Modem dynamic tests such as networked collaborative pseudo-dynamic testing （PDT） provide new tools to study the dynamic performance of large and complex structures. In this paper, several networked collaborative PDT...Modem dynamic tests such as networked collaborative pseudo-dynamic testing （PDT） provide new tools to study the dynamic performance of large and complex structures. In this paper, several networked collaborative PDT systems established in China and abroad are introduced, including a detailed description of the first networked collaborative platform that involved the construction of a standardized demonstration procedure for networked collaborative PDT. The example is a multi-span bridge with RC piers retrofitted by FRP, and a networked structural laboratory （NetSLab） platform is used to link distributed laboratories located at several universities together. Substructure technology is also used in the testing. The characteristics, resource sharing and collaborative work of NetSLab are described, and the results illustrate that use of the NetSLab is feasible for studying the dynamic performance of multi-span bridge structures.展开更多
In the AASHTO Guide Specifications for Seismic Bridge Design Provisions,ductile diaphragms are identified as Permissible Earthquake-Resisting Elements（EREs）,designed to help resist seismic loads applied in the trans...In the AASHTO Guide Specifications for Seismic Bridge Design Provisions,ductile diaphragms are identified as Permissible Earthquake-Resisting Elements（EREs）,designed to help resist seismic loads applied in the transverse direction of bridges.When adding longitudinal ductile diaphragms,a bidirectional ductile diaphragm system is created that can address seismic excitations acting along both the bridge’s longitudinal and transverse axes.This paper investigates bidirectional ductile diaphragms with Buckling Restrained Braces（BRBs）in straight multi-span bridge with simply supported floating spans.The flexibility of the substructures in the transverse and longitudinal direction of the bridge is considered.Design procedures for the bidirectional ductile diaphragms are first proposed.An analytical model of the example bridge with bidirectional ductile diaphragms,designed based on the proposed methodology,is then built in SAP2000.Pushover and nonlinear time history analyses are performed on the bridge model,and corresponding results are presented.The effect of changing the longitudinal stiffness of the bidirectional ductile diaphragms in the end spans connecting to the abutment is also investigated,in order to better understand the impact on the bridge’s dynamic performance.展开更多
Seismic pounding between adjacent frames in multiple-frame bridges and girder ends in multi-span simply supported bridges has been commonly observed in several recent earthquakes.The consequences of pounding include d...Seismic pounding between adjacent frames in multiple-frame bridges and girder ends in multi-span simply supported bridges has been commonly observed in several recent earthquakes.The consequences of pounding include damage to piers,abutments,shear keys,bearings and restrainers,and possible collapse of deck spans.This paper investigates pounding in bridges from an analytical perspective.A simplified nonlinear model of a multiple-frame bridge is developed including the effects of inelastic frame action and nonlinear hinge behavior,to study the seismic response to longitudinal ground motion.Pounding is implemented using the contact force-based Kelvin model,as well as the momentum-based stereomechanical approach.Parameter studies are conducted to determine the effects of frame period ratio,column hysteretic behavior,energy dissipation during impact and near source ground motions on the pounding response of the bridge.The results indicate that pounding is most critical for highly out-of-phase frames and is not significant for frame period ratios greater than 0.7.Impact models without energy dissipation overestimate the displacement and acceleration amplifications due to impact,especially for elastic behavior of the frames.Representation of stiffness degradation in bridge columns is essential in capturing the accurate response of pounding frames subjected to far field ground motion.Finally,it is shown that strength degradation and pounding can result in significant damage to the stiffer frames of the bridge when subjected to large acceleration pulses from near field ground motion records.展开更多
The nonlinear analysis of pounding between bridge deck segments subjected to multi-support excitations and multi-dimensional earthquake motion was performed.A novel bottom rigid element(BRE)method of the current displ...The nonlinear analysis of pounding between bridge deck segments subjected to multi-support excitations and multi-dimensional earthquake motion was performed.A novel bottom rigid element(BRE)method of the current displacement input model for structural seismic analysis under the multi-support excitations was used to calculate structural dynamic response.In the analysis,pounding between adjacent deck segments was considered.The seismic response of a multi-span bridge subjected to the multi-support excitation,considering not only the traveling-wave effect and partial coherence effect,but also the seismic non-stationary characteristics of multi-support earthquake motion,was simulated using finite element method(FEM).Meanwhile,the seismic response of the bridge under uniform earthquake was also analyzed.Finally,comparative analysis was conducted and some calculation results were shown for pounding effect,under multi-dimensional and multi-support earthquake motion,when performing seismic response analysis of multi-span bridge.Compared with the case of uniform/multi-support/multi-support and multi-dimensional earthquake input,the maximum values of pounding force in the case of multi-support and multi-dimensional earthquake input increase by about 5 8 times;the absolute value of bottom moment and shear force of piers increase by about50%600%and 23.1%900%,respectively.A conclusion can be given that it is very necessary to consider the pounding effect under multi-dimensional and multi-support earthquake motion while performing seismic response analysis of multi-span bridge.展开更多
In the Kigongo area of Mwanza Region,northwest Tanzania,fishmonger Neema Aisha remembers how the morning’s fresh catch would sour while she queued for the ferry,putting her business at risk.
