of Zhejiang Natural Science Foundation (Grant No.LQ24E080009)the Key Project of Natural Science Foundation of Zhejiang Province (Grant No.LXZ22E080001)the National Natural Science Foundation of China (Grant No.52108347).
文摘A rigorous analytical model is developed for simulating the vibration behaviors of large-diameter openended pipe piles(OEPPs)and surrounding soil undergoing high-strain impact loading.To describe the soil behavior,the soil along pile shaft is divided into slip and nonslip zones and the base soil is modeled as a fictitious-soil pile(FSP)to account for the wave propagation in the soil.True soil properties are adopted and slippage at the pile-soil interface is considered,allowing realistic representation of largediameter OEPP mechanics.The developed model is validated by comparing with conventional models and finite element method(FEM).It is further used to successfully simulate and interpret the behaviors of a steel OEPP during the offshore field test.It is found that the variation in the vertical vibrations of shaft soil along radial direction is significant for large-diameter OEPPs,and the velocity amplitudes of the internal and external soil attenuate following different patterns.The shaft soil motion may not attenuate with depth due to the soil slippage,while the wave attenuation at base soil indicates an influence depth,with a faster attenuation rate than that in the pile.The findings from the current study should aid in simulating the vibration behaviors of large-diameter OEPP-soil system under high-strain dynamic loading.
文摘The application of mass timber elements in different structures has gained publicity over the last few years,pri-marily due to climate change adaptation policies and net zero carbon targets.Timber is a renewable construction material that can outperform other building materials regarding environmental impact.However,when used in seismically active regions,its application has been limited due to the uncertainties on their seismic behaviour in respect with different design standards and limited ductility in conventional connections.Conventional timber connections typically suffer from stiffness and strength degradation under cyclic loads.Their repairability is also low due to permanent damage in the fasteners and the associated crushing in the wood fibres.The use of friction connections can be an efficient way to mitigate these issues.They offer many advantages as they are economical and yet provide a high level of reliable and continuous energy dissipation.In recent years,a new generation of friction connections has been developed that can provide self-centring behaviour(i.e.,the ability of the structure to return to its original position at the end of an earthquake).However,how these connections perform compared to a mass timber system with conventional timber connections is still unknown.Several studies in the literature have suggested that these connections can enhance the performance of mass timber structures.However,the seismic performance of such systems specifically in terms of base shear,response drifts and response accelerations-has not been thoroughly investigated.This paper examines various design aspects of conventional friction connections and self-centring friction connections,providing insights into their differences concerning key seismic performance indicators.It compares the seismic performance of mass timber buildings equipped with both solutions,highlighting their advantages and limitations and drawing conclusions based on the results.The key findings are that friction connections can provides a superior seismic performance for timber structures.However,that may need to be combined with a parallel system avoid residual displacements.
基金gratitude to WIDE Trust New Zealand for providing the opportunity and funding for this research,as well as QuakeCoRE,a New Zealand Tertiary Education Commission-funded Centre,for partially funding this research.This is QuakeCoRE,publication number 1013.
文摘Platform-style construction is a widely recognized and well-established approach among engineers and developers for multi-story mass timber buildings.This construction method offers many advantages,such as rapid assembly,an excellent strength-to-weight ratio,and appealing aesthetic features.In a platform-type construction,each story is constructed by placing the floor panels on top of the load-bearing wall,creating a platform for the level above.Although this method offers numerous advantages,recent research findings have revealed that cross-laminated(CLT)platform buildings with conventional connections,such as wall-to-floor hold-down brackets and shear connectors with nails and screws,are prone to experience a high degree of damage under design-level earthquakes.Consequently,conventional connections in platform-type construction are vulnerable to more damage under aftershocks and do not meet the damage avoidance requirements of seismic design.This paper introduces an innovative floor-to-wall connection for a platform-type low-rise mass timber building that mitigates the limitations of conventional connections.The effectiveness of the proposed connection has been investigated,and the seismic performance of the system,which incorporates the proposed connection,has been outlined in this paper.A numerical model with an innovative inter-story isolation system is developed in ETABS,and the seismic performance of the isolated structure was evaluated using Response Spectrum Analysis(RSA)and Nonlinear Time History Analysis(NLTHA).This study revealed that inter-story isolation systems significantly reduced the seismic demands on the mass timber components,demonstrating the system’s ability to dissipate seismic energy.Additionally,the system displayed effective energy dissipation while exhibiting self-centering behaviour.
