What is flat slab construction?
Flat slab construction method basically involves reinforcing concrete slab supported by concrete columns directly without any use of beams. This system is usually defined as a single-sided or double-sided support system with the entire load of slab being placed on supporting columns and a square shaped slab known as drop panels.
These drop panels play a major role in this construction method as they expand the sturdiness and capacity of the flooring system below the vertical loads and in this ways boost the cost effectiveness of construction. Generally, the height of drop panels is almost two times the height of the slab.
Flat slabs are suitable for most of the construction, especially for asymmetrical column layouts like ramps and curved shaped floors etc. There are several advantages of using flat slabs like flexibility in design layout, flat soffit, and depth solution. Although building flat slabs can be a bit costly but it gives architects and engineers immense freedom in designing. The advantages of flat slabs do not end at layout and design efficacy, they also help the construction teams by easing off installation process and saving considerable amount of construction time.
Types of Flat Slab Construction
There are four major types of flat slab construction:
- Simple flat slab construction
- Flat slab construction with column heads
- Flat slab construction with drop panels
- Flat slab construction with both column heads and drop panels
Uses of Column Heads in Flat Slab Construction
- They increase the sheer strength of flat slabs.
- They reduce the moment in flat slabs by reducing effective or clear span.
Uses of Drop Panels in Flat Slab Construction
- They increase the absolute strength of the slabs.
- They increase the negative moment capacity of the slabs.
- They stiffen the slabs and thus reduce deflection.
Advantages of Flat Slab Construction
There are several advantages of flat slabs, including:
- It is a known fact that flab slabs without the use of drop panels can be manufactured in very less time as the framework of structure is diminished and simplified. Therefore, in such a case, the construction time is significantly reduced.
- Flat slab construction can significantly reduce floor-to-floor height especially in cases where deep false ceiling is absent. It is because flat slab construction does not restrict the placement of horizontal partitions and services. This can be very beneficial in terms of reduced cladding expense and pre-fab services.
- In case the client wants to make changes in the interior plans and use the accommodation according to his changing needs, flat slab construction is the best choice as it offers flexibility in terms of design and layout. This flexibility is mainly possible due to square lattice and absence of beam that makes allocation of partitions and channelling of services difficult.
Types of Flat Slab Design
Several methods and processes are involved in the designing the flat slabs and assessing these slabs in flexures. These methods include:
- The empirical method: This method is usually used for designing smaller frames.
- The sub-frame method: This method is usually used to design irregular frames. Their designs are conceptualized by using appropriate software. However, using sub-frame methods for very complex designs can be very costly.
- The yield line method: This is the most cost effective method that is best suited for homogenous installation of reinforcements. A detailed visualization and thorough examination of cracking and deflection is needed since this method utilizes only collapse mechanism.
- Finite-element analysis: Application of this method is very advantageous in case of structures that have floor with irregular supports, bear heavy loads, or have large openings. Finite-element analysis can also be used to calculate cracked width and deflections.