1.1 THE DESIGN PROCESS:
The entire process of structural planning and design requires not only imagination and conceptual thinking but also sound knowledge of practical aspects, such as recent design codes and bye-laws, backed up by ample experience, institution and judgment.
It is emphasized that any structure to be constructed must satisfy the need efficiency for which it is intended and shall be durable for its desired life span. Thus, the design of any structure is categorizes into following two main types:- 1. Functional design
2. Structural design
1.1.1 FUNCTIONAL DESIGN:
The structure to be constructed should primarily serve the basic purpose for which it is to be used and must have a pleasing look.
The building should provide happy environment inside as well as outside. Therefore, the functional planning of a building must take into account the proper arrangements of room/halls to satisfy the need of the client, good ventilation, lighting, acoustics, unobstructed view in the case of community halls, cinema theatres, etc.
1.1.2 STRUCTURAL DESIGN:
Once the form of the structure is selected, the structural design process starts. Structural design is an art and science of understanding the behavior of structural members subjected to loads and designing them with economy and elegance to give a safe, serviceable and durable structure.
1.2 STAGES IN STRUCTURAL DESIGN:
The process of structural design involves the following stages. 1) Structural planning.
2) Action of forces and computation of loads.
3) Methods of analysis.
4) Member design.
5) Detailing, Drawing and Preparation of schedules.
1.2.1 STRUCTURAL PLANNING:
After getting an architectural plan of the buildings, the structural planning of the building frame is done. This involves determination of the following. a. Position and orientation of columns.
b. Positioning of beams.
c. Spanning of slabs.
d. Layouts of stairs.
e. Selecting proper type of footing.
220.127.116.11 Positioning and orientation of columns:
Following are some of the building principles, which help in deciding the columns positions.
1. Columns should preferably be located at (or) near the corners of a building, and at the intersection of beams/walls.
2. Select the position of columns so as to reduce bending moments in beams.
3. Avoid larger spans of beams.
4. Avoid larger centre-to-centre distance between columns.
5. Columns on property line.
Orientation of columns:
1. Avoid projection of columns:
The projection of columns outside the wall in the room should be avoided as they not only give bad appearance but also obstruct the use of floor space, creating problems in placing furniture flush with the wall. The width of the column is required to be kept not less than 200mm to prevent the column from being slender. The spacing of the column should be considerably reduced so that the load on column on each floor is less and the necessity of large sections for columns does not arise.
2. Orient the column so that the depth of the column is contained in the major plane of bending or is perpendicular to the major axis of bending.
This is provided to increase moment of inertia and hence greater moment resisting capacity. It will also reduce Leff/d ratio resulting in increase in the load carrying capacity of the column.
18.104.22.168 POSITIONING OF BEAMS:
1. Beams shall normally be provided under the walls or below a heavy concentrated load to avoid these loads directly coming on slabs. 2. Avoid larger spacing of beams from deflection and cracking criteria. (The deflection varies directly with the cube of the span and inversely with the cube of the depth i.e. L3/D3. Consequently, increase in span L which results in greater deflection for larger span).
22.214.171.124 SPANNING OF SLABS:
This is decided by supporting arrangements. When the supports are only on opposite edges or only in one direction, then the slab acts as a one way supported slab. When the rectangular...