The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Xiaowei Wang - One of the best experts on this subject based on the ideXlab platform.
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seismic response prediction and variable importance analysis of extended Pile Shaft supported bridges against lateral spreading exploring optimized machine learning models
Engineering Structures, 2021Co-Authors: Xiaowei Wang, Abdollah ShafieezadehAbstract:Abstract Reliable prediction of seismic responses of bridges against lateral spreading is critical for fragility and resilience assessment of transportation infrastructure. This problem, however, has remained a significant challenge due to the high complexity of the liquefaction phenomenon and its significance for the seismic performance of structures. The present study explores machine learning (ML) approaches, particularly for bridges supported by extended Pile-Shafts, for reliable estimation of bearing deformation and column drift ratio responses of bridges. The study considers a large set of covariates across soil, structural, and ground motion features. Five ML algorithms are examined including the traditional multiple linear regression (MLR) as the baseline reference, as well as Lasso regression, neural network (NN), random forests (RF), and gradient tree boosting (GTB). A large number of nonlinear soil-bridge finite element models considering the soil and structural uncertainties are dynamically analyzed under 720 ground motions, and the optimal parameters of the ML models are determined via five-fold cross validation. The results indicate that NN and GTB can well predict the seismic responses of the studied soil-bridge systems, followed by RF, while Lasso and MLR are generally not able to yield reliable estimates. Furthermore, a variable importance analysis is conducted using the produced regression models. Results indicate that intensity measures (IMs) (particularly the spectral acceleration at 2.0 s) are generally more significant than the soil- and structure-related variables. In addition to the IMs, variables associated with the nonliquefiable crust layer (i.e., thickness, strength, and sloping angle) and the concrete strength and longitudinal reinforcement ratio are generally significant variables, whereas the column diameter and rebar yielding strength are relatively insignificant.
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fosid a fractional order spectrum intensity for probabilistic seismic demand modeling of extended Pile Shaft supported highway bridges under liquefaction and transverse spreading
Bulletin of Earthquake Engineering, 2021Co-Authors: Xiaowei Wang, Abdollah Shafieezadeh, Jamie E PadgettAbstract:An appropriate seismic intensity measure (IM) for response prediction is central to reliable probabilistic seismic demand modeling of structures and subsequently, risk and resilience quantification. Bridges in liquefiable and laterally spreading ground may undergo nonlinear responses with large uncertainties when subjected to earthquakes. These issues often lead to low-confidence demand models based on traditional IMs. Fractional order IMs have shown the potential to yield improved demand models in recent studies. To further increase confidence in demand models, this study proposes Fractional Order Spectrum intensity considering Integral period and Damping ratio (named FOSID). The viability of FOSID for use in probabilistic seismic demand modeling of structures is evaluated in the context of extended Pile-Shaft-supported bridges against liquefaction-induced lateral spreading. The performance of FOSID is systematically assessed by comparisons to an existing fractional order spectrum intensity (SIr,α), Housner intensity (HI)—an optimal traditional IM for these structures, and the average spectral acceleration (Saavg)—a state-of-the-art non-fractional-order IM. Multiple metrics for characterizing an optimal IM are adopted, including practicality, efficiency, proficiency, sufficiency, and relative sufficiency. Optimal variables of integral period, damping ratio, and fractional order for FOSID are identified for different demand parameters such as peak and residual column-drift-ratios. Results show that FOSID is generally more practical, efficient, proficient and sufficient than SIr,α, HI and Saavg. In particular, FOSID significantly outperforms HI by improving the proficiency by nearly 40% and 20% for the peak and residual column-drift-ratios, respectively. With respect to SIr,α, FOSID improves the proficiency by 20% and 15% on average. When compared with Saavg, such improvements are as large as 13% and 24% on average for the peak and residual column-drift-ratios, respectively.
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optimal edps for post earthquake damage assessment of extended Pile Shaft supported bridges subjected to transverse spreading
Earthquake Spectra, 2019Co-Authors: Xiaowei Wang, Abdollah ShafieezadehAbstract:During earthquakes, extended Pile-Shaft–supported bridges in laterally spreading ground can undergo inelastic deformations, especially in their embedded portions. Following earthquakes, it is criti...
