Lecture 8
Load Transfer from Slabs to Beams
One-way slab
Two-way slab
Two types of load distribution to beams
Isolated One Way Slab
Continuous One Way Slab
Continuous One Way Slab
Continuous One Way Slab
Isolated Two Way Slab
Continuous Two Way Slab
One-way slab
Two-way slab
Two types of load distribution to beams
Load Carried by the Beam
Beam Supporting One-way Slab(ly/lx > 2)
Interior Beam Exterior Beam
Width of slab supported by interior beam = lx
Width of slab supported by exterior beam = lx/2 + Cantilever width
Load Carried by the Beam
Beam Supporting Two-way Slab (ly/lx≤ 2)
Exterior Long Beam
Interior Short Beam
Beam Supporting Two-way Slab (ly/lx≤2) contd…
Interior Shorter Beams
For simplification this triangular load on both the sides is to be replaced by equivalent UDL, which gives same Mmax as for the actual triangular load.
Beam Supporting Two-way Slab (ly/lx≤2) contd…
Beam Supporting Two-way Slab (ly/lx≤ 2)contd…
Exterior Long Beam lx/2
Beam Supporting Two-way Slab (ly/lx≤ 2)contd…
Exterior Long Beam
- Factor F converts trapezoidal load into equivalent UDL for maximum B.M. at center of simply supported beam.
For Square panel R = 1 and F = 4/3
Beam Supporting Two way Slab (ly/lx≤2)contd…
Exterior Long Beam
Beam Supporting Two-way Slab (ly/lx≤2) contd…
Wall Load (if present) on Beam
UDL on beam
Wall Load on the Lintel
Equivalent UDL on lintel if height of slab above lintel is greater than 0.866L
kN/m
tw= wall thickness in “mm”
L = Opening size in “m”
If the height of slab above lintel is less than 0.866L
Total Wall Load + Load from slab in case of load bearing wall
UDL = (Equivalent width of slab supported) x (Slab load per unit area)
= m x kN/m2 = kN/m
Slab Load per Unit Area
Top Roof
Slab Thickness = 125 mm
Earth Filling Brick Tiles
= 100 mm
= 38 mm
Slab Load per Unit Area (contd…)
Top Roof
Live Load
WL = 200 kg/m2
Total Factored Load, Wu
Slab Load per Unit Area (contd…)
Intermediate Floor
Slab Thickness = 150 mm
Screed (brick ballast + 25% sand) = 75 mm
P.C.C. = 40 mm
Terrazzo Floor = 20 mm
Slab Load per Unit Area (contd…)
Intermediate Floor
Live Load
Occupancy Live Load = 250 kg/m2
Moveable Partition Load = 150 kg/m2
WL = 250 + 150 = 400 kg/m2
Slab Load per Unit Area (contd…)
Service Self Wight of Beam = b x h x 1m x 2400
Self Weight of Beam
Self weight of beam is required to be calculated in at the stage of analysis, when the beam sizes are not yet decided, so approximate self weight is computed using above formula.
Concluded
