Identification of Cracks
QUESTION 1.) WHAT IS THE MODE OF FAILURE OR DAMAGE OF THE BEAM IN THE FIGURE ABOVE ? ARE THE DAMAGES REPAIRABLE ? ELABORATE .
ANSWER1:
a) 
OBSERVATION :
- CONCRETE CRUSHED AND THE REINFORCEMENT IS EXPOSED .
- CONCRETE SPALLED BEYOND THE REINFORCEMENT WHICH MAY BE A SIGN OF RUPTURE .
- BEAM TOP PORTION LOOKS SAFE BECAUSE OF THE FLANGE ADVANTAGE FROM SLAB .
- THE CRACK DEVLOPED FROM BOTTOM TO TOP MEANS REBAR YIELDING OCCURS IN SUPPORT BOTTOM ONLY .
EXPLAIN ABOUT FAILURE :
- THIS CRACK WILL BE FORMED DUE TO THE FLEXURAL FAILURE OF A BEAM . THE FLEXURAL STRENGTH , KNOWN AS MODULUS OF RUPTURE , BEND STRENGTH , OR FRACTURE STRENGTH ,IS A MATERIAL PROPERTY , DEFINED AS THE STRESS IN A MATERIAL JUST BEFORE IT YIELDS IN A FLEXURE TEST .
- THE FLEXURAL STRENGTH REPRESENTS THE HIGHEST STRESS EXPERINCED WITHIN THE MATERIAL AT ITS MOMENT OF RUPTURE . IT IS MESURE IN TERMS OF STRESS.
- TO OVER COME THIS TYPE OF FAILURE, MAIN STEEL IS PROVIDED AT THE BOTTOM /TOP OF THE BEAM .
- DURING STRESS REVERSAL , SUPPORT TOP EXPERINCE COMPRESSION AND BOTTOM EXPERINCES TENSION .
- TOP COMPRESSION IS MANAGED BY SLAB ADVANTAGE BOTTOM TENSION WAS NOT SATISFIED BY PROVIDED REINFORCEMENT .
- SINCE THE REINFORECEMENT GOT YIELDED .IT CAN NOT BE REPAIRED .
b)
OBSERVATION :
- CRACKS ALONG BEAM -COLUMN EDGE .
- CRACK SEEM TO HAVE DEVELOPED THROUGH THE STRUCTURE AS IT LOOK MUCH WIDER .
- BEAM LOOKS SEPARATED FROM THE COLUMN AT JOINTS.
- CONCRETE IS NOT SEVERELY CRUSHED .
EXPLAIN ABOUT FAILURE:
- THIS CRACKS ARE FORMED DUE TO THE MISTAKES DONE IN THE CONSTRUCTION AND HONEYCOMBING IN CONCRETE .
- TO AVOID CRACKS IN CONCRETE, AVOID USING HIGH SLUMP CONCRETE .
- CONCRETE OF MODERATE SLUMP ( LESS THAN 5 INCHES) RESULT IN LESS CRACKING.
- HIGH SLUMP CONCRETE CAN ONLY BE USED IF IT IS CONTROLLED BY CONCRETE ADMIXTURE OR DESIGNED SUCH THAT SEGREGATION AND BLEEDING OF CONCRETE IS CONTROLLED .
- RECOMMENDED VALUE OF SLUMP CAN BE DIFFERENT APPLICATION
- ITS BEAM PULL OUT FAILURE DUE TO INSUFFICIENT DEVELOPMENT LENGTH OF REINFORCEMENT IN JOINTS.
- DURING EARTHQUAKE, THE HORIZONTAL MOVEMENT OF STRUCTURE MAKES THIS CONDITION WORSE AND DETACHED THE BEAM MEMBER FROM COLUMN .
- PROVIDING ANCHORAGE LENGTH BETWEEN TWO EXISTING CONCRETE IS VERY DIFFICULT . SO NOT REPAIRABLE .
C)
OBSERVATION :
- CRACK ARE EXACTLY AT THE JOINT OF COLUMN -BEAM.
- CRACK IN BEAM DEVELOPED THROUGH ITS ENTIRE WIDTH
- SLAB ALSO DEVELOPED MORE CRACK ALONG THE BEAM WIDTH DIRECTION .
EXPLAIN ABOUT FAILURE :
- THIS CRACK ARE FORMED DUE TO THE BEAM -COLUMN JOINT FAILURE .
- IN THE STRONG COLUMN -WEAK BEAM DESIGN, BEAM ARE EXPECTED TO FORM PLASTIC HINGES AT THEIR ENDS AND DEVELOP FLEXURAL OVERSTRENGTH BEYOND THE DESIGN STRENGTH .
