The precise control of the shape of transversely stiffened suspended cable systems is crucial. However, existing form-finding methods primarily rely on iterative calculations that treat loads as fixed known conditions...The precise control of the shape of transversely stiffened suspended cable systems is crucial. However, existing form-finding methods primarily rely on iterative calculations that treat loads as fixed known conditions. These methods are inefficient and fail to accurately control shape results. In this study, we propose a form-finding method that analyzes the load response of models under different sag and stress levels, taking into account the construction process. To analyze the system, a structural finite element model was established in ANSYS, and geometric nonlinear analysis was conducted using the Newton-Raphson method. The form-finding analysis results demonstrate that the proposed method achieves precise control of shape, with a maximum shape error ranging from 0.33% to 0.98%. Furthermore, the relationships between loads and tension forces are influenced by the deformed shape of the structures, exhibiting significant geometric nonlinear characteristics. Meanwhile, the load response analysis reveals that the stress level of the self-equilibrium state in the transversely stiffened suspended cable system is primarily governed by strength criteria, while shape is predominantly controlled by stiffness criteria. Importantly, by simulating the initial tensioning process as an initial condition, this method solves for a counterweight that satisfies the requirements and achieves a self-equilibrium state with the desired shape. The shape of the self-equilibrium state is precisely controlled by simulating the construction process. Overall, this work presents a new method for analyzing the form-finding process of large-span transversely stiffened suspended cable system, considering the construction process which was often overlooked in previous studies.展开更多
To balance the contradiction between higher flexibility and heavier load bearing capacity,we present a novel deformable manipulator which is composed of active rigid joints and deformable links.The deformable link is ...To balance the contradiction between higher flexibility and heavier load bearing capacity,we present a novel deformable manipulator which is composed of active rigid joints and deformable links.The deformable link is composed of passive spherical joints with preload forces between socket-ball surfaces.To estimate the load bearing capacity of a deformable link,we present a static force-based model of spherical joint with preload force and analyze the static force propagation in the deformable link.This yields an important result that the load bearing capacity of a spherical joint only depends on its radius,preload force,and static friction coefficient.We further develop a parameter estimation method to estimate the product of preload force and static friction coefficient.The experimental results validate our model.80.4%of percentage errors on the maximum payload mass prediction are below 15%.展开更多
Motivated by the early works on bidirectional interaction and the breakthrough to estimate seismic response to bidirectional shaking via unidirectional analysis,it is essential to answer the question:When is the inter...Motivated by the early works on bidirectional interaction and the breakthrough to estimate seismic response to bidirectional shaking via unidirectional analysis,it is essential to answer the question:When is the interaction effect significant?Early works concluded that the effect of interaction is pronounced for stiff systems;consequently,the straightforward method for estimating seismic response to bidirectional excitation by using unidirectional analyses is verified primarily for short period systems.Hence,it is essential to identify the domain of significance for bidirectional interaction before adopting this simple methodology in design.Several parametrically defined systems with elastoplastic and degrading hysteresis models are studied under near-fault motions,assuming strength-independent and strength-dependent stiffness.The force-based and displacement-based analyses,conducted in parallel,reveal that the interaction effect is considerable for stiff systems,especially with degrading characteristics in a relatively low inelasticity range.However,the bidirectional effect may be significant even for highly flexible systems,especially for residual deformation,which in earlier works was shrouded.The range of significance depends on the hysteresis model,system parameters,and response indices.Regression analysis is carried out with the results of the case studies,and the derived regression models may be used for a preliminary assessment of the impact of interaction in advance.展开更多
Efficiency and safety are paramount concerns for commuters, operators, and designers in subway stations. This study conducted controlled experiments and developed a modified force-based model to investigate the dynami...Efficiency and safety are paramount concerns for commuters, operators, and designers in subway stations. This study conducted controlled experiments and developed a modified force-based model to investigate the dynamics of pedestrian counterflow at bottlenecks, utilizing subway passenger alighting and boarding as a case study. Specifically, the efficiency and safety of three distinct movement modes: the cooperative mode(Coop), the combination of cooperative and competitive mode(C & C), and the competitive mode(Comp), were examined and compared. The experimental findings revealed that the C & C mode exhibited a clear lane formation phenomenon and demonstrated a higher flow rate than the Comp and Coop modes. This observation suggests that a combination of cooperative and competitive behaviors among pedestrians can positively enhance traffic efficiency and safety during the alighting and boarding process. In contrast, pedestrians exhibited increased detouring in their paths and more fluctuating trajectories in the Comp mode. Additionally, a questionnaire survey assessing the level of competition and cooperation among pedestrians provided a comprehensive analysis of the psychological dynamics of passengers during the alighting and boarding activities. Lastly, the proposed force-based model was calibrated and validated, demonstrating a good performance in accurately replicating the overall characteristics of the experimental process. Overall, this study offers valuable insights into enhancing the pedestrian traffic efficiency and safety within subway systems.展开更多
