This presentation is about the structural systems in tall buildings and also consists of overview of methods of analysis in tall buildings like linear and non linear seismic analysis.

1. HIGH RISE BUILDINGS AND
METHODS OF ANALYSIS
BY: D P Nithin

2. CONTENTS:
INTRODUCTION
EVOLUTION OF HIGH RISE BUILDINGS
DEMANDS AND CHALLENGES
GENERAL REQUIREMENTS OF HIGH RISE BUILDINGS
LOADS ACTING ON HIGH RISE BUILDING
STRUCTURAL SYSTEMS
STABILITY ANALYSIS OF TALL BUILDINGS
DISCUSSION
REFERENCES

3. INTRODUCTION:
Definition of High Rise Building by different bodies
 Emporis standards-
A multi storey structure between 35-100 meters tall or building of unknown height
from 12-39 floors .
Skyscraper is a multi-story building whose architectural height is at least
100m(300 ft).
For buildings above a height of 300m(984 ft) termed as Super tall .
While skyscrapers reaching beyond 600m (1969 ft) are classified as mega tall.
 INDIAN STANDARDS
As per NBC, structure having height more than 15m (5 storey) is called high rise
As per BMC, high rise is above 24m.
As per NMMC(2006), high rise is above 16m height.

4. EVOLUTION OF THE HIGH RISE BUILDINGS.

5. Fig2 Home Insurance Building
,Chicago
Fig3.Ingalls Building,Chicago Fig4.Burj Khalifa, Dubai

6. Fig5.World One Tower, Mumbai Fig6.Mantri Pinnacle

7. DEMANDS FOR HIGH RISE BUILDINGS.
High rise buildings are becoming more prominent these days due to following
reasons
• Scarcity of land
• Greater demand for the business and residential space
• Economic growth
• Innovations in structural systems.
• They have technical and economical advantage in the areas of high population
density.
CHALLENGES:
• Underlying soil having geotechnical risk factors such as bay mud.
• Problems of Elevators and HVAC systems.
• Challenges to fire fighters during emergency

8. GENERAL REQUIREMENTS FOR HIGH RISE BUILDINGS
(IS 16700-2017)
1. ELEVATION
• Height Limit for Structural Systems
• Slenderness ratio (Ht/Bt)

9. • Aerodynamic effects: Elevation profile, facade features of the building and plan,
shape of the building shall be such as to attract minimum wind drag effects.
2.PLAN
• Plan geometry: The plan shall be rectangular (including square) or elliptical
(including circular)
• Plan aspect ratio(Lt/Bt) should not exceed 5
3.STOREY STIFFNESS AND STRENGTH:
• Lateral translational stiffness of any storey shall not be less than 70% percent of the
storey above.
• Lateral translational strength of any storey shall not be less than that of the storey
above.
Lt
Bt

10. 4.DEFORMATION:
• Lateral Drift: Limited to H/500.
• For earth quake load (factored load combinations)-hi/250
5.FLOOR SYSTEM:
• For precast floor systems a minimum screed of 75mm (seismic zone3,4,5) and
50mm (Zone 2).
• Openings in floor diaphragm shall not be permitted along any floor edge.
Unless perimeter are shown to have stability and adequate strength.
• Maximum area of opening in any floor shall not exceed 30% of the plan area of
diaphragm
6.MATERIALS:
• The minimum grade of concrete shall be M30.
• Ultimate strength of reinforcement shouldn’t exceed (1.25 characteristic yield
strength/0.2 percent proof stress)
• No lapping of bars shall be allowed in RC Columns and walls, when diameter
of bar is 16mm or higher as per IS 16172

11. LOADS ACTING ON THE TALL BUILDING:
1.Gravity Loads:
• Dead Loads
• Live Loads
• Snow Loads
2.Lateral Loads:
• Wind Loads
• Seismic Loads
3.Other Loads:
• Impact loads
• Blast Loads

12. STRUCTURAL SYSTEMS IN HIGH RISE BUILDINGS:
The Classification of the structural System was introduced in 1969 by Fazlur Khan.

13. 1.BRACED FRAME STRUCTURAL SYSTEM:
• Braced Frames are considered as vertical trusses resisting lateral loads,
primarily diagonal members that together with the girders, form the web of
the vertical truss and columns acts as a chords.

