OMRF and SMRF: What is the Main Difference?

OMRF and SMRF: what is the main difference
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In structural engineering, two key systems, OMRF and SMRF, address different forces. OMRFs ensure wind stability for low to mid-rise buildings economically, while SMRFs guarantee seismic safety in high-rises with specialized techniques, vital for earthquake-prone areas.

What is OMRFs?

An Ordinary Moment Resisting Frame (OMRF) is a structural system used in building construction to resist lateral forces. Beams an columns are interlinked to withstand bending moments without the need for additional features such as outriggers. They are cost-effective and widely applied in stable low to mid-rise building.

What is SMRF?

A Special Moment-Resisting Frame (SMRF) is a framing system for buildings which are resistant to seismic forces. The SMRFs provide high ductility and they can withstand large deformations without collapsing. They are essential in high-rise and critical buildings, complying with stringent safety requirements. SMRFs use special detailing and construction methods, which increase their resistance to earthquake.

Difference between OMRF and SMRF

Both OMRF and SMRF are used in structural engineering to address different types of forces that buildings may encounter.

AspectOrdinary Moment Resisting Frame (OMRF)Special Moment-Resisting Frame (SMRF)
PurposeProvides lateral stability primarily against wind loads.Specifically designed to resist seismic forces, ensuring safety during earthquakes.
Structural DesignFocuses on providing structural stability without additional elements like outriggers.Incorporates special detailing and construction techniques to enhance seismic resistance.
Deformation CapacityLimited ductility, typically with a lower ability to withstand large deformations.Designed with significant ductility, enabling the structure to absorb seismic energy.
ApplicationCommonly used in low to mid-rise buildings where lateral forces are generally lower.Utilized in high-rise buildings and critical structures where strict seismic criteria must be met.
Construction CostGenerally cost-effective due to simpler structural design.May involve higher construction costs due to specialized detailing and seismic-resistant features.
Performance Under Seismic LoadingProvides basic resistance to seismic forces but may not meet stringent seismic performance criteria.Engineered to meet strict seismic performance standards, offering enhanced safety during earthquakes.
Structural RobustnessRelies on the inherent strength of structural members for stability.Designed with robust detailing and construction to withstand extreme seismic events.

For more detailed explanation on OMRF and SMRF, go to this video


OMRFs offer wind stability to low and mid-rise buildings while SMRF provide seismic safety for high rises. OMRFs are cost-effective solutions; SMRFs use specialized methods for seismic resistance. The decision hinges on the height of buildings and seismic risk, where SMRFs provide increased resilience but may come with higher costs.

By employing both OMRF and SMRF, engineers can effectively address a broader range of structural challenges, ensuring buildings are resilient to both wind and seismic forces, depending on their location and design requirements.

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