In order to effectively improve the horizontal bearing capacity of pile foundations,this study proposes post-expanded arm grouting technology and associated pile foundations.The horizontal bearing characteristic of th...In order to effectively improve the horizontal bearing capacity of pile foundations,this study proposes post-expanded arm grouting technology and associated pile foundations.The horizontal bearing characteristic of the post-expanded arm grouting pile was explored through model tests.The test results indicate that the post-expanded arm grouting pile can increase the contact area between the pile and soil,and can improve the strength of the soil.The horizontal bearing capacity of the post-expanded arm grouting pile was approximately 3 times that of the conventional pile.It also shows that the larger the plate diameter ratio or grouting volume,the higher the horizontal bearing capacity of the post-expanded arm grouting pile.The maximum bending moment of the post-expanded arm grouting pile was located at the pile plate,and the displacement zero point of the new pile was higher than that of the conventional pile.The soil resistance at the pile plate was significantly higher than that of conventional piles,indicating that the pile plate effectively enhances the soil resistance.The improved p-y curve model and horizontal bearing capacity calculation method for the post-expanded arm grouting pile were proposed by considering the pile plate diameter factor.This method was finally verified by experimental results.The results of this study can provide a reference for calculating the horizontal bearing capacity of the post-expanded arm grouting pile.展开更多
Simulation for stochastic wind field is very important in analyzing dynamic responses of large complex structures due to strong wind.The typical simulation method is the spectrum representation method (SRM),but the SR...Simulation for stochastic wind field is very important in analyzing dynamic responses of large complex structures due to strong wind.The typical simulation method is the spectrum representation method (SRM),but the SRM has drawbacks of inferior precision in lower frequency and slow calculating speed.In view of this,the modified Fourier spectrum method (MFSM) is introduced into the simulation of stochastic wind field in this paper.In this method,phase information of wind velocity time history is determined by cross power spectral density (CPSD) between adjacent points,and the wind velocity time history with time and space correlation is generated by iterative modification for CPSD considering auto power spectral density (APSD).Simulation of the wind field for a long-span bridge is undertaken to verify the effectiveness of the MFSM.Simulation results of the SRM and the MFSM are compared.It can be concluded that the MFSM is more accurate and has higher calculation speed than the SRM.展开更多
Alternate path(AP) method is the most widely used method for the progressive collapse analysis,and its application in frame structures has been well proved.However,the application of AP method for other structures,esp...Alternate path(AP) method is the most widely used method for the progressive collapse analysis,and its application in frame structures has been well proved.However,the application of AP method for other structures,especially for cable-stayed structures,should be further developed.The four analytical procedures,i.e.,linear static,nonlinear static,linear dynamic,and nonlinear dynamic were firstly improved by taking into account the initial state.Then a cable-stayed structure was studied using the four improved methods.Furthermore,the losses of both one cable and two cables were discussed.The results show that for static and dynamic analyses of the cable-stayed bridges,there is large difference between the results obtained from simulations starting with either a deformed or a nondeformed configuration at the time of cable loss.The static results are conservative in the vicinity of the ruptured cable,but the dynamic effect of the cable loss in the area farther away from the loss-cable cannot be considered.Moreover,the dynamic amplification factor of 2.0 is found to be a good estimate for static analysis procedures,since linear static and linear dynamic procedures yield approximately the same maximum vertical deflection.The results of the comprehensive evaluation of the cable failure show that the tread of the progressive failure of the cable-stayed bridges decreases when the location of the failed cables is closer to the pylon.展开更多
