6. cperez.eps@ceu.es
molina.eps@ceu.es
STRUCTURAL ANALYSIS I
DEGREE IN ARCHITECTURE
Year 3 Term 1
19/20 CLASS 4
WHEN THE DEGREE OF INDETERMINACY IS HIGH,
THE NUMBER OF DEGREES OF FREEDOM IS LOW
SO IT IS LESS TIRING TO APPLY THE SLOPE DEFLECTION METHOD
INSTEAD OF THE COMPATIBILITY METHOD
7. cperez.eps@ceu.es
molina.eps@ceu.es
STRUCTURAL ANALYSIS I
DEGREE IN ARCHITECTURE
Year 3 Term 1
19/20 CLASS 4
EQUATIONS UNKNOWNS COEFFICIENTS
Compatibility Method
(force method or flexibility
method)
COMPATIBILITY between
movements (rotations or
displacements)
Redundant reaction forces
or Moments or internal
forces or moments
Flexibility coefficients(L/EI)
Slope Deflection Method
(equilibrium method or
displacement method)
EQUILIBRIUM of end
moments or joint forces
MOVEMENTS: rotations or
displacements
Bending stiffness (EI/L)
8. cperez.eps@ceu.es
molina.eps@ceu.es
STRUCTURAL ANALYSIS I
DEGREE IN ARCHITECTURE
Year 3 Term 1
19/20 CLASS 4
TO APPLY THE SLOPE DEFLECTION METHOD WE NEED TO KNOW
THE EFFECT OF LOADS applied along the bars IN THE BAR ENDS
(end moments produced by the loads applied along the bars)
THE EFFECT OF JOINT ROTATIONS IN THE BAR ENDS
(end moments produced by the joints rotations)
THE EFFECT OF JOINT DISPLACEMENTS IN THE BAR ENDS
(end moments produced by the joints displacements)
14. cperez.eps@ceu.es
molina.eps@ceu.es
STRUCTURAL ANALYSIS I
DEGREE IN ARCHITECTURE
Year 3 Term 1
19/20 CLASS 4
LET’S SOLVE THIS BEAM APPLYING THE SLOPE DEFLECTION METHOD
THIS METHOD IS ATTRACTIVE IN THIS CASE BECAUSE
THE DEGREE OF INDETERMINACY IS HIGH
THERE IS ONLY ONE DEGREE OF FREEDOM:
the rotation at B
15. cperez.eps@ceu.es
molina.eps@ceu.es
STRUCTURAL ANALYSIS I
DEGREE IN ARCHITECTURE
Year 3 Term 1
19/20 CLASS 4
SLOPE DEFLECTION METHOD STEP BY STEP
1.- HOW MANY DEGREES OF FREEDOM ARE THERE?
(degrees of freedom = unknowns)
2.- WE FIX THE JOINTS AND ANALYSE THE EFFECT OF THE LOAD
DISTRIBUTED ALONG THE BAR IN THE BAR ENDS (end moments
produced by the loads applied along the bars)
3.- WE MAKE THE JOINTS (which rotation is unknown) ROTATE
AND ANALYSE THE EFFECT OF THIS ROTATION IN THE BAR
ENDS (moments produced by the joints rotation)
4.- WE MAKE THE JOINTS (which displacement is unknown)
MOVE IN THE DIRECTION OF THE UNKNOWN DISPLACEMENT
AND ANALYSE THE EFFECT OF THIS MOVEMENT IN THE BAR ENDS
(moments produced by the joints displacements)
16. cperez.eps@ceu.es
molina.eps@ceu.es
STRUCTURAL ANALYSIS I
DEGREE IN ARCHITECTURE
Year 3 Term 1
19/20 CLASS 4
SLOPE DEFLECTION METHOD STEP BY STEP
5.- WE WRITE DOWN THE EQUILIBRIUM EQUATIONS (sum
of the moments at the joints should equal zero)
6.- WE SOLVE FOR OUR UNKNOWNS: ROTATIONS AND
DISPLACEMENTS.
7.- ONCE WE KNOW THE VALUES OF THE ROTATIONS AND
DISPLACEMENTS WE CAN CALCULATE THE BARS END MOMENTS
WATCH OUT!
END MOMENTS ARE NOT EQUAL TO BENDING
MOMENTS!
17. cperez.eps@ceu.es
molina.eps@ceu.es
STRUCTURAL ANALYSIS I
DEGREE IN ARCHITECTURE
Year 3 Term 1
19/20 CLASS 4
SLOPE DEFLECTION METHOD STEP BY STEP
8.- Once we know the values of the end moments WE CAN
CALCULATE SHEAR FORCES.
9.- Once we know the values of the shear forces WE CAN ANALYSE
JOINTS EQUILIBRIUM AND SOLVE FOR AXIAL FORCES.
10.- FINALLY WE CAN DRAW ALL THE DIAGRAMS: BENDING
MOMENTS DIAGRAM (also after 7), SHEAR FORCE DIAGRAM (also
after 8), AXIAL FORCE DIAGRAM.
11.- THE DEFORMED SHAPE SHOULD CONSIDER BOTH THE
ROTATIONS AND DISPLACEMENTS OBTAINED IN 6 AND THE
BENDING MOMENTS DIAGRAM. WE CAN ALSO CALCULATE
EASILY DISPLACEMENTS IN THE MIDDLE OF BEAMS SPANS.