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
Performance-based seismic design(PBSD) aims to assess structures at different damage states. Since damage can be directly associated to displacements, seismic design with consideration of displacement seems to be logi...Performance-based seismic design(PBSD) aims to assess structures at different damage states. Since damage can be directly associated to displacements, seismic design with consideration of displacement seems to be logical. In this study, simple formulae to estimate the peak floor displacement patterns of eccentrically braced frames(EBFs) at different performance levels subjected to earthquake ground motions are proposed. These formulae are applicable in a PBSD and especially in direct displacement-based design(DDBD). Parametric study is conducted on a group of 30 EBFs under a set of 15 far field and near field accelerograms which they scaled to different amplitudes to adapt various performance levels. The results of thousands of nonlinear dynamic analyses of EBFs have been post-processed by nonlinear regression analysis in order to recognize the major parameters that influence the peak displacement pattern of these frames. Results show that suggested displacement patterns have relatively good agreement with those acquired by an exact nonlinear dynamic analysis.展开更多
Performance-based design in earthquake engineering is a structural optimization problem that has, as the objective, the determination of design parameters for the minimization of total costs, while at the same time sa...Performance-based design in earthquake engineering is a structural optimization problem that has, as the objective, the determination of design parameters for the minimization of total costs, while at the same time satisfying minimum reliability levels for the specifi ed performance criteria. Total costs include those for construction and structural damage repairs, those associated with non-structural components and the social costs of economic losses, injuries and fatalities. This paper presents a general framework to approach this problem, using a numerical optimization strategy and incorporating the use of neural networks for the evaluation of dynamic responses and the reliability levels achieved for a given set of design parameters. The strategy is applied to an example of a three-story offi ce building. The results show the importance of considering the social costs, and the optimum failure probabilities when minimum reliability constraints are not taken into account.展开更多
In the field of earthquake engineering,the advent of the performance-based design philosophy,together with the highly uncertain nature of earthquake ground excitations to structures,has brought probabilistic performan...In the field of earthquake engineering,the advent of the performance-based design philosophy,together with the highly uncertain nature of earthquake ground excitations to structures,has brought probabilistic performance-based design to the forefront of seismic design.In order to design structures that explicitly satisfy probabilistic performance criteria,a probabilistic performance-based optimum seismic design(PPBOSD)framework is proposed in this paper by extending the state-of-the-art performance-based earthquake engineering(PBEE)methodology.PBEE is traditionally used for risk evaluation of existing or newly designed structural systems,thus referred to herein as forward PBEE analysis.In contrast,its use for design purposes is limited because design is essentially a more challenging inverse problem.To address this challenge,a decision-making layer is wrapped around the forward PBEE analysis procedure for computer-aided optimum structural design/retrofit accounting for various sources of uncertainty.In this paper,the framework is illustrated and validated using a proof-of-concept problem,namely tuning a simplified nonlinear inelastic single-degreeof-freedom(SDOF)model of a bridge to achieve a target probabilistic loss hazard curve.For this purpose,first the forward PBEE analysis is presented in conjunction with the multilayer Monte Carlo simulation method to estimate the total loss hazard curve efficiently,followed by a sensitivity study to investigate the effects of system(design)parameters on the probabilistic seismic performance of the bridge.The proposed PPBOSD framework is validated by successfully tuning the system parameters of the structure rated for a target probabilistic seismic loss hazard curve.The PPBOSD framework provides a tool that is essential to develop,calibrate and validate simplified probabilistic performance-based design procedures.展开更多
The seismic design criterion adopted in the existing seismic design codes is reviewed. It is pointed out that the presently used seismic design criterion is not satisfied with the requirements of nowadays social and e...The seismic design criterion adopted in the existing seismic design codes is reviewed. It is pointed out that the presently used seismic design criterion is not satisfied with the requirements of nowadays social and economic development. A new performance-based seismic design criterion that is composed of three components is presented in this paper. It can not only effectively control the economic losses and casualty, but also ensure the building's function in proper operation during earthquakes. The three components are: classification of seismic design for buildings, determination of seismic design intensity and/or seismic design ground motion for controlling seismic economic losses and casualties, and determination of the importance factors in terms of service periods of buildings. For controlling the seismic human losses, the idea of socially acceptable casualty level is presented and the 'Optimal Economic Decision Model' and 'Optimal Safe Decision Model' are established. Finally, a new method is recommended for calculating the importance factors of structures by adjusting structures service period on the base of more important structure with longer service period than the conventional ones. Therefore, the more important structure with longer service periods will be designed for higher seismic loads, in case the exceedance probability of seismic hazard in different service period is same.展开更多
This paper presents a performance-based methodology for the assessment of seismic vulnerability and capacity of buildings. The vulnerability assessment methodology is based on the HAZUS methodology and the improved ca...This paper presents a performance-based methodology for the assessment of seismic vulnerability and capacity of buildings. The vulnerability assessment methodology is based on the HAZUS methodology and the improved capacity- demand-diagram method. The spectral displacement (Sd) of performance points on a capacity curve is used to estimate the damage level of a building. The relationship between Sd and peak ground acceleration (PGA) is established, and then a new vulnerability function is expressed in terms of PGA. Furthermore, the expected value of the seismic capacity index (SCev) is provided to estimate the seismic capacity of buildings based on the probability distribution of damage levels and the corresponding seismic capacity index. The results indicate that the proposed vulnerability methodology is able to assess seismic damage of a large number of building stock directly and quickly following an earthquake. The SCev provides an effective index to measure the seismic capacity of buildings and illustrate the relationship between the seismic capacity of buildings and seismic action. The estimated result is compared with damage surveys of the cities of Dujiangyan and Jiangyou in the M8.0 Wenchuan earthquake, revealing that the methodology is acceptable for seismic risk assessment and decision making. The primary reasons for discrepancies between the estimated results and the damage surveys are discussed.展开更多