The buffeting performance of kilometer-level high-speed railway suspension bridges has a great impact on the smooth operation of high-speed trains.To investigate the buffeting performance of the structure significantl...The buffeting performance of kilometer-level high-speed railway suspension bridges has a great impact on the smooth operation of high-speed trains.To investigate the buffeting performance of the structure significantly different from traditional suspension bridges,the first long-span high-speed railway suspension bridge,Wufengshan Yangtze River Bridge(WYRB),is taken as a numerical example to demonstrate the effects of structural parameters and wind field parameters on the buffeting responses.Based on the design information,the spatial finite element model(FEM)of WYRB is established before testing its accuracy.The fluctuating wind fields are simulated via both classical and stochastic wave based spectral representation method(SRM).Finite element method is further taken to analyze the parametric sensitivity on wind induced buffeting responses in time domain.The results show that the vertical displacement is more sensitive to the changing dead load than the lateral and torsional ones.The larger stiffness of the main girder and the lower sag-to-span ratio are both helpful to reduce the buffeting responses.Wind spectrum and coherence function are key influencing factors to the responses so setting proper wind field parameters are essential in the wind-resistant design stage.The analytical results can provide references for wind resistance analysis and selection of structural and fluctuating wind field parameters for similar long-span high-speed railway suspension bridges.展开更多
Damage detection based on strain responses of vibration is highly attractive for monitoring long-span reticulated structures.However,there are a lot of structure members in reticulated structures and it is impossible ...Damage detection based on strain responses of vibration is highly attractive for monitoring long-span reticulated structures.However,there are a lot of structure members in reticulated structures and it is impossible to install strain sensors in each member.Therefore,how to locate and quantify damages with the incomplete mode shapes obtained from few strain sensors is a challenge topic.A new strategy,named incomplete strain mode damage detection（ISMDD） strategy,is proposed in this paper.In the strategy,the distribution of the strain sensors in the reticulated structures can be optimized through sensitive analysis on strain mode perturbation matrix,which can be obtained by perturbation theory.Mode assurance criterion（MAC） value is applied in damage location,and the members with relative large MAC values are defined as damage members.In addition,damage index obtained by solving the perturbation equation is used for damage quantification.Numerical analysis on a long-span reticulated structure,including damage location and quantification for single-and multi-member damages,detection for different damage quantity,the effect analysis of sensor quantity,are performed to verify the effectiveness of the proposed ISMDD strategy.It can be shown from the analysis that the ISMDD strategy is effective in damage location and quantification for both single-and multi-member damages.And the quantity of strain sensors has effect on damage location,but has no obvious influence on damage quantification.Additionally,the anti-noise pollution ability analysis of the ISMDD strategy is carried out,which shows that the ISMDD strategy has excellent anti-noise pollution ability for both single-and multi-damaged members.展开更多
Vibrations inherently generated by on-board disturbance sources degrade the performance of the instruments in an on-orbit spacecraft,which have stringent accuracy requirements.The Stewart platform enables both track-p...Vibrations inherently generated by on-board disturbance sources degrade the performance of the instruments in an on-orbit spacecraft,which have stringent accuracy requirements.The Stewart platform enables both track-positioning and vibration control.The strut of the Stewart platform is designed as a piezoelectric(PZT) element in series with a voice coil motor(VCM) element and a viscoelastic element.The track-positioning system uses a VCM as the main positioning control driver and a PZT as the positioning compensator.The vibration control system uses the characteristics of struts including active and passive control elements to attenuate the vibration.Simulation results indicate that the Stewart platform with the designed struts has good performance in tracking and vibration attenuation with different interference waves.展开更多
The mechanical properties of negative stiffness(NS)metamaterial could be customized and tuned in a wide range for various requirements,achieving programmable performances by the design from the aspect of structure and...The mechanical properties of negative stiffness(NS)metamaterial could be customized and tuned in a wide range for various requirements,achieving programmable performances by the design from the aspect of structure and material.This work investigates the viscoelastic NS metamaterial based on double curved beams using a combined approach of experiments,simulations,and analytical modeling with an emphasis on multistage loading bearing and programmable energy absorption ability.Numerical simulations are first implemented based on the finite element models of three types of metamaterial cells,which provide comparisons of load bearing and energy absorption properties.Further,the effects of geometric parameters of multistage metamaterial element and the mechanisms are analyzed.An analytical discrete model is then innovatively developed to provide straightforward understandings of the geometric effects and reveal the role of viscoelasticity by examining the instantaneous loading responses and rate-dependent behaviors.Experimentally,we fabricate the metamaterial samples using 3D-printing technique and perform compression tests to validate the properties based on different boundary conditions,loading rates and cyclic loading and unloading.Results of this work show the potential of wide programmable room for mechanical properties through structure and functional material design,such as multistage load bearing capacity and energy absorption ability.展开更多