- THE HIGH INTERNAL FORCES DEVELOPED AT PLASTIC HINGES CAUSE CRITICAL BOND CONDITION IN THE LONGITUDINAL REINFORCING BARS PASSING THROUGH THE JOINT AND ALSO IMPOSE HIGH SHEAR DEMAND IN THE JOINT CORE .
- THE BOND PEFORMANCE OF THE BARS ANCHORED IN A JOINT AFFECTS THE SHEAR RESISTING MEACHANISM TO A SIGNIFICANT EXTENT .
ANSWER 2:
a)
OBSERVATION:
- CONCRETE DAMAGED AT TOP OF A COLUMN
- CONCRETE DAMAGED ALL AROUND THE COLUMN FACE .
- BEAMS ARE SAFE .
- THE LOCATION OF COLUMN LOOKS AT EDGES OF THE BUILDING .
- NO WALLS ARE BUILT ALONG THE COLUMN MEANS IT IS PROBABLY AT GROUND FLOOR, FOR PARKING CAR MOVEMENT ACCESS.
EXPLAIN ABOUT FAILURE :
- THIS CRACK WILL BE FORMED DUE TO THE FLEXURAL FAILURE OF A COLUMN .
- COLUMN HAVE THE MOST IMPORTANT ROLE IN ALL STRUCTURAL MEMBERS OF A BUILDING .
- ITS A SOFT STOREY FAILURE , TECHNICALLY PLASTIC HINGE FORMATION .
- DUE TO ABSENCE OF INFILL WALLS AT THE GROUND FLOOR , THE PLASTIC HINGE FORMS AT THE TOP OF GROUND STOREY COLUMNS DURING LATERAL MOVEMENT .
- BASED ON THE DEVELOPMENT OF CRUSH OF CONCRETE IT CAN EITHER BE REPAIRABLE OR NON-REPAIRABLE .
b)
OBSERVATION :
- CONCRETE DEVELOPED COMPLETE BREAKAGE DIAGONALY .
- LONGITUDINAL REINFORCEMENT ARE INTACT
- SHEAR REINFORCMENT SPACING LOOKS WIDER ( WHICH MEANS PROBABLY LESSER SHEAR REBAR PROVIDED )
EXPLAIN ABOUT FAILURE :
- THIS CRACK WILL BE FORMED DUE TO THE SHEAR FAILURE OF A COLUMN .
- LATERAL LOADS IN A STRUCTURAL ARE CARRYING BY VERTICAL ELEMENTS SUCH AS COLUMNS AND SHEAR WALLS . WHEN THERE ARE NO SHEAR WALL, COLUMN CARRY THESE LATERAL LOADS. LATERAL LOAD ARE GENERATED BY WINDS , EARTHQUAKE LOADS , FROM RETAINING STRUCTURES ,ETC.
- SHEAR LINKS ARE PROVIDED TO COLUMNS BASED ON THE SHEAR FORCES EXCRETED ON THEM . FURTHER , THE SIZE OF THE COLUMN INCREASED IN THE DIRECTION OF SHEAR TO INCREASE THE SHEAR CAPACITY.
c)
OBSERVATION :
- COLUMN FAILED COMPLETELY.
- FAILURE AT TOP OF COLUMN
- THERE ARE TWO SLABS CONNECTED TO THE COLUMN, PROBABLY ONE AT MID HEIGHT OF THE COLUMN .
- THE WOODEN PILES MIGHT BE A POST FAILURE SUPPORT AFTER COLUMN FAILED , PROVIDING TEMPORARY PROP TO AVOID COLLAPSE OF THE ENTIRE STRUCTURE .
EXPLAIN ABOUT FAILURE :
- THIS CRACK ARE FORMED DUE TO THE BEAM-COLUMN JOINT FAILURE.
- ITS A SHORT COLUMN FAILURE.
- AN ADDITIONAL SLAB OR BEAM CONNECTED TO A COLUMN IN MID -HEIGHT LEADS TO THIS EFFECT .
- THIS LEADS TO FAILURE ESPECIALLY IF THE CONNECTION IS UNINTENTIONAL AND NOT ACCOUNTED IN DESIGN .
- IN THE STRONG COLUMN -WEAK BEAM DESIGN, BEAM ARE EXPECTED TO FORM PLASTIC HINGES AT THEIR ENDS AND DEVELOPED FLEXURAL OVERSTRENGTH BEYOND THE DESIGN STRENGTH .
- THE FAILURE GIVEN IN THE PICTURE IS NOT AT ALL REPAIRABLE.