Structural Engineering · Engineering Glossary
The Lateral Force Resisting System (LFRS) is the collection of structural elements — shear walls, moment frames, braced frames, diaphragms, and their connections — that work together to resist wind and seismic forces acting horizontally on a building. A properly designed LFRS transfers these forces from the roof and floors to the foundation.
Every building must have a complete and continuous LFRS in two orthogonal directions. The diaphragm collects lateral forces and delivers them to vertical elements (shear walls, frames, or braces), which carry the forces down to the foundation. The path of forces through the LFRS must be complete and uninterrupted — a break in the load path is a common cause of structural failure in earthquakes. The type of LFRS selected (shear walls for wood or masonry buildings, moment frames for open-plan steel buildings, braced frames for industrial structures) affects architectural planning because the resisting elements require specific locations and configurations.
Apex Grid Engineering maintains this glossary as a resource for architects, contractors, developers, and property owners who encounter unfamiliar engineering terminology on their projects.
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