Form Work System of JMC By Mr. Girish Verma
1.
Definition : Formwork is a mould / temporary structure used to shape the concrete and support the concrete until it gets the sufficient strength to carry its own weight.
2.
Essential Features of a proper formwork: •
•
•
•
3.
It must be built and erected so that the required shape, size, position and finish of the concrete can be obtained. It must be strong enough to take the pressure or weight of fresh concrete and any other loads, without distortion, leakage, failure or danger to workmen It should be designed and constructed so that it can be easily and quickly erected and struck , so saving both time and money ( i.e : Efficient movement of Form work with cost reduction ) It should be economical as well as available in stipulated time. Materials
• • • •
Timber and Plywood Structural Steel Aluminium Composite R C Member
4.
Important Parameters for Formwork Design :
a.
Correct assessment of vertical Loads over forms due to- -1. 2.
Weight of fresh concrete with impact due to drop height Weight of workmen and equipment
b.
Correct assessment of lateral pressure of green concrete on side forms and bracings.
c.
Correct assessment of Dead Weight of Formwork itself.
d.
Wind forces on side forms.
e.
Concrete, Concreting methodology and member data :
Density of Concrete Slump of Concrete Method of discharge Height of discharge Dimensions of sections to be cast Reinforcement detail
Vertical Loads :
The weight of concrete with reinforcement will be considered as 2500kg/cum. Self weight of Form work , for ordinary structure ,varies between 50 kg/sq.mt to 75 kg/sq.mt A minimum Live load of 250 kg/sq.mt will be considered for ordinary structures
Lateral Pressure due to concrete :
For the pressure calculations of concrete the following factors are taken in consideration . Weight of Concrete ( Kg/ cum ) Rate of Placing R ( m/hr ) Vibration Concrete Temperature Other Variables
Weight of Concrete : The weight of Concrete has a direct influence on Lateral Pressure. The hydrostatic pressure at any point in a fluid is a function of its density D ( gr ) and height of pour /depth to point at which pressure is considered H ( gr ).When concrete is in liquid form, it will create hydrostatic/ Liquid pressure, which is same in all direction at a given depth in the fluid. Rate of Placing : The average rate of rise of concrete in the form is called as Rate of placing. The rate of placing has a primary effect on lateral pressure.and the maximum lateral pressure will be proportional to the rate of placing, upto a limit equal to the full fluid pressure. Vibration : Internal Vibration is the primary method of consolidating concrete. It will cause temporary lateral pressure which will be more by 10 to 20 % then those occurs in simple sprading.
Revibration and external vibration system is also adopted for certain type of structure. External vibration is being done by attaching vibrators to the outside of form and due to such vibrations a great fluctuations can seen in lateral pressure.
Temperature : Temperature of the concrete at the time of placing has an important roll on pressure because it affects the setting of concrete. At low temperature, the concrete takes more time to stiffen and hence a great depth will be placed before the lower concrete becomes self supporting. Ultimately great liquid head will develop and result to higher lateral pressure.
Vertical Loads :
The weight of concrete with reinforcement will be considered as 2500kg/cum. Self weight of Form work , for ordinary structure ,varies between 50 kg/sq.mt to 75 kg/sq.mt A minimum Live load of 250 kg/sq.mt will be considered for ordinary structures
Lateral Pressure due to concrete :
For the pressure calculations of concrete the following factors are taken in consideration . Weight of Concrete ( Kg/ cum ) Rate of Placing R ( m/hr ) Vibration Concrete Temperature Other Variables
Weight of Concrete : The weight of Concrete has a direct influence on Lateral Pressure. The hydrostatic pressure at any point in a fluid is a function of its density D ( gr ) and height of pour /depth to point at which pressure is considered H ( gr ).When concrete is in liquid form, it will create hydrostatic/ Liquid pressure, which is same in all direction at a given depth in the fluid. Rate of Placing : The average rate of rise of concrete in the form is called as Rate of placing. The rate of placing has a primary effect on lateral pressure.and the maximum lateral pressure will be proportional to the rate of placing, upto a limit equal to the full fluid pressure. Vibration : Internal Vibration is the primary method of consolidating concrete. It will cause temporary lateral pressure which will be more by 10 to 20 % then those occurs in simple sprading.
Revibration and external vibration system is also adopted for certain type of structure. External vibration is being done by attaching vibrators to the outside of form and due to such vibrations a great fluctuations can seen in lateral pressure.
Temperature : Temperature of the concrete at the time of placing has an important roll on pressure because it affects the setting of concrete. At low temperature, the concrete takes more time to stiffen and hence a great depth will be placed before the lower concrete becomes self supporting. Ultimately great liquid head will develop and result to higher lateral pressure.
a)
Other variables : Other variables measured which have an effect on lateral pressure includes consistency of concrete, amount and location of reinforcement, ambient temperature, pore water pressure,maximum aggregate size, placing procedure, type of cement, depth of placement, cross section of the formwork and smoothness and permeability of the forms. Logic of Formwork Design
Green Concrete will exert hydrostatic pressure on forms which is function of its density D (gr) and height of pour H ( gr)
1)
2)
3)
a) b) c) d)
For horizontal Forms, design vertcal loads will be ( Hydrostatic pressure D (gr) x H (gr ) + D (dr) X H ( dr ) weight of dry concrete + allowable forces due to heaping of concrete & impact loads + Self weight of form work work For Vertical Forms , design hydrostatic pressure will vary from zero to maximum . At top the pressure will be zero and max. at bottom + impact pressure of approx. 1 T / sq.mt on account of falling concrete from height of about 2 mtr. Allowable deflection for shuttering as per I.S.Code is Span/270 where span is spacing between bearers/ supports.
Important References
IS 4990 : 1993 for use of Plywood for Concrete Shuttering IS 800 : latest for use of structural steel shuttering IRC : 87 : latest “ Guidelines for the design and Erection of Falsework for Road Bridges The code of Practice for Design and Construction of Formwork for concrete by P.W.D, Govt. of Maharashtra. Important Formulae
It is very important for the designer to understand the logics of different structural behaviours. Different case studies are given below to understand the structural behaviours : Legends : W w L I Z
Point Load in Kg U.D.l ( Uniform Distributed Load ) in Kg/mtr Length in mtr Moment of Inertia of Section in m 4 Sectional Modulus of Section in m 3 = I / Y
Y E A Fb Fs M.R S.R
Distance of Extreme fibre from Centre of gravity of section in mtr Modulus of Elasticity in Kg/m 2 Cross Sectiona Sectionall Area in m2 Permissible stress in bending in Kg/ m 2 Permissible stress in Shear in Kg/ m 2 Moment of Resistant in Kg-m = Fb x Z Shear Resistant in Kg = Fs x A
All the units units are in Kg & mtr.
I.
Simply supported structure with uniform Distributed Load U D L W Kg / mt A A
L L
B B
Max B.M @ Centre = w x L 2 / 8 Max Shear @ A & B = w x L / 2 Max. Deflection @ Centre = 5 w L 4 384 E I
If Partial fixidity or continuity over support is assumed, design B.M can be derated to w x L 2 / 10 Kg-m 2.
