The development of an innovative structural system with satisfactory seismic performance of braced systems is an important and challenging area of interest in structural engineering. In this paper, a device that can r...The development of an innovative structural system with satisfactory seismic performance of braced systems is an important and challenging area of interest in structural engineering. In this paper, a device that can release the compressive force in the bracing members is developed, and its performance is evaluated. For comparison, four steel braced RC frames were constructed and tested under reverse cyclic loads. Two of them had different amounts of bracing and the other two had the same amount of bracing but incorporated different type of device, called compression release device, which is developed and described in this paper. It can be concluded from the test results that the newly developed device can effectively be used in steel braced systems to prevent buckling failure of the bracing members. Therefore, the device enhances the ductility of brace-framed systems by allowing an adequate capacity for energy dissipation.展开更多
A large number of column-bracing systems were modeled and analyzed by second-order analysis using finite element program ANSYS,in which the random combination of the initial imperfections between columns and horizonta...A large number of column-bracing systems were modeled and analyzed by second-order analysis using finite element program ANSYS,in which the random combination of the initial imperfections between columns and horizontal braces was well considered by Monte Carlo Method.According to the analysis results,four kinds of instability modes of column-bracing systems were found,the probability density function of the mid-height horizontal bracing forces was established based on probability statistics,and the design bracing forces were also obtained.The results indicated that the above design bracing forces are smaller than that proposed by the "Code for design of steel structures"(GB50017-2003) when the top axial compressions on the braced columns are equal,and much smaller than the latter when the top axial compressions on the braced columns are unequal.The results also indicated that the random combination of the initial imperfections between columns and horizontal braces leads to the randomness of the mid-height horizontal bracing forces in compression or in tension,so that the design bracing forces can be reduced.展开更多
Based on energy dissipation and structural control principle, a new structural configuration, called the megasub controlled structure （MSCS） with friction damped braces （FDBs）, is first presented. Meanwhile, to ca...Based on energy dissipation and structural control principle, a new structural configuration, called the megasub controlled structure （MSCS） with friction damped braces （FDBs）, is first presented. Meanwhile, to calculate the damping coefficient in the slipping state a new analytical method is proposed. The damping characteristics of one-storey friction damped braced frame （FDBF） are investigated, and the influence of the structural parameters on the energy dissipation and the practical engineering design are discussed. The nonlinear dynamic equations and the analytical model of the MSCS with FDBs are established. Three building structures with different structural configurations, which were designed with reference to the conventional mega-sub structures such as used in Tokyo City Hall, are comparatively investigated. The results illustrate that the structure presented in the paper has excellent dynamic properties and satisfactory control effectiveness.展开更多
Curved twin I-girder bridges (CTIGBs) have low torsional stiffness that makes them vulnerable to dynamic loads. This study investigates the effects of bottom bracings on the torsional dynamic characteristics of CTIGBs...Curved twin I-girder bridges (CTIGBs) have low torsional stiffness that makes them vulnerable to dynamic loads. This study investigates the effects of bottom bracings on the torsional dynamic characteristics of CTIGBs. Five types of bottom bracings are designed to investigate their effects on the dynamic characteristics of CTIGBs with different curvatures under free and forced vibrations. To perform numerical investigations, three-dimensional (3-D) finite element (FE) bridge and vehicle models are established using commercial ANSYS code, and then a vehicle-bridge interaction analysis approach is proposed. Road roughness profiles generated from power spectral density and cross spectral functions are also taken into account in the analyses. The numerical results show that torsional frequencies increase significantly after providing bottom bracings, and the increasing rate depends on the type of bottom bracings and their locations of installation. Bottom bracings can act as load transmitting members from one main girder to the others. Large negative bearing forces that have occurred in bridges with small radii of curvatures can be remarkably reduced by providing bottom bracing systems. It is found that the performances of several bottom bracing systems are effective in improving the torsional dynamic characteristics of the bridges in this study.展开更多
A full-scale, two-story, two-by-one bay, steel braced-frame was subjected to a number of unidirectional ground motions using three shake tables at the UNR-NEES site. The test-bed frame was designed to study the seismi...A full-scale, two-story, two-by-one bay, steel braced-frame was subjected to a number of unidirectional ground motions using three shake tables at the UNR-NEES site. The test-bed frame was designed to study the seismic performance of nonstructural systems including steel-framed gypsum partition walls, suspended ceilings and fire sprinkler systems. The frame can be configured to perform as an elastic or inelastic system to generate large floor accelerations or large inter story drift, respectively. In this study, the dynamic performance of the linear and nonlinear test-beds was comprehensively studied. The seismic performance of nonstructural systems installed in the linear and nonlinear test-beds were assessed during extreme excitations. In addition, the dynamic interactions of the test-bed and installed nonstructural systems are investigated.展开更多