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fractional order optimal intensity measures for probabilistic seismic demand modeling of extended Pile Shaft supported bridges in liquefiable and laterally spreading ground
Soil Dynamics and Earthquake Engineering, 2019Co-Authors: Xiaowei Wang, Abdollah Shafieezadeh, Jamie E PadgettAbstract:Abstract In performance-based earthquake engineering, probabilistic seismic demand models of structures are essential components that provide probabilistic estimates of earthquake-induced demands as a function of a variable(s) called the ground motion intensity measure (IM). Uncertainties in these models are often dependent on the IM used. Extending from traditional integer order IMs, this study assesses the performance of fractional order (FO, order of α) IMs on the probabilistic seismic demand modeling of extended Pile-Shaft supported bridges sited in liquefiable and laterally spreading ground. Uncertainties in structural and geotechnical material properties as well as geometric parameters of the bridges are considered in finite element models to achieve comprehensive scenarios. The FO IMs considered include peak ground response (PGRα), cumulative absolute response (CARα) and its modified version (CAR5α), spectral acceleration at 2.0 s for a fractionally damped single degree of freedom (SDF) system (Sad-20α) and for a conventional SDF system with fractional response (Sar-20α), spectrum intensity for a fractionally damped SDF system (SIdα), as well as for a conventional SDF system with fractional response (SIrα). Metrics such as efficiency, practicality, proficiency and sufficiency are measured to assess the optimal α with respect to different demand parameters. Results show the advantages of FO IMs as they increase confidence in demand models compared to traditional integer order IMs. In particular, the proposed fractional spectrum intensities (SIdα and SIrα) with their optimal α values produce significant improvements in practicality, efficiency and proficiency, while maintaining sufficiency. Therefore, FO IMs can provide more reliable demand models for probabilistic seismic demand analysis of extended Pile-Shaft supported bridges in liquefiable and laterally spreading ground.
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optimal intensity measures for probabilistic seismic demand modeling of extended Pile Shaft supported bridges in liquefied and laterally spreading ground
Bulletin of Earthquake Engineering, 2018Co-Authors: Xiaowei Wang, Abdollah ShafieezadehAbstract:Seismic intensity measures (IMs) perform a pivotal role in probabilistic seismic demand modeling. Many studies investigated appropriate IMs for structures without considering soil liquefaction potential. In particular, optimal IMs for probabilistic seismic demand modeling of bridges in liquefied and laterally spreading ground are not comprehensively studied. In this paper, a coupled-bridge-soil-foundation model is adopted to perform an in-depth investigation of optimal IMs among 26 IMs found in the literature. Uncertainties in structural and geotechnical material properties and geometric parameters of bridges are considered in the model to produce comprehensive scenarios. Metrics such as efficiency, practicality, proficiency, sufficiency and hazard computability are assessed for different demand parameters. Moreover, an information theory based approach is adopted to evaluate the relative sufficiency among the studied IMs. Results indicate the superiority of velocity-related IMs compared to acceleration, displacement and time-related ones. In particular, Housner spectrum intensity (HI), spectral acceleration at 2.0 s (S a-20), peak ground velocity (PGV), cumulative absolute velocity (CAV) and its modified version (CAV 5) are the optimal IMs. Conversely, Arias intensity (I a ) and shaking intensity rate (SIR) which are measures often used in liquefaction evaluation or related structural demand assessment demonstrate very low correlations with the demand parameters. Besides, the geometric parameters do not evidently affect the choice of optimal IMs. In addition, the information theory based sufficiency ranking of IMs shows an identical result to that with the correlation measure based on coefficient of determination (R 2). This means that R 2 can be used to preliminarily assess the relative sufficiency of IMs.
Abdollah Shafieezadeh - One of the best experts on this subject based on the ideXlab platform.