The goal of this paper is to investigate the long-time dynamics of solutions to a Kirchhoff type suspension bridge equation with nonlinear damping and memory term.For this problem we establish the well-posedness and e...The goal of this paper is to investigate the long-time dynamics of solutions to a Kirchhoff type suspension bridge equation with nonlinear damping and memory term.For this problem we establish the well-posedness and existence of uniform attractor under some suitable assumptions on the nonlinear term g(u),the nonlinear damping f(u_(t))and the external force h(x,t).Specifically,the asymptotic compactness of the semigroup is verified by the energy reconstruction method.展开更多
With people living longer,the societal impact of age-related cognitive decline is becoming more pronounced(Crimmins,2015).Thus,it is increasingly important to comprehend the cognitive shifts linked to aging-whether th...With people living longer,the societal impact of age-related cognitive decline is becoming more pronounced(Crimmins,2015).Thus,it is increasingly important to comprehend the cognitive shifts linked to aging-whether they are physiological or pathological.展开更多
The fiber optic sensing technology provides data support in structural health monitoring of the macro facilities,including design,construction,and maintenance of bridges,tunnels,ports and other infrastructures.In this...The fiber optic sensing technology provides data support in structural health monitoring of the macro facilities,including design,construction,and maintenance of bridges,tunnels,ports and other infrastructures.In this paper,a distributed vibration sensing system is proved to be responsive to a single touch over a 1.8-m-long equivalent fiber segment,covering a vibration frequency from 5 Hz to 25 kHz.The sensing fiber was arranged as an S type layout on the bridge to recognize the standing state,windblown disturbance,and walking vibration.Moreover,the knocking and climbing events are recognized fiber laying spinning lines and hanging on the fences,respectively.The demonstration shows an accurate positioning and sensitive vibration monitoring applied on the automated three-dimensional(3D) printed bridge,which is applicable to all kinds of 3D printed facilities as intelligent sensory neuro-networks.展开更多
The purpose of this study is to analyze the application of ultrasonic non-destructive testing technology in bridge engineering.During the research phase,based on literature collection and reading,as well as the analys...The purpose of this study is to analyze the application of ultrasonic non-destructive testing technology in bridge engineering.During the research phase,based on literature collection and reading,as well as the analysis of bridge inspection materials,the principle of ultrasonic non-destructive testing technology and its adaptability to bridge engineering are elaborated.Subsequently,starting from the preparation work before inspection until damage assessment,the entire process of ultrasonic non-destructive testing is studied,and finally,a technical system of ultrasonic non-destructive testing for bridge engineering that runs through the entire process is formed.It is hoped that this article can provide technical reference value for relevant units in China,and promote the high-quality development of China’s bridge engineering from a macro perspective.展开更多
Purpose–The bridge expansion joint(BEJ)is a key device for accommodating spatial displacement at the beam end,and for providing vertical support for running trains passing over the gap between the main bridge and the...Purpose–The bridge expansion joint(BEJ)is a key device for accommodating spatial displacement at the beam end,and for providing vertical support for running trains passing over the gap between the main bridge and the approach bridge.For long-span railway bridges,it must also be coordinated with rail expansion joint(REJ),which is necessary to accommodate the expansion and contraction of,and reducing longitudinal stress in,the rails.The main aim of this study is to present analysis of recent developments in the research and application of BEJs in high-speed railway(HSR)long-span bridges in China,and to propose a performance-based integral design method for BEJs used with REJs,from both theoretical and engineering perspectives.Design/methodology/approach–The study first presents a summary on the application and maintenance of BEJs in HSR long-span bridges in China representing an overview of their state of development.Results of a survey of typical BEJ faults were analyzed,and field testing was conducted on a railway cable-stayed bridge in order to obtain information on the major mechanical characteristics of its BEJ under train load.Based on the above,a performance-based integral design method for BEJs with maximum expansion range 1600 mm(±800 mm),was proposed,covering all stages from overall conceptual design to consideration of detailed structural design issues.The performance of the novel BEJ design thus derived was then verified via theoretical analysis under different scenarios,full-scale model testing,and field testing and commissioning.Findings–Two major types of BEJs,deck-type and through-type,are used in HSR long-span bridges in China.Typical BEJ faults were found to mainly include skewness of steel sleepers at the bridge gap,abnormally large longitudinal frictional resistance,and flexural deformation of the scissor mechanisms.These faults influence BEJ functioning,and thus adversely affect track quality and train running performance at the beam end.Due to their simple and integral structure,deck-type BEJs with expansion range 1200 mm(±600 mm)or less have been favored as a solution offering improved operational conditions,and have emerged as a standard design.However,when the expansion range exceeds the above-mentioned value,special design work becomes necessary.Therefore,based on engineering practice,a performance-based integral design method for BEJs used with REJs was proposed,taking into account four major categories of performance requirements,i.e.,mechanical characteristics,train running quality,durability and insulation performance.Overall BEJ design must mainly consider component strength and the overall stiffness of BEJ;the latter factor in particular has a decisive influence on train running performance at the beam end.Detailed BEJ structural design must stress minimization of the frictional resistance of its sliding surface.The static and dynamic performance of the newlydesigned BEJ with expansion range 1600 mm have been confirmed to be satisfactory,via numerical simulation,full-scale model testing,and field testing and commissioning.Originality/value–This research provides a broad overview of the status of BEJs with large expansion range in HSR long-span bridges in China,along with novel insights into their design.展开更多
The rust layer is a critical factor in determining the corrosion resistance performance of weathering bridge steel.Understanding the evolution mechanism of this rust layer is fundamental for the design and optimizatio...The rust layer is a critical factor in determining the corrosion resistance performance of weathering bridge steel.Understanding the evolution mechanism of this rust layer is fundamental for the design and optimization of such steel.This study investigates the evolu-tion of the rust layer on high-Cr-content weathering bridge steel,using an atmospheric corrosion monitoring(ACM)sensor and big data mining techniques in a simulated tropical marine atmosphere.Results reveal that the protective properties of the rust layer follow a peri-odic pattern of“ascending–constant”rather than a continuous ascending.Correlation analysis indicates that this phenomenon is attributed to the introduction of Cr,which promotes the formation of FeCr_(2)O_(4) in the rust layer.FeCr_(2)O_(4) helps prevent chloride ions from penetrating the rust layer,exerting a protective effect.These findings provide a strong scientific foundation for the design and improvement of new high-Cr-content weathering bridge steels.展开更多