基金National Natural Science Foundation of China (59975076, 50175092)National Science Fund of China for Distinguished Young Scholars (50225518)
文摘Tube thinning control without wrinkling occurring is a key problem urgently to be solved for improving the forming qualities in numerical control （NC） bending processes of large-diameter Al-alloy thin-walled tubes （AATTs）. It may be a way solving this problem to exert axial compression loads （ACL） on the tube end in the bending. Thus, this article establishes a three-dimensional （3D） elastic-plastic explicit finite element （FE） model for the bending under ACL and has its reliability verified. Through a multi-index orthogonal experiment design, a combination of process parameters, each expressed by a proper range, for this FE model is derived to overcome the compression instability on tube ends. By combining the FE model with a wrinkling energy prediction model, an in-depth study is conducted on the forming characteristics of large-diameter AATTs with small bending radii and it can be concluded that （1） The larger the tube diameters and the smaller the bending radii, the larger the induced tangent tension stress zones on tube intrados, by which the tube maximum tangent compression stress zones will be partitioned in the bending processes; thus, the smaller the ACL roles in decreasing thinning degrees and the larger the compression instability possibilities on tube ends. （2） The tube wrinkling possibilities under ACL are larger than without ACL acting in the earlier forming periods, and smaller in the later ones. （3） For the tubes with a size factor less than 80, the ACL roles in decreasing thinning degrees are stronger than in increasing wrinkling possibilities.
基金supported by National Natural Science Foundation of China (Grant No. 50875017)
文摘The existing researches of the magnetic liquid rotation seal have been mainly oriented to the seal at normal temperature and the seal with the smaller shaft diameter less than 100 mm. However, the large-diameter magnetic liquid rotation seal at low temperature has not been reported both in theory and in application up to now. A key factor restricting the application of the large-diameter magnetic liquid rotation seal at low temperature is the high breakaway torque. In this paper, the factors that influence the breakaway torque including the number of seal stages, the injected quantity of magnetic liquid and the standing time at normal temperature are studied. Two kinds of magnetic liquid with variable content of large particles are prepared first, and a seal feedthrough with 140 mm shaft diameter is used in the experiments. All experiments are carried out in a low temperature chamber with a temperature range from 200℃ to -100℃. Different numbers of seal stages are tested under the same condition to study the relation between the breakaway torque and the number of seal stages. Variable quantity of magnetic liquid is injected in the seal gap to get the relation curve of the breakaway torque and the injecting quantity of magnetic liquid. In the experiment for studying the relation between the breakaway torque and the standing time at the normal temperature, the seal feedtrough is laid at normal temperature for different period of time before it is put in the low temperature chamber. The experimental results show that the breakaway torque is proportional to the number of seal stages, the injected quantity of magnetic liquid and the standing time at the normal temperature. Meanwhile, the experimental results are analyzed and the torque formula of magnetic liquid rotation seal at low temperature is deduced from the Navier-Stokes equation on the base of the model of magnetic liquid rotation seal. The presented research can make wider application of the magnetic liquid seal in general. And the large-diameter magnetic liquid rotation seal at low temperature designed by using present research results are to be used in some special fields, such as the military field, etc.
基金by the National Natural Science Foundation of China(Grant No.59679003)the Natural Science Foundation of Tianjin(Grant No.973606311)
文摘The large-diameter cylinder structure, which is made of large successive bottomless cylinders placed on foundation bed or partly driven into soil, is a recently developed retaining structure in China. It can be used in port, coastal and offshore works. The method for stability analysis of the large-diameter cylinder structure, especially for stability analysis of the embedded large-diameter cylinder structure, is an important issue. In this paper, an idea is presented that is, embedded large-diameter cylinder quays can be divided into two types, i.e. the gravity wall type and the cylinder pile wall type. A method for stability analysis of the large-diameter cylinder quay of the cylinder pile wall type is developed and a method for stability analysis of the large-diameter cylinder quay of the gravity wall type is also proposed. The effect of significant parameters on the stability of the large-diameter cylinder quay of the cylinder pile wall type is investigated through numerical calculation.
