**SOFTWARE FOR
INTEGRATED ANALYSIS DESIGN OF RCC BUILDINGS (IADB)**

It also carries out the load calculations and generates
the data for Analysis Module. The load calculation includes:

Transfer of floor loads acting on panel/sub-panel and end
reactions of secondary beams to the main beams and
Determination of fixed end forces at the end points of the main beams

The load calculations can
only be performed for rectangular panel supported on 4 or 5 columns and having
layout of the secondary beams similar to one of the pattern as given in the
user manual.

·
Slabs
and

·
Isolated
footings

according to relevant codal
provisions given in IS:456 and IS:13920. It also prepares the tables of details
of reinforcement for beams and columns in the format currently being used in
the structural drawings. It also estimates the quantities of steel for each
diameter of bars and volume of concrete used in beams and columns. In addition,
it also carries out analysis of raft foundation using the finite difference
method.

**1.2 SCOPE OF INPUT**

Only one data file is to be prepared by the user. This
data file comprises of the following details. In addition, the user is prompted
to key in few data during execution of various programs.

**A) Frame geometry
(required for analysis**)

The number of bays and storeys
define the geometry of a frame. The identification number of main beams defines
the bays. The main beams are defined by the identification number of left and
right end columns and length of beam measured centre to centre of the columns The storey heights are defined once for the whole building
and are identical for all the frames. The co-ordinates of first and the last
column points define the locations of frames.

**B)
****Panel geometry (required for load
calculation)**

The identification numbers of
surrounding main beams defines the panels. These panels are used only for load
calculation purpose. The structural stiffness of these panels is not considered
in structural analysis.

The layout
of secondary beams within a panel and floor loading on sub-panels and line
loads on secondary beams are defined in accordance with details given in user
manual.

·
For
each beam, the values of the fixed end moments and shears and mid span moments
due to dead and live loads.

·
For
each column, the values of axial loads due to dead and
live loads and self-weight of the column. The axial loads are calculated based
on fixed end shear transferred from beams connected to it.

·
For
each column, the values of the axial load per unit of contributory area
supported by the column.

The contributory area for a column is determined
considering the applicable part of the areas of the surrounding panels on which
loads are prescribed. In case the user has carried out the load calculation
manually for one or more surrounding panels of a column, the axial load per
unit area for such column will be calculated by ignoring the contributed area
of such panels. However, the load transferred from such panels to the column
will be considered in determining the load on the column if the user has
prescribed additional fixed end forces on surrounding beams of such
panels. Therefore, the value of axial
load per unit area for such columns will be higher than the actual axial load
per unit area, which considers the contribution of area from all the
surrounding, panels.

·
For
each floor, the values of the lateral storey forces due to earthquake

**B) Analysis output**

In
first part of analysis output, the details of data prepared by load module for
analysis module are reproduced. This part of the analysis output is not useful
for the users.

The second part of the analysis output i.e. including and
beyond structural displacements is useful for the user. This part of analysis
output comprises of following details.

·
For
each floor, the values of structural displacement along the global X and Y-axis
and rotation about centre of rigidity for the basic of five load cases.

The first 3 load cases:
that is (I)(II)(III) corresponds to the three
different distributions of vertical loads. Load case (I) corresponds to dead
loads on all the spans of the frame and load case (II) and (III) corresponds to
live loads on odd and even spans, respectively. Load case (A) corresponds to
lateral storey force applied along X- direction and load case (B) corresponds
to lateral storey forces applied along Y- direction.

·
The
details of the load combinations.

·
For
each floor, the values of lateral displacement of each frame for all the load
combinations.

·
For
each floor, the value of design forces for each column line of the frame for
all the load combinations.

For column design
forces, the user may only refer to major axis moment’s (top and bottom) axial
force and major shear. The other details like torsion moment, minor axis
moments and minor shear may be ignored as the torsional
stiffness and minor axis stiffness of the columns is neglected in structural modelling.

·
For
each floor, the value of the design forces for each beam for all the load
combinations.

**C) Column Design Output **

The column design output comprises of following details:

·
The
grade of concrete mix and height of column for each floor.

·
The
dimensions of column along X and Y-axes and effective cover for each column.

·
The
load factor for each load case

·
The
axial loads, bending moments about both the axes, percentage of area of
longitudinal reinforcement for all the load combinations of each column. The
quantity of steel required for all the column of a particular floor.

