Engineering Structure and Structural Design.
Structures in concrete have become very common in civil engineering construction. Concrete has established itself to be a universal building material because of its high compressive strength and its adaptability to take any form and shape. Its low tensile strength is compensated by the use of steel reinforcement. Thus , the concrete is strengthened by steel and the resultant composite mass is known as reinforced cememt concrete(R.C.C). It is this combination which allows almost unlimited use of reinforced concrete in construction of buildings, bridges ,tanks dams etc., with the result that almost every civil engineer is intimately concerned with reinforced concrete structures. It is , therefore, necessary that every civil engineer knows the basic principles involved in design of R.C structures.
An Engineering structure is an assembly of members or elements transferring load and providing a form, space, an enclosure or a cover to serve the desired function
Structural design is a science and art of designing , with economy and elegance , a durable structure which can safely carry the design forces and can serve the desired function satisfactorily in working environment during its intended service life span
Objective and Basic Requirements of Structural Design
The objective of structural Design is to plan a structure which meets the basic requirements of structural science and those of the client or the user. The basic requirements of structural design are as follows:
1) Safety 2) Serviceability 3) Durability 4) Economy 5) Aesthetics 6)Feasibility, Practicability and Acceptability.
1) Safety : It has been the prime requirement of structural design right from the history of civilization and construction that a structure shall be so designed that it will not collapse in any way during its expected life span. A brittle material like concrete does not give a prior warning of failure. It is , therefore, necessary to obtain the ductility in the structure by providing steel of such quality that it would yield prior to crushing of concrete
2) serviceability: The performance is rated by the fitness of the structure to maintain deflections, deformations, cracking and vibration effects within acceptable limits.
3) Durability: The structure shall resist effectively environmental action during its anticipated exposure conditions,such as rain , alternate wetting and drying or freezing, climatic variations in temperature and humidity
4) Economy: The design shall be economical. The economy shall be of material by optimum utilization of its strength or it maybe the economy of cost which includes cost of construction as well as cost of maintainance and repairs.
5) Aesthetics: The structure should be so designed that it should not only be safe, serviceable and durable but should also give a pleasing appearance without affecting the economy to a great extent.
6) Feasibility ,Practicability and Acceptability: The structure has to be so designed that the proposed solution is feasible, practicable and acceptable