Equation Stress on Aluminum Portion of Conductor
Equation Stress on Aluminum Portion of Conductor
(OP)
Hello,
Can anyone provide a reference document that would contain the equation for calculating the Aluminum Stress on a combo Steel-Aluminum Conductor?
I'm reviewing an old report and it uses an equation in MS Excel that appears something as follows, but I would like to know what the source for this equation was.
Sigma_a = T1 - (B_a-B_s)*(T_a-20)* E_sI * (A_t - A_a) * E_aI / (Es_I * (A_t - A_a) + E_aI * A_a)
where:
Sigma_a = Aluminum Stress
T1 = initial tension at -35C
B_a = ??? (I'm guessing its a coefficient of expansion for aluminum, units were noted as K-1)
B_s = ??? (I'm guessing this is coefficient of thermal expansion for steel, units noted as K-1)
T_a = temperature of ???
E_sI = ??? (Guessing initial modulus of elasticity for steel)
E_aI = ??? (Guessing initial modulus of elasticity for aluminum)
A_t = total conductor cross-sectional area
A_a = cross-sectional area of aluminum
If any of you can help out, thanks!
Can anyone provide a reference document that would contain the equation for calculating the Aluminum Stress on a combo Steel-Aluminum Conductor?
I'm reviewing an old report and it uses an equation in MS Excel that appears something as follows, but I would like to know what the source for this equation was.
Sigma_a = T1 - (B_a-B_s)*(T_a-20)* E_sI * (A_t - A_a) * E_aI / (Es_I * (A_t - A_a) + E_aI * A_a)
where:
Sigma_a = Aluminum Stress
T1 = initial tension at -35C
B_a = ??? (I'm guessing its a coefficient of expansion for aluminum, units were noted as K-1)
B_s = ??? (I'm guessing this is coefficient of thermal expansion for steel, units noted as K-1)
T_a = temperature of ???
E_sI = ??? (Guessing initial modulus of elasticity for steel)
E_aI = ??? (Guessing initial modulus of elasticity for aluminum)
A_t = total conductor cross-sectional area
A_a = cross-sectional area of aluminum
If any of you can help out, thanks!






RE: Equation Stress on Aluminum Portion of Conductor
If you don't have access to ALCOA's sag and tension program or Powerline System's CADD program which has sag and tension capability, I suggest you contact one of the conductor manufacturer's and ask them for the info for your particular application.
RE: Equation Stress on Aluminum Portion of Conductor
I do have access to both Alcoa's SAG10 and PLSCASS, but the report I am reviewing did not use it. The equation does not appear to be in the Southwire manual either, as that was the first source I checked.
The report back-calculates aluminum stress based on a specified required RTS (used to calculate T1), so it doesn't actually use a span length, as PLS-CADD and Sag10 require.
I'll see if I can track down an Aluminum Assoc. conductor manual and see if the equation is in there.
Thanks!
RE: Equation Stress on Aluminum Portion of Conductor
αAS = αAl·(EAl/EAS)·(AAl/Atotal) + αSt·(ESt/EAS)·(ASt/Atotal)
EAS = EAl·(AAl/Atotal) + ESt·(ASt/Atotal)
EAl = modulus of elasticity of aluminum, lb/in²
AAl = Area of aluminum strands, square units
αAl = aluminum coefficient of linear thermal expansion, °F-1
AS for aluminum-steel composite
St for Steel