Self-Centering Piston-Based Braced Frames(SC-PBBFs)are designed to curtail structural damage under severe ground motions.The self-centering mechanism in this bracing mitigates structural damage during an earthquake,th...Self-Centering Piston-Based Braced Frames(SC-PBBFs)are designed to curtail structural damage under severe ground motions.The self-centering mechanism in this bracing mitigates structural damage during an earthquake,thereby reducing post-earthquake repair costs and contributing to seismic resilience.However,non-structural components,particularly those sensitive to floor acceleration,remain vulnerable,resulting in prolonged func-tional recovery times.This paper aims to address this limitation by introducing a novel structural archetype,the Self-Centering Viscous-Based Braced Frame(SC-VBBF),which integrates superelastic shape memory alloy(SMA)bars,viscous dampers(VDs),and friction springs(FSs).A streamlined analytical approach relies on the strength decoupling of VD from other components using aλfactor to design SC-VBBFs.To evaluate the effectiveness of the hybrid brace,a set of 4-,8-,and 12-story archetypes equipped with SC-PBBs and SC-VBBFs are simulated in OpenSees and analyzed under various earthquake types,including crustal,subcrustal,and subduction events.The results demonstrate the superior performance of the SC-VBBF withλ≤0.5 system compared to SC-PBBFs in mitigating floor accelerations under design-level earthquakes and improving seismic resilience.展开更多
To investigate the impact of temporary structures on the mechanical behavior of shaped bridge towers during the construction process,the Dianbu River Special Bridge was selected as the engineering background.A finite ...To investigate the impact of temporary structures on the mechanical behavior of shaped bridge towers during the construction process,the Dianbu River Special Bridge was selected as the engineering background.A finite element model of the middle tower column during the construction stage was established using ABAQUS to analyze the effects of key parameters,including the angle and pretension of temporary cables,as well as the wall thickness and diameter of temporary diagonal braces.The study examines how these parameters influence the stresses at the towergirder consolidation.The results indicate that the angle of temporary cables significantly affects the tensile stresses at the tower-girder consolidation,while its impact on compressive stresses is minimal.Among all parameters,the pretension of temporary cables has the most pronounced effect on the stresses at the tower-girder consolidation.In contrast,the wall thickness of temporary diagonal braces has only a minor influence,whereas the diameter of temporary diagonal braces has an almost negligible impact.These findings provide valuable insights for optimizing the design and arrangement of temporary support structures in similar bridge construction projects.展开更多
The current deep learning models for braced excavation cannot predict deformation from the beginning of excavation due to the need for a substantial corpus of sufficient historical data for training purposes.To addres...The current deep learning models for braced excavation cannot predict deformation from the beginning of excavation due to the need for a substantial corpus of sufficient historical data for training purposes.To address this issue,this study proposes a transfer learning model based on a sequence-to-sequence twodimensional(2D)convolutional long short-term memory neural network(S2SCL2D).The model can use the existing data from other adjacent similar excavations to achieve wall deflection prediction once a limited amount of monitoring data from the target excavation has been recorded.In the absence of adjacent excavation data,numerical simulation data from the target project can be employed instead.A weight update strategy is proposed to improve the prediction accuracy by integrating the stochastic gradient masking with an early stopping mechanism.To illustrate the proposed methodology,an excavation project in Hangzhou,China is adopted.The proposed deep transfer learning model,which uses either adjacent excavation data or numerical simulation data as the source domain,shows a significant improvement in performance when compared to the non-transfer learning model.Using the simulation data from the target project even leads to better prediction performance than using the actual monitoring data from other adjacent excavations.The results demonstrate that the proposed model can reasonably predict the deformation with limited data from the target project.展开更多
