Saturday, November 30, 2019

International Codes for PT Beams


ALL INTERNATIONAL CODES REQUIRES TO SATISFY ALL DUCTILITY REQUIREMENTS OF RC BEAMS FOR PT BEAMS ALSO. THERE ARE CERTAIN ADDITIONAL REQUIREMENTS IN SOME CASES.

Seismic design of post-tension beams as per various codes:

SECONDARY ACTIONS DUE TO PT SHALL BE CONSIDERED IN ALL LOAD COMBINATIONS.





1 Newzealand code :

*PT system shall be preferably bonded. If the unbonded system selected contribution of cables in moment strength in the plastic region shall be limited to 20%.

Comment: the capacity of the unbonded system is mainly due to the integrity of anchorage unlike in the bonded system where capacity is due to bond with concrete and integrity of anchorage. Changes of loss of prestress due to damage to anchorage during a seismic event are more in the unbonded system so the contribution of the unbonded cable shall be reduced by lowering high point and by reducing the number of cables. This may result in beam size similar to that of RC.

* Duct for the bonded system shall be corrugated to ensure bond with concrete.

* Minimum compression reinforcement shall be 15% of total compressive force on the section.
Comment: it helps in stress reversal and increases ductility.

* Depth of neutral axis shall be limited to 0.25D to ensure ductile tension controlled failure.

*in high seismic zones duct of the bonded system can be specifically arranged in a layer in plastic hinge region and in joint to ensure proper confinement of beam-column joints.

Comment: As there is no bond with concrete, a recent version of ACI requires to exclude (deduct) area of unbonded cables from the total sectional area in the calculation of stresses. This reduces effective area and moment of inertia and increases stresses. Also, due to the presence of unbonded cables in the beam-column joint effective joint area will be less and joint may be weaker.

* spacing of stirrups shall be limited to 6d in the confined zone.



2 American code ACI 318:

* Contribution of unbonded cables in moment strength of section in plastic hinge region shall be limited to 25% in beams of SMRF.

* There are also some other requirements related to maximum precompression and testing of anchorages.



3 Chinese code:

The seismic design of the post-tension structure is extensively coveted in Chinese codes of seismic load, seismic design of concrete and prestressed structures.

* Unbonded system is not allowed in GRADE 1 (our SMRF) frames. The unbonded system is allowed in GRADE 2 & 3 (IMRF) frames if

-its contribution in moment strength is less than 35%

-in cantilever beam total moment strength is achieved through reinforcement.

-seismic overturning moment of the unbonded frame in shear wall building is less than 35%.

* Depth of neutral axis shall be limited to 0.25D in grade 1 frame and 0.35D in grade 2 & 3 frames.

*Prestress intensity ratio shall be less than 0.6 for grade 1 frame and 0.75 for grade 2 & 3 frames.

* Bottom reinforcement in the plastic hinge region shall be at least 0.2%.

* stirrups spacing in the confined zone shall not be more than 100 mm. The minimum dia of stirrups shall be 10 mm.





(Source- Social media)

Monday, November 25, 2019

Why Pull-Out test is necessary after rebaring Work? What is Standard procedure of Pull-Out Test?




In the previous blog, we got detailed information about What is rebarring and why rebarring is required? also, we discussed rebarring procedure which is using currently in the industry, but some contractor does not follow standard procedures, which is very dangerous to the strength of the structure and this is directly affected on the life of the structure. a lot of contractors are taking to much lightly when rebarring, and not follows standards procedures. for those contractors, we are providing some information about how to test rebarring work? this test is called as " Pull-Out Test".

now in this blog, we will discuss why the pull-out test is necessary and what is its procedure?


Setting time:

After rebarring of bar wait for 48 to 72 hours to execute this test. Some companies claim chemical setting time is 30 min to 1 hour, but wait up to 48 to 72 hours. because this is standard setting time for the final set of chemicals.



In meantime you can call and give order to your Chemical providing agency to provide Rebar pull-out test, those companies are offering free of cost pull out the test if rebarring quantity is more than 20 numbers. if the rebarring of the bar is less than 20 numbers companies will charge you some cost as per design, location, etc. but charges of particular companies depend on the situation.

