2330

An existing office building, constructed in 1975, has a reinforced concrete roof slab. The roof is to be converted to create a new office floor, which will require an increase in load capacity. As the structural engineer, you have been asked for advice on a suitable design to achieve this.
Information
The existing roof slab has the following characteristics: • Column spacing beneath: 9m x 8.4m • Roof slab: 250mm flat slab with 350mm drop panels • Roof load capacity (based on review of existing drawings, calculation checks and structural inspection) : Super Imposed Dead load (SDL = ceiling, services and finishes): 1.5kPa, Live load: 1kPa to 1.5 kPa • Inspection of the structure has revealed that the existing roof slab is uneven and varies in level by up to 50mm. It is not flat or level enough to be used directly as a floor. • The storey below the existing roof slab is occupied and access to it for construction activities is not possible. • The building has been found to have sufficient column strength and lateral capacity to support the options under consideration.
The required final load capacity for the new floor is: Super Imposed Dead load: 1.5kPa Live load: 3kPa

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