The knee bracing steel frame (KBF) is a new kind of energy dissipating frame, which combines excellent ductility and lateral stiffness. As the structural fuse of the frame, the knee element will yield first during a s...The knee bracing steel frame (KBF) is a new kind of energy dissipating frame, which combines excellent ductility and lateral stiffness. As the structural fuse of the frame, the knee element will yield first during a severe earthquake so that no damage occurs to the major structural members and the rehabilitation is easy and economical. To help fully understand the relations be- tween its seismic performance and the structural parameters, systematic elastoplastic analysis of the KBF structure with finite element method was conducted in this work. Finally, general design recommendations were made according to the results of the analysis.展开更多
BACKGROUND Whether operation is superior to non-operation for humeral shaft fracture remains debatable.We hypothesized that operation could decrease the nonunion and reintervention rates and increase the functional ou...BACKGROUND Whether operation is superior to non-operation for humeral shaft fracture remains debatable.We hypothesized that operation could decrease the nonunion and reintervention rates and increase the functional outcomes.AIM To compare the clinical efficacy between operative and nonoperative approaches for humeral shaft fractures.METHODS We searched the PubMed,Web of Science,ScienceDirect,and Cochrane databases from 1990 to December 2023 for clinical trials and cohort studies comparing the effects of operative and conservative methods on humeral shaft fractures.Two investigators independently extracted data from the eligible studies,and the other two assessed the methodological quality of each study.The quality of the included studies was assessed using the Cochrane risk bias or Newcastle-Ottawa Scale.The nonunion,reintervention and the overall complications and functional scores were pooled and analyzed using Review Manager software(version 5.3).RESULTS A total of four randomized control trials and 13 cohort studies were included,with 1285 and 1346 patients in the operative and nonoperative groups,respectively.Patients in the operative group were treated with a plate or nail,whereas those in the conservative group were managed with splint or functional bracing.Four studies were assessed as having a high risk of bias,and the other 13 were of a low risk of bias according to the Newcastle-Ottawa Scale or Cochrane risk bias tool.The operative group had a significantly decreased rate of nonunion[odds ratio(OR)0.30;95%CI:0.23 to 0.40,reintervention(OR:0.33;95%CI:0.24 to 0.47),and overall complications(OR:0.62;95%CI:0.49 to 0.78)].The pooled effect of the Disabilities of Arm,Shoulder,and Hand score showed a significant difference at 3[mean difference(MD)-8.26;95%CI:-13.60 to-2.92],6(MD:-6.72;95%CI:-11.34 to-2.10),and 12 months(MD:-2.55;95%CI:-4.36 to-0.74).The pooled effect of Visual Analog Scale scores and the Constant-Murley score did not significantly differ between the two groups.CONCLUSION This systematic review and meta-analysis revealed a trend of rapid functional recovery and decreased rates of nonunion and reintervention after operation for humeral shaft fracture compared to conservative treatment.展开更多
Determining initial pretension values of pre-stressed cables is one of the key problems for a steel mega frame and pre-stressed composite bracing structure.Through the mechanical analysis of the composite bracing unde...Determining initial pretension values of pre-stressed cables is one of the key problems for a steel mega frame and pre-stressed composite bracing structure.Through the mechanical analysis of the composite bracing under vertical loading,the critical factors deciding the initial pretention value were found.According to these factors,a rule for the initial pretension value was put forward.The determination equations were acquired based on the principle of force equilibrium at nodes.The numerical results indicate that the internal force disequilibrium in composite bracings resulted from symmetrical load can be eliminated only in a symmetrical way,so that initial pretention values are decided only by vertical loads.The influencing coefficient leveling method,taking into account interactions between story and story,is accurate and feasible.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
BACKGROUND Malignant obstructive jaundice(MOJ)is characterized by the presence of malignant tumors infiltrating or compressing the bile duct,causing poor bile drainage,generalized yellowing,pain,itching,and malaise.MO...BACKGROUND Malignant obstructive jaundice(MOJ)is characterized by the presence of malignant tumors infiltrating or compressing the bile duct,causing poor bile drainage,generalized yellowing,pain,itching,and malaise.MOJ is burdensome for both the society and the families of affected patients and should be taken seriously.AIM To evaluate the clinical effect of stent placement during endoscopic retrograde cholangiopancreatography for relieving MOJ and the efficacy of percutaneous transhepatic biliary drainage in terms of liver function improvement,complication rates,and long-term patient outcomes.METHODS The clinical data of 59 patients with MOJ who were admitted to our hospital between March 2018 and August 2019 were retrospectively analyzed.According to the treatment method,the patients were divided into an observation group(29 patients)and a control group(30 patients).General data,liver function indices,complications,adverse effects,and 3-year survival rates after different surgical treatments were recorded for the two groups.RESULTS There were no significant differences in baseline information(sex,age,tumor type,or tumor diameter)between the two groups(P>0.05).Alanine