Structural design involves studying how forces act on buildings and their components. Loads like weight are transferred through members like slabs, beams and columns down to the ground. An economical structure transfers loads through the shortest distance. Structures are designed to support various loads, both internal like self-weight and external like wind and seismic loads. Structural members must withstand these loads without significant deformation. Forces can be analyzed by their type, such as external or internal, and nature such as tensile, compressive or shear. Forces can act concurrently, parallel, or non-concurrently on structures. They are represented graphically with lines and arrows

1. STRUCTURAL DESIGN I
STRUCTURAL MECHANICS
LECTURE 1

2. INTRODUCTION
• Structural mechanics, or the start of structural
design, is concerned with the study of forces and
how these act on a body, in our case – buildings.
• Each building component has weight which is a
load. This load is a downward acting force that
has to be transferred through various building
members to the earth. These members are slabs,
beams, columns etc.
• An economical structure is that in which the load
transfer is through the shortest distance.

3. Common Characteristics Of Structures
• Structures are designed to support various kinds of loads.
These are self weight of members, live loads on these,
snow loads, water/ earth loads, wind loads, seismic loads,
thermal loads, shrinkage loads and sometimes construction
loads etc.
• All the structural loads are transferred to the ground.
• At the support points structural members generate reaction
forces to resist the various loads.
• External loads and the reactions that resist these loads
produce different kinds of stresses in the structural
member.
• The structural members have to be strong enough to resist
all these external stresses.
• Structural members should not substantively deform under
their own or external applied loads.

4. Types of structures.
Schematic representation

9. • As the structural load is basically a force that
has to be resisted, structural design becomes
a study of forces that act on a structure, the
stresses such forces generate and the
selection and design of materials and forms
that can resist these forces.
• Hence, it becomes important to know the
contemporary use of force units.

10. UNITS OF FORCE
• The Newton is the unit of force derived in the SI
system.
• it is equal to the amount of net force required to
accelerate a mass of one kilogram at a rate of one
meter per second.
• In dimensional analysis, F=ma, multiplying m (kg) by
a (m/s2).
• The dimension for 1 Newton unit is therefore

11. • The dimension for 1 Newton unit can be seen as:
– 1 N is the force of Earth’s gravity on an object with a mass
of about 102 g (1⁄9.81 kg) (such as a small apple).
– On Earth's surface, a mass of 1 kg exerts a force of
approximately 9.8 N [down] (or 1.0 kilogram-force; 1
kgf=9.80665 N by definition). The approximation of 1 kg
corresponding to 10 N is sometimes used as a rule of
thumb in everyday life and in engineering.
– The force of Earth's gravity on a human being with a mass
of 70 kg is approximately 686 N.
– It is common to see forces expressed in kilo-newtons or
kN, where 1 kN = 1,000 N.

12. Classification of forces
1. According to the effect produced by the
force-
a) External force (Push or Pull)
b) Internal force (Resistance)
c) Active force (Cause a body to move or
change its shape)
d) Passive force (prevents the motion or
deformation of a body)

13. Contd.
2. According to the nature of force
a) Action and Reaction
b) Attraction and Repulsion
c) Pull and Push
3. According to the nature of stress produced in the
body-
a) Tensile force
b) Compressive force
c) Shear force

14. COMPOSITION OF FORCES
• Forces can be acting on a number of planes in different
situations but here the study will be limited to ‘co-planer’
system of forces i.e. forces that are acting on only one
plane as that is what is normally required in calculations
required for structures of common buildings.
• Forces can be represented graphically. Force has a value
and a direction so, a line on a scale with an arrow can
represent a force.
• Forces can be:
– Parallel forces
– Concurrent forces
– Non concurrent forces

15. Parallel Forces
Resultant
Concurrent Forces
Resultant
Non-concurrent Forces
Equilibrant

16. • Write a paper on “Structures in Architecture”.