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seismic response prediction and variable importance analysis of extended Pile Shaft supported bridges against lateral spreading exploring optimized machine learning models
Engineering Structures, 2021Co-Authors: Xiaowei Wang, Abdollah ShafieezadehAbstract:Abstract Reliable prediction of seismic responses of bridges against lateral spreading is critical for fragility and resilience assessment of transportation infrastructure. This problem, however, has remained a significant challenge due to the high complexity of the liquefaction phenomenon and its significance for the seismic performance of structures. The present study explores machine learning (ML) approaches, particularly for bridges supported by extended Pile-Shafts, for reliable estimation of bearing deformation and column drift ratio responses of bridges. The study considers a large set of covariates across soil, structural, and ground motion features. Five ML algorithms are examined including the traditional multiple linear regression (MLR) as the baseline reference, as well as Lasso regression, neural network (NN), random forests (RF), and gradient tree boosting (GTB). A large number of nonlinear soil-bridge finite element models considering the soil and structural uncertainties are dynamically analyzed under 720 ground motions, and the optimal parameters of the ML models are determined via five-fold cross validation. The results indicate that NN and GTB can well predict the seismic responses of the studied soil-bridge systems, followed by RF, while Lasso and MLR are generally not able to yield reliable estimates. Furthermore, a variable importance analysis is conducted using the produced regression models. Results indicate that intensity measures (IMs) (particularly the spectral acceleration at 2.0 s) are generally more significant than the soil- and structure-related variables. In addition to the IMs, variables associated with the nonliquefiable crust layer (i.e., thickness, strength, and sloping angle) and the concrete strength and longitudinal reinforcement ratio are generally significant variables, whereas the column diameter and rebar yielding strength are relatively insignificant.
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fosid a fractional order spectrum intensity for probabilistic seismic demand modeling of extended Pile Shaft supported highway bridges under liquefaction and transverse spreading
Bulletin of Earthquake Engineering, 2021Co-Authors: Xiaowei Wang, Abdollah Shafieezadeh, Jamie E PadgettAbstract:An appropriate seismic intensity measure (IM) for response prediction is central to reliable probabilistic seismic demand modeling of structures and subsequently, risk and resilience quantification. Bridges in liquefiable and laterally spreading ground may undergo nonlinear responses with large uncertainties when subjected to earthquakes. These issues often lead to low-confidence demand models based on traditional IMs. Fractional order IMs have shown the potential to yield improved demand models in recent studies. To further increase confidence in demand models, this study proposes Fractional Order Spectrum intensity considering Integral period and Damping ratio (named FOSID). The viability of FOSID for use in probabilistic seismic demand modeling of structures is evaluated in the context of extended Pile-Shaft-supported bridges against liquefaction-induced lateral spreading. The performance of FOSID is systematically assessed by comparisons to an existing fractional order spectrum intensity (SIr,α), Housner intensity (HI)—an optimal traditional IM for these structures, and the average spectral acceleration (Saavg)—a state-of-the-art non-fractional-order IM. Multiple metrics for characterizing an optimal IM are adopted, including practicality, efficiency, proficiency, sufficiency, and relative sufficiency. Optimal variables of integral period, damping ratio, and fractional order for FOSID are identified for different demand parameters such as peak and residual column-drift-ratios. Results show that FOSID is generally more practical, efficient, proficient and sufficient than SIr,α, HI and Saavg. In particular, FOSID significantly outperforms HI by improving the proficiency by nearly 40% and 20% for the peak and residual column-drift-ratios, respectively. With respect to SIr,α, FOSID improves the proficiency by 20% and 15% on average. When compared with Saavg, such improvements are as large as 13% and 24% on average for the peak and residual column-drift-ratios, respectively.
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optimal edps for post earthquake damage assessment of extended Pile Shaft supported bridges subjected to transverse spreading
Earthquake Spectra, 2019Co-Authors: Xiaowei Wang, Abdollah ShafieezadehAbstract:During earthquakes, extended Pile-Shaft–supported bridges in laterally spreading ground can undergo inelastic deformations, especially in their embedded portions. Following earthquakes, it is criti...
