2.
METHODOLOGY
Each building has its own purposes and importance. Basically, buildings were constructed
based on client requirement, geographical condition of the site, safety, privacy, available
facilities, etc. and designed as:
2.1. Planning Phase
Planning of building is grouping and arrangement of different component of a building so as
to form a homogenous body which can meet all its function and purposes. Proper orientation,
safety, healthy, beautiful, and economic construction are the main target of building planning.
It is done based on the following criteria:
2.1.1. Functional Planning
• Client requirement is the main governing factor for the allocation of space required
which is based upon its purposes. Thus, demand, economic status and taste of owner features
the plan of building.
• Building design should favor with the surrounding structures and weather.
• Building is designed remaining within the periphery of building codes, municipal
bylaws and guidelines.
2.1.2. Structural Planning
The structural arrangement of building is chosen so as to make it efficient in resisting vertical
and horizontal load. The material of the structure for construction should be chosen in such
a way that the total weight of structure will be reduced so that the structure will gain less
inertial force (caused during earthquake). The regular geometrical shape building is designed
as an earthquake resistant structure based on IS1893 (part I):2016.
2.2. Load Assessment
Once the detailed architectural drawing of building is drawn, the building subjected to
different loads are found out and the calculation of load are done. The loads on building are
categorized as below
2.2.1. Gravity load
This includes the self-weight of the building such as structural weight, floor finish, partition
wall, other household appliances, etc. To assess these loads, the materials to be used are
chosen and their weights are determined based on Indian standard code of practice for design
loads (other than earthquake) for buildings and structures:
i. IS 875 (part I):1987 Dead Loads
ii. IS 875 (part II):1987 Imposed Loads
2.2.2. Lateral load
Lateral load includes wind load and earthquake load. Wind load acts on roof truss while an
earthquake act over the entire structure. Wind load calculation is based on IS 875
(part III):1987 and earthquake on IS 1893 (part I):2016
2.2.3. Load Combination
Combination of different loads are based on IS 875 (part V):1987 Load combinations.
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2.3. Preliminary Design
Before proceeding for load calculation, Preliminary size of slabs, beams and columns and the
type of material used are decided. Preliminary Design of structural member is based on the
IS Code provisions for slab, beam, column, wall, staircase and footing of serviceability
criteria for deflection control and failure criteria in critical stresses arising in the sections at
ultimate limit state i.e., Axial loads in the columns, Flexural loads in slab and beams, etc.
Appropriate sizing is done with consideration to the fact that the preliminary design based on
gravity loads is required to resist the lateral loads acting on the structure. Normally
preliminary size will be decided considering following points:
➢ Slab: The thickness of the slab is decided on the basis of span/d ratio assuming
appropriate modification factor.
➢ Beam: Generally, width is taken as that of wall i.e., 230 or 300 mm. The depth is
generally taken as 1/12-1/15 of the span.
➢ Column: Size of column depends upon the moments from both direction and the axial
load. Preliminary Column size may be finalized by approximately calculation of axial load
and moments.
2.4. Idealization of structure
2.4.1. Idealization of support
It deals with the fixity of the structure at the foundation level. In more detail terms, this
idealization is adopted to assess the stiffness of soil bearing strata supporting the foundation.
Although the stiffness of soil is finite in reality and elastic foundation design principles
address this property to some extent, our adoption of rigid foundation overlooks it. Elastic
property of soil is addressed by parameters like Modulus of Elasticity, Modulus of Subgrade
reaction, etc.
2.4.2. Idealization of load
The load acting on the clear span of a beam should include floor or any types of loads acting
over the beam on the tributary areas bounded by 450 lines from the corner of the panel i.e.,
Yield line theory is followed. Thus, a triangular or trapezoidal type of load act on the beam.
2.4.3. Idealization of structural system
Initially individual structural elements like beam, column, slab, staircase, footing, etc. are
idealized. Once the individual members are idealized, the whole structural system is idealized
to behave as theoretical approximation for first order linear analysis and corresponding
design. The building is idealized as unbraced space frame. This 3D space framework is
modeled in SAP for analysis. Loads are modeled into the structure in several load cases and
load combination.
2.5. Modeling and Analysis of structure
Salient Features of SAP2000 v20
SAP2000 v20 represents one of the most sophisticated and user-friendly release of SAP series
of computer programs. Creation and modification of the model, execution of the analysis,
and checking and optimization of the design are all done through this single interface.