Engineering facilities subjected to natural hazards(such as winds and earthquakes) will result in risk when any designed system(i.e.capacity) will not be able to meet the performance required(i.e.demand).Risk might be...Engineering facilities subjected to natural hazards(such as winds and earthquakes) will result in risk when any designed system(i.e.capacity) will not be able to meet the performance required(i.e.demand).Risk might be expressed either as a likelihood of damage or potential financial loss.Engineers tend to make use of the former(i.e.damage).Nevertheless,other non-technical stakeholders cannot get useful information from damage.However,if financial risk is expressed on the basis of probable monetary loss,it will be easily understood by all.Therefore,it is necessary to develop methodologies which communicate the system capacity and demand to financial risk,Incremental dynamic analysis(IDA) was applied in a performance-based earthquake engineering context to do hazard analysis,structural analysis,damage analysis and loss analysis of a reinforced concrete(RC) frame structure.And the financial implications of risk were expressed by expected annual loss(EAL).The quantitative risk analysis proposed is applicable to any engineering facilities and any natural hazards.It is shown that the results from the IDA can be used to assess the overall financial risk exposure to earthquake hazard for a given constructed facility.The computational IDA-EAL method will enable engineers to take into account the long-term financial implications in addition to the construction cost.Consequently,it will help stakeholders make decisions.展开更多
Conventional seismic evaluation of existing bridges explores the ability of a bridge to survive under significant earthquake excitations. This approach has several major drawbacks, such as only a single structural per...Conventional seismic evaluation of existing bridges explores the ability of a bridge to survive under significant earthquake excitations. This approach has several major drawbacks, such as only a single structural performance of near collapse is considered, and the simplified approach of adopting strength-based concept to indirectly estimate the nonlinear behavior of a structure lacks accuracy. As a result, performance-based concepts that include a wider variety of structural performance states of a given bridge excited by different levels of earthquake intensity is needed by the engineering community. This paper introduces an improved process for the seismic evaluation of existing bridges. The relationship between the overall structural performance and earthquakes with varying levels of peak ground acceleration （PGA） can successfully be linked. A universal perspective on the seismic evaluation of bridges over their entire life-cycle can be easily obtained to investigate multiple performance objectives. The accuracy of the proposed method, based on pushover analysis, is proven in a case study that compares the results from the proposed procedure with additional nonlinear time history analyses.展开更多
The seismic intensity is generally high in the Qinghai-Tibet Plateau region of China.The seismic performance of the new prefabricated modular pressurized buildings used to solve the plateau response is insufficient.To...The seismic intensity is generally high in the Qinghai-Tibet Plateau region of China.The seismic performance of the new prefabricated modular pressurized buildings used to solve the plateau response is insufficient.To solve this problem,the small friction pendulum bearing(FPB)isolation design is proposed for modular pressurized buildings.Firstly,a simplified model of cross-truss support for the pressurized module is proposed to simplify the modeling and calculation of the pressurized buildings.The reasonability of the simplified model is verified by comparing the refined finite element model.Subsequently,according to the FPB design process for modular pressurized buildings,a small FPB for isolation is provided for a two-story modular pressurized building under 8-degree fortification earthquakes.Lastly,the seismic effectiveness and constructional feasibility of the isolation structure are verified compared with the non-isolated structure using dynamic time-history analysis.The study results show that the size of FPBs for modular pressurized buildings should consider both displacement and dimension requirements to weigh seismic isolation performance and installation feasibility,respectively.When adopting FPBs,the response of the structure is significantly reduced,and the seismic isolation effect is obvious.The proposed construction process can improve the seismic resilience of the prefabricated modular pressurized buildings by replacing post-earthquake damaged components quickly.It provides ideas for the seismic isolation design of the prefabricated modular pressurized buildings in high seismic intensity areas.展开更多
Reasonable field acquisition geometry can not only guide seismic exploration to obtain sufficient geological information of target body,but also reduce acquisition cost to the maximum.In this study,building on convent...Reasonable field acquisition geometry can not only guide seismic exploration to obtain sufficient geological information of target body,but also reduce acquisition cost to the maximum.In this study,building on conventional ray-based geometry design methods,we incorporate imaging results as a constraint to optimize the geometry design and evaluate its effectiveness.Firstly,the geological model of the target layer is established based on the geological data of the study area and surface seismic data combined with exploration tasks.Then,the ray-tracing method is employed to simulate and assess the proposed geometry design,verifying whether its parameters meet the exploration requirements.Finally,the imaging effect of the designed geometry on the target layer is tested by the cross-well seismic reverse time migration method.This methodology was applied to design the cross-well seismic acquisition geometry for offshore deviated wells in the X Oilfield.The simulation results demonstrate that the imaging-driven geometry design approach effectively guides field operations,enhances the imaging quality of the target layer,and reduces acquisition costs.展开更多
