AD 2- starter bars for Columns.doc

Real Challenges for Civil Engineers – No.02 Client requirement – Build up another floor on top of existing slab Engineering challenge – Introduce starter bars for columns or walls

 +ew column or wall

Existing Beam Existing *lab

Conventional Method –  Break the existing beam to the extent of anchorage length of proposed column or wall reinforcement  Problems Encountered  Encountered 

1 Breaking of concrete slab and beam ma! weaken the structure " #ther structures ma! affect due to vibration while concrete breaking $ Minimum % da!s will be taken to complete the task  % &isk for the 'ob ( )igh cost and time incurred at the end of the 'ob

New Method introduced by the HI!I with the develo"#ent of !echnology ,rill holes to the existing concrete beam and fix reinforcement with HI!I RE $00 %R  HI!I H& '$0  bonding agent  Advantages

1 +o concrete breaking is required " +o vibration hence no chance to develop cracks $ Maximum 1 da! to complete the total task  % -ow cost . less than &s1(/0 to fix 21/ bar at nominal embedment depth 3 ( 4pplication is so simple and no chance for mistakes – (ero hu#an errors 5 +o risk for the 'ob 6 7ullout test will be done b! HI!I Engineers before concreting to ensure the strength 8 4ll technical support will be given b! HI!I Engineers

Method state#ent 1 " $ % ( 5

Consult !our structural Engineer for the design of column or wall reinforcement Calculate the stress to be developed in the reinforcement due to moment Call HI!I Engineer to get instruction for reinforcement fixing ,rill holes to specified diameter and depth Clean holes with blow out pump provided Insert HI!I RE $00 %R HI!I H& '$0  chemical with the use of dispenser  provided . +o hand mixing3 6 Insert the reinforcement bars and keep 8 hrs for RE $00 #& %/ minutes for H& '$0 to cure 8 4rrange reinforcement as usual 9 &oughen the concrete surface and appl! an! bonding agent if necessar! and do the concreting as usual

)a#"le calculation *ssu#"tions + Concrete grade "(+0mm" • Existing column si:e "6/ ; "6/ mm and clear cover $/mm • *imilar si:e column to be on top • Moment develop at the support of new column M < "/ k+m •

M<=>? where = < ultimate tension develop in the reinforcement at the connection ? < lever arm < /66(d < /66(."6/ – $/3 < 185 mm = < M0? < "/ 0 /185 < 1/6( k+ . for " bars of the column 3

Check for concrete / bond failure 4ssume "215 to be introduced with HI!I RE $00  as bonding agent and embedment depth of $//mm Existing bars  

 

 +ew bars to introduce

1(/mm

"6/mm

4ccording to the HI!I specifications for embedment depth of $//mm =ension capacit! of "215 bar with RE $00 < " ; %$6 x $//01(/ x 1// x /8 < 1$98 @ 1/6( k+ )ence application is satisfactory with *afet! Aactor of 1$9801/6( < 1$

Check for steel failure ltimate tension capacit! of "!15 steel bars < " ; /86 f!4s < " ; /86 ; %5/ ; "/1 < 15/9 k+ @ 1/6( k+ )atisfactory

Hole dia#eter , 22##

Hole de"th , -00##

che#ical consu#"tion , 0 #l

Technical Assistance  +eelanga *oori!arachchi B*c Eng .)ons3MB4 4MIE.*-3 Engineering *ervice Manager  /61661"958 =,Di'itha umara B*cEng.)ons3CEngMIE.*-3M**E.*-3MB4 =echnical Manager  /61666"81(

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