NEW BUILDING CONSTRUCTION METHODS- PRE-ENGINEERED STEEL BUILDINGS [PEB]
We are increasingly seeing the effects of building collapse due to earthquakes in regions such as Haiti and collapse due to poor workmanship such as the recent building collapses in Kiambu. With rapid urbanization, more high-rise buildings are coming up in major towns creating perfect recipes for disaster as people get trapped underneath tons and tons of concrete incase the building unfortunately collapses –either due to an earthquake or poor workmanship. There are solutions to avoid this kind of disaster by having flexible steel grid supported buildings with light-weight sandwich panel wall infill.
Several major towns in Kenya such as Nakuru sit right in the middle of the Rift Valley which is a seismically unstable region and earthquakes are not known to give notice before they strike.Measures should be taken to ensure that there are mechanisms in place to give early warning to avoid disasters.
Countries that are prone to earthquakes such as Japan have an average of 40% of new high-rise buildings coming up in Steel structural frames–one of the world’s highest-this is partly dues to steel’s ability to resist the impact of severe earthquakes. Past earthquakes in USA [San Francisco-1906, Long Beach-1933, and Japan [Kanto -1923] during the first part of this century gave engineers confidence in steel as a reliable material for earthquake resistant design.
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During these events, there were typically fewer problems observed in steel structures as compared with concrete and masonry buildings of similar size and scale.
“storeyed car park at the International Casino, Museum Hill roundabout, Westlands”
PEB system of construction is based on the U.S.A Building code. PEB system originated from U.S.A which produces over 1 million PEB Structures per year.
In Kenya, we mainly rely on the British Building code and standards for construction. The British Standard is mainly Reinforced –Concrete based as in most structures such as columns and beams are designed to be concrete-based with twisted steel reinforcement of between 8 mm to 20mm thickness in the inside. This is the type of building construction that you will see every day in Kenya and East Africa in general.
The PEB system replaces the concrete columns and beams with I Section steel beams and columns. With the rapidly increasing price of cement for making the concrete, this design is certainly more cost-effective.
The floor surface can be made of concrete or steel.
International Casino Car Park, Chiromo road roundabout.
A good example of this in Kenya is the Car Park at the International Casino hotel next to the Chiromo road roundabout near Westlands.
“International Casino-Museum Hill , Car Park”
This car park has a concrete surface suspended and supported by steel I beams and columns as shown below.
The car park is very strong-it has supported the weight of cars for very man years and it has not a slight sign of failure.
This means that if used to support a building where the loading is mainly human and furniture e.g. offices and residential buildings, the PEB system will work excellently since if it can support the heavy load of cars, then it can support the light load of humans and furniture.
Earthquake Loading design.
The structural design of the PEB will depend on the Live loads, Earthquake, collateral and wind loads that are specified by the consultant structural engineer in conjunction with the relevant Local Authority Building approval department.
PEB subsystems
The main building structure comprises of 2 subsystems:-[1]a rigid steel frame including columns,rafters,beams and purlins and [2] wall and roof panels.
The roof and walls are made of Sandwich panels. Sandwich panels comprise of an exterior metal skin, a polyurethane interior core and an interior flat skin made of metal. The core thickness is available in 35, 50, 75 and 100mm.The density of the polyurethane is 35-40Kg/m3.
Design Code.
The design code used is in accordance with the Steel Construction Manual published by the American Institute of Steel Construction [AISC].
All welding is done in accordance with the Structural Welding Code-Steel D1.1 of the American Welding Society[AWS].
PEBs are designed using guidelines published by Metal Building Manufacturers Association of U.S.A which is a world-recognized authority on pre-engineered steel buildings and its guidelines are accepted as standard practice in his industry.
The Universally recognized code is the International Building Code published by the International Code Council of U.S.A.
In Kenya, recently, a commission was formed under he Ministry of Hosing to review the country’s Building Code which was published in 1963 and is out-dated. This code is based on the British Building code and hence effectively discourages other cost-effective methods of construction such as PEB in Kenya. Once the new Building Code is published, we hope that it will include other innovative building construction methods found all over the world especially now that we have seen a few buildings collapsing around Kenya.
Available Suppliers
More technical details and cost estimates can be obtained by contacting Mr. Anis Gafoor of Mabani Steel -Tanzania [+255 688 025125] which is an U.A.E company with a branch in Tanzania. www.mabanisteel.com. Mr. Gafoor was recently in Nairobi in the week of January 17th 2010 to January 23rd 2010.
Frank Gichuhi.
Architect.
www.a4architect.com
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