Beams and Types of Loads on Beams

Introduction to Beams

• Beams are structural members which have their length large compared to their cross sectional dimensions.

• They are commonly used to support roofs in buildings.

• The beams are acted upon by different types of loads and are kept in equilibrium by providing different types of supports.

1. Types of Loads on Beams

i) Point loads or concentrated loads

• The loads acting at a point are called as point loads or concentrated loads. Refer Fig. 4.5.1.

ii) Couple moments

iii) Uniformly distributed load (u.d.l) 

• Uniformly distributed load (u.d.l.) or rectangular load is shown in Fig. 4.5.3.

• Let, W(N/m) be the intensity of u.d.l.

• We have to convert this load into a point load. The magnitude and location of point load is,

Magnitude = W × L

and Position = L/2 (at centre of u.d.l.)

iv) Uniformly varying load (u.v.l)

• Uniformly varying load (u.v.l.) or triangular load is shown in Fig. 4.5.4.

• Let, W(N/m) be the intensity of u.v.l.

• We have to convert this load into a point load. The magnitude and location of point load is,

Magnitude = ½ × W × L

and Position = L/3 (from right angle side)

v) Trapezoidal load

• For trapezoidal load (combination of rectangular and triangular load), we have to divide it into two parts like u.d.l. and u.v.l.

vi) General variable load

• This type of loads are variable or fluctuating loads.

• To convert such load into a point load we have to integrate. Refer Fig. 4.5.6.

Note: While drawing F.B.D. of beams, all distributed loads must be converted to corresponding point load.