1. CE-416
Pre-stressed Concrete Lab.
Course Teacher: MR. GALIB & MS. SABRINA
Influence Line for Reaction ,Moment & Shear
for Indeterminate Structure
Md. Enamus Salahin.
ID:08.01.03.099
Dept. of Civil Engineering
Ahsanullah University of Science &
Technology

2. INFLUENCE LINE
An influence line is a plot of the magnitude of the resulting
reaction/axial force/shear/moment generated in a beam or
structure as a unit load travels across its length. Influence
lines can be generated for any of these actions
(reactions, axial forces, shears, or moments) in a structure.

3. INFLUENCE LINE
WHY REQUIRED???
* Dead loads are fixed in positions ---- Live loads can change their positions
* Our objective is to establish how to position live loads (a truck or a train) to maximize
the value of certain type
of force (Shear or moment in a beam or axial force in a truss) at a designated section of a
structure.
* To establish maximum design forces at critical sections produced by moving loads, we
frequently construct
influence lines.

4. INFLUENCE LINE
METHODS FOR CONSTRUCTION OF INFLUENCE LINE
BRUTE FORCE METHOD[USES STATICS/MECHANICS TO CALCULATE THE
INTERNAL LOAD OR REACTION]
MULLER BRESLAU PRINCIPAL[DRAW INFLUENCE LINES BY APPLYING UNIT
DISPLACEMENT]
****MULLER BRESLAU PRINCIPAL IS THE MOST GENERAL METHOD FOR
CONSTRUCTING INFLUENCE LINE DIAGRAMS.

5. INFLUENCE LINE
TYPES OF STRUCTURE
**STATICALLY DETERMINATE
**STATICALLY INDETERMINATE

6. INFLUENCE LINE

7. INFLUENCE LINE

8. INFLUENCE LINE
INFLUENCE LINE FOR REACTION & MOMENT[INDETERMINATE BEAM]

9. INFLUENCE LINE
INFLUENCE LINE FOR MOMENT[INDETERMINATE
BEAM]

10. INFLUENCE LINE