دانلود رایگان مقاله مقاومت در برابر آتش سوزی ساختمانی و بیانیه خام سیستم امتیاز

abstract

This paper highlights a shortcoming in the current system of structural fire resistance design, proposes how it can be addressed and shows how the perceived barriers to change can be overcome. It is an opinion piece intended to stimulate discussion. Whilst structural fire engineering knowledge may be relatively underdeveloped compared to other engineering disciplines, the industry has made great progress in recent decades in understanding and analysing fire behaviour and the response of structures, as well as developing fire protection products that can be accurately specified to meet performance criteria. In addition, through modern fire and risk engineering there are also methods to establish the appropriate fire resistance rating for a building (or element) based on risk profile, fire loading, building fabric and potential ventilation amongst other things. It is the objective of many within the industry for structural fire engineering to become an integrated part of the design process, ultimately leading to safer and more efficient structures. However, this paper questions whether current structural fire resistance design methods achieve the consistent level of crudeness required for this, or whether the means by which structural performance in fire is quantified, standard fire resistance, represents a weak link that undermines the entire process.Although the concept of standard fire resistance, benchmarked against performance under normalised furnace test heating regimes, is useful in that it allows for the comparison necessary to safeguard consistency across products, design methods and geographies, the historic 15-min fire resistance increments (for example 60, 75, 90 min) result in inconsistent levels of safety. Refined grades, as in fact already allowed under fire resistance testing standards, would yield significant benefits for reliability and design efficiency. The paper uses hypothetical case studies to exhibit the merits of refined fire resistance grades and explains how implementing the enhanced classification system may be readily achievable.

An opportunity to make the process better

In considering how the design procedure for structural fire resistance may be improved, this paper identifies that the 15- min incremental grades upon which performance are based represent a factor of crudeness that undermines the entire process and proliferates to inconsistencies in the designed standards of safety. A number of concerns arise from rounding-up fire engineering analysis output to the nearest 15-min grade, primarily: – Inconsistent levels of contingency and, as a result, standards of safety. – Undue scepticism and prejudice from approvers, clients and design teams as to the merits of engineering solutions that propose deviations from prescriptive guidelines. – Inefficient design. This study presents and compares example buildings that highlight the above shortcomings in the current grade structure and show how a applying a ‘‘consistency of crudeness’’ in the design method, through the use of refined fire resistance ratings, leads to more robust and dependable outputs. Refined grades would also reduce the significance of movement between notional thresholds or ‘‘magic numbers’’ and, therefore, the focus of design and approvals discussions regarding performance-based methods could move away from comparing the outputs of the engineering analysis with the prescriptive guidelines, and towards the validity of the methodology, assumptions, input parameters and other facets of the design. With the design of more and more ‘‘uncommon’’ buildings that do not fit within the realms of prescriptive guidance, the application and integration of structural fire engineering is becoming increasingly critical in delivering structures that meet life safety and property protection goals. Although still an evolving discipline, modern structural fire engineering can incorporate risk-based and performance-based methodologies that seek to establish the appropriate fire resistance for a building to the minute based on the fire risks and consequences present, and has the capacity to incorporate a wide range of inputs, such as contingency factors, in order to meet particular project, regulatory or stakeholder objectives. A refined rating system would maximise the benefits of such a holistic approach, help promote its application by designers, incentivise future advancement in our understanding of structural behaviour in fire and facilitate the interrogation necessary by approvers and the wider fire safety community of the means by which structural stability is safeguarded in fire.