Graphical displays of the results, including real-time display of time-history displacements
are easily produced.
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The finite element library consists of different elements out of which the three-dimensional
FRAME element was used in this analysis. The Frame element uses a general, three-
dimensional, beam-column formulation which includes the effects of biaxial bending,
torsion, axial deformation, and biaxial shear deformations.
Structures that can be modeled with this element include:
• Three-dimensional frames
• Three-dimensional trusses
• Planar frames
• Planar grillages
• Planar trusses
A Frame element is modeled as a straight line connecting two joints. Each element has its
own local coordinate system for defining section properties and loads, and for interpreting
output. Each Frame element may be loaded by self-weight, multiple concentrated loads, and
multiple distributed loads. End offsets are available to account for the finite size of beam and
column intersections. End releases are also available to model different fixity conditions at
the ends of the element. Element internal forces are produced at the ends of each element and
at a user specified number of equally spaced output stations along the length of the element.
Loading options allow for gravity, thermal and pre-stress conditions in addition to the usual
nodal loading with specified forces and or displacements. Dynamic loading can be in the
form of a base acceleration response spectrum, or varying loads and base accelerations.
The building is modeled as a 3Dbare frame. Results from analysis are used in design of beams
and columns only (i.e., linear elements). SAP2000 doesn’t design shell elements. Joints are
defined with constraints to serve as rigid floor diaphragm and hence slabs are designed
manually as effect of seismic load is not seen on slab. The linear elements are also designed
primarily by hand calculation to familiarize with hand computation and exude confidence
where we are unable to trust fully on design results of SAP2000. This has been done as we
are quite unfamiliar with fundamentals of FEM analysis techniques based on which the
software package performs analysis and gives results.
As we are working with a computer-based system, the importance of data input is as
important as the result of output derived from analysis. Hence with possibility of garbage-in-
garbage-out, we need to check our input parameters in explicit detail.
Material properties are defined for elements in terms of their characteristic strength i.e., M25
for slabs, beams and M30 for columns. Also, section properties are defined as obtained from
preliminary design. Loading values are input as obtained from IS 875. Loading combination
based on IS 875 (part V):1987 and IS 1893 (part 1):2016 for ultimate limit state and IS
456:2000 for serviceability limit state is prepared. An envelope load case of all load
combinations is prepared to provide us with the envelope of stresses for design.
2.6. Design and Detailing
2.6.1. Design Philosophy
2.6.1.1. Limit State Method of Design for Reinforced Concrete Structures
Design of Reinforced Concrete Members is done based on the limit state method of design
following IS 456:2000 as the code of practice. The basic philosophy of design is that the
structure is designed for strength at the ultimate limit state of collapse and for performance
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at limit state of serviceability. A check for these two limit states is done based on code of
practice to achieve safe, economic, and efficient design
2.6.1.2. Working Stress Method of Design for Steel Truss Member
The design philosophy of working stress method of design is to use working loads at service
state and design the members to perform at characteristic loads with minimum factor of safety
in material strength. This approach makes the design conservative and deterministic and quite
obsolete compared to more logical Limit State Method of Design.
Hence by using different philosophy, the design of beam, column, footing, staircase and other
structural component are done.
2.7. Detailing Principle for Reinforced Concrete and Steel Structures
2.7.1 Ductile Detailing of Reinforced Concrete Structure
Ductile detailing of reinforced concrete structure is done based on IS 13920:2002 for the
provision of compliance with earthquake resistant design philosophy. Special consideration
is taken in detailing of linear frame elements (BEAMS & COLUMNS) to achieve ductility
in the concrete to localize the formation of plastic hinge in beams and not columns to assure
the capacity theory of STRONG COLUMN | WEAK BEAMS.
Detailing provisions of IS 13920:2002 and IS 456:2000 is used extensively for these
members to comply with the relevant codes of practice.
2.7.2. Ordinary Detailing of Reinforced Concrete Structure
SP 34 detailing handbook for IS 456 is used extensively for reinforcement detailing of area
elements (SLABS & STAIRCASE). Defining the slabs to function as rigid floor diaphragm
limits the necessity of special reinforcement provision for slabs eliminating the possibility of
out-of-plane bending. Hence same follows for staircase slabs and detailing is done with the
help of SP34.
