Pedestal Theory
STAAD Foundation Advanced can design pedestals for isolated footings complying with US, British, Indian, and European codes.
Pedestal design is performed same as a design of short column. STAAD Foundation Advanced can design pedestal subjected with:
- Axial Load only
- Axial Load & Uniaxial bending
- Axial Load & Biaxial bending
STAAD Foundation Advanced follows limit state method for section design.
Pedestal Force Transfer
In practice, pedestals are generally present in the case of footings that support steel columns. The pedestal is the block of concrete that supports the base plate beneath the column, and hence has a slightly larger plan dimensions than the base plate.
If a pedestal is present, you can specify that information through the Pedestal and Anchor Bolt table of the Foundation Plan page.
If Yes is selected for the Consider Pedestal option at a column location, then the forces from the column are assumed to act at the top of the pedestal. This is the point usually considered as a support for the superstructure. Thus, the support reactions for the superstructure analysis, which are the algebraic opposite of the loads transferred to the foundation from the columns, are assumed to act at the top of the pedestal.
- MX at footing base = MX at column base (from the column reaction) + FZ × Lever Arm
- MZ at footing base = MZ at column base (from the column reaction) - FX × Lever Arm
- Level at which forces from the column are transferred to the foundation
- Forces and moments are calculated here for finding the soil pressures and for the sliding and overturning checks
If No is selected for the Consider Pedestal option at a column location, then the forces from the column are assumed to act at the top of the footing. In other words, in the absence of a pedestal, the top of the footing is assumed as the point where the support is specified for the superstructure model.
Indian Code Pedestal Design Theory
Pedestal design for the Indian code is based on IS 465 – 2000 and SP: 16.
STAAD Foundation Advanced checks minimum area of reinforcement provided per IS 456 -2000 Section 26.5.3.1 (Clause 26.5.3.1.a to Clause 26.5.3.1.h). Program checks minimum bar size for longitudinal and main reinforcement. Pedestal spacing requirements are also checked per Indian code.
Minimum eccentricity subjected on pedestal is considered per IS 456 – 2000.
For Axial Load only pedestal design done per IS 456 – 2000 Section 39. For uniaxial and bi-axial moments, pedestal design follows SP16.
British Code Pedestal Design Theory
Pedestal design for the British code is based on per BS 8110-1 Section 3.
STAAD Foundation Advanced checks minimum area of reinforcement provided per BS 81100-1 Section 3. Program checks minimum bar size for longitudinal and main reinforcement. Pedestal spacing requirements are also checked per British code.
Minimum eccentricity subjected on pedestal is considered per BS 8110-1 Section 3.8.2.4.
For axial load only, uniaxial and bi-axial moments, pedestal design follows BS 8110-1 Section 3.