Architecture & Civil Engineering

Architecture & Civil Engineering

EFFECT OF EXTRA CANTILEVER SLABS OF VARIABLE SPAN ON THE STRUCTURAL ELEMENTS OF A FLAT PLATE BUILDING

Pages: 11  ,  Volume: 40  ,  Issue: 1 , November   2019
Received: 16 Nov 2019  ,  Published: 20 November 2019
Views: 48  ,  Download: 23

Authors

# Author Name
1 Dipa Sarker
2 Ariful Islam
3 Mirajul Alam
4 Mohammad Arman Ullah

Abstract

The flat plate system has been adopted in many buildings in Bangladesh specially in garments factory buildings. However,
it is observed that extra cantilevers sides which are not conforming to the actual plan and design are constructed to take
advantage of the extra floor space to meet the economical demands. Many structures in Bangladesh differ from their
actual plan due to the extra cantilever portion provided by the developers. So the various effects that take place in the
building due to this phenomenon are discussed in this research. The axial force, deflection, punching shear, horizontal &
vertical displacement of columns has been analyzed for increasing cantilever of 2ft, 4ft, 6ft, 8ft and 10 ft respectively.
Deflection at mid-point of a panel of a particular slab, column strip and middle strip are also determined. Percentage of
increase in column load for 2ft, 4ft, 6ft, 8ft & 10 ft is compared and their variability is observed. Factor of safety is OK for
a structure with no cantilever. For 2 ft. extra cantilever, the exterior column fails. For 4ft, 6ft, 8ft & 10ft, the factor of
safety for exterior and corner column is unsafe and thus fails. But it does not affect much to the interior columns and they
are found safe in every condition. It has been observed in all cases that corner and exterior columns are more susceptible
to extra cantilevers than interior column. According to the punching shear check, no shear reinforcement is required for
corner column and exterior column. Flat plates are also used by the engineers because it provides more space and stability.
Structural engineers commonly use manual calculations for the analysis of flat plate structures. The software STAAD.Pro
V8i has been used in this paper for the design and analysis of a six storied garments factory building. For the analysis, 3
load combinations are used in this paper. To understand the structural behavior of the slab due to increase in the cantilever
portion of the slab, different parameters are evaluated using the software. The manual calculations for axial force,
horizontal and vertical displacements, deflection and punching shear are also performed in order to compare them with the
results obtained from STAAD Pro. The obtained results are plotted against the various load combinations for a graphical
representation of effect of structural behavior of the columns and slabs. The analysis is done for a concrete structure and
slab thickness is also defined as per calculation.
 

Keywords

  • extra cantilever
  • structural behavior
  • STAAD.Pro V8i
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