EARTHQUAKE RESISTANT BUILDINGS Detailing drawings for the structural frame’s construction
Detailing drawings for the structural frame’s construction
General
The architectural, structural, mechanical design of a building, have three stages, the preliminary design, the final design and the detailing. The purpose of the preliminary design is to assess all the parameters of the building, to evaluate their effect both from a legislative and a practical point of view and to propose a solution. The final design presents the entire concept of the building, solves all issues regarding the designated proposal and determines the geometry and the way of construction. The detailing describes in every detail the constructional way of the building’s erection and provides all technical information regarding its realization.
All the stages of every single design are presented in drawings. During the preliminary design they have the form of a draft drawing, during the final design they are accurate drawings and during the detailing they analytically present every detail.
In order to have a correct and economic erection of a building, the detailing is mandatory in all three design categories: architectural, structural frames’, installations.
In the case of a structural frame that belongs to an earthquake resistant reinforced concrete building, the detailing is extremely complex and critical for the building’s integrity. The complex- ity of the structural frame’s detailing is caused mainly due to the hundreds of bars that compose its reinforcement. The rebar dimensions regard each individual structural frame and this distinct- iveness of the thousands of pieces is unique in the entire building when compared to all the other elements e.g. the casings are met in tens of different types and dimensions. The accuracy of the reinforcements schedules is extremely crucial because every mistake jeopardizes the building’s safety not during its usual service life but during the rare (but certain to come) mo- ment of a strong ground motion.
When the building is relatively small, there is a large possibility to make changes during its con- struction. For instance, prior to the excavation and due to special soil conditions, the foundation may be modified or due to an alteration of a floor’s use the formwork might be reformed. For this reason, when the work is small and there is a large possibility for changes it is preferred the de- tailing to follow the phase of the structural frame’s erection.
The methodical and detailed supervision of the structural frame’s erection is mandatory for the successful construction of a building. However, the proper supervision is feasible only when there is a meticulous detailing even if the supervisor engineer is the also the designer engineer.
The drawings are symbolic plans whose meaning must be comprehensible not only to the de- signer that composes them but also to all their users (supervisor engineers, foremen, contractors, quantity surveyors etc.). The symbolic language of the drawings is used and in the examples mentioned in the previous chapters. The drawings that accompany this book show the de- tailing of the multistory building <bkGR>, which is examined in the various chapters, while the following pages concisely explain the terminology and the practices followed.
The construction of a building’s structural frame requires two types of drawings: (a) the carpenter’s formwork drawings which provide all the necessary geometrical information regarding the formwork’s implementation and the concrete casting of the structural frame and (b) the steel fixer’s formwork drawings that present all reinforcements with their necessary details.
Usually, the detailing drawings are presented in 1:50 scale, while the details are presented in 1:20 or 1:10 scale.
The carpenter’s drawings have the prefix C, while the steel fixer’s drawings have the prefix R. The numbering of the drawings may follow any rule. In this specific example every drawing is
numbered by integer multiples of ten. This numbering has the advantage that various versions of a drawing theme can be added without altering the numbering of the following drawings. For instance, if another version of the carpenter’s drawing C.30 is created it can be numbered as
C.31 and so on.
When there are more than one steel fixer’s formwork drawings (like R.30 of the example draw- ings) these have the same number but with the addition of their characteristic (in this specific case R.30.B, is the detailing drawing1 of the beams). The same thing also applies to the carpen- ter’s drawings.
In every drawing C.xx, corresponds one R.xx and possibly a supplementary R.xx.yy.
Every structural element presented in the drawings has a number prefix which defines its level
e.g. the label 2b12 specifies the beam b12 of the 2nd floor. Usually, the prefix 1 corresponds to the 1st floor, 2 to the 2nd floor, -1 to the first basement and so on. This means that the beam pre- fix is numbered …,-2,-1,0,1,2,…. In the example of the project <bkGR>, which has a mezza- nine, the correspondence is presented at the title block of the following paragraph. The repre- sentation of every structural element with a unique way helps in the industrial cut and storage of the reinforcement order, for many floors at the same time without problems arising from confu- sions due to elements with the same name.
1 The beams detailing drawings are the traditional constructional drawings that accompanied every detailing and they had two roles. The first and most important was to provide the exact dimensions of rebars and stirrups so as to compose the reinforcement schedules. The second role was to accurately define the precise position of the additional rebars when this was not entirely obvious. Nowadays, with the use of proper software, like the one included in this book, the reinforcement schedules are automatically created with great accuracy and the specialties of the additional rebars’ implementation are shown upon the formwork drawing. Moreover, the simple 3D or the stereoscopic figures created by the software illustrate the exact reinforcement layout in all the critical parts. The same thing applies and for the rest of the traditionally accom- panying drawings.
