Evaluación preliminar

In conclusion, this section of the report was separated into three different components. First, there will be a fire resistance analysis of the NA893 Community Support Facility. The occupancy of the project building was determined to be a

combination of Assembly Group A-3 and Business Group B. Based on the International Building Code, the required construction classification has been identified at Type IIA. The structure of the facility is reinforced concrete. The fire resistance requirements for different elements of the building has been summarized for this building. The fire safety strategy of the fire resistance in the building has been discussed.

The second section of the project paper is the design fire analysis. In order to discuss the structural fire safety of the building, this report has considered three (3) potential realistic “worst-case scenario” design fires in your building. The three worst- case scenario design fires were determined to take place in Room 118B, Book Stack Area, Room 116, Periodical Room, and Rooms 111A-J, Media Rooms.

The third section of the project paper is the structural fire analysis. Based on the analysis of the effect of fire on the structural members in the second section, the time to failure for the structural members in the vicinity of each design fire was determined to not fail. Within the context of structural fire protection, the concepts of implicit or

prescriptive and explicit or performance-based safety were covered. In this project paper, these two types of fire safety engineering design methods were discussed and compared. For Rooms 116 and 111A-J, the implicit or prescriptive type of safety design has been used. For Room 118B, since the room was so large, the explicit or performance-based design assures safety through explicit demonstration of the adequacy of the design to meet the intent of the code with an accepted safety factor. However, in all of these fire scenarios, the facility did not lose its structural integrity.

Protection scheme for the structural members have been recommended. A general recommendation to use fire-resistant intumescent coating for all three scenarios. For Room 118B, it is recommended to make the book shelves discontinuous to create a fire break. For Room 116, it is recommended to add fire resistance to the entire room

since it acts like a storage occupancy. For Rooms 111A-J, it has been recommended to re-layout the current scheme so the rooms are not clumped together and do not occur under structural members.

Since the ability of this facility to structurally withstand the three different fire scenarios in this section of the report, the next section will concentrate on performance- based design issues. The net part of the report will consider if occupants of the NA893 Community Support Facility will be able to safely egress the building while considering other fire factors such as smoke inhalation, temperature effects, and visibility as well as the actual time necessary to exit the facility.

129 PERFORMANCE BASED DESIGN

For a new facility design, a relatively new concept that is being used for fire safety is performance–based design. In the United States and Japan, performance-based design is becoming more common as facilities incorporate unique features to achieve aesthetic, cost and functional goals while maintaining safety levels for building occupants and emergency responders. The easiest way to understand the concept of performance- based design is to start with the traditional prescriptive-based design. Building codes have typically prescribed specific design criteria, such as the number of exits or the number of feet to an exit; these are numeric criteria that can be easily measured. This analysis has already been done for the NA893 Community Support Facility for the majority of this report.

By contrast, a performance-based code allows the use of any design that demonstrates compliance with the fire safety goals of the code. Those fire safety goals are explicitly spelled out in the code, as are methods that can be used to demonstrate compliance. A performance-based design starts with an analysis of fire scenarios to determine which design alternatives will meet those fire safety goals. The performance- based approach affords the design team greater flexibility than the prescriptive code requirements. The maximum travel distance is flexible, depending on the method used to maintain tenability along the means of egress. Tenability might be maintained for a distance significantly longer than 300 feet in a building where neither radiant heat transfer nor a descending smoke layer are an issue, such as in a building with an

extremely large atrium. Other examples include modified smoke control configurations and means of egress arrangements, such as more exits or different exits to reduce travel time, resulting from timed egress analyses.

This section of the report is the performance-based analysis. The performance- based analysis will be analyzed in several sections. Performance-based life-safety design depends on a comparison between the time required for escape, also known as the

Required Safe Escape Time (RSET) and the time to loss of tenability, also known as the Available Safe Escape Time (ASET). Both include several stages, involving a variety of processes and requiring a range of input data. The Fire Protection Engineer must

evaluate all the stages in both ASET and RSET to develop a realistic outcome for the analysis. Some aspects of the RSET and the ASET are reasonably well understood and quantified, while others may be oversimplified. For this cumulative project paper, both RSET and ASET for NA893 Community Support Facility will be evaluated.

Figure 60: Visual of ASET versus RSET REQUIRED SAFE ESCAPE TIME (RSET)

RSET is the sum of the amount of time for the fire to be detected, the fire alarm to be noticed by the inhabitants, the time the inhabitants consider what to do, and the time to actually egress the premise. As shown in Figure 50, after the fire ignition, these are termed as the time to detection, time of alarm warning, pre-movement time which

includes the recognition time and response time, and the travel time. The detection time or alarm time is the time at which occupants first become aware of a fire through a building's automatic or manual fire alarm system. The evacuation delay time, or pre- movement time, is the time that elapses between activation of the occupant notification system and the time at which occupants make the decision to begin evacuating. Pre- movement activities might include an investigation to determine if the fire is real, gathering belongings, searching for friends and family, etc. Depending on the type of occupancy, the pre-movement time maybe a few seconds or a few minutes. Finally, the movement time is the time required for occupants to reach a protected exit enclosure or the exterior of the building once the decision to evacuate has been made and occupants begin moving toward exits. The movement time is calculated by applying empirical relations for walking speed and occupant flow rates through egress elements such as doors, stairs, and corridors.

131 Figure 61: Decision Making Process During Fire Evacuation

For the RSET time line, most emphasis is usually placed upon the travel time component, representing the physical movement of occupants into and through the escape routes. However, the time required for occupants to engage in a range of behaviors before the travel phase (pre-movement time), often represents a greater component of the total escape time. Pre-movement time distributions are dependent upon key features such as occupancy type, warnings, occupant characteristics, building complexity and fire safety management strategy. It is proposed that a practical solution for the engineer is to apply pre-movement time distributions measured from monitored evacuations, fire incidents, or derived using behavioral models, and specified in terms of a number of “design

behavioral scenarios” analogous to “design fire scenarios”, classified according to the key features listed.