In order to rapidly and accurately evaluate the mechanical properties of a novel origami-inspired tube structure with multiple parameter inputs,this study developed a method of designing origami-inspired braces based ...In order to rapidly and accurately evaluate the mechanical properties of a novel origami-inspired tube structure with multiple parameter inputs,this study developed a method of designing origami-inspired braces based on machine learning models.Four geometric parameters,i.e.,cross-sectional side length,plate thickness,crease weakening coefficient,and plane angles,were used to establish a mapping relationship with five mechanical parameters,including elastic stiffness,yield load,yield displacement,ultimate load,and ultimate displacement,all of which were calculated from load-displacement curves.Firstly,forward prediction models were trained and compared for single and multiple mechanical outputs.The parameter ranges were extended and refined to improve the predicted results by introducing the intrinsic mechanical relationships.Secondly,certain reverse prediction models were established to obtain the optimized design parameters.Finally,the design method of this study was verified in finite element methods.The design and analysis framework proposed in this study can be used to promote the application of other novel multi-parameter structures.展开更多
Triply periodic minimal surface(TPMS)structures with excellent properties of stable energy absorption,light weight,and high specific strength could potentially spark immense interest for novel and programmable functio...Triply periodic minimal surface(TPMS)structures with excellent properties of stable energy absorption,light weight,and high specific strength could potentially spark immense interest for novel and programmable functions by combining smart materials,e.g.shape memory polymers(SMPs).This work proposes TPMS lattices with hybrid configurations and materials that are composed of viscoelastic and shape-memory materials with the aim to bring temperature-dependent mechanical properties and additional dissipation mechanisms.Different configurations and diverse materials of polylactic acid(PLA),fiber-reinforced PLA,and polydimethylsiloxane(PDMS)are induced,generating five types of TPMS lattices,including(Schoen’s I-WP)IWP uniform lattice,IWP lattice with density gradient,hybrid configurations,hybrid materials,and filled PDMS,which are fabricated by 3D printing.The fracture morphologies and the distribution of carbon fibers are demonstrated via scanning electron microscopy with a focus on the influence of carbon fiber on shape-memory and mechanical properties.Shape recovery tests are conducted,which proves good shape memory properties and reusable capability of TPMS lattice.The combined methods of experiments and numerical simulation are adopted to evaluate mechanical properties,which presents multi-stage energy absorption ability and tunable vibration isolation performances associated with temperature and hybridization designs.This work can promote extensive research and provide substantial opportunities for TPMS lattices in the development of functional applications.展开更多
In the context of civil engineering applications,vibration responses are complex,exhibiting variations in time and space and often containing nonlinearity and uncertainties not considered during data collection.These ...In the context of civil engineering applications,vibration responses are complex,exhibiting variations in time and space and often containing nonlinearity and uncertainties not considered during data collection.These responses can also be contaminated by various sources,impacting damage identification processes.A significant challenge is how to effectively remove noise from these data to obtain reliable damage indicators that are unresponsive to noise and environmental factors.This study proposes a new denoising algorithm based on discrete wavelet transform(DWT)that addresses this issue.The suggested method offers a strategy for denoising using distinct thresholds for positive and negative coefficient values at each band and applying denoising process to both detail and trend components.The results prove the effectiveness of the technique and show that Bayes thresholding performs better than the other techniques in terms of the evaluated metrics.This suggests that Bayes thresholding is a more accurate and robust technique for thresholding compared to other common techniques.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.52208333 and 52378328)China Communications Construction Company Ltd.(Grant No.2023-ZJKJ-01).
