Home | Engineering | Behavior of Tied and Spiral Columns

Civil - Design of Reinforced Concrete Elements - Limit State Design Of Columns

Behavior of Tied and Spiral Columns

   Posted On :  16.07.2016 10:58 pm
Behavior of Tied and Spiral Columns

In a spiral column, the lateral expansion of the concrete inside the spiral (referred to as the core) is restrained by the spiral.

Behavior of Tied and Spiral Columns

 

Figure shows a portion of the core of a spiral column. Under a compressive load, the concrete in this column shortens longitudinally under the stress and so, to satisfy Poisson�s ratio, it expands laterally. In a spiral column, the lateral expansion of the concrete inside the spiral (referred to as the core) is restrained by the spiral. This stresses the spiral in tension. For equilibrium, the concrete is subjected to lateral compressive stresses. In a tied column in a non seismic region, the ties are spaced roughly the width of the column apart and, as a result, provide relatively little lateral restraint to the core. Outward pressure on the sides of the ties due to lateral expansion of the core merely bends them outward, developing an insignificant hoop-stress effect. Hence, normal ties have little effect on the strength of the core in a tied column. They do, however, act to reduce the unsupported length of the longitudinal bars, thus reducing the danger of buckling of those bars as the bar stress approaches yield. load-deflection diagrams for a tied column and a spiral column subjected to axial loads is shown in figure. The initial parts of these diagrams are similar. As the maximum load is reached, vertical cracks and crushing develop in the concrete shell outside the ties or spiral, and this concrete spalls off. When this occurs in a tied column, the capacity of the core that remains is less than the load on the column. The concrete core is crushed, and the reinforcement buckles outward between ties. This occurs suddenly, without warning, in a brittle manner. When the shell spalls off a spiral column, the column does not fail immediately because the strength of the core has been enhanced by the triaxial stresses resulting from the effect of the spiral reinforcement. As a result, the column can undergo large deformations, eventually reaching a second maximum load, when the spirals yield and the column finally collapses. Such a failure is much more ductile than that of a tied column and gives warning of the impending failure, along with possible load redistribution to other members. Due to this, spiral column carry little more load than the tied column to an extent of about 5%. Spiral columns are used when ductility is important or where high loads make it economical to utilize the extra strength. Both columns are in the same building and have undergone the same deformations. The tied column has failed completely, while the spiral column, although badly damaged, is still supporting a load. The very minimal ties were inadequate to confine the core concrete. Had the column ties been detailed according to ACI Code, the column will perform better as shown.


Tags : Civil - Design of Reinforced Concrete Elements - Limit State Design Of Columns
Last 30 days 449 views
Related words :

What is Behavior of Tied and Spiral Columns Define Behavior of Tied and Spiral Columns Definition of Behavior of Tied and Spiral Columns where how meaning of Behavior of Tied and Spiral Columns lecturing notes for Behavior of Tied and Spiral Columns lecture notes question and answer for Behavior of Tied and Spiral Columns answer Behavior of Tied and Spiral Columns study material Behavior of Tied and Spiral Columns assignment Behavior of Tied and Spiral Columns reference description of Behavior of Tied and Spiral Columns explanation of Behavior of Tied and Spiral Columns brief detail of Behavior of Tied and Spiral Columns easy explanation solution Behavior of Tied and Spiral Columns wiki Behavior of Tied and Spiral Columns wikipedia how why is who were when is when did where did Behavior of Tied and Spiral Columns list of Behavior of Tied and Spiral Columns school assignment college assignment Behavior of Tied and Spiral Columns college notes school notes kids with diagram or figure or image difference between Behavior of Tied and Spiral Columns www.readorrefer.in - Read Or Refer

​Read Or Refer

OTHER SUGEST TOPIC

Recent New Topics :