Performance-based Design Concept Research Articles

Current practices and future directions of steel design in Japan

Four design codes/regulations for steel structures in Japan are briefly reviewed. Some of them employ the limit state design concept while the others are still based on the allowable stress design concept. The process for revision is now in action. The directions in the development of structural design codes are also reported herein. It is noted that a current trend in this development is to employ the performance-based design concept that has been successfully implemented in some seismic design codes.

Expanded papers from an international workshop on performance-based design—concepts and implementation

An international workshop on performance-based design was held in Bled, Slovenia, on June 28–July 1, 2004. This workshop provided a valuable forum for the exchange of research results and design practice ideas on issues important for seismic risk reduction and the development of performance-based earthquake engineering concepts. The theme of the workshop was to assess the state of knowledge and practice related to performance-based design and to identify challenges that need to be addressed so that progress in research and implementation in engineering practice can be accelerated and a common foundation can be established on which to base the various approaches advocated in different countries. At the workshop, 45 invited participants and 12 observers from 14 countries addressed the following topics in four working groups: loss estimation, fragility and vulnerability, and impact on risk management; implementation in engineering practice; performance-based design concepts; and integration of experimental and analytical simulations. The workshop has led to a greater understanding of many of the issues involved in performance-based design, and much progress has been made in the development of concepts and procedures suitable for implementation in engineering practice. Nevertheless, many issues remain unresolved and additional research and studies are needed to implement rigorous performance-based design with confidence. Performance-based design concepts provide a suitable framework for future seismic code development. Common interests exist among researchers and practitioners of the countries represented at the workshop. Progress in research and implementation in engineering practice can be accelerated by the international dialog on new ideas and concepts. Cooperative research on issues of common interest should be encouraged. The participants recognize that performance-based design has many facets and may take on very different meaning and approaches depending on prevailing economic and societal priorities. Nevertheless, by continuing the international dialog, a common foundation can be established on which to base the various approaches advocated in different countries. An urgent need exists for worldwide sharing of data obtained from experimental and analytical studies and from field measurements taken during earthquakes. A protocol for international data sharing should be developed and efforts should be initiated for the creation of a worldwide data repository. In order to accelerate the transfer of knowledge from researchers to engineering practice, a need exists for incorporating performance-based design concepts and reliability theory into educational curricula. Recognizing the benefits of the exchange of ideas that occurred at the workshop, international gatherings should be held on a periodic basis to share information on the development of performance-based design. To further increase the impact of the work discussed in Bled, the workshop participants were encouraged to submit expanded versions of their papers to the Journal, provided they report on previously unpublished material appropriate for a journal publication. Submitted manuscripts have undergone the regular review process, which was handled by Anil K. Chopra. Seven papers, printed in this issue, have been accepted for publication. The full workshop proceedings, which contain 43 papers as well as the workshop resolutions, conclusions and recommendations, can be obtained from the Pacific Earthquake Engineering Research Center, 1301 South 46th Street, Richmond, CA 94804, U.S.A. (info@nisee.berkeley.edu).

Performance-Based Design Concept of Soil for Seepage Failure within Cofferdam

Performance-Based Design Concept of Soil for Seepage Failure within Cofferdam

RESTRATION OF PORT FACILITIES AFTER THE 1995 HYOGOKEN-NAMBU EARTHQUAKE

It is well known that the port facilities in Kobe Port suffered severe damages during the 1995 Hyogoken-Nambu earthquake. Especially, many caisson type quay walls were damaged during the earthquake. In order to mitigate hazards and losses due to earthquakes, seismic design methodologies have been developed and revised after each past earthquake event. The design practice of port structures in Japan introduced a performance based design concept as a result of damage investigations after the 1995 Hyogoken-Nambu earthquake. The restoration of Kobe Port was based on following philosophies: 1) quick recovery of the functions of the port, 2) improve seismic performance, 3) renewal with change the function of facilities and 4) continued operation of the port during restore works.

Seismic Design Recommendations for Precast Concrete Diaphragms in Long Floor Span Construction

The paper Effect of Dimension and Detail on the Capacity of Precast Concrete Parking Structure Diaphragms, published in the September-October 2003 PCI JOURNAL, presented the effect of structural dimension and construction detail on the capacity of precast concrete floor diaphragms, using parking structures as the prototype structure. Parallel research by the authors has established seismic demands for flexible diaphragm structures. In this paper, the findings of these two research steps are interpreted to propose design recommendations for precast concrete diaphragms in long floor span construction. These recommendations include provisions for diaphragm design strength, allowable flexibility, and ductility capacity based on seismic performance requirements. The provisions are incorporated into a design procedure employing performance-based design concepts. Application of the procedure is shown in a design example (Appendix B) for precast parking structure diaphragms. Research on this subject will continue over the next several years, with funding provided by both governmental and industry organizations.

