Introduction
Reinforced concrete slabs are the most important structural component in
the construction industry and the most common practice to design any
reinforced concrete slab is to start with the selection of slab type
(one way slabs, two way slabs, waffle slabs, flat slabs or pre-cast or
pre-stressed slabs) . The most common type of slabs used in the
construction industry is the flat slab due to the dominancy of
slab–column connection in the general behaviour of flat slab. Flat slab
is also an ease for the contractor to construct in shorter duration. The
flat slab sections with regular column layout are the most common type
of RC structures in the construction industry and it’s also the choice
for the contractor to construct the building with regular column
layouts. There are scenarios where the building needs to be constructed
having the irregular column layout based on the client’s preference.
There are several studies on analysis and design of slabs with irregular
column layouts. Baskaran, K. in his research study introduced the
structural membrane approach to design the flat slab on irregular column
grid. Further, he also performed some experimental results to validate
his theoretical approach. Hillerborg, Arne in his book introduced the
strip method of design for design of slabs having Irregular plan or that
carry unevenly distributed loads. Saether proposed an effective method
for determining the bending moments in flat plates. He also developed an
analytical design without the use of empirical formulas. His proposed
method made it possible to analyse irregular plates with regular column
layouts but gave an approximate results for irregular column layout flat
slabs. Wang and Teng in their research study presented a finite element
analysis of reinforced flat plate using the flexible layering scheme.
This proposed study is capable of analysing flat plate, flat slab with
drop panels and large size flat plate with irregular columns layout.
Aldwaik M. and Adeli H. presented the cost optimization of reinforced
concrete flat slabs for irregular high rise building structures. This
proposed model automates the design process of RC slabs in addition to
the cost optimization. The other similar research studies can be found
elsewhere .
This study proposed a simplified method to analyse and design the flat
plates with irregular column layout by first subdividing the irregular
panels into triangular panels (figure-1) and then design the largest
triangle slab panel using the ultimate-strength design method USD under
the provisions of ACI building code of design (ACI 318-14) . This
simplified and quick approach will be useful for the designers to
quickly analyse and design the flat slabs having the irregular column
layout to fulfil the client’s requirement. Moreover, this simplified
method approach will also be useful for the educational purposes where
the students can easily analyse and design the flat slabs having the
irregular column layout.
The design of flat slabs with irregular column layout is based on
structural safety and economy. Flexural design formulas are derived
based on the theoretical principles of plate and yield line theories and
ACI building code of design constraints . Numerical examples are
presented in this study to illustrate the method capability of designing
the flat slabs having the irregular column layout. Six different flat
slabs with irregular columns layout (FS-1 to FS-6) are selected to be
analysed and designed using the simplified design method approach. The
complete analysis and design for two of the flat slabs (FS-3 and FS-6)
are also provided in this study. Mathcad software is used in this
research work to formulate this simplified design approach.