This is part 3 in the series of presentations for understanding stresses in structure at First year level in Architecture.

1. Part 3:Architecture First Year
UNDERSTANDING STRESSES
IN STRUCTURES- Tension and
Compression together
Prepared By: Ar. Harshada A.Bramhe
For 1st yr B’Arch Students

2. ENGINEERING MECHANICS
• PHYSICAL SCIENCES THAT DEALS WITH THE
FORCES THAT ACT ON A BODY.
• A BODY: ANY PHYSICAL OBJECT EG. A BOX
• SAY ITS 2KG WHICH MEANS THAT THERE IS A
FORCE OF 2KG ACTING ON THIS BOX IN THE
DOWNWARD DIRECTION.

3. LOADS ( FORCE)
LIVEDEAD
REACTIONS
FORCE DEVELOPED
AT THE SUPPORTS
IN RESPONSE TO
THE APPLIED LOADS

4. CONCEPTS OF STRUCTURAL ANALYSIS
LOADS
REACTIONS( a force
developed at the
supports in response to
the applies loads
EXTERNAL
FORCES
TENSION
COMP
RESSI
ON
INTERNAL
FORCES(
CAUSED BY
THE EXTERNAL
FORCES)
TENSION
COMPRESSI
ON
STRESS( INTERNAL
FORCE DISTRIBUTED
OVER THE ENTIRE
CROSS SECTIONAL
AREA OF THE
MEMBER) always
expressed as force
per unit area
STRENGTH OF
MATERIAL (
VALUE OF STRESS
THAT THE MATERIAL
CAN CARRY)
EVALUATE THE PERFORMANCE OF MATERIAL
STRESS< STRENGTH OF MATERIAL THE MATERIAL WILL
NOT FAIL but
IF STRESS > STRENGTH OF THE MATERIAL IT WILL FAIL
1.
2
4
5.
3

5. What does it mean for a structure to
carry loads?
• A structure carries loads successfully if:
The stresses caused by external forces
are less than the strength of the
associated materials.

6. Number of beads on
shallower side balance
the no. of beads on
steeper side

7. All vertical forces are balanced
If a trains comes and slams its breaks from left we need a
horizontal reaction at support to counter balance that force
created . We need to also balance all horizontal forces so
that the bridge is in equilibrium

8. 1. TENSION AND COMPRESSION
(in different members of same
structure)
2. TENSION AND COMPRESSION
(together in members of same
structure) causes SHEAR AND
BENDING

9. TENSION AND
COMPRESSION IN
DIFFERENT MEMBERS
OF THE SAME
STRUCTURE

10. TENSIGRITY STRUCTURES

11. TENSEGRITY SCULPTURES AS
FLOATING COMPRESSION.
• Kenneth Snelson is a sculptor and one of the first to
build tensegrity sculptures. He defines tensegrity
“ As A Closed Structural System Composed Of
Compression Struts Within A Network Of Tension
Tendons”.
And the word tensegrity was coined by Buckminster
Fuller in the 1960s, by combining the words tension
and integrity.

12. • TENSIGRITY STRUCTURES

13. TRUSSES- THE POWER OF THE TRIANGLE

14. • According to Hibbeler, "a truss is a structure composed of
slender members joined Together at their end point." And
the joint at those end points is kind of the key to a truss.
• Truss members are pinned together. Every joint in a truss
will be pinned.
• They can rotate independently of each other.
• So if this structure somehow moves Horizontally or
vertically they'll move together. But they'll rotate
independently. And that's the definition of a pin joint.
• Another key, with trusses is all the loads will be applied to
the joints.