Simply Supported Structure with Centre Point Load W 2. Kg @ Center
Max B.M. @ Center = w x L / 4 Kg-m. Max. Shear @ A & B = w / 2 Kg
A
3.
L
B
Max. Defl.@ Center = w x L 3 In mtr 48 x E x I
Cantilever Structure with Uniformly Distributed Load UDL w Kg / mt
A
L
B
Max. B.M. @ A = w x L / 2 Kg-mt.. Max. Shear @ A = w x L Kg Max. Defl. @ B = w x L 4 in mtr 8xExI
4.
Cantilever structure with Point Load at end Max B.M. @ A
W Kg @ B
= w x L Kg-mt
Max. Shear @ A = w Kg L
A
5.
Max. Defl. @ B = w x L 3 In mtr. 3xExI
B
For Resolution of Forces the principle of Static Equilibrium is being used at any Junction of Forces: Y W
Kg
F1
X
Hinge
(90 –Q) Resolving along `X’ F1 – F2 Cos Q = 0 Resolving along ‘Y` F2 SinQ – W = 0 Solving above simultaneous equations, F2 = W / SinQ, ( Compression ) F1 = W Cos Q/ Sin Q ( Tension )
F2 Roller
5.
A
Permissible Stresses and General data
Permissible Permissible Stresses Stresses for Timber Timber
Classification
Sr. No.
Trade Name of Timber
GROUP A
1 2 3 4 5 6 7 8 9 10
KONGOO SAL CASUARINA GURJAN BENTAEAK SAL TEAK KINDAL LAURE IRUL
GROUP B
Basic Stresses in Kg/ Sq.mt for Timber Bending
Tensio n along grain
152
152
102
102
Compression II to I r grain Grain ( m ) l/r (m) < 10 106 46
63
18
Shear II to Grain
Modulus of Elasticity Kg/ Sq. c.m 5
12
1.26 X 10
9
1.12 X 10
5
GROUP C
B.
11 12 13 14
POON DEODAR MANGO CHIR
70
56
17
6
0.77 X 10
Permissible Stress in Axial Compression : Permissible stress in compression is dependent on slenderness ratio. For different Groups , the permissible stresses are mentioned for different slender
Slenderness ratio ( l/r) 0 5 10 15 20 25 30 35 40 45 50 C.
70
Group A
Group B
106 106 106 101 90 66 46 34 26 21 17
63 63 63 62 59 53 42 30 23 18 15
Group C 56 56 56 54 51 44 28 21 16 13 10
Permissible Stresses for Structural Steel ;
As per IS 800-1984 1. Permissible Shear Stress : 2. Permissible tensile Stress : 3. Permissible bearing Stress : 4. Permissible Compressive Stress : 5. Permissible tensile Stress in M.S rod : 6. Permissible tensile Stress in tor steel ;
1100 Kg/ Sq,c.m 1500 Kg/Sq. c.m 1875 Kg/Sq.c.m 1500 Kg/Sq.c.m 1400 Kg/Sq.c.m 2300 Kg/Sq.c.m
5
D.
General data for Plywood :
Plywood for concrete shuttering shall be mainly of three types as mentioned below : Type
Description
1
Plywood for concrete Shuttering work ( Plain )
2
Plywood for concrete Shuttering work with Plasting coating ( Coated )
CS
CSC
3
Plywood for concrete Shuttering work with Suitable overlay ( film Faced ) Tensile Strength of Plywood :
Designation
a. b. c.
Tensile Strength Shall be not less than 32.5 N/mm. 2 ( 325 Kg/c.m 2) in the direction parallel to the face grain Tensile Strength Shall be not less than 22.5 N/mm. 2 ( 225 Kg/c.m 2) in the direction perpendicular to face grain The sum of the tensile Strengths in both directions shall be not less than 60.0 N/m.m2 ( 600 Kg/ c.m 2)
Modulus of Elasticity of Plywood :
a.
b.
CSC
The Modulus of Elasticity shall not be less than 8000 N/m.m 2 ( 80000 Kg/C.m2) In the direction parallel to the face grain The Modulus of Elasticity shall not be less than 4000 N/m.m 2 ( 40000 Kg/c.m2) In the direction perpendicular to the face grain
Mass of Plywood :
Generally ,density of Shuttering plywood may be taken as 650 Kg/m 3. The Mass per Sq.mt in various thickness of plywood is given below :
Weight ( Kg/m 2)
Thickness 6 9 12 19 25
3.90 5.85 7.80 12.35 16.25
Bending Radius :
The following are approximately the minimum bending radius for the concrete shuttering ply , when it is in dry condition Thickness
Across the Grain of the outer Plies
Parallel with the Grain of the Outer Piles
m.m
mtr
mtr
6 9 12
0.90 1.65 2.55
1.25 2.15 3.30
Loading & Deflection :
Taking the maximum permitted deflection as 1:270 ( i.e : 1/270 th of the span between the bearers ) the following tables give the maximum loads per sq.mt ( A)
When the face grain of the Plywood is perpendicular to the bearers : Centre distance Of bearers
( B)
Maximum Load in Kg per Sq.mt
c.m
9m.m
12m.m
30 40 45 60
1270 540 320 170
1950 850 640 360
When the face grain of the Plywood is parallel to the bearers : Centre distance Of bearers
Maximum Load in Kg per Sq.mt
c.m
9m.m
30 40 45 60
760 320 195 110
12m.m 1220 540 390 170
Note : Above mentioned load carrying Capacities are for dry Plywood boards. If the wet plywoods are used, the maximum load carrying capacities will reduce upto 75 % of above mentioned values Example 1. Find out the load Carrying Capacities of 9 m.m Plywood for the bearers at 30 c.m c/c and face grains are perpendicular to the bearers.
When the face grains are perpendicular to the bearers E = 4000 N/ mm2 ( 40000 Kg/ c.m 2 ) R = 1.65 mtr= 1650 m.m Y = 4.5 m.m ( For 9 m.m ply ) M = I
So,
f = E Y R
( We are aware with this formula )
f = E/ R x Y = 40000 Kg / c.m 2 x 4.5 m.m 1650 m.m = 109.09 Kg/ c.m
2
Now,
M = I
f Y
I = bd3 12
M = f/YxI = 109.09 Kg/ c.m2 x 6.075 c.m 3 0.45 c.m
= 100 x ( 0.9 ) 3 12 = 6.075 c.m 3
= 1472.72 Kg-c.m = 14.73 Kg-mt
--------------- ( A )
Considering the plywood as simply supported on two adjacent bearers M=
wL2 8
=
w x ( 0.3 )
2
8 = 0.011 w Kg-mt -------------- ( B ) Comparing A = B 0.011 w = 14.73 w
= 14.73/ 0.011 = 1339.09 Kg/mt = 1339.0 Kg/mt
2
Which is equal to 1270 Kg/ m 2
Example 2. Find out the load Carrying Capacities of 12 m.m Plywood for the bearers at 30 c.m c/c and face grains are perpendicular to the bearers.
