Structural Detailing of a Reinforced Concrete Structure – Duplex
CHAPTER ONE
The objective summary of design specification is to provide information and structural consideration standard scales and abbreviation which are used to ensure the uniformity. The structural elements, beams, column, slabs, foundations will be detailed and shown in plans, elevations and sections.
CHAPTER TWO
REINFORCED CONCRETE
Reinforced concrete is a complicated structural material consisting of concrete and steel bar combined in a rational way for joint behavior in a member.
Basically, concrete consist of a mixture of cement and fine aggregates and water combined in a proportion specified by the code of practiced concrete is to use the concrete to resist compression and steel called reinforcement to resist tension. Thus the two materials is said to be complementary under building construction.
When the three materials that make up a concrete are combined, voids are created in the coarse aggregate which is induced by the fine aggregates. When water is added to the mixture of fine aggregate and cement, heat due to chemical reaction begin to evaporate to the atmospheres as the water reacts with the mixture of cement is called hydration reaction.
Also in fine aggregates, water reacts chemically with cement to produce a hard matrix solid stone like substance called concrete.
Moreover, since steel has high resistance to tension and compression, the introduction of a small amount of reinforcement increases the load bearing capacity of the compression number and increases the limit stage of the structure.
Concrete gradually gain strength as it hardens and its strength is measured relatively as the crushing strength of 28-days old concrete cube strength as a stipulated in B58110.
Concrete and steel are combined for joint work a qualitatively new material called reinforced concrete is created whose sphere application is broadly without limit. The basis of joint behaviour of concrete and steel is advangeous natural combination of several important physical and mechanical properties of the two like durability, fine ad weathering resistance, high resistance to static and dynamic loads.
Reinforced concrete therefore is a strong durable material which can be formed into many various shapes and sizes ranging from a single rectangular column to a slender curved shell which could be elements of permanent structures. This is an ideal method of achieving both lateral stability and good compression and tension strengths.
CHAPTER THREE
GENERAL PRINCIPLES OF DETAILING OF REINFORCED CONCRETE
PRINCIPLES AND PROCEDURES
The aim of detailing is to convey to the builder in its simplest form, the information needed to select and fixes each bar in its correct position. The principles and procedure laid down for detailing of reinforced concrete building is given in account issued by a joint committee of the concrete society and the institution of structural Engineers.
Consequently, for simplicity and legibility, details should be simple and bars having as few bends as possible, the written instructions should be clear and concise. It could be cumbersome drawing every bar producing a complicated dradwing and counter productive. To this end, the standard method of detailing stipulates and recommends according to BS4466 the following rules:
BEAMS:
All main bars should be shown in full in elevation and in section.
CHAPTER FOUR
DESIGN INFORMATION AND STRUCTURAL SUMMARY
PROJECT:
Structural detailing in reinforced concrete of a duplex
DESIGN CODES
CP110: structural use of concrete in building
BS8110: structural use of concrete in building (revised version)
CP3: loading of the structure
INTENDED USE OF STRUCTURE
Residential House or home
GENERAL LOADING CONDITIONS:
Floor: 1;5KN/M2
Roof 0.75KN/M2
CHAPTER FIVE
THE ENGINEERS DESIGN SPECIFICATIONS
FOUNDATION: NUMBER REQUIRED – 39
Base type A – (1200 x 1200 x 375mm) (39Nos)
Foundation wall – 225mm hollow block wall
Foundation wall footing (1300 x 225mm)
CHAPTER SIX
DETAILING OF THE ELEMENTS
FOUNDATION:
A typical base showing the tensile reinforcement at the bottom of the plan view is shown. A section is cut to show the cocumnaried out of the base and position of the starter bars. In the plan view only one bar is shown in full length in each direction and short lines are used to show the extension of each group of foundation base of similar bars.
In base type 1 – four 12mm high yield bars and (mark – 13 & 14) are arranged at 225c/c centre to centre at the bottom of the base in each direction.
In base 1, one column starter bar is shown in full in elevation standing on top tensile reinforcement at B links placed at 225mm centre to centre. Adequate bounding has been taken care of by providing lap length which is not less 30 time bar diameter bar plus 75 kickers given a total of 600mm projection for adequate bounding and stress distribution. At the bottom, the plan view of the base shows longitudinal bar with only 01 bar mark spaced at 150c/c. the transverse bar are shown as dots (.) which must represent number 8. In this case, a sectional elevation is cut to show the arrangement of the starter bar and links. The section also sources the dimension of the column from dating base is 25mm.
Columns
Two types of columns are used in this building and they are both (225 x 225)mm square and round column are 39 in number theoritically columns get small as loading decreases towards the top of the building but, in practice they are usually kept the same size and the quality of reinforcement is redeemed.