Synergy strategy of photocatalysts and polymer resins are promising technology for marine antifouling.However,it is still a main challenge to obtain a green,safe,and efficient antifouling coatings.Herein,carbon(graphe...Synergy strategy of photocatalysts and polymer resins are promising technology for marine antifouling.However,it is still a main challenge to obtain a green,safe,and efficient antifouling coatings.Herein,carbon(graphene or CNT)modified Ti O_(2)photocatalyst was synthesized via hydrothermal and annealing process and has successfully applied in acrylate fluoroboron polymer(ABFP)composite coating.Morphology and chemical composition were detailed characterized.The graphene or CNT acted as a bridge with supplemental spatial structures(petal gaps,entanglement)and new functional groups(C-O,C-Ti-O,etc.)on Ti O_(2)particle.Carbon nanotube(CNT)modified TiO_(2)-ABFP coatings(BTCP)achieved excellent antibacterial and anti-diatom adhesion rate of 89.3%-96.70%and 99.00%-99.50%,which was 1.84-4.94-fold more than that of the single ABFP.CNT or graphene served as electronic bridges was considered as the crucial mechanism,which significantly improved the light absorption range and capacity,conductivity,and photoelectric response of Ti O_(2),and further accelerated the generation and transfer of free radicals to the surface of BTCP or FTGP.Moreover,the improvement of catalyst activity synergizes with the smooth surface,hydrophilicity,and slow hydrolysis of composite coatings,achieved long-term and efficient antifouling performance.This work provides a new insight into the modification of Ti O_(2)and antifouling mechanism of polymer coating.展开更多
To overcome the limitations of low efficiency and reliance on manual processes in the measurement of geometric parameters for bridge prefabricated components,a method based on deep learning and computer vision is deve...To overcome the limitations of low efficiency and reliance on manual processes in the measurement of geometric parameters for bridge prefabricated components,a method based on deep learning and computer vision is developed to identify the geometric parameters.The study utilizes a common precast element for highway bridges as the research subject.First,edge feature points of the bridge component section are extracted from images of the precast component cross-sections by combining the Canny operator with mathematical morphology.Subsequently,a deep learning model is developed to identify the geometric parameters of the precast components using the extracted edge coordinates from the images as input and the predefined control parameters of the bridge section as output.A dataset is generated by varying the control parameters and noise levels for model training.Finally,field measurements are conducted to validate the accuracy of the developed method.The results indicate that the developed method effectively identifies the geometric parameters of bridge precast components,with an error rate maintained within 5%.展开更多
Main cable displacement-controlled devices(DCDs)are key components for coordinating the vertical deformation of the main cable and main girder in the side span of continuous suspension bridges.To reveal the mechanical...Main cable displacement-controlled devices(DCDs)are key components for coordinating the vertical deformation of the main cable and main girder in the side span of continuous suspension bridges.To reveal the mechanical action mechanisms of DCD on bridge structures,a three-span continuous suspension bridge was taken as the engineering background in this study.The influence of different forms of DCD on the internal force and displacement of the components in the side span of the bridge and the structural dynamic characteristics were explored through numerical simulations.The results showed that the lack of DCD caused the main cable and main girder to have large vertical displacements.The stresses of other components were redistributed,and the safety factor of the suspenders at the side span was greatly reduced.The setting of DCD improved the vertical stiffness of the structure.The rigid DCD had larger internal forces,but its control effect on the internal forces at the side span was slightly better than that of the flexible DCD.Both forms of DCD effectively coordinated the deformation of the main cable and main girder and the stress distribution of components in the side span area.The choice of DCD form depends on the topographic factors of bridge sites and the design requirements of related components at the side span.展开更多
Past earthquakes have revealed that topographic features have significant impacts on the characteristics of ground motions,which may cause the amplification and de-amplification of input seismic waves.The topographic ...Past earthquakes have revealed that topographic features have significant impacts on the characteristics of ground motions,which may cause the amplification and de-amplification of input seismic waves.The topographic effect with the assumption of plane seismic waves on the seismic responses of bridges has been investigated in the existing literature;however,the influence of near-source topographic effects has not been thoroughly understood.The objective of this study is to numerically explore the near-source topographic effects on the seismic behaviors of an existing railway bridge crossing a symmetrical V-shaped canyon.The influence of the source of incident waves is estimated.Numerical results demonstrate that the topographic effects can noticeably amplify the seismic responses of the bridge.Compared to the bridge without crossing a canyon,the peak displacements of the girder,pier,and bearing in the case of the canyon crossing bridge increase by 15.2%,2.9%−14.5%,and 24.2%−229.6%,respectively.The piers at the illuminated side of the canyon experience larger seismic responses compared to the piers at the shaded side of the canyon due to the unequal motion amplitudes at each support.As the source-to-canyon distance increases,the seismic responses of the piers show an increasing trend.展开更多
The girder end restraint devices such as bearings and dampers on long span suspension bridge will deteriorate over time.However,it is difficult to achieve the quantitative assessment of the performance of the restrain...The girder end restraint devices such as bearings and dampers on long span suspension bridge will deteriorate over time.However,it is difficult to achieve the quantitative assessment of the performance of the restraint device through existing detection methods in actual inspections,making it difficult to obtain the impact of changes in the performance of the restraint device on the bridge structure.In this paper,a random vehicle load model is firstly established based on the WIM data of Jiangyin Bridge,and the displacement of girder end under the actual traffic flow is simulated by using finite element dynamic time history analysis.On this basis,according to the performance test data of the bearings and dampers,the performance degradation laws of the above two restraint devices are summarized,and the performance degradation process of the two restraint devices and the effects of different restraint parameters on the bridge structure are simulated.The results show that the performance degradation of the damper will significantly reduce the damping force at low speed,resulting in a significant increase in the cumulative displacement of the girder end;in the presence of longitudinal dampers,the increase in the friction coefficient caused by the deterioration of the bearing sliding plate has little effect on the cumulative displacement,but excessive wear of the bearing sliding plate adversely affects the structural dynamic performance.展开更多
Multi-pylon multi-span suspension bridge is a new type super flexible structure system, and the rigidity design of middle pylon is one of the main difficult technical issues. Due to the requirements of longitudinal ri...Multi-pylon multi-span suspension bridge is a new type super flexible structure system, and the rigidity design of middle pylon is one of the main difficult technical issues. Due to the requirements of longitudinal rigidity, the structural form and the corresponding foundation type of middle pylon are different from those of the ordinary steel pylon, and the complicated dynamic characteristics make the calculation quite difficult. In this article, exploration has been made in selection of similarity ratio and model materials, section simulation, restriction conditions simulation, fixing of mass blocks, fabrication scheme and testing method by taking into account different construction and working conditions such as restriction conditions and working environment of a three-pylon suspension bridge, to conduct the test experimental design of the dynamic behavior of the middle pylon, with the purpose to reveal its dynamic characteristics and make comparison and analysis with theoretical assumptions, to provide basis for anti-wind and anti-seismic design and reference for the design and research of three-pylon two-span suspension bridges in the future.展开更多
The Beipanjiang Bridge sits over 565 meters above the Beipan River Valley nestled between two very steep cliffs,making it the world's highest bridge.Also known as the Duge Bridge or“China's Impossible Enginee...The Beipanjiang Bridge sits over 565 meters above the Beipan River Valley nestled between two very steep cliffs,making it the world's highest bridge.Also known as the Duge Bridge or“China's Impossible Engineering Feat”,the world's highest bridge may not look that impressive at first sight,but it is a testament to Chinese engineering and innovation.展开更多
