Original Version
Rule 48
48 Ultimate Strength Of Materials
Values used for the ultimate strength of materials, in connection with the safety specified in Rule 44 shall be not more than as follows:
48.1 Wood
Values used for moduli of rupture for wood in bending, in conjunction with the safety factors given in Rule 44, shall not exceed those shown in Table 5.
Table
5 

Species 
Modulus of rupture in bending 

Sawed rectangular poles, crossarm, etc. (a) 
Round Poles 

Cedar, western red 
4,700 lbs. Per sq in 
6,000 lbs. Per sq in 
Douglas fir, sense 
6,300 lbs. Per sq in 
6,800 (b) lbs. Per sq in 
Douglas fir, not dense 
5,800 lbs. Per sq in 
6,800 (b) lbs. Per sq in 
Fir, white or red, local 
4,700 lbs. Per sq in 
5,600 lbs. Per sq in 
Pine, southern yellow, dense 
6,300 lbs. Per sq in 
6,800 (b) lbs. Per sq in 
Pine, southern yellow, not dense 
5,800 lbs. Per sq in 
6,800 (b) lbs. Per sq in 
Redwood, virgin 
5,300 lbs. Per sq in 
6,200 lbs. Per sq in 
Redwood, second growth 
3,900 lbs. Per sq in 
4,600 lbs. Per sq in 
(a) Figures given are for select structural
grade of material under short time loading with the neutral plane parallel
to a side. Multiply the values shown by 1.4 where the neutral plane
is on the diagonal of a square. Multiply the given values by 0.55 where
the loading being considered is a long time loading (continuous load for
one year or more).
(b)
Where poles meet specifications of American Standards
Association, 05.11963 for Douglas Fir Poles and for southern Pine
Poles this value may be increased to not more than 8,000 lbs. Per square
inch. Such poles shall be suitable preservative treatment.
48.2 Structural Material (other than wood)
Structural members and their connections, shall be designed and constructed so that the structures and parts thereof will not fail or be seriously distorted at any load less than the maximum working loads developed under the construction arrangement with loadings as specified in Rule 43) multiplied by the safety factors specified in Rule 44.
The safety factors specified in Rule 44 shall be applied as follows to structural steel:
Tensions and Bending: The yield point, 33,000 pounds per square inch, shall be divided by the safety factor to determine the maximum allowable working stress.
Compression: The maximum allowable working stress shall be calculated by the following formula:
where S_{max} = maximum allowable working stress, lbs per sq in.
f_{s} = safety factor specified in Rule 44
YP = yield point of the steel, 33,000 lbs per sq in.
l = unsupported length of member, inches
r = radius of gyration of member, inches
Shear: The ultimate tensile strength, 60,000 pounds per square inch, shall be multiplied by 2/3 and divided by the safety factor specified in Rule 44 to determine the maximum allowable working stress.
Where the figures given are used, structural steel shall conform to Standards Specifications A739 of American Society for Testing Materials for carbon steel of structural quality. Other values may be used for steel of other strength provided the yield point and ultimate tensile strength are determined by test.
For other structural materials (other than concrete), the safety factor specified in Rule 44 shall be applied as follows:
Tension: The yield strength of the material used shall be divided by the safety factor specified in Rule 44 to determine the maximum allowable working stress.
Compression: The ultimate compressive strength of the material used be divided by the safety factor specified in Rule 44 to obtain the allowable working stress. The ultimate compressive strength shall be determined by suitable formulas for material used, considering yield strength of the material, modulus of elasticity, slenderness ratio and eccentricity of connection. In no case shall the ultimate compressive stress be greater than the yield strength of the material.
Shear: The ultimate shear strength of the material used be divided by the safety factor specified in Rule 44 to determine the maximum allowable working stress.
48.3 Concrete
A. Reinforced Concrete
Values used for ultimate strengths of reinforced concrete, in conjunction with safety factors given in Rule 44, shall not exceed the following:
Reinforcing steel, tensile or compressive strength, pounds per square inch 
55,000 
Concrete, 1:2:4 mixture 
Age 
Compressive Strength 
7 days 
900 lbs per sq in. 

30 days 
2,400 lbs per sq in. 

90 days 
3,100 lbs per sq in. 