Detailing of Substructures (MAT FOUNDATION) is also done based on SP34 to comply
with the design requirement of IS 456:2000.
Reinforcement Detail drawings for typical representative elements are shown in detail in
chapter 7 on structural drawings.
Thus, the detailing rules from different handbooks are followed along with enlisted codes of
practice and then rebar arrangement is finalized. In this way, detailing of reinforcement is
achieved to required specifications by code.
2.7.3 Codal References
The project report has been prepared in complete conformity with various stipulations in
Indian Standards, Code of Practice for Plain and Reinforced Concrete IS 456:2000, Design
Aids for Reinforced Concrete to IS 456:2000(SP-16), Criteria Earthquake Resistant Design
Structures IS 1893 (Part 1):2016, Ductile Detailing of Reinforced Concrete Structures
Subjected to Seismic Forces- Code of Practice IS 13920:2002, Handbook on Concrete
Reinforcement and Detailing SP-34. Use of these codes have emphasized on providing
sufficient safety, economy, strength, and ductility besides satisfactory serviceability
requirements of cracking and deflection in concrete structures. These codes are based on
principles of Limit State of Design.
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2.8. Drawings
As specified in the requirement of the project assignment, the report also includes the
following drawings:
1. Architectural Plan of Typical floors, Elevation and Cross Section of the building.
2. Detailed Structural drawing of full-size beam, full size column, slab, staircase, and mat
foundation. Longitudinal and Cross section drawings are made to represent specifically the
proper detailing of rebar in individual elements, at beam column joints, at the end support of
slabs, in staircase and in the foundation.
2.9. Organization and Preparation of Project Work Report
The project work report is prepared in the standard format availed by the Department of Civil
Engineering.
This project report has been broadly categorized into five chapters; summary of each chapter
is mentioned below:
Chapter 1: Introduction to Project Work
This chapter gives an overview of the project as a whole.
Chapter 2: Methodology
This chapter presents the method used in execution of project from initiation till completion
with brief details of processes.
Chapter 3: Functional and Structural Planning of the Building
The first part of this chapter presents the functional planning of building with reference to
architectural provisions of space, light, ventilation, etc. for specific areas of the building.
The second part deals with the structural planning for seismic resistant design and
justification of number of beams and columns, frames, their orientation/ arrangement.
Chapter 4: Load Assessment and Preliminary Design
In this chapter, justification of material selection, material characteristics are shown. It also
includes calculation of preliminary design of slabs, beams, column, truss and other structural
components.
It also includes idealization of loads and load assessments with load combinations.
Chapter 5: Idealization and Analysis of Structure
This chapter includes the details of idealization of structure and idealization of load for
modeling in computer.
It comprises the analysis result obtained from SAP2000 analysis and the tabular presentation
of storey drift calculation and check of columns for sway and no-sway case. Critical
responses are also tabulated.
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Chapter 6: Design and Detailing
It deals with the earthquake resistance design of beams, columns, slabs, and footings
considering limit state of collapse and serviceability. Design is further influenced by the use
of codes pertinent to earthquake resistant design of building structures. Manual design of
structural elements is done from the analysis results of SAP2000 using IS 456:2000 and
compared with the design given by SAP2000. However, consideration for earthquake
resistant design is incorporated in manual design with reference to IS 1893 (part 1):2002 with
ductile detailing rules governed by IS 13920:2002.
Detailing of structures with ordinary detailing rules for area elements and ductile detailing
for linear elements is done conforming to IS 456:2000 and IS 13920:2002 respectively.
Chapter 7: Drawings
Drawing includes architectural drawing of the building and the structural drawings with
correct detailing as stated in the assignment.
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Flowchart showing Method of design:
STUDY OF ARCHITECTURE
DRAWING
PRELIMINARY SIZE OF
STRUCTURAL MEMBER
MANUAL CALCULATION SAP MODEL ANALYSIS
INCORRECT
TIME ANALYSIS
CORRRECT
LOAD CALCULATION
DESIGN OF STRUCTURAL
MEMBER
CHECK FOR SHEAR, DEVELOPMENT
LENGTH, REINFORCEMENT AND OTHERS
Detailing of structural member
And drawing presentation
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