A self-centering bridge bent equipped with energy-dissipation(ED)beams is proposed.Quasi-static tests are conducted on self-centering bridge bents,both with and without ED beams,to validate the accuracy of the corresp...A self-centering bridge bent equipped with energy-dissipation(ED)beams is proposed.Quasi-static tests are conducted on self-centering bridge bents,both with and without ED beams,to validate the accuracy of the corresponding numerical models.The effects of various param-eters,such as the web area of ED beams,prestressing force of tendons,tendon arrangements,and number of column segments,on the seismic performance of self-centering bridge bents with ED beams are evaluated using the validated numerical model.The results demonstrate that the nu-merical models accurately replicate the quasi-static test results,with average errors in the lateral force remaining below 9.6%.The web area of ED beams significantly affects the strength,cumulative energy dissipation,and relative self-centering index(RSI)of the self-centering bridge bents.Increasing the prestressing force enhances the lateral force and self-centering capability of the bridge bents but has minimal effect on their ED capacity.Reducing the num-ber of segments in each column enhances the lateral force and cumulative hysteretic energy dissipation of the self-centering bridge bents while exerting an insignificant effect on the RSI.Thus,the proposed novel system is highly suitable for doubleor multicolumn piers supporting bridges in regions prone to strong earthquakes.展开更多
To address local concrete damage in joint areas at the footing of prefabricated assembled self-centering bridge piers(PASPs)in seismic design,a damage transfer configuration(DTC)was proposed,based on the bridge pier s...To address local concrete damage in joint areas at the footing of prefabricated assembled self-centering bridge piers(PASPs)in seismic design,a damage transfer configuration(DTC)was proposed,based on the bridge pier structure configuration and the mechanism of local damage formation.Integrating the DTC into the PASP,numerical models of a previous experimental reference PASP and a PASP with damage transfer configuration(DTPASP)were established using the finite element software ABAQUS with a concrete damage plasticity(CDP)model.The models were then compared with experimental results regarding damage distribution,hysteresis curves,energy dissipation capacity,the joint opening degree,and residual displacement.The findings indicate that the finite element model developed in this study can well reflect the experimental results of the reference PASP.The incorporation of the DTC proved to be beneficial in preserving structural integrity,bearing capacity,and the functionality of the core structure of bridge piers following an earthquake.Meanwhile,this addition did not exert a significant influence on the seismic behavior of the core structure of the bridge pier.展开更多
A new type of beam-to-column connection for steel moment flames, designated as a ＂self-centering connection,＂ is studied. In this connection, bolted top-and-seat angles, and post-tensioned （PT） high-strength steel...A new type of beam-to-column connection for steel moment flames, designated as a ＂self-centering connection,＂ is studied. In this connection, bolted top-and-seat angles, and post-tensioned （PT） high-strength steel strands running along the beam are used. The PT strands tie the beam flanges on the column flange to resist moment and provide self-centering force. After an earthquake, the connections have zero deformation, and can be restored to their original status by simply replacing the angles. Four full-scale connections were tested under cyclic loading. The strength, energy-dissipation capacity, hysteresis curve, as well as angles and PT strands behavior of the connections are investigated. A general FEM analysis program called ABAQUS 6.9 is adopted to model the four test specimens. The numerical and test results match very well. Both the test and analysis results suggest that： （1） the columns and beams remain elastic while the angles sustain plastic deformations for energy dissipation when the rotation of the beam related to the column equals 0.05 tad, （2） the energy dissipation capacity is enhanced when the thickness of the angle is increased, and （3） the number of PT strands has a significant influence on the behavior of the connections, whereas the distance between the strands is not as important to the performance of the connection.展开更多
The seismic performance of a self-centering precast reinforced concrete （RC） frame with shear walls was investigated in this paper. The lateral force resistance was provided by self-centering precast RC shear walls ...The seismic performance of a self-centering precast reinforced concrete （RC） frame with shear walls was investigated in this paper. The lateral force resistance was provided by self-centering precast RC shear walls （SPCW）, which utilize a combination ofunbonded prestressed post-tensioned （PT） tendons and mild steel reinforcing bars for flexural resistance across base joints. The structures concentrated deformations at the bottom joints and the unbonded PT tendons provided the self-centering restoring force. A 1/3-scale model of a five-story self-centering RC frame with shear walls was designed and tested on a shake-table under a series of bi-directional earthquake excitations with increasing intensity. The acceleration response, roof displacement, inter-story drifts, residual drifts, shear force ratios, hysteresis curves, and local behaviour of the test specimen were analysed and evaluated. The results demonstrated that seismic performance of the test specimen was satisfactory in the plane of the shear wall; however, the structure sustained inter-story drift levels up to 2.45%. Negligible residual drifts were recorded after all applied earthquake excitations. Based on the shake-table test results, it is feasible to apply and popularize a self-centering precast RC frame with shear walls as a structural system in seismic regions.展开更多
This paper presents the results of a parametric study of self-centering seismic retrofit schemes for reinforced concrete (RC) frame buildings. The self-centering retrofit system features flag-shaped hysteresis and min...This paper presents the results of a parametric study of self-centering seismic retrofit schemes for reinforced concrete (RC) frame buildings. The self-centering retrofit system features flag-shaped hysteresis and minimal residual deformation. For comparison purpose,an alternate seismic retrofit scheme that uses a bilinear-hysteresis retrofit system such as buckling-restrained braces (BRB) is also considered in this paper. The parametric study was carried out in a single-degree-of-freedom (SDOF) system framework since a multi-story building structure may be idealized as an equivalent SDOF system and investigation of the performance of this equivalent SDOF system can provide insight into the seismic response of the multi-story building. A peak-oriented hysteresis model which can consider the strength and stiffness degradation is used to describe the hysteretic behavior of RC structures. The parametric study involves two key parameters -the strength ratio and elastic stiffness ratio between the seismic retrofit system and the original RC frame. An ensemble of 172 earthquake ground motion records scaled to the design basis earthquake in California with a probability of exceedance of 10% in 50 years was constructed for the simulation-based parametric study. The effectiveness of the two seismic retrofit schemes considered in this study is evaluated in terms of peak displacement ratio,peak acceleration ratio,energy dissipation demand ratio and residual displacement ratio between the SDOF systems with and without retrofit. It is found from this parametric study that RC structures retrofitted with the self-centering retrofit scheme (SCRS) can achieve a seismic performance level comparable to the bilinear-hysteresis retrofit scheme (BHRS) in terms of peak displacement and energy dissipation demand ratio while having negligible residual displacement after earthquake.展开更多