Types of Rebarring Chemicals.

Hilti, Fischer, Wurth, Fosroc, etc are providing a wide range of rebarring chemicals.

1. Hilti: HIT RE 100, HIT HY 170, HIT HY 200R RE 500V3, etc.

2. Fischer: FIS V 360, etc.

3. Wurth: PE 500, etc.

Above mentioned chemical name and it's typed, currently in the market there are other brands are also available, but we are trying to cross-check it with pull out test.
Calculate the chemical requirements as per standards.

1. 16mm Dia. : 20mm Drill: 480mm Depth: 85ml chemical required per Hole.

2. 20mm Dia. : 25mm drill hole: 600mm Depth: 160ml chemical Required per hole.
Mark the test Bar.

Locate the test bar where you are doing pull out test, Clean the surrounding area around the bar. also, keep the leveling surface to put the Machine of Pull out the test.

Test Process

The operator will come at the site will all tools required for testing.

1 Insert Hydraulic Jack in Bar.

Insert the hydraulic Jack in the designated bar where we want to check the pull-out test. This Hydraulic jack is cylindrical shape and hollow from the middle like a pipe, which can be easily inserted in any diameter of the bar.



2 Insert the loading ring around the bar.

This ring is Square Shape or round shape depend as per the situation. which has made by heavy ms material to bare load and pressure while testing. please keep a minimum distance from hydraulic jack and rising.





3 Push Loading shoes between the loading ring and bar.

Push loading shoes are both equal shapes, which are needed to insert both sides of the ring and cover the bar. those shoes are conical shapes with zig-zag shape, which can behold any diameter of the bar tightly.




4  Press and apply load by hammer and fix this properly.

After inserting g the loading shoes in-ring and hold the bar, press and tight the loading shoes by Hamner. Loading ring, loading shoes, and bar should be tight, please check once about it, if any part of loading shoes are moving please press again by hammer and tight it.




5. Connect Hydraulic Pump to hydraulic Jack.

After cross-checking of above all setting please connect the hydraulic pump to hydraulic jack with help of a hydraulic pipe. and please tight it properly.



6. Connect Loading scale meter to pump.

Connect the Meter gauge to the hydraulic pressure pump,  which can show the exact applied load on the bar, and this will help us to measure the actual applied load on Bar. also tight pressure release valve.


                                  



7. Start the Pump by hand press.

After all, set up completed, now you can start the test by using the handle to give pressure on the bar, which rebar by using chemical. now need to focus on the meter gauge to track the currently applied load on the bar. Also, notify to push the handle on uniformly. In the meter gauge, there are 2 pointers red and Black which are located for the load applied to the bar in Kilo Newton. but Red pointer in depending on the black pointer, The red pointer is locating the highest point of black pointer the red pointer is always steady, not moving like a black pointer. that means we need to assume the red pointer reading is final. and calculate the load as per the red pointer data.






Team
CBEC India

Monday, November 18, 2019

What is Rebarring? Why Rebarring is required?


What is Rebarring?

Fixing of new reinforcement steel to existing concrete structure with drilling in concrete 150mm or 10 times of Diameter whichever in maximum to 600mm deep as per depend on structural design with applying chemical to bar with testing as per the design standards requirement.



Why need to rebar?

 When some changes in design of structures or failure of the existing structure or existing steel reinforcement is found low in quality or cut or break of any bar in existing structure all those locations need to rebar as per standard norms are given by structural consultant or RCC designer.

Where & Why we can rebar?

We can rebar the steel reinforcement at the following locations.
Rebarring for Footing and Column: For Column Jacketing.
Rebarring for Beam: For Chajja/Projection.
Rebarring for Beam: New beam structure introduced by RCC designer.
Rebarring at Slab: Extension of Slab.
Rebarring in Column: Fixing of Lintel at door and windows and
Rebarring at Column, Beam, Slab, Lift Wall, Retaining Wall, etc: if any bar cut/break due to by mistake.



What is Current Practice of Rebarring?