Deployable high-frequency mesh reflector antennas for future communications and obser- vations are required to obtain high gain and high directivity. In order to support these new missions, reflectors with high surfac...Deployable high-frequency mesh reflector antennas for future communications and obser- vations are required to obtain high gain and high directivity. In order to support these new missions, reflectors with high surface accuracy are widely required. The form-finding analysis of deployable mesh reflector antennas becomes more vital which aims to determine the initial surface profile formed by the equilibrium prestress distribution in cables to satisfy the surface accuracy requirement. In this paper, two form-finding methods for mesh reflector antennas, both of which include two steps, are pro- posed. The first step is to investigate the prestress design only for the cable net structure as the circum- ferential nodes connected to the supporting truss are assumed fixed. The second step is to optimize the prestress distribution of the boundary cables connected directly to the supporting truss considering the elastic deformation of the antenna structure. Some numerical examples are carried out and the simulation results demonstrate the proposed form-finding methods can warrant the deformed antenna reflector surface matches the one by design and the cable tension forces fall in a specified range.展开更多
In this paper,an experimental study of an air inflated membrane was carried out based on the China National Stadium (the Bird's Nest). After the 2008 Olympic Games,it was apparent that the future use of the Bird&#...In this paper,an experimental study of an air inflated membrane was carried out based on the China National Stadium (the Bird's Nest). After the 2008 Olympic Games,it was apparent that the future use of the Bird's Nest would be enhanced if rainfall could be prevented from entering the stadium. The installation of an air inflated membrane across the opening of the steel structure was proposed as a solution to this problem. To verify the scheme,a theoretical analysis and experimental study of an air inflated membrane was carried out. Experimental and computational models were developed,form-finding was carried out using both experimental and theoretical methods,and the results from the two approaches,including the deflection of the air inflated membrane and deformation of the support structure,were analyzed and compared. The force-transfer path and deformation of the air inflated membrane under loads was studied. Conclusions and suggestions are presented.展开更多
Deployable mechanisms with light weight and high storage ratio have received considerable attention for space applications. To meet the requirements of space missions, a parabolic cylindrical deployable antenna based ...Deployable mechanisms with light weight and high storage ratio have received considerable attention for space applications. To meet the requirements of space missions, a parabolic cylindrical deployable antenna based on cable-rib tension structures is proposed and verified by a physical prototype. The parabolic cylindrical antenna adopts simple parallel four-bar mechanisms to construct the basic deployable unit, and the cylindrical direction dimension can be easily extended by modularization, which has obvious advantages in storage ratio and area density. Considering the complexity of the entire antenna structure design, including cable networks and flexible trusses, the form-finding design optimization model of a parabolic cylindrical antenna is established using the force density sensitivity method, and then the kinematics analysis of the deployable mechanism is carried out. Finally, a single-module prototype with a deployable diameter of 4 m × 2 m was designed and fabricated. The results of the ground deployment process test and surface accuracy measurements show that the antenna has good feasibility and practicability.展开更多
The capability to image, as well as control and manipulate single molecules such as nucleic acids(DNA or RNA) can greatly enrich our knowledge of the roles of individual biomolecules in cellular processes and their be...The capability to image, as well as control and manipulate single molecules such as nucleic acids(DNA or RNA) can greatly enrich our knowledge of the roles of individual biomolecules in cellular processes and their behavior in native environments. Here we summarize the recent advances of single nucleic acid imaging based on optical observation and force manipulation. We start by discussing the superiority of single molecule image, the central roles nucleic acids play in biosystems, and the significance of single molecule image towards nucleic acids. We then list a series of representative examples in brief to illustrate how nucleic acid of various morphologies has been imaged from different aspects, and what can be learned from such characterizations. Finally,concluding remarks on parts of which should be improved and outlook are outlined.展开更多