Introduction The predominant characteristics of high-altitude climates include low air pressure,low humidity,and large diurnal temperature fluctuations.In practical engineering scenarios in high-altitude regions,many ...Introduction The predominant characteristics of high-altitude climates include low air pressure,low humidity,and large diurnal temperature fluctuations.In practical engineering scenarios in high-altitude regions,many pier surface cracks only appear several months after erection,and cyclic thermal stress is identified as the main trigger for such cracking.The thermal stress in concrete structures has been investigated for decades but remains incompletely understood.Structural engineers typically regard concrete as an isotropic material and calculate the thermal stress using code-specified coefficients of thermal expansion(CTEs)along with temperature conditions and constraints.Because the CTE of hardened cement paste is more than twice that of many aggregates,reducing the CTE of coarse aggregates can further exacerbate the thermal deformation incompatibility between the coarse aggregate and mortar matrix.In this paper,a comprehensive thermal-elastic mechanics model for pier concrete was developed to analysis the temperature-induced surface stress.Methods A series of mechanical and thermophysical tests were conducted on the diorite aggregate,ITZ cement paste,and mortar,and concrete.A test pier was constructed on open ground near the Yarlung Zangbo River at an altitude of 3800 m.The pier had a diameter of 1.8 m and height of 2 m.Temperature sensors were embedded in the cross-section at a height of 1 m,positioned along the southnorth and east-west directions.The embedding depths(distances from the pier surface)were 0,1.5,3,4.5,6,7.5,9,12,15,20,25,30,35,40,50,60,70,80 cm,and 90 cm.A model of the bridge pier concrete for surface-level analysis was constructed.The model consists of a concrete unit formed as a sphere-shell-shell composite,including the aggregate,ITZ,and mortar layers,embedded in the surface layer of a bridge pier.Outside this unit,the pier concrete was treated as an isotropic,homogeneous elastic material.The real-time internal temperature fields of high-altitude concrete bridge piers,measured on-site,were incorporated into the model.By applying thermoelastic mechanics theory and finite element solutions for plane strain problems,the three-dimensional thermal stresses on the surface layer of high-altitude bridge piers were analyzed Results and discussion During the experimental period,the lowest and highest temperatures on the bridge pier in the high-altitude region were 9.6 ℃ and 42.6 ℃,respectively.These occurred before sunrise and sunset on sunny days,respectively,corresponding to the local maximum temperature gradients during the surface heating and cooling stages,as well as the maximum temperature difference between the surface and center during these stages.The thermal stress on the pier concrete surface was obtained by superimposing the stresses caused by the uneven distribution of the internal temperature field and those caused by the incompatible thermal deformation among the different components in the surface concrete Before the erection of the upper structures,the absolute values of the tangential and vertical stresses were the same;therefore,only one curve was observed.From 22:00 to 8:00,the pier concrete surface was in tension,whereas from 11:00 to 22:00,the pier concrete surface was in compression.The surface of the pier concrete was subjected to biaxial forces of equal magnitude with a maximum compressive stress of 12.52 MPa and maximum tensile stress of 2.15 MPa,respectively at 18:00 and 8:00.According to the fatigue equation,the concrete was predicted to crack after 21 d of temperature cycling.Moreover,if humidity-induced stress is added on top of this,the tensile stress may approach or even exceed the concrete's tensile strength,thereby posing a significant risk of cracking.After the erection of upper structures,the tangential and vertical stresses no longer coincide because the upper structures have been erected.The curve of the tangential stress is unchanged,whereas the curve of the vertical stress is translated downwards by 1.57 MPa due to the structural deadweight.Therefore,the maximum tangential compressive stress remained 12.52 MPa,whereas the maximum vertical compressive stress increased to 14.09 MPa.Additionally,the maximum tangential tensile stress was 2.15 MPa,and the maximum vertical tensile stress was 0.58 MPa.According to Appendix C of GB/T 50010 and the fatigue equation,stresses are unlikely to cause cracking of the pier concrete surface.Although a higher CTE of the coarse aggregate slightly increased the maximum compressive stress,the differences among the three groups of concrete were minimal and could be ignored.Specifically,the maximum compressive stresses on the pier concrete surface were 12.54,12.45 MPa,and 12.56 MPa when using diorite,limestone,and basalt,respectively.By contrast,a lower CTE of the coarse aggregate results in a greater maximum tensile stress on the pier concrete surface.For example,when using limestone,which has a low CTE,the maximum tensile stress on the pier concrete surface is 2.28 MPa,compared to 2.17 MPa when using diorite and 2.14 MPa when using basalt.The finite element simulation results indicated that the maximum compressive stress on the pier concrete surface was 11.72 MPa,whereas the maximum tensile stress was 2.10 MPa.These results are approximately consistent with the theoretical calculations.This consistency provides mutual verification.Conclusions Surface cracking in pier concrete occurs predominantly before the erection of upper structures.Under sunny conditions,the orthogonal decomposition of the superficial stress revealed that the maximum compressive stress during the day was approximately 12.52 MPa,whereas the maximum tensile stress was approximately 2.15 MPa.This tensile stress approached the tensile strength of the C35 concrete under biaxial tension.The risk of cracking increased significantly when humidity-induced stress was considered.After the erection of upper structures,the maximum tangential tensile stress on the pier surface remained at 2.15 MPa while the maximum vertical stress decreased to 0.58 MPa,both of which are well below the tensile strength of C35 concrete under biaxial tension.Although the use of coarse aggregates with a lower coefficient of thermal expansion reduced the tensile stress induced by temperature gradients,it increased the stress owing to material deformation incompatibility,leading to a slight increase in the maximum tensile stress on the pier concrete surface.展开更多
As Thailand and China mark the 50th anniversary of their diplomatic ties this year,most headlines will naturally focus on trade deals,railways,and strategic partnerships.But tucked behind the golden spires of Bangkok...As Thailand and China mark the 50th anniversary of their diplomatic ties this year,most headlines will naturally focus on trade deals,railways,and strategic partnerships.But tucked behind the golden spires of Bangkok’s Wat Po temple lies a quieter,gentler form of diplomacy—one that happens through kneading hands,respectful bows,and an ancient art passed down across generations.At the Wat Po Thai Traditional Medical School,headmaster Serat Tangtrongchitr sees Thai massage not only as a healing craft,but as a cultural bridge—one that connects people across borders,languages,and belief systems.“We don’t just teach massage,”Serat said,his voice calm but assured.“We teach a way of life.And when people from other cultures learn this with us—Chinese students included—they come to understand not just the techniques,but the heart of Thai culture.”展开更多
基金The Key Project of the Major Research Plan of Natural Science Foundation of China Under Grant No.90715036the Key Project of the Natural Science Foundation of China Under Grant No.50338020
文摘Modem dynamic tests such as networked collaborative pseudo-dynamic testing （PDT） provide new tools to study the dynamic performance of large and complex structures. In this paper, several networked collaborative PDT systems established in China and abroad are introduced, including a detailed description of the first networked collaborative platform that involved the construction of a standardized demonstration procedure for networked collaborative PDT. The example is a multi-span bridge with RC piers retrofitted by FRP, and a networked structural laboratory （NetSLab） platform is used to link distributed laboratories located at several universities together. Substructure technology is also used in the testing. The characteristics, resource sharing and collaborative work of NetSLab are described, and the results illustrate that use of the NetSLab is feasible for studying the dynamic performance of multi-span bridge structures.
