Railway bridges are susceptible to over-height truck collisions and to address this issue,it is necessary to attenuate the effect of these impacts to ensure the safety of transportation operations.This study experimen...Railway bridges are susceptible to over-height truck collisions and to address this issue,it is necessary to attenuate the effect of these impacts to ensure the safety of transportation operations.This study experimentally investigates the effectiveness of crash beams as a cushioning mechanism for railway bridges against collisions.Over-height truck and railway bridge impact events were simulated in a 1:5 scale experiment.The design parameters such as the stiffness of the crash beam and the bridge supports were scaled to evaluate different levels of attenuation.Seventeen experiments were conducted with five configurations consisting of four different types of crash beams and one no-crash beam arrangement.The results show that crash beams attenuate bridge total peak dynamic displacement responses between 14.5%and 35.7%,depending on the intensity of the impact and crash beam type.In addition,the results show that the average effectiveness in attenuating residual deformation for all four crash beams ranges from 43.03%to 83.40%.Finally,various designs and their effectiveness against lateral impacts with different speeds are discussed.The overall scope of this research is to provide objective information about the design of crash beams for railway bridges based on their response to over-height truck collisions at various speeds.展开更多
Long-span bridges are usually constructed over waterways that involve substantial ship traffic,resulting in a risk of collisions between the bridge girders and over-height ships.The consequences of this can be severe ...Long-span bridges are usually constructed over waterways that involve substantial ship traffic,resulting in a risk of collisions between the bridge girders and over-height ships.The consequences of this can be severe structural damage or even collapse.Accurate measurement of ship dimensions is an effective way to monitor approaching over-height ships and avoid collisions.However,the performance of current techniques for estimating the size of moving objects can be undermined by large sensor-to-object distance,limiting their applicability.In this study,we propose a digital twin-assisted ship size measurement framework that can overcome such limitations through a predictive model and virtual-to-real-world transfer learning.Specifically,a 3D synthetic environment is first established to generate a synthetic dataset,which includes ship images,positions,and dimensions.Then the pixel information and spatial coordinates of ships are adopted as regressors,and ship dimensions are selected as the output variables to pre-train deep learning models using the generated dataset.Coordinate system transformations are applied to address dataset bias between the simulated world and real-world,as well as improve the model’s generalization.The pre-trained models are compared using supervised virtual-to-real-world transfer learning to select the version with optimal real-world performance.The mean absolute percentage error is only 3.74%across varying camera-to-ship distances,which demonstrates that the proposed method is effective for over-limit ship monitoring.展开更多
Deriving analytical solutions for tide-induced groundwater fluctuations in unconfined aquifers confronts two problems： （1） As the Boussinesq equation itself contains nonlinear terms, the ＂secular term＂ would be g...Deriving analytical solutions for tide-induced groundwater fluctuations in unconfined aquifers confronts two problems： （1） As the Boussinesq equation itself contains nonlinear terms, the ＂secular term＂ would be generated in derivation, thus making perturbation solution unable to be deduced to higher order; （2） for aquifers with sloping beaches, the perturbation parameter in existing analytical solution integrating the beach slope and hydrogeological property would be sometimes larger than 1. So the application of perturbation solutions is relatively limited. Furthermore, as the beach slope decreases, the error of analytical solution would gradually increase. Given that water table over-height would increase the aquifer thickness and speed up wave propagation, this paper integrates over-height into the perturbation parameter and adjusts boundary conditions to settle the problem of ＂secular term＂ and to derive a new high-order analytical solution for nonlinear Boussinesq equation in terms of sloping beaches. Results show that the new analytical solution is more reasonable, and the analytical accuracy is obviously improved in comparison with the existing analytical solution for a gentle slope. The new analytical solution provides a theoretical basis for analyzing the propagation characteristics （e.g., wave length and over-height variation） of tide-induced groundwater wave in unconfined aquifers, particularly those with sloping beaches.展开更多
基金Scientific Research Fund of Institute of Engineering Mechanics,China Earthquake Administration under Grant Nos.2016A06 and 2017A02the National Natural Science Foundation of China under Grant Nos.51678538 and 51878630+1 种基金the Transportation Consortium of South-Central States(TRANSET)US Department of Transportation(USDOT),Project No.17STUNM02。
文摘Railway bridges are susceptible to over-height truck collisions and to address this issue,it is necessary to attenuate the effect of these impacts to ensure the safety of transportation operations.This study experimentally investigates the effectiveness of crash beams as a cushioning mechanism for railway bridges against collisions.Over-height truck and railway bridge impact events were simulated in a 1:5 scale experiment.The design parameters such as the stiffness of the crash beam and the bridge supports were scaled to evaluate different levels of attenuation.Seventeen experiments were conducted with five configurations consisting of four different types of crash beams and one no-crash beam arrangement.The results show that crash beams attenuate bridge total peak dynamic displacement responses between 14.5%and 35.7%,depending on the intensity of the impact and crash beam type.In addition,the results show that the average effectiveness in attenuating residual deformation for all four crash beams ranges from 43.03%to 83.40%.Finally,various designs and their effectiveness against lateral impacts with different speeds are discussed.The overall scope of this research is to provide objective information about the design of crash beams for railway bridges based on their response to over-height truck collisions at various speeds.
