EXAMPLE 7.8.1. ESTIMATING COLUMN REINFORCEMENT (LOW-RISE)

Estimate the reinforcement and tie wire needed for the 8 columns of a two storey residential building. Depth of column into the footing is 1.0 meters and the height of each floor from ground to second and from second floor to roof is 3.00m. Column dimensions are 0.30m x 0.30m. Use 8pcs D16mm vertical reinforcement and D12mm ties are spaced at 3 @ 0.05m; 4 @ 0.075m; 4@0.10m; and rest @ 0.15m to center line.

MAIN REINFORCEMENT:

As the number of bars in a column is already given, determine the length of each bar.

So:

 


LATERAL TIES:


     

     

To easily visualize the number of ties, draw a line representing the height of the column. Place the lateral ties from the spacing given in the plans.

The center line is located at the midlength of the column and the lateral ties will be mirrored at the other side from this line.

For the column length: Footing to Ground floor, there are 7 ties needed until center line. If these ties are mirrored to the upper half, there will be a middle (remaining) space of 0.10m. Note that 0.10m is still within the range of the next lateral tie spacing.

Thus for footing to Ground flr:

     

For Ground floor to Second flr:

   

There are 240 ties from Second flr to Roof beam.

Finally, 





#16 GI TIE WIRE

The required tie wire depends on the number of intersections between the main reinforcement and the lateral ties.

For every column, there are 8 main bars and 74 lateral ties (14+30+30).


      


     


With the combination of D16mm and D12mm to be tied, it is safer to take a longer tie wire, use 30cm.



In summary:

Materials required:

      64    pcs       D16mm by 7.50m
      592 pcs        D12mm x 1.10m
      27   kg         #16 GI Tie Wire




Back to 7.0. Estimating Concrete Reinforcement

EXAMPLE 7.7.2. ESTIMATING ISOLATED FOOTING REINFORCEMENT OF A SMALL STRUCTURE

Estimate the rebars and the tie wire for 8 footings specified as shown.

credits to BuildingHow.com

From the plans, we can count the number of rebars used (D12mm). For isolated footing, bars are usually placed both ways, hence, the number of bars laid horizontally is the same number laid vertically. For the length of the bars, specification already shows the clear length and hooks' length.

         
                 

             

Thus:  

             

Commercial lengths can be exactly divided by 1.50, so it's the estimator's discretion on which commercial length the rebars be converted.

#16 GI Tie Wire:

          


D12mm rebars can be tied using 25cm wire.

            






Back to 7.0. Estimating Concrete Reinforcement

EXAMPLE 7.7.1. ESTIMATING ISOLATED FOOTING REINFORCEMENT

Estimate the reinforcement required for the 1.50m square footing shown. Reinforcement used is D12mm steel bars. Determine the tie wire needed.

credits to The Constructor

The configuration of the rebars is shown from the plan. There is no need for any hook or bend on the rebars. This means that the length of the bars only includes the size of the column less the clear cover.

              

From plans, number of bars can be determined. (Specification is usually the number of bars used both ways, or the spacing between bars)

                

Thus, rebars required:

                24pcs D12mm RSB at 1.35m

It is the estimator's discretion on which commercial length these bars are to be taken from. Note the remaining length if they can still be used in the construction for other purposes.


#16 GI Tie Wire:

             

  





Back to 7.0. Estimating Concrete Reinforcement

EXAMPLE 7.6.1. ESTIMATING TIE WIRE FOR CHB REINFORCEMENT

From the previous example of a 4.0m x 3.0m wall, estimate the tie wire required in kilograms.

From the previous example: 

      Vertical reinforcement spacing: 80cm

      Horizontal reinforcement spacing: at every 3 layers

Tie wire estimation can be done in two ways:

a. Direct count. identify the number of intersections created with the vertical and horizontal reinforcements.

   From previous results: 5 horizontal layers of 4m
                                     5 vertical layers of 3m

      


Because CHB reinforcement only uses D10mm rebars, the applicable length of tie wire needed is 25cm.





b. Block method. Using a table, determine the weight of tie wire needed.


   

   Use the table with 25cm tie wire:


  





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EXAMPLE 7.5.1. ESTIMATING CHB WALL REINFORCEMENT

Determine the 10mm vertical and horizontal reinforcement fr the CHB wall 4.0m length and 3.0m high. Reinforcement is spaced at 80cm on centers vertically and every three layers respectively.

a. Direct counting:

For horizontal reinforcement: Horizontal reinforcement is every three layers of CHB height as 0.20m, thus total height of each layer is 0.60m.

          

        
          

       
So, for horizontal reinforcement: 5 layers of 4.00m D10mm rebars.

For vertical reinforcement:

       

         

So, for vertical reinforcement: 5 layers of 3.00 D10 rebars.


To convert the needed steel bars in commercial sizes, the least wastage is by using 7.5m lengths cut into 4m and 3m (wastage: 0.50m each bar).