文摘In the AASHTO Guide Specifications for Seismic Bridge Design Provisions,ductile diaphragms are identified as Permissible Earthquake-Resisting Elements（EREs）,designed to help resist seismic loads applied in the transverse direction of bridges.When adding longitudinal ductile diaphragms,a bidirectional ductile diaphragm system is created that can address seismic excitations acting along both the bridge’s longitudinal and transverse axes.This paper investigates bidirectional ductile diaphragms with Buckling Restrained Braces（BRBs）in straight multi-span bridge with simply supported floating spans.The flexibility of the substructures in the transverse and longitudinal direction of the bridge is considered.Design procedures for the bidirectional ductile diaphragms are first proposed.An analytical model of the example bridge with bidirectional ductile diaphragms,designed based on the proposed methodology,is then built in SAP2000.Pushover and nonlinear time history analyses are performed on the bridge model,and corresponding results are presented.The effect of changing the longitudinal stiffness of the bidirectional ductile diaphragms in the end spans connecting to the abutment is also investigated,in order to better understand the impact on the bridge’s dynamic performance.
基金Earthquake Engineering Research Centers Program of the National Science Foundation Under Award Number EEC-9701785(Mid-America Earthquake Center)
文摘Seismic pounding between adjacent frames in multiple-frame bridges and girder ends in multi-span simply supported bridges has been commonly observed in several recent earthquakes.The consequences of pounding include damage to piers,abutments,shear keys,bearings and restrainers,and possible collapse of deck spans.This paper investigates pounding in bridges from an analytical perspective.A simplified nonlinear model of a multiple-frame bridge is developed including the effects of inelastic frame action and nonlinear hinge behavior,to study the seismic response to longitudinal ground motion.Pounding is implemented using the contact force-based Kelvin model,as well as the momentum-based stereomechanical approach.Parameter studies are conducted to determine the effects of frame period ratio,column hysteretic behavior,energy dissipation during impact and near source ground motions on the pounding response of the bridge.The results indicate that pounding is most critical for highly out-of-phase frames and is not significant for frame period ratios greater than 0.7.Impact models without energy dissipation overestimate the displacement and acceleration amplifications due to impact,especially for elastic behavior of the frames.Representation of stiffness degradation in bridge columns is essential in capturing the accurate response of pounding frames subjected to far field ground motion.Finally,it is shown that strength degradation and pounding can result in significant damage to the stiffer frames of the bridge when subjected to large acceleration pulses from near field ground motion records.
基金Project(51078242)supported by the National Natural Science Foundation of China
文摘The nonlinear analysis of pounding between bridge deck segments subjected to multi-support excitations and multi-dimensional earthquake motion was performed.A novel bottom rigid element(BRE)method of the current displacement input model for structural seismic analysis under the multi-support excitations was used to calculate structural dynamic response.In the analysis,pounding between adjacent deck segments was considered.The seismic response of a multi-span bridge subjected to the multi-support excitation,considering not only the traveling-wave effect and partial coherence effect,but also the seismic non-stationary characteristics of multi-support earthquake motion,was simulated using finite element method(FEM).Meanwhile,the seismic response of the bridge under uniform earthquake was also analyzed.Finally,comparative analysis was conducted and some calculation results were shown for pounding effect,under multi-dimensional and multi-support earthquake motion,when performing seismic response analysis of multi-span bridge.Compared with the case of uniform/multi-support/multi-support and multi-dimensional earthquake input,the maximum values of pounding force in the case of multi-support and multi-dimensional earthquake input increase by about 5 8 times;the absolute value of bottom moment and shear force of piers increase by about50%600%and 23.1%900%,respectively.A conclusion can be given that it is very necessary to consider the pounding effect under multi-dimensional and multi-support earthquake motion while performing seismic response analysis of multi-span bridge.
文摘In the Kigongo area of Mwanza Region,northwest Tanzania,fishmonger Neema Aisha remembers how the morning’s fresh catch would sour while she queued for the ferry,putting her business at risk.
基金Supported by the National Natural Science Foundation of China(Grant Nos.11961059,1210502)the University Innovation Project of Gansu Province(Grant No.2023B-062)the Gansu Province Basic Research Innovation Group Project(Grant No.23JRRA684).
文摘The goal of this paper is to investigate the long-time dynamics of solutions to a Kirchhoff type suspension bridge equation with nonlinear damping and memory term.For this problem we establish the well-posedness and existence of uniform attractor under some suitable assumptions on the nonlinear term g(u),the nonlinear damping f(u_(t))and the external force h(x,t).Specifically,the asymptotic compactness of the semigroup is verified by the energy reconstruction method.
基金Clévio Nóbrega’s laboratory is funded by the Cure CSB projectthe Viljem Julijan Association for Children with Rare Diseases(Slovenia)+1 种基金the Algarve Biomedical Center Research Institute(ABC-Ri)funded by CRESC Algarve 2020(Operation Code:ALG-01-0145-FEDER-072586)(to CN)。
文摘With people living longer,the societal impact of age-related cognitive decline is becoming more pronounced(Crimmins,2015).Thus,it is increasingly important to comprehend the cognitive shifts linked to aging-whether they are physiological or pathological.
