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Module
6
Shear, Bond,
Anchorage,
Development Length
and Torsion
Version 2 CE IIT, Kharagpur
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View Full Document Lesson
13
Limit State of Collapse
in Shear
Version 2 CE IIT, Kharagpur
Instructional Objectives:
At the end of this lesson, the student should be able to:
•
name and explain the three different failure modes of reinforced concrete
beams under the combined effects of bending moment and shear force,
•
define nominal shear stress
τ
v
of rectangular and
T
beams of uniform and
varying depths under the combined effects of bending moment and shear
force,
•
name the two parameters on which the design shear strength of concrete
depends,
•
find out the maximum shear stress of concrete beams
τ
cmax
with shear
reinforcement,
•
locate the critical sections for shear in beams,
•
explain when and why do we consider enhanced shear strength of concrete,
•
explain why the minimum shear reinforcement is provided in any beam,
•
determine the amount of minimum shear reinforcement to be provided in
any beam,
•
specify the three different ways of providing shear reinforcement in a beam,
•
design the shear reinforcement in a beam for each of the three methods
mentioned above,
•
design the shear reinforcement closed to the support of a beam,
•
specify the conditions to be satisfied for the curtailment of tension
reinforcement when designing shear reinforcement,
•
place the vertical stirrups in a beam.
6.13.1
Introduction
This lesson explains the three failure modes due to shear force in beams
and defines different shear stresses needed to design the beams for shear. The
critical sections for shear and the minimum shear reinforcement to be provided in
beams are mentioned as per IS 456. The design of shear reinforcement has
been illustrated in Lesson 14 through several numerical problems including the
curtailment of tension reinforcement in flexural members.
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Failure Modes due to Shear
Bending in reinforced concrete beams is usually accompanied by shear,
the exact analysis of which is very complex. However, experimental studies
confirmed the following three different modes of failure due to possible
combinations of shear force and
bending moment at a given section (Figs.
6.13.1a to c):
(i)
Web shear (Fig. 6.13.1a)
(ii)
Flexural tension shear (Fig. 6.13.1b)
(iii) Flexural compression shear (Fig. 6.13.1c)
Web shear causes cracks which progress along the dotted line shown in
Fig. 6.13.1a. Steel yields in flexural tension shear as shown in Fig. 6.13.1b, while
concrete crushes in compression due to flexural compression shear as shown in
Fig. 6.13.1c. An indepth presentation of the three types of failure modes is
beyond the scope here. Only the salient points needed for the routine design of
beams in shear are presented here.
Version 2 CE IIT, Kharagpur
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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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