(a) General
Requirements.
(1) Steel, where used in the
construction of car frames and platforms, shall conform to the following
requirements:
(A) Steel shall be rolled,
formed, forged, or cast, conforming to the requirements of the following
specifications of the American Society for Testing and Materials:
1. Rolled and Formed Steel, ASTM A36 or ASTM
A283 Grade D
2. Forged Steel, ASTM
235 Class C.
3. Cast Steel, ANSI
G50.1 ASTM A27 Grade 60/30.
(B) Steel used for rivets, bolts, and rods
shall conform to the following specifications of the American Society for
Testing and Materials.
1. Rivets, ASTM
A502.
2. Bolts and Rods, ASTM A307.
EXCEPTION: Steels of greater strength than those
specified may be used provided they have an elongation of not less than 22
percent in a length of 2 inches, and provided that the stresses and deflections
conform to the requirements of Design Sections
3101(a)(4) and
(a)(5).
(2) Wood used for platform stringers and for
platform floors and subfloors shall conform to the requirements of ANSI
04.3--(ASTM D245-687).
(3) Paint
used for protection against fire shall be of an approved type having a flame
spread rating of not over 50, applied in accordance with the instructions of
the manufacturer. Such ratings shall be based on the test procedures specified
in ANSI A2.5.
(4) The stresses in
car frame members and their connections, based on the static loads imposed upon
them, shall not exceed the following:
(A) For
steels meeting the requirements of Sections
3101(a)(1)(A) and
3101(a)(1)(B), the
stresses listed in Table 3101 A4.
(B) For steels of greater strength, the
stresses listed in Table 3101 A4 may be increased proportionately based on the
ratio of the ultimate strengths.
(C) For metals other than steel, the factor
of safety shall be not less than is required for steel.TABLE 3101 A4 Maximum
Allowable Stresses in Car Frame and Platform Members and Connections, for
Steels Specified in Sections
3101(a)(1)(A) and
3101(a)(1)(B)
Member |
Type
of stress |
Max stress
psi |
Area basis |
Car
Crosshead |
Bending |
12,500 |
Gross Section |
Car Frame Plank Normal
Loading |
Bending |
12,500 |
Gross Section |
Car Frame Plank Buffer
Reaction |
Bending |
25,000 |
Gross Section |
Car Frame Uprights (Stiles) |
Bending
plus |
15,000 |
Gross Section |
|
Tension |
18,000 |
Net
Section |
Hoisting Rope |
Bending plus |
|
|
Hitch Shapes |
Tension |
8,000 |
Net Section |
Platform
Framing |
Bending |
12,500 |
Gross Section |
Platform
Stringers |
Bending |
15,000 |
Gross Section |
Threaded Brace Rods and other Tension
Members |
Tension |
8,000 |
Net Section |
Except Bolts |
|
|
|
Bolts |
Tension |
7,000 |
Net
Section |
Bolts in Clearance
Holes |
Shear |
7,000 |
Actual Area in Shear Plane |
Bolts in Clearance
Holes |
Bearing |
16,000 |
Gross Section |
Rivets or Tight Body-fit
Bolts |
Shear |
10,000 |
Actual Area in Shear Plane |
Rivets or Tight Body-fit
Bolts |
Bearing |
18,000 |
Gross Section |
Any Framing Member,
Normal |
Compression |
14,000 |
Gross Section |
Loading |
|
59L/R |
|
(5) The deflections of car frame and platform
members, based on the static loads imposed upon them, shall be not more than
the following, irrespective of the type of steel or other metal used:
(A) For crosshead, 1/960th of the
span.
(B) For plank, 1/960th of the
span.
(C) For stiles or uprights,
as determined by Section
3101(e)(3).
(D) For platform frame members, 1/960th of
the span.
(6) The
stresses and deflections in side-post-type car frame and platform members shall
be based on the data and formulas listed in this section.
(7) For cars with corner-post or
underslung-type car frames, the formulas and specified methods of calculation
do not generally apply and shall be modified to suit the specific conditions
and requirements in each case.
