TOPIC: SUPERSTRUCTURE OF A BUILDING
By the end of this lesson, students must be able to:
- explain the term Superstructure.
- identify parts of a superstructure.
- describe the types of loads of a superstructure.
- distinguish between a substructure and a superstructure in construction technology.
- Explain the term Superstructure.
- Identify five parts of a superstructure.
- Briefly describe three types of loads of a superstructure.
- State five common materials used in the construction of a building.
- With the aid of a sketch, distinguish between a substructure and a superstructure in construction technology.
BASIC COMPONENTS OF A BUILDING
Generally, there are two major components of a building project which are Substructure and Superstructure.
- Sub-Structure or Foundation: – The part of the building that is built below the ground level. The function of substructure/foundation is to transfer the loads from the superstructure to the underlying soil. Hence, the substructure is in direct contact with supporting soil. A foundation is therefore that part of the structure which is in direct contact with the ground to which the loads are transmitted. Substructure involves footing and plinth of a building.
Sometimes, a part of a major building is constructed below ground level which provides accommodation. In such cases, basement along with other portions of the building is supported by the foundation lying below it. The part of the building which acts as a foundation does not provide any accommodation but simply transmits the load of the building safely to the soil lying underneath.
Super-structure is that part of the structure which is above ground level, and which serves the purpose of its intended use. A part of the super-structure, located between the ground level and the floor level is known as plinth.
Plinth is therefore defined as the portion of the structure between the surface of the surrounding ground and surface of the floor, immediately above the ground. The level of the floor is usually known as the plinth level. The built-up covered area measured below the floor level is known as plinth area.
SUPERSTRUCTURE OF A BUILDING
The term superstructure refers to all parts of a building above the ground level. The superstructure of a building usually consists of roof, parapet, beams, lintels, columns, slab, walls, floor, verandah, lintel, doors and windows, stair, etc. These components safely transfer the dead loads, live loads and other loads to the substructure (foundation and plinth) which further distributes it to the underlying earth.
The functions and components of some of the important superstructure elements are explained briefly below:
Roof is the exterior and the uppermost part of any building structure. This structure is a covering that is provided to protect the building from rain, snow, wind, sun and other adverse effects. A roof deck and roof cover form the two main parts of a roof structure. The structural component that supports the roof cover is called a roof deck. This can be either constructed flat or sloped in the form of truss, shell, dome or flat slab based on the type of building the structure. The roof cover is laid over the roof deck. The roof cover can be either tiles, slates, shingles, corrugated sheets, asbestos cement or thatch coverings.
Parapet is a short wall barrier that is constructed at the edge of a terrace roof, balcony or walkway as a means of protection. This can be constructed by means of block, steel, aluminum, reinforced concrete or glass.
- 3. Beams A beam is a horizontal structural element with a specific depth and width running with a span. It withstands vertical loads, bending moments and shear forces. The loads coming on the beams are transferred to the beam endpoints where it is supported. This is then transferred to the columns or the it supporting structural elements.
The column is a vertical structural element that carries compressive loads. This is one of the critical structural elements in any building structure whose failure can result in progressive collapse. The column transfers loads from the slab or the beam to the foundation below
- Lintels A lintel is a type of beam structure constructed above all the wall openings to support the load coming over it and transfer safely to the side walls. The width of the lintel is the same as that of wall width and it ends into the masonry wall.
Slabs are horizontal structural elements that serve the purpose of floor, roofs or ceilings. These are flat surfaces with top and bottom face parallel to each other. Slabs are supported mainly by columns, beams, walls or the ground. The depth of the slab is very small when compared to its width and length.
- Walls Walls are vertical surfaces constructed in continuance that divide or enclose space. Walls can be constructed either by means of masonry or by means of concrete. Walls take up the load from the beams, the slabs or the roof above and transfer it onto the floor slab for onward transmission into the foundation.
The floor is defined as a finished horizontal surface of a building or a room where people walk. Any floor has two main components- sub-floor and floor cover. The sub-floor is constructed to support the imposed loads coming over it. This component imparts strength and stability for the floor structure. A floor cover or flooring is a suitable floor finish provided in the form of tiles, granite, marbles, concrete, etc.
A stair is a series of steps or flight that is constructed to move from one floor to another in a building structure. A staircase is a room or an enclosure where the stair is constructed. The space occupied by the stair is called as a stairway. There are different types of stairs like continuous stairs, straight stairs, turning stairs etc.
Figure 1 showing Superstructure of a General Building
What Are the Loads of Superstructure?
1: Dead Loads: Are permanent or stationary loads which are transferred to the structure throughout the life span. Dead load is primarily due to self-weight of structural members like walls, roofs, permanent partition walls and other fixed components of the building, fixed permanent equipment, furniture and weight of different materials etc.
- 2. Live loads: – Are either movable or moving loads without any acceleration or impact. Live loads do, or can, change over time. Live loads include any temporary or transient forces that act on a building or structural element. Typically, they include people, movable partitions and furniture, vehicles, and almost everything else that can be moved in a building.
- Impact Loads: – This type of load is caused by vibration or impact or acceleration. Thus, impact load is equal to imposed load incremented by some percentage called impact factor or impact allowance depending upon the intensity of the impact.
- Environmental Loads: -Are loads that are created naturally by the environment and include wind, snow, seismic, and lateral soil pressures.
MATERIALS USED IN THE CONSTRUCTION OF BUILDING
The following materials are use in the construction of building;
- Bricks/Blocks and other clay products such as floor tiles, roofing tiles, etc
- Cement such as Portland cement, coloured cement, etc
- Aggregates in the form of crushed stones, gravels, sand, etc
- Metals in the form of rolled steel section, mild steel and medium tensile steel bars for concrete reinforcement. High tensile structural steel, corrugated galvanized iron sheets,
- Paints, and varnishes etc
- Glass in various forms such as glass wool, flint glass
- Plastic materials
- Insulating materials
- Asbestos cement corrugated sheets and fittings
- Bituminous materials such as asphalt, tar, etc
- Door and window fittings