ANALYSIS OF G+3 RCC STORIED BUILDING

K. TARUN KUMARROLL NO: 14951D2009

CONTENTS:

• Introduction and Aim• Details of structure• Gravity Loads Distribution• Equivalent Static Analysis• Design of structure a) Slabb) Beams c) Columnsd) Footing• Response of Structure for different ground motions

AIM:

• To complete analysis and design for a G+3 structure.

• Analysis of a structure is done for both gravity loads and lateral

loads.

• Analysis for gravity loads is done using substitute frame

method and that of lateral loads can be done using two methods

namely static analysis and Dynamic analysis.

• For the analysis of lateral loads, portal frame method is

adopted. Coming to the dynamic analysis seismic analysis are

done.

SCOPE OF THESIS:

Following points will be covered in thesis work :

• Study of design of various elements of building.

• Planning of various components of a building with column positioning

• Introduction of STAAD. Pro.

• Modeling of the building in the STAAD. Pro giving all boundary

conditions (supports, loading etc…) .

• Analysis and Design of various structural components of the modal

building

• Detailing of beams, columns, slab with section proportioning and

reinforcement.

DETAILS OF THE STRUCTURE:

• Floor to floor height = 3m

• Height of plinth = 0.45m above ground level

• Depth of foundation = 1m below ground level

• Bearing capacity of soil = 200 kN/m2

• External wall thickness = 0.23m

• Internal wall thickness = 0.11m

• Thickness of the slab = 0.12m

• Dimensions of beam as 0.3m X 0.23m

• Dimensions of column as 0.3m X 0.3m

MATERIAL PROPERTIES:

As per IS456:2000, table 2;

• Grade of concrete: M20

As per IS456:2000, table 2;

• Characteristic compressive strength of M20 grade: 20N/mm2

• Grade of steel: Fe415

• Density of concrete: 25 kN/m3

LOCATION OF BEAMS AND COLUMNS::

LOAD DISTRIBUTION ON BEAMS :

LX = length of short span = 3.35m

LY = length of long span = 5.48m

W = load per unit area

As per SP 24-1983, clause 23.5;

• Load distribution on short span =

• Load distribution on long span =

Load Calculation according to IS 875:1987 -

• Dead load = slab thickness X density of concrete

= 0.12 X 25

= 3 kN/m2

Slab panel considered is 5.48m X 3.35m

• Live load = 2 kN/m2

Total load acting on beam = 3 + 2 + 1 = 6 kN/m2

S1 is the slab numbering:

• Self- weight of beam = 0.3 X 0.23 X 25 = 1.725 kN/m

B4

B1

B3

B2

The loading is equivalent to uniform load per unit length of the beam :

Load on S1B1 = = 8.425 kN/m

Load on S1B2 = 10.523 kN/m

Load on S1B3 = = 8.425 kN/m

Load on S1B4 = 10.523 kN/m

LEVEL SLAB DEAD LOAD

LIVE LOAD

FLOOR LOAD Lx Ly BEAM1 BEAM2 BEAM3 BEAM4

S1 3 2 1 3.35 5.48 8.425 10.523 8.425 10.523

S2 3 2 1 3.35 4.57 8.425 9.974 8.425 9.974

S3 3 2 1 4.15 5.48 10.025 11.795 10.025 11.795

S4 3 2 1 4.15 4.57 10.025 10.753 10.025 10.753

GROUNDFLOOR

S5 3 2 1 1.2 2.2 8.125 4.968 8.125 4.968

S6 3 2 1 1.2 2.2 4.125 4.968 4.125 4.968

S7 3 2 1 1.2 4.57 6.125 7.815 6.125 7.815

S8 3 2 1 4.15 5.48 10.025 11.795 10.025 11.795

S9 3 2 1 4.15 4.57 10.025 10.753 10.025 10.753

S10 3 2 1 3.35 5.48 8.425 10.523 8.425 10.523

S11 3 2 1 3.35 4.57 8.425 9.974 8.425 9.974

• The loads on each frame in both X and Y-directions after the distribution of load on to beams :

BENDING MOMENT DIAGRAM OF STRUCTURE:

SHEAR FORCE DIAGRAM OF STRUCTURE:

EQUIVALENT STATIC

ANALYSIS

OBJECTIVES:

• The objective of seismic analysis is to access the force and

deformation demands and capacities on the structural system and

its individual components.