文摘In order to effectively improve the horizontal bearing capacity of pile foundations,this study proposes post-expanded arm grouting technology and associated pile foundations.The horizontal bearing characteristic of the post-expanded arm grouting pile was explored through model tests.The test results indicate that the post-expanded arm grouting pile can increase the contact area between the pile and soil,and can improve the strength of the soil.The horizontal bearing capacity of the post-expanded arm grouting pile was approximately 3 times that of the conventional pile.It also shows that the larger the plate diameter ratio or grouting volume,the higher the horizontal bearing capacity of the post-expanded arm grouting pile.The maximum bending moment of the post-expanded arm grouting pile was located at the pile plate,and the displacement zero point of the new pile was higher than that of the conventional pile.The soil resistance at the pile plate was significantly higher than that of conventional piles,indicating that the pile plate effectively enhances the soil resistance.The improved p-y curve model and horizontal bearing capacity calculation method for the post-expanded arm grouting pile were proposed by considering the pile plate diameter factor.This method was finally verified by experimental results.The results of this study can provide a reference for calculating the horizontal bearing capacity of the post-expanded arm grouting pile.
基金Project supported by the National Natural Science Foundation of China (No.90915004)the Six Talents Peak in Jiangsu Province(No.2008178)the 333 High-Level Talent Training Project of Jiangsu Province,China
文摘Simulation for stochastic wind field is very important in analyzing dynamic responses of large complex structures due to strong wind.The typical simulation method is the spectrum representation method (SRM),but the SRM has drawbacks of inferior precision in lower frequency and slow calculating speed.In view of this,the modified Fourier spectrum method (MFSM) is introduced into the simulation of stochastic wind field in this paper.In this method,phase information of wind velocity time history is determined by cross power spectral density (CPSD) between adjacent points,and the wind velocity time history with time and space correlation is generated by iterative modification for CPSD considering auto power spectral density (APSD).Simulation of the wind field for a long-span bridge is undertaken to verify the effectiveness of the MFSM.Simulation results of the SRM and the MFSM are compared.It can be concluded that the MFSM is more accurate and has higher calculation speed than the SRM.
基金supported by the National Natural Science Foundation of China(No. 50478075)the Jiangsu "Six Top Talent" Program of China(No. 07-F-008)+1 种基金the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe Scientific Research Foundation of Graduate School of Southeast University (No. YBJJ0817),China
文摘Alternate path(AP) method is the most widely used method for the progressive collapse analysis,and its application in frame structures has been well proved.However,the application of AP method for other structures,especially for cable-stayed structures,should be further developed.The four analytical procedures,i.e.,linear static,nonlinear static,linear dynamic,and nonlinear dynamic were firstly improved by taking into account the initial state.Then a cable-stayed structure was studied using the four improved methods.Furthermore,the losses of both one cable and two cables were discussed.The results show that for static and dynamic analyses of the cable-stayed bridges,there is large difference between the results obtained from simulations starting with either a deformed or a nondeformed configuration at the time of cable loss.The static results are conservative in the vicinity of the ruptured cable,but the dynamic effect of the cable loss in the area farther away from the loss-cable cannot be considered.Moreover,the dynamic amplification factor of 2.0 is found to be a good estimate for static analysis procedures,since linear static and linear dynamic procedures yield approximately the same maximum vertical deflection.The results of the comprehensive evaluation of the cable failure show that the tread of the progressive failure of the cable-stayed bridges decreases when the location of the failed cables is closer to the pylon.
基金Projects(51908125,51978155) supported by the National Natural Science Foundation of ChinaProject(W03070080)supported by the National Ten Thousand Talent Program for Young Top-notch Talents,China+1 种基金Project(BK20190359)supported by the Natural Science Foundation of Jiangsu Province,ChinaProject(BE2018120) supported by the Key Research and Development Plan of Jiangsu Province,China。
文摘The buffeting performance of kilometer-level high-speed railway suspension bridges has a great impact on the smooth operation of high-speed trains.To investigate the buffeting performance of the structure significantly different from traditional suspension bridges,the first long-span high-speed railway suspension bridge,Wufengshan Yangtze River Bridge(WYRB),is taken as a numerical example to demonstrate the effects of structural parameters and wind field parameters on the buffeting responses.Based on the design information,the spatial finite element model(FEM)of WYRB is established before testing its accuracy.The fluctuating wind fields are simulated via both classical and stochastic wave based spectral representation method(SRM).Finite element method is further taken to analyze the parametric sensitivity on wind induced buffeting responses in time domain.The results show that the vertical displacement is more sensitive to the changing dead load than the lateral and torsional ones.The larger stiffness of the main girder and the lower sag-to-span ratio are both helpful to reduce the buffeting responses.Wind spectrum and coherence function are key influencing factors to the responses so setting proper wind field parameters are essential in the wind-resistant design stage.The analytical results can provide references for wind resistance analysis and selection of structural and fluctuating wind field parameters for similar long-span high-speed railway suspension bridges.