基金supported by the National Natural Science Foundation of China (No.6210031560)the Natural Science Foundation of Hebei Province (No.A2020202013)the Natural Science Foundation of Tianjin City (No.21JCQNJC00780)。
文摘The fiber optic sensing technology provides data support in structural health monitoring of the macro facilities,including design,construction,and maintenance of bridges,tunnels,ports and other infrastructures.In this paper,a distributed vibration sensing system is proved to be responsive to a single touch over a 1.8-m-long equivalent fiber segment,covering a vibration frequency from 5 Hz to 25 kHz.The sensing fiber was arranged as an S type layout on the bridge to recognize the standing state,windblown disturbance,and walking vibration.Moreover,the knocking and climbing events are recognized fiber laying spinning lines and hanging on the fences,respectively.The demonstration shows an accurate positioning and sensitive vibration monitoring applied on the automated three-dimensional(3D) printed bridge,which is applicable to all kinds of 3D printed facilities as intelligent sensory neuro-networks.
文摘The purpose of this study is to analyze the application of ultrasonic non-destructive testing technology in bridge engineering.During the research phase,based on literature collection and reading,as well as the analysis of bridge inspection materials,the principle of ultrasonic non-destructive testing technology and its adaptability to bridge engineering are elaborated.Subsequently,starting from the preparation work before inspection until damage assessment,the entire process of ultrasonic non-destructive testing is studied,and finally,a technical system of ultrasonic non-destructive testing for bridge engineering that runs through the entire process is formed.It is hoped that this article can provide technical reference value for relevant units in China,and promote the high-quality development of China’s bridge engineering from a macro perspective.
基金National Key R&D Program of China(2022YFB2602900)R&D Fund Project of China Academy of Railway Sciences Corporation Limited(2021YJ084)+2 种基金Project of Science and Technology R&D Program of China Railway(2016G002-K)R&D Fund Project of China Railway Major Bridge Reconnaissance&Design Institute Co.,Ltd.(2021)R&D Fund Project of China Railway Shanghai Group(2021141).
文摘Purpose–The bridge expansion joint(BEJ)is a key device for accommodating spatial displacement at the beam end,and for providing vertical support for running trains passing over the gap between the main bridge and the approach bridge.For long-span railway bridges,it must also be coordinated with rail expansion joint(REJ),which is necessary to accommodate the expansion and contraction of,and reducing longitudinal stress in,the rails.The main aim of this study is to present analysis of recent developments in the research and application of BEJs in high-speed railway(HSR)long-span bridges in China,and to propose a performance-based integral design method for BEJs used with REJs,from both theoretical and engineering perspectives.Design/methodology/approach–The study first presents a summary on the application and maintenance of BEJs in HSR long-span bridges in China representing an overview of their state of development.Results of a survey of typical BEJ faults were analyzed,and field testing was conducted on a railway cable-stayed bridge in order to obtain information on the major mechanical characteristics of its BEJ under train load.Based on the above,a performance-based integral design method for BEJs with maximum expansion range 1600 mm(±800 mm),was proposed,covering all stages from overall conceptual design to consideration of detailed structural design issues.The performance of the novel BEJ design thus derived was then verified via theoretical analysis under different scenarios,full-scale model testing,and field testing and commissioning.Findings–Two major types of BEJs,deck-type and through-type,are used in HSR long-span bridges in China.Typical BEJ faults were found to mainly include skewness of steel sleepers at the bridge gap,abnormally large longitudinal frictional resistance,and flexural deformation of the scissor mechanisms.These faults influence BEJ functioning,and thus adversely affect track quality and train running performance at the beam end.Due to their simple and integral structure,deck-type BEJs with expansion range 1200 mm(±600 mm)or less have been favored as a solution offering improved operational conditions,and have emerged as a standard design.However,when the expansion range exceeds the above-mentioned value,special design work becomes necessary.Therefore,based on engineering practice,a performance-based integral design method for BEJs used with REJs was proposed,taking into account four major categories of performance requirements,i.e.,mechanical characteristics,train running quality,durability and insulation performance.Overall BEJ design must mainly consider component strength and the overall stiffness of BEJ;the latter factor in particular has a decisive influence on train running performance at the beam end.Detailed BEJ structural design must stress minimization of the frictional resistance of its sliding surface.The static and dynamic performance of the newlydesigned BEJ with expansion range 1600 mm have been confirmed to be satisfactory,via numerical simulation,full-scale model testing,and field testing and commissioning.Originality/value–This research provides a broad overview of the status of BEJs with large expansion range in HSR long-span bridges in China,along with novel insights into their design.
基金supported by the National Natural Science Foundation of China(No.52171063).
文摘The rust layer is a critical factor in determining the corrosion resistance performance of weathering bridge steel.Understanding the evolution mechanism of this rust layer is fundamental for the design and optimization of such steel.This study investigates the evolu-tion of the rust layer on high-Cr-content weathering bridge steel,using an atmospheric corrosion monitoring(ACM)sensor and big data mining techniques in a simulated tropical marine atmosphere.Results reveal that the protective properties of the rust layer follow a peri-odic pattern of“ascending–constant”rather than a continuous ascending.Correlation analysis indicates that this phenomenon is attributed to the introduction of Cr,which promotes the formation of FeCr_(2)O_(4) in the rust layer.FeCr_(2)O_(4) helps prevent chloride ions from penetrating the rust layer,exerting a protective effect.These findings provide a strong scientific foundation for the design and improvement of new high-Cr-content weathering bridge steels.
基金supported by the National Natural Science Foundation of China(Nos.42277315,22066009)the Scientific Research Startup Fund of Hainan University(Nos.XJ2300005916,kyqd(zr)22185)+1 种基金supported by Scientific Research Project of Hainan Higher Education Institutions(No.Hnky2023-9)Innovational Fund for Scientific and Technological Personnel of Hainan Province(No.KJRC2023C12)。
文摘Synergy strategy of photocatalysts and polymer resins are promising technology for marine antifouling.However,it is still a main challenge to obtain a green,safe,and efficient antifouling coatings.Herein,carbon(graphene or CNT)modified Ti O_(2)photocatalyst was synthesized via hydrothermal and annealing process and has successfully applied in acrylate fluoroboron polymer(ABFP)composite coating.Morphology and chemical composition were detailed characterized.The graphene or CNT acted as a bridge with supplemental spatial structures(petal gaps,entanglement)and new functional groups(C-O,C-Ti-O,etc.)on Ti O_(2)particle.Carbon nanotube(CNT)modified TiO_(2)-ABFP coatings(BTCP)achieved excellent antibacterial and anti-diatom adhesion rate of 89.3%-96.70%and 99.00%-99.50%,which was 1.84-4.94-fold more than that of the single ABFP.CNT or graphene served as electronic bridges was considered as the crucial mechanism,which significantly improved the light absorption range and capacity,conductivity,and photoelectric response of Ti O_(2),and further accelerated the generation and transfer of free radicals to the surface of BTCP or FTGP.Moreover,the improvement of catalyst activity synergizes with the smooth surface,hydrophilicity,and slow hydrolysis of composite coatings,achieved long-term and efficient antifouling performance.This work provides a new insight into the modification of Ti O_(2)and antifouling mechanism of polymer coating.