To improve the resilience of railway stations,a typical station was selected as the research object,and an isolation design was introduced.Twenty-four groups of near-fault pulse-like ground motions were selected.The s...To improve the resilience of railway stations,a typical station was selected as the research object,and an isolation design was introduced.Twenty-four groups of near-fault pulse-like ground motions were selected.The seismic resilience of the no-isolation railway stations(NIRS)and the isolation railway stations(IRS)were compared to provide a numerical result of the improvement in resilience.The results show that in the station isolation design,the station's functional requirements and structural characteristics should be considered and the appropriate placement of isolation bearings is under the waiting room.Under the action of a rare earthquake,the repair cost,repair time,rate of harm and death of the IRS were decreased by 8.04 million,18.30 days,6.93×10^(-3)and 1.21×10^(-3),respectively,when compared to the NIRS.The IRS received a seismic resilience grade of three-stars and the NIRS only one-star,indicating that rational isolation design improves the seismic resilience of stations.Thus,for the design of stations close to earthquake faults,it is suggested to utilize appropriate isolation techniques to improve their seismic resilience.展开更多
The objective of Performance-Based Earthquake Engineering （PBEE） is the analysis of performance objectives with a specified annual probability of exceedance. Increasingly undesirable performance is caused by increas...The objective of Performance-Based Earthquake Engineering （PBEE） is the analysis of performance objectives with a specified annual probability of exceedance. Increasingly undesirable performance is caused by increasing levels of strong ground motion having decreasing annual probabilities of exceedance. The development of this methodology includes three steps： （1） evaluation of the distribution of ground motion at a site; （2） evaluation of the distribution of system response; （3） evaluation of the probability of exceeding decision variables within a given time period, given appropriate damage measures. The work has taken a systematic approach to determine the impact of increasing levels of detail in site characterization on the accuracy of ground motion and site effects predictions. Complementary studies have investigated the use of the following models for evaluating site effects： （1） amplification factors defined on the basis of generalized site categories, （2） one-dimensional ground response analysis, and （3） two-dimensional ground response analysis for surface topography on ground motion. The paper provides a brief synthesis of ground motion and site effects analysis procedures within a Performance-Based Design framework. It focuses about the influence on the evaluation of site effects in some active regions by different shear waves velocity measurements Down Hole （D-H）, Cross Hole （C-H）, Seismic Dilatometer Marchetti Test （SDMT） and by different variation of shear modulus and damping ratio with strain level and depth from different laboratory dynamic tests for soil characterization： Resonant Column Test （RCT）, Cyclic Loading Torsional Shear Test （CLTST）.展开更多
An investigation of girder bridges on National Highway 213 and the Doujiangyan-Wenchuan expressway after the Wenchuan earthquake showed that typical types of damage included： span collapses due to unseating at expans...An investigation of girder bridges on National Highway 213 and the Doujiangyan-Wenchuan expressway after the Wenchuan earthquake showed that typical types of damage included： span collapses due to unseating at expansion joints; shear key failure; and damage of the expansion joint due to the slide-induced large relative displacement between the bottom of the girder and the top of the laminated-rubber bearing. This slide, however, can actually act as a form of isolation for the substructure, and as a result, the piers and foundation of most of the bridges on state route 213 suffered minor damage. The exception was the Baihua Bridge, which suffered severe damage. Corresponding seismic design recommendations are presented based on this investigation.展开更多
When evaluating the seismic safety and reliability of complex engineering structures,it is a critical problem to reasonably consider the randomness and multi-dimensional nature of ground motions.To this end,a proposed...When evaluating the seismic safety and reliability of complex engineering structures,it is a critical problem to reasonably consider the randomness and multi-dimensional nature of ground motions.To this end,a proposed modeling strategy of multi-dimensional stochastic earthquakes is addressed in this study.This improved seismic model has several merits that enable it to better provide seismic analyses of structures.Specifically,at first,the ground motion model is compatible with the design response spectrum.Secondly,the evolutionary power spectrum involved in the model and the design response spectrum are constructed accordingly with sufficient consideration of the correlation between different seismic components.Thirdly,the random function-based dimension-reduction representation is applied,by which seismic modeling is established,with three elementary random variables.Numerical simulations of multi-dimensional stochastic ground motions in a specific design scenario indicate the effectiveness of the proposed modeling strategy.Moreover,the multi-dimensional seismic response and the global reliability of a high-rise frame-core tube structure is discussed in detail to further illustrate the engineering applicability of the proposed method.The analytical investigations demonstrate that the suggested stochastic model of multi-dimensional ground motion is available for accurate seismic response analysis and dynamic reliability assessment of complex engineering structures for performance-based seismic resistance design.展开更多
Many different types of buildings were severely damaged or collapsed during the May 12, 2008 Great Wenchuan Earthquake. Based on survey data collected in regions that were subjected to moderate to severe earthquake in...Many different types of buildings were severely damaged or collapsed during the May 12, 2008 Great Wenchuan Earthquake. Based on survey data collected in regions that were subjected to moderate to severe earthquake intensities, a comparison between the observed building damage, and the three earthquake performance objectives and seismic conceptual design principles specified by the national ＂Code for Seismic Design of Buildings GB50011-2001,＂ was carried out. Actual damage and predicted damage for a given earthquake level for different types of structures is compared. Discussions on seismic conceptual design principles, with respect to multiple defense lines, strong column-weak beam, link beam of shear walls, ductility detailing of masonry structures, exits and staircases, and nonstructural elements, etc. are carried out. Suggestions for improving the seismic design of structures are also proposed. It is concluded that the seismic performance objectives for three earthquake levels, i.e., ＂no failure under minor earthquake level, ＂＂repairable damage under moderate earthquake level＂ and ＂no collapse under major earthquake level＂ can be achieved if seismic design principles are carried out by strictly following the code requirements and ensuring construction quality.展开更多