Currently all the contractor, developers, and some engineers are doing wrong practice for doing rebarring because they are always doing rebarring at various location any levels due to forgotten to keep dowels, or keep wrong diameter steel dowels, etc. but all the time everyone is following the wrong practice to close his mistakes in concrete. Because no one can find any mistakes after concreting. And some contractors are using this practice normally with mutual understanding and discussion with the site engineer or project manager.
                Some builders, developers, contractors and engineers also don’t know the standard practice of Rebarring. But due to avoid the hurdles of breaking of the existing structure, and re-reinforcement of this structure, they are always thinking to save the cost of material, labour, and to save time. Some contractors are giving this benefit behind at builder, developer, project manager, etc.


This is the current process of rebarring which is using at everyone was.


1. Drilling in the existing structure. :

Sometimes the bore depth is not up to 10 times the diameter of the bar or 150mm, because there will be some obstructions of steel bars of existing steel in the existing structure. Also not proper care is taken when drilling like the diameter of the bar. Depth of drill, perpendicular to the existing structure to keep dowels in line. Spacing is not maintained properly due to obstructions of existing steel bars. Contractors are always using a small drill machine that is needed to use by a single hand and needs to operate manually. But due to that drills and the bore is not perpendicular to the existing structure.



2. Cleaning of Drills/bore:

No one is clean the bore properly and remove all the dust particles where can put the bar. Also, no one is using blower on any other tools to clean the drill or bore.

3. Fixing of Bar:

Some contractors are directly fixing the bar in the drill without using any chemicals. Some contractors are using GP2 cement to show the engineer and project manager. Also some contractors are using any diameter of bar as well as rusted, dirty, oily bars are used to rebarring without discussing with a technical person.


4. Immediate shuttering and concreting:

Contractors are always want to close the mistakes of steel reinforcements, shuttering, sizes, etc. at this time contractor is immediate complete rebarring, same day shuttering will fix and concrete work also complete, but no one can cross-check the quality of rebarring an all after concreting.


5. No rebarring test

When work is completed with the above procedure, no one can check the pull-out test of the bar.

What is Standard Rebarring Procedure?

Before Rebarring always keep one sentence in mind “Rebarring is 2nd option to rectify the Mistakes from someone like a structural designer, contractor, engineer, architect,  or permission changed, government rules changed, etc. to avoid losses of material, labour and time.

Following are the steps to show the standard procedure of rebarring.


1. Check the Drawing.

Check the drawing and compare the existing drawing and changed drawing, with the help of drawing we can easily cross-check the exact location of the drawing.

2. discuss with the project manager and RCC designer or structural consultant.

You need to discuss the details of the situation with RCC designer or structural consultant and project manager to given the decision on this situation. You can arrange the site visit of the structural consultant to understand the site condition.

 3. rebarring drawings from a consultant.

After the written direction given by a structural consultant or RCC designer, request to issue the revise drawing with rebarring details. They can give you all the details about the rebarring of steel as per load calculations as well as they will give you the diameter of the bar, the diameter of the drill, depth of bore. Which chemical should be used, what type of tests needs to do, etc.

4. Drilling of Bore:

Drilling of Bore from the standard agency which is certified by rebarring chemical manufacturers like Hilti, Fischer, Wurth, Fosroc, etc. those standards companies are giving you pull out tests at your site, with a quality report. Drilling should be 10 times dia. Or as per given by the structural designer.

5. Cleaning of bore:

When the drilling process is complete, there may be a lot of dust balance in the bore which is need to remove properly, for cleaning of bore you can use water pressure, or air blower. But all dust should be removed from the bore.



6. Application of Chemical:

Drilling the agency is certified from the standard chemicals, those agencies are expert in rebarring and application of rebarring chemicals. They are using chemical guns to fill full of chemicals in the bore as per the standard procedure. Generally, 60% to 75% of the bore will be fill by the chemical.



7. Fixing of Bar:

This agency will fix & press the cleaned and rust-free bar in this bore which is filled by the chemical. At the time of fixing and pressing the bar in bore some chemicals will come out near the bar, but don’t worry this is standard practice. After rebarring work complete wait for 4 to 5 hours to gain the strength. Some chemical companies are giving 30min time to set the chemical but you should wait for 3 to 4 hours to further process.