When the face grains are perpendicular to the bearers E = 4000 N/ mm2 ( 40000 Kg/ c.m 2 ) R = 2.55 mtr= 2550 m.m Y = 6 m.m ( For 12 m.m ply ) M = I
So,
f = E Y R
( We are aware with this formula )
f = E/ R x Y = 40000 Kg / c.m 2 x 6 m.m 2550 m.m = 94.12 Kg/ c.m
2
Now, M I
=
f Y
I = bd3 12
M = f/YxI = 94.12 Kg/ c.m2 x 14.40 c.m 3 0.60 c.m
= 100 x ( 1.2 )3 12 = 14.4 c.m 3
= 2258.88 Kg-c.m = 22.59 Kg-mt
--------------- ( A )
Considering the plywood as simply supported on two adjacent bearers M= wL2 8 =
w x ( 0.3 )
2
8 = 0.011 w Kg-mt -------------- ( B ) Comparing A = B 0.011 w = 22.59 w = 22.59/ 0.011 = 2053.63 Kg/mt = 2053.63 Kg/mt
2
Which is equal to 1950 Kg/ m 2
6.
Deshuttering of Form Work
A.
Precautions :
(a)
When the forms are stripped, there must be no excessive deflection and no damage to the concrete due to the removal of supports or due to the stripping operation.
(b)
Where stripping time is less than the specified curing time,provide adequate curing and protection from direct sun and dry winds.
(c)
Do not remove supporting props and shores from beams and slabs until the concrete has attained sufficient strength to carry both the dead load and live load that might be imposed,with a factor of safety of 1.5.
(d)
Detail the forms and scaffolding in such a way that they can be removed easily and safely without impact or shock. Remove the supports in such a way as to permit the concrete to take its share of the load gradually and uniformly.
(e)
When test cubes are used to determine the supporting time, cure them under the same conditions as the concrete they represent.
B.
Stripping Time :
As per IS Code 456, under ordinary conditions, forms and supports should remain in place for minimum time period as mentioned below : (a)
Walls, Columns, Vertical Sides of Beams
(b)
Slabs ( Props left under )
3 days
(c)
Beam Soffits ( Props left under )
7 days
(d)
Removal of Props from Slabs (i) ( ii )
(e)
Spanning upto 4.5 m Spanning over 4.5 m
16 to 24 hours
7 days 14 days
Removal of Props to beams and arches: (i) ( ii )
Spanning upto 6.0 m Spanning over 6.0 m
14 days 21 days
These periods are for concrete prepared using ordinary Portland cement . Depending upon the type of pozzolona cement etc. used, these periods may be altered at the discretion of the Engineer.
7.
Deflection :
As per IS Codes , the deflection should not be more than ( Span/325 ) or 3 m.m , whichever is less. In absence of job specification to the contrary an acceptable and frequently used values of permissible deflections are :
8.
For Sheathing
-
1.6 m.m
For Members spanning Upto 1.5 mtr
-
3.0 m.m
For Members spanning More than 1.5 mtr
-
6.0 m.m or span 360 whichever is less.
Vibration :
The concrete should be vibrated as far as possible with a uniform density and with a horizontal surface, as far as the conditions of the structural component will permit. The following table gives the recommended values for the diameter of the effective range of action and for the spacing of points of immersion..
Vibrator Group 1 2 3
Diameter of internal Vibrator ( m.m ) < 40 40 to 60 >60
Diameter of effective range of action ( c.m ) 30 50 80
Spacing of point of immersion ( c.m ) 25 40 70
The above values are given for ordinary concrete. For heavy concrete , the diameter of effective range of vibrator is smaller than medium density concrete. The spacing of immersion points shall therefore be chosen nearby accordingly.
9.
Safety :
a.
While erecting and dismantling form work, it is essential to ensure that the structure is stable and safe at every stage and is adequately braced, temporarily strengthened, if necessary, to withstand loads like wind. This should be kept in mind while deciding on the sequence of erection and dismantling.
b.
The accessories should be properly fastened at every stage and there should not be loose materials lying around the place of work. They can fall from heights endangering safety of men.
c.
Form work should be continuously watched during and after conreting by a competent person. It is advisable to watch for loosening of nut washers and wedges during vibration.
d.
Rate of rise of concrete in the forms should not exceed that for which they are designed. Limits set by the designer on vibration should alsobe followed. Reasonable care by the operator is necessary to avoid scarring or roughening the forms by operating vibrators against them.
e.
The access walkways and working platforms should be suffiently wide and with adequate safety provisions like proper toe boards and hand rails.
f.
While deshuttering and dismantling form work, apart from considering the safety of form work and staging , the safety of concrete structure itself should be kept in mind. The removal of form should permit the concrete to take its load gradually and uniformly without impact or shock
g.
Improper sequence of stripping can lead to sudden dropping of form components causing injury to workmen and also causing damage to form work materials reducing its reuse value.
10.
Specifications of JMC Centering/Shuttering/Scaffolding Material
a.
H-Frame :-
Size 1.5 mt x 1.22 mt / 2.0 mt x 1.22 mt ( Cap 5.0 M.T )
Raw Material :
a) M.S.Pipes- IS 1161/1239 b) M.S Rod - IS 226/2062
Vertical Pipe
40 mm NB ‘B’ class- 48.3 mm O.D x 3.25 mm thk -2 Nos
Socket
50 mm NB ‘B’ class- 63.0 mm O.D x 3.25 mm thk - 2 Nos
HorizontalPipe
Top-40 mm NB ‘ A’ class -48.3 mm O.D x 3.25 mm thk- 1 No
M.S.Pin
Bottom- 32 mm NB ‘ A ‘ class - 2.9 mm thk -
1 No
16 mm dia 32 mm long with 2 Nos holes Each at right angle at 12 mm c/c
4 Nos
-
Test certificate Required : Sketch Painting
Tensile and compressive strength as per IS 1162/1239 is required for M.S.Pipes used in fabrication of H- frames supplied As per JMC standard attached herewith One coat of red oxide primer & two coats of Enamel paint in Oxford Blue shed Dip painted. 1220mm 40 NB A
16mm PIN (TYP.)
16mm PINS FOR BRACING @ 32mm Long with 2 Nos. Pin holes of 12mm c/c on each pin
1000 mm
40NB B CLASS
1500mm 55 m.m
150 m.m
32 ND A CLASS
50NB B CLASS
H-Frame 1.5 mtr ( JMC CODE – 301 )
b.
ISLC Runner 75 x 40 m.m :*
Back to back ISLC 75 x 40 mm Channel of standard length in 3 mtr. or 4 mtr at length connected by 50 x 6 m.m M.S Flat at every 90 c.m distance only on one side flange with 50 mm gap between two channels.
