The severe earthquake that struck Nepal on April 25, 2015, claimed almost 9,000 lives, many thousands more were injured, and 600,000 structures in Kathmandu and other nearby towns were either damaged or destroyed. The staggering figure of structural damages forces us to believe that it is not the earthquake that kills but poorly built buildings.
The Supreme Court order of demolition of five buildings in Marad, Kerala has come as hot news in media with the people applauding the order as well as a few condemning them. This has not been the first instance of demolition of buildings for illegal construction in coastal lines against the CRZ regulations. Rainbow restaurant, in the banks of Periyar, Aluva also met a similar fate of demolition for illegal construction on CRZ regulations in 2014. Why were these construct to be taken down and what does the coastal regulation zone mean. It has been a question that plagues us.
Over the past few months, a slew of fire accidents has occurred In India damaging human lives, properties and goods. In a tragic incident, 20 students died after a fire broke out in a private coaching center in Surat, Gujarat last month. Eyewitness recall that in a bid to escape the blaze, students were seen jumping and falling from the third and fourth floors of the building. This accident is just one of the countless fire tragedies in the country.
Engineers build leaving a wide berth of safe loading capacity to construct, let’s get a brief view on how the same is for steel reinforcement bars. We have talked enormously on safety codes listed in IS 1786:2008, in the manufacture of reinforcement bars. Now, let’s discuss how safe loads are calculated in a construction material like reinforcement bars. The min. yield strength a reinforcement bar should have is easily inferred from the grade of the reinforcement purchased. Grade Fe 415 having a min. yield strength of 415 N/mm2, similarly for grade Fe 500 having min. yield strength of 500 N/mm2 and Fe 550 with min. yield strength of 550 N/mm2, so goes for every steel reinforcement grade.
We have been talking about the pros and cons of steel and concrete as a construction material. Let’s get a better understanding on why they work better together. Anyone reading about construction materials would have come across the saying – Concrete is good against compression, but weak in tension whereas steel bars are good in tension, but weak in compression. What a few had inferred from the statement is that, steel is naturally weak in the face of compressive forces, which is not the case. Steel is good in both compression and tension. Steel bars or steel reinforcement bars are weak in the face of compressive force due to their dimensional property. Steel reinforcement bars have an insignificant cross sectional area when compared to the length of the steel bars, and thus the ability to withstand compressive forces are naturally less.
Our last blog described the TMT steel bars and its importance as reinforcement for the construction of commercial buildings. More specifically, it described the standard IS 1786:2008 that every reinforced steel bar should conform to. The IS standard defines certain guidelines that must be followed when manufacturing the reinforced steel bar.
The introduction of reinforcement drastically changed the phase of construction of building structures of steel. Reinforced steel provided the necessary tensile strength which the concrete lacks. Today, very few constructions are done without using reinforced cement concrete. At the current scenario, the most used reinforced steel bars are the Thermomechanically Treated (TMT) steel reinforced bars. They are preferred for their excellent tensile strength and optimum ductility. The TMT steel bars are of different grades namely Fe 415, Fe 500, Fe 550 and Fe 600.
When it comes to constructing a building structure, the right set of resources must be used for ensuring the overall life and the integrity of the building. The introduction of reinforcement in construction improved the overall life expectancy of the structure and made them strong enough to withstand the forces of nature. Steel is the primary component used as reinforcement because of its excellent tensile strength, recyclability and similar thermal coefficient of expansion to that of concrete.
Natural disasters are usually one of the troublesome challenges for building structures to overcome particularly, the reinforced steel. Natural disasters are of many types, but the most common disaster occurrence in our country are earthquakes. There are many scenarios of structural collapses due to earthquakes. Although the causes can be attributed to several factors such as the age of building structure, lack of maintenance etc, the most important factor to be attributed is the ductile nature.
In reinforcement of steel bars, splicing technique is generally used to produce a single large reinforced steel bar by joining two similar length reinforced bars and wiring them.