8. Pull-Out test:

After rebarring work completed wait for 48 to 72 hours to pull out tests.  
What is pull out a test of rebarring? We can check in the next blog.









Team
CBEC India

Tuesday, November 5, 2019

Material Constant and Unit Conversation

Material Constant and Unit Conversation

We need Material Constant on a daily basis when working on site. the following data is recorded for you to use daily working. please shear this data with your friends and engineers.


Important Engg Information to be kept for Record.:

1 Gunta = 121 Sq yards.
1 Gunta = 101.171 Sq Meter.
1 Gaj = 1 Yard
1 Yard = 36 inch
1 Yard = 3 feet
1 Yard = 0.9144 meter =1 meter.
1 sq Yard = 0.83612 Sq meter.
1 sq Yard = 9 sq feet.
1 Sq yard = 1296 Sq inch.
1 Meter = 1.0936 Yards.
1 Meter = 39.370 inch.
1 Meter = 3.280 feet.
1 Sq meter = 1.1959 Sq yard.
1 Sq meter = 1550 Sq inch.
1 Sq Meter = 10.763 Sq feet.
1 feet = 0.304 meter.
1 feet = 0.333 yards.

1 feet =12 inch
1 Sq feet = 0.111 Sq Yard.
1 Sq feet = 0.09290 Sq Meter.
1 Sq feet = 144 Sq inch.
1 inch = 2.54 cm.
1 Inch = 0.0254 meter.
1 Inch = 0.0277 yards.
1 Inch = 0.0833 feet.
1 Sq Inch = 0.00064516 Sq Meter.
1 Sq Inch = 0.00077160 Sq Yards.
1 Sq Inch = 0.00694444 Sq feet.
1 Acre = 4046.86 Sq Meter.
1 Acre = 4840 Sq yards.
1 Acre = 43560 Sq feet.



CONCRETE GRADE:

M5 = 1:4:8
M10= 1:3:6
M15= 1:2:4
M20= 1:1.5:3
M25= 1:1:2


CLEAR COVER TO MAIN REINFORCEMENT:

1.FOOTINGS: 50 mm
2.RAFT FOUNDATION.TOP: 50 mm
3.RAFT FOUNDATION.BOTTOM/SIDES: 75 mm
4.STRAP BEAM: 50 mm
5.GRADE SLAB: 20 mm
6.COLUMN: 40 mm
7.SHEAR WALL: 25 mm
8.BEAMS: 25 mm
9.SLABS: 15 mm
10.FLAT SLAB: 20 mm
11.STAIRCASE: 15 mm
12.RET. WALL: 20/ 25 mm on earth
13.WATER RETAINING STRUCTURES: 20/30 mm

WEIGHT OF ROD PER METER LENGTH:

DIA WEIGHT PER METER

6mm = 0.222Kg
8mm = 0.395 Kg
10mm = 0.616 Kg
12mm = 0.888 Kg
16mm = 1.578 Kg
20mm = 2.466 Kg
25mm = 3.853 Kg
32mm = 6.313 Kg
40mm = 9.865 Kg

AREA AND VOLUME PER UNIT

1 bag cement-50kg
1 feet-0.3048m
1 m-3.28ft
1 sq.m-10.76sq.ft
1 cu.m-35.28cu.ft
1 acre-43560 sq.ft
1 cent-435.6sq.ft
1 hectare-2.47acre
1 acre-100 cent-4046.724sq.m
1 ground-2400 sq.ft
1 unit-100 cu.ft- 2.83cu.m 1 square-100 sq.ft

1 M LENGTH STEEL ROD AND ITS VOLUME

V=(Pi/4)*Dia x Dia X L=(3.14/4)x D x D X 1 (for1m length) Density of Steel=7850 kg/ cub meter
Weight = Volume x Density=(3.14/4)x D x D X1x7850 (if D is in mm ) 
So = ((3.14/4)x D x D X1x7850)/(1000x1000) = D*D/162.27


DESIGN MIX:

M10 ( 1 : 3.92 : 5.62)

Cement : 210 Kg/ M 3
20 mm Jelly: 708 Kg/ M 3
12.5 mm Jelly: 472 Kg/ M 3
River sand: 823 Kg/ M 3
Total water: 185 Kg/ M 3
Fresh concrete density: 2398 Kg/M 3