These details are arranged storey wise for each column.

**D) Beam
Design Output**

The beam design output comprises of following details:

·
The
design percentages and areas of
longitudinal steel at the top
and bottom of three sections of each beam i.e. at left end, right end and mid
span

If the design percentage of steel is less than the minimum
prescribed in the code, the minimum percentage of steel is adopted.

·
The
area of stirrups at both ends of the beam.

**E) Column Detailing Output**

The output of column detailing comprises of the following
details for each column

·
Dimensions
of columns along X and Y-axes.

·
Grade
of concrete mix for each floor.

·
Longitudinal
bars at corners and both the faces in each floor.

·
Spacing
of stirrups and reference number of stirrup type in each floor.

**F) Beam Detailing Output**

This output comprises of following details for each frame
and for each floor:

·
Grade
of concrete and steel.

·
The
number and dia. of bars at top and bottom the various
sections of the frame.

**Beam Drawing Table**

It comprises of the following details for each beam in a
standard tabular format currently being used in CPWD

·
Size
and span of the beam

·
Longitudinal
reinforcement bars and

·
Stirrups

These details are arranged frame wise and level wise.

**Column Drawing Table**

**G) Slab Design Output**

Following outputs are generated.

a)
Complete
design details

b)
Detailing
of bars in tabular form

The design details comprises:

·
Input
details

·
Detailing
notes

·
Factored
moments

·
Required
and provided steel area

·
Detailing
of bars

·
Check
for shear stress and effective span to effective depth ratio

·
Deflection
details

The detailing of bars in tabular form comprises:

·
Identification
of slab panel

·
Plan
dimensions and thickness of slab

·
Detailing
of bars at bottom and top along shorter and longer spans.

**H) Isolated footing Design
Output**

The output comprises the following
details for the footing of each column:

·
Size
of footings and pedestal.

·
Depth
of footing.

·
Reinforcement
along the two directions and detailing.

·
Quantities
of concrete, steel and shuttering.

·
Cost
of concrete, steel and shuttering.

**I) Estimate of Steel and
Concrete in Beams**

The output gives the following details for each floor

·
The
length and weight of longitudinal steel for each diameter.

·
The
length and weight of stirrups for each diameter

·
Volume
of concrete in main beams for each floor.

**J) Estimate of Steel and
Concrete in Columns**

The output gives the following details:

·
The
length and weight of longitudinal steel for each diameter.

·
The
length and weight of stirrups for each diameter

·
Volume
of concrete in column for each grade of concrete.

**1.4 ADVANTAGES**

**1.4.1 Analysis Model**

General structural analysis programs e.g. Space Frame
Program and Finite Element Program etc. have flexibility to model any
complicated shapes of structures. But the input and output of these programs do
not take the advantage of regular characteristic of a building i.e. the
continuity of column lines all through the floors, beams at same floor levels
and rigid floor diaphragm at each storey. Thus, in such programs a building can
not be modelled as assemblage of columns, beams and
floors. That is why the input and output of such programs are
not user friendly and it is difficult to visualize the structural behaviour of a typical building in terms of displacement of
floors and forces in columns and beams.

The analysis program considered here i.e. Three-dimensional
Analysis of Building “(ETABS – Extended Version of TABS) takes the advantages
of the characteristics of buildings stated above. Thus, the input and output of
this analysis program are easy to comprehend.

**1.4.2 Results**

The results of analysis are given column/beam wise for
each floor. Thus, it is easy to understand the outputs by the user. In
addition, the outputs are easy for post processing for design and detailing of
beams and columns.

All the results of analysis, design and detailing of
various structural members are tabulated in very user-friendly format.

**1.4.3 Detailing**

The detailing of longitudinal reinforcement in beams is
carried out considering the continuity of reinforcement at supports. Similarly,
the continuity of longitudinal reinforcement is maintained among various floors
in the columns. Beside, the number of bars in a column is optimised
to provide minimum quantity of steel for longitudinal bars and lateral ties.

The pattern of lateral ties in rectangular columns is
automatically selected by the program based on the numbers of bars on two
adjacent faces. While doing so all the provisions given in I.S 456 are
followed. The length of ties for a particular pattern is determined based on
actual size of the column. This information is used in optimisation
of steel in columns and in determination of quantity of steel of lateral ties.