*
Box Stiffner made out of 50 x 6 x 600 m.m long for connecting two channel runners end to end. 300m.m long portion will be welded on one side of runner and balance 300 m.m will be kept outside to receive the another end of runner.
*
3 Nos. holes of 14 m.m dia will be made on another end of channel runner for fixing box stiffner.
*
One Coat of red oxide and two coats of enamel paint of oxford blue shed dip painted.
300 m.m
3 mtr / 4 mtr 4 mm Hole
ISLC RUNNER ( JMC CODE- 324 )
M.S. Flat 50 x 6 mm 130 mm Long
40
50 40
Section of ISLC Runner 600 mm 50 mm M.S.Flat 50 x6 m.m
Plan Of Runner Box.
c.
Cross Bracing:
M.S. Angle – 37 mm x 37mm x 3mm Angle pressed on both ends. 300mm & 3Nos. holes at every 50mm c/c distance 2 Nos. M.S. angles bolted with 16mm dia bolt with nut & washer to make X design. One Coat of red oxide and two coats of enamel paint of oxford blue shed dip painted.
20 mm hole
34 mm hole
M.S. Angle 40mmx40mmx3mm
CROSS BRACING ( JMC CODE-302 )
d.
Cross Runner :
M.S Square Hollow Tube of Size 49.5 x 49.5 x 2.9 m.m thk of 1.75/2.00/6.00 mtr length as a cross runner for the beam bottom and slab. M.S Flat of 50 x 6 m.m & 50 m.m long will be welded on both sides of Square tube as shown in drg. to hold the wooden patti and this wooden patti will facilitate the fixing of M.S.Plate / Wall form for the slab shuttering. M.S Flat of size 40 x 6 m.m & 300 m.m length will be welded at bottom as shown in drg. to fix the cross runner with the flange of ISLC Runner . One Coat of red oxide and two coats of enamel paint of oxford blue shed dip painted.
CLEAT M.S. FLAT 50x50 x 6M.M 1750mm OR 2000mm 10
770 mm
300 m
M.S. SQ PIPE
49.5x49.5x2.9 m.m thk CROSS RUNNER ( JMC CODE-327 & 337 )
M.S. FLAT 50x50x6M
(32M) 1¼
M.S. SQ PIPE 49.5 x49.5x2.9 m.m thk. M.S. FLAT 40x100x6mm TH (BOTTOM CLEAT)
SECTION Height Closed Extended e.
ON 1N 2N 3N 4N Steel tube: IS: 1239 / 1161 YST – 210
Props:-
Outer pipeInner pipeNut-
Type-
1.10 1.30 2.00 2.00 3.00
60.3mm OD x 3.25mm thk (“B” class) 48.3mm OD x 3.25mm thk (“B” class) Graded malleable casting
1.75 2.75 3.25 3.75 4.65
Props shall be dip painted in zinc chromate and the enamel paint to coat the prop from both inside as well as out side. The enamel paint shall be of oxford blue colour shade.
PROP ( JMC CODE – 311 & 312 )
Operating Length
f.
SO + S1 LO + L1 Max. B.M. Max.Total load Factor of safety -
SPANS:-
Outer Span:-
Min. Max. ----------245 Cm 412 Cm 315 Cm 550 Cm 1040 Kg-.m 2700 Kg 2:1
Top member Bottom member Diagonal member Stiffner Bearing plate Depth of member Width of member
-
Wt --40.0 Kg 55.8 Kg
2mm sheet with ribbed section 63 x 6mm flat 32 x 5mm flat 10mm MS. Rounds 75 x 75 x 8mm 254mm 100mm
Inner Span:-
Bottom member 40 x 90 x 4mm Tee section All other specifications shall be as above Depth of member 222mm Width of member 92mm
Painting:
One coat of red oxide primer & two coats of oxford blue Colour paint dip painted.
Inner Span
Outer Span
40 x 40 x 5 m.m Tee Section SPAN ( JMC CODE- 313 & 314 )
63 x 6 m.m flat
10 m.m round bar
32 x 5 m.m flat
g.
Wall form panel:- Diff.sizes available 1250 x 500mm 1250 x 450mm 1250 x 400mm 1250 x 350mm 1250 x 300mm 1250 x 250mm 1250 x 150mm 1250 x 230mm
1.25mt. Long stiffner -do-do-do0.30mt. Long stiffner 0.25mt. Long stiffner 0.15mt. Long stiffner 0.23mt. Long stiffner
M.S. Sheet – 2.5mm (12 gauge) M.S. Angle – 45mm x 30mm x 4mm – Periphery & 1 No Vertical Plug welding at every 150mm for end angle stitch welding to vertical stiffner at both joints Bottom side painted with red oxide primer M.S. Angle & flat shall confirm to IS 2062. Sketch
As enclosed herewith
Painting
One coat of red oxide primer and two coats of oxford blue Enamel paint spray painted.
M.S Angle 45 x 30 x 4 m.m
Slotted angles alaround Plug Welding Inside
Wall Form
h.
Channel Soldier :- Size availability:
1250mm x 100mm 2500mm x 100mm
M.S. Sheet – 2.5mm thk (12 Swg) M.S. Angle – 45mm x 45mm x 5mmconfirm to IS 2062. Stiffner plate of 50mm x 6mm at each hole End plate – 32mm x 4mm Sketch
As enclosed herewith
Painting
One coat of red oxide primer & two coats of Enamel paint in oxford blue shed spray Painted on bottom & Periphery
Stiffner 50 x 6
45 m.m
Angle :- 45 x45 x4 Sheet : 12 G Stiffner : 2500 x 50 x 6 End Plate : 32 x 4 m.m
100 m.m
12 G Sheet
5 . 2 1
Holes at distance as shown 5 2
5 2
50 X 6 mm flat 5 m 2 c
M C 0 0 5 2
5 m 2 c
5 . 2 1
5 . 2 1
10 CM CHANNEL SOLDIER ( ELEVATION )- JMC CODE 421 & 427
i.
M.S. Centering Plate 600m.m X 900m.m :-
Top Surface
14 swg / 2.00mm black plain sheet of TATA / SAIL of prime quality.
Size
600mm x 900mm
Supporting Framing
M.S. angle 37mm x 37mm x 3mm on all periphery,welded to each other at all corners to make sharp 90 0corner & riveted top M.S. sheet at every 160mm c/cwith good quality rivets on all sides.
Stiffner/Supports
M.S. Angle 25mm x 25mm x 3mm – 2 Nos. At 200mm away from the edge of 900mm long & in the verticle direction (along the length of 900mm). Angle shall be riveted with sheets at every 150mm c/c.