The seismic performance of a five-story,four-bay,self-centering precast reinforced concrete frame(SC-RCF),which was redesigned using the direct displacement-based design method,was analytically investigated.The analyt...The seismic performance of a five-story,four-bay,self-centering precast reinforced concrete frame(SC-RCF),which was redesigned using the direct displacement-based design method,was analytically investigated.The analytical model of the overall structure was developed in OpenSees.The multi-spring contact element was adopted to simulate gap open-close behavior at connection interfaces.The limit states of external mild steel dampers and unbonded post-tensioning strands were considered.Static pushover analyses were performed up to the roof drift of 10%.The nonlinear dynamic responses under four groups of ground motions(with different fault distances and site conditions)at six hazard levels(from the service to the very rare earthquake(VRE))were compared.Incremental dynamic analyses were implemented to quantify the structural collapse risk.The results showed that the structural responses of SC-RCF were satisfactory under all levels of earthquakes.The collapse safety of the structure under earthquakes up to VRE1 was adequate,while the structure would collapse to a large extent under VRE2 and VRE3.展开更多
A new type of steel moment resisting frame with bottom flange friction devices （BFFDs） has been developed to provide self-centering capacity and energy dissipation, and to reduce permanent deformations under earthqu...A new type of steel moment resisting frame with bottom flange friction devices （BFFDs） has been developed to provide self-centering capacity and energy dissipation, and to reduce permanent deformations under earthquakes. This paper presents a numerical simulation of self-centering beam-column connections with BFFDs, in which the gap opening/closing at the beam-column interfaces is simulated by using pairs of zero-length elements with compression-only material properties, and the energy dissipation due to friction is simulated by using truss elements with specified hysteretic behavior. In particular, the effect of the friction bolt bearing against the slotted plate in the BFFDs was modeled, so that the increase in lateral force and the loss of friction force due to the bolt bearing could be taken into account. Parallel elastic-perfectly plastic gap （ElasticPPGap） materials in the Open System for Earthquake Engineering Simulation （OpenSees） were used with predefined gaps to specify the sequence that each bolt went into the bearing and the corresponding increase in bending stiffness. The MinMax material in OpenSees is used to specify the minimum and maximum values of strains of the ElasticPPGap materials. To consider the loss of friction force due to bok bearing, a number of parallel hysteretic materials were used, and the failure of these materials in sequence simulated the gradual loss of friction force. Analysis results obtained by using the proposed numerical model are discussed and compared with the test results under cyclic loadings and the seismic loading, respectively.展开更多
Firstly, in view of the respective defects of existing self-centering devices for vehicle suspension height, the design scheme of the proposed mechanical self-centering device for suspension height is described. Takin...Firstly, in view of the respective defects of existing self-centering devices for vehicle suspension height, the design scheme of the proposed mechanical self-centering device for suspension height is described. Taking the rear suspension of a certain light bus as a research example, the structures and parameters of the novel device are designed and ascertained. Then, the road excitation models, the performance evaluation indexes and the half-vehicle model are built, the simulation outputs of time and frequency domain are obtained with the road excitations of random and pulse by using MATLAB/Simulink software. So the main characteristics of the self-centering suspension are presented preliminarily. Finally, a multi-objective parameter design optimization model for the self-centering device is built by weighted sum approach, and optimal solution is obtained by adopting complex approach. The relevant choosing-type parameters for self-centering device components are deduced by using discrete variable optimal method, and the optimal results are verified and analyzed. So the performance potentials of the self-centering device are exerted fully in condition of ensuring overall suspension performances.展开更多
Self-centering earthquake-resistant structures have received increased attention due to their ability to reduce post-earthquake residual deformations and,thus,repair time and cost.This stimulated the development of re...Self-centering earthquake-resistant structures have received increased attention due to their ability to reduce post-earthquake residual deformations and,thus,repair time and cost.This stimulated the development of recentering shape memory alloy(SMA)dampers that use superelastic nitinol wires to dissipate energy and self-center the structure.However,there are still a few case studies applications on full-scale RC buildings in the literature.Moreover,general guidelines or even simplified approaches for the practical design of SMA damped braces are still lacking.This paper focuses on evaluating the effect of using self-centering shape memory alloy dampers for buckling-restrained braces applied for the seismic retrofit of a complex RC building structure.A design method originally proposed for elastoplastic dampers was implemented to size the SMA dampers to be placed on selected spans and stories of a building.The effectiveness of the design procedure was demonstrated by nonlinear time-history analyses under different sets of earthquake strong ground motions.The analysis results show that the recentering shape memory alloy bracing system is effective in limiting the maximum transient inter-story drifts and reducing the residual inter-story drifts after strong seismic events,due to its excellent recentering behavior together with its not negligible energy dissipation capacity.展开更多
Self-centering systems exhibit superior performance during earthquake shaking with lower damage and less resid-ual deformations.Although the equivalent static force design procedure is the commonly used one for most s...Self-centering systems exhibit superior performance during earthquake shaking with lower damage and less resid-ual deformations.Although the equivalent static force design procedure is the commonly used one for most structural systems for seismic applications,the cumulative damage and the effective duration of earthquakes cannot be explicitly considered,which has significantly affected the behaviors and post-earthquake performance of self-centering systems.Energy-based design theory(EBDT),which introduces the energy demand as the crit-ical parameter to establish relations with structural damage,has gained attention around the world in recent decades.The EBDT can provide comprehensive considerations for structural responses and damage in design procedures,especially for self-centering systems.However,few researches and actual energy design projects fo-cus on the use of EBDT for self-centering systems.This paper intends to present thorough review of several critical issues in EBDT.Meanwhile,pivotal gaps that need to be further investigated towards the application of EBDT to self-centering systems are identified and discussed in the paper.展开更多
