Nonstructural components(NSCs)are parts,elements,and subsystems that are not part of the primary loadbearing system of building structures but are subject to seismic loading.Damage to NSCs may disrupt the functionalit...Nonstructural components(NSCs)are parts,elements,and subsystems that are not part of the primary loadbearing system of building structures but are subject to seismic loading.Damage to NSCs may disrupt the functionality of buildings and result in significant economic losses,injuries,and casualties.In past decades,extensive studies have been conducted on the seismic performance and seismic design methods of NSCs.As the input for the seismic design of NSCs,floor response spectra(FRS)have attracted the attention of researchers worldwide.This paper presents a state-of-the-art review of FRS.Different methods for generating FRS are summarized and compared with those in current seismic design codes.A detailed review of the parameters influencing the FRS is presented.These parameters include the characteristics of ground motion excitation,supporting building and NSCs.The floor acceleration response and the FRS obtained from experimental studies and field observations during earthquakes are also discussed.Three RC frames are used in a case study to compare the peak floor acceleration(PFA)and FRS calculated from time history analyses(THA)with that generated using current seismic design codes and different methods in the literature.Major knowledge gaps are identified,including uncertainties associated with developing FRS,FRS generation methods for different types of buildings,the need for comprehensive studies on absolute acceleration,relative velocity,and relative displacement FRS,and the calibration of FRS by field observations during earthquakes.展开更多
With the development and implementation of performance-based earthquake engineering,harmonization of performance levels between structural and nonstructural components becomes vital. Even if the structural components ...With the development and implementation of performance-based earthquake engineering,harmonization of performance levels between structural and nonstructural components becomes vital. Even if the structural components of a building achieve a continuous or immediate occupancy performance level after a seismic event,failure of architectural,mechanical or electrical components can lower the performance level of the entire building system. This reduction in performance caused by the vulnerability of nonstructural components has been observed during recent earthquakes worldwide. Moreover,nonstructural damage has limited the functionality of critical facilities,such as hospitals,following major seismic events. The investment in nonstructural components and building contents is far greater than that of structural components and framing. Therefore,it is not surprising that in many past earthquakes,losses from damage to nonstructural components have exceeded losses from structural damage. Furthermore,the failure of nonstructural components can become a safety hazard or can hamper the safe movement of occupants evacuating buildings,or of rescue workers entering buildings. In comparison to structural components and systems,there is relatively limited information on the seismic design of nonstructural components. Basic research work in this area has been sparse,and the available codes and guidelines are usually,for the most part,based on past experiences,engineering judgment and intuition,rather than on objective experimental and analytical results. Often,design engineers are forced to start almost from square one after each earthquake event: to observe what went wrong and to try to prevent repetitions. This is a consequence of the empirical nature of current seismic regulations and guidelines for nonstructural components. This review paper summarizes current knowledge on the seismic design and analysis of nonstructural building components,identifying major knowledge gaps that will need to be filled by future research. Furthermore,considering recent trends in earthquake engineering,the paper explores how performance-based seismic design might be conceived for nonstructural components,drawing on recent developments made in the field of seismic design and hinting at the specific considerations required for nonstructural components.展开更多
Extreme heat stress events are becoming more frequent under anticipated climate change,which can have devastating impacts on rice growth and yield.To quantify the effects of short-term heat stress at booting stage on ...Extreme heat stress events are becoming more frequent under anticipated climate change,which can have devastating impacts on rice growth and yield.To quantify the effects of short-term heat stress at booting stage on nonstructural carbohydrates(NSC)remobilization in rice,two varieties(Nanjing 41 and Wuyunjing 24)were subjected to 32/22/27°C(maximum/minimum/mean),36/26/31°C,40/30/35°C,and 44/34/39°C for 2,4 and 6 days in phytotrons at booting stage during 2014 and 2015.Yield and yield components,dry matter partitioning index(DMPI),NSC accumulation and translocation were measured and calculated.The results showed that the increase of high-temperature level and duration significantly reduced grain yield by suppressing spikelet number per panicle,seed-setting rate,and grain weight.Heat stress at booting decreased DMPI in panicles,increased DMPI in stems,but had no significant effect on photosynthetic rate.Stem NSC concentration increased whereas panicles NSC concentration,stem NSC translocation efficiency,and contribution of stem NSC to grain yield decreased.Severe heat stress even transformed the stem into a carbohydrate sink during grain filling.The heat-tolerant Wuyunjing 24 showed a higher NSC transport capacity under heat stress than the heat-sensitive Nanjing 41.Heat degree-days(HDD),which combines the effects of the intensity and duration of heat stress,used for quantifying the impacts of heat stress indicates the threshold HDD for the termination of NSC translocation is 9.82°C day.Grain yield was negatively correlated with stem NSC concentration and accumulation at maturity,and yield reduction was tightly related to NSC translocation reduction.The results suggest that heat stress at booting inhibits NSC translocation due to sink size reduction.Therefore,genotypes with higher NSC transport capacity under heat stress could be beneficial for rice yield formation.展开更多
