Ultimate Stress Design (Factored Load), U
Structure and structural members should be designed to have design strength at all sections at least equal to required strengths calculated for the factored loads and forces in any combination loads
Required strength U to resist dead load DL and Live Load LL shall be at least equal to:
U=1.4DL+1.7LL
If Wind Load resistance WL is in included in the design where load combinations includes both full value and zero value of Live Load
U=0.75(1.4DL+1.7LL+1.7WL)
And
U=0.9DL+1.3WL
The greater shall be applied into the design but not less than U=1.4DL+1.7LL
If the Earthquake loads E are included in the design where load combinations includes both full value and zero value of Live Load
U=0.75(1.4DL+1.7LL+1.87E)
And
U=0.9DL+1.43E
The greater shall be applied into the design but not less than U=1.4DL+1.7LL
If Earth resistance pressure H is included in the design
U=1.4DL+1.7LL+1.7H
Where DL and LL reduce the effect of H
U=0.9DL
But not less than 1.4DL+1.7LL
If the resistance to loadings due to weight and pressure of fluids with well-defined densities and controllable maximum heights F is included in Design such as loading shall have a load factor of 1.4 and be added to all loading combinations that included live load.
If the resistance to impact effects is taken into account in design, such effects shall be included with live load LL
Where structural T of differential settlement, creep, shrinkage, or temperature change are significant in the design
U=0.75(1.4DL+1.4T+1.7LL)
But required strength U shall not be less than U= 1.4(DL+T)
Strength Reduction Factors, (phi)
The design strength provided by a concrete member, its connection to other member’s and it cross sections, in term of flexure, axial load, shear, and torsion shall be taken as the nominal strength multiplied by a strength reduction factors phi having the following values:
a. Flexure without axial load______________________________0.90
b. Axial Tension, and axial tension with flexure_________________0.90
c. Axial Compression, and axial Compression with Flexure
1. Spiral reinforcement_____________________________0.75
2. Tie Reinforcement and other reinforced members_______0.70
d. Shear and Tension____________________________________0.85
e. Bearing on Concrete___________________________________0.70
f. Post-Tensioned anchorage zones__________________________0.85
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