Der-Wen Chang - Academia.edu (original) (raw)

Papers by Der-Wen Chang

Research paper thumbnail of An Approximate Analysis For Stress And Failure Potential Of Earth Slopes

Journal of Applied Science and Engineering, 1997

ABSTRACT An approximate analysis for stress and failure of earth slopes is proposed. To simulate ... more ABSTRACT An approximate analysis for stress and failure of earth slopes is proposed. To simulate the stress variation along the slope, elastic stress influence from the presumable uplift pressure acting on a level ground is superimposed to the stress state of the ground. Stability condition of the slope is verified by comparing the mobilized Mohr’s circle with the presumable failure envelope for material points along the slope. It is found that the stress variation obtained is similar to the previous solutions. The results are closest to other solutions in the case where the Poisson’s ratio is relatively large. The failure potential of the slope obtained is more conservative in comparison with the one from limit equilibrium analysis. The averaged stability of that critical plane from the proposed method is compatible with the conventional solution.

Research paper thumbnail of Length Influences on Lateral Performance of Barrette from Three-Dimensional Finite Element Analysis

DOAJ (DOAJ: Directory of Open Access Journals), Feb 1, 2022

The performance of a single barrette subjected to lateral load applied at its top is presented in... more The performance of a single barrette subjected to lateral load applied at its top is presented in this paper using three-dimensional finite element analyses based on Midas GTS program. Nonlinear behaviors of the barrettes buried in clayey and sandy soils were monitored using Mohr-Coulomb soil model. Performances of the barrettes with lateral loads applied in both longitudinal and transverse directions were examined. Displacements of the barrettes affected by stiffness and strength of the soils were obtained and normalized with the nominal length of the barrette. The criteria for long and rigid barrettes with loads in different directions were suggested. For the barrettes with loads in the transverse direction, the conventional analytical solution suggested by Chang for a single pile was found applicable to the predictions. In such case, the equivalent diameter calculated from moment of inertia of the barrette was found more adequate to be used in the analytical solution. Results of this study can help the engineers to understand more about the barrette performance under lateral loads.

Research paper thumbnail of Performance Based Design of Piles Due Seismic Ground Motions

[[conferencetype]]國際[[conferencedate]]20131205~20131206[[booktype]]紙本[[iscallforpapers]]Y[[confer... more [[conferencetype]]國際[[conferencedate]]20131205~20131206[[booktype]]紙本[[iscallforpapers]]Y[[conferencelocation]]Singapor

Research paper thumbnail of Study on Data Interpretation and Structural Index of Flexible Pavement

Journal of Applied Science and Engineering, 1998

ABSTRACT Based on dynamic analysis of steady-state and impulsive nondestructive deflection tests ... more ABSTRACT Based on dynamic analysis of steady-state and impulsive nondestructive deflection tests on pavement, new deflection indexes representing for the qualitative structural capacity of flexible pavements in Taiwan are suggested in this study. As the result of statistics analysis, the newly developed indexes are more generalized than the conventional ones. Layer conditions can be verified more accurately by using this method. By comparing with the dynamic backcalculations on experimental deflections, rehabilitation efficiency of the overlay construction is revealed; the weak layer of the structure is effectively shown. Neglecting the influences from bedrock and layer thickness, similar pavement conditions can be interpreted by dynamic backcalculation and this method. Incorporation of both methods shall make deflection tests more applicable in engineering practice.

Research paper thumbnail of Lateral load distributions on grouped piles from dynamic pile-to-pile interaction factors

International Journal for Numerical and Analytical Methods in Geomechanics, Feb 10, 2009

The load distributions of the grouped piles under lateral loads acting from one side of the pile ... more The load distributions of the grouped piles under lateral loads acting from one side of the pile cap could be approximately modeled using the elasticity equations with the assumptions that the underground structure is rigid enough to sustain the loads, and only small deformations of the soils are yielded. Variations of the soil-pile interactions along the depths are therefore negligible for simplicity. This paper presents the analytical modeling using the dynamic pile-to-pile interaction factors for 2 2 and 2 3 grouped piles. The results were found comparative to the experimental and numerical results of other studies. Similar to others' finding, it was shown that the leading pile could carry more static loads than the trailing pile does. For the piles in the perpendicular direction with the static load, the loads would distribute symmetrically with the centerline whereas the middle pile always sustains the smallest load. For steady-state loads with operating frequencies up to 30 Hz, the pile load distributions would vary significantly with the frequencies. It is interesting to know that designing the pile foundation needs to be cautioned for steady state vibrations as the problem of machine foundation. However for transient loads or any harmonic loads acting upon relatively higher frequencies, the pile loads could be regarded as uniformly distributed. It is hoped that the numerical results of this paper could be helpful to the design practice of pile foundation.

