Incorporating Elevators and Escalators into Emergency Evacuation Models

Incorporating Elevators and Escalators into Emergency Evacuation Models Richard W. Bukowski, P. E. , FSFPE Senior Consultant Rolf Jensen and Associates Baltimore, MD 20708

Background • 2009 editions of IBC and NFPA 5000 permit occupant egress elevators • ASME A 17. 1 balloting Occupant Evacuation (elevator) Operation for 2013 edition, new section 2. 27. 10 • NFPA 130: 2010 permits escalators to be use for 50% of required egress capacity from a station platform – Fixed Guideway Transit

Elevators History (1) • Material lifts since 236 BC but not considered safe for people • Elisha Otis safety brake prevents car from falling if rope breaks (1852) • Passenger elevators are enabling technology for buildings taller than 6 floors

Elevators History (2) • • In 1970’s stories of fire fatalities from heat sensitive call buttons and firefighters falling down hoistways through open landing doors 2006 NFPA review of fatalities involving egress – 7 fires, 19+ fatalities in elevators • • • All but 2+ would have been prevented by FEO USA Today est. 200 in WTC not included – 3 fires where elevators used for egress, no fatalities in elevators – 3 fires where occupant survival credited to elevators including 3000 in WTC 2 – No firefighters falling down hoistways FEO recalls (Phase 1) elevators when threatened by fire – Firefighters can drive recalled cars on Phase 2

Occupant Evacuation Operation (OEO) • • Developed by ASME task groups Initially evacuate 5 floors at greatest risk Wait for IC decision for full evacuation Evacuate building from top down – Voice instructions – Information systems – Protected lobby with access to stair • Evacuate entire population of any building in under 1 hour with no additional elevators

Modeling OEO Occupant Load • Elevators usually designed for actual load for which the building is designed – Software can usually compensate for changes in occupant load, later • Design load factors (code) can be used for spec buildings • Assume load factor for cars of 85%

Modeling OEO Number of Cars • Max of 4 cars per bank (single hoistway) • Usually 2 banks per group (single controller) • Max travel distance of 150 ft to an elevator • Cars serving different groups of floors in different banks • One service car per 300, 000 to 500, 000 sqft – Smaller footprints use swing cars

Modeling OEO Handling Capacity • Common metric for design service level • Percent of building population that can be moved in 5 minutes – Up-peak or down-peak – Office buildings - 13% – Residential – 8% • IBC/NFPA require use of all publicuse cars for occupant evacuation, to maximize handling capacity and minimize egress time

Modeling OEO Passenger Capacity • Rated load (based on platform area) @ 160 lb per passenger – 3000 lb car, 19 passengers • Observed that at 2. 3 ft 2/person people will wait for next car – 0. 56 ft 2/person max in emergency • Double deck cars double capacity without increasing hoistway space • Optimized elevator designs maximize capacity while minimizing hoistway space – Terminating local hoistways to return leasable space above

Modeling OEO Startup of OEO • Unoccupied cars begin to evacuate 5 floor block • Occupied cars return to LED and discharge before joining • Shuttle mode • Sequence is fire floor, then 2 above, then 2 below, then recall to LED – One parks at lowest floor of block to retrieve stragglers

Modeling OEO Door opening and closing times • Doors open after leveling in 2 seconds • Close slower to avoid injuring people – 3 seconds for 48 in door – Code limits kinetic energy, so time depends on door weight – Some systems include a disabled button that increases dwell time and slows closing of doors

Modeling OEO Dwell Times • Time based on distance from call buttons to door established by ADA – 5 -8 sec + 1 sec person breaking light beam • Close at 85% capacity or 20 sec – Nudging – half speed close + buzzer

Modeling OEO Travel Speed • Speed selected based on travel time objectives • < 5 floors, hydraulic – 150 fpm • Traction elevators – – – 10 floor, 400 fpm 45 floor, 1000 fpm 60 floor, 1800 fpm Fastest, 3300 fpm Service cars, half speed

Modeling OEO Travel Time • Cars accelerate and decelerate slowly to avoid discomfort – 2 -8 ft/s 2 between 60% and 100% rated speed • Short trips may not reach rated speed

Modeling OEO Zoned Elevators • Industry practice to limit car stops to 15 -20 – Local and express – Low- and high-rise banks – Transfer floors (sky lobbies) • Vertical zones – Mixed use buildings – Separated lobbies – Travel through blind shaft sections

Escalators History • Nathan Ames revolving stair 1859 • First installed at Coney Island in 1896 • Not egress stairs because of variable geometry and riser height (<8. 5 in) – Stairs <7. 5 in – More comfortable but slower going up a stopped escalator • Tread depth >15. 75 in – Stairs >11 in

Escalators per NFPA 130 • Not more than 50% of required capacity – Max 2/step on 48 in width – 1. 41 p/min/in (same as stairs) • • • Escalators moving in the direction of egress travel continue moving Moving opposite the direction of egress travel are stopped Speed – 100 ft/min moving – Stopped • • • 48 ft/min down 40 ft/min up Assume 1 out of service

Modeling Egress by Stairs, Elevators and Escalators • Survey showed elevator preference on higher floors – Some will use stairs – Escalators used where present • Default to OEO – Time to initiate full evacuation user set (IC decision) – Fraction disabled and # of stragglers user set – Incorporate distributed variables (mean, SD) and batch run to obtain range of performance

Questions?