With rapid advances in design methods and structural analysis techniques,computational generative design strategies have been adopted more widely in the field of architecture and engineering.As a performance-based des...With rapid advances in design methods and structural analysis techniques,computational generative design strategies have been adopted more widely in the field of architecture and engineering.As a performance-based design technique to find out the most efficient structural form,topology optimization provides a powerful tool for designers to explore lightweight and elegant structures.Building on this background,this study proposes an innovative pedestrian bridge design,which covers the process from conceptualization to detailed design implementation.This pedestrian bridge,with a main span of 152 m,needs to meet some unique architectural requirements,while addressing multiple engineering challenges.Aiming to reduce the depth of the girder but still meeting the load-carrying capacity requirements,the superstructure of this bridge adopts a variable-depth spinal-shaped girder in the center of its deck,thus forming an elegant curving facade,from which one pathway cantilevers on either side.At one end of the bridge,given considerable elevation difference between the bridge deck and the ground,a two-level Fibonacci-type spiral-shaped bicycle ramp is provided.The superstructure is supported by a series of organic tree-shaped branching piers resulting from the topology optimization.The ingenious design for the elegant profile of the bicycle ramp generates an enjoyable and dynamic crossing experience,with scenic views in all directions.By virtue of technological innovation,the pedestrian bridge is expected to create an iconic,cost-effective,and low-maintenance solution.A brief overview of the theoretical background of the bi-directional evolutionary structure optimization(BESO)and the multi-material BESO approach is also offered in this paper,while the construction requirements and challenges,conceptual development process,form-finding strategy,detailed design,and construction method of the bridge are presented.展开更多
This research aims at developing an innovative methodology and the related computational workflow to design energy efficient buildings equipped with climate responsive building skins able to respond dynamically to env...This research aims at developing an innovative methodology and the related computational workflow to design energy efficient buildings equipped with climate responsive building skins able to respond dynamically to environmental conditions changing over the time.This methodology,called Adaptive Building and Skin(AB&S),is applicable in different climate zones and consists of a computational form-finding method,which supports architects and engineers in the buildings’design process resulting in buildings with optimized energy performance and a high level of indoor and outdoor comfort under changing environmental conditions.The innovativeness of AB&S lies in the fact that it includes the entire design process and considers several internal and external inputs to find the best solutions at all scales of a project:starting from the micro urban-scale with the design of the site and of the building shape,down to the building-scale and finally the skin-scale.Applicability and functionality of AB&S has been tested and improved in the design of office buildings located in specific cities located in different climate zones(cold,temperate,tropical and subtropical).Results of the application in Berlin,Germany,are presented in detail in this paper.展开更多
文摘The precise control of the shape of transversely stiffened suspended cable systems is crucial. However, existing form-finding methods primarily rely on iterative calculations that treat loads as fixed known conditions. These methods are inefficient and fail to accurately control shape results. In this study, we propose a form-finding method that analyzes the load response of models under different sag and stress levels, taking into account the construction process. To analyze the system, a structural finite element model was established in ANSYS, and geometric nonlinear analysis was conducted using the Newton-Raphson method. The form-finding analysis results demonstrate that the proposed method achieves precise control of shape, with a maximum shape error ranging from 0.33% to 0.98%. Furthermore, the relationships between loads and tension forces are influenced by the deformed shape of the structures, exhibiting significant geometric nonlinear characteristics. Meanwhile, the load response analysis reveals that the stress level of the self-equilibrium state in the transversely stiffened suspended cable system is primarily governed by strength criteria, while shape is predominantly controlled by stiffness criteria. Importantly, by simulating the initial tensioning process as an initial condition, this method solves for a counterweight that satisfies the requirements and achieves a self-equilibrium state with the desired shape. The shape of the self-equilibrium state is precisely controlled by simulating the construction process. Overall, this work presents a new method for analyzing the form-finding process of large-span transversely stiffened suspended cable system, considering the construction process which was often overlooked in previous studies.
基金supported by National Natural Science Foundation of China(NSFC)(61573198,61375087)the Natural Science Foundation of Tianjin(15JCZDJC31200)。
文摘To balance the contradiction between higher flexibility and heavier load bearing capacity,we present a novel deformable manipulator which is composed of active rigid joints and deformable links.The deformable link is composed of passive spherical joints with preload forces between socket-ball surfaces.To estimate the load bearing capacity of a deformable link,we present a static force-based model of spherical joint with preload force and analyze the static force propagation in the deformable link.This yields an important result that the load bearing capacity of a spherical joint only depends on its radius,preload force,and static friction coefficient.We further develop a parameter estimation method to estimate the product of preload force and static friction coefficient.The experimental results validate our model.80.4%of percentage errors on the maximum payload mass prediction are below 15%.
