19.1 Overturning
The stability of a structure as a whole against overturning shall be ensured so that the restoring moment shall be not less than the sum of 1.2 times the maximum overturning moment due to the characteristic dead load and 1.4 times the maximum overturning moment due to the characteristic imposed loads. In cases where dead load provides the restoring moment, only 0.9 times the characteristic dead load shall be considered. Restoring moment due to imposed loads shall be ignored.
19.1.1 The anchorages or counterweights provided for overhanging members (during construction and service) should be such that static equilibrium should remain, even when overturning moment is doubled.
19.2 Sliding
The structure shall have a factor against sliding of not less than 1.4 under the most adverse combination of the applied characteristic forces. In this case only 0.9 times the characteristic dead load shall be taken into account.
19.3 Probable Variation in Dead Load
To ensure stability at all times, account shall be taken of probable variations in dead load during construction, repair or other temporary measures. Wind and seismic loading shall be treated as imposed loading.
19.4 Moment Connection
In designing the framework of a building, provisions shall be made by adequate moment connections or by a system of bracings to effectively transmit all the horizontal forces to the foundations.
19.5 Lateral Sway
Under transient wind load the lateral sway at the top should not exceed H/500, where H is the total height of the building. For seismic loading, reference should be made to 5 of Part 6 ‘Structural Design, Section 1 Loads, Forces and Effects’ of the Code.
20 FIRE RESISTANCE
20.1 A structure or structural element required to have fire resistance should be designed to possess an appropriate degree of resistance to flame penetration;
PART 6 STRUCTURAL DESIGN — SECTION 5 CONCRETE: 5A PLAIN AND REINFORCED CONCRETE
heat transmission and failure. The fire resistance of a structural element is expressed in terms of time in hours in accordance with 3 of Part 4 ‘Fire and Life Safety’ of the Code. Fire resistance of concrete elements depends upon details of member size, cover to steel reinforcement detailing and type of aggregate (normal weight or light weight) used in concrete. Essential requirements of fire safety of buildings with respect to details of construction are also given in 3 of Part 4 ‘Fire and Life Safety’ of the Code.
20.2 Minimum requirements of concrete cover and member dimensions for normal-weight aggregate concrete members so as to have the required fire resistance shall be in accordance with 25.4.3 and Fig. 1, respectively.
20.3 The reinforcement detailing should reflect the changing pattern of the structural action and ensure that both individual elements and the structure as a whole contain adequate support, ties, bonds and anchorages for the required fire resistance.
20.3.1 Additional measures such as application of fire resistant finishes, provision of fire resistant false ceilings and sacrificial steel in tensile zone, should be adopted in case the nominal cover required exceeds 40 mm for beams and 35 mm for slabs, to give protection against spalling.
20.4 Specialist literature may be referred to for determining fire resistance of the structures which have not been covered in Fig. 1 or Table 16A.