针对三维激光标靶球定位模型中的系数矩阵存在随机元素和非随机元素以及考虑到观测向量与系数矩阵存在相关的情况,引入基于Partial EIV模型的相关观测加权总体最小二乘(Weighted Total Least Squares,WTLS)方法进行求解。模拟实验结果表...针对三维激光标靶球定位模型中的系数矩阵存在随机元素和非随机元素以及考虑到观测向量与系数矩阵存在相关的情况,引入基于Partial EIV模型的相关观测加权总体最小二乘(Weighted Total Least Squares,WTLS)方法进行求解。模拟实验结果表明,在顾及观测向量与系数矩阵存在相关性时,基于Partial EIV模型的相关观测加权总体最小二乘方法解算的参数结果更加接近真值,且精度更高。进一步将该方法应用于实际案例数据中,结果表明,在实际计算时有必要考虑到观测向量与系数矩阵之间的相关性,以提高参数解算精度。本文可补充和完善三维激光扫描标靶球定位技术方法。展开更多
Frame and rocking wall(FRW)structures have excellent resilient performance during earthquakes.However,the concrete at interfacial corners of rocking walls(RWs)is easily crushed due to local extreme compression during ...Frame and rocking wall(FRW)structures have excellent resilient performance during earthquakes.However,the concrete at interfacial corners of rocking walls(RWs)is easily crushed due to local extreme compression during the rocking process.An innovative RW with a curved interface is proposed to prevent interfacial corners from producing local damage,enhancing its earthquake resilient performance(ERP).The precast wall panel with a curved interface is assembled into an integral self-centering hybrid rocking wall(SCRW)by two post-tensioned unbonded prestressed tendons.Moreover,two ordinary energy dissipation steel rebars and two shear reinforcements are arranged to increase the energy dissipation capacity and lateral resistance.Two SCRW specimens and one monolithic reinforced concrete(RC)shear wall(SW)were tested under pseudo-static loading to compare the ERPs of the proposed SCRW and the SW,focusing on studying the effect of the curved interface on the SCRW.The key resilient performance of rocking effects,failure modes,and hysteretic properties of the SCRW were explored.The results show that nonlinear deformations of the SCRW are concentrated along the interface between the SCRW and the foundation,avoiding damage within the SCRW.The restoring force provided by the prestressed tendons can effectively realize self-centering capacity with small residual deformation,and the resilient performance of the SCRW is better than that of monolithic SW.In addition,the curved interface of the SCRW makes the rocking center change and move inward,partially relieving the stress concentration and crush of concrete.The rocking range of the rocking center is about 41.4%of the width of the SCRW.展开更多
This paper develops a practice-oriented seismic design procedure for an emerging lateral force resisting system.The system combines the favorable re-centering feature with the attractive hybrid damping capacity.The sy...This paper develops a practice-oriented seismic design procedure for an emerging lateral force resisting system.The system combines the favorable re-centering feature with the attractive hybrid damping capacity.The system overcomes the detrimental frame expansion effect that occurs in conventional self-centering building frames without the cost of building space.Following the proposed design procedure,multiple designs with different parameters to achieve performance objectives were performed for a representative three-story building in which the considered lateral force resisting system is used to resist the seismic forces.Nonlinear response history analyses were performed for the designs to evaluate the applicability and adequacy of the proposed design approach.Based on the analyses conducted in this research,it was found that the considered system designed using the proposed approach can meet both transient and residual inter-story drift requirements specified for the selected performance objectives.While an initial design per the proposed design approach may be inadequate,the re-design strategy recommended can help transform the design to an acceptable one after only one round of modification.Moreover,the composition of hybrid damping may affect the maximum floor acceleration responses.In this study,the maximum floor acceleration can be reduced 12.75%at most by replacing hysteretic damping with viscous damping.This should be included in design consideration in the proposed approach through adjusting the hybrid damping composition.展开更多
Traditional retrofit methods often focus on increasing the structure’s strength,stiffness,or both.This may in-crease seismic demand on the structure and could lead to irreparable damage during a seismic event.This pa...Traditional retrofit methods often focus on increasing the structure’s strength,stiffness,or both.This may in-crease seismic demand on the structure and could lead to irreparable damage during a seismic event.This paper presents a retrofit method,integrating concepts of selective weakening and self-centering(rocking)to achieve low seismic damage for non-code compliant reinforced concrete shear walls.The proposed method involves con-verting traditional cast-in-place concrete shear walls into rocking walls,which helps to lower the shear demand,while allowing re-centering.Two large-scale lateral load tests were performed to validate the retrofit concept on a concrete shear wall designed according to pre-1970s standards.The design parameters investigated were amount of energy dissipating reinforcements and confinement enhancement.Two different methods using Ultra High Performance Concrete(UHPC)were investigated to provide additional confinement to boundary elements of older shear walls.Observations from the tests showed minimized damage and enhanced recentering in the retrofitted wall specimens.Use of UHPC in the boundary elements of the retrofitted walls provided additional confinement and reduced damage in the rocking corners.展开更多
When multifunctional pipeline repair machinery(MPRM)is used in the deep sea area,it is difficult to grip the pipeline and ensure concentricity between the cutter heads and the pipeline during its operation.In view of ...When multifunctional pipeline repair machinery(MPRM)is used in the deep sea area,it is difficult to grip the pipeline and ensure concentricity between the cutter heads and the pipeline during its operation.In view of this,a new system of two-arm holding self-centering pipeline clamping device was proposed.The system is composed of two groups of parallelogram double-rocker mechanism and cranking block mechanism which are symmetrically distributed on the frame.The geometric parameter solutions of the clamping device were analyzed with motion and transmission as the constraints.A mechanical model was established to associate the friction torque of clamping points with the driving force.Clamping device and machinery were designed and manufactured for theØ304.8e457.2 mm pipelines used in this test.ADAMS simulation experiments were conducted underwater,and the cutting and beveling tests were carried out onshore.The following results are achieved.First,the smaller the pipe diameter,the smaller the transmission angle of the oscillating slider mechanism;the longer the hydraulic cylinder stroke,the greater the transmission angle of the double rocker mechanism.Second,the driving force of the clamping device increases with the increase of the pipe diameter.When the diameter reaches 457.2 mm,the hydraulic cylinder driving force of the clamping device should be greater than 10219 N.Third,the feed rate of the cutters increases suddenly due to the slight shaking of the machinery which occurs at the beginning of the pipe cutting,so it is necessary to adopt a small feed rate.And fourth,onshore experiment results agree well with the theoretical design and simulation results,proving the rationality of the system.The research results in this paper provide technical basis for the research and development of similar engineering prototypes.展开更多
