Substructure

EXISTING BUILDING

Base on the structural assessment report by the Structural Engineer taken to the site for the site investigation. The soil has good bearing capacity and structure loads are relatively heavy, hence the pile foundation used for the existing building transfers the heavy loads through columns to hard soil strata which is much below ground which makes the structural frame in a re-usage condition.

SUBSTRUCTURE OF THE NEW BUILD

The suitability of soils for foundations is principally determined by their strength, cohesion, and consolidation characteristic of the soils. By visual examination, the soil of the proposed site is found to be a mixture of varying proportion of particles of different sizes which are most suitable for foundations when well drained and well confined. The soil is coarse grain; has a good strength, moisture, and plasticity.

Thus, a raft foundation with structural steel frame is proposed for the site using a structural steel frame. it is constructed by first excavating the ground to a uniform, flat level. Then, a waterproof plastic sheet is laid over the earth, and a thin 3" layer of plain cement concrete (PCC) is poured just to create a perfectly flat and level base for the foundation. The choice of pad and raft foundation is because of the soil water table and the loads coming from superstructure are distributed over a larger area and differential settlement of soil can be reduced.

CONSTRUCTION ACTIVITIES F THE NEW BUILD

The Proposed Site

SITE PREPARATION

This is the first step in the construction process, the shrubs, vegetation, rocks, and other debris are removed to make the construction site conducive to the project, allowing the construction team to start working on building the actual structure. It is important to clear out anything that can get in the way of the construction project to allow for a safe and secure structure.

Prior to the commencement of the site clearance, the outer boundaries of the site is set out using surveying equipment

BULLDOZER AND EXCAVATOR

Bulldozers and excavators will be used on the site. bulldozers is recognizable construction equipment typically used to push debris away from the site while levelling the ground and prepping it for the construction project and excavators can remove debris while also being used for digging, excavation, and earthmoving operations. Excavators have various attachments tha.t teams can use to target specific debris.

Bulldozer and Excavator clearing the Site

Padfoot and Tamping Foot Roller

SOIL COMPACTION

The strength and consolidation make up the compaction characteristics of the soil which determines its suitability for building foundations (Weser, 2020). The soil will be compacted to reduce the void space between soil particles as well as decreases the likelihood of settlement after the building is constructed. Compaction increases the shear strength of soils, and it decreases water seepage that would lead to deleterious shrinking and swelling soil properties.

Padfoot and Tamping foot roller will be employed because it uses manipulative force to break the natural bonds between particles for better compaction, especially in cohesive soils.

SITE EXCAVATION

Excavation is a crucial step in the construction process as it sets the foundation for the rest of the project. There are different types of excavation. For this proposed project, topsoil, earth, and footing excavation will be employed. Earth, rocks, and other materials will be removed by the excavator to create a level and stable foundation for the structure.

CONSTRUCTION TRUCK

Every construction work involves the transportation of debris and construction materials from one place to another. The construction truck is well suited for this task. They are essential for all types of construction jobs, regardless of the size and scale.

: Construction Truck with Debris

:Construction Truck with Construction Materials

Beam Reinforcement

BEAM AND SLAB RAFT FOUNDATION

There are different types of raft foundation. Beam and slab type raft foundation with structural steel frame will be used for the proposed project. The beams are laid in perpendicular directions and all these beams connected by raft slab. The steel columns are situated exactly on intersections of beams of raft foundation. The choice of this foundation is because the load of the structure must be distributed over a large area, the stress on soil needs is reduced and the possibility of differential settlement in case individual footing is used is prevented.

STEEL FRAME STRUCTURE FOUNDATION

Steel framed structure construction begins with the construction of its foundation. When moderate loads are imposed, then it is advised to use reinforced concrete bearing pads or strip foundation to transfer loads to soil capable of supporting transferred loads.

