# 8.2.9 Hydraulic Elevator Car Frame and Platform Stresses and Deflections

All stresses and their resultant deflections, not only those based on the data and formulas in this Section, shall be considered when side-post-type car frames are located off the platform centerline by more than one-eighth of the distance from the front to the back of the platform.

For cars and corner-post, sub-post, or other special car frame and platform construction, the formulas and specified methods of calculation of loads and the resulting stresses and deflections do not generally apply and shall be modified to suit the specific conditions and requirements in each case.

The maximum allowable stresses and deflections of members of all car frames and platforms shall be not more than those permitted by 3.15.2.

*f*/

_{a}*F*) + (

_{a}*f*/

_{b}*F*)] does not exceed unity

_{b}where

F_{a} | = | allowable axial compressive unit stress [not exceeding 117 200 — 3.344 (L/R)^{2} in SI units and 17,000 — 0.485 (L/R)^{2} in Imperial units] |

f_{a} | = | actual axial compressive unit stress based on gross section |

F_{b} | = | allowable bending unit stress [113 MPa (16,500 psi), if area basis is gross section or 138 MPa (20,000 psi) if area basis is net section] |

f_{b} | = | actual bending unit stress |

L | = | free length of uprights (distance from lowest fastening in crosshead to top fastening in plank), mm (in.) |

R | = | least radius of gyration of section, mm (in.) |

The crosshead member(s) and connection between the crosshead and upright (stile) shall be designed to resist the bending moment and shear and axial forces transferred between the upright and the crosshead.

*(a)* concentrated load(s) located at their point of application equal to the total maximum static load on all the driving members lifting the car divided by the number of lifting members [see Figure 8.2.9.1.3, sketch (a)]

*(b)* five-eighths of the platform weight uniformly distributed over the length of the planks when the platform members are supported directly by the plank members [see Figure 8.2.9.1.3, sketch (b)]

*(c)* the duty load distribution is as follows:

*(1)* for passenger and Class A freight loading, five-eighths of the rated load uniformly distributed over the length of the planks when the platform members are supported directly by the plank members [see Figure 8.2.9.1.3, sketch (c)]

*(2)* for Class B and Class C freight loading, the loading in conformance with 8.2.2.6

*(d)* the balance of loads shall be taken as acting at their respective point(s) of application [see Figure 8.2.9.1.3, sketch (d)]

*(e)* where the platform members are only supported directly by the planks at or adjacent to the ends of the planks, (b) and (c)(1) do not apply, and concentrated loads equal to one-half of the total maximum static load on all the driving members shall be applied at each end of the planks [see Figure 8.2.9.1.3, sketch (e)]

**Figure 8.2.9.1.3 Load Distribution**

D | = distance between guide rails, m (in.) |

P_{1}, P_{2},P _{3}, P_{m} | = balance of loads acting on the plank members located at their respective points of application. Such loads typically include the weights of cab and doors, carframe members and guide shoes, traveling cables, electrical devices, door devices, and the balance of load distributions of the platform weight and rated load not distributed to the plank members. |

P_{s} | = total maximum static load on all the driving members, kg (lb) |

W | = rated load, kg (lb) (passenger or Class A freight) |

W_{P} | = platform weight, kg (lb) |

GENERAL NOTES:

- 1 mm = 1 in./25.4 (1 in. = 25.4 mm).
- 1 kg = 1 lb/0.454 (1 lb = 0.454 kg).

*(a) Stresses Due to Bending*

where

f_{b} | = | the bending stress in each upright in the plane of the frame due to the live load W on the platform for the class of loading (A, B, or C) for which the elevator is to be used (see 2.16.2.2 and Section 3.16) |

K | = | turning moment, N•m (lbf-in.) as determined by the class of loading (see Figure 8.2.2.5.1) by the following formulas: |

*(1)* For Class A freight loading or passenger loading

*(SI Units)*

*(Imperial Units)*

*(2)* For Class B freight loading

*(SI Units)*

whichever is greater

*(Imperial Units)*

whichever is greater

*(3)* For Class C freight loading

*(SI Units)*

*(Imperial Units)*

NOTE [8.2.9.1.4(a)]: Symbols used in the above formulas are defined in 8.2.2.1.1.

*(b) Stresses Due to Compression*

*f _{a}* = compressive stress in each upright

*(c) Slenderness Ratio.* The slenderness ratio *L/R* for uprights subject to compressions other than those resulting from buffer or safety action shall not exceed 120. Where the upper side-brace connections on passenger elevator car frame uprights are located at a point less than two-thirds of *L* from the bottom (top fastening in car frame plank), a slenderness ratio of *L/R* not exceeding 160 is permissible.

*(d) Moment of Inertia.* The moment of inertia of each upright shall be not less than determined by the following formula:

*(SI Units)*

*(Imperial Units)*

NOTE [8.2.9.1.4(d)]: Symbols used in the above formula are defined in 8.2.2.1.1.

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