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Module
10
Compression Members
Version 2 CE IIT, Kharagpur
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View Full Document Lesson
22
Short Axially Loaded
Compression Members
Version 2 CE IIT, Kharagpur
Instructional Objectives:
At the end of this lesson, the student should be able to:
•
state additional assumptions regarding the strengths of concrete and steel
for the design of short axially loaded columns,
•
specify the values of design strengths of concrete and steel,
•
derive the governing equation for the design of short and axially loaded
tied columns,
•
derive the governing equation for the design of short and axially loaded
spiral columns,
•
derive the equation to determine the pitch of helix in spiral columns,
•
apply the respective equations to design the two types of columns by
direct computation,
•
use the charts of SP16 to design these two types of columns subjected to
axial loads as per IS code.
10.22.1
Introduction
Tied and helically bound are the two types of columns mentioned in
sec.10.21.3 of Lesson 21. These two types of columns are taken up in this
lesson when they are short and subjected to axially loads. Out of several types of
plan forms, only rectangular and square crosssections are covered in this lesson
for the tied columns and circular crosssection for the helically bound columns.
Axially loaded columns also need to be designed keeping the provision of
resisting some moments which normally is the situation in most of the practical
columns. This is ensured by checking the minimum eccentricity of loads applied
on these columns as stipulated in IS 456. Moreover, the design strengths of
concrete and steel are further reduced in the design of such columns. The
governing equations of the two types of columns and the equation for
determining the pitch of the helix in continuously tied column are derived and
explained. The design can be done by employing the derived equation i.e., by
direct computation or by using the charts of SP16. Several numerical examples
are solved to explain the design of the two types of columns by direct
computation and using the charts of SP16.
Version 2 CE IIT, Kharagpur
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View Full Document 10.22.2
Further Assumptions Regarding the Strengths of
Concrete and Steel
All the assumptions required for the derivation of the governing equations
are given in sec.10.21.11 of Lesson 21. The stressstrain diagrams of mild steel
(Fe 250) and cold worked deformed bars (Fe 415 and Fe 500) are given in
Figs.1.2.3 and 4, respectively of Lesson 2. The stress block of compressive part
of concrete is given in Fig.3.4.1.9 of Lesson 4, which is used in the design of
beam by limit state of collapse. The maximum design strength of concrete is
shown as constant at 0.446
f
ck
when the strain ranges from 0.002 to 0.0035. The
maximum design stress of steel is 0.87
f
y
.
Sections 10.21.4 and 12 of Lesson 21 explain that all columns including
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This note was uploaded on 03/17/2012 for the course CENG 3012 taught by Professor Prof.j.n.bandopadhyay during the Summer '01 term at Indian Institute of Technology, Kharagpur.
 Summer '01
 Prof.J.N.Bandopadhyay

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