GRILLAGE FOOTING

In concrete High rise buildings are built with steel columns encased. Such columns carry very heavy load and therefore they need special foundations to spread the load to a larger area of soil. Grillage foundation is one such type of special foundation. It consists of one or more tiers of I-sections steel beams. Given figure shows a typical two tier grillage foundation. The top tier consists of less number but large size steel section whereas lower tier consists of larger number but smaller size steel sections. Through a base plate Column load is transferred to the top tier. The grillage beams are unpainted and are encased with minimum cover of 100 mm beyond the edges of steel sections in concrete. A minimum clear space of 75 mm must be maintained between the flanges of adjacent grillage beams so that concreting may be made properly.

Pipe separators are used to maintain spacing.

                                            Grillage foundation