14. 1.BRACED FRAME STRUCTURAL SYSTEM:
• Bracing members eliminate bending in beams and columns.
• It is majorly used in steel construction
• This system is suitable for multi-story building in low to mid height range.
• Efficient and economical for enhancing the lateral stiffness.
• This system permits the use of slender members in the building.
 An outstanding advantage of braced frame is that ,it can be repetitive with obvious
economy in design and fabrication.
 However, it might obstruct internal planning.
Fig. John Hancock Tower
(241m)

15. 2.RIGID FRAME STRUCTURAL SYSTEM
• In Rigid Frame Structures, beams and columns are constructed monolithically to
withstand moments imposed due to loads.
• The lateral stiffness of a rigid frame depends on the bending stiffness of the columns,
girders and connections in-plane
Rigid End cap

16. 2.RIGID FRAME STRUCTURAL SYSTEM
• It is suitable for reinforced concrete buildings.
• Members of the rigid frame system withstand bending moment, shear force,
and axial force
• 20-25 storey buildings can be constructed.
• One of the advantages of rigid frame is the planning and fitting of windows
due to open rectangular arrangement.
• Advantages of rigid frame include ease of construction ,labor can learn
construction skills easily
• A disadvantage is that the self weight is resisted by the action from rigid
frames.

17. 3.SHEAR WALL SYSTEM:
• It is a continuous vertical wall constructed from reinforced concrete or masonry
wall.
• Shear walls withstand both gravity and lateral loads and it acts as narrow deep
cantilever beam.
• Commonly constructed as core of the buildings.
• It is highly suitable for bracing tall structure either RC or steel structure.This is
because shear walls have substantial in plane stiffness and strength
• Shear wall can economical up to 35 stories.
• Shear walls need not to be symmetrical in plan,but Symmetry is preferred in
order to avoid torsional effects
.

18. 4.CORE AND OUTRIGGER STRUCTURAL SYSTEM
a. Outriggers are rigid horizontal structures designed to improve building overturning
stiffness and strength by connecting the core or spine to closely spaced outer columns.
b. The central core contains shear wall or braced frames.
c. Outrigger systems functions by tying together two structural systems (core system
and perimeter system) and render the building to behave nearly as composite cantilever.
d. Practically, Outrigger systems are used for
buildings up to 70 stories.
e. Not only does the outrigger system decline
building deformations resulting from the
overturning moments but also greater
efficiency is achieved in resisting forces.

19. Fig.Outrigger System.

20. 5. TUBE STRUCTURAL SYSTEM:
• This system consists of exterior columns and beams that create rigid frame, and
interior part of the system which is simple frame designed to support gravity
loads.
• The building behaves like equivalent hollow tube.
• It is substantially economic and needs half of the materials required for the
construction of ordinary framed buildings.
• Lateral loads are resisted by various connections, rigid or semi rigid,
supplemented where necessary by bracing and truss element.
Fig. Types of Tube system

21. Advantages of Tube Structural System
• Offers some clear advantage from material standpoint.
• Allows greater flexibility in planning of interior space since all the columns
and lateral systems is concentrated on the perimeter of structure .
• This allows column free space in the interior.
• Wind resisting system since located on the perimeter of the building means
that maximum advantage is taken of the total width of the building to resist
overturning moment.

22. Dewitt Chestnut
Fig. Framed Tube Structures

23. Trussed Tube System
Fig.Bank of China, Hong Kong
Bundled Tube System
Fig. Willis tower

24. 6.BUTTRESSED CORE
• The buttresses core permits a dramatic
increase in height.
• Its design employs conventional
materials and construction techniques.
• The system consists of a tripod shaped
structure in which strong central core
anchors three building wings.
• It is stable system in which each wings
is buttressed by other two.
• The central core provides the torsional
resistance for the building while the wings
provide shear resistance and increase the
moment of inertia.
• Example –Burj Khalifa.