• ESA determines the displacement, and forces in a structure or

components caused by the loads that do not induce significant

inertia and damping effects.

• ESA can be used to calculate the structural response of bodies

spinning with constant velocities or travelling with constant

accelerations since the generated loads do not change with time.

• Initially there was no understanding of origin and occurrence of

earthquakes.

• Now we have significant information about origin of earthquakes

and their recurrence periods in different parts of the world.

• Earthquakes are occasional forces on structures that may occur

rarely during the lifetime of buildings.

• Among the several prevalent scales, Richter scale is the most

commonly used scale for magnitude of earthquake.

• Steady loading and response conditions are assumed in ESA.

The main factors that should be taken into consideration in constructing a building with earthquake forces are as follows:

• Zone factor (Z):

Zone II III IV V

Zone factor(Z) 0.1 0.16 0.24 0.36

SOIL TYPE:

• Soils are of different types namely, soft, medium and hard soils.• Recorded earthquake motions show that the response spectrum shape

varies with the soil profile at the site.

IMPORTANCE FACTOR ( I ):

• Importance factor is used to obtain the design seismic force depending on the functional use of the structure, characterized by hazardous consequences of the risk resulting from its failure.

• However, critical and important facilities must respond better in a earthquake than an ordinary structure.

I = Importance factor

= 1.5 for hospitals, schools, cinema halls, monumental structures, telephone exchanges, and 1.0 for others

Therefore, for residential buildings; Importance factor = 1

RESPONSE REDUCTION FACTOR ( R ):

• Response reduction factor is the factor by which elastic responses of the structure, such as base shear and element forces.

• Generated under the action of earthquake shaking as specified in IS1893:2002 are reduced to obtain the design values of the responses.

For an ordinary RC moment resisting frame (OMRF) = 3(IS 1893-2002, Provisions, clause 5)

CALCULATION OF DESIGN BASE SHEAR:

• Design base shear is the maximum expected lateral force that will occur due to seismic ground motion at base of the structure.

• Design Base Shear = design acceleration coefficient x seismic weight of the structure

Vb = Ah x W (Clause 7.5.3 of IS 1893, Part 1)

• Design horizontal acceleration coefficient, Ah = (Clause 6.4.2 of IS 1893, Part 1)

Sa/g values can be taken for different soils and for 5% damping from the graph provided in IS1893:2002 shown below.

• Sa/g = Spectral acceleration coefficient for Hard, Medium or Soft soil, 5% damping

= 2.5 for T <= 0.40 and 1.00/T for T > 0.40 (Hard soil) = 2.5 for T <= 0.55 and 1.36/T for T > 0.55 (Medium soil) = 2.5 for T <= 0.67 and 1.67/T for T > 0.67 (Soft soil) 

Natural time period (T) is defined as the time period of un-damped free vibration.

As per IS 1893:2002,• T = 0.1n (for moment resisting frames without bracing or shear walls) • T = 0.075h0.075 (for RC framed buildings)• T = 0.09h/d0.5 (for framed buildings with in-filled masonry walls)

where h is the height of the structure and

d is base dimension of the building along the considered direction of earthquake.

Lateral load distribution with height by static analysis method:

storey level

WI

(kN)HI

(m)Wi x Hi2 1000

Wi x Hi2

∑Wix Hi2

lateral force in ith level for earthquake loads in

directions (kN)

X Y

4 18.5825 12 103.475 0.4424 69.343 69.343

3 1034.812 9 83.819 0.3584 56.176 56.176

2 1034.812 6 7.253 0.1592 24.967 24.967

1 1034.812 3 9.313 0.0398 6.241 6.241

∑ 233.86 156.743 156.743

DESIGN OF SLAB:

Length in X-direction, Lx = 3.35m

Length in Y-direction, Ly = 5.48m

Ly/Lx = 5480/3350 = 1.635 < 2

Hence it is two way slab.

DESIGN OF EXTERIOR BEAM:

RCC beam construction is of two types:• Singly reinforced beam• Doubly reinforced beam