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Advanced Construction Technology By Professor Chris Gorse & Ian Dickinson – licensed under the Creative Commons Attribution – Non- Commercial – Share Alike License
Pad Foundations Chris Gorse and Ian Dickinson These slides should be read in conjunction with Emmitt, S. and Gorse, C. (2010) Barrys Advanced Construction of Buildings. Oxford, Blackwell Publishing
Pad foundations Ground beams Pads Pad foundations. More commonly used under point loads such as columns, but can be used under ground beams to transfer continuous loads. The width and depth of each pad foundation will depend on the soil conditions and building loads.
Pad foundation Pad foundations are often rectangular or square and are placed to receive point loads at a central position Loads transferred through column to base-plate then to concrete pad foundation Base plate Pad foundation
Excavation for pad foundation Bolt boxes for steel columns ready to be positioned in the concrete
Excavation of pad foundation
Pad foundations neatly excavated
Pad foundations – ground beams Point loads from columns transferred to pad foundation Stable load bearing strata Any continuous loads applied through walls are transferred along reinforced concrete beams to the pad foundation Ground beam Pad foundation
Pad foundation and ring beam excavation. String lines mark out the centre lines for the holding down bolts. The holding down bolt box will be positioned when the concrete is poured.
Pad foundation and ground beam excavation. Ready to receive steel reinforcement cages and concrete
Pad foundation, with holding-down bolts for column. Reinforcement starter bars are evident, these will be used to tie the ground beam into the foundation.
Reinforced pad foundation Point loads from columns transferred to pad foundation Reinforced Pad foundation Exploded view showing reinforcement Reinforcement runs in both directions Load from column distributed across the full area of the foundation
Distributing the load The reinforcement in the pad foundation adds tensile strength allowing the loads to be distributed over a larger area. Large point load As the load is distributed over a larger area the load per unit area is reduced
Mass fill pad foundation Point loads from columns transferred to pad foundation By excavating deeper into the ground and filling with concrete the loads of the building can be transferred to lower strata. Where the surface soil and strata is week it may be possible to excavate deeper to good load-bearing strata.
Pad foundation and column base (prior to filling with grout)
Base of column fastened to the pad foundation by holding down bolts. Wedges hold the column in position until the bolts and column base is grouted. Expanding grout will be poured under and around the base plate filling all the voids and making sure the column and pad foundation make proper contact with each other.
Steel wedge holds the steel column in the correct position
Sand position around the column ready to receive expanding grout. The group secures the base plate in its final position.
Discussion Identify and discuss the situations where pad foundations are most likely to be used. What is the most common type of structure that would be founded on a pad foundation.
Further information supporting these slides can be found in the following publication and websites. Emmitt, S. and Gorse, C. (2010) Barrys Introduction to Construction of Buildings. Oxford, Blackwell Publishing Emmitt, S. and Gorse, C. (2010) Barrys Advanced Construction of Buildings. Oxford, Blackwell Publishing Virtual Site (2010) Virtual Site at Leeds Met University Virtual Site Gallery (2010) Virtual Site Gallery at Leeds Met University