6 mos 
4,400 lbs per sq in. 
If reinforced concrete is designed for higher strength values which are proven by test, such values may be used in lieu of the figures given.
B. Prestressed Concrete
Structural Members and their connections shall he designed and constructed so that the structures and parts thereof will not fail or be seriously distorted at any load less than their maximum working loads (developed under the current construction arrangements with loadings as Specified in Rule 43) multiplied by the safety factor specified in Rule 44."
The minimum strength of the materials used in prestressed concrete structures used in conjunction with the safety factors given in Table 4 shall be as follows:
Prestressing 
yield strength 40,000 lb.. per sq. inch 
SteelReinforcing Steel 
yield strength 188,000 lbs. per sq. inch 
Concrete 
compressive strength 4,000 lbs. per sq. inch at 28 days 
Other strength Values may be used provided the strength values used for design are proven by tests.
48.4 Conductors, Span Wires, Guys and Messengers
Values used for ultimate strengths of wires and cable shall not exceed those given in Appendix B. The ultimate strengths given in Tables 17 to 24 of Appendix B, except for mediumharddrawn copper, are based on the minimum ultimate strengths given in the standards specifications of the American Society for Testing Materials. The ultimate strengths given in Appendix B for mediumharddrawn copper based on the standard specifications of the ASTM and provide an allowance above the minimum values of onequarter of the range between minimum and maximum values. For use of types of wires and cables of other materials not included in Appendix B, values for ultimate strengths similarly derived from specifications are nonexistent, maker’s specifications may be used provided that tests have been made which shall justify the maker’s rating for ultimate strength.
48.5 Tower or Pole Foundations and Footings
In calculating the resistance of foundations or footings of towers, poles and pole line structures to uplifts, the weight of concrete shall be taken as not more than 145 pounds per cubic foot and the weight of earth (calculated 30 degrees from the vertical) shall be taken as not more than 90 pounds per cubic foot. The resistance of soil to the depression of foundations or footings shall be calculated from the best available data on the soil in question. In lieu of calculation, the strength of foundations or footings against uplift or depression may be determined by tests under the soil conditions obtaining.
48.6 Metallic Service and Meter Poles
Metallic service and meter poles shall be designed and constructed so that the poles and parts thereof will not fail or be seriously distorted at any load less than the maximum working loads (see Rule 43 for loadings) multiplied by the safety factors specified in Table 4, Rule 44. The safety factors specified in Table 4, Rule 44 shall be applied as follows:
Tension: The yield strength of the metal used shall be divided by the safety factor specified in Table 4, Rule 44 to determine the maximum allowable working stress.
Compression: The critical. buckling strength of the material used, as determined by applicable formulas employing the effective slenderness ratio and yield strength, shall be divided by the safety factors specified in Table 4, Rule 44, to determine the maximum allowable working stress.
Strikeout and Underline Version
Rule 48
48 Ultimate Strength Of Materials
Structural members and their connections shall be designed and constructed so that the structures and parts thereof will not fail or be seriously distorted at any load less than their maximum working loads (developed under the current construction arrangements with loadings as specified in Rule 43 multiplied by the safety factor specified in Rule 44.
Values used for the ultimate strength of materials shall comply with the safety factors specified in Rule 44.
Values used for the ultimate strength of materials, in connection
with the safety specified in Rule 44 shall be not more than as follows:
48.1 Wood
Values used for moduli of rupture for wood in bending, in conjunction with the safety factors given in Rule 44, shall not exceed those shown in Table 5.
Table
5 