Research paper thumbnail of Effect of Depth to Bedrock on Deflection Basins Obtained with Dynaflect and Falling Weight Deflectometer Tests

Transportation Research Record, 1992

Research paper thumbnail of A time-domain viscous damping model based on frequency-dependent damping ratios

Soil Dynamics and Earthquake Engineering, Dec 1, 2000

This paper introduces the mathematics and procedures used in developing a time-dependent damping ... more This paper introduces the mathematics and procedures used in developing a time-dependent damping model for integration analyses of structural response. To establish the time-dependent viscous damping model, frequency-dependent damping ratios of the structure under a series of steady-state unit impulses corresponding to actual loads are ®rst calculated. For simplicity, the ratios can be incorporated with the static stiffness of the structure to model approximately the impulse induced damping spectrum. According to the nature of the problem, these ratios can be calculated from the theoretical impedance functions and experimental observations. With the computed damping spectrum, the damping coef®cient in the time domain can be obtained with the Fourier transform technique. Adopting the impulse±response method, the damping can be modeled rationally through integration with changing loads. Numerical examples are presented to show the feasibility of this model while the transform criterion is satis®ed.

Research paper thumbnail of Modified lysmer’s analog model for two dimensional mat settlements under vertically uniform load

Geomechanics and Engineering, 2021

A two dimensional model of linearly elastic soil spring used for the settlement analysis of the f... more A two dimensional model of linearly elastic soil spring used for the settlement analysis of the flexible mat foundation is suggested in this study. The spring constants of the soils underneath the foundation were modeled assuming uniformly vertical load applied onto the foundation. The soil spring constants were back calculated using the three-dimensional finite element analysis with Midas GTS NX program. Variation of the soil spring constants was modeled as a two-dimensional polynomial function in terms of the normalized spatial distances between the center of foundation and the analytical points. The Lysmer's analog spring for soils underneath the rigid foundation was adopted and calibrated for the flexible foundation. For validations, the newly proposed soil spring model was incorporated into a two dimensional finite difference analysis for a square mat foundation at the surface of an elastic half-space consisting of soft clays. Comparative study was made for elastic soils where the shear wave velocity is 120~180 m/s and the Poisson's ratio varies at 0.3~0.5. The resulting foundation settlements from the two dimensional finite difference analysis with the proposed soil springs were found in good agreement with those obtained directly from three dimensional finite element analyses. Details of the applications and limitations of the modified Lysmer's analog springs were discussed in this study.

Research paper thumbnail of Study of Dynamic Backcalculation Program with Genetic Algorithms for FWD on Pavements

Journal of Applied Science and Engineering, Dec 1, 2007

This paper introduces an inversion-modeling of Falling Weight Deflecometer (FWD) test for evaluat... more This paper introduces an inversion-modeling of Falling Weight Deflecometer (FWD) test for evaluation of pavement structure. Development of a dynamic backcalculation program DBFWD-GA with genetic algorithms for the FWD data is presented. This program can be used to interpret the FWD data. A number of variables were studied to suggest an optimized algorithm of the genetic method for flexible pavements consisting of three-layer and four-layer structures. Comparisons were made for the evaluations with those from the DBFWD program, in which the iterative procedure is applied, and the IDBAC program, as well as the MODULUS program that are founded on the database method. The results were found reasonable for the suggested program with the in-situ FWD data of national Chung-Shan Freeway. This program has the capacity to explore a broad domain of the solutions. It can be applied to the design strategies for the rehabilitation management on the flexible pavement structure.

Research paper thumbnail of EQWEAP Analysis and Its Applications to Seismic Performance Based Design for Pile Foundations

Journal of Applied Science and Engineering, Mar 1, 2013

One-dimensional wave equation can be used to model the seismic responses of piles. This paper int... more One-dimensional wave equation can be used to model the seismic responses of piles. This paper intends to discuss the corresponding analysis EQWEAP and its application to seismic performance based design of the pile foundations. Probability analysis suggested by PEER is adopted to analyze the seismic performance of a typical bridge pile foundation in Taipei. With simplified procedures, the single piles subjected to seismic ground motions can be investigated with various design concerns. In the analysis, the time-dependent displacements and bending moments of the pile are closely monitored during the earthquake shaking, and the nonlinear moment-curvature relationship is used for damage measure. It is found that the EQWEAP analysis can provide fast and effective solution to pile foundation design where the seismic ground motion is extremely important.