リスク移転を考慮した耐震性能レベル設定の考え方

Following the amendment of Japanese building standard, the concept of performance-based design was introduced. The previous design standard is still employed as the basic one though it may bring the insufficient seismic performance, if buildings are designed just to reduce the initial cost. In this paper, the seismic performance of buildings was determined from the viewpoint of minimizing the life cycle cost, considering the risk transfer by insurance or other financial techniques. A portfolio consisting of 25 buildings in the Kanto district was employed in the analysis. Through the application, the following findings were obtained; combination of risk control and risk finance reduces the life cycle cost significantly, life time has a large effect on the selection of risk management scheme, and the trend of risk aversion has also a effect on the selection of risk transfer techniques.

A performance-based optimization method for topology design of continuum structures with mean compliance constraints

A performance-based optimization (PBO) method for optimal topology design of linear elastic continuum structures with mean compliance constraints is presented in this paper. The performance-based design concept is incorporated in continuum topology optimization, which is treated as the problem of improving the performance of a continuum design domain in terms of the efficiency of material usage and overall stiffness. A simple scheme is employed in the proposed method to suppress the formation of checkerboard patterns. Two energy-based performance indices are derived for quantifying the topology performance of plane stress structures and plates in bending. Performance-based optimality criteria incorporating performance indices are proposed, and can be used in any continuum topology optimization methods for compliance minimization problems to obtain the optimum. Numerical examples are provided to demonstrate the effectiveness and validity of the PBO method in producing optimal topologies of continuum structures.

Assessment of legibility of egress route in a building from the viewpoint of evacuation behavior

A new framework for a fire safety design method is now in preparation based on the concept of performance-based design in Japan (Tanaka, 1995. State of the Art — Development of a Performance-based Fire Safety Design Method of Building in Japan. Proceedings of Mini-Symposium Fire Safety Design of Buildings and Fire Safety Engineering. Building Research Institute). In this paper, the authors focus on the legibility of the egress route as an important performance factor in assuring the safety of occupants in buildings, and intensively discuss its assessment. Relevant, previous work on the evaluation of the legibility of the egress route is reviewed and studied. The paper considers the legibility of egress route as the geometric access potential of the egress route network in the architectural plan. The legibility of the egress route is a function of the physical measures that allow quantitative evaluation of how quickly occupants can escape or how easily they can find exits. From this point of view, the travel distance during an evacuation is one of the most effective and quantifiable measures of the legibility of the egress route. The assessment of the travel distance based on several assumptions of the occupants' probable choice of egress route is introduced. A network modeling technique is utilized to represent the configuration of the egress route and to calculate the travel distance. Through numerical computations, an effective configuration is determined such that the average expected travel distance across the possible layouts of the egress route is minimized.

Optimal topology selection of continuum structures with displacement constraints

This paper deals with the optimal topology selection of continuum structures subject to displacement constraints by using the performance-based design concept. The optimal topology of a continuum structure is generated by gradually eliminating underutilized elements from the discretized design domain. A performance index is developed for monitoring the optimization process and is used as a termination criterion in the optimization algorithm so that the global optimum can be selected from the optimization history. Maximizing the performance index in the design space is proposed as the performance-based optimization criterion. The performance index can be utilized to compare the efficiency of structural topologies produced by different continuum topology optimization methods. Several examples are provided to demonstrate the capabilities of the performance-based optimization approach in selecting the best configuration for the minimum-weight design of continuum structures with maximum stiffness.

Seismic Performance and Design of Bolted Steel Moment-Resisting Frames

Bolted moment-resisting frames, and their predecessors riveted frames, were used for many decades prior to the use of welded frames in steel structures. Riveted and bolted steel structures have performed well during past earthquakes from the 1906 San Francisco earthquake to the infamous 1994 Northridge, Los Angeles earthquake. This paper presents information on past performance of bolted steel moment-resisting frames, a summary of shaking table tests, comparative studies of bolted and welded moment frames and a summary of results of cyclic tests of bolted top-and-bottom flange plate moment connections. The paper also presents the concept of performance-based design of steel connections using a failure mode hierarchy. In this concept, all failure modes of the connection are identified and then an order of desirability is assigned to each failure mode based on its ductility. The more ductile the failure mode is the higher its place in the hierarchy. Then, for each failure mode, design equations are developed. These equations ensure that, the more ductile failure modes, such as yielding of steel, will occur first and protect the connection from experiencing the more brittle and undesirable failure modes, such as fracture of welds, bolts or net sections. As an illustration of the procedure, this paper presents application of a proposed "hierarchical" approach to failure modes of bolted top-and bottom flange plate moment connections and provides corresponding design equations.