# Composite Concrete Construction

Urban and Civil

Nov 26, 2013 (4 years and 7 months ago)

107 views

6
-

Calculation of shear stress at

composite interface:

Strain and stress distributions across composite beam
cross
-

section, under service and ultimate loads.

V =

V * S

I

* b

THE SHEAR STREES AT ANY POINT ALONG THE
COMPOSITE INTERFACE CAN BE COMPUTED AS:

WHERE:

V : Shear force at any section under consideration

S : Statical moment of area on one side of the composite inter

I : Moment of inertia of the transformed composite section,

neglecting the tensile resistance of concrete

b : Breadth of the composite interface at the section under

consideration

b)

Horizontal shear stress distribution along

V
h

=

C
1

b * L
s

The horizontal shear stress:

WHERE :

C
1
: 0.85
F
c
’ * b * t
1

L
s
:
D
istance between maximum and zero moment points.

T
1
: Depth of equivalent rectangular stress distribution over the

composite interface

7
-

Code Requirements:

A)
BS 8110 (1995):

i
) Average horizontal design shear stress:

the average design shear stress should then be distributed in proportion

to the vertical design shear force diagram to give the horizontal shear

stress at any point along the length of member .

Design

shear force

Beam width * length between max +
ve

or
-
ve

moment and zero moment

=

ii)
:

1) should be at least 0.15% of the contact area.

2) the spacing in T
-

beam ribs with composite flange should not

exceed the max of :

a) Thickness of in situ concrete

b) 600 mm

iii)
:

when the horizontal shear stress exceeds the value given in table

all horizontal shear force should be carried reinforcement anchored

on either side of interface

Where:

A
h

(in mm
2
/m)

A
h

=

1000 * b * V
h

0.87* fy

B)
DIN 1045 (1978):

a) In case of floors, with live loads up to 500 kg/m
2

it is not

necessary to check direct shear strength at interface

provided that the contact surface is rough.

b) For