M20 ( 1 : 2.48 : 3.55)

Cement : 320 Kg/ M 3
20 mm Jelly: 683 Kg/ M 3
12.5 mm Jelly: 455 Kg/ M 3
River sand: 794 Kg/ M 3
Total water: 176 Kg/ M 3
Admixture : 0.7%
Fresh concrete density: 2430 Kg/ M 3

M25 ( 1 : 2.28 : 3.27)

Cement : 340 Kg/ M 3
20 mm Jelly: 667 Kg/ M 3
12.5 mm Jelly: 445 Kg/ M 3
River sand: 775 Kg/ M 3
Total water: 185 Kg/ M 3
Admixture : 0.6%
Fresh concrete density: 2414 Kg/ M 3
Note: sand 775 + 2% moisture, Water 185 -20.5 =164 Liters,
Admixture = 0.5% is 100ml

M30 ( 1 : 2 : 2.87)

Cement : 380 Kg/ M 3
20 mm Jelly: 654 Kg/ M 3
12.5 mm Jelly: 436 Kg/ M 3
River sand: 760 Kg/ M 3
Total water: 187 Kg/ M 3
Admixture : 0.7%
Fresh concrete density: 2420 Kg/ M 3
Note: Sand = 760 Kg with 2% moisture (170.80+15.20)

STANDARD CONVERSION FACTORS

INCH = 25.4 MILLIMETRE
FOOT = 0.3048 METRE
YARD = 0.9144 METRE
MILE = 1.6093 KILOMETER
ACRE = 0.4047 HECTARE
POUND = 0.4536 KILOGRAM
DEGREE FARENHEIT X 5/9 – 32 = DEGREE CELSIUS
MILLIMETRE= 0.0394 INCH
METRE = 3.2808FOOT
METRE = 1.0936YARD
MATERIAL CALCULATION:

CEMENT IN BAGS

01. PCC 1:5:10 1440/5*0.45 129.60Kg 2.59
02. PCC 1:4:8(M 7.5) 1440/4*0.45 162.00Kg 3.24
03. PCC 1:2:4(M 15) 1440/2*0.45 324.00Kg 6.48
04. PCC 1:3:6(M 10) 1440/3*0.45 216.00Kg 4.32
05. RCC 1:2:4(M 15) 144/2*0.45 324.00Kg 6.48
06. RCC 1:1.5:3(M 20) 1440/1.5*0.45 32.00Kg 8.64
07. RCC 1:1:2(M 25) 370.00Kg 7.40
08. RCC M 30 410.00Kg 8.20
09. RCC M35 445.00Kg 8.90
10. RCC M40 480.00Kg 9.60
11. Damp Proof Course CM1:3,20mm tk 1440/3*0.022 10.56Kg 0.21
12. 2"tk precast slab M15 324*0.05 16.20Kg 0.32
13. 3"tk precast slab M15 324*0.075 24.30Kg 0.49
14. GC Masonry CM 1:7 1440/7*0.34 70.00Kg1.40
15. Brick Work CM 1:6 1440/6*0.25 60.00Kg 1.20
16. Brick Work CM 1:4, 115tk 1440/4*0.25*0.115 10.35Kg 0.21
17. Grano Flooring CC 1:1.5:3 1440/1.5*0.45*0.05 21.60Kg 0.43
18. Plastering CM 1:3, 12mm tk 1440/3*0.014 6.72Kg 0.13
19. Wall Plastering CM 1:4, 12mm tk 1440/4*0.014 5.00Kg 0.10
20. Laying Pressed Tiles Over a CM 1:4, 20mm tk 1440/4*0.022 7.92Kg 0.16
21. Ceramic Tiles, Marble, Granite, Cuddapah Slab CM 1:4, 20mm tk 1440/4*0.022 7.92Kg 0.16
22. Hollow Block Masonry CM 1:6, 200mm tk/m¬2¬ 10.00Kg 0.20 



SAND CALCULATION (CFT):