Remarks
A] M.S. plate shall be perfect in right angle at each Corner. B] No undulation shall be seen on the surface of the Plate. C] Each corner shall be perfectly sharp & all cornerShall be welded for full length. D] Wt. Of each M.S. plate shall be approx 13.600 Kg/each
Nail’s Hole 4m.m L. 37x37x3
L. 25x25x3
Capsule type hole16 NO Revet
0 m 0 9 m
600 mm
Welded Centering Plate
NAIL’S HOLE
L. 37x37x3
L. 25x25x3 m m 0 0 9
16 NO Rivets
18 NO Rivets 600 mm
Riveted Centering Plate
Welding
14 sw M.S. Sheet
0 m 0 6 m
37 x37x3 m.m
25 x 25 x 3 mm
900 mm
M.S.PLATE ( JMC CODE- 402 )
j.
Adjustable StirrupHead Jack / Screw Jack :-
•
•
•
•
•
•
M.S. Rod – 32mm dia bright bar as per IS Standard - 750mm long with 550mm sq. threaded 90 deg. With pitch of 6mm Suitable “C” class M.S. Pipe 75mm long is welded to head fitment of M.S. Plate in “U” shape having dimension 150mm x 100mm x 75mm high. 12 dia M.S. nut / bolt for fixing 32mm dia rod with head fitment and shall be hampered such that nut do not come out. Malleable / S.G. Iron casting nut of round shape of minimum 60mm dia shape to match the rigid fixity with H-frame of 40mm NB “B” class M.S. Pipe. Diagonal stiffner of M.S. flat 40mm x 6mm shall be welded at bottom of Uhead fitment connecting “C” class 75mm long pipe as per sketch. Sketch as per JMC standard enclosed herewith.
C Clamp 150x100 x 75 mm ht Stiffner (40x6m.m thk )
12mm dia bolt /Nut
NB ‘32`’C` CLASS PIPE 75MM LONG
G N I D A m E m 0 R 5 H 5 T
60 m.m dia Nut
0 5 7
32m.m M.S. Bright Bar
k.
ADJ. SCREW JACK Wt. – 7.00 to 7.5 kg
Column Clamp : - Size
Min & Max. dist. between inside of
opposite arms in c.m No : 1 No : 2 No : 3
30.5 - 73.0 44.0 - 104.0 67.5 - 133.0
For Column Clamp No.1 & 2 63 x 8 m.m Flat & for clamp No 3 75 x 8 m.m Flat shall be used . Wedges shall be of 200 x 8 m.m. Flat shall confirm to IS 2062.
Painting
One Coat of red oxide primer and two coats of oxford Blue Colour paint ( Dip painted ) .
Clamp
COLUMN CLAMP ( JMC CODE-308 )
l.
Light H-Frame :
Size 2.0 x 0.8 mt
Raw Material :
a) M.S.Pipes- IS 1161/1239 b) M.S Rod - IS 226/2062
Vertical Pipe
25 mm NB ‘B’ class- 33.7 mm O.D x 3.25 mm thk -2 Nos
Socket
32 mm NB ‘B’ class- 42.4 mm O.D x 3.25 mm thk - 2 Nos
Horizontal Pipe
Top-20 mm NB ‘ A’ class –26.9 mm O.D x 2.35 mm thk- 1No Bottom- 25 mm NB ‘ B ‘ class - 3.25 mm thk - 2 No
M.S.Pin
12 mm dia ,50 mm long
- 4 Nos
Sketch
As per JMC standard attached herewith
Painting
One coat of red oxide primer & two coats of Enamel paint in Oxford Blue shed Dip painted.
20 NB “ A” Class Pipe M.S Round 12 m.m dia 225 m.m long m . m 9 3 9 1
m . m 0 0 0 2
1000 m.m
800 m.m 25 NB “ B ” Class Pipe
445 m.m
32 “ NB ” B Class Pipe
150 m.m 10 m.m dia M.S.Round 835 m.m lon
20 NB A CLASS
Tower Structure
LIGHT H-FRAME – ( JMC CODE – 328 )
SIDE ELEVATION
m.
M.S.Khapeda :-
Size : 380 m.m ( Width ) x 3000 m.m ( Length )
M.S.Square hollow Tubes of size 25 x 25x 1.7 m.m , 3.0 mtr long – 6 Nos. M.S Angles of size 30 x30 x 3 m.m will be welded at both ends keeping the square pipes at equi. distance. M.S Flats of size 25 x 3 m.m at every 600 m.m c/c on both faces along the length. One coat of red oxide primer & two coats of Enamel paint in Oxford Blue shed Dip painted.
M.S.Angle 30 x30 x 3 m.m 3.00 mtr
380 m.m
Sq. Pipe 25 x25 x 1.7 m.m
Flat 25 x 3 m.m
M.S.Khapeda
11.
Load Carrying Capacities of JMC Manufactured/ Purchsed Centering/ Shuttering Items :-
1.
H-Frame – 1.5 mtr
H-Frame made out of 40 m.m NB “ B ” Class Pipe ( 3.25m.m thick ) Verticals. Unsupported Legth l = 150 c.m Consider the Effective Length le = 150 c.m ( Though Actual Effective Length is 100 c.m ) Radius of Gyration rxx = 1.60 c.m Slenderness Ratio ( Lembda ) = le/rxx = 150/1.60 = 93.75 Permissible Stress Pc computed from Table 5.1 of IS 800 – 1984
Select fy = 250 Mpa
( fy = Yield Stress of Steel , in Mpa )
For ( Lembda ) le/rxx = 90 , Pc = 90 Mpa & For le/rxx = 100 , Pc =80 Mpa So for le / rxx = 93.75 , Pc = 90 – ( 90 –80 ) x 3.75 ( 100-90 ) = 86.25 N/mm 2 ( Mpa ) = 862.5 kg / c.m 2 Cross Sectional Area of 40 m.m NB “ B” Class Pipe A = 4.6 c.m
2
Total Load Carrying Capacity of One Vertical = Pc x A = 862.5 Kg / c.m 2 x 4.6 c.m2 = 3967.50 Kg = 3.97 M.T Total Capacity of One frame having Two Verticals = 7.94 M.T But We will Consider Load Carrying Capacity of 5 M.T only keeping factor of Safety in mind. •
The load Carrying Capacity of H-Frame ( 5.0 M.T.) is for single tier . As well as the no. of tiers will increase ( ht. Will increase ) , the load carrying capacity will decrease.
•
2.
