ASME A17.1A-2008 pdf – Safety Code for Elevators and Escalators.
Where the applicable building code does not make reference to seismic risk zones, the ground motion parameters shown in 8.4.13 shall be used. The escalator or moving walk is considered a nonbuilding structure component. The value of 1 shall be considered to be 1.0 unless the building is specified as an essential facility in which case a value of 1.25 shall be used. The value of C shall be 0.75 when any portion of an escalator is located above grade and 0.50 when an escalator is located below grade.
NOTE: When more than six stories above grade other values of C,, may apply and should be determined based upon the fundamental period of the building. Vertical forces shall be split equally between
the two end supports. The total vertical force shall be
(1 ± 0.25) X (W + Wr) for zone 2 and (1 ± 0.50) x (Wi,
+ Wr) for zone 3 or greater. W, and W,. are defined in Truss Calculations. The members in the truss shall be calculated by the Allowable Stress Method of the AISC Specification for Design, Fabrication, and Erection of Structural Steel for Buildings. The allowable stress as stipulated by the various sections is required to be used in lieu of yield stress. (See AISC example Dl for tension, E2 for compression, and F4 for shear stress. There are multiple rules for bending depending on type of section; therefore, examples are not listed.) Truss analysis, whether verified by computer or hand calculations, shall consider axial stresses of either compression or tension, combined axial compressive and bending stress, and combined axial tension and bending stress. There is no requirement for the escalator truss to be considered as a structural member of the building.
8.5.3 Supporting Connections Between the Truss and the Building The end supports shall provide lateral restraint for forces in both principle horizontal directions imposed by seismic forces on the truss. Vertical restraint is not required since per formula downward force will be 0.50 (W1, + Wr) or greater (see Calculations shall be permitted to be based on either rigid or flexible restraints. Where suitable flexible restraints are used, forces resulting from movement of building structure members are not considered as being applied to the truss. The design connections shall account for maximum design story drift. Where seismic restraint is provided at one end, the design shall account for the forces developed by building movement in a manner that restricts transfer of these forces to the truss. All other supports shall be free to slide in the longitudinal direction. Where seismic restraint, that allows some degree of longitudinal and transverse motion, is provided at both ends, additional means shall be provided to prevent the upper end of the truss from slipping off the building support. All other supports shall be free to slide in the longitudinal direction sufficiently to accommodate the remainder of the design story drift. At the sliding end or ends, the width or widths of the beam seat shall be capable of accommodating, without damage, at least 1.5 times story drift as obtained by either of the following:
(a) through engineering calculations
(b) by using the maximum code allowed story drift per the NEHRP Table 4.5-1 for Allowable Story Drifts. This table allows story drifts of 0.025 h where h is the building story height.
8.5.4 Earthquake Protective Devices
Earthquake protective devices shall be of the failsafe type.
A minimum of one seismic switch shall be provided in every building in which an escalator or moving walk is installed.
(a) The seismic switch shall conform to
(b) Activation of the seismic switch(es) shall remove power from the escalator driving machine motor and brake.
(c) Where a seismic switch(es) is used exclusively to control the escalator or moving walk, it shall be located in a machine room, 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 switch at the nearest accessible vertical load-bearing member at approximately the same horizontal level as the upper machinery space or machine room.