文摘Motivated by the early works on bidirectional interaction and the breakthrough to estimate seismic response to bidirectional shaking via unidirectional analysis,it is essential to answer the question:When is the interaction effect significant?Early works concluded that the effect of interaction is pronounced for stiff systems;consequently,the straightforward method for estimating seismic response to bidirectional excitation by using unidirectional analyses is verified primarily for short period systems.Hence,it is essential to identify the domain of significance for bidirectional interaction before adopting this simple methodology in design.Several parametrically defined systems with elastoplastic and degrading hysteresis models are studied under near-fault motions,assuming strength-independent and strength-dependent stiffness.The force-based and displacement-based analyses,conducted in parallel,reveal that the interaction effect is considerable for stiff systems,especially with degrading characteristics in a relatively low inelasticity range.However,the bidirectional effect may be significant even for highly flexible systems,especially for residual deformation,which in earlier works was shrouded.The range of significance depends on the hysteresis model,system parameters,and response indices.Regression analysis is carried out with the results of the case studies,and the derived regression models may be used for a preliminary assessment of the impact of interaction in advance.
基金Project supported by the National Natural Science Foundation of China (Grant No. 72301184)the Natural Science Foundation of Sichuan Province of China (Grant No. 2024NSFSC1073)the Fundamental Research Funds for the Central Universities (Grant No. YJ202329)。
文摘Efficiency and safety are paramount concerns for commuters, operators, and designers in subway stations. This study conducted controlled experiments and developed a modified force-based model to investigate the dynamics of pedestrian counterflow at bottlenecks, utilizing subway passenger alighting and boarding as a case study. Specifically, the efficiency and safety of three distinct movement modes: the cooperative mode(Coop), the combination of cooperative and competitive mode(C & C), and the competitive mode(Comp), were examined and compared. The experimental findings revealed that the C & C mode exhibited a clear lane formation phenomenon and demonstrated a higher flow rate than the Comp and Coop modes. This observation suggests that a combination of cooperative and competitive behaviors among pedestrians can positively enhance traffic efficiency and safety during the alighting and boarding process. In contrast, pedestrians exhibited increased detouring in their paths and more fluctuating trajectories in the Comp mode. Additionally, a questionnaire survey assessing the level of competition and cooperation among pedestrians provided a comprehensive analysis of the psychological dynamics of passengers during the alighting and boarding activities. Lastly, the proposed force-based model was calibrated and validated, demonstrating a good performance in accurately replicating the overall characteristics of the experimental process. Overall, this study offers valuable insights into enhancing the pedestrian traffic efficiency and safety within subway systems.
基金supported by National Natural Science Foundation of China (Grant No.51375360)
文摘Deployable high-frequency mesh reflector antennas for future communications and obser- vations are required to obtain high gain and high directivity. In order to support these new missions, reflectors with high surface accuracy are widely required. The form-finding analysis of deployable mesh reflector antennas becomes more vital which aims to determine the initial surface profile formed by the equilibrium prestress distribution in cables to satisfy the surface accuracy requirement. In this paper, two form-finding methods for mesh reflector antennas, both of which include two steps, are pro- posed. The first step is to investigate the prestress design only for the cable net structure as the circum- ferential nodes connected to the supporting truss are assumed fixed. The second step is to optimize the prestress distribution of the boundary cables connected directly to the supporting truss considering the elastic deformation of the antenna structure. Some numerical examples are carried out and the simulation results demonstrate the proposed form-finding methods can warrant the deformed antenna reflector surface matches the one by design and the cable tension forces fall in a specified range.
文摘In this paper,an experimental study of an air inflated membrane was carried out based on the China National Stadium (the Bird's Nest). After the 2008 Olympic Games,it was apparent that the future use of the Bird's Nest would be enhanced if rainfall could be prevented from entering the stadium. The installation of an air inflated membrane across the opening of the steel structure was proposed as a solution to this problem. To verify the scheme,a theoretical analysis and experimental study of an air inflated membrane was carried out. Experimental and computational models were developed,form-finding was carried out using both experimental and theoretical methods,and the results from the two approaches,including the deflection of the air inflated membrane and deformation of the support structure,were analyzed and compared. The force-transfer path and deformation of the air inflated membrane under loads was studied. Conclusions and suggestions are presented.
