This study focuses on variations in the hysteretic behavior of buckling-restrained braces(BRBs)configured with or without out-of-plane eccentricity under cyclic loading.Quasi-static experiments and numerical simulatio...This study focuses on variations in the hysteretic behavior of buckling-restrained braces(BRBs)configured with or without out-of-plane eccentricity under cyclic loading.Quasi-static experiments and numerical simulations were carried out on concentrically and eccentrically loaded BRB specimens to investigate the mechanical properties,energy dissipation performance,stress distribution,and high-order deformation pattern.The experimental and numerical results showed that compared to the concentrically loaded BRBs,the stiffness,yield force,cumulated plastic ductility(CPD)coefficient,equivalent viscous damping coefficient and energy dissipation decreased,and the yield displacement and compression strength adjustment factor increased for the eccentrically loaded BRBs.With the existence of the out-of-plane eccentricity,the initial yield position changes from the yield segment to the junction between the yield segment and transition segment under a tensile load,while the initial high-order buckling pattern changes from a first-order C-shape to a secondorder S-shape under a compressive load.展开更多
The Fort d’Issy-Vanves-Clamart(FIVC)braced excavation in France is analyzed to provide insights into the geotechnical serviceability assessment of excavations at great depth within deterministic and probabilistic fra...The Fort d’Issy-Vanves-Clamart(FIVC)braced excavation in France is analyzed to provide insights into the geotechnical serviceability assessment of excavations at great depth within deterministic and probabilistic frameworks.The FIVC excavation is excavated at 32 m below the ground surface in Parisian sedimentary basin and a plane-strain finite element analysis is implemented to examine the wall deflections and ground surface settlements.A stochastic finite element method based on the polynomial chaos Kriging metamodel(MSFEM)is then proposed for the probabilistic analyses.Comparisons with field measurements and former studies are carried out.Several academic cases are then conducted to investigate the great-depth excavation stability regarding the maximum horizontal wall deflection and maximum ground surface settlement.The results indicate that the proposed MSFEM is effective for probabilistic analyses and can provide useful insights for the excavation design and construction.A sensitivity analysis for seven considered random parameters is then implemented.The soil friction angle at the excavation bottom layer is the most significant one for design.The soil-wall interaction effects on the excavation stability are also given.展开更多
BRBF(buckling restrained braced frame)is a relatively new lateral force resisting system for building structures.BRBFs are used mostly to resist seismic force due to their high ductility after yielding and the ability...BRBF(buckling restrained braced frame)is a relatively new lateral force resisting system for building structures.BRBFs are used mostly to resist seismic force due to their high ductility after yielding and the ability to absorb higher strain energy.ASCE(American Society of Civil Engineers)first permits the use of BRBFs as a single seismic force-resisting system by quantifying the seismic parameters such as response modification coefficient(R),over-strength factor(Ωo)and deflection amplification factor(Cd)for a structure built with BRBF,in their 2010 code(ASCE 7-10).But it has not been investigated how a structure built with BRBF,which is primarily designed to resist seismic force,and behaves under sudden occurrence of a blast load.This research investigates the performance of a BRBF subjected to blast loading.In other words,this paper focuses on the effect of blast loading on BRBF.The architype for this investigation is a chevron type braced frame.The frame is subjected to a short duration blast load that lasts only 21.7 mili-second(ms).Blast loading effects on the braced frame are assessed by identifying the weakest plane of failure,deformation characteristics and out of plane bending.The research investigates how the properties of the surrounding concrete,especially compressive strength,affect the overall strength of the BRBF on resisting blast loading.It is observed that the compressive strength of the surrounding concrete plays a significant role in reducing the deformation characteristics,both in-plane and out-of-plane.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
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
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
Buckling restrained braces （BRBs） have been widely applied in seismic mitigation since they were introduced in the 1970s. However, traditional BRBs have several disadvantages caused by using a steel tube to envelope...Buckling restrained braces （BRBs） have been widely applied in seismic mitigation since they were introduced in the 1970s. However, traditional BRBs have several disadvantages caused by using a steel tube to envelope the mortar to prevent the core plate from buckling, such as： complex interfaces between the materials used, uncertain precision, and time consumption during the manufacturing processes. In this study, a new device called the multi-curve buckling restrained brace （MC-BRB） is proposed to overcome these disadvantages. The new device consists of a core plate with multiple neck portions assembled to form multiple energy dissipation segments, and the enlarged segment, lateral support elements and constraining elements to prevent the BRB from buckling. The enlarged segment located in the middle of the core plate can be welded to the lateral support and constraining elements to increase buckling resistance and to prevent them from sliding during earthquakes. Component tests and a series of shaking table tests on a full-scale steel structure equipped with MC-BRBs were carried out to investigate the behavior and capability of this new BRB design for seismic mitigation. The experimental results illustrate that the MC-BRB possesses a stable mechanical behavior under cyclic loadings and provides good protection to structures during earthquakes. Also, a mathematical model has been developed to simulate the mechanical characteristics of BRBs.展开更多
基金National Natural Science Foundation of China under Grant No.51978184。
文摘This study focuses on variations in the hysteretic behavior of buckling-restrained braces(BRBs)configured with or without out-of-plane eccentricity under cyclic loading.Quasi-static experiments and numerical simulations were carried out on concentrically and eccentrically loaded BRB specimens to investigate the mechanical properties,energy dissipation performance,stress distribution,and high-order deformation pattern.The experimental and numerical results showed that compared to the concentrically loaded BRBs,the stiffness,yield force,cumulated plastic ductility(CPD)coefficient,equivalent viscous damping coefficient and energy dissipation decreased,and the yield displacement and compression strength adjustment factor increased for the eccentrically loaded BRBs.With the existence of the out-of-plane eccentricity,the initial yield position changes from the yield segment to the junction between the yield segment and transition segment under a tensile load,while the initial high-order buckling pattern changes from a first-order C-shape to a secondorder S-shape under a compressive load.