15. TRUSSES

16. WHAT IS THE OPTIMUM MEMBERS IN
A TRUSS ?
NO. OF BARS + 3 = 2 x NO.OF JOINTS
FORMULAE

17. WHAT HAPPENS WHEN FORCES ARE APPLIES?
LOAD IS APPLIED AT THE JOINTS
COMPRESSION TENSION

18. IF DIAGONALS ARE REVERSED THE MEMBERS CARRYING TENSION AND
COMPRESSION CHANGE
IF HEIGHT OF TRUSS INCREASED THE FORCES WILL DECREASE
COMPRESSION TENSION

19. TENSION AND
COMPRESSION IN
SAME MEMBERS OF
STRUCTURE

20. OLDEST EXAMPLE OF USE OF BEAM LION GATEIN
GREECE BRONZE AGE CIVILIZATION
USE OF BEAMS
WHAT IS A BEAM?
IT IS A STRUCTURAL MEMBER THAT IS
SUBJECTED TO TRANSVERSE LOADING I.E.
LOADING THAT IS APPLIED PERPENDICULAR TO
THE AXIS OF THE MEMBER.IT resists load BY
BENDING WHICH IS ALSO CALLED FLEXURE.

21. A BEAM HAS 3 MAIN
PHYSICAL
CHARACTERISTICS:
1. How its supported i.e
support configuration
(simple, continuous
,cantilever
2. 2.Cross section area
3. Profile
SIMPLE SUPPORT
CANTILEVER
CONTINUOUS SUPPORT

22. EG OF HOW TO ANALYSE A BEAM
ON THE CROSS SECTION OF THE
MEMBER THE 2 INTERNAL FORCE
DUE TO EQULIBRIUM BOTH THE
FORCES ARE HORIZONTALAND HAVE
TO COUNTER BALANCE EACH

23. DUE TO THESE EQUALAND
OPPOSITE FORCE A ROTATION IS
CAUSED AT THE CUT END OF THE
BEAM SECTION
THE TENDENCY OF A FORCE TO
CAUSE ROTATION IS CALLED A
MOMENT.
THE EFFECT OF INTERNAL
TENSION AND COMPRESSION IS
EQUAL TO THE MOMENT.

24. HIGHER MOMENT OF INERTIA ( MASS IS AWAY FROM NEUTRAL AXIS)
PRODUCES LESSER STRESS.

25. TORSION OR TWISTING
I SHAPED BEAM HAS
LOWER RESISTANCE
TO TORSION OR
TWISITING SINCE ITS
AN OPEN SHAPE NOT
CLOSED.
HOLLOW BOX SECTION IS A CLOSED
FIGURE, HENCE IT HAS HIGHER
RESISTANCE TO TORSION OR
TWISTING AND ALSO HAS A HIGHER
MOMENT OF INERTIA.

26. THE DEPTH OF BEAM IS
GOVERENED BY MOMENT
DIAGRAM
MAX. BENDING MOMENT
MAX DEPTH OF BEAM
THE DEPTH OF BEAM IS
GOVERENED BY
NEGATIVE MOMENT
DIAGRAM
MAX. NEGATIVE
BENDING MAX.
MAGNITUDE HENCE
MAX. DEPTH OF BEAM

29. IMPORTANT POINTERS
• Ropes, chains ,cables will always be in tension they cannot take
compression.
• Strength of member in tension is not dependent on it length but is
dependent on the cross sectional area of the member.
• If body is in equilibrium then the External forces= Internal forces
• If stress < strength of material it will not fail.
• Stress is independent of geometry and material.
• Hollow members have higher moment of inertia
• Members with higher moment of inertia have more resistance to bending
AND buckling.
• Tall columns fail in buckling before they fail in compression
• Short columns will fail in compression before buckling
• Columns are axially loaded beams are transversely loaded.
• “I” shape /open shapes are weaker in twisting and torsion, closed shape
in stronger.
• Optimum members in a truss (3+ NO. OF BARS = 2 X NO. OF JOINTS)

30. References & Acknowledgement
Lectures and videos :Understanding the World’s Greatest Structures: Science
and Innovation from Antiquity to Modernity
Professor Stephen Ressler United States Military Academy at West Point
Lectures and videos : Youtube DartmouthX –The Engineering of Structures
around us.
Images from Google.com

31. Thank You
This Presentation has been developed by Ar. Harshada A Bramhe( Academician) .It is in 3
parts for First year B’Arch students to understand the Basics of Stresses- in Structures.