1. 1.6 Allowable Stress Allowable Load < Failure Load
Task: Design of safe structural member or mechanical element.
Requirement for safe design:
Material Testing
Allowable Load < Failure Load

2. Factor of Safety F.S. Factor of Safety : accounts for
If the load applied is linearly related to the stress:
Factor of Safety : accounts for
Unknown natural factors
Errors in manufacturing and assembly
Errors in load estimation
Material weathering

3. 1.7 Design of Simple Connections
Typical scenario:
Given:
allowable stress (shear or normal) and the desired load.
Task:
find the required thickness of a bolt, rod, or area of support plate etc.

4. Examples: Given: tension P of a tension member
Task: find the required cross-sectional area

5. Examples:
Given: shear force V of a bolt
Task: find the required cross-sectional area or diameter of the bolt

6. Examples:
Given: allowable bearing stress of foundation and normal load
Task: find the required cross-sectional area of the column base plate

7. Examples: Given: axial load on rod embedded in concrete Note:
The rod is held in the concrete by shear forces on its surface
Task:
find the required area

8. Lecture Example: Rods A and B are made of steel having failure stress 510 MPa. Use Factor of Safety 1.75, determine the smallest diameter to support the given load. Beam is assumed to be pin connected at A and C.

9. Lecture Example: Determine the intensity w of the maximum distributed load that can be supported by the hanger assembly so that an allowable shear stress of 13.5 ksi is not exceeded in the 0.4 in diameter bolts at A and B and an allowable tensile stress of 22 ksi is not exceeded in the 0.5 in diameter rod AB.