(b) Car Frame Crosshead. The stresses in the
car frame crosshead shall be based on the total load supported by the crosshead
with the car and its rated load at rest at the top terminal landing.
(1) Where a hoisting rope sheave is mounted
on the car frame, the construction shall conform to the following:
(A) Where multiple sheaves mounted on
separate sheave shafts are used, provision shall be made to take the
compressive forces, developed by tension in the hoist ropes between the
sheaves, on a strut or struts between the sheave shaft supports, or by
providing additional compressive strength in the car frame or car frame members
supporting the sheave shafts.
(B)
Where the sheave shaft extends through the web of a car frame member, the
reduction in area of the member shall not reduce the strength of the member
below that required. Where necessary, reinforcing plates shall be welded or
riveted to the member to provide the required strength. The bearing pressure
shall in no case be more than that permitted in Table 3101 A4 for bolts in
clearance holes.
(C) Where the
sheave is attached to the car crosshead by means of a single threaded rod or
specially designed member or members in tension, the following requirements
shall be conformed to:
1. The single rod,
member or members, in tension shall have a factor of safety 50 percent higher
than the factor of safety required for the suspension wire ropes, but in no
case less than 15.
2. The means for
fastening the single threaded rod, member or members, in tension to the car
frame shall conform to Section
3033(m).
(c) Car Frame Plank (Normal). The stresses in
the car frame plank shall be based on a uniformly distributed load equal to not
less than the sum of 5/8 of the rated load, 5/8 of the platform weight, and the
concentrated loads due to the tensions in the compensating ropes and traveling
cables.
(d) Car Frame Plank (Buffer
Engagement). In calculating the stress resulting from oil-buffer engagement,
½ the sum of the weight of the car and its rated load shall be
considered as being concentrated at each end of the plank with the buffer force
applied at the middle. The buffer force shall be considered to be that required
to produce gravity retardation with rated load in the car.
The following formula shall be used to determine the
stress resulting from buffer engagement:
Stress = (D[C + W]) /2Z
Where more than one oil buffer is used, the formula
shall be modified to suit the location of the buffers.
NOTE: Symbols used in the above and subsequent formulas
are defined in Section
3101(g).
(e) Car Frame Stiles (Uprights). The total
stress in each car frame upright due to tension and bending, and the
slenderness ratio of each upright and its moment of inertia, shall be
determined in accordance with the following formulas:
(1) Stress Due to Bending and Tension.
Total Stress = (KL/4HZu) +
(G/2A)
Where KL/4HZu is 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, and G/2A is the tensile stress in each upright.
K is determined by the following formulas (See Figure
3101 E):
(A) For class A freight
loading or passenger loading, K = WE/8
(B) For class B freight loading, K = W([E/2]
- 48) or K = WE/8, whichever is greater
(C) For class C freight loading, K = WE/4
NOTE: Symbols used in the above formulas are defined in
Section 3101(h).
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(2) Slenderness Ratio. The slenderness ratio
L/R for uprights subject to compressions other than those resulting from safety
and buffer action shall not exceed 120.
EXCEPTION: Where the upper side-brace connections on
passenger elevator car frame uprights are located at a point less than
2/3 of L
from the bottom (top fastening in car frame plank), a slenderness ratio of L/R
not exceeding 160 shall be permissible.
NOTE: Symbols used in the above formulas are defined in
Section 3101(h).
(3) Moment of Inertia. The moment of inertia
of each upright shall be not less than determined by the following formula:
I = KL3 /18EH
NOTE: Symbols used in the above formula are defined in
Section 3101(h).
(f) Freight Elevator Platforms.
(1) The calculations for the stresses in the
platform members of freight elevators shall be based on the following
concentrated loads assumed to occupy the position which will produce the
maximum stress:
(A) Class A Loading:
11/4 of the
rated load.
(B) Class B Loading: 75
percent of the rated load divided into two equal loads 5 feet apart.