Liver regeneration(LR)following partial hepatectomy(PH)is a unique and complex physiological response that restores hepatic mass and function through tightly orchestrated cellular and molecular events.Traditionally vi...Liver regeneration(LR)following partial hepatectomy(PH)is a unique and complex physiological response that restores hepatic mass and function through tightly orchestrated cellular and molecular events.Traditionally viewed as a proliferation-driven process,LR is now understood to involve both hepatocyte hyperplasia and hypertrophy,triggered primarily by hemodynamic alterations such as increased portal pressure and shear stress.These promote LR through endothelial–hepatocyte communication via activation of Piezo1-a mechanosensitive ion channel highly expressed in vascular endothelial cells.This channel is considered one of the potential upstream activators of molecular cascades including the interleukin(IL)-6/signal transducer and activator of transcription 3,tumour necrosis factor-alpha/nuclear factor-kappa B,Wnt/β-catenin,Hippo/YAP,transforming growth factor-beta,and Notch pathways,which contribute variably to the proliferation,differentiation,or suppression of hepatic cells.Novel insights into the IL-22 and IL-33 signaling axes,bile acid and glutamine metabolism,and the role of intestinal microbiota are also presented as promising emerging targets.This review synthesizes current insights into the interplay between mechanical cues,key signaling pathways,and metabolic reprogramming that govern early regenerative responses.We explore the mechanisms dictating the balance between hyperplasia and hypertrophy,noting that hypertrophy predominates after minor resections,while proliferation is dominant in larger resections.Polyploidization emerges as a significant adaptive mechanism,contributing to hepatocyte survival and tissue remodeling.The importance of ductular reactions,microvascular adjustments,and extracellular matrix dynamics in lobular architecture remodeling is also highlighted.The study explores the occurrence of ductular reactions in both minor and major resections,particularly within the granulation tissue near dissection areas.The paper also examines structural remodeling in regenerated liver tissue,demonstrating ongoing transformations in hepatocyte morphology and sinusoidal architecture even months after PH,and emphasizing that the termination of liver mass regrowth does not equate to the cessation of LR.展开更多
By introducing noncanonical vortex pairs to partially coherent beams, spatial correlation singularity (SCS) and orbital angular momenta (OAM) of the resulting beams are studied using the Fraunhofer diffraction integra...By introducing noncanonical vortex pairs to partially coherent beams, spatial correlation singularity (SCS) and orbital angular momenta (OAM) of the resulting beams are studied using the Fraunhofer diffraction integral. The effect of noncanonical strength, off-axis distance and vortex sign on spatial correlation singularities in far field is stressed. Furthermore, far-field OAM spectra and densities are also investigated, and the OAM detection and crosstalk probabilities are discussed. The results show that the number of dislocations of SCS always equals the sum of absolute values of topological charges for canonical or noncanonical vortex pairs. Although the sum of the product of each OAM mode and its power weight equals the algebraic sum of topological charges for canonical vortex pairs, the relationship no longer holds in the noncanonical case except for opposite-charge vortex pairs. The changes of off-axis distance, noncanonical strength or coherence length can lead to a more dominant power in adjacent mode than that in center detection mode, which also indicates that crosstalk probabilities of adjacent modes exceed the center detection probability. This work may provide potential applications in OAM-based optical communication, imaging, sensing and computing.展开更多
Highlights●CRISPR/Cas9 RNP complex-based strategy demonstrates robustness and accuracy in generating gene-edited sheep.●Sheep horn development remains unaffected by partial RXFP2 knockout.●Partial RXFP2 knockout re...Highlights●CRISPR/Cas9 RNP complex-based strategy demonstrates robustness and accuracy in generating gene-edited sheep.●Sheep horn development remains unaffected by partial RXFP2 knockout.●Partial RXFP2 knockout results in unilateral cryptorchidism in sheep.展开更多
Aiming at the problem that infrared small target detection faces low contrast between the background and the target and insufficient noise suppression ability under the complex cloud background,an infrared small targe...Aiming at the problem that infrared small target detection faces low contrast between the background and the target and insufficient noise suppression ability under the complex cloud background,an infrared small target detection method based on the tensor nuclear norm and direction residual weighting was proposed.Based on converting the infrared image into an infrared patch tensor model,from the perspective of the low-rank nature of the background tensor,and taking advantage of the difference in contrast between the background and the target in different directions,we designed a double-neighborhood local contrast based on direction residual weighting method(DNLCDRW)combined with the partial sum of tensor nuclear norm(PSTNN)to achieve effective background suppression and recovery of infrared small targets.Experiments show that the algorithm is effective in suppressing the background and improving the detection ability of the target.展开更多
To explore the impact of partial centralization on supply chain performance,this study constructs a two-period game model of a closed-loop supply chain involving a manufacturer and an online retail platform participat...To explore the impact of partial centralization on supply chain performance,this study constructs a two-period game model of a closed-loop supply chain involving a manufacturer and an online retail platform participating in the trade-in strategy.Through mathematical modeling and numerical simulation methods,the optimal decisions were analyzed under conditions where the manufacturer partially owns the retail platform’s partial equity.This study finds that partial centralization yields the highest profits,followed by full centralization,with decentralized decisions yielding the lowest profits.Moderate centralization enhances overall profits by optimizing incentive mechanisms,whereas excessive ownership concentration reduces the flexibility of the retail platform,leading to a decline in profits.Additionally,product durability and trade-in subsidy significantly influence supply chain profitability:high-durability products reduce renewal frequency,while trade-in subsidy effectively stimulates consumer demand and increase overall profits.This study provides theoretical support and practical guidance for companies implementing the trade-in strategy.展开更多
基金The National Natural Science Foundation of China(No.52278189)Zhejiang Provincial Natural Science Foundation of China(No.LY24E080002).
