18-Structural Concrete by Nadim Hassoun-7th Edition (ACI318-19) 

   The design of different structures is achieved by performing, in general, two main steps: (1) determining the different
forces acting on the structure using proper methods of structural analysis and (2) proportioning all structural
members economically, considering the safety, stability, serviceability, and functionality of the structure. Structural
concrete is one of the materials commonly used to design all types of buildings. Its two component materials, concrete
and steel, work together to form structural members that can resist many types of loadings. The key to its
performance lies in strengths that are complementary: Concrete resists compression and steel reinforcement resists
tension forces.
The term structural concrete indicates all types of concrete used in structural applications. Structural concrete
may be plain, reinforced, prestressed, or partially prestressed concrete; in addition, concrete is used in composite
design. Composite design is used for any structural member, such as beams or columns, when the member contains
a combination of concrete and steel shapes.

The advantages of reinforced concrete can be summarized as follows:

     1. It has a relatively high compressive strength.

     2. It has better resistance to fire than steel.

     3. It has a long service life with low maintenance cost.

     4. In some types of structures, such as dams, piers, and footings, it is the most economical                 structural material.

     5. It can be cast to take the shape required, making it widely used in precast structural components.        It yields rigid members with minimum apparent deflection.

The disadvantages of reinforced concrete can be summarized as follows:

     1. It has a low tensile strength of about one-tenth of its compressive strength.

     2. It needs mixing, casting, and curing, all of which affect the final strength of concrete.

     3. The cost of the forms used to cast concrete is relatively high. The cost of form material and         artisanry may qual the cost of concrete placed in the forms.

    4. It has a low compressive strength as compared to steel (the ratio is about 1:10, depending on      materials), which leads to large sections in columns of multistory buildings.

   5. Cracks develop in concrete due to shrinkage and the application of live loads.

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