7/28/2019 An Architect's Approach to Structures
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:AN ARCHITECTS APPROACH TO
STRUCTURES-by Prof. A.J.Sanyal:
An Architect is basically space planner.
He has to co-ordinate works of various
consultant e.g. structural, HVAC, Mechanical
& Electrical, Acoustics & Illumination etc.
Hence he should have at least working
knowledge of above fields.
Structural options & possibilities & their
behavior under the influence of loads being
most important.
7/28/2019 An Architect's Approach to Structures
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:AN ARCHITECTS APPROACH TO
STRUCTURES-by Prof. A.J.Sanyal:
Structural design of building may be defined as to
channelized all types of loads acting on building during its
lifetime by shortest possible route to the foundation below so
that bearing capacity of soil is not exceeded & structure is safeto use during its life time.
The loads which will be acting on a building during its lifetime
can be classified as:
a) Dead load such as self weight, permanent fixtures etc.
b) Live load such as occupancy loads, movable loads etc.c) Dynamic loads such as wind loads, Earthquake loads etc.
d) Hydraulic loads such as load due to water table in rainy
seasons etc.
e) Impact loads etc.
7/28/2019 An Architect's Approach to Structures
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:AN ARCHITECTS APPROACH TO
STRUCTURES-by Prof. A.J.Sanyal:
Loads can be also classified as:
UDL (Uniformly distributed loads e.g. self weight of
structural members.
Point loads (Loads which acts on very small area e.g.
secondary beam transferring loads on main beam.
Triangular loads e.g. water pressure in water tank,
soil pressure on retaining wall etc.Trapezoidal loads e.g. loads transferred on long beam
of two way slab.
Combination of above loads.
7/28/2019 An Architect's Approach to Structures
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:AN ARCHITECTS APPROACH TO
STRUCTURES-by Prof. A.J.Sanyal:
Due to action of loads three types of stresses are set up in structural
members :
1. Tensile e.g. shell structures, cables etc.
2. Compression e.g. column, struts etc.
3. Bending & tension or bending & compression e.g. beams, truss etc.
4. Stress is force per unit area, while strain is change in length divided by
original length.
5. Standard bending formula is: M/I=F/y or M=fZ , where M= External B.M,
I=Moment of inertia, f= allowable stress in structural members , y=
position of extreme fiber from N.A; Z= Modulus of section.6. In building we are encountered with members as mentioned in type 3
stress category.
7/28/2019 An Architect's Approach to Structures
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:AN ARCHITECTS APPROACH TO
STRUCTURES-by Prof. A.J.Sanyal:
Bending moment & shear force diagrams:
Bending moment about any point can be defined as force x
perpendicular distance from the point in question.
Shear force can be defined as unbalanced force to the right or
left of the section.
B.M. & S.F. diagram is graphical representation of B.M. & S.F.
In general B.M. is maximum where S.F. is zero & S.F. is
maximum where B.M. is zero (Point of inflection).
In cantilever structure B.M. & S.F. is maximum at support.
In a continuous beam/slab advantage can be taken of
cantilever projection, which reduces span moments of adjacent
span.
Propped cantilever is better option as compared to cantilever
projections.
7/28/2019 An Architect's Approach to Structures
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:AN ARCHITECTS APPROACH TO
STRUCTURES-by Prof. A.J.Sanyal:
In simple beam moment is zero at ends & maximum at centre:
wl2/8, while in fixed beam at ends FEM=wl2/12 & centre it is
wl2/24.
In reality beam/slab is neither completely free or simply
supported or completely fixed, but it can be assumed eithernominally fixed or partially fixed.
Hence for practical design for initial sizing of members can be
based on wl2/10 for UDL.
Deflection of beam/slab depends on load , span & end condition
of beam. Fixed beam is stiffer as compared to simple beam.
If the load is doubled BM in beam/slab is also doubled , but
deflection becomes 16 times as deflection= k.wl4 where k= 5/384
for simple beam & 1/384 for fixed beam.
7/28/2019 An Architect's Approach to Structures
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:AN ARCHITECTS APPROACH TO
STRUCTURES-by Prof. A.J.Sanyal:
Important components of any building are :
1.Roof/Floor-truss with roofing materials,
slabs, plank. Decking etc.2.Beams plinth, floor beams etc.
3.Columns/wall-corner column, side column,
central column etc.
4.Foundation/footing-strip footing, isolated
footing, combined footing etc.
7/28/2019 An Architect's Approach to Structures
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:AN ARCHITECTS APPROACH TO
STRUCTURES-by Prof. A.J.Sanyal:
Slabs/beams can be classified based on spanning e.g. one way slab, two
way slab etc.
It can be also classified as per shape e.g. rectangular, square, triangular,
circular etc.
It ca be also classified as per support condition e.g. simple support, fixed
support, continuous support, cantilever etc.
Columns can be classified as/ its effective length e.g. short or long column.
It can be also classified as per position e.g. corner column, side column or
central column etc.
Foundation can be classified as shallow or deep foundation/ pile
foundation. Again it can be strip foundation, isolated footing, eccentric
footing, combined footing, raft foundation etc.
Roof can be sloping roof in A.C./G.I. sheets or tiles, r.c.c. slabs, folded slabs,
shell structures, pneumatic/fabric structures etc.