基金supported by the National Natural Science Foundation of China (Nos. 51705388 and 51675398)the Youth Talent Fund of Science and Technology Association of Shaanxi University of Chinathe Aerospace information Research Institute, Chinese Academy of Sciences for its financial support
文摘Deployable mechanisms with light weight and high storage ratio have received considerable attention for space applications. To meet the requirements of space missions, a parabolic cylindrical deployable antenna based on cable-rib tension structures is proposed and verified by a physical prototype. The parabolic cylindrical antenna adopts simple parallel four-bar mechanisms to construct the basic deployable unit, and the cylindrical direction dimension can be easily extended by modularization, which has obvious advantages in storage ratio and area density. Considering the complexity of the entire antenna structure design, including cable networks and flexible trusses, the form-finding design optimization model of a parabolic cylindrical antenna is established using the force density sensitivity method, and then the kinematics analysis of the deployable mechanism is carried out. Finally, a single-module prototype with a deployable diameter of 4 m × 2 m was designed and fabricated. The results of the ground deployment process test and surface accuracy measurements show that the antenna has good feasibility and practicability.
基金supported by the National Natural Science Foundation of China (21525523, 21574048, 21375042, 21405054)the National Basic Research Program of China (2015CB932600, 2013CB933000)+1 种基金the Special Fund for Strategic New Industry Development of Shenzhen, China (JCYJ20150616144425376)1000 Young Talent (to Fan Xia)
文摘The capability to image, as well as control and manipulate single molecules such as nucleic acids(DNA or RNA) can greatly enrich our knowledge of the roles of individual biomolecules in cellular processes and their behavior in native environments. Here we summarize the recent advances of single nucleic acid imaging based on optical observation and force manipulation. We start by discussing the superiority of single molecule image, the central roles nucleic acids play in biosystems, and the significance of single molecule image towards nucleic acids. We then list a series of representative examples in brief to illustrate how nucleic acid of various morphologies has been imaged from different aspects, and what can be learned from such characterizations. Finally,concluding remarks on parts of which should be improved and outlook are outlined.
基金supported by the Technological Innovation and Construction Science and Technology Project of Chongqing City(cstc2022-1-5-3)the Australian Research Council(FL190100014,DP200102190).
文摘With rapid advances in design methods and structural analysis techniques,computational generative design strategies have been adopted more widely in the field of architecture and engineering.As a performance-based design technique to find out the most efficient structural form,topology optimization provides a powerful tool for designers to explore lightweight and elegant structures.Building on this background,this study proposes an innovative pedestrian bridge design,which covers the process from conceptualization to detailed design implementation.This pedestrian bridge,with a main span of 152 m,needs to meet some unique architectural requirements,while addressing multiple engineering challenges.Aiming to reduce the depth of the girder but still meeting the load-carrying capacity requirements,the superstructure of this bridge adopts a variable-depth spinal-shaped girder in the center of its deck,thus forming an elegant curving facade,from which one pathway cantilevers on either side.At one end of the bridge,given considerable elevation difference between the bridge deck and the ground,a two-level Fibonacci-type spiral-shaped bicycle ramp is provided.The superstructure is supported by a series of organic tree-shaped branching piers resulting from the topology optimization.The ingenious design for the elegant profile of the bicycle ramp generates an enjoyable and dynamic crossing experience,with scenic views in all directions.By virtue of technological innovation,the pedestrian bridge is expected to create an iconic,cost-effective,and low-maintenance solution.A brief overview of the theoretical background of the bi-directional evolutionary structure optimization(BESO)and the multi-material BESO approach is also offered in this paper,while the construction requirements and challenges,conceptual development process,form-finding strategy,detailed design,and construction method of the bridge are presented.
文摘This research aims at developing an innovative methodology and the related computational workflow to design energy efficient buildings equipped with climate responsive building skins able to respond dynamically to environmental conditions changing over the time.This methodology,called Adaptive Building and Skin(AB&S),is applicable in different climate zones and consists of a computational form-finding method,which supports architects and engineers in the buildings’design process resulting in buildings with optimized energy performance and a high level of indoor and outdoor comfort under changing environmental conditions.The innovativeness of AB&S lies in the fact that it includes the entire design process and considers several internal and external inputs to find the best solutions at all scales of a project:starting from the micro urban-scale with the design of the site and of the building shape,down to the building-scale and finally the skin-scale.Applicability and functionality of AB&S has been tested and improved in the design of office buildings located in specific cities located in different climate zones(cold,temperate,tropical and subtropical).Results of the application in Berlin,Germany,are presented in detail in this paper.