Research paper thumbnail of FD Solutions for Static and Dynamic Winkler Models with Lateral Spread Induced Earth Pressures on Piles

Research paper thumbnail of Train-induced wave propagation in layered soils using finite/infinite element simulation

Soil Dynamics and Earthquake Engineering, Jun 1, 2003

ABSTRACT In this paper, the transmissibility of soils for vibrations induced by trains moving at ... more ABSTRACT In this paper, the transmissibility of soils for vibrations induced by trains moving at different speeds is studied. The 2.5 D finite/infinite element approach adopted herein allows us to consider the load-moving effect of the train in the direction normal to the two-dimensional profile of the soils considered, and, therefore, to obtain three-dimensional responses for the soils using only plane elements. The moving train is simulated by a sequence of moving wheel loads that may vibrate with certain frequency. Two train speeds are considered, one is smaller and the other is greater than the Rayleigh wave speed of the layered soils, to represent the effects of speed in the sub-critical and super-critical ranges. In order to evaluate the effect of each parameter on the ground response induced by moving trains, parametric studies are conducted for the following parameters: the shear wave speed, damping ratio and stratum depth of the supporting soils, and the moving speed and vibration frequency of the traveling trains. Conclusions concerning the mechanism of wave propagation in layered soils are drawn from the parametric studies, which should prove useful to practicing engineers.

Research paper thumbnail of Pile Responses under Seismic Earth Pressures of Lateral Spread Using Wave Equation Analysis

Soil Dynamics and Earthquake Engineering, May 14, 2010

This study presents a simplified method to conduct the behavior of pile foundations due to latera... more This study presents a simplified method to conduct the behavior of pile foundations due to lateral spreading. Wave equation analysis applied to model the pile behavior under seismic motions. According to the concept of force-based method, the authors suggest to adopt the dynamic earth pressure in the wave equation analysis. Numerical procedures were validated with the well-documented cases of damaged piles in 1995 Kobe earthquake. In the meantime, comparing the numerical results with the case histories, one can again evaluate the damaged features of piles and distinguish the actual failure pattern of piles. The predictions and the observations were found in good correspondences.

Research paper thumbnail of Time-Domain Wave Equation Analyses of Single Piles Utilizing Transformed Radiation Damping

Soils and Foundations, Apr 1, 1999

Research paper thumbnail of Seismic Performance Of Piles In Taipei Using Probability And Wave–Equation Analyses

[[notice]]缺頁數[[conferencetype]]國際[[conferencedate]]20130529~20130531[[conferencelocation]]Singapor

Research paper thumbnail of Dynamic Interpretation for Impulsive Deflection Test on Flexible Pavements

Journal of Mechanics, Jun 1, 1998

In this study, a computer program DBFWD is developed for data analysis of Falling Weight Deflecto... more In this study, a computer program DBFWD is developed for data analysis of Falling Weight Deflectometer (FWD) test on flexible pavements. To backcalculate the layer moduli of the pavement, a number of iterative backcalculation schemes were employed with the forward analysis of the Green's flexibility influence functions. The temperature and the moisture influences on material moduli of the asphalt surface and the subgrade soils were considered in the analysis. As the result, the iterative scheme based on the peak deflection ratios was selected to backcalculate the layer moduli of local pavements. Owing to the correction procedure used in the program, interpretations with four original deflections were found more accurate than those with equivalent number of modified deflections. Comparisons of program DBFWD with other static backcalculation programs on theoretical and experimental deflections indicated that dynamic interpretation is more effective in providing the layer modulus information. Despite of the requirements of accurate inputs of the layer thickness and the testing load for the analysis, a generalized application of the program needs to be clarified with model road test in demand.

