The Effect of Reinforced Concrete on Safety of Residential Buildings in Nigeria
AIM AND OBJECTIVE
The reinforced concrete uses extra materials like steel bars, wooden beams or fibers, along with a wire frame to help mold the concrete and ensure the safe construction under the worst condition of the force that may be applied within and outside the building.
The reinforcement interacts with the concrete, strengthening it and providing support houses and other structures. The concrete provide shielding for the steel so it doesn’t corrode as quickly and together they are a common component in the modern construction
A slab is a structural part of a horizontal supporting element in a building. It is also a part of reinforced concrete structure which more often than not subjected to bending (ie tensile or compression) but in rare cases,(such as in bridge deck) are subjected to shear. In most cases, slabs are horizontal members but they can be used as vertical members, such as walls to infill panels, side walls to drains and sewer, and appurtenances etc. slab design centers more on flexure rather than direct shear. Where slab is thicker than 200mm, or where action of point or line is predominant, slab should be cheeked for direct shear and punching shear but in this project, the slab thickness is 150mm, there does not require to cheek for any shear like punching or direct shear.
Types of slab
There are many types of slab, and the type to be preferred may depend on
- the span of the slab
- the usage of the space which may determine the span
- the load to be carried by the slab
- Architectural aesthetics that is required.
The various types includes:-
(a) solid slab (cantilever, simply supported, continuous, one and two ways slab)
(b) Flat slab (although solid but of different construction)
(c) Ribbed floor slab
(d) Waffle slab
In this project, solid slab is been considered which are the most common especially in residential buildings which is the case study of this project.
Slab to be considered in this project are continuous one way spanning slab, continuous two ways spanning slab and cantilever slab.
Beam is a horizontal member of a reinforced concrete structure. Loads from slabs, walls etc. are transmitted through the beam to the columns and finally to the foundation below.
A beam like any other member is designed to resist the ultimate bending moment, shear force and torsional moment if any. Serviceability requirements must be adequately considered to ensure that the member will behave satisfactorily under the working load. However, much emphasis is generally placed on the ultimate limit state requirement s of the beam. The serviceability limit state of deflection being taken care of through the span effective depth ratio.
The load/moment on beams can be generated as follow
- Beam own weight (self)
- Beam finishes
- Wall or partition load
- Slab load including live load and finishes etc.
The loads are summed up to obtain the total load on the beam and then analysed using the various methods of determinate and indeterminate beam analysis such as movement distribution method or three movements equation method etc.
Columns are compression members although may be subjected to bending either due to their slenderness or due to the asymmetrical loading from beams. In structures, columns carry the loads from slab, beams, walls down to the foundation.
Columns are classified and designed as short column based on their slenderness ratio. A column is said to be short column if the ratio of the effective height to the corresponding total thickness is less than 10, otherwise, it is called a slender column (un-braced).
In other words, column can fundamentally be categorized as axially loaded column, column subjected to uniaxial bending and column subjected to biaxial bending
Lex/h <15 short (braced column)
Ley/h <10 short(unbraced column)
Column in this project are subjected to biaxial bending which are short in one direction and slender in the other direction and the worst condition as been designed for which the slender once are designed.
To conserve space, the analysis of checking the worst condition has not been shown in the manuscript. Shear walls provides lateral stability of the structures and the column gains lateral support, hence all braced column and only one unbraced.
The load transfer from the super structure to the soil is obtained through appropriate foundation works. Foundations are horizontal or vertical members supporting the entire structure and transmitting the loads to the soil below. They are sub – structures supporting the super – structures of column, beams, walls, slabs and roofs.
Foundation can generally be classified as shallow or deep foundation. The choice between shallow or deep foundation can be affected after thorough examination of the transmitted loads from supper structures, the nature of the soil, the economic aspect of the elements of the foundation work and the problem concerning foundation construction.
In this project, isolated pad footing has been adopted to transmit loads from the entire structure through columns to the soil.
Stair case is s set of steps or flight landing from one floor to another. Each step consists of horizontal portion or tread connected to a front part known as riser. The going of a step is the horizontal distance between the face of two consecutive risers. The riser of the step is the vertical distance between the tops of two consecutive treads. The materials for construction may include timber, stone, and concrete (reinforced)
Having designed the basic elements of the typical reinforcement concrete framed structure, it is important to mention that the structural presented problems which the code provides the requirement guiding the design. But a lot depends on the writer’s ability to reason as well as practical solution is to the problems that arose, this implies a classroom examples.
For the fact that the precise loading condition of the building cannot be achieved during the load estimating, their respective partial safety factor provided by the BS 8110 part 1and 3 1997 and 1985 has been applied on the affected loads and strength of the concrete and that of steel.
- Simplified Reinforced Concrete Design (By Victor Onyenuga. Second Edition)
- Reinforced Concrete Design (By Bill Mosley and John Bungey fifth edition)
- Structural use of Concrete part 3, design chart for singly reinforced beams, doubly reinforced beams and rectangular columns (BS 8110: part 3:1985)
- Structural use of concrete part 1, code of practice for design and construction (BS 8110: part 1:1997)
- Structural use of concrete part 2, code of practice for special circumstances.
- Sectional Areas of group of bars for the selection of reinforcements.