基金gratefully the China Scholarship Council for providing a PhD Scholarship(CSC No.201906690049).
文摘The Fort d’Issy-Vanves-Clamart(FIVC)braced excavation in France is analyzed to provide insights into the geotechnical serviceability assessment of excavations at great depth within deterministic and probabilistic frameworks.The FIVC excavation is excavated at 32 m below the ground surface in Parisian sedimentary basin and a plane-strain finite element analysis is implemented to examine the wall deflections and ground surface settlements.A stochastic finite element method based on the polynomial chaos Kriging metamodel(MSFEM)is then proposed for the probabilistic analyses.Comparisons with field measurements and former studies are carried out.Several academic cases are then conducted to investigate the great-depth excavation stability regarding the maximum horizontal wall deflection and maximum ground surface settlement.The results indicate that the proposed MSFEM is effective for probabilistic analyses and can provide useful insights for the excavation design and construction.A sensitivity analysis for seven considered random parameters is then implemented.The soil friction angle at the excavation bottom layer is the most significant one for design.The soil-wall interaction effects on the excavation stability are also given.
基金The authors are acknowledging the contributions and support from:(a)Department of Civil Engineering&Construction Management,California State University,Northridge,and(b)Star Seismic Inc.
文摘BRBF(buckling restrained braced frame)is a relatively new lateral force resisting system for building structures.BRBFs are used mostly to resist seismic force due to their high ductility after yielding and the ability to absorb higher strain energy.ASCE(American Society of Civil Engineers)first permits the use of BRBFs as a single seismic force-resisting system by quantifying the seismic parameters such as response modification coefficient(R),over-strength factor(Ωo)and deflection amplification factor(Cd)for a structure built with BRBF,in their 2010 code(ASCE 7-10).But it has not been investigated how a structure built with BRBF,which is primarily designed to resist seismic force,and behaves under sudden occurrence of a blast load.This research investigates the performance of a BRBF subjected to blast loading.In other words,this paper focuses on the effect of blast loading on BRBF.The architype for this investigation is a chevron type braced frame.The frame is subjected to a short duration blast load that lasts only 21.7 mili-second(ms).Blast loading effects on the braced frame are assessed by identifying the weakest plane of failure,deformation characteristics and out of plane bending.The research investigates how the properties of the surrounding concrete,especially compressive strength,affect the overall strength of the BRBF on resisting blast loading.It is observed that the compressive strength of the surrounding concrete plays a significant role in reducing the deformation characteristics,both in-plane and out-of-plane.
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.
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.
基金Science Council in Chinese Taipei Under Grant No.NSC 94-2211-E-035-015
文摘Buckling restrained braces （BRBs） have been widely applied in seismic mitigation since they were introduced in the 1970s. However, traditional BRBs have several disadvantages caused by using a steel tube to envelope the mortar to prevent the core plate from buckling, such as： complex interfaces between the materials used, uncertain precision, and time consumption during the manufacturing processes. In this study, a new device called the multi-curve buckling restrained brace （MC-BRB） is proposed to overcome these disadvantages. The new device consists of a core plate with multiple neck portions assembled to form multiple energy dissipation segments, and the enlarged segment, lateral support elements and constraining elements to prevent the BRB from buckling. The enlarged segment located in the middle of the core plate can be welded to the lateral support and constraining elements to increase buckling resistance and to prevent them from sliding during earthquakes. Component tests and a series of shaking table tests on a full-scale steel structure equipped with MC-BRBs were carried out to investigate the behavior and capability of this new BRB design for seismic mitigation. The experimental results illustrate that the MC-BRB possesses a stable mechanical behavior under cyclic loadings and provides good protection to structures during earthquakes. Also, a mathematical model has been developed to simulate the mechanical characteristics of BRBs.