Reinforced Concrete Bearing Pad Foundation for Steel Frame Structure

Structural Steel Foundation Base

Structural Steel Column

The next step of steel frame construction is the placement of steel columns. The section of the steel is specified based on the load imposed. These the size of the steel columns are commonly produced in advance. The most significant point in column installation is the connection between foundation and column and splices between columns

Steel plate will be wielded to the bottom end of the column that is connected to the foundations through anchors. The Base Plate connection can also have a different configuration with sloped or vertical stiffeners. The most desired shape of base plate is rectangular and square shape because such plates provide largest spacing between the bolts which is desirable.

Structural Steel Columns and Base Plate

Steel Column to Foundation Details, (A) Top bolt places created in base plate, (B) Side view of column base to foundation.

COLUMN SPLICE

Column splices are provided to ease erection process in addition to simplify steel column production and deliveries. The distance between floor and column splice is about 60cm.

REINFORCEMENT BEAM AND SLAB RAFT FOUNDATION

The steel reinforcement provides additional strength and stability to the foundation, and it is typically arranged in a grid pattern to help distribute the weight of the building evenly. The size of the reinforcement bar ranges from 16mm to 25mm diameter to improve tensile strength and prevent cracks.

PERI TRIO FORMWORK PANELS FOR RAFT FOUNDATION

The reinforced concrete raft will be built with 'Peri Trio formwork panels. Prior to the start of construction, all required formwork will be planned, specified, and approved by the supplier, the subcontractor's engineer, and then checked and approved by a consultant engineer. The choice of Peri Trio formwork is because it is easy to handle and efficient logistics, provide a high level of surface evenness and the excellent product quality guarantees a long service life.

Reinforcement Bar for Raft Foundation

Peri Trio Formwork Panels

Concrete Footing and Beam

CONCRETE WORK IN FOUNDATION

The foundation footing will be constructed with concrete to act as a base to the floor columns and floor walls. The main function of footing is to transfer the vertical loads directly to the soil. The thickness of the raft is 100mm.

Hussaini, S. A. (2020) pointed out that the Standard Grade of Concrete Raft Foundation: C40 to C50 (40 to 50 N/sq.mm) MP. The need for high strength grade of concrete is to resist extremely high compressive load in walls and columns, to optimize the thickness of the wall and to minimize the size of columns, especially in lower floors.

DAMP PROOF MEMBRANE (DPM) AND DAMP PROOF COURSE (DPC)

DPM is one of the most reliable damp proofing solutions for getting rid of damp from the project. It is often used underneath a concrete floor to stop it from gaining moisture. Damp proof membrane is usually made of plastic material, such as polyethylene. Plastic is long-lasting and resistant to moisture, helping to protect other elements. The damp proof membrane can also be placed above the concrete in the walls in conjunction with a damp proof course (DPC).

Concrete Floor Waterproof

Concrete Wall Waterproof

FLOOR AND WALL INSULATION IN FOUNDATION

Insulation regulates floor temperatures, which helps control room temperatures during the summer, and is also great for keeping warm once the winter season rolls in. Kingspan fiberglass insulation is the best choice for this project because it is cost effective, light weight, easy to install, cutting the fiberglass is a relatively easy process and high insulation value. A good insulation is more energy efficient. The floor insulation will be laid on top of the raft, with a concrete floor. The wall insulation will be fixed to the concrete wall.

Kingspan Thermal Floor Insulation Board

Kingspan Thermal Wall Insulation Board

Kingspan Thermal Floor and Wall Insulation Board

RAFT SLAB

The slab portion of a raft is normally 100mm (4 inches) thick. Sometimes the slab is made thicker, up to 150mm (6 inches) thick, to make it stronger or able to span further. The slab will be constructed on a compacted hardcore base (perhaps 100 mm thick). A layer of blinding concrete (typically 50 mm) will then be laid with a waterproof membrane above to create an even, dry surface to allow formation of the raft.

Concrete Raft Slab

Benedicta Adekunle

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