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fractional order optimal intensity measures for probabilistic seismic demand modeling of extended Pile Shaft supported bridges in liquefiable and laterally spreading ground
Soil Dynamics and Earthquake Engineering, 2019Co-Authors: Xiaowei Wang, Abdollah Shafieezadeh, Jamie E PadgettAbstract:Abstract In performance-based earthquake engineering, probabilistic seismic demand models of structures are essential components that provide probabilistic estimates of earthquake-induced demands as a function of a variable(s) called the ground motion intensity measure (IM). Uncertainties in these models are often dependent on the IM used. Extending from traditional integer order IMs, this study assesses the performance of fractional order (FO, order of α) IMs on the probabilistic seismic demand modeling of extended Pile-Shaft supported bridges sited in liquefiable and laterally spreading ground. Uncertainties in structural and geotechnical material properties as well as geometric parameters of the bridges are considered in finite element models to achieve comprehensive scenarios. The FO IMs considered include peak ground response (PGRα), cumulative absolute response (CARα) and its modified version (CAR5α), spectral acceleration at 2.0 s for a fractionally damped single degree of freedom (SDF) system (Sad-20α) and for a conventional SDF system with fractional response (Sar-20α), spectrum intensity for a fractionally damped SDF system (SIdα), as well as for a conventional SDF system with fractional response (SIrα). Metrics such as efficiency, practicality, proficiency and sufficiency are measured to assess the optimal α with respect to different demand parameters. Results show the advantages of FO IMs as they increase confidence in demand models compared to traditional integer order IMs. In particular, the proposed fractional spectrum intensities (SIdα and SIrα) with their optimal α values produce significant improvements in practicality, efficiency and proficiency, while maintaining sufficiency. Therefore, FO IMs can provide more reliable demand models for probabilistic seismic demand analysis of extended Pile-Shaft supported bridges in liquefiable and laterally spreading ground.
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optimal intensity measures for probabilistic seismic demand modeling of extended Pile Shaft supported bridges in liquefied and laterally spreading ground
Bulletin of Earthquake Engineering, 2018Co-Authors: Xiaowei Wang, Abdollah ShafieezadehAbstract:Seismic intensity measures (IMs) perform a pivotal role in probabilistic seismic demand modeling. Many studies investigated appropriate IMs for structures without considering soil liquefaction potential. In particular, optimal IMs for probabilistic seismic demand modeling of bridges in liquefied and laterally spreading ground are not comprehensively studied. In this paper, a coupled-bridge-soil-foundation model is adopted to perform an in-depth investigation of optimal IMs among 26 IMs found in the literature. Uncertainties in structural and geotechnical material properties and geometric parameters of bridges are considered in the model to produce comprehensive scenarios. Metrics such as efficiency, practicality, proficiency, sufficiency and hazard computability are assessed for different demand parameters. Moreover, an information theory based approach is adopted to evaluate the relative sufficiency among the studied IMs. Results indicate the superiority of velocity-related IMs compared to acceleration, displacement and time-related ones. In particular, Housner spectrum intensity (HI), spectral acceleration at 2.0 s (S a-20), peak ground velocity (PGV), cumulative absolute velocity (CAV) and its modified version (CAV 5) are the optimal IMs. Conversely, Arias intensity (I a ) and shaking intensity rate (SIR) which are measures often used in liquefaction evaluation or related structural demand assessment demonstrate very low correlations with the demand parameters. Besides, the geometric parameters do not evidently affect the choice of optimal IMs. In addition, the information theory based sufficiency ranking of IMs shows an identical result to that with the correlation measure based on coefficient of determination (R 2). This means that R 2 can be used to preliminarily assess the relative sufficiency of IMs.
Jamie E Padgett - One of the best experts on this subject based on the ideXlab platform.