文摘A self-centering bridge bent equipped with energy-dissipation(ED)beams is proposed.Quasi-static tests are conducted on self-centering bridge bents,both with and without ED beams,to validate the accuracy of the corresponding numerical models.The effects of various param-eters,such as the web area of ED beams,prestressing force of tendons,tendon arrangements,and number of column segments,on the seismic performance of self-centering bridge bents with ED beams are evaluated using the validated numerical model.The results demonstrate that the nu-merical models accurately replicate the quasi-static test results,with average errors in the lateral force remaining below 9.6%.The web area of ED beams significantly affects the strength,cumulative energy dissipation,and relative self-centering index(RSI)of the self-centering bridge bents.Increasing the prestressing force enhances the lateral force and self-centering capability of the bridge bents but has minimal effect on their ED capacity.Reducing the num-ber of segments in each column enhances the lateral force and cumulative hysteretic energy dissipation of the self-centering bridge bents while exerting an insignificant effect on the RSI.Thus,the proposed novel system is highly suitable for doubleor multicolumn piers supporting bridges in regions prone to strong earthquakes.
基金National Natural Science Foundation of China under Grant Nos.51408359,52278527 and 52478536。
文摘To address local concrete damage in joint areas at the footing of prefabricated assembled self-centering bridge piers(PASPs)in seismic design,a damage transfer configuration(DTC)was proposed,based on the bridge pier structure configuration and the mechanism of local damage formation.Integrating the DTC into the PASP,numerical models of a previous experimental reference PASP and a PASP with damage transfer configuration(DTPASP)were established using the finite element software ABAQUS with a concrete damage plasticity(CDP)model.The models were then compared with experimental results regarding damage distribution,hysteresis curves,energy dissipation capacity,the joint opening degree,and residual displacement.The findings indicate that the finite element model developed in this study can well reflect the experimental results of the reference PASP.The incorporation of the DTC proved to be beneficial in preserving structural integrity,bearing capacity,and the functionality of the core structure of bridge piers following an earthquake.Meanwhile,this addition did not exert a significant influence on the seismic behavior of the core structure of the bridge pier.
基金National Natural Science Foundation of China under Nos.50808107,51178250 and 51261120377
文摘A new type of beam-to-column connection for steel moment flames, designated as a ＂self-centering connection,＂ is studied. In this connection, bolted top-and-seat angles, and post-tensioned （PT） high-strength steel strands running along the beam are used. The PT strands tie the beam flanges on the column flange to resist moment and provide self-centering force. After an earthquake, the connections have zero deformation, and can be restored to their original status by simply replacing the angles. Four full-scale connections were tested under cyclic loading. The strength, energy-dissipation capacity, hysteresis curve, as well as angles and PT strands behavior of the connections are investigated. A general FEM analysis program called ABAQUS 6.9 is adopted to model the four test specimens. The numerical and test results match very well. Both the test and analysis results suggest that： （1） the columns and beams remain elastic while the angles sustain plastic deformations for energy dissipation when the rotation of the beam related to the column equals 0.05 tad, （2） the energy dissipation capacity is enhanced when the thickness of the angle is increased, and （3） the number of PT strands has a significant influence on the behavior of the connections, whereas the distance between the strands is not as important to the performance of the connection.
基金National Natural Science Foundation of China(NSFC)under Grant Nos.51638012 and 51578401
文摘The seismic performance of a self-centering precast reinforced concrete （RC） frame with shear walls was investigated in this paper. The lateral force resistance was provided by self-centering precast RC shear walls （SPCW）, which utilize a combination ofunbonded prestressed post-tensioned （PT） tendons and mild steel reinforcing bars for flexural resistance across base joints. The structures concentrated deformations at the bottom joints and the unbonded PT tendons provided the self-centering restoring force. A 1/3-scale model of a five-story self-centering RC frame with shear walls was designed and tested on a shake-table under a series of bi-directional earthquake excitations with increasing intensity. The acceleration response, roof displacement, inter-story drifts, residual drifts, shear force ratios, hysteresis curves, and local behaviour of the test specimen were analysed and evaluated. The results demonstrated that seismic performance of the test specimen was satisfactory in the plane of the shear wall; however, the structure sustained inter-story drift levels up to 2.45%. Negligible residual drifts were recorded after all applied earthquake excitations. Based on the shake-table test results, it is feasible to apply and popularize a self-centering precast RC frame with shear walls as a structural system in seismic regions.