Self-centering systems are increasingly studied after devastating earthquakes in the 2010s that caused irreparable damage to buildings.Currently,there is conflicting evidence as to whether the re-centering(restoring)c...Self-centering systems are increasingly studied after devastating earthquakes in the 2010s that caused irreparable damage to buildings.Currently,there is conflicting evidence as to whether the re-centering(restoring)capabilities are gained at the expense of hysteretic damping,potentially leading to larger peak displacements and damage to non-structural elements.This study examines the earthquake response of self-centering and non-self-centering systems through analyses of 4-storey and 8-storey steel-braced frames.The Resilient Slip Friction Joint(RSFJ)dampers,combined with steel braces in series,represent the self-centering bracing system,whereas the Buckling Restrained Braces(BRBs)represent the non-self-centering bracing system.Results suggest that peak displacements,base shears,and floor accelerations were comparable between the two systems.A possible explanation is that the peak response occurs on the first major excursion;similar peaks result from similar backbone curves in the run-up to the peak.Conversely,the amount of hysteretic damping only begins to affect the post-peak behavior.For instance,the RSFJ system reintroduces seismic energy into the structure post-peak(rather than dissipating it like the BRB).Subsequently,it leads to larger vibration amplitudes about the central position,increasing the risk of secondary peaks.This contrasts with the BRB system,which exhibits smaller vibration amplitudes about an increasingly deformed position due to seismic ratcheting.Unsurprisingly,residual deformations were high for the BRBs(1.7%on average)and negligible for the RSFJ.However,RSFJ produced smaller peak inter-storey drifts between 13%–18%but higher peak accelerations by 4%–5%.The results suggest that multi-storey braced frames could be designed with similar or smaller forces when self-centering systems are used.展开更多
This paper presents a review of how the ductile diaphragm concept was formulated,evaluated,improved,and implemented over time to achieve seismically resilient bridges.A particular emphasis is placed on the most recent...This paper presents a review of how the ductile diaphragm concept was formulated,evaluated,improved,and implemented over time to achieve seismically resilient bridges.A particular emphasis is placed on the most recent work that has provided a more fully,and more widely applicable,version of the concept.The paper also addresses how to design buckling restrained braces used as energy dissipating elements in the longitudinal di-rection of multi-span bridges(simple spans or continuous bridges)as part of the ductile diaphragm concept.In all cases,the objective of the ductile diaphragm concept is to concentrate ductility demands in steel energy dissi-pating elements located at the ends of the superstructure spans to protect the substructure(and rest of the su-perstructure)from damage,to ensure that the bridge can remain open to full traffic immediately following an earthquake.展开更多
文摘Self-Centering Piston-Based Braced Frames(SC-PBBFs)are designed to curtail structural damage under severe ground motions.The self-centering mechanism in this bracing mitigates structural damage during an earthquake,thereby reducing post-earthquake repair costs and contributing to seismic resilience.However,non-structural components,particularly those sensitive to floor acceleration,remain vulnerable,resulting in prolonged func-tional recovery times.This paper aims to address this limitation by introducing a novel structural archetype,the Self-Centering Viscous-Based Braced Frame(SC-VBBF),which integrates superelastic shape memory alloy(SMA)bars,viscous dampers(VDs),and friction springs(FSs).A streamlined analytical approach relies on the strength decoupling of VD from other components using aλfactor to design SC-VBBFs.To evaluate the effectiveness of the hybrid brace,a set of 4-,8-,and 12-story archetypes equipped with SC-PBBs and SC-VBBFs are simulated in OpenSees and analyzed under various earthquake types,including crustal,subcrustal,and subduction events.The results demonstrate the superior performance of the SC-VBBF withλ≤0.5 system compared to SC-PBBFs in mitigating floor accelerations under design-level earthquakes and improving seismic resilience.
