WHY THE LANGATA SOUTHERN BYPASS BUILDING COLLAPSED
PICTURES OF THE RECENTLY [9/9/2011 @ 10.30 AM] COLLAPSED MATIGARI BUILDING ALONG THIKA ROAD NEAR MATHARE NORTH
|From MATIGARI MATHARE NORTH THIKA ROAD COLLAPSED BUILDING|
The Langata Building near Carnivore restaurant along the bypass collapsed due to a myriad of reasons as analyzed by Architect Francis Gichuhi of www.a4architect.com. Lets first study the history of cement and reinforced concrete .
The earliest recordings of cement use are in 3000 BC in Egypt on the building of the Pyramids. In 300 BC, Romans were using cement to build magnificent structures such as the Colloseum and the Pantheon. This cement had cow-dung as an ad-mixture to strengthen it.
In Africa , we have used clay and cow-dung for thousands of years in making pots and house walls.
Reinforced concrete use was discovered by Frenchmen Joseph Lois Lambot [May 1814-August 1887] and Joseph Monier [November 1823-March 1906].
Joseph Louis Lambot was born in Montfont,France and worked in the Agriculture sector where he constructed water tanks using cement and steel. He constructed a boat in 1848 using cement and steel and patented it in 1855.
In 1851, he patented the use of iron and cement.
Joseph Monier was born in Saint-Quentin-La-Poterie, France and was a gardener. He was not satisfied with the clay plant containers since they were brittle. He strengthened the clay using wire mesh. In 1867, he obtained the patent of using reinforced concrete on horticulture flower pots. He later on patented more reinforced concrete products as other inventors into the reinforced concrete field came into play.
In America, Thaddeus Hyatt [1816-1901] , a campaigner against slavery, invented the use of ‘illuminating vault covers’ which are glass panels with reinforced concrete around it. These were used to illuminate underground cellars below city sidewalks. In 1878, he patented reinforced concrete floors, roofs and pavements in the U.S.A.
In 1903, the first concrete high-rise was constructed-The Ingalls Building. It was 16 floors in height. It was designed by the architectural firm of Elzner and Anderson.
REASONS FOR COLLAPSE:
POOR AGGREGATE MIX.
The materials used to mix the reinforced concrete were of poor quality.
There are several deposits of quarry dust around the site, which shows that the aggregate used instead of sand was quarry dust. The ballast at the site was ok.
River sand has small sugar-like granules which assist in providing the necessary friction that tightly holds the concrete to the steel which is twisted to give it more grip.
Quarry dust as the name suggests is very fine and flour-like. It has no ‘bonding’ capacity. Quarry dust also has a lot of impurities which lessen the strength of the reinforced concrete.
The bond between cement and the quarry dust is weaker than cement and sand due to the flakiness and smoothness of quarry dust as opposed to river sand.
Some columns were not well vibrated during construction. This resulted in the steel being exposed hence not bonding with the concrete to offer the required structural strength.
These weak columns could not withstand the pulling forces. Notice that the building fell forward facing the entrance with the front part completely heaving till the bottom while the behind part having less damage. The building also twisted off the plot boundary into the compound.
The columns could not withstand the ‘pull’ resulting into total collapse.
Since 1903, when the first concrete high rise was constructed, the world has slowly moved into newer methods of construction. In America, China and the Arab world, use of Pre Engineered Steel Buildings [PEB] is very common. These are buildings that use Steel as a structural member as opposed to using concrete reinforced with steel bars.
Now that we have a new Constitution in Kenya, the new Building Code allows for use of new technology such as PEB. The previous use of the British Standard in Kenyan engineering standards should be revised and new standards included.
The reason that the Langata Building owner used quarry dust instead of river sand as aggregate is most probably due to the fact that river sand is not easily accessible. River sand harvesting degrades the environment hence discouraged by the Government through the Environmental protection agency-N.E.M.A. This creates a shortage which can be solved by use of steel members instead of reinforced concrete for construction.
It’s high time we moved over to new methods of construction which consume less sand and hence less environmental degradation. These methods are also safe in that in case of building collapse, there will be less fatalities and injuries since these are lighter than reinforced concrete buildings. They are also easy to demolish and dismantle since the steel members are screwed on to each other. For more information regarding this, please contact www.a4architect.com .
Architect Francis Gichuhi Kamau.
B.Arch. Nrb. M.A.A.K[A] Registered Architect.