aminotransferase,aspartate aminotransferase,and total bilirubin levels were significantly better in both groups after surgery than before surgery(P<0.05).The overall incidence of biliary bleeding,gastrointestinal bleeding,pancreatitis,and cholangitis was 6.9%in the observation group and 30%in the control group(P<0.05).No significant differences in the rates of blood transfusion,intensive care unit admission,or death within 3 years were observed between the two groups at the 1-month follow-up(P>0.05).The 3-year survival rates were 46.06%and 39.71%in the observation and control groups,respectively.CONCLUSION Endoscopic biliary stenting effectively relieves MOJ and significantly improves liver function,with minimal complications.This technique is a promising palliative approach for patients ineligible for radical surgery.However,further research is needed to optimize current treatment strategies and to explore their potential in treating nonmalignant cases of obstructive jaundice.展开更多
This study numerically investigates the seismic response of a nine-story self-centering concentrically braced frame building incorporating force-limiting connections between the floor system and the lateral force-resi...This study numerically investigates the seismic response of a nine-story self-centering concentrically braced frame building incorporating force-limiting connections between the floor system and the lateral force-resisting system.Nonlinear earthquake simulations are conducted under design basis earthquake ground motions,and the results are compared against a baseline model with rigid-elastic connections.The study discusses connection design considerations and evaluates the effectiveness of force-limiting connections in mitigating higher-mode effects.The findings show that force-limiting connections significantly reduce the magnitude and variability of floor accelerations,brace forces,and connection forces,while maintaining comparable story drifts.limiting Force-connections primarily reduce the contribution of higher-mode responses,while the controlled rocking base mechanism modifies the first-mode response.Overall,the reduced dispersion in structural response improves the reliability of seismic design and enhances resilience by minimizing damage to both structural components and acceleration-sensitive nonstructural elements.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
Structures modelled with flexible-base assumptions,incorporating soil effects,generally exhibit longer natural periods and higher damping compared to fixed-base models that exclude soil-structure interaction(SSI).Howe...Structures modelled with flexible-base assumptions,incorporating soil effects,generally exhibit longer natural periods and higher damping compared to fixed-base models that exclude soil-structure interaction(SSI).However,the beneficial or detrimental nature of SSI remains contentious in current earthquake damage analyses and research findings.This study introduces a numerical modelling technique,validated by experimental shaking table tests,to examine the effects of SSI on high-rise buildings.The study considers various substructure parameters,including foundation types,soil types,and bedrock depths.Both advantageous and adverse impacts of SSI are identified and analysed.Numerical simulations reveal that increased subsoil stiffness significantly amplifies the base shear of structures compared to bedrock depth effects.Additionally,increased foundation rocking results in higher inter-storey drifts and reduced base shear.Overall,SSI tends to amplify inter-storey drifts,indicating detrimental effects.Specifically,the study found that the inclusion of SSI increased maximum inter-storey drifts by up to 38%,particularly in softer soils,while reducing base shear by up to 44%in structures with classical compensated foundations on D_(e)and E_(e)soil types.In contrast,piled foundation systems experienced an increase in base shear of up to 27%under the same conditions.Conversely,SSI has beneficial impacts on base shear for structures with classical compensated foundations on soil types of D_(e)and E_(e),as it reduces the base shear.For structures with piled foundations and those with classical compensated foundations on C_(e)soil,SSI effects are detrimental.C_(e),D_(e),and E_(e)soils correspond to geotechnical classifications per AS1170,representing stiff,medium,and soft soils respectively.The study also presents minimum base shear ratios considering SSI reduction effects for various foundation types.展开更多
Actuator dynamics introduce a synchronization disparity between commanded displacements transmitted to the actuator and the actual displacements generated by the actuator,thereby affecting its precision and potentiall...Actuator dynamics introduce a synchronization disparity between commanded displacements transmitted to the actuator and the actual displacements generated by the actuator,thereby affecting its precision and potentially leading to instability in real-time hybrid simulation(RTHS).This study aims to elucidate the relationship between calculated and measured displacements by analyzing their magnitude and phase in the frequency domain via transformations.The physical implications of these relationships are explored in the context of frequency domain evaluation indices(FEI),the transfer function of actuator dynamics,and delay compensation.Formulations for achieving perfect compensation of actuator dynamics are developed,and an enhanced compensation approach,termed improved windowed frequency domain evaluation index-based compensation(IWFEI),is introduced.The efficacy of IWFEI is assessed using a RTHS benchmark model,with perturbed simulations conducted to validate its robustness.Uncertainties inherent in actuator dynamics are represented as random variables in these simulations.Comparative analysis of the mean values and variances of evaluation criteria demonstrates that IWFEI enables more accurate and robust compensation.Furthermore,strong correlations observed among criteria in the time and frequency domains underscore the effectiveness of the proposed frequency domain-based compensation method in mitigating amplitude errors and phase delays in RTHS.展开更多