Following several damaging earthquakes in China, research has been devoted to find the causes of the collapse of reinforced concrete （RC） building sand studying the vulnerability of existing buildings. The Chinese C...Following several damaging earthquakes in China, research has been devoted to find the causes of the collapse of reinforced concrete （RC） building sand studying the vulnerability of existing buildings. The Chinese Code for Seismic Design of Buildings （CCSDB） has evolved over time, however, there is still reported earthquake induced damage of newly designed RC buildings. Thus, to investigate modern Chinese seismic design code, three low-, mid- and high-rise RC frames were designed according to the 2010 CCSDB and the corresponding vulnerability curves were derived by computing a probabilistic seismic demand model （PSDM）.The PSDM was computed by carrying out nonlinear time history analysis using thirty ground motions obtained from the Pacific Earthquake Engineering Research Center. Finally, the PSDM was used to generate fragility curves for immediate occupancy, significant damage, and collapse prevention damage levels. Results of the vulnerability assessment indicate that the seismic demands on the three different frames designed according to the 2010 CCSDB meet the seismic requirements and are almost in the same safety level.展开更多
As there are no specific guidelines on design of subsea pipelines crossing active seismic faults, methods for land buried pipelines have been applied to. Taking the large seismic fault movement into account, this pape...As there are no specific guidelines on design of subsea pipelines crossing active seismic faults, methods for land buried pipelines have been applied to. Taking the large seismic fault movement into account, this paper proposes improved methods for seismic designs of subsea pipelines by comprehensively investigating the real constraining of soil on the pipelines, the interaction processes of soil with the pipeline, the plastic slippage of the soil, and the elastic-plastic properties of the pipeline materials. New formulas are given to calculate the length of transition section and its total elongation. These formulas are more reasonable in mechanism, and more practical for seismic design of subsea pipelines crossing active faults.展开更多
The 285.5 m-high Xiluodu Arch Dam is located in a seismic region along the Jinsha River in China, where the horizontal components of peak ground accelerations for design and checking earthquakes have been estimated to...The 285.5 m-high Xiluodu Arch Dam is located in a seismic region along the Jinsha River in China, where the horizontal components of peak ground accelerations for design and checking earthquakes have been estimated to be 0.355 g and 0.423 g, respectively( g is the gravitational acceleration). The ground motion parameters of design and checking earthquakes are defined by exceedance probabilities of 2% over 100 years and 1% over 100 years, respectively. The dam shape was first selected and optimized through static analysis of the basic load combinations, and then adjusted after taking into account the seismic loads. The dam should be operational during and after the design earthquake with or without minor repairs, and maintain local and global stabilities during an extreme earthquake. Both linear elastic dynamic analysis and nonlinear dynamic analysis considering radiation damping, contraction joints, and material nonlinearity were conducted to assess the stress in the arch dam.The dynamic analysis shows that the maximum dynamic compressive stresses are less than the allowable levels, while the area with tensile stress over the limit is less than 15% of the dam surface and the maximum contraction openings range from 10 mm to 25 mm. The arch dam has sufficient earthquake-resistance capacity and meets the safety requirements. Nevertheless, steel reinforcement has been provided at the dam toe and in the zones of high tensile stress on the dam surface out of extra precaution.展开更多
The natural landscape in China exposes many existing RC buildings to aggressive environments.Such exposure can lead to deterioration in structural performance with regard to resisting events such as earthquakes.Corros...The natural landscape in China exposes many existing RC buildings to aggressive environments.Such exposure can lead to deterioration in structural performance with regard to resisting events such as earthquakes.Corrosion of embedded reinforcement is one of the most common mechanisms by which such structural degradation occurs.There has been increasing attention in recent years toward seismic resilience in communities and their constituent construction;however,to date,studies have neglected the effect of natural aging.This study aims to examine the effect of reinforcement corrosion on the seismic resilience of RC frames that are designed according to Chinese seismic design codes.A total of twenty RC frames are used to represent design and construction that is typical of coastal China,with consideration given to various seismic fortification levels and elevation arrangements.Seismic fragility relationships are developed for case frames under varying levels of reinforcement corrosion,i.e.,corrosion rates are increased from 5%to 15%.Subsequently,the seismic resilience levels of uncorroded and corroded RC frames are compared using a normalized loss factor.It was found that the loss of resilience of the corroded frames is greater than that of their uncorroded counterparts.At the Rare Earthquake hazard level,the corrosioninduced increase in loss of resilience can be more than 200%,showing the significant effect of reinforcement corrosion on structural resilience under the influence of earthquakes.展开更多
The Federal Highway Administration (FHWA) sponsored a large,multi-year project conducted by the Multidisciplinary Center for Earthquake Engineering Research (MCEER) titled'Seismic Vulnerability of New Highway Cons...The Federal Highway Administration (FHWA) sponsored a large,multi-year project conducted by the Multidisciplinary Center for Earthquake Engineering Research (MCEER) titled'Seismic Vulnerability of New Highway Construction'(MCEER Project 112),which was completed in 1998.MCEER coordinated the work of many researchers,who performed studies on the seismic design and vulnerability analysis of highway bridges,tunnels,and retaining structures. Extensive research was conducted to provide revisions and improvements to current design and detailing approaches and national design specifications for highway bridges.The program included both analytical and experimental studies,and addressed seismic hazard exposure and ground motion input for the U.S.highway system;foundation design and soil behavior: structural importance,analysis,and response:structural design issues and details;and structural design criteria.展开更多
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.
