DOB Findings and Recommendations for WTC, Feb 2003

NYC 9/11 Public Portal Document

I In lieu of formulating an appropriate performance standard for this type of construction, a determination the group thought would be better undertaken by NIST, and in light of the near absence of this type of high-rise construction in New York City, the Structural Strength Working Group has recommended a terriporary prohibitiori of the use of open web bar trusses in new commercial high-rise construction over 75 feet in height, pending the development of an appropriate standard recommended by NIST.

Recommendation 2. Prohibit the use of open web bar trusses in new commercial, high-rise construction over 75 feet in height, pending the development of an appropriate standard recommended by NIST.

4.1.3 Hardening of Stairwell and Elevator Shaft Enclosures At the request of the Mechanical Systems, Evacuation and Fire Protection Working Groups, the Structural Strength Working Group further examined the question of hardening of stairwells and elevator shafts.

Currently, stairwells and elevator shafts are required to meet the ASTM 2-hour rating standard, one which includes a fire test followed by a hose stream test. However, anecdotal information from the Fire Department indicates that materials that meet these standards in test trials do not successfully resist a fire fighter's hose stream in the field. The Task Force recommends that ASTM and NIST study impact loading for stair and elevator shaft enclosures to determine whether further hardening should be required and if so, to develop a testing method that ensures that materials and assemblies used can achieve this. Until this is determined, the committee notes that there are several materials currently available on the market that provide greater resistance to impact and recommends their use for stair and elevator shaft enclosures be considered.

Recommendation 3. Encourage use of available impact resistant materials in the construction of stair and elevator shaft enclosures until appropriate standards can be developed.

4.2 Evacuation and Egress Successful evacuation of building occupants requires appropriate and effective egress systems. The Emergency Evacuation Working Group focused on five interrelated areas of concern highlighted in the findings; • capacity and location of stairwells • clarity of the egress pathway • planning and training for evacuation • auxilliary systems, technologies and construction (such as fire towers, protected elevator vestibules and "phase III" elevators) L • evacuation of those with special needs (temporary and permanent disabilities)

February 2003 WTC Building Code Task Force Page 19 , Findings and Recommendations

NYC-WTC_000166505