Operative management of humeral shaft fractures demonstrates superior early functional recovery(6-month Disabilities of the Arm,Shoulder,and Hand scores)and significantly lower nonunion rates(63.9%reduction)compared t...Operative management of humeral shaft fractures demonstrates superior early functional recovery(6-month Disabilities of the Arm,Shoulder,and Hand scores)and significantly lower nonunion rates(63.9%reduction)compared to functional bracing,particularly in complex cases,while conservative treatment remains viable for low-demand patients.Surgical techniques,including open reduction internal fixation,intramedullary nailing,and minimally invasive plate osteosynthesis,offer trade-offs between anatomic precision and complication risks(e.g.,radial nerve injury vs rotator cuff damage),with over 90%of radial nerve injuries resolving spontaneously.Ultrasound-guided diagnosis(89%sensitivity,95%specificity)optimizes decision-making for nerve entrapment.Individualized treatment selection,prioritizing fracture complexity and patient needs,is critical to balance accelerated rehabilitation with minimized complications.展开更多
After nearly a decade of application and investigation, a motion amplification device with viscous dampers for energy dissipation has been recognized as an effective solution to mitigate wind or seismic excitation, es...After nearly a decade of application and investigation, a motion amplification device with viscous dampers for energy dissipation has been recognized as an effective solution to mitigate wind or seismic excitation, especially for stiff structural systems. As a result of compensation of amplified motion, it has been proved that the efficiency of viscous damper largely depends on the motion amplification device configuration, particularly for device stiflhess. In this paper, a ＂scissor-jack＂ type of motion amplification device, called a ＂toggle brace damper＂ system, is studied. It is demonstrated that the efficiency of such a device reflected by its amplification factor is not merely a function of its geometric configuration, but is highly dependent on the support elements＇ stiffness as well, similar to the mechanism of a leverage arm. Accordingly, a mathematical model in terms of complex modulus of the viscous damper with consideration of the support brace＇s stiffness is established. The results indicate that the efficiency of the motion amplification device with viscous dampers significantly depends on the stiffness of the support elements. Other parameters, such as toggle brace configuration and damping values of the viscous damper, are studied and compared. As an application example, numerical analyses are conducted to study the dynamic performance of a 39-story office tower installed with toggle brace dampers constructed on soft soil in a reclaimed area, under a combined effect of the vortex shedding of an adjacent existing 52-story building and earthquakes. The results show that viscous dampers with a motion amplification system using a properly designed toggle brace device proved to be an effective solution to alleviate the external excitations.展开更多
Accurate estimates of ductility demands on buckling-restrained braced frames(BRBFs)are crucial to performance-based design of BRBFs.An analytical study on the seismic behavior of BRBFs has been conducted at the ATLSS ...Accurate estimates of ductility demands on buckling-restrained braced frames(BRBFs)are crucial to performance-based design of BRBFs.An analytical study on the seismic behavior of BRBFs has been conducted at the ATLSS Center,Lehigh University to prepare for an upcoming experimental program.The analysis program DRAIN-2DX was used to model a one-bay,four-story prototype BRBF including material and geometric nonlinearities.The buckling- restrained brace(BRB)model incorporates both isotropic and kinematic hardening.Nonlinear static pushover and time- history analyses were performed on the prototype BRBF.Performance objectives for the BRBs were defined and used to evaluate the time-history analysis results.Particular emphasis was placed on global ductility demands and ductility demands on the BRBs.These demands were compared with anticipated ductility capacities.The analysis results,along with results from similar previous studies,are used to evaluate the BRBF design provisions that have been recommended for codification in the United States.The results show that BRB maximum ductility demands can be as high as 20 to 25.These demands significantly exceed those anticipated by the BRBF recommended provisions.Results from the static pushover and time- history analyses are used to demonstrate why the ductility demands exceed those anticipated by the recommended provisions. The BRB qualification testing protocol contained in the BRBF recommended provisions is shown to be inadequate because it requires only a maximum ductility demand of at most 7.5.Modifications to the testing protocol are recommended.展开更多
This paper aims to establish an intelligent procedure that combines the observational method with the existing deep learning technique for updating deformation of braced excavation in clay.The gated recurrent unit(GRU...This paper aims to establish an intelligent procedure that combines the observational method with the existing deep learning technique for updating deformation of braced excavation in clay.The gated recurrent unit(GRU) neural network is adopted to formulate the forecast model and learn the potential rules in the field observations using the Nesterov-accelerated Adam(Nadam) algorithm.In the proposed procedure,the GRU-based forecast model is first trained based on the field data of previous and current stages.Then,the field data of the current stage are used as input to predict the deformation response of the next stage via the previously trained GRU-based forecast model.This updating process will loop up till the end of the excavation.This procedure has the advantage of directly predicting the deformation response of unexcavated stages based on the monitoring data.The proposed intelligent procedure is verified on two well-documented cases in terms of accuracy and reliability.The results indicate that both wall deflection and ground settlement are accurately predicted as the excavation proceeds.Furthermore,the advantages of the proposed intelligent procedure compared with the Bayesian/o ptimization updating are illustrated.展开更多