文摘Performance-based seismic design(PBSD) aims to assess structures at different damage states. Since damage can be directly associated to displacements, seismic design with consideration of displacement seems to be logical. In this study, simple formulae to estimate the peak floor displacement patterns of eccentrically braced frames(EBFs) at different performance levels subjected to earthquake ground motions are proposed. These formulae are applicable in a PBSD and especially in direct displacement-based design(DDBD). Parametric study is conducted on a group of 30 EBFs under a set of 15 far field and near field accelerograms which they scaled to different amplitudes to adapt various performance levels. The results of thousands of nonlinear dynamic analyses of EBFs have been post-processed by nonlinear regression analysis in order to recognize the major parameters that influence the peak displacement pattern of these frames. Results show that suggested displacement patterns have relatively good agreement with those acquired by an exact nonlinear dynamic analysis.
文摘Performance-based design in earthquake engineering is a structural optimization problem that has, as the objective, the determination of design parameters for the minimization of total costs, while at the same time satisfying minimum reliability levels for the specifi ed performance criteria. Total costs include those for construction and structural damage repairs, those associated with non-structural components and the social costs of economic losses, injuries and fatalities. This paper presents a general framework to approach this problem, using a numerical optimization strategy and incorporating the use of neural networks for the evaluation of dynamic responses and the reliability levels achieved for a given set of design parameters. The strategy is applied to an example of a three-story offi ce building. The results show the importance of considering the social costs, and the optimum failure probabilities when minimum reliability constraints are not taken into account.
文摘In the field of earthquake engineering,the advent of the performance-based design philosophy,together with the highly uncertain nature of earthquake ground excitations to structures,has brought probabilistic performance-based design to the forefront of seismic design.In order to design structures that explicitly satisfy probabilistic performance criteria,a probabilistic performance-based optimum seismic design(PPBOSD)framework is proposed in this paper by extending the state-of-the-art performance-based earthquake engineering(PBEE)methodology.PBEE is traditionally used for risk evaluation of existing or newly designed structural systems,thus referred to herein as forward PBEE analysis.In contrast,its use for design purposes is limited because design is essentially a more challenging inverse problem.To address this challenge,a decision-making layer is wrapped around the forward PBEE analysis procedure for computer-aided optimum structural design/retrofit accounting for various sources of uncertainty.In this paper,the framework is illustrated and validated using a proof-of-concept problem,namely tuning a simplified nonlinear inelastic single-degreeof-freedom(SDOF)model of a bridge to achieve a target probabilistic loss hazard curve.For this purpose,first the forward PBEE analysis is presented in conjunction with the multilayer Monte Carlo simulation method to estimate the total loss hazard curve efficiently,followed by a sensitivity study to investigate the effects of system(design)parameters on the probabilistic seismic performance of the bridge.The proposed PPBOSD framework is validated by successfully tuning the system parameters of the structure rated for a target probabilistic seismic loss hazard curve.The PPBOSD framework provides a tool that is essential to develop,calibrate and validate simplified probabilistic performance-based design procedures.
基金Chinese National Natural Science Foundation with the grant No.59895410the China Basic Research and Development Project:the Mechanism and Prediction of the Strong Earthquake of the Continental under the Grant No.95130603
文摘The seismic design criterion adopted in the existing seismic design codes is reviewed. It is pointed out that the presently used seismic design criterion is not satisfied with the requirements of nowadays social and economic development. A new performance-based seismic design criterion that is composed of three components is presented in this paper. It can not only effectively control the economic losses and casualty, but also ensure the building's function in proper operation during earthquakes. The three components are: classification of seismic design for buildings, determination of seismic design intensity and/or seismic design ground motion for controlling seismic economic losses and casualties, and determination of the importance factors in terms of service periods of buildings. For controlling the seismic human losses, the idea of socially acceptable casualty level is presented and the 'Optimal Economic Decision Model' and 'Optimal Safe Decision Model' are established. Finally, a new method is recommended for calculating the importance factors of structures by adjusting structures service period on the base of more important structure with longer service period than the conventional ones. Therefore, the more important structure with longer service periods will be designed for higher seismic loads, in case the exceedance probability of seismic hazard in different service period is same.
基金National Natural Science Foundation of China Under Grant No.50908216Postdoctoral Science Foundation of China Under Grant No.20070420878
文摘This paper presents a performance-based methodology for the assessment of seismic vulnerability and capacity of buildings. The vulnerability assessment methodology is based on the HAZUS methodology and the improved capacity- demand-diagram method. The spectral displacement (Sd) of performance points on a capacity curve is used to estimate the damage level of a building. The relationship between Sd and peak ground acceleration (PGA) is established, and then a new vulnerability function is expressed in terms of PGA. Furthermore, the expected value of the seismic capacity index (SCev) is provided to estimate the seismic capacity of buildings based on the probability distribution of damage levels and the corresponding seismic capacity index. The results indicate that the proposed vulnerability methodology is able to assess seismic damage of a large number of building stock directly and quickly following an earthquake. The SCev provides an effective index to measure the seismic capacity of buildings and illustrate the relationship between the seismic capacity of buildings and seismic action. The estimated result is compared with damage surveys of the cities of Dujiangyan and Jiangyou in the M8.0 Wenchuan earthquake, revealing that the methodology is acceptable for seismic risk assessment and decision making. The primary reasons for discrepancies between the estimated results and the damage surveys are discussed.
