Formwork is one of the important components due to its cost factor and plays a major role in deciding the construction method especially when it comes to residential structures. The emerging trends in concrete and construction technologies have resulted in tremendous advancements in Form work technology. Given that the Formwork has a significant impact on the cost, time and quality of the completed project. Lafarge Construction Development Lab, India demonstrates the benefits and the inevitable choices for cost-effective designing of RCC wall structures.
The RCC frame construction, as per IS 13920:2002 should have the minimum thickness of column as 200mm and if the center to center distance between the beams is more than five meter, then the minimum column thickness needed is 300mm. But in case of RCC wall structure, the minimum thickness of walls required is 150mm and buildings up to 10 stories can be easily designed with this wall thickness. There are other advantages of RCC wall structure over RCC frame construction that make it much more cost effective.
Conventional RCC Structures:- Conventional columns, beam and slab based framework using reinforced cement concrete.
RCC Wall Structure:- Shear wall and slab based framework using reinforced cement concrete.
Ductile detailing has to be followed in case of frame construction wherein the junction of beams and columns are densely reinforced making concrete pouring very difficult. Since there will be no ductile detailing in RCC wall structure, the reinforcement is uniformly placed making concrete pouring much easier as also saving on the amount of reinforcement. Also, the non-uniformity of column & beam sizes depending on the load carried require form works of different sizes: Such issues does not arise while designing the building with cost-effective RCC wall system.
Depending on loads and member sizes, different diameter reinforcement bars have to be used in conventional method whereas, uniform bar diameter is used throughout the RCC wall structure construction. Moreover, special confining zone reinforcement required in columns in frame structure is not needed in the promoted system. Finally, footings of different sizes and depths in conventional RCC structure might lead to differential settlement while, uniform strip footing of same depth in RCC wall system avoids any differential settlement.
Seismic Design Performance
As per IS standards, deflection at top most storey should not exceed Hl500 (where H is the height of building). The distance between two adjacent buildings in a township project depends upon the value of deflection at the top storey. Greater the deflection, greater has to be the distance between the two buildings. If the deflection is more, there are greater chances of damage to the adjacent buildings in case of an earthquake.
RCC wall structure has more dead load compared to conventional RCC structure thereby showing more resistance to earthquake forces even with less thickness walls. The deflections under earthquake and wind forces fall down by a significant amount when RCC wall structure is adopted in place of conventional one. Stability of a structure also depends upon its time period. Greater time period indicates flexible building which can be critical in the stability of the structure.