CONCRETE BRIDGE CODE Reprint2014 Corrected up to CS

CONCRETE BRIDGE CODE Reprint-2014 Corrected up to CS no. 3 VINEET GUPTA SPB-1

APPLICABLE TO: - USE OF PCC, RCC & PSC IN RLY. BRIDGE CONSTRUCTION. - ROAD BRIDGE – IRC TERMINOLOGY – AS PER IS 4845 & IS 6461.

SCOPE 4 MATERIALS 5. CONCRETE 6. FALSEWORK AND FORM WORK 7. REINFORCEMENT & PRESTRESSING TENDONS • 8. TRANSPORTATION, PLACEMENT, COMPACTION & CURING OF CONCRETE • 9. GROUTING OF PRESTRESSING CABLE • •

SCOPE • 10. LIMIT STATE REQUIREMENTS • 11. LOADS, LOAD COMBINATIONS AND PARTIAL LOAD FACTORS • 12. CHARACTERSTIC STRENGTHS AND PARTIAL SAFETY FACTORS FOR MATERIALS • 13. ANALYSIS OF STRUCTURE AND SECTION • 14. PLAIN CONCRETE WALLS • 15. DESIGN AND DETAILING: REINFORCEMENT CONCRETE

SCOPE • 16. DESIGN AND DETAILING: PRESTRESSED CONCRETE • 17. DESIGN AND DETAILING: PRECAST AND COMPOSITE CONSTRUCTION • 18. LOAD TESTING

SCOPE • Materials • Grades of concrete and basic design values • Production and placement of concrete • Limit state requirements, load combinations • RCC design • PSC design • Quality check of materials

FEW DEFINITIONS • CAMBER – INTENTIONAL INITIAL CURVATURE GIVEN TO A MEMBER TO COMPENSATE DEFLECTION UNDER LOAD • COLD JOINT- JOINT OR DISCONTINUITY FORMED DUE TO HARDENING OF CONCRETE BEFORE NEXT BATCH IS PLACED • COMPOSITE CONSTRUCTION – CONSTRUCTION MADE UP OF DIFFERENT MATERIALS • CRACKING LOAD – TOTAL LOAD CAUSING FIRST VISIBLE CRACK

FEW DEFINITIONS • CREEP IN CONC. – PROGRESSIVE INCREASE IN PLASTIC DEFORMATION UNDER SUSTAINED LOADING • CREEP IN STEEL- PROGRESSIVE DECREASE OF STRESS AT CONSTANT STRAIN • BLEEDING – AUTOGENEOUS FLOW OF MIXING WATER WITHIN OR ITS EMERGENCE FROM NEWLY PLACED CONC. -DUE TO SETTLEMENT OF SOLID MATERIAL OR DRAINAGE OF MIXING WATER • SEGREGATION- DIFF. CONCENTRATION OF CONSTITUENTS OF MIXED CONC.

MATERIAL • Cement – 33 Grade OPC IS: 269 – 43 Grade OPC IS: 8112 – 53 Grade OPC IS: 12269 – Rapid hardening PC IS : 8041 – High Strength PC IRS: T-40 – Portland Slag cement IS: 455 – Portland Pozzolona Cement IS: 1489 – Sulphate resistance cement IS: 12330

MATERIAL - CEMENT • Mixing of 50% blast furnace slag not permitted at site. CE may permit in special circumstances. • Portland Pozzolana Cement shall not be used for PSC Works. – Can be used in RCC with 14 days damp curing and removal of formwork after 75% strength gain • Rate of development of strength in blended cement to be taken care of in stages of PSC, curing and formwork removal • Compatibility of admixtures to be ascertained by trials

SIZE OF AGGREGATE • ≤ ¼ OF MIN THICKNESS OF MEMBER • LESSER OF – 5 mm LESS THAN THE MIN CLEAR DISTANCE BETWEEN MAIN BARS – 5 mm LESS THAN THE CLEAR COVER • NOMINAL SIZE 20 mm • SPECIAL CASES MAX 40 mm • (MARINE AGG. TO BE WASHED BEFORE USING)

MATERIAL - WATER • p. H VALUE – 6 TO 8 • NOT LESS THAN 6 • NORMALLY POTABLE WATER IS GOOD ENOUGH

ADMIXTURES • SHOULD NOT ADVERSELY AFFET – STRENGTH – VOLUME CHANGE – DURABILITY • SHOULD NOT HAVE ANY DELETERIOUS EFFECT ON REINFORCEMENT • Ca. Cl 2, containing Ca. Cl 2, Cl & SO 3 ion, Nitrates &Thiocynate based NOT TO BE USED

