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UNIT: 2 Construction Technology
OBUDE JOHN

Introduction

Residential Building: If more than half of the floor area is typical used for living purposes. Typical houses whether they be terraced or detached as long a as they have each have their own entrance leading in from the ground floor. The figure below illustrates a residential building.

The differences between these building are that residential buildings tend to have general requirements most commonly kitchens, bedrooms, and bathroom. Flats, Houses, or bungalows are the main examples of residential buildings. These buildings will need to take into consideration day to day requirements of residents. Commercial buildings are generally

laid out according to its uses. An office environment would usually have meeting rooms, offices, and storage spaces. Different building codes are used for commercial spaces, an example of this would-be maximum occupancy limit, bathrooms that are DDA Compliant, fire extinguishers, lighting requirements. These deviations determine the best method to construct the build with. Industrial buildings tend to be large open spaces; factories or warehouses are most common. These buildings are usually machinery workshops. These buildings will have similar codes to commercial buildings for fire protection and life safety. All these buildings and property that are designated as commercial or industrial in nature are subject to different tax and financial rules, as well as additional or different legal requirements and prohibitions, in many cases. Commercial and industrial designations also trigger different financing rules for purchase, lease, and improvement.These are generalizations, of course, buildings are built individually and have distinct design differences specific to the user’s needs.

Protective function: protection of people and property against harmful influences and dangers, e.g., wind and rain, inquisitive onlookers, interference.

Domain or territorial function: buildings make it possible to operate in a place of one’s own, without disturbance from others. Key words are privacy, safety, and security. Social function: buildings create spaces and places in which people can carry on their activities optimally. Primary elements here are health, welfare, communication, and quality of life.

Ways in which sustainability can be promoted in buildings projects are summarised in the table below.

The use of such careful planning to promote a sustainably designed project will often reduce the running and maintenance costs of a building, will is always appealing to a client.

D1 Evaluate how the functional characteristics and design selection criteria impact on the eventual design solution.

 adequate damp proofing means at critical position.

Fire Resistance

 external walls – less window openings for office building.

 Internal walls (prevention of passage of sound from one space to another)

Commercial buildings are generally use bigger pipes. From office buildings and residential complexes to retail buildings and high rises, all these structures need a plumbing system. Because they are typically occupied by more individuals, they need more pipes and outlets for sinks and toilets. This also means increased demand by employees and costumers which could result in more routine maintenance and emergencies. Commercial buildings also require larger pipes to provide more water since they are occupied by more people than say a small family house.

Multiple floors require plumbing on each level of the structure. In commercial buildings, all branch lines stem from one large main line. All branch lines may have to reach as high as 30 floors which also brings gravity into play. Water pressure must be strong enough to keep the whole system working efficiently.

High-rise design and construction present more than a few special challenges, especially regarding the design of plumbing systems. For plumbing purposes, the term “multi-story” or“high-rise” is applied to buildings that are too tall to be supplied throughout by the normal pressure in the public water mains. These buildings have needs in the design of their sanitary drainage and venting systems. Some of the biggest challenges to high-rise plumbing design relate to controlling pressure, proper venting, and drainage.

LO2 Describe the different techniques used to construct a range of substructures and superstructures, including their function and design selection criteria.

2. Site Analysis

3. Existing Building analysis

In the Pre-design analysis of a project, surveys and reports will be conducted such as, Soil sampling and existing structure surveys in order to determine the condition of the land or existing site. These results and surveys are used to identify the constraints that may be imposed on a project and its design. Reports such as Geotechnical report will identify Areas that are at risk from subsidence and

landslides, while soil samples will determine Depth of groundwater, depth of bedrock, shrink and swell potential and bearing capacity. These results and surveys are used to identify the constraints that may impose on a project or the design. Soil surveys determine depth of groundwater & shrink and swell potential. All these surveys are compiled and use to best determine the best substructure for the land.

Columns: The vertical supports. Columns can come shaped as tubes or with a cross-sectional shape of a capital H, I, L or U.

Beams: The horizontal supports that rest atop the columns. Usually I or H-shaped with flanges perpendicular to the “web” or main plate.

Anchor Bolts: The bolts that fasten the columns to the foundation.

Secondary Framing

• Struts: A brace stabilizer that takes loads along its axis.

• Girts: Horizontal stabilizer bars between exterior columns. Wall cladding attaches to these.

• Joists: Floor support beams.

• Headers and Jambs: The framework for openings such as doors, windows and bays.

Despite the foregoing, the seismic design of structures usually gives little importance to these elements, so much so that many design codes do not include standards in this regard. Experience with recent earthquakes shows in many cases excellent behavior of the structure designed in accordance with modern criteria of seismic-resistance, accompanied unfortunately by a poor response of the non-structural elements. However, if the safety of the occupants of a building and of people endangered by the collapse of such elements is taken into account, as the cost of replacing these elements, and the losses involved in interrupting the operations of the building itself, the importance of seismic design of the non-structural elements within the general layout of the building can be understood.

In the case of hospitals, the problem is of major importance, for the following reasons:

The choice of the appropriate type of foundation is governed by some important factors such as

• The nature of the structure
• The loads exert by the structure.
• The subsoil characters.

• Lateral displacement.
• Ground heave.

• Tilt.

Soil bearing capacity. This determines how much load (weight or force) the existing soil can withstand.

Soil type. Different types of soil have different properties that can affect their suitability for supporting a foundation.

