Let us consider with simple examples the mechanical properties of different materials and how they react when forces are imposed on them. A candle with the wick, it is like a pillar of reinforced concrete. Say the candle is concrete, and the wick the steel reinforcement. The candle sticks to the wick like concrete sticks to the steel and we can not pull the wick out of the candle and steel out of concrete. This collaboration of materials is called the relevance mechanism. The dynamics of relevance depend on the dynamics of both materials. For example, if we put steel in butter, the relevance mechanism will be weak, than if we place the steel in concrete. That is, the steel in a pull slides and comes out more easily when it is in butter than if it is in concrete. What do we see here? We see that good relevance requires two equivalent materials. If one of the two materials that work with the mechanism of relevance is weaker than the other will be the first to be destroyed, canceling the co-operation mechanism. Have you ever wondered why after an earthquake? around a quake-hit structure you can see broken pieces of concrete but you will never see a steel cut; Answer. Because concrete is like butter compared to the strength of steel. Have you ever wondered how many kilos a 50 mm section prestressing steel lifts? Answer 140 tons Have you ever wondered how many kilos a complete floor weighs? with an area of 100 square meters (with the walls, the furniture, the concrete, the floors and the people without the bases?) Answer It weighs about 100 tons. Conclusion A single steel (of the many that are placed in the construction) comfortably lifts the construction of the building (with an area of 100 sq.m.) in the air without breaking. The question is? Then with so much reinforcement that we place in the construction why do we have failures? Answer Because concrete is the first to fail due to shear forces, because it can not withstand the tensile strength of steel. This is just one factor in the failure of the structures. And then we wonder why the constructions fall in the earthquake. Put more steel in the constructions. Maybe with more irons the butter will work better!
Dear Apama Sathya Murthy. Every country produces different materials at different costs. Canada must have a lot of forests so good and cheap wood. Greece produces cement. So in Greece it is advantageous to build houses from cement and in Canada houses from wood. This saves shipping costs.
If a reinforced structure is well designed by an expert, the amount of steel reinforcement used calculated based on code requirements. Code requirements recommend the design equations based on the balance between compression in concrete and tension in the rebars. In this process, the differences between the strength of concrete and steel are seen. Thus in a perfectly designed section, compression concrete and tension steel will fail simultaneously.
The other point is that, pieces of broken concrete around a damaged structure after earthquake may be due to failure of concrete cover on the rebars which is unreinforced. Many reinforced structures do well during sever earthquakes.
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