Performance-Based Design is an approach to the design of any complexity of structures including high-rise apartments and office buildings. A structure constructed is required to meet certain measurable or predictable performance requirements, such as energy efficiency or seismic load, without a specific prescribed method by which to attain those requirements. Performance-Based Design helps structural engineers to set project performance goals early in the design phase so that they can understand and influence the elements that are impacting the design’s performance. Once goals are set, analysis is used from the very start of the design process to assess the impact that various design decisions will have on performance goals.
Performance Based Design enables a structure designed by a structural designer to be safe and resilient for earthquakes. The structure is analysed and designed by following standard codes and regulations. Therefore, to give a predictable response of structure under the application of hazards and disasters, performing based design has been put up front in recent years. To reduce the risk of disaster and losses, it should be quantified so that the response of structure can be predicted. Because to increase safety it is necessary to understand the intensity of hazard and its vulnerability to the structure.
The objective of performance-based design
In a Performance-based approach, the focus of all decisions is on the required performance-in-use and on the evaluations and testing of building assets. It is applicable to the procurement of constructed assets and to any phase of the whole life cycle Building Process, such as strategic planning, asset management, briefing/programming, design and construction, operation and maintenance, management and use, renovations and alterations, codes, regulations and standards. It includes many topics and criteria, which can be categorized as physical, functional, environmental, financial, economical, psychological, social, facilities, and other more. These criteria are related to a singular project, according to the context and the situation.
The basic concept of performance-based design is to provide engineers with the capability to design predictable and reliable performance in earthquake situations. The design should begin with the selection of design criteria based on the form of performance objectives. Performance objectives can be;
➢ Immediate Occupancy
➢ Life Safety &
➢ Collapse Prevention.
Approach for performance-based design
Performance objective should be a statement of acceptable risk & discovering severe levels of damage, consequential losses that may occur as a result of this damage. In a traditional approach the engineer uses the rules and regulation of standardized codes for designing and detailing of frames to ensure the safety against hazards and disasters.
Before designing the structure, the purpose of the structure should be prioritised for good performance of a structure. And if some rules are not followed due to various conditions or some reasons then that structure is unsafe for living.
The approach in India
Now in a country like India there are many structures which are more than 40 years old. These structures might require retrofitting at some point. For this retrofitting, if we go with a traditional approach that is design based on codes, then it may suggest the retrofitting for every beam and columns which will increase the work as well as cost. But in actuality it might not require that much quantity of work. Therefore, if we go with a performance design-based approach then that quantity of work as well as cost of repair will be reduced marginally.
Though the structure is designed by using codes no one can design the structure which will not be damaged or will not collapse. But if we carry out performance-based design by quantifying levels of hazards and disasters based on which response of the structure is calculated. Then it might give better resilience to earthquake loads and safety of human lives can be achieved.
Basically, performance-based design gives the ability to innovate, to evaluate and have alternate things with explicit approach towards the solution. Ita analysis is beneficial to designers and projects because this feedback helps them better understand the spaces they are designing, see how design options will impact these spaces, and make more informed decisions about their design.
Sujit Ashok Kadam, Structural Engineer [MTech]