01. Any Concrete Work (PCC, RCC) 0.45*35.315= 20.00
02. Damp Proof Course CM `1:3, 20mm tk 1.00
03. 2"tk Precast slab M15 1.00
04. 3"tk Precast slab M15 1.50
05. SS Masonry in CM 1:7 15.00
06. Brick Work in CM 1:6 15.00
07. Brick Work in CM 1:4,115mm tk 2.00
08. Grano Flooring in CC 1:1.5:3 1.00
09. Plastering in CM 1:3, 12mm tk 1.00
10. Wall Plastering CM 1:4, 12mm tk 1.00
11. Laying Pressed Tiles over a CM 1:4, 20mm tk 1.00
12. Ceramic Tiles, Marble, Granite, Cuddapah slab CM 1:4, 20mm tk 1.00

METAL CALCULATION:

01. Any Concrete Work 32.00 cft
02. Grano Flooring in CC 1:1.5:3, 50mm tk 1.60cft
03. Grano Flooring in CC 1:1.5:3, 75mm tk 2.40cft
04. Grano Flooring in CC 1:1.5:3, 100mm tk 3.20cft
05. Bricks/cum 450.00 Nos
06. Size Stone/ cum 90.00 Nos
07. Rough Stone 10.00 cft
08. Bond Stone/ cum 10.00 Nos
09. Cement Paint/100 Sq Ft 2.00 Kg
10. White Cement/100 Sft 2.00 Kg
11. Janathacem/100 Sft 1.50 Kg
12. Enamel Paint/100 Sft - 2 Coats 1.25 Litre
13. Wall Putty/100 Sft 10.00 Kg
14. Plaster of Paris/100 Sft 25.00 Kg
15. Distemper/100 Sft 2.00 Kg
16. Cement Primer 0.60 Litre 0.40 Litre
17. Weathering Course Lime 12.50 Kg Brickbats 32.00 Kg
18. Providing Sand Gravel Mix- Cum Sand 20.00 Cft Gravel 40.00 Cft
19.WBM - 75mm tk - 1st Layer - 10 Sqm Metal(60-40 mm) 35.00 Cft Gravel 10.00 Cft
20. Pressed Tiles - Sqm 20.00 Nos
21. Hollow Block - 200mm tk 14.00 Nos

CONVERSION TABLE:

01. 1 RM 3.28 RFT
02. 1 Sqm 10.76 Sq Ft
03. 1 Cum 35.32 Cft
04. 1 Inch 2.54 cm
05. 1 sft 0.09Sqm
06. 1 Acre 0.04 Hectare
07. 1 Hectare 2.47 Acres
08. 1 Cft 0.028 Cum
09. 1 Feet 12.00 Inch
10. 1 Feet 0.305 M
11. 1 Cum 1000.00 Litre

UNIT WEIGHT:

01. Concrete 25 kN/m3
02. Brick 19 kN/m3
03. Steel 7850 Kg/m3
04. Water 1000 Lt/m3
05. Cement 1440 Kg/m3
06. 1 Gallon 4.81 Litres
07. Link 8" = 200mm
08. 1 Hectare 2.471 acres(10000m2)
09. 1 Acr 4046.82m2 = 100 cent


DEVELOPMENT LENGTH:

01. Compression 38d
02. Tension 47 & 60d
03. 1 Cent 435.60 Sft
04. 1 Meter 3.2808 ft
05. 1 M2 10.76 ft2
06. 1 Feet 0.3048m
07. 1 KN 100Kg
08. 1kN 1000N
09. 1 Ton 1000Kg = 10,000 N = 10 kN
10. 1 kG 9.81N

CEMENT PER CUM:

M5=2.54Bg/m3, 
M7.5=3.18Bg/m3, 
M10=4.32Bg/m3,
M20=8.64Bg/m3, 
M25=12.9 Bg/m3,
M40=500+100 Kg/m3
1m3 Concrete = 0.9 m3 Jelly + 0.55 m3 Sand + 0.225 m3

BRICK:

Weight = 3.17 - 3.80 Kg
Water absorption 12 to 15%
Compressive strength = 36 Kn/cm2
230mm Wall/m3 = 460 Bricks + 20 Cft Sand + 66 Kg Cement


Source: Social Media


Team
CBEC INDIA