Species 
Modulus of rupture in bending 

Sawed rectangular poles, crossarm, etc. (a) 
Round Poles 

Cedar, western red 
4,700 lbs. Per sq in 
6,000 lbs. Per sq in 
Douglas fir, sense 
6,300 lbs. Per sq in 
6,800 (b) lbs. Per sq in 
Douglas fir, not dense 
5,800 lbs. Per sq in 
6,800 (b) lbs. Per sq in 
Fir, white or red, local 
4,700 lbs. Per sq in 
5,600 lbs. Per sq in 
Pine, southern yellow, dense 
6,300 lbs. Per sq in 
6,800 (b) lbs. Per sq in 
Pine, southern yellow, not dense 
5,800 lbs. Per sq in 
6,800 (b) lbs. Per sq in 
Redwood, virgin 
5,300 lbs. Per sq in 
6,200 lbs. Per sq in 
Redwood, second growth 
3,900 lbs. Per sq in 
4,600 lbs. Per sq in 
(a) Figures given are for select structural
grade of material under short time loading with the neutral plane parallel
to a side. Multiply the values shown by 1.4 where the neutral plane
is on the diagonal of a square. Multiply the given values by 0.55 where
the loading being considered is a long time loading (continuous load for
one year or more).
(b)
Where poles meet specifications of American Standards
Association, 05.11963 for Douglas Fir Poles and for southern Pine
Poles this value may be increased to not more than 8,000 lbs. Per square
inch. Such poles shall be suitable preservative treatment.
48.2 Structural
Material (other than wood) Steel
Structural members
and their connections, shall be designed and constructed so that the structures
and parts thereof will not fail or be seriously distorted at any load less than
the maximum working loads developed under the construction arrangement with
loadings as specified in Rule 43) multiplied by the safety factors specified in
Rule 44.
The safety factors specified in Rule 44 shall be applied as follows to structural steel:
Tensions and Bending: The yield point, 33,000 pounds per square inch, shall be divided by the safety factor to determine the maximum allowable working stress.
Compression: The maximum allowable working stress shall be calculated by the following formula:
where S_{max} = maximum allowable working stress, lbs per sq in.
f_{s} = safety factor specified in Rule 44
YP = yield point of the steel, 33,000 lbs per sq in.
l = unsupported length of member, inches
r = radius of gyration of member, inches
Shear: The ultimate tensile strength, 60,000 pounds per square inch, shall be multiplied by 2/3 and divided by the safety factor specified in Rule 44 to determine the maximum allowable working stress.
Where the figures given are used, structural steel shall conform to Standards Specifications A739 of American Society for Testing Materials for carbon steel of structural quality. Other values may be used for steel of other strength provided the yield point and ultimate tensile strength are determined by test.
For other structural
materials (other than concrete), the safety factor specified in Rule 44 shall
be applied as follows:
Tension: The yield
strength of the material used shall be divided by the safety factor specified
in Rule 44 to determine the maximum allowable working stress.
Compression: The
ultimate compressive strength of the material used be divided by the safety
factor specified in Rule 44 to obtain the allowable working stress. The ultimate compressive strength shall be
determined by suitable formulas for material used, considering yield strength
of the material, modulus of elasticity, slenderness ratio and eccentricity of
connection. In no case shall the
ultimate compressive stress be greater than the yield strength of the material.
Shear: The ultimate shear strength of the material
used be divided by the safety factor specified in Rule 44 to determine the
maximum allowable working stress.
48.3 Concrete
A. Reinforced Concrete
Values used for ultimate strengths of reinforced concrete, in conjunction with safety factors given in Rule 44, shall not exceed the following:
Reinforcing steel, tensile or compressive strength, pounds per square inch 
55,000 
Concrete, 1:2:4 mixture 
Age 
Compressive Strength 
7 days 
900 lbs per sq in. 

30 days 
2,400 lbs per sq in. 

90 days 
3,100 lbs per sq in. 