基金The National Natural Science Foundation of China(No.52338011,52378291)Young Elite Scientists Sponsorship Program by CAST(No.2022-2024QNRC0101).
文摘To overcome the limitations of low efficiency and reliance on manual processes in the measurement of geometric parameters for bridge prefabricated components,a method based on deep learning and computer vision is developed to identify the geometric parameters.The study utilizes a common precast element for highway bridges as the research subject.First,edge feature points of the bridge component section are extracted from images of the precast component cross-sections by combining the Canny operator with mathematical morphology.Subsequently,a deep learning model is developed to identify the geometric parameters of the precast components using the extracted edge coordinates from the images as input and the predefined control parameters of the bridge section as output.A dataset is generated by varying the control parameters and noise levels for model training.Finally,field measurements are conducted to validate the accuracy of the developed method.The results indicate that the developed method effectively identifies the geometric parameters of bridge precast components,with an error rate maintained within 5%.
基金The National Natural Science Foundation of China(No.52338011)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.SJCX23_0067).
文摘Main cable displacement-controlled devices(DCDs)are key components for coordinating the vertical deformation of the main cable and main girder in the side span of continuous suspension bridges.To reveal the mechanical action mechanisms of DCD on bridge structures,a three-span continuous suspension bridge was taken as the engineering background in this study.The influence of different forms of DCD on the internal force and displacement of the components in the side span of the bridge and the structural dynamic characteristics were explored through numerical simulations.The results showed that the lack of DCD caused the main cable and main girder to have large vertical displacements.The stresses of other components were redistributed,and the safety factor of the suspenders at the side span was greatly reduced.The setting of DCD improved the vertical stiffness of the structure.The rigid DCD had larger internal forces,but its control effect on the internal forces at the side span was slightly better than that of the flexible DCD.Both forms of DCD effectively coordinated the deformation of the main cable and main girder and the stress distribution of components in the side span area.The choice of DCD form depends on the topographic factors of bridge sites and the design requirements of related components at the side span.
基金Projects(51908123,51678140,U1934205)supported by the National Natural Science Foundation of ChinaProjects(BK20190370,BK20180383) supported by the Natural Science Foundation of Jiangsu Province,China+1 种基金Project(18KJA580005) supported by the Natural Science Foundation of Jiangsu Higher Education Institutions of ChinaProject(KYY2019096(19-21)) supported by the Science and Technology Research Plan of China Railway Eryuan Engineering Group Corporation。
文摘Past earthquakes have revealed that topographic features have significant impacts on the characteristics of ground motions,which may cause the amplification and de-amplification of input seismic waves.The topographic effect with the assumption of plane seismic waves on the seismic responses of bridges has been investigated in the existing literature;however,the influence of near-source topographic effects has not been thoroughly understood.The objective of this study is to numerically explore the near-source topographic effects on the seismic behaviors of an existing railway bridge crossing a symmetrical V-shaped canyon.The influence of the source of incident waves is estimated.Numerical results demonstrate that the topographic effects can noticeably amplify the seismic responses of the bridge.Compared to the bridge without crossing a canyon,the peak displacements of the girder,pier,and bearing in the case of the canyon crossing bridge increase by 15.2%,2.9%−14.5%,and 24.2%−229.6%,respectively.The piers at the illuminated side of the canyon experience larger seismic responses compared to the piers at the shaded side of the canyon due to the unequal motion amplitudes at each support.As the source-to-canyon distance increases,the seismic responses of the piers show an increasing trend.
基金supported by the National Key Research and Development Program of China(No.2022YFB3706704)the Academician Special Science Research Project of CCCC(No.YSZX-03-2022-01-B).
文摘The girder end restraint devices such as bearings and dampers on long span suspension bridge will deteriorate over time.However,it is difficult to achieve the quantitative assessment of the performance of the restraint device through existing detection methods in actual inspections,making it difficult to obtain the impact of changes in the performance of the restraint device on the bridge structure.In this paper,a random vehicle load model is firstly established based on the WIM data of Jiangyin Bridge,and the displacement of girder end under the actual traffic flow is simulated by using finite element dynamic time history analysis.On this basis,according to the performance test data of the bearings and dampers,the performance degradation laws of the above two restraint devices are summarized,and the performance degradation process of the two restraint devices and the effects of different restraint parameters on the bridge structure are simulated.The results show that the performance degradation of the damper will significantly reduce the damping force at low speed,resulting in a significant increase in the cumulative displacement of the girder end;in the presence of longitudinal dampers,the increase in the friction coefficient caused by the deterioration of the bearing sliding plate has little effect on the cumulative displacement,but excessive wear of the bearing sliding plate adversely affects the structural dynamic performance.
文摘Multi-pylon multi-span suspension bridge is a new type super flexible structure system, and the rigidity design of middle pylon is one of the main difficult technical issues. Due to the requirements of longitudinal rigidity, the structural form and the corresponding foundation type of middle pylon are different from those of the ordinary steel pylon, and the complicated dynamic characteristics make the calculation quite difficult. In this article, exploration has been made in selection of similarity ratio and model materials, section simulation, restriction conditions simulation, fixing of mass blocks, fabrication scheme and testing method by taking into account different construction and working conditions such as restriction conditions and working environment of a three-pylon suspension bridge, to conduct the test experimental design of the dynamic behavior of the middle pylon, with the purpose to reveal its dynamic characteristics and make comparison and analysis with theoretical assumptions, to provide basis for anti-wind and anti-seismic design and reference for the design and research of three-pylon two-span suspension bridges in the future.
