Many researchers have developed new calculation methods to analyze seismic slope stability problems, but the conventional pseudo-static method is still widely used in engineering design due to its simplicity. Based on...Many researchers have developed new calculation methods to analyze seismic slope stability problems, but the conventional pseudo-static method is still widely used in engineering design due to its simplicity. Based on the Technical Code for Building Slope Engineering(GB 50330-2013) of China and the Guidelines for Evaluating and Mitigating Seismic Hazards in California(SP117), a comparative study on the pseudo-static method was performed. The results indicate that the largest difference between these two design codes lies in determination of the seismic equivalence reduction factor( f;). The GB 50330-2013 code specifies a single value for f;of 0.25. In SP117, numerous factors,such as magnitude and distance, are considered in determining f;. Two case studies show that the types of slope stability status evaluated by SP117 are in agreement with those evaluated by the seismic time-history stability analysis and Newmark displacement analysis. The factors of safety evaluated by SP117 can be used in practice for safe design. However, the factors of safety evaluated by GB 50330-2013 are risky for slope seismic design.展开更多
A large number of buildings were seriously damaged or collapsed in the"5.12"Wenchuan earthquake.Based on field surveys and studies of damage to different types of buildings,seismic design codes have been upd...A large number of buildings were seriously damaged or collapsed in the"5.12"Wenchuan earthquake.Based on field surveys and studies of damage to different types of buildings,seismic design codes have been updated.This paper briefly summarizes some of the major revisions that have been incorporated into the"Standard for classification of seismic protection of building constructions GB50223-2008"and"Code for Seismic Design of Buildings GB50011-2001."The definition of seismic fortification class for buildings has been revisited,and as a result,the seismic classifications for schools,hospitals and other buildings that hold large populations such as evacuation shelters and information centers have been upgraded in the GB50223-2008 Code.The main aspects of the revised GB50011-2001 code include:(a)modification of the seismic intensity specified for the Provinces of Sichuan,Shanxi and Gansu;(b)basic conceptual design for retaining walls and building foundations in mountainous areas;(c)regularity of building configuration;(d)integration of masonry structures and precast RC floors;(e)requirements for calculating and detailing stair shafts;and(f)limiting the use of single-bay RC frame structures.Some significant examples of damage in the epicenter areas are provided as a reference in the discussion on the consequences of collapse,the importance of duplicate structural systems,and the integration of RC and masonry structures.展开更多
In recent years,with the continuous expansion of China's infrastructure construction,related construction work,including highway and bridge construction,has been steadily progressing.Among them,bridges are an impo...In recent years,with the continuous expansion of China's infrastructure construction,related construction work,including highway and bridge construction,has been steadily progressing.Among them,bridges are an important component of infrastructure construction,and their safety and stability are related to the travel of the masses and even the safety of their lives.China has a strict management system for bridge design specifications.This article mainly takes long-span highway bridges as an example to study the key issues of its design specifications and proposes countermeasures for related work.展开更多
TB 10031-2021 J 73-2021 Prepared by:China Railway SIYUAN Survey and Design Group Co.,Ltd.Approved by:National Railway Administration Effective date:February 1,2022 China Railway Publishing House Co.,Ltd.Beijing 2022 N...TB 10031-2021 J 73-2021 Prepared by:China Railway SIYUAN Survey and Design Group Co.,Ltd.Approved by:National Railway Administration Effective date:February 1,2022 China Railway Publishing House Co.,Ltd.Beijing 2022 Notice of National Railway Administration on the Issue of Railway Industry Standards(Engineering and Construction Standard Batch No.6,2021)Document GTKF[2021]No.34 Code for Design of Railway Freight Car Facilities(TB 10031-2021)is hereby issued and will come into effect on February 1,2022.Code for Design of Railway Freight Car Facilities(TB 10031-2009)is withdrawn.China Railway Publishing House Co.,Ltd.is authorized to publish this Code.展开更多
DAYU3D is a modern three-dimensional(3D)computer code for thermal-hydraulic design and accident analysis in hightemperature gas-cooled reactors(HTGRs),developed by the Institute of Nuclear and New Energy Technology(IN...DAYU3D is a modern three-dimensional(3D)computer code for thermal-hydraulic design and accident analysis in hightemperature gas-cooled reactors(HTGRs),developed by the Institute of Nuclear and New Energy Technology(INET)at Tsinghua University.Compared to the traditional codes like TINTE,the DAYU3D code has advantages due to its refined framework,improved models,and more efficient algorithms.It is able to simulate the continuous movement of control rods and is more rigorous in treating radiation heat transfer and the break mass flow.Advanced computational methods significantly improve the computational efficiency of DAYU3D,achieving a time reduction of over 60%compared to TINTE.Extensive verification and validation with more than 100 cases demonstrate that DAYU3D is promising for HTGR 3D thermal-hydraulic design and accident analyses.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
