This is called the 'fundamental mode', and is the lowest frequency of building response. Most buildings, however, have higher modes of response, which are uniquely activated during earthquakes. The figure just shows the second mode, but there are higher 'shimmy' (abnormal vibration) modes. Nevertheless, the first and second modes tend to cause the most damage in most cases.

1. By
Prof SenthilPandian M
Analysis of building frames

2. Introduction

3. Structural engineering projects can be divided into 4 stages.
1. Planning phase
• Material
• Structural form
• Loads
2. Analysis
3. Design
4. Construction
The design of a structure involves many considerations, among which are 4 major
objectives that must be satisfied.
1) Safety (the structure must carry loads safely)
2) Economy (the stucture should be economical in material and overall costs)
3) Utility (the structure must meet the performance requirement)
4) Beauty (the stucture should have a good performance)

4. Therefore, the purpose of structural analysis is to determine the reactions, internal forces
and deformations at any point of a given structure caused by applied loads and forces.
Types of Structural forms
• Tension and Compression structures
• Flexural beam and frame structures (load carrying is achieved by bending)
• Surface structures (load carrying is by membrane action)

5. 1 kN
Compression
1 kN
Tension

6. Tensile Failure Compressive Failure

7. Strength : Ability to withstand a given stress without failure. Depends on type of material
and type of force (tension or compression).
Stiffness : Property related to deformation. Stiffer structural elements deform less under
the same applied load. Stiffness depends on type of material (E), structural shape, and
structural configuration.Two main types; Axial stiffness and Bending stiffness.
Important Structural Properties

8. Stiffest
Stiffer
Stiff

10. Arch
Arches carry the dominant permanent load case
(usually full dead load) in pure axial
compression.

11. Truss
C
T
C
C
T
Forces in Truss Members

12. 1 kN
Bending

13. Frame
Flat Plate

14. Folded Plate
Shells

15. Support Connections
• Roller support (allows rotation/translation)
• Pin connection (allows rotation)
• Fixed joint (allows no rotation/translation)

16. A beam have a variety of supports.
- roller ( 1-DOF)
- pinned ( 2-DOF)
- fixed ( 3-DOF)

17. The process of defining an ideal structure from a real structure is called modeling. To carry
out practical analysis it becomes necessary to idealize a structure.

18. 18
A beam have a variety of loads.
- point loads
- distributed loads
- applied moments

19. A beam can be classified as statically determinate
beam, which means that it can be solved using
equilibrium equations, or it is ...

20. A beam can be classified as statically indeterminate
beam, which can not be solved with equilibrium
equations. It requires a compatibility condition.

21. Methods of structural analysis
 Force methods - developed by James Clerk Maxwell
in 1864, later developed by Otto Mohr and Heinrich
Muller-Breslau,
 Displacement methods –
 Slope deflection method
 Moment distribution method
 Kani’s method

22. Analyse building frames
1. Approximate methods for vertical loads.
2. Cantilever method for horizontal loads.
3. Portal method for horizontal loads.

23. Substitute frame method
 The moments carried from floor to floor through
columns are very small as compared to the beam
moments; therefore, the moments in one floor have
negligible effect on the moments on the floors above
and below. Therefore, in this method, the analysis of
the multi-storeyed frames is carried out by taking one
floor at a time. Each floor is taken with columns above
and below fixed at far ends, and the moments and
shears are calculated in beams and columns.
 The method is very effective in analyzing any framed
structure under vertical loadings

43.  Motivation talk has to be given to the student
regarding placements in the various fields.
Example structural design concrete building,
Steel structure, evaluation of building etc.,
 At least one or two per semester and all the
student from the school must attended it.

47. Bending Moment in Columns

48. Cont.,

49. Analysis of Multistory frames
subjected to horizontal load
 Height to least lateral dimension greater than 2.
 Load due to Wind
 Seismic forces
 Unsymmetrical building
 Geometric
 Plan
 Mass etc.,

50. Moment and forces
 Portal method
 Cantilever method

51. Portal Method

56. Cantilever method