Concrete Floor Deflection

The australian standard as 3600 2001 recommends a limit of l 250 table 1.

Concrete floor deflection.

This rigorous method is described in greater detail elsewhere e g. For example the allowable deflection of a 12ft span floor joist with plaster l 360 is 0 4 12ft divided by 360. If that same joist had gypsum ceiling l 240 the allowable deflection is 0 6. This difference in the values of modulus of elasticity shows that concrete can only withstand a small amount of deflection and will experience cracking sooner than steel.

Detailed numerical examples illustrate the application of each of the methods presented. Per aci 117 these measurements are to be taken at a maximum of 72 hours after the concrete has been poured ie prior to shoring being removed. The concrete society publication. A comparative evaluation of.

For new home builders a squeaky or bouncy floor is a sign of substandard or code minimum construction practices the effect of which can erode their reputation for delivering comfortable quality. To minimize floor leve l n e s s p r oblems in composite constru c tion both the designer and con t r actor should be aware of design and construction decisions that af fect deflection. Note it gives the allowable deflection based on a fractional span quantity so a larger denominator will yield less deflection. In our concrete specifications we indicated required f f and f l numbers for floor flatness and levelness.

Concrete structures codes also recommend limits for the calculated total deflection of floors. Deflection calculations it is backed by site based research. The concrete structures code limits the maximum mid span deflection of a beam spanning either between columns or in a two way beam system between its supporting beams. See the table below.

The main reason these are spec d is for requirements of the flooring. Curvature in a simply supported slab. Got bounce appeared in the august 2012 issue of prosales and dealt with mitigating floor deflection in new home construction. Design issues a few years ago floors we r e de signed using astm a36 steel 36 000 psi yield strength and al.

Concrete s modulus of elasticity is between 15 50 gpa gigapascals while steel s tends to be around 200 gpa and above. It covers the consideration of crack formation and its impact on a concrete floor s deflection a critical consideration for conventionally reinforced slabs.