6 mos 
4,400 lbs per sq in. 
If reinforced concrete is designed for higher strength values which are proven by test, such values may be used in lieu of the figures given.
B. Prestressed Concrete
Structural Members and their connections shall he designed and constructed so that the structures and parts thereof will not fail or be seriously distorted at any load less than their maximum working loads (developed under the current construction arrangements with loadings as Specified in Rule 43) multiplied by the safety factor specified in Rule 44."
The minimum strength of the materials used in prestressed concrete structures used in conjunction with the safety factors given in Table 4 shall be as follows:
Prestressing 
yield strength 40,000 lb.. per sq. inch 
SteelReinforcing Steel 
yield strength 188,000 lbs. per sq. inch 
Concrete 
compressive strength 4,000 lbs. per sq. inch at 28 days 
Other strength Values may be used provided the strength values used for design are proven by tests.
48.4 Other Structural Materials
For other structural materials (other than concrete), the safety factor specified in Rule 44 shall be applied as follows:
Tension: The yield strength of the material used shall be divided by the safety factor specified in Rule 44 to determine the maximum allowable working stress.
Compression: The ultimate compressive strength of the material used be divided by the safety factor specified in Rule 44 to obtain the allowable working stress. The ultimate compressive strength shall be determined by suitable formulas for material used, considering yield strength of the material, modulus of elasticity, slenderness ratio and eccentricity of connection. In no case shall the ultimate compressive stress be greater than the yield strength of the material.
Shear: The ultimate shear strength of the material used be divided by the safety factor specified in Rule 44 to determine the maximum allowable working stress.
48.45
Conductors,
Span Wires, Guys and Messengers
Values used for ultimate strengths of wires and cable shall not exceed those given in Appendix B. The ultimate strengths given in Tables 17 to 24 of Appendix B, except for mediumharddrawn copper, are based on the minimum ultimate strengths given in the standards specifications of the American Society for Testing Materials. The ultimate strengths given in Appendix B for mediumharddrawn copper based on the standard specifications of the ASTM and provide an allowance above the minimum values of onequarter of the range between minimum and maximum values. For use of types of wires and cables of other materials not included in Appendix B, values for ultimate strengths similarly derived from specifications are nonexistent, maker’s specifications may be used provided that tests have been made which shall justify the maker’s rating for ultimate strength.
48.56
Tower
or Pole Foundations and Footings
In calculating the resistance of foundations or footings of towers, poles and pole line structures to uplifts, the weight of concrete shall be taken as not more than 145 pounds per cubic foot and the weight of earth (calculated 30 degrees from the vertical) shall be taken as not more than 90 pounds per cubic foot. The resistance of soil to the depression of foundations or footings shall be calculated from the best available data on the soil in question. In lieu of calculation, the strength of foundations or footings against uplift or depression may be determined by tests under the soil conditions obtaining.
48.67
Metallic Service and Meter Poles
Metallic service and meter poles shall be designed and constructed so that the poles and parts thereof will not fail or be seriously distorted at any load less than the maximum working loads (see Rule 43 for loadings) multiplied by the safety factors specified in Table 4, Rule 44. The safety factors specified in Table 4, Rule 44 shall be applied as follows:
Tension: The yield strength of the metal used shall be divided by the safety factor specified in Table 4, Rule 44 to determine the maximum allowable working stress.
Compression: The critical. buckling strength of the material used, as determined by applicable formulas employing the effective slenderness ratio and yield strength, shall be divided by the safety factors specified in Table 4, Rule 44, to determine the maximum allowable working stress.
Final Version
Rule 48
48 Ultimate Strength Of Materials
Structural members and their connections shall be designed and constructed so that the structures and parts thereof will not fail or be seriously distorted at any load less than their maximum working loads (developed under the current construction arrangements with loadings as specified in Rule 43 multiplied by the safety factor specified in Rule 44.
Values used for the ultimate strength of materials shall comply with the safety factors specified in Rule 44.
48.1 Wood
Values used for moduli of rupture for wood in bending, in conjunction with the safety factors given in Rule 44, shall not exceed those shown in Table 5.
Table
5 

Species 
Modulus of rupture in bending 

Sawed rectangular poles, crossarm, etc. (a) 
Round Poles 

Cedar, western red 
4,700 lbs. Per sq in 
6,000 lbs. Per sq in 
Douglas fir, sense 
6,300 lbs. Per sq in 
6,800 (b) lbs. Per sq in 
Douglas fir, not dense 
5,800 lbs. Per sq in 
6,800 (b) lbs. Per sq in 
Fir, white or red, local 
4,700 lbs. Per sq in 
5,600 lbs. Per sq in 
Pine, southern yellow, dense 
6,300 lbs. Per sq in 
6,800 (b) lbs. Per sq in 
Pine, southern yellow, not dense 
5,800 lbs. Per sq in 
6,800 (b) lbs. Per sq in 
Redwood, virgin 
5,300 lbs. Per sq in 
6,200 lbs. Per sq in 
Redwood, second growth 
3,900 lbs. Per sq in 
4,600 lbs. Per sq in 
(a) Figures given are for select structural
grade of material under short time loading with the neutral plane parallel
to a side. Multiply the values shown by 1.4 where the neutral plane
is on the diagonal of a square. Multiply the given values by 0.55 where
the loading being considered is a long time loading (continuous load for
one year or more).
(b)
Where poles meet specifications of American Standards
Association, 05.11963 for Douglas Fir Poles and for southern Pine
Poles this value may be increased to not more than 8,000 lbs. Per square
inch. Such poles shall be suitable preservative treatment.
48.2 Steel
The safety factors specified in Rule 44 shall be applied as follows to structural steel:
Tensions and Bending: The yield point, 33,000 pounds per square inch, shall be divided by the safety factor to determine the maximum allowable working stress.
Compression: The maximum allowable working stress shall be calculated by the following formula:
where S_{max} = maximum allowable working stress, lbs per sq in.
f_{s} = safety factor specified in Rule 44
YP = yield point of the steel, 33,000 lbs per sq in.
l = unsupported length of member, inches
r = radius of gyration of member, inches
Shear: The ultimate tensile strength, 60,000 pounds per square inch, shall be multiplied by 2/3 and divided by the safety factor specified in Rule 44 to determine the maximum allowable working stress.
Where the figures given are used, structural steel shall conform to Standards Specifications A739 of American Society for Testing Materials for carbon steel of structural quality. Other values may be used for steel of other strength provided the yield point and ultimate tensile strength are determined by test.
48.3 Concrete
A. Reinforced Concrete
Values used for ultimate strengths of reinforced concrete, in conjunction with safety factors given in Rule 44, shall not exceed the following:
Reinforcing steel, tensile or compressive strength, pounds per square inch 
55,000 
Concrete, 1:2:4 mixture 
Age 
Compressive Strength 
7 days 
900 lbs per sq in. 

