Edited by Namakhonje
After complete construction, a building is supposed to be able to hold its own dead weight and any other secondary weight of the occupants and safely channel it to the foundation. There are two main modes of construction that hold weight in two different ways, framed structures and load bearing components and this is the difference.
Load bearing components
This is the traditional construction method where a foundation is constructed, then walls raised and a roof to placed. In load bearing components, dead and secondary weight is held by the walls then channeled to the foundation. For this reason, walls are built thick and firm to suit their purpose. The type of foundation used is a strip foundation. For that reason, walls are made up of either bricks or blocks, glued together by mortar to give one solid mass when set. Load bearing components are the most commonly used mode of construction for mostly single storied structures or structures with a few stories. However, for higher multi-storied buildings, this mode of construction becomes less efficient since the walls become very heavy as they are built upwards imposing a substantial amount of dead weight onto the foundation.
Pros of Load Bearing Components
This is the most commonly used construction method, it is simpler than framed structures hence requires a minimum level of skill set. Anyone with a minimum level of education in construction can lay bricks and mortar to raise a wall. No rocket science there.
The simplicity associated with this construction translates into lower construction costs. No complex lifting machines like cranes required since bricks are laid by hand. Cheaper semi-skilled labor required to do the job.
Cons of Load Bearing Components
Since this method relies on load bearing walls, it is associated with a lot of dead-weight which is all imposed onto the foundation. This makes it less efficient. It also means, the load-capacity such a building can withstand is limited.
Affects the ease and speed of construction.
Unlike framed structures, load bearing component structures raise each wall and each level, one at a time. This is not only tedious, it is time consuming placing all those layers of bricks, compared to just raising two columns and installing a glass panel.
Limited construction height.
Constructing a brick wall eighty meters from the ground can put a lot of stress on the lower walls as well as the foundation and increase chances of collapsing. Hence constructing a sky scraper using this mode of construction isn’t feasible or even reasonable.
Takes up alot of material.
Load bearing components rely on mass of the wall for its strength, the bigger the wall, the stronger it is. This means they take up a lot of material in terms of bricks or blocks and cement. This raises their cost of construction.
Less floor area.
These structures have a lesser floor area compared to framed structures because they rely on big load bearing walls instead of single columns. This may mean lower revenue if rented out.
There is no flexibility.
Unlike framed structures, these structures are not so flexible in design. A brick wall remains a brick wall. Cladding panels cannot be switched like the case of framed structure.
Like the name suggests, these are structures that consist a frame that takes up all the dead and secondary weight of the building. The frame is then dressed using non-load bearing walls called curtain walls in a process known as cladding. Cladding material like glass, wood, vinyl, aluminum is used to enclose the interior for privacy, protection from weather elements, sound insulation, thermal insulation among others. The frame is made of an interconnection of columns as vertical members, beams and slabs as horizontal members and all these are interwoven into a single strong frame which is grounded to the foundation. Components of the frame can be made of reinforced concrete, steel or wood.
The foundation type mostly used is the pad foundation. The frame is the skeleton of the building and it gives the building rigidity. Cladding is the skin that dresses up the building giving it a nice exterior outlook. One of the draw backs of load bearing components is their inefficiency when constructing multi-storied buildings and this is where framed structures come in handy. Since most of the load is taken up by a relatively light frame, the number of stories a building can be is limitless due to the reduced dead weight. The only dead weight is contributed by the frame and the cladding which is virtually weightless. That is why, most high rise buildings and sky scrapers make use of this technology. Industrial and factory structures like warehouses are also constructed by this method. Framed structures are divided into two main categories, Rigid framed structure and Braced framed structure.
When considering which mode of construction you prefer, you should put into consideration the pros and cons associated with either one.
Pros of Framed Structures
The absence of heavy load-bearing walls means a substantial reduction in dead-weight of the structure. This means less load will be transferred to the foundation though the structure still remains as stable or even more stable than its counterpart. It also means a frame structure can even carry more load than load bearing components.
Ease and speed of construction.
Framed structures consist a series of slabs, columns and beams interconnected. For this reason, its assembly is relatively easy and fast compared to load bearing components. It is made even easier if these elements are pre-fabricated prior to their assembly in which case the only task that is required is to put those elements in place and bolt them. The joints are covered with mortar to protect them from weather elements.
Since framed structures use less material compared to load bearing components, they are relatively cheaper to construct. Whereas for load bearing components, you would require trips and trips of bricks and a lot of bags of cement to raise walls, for framed structures a few columns and beams with glass cladding can do.
Strength and durability
When it comes to earthquakes and any other natural hazards, framed structures can hold their own better than load bearing components because of two reasons. First, the frame is rigid hence can firmly hold the rest of the building components like cladding which is even usually light. Secondly, with advancements in technology, engineers now make framed structures that are flexible and adapt to various weather conditions are hazardous conditions like earthquakes. This technology allows the frame to absorb vibrations and shock that may compromise the integrity of a structure. It does so in a number of ways including using unique shapes to tame strong wind, and using dampers to absorb vibrations. Very tall skyscrapers are usually curved around the edges to reduce drag and allow free wind flow to minimize the effect of strong wind. Dampers are very heavy objects in form of either a water tank or solid mass. Such objects are allowed to sway slightly at the onset of extreme vibrations like earthquakes and then bring the building to rest. That is why, despite the height of sky scrapers in places like japan which are prone to serious eight-point magnitude earthquakes, sky scrapers may very well still be the safest places you can be in case of an earthquake.
As earlier mentioned, when it comes to very tall buildings, framed structures are the most ideal mode of construction. This is because of reduced dead weight of framed structures in comparison to load bearing components. Using this mode of construction, the height to which you can construct a building is almost limitless. The Burj Khalifa, in Dubai, the tallest building in the world stands at a jaw dropping eight-hundred-thirty meters, more than ten times the height of the Mapeera building, one of the tallest buildings in Kampala.
Framed structures have larger floor areas. This is because, instead of large walls, they make use of columns that take up far less space. In case of renting out such a building, a framed structure would command higher rental fees as compared to its counterpart.
A framed structure is flexible in design. You can easily make alterations within the limits of the frame. You can change the cladding material from glass to perhaps wood or any other material of your choice as long as it fits into the frame.
Cons of Framed Structures
The design of framed structures calls for a certain level of complexity. It involves many connections to various parts to create a single rigid frame. It requires high level knowledge and expertise to design and oversee the construction of such buildings. Since the all the load is taken up by the frame, designs should be made and executed as accurately as possible, a faulty connection could be catastrophic.
Despite the fact that this mode of construction uses less material, there are overhead expenses necessary like use of cranes to lift the construction elements up to greater heights. Other expenses are also incurred in putting in place form work for the case you’re using reinforced concrete for your frame.
These are the features, pros and cons of the two construction methods. When choosing either one, you should consider various factors like, budgeted cost of construction, function of proposed structure, government regulations, available materials, owner’s preference among other factors. However, considering the low supply and high demand of land and ever increasing population, storied buildings are becoming increasingly popular since they give more accommodation for less land space, hence, framed structures are becoming increasing popular compared to load bearing components.
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