Research paper thumbnail of Studies on Soil Parameter Reduction Coefficient from One-Dimensional Ground Response Analyses

Research paper thumbnail of Monotonic and cyclic pushover analyses of pile foundations in laterally spreading ground

Research paper thumbnail of Inertia and spreading load combinations of soil-pile-structure system during liquefaction-induced lateral spreading in centrifuge tests

Combinaisons de charge d'inertie et de propagation sur des systèmes sol-pieu-structure pendant la... more Combinaisons de charge d'inertie et de propagation sur des systèmes sol-pieu-structure pendant la propagation latérale provoquée par la liquéfaction dans des essais de centrifugeuse

Research paper thumbnail of A Simplified Modeling for Seismic Responses of Rectangular Foundation on Piles Subjected to Horizontal Earthquakes

Journal of GeoEngineering, Dec 1, 2016

This paper presents a simplified modeling for seismic responses of rectangular foundation on pile... more This paper presents a simplified modeling for seismic responses of rectangular foundation on piles subjected to horizontal earthquakes. The motions of foundation can be derived simply assuming that the foundation is vibrating in one direction. Timedependent foundation responses under the earthquake with a bevel angle to the foundation were able to decompose and compute in both longitudinal and transverse directions. Using the explicit finite difference scheme, discrete wave equation analysis was suggested presuming that the lateral boundaries of foundation are free of tractions. The pile-soil-pile and soil elements underneath the rectangular foundation were modeled by springs. Seismic motions of the equivalent piers representing for the pile-soil-pile elements were analyzed using one-dimensional analysis of the single piles. Seismic forces transmitting through these elements to the foundation were able to obtain. The superstructure influences can be monitored assuming that the ratio of superstructure displacement and foundation displacement is constant. The proposed solutions were found compatible to three dimensional finite element ones. Factors to influence the seismic responses of foundation are discussed. The proposed analysis is concluded to provide efficient solutions to the preliminary design of piled raft foundation.

Research paper thumbnail of An Approximate Analysis For Stress And Failure Potential Of Earth Slopes

Journal of Applied Science and Engineering, 1997

ABSTRACT An approximate analysis for stress and failure of earth slopes is proposed. To simulate ... more ABSTRACT An approximate analysis for stress and failure of earth slopes is proposed. To simulate the stress variation along the slope, elastic stress influence from the presumable uplift pressure acting on a level ground is superimposed to the stress state of the ground. Stability condition of the slope is verified by comparing the mobilized Mohr’s circle with the presumable failure envelope for material points along the slope. It is found that the stress variation obtained is similar to the previous solutions. The results are closest to other solutions in the case where the Poisson’s ratio is relatively large. The failure potential of the slope obtained is more conservative in comparison with the one from limit equilibrium analysis. The averaged stability of that critical plane from the proposed method is compatible with the conventional solution.

Research paper thumbnail of Length Influences on Lateral Performance of Barrette from Three-Dimensional Finite Element Analysis

DOAJ (DOAJ: Directory of Open Access Journals), Feb 1, 2022

The performance of a single barrette subjected to lateral load applied at its top is presented in... more The performance of a single barrette subjected to lateral load applied at its top is presented in this paper using three-dimensional finite element analyses based on Midas GTS program. Nonlinear behaviors of the barrettes buried in clayey and sandy soils were monitored using Mohr-Coulomb soil model. Performances of the barrettes with lateral loads applied in both longitudinal and transverse directions were examined. Displacements of the barrettes affected by stiffness and strength of the soils were obtained and normalized with the nominal length of the barrette. The criteria for long and rigid barrettes with loads in different directions were suggested. For the barrettes with loads in the transverse direction, the conventional analytical solution suggested by Chang for a single pile was found applicable to the predictions. In such case, the equivalent diameter calculated from moment of inertia of the barrette was found more adequate to be used in the analytical solution. Results of this study can help the engineers to understand more about the barrette performance under lateral loads.

Research paper thumbnail of Performance Based Design of Piles Due Seismic Ground Motions

[[conferencetype]]國際[[conferencedate]]20131205~20131206[[booktype]]紙本[[iscallforpapers]]Y[[confer... more [[conferencetype]]國際[[conferencedate]]20131205~20131206[[booktype]]紙本[[iscallforpapers]]Y[[conferencelocation]]Singapor

Research paper thumbnail of Study on Data Interpretation and Structural Index of Flexible Pavement

Journal of Applied Science and Engineering, 1998

ABSTRACT Based on dynamic analysis of steady-state and impulsive nondestructive deflection tests ... more ABSTRACT Based on dynamic analysis of steady-state and impulsive nondestructive deflection tests on pavement, new deflection indexes representing for the qualitative structural capacity of flexible pavements in Taiwan are suggested in this study. As the result of statistics analysis, the newly developed indexes are more generalized than the conventional ones. Layer conditions can be verified more accurately by using this method. By comparing with the dynamic backcalculations on experimental deflections, rehabilitation efficiency of the overlay construction is revealed; the weak layer of the structure is effectively shown. Neglecting the influences from bedrock and layer thickness, similar pavement conditions can be interpreted by dynamic backcalculation and this method. Incorporation of both methods shall make deflection tests more applicable in engineering practice.