文摘The development of an innovative structural system with satisfactory seismic performance of braced systems is an important and challenging area of interest in structural engineering. In this paper, a device that can release the compressive force in the bracing members is developed, and its performance is evaluated. For comparison, four steel braced RC frames were constructed and tested under reverse cyclic loads. Two of them had different amounts of bracing and the other two had the same amount of bracing but incorporated different type of device, called compression release device, which is developed and described in this paper. It can be concluded from the test results that the newly developed device can effectively be used in steel braced systems to prevent buckling failure of the bracing members. Therefore, the device enhances the ductility of brace-framed systems by allowing an adequate capacity for energy dissipation.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51008055)the China Postdoctoral Science Foundation(Grant No.20100471124)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.DL09BB09)the Heilongjiang Province Postdoctoral Sicence Foundation
文摘A large number of column-bracing systems were modeled and analyzed by second-order analysis using finite element program ANSYS,in which the random combination of the initial imperfections between columns and horizontal braces was well considered by Monte Carlo Method.According to the analysis results,four kinds of instability modes of column-bracing systems were found,the probability density function of the mid-height horizontal bracing forces was established based on probability statistics,and the design bracing forces were also obtained.The results indicated that the above design bracing forces are smaller than that proposed by the "Code for design of steel structures"(GB50017-2003) when the top axial compressions on the braced columns are equal,and much smaller than the latter when the top axial compressions on the braced columns are unequal.The results also indicated that the random combination of the initial imperfections between columns and horizontal braces leads to the randomness of the mid-height horizontal bracing forces in compression or in tension,so that the design bracing forces can be reduced.
基金Science and Technology Fund of NWPU Under Grant No. M450211 Seed Fund of NWPU Under Grant No. Z200729
文摘Based on energy dissipation and structural control principle, a new structural configuration, called the megasub controlled structure （MSCS） with friction damped braces （FDBs）, is first presented. Meanwhile, to calculate the damping coefficient in the slipping state a new analytical method is proposed. The damping characteristics of one-storey friction damped braced frame （FDBF） are investigated, and the influence of the structural parameters on the energy dissipation and the practical engineering design are discussed. The nonlinear dynamic equations and the analytical model of the MSCS with FDBs are established. Three building structures with different structural configurations, which were designed with reference to the conventional mega-sub structures such as used in Tokyo City Hall, are comparatively investigated. The results illustrate that the structure presented in the paper has excellent dynamic properties and satisfactory control effectiveness.
文摘Curved twin I-girder bridges (CTIGBs) have low torsional stiffness that makes them vulnerable to dynamic loads. This study investigates the effects of bottom bracings on the torsional dynamic characteristics of CTIGBs. Five types of bottom bracings are designed to investigate their effects on the dynamic characteristics of CTIGBs with different curvatures under free and forced vibrations. To perform numerical investigations, three-dimensional (3-D) finite element (FE) bridge and vehicle models are established using commercial ANSYS code, and then a vehicle-bridge interaction analysis approach is proposed. Road roughness profiles generated from power spectral density and cross spectral functions are also taken into account in the analyses. The numerical results show that torsional frequencies increase significantly after providing bottom bracings, and the increasing rate depends on the type of bottom bracings and their locations of installation. Bottom bracings can act as load transmitting members from one main girder to the others. Large negative bearing forces that have occurred in bridges with small radii of curvatures can be remarkably reduced by providing bottom bracing systems. It is found that the performances of several bottom bracing systems are effective in improving the torsional dynamic characteristics of the bridges in this study.
基金National Science Foundation under Grant No.0721399
文摘A full-scale, two-story, two-by-one bay, steel braced-frame was subjected to a number of unidirectional ground motions using three shake tables at the UNR-NEES site. The test-bed frame was designed to study the seismic performance of nonstructural systems including steel-framed gypsum partition walls, suspended ceilings and fire sprinkler systems. The frame can be configured to perform as an elastic or inelastic system to generate large floor accelerations or large inter story drift, respectively. In this study, the dynamic performance of the linear and nonlinear test-beds was comprehensively studied. The seismic performance of nonstructural systems installed in the linear and nonlinear test-beds were assessed during extreme excitations. In addition, the dynamic interactions of the test-bed and installed nonstructural systems are investigated.
