Understanding Load Calculations | Structural Design

Load Calculations | Design of Buildings

In our earlier article, we discussed “Different types of loads” and their importance in Structural design.

Now we will move on with our further discussion on the following points:

• Design principle assumption and notation assumed
• Design Constant
• Assumptions regarding Design
• Loads on Beams
• Loads on slabs

Design principle assumption and notation assumed:

The notations adopted throughout are same as given in IS:456:2000

Density of material used in accordance with reference to IS:857-1987s

Sr.no	Material	Density
1	Plain concrete	24 KN/m3
2	Reinforced cement concrete	25 KN/m3
3	Flooring material (cement mortar)	1.00 KN/m3
4	Brick masonry	19 KN/m3

Design constant

Using M20 and Fe415 grade of concrete and steel respectively for columns and footings

Therefore:

Fck – i. e. Characteristic strength for M15 – 15 N/mm2

Fck – i. e. Characteristic strength for M15 – 15 N/mm2

Fck – i. e. Characteristic strength for M20 – 20 N/mm2

Fy – i. e. Characteristic strength for steel – 415 N/mm2

Assumption regarding Design

1. Slab is assumed to be continuous over interior support and partial fixed on the edge, due to monolithic construction of walls over it.
2. Beams are assumed to be continuous over interior support and they frame in to the column at the ends.

Load on Beams

Description of load of slab on beam

The load of slab is dispersed on to the supporting beams in accordance with clause 23.5 of IS:456-1978, which states that the load on beams supporting solid spans, spacing in two directions at right angles and supporting uniformly distributed loads.

Self weight of beams

This load acts on the beams as a UDL, this is calculated after assuming the suitable cross section (by stiffness/deflection consideration) of the beam.

Load due to brick masonry wall

In a framed structure, brick masonry are used to construct curtain walls. They do not carry or transfer any load. Hence, the masonry walls do not have to thick.

Point load from intersecting beam

If there is any beam meeting the beam then the load of that beam is considered as point load.

Loads on slabs

Three types of loads are to be considered for the design of slabs:

1. Dead load of the slab
2. Live load of the slab
3. Floor finish load

Dead load of the slab

Self weight of slab acts:

This load acts as UDL, this is calculated after assuming the 1m wide square strip and suitable thickness consideration.

Floor finish load

This load also acts as UDL and this is calculated after assuming suitable intensity over 1m wide strip.

Live load on the slab

This is the temporary load on its intensity depends on type and occupancy of building.

The intensity can vary with the type of building.