文摘The Beipanjiang Bridge sits over 565 meters above the Beipan River Valley nestled between two very steep cliffs,making it the world's highest bridge.Also known as the Duge Bridge or“China's Impossible Engineering Feat”,the world's highest bridge may not look that impressive at first sight,but it is a testament to Chinese engineering and innovation.
文摘Introduction The predominant characteristics of high-altitude climates include low air pressure,low humidity,and large diurnal temperature fluctuations.In practical engineering scenarios in high-altitude regions,many pier surface cracks only appear several months after erection,and cyclic thermal stress is identified as the main trigger for such cracking.The thermal stress in concrete structures has been investigated for decades but remains incompletely understood.Structural engineers typically regard concrete as an isotropic material and calculate the thermal stress using code-specified coefficients of thermal expansion(CTEs)along with temperature conditions and constraints.Because the CTE of hardened cement paste is more than twice that of many aggregates,reducing the CTE of coarse aggregates can further exacerbate the thermal deformation incompatibility between the coarse aggregate and mortar matrix.In this paper,a comprehensive thermal-elastic mechanics model for pier concrete was developed to analysis the temperature-induced surface stress.Methods A series of mechanical and thermophysical tests were conducted on the diorite aggregate,ITZ cement paste,and mortar,and concrete.A test pier was constructed on open ground near the Yarlung Zangbo River at an altitude of 3800 m.The pier had a diameter of 1.8 m and height of 2 m.Temperature sensors were embedded in the cross-section at a height of 1 m,positioned along the southnorth and east-west directions.The embedding depths(distances from the pier surface)were 0,1.5,3,4.5,6,7.5,9,12,15,20,25,30,35,40,50,60,70,80 cm,and 90 cm.A model of the bridge pier concrete for surface-level analysis was constructed.The model consists of a concrete unit formed as a sphere-shell-shell composite,including the aggregate,ITZ,and mortar layers,embedded in the surface layer of a bridge pier.Outside this unit,the pier concrete was treated as an isotropic,homogeneous elastic material.The real-time internal temperature fields of high-altitude concrete bridge piers,measured on-site,were incorporated into the model.By applying thermoelastic mechanics theory and finite element solutions for plane strain problems,the three-dimensional thermal stresses on the surface layer of high-altitude bridge piers were analyzed Results and discussion During the experimental period,the lowest and highest temperatures on the bridge pier in the high-altitude region were 9.6 ℃ and 42.6 ℃,respectively.These occurred before sunrise and sunset on sunny days,respectively,corresponding to the local maximum temperature gradients during the surface heating and cooling stages,as well as the maximum temperature difference between the surface and center during these stages.The thermal stress on the pier concrete surface was obtained by superimposing the stresses caused by the uneven distribution of the internal temperature field and those caused by the incompatible thermal deformation among the different components in the surface concrete Before the erection of the upper structures,the absolute values of the tangential and vertical stresses were the same;therefore,only one curve was observed.From 22:00 to 8:00,the pier concrete surface was in tension,whereas from 11:00 to 22:00,the pier concrete surface was in compression.The surface of the pier concrete was subjected to biaxial forces of equal magnitude with a maximum compressive stress of 12.52 MPa and maximum tensile stress of 2.15 MPa,respectively at 18:00 and 8:00.According to the fatigue equation,the concrete was predicted to crack after 21 d of temperature cycling.Moreover,if humidity-induced stress is added on top of this,the tensile stress may approach or even exceed the concrete's tensile strength,thereby posing a significant risk of cracking.After the erection of upper structures,the tangential and vertical stresses no longer coincide because the upper structures have been erected.The curve of the tangential stress is unchanged,whereas the curve of the vertical stress is translated downwards by 1.57 MPa due to the structural deadweight.Therefore,the maximum tangential compressive stress remained 12.52 MPa,whereas the maximum vertical compressive stress increased to 14.09 MPa.Additionally,the maximum tangential tensile stress was 2.15 MPa,and the maximum vertical tensile stress was 0.58 MPa.According to Appendix C of GB/T 50010 and the fatigue equation,stresses are unlikely to cause cracking of the pier concrete surface.Although a higher CTE of the coarse aggregate slightly increased the maximum compressive stress,the differences among the three groups of concrete were minimal and could be ignored.Specifically,the maximum compressive stresses on the pier concrete surface were 12.54,12.45 MPa,and 12.56 MPa when using diorite,limestone,and basalt,respectively.By contrast,a lower CTE of the coarse aggregate results in a greater maximum tensile stress on the pier concrete surface.For example,when using limestone,which has a low CTE,the maximum tensile stress on the pier concrete surface is 2.28 MPa,compared to 2.17 MPa when using diorite and 2.14 MPa when using basalt.The finite element simulation results indicated that the maximum compressive stress on the pier concrete surface was 11.72 MPa,whereas the maximum tensile stress was 2.10 MPa.These results are approximately consistent with the theoretical calculations.This consistency provides mutual verification.Conclusions Surface cracking in pier concrete occurs predominantly before the erection of upper structures.Under sunny conditions,the orthogonal decomposition of the superficial stress revealed that the maximum compressive stress during the day was approximately 12.52 MPa,whereas the maximum tensile stress was approximately 2.15 MPa.This tensile stress approached the tensile strength of the C35 concrete under biaxial tension.The risk of cracking increased significantly when humidity-induced stress was considered.After the erection of upper structures,the maximum tangential tensile stress on the pier surface remained at 2.15 MPa while the maximum vertical stress decreased to 0.58 MPa,both of which are well below the tensile strength of C35 concrete under biaxial tension.Although the use of coarse aggregates with a lower coefficient of thermal expansion reduced the tensile stress induced by temperature gradients,it increased the stress owing to material deformation incompatibility,leading to a slight increase in the maximum tensile stress on the pier concrete surface.
文摘As Thailand and China mark the 50th anniversary of their diplomatic ties this year,most headlines will naturally focus on trade deals,railways,and strategic partnerships.But tucked behind the golden spires of Bangkok’s Wat Po temple lies a quieter,gentler form of diplomacy—one that happens through kneading hands,respectful bows,and an ancient art passed down across generations.At the Wat Po Thai Traditional Medical School,headmaster Serat Tangtrongchitr sees Thai massage not only as a healing craft,but as a cultural bridge—one that connects people across borders,languages,and belief systems.“We don’t just teach massage,”Serat said,his voice calm but assured.“We teach a way of life.And when people from other cultures learn this with us—Chinese students included—they come to understand not just the techniques,but the heart of Thai culture.”
