Deflection (smile)


What does Deflection ( smile ) Mean?

Definition of Deflection ( smile ) in Construction
Deflection is the downward position of a structural element, or a smile.

In most cases, the initial proper structural position of any structural component, is with a crown, or camber. or looking like a frown. This means that the profile of the component is like a frown and not a smile. A smile means deflection, which in most cases, is a properly loaded beam or structural component. The strength of most structural members is with a crown or camber in the member , until it is loaded, then, unless the element has been designed to go flat, such as a parking deck or possibly a roadway, the structural element starts to deflect and wear the frown. This is a properly designed structural component.

However, if the component is loaded past its designed limits and the frown deepens with increased deflection, failure or permanent yield of the component can take place. This is not a preferred situation, and normally means that the load increased beyond the design limits, or the structural component had a failure within itself, that caused the deflection beyond the design limits. All structural components deflect, failure to deflect would cause rigidity or brittleness that could fail disastrously. Designed deflection is good and indicates a ” happy ” beam ( smile ) or component, severe deflection beyond the stress limits of the component is not good and can cause failure.