CHLORIDE CONTENT Coarse Aggregate Max. 0. 02% Fine Aggregate Max. 0. 04% Water Max. 50 mg/l for PSC Cement Max. 0. 06% PSC and severe • Total Max 2000 mg/l for Plain CONC • • • 1000 mg/l for RCC • 500 mg/l for PSC

CONCRETE • Concrete shall be in designated in table 2 grades as • The characteristics strength is defined as strength of material below which not more than 5% of the test results expected to fail

TABLE 2 GRADE DESIGNATION SPECIFIED CHARACTRISTIC COMPRESSIVE STRENGTH AT 28 DAYS N/mm 2 M 20 M 25 M 30 M 35 M 40 M 45 M 50 M 55 M 60 20 25 30 35 40 45 50 55 60

CONC. - ELASTIC DEFORMATION • MODULUS OF ELASTICITY – INFLUENCED BY – ELASTIC PROPERTIES OF AGREGATE – CONDITION OF CURING – AGE OF CONCRETE – TYPE OF CEMENT – Normally related to compressive strength of concrete – In absence of data, value may be taken from para 5. 2. 2. 1 • SHRINKAGE – DEPENDS ON – CONSITUENTS OF CONCRETE – SIZE OF MEMBER – ENVIORNMENTAL CONDITIONS – MOST INFLUENCED BY TOTAL AMOUNT OF WATER AT THE TIME OF MIXING • TOTAL SHRINKAGE STRAIN – 0. 0003

CREEP • DEPENDS ON FACTORS AFFECTING SHRINKAGE + – STRESS IN CONCRETE – AGE AT LOADING – DURATION OF LOADING • TILL STRESS IN CONC. ≤ ⅓ fck – CREEP ∞ STRESS • 50% OF CREEP TAKES PLACE IN FIRST MONTH OF LOADING • 75% OF TOTAL CREEP TAKES PLACE IN THE FIRST 6 MONTH OF LOADING • Creep in concrete be taken as 43 x 10 -6 per N/mm 2 of stress at the centriod of prestressing steel for PSC

THERMAL EXPANSION • COEFFICIENT OF THERMAL EXPANSION DEPENDS ON– NATURE OF CEMENT – AGGREGATE – CEMENT CONTENT – RELATIVE HUMIDITY – SIZE OF SECTION • Value for different types of aggregate may be taken from para 5. 2. 5

CONCRETE - WORKABILITY • WORKABILITY – ADEQUATE FOR PLACEMENT AND COMPACTION • MEASURED BY SLUMP

CONCRETE- DURABILITY • DEPENDS ON RESISTANCE TO DETERIORATION AND ENVIORNMENT • RESISTANCE TO WEATHERING, CHEMICAL ATTACK, ABRASION, FROST AND FIRE • SUSCEPTIBILITY TO CORROSIONCOVER PROVIDED, PERMEABILITY

GENERAL ENVIRONMENT • Moderate: sheltered from severe rain or freezing whilst wet concrete exposed to condensation. In contact with non aggressive soil/ground water • Severe: exposed to severe rain or alternate wetting and drying or occasional freezing or severe condensation. Exposed to aggressive sub-soil water or coastal environment • Extreme: exposed to sea water, corrosive fumes, abrasive action, surfaces of members in tidal zone.

REQUIREMENTS – BASED ON ENVIORNMENT – Maximum water cement ratio • Moderate PCC 0. 50 RCC 0. 45 PSC 0. 40 • Severe PCC 0. 45 RCC 0. 40 PSC 0. 40 • Extreme PCC 0. 40 RCC 0. 35 PSC 0. 35 – Minimum grade of concrete ( PSC and Imp) • Moderate PCC M-25 RCC M-30 PSC M-35 • Severe PCC M-30 RCC M-35 PSC M-40 • Extreme PCC M-35 RCC M-40 PSC M-45 – Minimum grade of concrete ( other and sub. Str) • Moderate PCC M-15 RCC M-20 • Severe PCC M-20 RCC M-25 • Extreme PCC M-25 RCC M-30

– Minimum Cement Content (Kg/m 3) • Moderate • Severe PCC 240 PCC 250 RCC 300 PSC 400 RCC 350 PSC 430 • Extreme PCC 300 RCC 400 PSC 440 – Maximum cement content should be limited to 500 Kg/m 3

– Minimum Cover in MM • Moderate • Severe • Extreme Slab 25 Slab 35 Slab 50 Beam 35 Beam 50 Beam 60 Col 50 Col 75 Found 50 Found 75