Research paper thumbnail of Lateral load distributions on grouped piles from dynamic pile-to-pile interaction factors

International Journal for Numerical and Analytical Methods in Geomechanics, Feb 10, 2009

The load distributions of the grouped piles under lateral loads acting from one side of the pile ... more The load distributions of the grouped piles under lateral loads acting from one side of the pile cap could be approximately modeled using the elasticity equations with the assumptions that the underground structure is rigid enough to sustain the loads, and only small deformations of the soils are yielded. Variations of the soil-pile interactions along the depths are therefore negligible for simplicity. This paper presents the analytical modeling using the dynamic pile-to-pile interaction factors for 2 2 and 2 3 grouped piles. The results were found comparative to the experimental and numerical results of other studies. Similar to others' finding, it was shown that the leading pile could carry more static loads than the trailing pile does. For the piles in the perpendicular direction with the static load, the loads would distribute symmetrically with the centerline whereas the middle pile always sustains the smallest load. For steady-state loads with operating frequencies up to 30 Hz, the pile load distributions would vary significantly with the frequencies. It is interesting to know that designing the pile foundation needs to be cautioned for steady state vibrations as the problem of machine foundation. However for transient loads or any harmonic loads acting upon relatively higher frequencies, the pile loads could be regarded as uniformly distributed. It is hoped that the numerical results of this paper could be helpful to the design practice of pile foundation.

Research paper thumbnail of Effect of Depth to Bedrock on Deflection Basins Obtained with Dynaflect and Falling Weight Deflectometer Tests

Transportation Research Record, 1992

Research paper thumbnail of A time-domain viscous damping model based on frequency-dependent damping ratios

Soil Dynamics and Earthquake Engineering, Dec 1, 2000

This paper introduces the mathematics and procedures used in developing a time-dependent damping ... more This paper introduces the mathematics and procedures used in developing a time-dependent damping model for integration analyses of structural response. To establish the time-dependent viscous damping model, frequency-dependent damping ratios of the structure under a series of steady-state unit impulses corresponding to actual loads are ®rst calculated. For simplicity, the ratios can be incorporated with the static stiffness of the structure to model approximately the impulse induced damping spectrum. According to the nature of the problem, these ratios can be calculated from the theoretical impedance functions and experimental observations. With the computed damping spectrum, the damping coef®cient in the time domain can be obtained with the Fourier transform technique. Adopting the impulse±response method, the damping can be modeled rationally through integration with changing loads. Numerical examples are presented to show the feasibility of this model while the transform criterion is satis®ed.

Research paper thumbnail of Modified lysmer’s analog model for two dimensional mat settlements under vertically uniform load

Geomechanics and Engineering, 2021

A two dimensional model of linearly elastic soil spring used for the settlement analysis of the f... more A two dimensional model of linearly elastic soil spring used for the settlement analysis of the flexible mat foundation is suggested in this study. The spring constants of the soils underneath the foundation were modeled assuming uniformly vertical load applied onto the foundation. The soil spring constants were back calculated using the three-dimensional finite element analysis with Midas GTS NX program. Variation of the soil spring constants was modeled as a two-dimensional polynomial function in terms of the normalized spatial distances between the center of foundation and the analytical points. The Lysmer's analog spring for soils underneath the rigid foundation was adopted and calibrated for the flexible foundation. For validations, the newly proposed soil spring model was incorporated into a two dimensional finite difference analysis for a square mat foundation at the surface of an elastic half-space consisting of soft clays. Comparative study was made for elastic soils where the shear wave velocity is 120~180 m/s and the Poisson's ratio varies at 0.3~0.5. The resulting foundation settlements from the two dimensional finite difference analysis with the proposed soil springs were found in good agreement with those obtained directly from three dimensional finite element analyses. Details of the applications and limitations of the modified Lysmer's analog springs were discussed in this study.