基金Project (No. 2002CB412790) supported by the National BasicResearch Program (973) of China
文摘The knee bracing steel frame (KBF) is a new kind of energy dissipating frame, which combines excellent ductility and lateral stiffness. As the structural fuse of the frame, the knee element will yield first during a severe earthquake so that no damage occurs to the major structural members and the rehabilitation is easy and economical. To help fully understand the relations be- tween its seismic performance and the structural parameters, systematic elastoplastic analysis of the KBF structure with finite element method was conducted in this work. Finally, general design recommendations were made according to the results of the analysis.
基金Supported by Natural Science Foundation of Chongqing,China,No.CSTB2023NSCQ-MSX1080.
文摘BACKGROUND Whether operation is superior to non-operation for humeral shaft fracture remains debatable.We hypothesized that operation could decrease the nonunion and reintervention rates and increase the functional outcomes.AIM To compare the clinical efficacy between operative and nonoperative approaches for humeral shaft fractures.METHODS We searched the PubMed,Web of Science,ScienceDirect,and Cochrane databases from 1990 to December 2023 for clinical trials and cohort studies comparing the effects of operative and conservative methods on humeral shaft fractures.Two investigators independently extracted data from the eligible studies,and the other two assessed the methodological quality of each study.The quality of the included studies was assessed using the Cochrane risk bias or Newcastle-Ottawa Scale.The nonunion,reintervention and the overall complications and functional scores were pooled and analyzed using Review Manager software(version 5.3).RESULTS A total of four randomized control trials and 13 cohort studies were included,with 1285 and 1346 patients in the operative and nonoperative groups,respectively.Patients in the operative group were treated with a plate or nail,whereas those in the conservative group were managed with splint or functional bracing.Four studies were assessed as having a high risk of bias,and the other 13 were of a low risk of bias according to the Newcastle-Ottawa Scale or Cochrane risk bias tool.The operative group had a significantly decreased rate of nonunion[odds ratio(OR)0.30;95%CI:0.23 to 0.40,reintervention(OR:0.33;95%CI:0.24 to 0.47),and overall complications(OR:0.62;95%CI:0.49 to 0.78)].The pooled effect of the Disabilities of Arm,Shoulder,and Hand score showed a significant difference at 3[mean difference(MD)-8.26;95%CI:-13.60 to-2.92],6(MD:-6.72;95%CI:-11.34 to-2.10),and 12 months(MD:-2.55;95%CI:-4.36 to-0.74).The pooled effect of Visual Analog Scale scores and the Constant-Murley score did not significantly differ between the two groups.CONCLUSION This systematic review and meta-analysis revealed a trend of rapid functional recovery and decreased rates of nonunion and reintervention after operation for humeral shaft fracture compared to conservative treatment.
基金Project of Ministry of Housing and Urban-Rural Development of China(No.2012-K2-28)
文摘Determining initial pretension values of pre-stressed cables is one of the key problems for a steel mega frame and pre-stressed composite bracing structure.Through the mechanical analysis of the composite bracing under vertical loading,the critical factors deciding the initial pretention value were found.According to these factors,a rule for the initial pretension value was put forward.The determination equations were acquired based on the principle of force equilibrium at nodes.The numerical results indicate that the internal force disequilibrium in composite bracings resulted from symmetrical load can be eliminated only in a symmetrical way,so that initial pretention values are decided only by vertical loads.The influencing coefficient leveling method,taking into account interactions between story and story,is accurate and feasible.
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BACKGROUND Malignant obstructive jaundice(MOJ)is characterized by the presence of malignant tumors infiltrating or compressing the bile duct,causing poor bile drainage,generalized yellowing,pain,itching,and malaise.MOJ is burdensome for both the society and the families of affected patients and should be taken seriously.AIM To evaluate the clinical effect of stent placement during endoscopic retrograde cholangiopancreatography for relieving MOJ and the efficacy of percutaneous transhepatic biliary drainage in terms of liver function improvement,complication rates,and long-term patient outcomes.METHODS The clinical data of 59 patients with MOJ who were admitted to our hospital between March 2018 and August 2019 were retrospectively analyzed.According to the treatment method,the patients were divided into an observation group(29 patients)and a control group(30 patients).General data,liver function indices,complications,adverse effects,and 3-year survival rates after different surgical treatments were recorded for the two groups.RESULTS There were no significant differences in baseline information(sex,age,tumor type,or tumor diameter)between the two groups(P>0.05).Alanine aminotransferase,aspartate aminotransferase,and total bilirubin levels were significantly better in both groups after surgery than before surgery(P<0.05).The overall incidence of biliary bleeding,gastrointestinal bleeding,pancreatitis,and cholangitis was 6.9%in the observation group and 30%in the control group(P<0.05).No significant differences in the rates of blood transfusion,intensive care unit admission,or death within 3 years were observed between the two groups at the 1-month follow-up(P>0.05).The 3-year survival rates were 46.06%and 39.71%in the observation and control groups,respectively.CONCLUSION Endoscopic biliary stenting effectively relieves MOJ and significantly improves liver function,with minimal complications.This technique is a promising palliative approach for patients ineligible for radical surgery.However,further research is needed to optimize current treatment strategies and to explore their potential in treating nonmalignant cases of obstructive jaundice.
