In a parallel chord truss, which chord is typically in compression under loading?

In a parallel chord truss, which chord is typically in compression under loading?

• A. Top chord
• B. Bottom chord
• C. Diagonal member
• D. None

Answer: (A)

Under vertical loading, a parallel-chord truss behaves like a shallow arch: the upper (top) chord is pushed together and takes compressive forces, while the lower (bottom) chord is pulled apart and takes tensile forces. The loads at the joints tend to push the top chord members toward each other, creating compression, whereas the bottom chord resists the outward movement of the joints, pulling it into tension. The diagonal members then transfer the remaining shear between the chords, and their force state depends on the specific load pattern, but the most consistent outcome for typical loading is compression in the top chord.

Under vertical loading, a parallel-chord truss behaves like a shallow arch: the upper (top) chord is pushed together and takes compressive forces, while the lower (bottom) chord is pulled apart and takes tensile forces. The loads at the joints tend to push the top chord members toward each other, creating compression, whereas the bottom chord resists the outward movement of the joints, pulling it into tension. The diagonal members then transfer the remaining shear between the chords, and their force state depends on the specific load pattern, but the most consistent outcome for typical loading is compression in the top chord.