**1.4.4 Draft Drawing Tables**

The details of reinforcement in **beams, column, and isolated footings** are given in tabular form that
can readily be incorporated in structural drawings.

**1.5 LIMITATIONS**

·
The program is applicable
for regular frame buildings.

·
Member inclined in plane other than horizontal cannot be
considered.

·
Compatibility is not enforced with regard to joint displacement at joints that are common to more than
one frame. Thus axial deformations in columns common to many frames will not be
same; however for design purposes, these column axial forces may be added directly to give reasonable results.
Similarly, the joint rotations of the frames with common members
orthogonal in plan view are mutually uncoupled.

·
Floor levels must be same for all the frames.

·
Torsional stiffness is
neglected for all members.

**1.6 GRAPHICAL USER INTERFACE**

Graphical user interface of IADB
has been developed with the following objectives to perform following
activities in user friendly manner:

·
To
provide common platform for executing the various back-end programs.

·
To
prepare the input data file and simultaneous validation of data.

·
To
facilitate viewing the geometry of the building and properties of various
structural members.

·
To
adjust sizes of overlapping isolated footings.

·
To
determine the fixed and forces for any arbitrary loading on beams.

·
To
view various results of analysis, design and detailing including the draft
drawings.

**OTHER UTILITY PROGRAMMES OF STRUCTURAL ANALYSIS AND DESIGNS**

**3.1 ANALYSIS OF PLANE FRAME
AND TRUSSES**

This program is based on stiffness
matrix analysis. It analyses the plane frame and trusses. The programmer
accepts concentrated load, U.D.L, triangular load or trapezoidal load applied
on the members and joints load.

The output consists of
displacement and rotations of joints, moments at mid span and the ends of
beams, shear force at the ends of beams, axial force and end shears and moments
in columns.

**3.2 DESIGN OF COLUMNS WITH ****LIMIT**** ****STATE**

Two separate programmes
for design of columns are available as given below:-

a) Equal
steel on all four sides

b) Unequal
steel on adjacent sides

The program has been developed for
designing square/rectangular column sections for axial load and biaxial
moments. It is based on limit state method. The codal
provisions, as given in IS:456:2000, for minimum
reinforcement requirement and moments due to, minimum eccentricity in both the
directions are taken into account. In case of long columns, additional moments
due to slenderness can be added to the biaxial moments at the input stage, if
required. The grade of steel considered in this program is Fe 415 only. The
concrete of any grade can be specified for the design.

The program has been developed for
designing square/rectangular column sections for axial load and biaxial moments
and is based on limit state method. The codal
provisions, as given in IS:456, for minimum reinforcement
requirement and moments due to, minimum eccentricity in both the direction are
taken into account. In case of long column, additional moments due to
slenderness can be added to the biaxial moments at the input stage.

The input data consists of the
sectional dimensions of the column, grade of steel and concrete, axial load and
biaxial moments.

The program works out the
percentage and area of reinforcement, check factor and alpha factor of
interaction formula as given in IS:456. In program with
unequal steel on adjacent sides, it gives reinforcement area along both the
axes.

**3.3 ANALYSIS OF STRIP
FOOTINGS BY RIGID METHOD**

In this package, the combined and
raft foundations are analysed using rigid method. The
planer distribution of pressure underneath the foundation is assumed. The
analysis is carried out by simple statics without
taking into account soil-structure interaction. The strip footings can be
sub-divided into several elements as per the requirements of the user in
accordance to points at which moment/shear is to be determined. The nodal
points are defined at the two ends of the elements. This program gives soil
pressure, moments and shear at every node.

**3.4 ANALYSIS OF STRIP FOOTING BY FLEXIBLE METHOD**

Strip and raft foundations are analysed using flexible method wherein soil characteristic
and rigidity of the structure is taken into account. This software analyses the
strip or raft foundations by flexible method using the analogy of beam on
elastic foundation. The foundation is modelled as
beam supported over a bed of elastic springs representing the supporting soil.

The input consists of modulus of subgrade reactions (ks), modulus of elasticity of concrete , loading details at different nodal points and
geometry of the raft.

The program generates deflection,
rotations and soil pressure at different nodes along with moments and shears in
the members.

**3.5 ANALYSIS OF RAFT BY FINITE DIFFERENCE
METHOD.**

This software is based on flexible
method of analysis. The slab type rectangular type raft foundations is analysed as a plate supported on elastic foundation using
finite difference method.