25. DIFFERENT TYPE OF ANALYSIS FOR THE TALL
BUILDINGS
1.LINEAR STATIC ANALYSIS:
• Also known as Equivalent Static method.
• Based on formulas given in the code of practice (IS 1893 Part 1-2016)
Determination of storey shear and moment
Determination of lateral forces in each floor
Determination of Design base shear Vb
Determination of Fundamental natural period
Calculation of Lumped weight/Seismic weight

26. LIMITATIONS:
• High seismic zones and height of the structure
• Buildings having higher modes of vibration than the
fundamental mode

27. PUSH OVER ANALYSIS :
• Non linear static analysis.
• Used to estimate the strength and drift capacity of existing structure and the
seismic demand for this structure subjected to selected earthquake.
• It is an analysis in which, a mathematical model incorporates the nonlinear
load-deformation characteristics of individual components and elements of the
building which shall be subjected to increasing lateral loads representing
inertia forces in an earthquake until a ‘target displacement’ is exceeded.
Target displacement can be calculated by:
a. Displacement Coefficient Method (DCM)
b. Capacity Spectrum Method (CSM)

28. Response characteristics that can be obtained from the pushover analysis
are
 Estimates of force and displacement capacities of the structure.
 Sequences of the failure of elements and the consequent effect on the
overall structural stability.
 Identification of the critical regions, where the inelastic deformations are
expected to be high and identification of strength irregularities of the
building.

29. RESPONSE SPECTRUM METHOD
• It is a linear dynamic analysis .
• In this approach multiple mode shapes of the building are taken into account.
• For each mode, a response is read from the design spectrum, based on the
modal frequency and the modal mass.
• They are then combined to provide an estimate of the total response of the
structure using modal combination methods.
• Buildings with plan irregularities and with vertical irregularities cannot be
modeled for dynamic analysis by this method.
• Methods:
1.Absolute Sum method.
2.Square root sum of squares.
3.Complete quadratic combination

30. This method is used for the following:
1. Regular building:
• Greater than 40m in height and zone 4 and 5.
• Greater than 90m in height and zone 2 and 3.
2. Irregular buildings
• All frame buildings higher than 12m in zone 4 and 5 .
• Greater than 40m in zone 2 and 3.
Response vs time

31. TIME HISTORY ANALYSIS
• It is a Non Linear Dynamic Analysis.
• Also known as Time History Analysis(THA)
• To perform such an analysis, a representative earthquake time history is
required for a structure being evaluated.
• In this method, the mathematical model of the building is subjected to
accelerations from earthquake record.
• The method consists of a step- by- step direct integration over a time
interval.

32. Fig. Time History analysis

33. DISCUSSION:
• New improved structural systems and new materials in the future can lead
us to even greater heights and more stable building.
• Structural System should be selected such that the system would efficiently
resist the combination of loading that the structure is subjected to.
• The building weight, and thus the vertical load to be supported by the
foundation can be substantial.
• Static analysis is not sufficient for high rise building its necessary to
provide dynamic analysis because of specific & non linear distribution of
forces.
• Time history analysis should be performed as it predicts the structural
response more accurately than other two methods based on damage
assessment of building.
• Nonlinear relationship between force and displacement in multi-storey
building structures may be determined easy enough with the application of
nonlinear static pushover analysis.

34. REFERENCES:
1. Prof. S .Vijaya Bhaskar Reddy, M.Eadukondalu. Study of Lateral Structural
Systems in Tall Buildings, International Journal of Applied Engineering Research,
Volume 13, 2018
2. Mohd Zeeshan, Ahsan Khan. The Stability of High Rise Buildings, International
Journal of Advance research in Science and Engineering, Volume 7, October 2018
3.Sule Yılmaz Erten, Semiha Kartal, A Comparative Study on Structural Analysis
of High-Rise Buildings, International Journal of Scientific Research and
Innovative Technology, Volume 5, No 5, Dec 2018.
4. Christian Sandelin, Evgenij Budajev. The Stabilization of High rise buildings-
An evaluation of the tubed mega frame structure. Uppsala University, Dec 2013.
5. Erik Hallebrand and Wilhelm Jakobsson. Structural design of High rise
buildings, Department of construction Science. Lund's University, 2016.
6.IS Code- IS 1893(Part 1):2016, IS 16700-2017.

35. THANK YOU