Everything Structures

Foundations fail in a number of ways. When we say a foundation fails in sliding , we are not talking about cracking concrete or soil punching. We are talking about something more fundamental: The entire foundation block tries to move sideways as a rigid body. Sliding vs Other Failures Bearing failure → soil beneath fails in compression (local or general shear). Overturning → foundation rotates about an edge due to moment. Sliding → horizontal forces overcome lateral resistance at the base. These are independent failure modes . A footing can be: Safe in bearing ✔ Safe in overturning ✔ But, Unsafe in sliding ✖ Why Sliding Is Often Ignored 1. Engineers focus heavily on vertical loads and soil bearing capacities. 2. Sliding does not “ look dramatic ” in drawings. 3. Friction is assumed to be “ automatically sufficient. ” There isn't heavy settlement if sliding failure occurs and you always have good frictional force that resists sliding which itself increases with vertical lo...

Designing any structure involves a lot of assumptions that are based on analysis, experimentation and safety considerations. we typically  assume  loads are transferred via centerline of the footing and that the entire base of the foundation remains in full contact with the ground. But in real-world conditions, columns may experience  eccentric vertical loads from machinery ,  lateral forces/moments due to wind or seismic forces ,  tension and unsymmetrical geometry. Eccentricity can be caused due to off-center application of loading or from centric loading with bending moments. All this leads to non-uniform soil pressure below the footing, which is difficult to calculate, especially in case of Loss of Contact.  (Refer Loss of Contact  in Concrete Foundation Design ) Teng's method helps us modify the bearing pressure to realistically account for  E ccentricity Loss of Contact Non-Linear Soil Response while still using simple mechanics. Assumption...