Type of Footings and Description

Heading 1: Prepare a brief report on the footings detailed on the plans for Project 3 (factory complex).  

The footings detailed in the plans for project 3 are strip footing foundation, pad footings and piers.

Heading 2: Describe the type of footings that are detailed on the plans. 

Strip footing foundation – the continuous (strip) footing foundations are a type of shallow foundations that are used in load bearing walls. They can either be level or stepped. In project 3, there are four types of strip footings as indicated by the notation SF1, SF2, SF3 and SF4.

The width of the footings are 600mm for SF1, SF2 and SF3. The width for SF4 is 400mm and a thickness of 450mm at every section except in areas where it is stepped from one level to another. In such sections the thickness is 850mm with an overlapping distance of 790mm. The reinforcement in such areas is 2N16 Z-bars as shown in drawing number 1262R/2 Page 26 of 31. 

At various intervals of the strip footing foundation, we have pad footings.

Pad footing – The pad footings are used to carry concentrated load from columns. Project 3 has four types of pad footing foundations. The pads are 1200x1200mm square bases with a thickness of 600mm. The reinforcement details are shown in drawing number 1262R/2 from page 24 to 27. The pad footings are then connected to piers that transfer the load carried by the structure further downwards.

Piers – The project 3 uses 2 types of piers. 450mm diameter piers are used to support the strip footing foundation and to stiffen the clay strata. 750mm diameter piers are used beneath the pad footings. The 450mm diameter piers have a reinforcement of 6N16 bars with N12 ties at 240mm centres while the 750mm diameter piers have a reinforcement of 8N16 bars with N10 ties at 250mm centres. 

Heading 2: Outline the construction method and sequence to construct these footings. 

Pier construction – the excavated portions where the piers are located are fixed with the required reinforcement cage as specified in the structural drawings. A starter of 250mm thickness is provided so as to act as a base for shuttering. The shuttering involves placing of the necessary bracing in order for the pier to receive concrete. Concreting is done via a fully automated operating pump with boom pressure. The concrete grade is M40 and it is after curing for the required period that the pad footings are concreted into the pier caps. The surface of the pier caps that are in contact with the pad footing are left rough in readiness to receive concrete of the pad footings. Backfilling and compaction is done on the sides of the pier up to the level where the pad footing is to be concreted. 

Construction Method and Sequence for Footings

Pad footing foundation – The reinforcement cage of the pad footing is then laid on top of the pier cap. The formwork shuttering of the pad footings is done in readiness to receive concrete. The surface of the pier cap which was left rough is watered before the placing of concrete to ensure a monolithic at the end of the day between the pier cap and the pad footing. The pad footing is cured according to the requirements of the project and then the strip footing is concreted as explained.

Strip footing foundation – excavation strips along which the strip footing is to be concreted are done to the required level. The ground is adequately compacted to the specifications of the project (98% compaction). The reinforcement of the strip footing is laid and the formwork shuttering is done in readiness to receive concrete. The ground is sprayed with water so as to prepare it to receive the concrete. Concreting is done and the formwork shuttering removed after one day elapses. The footings are adequately cured for a specific period of time before the ground is backfilled and walling commenced.

Heading 2: Include a description of the type of plant and equipment necessary to construct the footings.

Concrete mixer – This is a mechanical equipment that is used in production of a homogeneous combination of cement, sand, gravel and water to form a concrete paste. The mixers can either be self-loading transit mixers or hand fed mixers. They help in the delivery of ready to pour concrete to the footings. The batching ratios are controlled by the strength class of concrete specified for the project.

Concrete pumps – This equipment is used to transfer liquid concrete to the place where it is required by pumping. This is the most efficient method of placing concrete in not so easily accessible areas such as the piers.

Poker vibrators – This equipment is used to ensure that the concrete that is placed is compacted and that no air is entrained in the concrete that could compromise on its strength. Compaction is carried out concurrently as concrete is poured in layers.

Slump cone and cube moulds – as the concreting is done, workability tests need to be carried out to ensure that the consistency of the concrete is to required specifications. The workability test is carried out on fresh concrete. The compressive strength of concrete is also measured using the cube moulds which will have to be tested after specific periods of curing. The compressive strength test is carried out on hardened concrete.

Plant and Equipment Necessary for Footings

Float blades – This can either be a hand-held tool or a power trowel that is used to smoothen the surfaces of fresh concrete. They are used to ensure that the finishing of concrete works is up to the required standard since they produce different finishes on concrete surfaces.

