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by System Administrator - Friday, 3 February 2017, 5:10 AM

By: M.S.Yatnatti Editor and Video Journalist Bengaluru : According to few reports it is said that Mantri Square building is not safe .If so then BBMP should demolish it mercilessly before it kills several innocent people .To me it is necessary that BBMP engineers should check all buildings and supervise them properly before any mishap happens. Verticality of framed stature is very important. Before concreting and after concreting it is must to Check the plumb of column by using plumb bob. Check that columns are in plumb, Verticality Checks for column formwork is of paramount important. The most common method adopted and also the most easiest one that you can adopt on the site and instantly find out the vertical alignment of any type of column is the Plumb-Bob method. RCC (Reinforced Cement Concrete) column is a structural member of RCC frame structured building. It's a vertical member which transfers loads from slab and beam directly to subsequent soil.A whole building stands on columns. Most of the building failure happens due to column failure and if t is not truly vertical . And most of the column failure happens not for design fault but for the poor construction practice and not checking verticality of column.. So, it is very important to know the construction process of the RCC column properly.

According to few reports it is said that Mantri Square building is not safe .If so then BBMP should demolish it mercilessly before it kills several innocent people .According to reports a six-member expert committee has been constituted to study the stability of Mantri Square Mall building, where a portion of a wall collapsed on Monday, injuring two people. Bruhat Bengaluru Mahanagara Palike (BBMP) Commissioner N Manjunath Prasad is the chairperson of the committee.The order, a copy of which is available with reporters , says that keeping public safety in mind, there is a need to take an expert opinion. Hence, a six-member expert committee has been constituted, headed by BBMP Commissioner N Manjunath Prasad. BBMP Additional Director (Town Planning) will act as Secretary and other members include Prof Radhakrishna of R V Engineering College, K S Jayasimha, R Nagendra and M S Sudarshan of CIVIL-AID Technoclinic Pvt Ltd.BBMP officials are also inspecting the collapsed portion of the wall.The committee members are required to file a report in 15 days after inspecting the building and conducting tests to check the stability of building as per Indian standards.

'Building structurally safe' Mantri Developers has issued a press release where T S Gururaj, a technical advisor, has stated that the wall collapse on the terrace level may be attributed to salty water collecting over a period of time on the terrace, thus weakening the portion of the structure and causing the partial collapse of the balcony. Puddles of salty water were found on the terrace at the cantilever areas only. The water on the terrace is attributed to leaks from AC pipes on the balcony.The press release added that the structure was inspected on all levels and was observed to have no distress at any location. Hence, the structure consisting of shopping areas, public areas, multiplex and food court are safe and can be used. However, the area beyond the balconies at the rear location shall be barricaded, supported temporarily with props and restructured before being used, the release said.

Reportedly Structural failure is concerning reduction in the load bearing capability of a structural component or element, or the main structure. Structural failure is commenced when the material is stressed to its upper strengthlimit, thus causing rupture or extreme deformations. The ultimate strength of the material or the system is the limit of the load bearing capacity. On reaching this limit, the construction materials could already been damaged, and their load carrying capacity is suddenly decreased permanently. If the system is properly designed, a local collapse should normally not be a cause of instant or gradual failure of the complete building. The ultimate failure strength of the construction elements should be carefully considered in the design of structures to prevent failure.Concrete is more widely used than any other manmade material and has been a construction staple for centuries. The early use of primarily lime-based concrete by the Egyptians and Greeks dates back to 2000 B.C. In the mid-1800s, steel-reinforced concrete was developed using steel ropes, I-beams, and bars; and prestressed concrete was invented in 1928 by Eugène Freyssinet while working on the plans for the Halle Freyssinet, a Paris freight terminal still in use today.

According to reports a progressive collapse of a building or structure is initiated from local fracture that later spreads to include the main section of the facility. Current concerns with such collapses stem basically from modifications in building practices and improper structural designs. Strategies for mitigating the structural failures can be evaluated using a thoughtful risk assessment, supported by modern computational tools. It is important to arrange soil testing on the actual site before the detailed planning starts. Buildings, like all construction, are designed to sustain specific loads without excessive deformation to prevent failure. The live loads consist of the weights of humans, objects, rain, snow, and the wind pressure, while the dead load is that of the building itself. With buildings consisting of a few floors, strength usually involves adequate rigidity, and the vital design is essentially that of the roof that will endure the weather effects. However, the roof design is of a minor significance for tall buildings, and the major considerations are that of the building supports.Structures may fail due to numerous reasons that need to be thoroughly deliberated during the initiation, design, planning, executing, and the monitoring processes of the project. It is essential to understand the load conditions on the structure, and accordingly design the structural elements and the materials used on the construction. Faulty construction has been the most important cause of structural failure. This includes the use of salty sand to produce concrete, use of inferior steel, improver riveting, incorrect nut tightening torques, defective welding, and other wrong engineering practices. Design of structures should also consider the seismic effects to prevent damage due to the earthquakes. Earthquakes may cause problems concerning the foundations when the damp land liquefliquefies

Concreting of any structural element of R.C.C. framed building is very important and crucial for achieving the desired life and durability of any building. Being done on the site it needs special and extra precautions as you have to practically establish 'factory like' controlled concreting on site. this is more important for developing country like India and Asain Countries where technology is developing and availability of the skilled labour force in scare with respect to demand. General practice is to check when the column element is ready for concreting i.e. reinforcement entirely tied up but ideal practice would be to check it in two phases

Check Formwork: Before you allow placing of reinforcement, thoroughly check the formwork. This step is mandatory as certain formwork defects can't be corrected or are difficult to correct after reinforcement is placed in position.Checking reinforcement: The second stage is to check reinforcement of column. Hence as a standard engineering practice, one should check the formwork before reinforcement gets placed/laid or tied.

Curing is the process in which the concrete is protected from loss of moisture and kept within a reasonable temperature range. The result of this process is increased strength and decreased permeability. Curing is also a key player in mitigating cracks in the concrete, which severely impacts durability. The figure is self explanatory, the amount of strength desired is related to the duration of curing.The period of curing of concrete is most important as it is very essential for keeping the hydration process of cement with water until concrete attains the maximum compressive strength, which increases but slowly after 28 days from initial placing time. Compressive strength reduces to 50%, If it would be in air without curing.From the above figure, you can analyse that moist curing is essential for concrete to achieve the approximate maximum strength (Not 100%).  Ideally the curing period depends upon the type of cement used, mixture proportions, required strength, size and shape of member, ambient weather, future exposure conditions, and method of curing.The period should be as long as practical.Environmental temperature plays very big part in the process of curing as the hydration process is an exothermic reaction. Maintaining proper temperature is also very important and it affects the duration of curing. For most concrete structures, the curing period at temperatures above 5º C should be a minimum of 7 days or until 70% of the specified compressive or flexural strength is attained. The period could be reduced to 3 days if high early strength concrete is used and the temperature is above 10º C.As the early strength of concrete is supportive towards the ultimate strength of concrete achieved, we should do proper curing according to the environment condition, type of member etc.So 7 days, it is in normal condition but there is never a thing called normal, So considering the factor of safety in Civil engineering is more (Tolerance too), 10 to 12 days of curing with proper method will ensure the achievement of 80% of 28 days strength of concrete.