Input consists of number of grid
liens and spacing between grid lines along X and Y direction, raft thickness,
modulus of subgrade reaction and loading details.

Output consists of deflections at
each grid points, bending moments per unit width in both X and Y directions at
each grid points as well as nodal reactions and soil pressures at each grid
point.

**3.6 ANALYSIS OF GRID FLOORS**

This programme analyses the grid
floors consisting of intersecting secondary beams supported on main beams or on
load bearing walls. Mathematically, the grid floors are modelled
as a structure that lies in a horizontal plane with loads acting perpendicular
to the plane of the structure. This programme can
take into account the nonorthogonally intersecting
secondary beams also The connection between intersecting beams are considered
as rigid joints and each joint is assigned a maximum of three components of
displacement i.e. one vertical and two rotational displacements. The programme calculates flexural moments, torsional
moments and shear force for each member.

**3.7 PROJECT MANAGEMENT THROUGH CPM/PERT**

This software essential carries out the analysis of
the project network, comprising of activities and their duration. It identifies
the critical path and critical activities along with the dates of early start,
early finish, late start and late finish. This program also gives the total and
free floats of non-critical activities.

The programme
also projects the Resource allocation for maximum three resources based on
early and late finish dates of activities for each month. The programme also works out the completion dates of
milestones.

**3.8 ANALYSIS OF SPACE FRAME
AND TRUSSES**

This program analyses three
dimensional space trusses / frames of any configuration .This program has been
developed based on stiffness matrix approach. All joints are assumed to be
pinned in space truss and restrained in space frame problem. The program
accepts the data that describe the geometry and loading. It calculates the
joints displacement and end forces for each member.

**3.9 DESIGNING AND DETAILING
OF ISOLATED FOOTING**

The design of isolated footing is
carried out for various combinations of axial loads and biaxial moments. If the user has not opted for fixing one or
both the dimension of footing, the software designs a square footing. The user is given the flexibility of fixing
one or both the dimensions. The software considers only the constant depth
footing. Sloped or stepped footings have not been considered

The software finds out the size of
footing, size and
height of pedestal, depth of footing and the details of reinforcement along both the axes. The
software performs the detailing according to IS:456. The diameter of the bar is also checked for
the requirements of development length. It also calculates the quantity of
concrete, steel and shuttering and cost based on DSR-97.

User has been given the
flexibility of fixing the depth of footing and the pedestal size. In cases
where the parameters fixed by the user lead to unsafe design, appropriate
message is given, accordingly.

**3.10 DESIGN AND DETAILING OF
SLABS**

The software designs and details
the rectangular slab panels in accordance with IS:456-2000.
The depth is optimised satisfying bending, shear and
deflection criteria. Two ways slabs
supported on four sides and one way slabs supported on two opposite sides are
considered. The moments are computed as
per the coefficients given in the code.
Detailing requirements of IS:456 are satisfied.
Though span to effective depth ratio is controlled to satisfy deflection
requirements, deflection is also calculated using expression of moment of
inertia as specified in the code. Sound
engineering practice has been followed for detailing, in addition to the
provisions given in IS:456-2000. The quantity of
concrete and cost of concrete on DSR 97 have also been computed. ** **

**3.11 DESIGN OF
COLUMNS OF ANY SHAPE**

It designs the columns, with axial load and bi-axial
bending moments, of any shape. The regular shapes of columns considered are

i) Rectangular

ii) 'T' (symmetrical about Y axis)

iii) '+' shape (symmetrical about both the
axis)

iv) 'L'

v) 'O' ( Solid )

For regular
shape the programme defines the co-ordinates of the
boundary points of the column section and reinforcement bars. The user may
select the spacing between the main bars, layer of main bars and skin
reinforcement bars.

For any odd
shape (other than regular shapes) the user is to define the co-ordinates of
boundary points of the column and Rbar

For
rectangular sections, it assumes equal amount of steel on opposite sides and
unequal amount of steel on adjacent sides. If user desires, equal amount of
steel can be assumed on all the faces.

For column
sections of shape 'T', '+' and 'L', the program places main bars on the outer
faces of the column and skin reinforcement on the inner faces at the rate of 8
cm^{2} per meter length. This way, the program optimises
the amount of reinforcement required to the carry design loads applied on the
columns.

The program
can take different grades of concrete but only one grade of steel, at present.