House Information 03 – House Structural
House structural materials are usually built using either structural steel or reinforced concrete. In some cases, both structures may be used and this is decided by the engineer after accessing the suitability for the design.
Factors for choosing house structural building materials:
1. Cost: Depending on location of the project, the design engineer will decide for reinforced concrete, precast concrete or structural steel. Structural steel costs more; therefore the structural designer will specify the lightest steel members possible while still maintaining a safe house structural design.
2. Strength/Weight Ratio: Construction materials are commonly categorized by their strength to weight ratio, or specific weight. This gives the engineer a gauge of the usefulness of the material in comparison to its weight; the weight can be an indication of the cost of the material. Concrete is typically ten times stronger in compression than in tension, giving it a higher strength to weight ratio in compression.
3. Sustainability: As many building and construction companies (like us, Central Constructer) and suppliers are working towards “GREEN” (Environment-Friendly) building concepts, sustainable construction materials plays a part. Sustainable construction materials are supposedly to be able to reduce negative impacts to the environment from installation till throughout its life span. For instances, reinforced concrete and structural steel are both sustainable construction materials. The components of concrete are naturally occurred materials which are not harmful to the environment. Concrete can also be crushed and used as composite in future concrete applications.
4. Fire-Resistance: Fire hazard is one of the most dangerous factors in a building especially in a country with tropical climate, Singapore. It is crucial to make sure that structural steel is not under fire hazard condition. Reinforced concrete is not a threat in a situation of fire and is able to resist the spreading of fire which makes it a good insulation and improves the sustainability of a building.
5. Corrosion: It is important to choose a structural material carefully as some materials are prone to corrosion from possible surrounding elements such as heat, water or salt. The owners of the houses/occupants of the buildings must also be aware of this as there may be a need for maintenance to prevent corrosion. For instance, house structural steel can post as a threat when it rusts as it may affect the structural integrity of the house/building.
House structural steel differs from concrete in its attributed compressive strength as well as tensile strength. Structural steel is one of the commonly used materials in industrial and commercial building and construction given its high strength and ductile properties. As it is ductile, structural steel can be developed into almost shape which are either welded or bolted together in construction.
Steel is naturally a noncombustible material. However, when heated to high temperatures, the strength and stiffness of the material is significantly reduced. Steel will also corrode when it comes in contact with water, creating a potentially dangerous structure. Therefore, it is important to take preventive measures such as painting or coating it.
Reinforced concrete is a composite material, combination of portland cement, coarse (stone or brick chips) and fine (usually crushed stones), water and steel reinforcing bars (rebar). Concrete possesses high compressive strength properties (making it useful for carrying the weight of a structure), but low in tensile strength and ductility. However, when concrete is reinforced with steel rebar, it gives the house structural a stronger tensile capacity and increases its ductility. Concrete is also generally less costly as compared to structural steel.
Reinforced concrete takes 1-2 days to set after it is poured and takes approximately 28 days to cure. However, construction is able to continue after 7-14 days from setting depending on the nature of the structure. In order to save time, structural concrete members may be pre-casted; reinforced concrete beam, column or slab being fabricated off site.
Concrete is fire resistant but other materials which are used for constructing the building may not be, thus, the designer has to consider the complications for the overall building design to minimise fire hazard(s). Reinforced concrete also possesses excellent corrosion resistance properties. However, preventive measures have to be taken as the concrete may crack at areas carrying tension which allows water to come in contact with the steel reinforcement causing corrosion. Reinforced concrete members must be designed stronger and larger to balance the loss of friction between reinforcing bars and concrete as this friction serves as bond strength and is crucial to the structural integrity of a concrete member.
House Structural Reinforcement Steel Bar
The deformed steel bar for reinforcement of concrete is also known as ribbed steel bar. It is has transverse rib and vertical rib on surface, such as spiral, crescent and herringbone.
Bar Diameter: 6mm-45mm
Steel Bar Length: 6m, 9, 12m
Packing: Bundle Packing
Usage: This kind of steel bar mainly takes drawing stress together with concrete. Because of ribs effects it can take the power from outside. Deformed steel bar is commonly used for all kinds of house structural.
Benefits of Steel Reinforced Concrete Slabs:
- Easy to install
- Reduces cracking
- Controls crack width
- Maintaining interlock of aggregate
- Minimises curling and displacement
- Increase of strength even for the smallest cross-sectional area of steel reinforcement will provide reserve strength of approximately 16 percent
- Lower in cost
As admixtures are not an alternative to steel reinforcement, it cannot be substituted. It is important to make sure that steel reinforcement is spaced, sized and installed properly.
Combining House Structural Steel and Reinforced Concrete
There are many designs which will produce safe, efficient and affordable building. It is the responsibility of the Structural Engineer to work closely with the house/building owner(s), contractors and other stakeholders in order to develop an ideal property taking into considerations the primary requirements of everyone.