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fosid a fractional order spectrum intensity for probabilistic seismic demand modeling of extended Pile Shaft supported highway bridges under liquefaction and transverse spreading
Bulletin of Earthquake Engineering, 2021Co-Authors: Xiaowei Wang, Abdollah Shafieezadeh, Jamie E PadgettAbstract:An appropriate seismic intensity measure (IM) for response prediction is central to reliable probabilistic seismic demand modeling of structures and subsequently, risk and resilience quantification. Bridges in liquefiable and laterally spreading ground may undergo nonlinear responses with large uncertainties when subjected to earthquakes. These issues often lead to low-confidence demand models based on traditional IMs. Fractional order IMs have shown the potential to yield improved demand models in recent studies. To further increase confidence in demand models, this study proposes Fractional Order Spectrum intensity considering Integral period and Damping ratio (named FOSID). The viability of FOSID for use in probabilistic seismic demand modeling of structures is evaluated in the context of extended Pile-Shaft-supported bridges against liquefaction-induced lateral spreading. The performance of FOSID is systematically assessed by comparisons to an existing fractional order spectrum intensity (SIr,α), Housner intensity (HI)—an optimal traditional IM for these structures, and the average spectral acceleration (Saavg)—a state-of-the-art non-fractional-order IM. Multiple metrics for characterizing an optimal IM are adopted, including practicality, efficiency, proficiency, sufficiency, and relative sufficiency. Optimal variables of integral period, damping ratio, and fractional order for FOSID are identified for different demand parameters such as peak and residual column-drift-ratios. Results show that FOSID is generally more practical, efficient, proficient and sufficient than SIr,α, HI and Saavg. In particular, FOSID significantly outperforms HI by improving the proficiency by nearly 40% and 20% for the peak and residual column-drift-ratios, respectively. With respect to SIr,α, FOSID improves the proficiency by 20% and 15% on average. When compared with Saavg, such improvements are as large as 13% and 24% on average for the peak and residual column-drift-ratios, respectively.
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fractional order optimal intensity measures for probabilistic seismic demand modeling of extended Pile Shaft supported bridges in liquefiable and laterally spreading ground
Soil Dynamics and Earthquake Engineering, 2019Co-Authors: Xiaowei Wang, Abdollah Shafieezadeh, Jamie E PadgettAbstract:Abstract In performance-based earthquake engineering, probabilistic seismic demand models of structures are essential components that provide probabilistic estimates of earthquake-induced demands as a function of a variable(s) called the ground motion intensity measure (IM). Uncertainties in these models are often dependent on the IM used. Extending from traditional integer order IMs, this study assesses the performance of fractional order (FO, order of α) IMs on the probabilistic seismic demand modeling of extended Pile-Shaft supported bridges sited in liquefiable and laterally spreading ground. Uncertainties in structural and geotechnical material properties as well as geometric parameters of the bridges are considered in finite element models to achieve comprehensive scenarios. The FO IMs considered include peak ground response (PGRα), cumulative absolute response (CARα) and its modified version (CAR5α), spectral acceleration at 2.0 s for a fractionally damped single degree of freedom (SDF) system (Sad-20α) and for a conventional SDF system with fractional response (Sar-20α), spectrum intensity for a fractionally damped SDF system (SIdα), as well as for a conventional SDF system with fractional response (SIrα). Metrics such as efficiency, practicality, proficiency and sufficiency are measured to assess the optimal α with respect to different demand parameters. Results show the advantages of FO IMs as they increase confidence in demand models compared to traditional integer order IMs. In particular, the proposed fractional spectrum intensities (SIdα and SIrα) with their optimal α values produce significant improvements in practicality, efficiency and proficiency, while maintaining sufficiency. Therefore, FO IMs can provide more reliable demand models for probabilistic seismic demand analysis of extended Pile-Shaft supported bridges in liquefiable and laterally spreading ground.
Kui-hua Wang - One of the best experts on this subject based on the ideXlab platform.
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analytical model for laterally loaded soil extended Pile Shaft applied to verifying the applicability of lateral ps method
Journal of Geotechnical and Geoenvironmental Engineering, 2021Co-Authors: Hesham El M Naggar, Kui-hua WangAbstract:AbstractThis paper investigates the dynamic response of soil around a laterally vibrating extended Pile Shaft and its application to the lateral parallel seismic (PS) integrity testing method. Cons...
