Earthquakes are one of the most destructive forces on earth and can destroy buildings with their seismic waves, cost human lives and cause enormous losses. Even when the earthquake is of a lesser magnitude, it can lead to massive destruction. That is why it is important to build an earthquake-resistant structure.
Kenya has a history of its own in relation to natural disasters. People in different parts of the country have lost their homes to natural disasters such as floods and mudslides. Rebuilding these homes is very expensive and traumatic.
Kenya and Earthquakes
Based on the information currently available on the Think hazard report about Kenya, this country is rated as a medium-risk earthquake-prone area. “This means that there is a 10% chance of a potentially damaging earthquake occurring in Kenya over the next 50 years,” the report states.
The most significant one in history being the 6.9 magnitude earthquake that occurred in Subukia Valley on January 6th, 1928, based on the research published on Research Gate, no other major earthquakes have occurred, only minor tremors.
Do you need an earthquake-resistant structure?
An earthquake of any magnitude can affect small remote areas and cities like Nairobi. Therefore, to mitigate the consequences, you need a structurally sound building. This means the building should be able to reduce the earthquake’s impact and effectively cope with seismic forces.
According to Kenya Earthquake Code (1973), “Builders do not require seismic design for many structures 4 – 6 storeys or less. The design all depends on the zone and the usage of the structure.” The report doesn’t give specific requirements for people planning to build residential or three-story apartments. There are still rules to follow when building a structure whether it’s a skyscraper or a residential home. The rules in the building code help people build strong and sturdy buildings.
Other benefits associated with building an earthquake-resistant structure including:
- Loss of cash flow: A disruption in business can mean a loss of revenue, putting a heavy strain
on a business owner’s ability to pay ongoing expenses.
- Loss of equipment/inventory: Damage to equipment and inventory can stifle or halt production. This adds another burden to the initial costs of replacing what was lost.
- Loss of workforce: Operational delays caused by earthquake damage may result in employees
resigning to take jobs elsewhere. This may lead to lowered production once operations resume.
- Liability: Business owners may be held liable for losses incurred by employees or customers
caused by the failure of buildings vulnerable to earthquakes.
- Environmental concerns: Many businesses manage toxic substances that may pose hazards
if exposed to the environment during an earthquake. Businesses are liable for clean-up
costs associated with spills.
- Loss of market share to competitors: If business operations are slowed down or halted after an earthquake, competitors will likely absorb the difference — temporarily or permanently, depending on the situation. Conversely, businesses that come out of a major earthquake unscathed may be better positioned to fill voids left by less fortunate competitors.
Keys to designing an Earthquake-resistant building
Kenya’s building code has guidelines to follow when you want to build a structure. This code classifies buildings according to usage and design structure and gives several considerations for building a structurally sound building.
The Basic consideration to keep in mind when designing an earthquake-proof building include:
The design and performance of foundations depend on these factors:
- The nature of the ground at the site
- The load placed on the foundation
These two are the key factors in designing a sturdy structural foundation for a stable house or structure.
According to KABCEC, “Foundations should be built on the hardest material available and within a reasonable depth”.
Load bearing and distribution
The anticipated load of a building is influenced by the:
- Function and occupancy of the building
- The size and shape
- Climate or site conditions
Ultimately, the type and level of design loads affect important decisions such as structural details, material selection, and building installation. Understanding the importance of firmly connecting the walls, floors, and roof to the reinforced column and ring beams is very important. Distributing the design load correctly is crucial
The design of the structure
The principal components of the building structure are the walls, beams, columns, foundation, and stairs. These elements support and protect the building structure.
Because of advances in technologies in the construction industry and other related industries like engineering, construction has come a long way. There are various construction techniques and methods that can greatly minimize the risk of earthquakes in buildings to a greater extent.
Engineers and architects have various methods for strengthening a building’s structure to withstand potential earthquakes. Many of those reinforcements focus on the foundation, column, and beams. Eng. Arif Ali PEng MIEK, states, “It is a well-known fact that concrete elements tend to have high rigidity and will perform better in an earthquake scenario. When concrete elements are monolithically cast, they can provide a continuous and undisrupted load path for gravity loads and at the same time maintain its structural integrity during an earthquake, albeit with an acceptable level of damage.” The aim of reinforcements is the redirect seismic forces away from the building.
Beam and Block Flooring.
Beam and Block flooring is a new entrant to the Kenyan market. Apart from all its other benefits, used in a well-designed building using elements such as reinforced concrete columns and ring beams, and a strong foundation, your building can be earthquake resistant.
A good example of reinforced structure and beam and block performance against the earth is the Bam earthquake in 2003. A large earthquake with a magnitude of Mw=6.6 (USGS) struck the city of Bam, located approximately 1000km southeast of Tehran, at 05:26:56 local time (01:56:56 GMT) on Friday 26th December 2003. The earthquake destroyed most of Bam city and the nearby villages and the official death toll exceeded 26,000 with more than 30,000 injuries and 75,000 left homeless.
The seismic performance of concrete beam and block systems was generally more favourable than the other slabs. Mahmoud R. Maheri, a professor of civil engineering at Shiraz University, studied the impact of the quake. He stated, “In recent years, the concrete beam-hollow block roofing system has become popular in flooring framed structures.
As a result, several buildings in the city of Bam, Iran were floored with this type of construction. The seismic performance of concrete beam/ hollow block roofing systems was generally more favourable than the jack-arch slabs. The materials and construction details of the floor provide homogeneous slabs capable of diaphragm action.
Although the concrete beam/hollow block floor is inherently robust and has a favourable seismic response, poor workmanship was identified as the main reason behind the failure and collapse of several floors of this type during the Bam earthquake.”
Building a house takes a lot of planning, knowledge, skills, and good workmanship. At Ecoconcrete, we can design and supply your beam and block floor observing the legal requirements of building an earthquake-proof home and the family lifestyle and comfort. Contact us now and let us help with the floor design of your dream home in Kenya.