load calculation with practical example

load calculation of any structure can be determined by calculating the load of element acting on it, to calculate the load of an element we have to multiply the density with dimension of that particular element and finally calulating the reaction force.

As we can see in the above picture two walls and one column is acting on the beam, first we need to draw FBD or the loading diagram.

Assumption

we will assume the beam beam is having pinned support at both the ends, though in practical almost any building structure is supported with fixed support but here just for example we will assume it to be pinned supported.

beam size = (0.3×0.25×3)m

column size = (0.3×0.3×3)m

wall size –

wall1 = (0.25×1.5*3)m

wall2 = (0.25×1.2×3)m

Drawing the FBD for load calculation

To draw the loading diagram or FBD we need to calculate the wall of column and walls.

calculation of loads –

density of brick = 19KN/m^3

load of Wall1 = 0.25*1.5*19 = 7.125 KN/m

load of Wall2 = 0.25*1.2*19 = 5.75 KN/m

density of RCC = 25KN/m^3

column load = 0.3*0.3*25 = 2.25 KN/m

since, we have two unknown reaction on the beam i.e., RA and RB.

to solve two unknowns, we need two equation.

1st equilibrium equation

∑FY=0, (SUMMATION OF VERTICAL FORCE) 

we will take upward force as positive and downward force as negative.

RA – (7.125*1.5) – (2.25*0.3) – (5.75*1.2) + RB = 0

RA+RD = 18.262 KN – (1)

2nd equilibrium equation

∑M=0, (SUMMATION OF MOMENTS) 

∑MD=0

we will take clockwise moment as positive and anti clockwise moment as negative.

(RA*3)-(7.125*1.5*2.25)-(2.25*0.3*1.35)-(5.75*1.2*0.6) = 0

RA = 9.699 KN

from eqn -1

RD = 18.262-9.699 = 8.563 KN

Staad FBD

Staad Reaction

load calculation staad

Note

we are only calculating the reaction of the load acting on the beam and will leave shear force and bending moment, to understand the concept of shear force and bending moment check out the other post.

we have not considered dead load here as its just an example to show how to draw FBD of loading and to analyze a structure to find the reaction force of that particular structure.

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