基金supported by the National Natural Science Foundation of China(Nos.52338011 and 52108274)the Start-up Research Fund of Southeast University(No.RF1028624058),Chinasupport from the SEU Innovation Capability Enhancement Plan for Doctoral Students(No.CXJH_SEU 26112),China.
文摘Long-span bridges are usually constructed over waterways that involve substantial ship traffic,resulting in a risk of collisions between the bridge girders and over-height ships.The consequences of this can be severe structural damage or even collapse.Accurate measurement of ship dimensions is an effective way to monitor approaching over-height ships and avoid collisions.However,the performance of current techniques for estimating the size of moving objects can be undermined by large sensor-to-object distance,limiting their applicability.In this study,we propose a digital twin-assisted ship size measurement framework that can overcome such limitations through a predictive model and virtual-to-real-world transfer learning.Specifically,a 3D synthetic environment is first established to generate a synthetic dataset,which includes ship images,positions,and dimensions.Then the pixel information and spatial coordinates of ships are adopted as regressors,and ship dimensions are selected as the output variables to pre-train deep learning models using the generated dataset.Coordinate system transformations are applied to address dataset bias between the simulated world and real-world,as well as improve the model’s generalization.The pre-trained models are compared using supervised virtual-to-real-world transfer learning to select the version with optimal real-world performance.The mean absolute percentage error is only 3.74%across varying camera-to-ship distances,which demonstrates that the proposed method is effective for over-limit ship monitoring.
基金supported by the National Natural Science Foundation of China (Grant No. 51009059)the Natural Science Foundation of Jiangsu Higher Education Institutions of China (Grant No. 09KJA170003)+2 种基金the Fundamental Research Funds for the Central Universities (Grant No. 2010B02914)the Special Commonweal Research Foundation of the Ministry of Water Conservancy (Grant No. 200901032)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘Deriving analytical solutions for tide-induced groundwater fluctuations in unconfined aquifers confronts two problems： （1） As the Boussinesq equation itself contains nonlinear terms, the ＂secular term＂ would be generated in derivation, thus making perturbation solution unable to be deduced to higher order; （2） for aquifers with sloping beaches, the perturbation parameter in existing analytical solution integrating the beach slope and hydrogeological property would be sometimes larger than 1. So the application of perturbation solutions is relatively limited. Furthermore, as the beach slope decreases, the error of analytical solution would gradually increase. Given that water table over-height would increase the aquifer thickness and speed up wave propagation, this paper integrates over-height into the perturbation parameter and adjusts boundary conditions to settle the problem of ＂secular term＂ and to derive a new high-order analytical solution for nonlinear Boussinesq equation in terms of sloping beaches. Results show that the new analytical solution is more reasonable, and the analytical accuracy is obviously improved in comparison with the existing analytical solution for a gentle slope. The new analytical solution provides a theoretical basis for analyzing the propagation characteristics （e.g., wave length and over-height variation） of tide-induced groundwater wave in unconfined aquifers, particularly those with sloping beaches.