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field behavior of pre bored grouted planted nodular Pile embedded in deep clayey soil
Acta Geotechnica, 2019Co-Authors: Jiajin Zhou, Ri-hong Zhang, Hesham El M Naggar, Xiaonan Gong, Kui-hua WangAbstract:This paper presents the results of field tests performed to investigate the behavior of pre-bored grouted planted nodular (PGPN) Pile embedded in deep clayey soil. The test Piles were all instrumented to measure the Shaft and tip resistance and to determine the load transfer along the Pile Shaft. The test results show that the displacement necessary to fully mobilize the Shaft resistance of PGPN Pile is in the range of 1.83–3.32% D (D is Pile diameter), and that the ultimate skin frictions of grout–soil interface of different soil layers are larger than the conventional proposed ultimate skin frictions for non-displacement Piles. Furthermore, the Pile tip resistance accounts for about 16% of the total applied Pile head load corresponding to a Pile head displacement of 0.1 D, and the Pile tip resistance continues to increase after tip displacement reaches 5% of Pile tip diameter.
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lateral vibration characteristics of an extended Pile Shaft under low strain integrity test
Soil Dynamics and Earthquake Engineering, 2019Co-Authors: Hesham El M Naggar, Kui-hua WangAbstract:Abstract The integrity of extended Pile Shaft is paramount for ensuring safe and acceptable performance of supported bridge structures. However, it is difficult to conduct the vertical excitation low-strain integrity test for an extended Pile Shaft that supports an existing bridge. This paper investigates the feasibility of employing lateral low-strain test to predict the Pile length of an extended Pile Shaft. An analytical model is developed to simulate the behavior of a Pile, partially embedded in soil, with a Pile cap and superstructure under a lateral low-strain excitation. Considering the frequency spectrum of an impulse excitation, the developed model employs the modified Timoshenko beam theory to accurately simulate the lateral Pile vibration accounting for both rotary inertia and shear. The analytical solution is then utilized to analyze the dispersion of the Pile-soil system when subjected to the lateral excitation. The effects of Pile and soil properties on the Pile dynamic response and wave propagating velocity are investigated through a comprehensive parametric study. A simplified method is proposed to approximately evaluate the Pile length of this case on site.
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FEM Analysis and Simplified Approach for a Single Energy Pile Subjected to Thermomechanical Loads
Hindawi Limited, 2019Co-Authors: Zhong-jin Wang, Peng-fei Fang, Ri-hong Zhang, Kui-hua Wang, Xin-yu XieAbstract:The distribution of temperature in sand soils was measured through laboratory tests, and the temperature influence on friction resistances at the concrete-soil interface was analyzed. Based on the results of laboratory tests, the finite element model was established using the sequential thermal coupling method. The influences of temperature on the bearing characteristics of energy Pile were analyzed. The analysis results show that the cyclic temperature will cause additional displacement along Pile depth. It is pointed out that if applied vertical loads at energy Pile head exceed the value from which nonlinear settlements would be initiated, irrecoverable additional settlement will occur at Pile head. Based on the analysis results, a simplified approach was proposed to estimate the zero point of additional displacement along Pile Shaft and the additional axial Pile force. The comparison between the calculated results obtained by the proposed method and that of ABAQUS on single energy Pile was given to verify the accuracy of the proposed method. It is shown that reasonable predictions can be obtained without expensive and time-consuming analyses by the proposed method in this paper
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analytical solution for the dynamic response of a Pile with a variable section interface in low strain integrity testing
Journal of Sound and Vibration, 2017Co-Authors: Liu Gao, Kui-hua Wang, Si Xiao, Ning WangAbstract:Abstract Considering the displacement and stress continuity conditions at the Pile-soil interface, ring-soil Pile theory (RSPT) and an amended impedance function transfer method (AIFTM) are proposed as models of rigid Pile-soil interaction that consider the interaction at the variable-section interface of a Pile with the surrounding soil. The interactions between adjacent three-dimensional soil layers are simplified as uniformly distributed Voigt models to derive the impedance function at the Pile top. An inverse Fourier transform is applied to derive the velocity response at the top of the Pile under transient excitation. An engineering example is described to confirm the rationality of the proposed solution. The solution simplifies into other previously proposed solutions for specific geometric parameters of the Pile Shaft. The proposed solution is compared with one that neglects the interaction at the variable-section interface of the Pile with the surrounding soil; additionally, the coupled effects of the related Pile-soil parameters and the interaction at the variable-section interface with the surrounding soil are analyzed.