基金financial support provided by Lehigh University,the Advanced Technology for Large Structural Systems(ATLSS)Engineering Research Center,and the Department of Structural Engineering at the University of California,San Diegolarge research team led by Professor Robert B.Fleischman under the project“NEESR:Inertial Force-Limiting Floor Anchorage Systems for Seismic Resistant Building Structures”with the support of grants from the National Science Foundation,award no.CMMI-1135033in the George E.Brown,Jr.Network for Earthquake gineering En-Simulation Research(NEESR)program and award no.CMMI-0402490 for the George E.Brown,Jr.Network for Earthquake ing Engineer-Simulation(NEES)consortium operations.
文摘This study numerically investigates the seismic response of a nine-story self-centering concentrically braced frame building incorporating force-limiting connections between the floor system and the lateral force-resisting system.Nonlinear earthquake simulations are conducted under design basis earthquake ground motions,and the results are compared against a baseline model with rigid-elastic connections.The study discusses connection design considerations and evaluates the effectiveness of force-limiting connections in mitigating higher-mode effects.The findings show that force-limiting connections significantly reduce the magnitude and variability of floor accelerations,brace forces,and connection forces,while maintaining comparable story drifts.limiting Force-connections primarily reduce the contribution of higher-mode responses,while the controlled rocking base mechanism modifies the first-mode response.Overall,the reduced dispersion in structural response improves the reliability of seismic design and enhances resilience by minimizing damage to both structural components and acceleration-sensitive nonstructural elements.
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Structures modelled with flexible-base assumptions,incorporating soil effects,generally exhibit longer natural periods and higher damping compared to fixed-base models that exclude soil-structure interaction(SSI).However,the beneficial or detrimental nature of SSI remains contentious in current earthquake damage analyses and research findings.This study introduces a numerical modelling technique,validated by experimental shaking table tests,to examine the effects of SSI on high-rise buildings.The study considers various substructure parameters,including foundation types,soil types,and bedrock depths.Both advantageous and adverse impacts of SSI are identified and analysed.Numerical simulations reveal that increased subsoil stiffness significantly amplifies the base shear of structures compared to bedrock depth effects.Additionally,increased foundation rocking results in higher inter-storey drifts and reduced base shear.Overall,SSI tends to amplify inter-storey drifts,indicating detrimental effects.Specifically,the study found that the inclusion of SSI increased maximum inter-storey drifts by up to 38%,particularly in softer soils,while reducing base shear by up to 44%in structures with classical compensated foundations on D_(e)and E_(e)soil types.In contrast,piled foundation systems experienced an increase in base shear of up to 27%under the same conditions.Conversely,SSI has beneficial impacts on base shear for structures with classical compensated foundations on soil types of D_(e)and E_(e),as it reduces the base shear.For structures with piled foundations and those with classical compensated foundations on C_(e)soil,SSI effects are detrimental.C_(e),D_(e),and E_(e)soils correspond to geotechnical classifications per AS1170,representing stiff,medium,and soft soils respectively.The study also presents minimum base shear ratios considering SSI reduction effects for various foundation types.
基金Ministry of Science and Technology of China under Grant No.2023YFC3804300National Science Foundation of China under Grant No.52178114。
文摘Actuator dynamics introduce a synchronization disparity between commanded displacements transmitted to the actuator and the actual displacements generated by the actuator,thereby affecting its precision and potentially leading to instability in real-time hybrid simulation(RTHS).This study aims to elucidate the relationship between calculated and measured displacements by analyzing their magnitude and phase in the frequency domain via transformations.The physical implications of these relationships are explored in the context of frequency domain evaluation indices(FEI),the transfer function of actuator dynamics,and delay compensation.Formulations for achieving perfect compensation of actuator dynamics are developed,and an enhanced compensation approach,termed improved windowed frequency domain evaluation index-based compensation(IWFEI),is introduced.The efficacy of IWFEI is assessed using a RTHS benchmark model,with perturbed simulations conducted to validate its robustness.Uncertainties inherent in actuator dynamics are represented as random variables in these simulations.Comparative analysis of the mean values and variances of evaluation criteria demonstrates that IWFEI enables more accurate and robust compensation.Furthermore,strong correlations observed among criteria in the time and frequency domains underscore the effectiveness of the proposed frequency domain-based compensation method in mitigating amplitude errors and phase delays in RTHS.
