Pennsylvania Code › Title 34 - LABOR AND INDUSTRY › Part I - Department of Labor and Industry › Chapter 15 - GRANDSTANDS › RULES OF CONSTRUCTION › Section 15.18 - Allowable stresses

Current through Register Vol. 54, No. 28, July 13, 2024
(a)
For steel.
Parts of the structure shall be so proportioned
				  that the sum of the maximum stresses in pounds per square inch does not exceed
				  the following:
(1)
Tension.
Tension shall be regulated as follows:
Item
Maximum
							 Stresses (pounds per square inch)
Structural steel, net section
20,000
Butt welds, section through throat
20,000
Rivets on area based on nominal
							 diameter
20,000
Bolts and other threaded parts, on nominal area at
							 root of thread
20,000
(2)
Compression.
Compression shall be regulated as follows:
(i) For the purposes of this paragraph,
				  symbols represent the following:
L = The unsupported length of the column.
r = The corresponding least radius of gyration of the
					 section.
(ii) Rolled steel,
				  on short length or where lateral deflection is prevented, may not exceed 20,000
				  pounds per square inch.
(iii) On a
				  gross section of columns, L/r does not exceed 120:
1,700 - .485 L2 /r2
if L/r exceeds 120:
1 + [(18,000 ÷ L2 )
					 ÷,18,000r2 ]
(iv) The ratio of unbraced length to least
				  radius of gyration L/r for compression members and for tension members other
				  than rods shall not exceed the following:
Item
Maximum
							 Stresses (pounds per square inch)
For main compression members
120
For bracing and other secondary members in
							 compression
200
For main tension members
240
For bracing and other secondary members in
							 tension
300
(3)
Bending.
Bending shall
				  be regulated as follows:
(i) For the purposes
				  of this paragraph, the following designations will apply:
L = The unsupported length of the column.
b = The width of the compression flange.
(ii) Extreme fibres of rolled shapes, and
				  built up sections, net section, if lateral deflection is prevented, may not
				  exceed 20,000 pounds per square inch.
(iii) Where L exceeds 15 times b, the stress
				  in pounds per square inch in b may not exceed the following:
1 + [(20,000 ÷ L2  )
					 ÷2,000b2 ]
(iv) The laterally unsupported length of
				  beams and girders may not exceed 40 times b in width of the compression
				  flange.
(v) Extreme fibres of pins,
				  when the forces are assumed as acting at the center of gravity of the pieces
				  may not exceed 30,000 pounds per square inch.
(4)
Shearing.
Shearing shall
				  be regulated as follows:
(i) For the purposes
				  of this paragraph, the following designations will apply:
A = The gross area of the web in inches.
V = The total shear.
h = The height between flanges in inches.
t = The thickness of the web in inches.
(ii) The following table will apply:
Item
Maximum
							 Stresses (pounds per square inch)
Pins
15,000
Power-driven rivets
15,000
Turned bolts in reamed holes with a clearance of not
							 more than 1/50 inch
15,000
Hand-driven rivets
10,000
Unfinished bolts
10,000
The gross area of the webs of beams and girders where
							 h is not more than 60 times t
13,000
(iii) The gross area of the webs of beams and
				  girders if the web is not stiffened, where h is more than 60 times t, the
				  thickness of the web, the maximum shear per square inch, V/A may not exceed:
1 + [(18,000 ÷h2  )
					 ÷7,200t2 ]
(iv) A section through the throat of a fillet
				  weld may not exceed 13,600 pounds per square inch.
(5)
Bearing.
Bearing shall
				  be regulated as follows:
(i) For the purposes
				  of this paragraph, the letter "d" shall designate the diameter of the roller in
				  inches.
(ii) The following table
				  will apply:
Maximum Stresses (pounds
							 per square inch)
Item
Single
							 Shear
Double Shear
Pins
32,000
32,000
Power-driven rivets
32,000
40,000
Turned bolts in reamed holes
32,000
40,000
Hand-driven bolts
20,000
25,000
Unfinished bolts
20,000
25,000
(iii) On expansion rollers, pounds per linear
				  inch, -600d.
(6)
Combined stresses.
Combined stresses shall conform with the
				  following:
(i) For the purposes of this
				  paragraph, the following designations will apply:
Fa = Axial unit stress that would be permitted by this
					 specification if axial stress only existed.
Fb = Bending unit stress that would be permitted by this
					 specification if bending stress only existed.
fa = Axial unit stress (actual) = axial stress divided by
					 area of member.
fb = Bending unit stress (actual) = bending moment divided
					 by section modulus of member.
(ii) For stresses due to wind sway loads,
				  combined with those due to dead or live loads, the permissible total working
				  stress may be increased 33 1/3%, if the section thus found is not less than
				  that required by the dead or live loads alone.
(iii) Members subject to both axial and
				  bending stresses shall be so proportioned that the quantity fa/Fa+fb/Fb does
				  not exceed unity.
(7)
Members carrying wind and sway only.
For members carrying wind
				  and sway stresses only, the permissible working stresses may be increased 33
				  1/3%.
(8)
Welding.
Welds shall be made only by operators who have qualified by the tests
				  prescribed in the Standard Qualification Procedure of the American Welding
				  Society to perform the type of work required, except that this provision need
				  not apply to tack welds not later incorporated into finished welds carrying
				  calculated stress.