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Analysis of g+3 rcc storied building
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Transcript of Analysis of g+3 rcc storied building
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