They are two types of columns: type 1 and 2 the two columns has no different, the type C and D are double column and are the same everthing. A typical elevation of the column is presented showing one bar in full and a short line to show the extent of the bars. A dimension line is drawn across the set of bar carrying their description 4600-4. The bars will stand on the kicker and therefore start 75mm above the foundation or floor slab. Because these cannot occupy the same space, the starter bars are bent towards inside at top length while the main reinforcement for column remained straight.
The section of typical column is cut to show the arrangement of the starter bar mark 17 and the link 8 in number space at (150c/c 3mark 8) the link are provided in accordance with CP110 clause (3:11:4:3) spell out the rules as follows:-
- The diameter of the link shall beat least one –quarter the size of the largest compression bar.
- They shall be spaced at not more than twelve times the size of the small compression bar.
- They must be full anchorage of the link at each compression bar, of at least 1350 unless there is a restrained bar within 150mm.
- In circular columns a circular links are adequate, the cover to reinforcement is 20mm for the column.
BEAMS
Beams are rectangular in cross section. The have width that are commonly the same as columns that support them and their depth usually includes the floor slab. The beams have tensile reinforcement to resist shearing forces across the depth of the beam and also the compression reinforcement at the top with link. The beams have been detailed in elevation with sufficient section to illustrate the position of all the longitudinal bars and shape of the links. All description of bars has been given on the elevation and the bar marks, only one repeated in sections.
The slab is supported by longitudinal and transverse beam running in both directions with slab.
In detailing, each beam is referenced by grid lines on which it is located, example (A-B-C-D-E) indicated the grid lines that specify and shows the outline of the spporting column and the intersection beams and floor slab.
Although, there are several bars bearing the top and bottom of the beam only one line drawn to represent them. Bars which do not run the full length of reinforcement concerned, written along side. Every main reinforcement bars or set of similar bars is described once only in full in elevation and their mark numbers only are used to indicate their termination and their position in section. The links are described in full in elevation and their position and in section. The cover to reinforcement is 25mm.
FLOOR SLAB DETAIL
The slab is supported by a continues beam. The floor slab is cast monolithically with the supporting beams and continuous beam.
The tension zones are at the bottom of the slab and the top is over the supports. The slab is detailed in plan with sufficient sections to show the position of all the reinforcement. Descriptions of the bars are given in full on the plan view and only the bar marks are repeated in sections. Dimension showing the position of bars are indicated by one bar drawn in full and short line to their descriptions. The dimension of bent bars are given in sections. Shapes of bent bars are not shown in plan view but in section except where they are placed at the slab edge where there is beam underneath. For instance, the bar 36-Y12-04-150c/cT is bent at the end because it terminates at the edge of the slab. The bent is always in compliance with relevant code requirements.
If the slab is thin, bar must be taken to ensure that the standard hooks and bends will be accommodated without reducing the cover. Secondary or distribution bar are provided in slab to spread any point load sideways over the primary reinforcement and combined with reinforcement.
DETAILING OF STAIRCASE
The staircase virtually a shopping slab upon which treads and going is been cast
Stairs are normally constructed after the floor slab has been constructed and left within projected starter bars both at the top and at the around floor to accommodate the flight. One stair case si provided in this building. The two flights are provided in each staircase. The two flights are provided in each staircase. The first flight has equal risers at 150mm and 12 equal tread at 399mm. The half landing is 1500mm and full landing is 1200mm and continuous with slab. The plan of staircase shows different short and long lines, which indicates reinforcement, (main reinforcement bars, continuity bars, the distribution bars) each bar is described in the plan. Main reinforcement 6-y12-03-150c/c.
A section of plan is cut to show the detailing of the flight of the staircase. Sectional elevation through the flight shows the arrangement of the main reinforcement in the tension zone. It is placed near the bottom of the stair slab and shown with one line (mamrk 11 and 12) remaining from the landing to first riser from the ground floor.
The cover to reinforcement is 25mm and waist is 150mm thick.
BIBLIOGRAPHY
- Ugwu G.O. (Engr.) 2003: lesson and notes on reinforced concrete structure and theory of structures IMT-library.
- Newton,, P.H. 1985: Structural Detailing Macmillian publisher ltd London.
- C.E. Reynolds (1981) reinforced concrete design manual 4th edition view point publication.
- Bs1192: 1969 Drawing office practice for architects and builders.
- Dr. Orhafe 91986) Element of reinforcement concrete design department of Civil Engineering UNILAG.
- H. Mosley and J.H. Bungey (1990): Reinforced concrete design 4thedition.
