Structural Design Criteria and Minimum Requirements

1. General Notes:

• Design method used is USD according to Bangladesh National Building code (BNBC) 1993, UBC 1997 and ACI 1999.

• All structural drawings shall be discovered in link with topical architectural drawings.

• Maintain BNBC / 1993 for structural requisite not allusion in the drawings or in this note sheet.

• Any details not shown in the drawing should be done according to ACI detailing manual – 1999.

• Basic wind speed = 210 km/hr

• Seismic zone – 2.

• Other loads as per BNBC 1993.

2. Foundation:

• The complex has been designed for 6-storied building (no basement)

• Foundation type -footing foundation on bolli pile.

• Any loose pocket found in foundation bed is to be filled up with compacted sand of fm 1.5 min.

• Depth of foundation as per drawing.

3. Concrete:

• Type: all concrete compressive strength considered as follows:

I) f 'c = 3500 psi at 28 days cylinder strength for stone chips against.

Mixing ratio = 1:11/2:3. (for column, footing, stair, uwr, owt, lc etc.).

Ii) f 'c = 2500 psi at 28 days cylinder strength for brick chips against mixing ratio = 1:1/2:3. (for beam, slab, grade beam, lintel, drop wall, false ceiling etc.).

• Lowest cylinder strength flourished on cylinder test of

Diameter d =150mm & height 300mm

I) 28 days strength as specified in 3(a)

II) Days strength = 75% of the 28 days strength

• Curing of R.C.C work:

I) Curing time minimum 28 days

II) Method of curing:

* Horizontal surface - by pounding of water

* Other Ground - by envelop moist jute fabric and sprinkling water by huise pipe.

4. Cement:

• Ordinary Portland Cement/Type-1 Conforming 70 BOIS 232: 1974/ASTMI C150.

5. Concrete Aggregate:

A. Fine aggregates:

• 50:50 = Sylhet Sand: Local Sand for Column, Footing, UWR, OWT, Lift Core (LC), Beam, Slab, Stair etc.

• 100% Local Sand (F.M. >=1.5) for Plastering, Lintel, Drop Wall, False Ceiling etc.

B. Course Aggregates:

• Stone Chips of 3/4" down grade for Column, Footing, Stair, UWR, OWT, LC etc.

6. Water

• Potable water to be used in concrete mix.

7. Steel reinforcement

• All reinforcements are 60 grade high strength deformed bar except slab and shear reinforcement (40 grades for slab & shear).

• Yield strength of steel fy = 60,000 psi conformed to one of the following specifications: i) BDS 1313 : 1991, ii) ASTM A615m

• The following tests for reinforcing bars from random samples shall be conducted at BUET as per ODS 1313 : 1991 and test result shall be submitted to the engineer for checking and record:

i) Tensile strength test

ii) Percentage elongation test

iii) Bend/rebind test

8. Lap Length

• For tension, lap length = 30d & compression, lap length = 24d. (d = diameter of steel)

• Column laps shall be tension laps.

9. Hooks of Rebar

• For all re-bar: provide 90° standard hooks (l-bent) if not shown in the drawings.

10. Spacer Bars

• To support second layer bars in beams / slabs, use ∅25 spacer bars @ 2'-6" where required.

11. Chairs

• Use chairs of necessary dimension made of ∅10/∅12/∅16 bar to support top bars @2'-6" c/c.

12. Lap Location:

• For beam bottom bar, crease not to be give at central third axis of the span.

• For beam top bar, crease may be give at central third axis of the span.

• No more than 50% of the bars shall be attached at one place.

• Crease attached are to be fell by clamp with highest spacing or tar of d/4 or 4" where d is the effective depth of the beam.

at lap splice spacing of hoops <= d/4 but not greater than 4".

13. Development Length

• All beam and slab rears should be extended into the support up to development length.

14. Admixture

• Water proofing admixture, plasticize and jointing admixture shall be used as mentioned in the respective drawings and in the specification after approval by the engineer.

15. Water Stopper

• 12" wide PVC water stopper to be used at all construction joints bellow ground in mat, shear wall, water tank wall etc.

16. Concrete Clear Cover for Reinforcing Bars

Concrete Clear Cover for Reinforcing Bars

17. Maximum Bars in Beams In Single Layer

• Maximum number of bars as a single layer in beam stem shall be as per aci detailing manual 1994.

18. Minimum Bar Spacing Of Column Longitudinal Bars

• Clear distance between longitudinal bars shall not be less than 1.5 times bar diameter, 1.5 times the size of course neither aggregate nor 1.5".

19. Slab End Reinforcing Details

• Free end of slab incapable of embedding of steel bar in beam / wall

• Others

Slab End Reinforcing Detail

20. Reinforcement Details for Slab Openings

n1, n2: The number of bars which ore cut off for opening

a) The number of extra bars > n1/2

(Top and bottom bars)

b) The number of extra bars > n2/2

(Top and bottom bars)

c) The number of extra bars = 2-D12

(Top and bottom bars)

21. Recommended End Hooks

Recommended End Hooks

22. Scope of Embedment

Scope of Embedment

23. Additional Bar, Fastening Bar In Beam

Unless shown otherwise in the drawing(s)

24. End Hook of Stirrups

End Hook of Stirrups

End hooks of stirrups are located alternately at top corner bar of the section.

25. Column Spice Location

Column Spice Location

• Is area for splice of column reinforcement. Maximum 50% of total bar is spliced at one level

• H = clear column height

26. Confinement Requirements of Column At Joints For Earthquake Loading

27. Confinement Requirements Of Beam At Joints For Earthquake Loading

28. Bundle Bar

• Bars in a bundle must terminate with at least 40 bar dia stagger except where the bundle terminated.

29. Opening in R.C.C. Wall

• Not less than two no.16 bars shall be provided around all door and window openings in R.C.C. walls. The bar shall be extended beyond the corners of the openings to a distance equal to the development length but not less than 2'-0".