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* BAMBOO REINFORCED CONCRETE Guided by PIJUS KANTI MANDAL
LecturerPresented by PEKASO SADHUKHAN ROLL NO. 17776
It is estimated that about 20 million ha in 50 countries
are irrigated with raw or partially treated wastewater.
The area irrigated with waste water varies around 10 %
of the total world irrigated area
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*What is Wastewater (WW) Wastewater (WW) is a combination of the
liquid, or water carried wastes , removed from domestic ,
institutions, commercial and industrial establishments together
with surface/ ground/storm water.
It is estimated that about 20 million ha in 50 countries are
irrigated with raw or partially treated wastewater. The area
irrigated with waste water varies around 10 % of the total world
irrigated area
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*Waste Water Categories Water treated after domestic &
public uses Industrial Waste Water Saline agricultural drainage
water Brackish ground water Sea water in coastal regions
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*Components of Wastewater Suspended solids Soluble/
biodegradable organic matters Inorganic soluble salts Ca, Mg, Na,
K, B, CL, carbonates and sulphides Plant micro-nutrients N, P, K
Faecal pathogenic micro-organisms Trace elements: Heavy metals: As,
Cd, Cr, Cu, Pb, Hg, Zn Inorganic elements: Al, Be, Co, F, Fe, Li,
Mn, Mo,Se, Sn, Ti, W and V
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*VARIOUS SPECIES OF BAMBOO
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*PREPARATIONSizing
Splitting
Seasoning
Bending
Waterproof Coating
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*CONSTRUCTION PRINCIPLES
Concrete Mix Proportions The same mix designs can be used as
would normally be used with steel reinforced concrete. Concrete
slump should be as low as workability will allow. Excess water
causes swelling of the bamboo. High early-strength cement is
preferred to minimize cracks caused by swelling of bamboo when
seasoned bamboo cannot be waterproofed.
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*
Placement of bamboo
Bamboo reinforcement should not be placed less than 1 inches
from the face of the concrete surface. The clear spacing between
bamboo rods or splints should not be less than the maximum size
aggregate plus inch.Reinforcement should be evenly spaced and
lashed together on short sticks placed at right angles to the main
reinforcement.The ties can be maid with vegetation strips.This
embedded depth is approximately 10 times the diameter of whole
culms or 25 times the thickness of inch wide splints. Spacing of
the stirrups should not exceed 6 inches.
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*DESIGN PRINCIPLES
Bamboo reinforced concrete design is similar to steel
reinforcing design. Bamboo reinforcement can be assumed to have the
following mechanical properties.
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*
Mechanical properties of bamboo reinforcementMechanical
PropertySymbolValue (psi)Value (psi)Ultimate compressive
strength---8,000Allowable compressive stresss4,000Ultimate tensile
strength---18,000Allowable tensile stresss4,000Allowable bond
stressu50Modulus of elasticityE2.5x106
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*When design handbooks are available for steel reinforced
concrete, the equations and design procedures can be used to design
bamboo reinforced concrete if the above mechanical properties are
substituted for the reinforcement.
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*BEAMS AND GIRDERS Bamboo longitudinal reinforcement should be
between 3 and 4 percent of the concrete cross section.It have the
same bending moment resistance coefficient as a balanced steel
reinforced beam, singly reinforced. Economy of concrete increases
going to the left on the curve; therefore, deeper, narrower
replacement beams are recommended. A minimum number of rods should
be used to provide adequate spacing. The bamboo stirrup area should
always be about 4 times the steel stirrup area.
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*Example Design of Bamboo Reinforced Beam:Design a bamboo
reinforced concrete beam to span 2.43m and to carry a uniform dead
load plus live load of 450 KN/m and two concentrated loads of 108
KN each symmetrically located 0.6m each side of the center line of
span. Assume the ultimate strength of the concrete is 240KN/m2; the
allowable compression stress is 108 KN/m2 Allowable unit diagonal
tension stress,V , in the concrete is 72 KN/m2. Allowable tension
stress, s, in the bamboo is 400 KN/m2; the allowable unit bond
stress between bamboo and concrete is 40 KN/m2.
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* Solution
At the intersection of the allowable stress curves for concrete
and bamboo, find R = 115 and p = 3.1 percent.
2. Maximum bending moment, M, is given by: M =
[450(2.43)2(12)]/2.43 + 108(0.6)(12) =13899.6 KN m. R = M/bd2
3. From bd2 = 13899.6/115 = 120.86 m3
4. If b = 2.43m. is chosen, then d = (120.86(10)/2.43) =
7.05mm.