Heading 2: methods used for the placement of steel columns onto footings ensuring that placement and verticality are precise. 

The method used in the placement of the steel columns involves the exact placing of the anchor bolts. The anchor bolts will be used to make sure the steel columns are located exactly as specified in the drawings.

The location of the anchor bolts is set by stays that are fixed in the shutters as illustrated by the figure below.

 Fundamentals of geotechnical engineering by Braja M Das and Nagaratnam Sivakugan, Cengage Learning 2016.

The levels in the columns are set using one of the following methods; by use of levelling nuts and washers that are placed on the anchor rods, use of levelling screws, use of shim stacks put between the supporting foundation and the baseplate or by use of levelling plates.

The levels for all the above techniques are achieved using a levelling instrument such as a level, theodolite or a total station. The columns are held plumb by the anchor bolts that snug tight the baseplate of the columns. Non-shrink grout is finally placed between the baseplate and the concrete footing. The diagram illustrates the shim stacks used in levelling of columns.

Heading 1: outline suitable method for the temporary support of the concrete wall panels (for Project 3) during their erection, and their connection to the footing. 

The concrete wall panels will need temporary bracing and propping systems to resist wind and construction loads.

The bracing are required to have an identification plate indicating the manufacturer, the load capacity of the bracing and the model type. Bracing should be installed in conformity to AS 3850.

The bracing is installed at an inclination of 45 to 60 to the horizontal and square to the line of the element of concrete as illustrated in the figure below.

Placement of Steel Columns onto Footings

Figure 3Bracing elevation

Bracing is installed perpendicularly to the concrete panel in the plan view as shown in the figure below.

Skewed braces tend to reduce the stability of the concrete panel when the angle is ±5 to the perpendicular as shown in the figure above.

The corner elements can be erected without skewing the braces by following the figure below. The braces are attached to deadmen located in the leave out area between the concrete walls and the floor slab as illustrated in the figure below.

Lateral displacement of the bracing feet is prevented by adequate design. The points on which the bracing is located is at two thirds of the wall height of at least 600mm above the wall’s centre of gravity.

Heading 1Comment on the need for termite protection for the building in Project 2 (medium rise apartments), making reference to the Building Code of Australia.

Termite protection for buildings is outlined in AS 3660. As outlined in AS 3660, total building protection can be attained via appropriate design, taking precautionary measures during site preparation and periodical inspection and maintenance of the structure. The traditional method for control of termites involved the provision of barriers for the whole building. Termite resistant materials can also be used in the structural frame during the constructions process.

In project 3, the strip footings and slabs should be designed as integral parts of the structure. The following precautions need to be taken

Minimizing the number of construction joints. These points serve as the entry points of termites.

Services (plumbing and wiring) should also be designed such that they do not breach through footings or slabs. In cases where the penetrations are unavoidable, the services are chemically protected to prevent termite entry.

Use of hollow masonry below ground should also be avoided.

Upon completion of the project, all debris should be cleared from site especially those next to the subfloor space.

All materials in contact with the ground must be termite resistant.

The strip footings are to be protected by use of barriers such as chemical barriers or the following range of physical barriers that is Stainless steel mesh or Crushed granite.

Periodic building inspections

The structure should be inspected for all the potential entry points of termites

The installed barriers should be inspected for any signs of breaching by termites.

Introduction:

This assignment tackles information about project 3 which is a proposed factory complex located on 7 Layland way, Banksia and project 2 located which is a medium rise apartment building located on 2135 The Boulevard, Strathfield.

References:

Principles of geotechnical engineering by Das M. Braja and Sobhan Khaled date of publication 2013.

² Foundation design: principles and practices by Donald P Coduto, Published by Pearson publishers in 2015.

³ Fundamentals of geotechnical engineering by Braja M Das and Nagaratnam Sivakugan, Cengage Learning 2016.

⁴ Geotechnical engineering: unsaturated and saturated soils by Jean-Louis Briaud. Published by John Wiley & Sons in 2013.

⁵ Handbook of port and harbor engineering: geotechnical and structural aspects by Gregory Tsinker. Published by Springer in 2013.

⁶ Handbook of port and harbor engineering: geotechnical and structural aspects by Gregory Tsinker. Published by Springer in 2013.

⁷ Foundation engineering handbook by Hsai-Yang Fang. Published by Springer Science & Business Media in 2013.