So, use:     5pcs D10mm x 7.50m RSB


b. Square Meter Method or Area Method:


           

For vertical reinforcement, using the table:

SPACING	LENGTH OF BARS	LENGTH OF BARS
	PER BLOCK	PER SQ.M.
cm.	m.	m.
40	0.235	2.930
60	0.171	2.130
80	0.128	1.600

Convert into commercial lengths:  4pcs D10mm x 5.00m

For horizontal reinforcement, using the table:

SPACING	LENGTH OF BARS	LENGTH OF BARS
LAYERS	PER BLOCK	PER SQ.M.
	m.	m.
2	0.264	3.30
3	0.172	2.15
4	0.138	1.72

This can be converted to:      4pcs D10mm x 5.00m
                                           1pc  D10mm x 6.00m


In summary, order:               8pcs D10mm x 5.00m RSB
                                           1pc  D10mm x 6.00m  RSB

c. Unit Block Method. This method requires the number of CHB.

       


From the table above:

Vertical reinforcement:

                

Convert into commercial lengths:  4pcs D10mm x 5.00m

Horizontal reinforcement:

                     

This can be converted to:      4pcs D10mm x 5.00m
                                           1pc  D10mm x 6.00m


In summary, order:               8pcs D10mm x 5.00m RSB

                                           1pc  D10mm x 6.00m  RSB

Note: The results of the two last methods yield the total number of bars needed. The estimator would have no means of knowing the lengths of bars to be installed vertically and horizontally. Bar scheduling with these methods would be hard to identify.



Back to 7.0. Estimating Concrete Reinforcement

EXAMPLE 7.2.1. DETERMINING SPLICE LENGTHS

Determine the length of the splice joint for a 16mm steel bars if they are used as:

   a. Tensile reinforcement of a beam

   b. Compressive reinforcement of a beam

a. Used as tensile reinforcement:

               

b. Used as a compressive reinforcement:

                



Back to 7.0. Estimating Concrete Reinforcement

EXAMPLE 6.1.3. ESTIMATING STRINGERS

Determine the length of an open wood stringer with the following data: run distance = 3.50m and height of the rise =2.50m.

Using the Pythagorean Theorem:

Assuming 18cm riser, calculate the number of steps:




Use the table for determination of rise and tread:

NO OF STEPS	LENGTH OF	STRINGER	LENGTH OF	RUN	HEIGHT	OF RISE
	TREAD	TREAD	TREAD	TREAD	RISER	RISER
	WIDTH	WIDTH	WIDTH	WIDTH	HEIGHT	HEIGHT
	25cm	30cm	25cm	30cm	17cm	18cm
4	1.05	1.23	0.80	1.00	0.68	0.72
5	1.31	1.54	1.00	1.25	0.85	0.90
6	1.57	1.85	1.20	1.50	1.02	1.08
7	1.84	2.16	1.40	1.75	1.19	1.26
8	2.10	2.47	1.60	2.00	1.36	1.44
9	2.36	2.78	1.80	2.25	1.53	1.62
10	2.62	3.08	2.00	2.50	1.70	1.80
11	2.89	3.39	2.20	2.75	1.87	1.98
12	3.15	3.70	2.40	3.00	2.04	2.16
13	3.41	4.00	2.60	3.25	2.21	2.34
14	3.67	4.31	2.80	3.50	2.38	2.52
15	3.94	4.62	3.00	3.75	2.55	2.70
16	4.20	4.93	3.20	4.00	2.72	2.88
17	4.46	5.24	3.40	4.25	2.89	3.06
18	4.73	5.55	3.60	4.50	3.06	3.24
19	5.00	5.85	3.80	4.75	3.23	3.42
20	5.62	6.16	4.00	5.00	3.40	3.60

Identify 14 steps yields 4.31 stringer length by 30cm tread width; the run at 30cm = 3.50 and the height of rise at 18cm = 2.52.

Back to 6.0. Estimating Staircases

EXAMPLE 6.1.2. ESTIMATING A STAIRCASE II

Determine the height of the riser and the width of the tread when the rise is 2.65m and the run is 2.75m.

Assuming rise height of 18cm, compute the number of steps for the total rise of 2.65m.

Re-check the height of each riser:


     

Assuming a run of 30cm, compute the total run of the stairs:





Have another trial of tread width = 25cm:





Thus:  15 steps of 0.177m rise and 20cm tread




Back to 6.0. Estimating Staircases

EXAMPLE 6.1.1. ESTIMATING A STAIRCASE

Determine the number of steps and the height of the riser if the total height of the rise is 2.20m using a 30 cm. width of the tread.

Assuming 17cm height of rise, compute for the number of steps to reach the upper level:

Re-check the height of the riser:


     

Determine the distance of the run:




   where:

       

     







Back to 6.0. Estimating Staircases