基金Project(2011CB013804) supported by the National Basic Research Program of ChinaProject(50925828) supported by the National Natural Science Funds for Distinguished Young Scholars of China
文摘Engineering facilities subjected to natural hazards(such as winds and earthquakes) will result in risk when any designed system(i.e.capacity) will not be able to meet the performance required(i.e.demand).Risk might be expressed either as a likelihood of damage or potential financial loss.Engineers tend to make use of the former(i.e.damage).Nevertheless,other non-technical stakeholders cannot get useful information from damage.However,if financial risk is expressed on the basis of probable monetary loss,it will be easily understood by all.Therefore,it is necessary to develop methodologies which communicate the system capacity and demand to financial risk,Incremental dynamic analysis(IDA) was applied in a performance-based earthquake engineering context to do hazard analysis,structural analysis,damage analysis and loss analysis of a reinforced concrete(RC) frame structure.And the financial implications of risk were expressed by expected annual loss(EAL).The quantitative risk analysis proposed is applicable to any engineering facilities and any natural hazards.It is shown that the results from the IDA can be used to assess the overall financial risk exposure to earthquake hazard for a given constructed facility.The computational IDA-EAL method will enable engineers to take into account the long-term financial implications in addition to the construction cost.Consequently,it will help stakeholders make decisions.
基金the Science Council of Taiwan Under Grant No. NSC-96-2625-Z-027-002
文摘Conventional seismic evaluation of existing bridges explores the ability of a bridge to survive under significant earthquake excitations. This approach has several major drawbacks, such as only a single structural performance of near collapse is considered, and the simplified approach of adopting strength-based concept to indirectly estimate the nonlinear behavior of a structure lacks accuracy. As a result, performance-based concepts that include a wider variety of structural performance states of a given bridge excited by different levels of earthquake intensity is needed by the engineering community. This paper introduces an improved process for the seismic evaluation of existing bridges. The relationship between the overall structural performance and earthquakes with varying levels of peak ground acceleration （PGA） can successfully be linked. A universal perspective on the seismic evaluation of bridges over their entire life-cycle can be easily obtained to investigate multiple performance objectives. The accuracy of the proposed method, based on pushover analysis, is proven in a case study that compares the results from the proposed procedure with additional nonlinear time history analyses.
基金supported by Technology Research and Development Program of China Construction Advanced Technology Research Institute(Grant No.XJY-2024-16)。
文摘The seismic intensity is generally high in the Qinghai-Tibet Plateau region of China.The seismic performance of the new prefabricated modular pressurized buildings used to solve the plateau response is insufficient.To solve this problem,the small friction pendulum bearing(FPB)isolation design is proposed for modular pressurized buildings.Firstly,a simplified model of cross-truss support for the pressurized module is proposed to simplify the modeling and calculation of the pressurized buildings.The reasonability of the simplified model is verified by comparing the refined finite element model.Subsequently,according to the FPB design process for modular pressurized buildings,a small FPB for isolation is provided for a two-story modular pressurized building under 8-degree fortification earthquakes.Lastly,the seismic effectiveness and constructional feasibility of the isolation structure are verified compared with the non-isolated structure using dynamic time-history analysis.The study results show that the size of FPBs for modular pressurized buildings should consider both displacement and dimension requirements to weigh seismic isolation performance and installation feasibility,respectively.When adopting FPBs,the response of the structure is significantly reduced,and the seismic isolation effect is obvious.The proposed construction process can improve the seismic resilience of the prefabricated modular pressurized buildings by replacing post-earthquake damaged components quickly.It provides ideas for the seismic isolation design of the prefabricated modular pressurized buildings in high seismic intensity areas.
基金funded by the Young Scientists Fund of the National Natural Science Foundation of China(42304135)the scientific research project of Gansu Coal Geology Bureau(2023-07).
文摘Reasonable field acquisition geometry can not only guide seismic exploration to obtain sufficient geological information of target body,but also reduce acquisition cost to the maximum.In this study,building on conventional ray-based geometry design methods,we incorporate imaging results as a constraint to optimize the geometry design and evaluate its effectiveness.Firstly,the geological model of the target layer is established based on the geological data of the study area and surface seismic data combined with exploration tasks.Then,the ray-tracing method is employed to simulate and assess the proposed geometry design,verifying whether its parameters meet the exploration requirements.Finally,the imaging effect of the designed geometry on the target layer is tested by the cross-well seismic reverse time migration method.This methodology was applied to design the cross-well seismic acquisition geometry for offshore deviated wells in the X Oilfield.The simulation results demonstrate that the imaging-driven geometry design approach effectively guides field operations,enhances the imaging quality of the target layer,and reduces acquisition costs.
