Development length

All the concepts of Development length

1. PREPARED BY: Asst. Prof. GAURANG PRAJAPATI CIVIL DEPARTMENT DEVELOPMENT LENGTH Mahatma Gandhi Institute Of Technical Education & Research Centre, Navsari (396450) ELEMENTARY STRUCTURAL DESIGN 6 TH SEMESTER CIVIL ENGINEERING

2. INTRODUCTION DEVELOPMENT LENGTH ( L d ) : A length of reinforcement embedded in concrete so that it can develop the bond stress, is termed as Development length. ESD 2160607 2 DEVELOPMENT LENGTH

3. INTRODUCTION ESD 2160607 3 DEVELOPMENT LENGTH Where, L d = Development length = Dia. Of bar = Stress in bar = 0.87 f y = Design bond stress in concrete   L d =   IS 456 Clause No.: 26.2.1 Page No.: 42 IS 456 Clause No.: 26.2.1 Page No.: 42

4. DESIGN BOND STRESS IN CONCRETE ( )   ESD 2160607 4 DEVELOPMENT LENGTH Grade of concrete M 20 M 25 M 30 M 35 M 40 & Above IS 456 Clause : 26.2.1.1 Page No.: 43 (N/mm 2 ) 1.2 1.4 1.5 1.7 1.9 Grade of concrete M 20 M 25 M 30 M 35 M 40 & Above IS 456 Clause : 26.2.1.1 Page No.: 43 1.2 1.4 1.5 1.7 1.9 For plain bars in tension are as follow: For Deformed bars (Fe 415 & Fe 500) (Tor Steel), these values shall be increased by 60%. (multiplied by 1.6) For bars in compression (column) , these values shall be increased by 25%. (multiplied by 1.25)

5. DESIGN BOND STRESS IN CONCRETE ( )   ESD 2160607 5 DEVELOPMENT LENGTH For Example : Type of bars (N/mm 2 ) M 20 grade, Plain bars in tension 1.2 M 20 grade, Plain bars in compression 1.2 × 1.25 M 20 grade, Deformed bars in tension 1.2 × 1.6 M 20 grade, Deformed bars in compression 1.2 × 1.6 × 1.25 Type of bars M 20 grade, Plain bars in tension 1.2 M 20 grade, Plain bars in compression 1.2 × 1.25 M 20 grade, Deformed bars in tension 1.2 × 1.6 M 20 grade, Deformed bars in compression 1.2 × 1.6 × 1.25

6. LAP LENGTH : ESD 2160607 6 DEVELOPMENT LENGTH The length of bar extended over the other bars in beam, column, etc. is called lap length.

7. LAP LENGTH : ESD 2160607 7 DEVELOPMENT LENGTH The lap length in compression shall be equal to Development length ( L d ), but not less than 24ф Lap length = L d 24 ф   IS 456 Clause No.: 26.2.1 Page No.: 42 IS 456 Clause No.: 26.2.1 Page No.: 42