A Series of 3 presentations for Understanding basics of stresses in structures for Architecture students.

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

2. Introduction
An understanding of scientific principles allows
us to understand and even to design any
structure, even if we have no experience with
that structure previously. And this is true even
for the empirically designed structures of the
ancient, medieval, and Renaissance eras,
because the science is always there, manifested
in the actual behavior of the physical structure.

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

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

5. 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

6. 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.

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

9. 1. TENSION (pure)
2. COMPRESSION (pure)
3. TENSION AND COMPRESSION
(in different members of same
structure)
4. TENSION AND COMPRESSION
(together in members of same
structure) causes SHEAR AND
BENDING

10. TENSION
LESSON 1

12. TENSION MEMBERS
• Strength of a member in tension is not dependent
on its length( as stated by Leonardo DiVinci) but is
directly dependent on the cross sectional area
of the member( as stated by Galelio).
• Hence a member of cross sectional area 10 sq
inches is twice stronger than a member with cross
sectional area of 5 sq inches. if they of the same
material.

13. What is this internal reaction that resists
the external load?
• When a load is applied it causes the molecules in
the body to move away from each other due to the
elongation , the internal force is the attraction
between the molecules these molecules tend to
move away, but the chemical bonds between the
molecules are strong and they resist this
deformation hence this resistance over the entire
Cross sectional area keeps the lower portion in
equilibrium.

14. Stress is independent of geometry and material
A steel square 2sqmt and a circular
concrete10sqmt. col. can have the
same stress as stress is force
/area so eg. 2000kg/2 and
10000kg/10 both have 1000kg/m2
stress.
Area =2 sqmt Area = 10 sqmt
2000 kg
10000 kg
steel concrete

18. FUNICULAR FORMS
( Tension forms)

19. Ans: CANTENARY
no load
What is The form taken by a
chain , rope, under its own
weight called?

21. Ans: PARABOLA
under loading
What is The form taken by a
main cables of a suspension
bridge called?

23. FUNICULAR FORMS are
forms taken by cables
under any given loads.
hence they are always in
TENSION

25. • If the angle of the cables is steeper the forces
are reduced.
• As cables become horizontal they will fail to
support the forces/loads

26. SUSPENSION BRIDGES
• By distributing the loads evenly along the length of cable ,the
tensile forces acting on cable can be reduced.
• Cables not connected to
tower they run over
them, hence tower have
no horizontal forces.
Tower is purely in
compression.

28. GOLDEN GATE BRIDGE

29. CABLE STAY BRIDGES

30. • Cables are connected to the towers
hence tower have horizontal forces
which cause buckling along with
compression hence they are bigger
in size.
• They are not purely in compression
• If Spans are Shorter ,towers are
thicker and stiffer

31. FAN SHAPE

32. HARP ARRANGMENT

33. HARP ARRANGMENT

34. PERTH AUSTRALIA

35. 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

36. 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.