Roof Truss System
Groups: 1 to 3 students
Objective
Design a roof truss system to support the following loads.
1. Dead Load 15 1b/ft2
(roofing plywood, paper, asphalt shingles)
2. Snow Load 25 lb/ft2
(code requirement for Philadelphia, PA)
3. Maintenance Workers (300 lb concentrated load on each joint)
Constraints
1. Material: No. 2 Southern Pine, 2×4 (1.5 in x3.5 in)
Allowable Tensile Stress= 825 lb/in2
(Stress= Force/Area)
Allowable Compressive Stress = 1650 lb/in2
(Stress= Force/Area)
2. Truss Spacing Not to Exceed 24 inches (typical code requirement). Building Depth is fixed at 30 feet.
3. ASSUME ALL FORCES ARE APPLIED THROUGH THE JOINTS. Convert Dead Load and Snow Load to a
distributed load on each truss. Replace the total load on each of the upper members with a vertical force,
half of the force applied to the joint on each end of the member. Apply the maintenance worker
concentrated load at each of the upper joints.
4. Assume that each truss is simply supported (use pin/roller support conditions).
5. Roof Pitch assigned by Dr. Behrmann when group members are chosen.
Requirements
1. Provide a brief report and summary of calculations that document your design.
2. Verify that constraints are met.
3. Estimate the total length of 2×4 material needed.
4. Estimate total cost to purchase 2×4 material by using an internet source for pricing
statics project
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