基金Project(U1134207)supported by the National Natural Science and High Speed Railway Jointed Foundation of ChinaProject(B13024)supported by the "111" Program of China+1 种基金Project(BK2012811)supported by the Nature Science Foundation of Jiangsu Province,ChinaProject(NCET-12-0843)supported by the Fund for New Century Excellent Talents in Universities,China
文摘Considering the viscous damping of the soil and soil-pile vertical coupled vibration,a computational model of large-diameter pipe pile in layered soil was established.The analytical solution in frequency domain was derived by Laplace transformation method.The responses in time domain were obtained by inverse Fourier transformation.The results of the analytical solution proposed agree well with the solutions in homogenous soil.The effects of the shear modulus and damping coefficients of the soil at both outer and inner sides of the pipe pile were researched.The results indicate that the shear modulus of the outer soil has more influence on velocity admittance than the inner soil.The smaller the shear modulus,the larger the amplitude of velocity admittance.The velocity admittance weakened by the damping of the outer soil is more obvious than that weakened by the damping of the inner soil.The displacements of the piles with the same damping coefficients of the outer soil have less difference.Moreover,the effects of the distribution of soil layers are analyzed.The results indicate that the effect of the upper soil layer on dynamic response of the pipe pile is more obvious than that of the bottom soil layer.A larger damping coefficient of the upper layer results in a smaller velocity admittance.The dynamic response of the pipe pile in layered soil is close to that of the pipe pile in homogenous soil when the properties of the upper soil layer are the same.
文摘A method of coupled BEM-FEM analysis for the elastic spatial structure system is presented. It can be applied to the calculation of the stress and deformation of the large-diamater cylinder structure system and it is suitable for symmetric or non-symmetric structures under the distributed or concentrated load. Numerical examples show that the proposed method and computer program BEFEM are quite efficient in the analysis of the large-diameter cylinder structure problems in ocean engineering.
基金supported by the Joint High Speed Railway Key Program of National Natural Science Foundation of China (Grant No.U1134207)the National Natural Science Foundation of China (Grant No.51378177)+1 种基金the Program for Excellent University Talents in New Century (Grant No.NCET-12-0843)the Fundamental Research Fund for the Central Universities (Grant No.106112014CDJZR200007)
文摘This paper aims to present a theoretical method to study the bearing performance of vertically loaded large-diameter pipe pile groups.The interactions between group piles result in different bearing performance of both a single pile and pile groups.Considering the pile group effect and the skin friction from both outer and inner soils,an analytical solution is developed to calculate the settlement and axial force in large-diameter pipe pile groups.The analytical solution was verified by centrifuge and field testing results.An extensive parametric analysis was performed to study the bearing performance of the pipe pile groups.The results reveal that the axial forces in group piles are not the same.The larger the distance from central pile,the larger the axial force.The axial force in the central pile is the smallest,while that in corner piles is the largest.The axial force on the top of the corner piles decreases while that in the central pile increases with increasing of pile spacing and decreasing of pile length.The axial force in side piles varies little with the variations of pile spacing,pile length,and shear modulus of the soil and is approximately equal to the average load shared by one pile.For a pile group,the larger the pile length is,the larger the influence radius is.As a result,the pile group effect is more apparent for a larger pile length.The settlement of pile groups decreases with increasing of the pile number in the group and the shear modulus of the underlying soil.
基金Project(41202220) supported by the National Natural Science Foundation of ChinaProject(2011YYL034) supported by the Fundamental Research Funds for the Central Universities,China
文摘A new technique for the analysis of the three-dimensional collapse failure mechanism and the ground surface settlements for the large-diameter shield tunnels were presented.The technique is based on a velocity field model using more different truncated solid conical blocks to clarify the multiblock failure mechanism.Furthermore,the shape of blocks between the failure surface and the tunnel face was considered as an entire circle,and the supporting pressure was assumed as non-uniform distribution on the tunnel face and increased with the tunnel embedded depth.The ground surface settlements and failure mechanism above large-diameter shield tunnels were also investigated under different supporting pressures by the finite difference method.
