Q.
a) Define the term 'load bearing structure' and 'frame structure'. State the differences between these two (2) structures. (15 marks)
b) Concrete is usually used to construct a building structure rather than timber. Explain. (10 marks)
(25 marks, 2019 Q2)
A.
a) Load bearing structure vs frame structure.
Earlier on there was a posting on this with Vivacity in Kuching. See here.
Ref:
Earlier post.
b) Concrete is usually used to construct a building structure rather than timber.
Timber is less used now being expensive and because of conservation of rain forest (environment factors).
Generally, the reasons are below:
ADVANTAGES OF REINFORCED CONCRETE
1) Reinforced concrete has a high compressive strength compared to other building materials.
2) Due to the provided reinforcement, reinforced concrete can also withstand a good amount tensile stress.
3) Fire and weather resistance of reinforced concrete is fair.
4) The reinforced concrete building system is more durable than any other building system.
5) Reinforced concrete,as a fluid material in the beginning, can be economically molded into a nearly limitless range of shapes.
6) The maintenance cost of reinforced concrete is very low.
7) In structure like footings, dams, piers etc. reinforced concrete is the most economical construction material.
8) It acts like a rigid member with minimum deflection.
9) As reinforced concrete can be molded to any shape required, it is widely used in precast structural components. It yields rigid members with minimum apparent deflection.
10) Compared to the use of steelin structure, reinforced concrete requires less skilled labor for the erection of structure.
DISADVANTAGES OF WOOD
Shrinkage and Swelling of Wood:
Wood is a hygroscopic material. This means that it will adsorb surrounding condensable vapors and loses moisture to air below the fiber saturation point.
Deterioration of Wood:
The agents causing the deterioration and destruction of wood fall into two categories: Biotic (biological) and a biotic (non-biological). Biotic agents include decay and mold fungi, bacteria and insects. Abiotic agents include sun, wind, water, certain chemicals and fire.
Biotic Deterioration of Wood:
Woods are organic goods. Like any organic good, wood is a nutritional product for some plants and animals. Humans cannot digest cellulose and the other fiber ingredients of wood, but some fungi and insects can digest it, and use it as a nutritional product. Insects drill holes and drive lines into wood. Even more dangerously, fungi cause the wood to decay partially and even completely. Biological deterioration of wood due to attack by decay fungi, wood boring insects and marine borers during its processing and in service has technical and economical importance.
Insects:
Insects are only second to decay fungi in the economic loss they cause to lumber and wood in service. Insects can be separated into four categories: Termites, powder post beetles, carpenter ants and marine borers.
Carpenter ants
Carpenter ants do not feed on wood. They tunnel through the wood and create shelter. They attract most often wood in ground contact or wood that is intermittently wetted.
Carpenter bees
They cause damage primarily to unpainted wood by creating large tunnel in order to lay eggs.
Marine borers
They attack and can rapidly destroy wood in salt water and brackish water.
Ref:
Earlier post.