🕑 Reading time: 1 minuteDeflection of reinforced concrete slabs is acceptable to a certain limit which are specified by applicable Codes such as ACI, IS Codes and Euro Codes. These codes to specify the amount of deflection which is acceptable. When the deflection limitation is exceeded, then it will probably lead to several problems for example aesthetic issues, occupants will not be comfortable to life in the building, cracks may develop in partitions, and occasionally cause malfunctioning of doors and windows. Excessive deflections in reinforced concrete slabs possibly results in neighboring balcony to deflect inward. This is seriously problematic and unacceptable because rain water fallen on the balcony will move inside the building and can damage the building content. This is one of the crucial factors that make the prevention of excessive deflection of reinforced concrete slab substantially significant. There are various causes that lead to excessive deflections in reinforced concrete slabs, and it is possible that one single factor or combination of them result in the deflection that is over limitations. The best way to avoid excessive deflection is to understand the cause of the problems which will be explained in the following sections and only then specify proper solutions.
Fig.1: Deflections in Reinforced Concrete Slab
Causes of Excessive Deflections in Reinforced Concrete SlabsFollowing are the different causes responsible for excessive deflections in RCC slabs:
- Design of reinforced concrete slab
- Material properties used in the reinforced concrete slab
- Construction of reinforced concrete slab
- Change the function of the reinforced concrete slab
- Environmental conditions
Design of the Reinforced Concrete SlabsBy and large, both reinforced concrete slab thickness and reinforcement ratio of the slab are common causes that may lead to excessive deflection. Selecting small slab thickness can be appropriate in terms of strength but in most cases lead to excessive deflection and due to this issue applicable Codes such as ACI Code recommends minimum slab thickness to contain deflection within acceptable limit. Similarly, if the computed reinforcement ratio is small, then it will yield pretty soon and consequently flexural stiffness of the slab decrease substantially and finally the deflection of the slab will be quite large.
Fig.2: Details of Reinforced Concrete Slabs