基金National Natural Science Foundation of China under Grant No.52278534Sichuan Provincial Natural Science Foundation of China under Grant No.2022NSFSC0423。
文摘To improve the resilience of railway stations,a typical station was selected as the research object,and an isolation design was introduced.Twenty-four groups of near-fault pulse-like ground motions were selected.The seismic resilience of the no-isolation railway stations(NIRS)and the isolation railway stations(IRS)were compared to provide a numerical result of the improvement in resilience.The results show that in the station isolation design,the station's functional requirements and structural characteristics should be considered and the appropriate placement of isolation bearings is under the waiting room.Under the action of a rare earthquake,the repair cost,repair time,rate of harm and death of the IRS were decreased by 8.04 million,18.30 days,6.93×10^(-3)and 1.21×10^(-3),respectively,when compared to the NIRS.The IRS received a seismic resilience grade of three-stars and the NIRS only one-star,indicating that rational isolation design improves the seismic resilience of stations.Thus,for the design of stations close to earthquake faults,it is suggested to utilize appropriate isolation techniques to improve their seismic resilience.
文摘The objective of Performance-Based Earthquake Engineering （PBEE） is the analysis of performance objectives with a specified annual probability of exceedance. Increasingly undesirable performance is caused by increasing levels of strong ground motion having decreasing annual probabilities of exceedance. The development of this methodology includes three steps： （1） evaluation of the distribution of ground motion at a site; （2） evaluation of the distribution of system response; （3） evaluation of the probability of exceeding decision variables within a given time period, given appropriate damage measures. The work has taken a systematic approach to determine the impact of increasing levels of detail in site characterization on the accuracy of ground motion and site effects predictions. Complementary studies have investigated the use of the following models for evaluating site effects： （1） amplification factors defined on the basis of generalized site categories, （2） one-dimensional ground response analysis, and （3） two-dimensional ground response analysis for surface topography on ground motion. The paper provides a brief synthesis of ground motion and site effects analysis procedures within a Performance-Based Design framework. It focuses about the influence on the evaluation of site effects in some active regions by different shear waves velocity measurements Down Hole （D-H）, Cross Hole （C-H）, Seismic Dilatometer Marchetti Test （SDMT） and by different variation of shear modulus and damping ratio with strain level and depth from different laboratory dynamic tests for soil characterization： Resonant Column Test （RCT）, Cyclic Loading Torsional Shear Test （CLTST）.
基金National Natural Science Foundation Under Grant No.50578118
文摘An investigation of girder bridges on National Highway 213 and the Doujiangyan-Wenchuan expressway after the Wenchuan earthquake showed that typical types of damage included： span collapses due to unseating at expansion joints; shear key failure; and damage of the expansion joint due to the slide-induced large relative displacement between the bottom of the girder and the top of the laminated-rubber bearing. This slide, however, can actually act as a form of isolation for the substructure, and as a result, the piers and foundation of most of the bridges on state route 213 suffered minor damage. The exception was the Baihua Bridge, which suffered severe damage. Corresponding seismic design recommendations are presented based on this investigation.
基金National Natural Science Foundation of China under Grant Nos.51978543,52108444,and 51778343Plan of Outstanding Young and Middle-aged Scientific and Technological Innovation Team in the Universities of Hubei Province with Project No.T2020010Natural Science Foundation of Hebei Province under Grant No.E2021512001。
文摘When evaluating the seismic safety and reliability of complex engineering structures,it is a critical problem to reasonably consider the randomness and multi-dimensional nature of ground motions.To this end,a proposed modeling strategy of multi-dimensional stochastic earthquakes is addressed in this study.This improved seismic model has several merits that enable it to better provide seismic analyses of structures.Specifically,at first,the ground motion model is compatible with the design response spectrum.Secondly,the evolutionary power spectrum involved in the model and the design response spectrum are constructed accordingly with sufficient consideration of the correlation between different seismic components.Thirdly,the random function-based dimension-reduction representation is applied,by which seismic modeling is established,with three elementary random variables.Numerical simulations of multi-dimensional stochastic ground motions in a specific design scenario indicate the effectiveness of the proposed modeling strategy.Moreover,the multi-dimensional seismic response and the global reliability of a high-rise frame-core tube structure is discussed in detail to further illustrate the engineering applicability of the proposed method.The analytical investigations demonstrate that the suggested stochastic model of multi-dimensional ground motion is available for accurate seismic response analysis and dynamic reliability assessment of complex engineering structures for performance-based seismic resistance design.
文摘Many different types of buildings were severely damaged or collapsed during the May 12, 2008 Great Wenchuan Earthquake. Based on survey data collected in regions that were subjected to moderate to severe earthquake intensities, a comparison between the observed building damage, and the three earthquake performance objectives and seismic conceptual design principles specified by the national ＂Code for Seismic Design of Buildings GB50011-2001,＂ was carried out. Actual damage and predicted damage for a given earthquake level for different types of structures is compared. Discussions on seismic conceptual design principles, with respect to multiple defense lines, strong column-weak beam, link beam of shear walls, ductility detailing of masonry structures, exits and staircases, and nonstructural elements, etc. are carried out. Suggestions for improving the seismic design of structures are also proposed. It is concluded that the seismic performance objectives for three earthquake levels, i.e., ＂no failure under minor earthquake level, ＂＂repairable damage under moderate earthquake level＂ and ＂no collapse under major earthquake level＂ can be achieved if seismic design principles are carried out by strictly following the code requirements and ensuring construction quality.