(C) Class C1 and C2 Loading with a Full Load
Rating of 20,000 pounds or less: 80 percent of the rated load or of the loaded
truck, whichever is greater, divided into equal loads 2 feet 6 inches
apart.
(D) Class C1 and C2 Loading
with a Full Load Rating in excess of 20,000 pounds: 80 percent of 20,000 pounds
or of the loaded truck weight whichever is the greater, divided into two equal
parts 2 feet 6 inches apart.
(E)
Class C3 Loading: Determine on the basis of the actual loading conditions but
not less than that required for Class A loading.
(2) Freight elevators shall be designed for
one of the following classes of loading:
(A)
Class A--General Freight Loading. Where the load is distributed, the weight of
any single piece of freight or of any single hand truck and its load is not
more than ¼ of the rated load of the elevator, and the load is handled
on and off the car platform manually or by means of hand trucks.
For this class of loading, the rated load shall be
based on not less than 50 pounds per square foot of inside net platform
area.
(B) Class B--Motor
Vehicle Loading. Where the elevator is used solely to carry automobile trucks
or passenger automobiles up to the rated capacity of the elevator.
For this class of loading, the rated load shall be
based on not less than 30 pounds per square foot of inside net platform
area.
(C) Class C--These
loadings apply where the weight of the concentrated load, including an
industrial power or hand truck, if used, is more than ¼ of the rated
load and where the load to be carried does not exceed the rated load.
There are three types of Class C loading as
follows:
Class C1--Industrial Truck Loading where truck is
carried by the elevator.
Class C2--Industrial Truck Loading where truck is not
carried by the elevator but used only for loading and unloading.
Class C3--Other loading with Heavy Concentrations where
truck is not used.
The following requirements shall apply to all three
types of Class C loading:
1. The rated
load of the elevator shall be not less than the load (including any truck) to
be carried, and shall in no case be less than load based on 50 pounds per
square foot of inside net platform area.
2. The elevator shall be provided with a
two-way automatic leveling device.
For Class C1 and Class C2 loadings, the following
additional requirements shall apply:
3. For elevators with rated loads of 20,000
pounds or less, the car platform shall be designed for a loaded truck of weight
equal to the rated load or for the actual weight of the loaded truck to be
used, whichever is greater. For elevators with rated loads exceeding 20,000
pounds, the car platform shall be designed for a loaded truck weighing 20,000
pounds, or for the actual weight of the loaded truck to be used, whichever is
greater.
4. For Class C2 loading,
the maximum load on the car platform during loading or unloading shall not
exceed 150 percent of rated load. For any load in excess of the rated load, the
driving machine motor, brake, and traction relation shall be adequate to
sustain and level the full 150 percent of rated load.
NOTE: When the entire rated load is loaded or unloaded
by an industrial truck in increments, the load imposed on the car platform
while the last increment is being loaded or the first increment unloaded will
exceed the rated load by part of the weight of the empty industrial
truck.
(g) Passenger Elevator Platforms. The
stresses in platform members of passenger elevators shall be based on
concentrated loads not less than those which apply to Class A freight
loading.
(h) Formula Symbols. The
symbols used in the formulas in Section
3101 shall have the following
meanings:
W = Rated load in pounds.
C = Net weight in pounds of complete elevator
car.
G = Load in pounds supported by crosshead with rated
load in car at rest at top terminal landing.
K = Turning moment in inch-pounds as determined by
class of loading.
D = Distance in inches between guide rails.
E = Inside clear width of car in inches, except in
formulas in Sections
3101(e)(3) and
3103(a)(4)(D)
where E = modules of elasticity (psi) of the material used.
H = Vertical center distance between upper and lower
guide shoes (or rollers) in inches.
L = Free length of uprights in inches (distance from
lowest fastening in crosshead to top fastening in plank).
A = Net area of section in
(inches)2.
R = Least radius of gyration of section in
inches.
I = Moment of inertia of member, gross section in
(inches)4.
Z = Combined section moduli of plank members, gross
section, (inches)3.
Zu =Section modulus of one
upright, gross section, (inches)3.