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.