Explain the difference between a rigid-frame expansion joint and a modular expansion joint.

• A. Rigid-frame joints transfer load across a joint without a flexible carrier; modular joints use interlocking plates or modules with seals to accommodate movement
• B. Rigid-frame joints use interlocking plates to permit movement; modular joints transfer load across a joint without flexibility
• C. Both joints function identically with no differences
• D. Rigid-frame joints are hydraulic; modular joints are mechanical only

Answer: (A)

The difference comes down to how each joint handles movement and carries load across the gap. A rigid-frame expansion joint uses a single, stiff carrier that spans the joint without a flexible, sliding element. The joint transfers the traffic load across the gap through that rigid framing, while movement is not absorbed by the joint itself with sliding parts. In contrast, a modular expansion joint is built from multiple interlocking modules that can slide and separate relative to one another. The modules, along with seals, allow and control movement while keeping water out, so the joint can accommodate larger expansions and contractions.

So the best description is that rigid-frame joints transfer load across the joint with a rigid, nonflexible carrier, while modular joints use interlocking plates or modules with seals to absorb and accommodate movement. The other statements don’t fit this distinction, since rigid-frame joints aren’t defined by interlocking plates, both types don’t function identically, and hydraulic versus mechanical is not the defining difference.