文摘To investigate the impact of temporary structures on the mechanical behavior of shaped bridge towers during the construction process,the Dianbu River Special Bridge was selected as the engineering background.A finite element model of the middle tower column during the construction stage was established using ABAQUS to analyze the effects of key parameters,including the angle and pretension of temporary cables,as well as the wall thickness and diameter of temporary diagonal braces.The study examines how these parameters influence the stresses at the towergirder consolidation.The results indicate that the angle of temporary cables significantly affects the tensile stresses at the tower-girder consolidation,while its impact on compressive stresses is minimal.Among all parameters,the pretension of temporary cables has the most pronounced effect on the stresses at the tower-girder consolidation.In contrast,the wall thickness of temporary diagonal braces has only a minor influence,whereas the diameter of temporary diagonal braces has an almost negligible impact.These findings provide valuable insights for optimizing the design and arrangement of temporary support structures in similar bridge construction projects.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFC3009400)the National Natural Science Foundation of China(Grant Nos.42307218 and U2239251).
文摘The current deep learning models for braced excavation cannot predict deformation from the beginning of excavation due to the need for a substantial corpus of sufficient historical data for training purposes.To address this issue,this study proposes a transfer learning model based on a sequence-to-sequence twodimensional(2D)convolutional long short-term memory neural network(S2SCL2D).The model can use the existing data from other adjacent similar excavations to achieve wall deflection prediction once a limited amount of monitoring data from the target excavation has been recorded.In the absence of adjacent excavation data,numerical simulation data from the target project can be employed instead.A weight update strategy is proposed to improve the prediction accuracy by integrating the stochastic gradient masking with an early stopping mechanism.To illustrate the proposed methodology,an excavation project in Hangzhou,China is adopted.The proposed deep transfer learning model,which uses either adjacent excavation data or numerical simulation data as the source domain,shows a significant improvement in performance when compared to the non-transfer learning model.Using the simulation data from the target project even leads to better prediction performance than using the actual monitoring data from other adjacent excavations.The results demonstrate that the proposed model can reasonably predict the deformation with limited data from the target project.
文摘Self-centering systems are increasingly studied after devastating earthquakes in the 2010s that caused irreparable damage to buildings.Currently,there is conflicting evidence as to whether the re-centering(restoring)capabilities are gained at the expense of hysteretic damping,potentially leading to larger peak displacements and damage to non-structural elements.This study examines the earthquake response of self-centering and non-self-centering systems through analyses of 4-storey and 8-storey steel-braced frames.The Resilient Slip Friction Joint(RSFJ)dampers,combined with steel braces in series,represent the self-centering bracing system,whereas the Buckling Restrained Braces(BRBs)represent the non-self-centering bracing system.Results suggest that peak displacements,base shears,and floor accelerations were comparable between the two systems.A possible explanation is that the peak response occurs on the first major excursion;similar peaks result from similar backbone curves in the run-up to the peak.Conversely,the amount of hysteretic damping only begins to affect the post-peak behavior.For instance,the RSFJ system reintroduces seismic energy into the structure post-peak(rather than dissipating it like the BRB).Subsequently,it leads to larger vibration amplitudes about the central position,increasing the risk of secondary peaks.This contrasts with the BRB system,which exhibits smaller vibration amplitudes about an increasingly deformed position due to seismic ratcheting.Unsurprisingly,residual deformations were high for the BRBs(1.7%on average)and negligible for the RSFJ.However,RSFJ produced smaller peak inter-storey drifts between 13%–18%but higher peak accelerations by 4%–5%.The results suggest that multi-storey braced frames could be designed with similar or smaller forces when self-centering systems are used.
文摘This paper presents a review of how the ductile diaphragm concept was formulated,evaluated,improved,and implemented over time to achieve seismically resilient bridges.A particular emphasis is placed on the most recent work that has provided a more fully,and more widely applicable,version of the concept.The paper also addresses how to design buckling restrained braces used as energy dissipating elements in the longitudinal di-rection of multi-span bridges(simple spans or continuous bridges)as part of the ductile diaphragm concept.In all cases,the objective of the ductile diaphragm concept is to concentrate ductility demands in steel energy dissi-pating elements located at the ends of the superstructure spans to protect the substructure(and rest of the su-perstructure)from damage,to ensure that the bridge can remain open to full traffic immediately following an earthquake.