基金supported by the Six Kinds of Peak Talents in Jiangsu Provincethe Momentous Research Plan in National Natural Science Foundation of China (No. 90915004)+1 种基金333 High-level Talent Project in Jiangsu Provincethe National Key Technology R&D Program of China (No. 2011BAK02B03)
文摘Damage detection based on strain responses of vibration is highly attractive for monitoring long-span reticulated structures.However,there are a lot of structure members in reticulated structures and it is impossible to install strain sensors in each member.Therefore,how to locate and quantify damages with the incomplete mode shapes obtained from few strain sensors is a challenge topic.A new strategy,named incomplete strain mode damage detection（ISMDD） strategy,is proposed in this paper.In the strategy,the distribution of the strain sensors in the reticulated structures can be optimized through sensitive analysis on strain mode perturbation matrix,which can be obtained by perturbation theory.Mode assurance criterion（MAC） value is applied in damage location,and the members with relative large MAC values are defined as damage members.In addition,damage index obtained by solving the perturbation equation is used for damage quantification.Numerical analysis on a long-span reticulated structure,including damage location and quantification for single-and multi-member damages,detection for different damage quantity,the effect analysis of sensor quantity,are performed to verify the effectiveness of the proposed ISMDD strategy.It can be shown from the analysis that the ISMDD strategy is effective in damage location and quantification for both single-and multi-member damages.And the quantity of strain sensors has effect on damage location,but has no obvious influence on damage quantification.Additionally,the anti-noise pollution ability analysis of the ISMDD strategy is carried out,which shows that the ISMDD strategy has excellent anti-noise pollution ability for both single-and multi-damaged members.
基金Project supported by the NSAF of China(No.11176008)the Jiangsu Provincial 333 High Talent Program,and the Priority Academic Program Development of Jiangsu Higher Education Institutions, China
文摘Vibrations inherently generated by on-board disturbance sources degrade the performance of the instruments in an on-orbit spacecraft,which have stringent accuracy requirements.The Stewart platform enables both track-positioning and vibration control.The strut of the Stewart platform is designed as a piezoelectric(PZT) element in series with a voice coil motor(VCM) element and a viscoelastic element.The track-positioning system uses a VCM as the main positioning control driver and a PZT as the positioning compensator.The vibration control system uses the characteristics of struts including active and passive control elements to attenuate the vibration.Simulation results indicate that the Stewart platform with the designed struts has good performance in tracking and vibration attenuation with different interference waves.
基金supported by National Natural Science Foundation of China[12402155]Natural Science Foundation of Jiangsu Province[BK20241357]+2 种基金China Postdoctoral Science Foundation[2024T170138,2022M720721]the Science Foundation of National Key Laboratory of Science and Technology on Advanced Composites in Special Environments[JCKYS2023603C017]Jiangsu Funding Program for Excellent Postdoctoral Talent[No.2022ZB133].
文摘The mechanical properties of negative stiffness(NS)metamaterial could be customized and tuned in a wide range for various requirements,achieving programmable performances by the design from the aspect of structure and material.This work investigates the viscoelastic NS metamaterial based on double curved beams using a combined approach of experiments,simulations,and analytical modeling with an emphasis on multistage loading bearing and programmable energy absorption ability.Numerical simulations are first implemented based on the finite element models of three types of metamaterial cells,which provide comparisons of load bearing and energy absorption properties.Further,the effects of geometric parameters of multistage metamaterial element and the mechanisms are analyzed.An analytical discrete model is then innovatively developed to provide straightforward understandings of the geometric effects and reveal the role of viscoelasticity by examining the instantaneous loading responses and rate-dependent behaviors.Experimentally,we fabricate the metamaterial samples using 3D-printing technique and perform compression tests to validate the properties based on different boundary conditions,loading rates and cyclic loading and unloading.Results of this work show the potential of wide programmable room for mechanical properties through structure and functional material design,such as multistage load bearing capacity and energy absorption ability.