A uniaxial tension test is commonly used to determine the mechanical properties of steel,but it has no meaning for the response of the material in a structure.The test was developed as a consensus solution by producer...A uniaxial tension test is commonly used to determine the mechanical properties of steel,but it has no meaning for the response of the material in a structure.The test was developed as a consensus solution by producers,fabricators,designers and code writers,to have a standard by which similar materials could be compared to a common base.It does not represent the actual behavior of the steel in a structure,and was never intended to do so.To study the true behavior of the structure and how the material responds it would be better to determine the strains and deformations that will take place during actual service condition.Such characteristics reflect the real behavior,whether in the elastic or inelastic range.If stresses or forces are needed,these are easily determined by the value of the strain and the relevant material modulus,along with the type of cross section,whether elastic or inelastic.The paper addresses the properties of a range of structural steels,how these are incorporated into design standards and how the standards define deformation characteristics and demands for bolted and welded connections.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
Unreinforced Masonry (URM) is the most common partitioning material in framed buildings in India and many other countries. Although it is well-known that under lateral loading the behavior and modes of failure of the ...Unreinforced Masonry (URM) is the most common partitioning material in framed buildings in India and many other countries. Although it is well-known that under lateral loading the behavior and modes of failure of the frame buildings change significantly due to infill-frame interaction, the general design practice is to treat infills as nonstructural elements and their stiffness, strength and interaction with the frame is often ignored, primarily because of difficulties in simulation and lack of modeling guidelines in design codes. The Indian Standard, like many other national codes, does not provide explicit insight into the anticipated performance and associated vulnerability of infilled frames. This paper presents an analytical study on the seismic performance and fragility analysis of Indian code-designed RC frame buildings with and without URM infills. Infills are modeled as diagonal struts as per ASCE 41 guidelines and various modes of failure are considered. HAZUS methodology along with nonlinear static analysis is used to compare the seismic vulnerability of bare and infilled frames. The comparative study suggests that URM infills result in a significant increase in the seismic vulnerability of RC frames and their effect needs to be properly incorporated in design codes.展开更多
Neuroscience (also known as neurobiology) is a science that studies the structure, function, development, pharmacology and pathology of the nervous system. In recent years, C. Cotardo has introduced coding theory into...Neuroscience (also known as neurobiology) is a science that studies the structure, function, development, pharmacology and pathology of the nervous system. In recent years, C. Cotardo has introduced coding theory into neuroscience, proposing the concept of combinatorial neural codes. And it was further studied in depth using algebraic methods by C. Curto. In this paper, we construct a class of combinatorial neural codes with special properties based on classical combinatorial structures such as orthogonal Latin rectangle, disjoint Steiner systems, groupable designs and transversal designs. These neural codes have significant weight distribution properties and large minimum distances, and are thus valuable for potential applications in information representation and neuroscience. This study provides new ideas for the construction method and property analysis of combinatorial neural codes, and enriches the study of algebraic coding theory.展开更多
We study the construction of minimum bandwidth regenerating code with combinatorial design. At first, a method of constructing minimum storage regenerating (MBR) codes is presented, which can tolerate only one-node ...We study the construction of minimum bandwidth regenerating code with combinatorial design. At first, a method of constructing minimum storage regenerating (MBR) codes is presented, which can tolerate only one-node failure. Then, we give examples to explain the code. Finally, we discuss the case of repairing multiple nodes, and analyze the performance with an example.展开更多