The seismic design forces of nonstructural components(NSCs)in buildings are closely related to floor acceleration response amplification.To investigate the differences in acceleration responses of structures with diff...The seismic design forces of nonstructural components(NSCs)in buildings are closely related to floor acceleration response amplification.To investigate the differences in acceleration responses of structures with different structural types,fundamental periods,and seismic design levels,56 reinforced concrete and steel structures with fundamental periods ranging from 0.37 s to 5.68 s were selected.For each structure,100 sets of earthquake motions were used as inputs for elastic time history analysis.Based on the resulting 26,500 sets of floor acceleration response data,the amplification rules of peak floor acceleration/peak ground acceleration(PFA/PGA)along the height of various structures and the corresponding floor response spectrum characteristics were studied.The nonlinear changes of PFA/PGA along the height of long period structures were compared with the codes of different countries.Moreover,more suitable prediction equations were proposed based on the structural characteristics.Finally,to solve the issue that existing research still cannot accurately reflect the acceleration amplification coefficient of NSCs with different dynamic characteristics in main structures with different periods,a normalized floor response spectrum is proposed that can simultaneously consider the effects of input ground motion characteristics and the main structure,which can be better used in the seismic design of NSCs.展开更多
基金Scientific Research Fund of Institute of Engineering Mechanics,China Earthquake Administration under Grant Nos.2019EEEVL0505,2019A02 and 2019B02。
文摘Nonstructural components(NSCs)are parts,elements,and subsystems that are not part of the primary loadbearing system of building structures but are subject to seismic loading.Damage to NSCs may disrupt the functionality of buildings and result in significant economic losses,injuries,and casualties.In past decades,extensive studies have been conducted on the seismic performance and seismic design methods of NSCs.As the input for the seismic design of NSCs,floor response spectra(FRS)have attracted the attention of researchers worldwide.This paper presents a state-of-the-art review of FRS.Different methods for generating FRS are summarized and compared with those in current seismic design codes.A detailed review of the parameters influencing the FRS is presented.These parameters include the characteristics of ground motion excitation,supporting building and NSCs.The floor acceleration response and the FRS obtained from experimental studies and field observations during earthquakes are also discussed.Three RC frames are used in a case study to compare the peak floor acceleration(PFA)and FRS calculated from time history analyses(THA)with that generated using current seismic design codes and different methods in the literature.Major knowledge gaps are identified,including uncertainties associated with developing FRS,FRS generation methods for different types of buildings,the need for comprehensive studies on absolute acceleration,relative velocity,and relative displacement FRS,and the calibration of FRS by field observations during earthquakes.
文摘With the development and implementation of performance-based earthquake engineering,harmonization of performance levels between structural and nonstructural components becomes vital. Even if the structural components of a building achieve a continuous or immediate occupancy performance level after a seismic event,failure of architectural,mechanical or electrical components can lower the performance level of the entire building system. This reduction in performance caused by the vulnerability of nonstructural components has been observed during recent earthquakes worldwide. Moreover,nonstructural damage has limited the functionality of critical facilities,such as hospitals,following major seismic events. The investment in nonstructural components and building contents is far greater than that of structural components and framing. Therefore,it is not surprising that in many past earthquakes,losses from damage to nonstructural components have exceeded losses from structural damage. Furthermore,the failure of nonstructural components can become a safety hazard or can hamper the safe movement of occupants evacuating buildings,or of rescue workers entering buildings. In comparison to structural components and systems,there is relatively limited information on the seismic design of nonstructural components. Basic research work in this area has been sparse,and the available codes and guidelines are usually,for the most part,based on past experiences,engineering judgment and intuition,rather than on objective experimental and analytical results. Often,design engineers are forced to start almost from square one after each earthquake event: to observe what went wrong and to try to prevent repetitions. This is a consequence of the empirical nature of current seismic regulations and guidelines for nonstructural components. This review paper summarizes current knowledge on the seismic design and analysis of nonstructural building components,identifying major knowledge gaps that will need to be filled by future research. Furthermore,considering recent trends in earthquake engineering,the paper explores how performance-based seismic design might be conceived for nonstructural components,drawing on recent developments made in the field of seismic design and hinting at the specific considerations required for nonstructural components.