7/28/2019 An Architect's Approach to Structures
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:AN ARCHITECTS APPROACH TO
STRUCTURES-by Prof. A.J.Sanyal:
Most of the structure falls under the category of bending & tension or bending
& compression , general guide lines can be given as under:
1. Prefer short span as compared to long span from deflection point.
2. Doubling of load will double the BM but doubling of span will increase the
deflection 16 times for UDL.
3. Prefer propped cantilever in place of isolated cantilever.4. Isolated cantilever structure should be limited in use & adequate counter
weight shall be provided for the same generally 1.5 times the load on
cantilever.
5. In a continuous structure overhang reduces the BM in the adjoining span.
6. Beams/slabs are not completely free to rotate or completely fixed but it is
either nominally/partially fixed.7. Prefer ULD as compared to point load as BM & SF is less in common types
beams/slabs.
8. If point loads cannot be avoided then try to ensure that is more than 10,
which is practically very near to UDL.
7/28/2019 An Architect's Approach to Structures
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:AN ARCHITECTS APPROACH TO
STRUCTURES-by Prof. A.J.Sanyal:
9. In corner column there will be biaxial bending, in side column it be uniaxial
bending & in central column it may be axial loading for symetrical beam &
loading.
10. Short column if preferable to long & slender column.
11. Braced column if preferable to un-braced column.
12. Concentric isolated footing is preferable to isolated eccentric/strip footing.RULE OF THUMBS:
a) For isolated footing Length x breadth = 1.1nwA/B.C.
b) Plinth beam (lintel at 2.1mt) d= 50mm/mt run & Ast= 10mm , no. being
equal to span in mts.
c) Tee or beam= 60mm/mt Ast= d/3 for tee beam & d/4 for ell beam
d) Column with 1% reinf. = 15.57Sq. Cms/tonne load.e) Slabs= 40 mm/mt. run
7/28/2019 An Architect's Approach to Structures
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:AN ARCHITECTS APPROACH TO
STRUCTURES-by Prof. A.J.Sanyal:Sr. No. Member Span/Overall
depth ratio.
1. Plinth beam 15 to 18
2. Tie beam 18 to 20
3. Floor beam 12 to 15
4. Grid beam 20 to 30
7/28/2019 An Architect's Approach to Structures
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:AN ARCHITECTS APPROACH TO
STRUCTURES-by Prof. A.J.Sanyal:Sr.No. Slab type Span to overall
depth ratio.
1. One-way simply
supported
30
2. One-way
continuous
35
3. Two-way simply
supported
38 for L/B=1.5
35 for L/B>1.5
4. Two-way
continuous
40 for L/B=1.5
38for L/B>1.5
7/28/2019 An Architect's Approach to Structures
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:AN ARCHITECTS APPROACH TO
STRUCTURES-by Prof. A.J.Sanyal:
Miscellaneous structures :
Truss depth/span= 10
Virendell truss = 1/8 to 1/10 span, compression & tension
at top & bottom cords is given by: C=T= qL2/8h, where
q=UDL & L=Span in mts & h=depth of V. truss.
Arch. Optimum rise= 1/6 to , d=Span/40 to span/70
Folded plate: depth of fold= Span/15 to Span/10.
Flat plate: d=Effe.Span/22 to E.Span/18.
Two way ribbed slab= Eff. Short span/30 to 1/25.Flat plate ribbed slab= Eff. Span/20 to 1/17
Domes: Rise/span=1/8 to for nomal dome & 1/5 to for
shallow domes.
7/28/2019 An Architect's Approach to Structures
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:AN ARCHITECTS APPROACH TO
STRUCTURES-by Prof. A.J.Sanyal:
Rule of thumbs for M20concrete mix (AJS):
1. Beam in general: d= 15.41[w/k]1/2 , Ast=1.94[w/k]1/2 & of bar= 0.884[w/k]1/4
2. Plinth beam: d= 50mm/mt. run & Ast=10mm , number =span in mts.
3. Tee or Ell beam: MR=Qbd2, where Q= 40xy(2-y), x=Bf/br, y=ds/d, Bf=Effe. Flange
width, br=width of rib, ds=thickness of slab, d= effe. Depth of beam.
4. dofTee/Ell beam=12.77[w/{40kxyb(2-y)}]1/2, Ast=6.527[w/{40kxyb(2-y)}]1/2
d/2
5. Column: Load carrying capacity Pu=[72+24.3p], where Pu= Ultimate load, p=% of
reinf. 15.57 sq. cms./tonne load with 1% reinf.
6. Slab: d= 12.2474l[w/k]1/2=3.873l[w]1/2, Ast
7. Approximate UDL on columns: Corner-2T/M2, Side-1.5/M2, Central-1.1T/M2
7/28/2019 An Architect's Approach to Structures
15/15
:AN ARCHITECTS APPROACH TO
STRUCTURES-by Prof. A.J.Sanyal:
Sorry I could not go in details due to constrain of time. If you want detail seminar
it should be minimum 2-3 days seminar, where basic theory, derivation of
common formula, numerical & assignments with probable solutions etc. can be
covered comfortably.
Any way if like my presentation, tell your friends, else tell your enemies so you can
Pleasure of revenge. But tell somebody.
THANK YOU
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