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I am really happy to join and I would like to ask what are items to be taken into consideration when preparing quotation for construction works and approximate cost of each item on the post of construction work supervisor. Simply I ...
What is the difference between Mild steel, high yield strength deformed bars, cold twisted deformed bars and QST bars?
Steel reinforcing bars are used to enhance the tensile strength of concrete though concrete is weak in tension, and its because both have the same coefficient of thermal expansion. Also, structural steel is used as such to construct steel buildings, which is more easier in erection and is having lesRead more
Steel reinforcing bars are used to enhance the tensile strength of concrete though concrete is weak in tension, and its because both have the same coefficient of thermal expansion. Also, structural steel is used as such to construct steel buildings, which is more easier in erection and is having less strength to weight ratio compared to concrete. Also steel have 100% scrap value.
MILD STEEL REINFORCING BARS
The mild steel bars are smooth and round in shape having diameter ranges from 6mm to 50mm used for small scale construction works.
Mild steel is also known as low carbon steel having 0.1% to 0.25% of carbon. But mild steel is not considered as an alloy steel though it doesn’t contain other elements in it compared to different steel varieties. As carbon content increases, ultimate strength and hardness will increase, but ductility and toughness decreases. Though mild steel contains very little carbon, it is ductile and weldable but having low strength. Also, mild steel is highly prone to corrosion.
HIGH YIELD STRENGTH DEFORMED BARS
High yield strength deformed bars (HYSD) are manufactured under heat treatment followed by either heat rolled or cold twisted for shaping.
HYSD bars moderately resistant to corrosion and the manufacturing process itself cause surface flaws in it. It is heavily weighted, and its transportation cost is high. Residual stress is high and tensile stress is low in HYSD bars that cause deformation.
THERMO-MECHANICALLY TREATED BARS
TMT bars are having much more advantages than hysd bars and nowadays hysd bars are not using.
TMT bars are having a hardened outer core and soft inner core. These bars are passed through water after they get hot rolled, which makes the surface more firm, and the inner core stays warmer itself. Hence core became more ductile, and no deformation process employed like in hysd makes it more strengthened. TMT bars are having soft ferrite-pearlite core with a hard martensitic rim.TMT bars help to reduce steel consumption to 8 to 11% compared to hysd bars. TMT bars are having more corrosion resistive property and is highly flexible than hysd bars. It is highly earthquake resistant with high tensile strength and low residual strength. TMT bars can absorb about 400 to 600°C of heat and highly fire-resistant.
COLD TWISTED DEFORMED BARS
The specifications related to CTD bars are provided in IS: 1786–1985. They are commonly known as TOR steel bars.
TOR is a kind of high adherence steel. TOR bars have surface deformation formed by twisting the steel after lengthening. This imparts high yield strength to steel and furnishes legitimate proper bondage with concrete.TOR is a type of hysd steel, where the steel bars, subsequent to experiencing the required heat treatment process, are cold twisted and distorted.
QUENCHED AND SELF TEMPERED STEEL
These are very much similar to TMT bars where annealing is the process which is not conducted for QST steel manufacturing. These have adequate quality and malleability. QST steel bars are also having the same cross-sectional material of soft ferrite-pearlite core with a hard martensitic rim as that of TMT bars.
See lessWhat is the height of brickwork after which an extra cost for brickwork is provided as per schedule of rates?
Normally, after three meter from the DPC of ground floor level or one floor which should not be more than 4 m height, contactor can charge for extra height if it is not mentioned in the contract about this .
Normally, after three meter from the DPC of ground floor level or one floor which should not be more than 4 m height, contactor can charge for extra height if it is not mentioned in the contract about this .
See lessWhen we calculate quantity of materials for cement mortar, the voids are considered for sand. So, my question is why these voids are considered while calculating quantities of materials in cement mortar?
Have you heard about bulking of sand. The free moisture content in fine aggregates results in bulking of volume. The moisture in the sand forms a thin film around each particle which exerts surface tension and keeps the nearby particles away from it. Thus due to surface tension, every particles keepRead more
Have you heard about bulking of sand. The free moisture content in fine aggregates results in bulking of volume. The moisture in the sand forms a thin film around each particle which exerts surface tension and keeps the nearby particles away from it. Thus due to surface tension, every particles keeps away from each other.
This bulking of sand increases with increase in moisture content upto a certain limit and decreases with further increase in moisture. This can be seen in the figure.