Y H Chai - One of the best experts on this subject based on the ideXlab platform.
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inelastic seismic response of extended Pile Shaft supported bridge structures
Earthquake Spectra, 2004Co-Authors: Tara C Hutchinson, Y H Chai, Ross W Boulanger, Izzat M. IdrissAbstract:Abstract Nonlinear static and dynamic analyses were used to evaluate the inelastic seismic response of bridge and viaduct structures supported on extended cast-in-drilled-hole (CIDH) Pile Shafts. The nonlinear dynamic analyses used a beam-on-nonlinear-Winkler foundation (BNWF) framework to model the soil-Pile interaction, nonlinear fiber beam-column elements to model the reinforced concrete sections, and one-dimensional site response analyses for the free-field soil profile response. The study included consideration of ground motion characteristics, site response, lateral soil resistance, structural parameters, geometric nonlinearity (P-Δ effects), and performance measures. Results described herein focus on how the ground motion characteristics and variations in structural configurations affect the performance measures important for evaluating the inelastic seismic response of these structures. Presented results focus on a representative dense soil profile and thus are not widely applicable to dramaticall...
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estimating inelastic displacements for design extended Pile Shaft supported bridge structures
Earthquake Spectra, 2004Co-Authors: Tara C Hutchinson, Y H Chai, Ross W Boulanger, Izzat M. IdrissAbstract:Abstract Accurate estimation of inelastic displacements is important for the evaluation of the seismic performance of structures with desired ductile response. In this paper, nonlinear dynamic analyses results from a companion numerical study investigating the response of ductile-designed bridge structures, were compared with a commonly applied inelastic displacement estimation approach and an alternative approach. The extended Pile-Shaft-supported bridge structures considered are susceptible to amplified response under long-period velocity pulses, and hence an evaluation of design methods for estimating inelastic displacement demands is warranted. In this case, force-reduction–displacement-ductility–period (R−μΔ−T) relations and a mean spectral displacement approach are investigated. The alternative approach estimates inelastic displacement demand using the mean elastic spectral displacement between two spectral periods that are important for the structure’s response. Results support the conceptual merit...
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flexural strength and ductility of extended Pile Shafts i analytical model
Journal of Structural Engineering-asce, 2002Co-Authors: Y H ChaiAbstract:An analytical model, based on the commonly used equivalent cantilever concept, is developed for assessing the local ductility demand of a yielding Pile-Shaft when subjected to lateral loading. For elastic response of the Pile-Shaft, an equivalent depth-to-fixity is assumed, which can be derived by equating the lateral stiffness of the cantilever to that of the elastic soil-Pile system. In adapting the equivalent cantilever model to yielding Pile-Shafts, however, the depth-to-maximum-moment is assumed to occur at a depth above the depth-to-fixity. The lateral strength, which depends on the depth-to-maximum-moment, is determined using the flexural strength of the Pile and the ultimate pressure distribution of the soil. By assuming a concentrated plastic hinge rotation at the depth-of-maximum- moment, a kinematic model relating the local curvature ductility demand to global displacement ductility demand is developed. The kinematic relation is shown to depend on the aboveground height, depth-to-maximum-moment, depth-to-fixity, and equivalent plastic hinge length. The model is illustrated using a Pile-Shaft embedded in cohesive and cohesionless soils.