基金the National Key Research and Development Program of China(2016YFD0300110)the National Natural Science Foundation of China(31571566)+1 种基金the National Science Fund for Distinguished Young Scholars(31725020)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD).We would like to thank Arielle Biro at Yale University for her assistance with English language and grammatical editing.
文摘Extreme heat stress events are becoming more frequent under anticipated climate change,which can have devastating impacts on rice growth and yield.To quantify the effects of short-term heat stress at booting stage on nonstructural carbohydrates(NSC)remobilization in rice,two varieties(Nanjing 41 and Wuyunjing 24)were subjected to 32/22/27°C(maximum/minimum/mean),36/26/31°C,40/30/35°C,and 44/34/39°C for 2,4 and 6 days in phytotrons at booting stage during 2014 and 2015.Yield and yield components,dry matter partitioning index(DMPI),NSC accumulation and translocation were measured and calculated.The results showed that the increase of high-temperature level and duration significantly reduced grain yield by suppressing spikelet number per panicle,seed-setting rate,and grain weight.Heat stress at booting decreased DMPI in panicles,increased DMPI in stems,but had no significant effect on photosynthetic rate.Stem NSC concentration increased whereas panicles NSC concentration,stem NSC translocation efficiency,and contribution of stem NSC to grain yield decreased.Severe heat stress even transformed the stem into a carbohydrate sink during grain filling.The heat-tolerant Wuyunjing 24 showed a higher NSC transport capacity under heat stress than the heat-sensitive Nanjing 41.Heat degree-days(HDD),which combines the effects of the intensity and duration of heat stress,used for quantifying the impacts of heat stress indicates the threshold HDD for the termination of NSC translocation is 9.82°C day.Grain yield was negatively correlated with stem NSC concentration and accumulation at maturity,and yield reduction was tightly related to NSC translocation reduction.The results suggest that heat stress at booting inhibits NSC translocation due to sink size reduction.Therefore,genotypes with higher NSC transport capacity under heat stress could be beneficial for rice yield formation.
基金Natural Science Foundation of China under Grant Nos.52078471,52078472 and 52208509National Key Research and Development Plan of China under Grant No.2019YFE0112700+2 种基金Natural Science Foundation of Heilongjiang Province under Grant No.LH2022E121Special Project for Basic Scientific Research Business Expenses of the Institute of Engineering Mechanics,China Earthquake Administration under Grant No.2022C04Director’s Fund Director’s Fund of Earthquake Agency of Inner Mongolia Autonomous Region under Grant No.2023MS10。
文摘The seismic design forces of nonstructural components(NSCs)in buildings are closely related to floor acceleration response amplification.To investigate the differences in acceleration responses of structures with different structural types,fundamental periods,and seismic design levels,56 reinforced concrete and steel structures with fundamental periods ranging from 0.37 s to 5.68 s were selected.For each structure,100 sets of earthquake motions were used as inputs for elastic time history analysis.Based on the resulting 26,500 sets of floor acceleration response data,the amplification rules of peak floor acceleration/peak ground acceleration(PFA/PGA)along the height of various structures and the corresponding floor response spectrum characteristics were studied.The nonlinear changes of PFA/PGA along the height of long period structures were compared with the codes of different countries.Moreover,more suitable prediction equations were proposed based on the structural characteristics.Finally,to solve the issue that existing research still cannot accurately reflect the acceleration amplification coefficient of NSCs with different dynamic characteristics in main structures with different periods,a normalized floor response spectrum is proposed that can simultaneously consider the effects of input ground motion characteristics and the main structure,which can be better used in the seismic design of NSCs.
