Attachment B Eng report

5.5 Screw Piling

All screw piling is to be hot dipped galvanised and epoxy painted
for the upper 2m, as well as filled with concrete grout.

6.0 Structural Framing System

6.1 General Structural System:

The proposed building is a three-storey reinforced concrete
structure with a reinforced concrete contiguous piled retaining wall
system to support excavations of up to about 3.5m. A mixture of
grout replacement piles and concrete-filled galvanised screw piles
are proposed to support vertical loads, and a range of raking
painted and galvanised screw pile are intended to provide
additional horizontal stability to the foundation by acting in either
tension or compression.

Structural System Summary:

e 450mm diameter contiguous CFA piled retaining walls, founded
sufficiently below excavation level to provide vertical capacity
and passive resistance to horizontal soil pressures
Screw piles ranging from 50-80T to support column loads
Raking screw piles to provide additional horizontal resistance to
soil loads, wind and earthquake loads

e Reinforced concrete ground beams and slabs will be used to
provide adequate permanent horizontal “strutting” of retaining
walls and rotational stability to pile/slab/upper column
connections, and to resist bending moments caused by pile
eccentricity

e Sub-floor areas will be drained to relieve any potential build-up
of ground water pressure

e Areas behind contiguous piled walls will be fully drained by
using drilled-in steel “wick” drains, connected through the base
of the wall and discharged appropriately

e Upper structure comprises reinforced concrete columns, walls
and beam/slab system

e Roof slabs will need a high grade trafficable waterproof
membrane or a trafficable slab may be considered over an
insulated waterproofing layer on the structural slabs.

e Garden terrace and mounded soil areas will be generally
constructed on suspended slabs over voids to avoid imposing
additional soil loads to the steep sandy slopes

e The elevated timber walkway running east-west from R.L.34 to
R.L.26.2 will be supported on 7-8m deep piles, designed to
withstand lateral drag of the loose surface sands.

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