Section 8.5 Escalator and Moving Walk Seismic Requirements
(3) the product of the acceleration-based site coefficient and the spectral response acceleration for a 0.2 s time period [FaSa(0.2)] greater than 0.12 for any building designated as a "post-disaster building", or IEFaSa(0.2) equal to or greater than 0.35 as defined by NBCC-2005 or NBCC-2010 (see Section 1.3, building code)
(4) Seismic Performance Category C with Seismic Hazard Exposure Group II or higher as defined by earlier model building codes (see Note)
(5) Seismic risk zone 2 or greater as defined by earlier building codes (see Note)
NOTE [8.5(a)(4) and 8.5(a)(5)]: For example, SBC 1982 or SBC 1994.
(1) Where the applicable building code references seismic design categories or design spectral response acceleration [Sa(0.2)], force levels as referenced by 8.4.14 shall be used (see Section 1.3, building code).
(3) Where the applicable building code makes reference to seismic risk zones or to seismic risk zones and component force level equations, force levels for the appropriate zone, as listed throughout Section 8.5, or the calculated component force level, whichever is greater, shall be used.
(c) The escalator and moving walk safety requirements contained in Section 8.5 shall be used considering the requirements in the other parts of the Code. These requirements are to be applied as well as those in Sections 6.1 and 6.2 but are not additive. Where multiple requirements are applicable to the same component, the most stringent requirement shall control.
Balustrades shall be designed to withstand the vertical inertial force due to the weight of the balustrade and the horizontal seismic forces as follows:
(a) The component operating weight, Wp, is the sum of the balustrade dead load, decking weight if supported by the balustrade, and 70% of the machinery rated load (see 184.108.40.206.2) and the seismic force computed as defined in 8.4.13 and 8.4.14.
(b) The seismic forces resulting from the machinery rated load shall be distributed along the exposed length of the handrail from the entry newel tangent to the exit newel tangent as depicted in Figure 8.5.1.
Figure 8.5.1 Balustrade Handrail Force
Structural items not covered in Table 8.5.5 shall be capable of withstanding the inertia effect of the applicable masses without permanent deformation.
(a) For jurisdictions enforcing seismic zones or an equivalent ground motion parameter (see 8.4.13), the horizontal (see 220.127.116.11) and vertical (see 18.104.22.168) seismic forces shall be applied separately (not simultaneously).
(b) For jurisdictions enforcing IBC/NBCC, earthquake forces shall be applied simultaneously as defined by 8.4.14, except Wp = Wt + Wr where
|Wr||=||25% of the structural rated load calculated per 22.214.171.124.1|
|Wt||=||total dead load of the escalator, including all components supported by the truss|
Fp = ZICp(Wt + Wr)
|Cp||=||horizontal seismic force factor|
|Fp||=||total horizontal seismic force|
|Z||=||seismic zone factor|
|=||0.25 for seismic zone 2|
|=||0.5 for seismic zone 3 or greater|
(a) For zone 2, Z = 0.25.
(b) For zone 3 or 4, Z = 0.5.
NOTE: When local building codes are more stringent, higher values may be applicable.
|Zone||Total Vertical Force, Ftv|
|2||(1 ± 0.25)(Wt + Wr)|
|3 or greater||(1 ± 0.50)(Wt + Wr)|
(a) clearance between the truss and the building is sufficient to prevent truss compression damage
(b) seat depth (the longitudinal overlap and bearing surface between the building support and the truss support) is sufficient to prevent disengagement of the truss end with the building support
When both ends are designed to accommodate story drift
(a) means shall be provided to prevent any truss end from disengaging from its building support seat
(b) the end supports shall be permitted to be free to slide in the longitudinal direction such that the sum of the motions accommodates the total design story drift
(a) the structural engineer of record
(b) the maximum story drift value per ASCE/SEI-7, Table 12.2-1
NOTE [126.96.36.199.2(b)]: ASCE/SEI-7, Table 12.2-1 specifies a maximum story drift of 0.025hsx, where hsx is the building story height.
A minimum of one seismic detection device shall be provided in each escalator (nontandem operation or non-side-by-side arrangement) or moving walk. For escalators or moving walks in a tandem operation (see 188.8.131.52) or side-by-side arrangement, a minimum of one seismic detection device is required. The seismic detection device shall be mounted in the machinery space or adjacent to the escalator or moving walk. Where possible, a seismic detection device shall be mounted adjacent to a vertical load-bearing building structural member when installed at an elevation above ground level, or any structural member if mounted at or below ground level, or any other location approved by the structural engineer of record.
(b) Actuation of the seismic detection device shall cause removal of power from the escalator and moving walk driving-machine motor(s) and brake(s) on all units controlled by the seismic detection device.
(c) Where a seismic detection device is used exclusively to control the escalator or moving walk, it shall be located in a machine room or machinery space and, where possible, shall be mounted adjacent to a vertical load-bearing member. Should no vertical load-bearing member be in close proximity, it shall be permitted to locate the seismic detection device at the nearest accessible vertical load-bearing member at approximately the same horizontal level as the upper machinery space or machine room.
The allowable stress limits to be used in the design of all escalator and moving walk components are listed in Table 8.5.5. An escalator or moving walk subjected to seismic loading shall be capable of withstanding the specified seismic forces in combination with the dynamic or static loads occurring during normal operation.
Table 8.5.5 Component-Based Allowable Design Stresses
|Allowable Design Parameter|
|Component||Seismic Zones Criteria |
|IBC, ASCE/SEI-7||NBCC 2005 or Later|
|Structural, steel||0.88 Fy||0.6 Fy||0.6 Fy|
|Structural, other materials||Follow allowable limits as recommended by design specifications for material of use||Follow allowable limits as recommended by design specifications for material of use||Follow allowable limits as recommended by design specifications for material of use|
|Balustrades||< Fy||0.6 Fy||0.6 Fy|
|Structural glass in balustrades||Minimum factor of safety = 2 based on the modulus of rupture||Minimum factor of safety = 2 based on the modulus of rupture||Minimum factor of safety = 2 based on the modulus of rupture|
|Structural fastenings and/or connections||See 184.108.40.206.3||Per 220.127.116.11||Per 18.104.22.168|
GENERAL NOTE: Fy = yield strength.
NOTE: (1) See 8.5.2(a).