5. Bamboo reinforcement = pbd = 0.031(2.43)(7.05) = 4.75
6. Use -inch-thick splints, area = 0.563 m2. Number required =
4.75/0.563 = 8.4; round up to 9. Space evenly in three rows. Bend
up top row randomly in the outer one-third ends of the beam.
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* 7. Check the bond stress. Maximum shear at the support, V, is
determined as: V = 450(2.43)/2 + 108 = 860 KN/m2.The perimeter of
one splint is 4(3/4) or 3 m.; the total perimeter of the
longitudinal reinforcement, 0, is 9(3) = 27 m. The value of j =
0.925 u = V ojd = 654.7 27(0.925)(7.06) = 13 KN/m2This is less than
the allowable bond stress of 40 KN/m2.8. Calculate the shear, V',
taken by the concrete fromV' = bjd = 72(2.4)(0.925)(4.75) = 759.2
KN/m2Where is the allowable diagonal tension stress of the
concrete.9. Provide 0.4 mm thick splints for stirrups. The area
provided by one stirrup bent into a U-shape, A, is 4(0.4) = 1.6 mm2
(Stirrup area 4 times the dia). Maximum spacing, s, is given by:s =
Ajd (V - V') = 1.6(400)(0.925)(4.75) (860 759.2) = 10.1mm.
Common practice is to include two additional stirrups past the
point where diagonal tension reinforcement is not needed.
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*COLUMNS Bamboo reinforcement in columns serves to resist a
compression load equal to that taken by the concrete it displaces;
it also will resist shear and tensile stresses. Of the full cross
section of concrete, only 80 percent is considered effective in
rectangular tied, columns. Allowable concrete stress should not
exceed 0.225 f'c where f'c is the ultimate compressive strength of
the concrete.Vertical reinforcement should be approximately 4
percent of the column cross section for rectangular columns. When
bamboo is used as lateral tie reinforcement, the ties should be
spaced not over 16 times the least dimension of the vertical
reinforcement nor farther apart than the least dimension of the
column.
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*ExampleDesign of Bamboo Reinforced ConcreteColumn:Determine the
cross section and bamboo reinforcement of a column required to
carry an axial load of 700 KN. Ultimate compression strength of the
concrete, 240.KN/m2Solution:1. For an unreinforced rectangular
column the safe axial load, P, is given by:P = 0.8Ac (0.225
f'c)Where Ac is the cross-sectional area of the concrete column and
f'c is the ultimate compressive strength of concrete. 2. The column
should have a cross-sectional area of:Ac = 700 0.8 (0.225)
(240)(10) 3 = 16.20 m2.
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*
3. If a square column is chosen, it will have face dimensions
ofb = (16.20) = 4.0 m
4. The amount of vertical reinforcement should be 4 percent of
the concrete area .These should be spaced evenly around the
perimeter of 1 to 1 mm of cover. Provide each vertical splint with
a 90-degree corner.
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*COMPARISON OF BAMBOO AND STEELThe strength of bamboo is greater
than steel.Bamboo is easily accessible. Bamboo lowers the cost of
construction. Increases the strength of the buildings .Bamboo can
crack and deflect more than steel reinforcement.
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*Other Applications Of BambooBamboo bridge in the Amsterdam
Woods
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* Bamboo theatre during the Festival of Vision, Berlin, 2000
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* Bamboo scaffolding at the top of a new high-rise building in
Hong kong
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*CONCLUSION
The environmental and financial comparison demonstrates that
bamboo can compete with building material. Bamboo is a natural
product and will therefore always have some extent of irregularity.
It is therefore suggested that the bamboo culm should be used in
functions were the measurement requirements are not entirely
precise or fixed, as in temporary buildings (e.g., pavilions and
tents) or small civil projects. Furthermore, bamboo can play a role
as a non-supporting or finishing material.
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*REFERENCES
1. H. E. Glenn. "Bamboo reinforcement in portland cement
concrete," Engineering Experiment Station, Clemson Agricultural
College, Clemson, South Carolina, Bulletin No. 4, May 1950. 2. U.
S. Army Engineer Waterways Experiment Station. Technical Report No.
6-646: "Precast concrete elements with bamboo reinforcement," by E.
F. Smith and K. L. Saucier. Vicksburg, Mississippi, May 1964. 3. S.
R. Mehra and R. G. Ghosh. "Bamboo-reinforced soil-cement," Civil
Engineering and Public Works Review, Vol. 60, no. 711, October
1965; vol. 60, no. 712. November 1965. 4. "Concrete floors on
ground," Portland Cement Association Concrete Information, ST-51.
5. American Concrete Institute. "Building code requirements for
reinforced concrete," (ACI 318-56). May 1956. 6. Department of the
Navy, Bureau of Yards and Docks. Design Manual NAVDOCKS DM-2,
Structural Engineering. October 1964.
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*