Foundations typically are built with masonry, such as concrete block or brick, or with poured concrete. Masonry materials offer high compressive strength and are much more resistant to damage from moisture and soil than wood and metal materials. A masonry foundation typically extends above the ground to protect other building materials from moisture and other damaging effects of ground contact. Masonry foundations usually are reinforced internally with metal rebar or other materials. Contractors will often use hydraulic cement to seal around pipes or raceways that penetrate the masonry or concrete foundation.

Some building foundations are built with treated wood posts or piers. In this case, the foundation supports are driven deep into the earth and/or rest on rock or concrete pads.

The performance or choices of foundation depends on a number of factors, these include:

• Nature of sub-soil
• Materials used for the foundation.

Raft foundation is a large combined thick slab designed to seat and support the whole or a large part of a structure. A raft is usually used when subsoil is weak, or columns are closely located and with deviated loadings. It also serves as a transfer slab to combine and tie up all

the vertical loading elements to the plate-form foundation. By doing so, differential settlement can be avoided.

• Skin friction – load is support by the frictional resistance so created between the contact surface of the pile and the embracing soil.

• Classification of Piled Foundation

4. Displacement or replacement piles

Foundation using steel H-pile Steel H-pile – Standard universal sections are used as pile with the load taken up both by skin friction and end-bearing. The installation and equipment requirements are relatively simple, but the noise and vibration generated have restricted its use in urban areas.

Foundation using precast concrete pile Precast concrete pile – Precast pile can be of square or circular in section, usually in modulated manner. The Daido Pile is a typical example being used in Hong Kong. It is a pre-stressed hollow-section circular piles, 12m in length and in size between 400mm to 600mm. Pile sections are usually welded together using steel end plate.

Foundation using precast concrete pile Features of Daido Pile:

Foundation using Mini-pile Features of this type of pile:

• Usual working load about 700 kN
• Piles are not designed for end bearing.

1. How to form the bore (using what kind of machine and method to drill a hole in the ground)

2. How to protect the soil from collapsing into the bore hole during drilling (usually by inserting a steel casing or using a drilling fluid)

D2 Prepare a design report identifying superstructure, substructure and engineering structures necessary for a given building construction project.

The purpose of site formation is to prepare a piece of land in order to: Accommodate building/s or other facilities which will be placed within the area. Form the land to the required orientation, shape or levels in order to accommodate such facilities.

1. Topography and its surrounding physical conditions. Detail analysis can be done by appropriate site investigation process.

2. Geological conditions such as the nature and depth of its subsoil, degree of decomposition, or location of fracture etc. This data can be obtained by soil investigation.

2. A subsoil drain system that is laid below surface for the discharging of ground water and to maintain the water pressure be kept in a safe level - filter layer behind the slope leading water to outlets - weepholes - cut-off drain - subsoil drain pipe.

Protection and treatment to Rock Slope Most rock slopes need some forms of treatment to ensure continued stability. Improvement methods include:

Protect a slope by the use of retaining wall Retaining wall are structures usually provided at the toe of a slope to stabilize it from slide, overturn or collapse. A slope will be relatively stable when its profile (section angle) is kept below its angle of repose. Angle of repose is an angle that maintains naturally to a safe equilibrium by the composing material of a slope. This angle deviates from differing materials depending on their compaction, particle size and the nature of the material itself. (e.g., cohesiveness and shear strength) Principle to retaining wall design can be of 2 main types - cantilever type - Gravity type - Earth reinforced type.

The construction methods of various types of Foundations

Raft foundations - have large areas with multiple supported columns. Usually, all the columns in the building are supported on one foundation. Mat foundations are preferred when the soil has low bearing capacity.

All the loads are distributed to a large area, which reduces the stress exerted on the low-bearing capacity soil. Pat foundations are economic in situations where piles cannot be constructed and spread footings are not practical, such as the case with low-rise, multistorey buildings, if the top layers of the soil are weak.

This situation will create very difficult coordination problems that involve various contractors and complicate the contractual position of the entire job.

The common managerial problems identified in the construction of deep basement:

Deep basement can be constructed using some traditional ways such as cut & fill or bottom up methods. These methods are relatively economical and effective when dealing with certain jobs which are simpler in nature.

On the other hand, where basement is going deeper and the surrounding environment getting more complex and sensitive, top-down, or combined method may be a more appropriate option to construct.

• Quality of the management and the executing parties, as well as the problems solving ability of the frontline personnel, also seriously affects the performance and effectiveness of works.

• The Common issues found in recent basement projects:-
The recent basement projects are usually very deep (below 20m) and excessively•
big in size.

• The diaphragm walling is the most common cut-off provision being used.

The system formwork can hardly be applied for most basement works due to•
access problems as well as the confined working condition inside the excavated.

• Basement of buildings
• Semi-basement with slope stabilization purpose
• Transport facilities such as railway station, tunnel and pedestrian subway • Access or services shaft
• Involvement/provision when constructing these structures
• Ground stabilization provisions
• Cut-off walling provisions
• Lateral soil support provisions
• Excavation arrangement
• Dewatering arrangement
• Spoil removal arrangement
• Basement construction arrangement

Dewatering Ground water exists usually within a few metres down from the ground surface in Hong Kong depending on which season it is. An imaginary line called water table usually referred to indicate the level of the underground water. Soil above the water table is with water under a non-saturated condition. Below which water is over-saturated. That means, when there is a void exists below the water table, water will leak out toward the void for the soil cannot hold any extra water. This is the principle of dewatering, a process to remove the over-saturated water in ground and keep the subsoil within a non-saturated condition.