Different Types of Failures in RCC Buildings with Case Studies

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Types of failures in reinforced concrete buildings such as failure due to poor concrete quality, reinforcement corrosion, failure of foundations due to soil etc. with case studies are discussed. In small residential buildings the quality of construction is seldom questionable. The reason varies from poor building material quality to lack of knowledge of good construction practices. Most of the times, engineers are ignored by individual house owners and masons are given sole responsibility of both design and construction. Almost all structural engineers practicing in India will agree that 99% of the failures of structures in India are not due to design failure. Explaining the different aspect of construction that a normal home builder, engineer or contractor needs to remember.

Case Studies of Different Types of Failures in Reinforced Concrete Buildings:

Case 1: Failure of RCC Column Due to Corrosion of Reinforcement

Observation month : October, 2015 Site condition : Good quality soil, 1 km from sea coast Observation : Excessive rust in dowel rebars in column Investigation : The foundation was completed 3 months back and the dowels were exposed to atmosphere unguarded for 3 months in the rainy season. Precaution to be taken : If a rebar or dowel is kept exposed, it should be covered with cement sand slurry and the coating needs to be applied every fortnight.

Case 2: Failure of Building Due to Improper transfer of load

Observation month : November, 2015 Site condition : Good quality soil, No engineer consulted Observation : Poor workmanship (Improper transfer of load due to poor centering) Investigation : The centering was done by a normal mason and proper techniques were not used. Also due to congestion of rebars at beam column junction the mason avoids compaction which leads to honeycombing. Precaution to be taken : Centering has to be done by training centering masons and site supervision by engineers is necessary during foundation centering, casting and casting at every slab. Compaction needs to be done homogeneously at every stage of construction

Case 3: Failure of Reinforced Concrete Structure due to Poor concrete mix and water quality

Observation month : August, 2015 Site condition : Good quality soil, design by engineer ignored during construction Observation : Poor concrete mix and water quality Investigation : The water quality was not checked before use. After testing it was found that the concrete did not achieve the desired strength of 20 MPa due to poor quality of concrete mix and water. Precaution to be taken : The quality of all building material (cement, stone chips, sand and water) needs to be checked before mixing. Also the pH of water should be more than 6, i.e. not acidic. Any deviation from design should be approved by the structural engineer.

Case 4: Failure of RCC Structure due to use of Beach Sand in Construction

Observation month : August, 2015 Site condition : Good quality soil, 1 km from sea coast Observation : Deep cracks in ground floor columns and concrete chipping all over the building Investigation : Beach sand (high salinity) was used for construction. Also ground water (without chemical testing done) was used in concrete. Precaution to be taken : The quality of building materials should follow the quality norm as mentioned in IS 456: 2008 Section 2. The detail is given in the chart.

Fig: Deep cracks formed in RCC Column, Rebar gets exposed

Case 5: Structural Damage to Failure of Soil

Observation month : August, 2015 Site condition : Good quality soil, Good construction quality, no soil testing done Observation : Column bars bent due to sudden thunderstorm and landslide Investigation : The soil was not tested before construction. Hence when sudden thunderstorm came and flooding at site occurred, the soil of straight cut walls failed and the landslide occur.

Precaution to be taken : Soil has to be tested for both chemical properties and strength before design and construction starts. The side wall of excavated site should have a slope of more than 30 degrees. In case of weak soil, micropile or wooden sheet pile needs to be used to arrest soil. Article by: Priyanka Gupta, Manager, Tata Steel Ltd.