文摘Operative management of humeral shaft fractures demonstrates superior early functional recovery(6-month Disabilities of the Arm,Shoulder,and Hand scores)and significantly lower nonunion rates(63.9%reduction)compared to functional bracing,particularly in complex cases,while conservative treatment remains viable for low-demand patients.Surgical techniques,including open reduction internal fixation,intramedullary nailing,and minimally invasive plate osteosynthesis,offer trade-offs between anatomic precision and complication risks(e.g.,radial nerve injury vs rotator cuff damage),with over 90%of radial nerve injuries resolving spontaneously.Ultrasound-guided diagnosis(89%sensitivity,95%specificity)optimizes decision-making for nerve entrapment.Individualized treatment selection,prioritizing fracture complexity and patient needs,is critical to balance accelerated rehabilitation with minimized complications.
文摘After nearly a decade of application and investigation, a motion amplification device with viscous dampers for energy dissipation has been recognized as an effective solution to mitigate wind or seismic excitation, especially for stiff structural systems. As a result of compensation of amplified motion, it has been proved that the efficiency of viscous damper largely depends on the motion amplification device configuration, particularly for device stiflhess. In this paper, a ＂scissor-jack＂ type of motion amplification device, called a ＂toggle brace damper＂ system, is studied. It is demonstrated that the efficiency of such a device reflected by its amplification factor is not merely a function of its geometric configuration, but is highly dependent on the support elements＇ stiffness as well, similar to the mechanism of a leverage arm. Accordingly, a mathematical model in terms of complex modulus of the viscous damper with consideration of the support brace＇s stiffness is established. The results indicate that the efficiency of the motion amplification device with viscous dampers significantly depends on the stiffness of the support elements. Other parameters, such as toggle brace configuration and damping values of the viscous damper, are studied and compared. As an application example, numerical analyses are conducted to study the dynamic performance of a 39-story office tower installed with toggle brace dampers constructed on soft soil in a reclaimed area, under a combined effect of the vortex shedding of an adjacent existing 52-story building and earthquakes. The results show that viscous dampers with a motion amplification system using a properly designed toggle brace device proved to be an effective solution to alleviate the external excitations.
文摘Accurate estimates of ductility demands on buckling-restrained braced frames(BRBFs)are crucial to performance-based design of BRBFs.An analytical study on the seismic behavior of BRBFs has been conducted at the ATLSS Center,Lehigh University to prepare for an upcoming experimental program.The analysis program DRAIN-2DX was used to model a one-bay,four-story prototype BRBF including material and geometric nonlinearities.The buckling- restrained brace(BRB)model incorporates both isotropic and kinematic hardening.Nonlinear static pushover and time- history analyses were performed on the prototype BRBF.Performance objectives for the BRBs were defined and used to evaluate the time-history analysis results.Particular emphasis was placed on global ductility demands and ductility demands on the BRBs.These demands were compared with anticipated ductility capacities.The analysis results,along with results from similar previous studies,are used to evaluate the BRBF design provisions that have been recommended for codification in the United States.The results show that BRB maximum ductility demands can be as high as 20 to 25.These demands significantly exceed those anticipated by the BRBF recommended provisions.Results from the static pushover and time- history analyses are used to demonstrate why the ductility demands exceed those anticipated by the recommended provisions. The BRB qualification testing protocol contained in the BRBF recommended provisions is shown to be inadequate because it requires only a maximum ductility demand of at most 7.5.Modifications to the testing protocol are recommended.
基金The financial supports provided by the Research Grants Council(RGC)of Hong Kong Special Administrative Region Government(HKSARG)of China(Grant Nos.15209119 and PolyU R5037-18F)Zhongtian Construction Group Co.Ltd.(Grant No.ZTCG-GDJTYJSJSFW-2020002)。
文摘This paper aims to establish an intelligent procedure that combines the observational method with the existing deep learning technique for updating deformation of braced excavation in clay.The gated recurrent unit(GRU) neural network is adopted to formulate the forecast model and learn the potential rules in the field observations using the Nesterov-accelerated Adam(Nadam) algorithm.In the proposed procedure,the GRU-based forecast model is first trained based on the field data of previous and current stages.Then,the field data of the current stage are used as input to predict the deformation response of the next stage via the previously trained GRU-based forecast model.This updating process will loop up till the end of the excavation.This procedure has the advantage of directly predicting the deformation response of unexcavated stages based on the monitoring data.The proposed intelligent procedure is verified on two well-documented cases in terms of accuracy and reliability.The results indicate that both wall deflection and ground settlement are accurately predicted as the excavation proceeds.Furthermore,the advantages of the proposed intelligent procedure compared with the Bayesian/o ptimization updating are illustrated.