Research paper thumbnail of Study of Dynamic Backcalculation Program with Genetic Algorithms for FWD on Pavements

Journal of Applied Science and Engineering, Dec 1, 2007

This paper introduces an inversion-modeling of Falling Weight Deflecometer (FWD) test for evaluat... more This paper introduces an inversion-modeling of Falling Weight Deflecometer (FWD) test for evaluation of pavement structure. Development of a dynamic backcalculation program DBFWD-GA with genetic algorithms for the FWD data is presented. This program can be used to interpret the FWD data. A number of variables were studied to suggest an optimized algorithm of the genetic method for flexible pavements consisting of three-layer and four-layer structures. Comparisons were made for the evaluations with those from the DBFWD program, in which the iterative procedure is applied, and the IDBAC program, as well as the MODULUS program that are founded on the database method. The results were found reasonable for the suggested program with the in-situ FWD data of national Chung-Shan Freeway. This program has the capacity to explore a broad domain of the solutions. It can be applied to the design strategies for the rehabilitation management on the flexible pavement structure.

Research paper thumbnail of EQWEAP Analysis and Its Applications to Seismic Performance Based Design for Pile Foundations

Journal of Applied Science and Engineering, Mar 1, 2013

One-dimensional wave equation can be used to model the seismic responses of piles. This paper int... more One-dimensional wave equation can be used to model the seismic responses of piles. This paper intends to discuss the corresponding analysis EQWEAP and its application to seismic performance based design of the pile foundations. Probability analysis suggested by PEER is adopted to analyze the seismic performance of a typical bridge pile foundation in Taipei. With simplified procedures, the single piles subjected to seismic ground motions can be investigated with various design concerns. In the analysis, the time-dependent displacements and bending moments of the pile are closely monitored during the earthquake shaking, and the nonlinear moment-curvature relationship is used for damage measure. It is found that the EQWEAP analysis can provide fast and effective solution to pile foundation design where the seismic ground motion is extremely important.

Research paper thumbnail of FD Solutions for Static and Dynamic Winkler Models with Lateral Spread Induced Earth Pressures on Piles

Research paper thumbnail of Train-induced wave propagation in layered soils using finite/infinite element simulation

Soil Dynamics and Earthquake Engineering, Jun 1, 2003

ABSTRACT In this paper, the transmissibility of soils for vibrations induced by trains moving at ... more ABSTRACT In this paper, the transmissibility of soils for vibrations induced by trains moving at different speeds is studied. The 2.5 D finite/infinite element approach adopted herein allows us to consider the load-moving effect of the train in the direction normal to the two-dimensional profile of the soils considered, and, therefore, to obtain three-dimensional responses for the soils using only plane elements. The moving train is simulated by a sequence of moving wheel loads that may vibrate with certain frequency. Two train speeds are considered, one is smaller and the other is greater than the Rayleigh wave speed of the layered soils, to represent the effects of speed in the sub-critical and super-critical ranges. In order to evaluate the effect of each parameter on the ground response induced by moving trains, parametric studies are conducted for the following parameters: the shear wave speed, damping ratio and stratum depth of the supporting soils, and the moving speed and vibration frequency of the traveling trains. Conclusions concerning the mechanism of wave propagation in layered soils are drawn from the parametric studies, which should prove useful to practicing engineers.

Research paper thumbnail of Pile Responses under Seismic Earth Pressures of Lateral Spread Using Wave Equation Analysis

Soil Dynamics and Earthquake Engineering, May 14, 2010

This study presents a simplified method to conduct the behavior of pile foundations due to latera... more This study presents a simplified method to conduct the behavior of pile foundations due to lateral spreading. Wave equation analysis applied to model the pile behavior under seismic motions. According to the concept of force-based method, the authors suggest to adopt the dynamic earth pressure in the wave equation analysis. Numerical procedures were validated with the well-documented cases of damaged piles in 1995 Kobe earthquake. In the meantime, comparing the numerical results with the case histories, one can again evaluate the damaged features of piles and distinguish the actual failure pattern of piles. The predictions and the observations were found in good correspondences.