This paper is a summarized account of the Chinese professional stantard—JB4732 Steel Pressure Vessels—Design by Analysis. As compared with similar standards in other countries, there are some features in elastic pla...This paper is a summarized account of the Chinese professional stantard—JB4732 Steel Pressure Vessels—Design by Analysis. As compared with similar standards in other countries, there are some features in elastic plastic analysis of pressure vessels and their components in JB4732. Three of them are introduced in brief. It includes: flat head design method considering plastic carrying capactities of structures; a reinforcement design method based on limit analysis of spherical shells with nozzles and the calculation method of stress concentration factors of two intersecting cylindrical shells with d/D≤0 7 based on an analytical solution. 展开更多
Secret sharing has been a subject of study for over 30 years. The coding theory has been an important role in the constructing of the secret sharing schemes. It is known that every linear code can be used to construct...Secret sharing has been a subject of study for over 30 years. The coding theory has been an important role in the constructing of the secret sharing schemes. It is known that every linear code can be used to construct the secret sharing schemes. Since the code of a symmetric (V, k, λ)-design is a linear code, this study is about the secret sharing schemes based on C of Fp-code C of asymmetric (v, k, λ)-design.展开更多
This paper presents new half rate Quasi Cyclic Low Density Parity Check (QC- LDPC) codes formed on the basis of combinatorial designs. In these codes, circulant matrices of the parity check matrix are formed on the ba...This paper presents new half rate Quasi Cyclic Low Density Parity Check (QC- LDPC) codes formed on the basis of combinatorial designs. In these codes, circulant matrices of the parity check matrix are formed on the basis of subsets in which the difference between any two elements of a subset is unique with all differences obtained from the same or different subsets. This structure of circulant matrices guarantees non-existence of cycle-4 in the Tanner graph of QC-LDPC codes. First, an irregular code with girth 6 constituted by two rows of circulant matrices is proposed. Then, more criteria will be considered on the structure of subsets with the mentioned feature aiming to represent a new scheme of regular QC-LPDC codes with girth at least 8. From simulations, it is confirmed that codes have similar to or better performance than other well-known half rate codes, while require lower complexity in their design.展开更多
Adequacy of structural fire design in uncommon structures is conceptually ensured through cost-benefit analysis where the future costs are balanced against the benefits of safety investment.Cost-benefit analyses,howev...Adequacy of structural fire design in uncommon structures is conceptually ensured through cost-benefit analysis where the future costs are balanced against the benefits of safety investment.Cost-benefit analyses,however,are complicated and computationally challenging,and hence impractical for application to individual projects.To address this issue,design guidance proposes target reliability indices for normal design conditions,but no target reliability indices are defined for structural fire design.We revisit the background of the cost-optimization based approach underlying normal design target reliability indices then we extend this approach for the case of fire design of structures.We also propose a modified objective function for cost-optimization which simplifies the evaluation of target reliability indices and reduces the number of assumptions.The optimum safety level is expressed as a function of a new dimensionless variable named“Damage-to-investment indicator”(DII).The cost optimization approach is validated for the target reliability indices for normal design condition.The method is then applied for evaluating DII and the associated optimum reliability indices for fire-exposed structures.Two case studies are presented:(i)a one-way loaded reinforced concrete slab and(ii)a steel column under axial loading.This study thus provides a framework for deriving optimum(target)reliability index for structural fire design which can support the development of rational provisions in codes and standards.展开更多
基金supported by the National Key R&D Program of China(Grant No.2017YFC0404804)the National Natural Science Foundation of China(Grant No.51509019)
摘要Many researchers have developed new calculation methods to analyze seismic slope stability problems, but the conventional pseudo-static method is still widely used in engineering design due to its simplicity. Based on the Technical Code for Building Slope Engineering(GB 50330-2013) of China and the Guidelines for Evaluating and Mitigating Seismic Hazards in California(SP117), a comparative study on the pseudo-static method was performed. The results indicate that the largest difference between these two design codes lies in determination of the seismic equivalence reduction factor( f;). The GB 50330-2013 code specifies a single value for f;of 0.25. In SP117, numerous factors,such as magnitude and distance, are considered in determining f;. Two case studies show that the types of slope stability status evaluated by SP117 are in agreement with those evaluated by the seismic time-history stability analysis and Newmark displacement analysis. The factors of safety evaluated by SP117 can be used in practice for safe design. However, the factors of safety evaluated by GB 50330-2013 are risky for slope seismic design.