基金Univeristy of Maryland,Start-up Grant to the First Author
文摘This paper presents the results of a parametric study of self-centering seismic retrofit schemes for reinforced concrete (RC) frame buildings. The self-centering retrofit system features flag-shaped hysteresis and minimal residual deformation. For comparison purpose,an alternate seismic retrofit scheme that uses a bilinear-hysteresis retrofit system such as buckling-restrained braces (BRB) is also considered in this paper. The parametric study was carried out in a single-degree-of-freedom (SDOF) system framework since a multi-story building structure may be idealized as an equivalent SDOF system and investigation of the performance of this equivalent SDOF system can provide insight into the seismic response of the multi-story building. A peak-oriented hysteresis model which can consider the strength and stiffness degradation is used to describe the hysteretic behavior of RC structures. The parametric study involves two key parameters -the strength ratio and elastic stiffness ratio between the seismic retrofit system and the original RC frame. An ensemble of 172 earthquake ground motion records scaled to the design basis earthquake in California with a probability of exceedance of 10% in 50 years was constructed for the simulation-based parametric study. The effectiveness of the two seismic retrofit schemes considered in this study is evaluated in terms of peak displacement ratio,peak acceleration ratio,energy dissipation demand ratio and residual displacement ratio between the SDOF systems with and without retrofit. It is found from this parametric study that RC structures retrofitted with the self-centering retrofit scheme (SCRS) can achieve a seismic performance level comparable to the bilinear-hysteresis retrofit scheme (BHRS) in terms of peak displacement and energy dissipation demand ratio while having negligible residual displacement after earthquake.
基金Key Project of the Key Laboratory of Earthquake Engineering and Engineering Vibration,China Earthquake Administration under Grant No.2019EEEVL0304National Natural Science Foundation of China(NSFC)under Grant No.51678543。
文摘The seismic performance of a five-story,four-bay,self-centering precast reinforced concrete frame(SC-RCF),which was redesigned using the direct displacement-based design method,was analytically investigated.The analytical model of the overall structure was developed in OpenSees.The multi-spring contact element was adopted to simulate gap open-close behavior at connection interfaces.The limit states of external mild steel dampers and unbonded post-tensioning strands were considered.Static pushover analyses were performed up to the roof drift of 10%.The nonlinear dynamic responses under four groups of ground motions(with different fault distances and site conditions)at six hazard levels(from the service to the very rare earthquake(VRE))were compared.Incremental dynamic analyses were implemented to quantify the structural collapse risk.The results showed that the structural responses of SC-RCF were satisfactory under all levels of earthquakes.The collapse safety of the structure under earthquakes up to VRE1 was adequate,while the structure would collapse to a large extent under VRE2 and VRE3.
基金National Natural Science Foundation of China Under Grant No. 51078075a grant from Southeast University (No. 3205000502)the financial support from the State Key Lab of Subtropical Building Science, South China University of Technology under Grant No. 2010KB05
文摘A new type of steel moment resisting frame with bottom flange friction devices （BFFDs） has been developed to provide self-centering capacity and energy dissipation, and to reduce permanent deformations under earthquakes. This paper presents a numerical simulation of self-centering beam-column connections with BFFDs, in which the gap opening/closing at the beam-column interfaces is simulated by using pairs of zero-length elements with compression-only material properties, and the energy dissipation due to friction is simulated by using truss elements with specified hysteretic behavior. In particular, the effect of the friction bolt bearing against the slotted plate in the BFFDs was modeled, so that the increase in lateral force and the loss of friction force due to the bolt bearing could be taken into account. Parallel elastic-perfectly plastic gap （ElasticPPGap） materials in the Open System for Earthquake Engineering Simulation （OpenSees） were used with predefined gaps to specify the sequence that each bolt went into the bearing and the corresponding increase in bending stiffness. The MinMax material in OpenSees is used to specify the minimum and maximum values of strains of the ElasticPPGap materials. To consider the loss of friction force due to bok bearing, a number of parallel hysteretic materials were used, and the failure of these materials in sequence simulated the gradual loss of friction force. Analysis results obtained by using the proposed numerical model are discussed and compared with the test results under cyclic loadings and the seismic loading, respectively.
基金supported by Youth Technological Phosphor Project of Shanghai City (No.04QMX1474).
文摘Firstly, in view of the respective defects of existing self-centering devices for vehicle suspension height, the design scheme of the proposed mechanical self-centering device for suspension height is described. Taking the rear suspension of a certain light bus as a research example, the structures and parameters of the novel device are designed and ascertained. Then, the road excitation models, the performance evaluation indexes and the half-vehicle model are built, the simulation outputs of time and frequency domain are obtained with the road excitations of random and pulse by using MATLAB/Simulink software. So the main characteristics of the self-centering suspension are presented preliminarily. Finally, a multi-objective parameter design optimization model for the self-centering device is built by weighted sum approach, and optimal solution is obtained by adopting complex approach. The relevant choosing-type parameters for self-centering device components are deduced by using discrete variable optimal method, and the optimal results are verified and analyzed. So the performance potentials of the self-centering device are exerted fully in condition of ensuring overall suspension performances.
文摘Self-centering earthquake-resistant structures have received increased attention due to their ability to reduce post-earthquake residual deformations and,thus,repair time and cost.This stimulated the development of recentering shape memory alloy(SMA)dampers that use superelastic nitinol wires to dissipate energy and self-center the structure.However,there are still a few case studies applications on full-scale RC buildings in the literature.Moreover,general guidelines or even simplified approaches for the practical design of SMA damped braces are still lacking.This paper focuses on evaluating the effect of using self-centering shape memory alloy dampers for buckling-restrained braces applied for the seismic retrofit of a complex RC building structure.A design method originally proposed for elastoplastic dampers was implemented to size the SMA dampers to be placed on selected spans and stories of a building.The effectiveness of the design procedure was demonstrated by nonlinear time-history analyses under different sets of earthquake strong ground motions.The analysis results show that the recentering shape memory alloy bracing system is effective in limiting the maximum transient inter-story drifts and reducing the residual inter-story drifts after strong seismic events,due to its excellent recentering behavior together with its not negligible energy dissipation capacity.
基金support received from the Distinguished Young Scientist Fund of National Natural Science Foun-dation of China(Grant No.52025083)the National Natural Science Foundation of China(Grant No.51778486)the Shanghai Science and Technology Innovation Action Plan(Grant No.19DZ1201200).
