A newly constructed open-plan office features long-span steel composite beams supporting a concrete floor deck.

Scenario: Shortly after occupancy, employees complain that the floor feels "bouncy," and their monitors shake when someone walks briskly down the main aisle.

Solution: The engineers confirm that the floor meets all code requirements for strength and static deflection. However, the floor system's natural frequency is too close to the human walking pacing rate (approx. 1.5 to 2.5 Hz).

Because serviceability (vibration) governed over strength, the engineers had to stiffen the floor system to increase its natural frequency. Since the beams were already installed, the retrofit involved welding steel plates to the bottom flanges of the existing beams, significantly increasing their moment of inertia ($I_x$) without altering the architectural floor-to-ceiling height, thereby stiffening the floor and reducing the vibrations to acceptable levels.

During the launch (installation) of a massive continuous steel bridge girder over a highway, the girder is temporarily supported on a central pier by a small hydraulic jack.

Scenario: A loud "pop" is heard, and the girder sags slightly. Inspection reveals that the web of the girder has buckled directly above the hydraulic jack.

Solution: The failure was caused by a highly concentrated reaction force applied over a very small bearing area. The failure mode was web crippling (local buckling of the web under concentrated load).

The engineers had checked the global shear capacity, but they failed to check the local limit states of web yielding and web crippling at the temporary jacking location. The solution required installing transverse bearing stiffeners (steel plates welded vertically to both sides of the web directly above the jack) to transfer the concentrated force safely from the bottom flange up into the full depth of the web.