Reinforced concrete covering( bnbc)

Reinforced Concrete Covering

According to

Bangladesh National Building Code

(BNBC)Prepared ByGROUP NO.03121025 121031121026 121032121027 121033121028 121034121029 121035121030 121036

Submitted ToDR. MD. MOZAMMEL HOQUEAssociate ProfessorDepartment of Civil Engineering, DUET

MD. KOBIR HOSSAINLecturerDepartment of Civil Engineering,DUET

Design of Concrete Structure – I Sessional

Dhaka University of Engineering & Technology, Gazipur,Bangladesh

Contents

1. Definition2.Methods of maintaining cover3.Slab Covering4.Wall Panel Covering5.Beam Covering6.Column Covering7.Footing Covering8.Shell and Folded Plate Member

❶ To protect the steel reinforcement bars ( rebar’s ) from environmental effects to prevent their corrosion.

❷ To provide thermal insulation, which protects the reinforcement bars from fire, and;

❸ To give reinforcing bars sufficient embedding to enable them to be stressed without slipping.

In reinforced concrete, is the least distance between the surface of embedded reinforcement and the outer surface of the concrete (ACI 130).

Why need covering ?

Concrete cover

Methods of maintaining cover

Plastic under layers.

Metal plastic tipped bar chairs..

Concrete Chairs

Plastic strip bar chairs supporting heavy rebar on suspended slab

40 mm φ to 57 mm φ

Slab Covering

Wall Covering

*Wall Panels(Precast): 1. 40 bars2. 20 36 mm φ bar and smaller

40 mm φ to 57 mm φ

1. 40 Primary reinforcement, Ties, stirrups, spirals 2. 20 ≤ ≤ 40 Primary reinforcement

3. 16 Ties, stirrups, spiral

Primary reinforcement

Beam Covering

Column Covering

1. 40 Primary reinforcement, Ties, stirrups, spirals 2. 20 ≤ ≤ 40 Primary reinforcement

3. 16 Ties, stirrups, spiral

Primary reinforcement

Same as beam

Minimum   concrete   cover   for   concrete   cast   against   and   permanently   exposed   to   earth   shall   be   75  mm .

Footing Covering

1. 19 mm φ bar and larger 2. 16mm φ bar and smaller

Shell and Folded Plate Member

Folded Plate Member

Shell Member

Bundled Bars

¿*Minimum concrete cover shall be equal to the equivalent diameter of the bundle, butneed not be greater than

Future Extension : Exposed reinforcement, inserts, and plates intended for bonding with futureextensions shall be protected from corrosion.Fire Protection : If a thickness of cover for fire protection greater than the concrete covers specified in8.1.7.1 through 8.1.7.6 is required, such greater thicknesses shall be specified.

Corrosive Environments: If a thickness of cover for corrosive environment or other severe exposureconditions greater than the concrete covers specified in 8.1.7.1 through 8.1.7.6 is required, such greaterthicknesses shall be specified. For corrosion protection, a specified concrete cover for reinforcementnot less than 50 mm for walls and slabs and not less than 65 mm for other members may be used. Forprecast concrete members a specified concrete cover not less than 40 mm for walls and slabs and notless than 50 mm for other members may be used.

Others

Reference

1. http://en.wikipedia.org/wiki/Concrete_cover2. Bangladesh National Building Code (BNBC) http://buildingcode.gov.bd

Thanksto

Everyone