文摘Self-centering systems exhibit superior performance during earthquake shaking with lower damage and less resid-ual deformations.Although the equivalent static force design procedure is the commonly used one for most structural systems for seismic applications,the cumulative damage and the effective duration of earthquakes cannot be explicitly considered,which has significantly affected the behaviors and post-earthquake performance of self-centering systems.Energy-based design theory(EBDT),which introduces the energy demand as the crit-ical parameter to establish relations with structural damage,has gained attention around the world in recent decades.The EBDT can provide comprehensive considerations for structural responses and damage in design procedures,especially for self-centering systems.However,few researches and actual energy design projects fo-cus on the use of EBDT for self-centering systems.This paper intends to present thorough review of several critical issues in EBDT.Meanwhile,pivotal gaps that need to be further investigated towards the application of EBDT to self-centering systems are identified and discussed in the paper.
文摘针对三维激光标靶球定位模型中的系数矩阵存在随机元素和非随机元素以及考虑到观测向量与系数矩阵存在相关的情况,引入基于Partial EIV模型的相关观测加权总体最小二乘(Weighted Total Least Squares,WTLS)方法进行求解。模拟实验结果表明,在顾及观测向量与系数矩阵存在相关性时,基于Partial EIV模型的相关观测加权总体最小二乘方法解算的参数结果更加接近真值,且精度更高。进一步将该方法应用于实际案例数据中,结果表明,在实际计算时有必要考虑到观测向量与系数矩阵之间的相关性,以提高参数解算精度。本文可补充和完善三维激光扫描标靶球定位技术方法。
基金National Key Research and Development Program of China under Grant No.2018YFC0705602。
文摘Frame and rocking wall(FRW)structures have excellent resilient performance during earthquakes.However,the concrete at interfacial corners of rocking walls(RWs)is easily crushed due to local extreme compression during the rocking process.An innovative RW with a curved interface is proposed to prevent interfacial corners from producing local damage,enhancing its earthquake resilient performance(ERP).The precast wall panel with a curved interface is assembled into an integral self-centering hybrid rocking wall(SCRW)by two post-tensioned unbonded prestressed tendons.Moreover,two ordinary energy dissipation steel rebars and two shear reinforcements are arranged to increase the energy dissipation capacity and lateral resistance.Two SCRW specimens and one monolithic reinforced concrete(RC)shear wall(SW)were tested under pseudo-static loading to compare the ERPs of the proposed SCRW and the SW,focusing on studying the effect of the curved interface on the SCRW.The key resilient performance of rocking effects,failure modes,and hysteretic properties of the SCRW were explored.The results show that nonlinear deformations of the SCRW are concentrated along the interface between the SCRW and the foundation,avoiding damage within the SCRW.The restoring force provided by the prestressed tendons can effectively realize self-centering capacity with small residual deformation,and the resilient performance of the SCRW is better than that of monolithic SW.In addition,the curved interface of the SCRW makes the rocking center change and move inward,partially relieving the stress concentration and crush of concrete.The rocking range of the rocking center is about 41.4%of the width of the SCRW.
基金financial supports from the Natural Science Foundation of China(NSFC)with Grant No.51820105013Top Discipline Plan of Shanghai Universities-Class I with Grant No.2022-3-YB-18 are gratefully acknowledged.
文摘This paper develops a practice-oriented seismic design procedure for an emerging lateral force resisting system.The system combines the favorable re-centering feature with the attractive hybrid damping capacity.The system overcomes the detrimental frame expansion effect that occurs in conventional self-centering building frames without the cost of building space.Following the proposed design procedure,multiple designs with different parameters to achieve performance objectives were performed for a representative three-story building in which the considered lateral force resisting system is used to resist the seismic forces.Nonlinear response history analyses were performed for the designs to evaluate the applicability and adequacy of the proposed design approach.Based on the analyses conducted in this research,it was found that the considered system designed using the proposed approach can meet both transient and residual inter-story drift requirements specified for the selected performance objectives.While an initial design per the proposed design approach may be inadequate,the re-design strategy recommended can help transform the design to an acceptable one after only one round of modification.Moreover,the composition of hybrid damping may affect the maximum floor acceleration responses.In this study,the maximum floor acceleration can be reduced 12.75%at most by replacing hysteretic damping with viscous damping.This should be included in design consideration in the proposed approach through adjusting the hybrid damping composition.
基金study described in this paper was made possible by a grant from the National Science Foundation’s Engineering for Natural Hazards(ENH)program,Grant#1662963.
文摘Traditional retrofit methods often focus on increasing the structure’s strength,stiffness,or both.This may in-crease seismic demand on the structure and could lead to irreparable damage during a seismic event.This paper presents a retrofit method,integrating concepts of selective weakening and self-centering(rocking)to achieve low seismic damage for non-code compliant reinforced concrete shear walls.The proposed method involves con-verting traditional cast-in-place concrete shear walls into rocking walls,which helps to lower the shear demand,while allowing re-centering.Two large-scale lateral load tests were performed to validate the retrofit concept on a concrete shear wall designed according to pre-1970s standards.The design parameters investigated were amount of energy dissipating reinforcements and confinement enhancement.Two different methods using Ultra High Performance Concrete(UHPC)were investigated to provide additional confinement to boundary elements of older shear walls.Observations from the tests showed minimized damage and enhanced recentering in the retrofitted wall specimens.Use of UHPC in the boundary elements of the retrofitted walls provided additional confinement and reduced damage in the rocking corners.
