(a)
The section for loads given loads using load and resistance factor design (LRFD) method.
Answer to Problem 3.8.1P
The section for loads given loads using load and resistance factor design (LRFD) method is
Explanation of Solution
Given data:
Length of the connection is
Spacing of truss in the roof system is
Snow load is
Weight of roofing is
Section for the purlins is
Weight of the truss is
Calculation:
Calculate the snow load.
Calculate the load due to purlins.
Calculate the weight of the truss.
Calculate the slant height of the roof.
Calculate the weight of the roof.
Write the expression to calculate the total dead load.
Here, total dead load is
Substitute
Calculate the factored load using following load combination.
Here, factored load is
Substitute
Write the expression to calculate the exterior joint load.
Here, load on the exterior joint is
Substitute
Consider the free body diagram of the truss shown below.
Figure-(1)
Write the expression to calculate the moment about point
Substitute
Solve further.
Consider joint
Write the expression for summation of forces acting in the horizontal direction.
Here, summation of all horizontal forces is
Substitute
Write the expression to calculate the required area.
Here, gross area is
Substitute
Write the expression to calculate the required area.
Here, effective area is
Substitute
Calculate the effective length of the truss.
Calculate the radius of gyration.
Substitute
Use section
Write the expression to calculate reduction factor.
Here, reduction factor is
Substitute
Write the expression to calculate the effective area for the section.
Substitute
Conclusion:
Since the gross area, net area and radius of gyration for this greater than the calculated value,
(b)
The section for loads given loads using allowable strength design (ASD) method.
Answer to Problem 3.8.1P
The section for loads given loads using allowable strength design (ASD) method is
Explanation of Solution
Given data:
Length of the connection is
Spacing of truss in the roof system is
Snow load is
Weight of roofing is
Section for the purlins is
Weight of the truss is
Calculation:
Calculate the ultimate load using the following load combination.
Here, ultimate load is
Substitute
Write the expression to calculate the exterior joint load.
Here, load on the exterior joint is
Substitute
Consider the free body of the truss as shown below.
Figure-(2)
Write the expression to calculate the moment about point
Substitute
Solve further.
Consider joint
Write the expression for summation of forces acting in the horizontal direction.
Here, summation of all horizontal forces is
Substitute
Write the expression to calculate the required area.
Here, gross area is
Substitute
Write the expression to calculate the required area.
Here, effective area is
Substitute
Calculate the effective length of the truss.
Calculate the radius of gyration.
Substitute
Use section
Write the expression to calculate reduction factor.
Here, reduction factor is
Substitute
Write the expression to calculate the effective area for the section.
Substitute
Conclusion:
Since the gross area, net area and radius of gyration for this greater than the calculated value,
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Chapter 3 Solutions
Steel Design (Activate Learning with these NEW titles from Engineering!)
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