EffectiveWidth of Composite Beams with Openings Abstract

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15 Νοε 2013 (πριν από 3 χρόνια και 7 μήνες)

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Effective

Width

of Composite Beams with Openings


Abstract


For many decades, steel beams and reinforced concrete slabs were integrated to
produce durable and economic well
-
known type of construction known as composite
beams. In most buildings, utility du
cts and pipes (
air conditioning, electricity services,
…etc
.) may pass in the slab, however, provision of such openings may cause some
weak regions and produces several cracks and excessive deformations, which will
surly affect the contribution of the slab

to the strength of the beam (effective width) as
a whole. Composite beams in most steel buildings are consisting of a hot rolled steel
section and concrete slab cast on profiled steel decking.


Most investigations and codes considered the slab effectiv
e width in composite
beams with solid slabs (without steel corrugated sheet or slab openings) as
described in chapter (1).


Modern codes of practice, such as Eurocode 8 [8], adopt capacity design
procedures for the seismic design of steel and composite
frames. This involves
failure mode control in which a strong column
-
weak beam behavior is sought by
appropriately proportioning the capacity of beam and column members. In order to
fulfil the weak beam
-
strong
-
column idealization, the capacity of both the b
eam and
column sections should be accurately estimated, including possible overstrength
reasons. One of the likely causes of overstrength is the effective width of the slab,
which is commonly used in design calculations and two
-
dimensional frame analysis
t
o represent the effective size of composite beams.


The subject of effective width of beam with flanges was investigated for the elastic
case of simply supported beams, first by Von Karman [7] and later by many others
for various loading and boundary con
ditions. In this research, interest has been
directed to finding the effective width of composite beams consisting of steel beam
connected to composite slab (connected upon steel sheeting). The effect of having
openings in different location of the slab i
s also studied at ultimate loads.


An
experimental investigation

of twelve simply supported full
-
scale composite
beams with and without slab opening under
different type of loading and beam
section
[included within chapters (2&3)]
.
Composite beam section

is built up steel I
-
section and composite R.C flange with corrugated steel sheet. The ribs of corrugation
are oriented perpendicular to the main steel beam. Many parameters are studied
such as the opening position, and loading type. A comparison is carrie
d out to
correlate the results with finite element models.


Three
-
dimensional non
-
linear finite element analysis till failure is performed on two
hundred and forty simply supported composite beams,
to investigate the effective
width of composite slab a
cting with steel beams (with T
-
section & L
-
section)
. Full
interaction is assumed between the used steel hot
-
rolled I
-
section and the overlaying
composite R.C. slab with corrugated steel sheet. The ribs of corrugation are oriented
perpendicularly to the ste
el beam longitudinal axis.
These details are included in
chapter (4).


Many variables are studied such as
slab rectangularity values, boundary
conditions, case and type of loading, concrete layer thickness, beam span ratio,
opening width a
nd length, and opening vertical position.

Any other structural feathers
of composite beams are considered constants. Interesting results, conclusions and
recommendations, which may be useful for designers, comparison with the famous
codes of specification
s are presented in
chapter (5)
.


Computer program was developed to calculate the effective width according to
current study and considered Codes of Practice for both exterior and interior beams.