To reduce the loss of load carrying capacity of staging , following is essential To Keep the staging in plumb to reduce the eccentricity and ultimately to reduce the loss in load carrying capacity. If the staging is not in plumb ( i.e eccentricity is there) then moment will create and which will generate additional load on staging. To Provide 100% bracing in both direction of staging to make the staging monolithic. 200 Centering Plates 600 x 900 m.m :-
25 x 25 x 3 m.m
900
37 x 37 x 3 m.m 600
There are two vertical angles at equivalent dist. in Plate of size 25 x25 x 3 m.m and peripherial angles are of 37 x 37 x 3 m.m For Angle 25 x 25 x 3 m.m Moment of Inertia Ixx = 0.8 c.m
4
, fy = 1650 Kg / c.m
2
Centre of Gravity Cxx = Y = 0.71 c.m Mcap =
=
fy x Ixx Cxx ( Y ) 1650 Kg / c.m 2 x 0.8 c.m 0.71 c.m
4
=
1859.15 Kg-c.m
=
18.59 Kg-mt ----------- ( A )
When the M.S Plate is spanned at 90 c.m c/c ( i.e cross runners are at 90 c.m c/c ) and the load on each angle of 25 x25 x 3 m.m will be of width 0.2 mtr D.L L.L
= = = =
2400 Kg / m 3 x 0.2 m x t ( slab thk ) 480 t Kg /m 200 Kg /m 2 x 0.2 m 40 kg /m 2
Total Load
M
= 1.5 ( Factor of Safety ) x ( 480 t + 40 ) = 720 t + 60
= w l2 8 = ( 720 t + 60 ) x (0.9) 8
2
= ( 72.9 t + 6.08 ) Kg-mt ----------- ( B ) Comparing A = B 18.59 = 72.9 t + 6.08 72.9 t = 18.59 – 6.08 t t
= 18.59 – 6.08 72.9 = 0.170 mt = 170 m.m
•
•
3.
Above Calculation indicates that the M.S.Plates itself is safe for the slab thickness of 170 m.m but it doesn’t means that all the members below M.S Centering Plates are also safe . we have to check for each & every item up to Hframe ( i.e bottom of Shuttering ) . If the slab thickness is more than 170 m.m , the same Centering Plate can be used by reducing the distance of Cross runner ( i.e by reducing the spanning of Plate ) ISLC Runner :
Light Channel Section 75 x 40 m.m back to back Ixx Yxx
= =
2 x 66.1 c.m 4 = 132.2 c.m 3.75 c.m
Z
=
Ixx / Yxx
=
132.2 3.75
=
35.25 c.m
3
4
Mcap =
4.
fxz
=
1400 Kg / c.m 2 x 35.25 c.m
=
49350 Kg-c.m
M cap =
493.50 Kg-mt
3
Cross Runner :-
For 49.5 x 49.5 x 2.9 m.m thick M.S.Hollow SquareTube Z = 7.46 c.m
3
f = 1400 Kg / c.m2 ( Permissible bending stress in tension ) Mcap =
5.
fxz
=
1400 x 7.46
=
10444 Kg-c.m
=
104.44 Kg-mt
Wall Form ( 1250 m.m x 500 m.m ) - When used in place of Centering Plate for slab Shuttering .
500
1250 m.m
250 There is one vertical angle at centre of Wall form of size 1250 x 500 m.m and all the angles in wall form are of size 45 x 30 x 4 m.m
For Angle 45 x 30 x 4 m.m Moment of Inertia Ixx = 5.7 c.m
4
, fy = 1650 Kg / c.m
2
Centre of Gravity from Extreme fibre Cxx = Y = 1.47 c.m Mcap =
=
fy x Ixx Cxx ( Y ) 1650 Kg / c.m 2 x 5.7 c.m 1.47 c.m
4
=
6397.95 Kg-c.m
=
63.97 Kg-mt ----------- ( A )
When the Wall form is spanned at 1.25 mt c/c ( i.e cross runners are at 1.25mt c/c ) and the load on each angle of 45 x30 x 4 m.m will be of width 0.25 mtr D.L L.L
= = = =
Total Load
M
2400 Kg / m 3 x 0.25 m x t ( slab thk ) 600 t Kg /m 200 Kg /m 2 x 0.25 m 50 kg /m 2 = 1.5 ( Factor of Safety ) x ( 600 t + 50 ) = 900 t + 75
= w l2 8 = ( 900 t + 75 ) x (1.25) 8
2
= ( 175.80 t + 14.65 ) Kg-mt Comparing A = B 63.97 = 175.80 t + 14.65 175.80 t = 63.97 – 14.65 t
= 63.97 – 14.65 175.80
t
= 0.280 mt
----------- ( B )
= 280 m.m •
Above Calculation indicates that the Wall form Panels itself is safe for the slab thickness of 280 m.m but it doesn’t means that all the members below Wall form are also safe . we have to check for each & every item up to H-frame ( i.e bottom member of Shuttering/ Staging ) . If the slab thickness is more than 280 m.m , the same Wall form can be used by reducing the distance of Cross runner ( i.e by reducing the spanning of Wall form )
•
12.
Types of Loading :-
Mainly there are three types of loading . Axial , uniaxial and biaxial. Axial Loading : Y
Leg of H-Frame / Prop
X
X
Load at Centre ( Axial )
Y
Above drg. Shows the axial loading , where the load P ( Kg ) is at Centre of HFrame / Props. Load will be transferred safely ,if it is equal / less than the load carrying capacity of H-Frame / Prop. Load at Centre = P Kg Uniaxial Loading : Y
Y
Leg of H-Frame / Prop
X
X
X
Eccentric Load ( Uniaxial )
X
Y Above drg. Shows the uniaxial loading , where the load P ( KgY) is at eccentricity of Ey on X-X axis of H-Frame / Props.
Moment My
= P x Ey
Add. Load due to moment Padd. = My / Ey So the Total Load at Centre = P + Padd ( My / Ey ) From above it is clear that due to eccentricity in one direction , the actual load at Centre will Increase and due to that the load carrying capacity of H-frame/ Props for the same load will decrease . Hence the staging should be always in plumb. When the loading is uniaxial the load carrying capacity of H-frame/ Props will be less than axial loading for the same load.
Biaxial Loading : Y
Leg of H-Frame / Prop
X
X
Eccentric Load ( Biaxial )
Y
Above drg. Shows the biaxial loading , where the load P ( Kg ) is at eccentricity of Ex and Ey with respect to X-X and Y-Y axis of H-Frame / Props. Moment My Moment Mx
= P x Ey = P x Ex
Add. Load due to moments Padd. = My / Ey + Mx / Ex So the Total Load at Centre = P + Padd { ( My / Ey ) + ( Mx / Ex ) } From above it is clear that due to eccentricity in both direction , the actual load at Centre will Increase and due to that the load carrying capacity of H-frame/ Props for the same load will decrease. When the loading is biaxial the load carrying capacity of H-frame/ Props will be less than axial loading as well as uniaxial loading for the same load.
13.
Cost Comparison :-
a.
Cost Comparison of Cross Runner
Sr. No. 1.
Description
Wooden Member 4”x 2 1/2”
M.S.Tube 49.5 x 49.5 x 2.7 / 2.9 m.m 49.5
Section 2 1/2” 4”
2.
Length of Member
3.
B.M.Capacity
4.
Cost Of Member
5.
L & T Doka H-16
49.5
1.83 mtr
1.75 mtr
1.8 mtr
9328 Kg-c.m
10444 Kg-c.m
30,600 Kg-c.m
Rs. 575 / No.
Rs. 695 / No.
No. of Repetitions
Rs. 125 / No. @ Rs. 300/ Cft 5
50
25
6.
Cost of Repetitions
Rs. 25 / Repeti.
Rs. 11.5 / Repeti.
Rs. 27.8 / Repetition
7.