PERMEABILITY TEST • Permeability test is mandatory for – All RCC/PSC bridges under severe and extreme environment – All major bridges in moderate environment • Depth of penetration not to exceed 25 mm when tested as per standard procedure

PERMEABILITY TEST • Test specimen is of 200 mm dia and 120 mm thick shall be used • After 24 hours of casting of specimen, central circular area of 100 mm diameter is roughened with a wire brush on the side on which the water pressure is to be applied. • The unroughened part of the side of the test specimen which is subjected to water pressure is to be sealed with two coats of cement water paste (W/C =0. 4)

PERMEABILITY TEST • After 28 days of curing at first, a pressure of 1 bar is applied for 48 hours, then 3 bar for 24 hours and 7 bar for 24 hours. • Sample is broken and depth of water penetration is measured

PERMEABILITY TEST APPARATUS

CONCRETE MIX – By designing the concrete mix, such concrete called ‘Design Mix Concrete’ IS: 10262 may be followed for mix design – By adopting nominal concrete mix, such concrete shall be called ‘Nominal mix concrete’. Applicable for M-15, M-20 only.

CONCRETE MIXING • MECHNICAL MIXING • UNIFORM IN THE DISTRIBUTION OF MATERIAL IN THE MASS • UNIFORM IN COLOUR AND CONSISTENCY • MIXING TIME – 1. 5 TO 2 MIN FOR NORMAL MIXER – 45 TO 60 SECONDS FOR HIGH RATED BATCHING PLANTS

RMC • IS 4926 • EFFECT OF TRANSPORTATION- REDUCTION IN WORKABILITY • ADMIXTURE - LIKE WATER REDUCING AGENT/RETARDERS • RETANKERING NOT PERMITTED • TIME PERIOD FOR DELIVERY – 1½ HRS WHEN TEMP > 20°C – 2 HRS WHEN TEMP ≤ 20°C – MILLER ROTATION – 2 TO 6 REV/MIN

FALSE WORK & FORM WORK • FINISHING– NO SURFACE FINISH TO BE PROVIDED – MINOR DEFECTS- SURFACE TO BE RENDERED – PRIOR APPROVAL OF ENGR FOR RECTIFICATION

TOLERANCE FOR FINISHED CONCRETE SHIFT FROM ALIGNMENT ± 25 mm DEVIATION FROM PLUMB/BATTER PIER 1 IN 150 MAX 0. 05 X LEAST LAT. DIM ABUTMENT 1 IN 125 CROSS SECTIONAL DIMENSION -5 mm + 20 mm PLAN DIM OF FOOTING + 50 mm - 25 mm THICKNES OF FOOTING + NO LIMIT - 5 FOOTING ECCENTRICITY 0. 02 X WIDTH, NOT MORE THAN 50 mm C/C DIST OF PIER & ABUTMENT ± 30 mm C/C DIST OF BEARINGS ALONG SPAN ± 5 mm

REINFORCEMENT AND PRESTRESSING TENDONS • BENT REBARS SHOULD NOT BE REBENT AT THE SAME LOCATION • COLD BENDING • NO TACK WELDING • 1. 6 MM DIA G I BINDING WIRE – FREE ENDS BENT INSIDE • TOLERANCE FOR PLACING REBARS – OVERALL DEPTH ≤ 200 MM - ± 10 MM – OVERALL DEPTH > 200 MM - ± 15 MM

WELDED JOINTS IN REINFORCEMENT • MAY BE USED WITH ENGR’S APPROVAL • TESTS TO PROVE STRENGH • IF PROVIDED – NOT NEAR BENDS – STAGGERED – IN LOW STRESS REGION

MECHANICAL JOINTS • • WITH ENGR’S APPROVAL SCREWED COUPLING BOTTLE NUTS OTHER PATENTED SYSTEMS

PRESTRESSING TENDONS • • • BENDING/STRAIGHTENING – NO HEATING CUTTING – MECHANICAL CUTTER HTS BARS MY BE JOINED BY COUPLING WELDING NOT PERMITTED PLACING TOLERENCE - ± 5 MM

STRESSING • ALL WIRES/STRANDS IN A TENDON TO BE STRESSED SIMULTENEOUSLY • SLACK TO BE REMOVED BY SMALL INITIAL TENSION • PRESTRESSING FORCE – MEASURED BY– GAUGES – EXTENSION – STRESS-STRAIN CURVE • TWO SHALL BE WITHIN ± 5%