基金National Natural Science Foundation of China Under Grant No.50439010NSFC and Korea Science and Engineering Foundation Under Grant No.50811140341
摘要A large number of buildings were seriously damaged or collapsed in the"5.12"Wenchuan earthquake.Based on field surveys and studies of damage to different types of buildings,seismic design codes have been updated.This paper briefly summarizes some of the major revisions that have been incorporated into the"Standard for classification of seismic protection of building constructions GB50223-2008"and"Code for Seismic Design of Buildings GB50011-2001."The definition of seismic fortification class for buildings has been revisited,and as a result,the seismic classifications for schools,hospitals and other buildings that hold large populations such as evacuation shelters and information centers have been upgraded in the GB50223-2008 Code.The main aspects of the revised GB50011-2001 code include:(a)modification of the seismic intensity specified for the Provinces of Sichuan,Shanxi and Gansu;(b)basic conceptual design for retaining walls and building foundations in mountainous areas;(c)regularity of building configuration;(d)integration of masonry structures and precast RC floors;(e)requirements for calculating and detailing stair shafts;and(f)limiting the use of single-bay RC frame structures.Some significant examples of damage in the epicenter areas are provided as a reference in the discussion on the consequences of collapse,the importance of duplicate structural systems,and the integration of RC and masonry structures.
摘要In recent years,with the continuous expansion of China's infrastructure construction,related construction work,including highway and bridge construction,has been steadily progressing.Among them,bridges are an important component of infrastructure construction,and their safety and stability are related to the travel of the masses and even the safety of their lives.China has a strict management system for bridge design specifications.This article mainly takes long-span highway bridges as an example to study the key issues of its design specifications and proposes countermeasures for related work.
摘要TB 10031-2021 J 73-2021 Prepared by:China Railway SIYUAN Survey and Design Group Co.,Ltd.Approved by:National Railway Administration Effective date:February 1,2022 China Railway Publishing House Co.,Ltd.Beijing 2022 Notice of National Railway Administration on the Issue of Railway Industry Standards(Engineering and Construction Standard Batch No.6,2021)Document GTKF[2021]No.34 Code for Design of Railway Freight Car Facilities(TB 10031-2021)is hereby issued and will come into effect on February 1,2022.Code for Design of Railway Freight Car Facilities(TB 10031-2009)is withdrawn.China Railway Publishing House Co.,Ltd.is authorized to publish this Code.
摘要DAYU3D is a modern three-dimensional(3D)computer code for thermal-hydraulic design and accident analysis in hightemperature gas-cooled reactors(HTGRs),developed by the Institute of Nuclear and New Energy Technology(INET)at Tsinghua University.Compared to the traditional codes like TINTE,the DAYU3D code has advantages due to its refined framework,improved models,and more efficient algorithms.It is able to simulate the continuous movement of control rods and is more rigorous in treating radiation heat transfer and the break mass flow.Advanced computational methods significantly improve the computational efficiency of DAYU3D,achieving a time reduction of over 60%compared to TINTE.Extensive verification and validation with more than 100 cases demonstrate that DAYU3D is promising for HTGR 3D thermal-hydraulic design and accident analyses.
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。
摘要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.
摘要A uniaxial tension test is commonly used to determine the mechanical properties of steel,but it has no meaning for the response of the material in a structure.The test was developed as a consensus solution by producers,fabricators,designers and code writers,to have a standard by which similar materials could be compared to a common base.It does not represent the actual behavior of the steel in a structure,and was never intended to do so.To study the true behavior of the structure and how the material responds it would be better to determine the strains and deformations that will take place during actual service condition.Such characteristics reflect the real behavior,whether in the elastic or inelastic range.If stresses or forces are needed,these are easily determined by the value of the strain and the relevant material modulus,along with the type of cross section,whether elastic or inelastic.The paper addresses the properties of a range of structural steels,how these are incorporated into design standards and how the standards define deformation characteristics and demands for bolted and welded connections.
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)
摘要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.
摘要Unreinforced Masonry (URM) is the most common partitioning material in framed buildings in India and many other countries. Although it is well-known that under lateral loading the behavior and modes of failure of the frame buildings change significantly due to infill-frame interaction, the general design practice is to treat infills as nonstructural elements and their stiffness, strength and interaction with the frame is often ignored, primarily because of difficulties in simulation and lack of modeling guidelines in design codes. The Indian Standard, like many other national codes, does not provide explicit insight into the anticipated performance and associated vulnerability of infilled frames. This paper presents an analytical study on the seismic performance and fragility analysis of Indian code-designed RC frame buildings with and without URM infills. Infills are modeled as diagonal struts as per ASCE 41 guidelines and various modes of failure are considered. HAZUS methodology along with nonlinear static analysis is used to compare the seismic vulnerability of bare and infilled frames. The comparative study suggests that URM infills result in a significant increase in the seismic vulnerability of RC frames and their effect needs to be properly incorporated in design codes.
