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Definition of braced & unbraced columns and differences among them

Based on the cross-section, length, behavior, cross bracing, longitudinal reinforcement; a column is classified as braced and unbraced column.

Braced Column – A column is treated as braced in a specified plane when the lateral strength to the structure on the whole is arranged with wall or bracing or buttressing to withstand all lateral forces in that plane. Alternatively, it can be said that if relative transverse displacement among the upper and lower ends of a column is restrained, the frame is defined as braced column.

Unbraced Column – If relative transverse displacement among the upper & lower ends of a column is not restrained, the frame is defined as unbraced column.

Given below, the variations among the braced and unbraced column :-

1) Braced column is treated as braced in a specified plan when lateral strength of the structure as a whole is arranged with walls or bracing.
Unbraced column is treated unbraced in a specified plan when lateral strength of the structure as a whole is arranged with columns only.

2) Braced columns can’t withstand lateral loads.
Unbraced columns can withstand lateral loads.

3) In braced frames various lateral loads ranging from wind, earthquake, etc can be countered with shear wall, bracings or special supports.
In unbraced frames lateral loads ranging from wind, earthquake etc. can be countered with columns.

4) Sideways or joint translation can’t be done in braced columns.
Sideways or joint translation take place in unbraced columns.

5) Braced columns contain zero value of sway.
Unbraced columns are dependent on sway.

6) Braced columns are mainly used to design the steel structures.
Unbraced columns are mainly used to design the RCC structures.

7) Braced columns have sufficient strength to withstand Earthquake.
Unbraced columns have less strength as compared to braced columns to withstand earthquake.

8) To arrange gap among two braced columns is very complicated.
The gap can be easily arranged among two unbraced columns.

9) Braced columns are suitable in tube structures where multistoried buildings are built up.
Unbraced columns are suitable in RCC framed structures where low storied buildings are built up.

10) Structural system with bracing are frequently utilized in vital/special structures.
Structural systems not containing bracing are frequently utilized in general structures.

Article Source: gharpedia.com

Definition of braced & unbraced columns and differences among them