Comments
1. Comperatively high nos. of repetitions.
1.Very high B.M Capacity, full capacity can not be utilised. 2. Less nos. of repet ations compare to M.S.Tube 3. No Scrap value.
1. Less Repetitions
2. No Scrap Value.
2. Approx. Rs. 50 / No. Scrap Value
3. Can be cut in to No. of pieces before repetitions are over.
3. Can not be cut by carpenter into pieces
4. Can be damaged by carpenter. Note : The rates mentioned in above comparison statement are indicative only which will vary place to place time to time.
Design Calculations of Cross Runner 1.
Wooden Cross Runner :
Size : 4” x 2 ½ “ , Z = 106 c.m 3 ( Z = 1/6 x 6.35 x 100 ) Permissible Stress in Bending 6bt = 88 Kg / c.m Moment Carrying Capacity of Section = M = = M =
2.
M.S. Square Hollow Tube :-
2
6bt x Z 88 x 106 9328 Kg-c.m
Design Calculations of Cross Runner 1.
Wooden Cross Runner :
Size : 4” x 2 ½ “ , Z = 106 c.m 3 ( Z = 1/6 x 6.35 x 100 ) Permissible Stress in Bending 6bt = 88 Kg / c.m Moment Carrying Capacity of Section = M = = M =
2.
2
6bt x Z 88 x 106 9328 Kg-c.m
M.S. Square Hollow Tube :-
Since we want replace wooden member by M.S.Square Hollow Tube , we will consider moment capacity 9328 Kg-c.m of wooden member to find out equivalent M.S. Square Hollow Tube Section. Permissible Stress in bending for M.S.Tube 6bt =
1400 Kg / c.m 2
Section Modulus Z = M / 6bt = 9328 / 1400 = 6.6 c.m 3 Provide M.S. Square Hollow Tube 49.5 x 49.5 x 2.9 m.m thk., Z = 7.46 c.m Capacity of M.S Square Hollow Tube M
=
1400 x 7.46
=
10444 Kg-c.m
3
b.
Cost Comparison Statement of ISLC Runner / Main Runner
Sr No.
Description
1.
Section
M.S.Channel Section Back to Back 75 x 40
Wooden Member 4”
75 m.m
8”
130 m.m
2.
Length of Member
3.00 mtr
3.00 mtr
3.
Weight
11.4 Kg / mt
4.
Bending Moment Capacity
493.50 Kg-mt
14 Kg /mt ( Density of wood – 700 Kg / m 3 ) 615. 27 Kg-mt
5.
Sectional Modulus
35.25 c.m
6.
Cost of member / No.
Rs. 750
Rs. 350
7.
No. of Repetitions
50
7
8.
Cost per Repetition
Rs. 15 / Repetition
Rs. 50 / Repetition
9.
Comments
1.
3
699.18 c.m
Comparatively high No. of Repetitions 2. Scrap value approx. Rs. 150 / No. 3. Can not cut by carpenter into pieces
Design Calculations of ISLC Runner/ Main Runner 1.
ISLC Runner :
Ixx Yxx
= =
2 x 66.1 c.m 4 3.75 c.m
Z
=
Ixx / Yxx
=
132.2 / 3.75
=
35.25 c.m 3
Mcap = =
6bt x z 1400 kg/c.m 2 x 35.25 c.m
3
3
1. Less Repetitions 2. No Scrap Value 3. Can be cut in to No. of pieces before repetations are over 4. Weight will be more than Back to Back Channel Section. 5. Chances of self bending is more due to its own dead weight.
Design Calculations of ISLC Runner/ Main Runner 1.
ISLC Runner :
Ixx Yxx
= =
2 x 66.1 c.m 4 3.75 c.m
Z
=
Ixx / Yxx
=
132.2 / 3.75
=
35.25 c.m 3
Mcap =
6bt x z
=
1400 kg/c.m 2 x 35.25 c.m
=
49350 Kg- c.m
=
493.50 Kg-mt
Zreq. = = =
3
M / 6bt 49350 / 88 560.80 c.m 3
Take the wooden member of size 8” x 4 “ Z
2
=
(10.16 ) x ( 20.32 ) 6
=
699.18 > 560.80 Hence the size selected is equivalent to ISLC Back to back Channel Section.
Mcap =
6bt x z
=
88 Kg/c.m 2 x 699.18 c.m
=
615.27 Kg-mt
3
C.
Cost Comparison For Staging Work using H-Frame, Light H-Frame & Cup Lock System
Consider 100 mtr length and 6 mtr height for the comparison of staging cost with different options . Surface Area of Staging = 600 m 2 1.
Structural H-Frame & Cross bracing
(A)
Using H-Frame 1.5 mtr ht. and Cross bracing
H-Frame 1.5 mtr = 100 / 1.5 = 66.66 Say 67 Nos. + 1 = 68 Nos. H-Frame required = 68 x 4 (tiers) = 272 Nos. Cross bracing = 67 bays x 4 tiers x 2 ( Both sides ) = 536 Nos. Approx. Cost :-
H-Frame 1.5 mtr = 272 Nos. x 520 = Rs. 1,41,440.00 Cross bracing 1.5 mtr = 536 Nos. x 150 = Rs. 80,400.00 ------------------------Rs. 2,21,840.00 Cost/Sq.mt of Surface Area = Rs. 370/Sq.mt
1.22 mt
Front View Side View
1.5 mt
1.5 mt
(B)
Using H-Frame 2.0 mtr ht. and Cross bracing
H-Frame 2.0 mtr = 100 / 1.5 = 66.66 Say 67 Nos. + 1 = 68 Nos. H-Frame required = 68 x 3 (tiers) = 204 Nos. Cross bracing = 67 bays x 3 tiers x 2 ( Both sides ) = 402 Nos. Approx. Cost :-
H-Frame 2.0 mtr = 204 Nos. x 620 = Rs. 1,26,480.00 Cross bracing 1.5 mtr = 402 Nos. x 150 = Rs. 60,300.00 ------------------------Rs. 1,86,780.00 Cost/Sq.mt of Surface Area = Rs. 311/Sq.mt 1.22 mt
2.00 mtr
Front View
2.00 mtr
Side View
2.00 mtr
2.
Structural H-Frame & Light duty Cross bracing
By using light duty cross bracing , the c/c distance of H-Frame will increase from 1.5 mtr to 2.72 mtr. (A)
Using H-Frame 1.5 mtr and light duty bracing
H-Frame 1.5 mtr = 100/2.72 = 36.76 Say 37 Nos. + 1 = 38 Nos.
H-Frame required = 38 x 4 ( tiers ) = 152 Nos. Light Bracings = 37 bays x 4 tiers x 2 ( Both sides ) x 2 Nos. = 592 Nos. Approx Cost :-
H-frame 1.5 mtr = 152 Nos. x 520 = Light Bracings = 592 Nos. x120 =
Cost / sq.mt of surface area = (B)
Rs. 79,040.00 Rs. 71,040.00 ----------------------Rs. 1,50,080.00
Rs. 250/Sq.mt
Using H-frame 2.0 mtr and light duty bracing.