Research paper thumbnail of Time-Domain Wave Equation Analyses of Single Piles Utilizing Transformed Radiation Damping

Soils and Foundations, Apr 1, 1999

Research paper thumbnail of Seismic Performance Of Piles In Taipei Using Probability And Wave–Equation Analyses

[[notice]]缺頁數[[conferencetype]]國際[[conferencedate]]20130529~20130531[[conferencelocation]]Singapor

Research paper thumbnail of Dynamic Interpretation for Impulsive Deflection Test on Flexible Pavements

Journal of Mechanics, Jun 1, 1998

In this study, a computer program DBFWD is developed for data analysis of Falling Weight Deflecto... more In this study, a computer program DBFWD is developed for data analysis of Falling Weight Deflectometer (FWD) test on flexible pavements. To backcalculate the layer moduli of the pavement, a number of iterative backcalculation schemes were employed with the forward analysis of the Green's flexibility influence functions. The temperature and the moisture influences on material moduli of the asphalt surface and the subgrade soils were considered in the analysis. As the result, the iterative scheme based on the peak deflection ratios was selected to backcalculate the layer moduli of local pavements. Owing to the correction procedure used in the program, interpretations with four original deflections were found more accurate than those with equivalent number of modified deflections. Comparisons of program DBFWD with other static backcalculation programs on theoretical and experimental deflections indicated that dynamic interpretation is more effective in providing the layer modulus information. Despite of the requirements of accurate inputs of the layer thickness and the testing load for the analysis, a generalized application of the program needs to be clarified with model road test in demand.

Research paper thumbnail of Studies on Soil Parameter Reduction Coefficient from One-Dimensional Ground Response Analyses

Research paper thumbnail of Monotonic and cyclic pushover analyses of pile foundations in laterally spreading ground

Research paper thumbnail of Inertia and spreading load combinations of soil-pile-structure system during liquefaction-induced lateral spreading in centrifuge tests

Combinaisons de charge d'inertie et de propagation sur des systèmes sol-pieu-structure pendant la... more Combinaisons de charge d'inertie et de propagation sur des systèmes sol-pieu-structure pendant la propagation latérale provoquée par la liquéfaction dans des essais de centrifugeuse

Research paper thumbnail of A Simplified Modeling for Seismic Responses of Rectangular Foundation on Piles Subjected to Horizontal Earthquakes

Journal of GeoEngineering, Dec 1, 2016

This paper presents a simplified modeling for seismic responses of rectangular foundation on pile... more This paper presents a simplified modeling for seismic responses of rectangular foundation on piles subjected to horizontal earthquakes. The motions of foundation can be derived simply assuming that the foundation is vibrating in one direction. Timedependent foundation responses under the earthquake with a bevel angle to the foundation were able to decompose and compute in both longitudinal and transverse directions. Using the explicit finite difference scheme, discrete wave equation analysis was suggested presuming that the lateral boundaries of foundation are free of tractions. The pile-soil-pile and soil elements underneath the rectangular foundation were modeled by springs. Seismic motions of the equivalent piers representing for the pile-soil-pile elements were analyzed using one-dimensional analysis of the single piles. Seismic forces transmitting through these elements to the foundation were able to obtain. The superstructure influences can be monitored assuming that the ratio of superstructure displacement and foundation displacement is constant. The proposed solutions were found compatible to three dimensional finite element ones. Factors to influence the seismic responses of foundation are discussed. The proposed analysis is concluded to provide efficient solutions to the preliminary design of piled raft foundation.

Research paper thumbnail of Three-dimensional Finite Element Analyses of Barrette Piles under Compression and Uplift Loads with Field Data Assessments

Geotechnical Engineering Journal of the SEAGS & AGSSEASEAGS-AGSSEA Journal – September 2019 Vol. 50 No. 3 September 2019 ISSN 0046-5828, 2019

This paper presents the three-dimensional finite element modeling of barrette piles in clayey and... more This paper presents the three-dimensional finite element modeling of barrette piles in clayey and sandy soils, in which the piles are subjected to statically compressive and uplift loads. Load displacement curves and load transfers were monitored and compared to solutions from one-dimensional finite difference analysis. Capacities of the barrette piles were examined by interpretation methods and bearing capacity equations. Pile load test data of barrette piles located in Xingyi District, Taipei Basin was used for simulation. It was found that the conventional bearing capacity equations are applicable to barrette piles. The interface elements between pile and soils were found to significantly affect the results. Finite element analysis can provide more complete solutions when compared with finite difference analysis. It was also found that the soil frictions due to pile uplift in soft clays at Taipei Basin were underestimated when using common strength reduction ratios.