Civil Thinking

Problem Statement

Simply Supported Beam with Point Load

A prismatic beam of span 1 m is subjected to the following loading and support conditions.

Supports:
• Support at x = 0 m
• Support at x = 1 m

Concentrated Loads:
• 10 kN downward at x = 0.5 m

Required:
• Determine the support reactions
• Draw the Shear Force Diagram (SFD)
• Draw the Bending Moment Diagram (BMD)

Structural Configuration

Beam structural configuration

Free Body Diagram

Beam free body diagram

Equations of Equilibrium

Equilibrium equation M = 0 Expanded form P1·0.5 + R2y·1 = 0 Substitution 10 kN×0.5 m + 5 kN×1 m = 0 Solved reaction

Equilibrium equation Fy = 0 Expanded form P1 + R1y + R2y = 0 Substitution 10 kN + 5 kN + 5 kN = 0 Solved reaction

ΣFy check 10 kN + 5 kN + 5 kN = 0 = 0 ΣM check 10 kN×0.5 m + 5 kN×1 m = 0 = 0

Shear Force Diagram

Shear Force Diagram for Simply Supported Beam with Point Load

Shear Force Values

Position (m)Shear (kN)Remark
05Start of beam
0.50Zero shear location
0.55Just before point load / reaction
0.5-5Just after point load / reaction
1-5End of beam
1-5Just before point load / reaction
10Just after point load / reaction

Bending Moment Diagram

Bending Moment Diagram for Simply Supported Beam with Point Load

Bending Moment Values

Position (m)Moment (kN·m)Remark
00BeamStartMoment
00AtPointLoadMoment
0.5-2.5AtPointLoadMoment
0.5-2.5ZeroShearMoment
10BeamEndMoment
10AtPointLoadMoment

Bending Moment Checks at Key Sections

s = 0
(5) × 0 = 0
ΣM = 0
s = 0
(5) × 0 = 0
ΣM = 0
s = 0.5
(5) × 0.5 = -2.5
(-10) × 0 = 0
ΣM = -2.5
s = 0.5
(5) × 0.5 = -2.5
(-10) × 0 = 0
ΣM = -2.5
s = 1
(5) × 1 = -5
(5) × 0 = 0
(-10) × 0.5 = 5
ΣM = 0
s = 1
(5) × 1 = -5
(5) × 0 = 0
(-10) × 0.5 = 5
ΣM = 0

Solution

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