What is Punching Shear? Punching Shear in Flat Slabs

Flat Slab Failure due to Punching shear

What is Punching Shear? Punching shear is a type of failure of reinforced concrete slabs subjected to high localized forces. In flat slab structures this occurs at column support points. The failure is due to shear. This type of failure is catastrophic because no visible signs are shown prior to failure. Punching shear failure disasters … Read more

Spalling of Concrete – Causes, Prevention & Repair

Spalling of Concrete slab due to corrosion

Spalling of Concrete – Causes, Prevention & Repair ingress of moisture of air into concrete causes corrosion of reinforcement and results in the volume expansion of steel bars, consequently causing cracks & spalling of concrete cover The word Spall in engineering, describes the chips or fragments of a material that is broken off a bigger … Read more

Diagonal Cracks in Foundation and Walls

Diagonal Crack at the corner of a strip footing

Diagonal Cracks in Foundation and Walls Diagonal cracking is an inclined crack beginning at the tension surface of a concrete member. Steep diagonal cracks appear in concrete foundation due to point loads that exceed the compressive strength of the concrete. This type of failure, known as settlement, can happen due to “volume changes in clay soils … Read more

Ductile Fracture of Metals by Necking – Cup and Cone Failure

Cup and cone of mild steel road after Necking

Ductile Fracture of Metals by Necking – Cup and Cone Failure extensive plastic deformation and energy absorption (“toughness”) before fracture Fracture: separation of a body into pieces due to stress, at temperatures below the melting point. Steps in fracture: crack formation crack propagation Major Fracture Mechanisms Depending on the ability of material to undergo plastic … Read more

Concrete Creep Definition, Creep deformation Stages & Design Strategies

Creep Cracks In Concrete Walk Way

Concrete Creep Definition, Creep deformation Stages & Design Strategies When load is applied on a concrete specimen, shows an instantaneous deformation followed by slow increase of deformation is called concrete creep. Creep is a time-dependent permanent (plastic) deformation under a certain applied load.  Generally, creep occurs at high temperature (thermal creep) but can also happen … Read more

Buckling of Columns – Euler Theory for Elastic Buckling

Buckling of Concrete Columns

Buckling of Columns – Euler Theory for Elastic Buckling BUCKLING – Loss of stability –Axial loads cause lateral deformations (bending-like deformations) Buckling of Columns is a form of deformation as a result of axial- compression forces. This leads to bending of the column, due to the instability of the column. This mode of failure is … Read more

Freeze Thaw Damage of Concrete – Effects & Preventive Measures

Damage of Bridge due to Freeze Thaw Cycles

Freeze Thaw Damage of Concrete – Effects & Preventive Measures “damage to concrete caused by extreme temperature variations as noted by random pattern cracking.” A severe exposure condition on portland cement concrete structures is exposure to cycles of freezing and thawing. Air entrainment is used to enhance the freeze-thaw resistance of portland cement concrete exposed … Read more

Significance of Delayed Ettringite Formation and Damage Mechanisms

Cracks due to delayed ettringite formation

Significance of Delayed Ettringite Formation and Damage Mechanisms Ettringite is formed in hydrated Portland cement system as a result of the reaction of calcium aluminate with calcium sulfate, both present in Portland cement. In the cement system, the presence of ettringite depends on the ratio of calcium sulfate to tri-calcium aluminate (C3A); when this ratio … Read more

Fracture in Steel – Brittle fracture in ductile material

Brittle Cracking of a Wide Flange Beam

Fracture in Steel – Brittle fracture in ductile material Brittle failure is the brisk propagation of cracks through a material. This typically occurs so quickly that no plastic deformation takes place before fracture occurs. In structure failures, brittle failure usually causes a failure in structural integrity. Because of the rapid nature of this failure, it often leads … Read more