If you find that a slab either fails deflection checks (or passes with a low utilization) then changes will need to be made. There are many areas where adjustments can be made. Adjust slab/panel depths? Adjust reinforcement?
Best way to deal with excess slab deflection is to increase thickness. That deflection is happening because the slab isn't stiff enough, and stiffness is based on moment of intertia. You can add more steel if you'd like, but I guarantee that increasing depth will be more efficient than adding steel.
According to the BCA and AS, for residential and commercial structures, the allowable total deflection for slabs is L/250, where L is the clear span of the slab. This means that the maximum deflection should be no more than 1/250th of the clear span.
If your cantilever is supporting elements that could be damaged by large deflections, your maximum allowable deflection is span/360 under live loads and span/240 under live load and long term deflections. Try not to exceed 40mm long term, or 20mm short term.
The maximum deflection of a fully loaded residential floor allowed by most modern building codes is L/360.
Generally, there is a rule of thumb that says deflection should not exceed L/360. This means that the maximum deflection should not be more than span divide by 360. For example if you have a 10 meter beam, then the deflection should not be more than 10000/360 = 27.8mm.
Deflection is often associated with denial and blame-shifting, which involve evading unpleasant thoughts or feelings and attributing responsibility for undesired outcomes to others.
Deflections in reinforced concrete floor slabs and balconies are caused by bending of the floor slabs due to both dead weight and imposed live loads. The creation of new access points can cause further problems of stability which will need to be addressed.
w = k (a4*q / E*h3 ) Where, w = deflection normal to slab; a = span along X-direction; E = Modulus of elasticity; and h = slab thickness.
Long-term deflection in slabs is the deflection or deformation that occurs over time due to creep, shrinkage and concrete cracking. This is an important consideration in the design of reinforced concrete structures.
The final deflection due to all loads including effects of temperatures ,creep and shrinkage and measured from the as cast level of the support of floors , should not normally exceed L/250.
To reinforce a concrete slab, rebar rods are positioned across the entire slab at regular intervals, both lengthways and widthways. The rods should be tied together with suitable reinforcement ties, and the entire rebar structure should be supported from below, using appropriate positioning tools.
Generally, we calculate deflection by taking the double integral of the Bending Moment Equation means M(x) divided by the product of E and I (i.e. Young's Modulus and Moment of Inertia). The unit of deflection, or displacement, will be a length unit and normally we measure it in a millimetre.
The deflection in compass needle is maximum when the conductor through A is perpendicular to the plane of paper and the magnetic field due to straight current conductor lies in the plane of paper.
Deflection could be reduced by increased the stiffness or flexural rigidity of the beam. It can be increased by using material with high Young's modulus, and/or by increasing the moment of inertia of the cross section of the beam.
(ii) The deflection including the effects of temperature, creep and shrinkage occurring after the erection of partitions and the application of finishes should not normally exceed span/350 or 20 mm whichever is less.
Subfloor unevenness cannot be greater than 3/16 of an inch over a 10-foot span or 1/8 inch over a 6-foot span. Subfloors must not slope more than ½ inch per 6 feet (25 mm per 1.8 m) Subfloors must be structurally sound.
Using a laser level: Set up the laser level so that it casts a horizontal line across the room at a fixed height from the floor. Measure the distance from the floor to the bottom of the straight edge or laser line at several points along its length, particularly where you expect the most sag. Record these measurements.
Answer: As a general rule, the allowable amount of deflection is l/360, where l is span length in inches. For a stiffer floor, it is common to use l/480. You can also use a length to depth ratio, which is typically 18 for good performance.
Measuring the Flatness and Levelness of a Slab
A laser level may be a more efficient option, because it uses more advanced technology that may reduce your margin for error. You want to measure any gaps between the surface and the level. And if it's less than 1/8 of an inch, it's considered level.