As you know that, we while calculating quantities of materials required for mortar, we consider the dry volume of the sand. But in practical cases, the sand has some free moisture due to which the volume of the sand is more than its dry volume.
Thus, while calculating the quantities of materials for mortar, the voids are considered in the sand and increased wet volume is used in the calculation. When the sand is dried up, the moisture in sand is replaced by the voids.
See lessBasically I want to know if there is a machine or equipment that can be used to test concrete mix during construction or during poring as we are making a high rise building. We want to that’s a concrete next ...
The concrete pressure on formwork can be calculated without measurement. However, I can see that you'd like to be sure about it with experimental verification. The device used for this kind of an experiment is called a dilatometer. It is more common in the geotechnical field but is also used for conRead more
The concrete pressure on formwork can be calculated without measurement. However, I can see that you’d like to be sure about it with experimental verification.
The device used for this kind of an experiment is called a dilatometer. It is more common in the geotechnical field but is also used for concrete pressure calculation.
What are the main differences between masonry and timber buildings? What are their benefits in aspects such as durability, insulation, construction, etc.?
Masonry building : Masonry is the building of structures from individual units, which are often laid in and bound together by mortar. The term masonry can also refer to the units themselves. For masonry construction, the common materials are brick, building stones,etc. Masonry is highly durable formRead more
Masonry is the building of structures from individual units, which are often laid in and bound together by mortar. The term masonry can also refer to the units themselves. For masonry construction, the common materials are brick, building stones,etc. Masonry is highly durable form of construction.
Timber construction is a category of framing styles typically characterized by the use of large solid wood panels for wall, floor and roof constrution. It also includes innovative forms of sculptural buildings and non-building structures formed from solid wood panel or framing system.
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Working on a building project in the Philippines, my contractor has just bent the longitudinal bars in the column because the columns were not in alignment at the base. The building is a two storey building with 25cm rebar frame. ...
Hi. First of all, it's a common problem. This kind of erratic workmanship often happens and there are ways to correct it although none will guarantee perfection as much as properly aligned coloumns. The site supervisor should have not allowed this to happen in the first place but now there's no choiRead more
Hi.
First of all, it’s a common problem. This kind of erratic workmanship often happens and there are ways to correct it although none will guarantee perfection as much as properly aligned coloumns. The site supervisor should have not allowed this to happen in the first place but now there’s no choice left to him.
Firstly, it is bending moment development you must be worried about more than shear. If not taken care of the eccentricity would have given rise to additional bending moments especially at the critical locations adding up to bending stresses. But, don’t panic. All building codes provide a factor of safety against these things in colomn design though I don’t know the exact number in the Phillipino code. If it’s an eccentricity of a few inches or less than 5%, then you need not worry much and trust the contractor. He must be providing crank bars in the longitudinal reinforcement after bending the bars which is the most common technique. You can see it in the image below.
It would be very costly and also time consuming to replace the entire colomn. Especially, when the floor slab has been constructed it’s nearly impossible. If the eccentricity is large enough, you should get an expert opinion from an experienced engineer by taking him to site. There are other methods apart from crank bar too.
Also, the adjustment regarding crank bars also requires additional processes like drilling, putting additional shear reinforcement which I can’t exactly tell. You must talk to the contractor or engineers regarding that.
Lastly, don’t go willy-nilly with my answer only. It’s there so you get an idea of what’s going on. I haven’t seen the site so I have only limited information. Best would be to have an engineer look at it at the site.
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Gopal Mishra
Preparation of quotation for construction works depends on the type of work to be carried out. Whenever a quotation is required by the client for particular work, they provide the detailed specification of works to be carried out. For example, if quote for brickwork is required by the client, the deRead more
Preparation of quotation for construction works depends on the type of work to be carried out. Whenever a quotation is required by the client for particular work, they provide the detailed specification of works to be carried out.
For example, if quote for brickwork is required by the client, the details about type of work such as brickwork in superstructure or substructure, or at particular height, the mix proportion of cement and sand, etc. are provided. All you have to do is to estimate the unit rate for the brickwork for the given specification of the work and provide the rate to the client.
For estimating unit rate of brickwork, the cost of materials such as bricks, cement, sand and water, the labor required for unit work done, cost / rent of tools and equipment, contractor’s profit, contingencies etc. need to be calculated and summed up.
Thus to estimate the cost of unit quantity of particular work, the cost of materials, tools, equipment, labor, transportation, profit, contingencies etc. shall be considered for the calculation.
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