基金supported by the Jiangsu Provincial Department of Science and Technology Projects(BZ2022049 and BE2023801).
文摘In order to rapidly and accurately evaluate the mechanical properties of a novel origami-inspired tube structure with multiple parameter inputs,this study developed a method of designing origami-inspired braces based on machine learning models.Four geometric parameters,i.e.,cross-sectional side length,plate thickness,crease weakening coefficient,and plane angles,were used to establish a mapping relationship with five mechanical parameters,including elastic stiffness,yield load,yield displacement,ultimate load,and ultimate displacement,all of which were calculated from load-displacement curves.Firstly,forward prediction models were trained and compared for single and multiple mechanical outputs.The parameter ranges were extended and refined to improve the predicted results by introducing the intrinsic mechanical relationships.Secondly,certain reverse prediction models were established to obtain the optimized design parameters.Finally,the design method of this study was verified in finite element methods.The design and analysis framework proposed in this study can be used to promote the application of other novel multi-parameter structures.
基金supported by China Postdoctoral Science Foundation[2022M720721]Jiangsu Funding Program for Excellent Postdoctoral Talent[No.2022ZB133]+1 种基金the Science Foundation of National Key Laboratory of Science and Technology on Advanced Composites in Special Environments[JCKYS2023603C017]Natural Science Foundation of Jiangsu Province[BK20241357].
文摘Triply periodic minimal surface(TPMS)structures with excellent properties of stable energy absorption,light weight,and high specific strength could potentially spark immense interest for novel and programmable functions by combining smart materials,e.g.shape memory polymers(SMPs).This work proposes TPMS lattices with hybrid configurations and materials that are composed of viscoelastic and shape-memory materials with the aim to bring temperature-dependent mechanical properties and additional dissipation mechanisms.Different configurations and diverse materials of polylactic acid(PLA),fiber-reinforced PLA,and polydimethylsiloxane(PDMS)are induced,generating five types of TPMS lattices,including(Schoen’s I-WP)IWP uniform lattice,IWP lattice with density gradient,hybrid configurations,hybrid materials,and filled PDMS,which are fabricated by 3D printing.The fracture morphologies and the distribution of carbon fibers are demonstrated via scanning electron microscopy with a focus on the influence of carbon fiber on shape-memory and mechanical properties.Shape recovery tests are conducted,which proves good shape memory properties and reusable capability of TPMS lattice.The combined methods of experiments and numerical simulation are adopted to evaluate mechanical properties,which presents multi-stage energy absorption ability and tunable vibration isolation performances associated with temperature and hybridization designs.This work can promote extensive research and provide substantial opportunities for TPMS lattices in the development of functional applications.
基金Project supported by the National Science Foundation of USA(Nos.CNS-1035748 and CNS-1035773)the Program for Jiangsu Province 333 TalentsFunds for Excellent Doctoral Dissertation of Southeast University(No.YBJJ1207),China
基金support from National Natural Science Foundation of China(Grant No.52178115)the support provided by the International Institeu for Urban Systems Engineering at Southeast University.
文摘In the context of civil engineering applications,vibration responses are complex,exhibiting variations in time and space and often containing nonlinearity and uncertainties not considered during data collection.These responses can also be contaminated by various sources,impacting damage identification processes.A significant challenge is how to effectively remove noise from these data to obtain reliable damage indicators that are unresponsive to noise and environmental factors.This study proposes a new denoising algorithm based on discrete wavelet transform(DWT)that addresses this issue.The suggested method offers a strategy for denoising using distinct thresholds for positive and negative coefficient values at each band and applying denoising process to both detail and trend components.The results prove the effectiveness of the technique and show that Bayes thresholding performs better than the other techniques in terms of the evaluated metrics.This suggests that Bayes thresholding is a more accurate and robust technique for thresholding compared to other common techniques.