基金Project(51674096)supported by the National Natural Science Foundation of ChinaProject(E2016203119)supported by Hebei Natural Science Foundation of ChinaProject(18211045)supported by the Key Research and Development Foundation in Hebei Province of China
文摘Cooling strength is one of the important factors affecting microstructure and properties of gas cylinders during quenching process,and reasonable water spray volume can effectively improve the quality of gas cylinders and reduce production costs.To find the optimal water spray parameters,a fluid-solid coupling model with three-phase flow was established in consideration of water-vapor conversion.The inner and outer walls of gas cylinder with the dimensions of d914 mm×38 mm×12000 mm were quenched using multi-nozzle water spray system.The internal pressure,average heat transfer coefficient(have)and stress of the gas cylinder under different water spray volumes during quenching process were studied.Finally,the mathematical model was experimentally verified.The results show that both the internal pressure and have increase along with the increase of spray volume.The internal pressure increases slowly first and then rapidly,but have increases rapidly first and then slowly.To satisfy hardenability of gas cylinders,the minimum spray volume should not be less than 40 m^3/(h·m).The results of stress indicate that water spray quenching will not cause deformation of bottle body in the range of water volume from 40 to 290 m^3/(h·m).
基金supported by the National Natural Science Foundation of China(No.51978623).
文摘Light-framed timber structure(LTS)buildings have been highly valued in recent years due to their low-carbon characteristics.However,the applicability of the building envelope is closely related to indoor and outdoor conditions.The hot summer and cold winter(HSCW)climate zone in China has high humidity and great temperature variation throughout the year,resulting in distinct outdoor environments in different seasons.The indoor environment is greatly affected by energy-consumption patterns and window-opening habits,which largely depend upon the regulation operations of occupants.All these interrelated factors lead to extremely complex boundary conditions on each side of the building envelope.Whether the structures of LTS buildings are applicable in this climate zone,therefore,needs to be carefully considered.In this study,two LTS buildings with different envelopes were established in Haining,China,situated in the HSCW climate zone,and selected as the study objects.Different operation modes were adopted to create a variety of indoor environments.Under each condition,the processes of heat and moisture transfer within the building envelopes and the indoor environment were monitored and compared.The comparison indicated that the building envelope with high moisture storage and insulation ability maintained a relatively stable indoor environment,especially when the environment changed abruptly.Conversely,if the outdoor environment was equable(e.g.,relative humidity within the range of 30%–60%)or intermittent energy consumption modes were adopted,the building envelope with a low thermal inertia index and weak moisture-buffering ability performed better because it enabled a faster response of the indoor environment to air conditioning.Moreover,a high risk of moisture accumulation between the thermal insulation layer and other materials with a large water vapour transfer resistance factor was also identified,suggesting a higher requirement for the vapour insulation of the envelopes of LTS buildings.
文摘The synchronous construction of the secondary lining during the boring of large-diameter shield faces challenges such as the design of the lining jumbo,the high requirements on the performance for the lining jumbo,the organization of the construction activities in the small and confined area,the horizontal transportation for shield boring and high safety management requirements.A super-long invert lining construction jumbo,as well as the matching California switch,is developed,which provides solution for the confliction between the invert lining construction and the horizontal transportation.The procedure and method for the synchronous operation of the shield boring and the secondary lining are developed by referring to the synchronous construction of the secondary lining during the boring of the TBMs in hard rocks.Due to the adoption of the synchronous operation of the shield boring and the secondary lining,the construction period is shortened and the construction cost is reduced.The paper can provide reference for the synchronous construction of the secondary lining in similar projects in the future.
文摘This paper conducts a comprehensive analysis of the export dynamics within the Ukrainian timber industry, emphasizing its pivotal role in the national economy. The study begins by outlining the research objectives, context, and innovative methodologies, setting the stage for a deep dive into the theoretical underpinnings of sustainable and competitive trade. It explores Ukraine’s rich forest biodiversity across varied vegetation zones and its geopolitical significance. Detailed evaluations of forest resource management, policy frameworks, and institutional support form the core of the analysis. Challenges such as imbalanced export structures and legal inconsistencies are critically examined. The research employs trade gravity models and competitive indicators like the Revealed Comparative Advantage (RCA) and Market Share (MS) to assess factors influencing exports and to forecast potential growth areas. The findings inform strategic recommendations aimed at enhancing export capacity through market diversification, brand development, and legal stability. The conclusion highlights the need for strategic interventions to harness Ukraine’s timber resources sustainably, balancing economic gains with environmental stewardship.
文摘Objective To discuss the postoperative curative effects of two surgical techniques of minimally invasive total hip arthroplasty (THA) using metal-on-metal largediameter and conventional diameter femoral head for the elderly patients
