Which statement describes a Transient Load due to temperature changes?

• A. Force due to uniform temperature
• B. Force effects due to creep
• C. Water load and stream pressure
• D. Downdrag force

Answer: (A)

Temperature changes can create internal forces when a structure is restrained from freely expanding or contracting. If the entire member experiences a uniform change in temperature, it tends to lengthen or shorten by an amount alpha times delta T, but if ends are fixed, this thermal strain is prevented and a force develops. This thermal force is a transient load because it varies with temperature over time. The magnitude, when the temperature change is uniform, is proportional to EA alpha delta T, producing a uniform axial force along the member.

The other phenomena described—creep being time-dependent deformation under sustained load, water load and stream pressure being external fluid pressures, and downdrag arising from soil-pile interaction—are not the transient thermal force generated by temperature change.