H-Frame 2.0 mtr = 100/2.72 = 36.76 Say 37 Nos. + 1 = 38 Nos. H-Frame required = 38 x 3 ( tiers ) = 114 Nos. Light Bracings = 37 bays x 3 tiers x 2 ( Both sides ) x 2 Nos. = 444 Nos. Approx. Cost :-
H-frame 1.5 mtr = 114 Nos. x 620 = Light Bracings = 444 Nos. x120 =
Cost / sq.mt of surface area = 3.
Rs. 70,680.00 Rs. 53,280.00 ----------------------Rs. 1,23,960.00
Rs. 207/Sq.mt
Light H-Frame & Light duty Cross bracing
Light duty H-frame 2.00 mtr = 100 / 2.72 = 36.76 Say 37 + 1 = 38 Nos. Light duty H-Frames req d = 38 x 3 ( tiers ) = 114 Nos. Light Bracings = 37 bays x 3 tiers x 2 both sides x 2 Nos. = 444 Nos. Approx. Cost :-
Light duty H-Frame 2.00 mtr = 114 Nos. x 410 = Rs. 46,740.00 Light Bracings = 444 Nos. x 120 = Rs. 53,280.00 --------------------Rs 1,00, 020.00 Cost / Sq.mt of surface area = Rs. 167 / sq.mt
4.
Cup-Lock System :-
Select the standards of 1.5 mtr height, ledgers of 2.5 mtr and 1.2 mtr. For Staging , provide first layer of ledger at 500 m.m from bottom and afterwards at 1500 m.m c/c. No. of standards required = 100 / 2.5 = 40 Say 40 Nos. + 1 = 41 Nos. Qty of standards = 41 x 4 tiers x 2 sides = 328 Nos. Ledger 2.5 mtr = 40 bays x 5 rows = 200 nos. Edger 1.2 mtr = 41 x 5 rows = 205 Nos. Spigots = 41 x 3 No. of vertical joints x 2 sides = 246 Nos. Approx. Cost :-
Standard 1.5 mtr = 328 Nos. x Rs. 231 = Rs. 75,768.00 Ledger 2.5 mtr = 200 Nos. x Rs. 270 = Rs. 54,000.00 Ledger 1.2 mtr = 205 Nos. x Rs. 141 = Rs. 28,905.00 Spigot = 246 Nos. x Rs. 32 = Rs. 7,872.00 --------------------Rs. 1,66,545.00 Cost / sq.mt of surface Area = Rs. 278 / sq.mt
From above comparison it is clear that the cost / sq.mt of surface area is lowest for the combination of light H-frame and light bracing and highest for the combination of H-Frame 1.5 mtr and cross bracing.
Sketch of Cup lock Staging :-
0.5 mtr 1.5 mtr
0.5 mtr
Spigot at joints 1.5 mtr
Cuplock 1.5 mtr 1.5 mtr
Standard 1.5 mtr
Ledger
2.5 mtr
2.5 mtr
Front view of cuplock system staging
14.
Advantages of Cup- Lock System Over H-Frame System for Staging :
Quick Erection and dismantling resulting in time and labour saving. Easy to store- More material can be transferred from site to site , resulting in less transportation cost. Four Horizontals/Ledgers can be joined to the standard/ Vertical in single operation. Also any single horizontal can be removed or added wherever required- More Flexibility. A Specific grid pattern can be ordered and the same can be used for varying loading conditions. Only additional ledgers/horizontals are required to increase the capacity of the verticals standard. As connecting point is available at every 500 m.m c/c , the capacity can be increased 5.7 tonne per leg of standard 40 m.m NB tube. As there are no loose parts and only hammer is required for fixing and dismantling Cup lock system is more fast and can be erected by unskilled labour too. Cantilever frame can be attached for additional working space. The standard have welded bottom cups pressed from High Quality steel And captive mobile cups made up of Malleable Cast iron for rough site handling. Similarly ledgers / horizontals have identical Forged blade ends which fit in the cups of standards. Cup lock towers can be converted into mobile towers using castor wheels. Standards can also be used as an individual props. Available in various size combinations of verticals and horizontals having suitability to load conditions.
Load Carrying Capacity of Cup lock System:-
Effective length= 0.50 mtr = 50 c.m ( When horizontals/Ledgers are placed at 500 m.m c/c) Radius of Gyration for 40 m.m NB “B” Class Pipe rxx = 1.59 c.m Slenderness ratio : le/rxx = 50 / 1.59 = 31.44 Permissible Stress Pc computed from Table 9 N/m.m2
for fy = 220 Grade = 127.4
Cross sectional Area of 40 m.m NB “ B “ Class Pipe = A= 4.6 Sq.c.m Total Load carrying capacity of One Vertical =
Pc x A = 127.4 x 4.6 x 100 = 58604 N = 58.604 Kn = 5860.4 Kgs = 5.86 tonne
15.
Sample Calculation for Repropping :-
Problem : Design the repropping for a slab of thickness 150 m.m and floor height of 3.5 mtr. Solution : Thickness of slab Age of Concrete Grade of Concrete Height of Floor
: : : :
150 m.m 4 days M 25 3.5 mtr
Load Calculations : 1.
Dead Load
= = Expected Live Load =
0.15 x 2500 Kg / m 3 375 Kg /m2 100 Kg/m2 -------------475 Kg/ m2
2.
Age of Concrete
=
4 days
fct
=
t x fck -----------------4.7 + 0.833 t
=
4 x 25 ----------------4.7 + 0.833 x 4
=
12.5 N / m.m 2
=
0.7 x sq.rt ( fct ) --------------------Factor of Safety
=
0.7 x sq.rt ( 12.5 ) -----------------------1.5
=
1.65 N/ m.m2
=
16.5 Kg / c.m 2
Compressive strength of Concrete
Allowable Tensile Stress
Modulus of Section of 1 mtr wide slab Z
2
=
bxt
/6
=
100 x 15 x 15 / 6
=
3750 c.m
3
Allowable bending Moment to avoid tensile Cracks, M
=
fct x z
=
16.5 x 3750
=
61875 Kg-c.m
=
620 Kg- m
Spacing of reprops to limit the B.M to above value, Wxl2 8 475 x l 8
2
l
=
620
=
620
=
3.23 m
Peprop are to be provided to limit the slab span not to exceed 3 m. Check for Prop Capacity :
Vertical load on prop spaced @ 3 m c/c V
=
3 x 3 x 0.475
=
4.275 t (Greater than prop Capacity, Unsafe )
=
2.1 t ( At 3.5 mtr ht )
=
2.1 / 0.475
=
4.42 m2
Maximum allowable prop load CT 410 Area of Load
Provide props @ 3 m c/c in one direction and 1.5 mtr c/c in other direction. Load On One Prop
=
0.475 x 3 x 1.5 = 2.1 t
