Importance of proper safety in buildings
It is not an easy picture to see when bodies are lying under the debris of a crumbled building. This has happened in many countries including Sri Lanka due to collapsing buildings. Builders have to be extremely careful when constructing a building to see that the structure is safe in every aspect.
File picture of the Wellawatte building collapse
The first thing that an engineer would like to ensure is that the foundations are strong enough to support a building. A Structural Engineer would carefully evaluate loads acting on each and every column and know the worst possible load combination that could be used as the maximum load on the column. Without doing these calculations, he cannot evaluate the type of foundation that has to be used in a building. When I say type of foundation, there are different types of foundations, provided by Structural Engineers to support a building. The type of foundation depends on the ground conditions and also the load acting on a column as discussed above.
I would recommend that if a building is more than a single storeyed building, soil investigation is extremely necessary. Sometimes even in single storeyed buildings, one cannot ignore an investigation of soil if the ground conditions are believed to be extremely poor. In some of the areas in and around Colombo, there is soil which cannot withstand any load because such soil consists of decomposed vegetation. This soil is identified as peat by engineers. Therefore there could be a failure even in a single-storeyed building if the ground consists of a peat layer.
I remember an instance in one of the hotels constructed about 25 years back where the water sump was founded on the existing ground. The depth of the water sump was approximately four metres, including the clear height. The designer, when evaluating the loads, found that the service load acting on a square metre is not more than 30 kilogrammes per sq. metre, which is considered as a fairly small loading. Therefore after filling that area with soil for a height equivalent to two metres for a period exceeding one year, construction was carried out of the sump. This is identified as pre-loading in engineering terminology, which means if the ground is subjected to a certain loading when the structure is constructed, the ground will be loaded to the same value and keep it for some time for probable settlements.
Later the pre-loading will be removed and the structure will be constructed. However, the period of one year had been insufficient and also the peat layer was so thick that there had been a process called secondary settlement. As a result of these factors water sump had settled more than three metres, i.e. the full height of the sump. Settlement of the water sump was so much that, the owners could not use the sump at all.
That is the very reason that proper soil investigation is necessary and a report has to be obtained from a specialist. Sometimes this may cost additional expenses, but when you consider the long term, it is going to save the entire cost of the structure that a person is going to build. After carrying out soil investigations and testing of soil samples, the engineer would decide what type of foundation that he should have in order to support the building. Therefore if you are advised that soil investigation is a waste of money, it is a serious mistake on the part of the consultant of the building.
It is also important that when an owner intends to construct a building, he should make up his mind for what purpose the building is constructed. The importance of this is that the load acting on the foundations depends on the usage of the building, for e.g. if you are constructing a library or a bookshop, the weight of books are much heavier than the usual loading. Therefore, when calculating the loading, the engineer takes into account the intended use of the structure and thereby foundation sizes will be decided based on the usage. Therefore the owners shall not change the usage of the building without obtaining advice from a Structural Engineer.
Collapsing buildings is far more severe in the other South Asian countries than in Sri Lanka. The famous collapse of Rana Plaza in Bangladesh led to the death of at least 1129 workers. In 2005 the Spectrum Garments Building collapsed killing over 60 workers. The following year at least another 60 died in a fire at KTS Textile Mill in Chittagong and in November 2012, 112 people were killed at a fire at Tazarene Fashion Factory outside Dhaka.
Apart from the safety of the building, one also has to be mindful about the functionality of the building. Presently people construct buildings for general use and convert them to various other specific uses. If buildings are used to stack material, it could cause an additional loading about 3-4 times more than what it was designed for. Under these circumstances, conversion of the usage of a building shall not be done in an ad-hoc manner.
Presently in the city of Colombo, many high rise buildings are being constructed and it is not uncommon to have buildings having more than 30-40 storeys. These buildings may have been designed by qualified Structural Engineers and also it may even fulfil most of the functional requirements described by the authorities.
However fire is going to be a major hazard which is going to affect the safety of buildings. Even in countries like UK there had been disasters due to fire in condominiums.
The recent fire which engulfed a 24-storey Greenfell Tower in West London has caused loss of lives and a severe damage to property. Survivors of the Greenfell Tower should be much thankful to fire fighters, since there was no way of escaping from the building in an emergency of this nature. The fire was reported at the 24-storey block in North Kensington at midnight, leading to 40 fire engines and more than 200 fire-fighters tackling the blaze. It took until the following day to bring it under control, with the fire affecting most floors of the building and destroying 151 homes, both in the tower and surrounding areas. The London Mayor has said that the fire fighters could reach only up to the 12th floor. Therefore there should be a way of handling fires in high rise buildings.
Several of the victims of the Grenfell Tower fire have now been identified. Police say that while 80 people are currently presumed to have died, the final toll will not be known. It is reported that there was only one fire exit staircase and no sprinklers or other fire extinguishing equipment functioning in the building. Presently various authorities take action to clear the state land by providing alternative accommodation for dwellers in multi-storeyed buildings. Therefore, the writer believes that priority has to be given to safety aspects. Very rarely I have seen a fire drill in a multi-storeyed building and therefore even if there are sufficient fire escapes, people may not know what to do in case of emergency.
Presently the Institution of Engineers, Sri Lanka publishes a directory of engineers, who are qualified to design multi-storeyed buildings. A copy of this directory could be purchased from the Institution of Engineers, Wijerama Mawatha and also a list of Engineers who could practice as Structural Engineers is listed in the IESL web (http://www.iesl.lk/page-1566050 ). Depending on the competency and experience, the Structural Engineers are categorised into difference classes. Any Chartered Civil Engineer registered in the Institution of Engineers could design buildings up to four storeys. Their names are separately listed in the directory. Similarly the second category of engineers who could design buildings up to eight storeys and the third category is engineers those who could design buildings up to 12 storeys.
Therefore depending on the height of your building, one should be mindful to select a suitable engineer from the directory published by the Institution of Engineers. For buildings more than 12 storeys and up to 20 storeys, there are two other categories and also engineers who are qualified to design more than 20 storeys are also listed in a separate category. Therefore when you are constructing a building or a house, the advice that we could give is to select a suitable Structural Engineer as it is the most important factor. Do not be misled by advertisements that show buildings collapsing buildings due to inferior steel. Poor steel or concrete may be one reason for a failure, but there are so many reasons for collapsing of a building. The writer recommends that it is always preferable to obtain the services of a qualified Structural Engineer when you are constructing a house or a building.
(The writer is a Chartered Civil Engineer, Member of the Council and Past President of Institution of Engineers Sri Lanka. He can be reached at enganada@gmail.com)