TRANSPORT, PLACEMENT , COMPACTION & CURING • • COVER BLOCKS OF SAME STRENGTH COMPACTION WITH VIBRATOR PSC – FORM VIBRATOR CURING – – MOIST – 14 DAYS – CURING COMPOUND – ALONGWITH STRIPPING – STEAM CURING- 18 HRS CURING CYCLE • RATE OF TEMP RISE – 22 -33°C PER HR • RAPID TEMP CHANGE TO BE AVOIDED

SAMPLING AND TESTING • SAMPLING AS PER IS 1199, TESTING- IS 516 • FREQUENCY OF SAMPLING CONC. QTY IN M 3 1 -5 6 -15 16 -30 31 -50 51 & ABOVE SAMPLES 1 2 3 4 4 + 1 FOR EVERY ADDL 50 M 3 OR PART

TESTING • TEST STRENGTH OF A SAMPLE-AVERAGE OF STRENGTH OF 3 SPECIMEN • INDIVIDUAL VARIATION - ± 15% OF AVERAGE • STANDARD DEVIATION- AT LEAST FOR 30 SAMPLES • TO BE BROUGHT UPTO DATE • TABLE 8 BE FOLLOWED FOR SD IF SUFFICIENT SAMPLE RESULTS NOT AVAILABLE

ACCEPTANCE CRITERIA • MEAN STRENGTH OF ANY GROUP OF FOUR CONSECUTIVE TEST RESULTSCOMPRESSIVE ST. > fck + 3 N/mm 2 FLEXURE > fck + 0. 3 N/mm 2 • INDIVIDUAL RESULTSCOMPRESSIVE ST. ≥ fck - 3 N/mm 2 FLEXURE ≥ fck - 0. 3 N/mm 2 • POROUS AND HONEYCOMBED CONC. IS LIABLE TO BE REJECTED

COATING OF CONCRETE

LIMIT STATE REQUIREMENTS • Serviceability Limit State (SLS) – No local damage – Crack width control in RCC, no crack in PSC • Ultimate Limit State (ULS) – No collapse due to rupture, buckling or overturning under extreme loads – No excessive deflection

CRACK WIDTH • • MODERATE ENVIRONMENT- 0. 25 MM SEVERE – 0. 20 MM EXTREME ENVIRONMENT- 0. 10 MM PSC – NO CRACKS AS NO TENSILE STRESS PERMITTED

SAFETY FACTORS FOR MATERIALS • SERVICEBILITY • CONCRETE – BENDING -0. 50 fck FOR RCC & 0. 40 fck FOR PSC – AXIAL COMPRESSION - 0. 38 fck FOR RCC & 0. 30 fck FOR PSC • STEEL REIN. 0. 75 fy • ULTIMATE – 1. 5 FOR CONCRETE AND 1. 15 FOR STEEL

SAFTY FACTORS FOR LOADS • AS PER TABLE 12 • FOR LOAD COMBINATION 1 LOAD DEAD WEIGTH OF CONCRETE SUPERIMPOSED DEAD LOADS EARTH PRESSURE RELIEVING EFFECT OF EARTH PRESSURE SLS 1. 00 1. 20 1. 00 - ULS 1. 25 2. 00 1. 70 1. 00 LIVE LOAD ON FOOT PATH 1. 00 1. 50 LIVE LOAD 1. 10 1. 75

LOAD COMBINATIONS 1. PEMANENT LOADS + LIVE LOAD 2. PEMANENT LOADS + LIVE LOAD + WL OR EQ + ERECTION 3. PEMANENT LOADS + LIVE LOAD + RESTRAINT + ERECTION 4. PEMANENT LOADS + LIVE LOAD + FRICTION AT BREARING 5. PEMANENT LOADS + DERAILMENT LOADS

IMPORTANT POINTS • For span greater than 30 m, temp. gradient to be considered • In analysis of a beam, axial forces can be neglected if does not exceed 0. 1 fck X cross-sectional area • Enhanced shear near supports • Construction joint details in appendix A • Form work to be designed for all forces including pre-stressing forces

LOAD TEST • Not a substitute for normal design and construction procedure – Additional test of quality • Mandatory? • Number of tests?

LOAD TEST • To be done as soon as possible after 28 days – Can be conducted early if quality of concrete is not in doubt and CS has reached • DL + 1. 25 LL • If DL is deficient >> compensate • To be properly supported on bearing • Maximum load to be kept for 24 hours • No cracks should appear

LOAD TEST • Measure deflection – If < 40 L 2/h mm OK – If > 40 L 2/h Remove load, measure recovery – If Recovery > 85 % OK – If Recovery < 85 % Again load and measure recovery – If Recovery > 85 % OK otherwise FAIL L is effective span in meters and h overall depth in mm