30 days 
2,400 lbs per sq in. 

90 days 
3,100 lbs per sq in. 

6 mos 
4,400 lbs per sq in. 
If reinforced concrete is designed for higher strength values which are proven by test, such values may be used in lieu of the figures given.
B. Prestressed Concrete
Structural Members and their connections shall he designed and constructed so that the structures and parts thereof will not fail or be seriously distorted at any load less than their maximum working loads (developed under the current construction arrangements with loadings as Specified in Rule 43) multiplied by the safety factor specified in Rule 44.
The minimum strength of the materials used in prestressed concrete structures used in conjunction with the safety factors given in Table 4 shall be as follows:
Prestressing 
yield strength 40,000 lb.. per sq. inch 
SteelReinforcing Steel 
yield strength 188,000 lbs. per sq. inch 
Concrete 
compressive strength 4,000 lbs. per sq. inch at 28 days 
Other strength Values may be used provided the strength values used for design are proven by tests.
48.4 Other Structural Materials
For other structural materials (other than concrete), the safety factor specified in Rule 44 shall be applied as follows:
Tension: The yield strength of the material used shall be divided by the safety factor specified in Rule 44 to determine the maximum allowable working stress.
Compression: The ultimate compressive strength of the material used be divided by the safety factor specified in Rule 44 to obtain the allowable working stress. The ultimate compressive strength shall be determined by suitable formulas for material used, considering yield strength of the material, modulus of elasticity, slenderness ratio and eccentricity of connection. In no case shall the ultimate compressive stress be greater than the yield strength of the material.
Shear: The ultimate shear strength of the material used be divided by the safety factor specified in Rule 44 to determine the maximum allowable working stress.
48.5 Conductors, Span Wires, Guys and Messengers
Values used for ultimate strengths of wires and cable shall not exceed those given in Appendix B. The ultimate strengths given in Tables 17 to 24 of Appendix B, except for mediumharddrawn copper, are based on the minimum ultimate strengths given in the standards specifications of the American Society for Testing Materials. The ultimate strengths given in Appendix B for mediumharddrawn copper based on the standard specifications of the ASTM and provide an allowance above the minimum values of onequarter of the range between minimum and maximum values. For use of types of wires and cables of other materials not included in Appendix B, values for ultimate strengths similarly derived from specifications are nonexistent, maker’s specifications may be used provided that tests have been made which shall justify the maker’s rating for ultimate strength.
48.6 Tower or Pole Foundations and Footings
In calculating the resistance of foundations or footings of towers, poles and pole line structures to uplifts, the weight of concrete shall be taken as not more than 145 pounds per cubic foot and the weight of earth (calculated 30 degrees from the vertical) shall be taken as not more than 90 pounds per cubic foot. The resistance of soil to the depression of foundations or footings shall be calculated from the best available data on the soil in question. In lieu of calculation, the strength of foundations or footings against uplift or depression may be determined by tests under the soil conditions obtaining.
48.7 Metallic Service and Meter Poles
Metallic service and meter poles shall be designed and constructed so that the poles and parts thereof will not fail or be seriously distorted at any load less than the maximum working loads (see Rule 43 for loadings) multiplied by the safety factors specified in Table 4, Rule 44 . The safety factors specified in Table 4, Rule 44 shall be applied as follows:
Tension: The yield strength of the metal used shall be divided by the safety factor specified in Table 4, Rule 44 to determine the maximum allowable working stress.
Compression: The critical. buckling strength of the material used, as determined by applicable formulas employing the effective slenderness ratio and yield strength, shall be divided by the safety factors specified in Table 4, Rule 44 , to determine the maximum allowable working stress.