Question

Discuss the four serviceability limit states (excessive vibration, excessive cracking, excessive drift or sway, excessive expansion) for a parking area

Answer 1

Serviceability in construction field refers to the condition when the structure is still considered useful.Should these limit states be exceeded, a structure that may still be structurally sound would nevertheless be considered unfit.Serviceability limit state design of structures includes factors such as durability, overall stability, fire resistance, deflection, cracking and excessive vibration.Now we will discuss the few of the serviceability limit states for a parking area.

1.EXCESSIVE VIBRATION:

If the vibration due to the movement of traffic around the parking area is increased it can affect its serviceability.The cars and other vehicles that are parked in the parking area undergoes vibration which can damage the vehicles and the structure itself.The increasing volume of road traffic, the higher vehicle speeds and the increasing axle loads are generally referred to as the cause for the increasing hindrance due to vibrations induced by road traffic.Heavy goods vehicles and buses are found to produce the most perceptible vibrations. The vehicle models used to describe the dynamic behaviour of a vehicle are composed of discrete masses, springs, friction elements and damper.

2. EXCESSIVE CRACKING:

Excessive cracking in the concrete floor of the parking area can also affect its seviceability to a large extent.it not only can be dangerous for the vehicles inside the parking area but can also affect its aesthetic look as well.Where the appearances of the structure is deemed important, the crack width on the concrete surface shall generally be kept within an allowable crack width considered acceptable for aesthetic considerations. Verification of cracking may be omitted for structures with particularly short service life, temporary structures, or structures where aesthetic considerations are not important.

3. EXCESSIVE DRIFT:

Exessive drift in any part of the structure can also hamper the serviceability of the structure.If any part of the parking area is drifted it can cause damage to the vehicles and also the health of the structure.Excessive drift in parking areas usually happens due to the shift of the infill walls which are made to resist the gravity loads.Itn this case the parking area will be no longer be used and thus it crosses the seviceability limits.

4.EXCESSIVE EXPANSION:

Parking areas are usually located in the basement of the buildings There are number of infill walls which are constructed to resist the gravity loads and lateral earth pressure from the soil.If any of the element in the structure expands excessively it can affect the serviceability of the structure.Expansion of the structure can be mainly due to the soundness property of the cement used in the member.Expansion in ny part of the structure should be checked upto a certain limit.If the expansion limit is crossed it can be said that the structure is no longer serviceable.