文摘When multifunctional pipeline repair machinery(MPRM)is used in the deep sea area,it is difficult to grip the pipeline and ensure concentricity between the cutter heads and the pipeline during its operation.In view of this,a new system of two-arm holding self-centering pipeline clamping device was proposed.The system is composed of two groups of parallelogram double-rocker mechanism and cranking block mechanism which are symmetrically distributed on the frame.The geometric parameter solutions of the clamping device were analyzed with motion and transmission as the constraints.A mechanical model was established to associate the friction torque of clamping points with the driving force.Clamping device and machinery were designed and manufactured for theØ304.8e457.2 mm pipelines used in this test.ADAMS simulation experiments were conducted underwater,and the cutting and beveling tests were carried out onshore.The following results are achieved.First,the smaller the pipe diameter,the smaller the transmission angle of the oscillating slider mechanism;the longer the hydraulic cylinder stroke,the greater the transmission angle of the double rocker mechanism.Second,the driving force of the clamping device increases with the increase of the pipe diameter.When the diameter reaches 457.2 mm,the hydraulic cylinder driving force of the clamping device should be greater than 10219 N.Third,the feed rate of the cutters increases suddenly due to the slight shaking of the machinery which occurs at the beginning of the pipe cutting,so it is necessary to adopt a small feed rate.And fourth,onshore experiment results agree well with the theoretical design and simulation results,proving the rationality of the system.The research results in this paper provide technical basis for the research and development of similar engineering prototypes.
文摘Liver regeneration(LR)following partial hepatectomy(PH)is a unique and complex physiological response that restores hepatic mass and function through tightly orchestrated cellular and molecular events.Traditionally viewed as a proliferation-driven process,LR is now understood to involve both hepatocyte hyperplasia and hypertrophy,triggered primarily by hemodynamic alterations such as increased portal pressure and shear stress.These promote LR through endothelial–hepatocyte communication via activation of Piezo1-a mechanosensitive ion channel highly expressed in vascular endothelial cells.This channel is considered one of the potential upstream activators of molecular cascades including the interleukin(IL)-6/signal transducer and activator of transcription 3,tumour necrosis factor-alpha/nuclear factor-kappa B,Wnt/β-catenin,Hippo/YAP,transforming growth factor-beta,and Notch pathways,which contribute variably to the proliferation,differentiation,or suppression of hepatic cells.Novel insights into the IL-22 and IL-33 signaling axes,bile acid and glutamine metabolism,and the role of intestinal microbiota are also presented as promising emerging targets.This review synthesizes current insights into the interplay between mechanical cues,key signaling pathways,and metabolic reprogramming that govern early regenerative responses.We explore the mechanisms dictating the balance between hyperplasia and hypertrophy,noting that hypertrophy predominates after minor resections,while proliferation is dominant in larger resections.Polyploidization emerges as a significant adaptive mechanism,contributing to hepatocyte survival and tissue remodeling.The importance of ductular reactions,microvascular adjustments,and extracellular matrix dynamics in lobular architecture remodeling is also highlighted.The study explores the occurrence of ductular reactions in both minor and major resections,particularly within the granulation tissue near dissection areas.The paper also examines structural remodeling in regenerated liver tissue,demonstrating ongoing transformations in hepatocyte morphology and sinusoidal architecture even months after PH,and emphasizing that the termination of liver mass regrowth does not equate to the cessation of LR.
文摘By introducing noncanonical vortex pairs to partially coherent beams, spatial correlation singularity (SCS) and orbital angular momenta (OAM) of the resulting beams are studied using the Fraunhofer diffraction integral. The effect of noncanonical strength, off-axis distance and vortex sign on spatial correlation singularities in far field is stressed. Furthermore, far-field OAM spectra and densities are also investigated, and the OAM detection and crosstalk probabilities are discussed. The results show that the number of dislocations of SCS always equals the sum of absolute values of topological charges for canonical or noncanonical vortex pairs. Although the sum of the product of each OAM mode and its power weight equals the algebraic sum of topological charges for canonical vortex pairs, the relationship no longer holds in the noncanonical case except for opposite-charge vortex pairs. The changes of off-axis distance, noncanonical strength or coherence length can lead to a more dominant power in adjacent mode than that in center detection mode, which also indicates that crosstalk probabilities of adjacent modes exceed the center detection probability. This work may provide potential applications in OAM-based optical communication, imaging, sensing and computing.
基金supported by the National Key Research and Development Program of China(2022YFD1300200)the National Natural Science Foundation of China(32161143010,32202646,and 32272848)+2 种基金the China Agriculture Research System(CARS-39)the Key Special Project of Ningxia Science and Technology Department,China(2021BEF02024)the local grants,China(NXTS2021-001,2022GD-TSLD-46,NK2022010207,and NXTS2022-001)。
文摘Highlights●CRISPR/Cas9 RNP complex-based strategy demonstrates robustness and accuracy in generating gene-edited sheep.●Sheep horn development remains unaffected by partial RXFP2 knockout.●Partial RXFP2 knockout results in unilateral cryptorchidism in sheep.
基金Supported by the Key Laboratory Fund for Equipment Pre-Research(6142207210202)。
文摘Aiming at the problem that infrared small target detection faces low contrast between the background and the target and insufficient noise suppression ability under the complex cloud background,an infrared small target detection method based on the tensor nuclear norm and direction residual weighting was proposed.Based on converting the infrared image into an infrared patch tensor model,from the perspective of the low-rank nature of the background tensor,and taking advantage of the difference in contrast between the background and the target in different directions,we designed a double-neighborhood local contrast based on direction residual weighting method(DNLCDRW)combined with the partial sum of tensor nuclear norm(PSTNN)to achieve effective background suppression and recovery of infrared small targets.Experiments show that the algorithm is effective in suppressing the background and improving the detection ability of the target.
文摘To explore the impact of partial centralization on supply chain performance,this study constructs a two-period game model of a closed-loop supply chain involving a manufacturer and an online retail platform participating in the trade-in strategy.Through mathematical modeling and numerical simulation methods,the optimal decisions were analyzed under conditions where the manufacturer partially owns the retail platform’s partial equity.This study finds that partial centralization yields the highest profits,followed by full centralization,with decentralized decisions yielding the lowest profits.Moderate centralization enhances overall profits by optimizing incentive mechanisms,whereas excessive ownership concentration reduces the flexibility of the retail platform,leading to a decline in profits.Additionally,product durability and trade-in subsidy significantly influence supply chain profitability:high-durability products reduce renewal frequency,while trade-in subsidy effectively stimulates consumer demand and increase overall profits.This study provides theoretical support and practical guidance for companies implementing the trade-in strategy.