摘要Neuroscience (also known as neurobiology) is a science that studies the structure, function, development, pharmacology and pathology of the nervous system. In recent years, C. Cotardo has introduced coding theory into neuroscience, proposing the concept of combinatorial neural codes. And it was further studied in depth using algebraic methods by C. Curto. In this paper, we construct a class of combinatorial neural codes with special properties based on classical combinatorial structures such as orthogonal Latin rectangle, disjoint Steiner systems, groupable designs and transversal designs. These neural codes have significant weight distribution properties and large minimum distances, and are thus valuable for potential applications in information representation and neuroscience. This study provides new ideas for the construction method and property analysis of combinatorial neural codes, and enriches the study of algebraic coding theory.
基金Supported by the National Natural Science Foundation of China(61271174,61301178)
摘要We study the construction of minimum bandwidth regenerating code with combinatorial design. At first, a method of constructing minimum storage regenerating (MBR) codes is presented, which can tolerate only one-node failure. Then, we give examples to explain the code. Finally, we discuss the case of repairing multiple nodes, and analyze the performance with an example.
摘要This paper is a summarized account of the Chinese professional stantard—JB4732 Steel Pressure Vessels—Design by Analysis. As compared with similar standards in other countries, there are some features in elastic plastic analysis of pressure vessels and their components in JB4732. Three of them are introduced in brief. It includes: flat head design method considering plastic carrying capactities of structures; a reinforcement design method based on limit analysis of spherical shells with nozzles and the calculation method of stress concentration factors of two intersecting cylindrical shells with d/D≤0 7 based on an analytical solution.
摘要Secret sharing has been a subject of study for over 30 years. The coding theory has been an important role in the constructing of the secret sharing schemes. It is known that every linear code can be used to construct the secret sharing schemes. Since the code of a symmetric (V, k, λ)-design is a linear code, this study is about the secret sharing schemes based on C of Fp-code C of asymmetric (v, k, λ)-design.
摘要This paper presents new half rate Quasi Cyclic Low Density Parity Check (QC- LDPC) codes formed on the basis of combinatorial designs. In these codes, circulant matrices of the parity check matrix are formed on the basis of subsets in which the difference between any two elements of a subset is unique with all differences obtained from the same or different subsets. This structure of circulant matrices guarantees non-existence of cycle-4 in the Tanner graph of QC-LDPC codes. First, an irregular code with girth 6 constituted by two rows of circulant matrices is proposed. Then, more criteria will be considered on the structure of subsets with the mentioned feature aiming to represent a new scheme of regular QC-LPDC codes with girth at least 8. From simulations, it is confirmed that codes have similar to or better performance than other well-known half rate codes, while require lower complexity in their design.
基金funded by the Ghent University Special Research Fund under grant 01N01219“Multi-objective societal optimization of structural fire safety investments for uncommon projects using advanced regression techniques”.
摘要Adequacy of structural fire design in uncommon structures is conceptually ensured through cost-benefit analysis where the future costs are balanced against the benefits of safety investment.Cost-benefit analyses,however,are complicated and computationally challenging,and hence impractical for application to individual projects.To address this issue,design guidance proposes target reliability indices for normal design conditions,but no target reliability indices are defined for structural fire design.We revisit the background of the cost-optimization based approach underlying normal design target reliability indices then we extend this approach for the case of fire design of structures.We also propose a modified objective function for cost-optimization which simplifies the evaluation of target reliability indices and reduces the number of assumptions.The optimum safety level is expressed as a function of a new dimensionless variable named“Damage-to-investment indicator”(DII).The cost optimization approach is validated for the target reliability indices for normal design condition.The method is then applied for evaluating DII and the associated optimum reliability indices for fire-exposed structures.Two case studies are presented:(i)a one-way loaded reinforced concrete slab and(ii)a steel column under axial loading.This study thus provides a framework for deriving optimum(target)reliability index for structural fire design which can support the development of rational provisions in codes and standards.