Concrete Floor Deflection

Deflection calculations it is backed by site based research.

Concrete floor deflection.

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. A comparative evaluation of. See the table below. For example the allowable deflection of a 12ft span floor joist with plaster l 360 is 0 4 12ft divided by 360.

Deflections in concrete slabs and beams 2005 or how to design concrete structures using eurocode 2. Crack width calculation where applicable is also discussed. This rigorous method is described in greater detail elsewhere e g. Note it gives the allowable deflection based on a fractional span quantity so a larger denominator will yield less deflection.

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. Design issues a few years ago floors we r e de signed using astm a36 steel 36 000 psi yield strength and al. 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. The concrete society publication.

Concrete s modulus of elasticity is between 15 50 gpa gigapascals while steel s tends to be around 200 gpa and above. Concrete structures codes also recommend limits for the calculated total deflection of floors. This is the second of two articles on proper floor framing. If that same joist had gypsum ceiling l 240 the allowable deflection is 0 6.

Detailed numerical examples illustrate the application of each of the methods presented. It covers the consideration of crack formation and its impact on a concrete floor s deflection a critical consideration for conventionally reinforced slabs. The australian standard as 3600 2001 recommends a limit of l 250 table 1. The main reason these are spec d is for requirements of the flooring.

Got bounce appeared in the august 2012 issue of prosales and dealt with mitigating floor deflection in new home construction. 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.