基金National Natural Science Foundation of China Under Grant No.51108105,90815029,50938006 Research Fund for the Doctoral Program of Higher Education of China Under Grant No.20094410120002+3 种基金 Major Program of National Natural Science Foundation of China Under Grant No.90815027Key Projects in the National Science&Technology Pillar Program during the Eleventh Five-Year Plan Period Under Grant No.2009BAJ28B03Fund for High School in Guangzhou (10A057)the Open Foundation of State Key Laboratory of Subtropical Building Science(2011KB15)
文摘Following several damaging earthquakes in China, research has been devoted to find the causes of the collapse of reinforced concrete （RC） building sand studying the vulnerability of existing buildings. The Chinese Code for Seismic Design of Buildings （CCSDB） has evolved over time, however, there is still reported earthquake induced damage of newly designed RC buildings. Thus, to investigate modern Chinese seismic design code, three low-, mid- and high-rise RC frames were designed according to the 2010 CCSDB and the corresponding vulnerability curves were derived by computing a probabilistic seismic demand model （PSDM）.The PSDM was computed by carrying out nonlinear time history analysis using thirty ground motions obtained from the Pacific Earthquake Engineering Research Center. Finally, the PSDM was used to generate fragility curves for immediate occupancy, significant damage, and collapse prevention damage levels. Results of the vulnerability assessment indicate that the seismic demands on the three different frames designed according to the 2010 CCSDB meet the seismic requirements and are almost in the same safety level.
基金supported by the National Natural Science Foundation of China (Grant No. 50979113)the National High Technology Research and Development Program of China (863 Program, Grant No. 2006AA09A105)the China National Offshore Oil Corporation
文摘As there are no specific guidelines on design of subsea pipelines crossing active seismic faults, methods for land buried pipelines have been applied to. Taking the large seismic fault movement into account, this paper proposes improved methods for seismic designs of subsea pipelines by comprehensively investigating the real constraining of soil on the pipelines, the interaction processes of soil with the pipeline, the plastic slippage of the soil, and the elastic-plastic properties of the pipeline materials. New formulas are given to calculate the length of transition section and its total elongation. These formulas are more reasonable in mechanism, and more practical for seismic design of subsea pipelines crossing active faults.
基金supported by the Program of Study on the Standard of Overall Safety Control of High Arch Dam of PowerChina Co.,Ltd.(Grant No.DJ-ZDXM-2014-19)
文摘The 285.5 m-high Xiluodu Arch Dam is located in a seismic region along the Jinsha River in China, where the horizontal components of peak ground accelerations for design and checking earthquakes have been estimated to be 0.355 g and 0.423 g, respectively( g is the gravitational acceleration). The ground motion parameters of design and checking earthquakes are defined by exceedance probabilities of 2% over 100 years and 1% over 100 years, respectively. The dam shape was first selected and optimized through static analysis of the basic load combinations, and then adjusted after taking into account the seismic loads. The dam should be operational during and after the design earthquake with or without minor repairs, and maintain local and global stabilities during an extreme earthquake. Both linear elastic dynamic analysis and nonlinear dynamic analysis considering radiation damping, contraction joints, and material nonlinearity were conducted to assess the stress in the arch dam.The dynamic analysis shows that the maximum dynamic compressive stresses are less than the allowable levels, while the area with tensile stress over the limit is less than 15% of the dam surface and the maximum contraction openings range from 10 mm to 25 mm. The arch dam has sufficient earthquake-resistance capacity and meets the safety requirements. Nevertheless, steel reinforcement has been provided at the dam toe and in the zones of high tensile stress on the dam surface out of extra precaution.
基金National Natural Science Foundation of China under Grant No.51778198the Natural Science Foundation for Excellent Young Scientists of Heilongjiang Province under Grant No.YQ2020E023。
文摘The natural landscape in China exposes many existing RC buildings to aggressive environments.Such exposure can lead to deterioration in structural performance with regard to resisting events such as earthquakes.Corrosion of embedded reinforcement is one of the most common mechanisms by which such structural degradation occurs.There has been increasing attention in recent years toward seismic resilience in communities and their constituent construction;however,to date,studies have neglected the effect of natural aging.This study aims to examine the effect of reinforcement corrosion on the seismic resilience of RC frames that are designed according to Chinese seismic design codes.A total of twenty RC frames are used to represent design and construction that is typical of coastal China,with consideration given to various seismic fortification levels and elevation arrangements.Seismic fragility relationships are developed for case frames under varying levels of reinforcement corrosion,i.e.,corrosion rates are increased from 5%to 15%.Subsequently,the seismic resilience levels of uncorroded and corroded RC frames are compared using a normalized loss factor.It was found that the loss of resilience of the corroded frames is greater than that of their uncorroded counterparts.At the Rare Earthquake hazard level,the corrosioninduced increase in loss of resilience can be more than 200%,showing the significant effect of reinforcement corrosion on structural resilience under the influence of earthquakes.
基金the Federal Highway Administration under contract number DTFH61-92-C-00112.
文摘The Federal Highway Administration (FHWA) sponsored a large,multi-year project conducted by the Multidisciplinary Center for Earthquake Engineering Research (MCEER) titled'Seismic Vulnerability of New Highway Construction'(MCEER Project 112),which was completed in 1998.MCEER coordinated the work of many researchers,who performed studies on the seismic design and vulnerability analysis of highway bridges,tunnels,and retaining structures. Extensive research was conducted to provide revisions and improvements to current design and detailing approaches and national design specifications for highway bridges.The program included both analytical and experimental studies,and addressed seismic hazard exposure and ground motion input for the U.S.highway system;foundation design and soil behavior: structural importance,analysis,and response:structural design issues and details;and structural design criteria.
