# Statically determinate and indeterminate structures- Example Concept

There are two types of structure to be design and analysis in civil engineering they are Statically determinate and indeterminate structures.

Here, I shall tell you the difference between Statically determinate and indeterminate structures. The most common structure like public building residential building are statically indeterminate structures.

In order to analyze a statically indeterminate structure, you have to know how to analyze the statically determinate structure.

## Statically Determinate Structure

If the structure can be analyzed by use of the equation of equilibrium is known as statically determinate structure. The equation of equilibrium are,

Sum of horizontal force is zero,
Sum of vertical force is zero,
Sum of the moment about any point is zero.

## Statically indeterminacy structure

The structure which cannot be analyzed by just using the equation of equilibrium is known as a statically indeterminate structure.

## Example of statically determinant structure

At (A) it is hinged support and at (B) it has roller support.

So, In the above beam, the reaction occurred at A is vertically upward and also in a horizontal direction. Because hinge support has two reactions.

But, the reaction occurred at B is only one reaction which is vertically upward.

So, in the above beam, Totally three unknown reaction which is two reactions at support (A) and one unknown reaction at (B).

So, this beam can be analysed with the help of those three equilibrium reaction.

If the number of unknown reactions is less than or equal to equilibrium reaction i.e three then the structure can be easily analyzed. and this structure is known as a statically determinant structure.

Analyzing is to calculate the shear force and bending moment of the structure.

## Example of statically indeterminate structure.

The above beam, It has two hinge support in which, (A) has two reactions and (B) has also two reactions.

So, the total unknown reaction is four which is greater than the equilibrium equation which is only three.

So, we can not analyze this structure. So, these types of structures are known as statically indeterminant structures.

If you see in the residential building then all the members like a beam, column, slabs are fixed with each other. So, they have a more unknown reaction than the equilibrium equation which is three.

Hence, they are statically indeterminate structure.

I hope you understood all about difference between Statically determinate and indeterminate structures.

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