Earthquake Resistant Model Steel Bars ASTM A615 ASTM A706
The Thermo Mechanical Treatment bars are manufactured after the incoming scraps are analyzed for chemical composition and are segregated for unwanted material like cast iron, non-ferrous etc. the billets are tested to maintain the certified composition of carbon, Sulfur & phosphorus much lower than the specification. This results in more longevity, excellent ductility, higher bendability, better corrosion resistance and superior weldability and enhances its intrinsic quality to withstand load under adverse conditions. Bars are manufactured from superior quality billets, in adherence with the international quality standards and norms to ensure quality consistency. All billets are casted from first class from high grade with exceptional chemical composition. The billets go through a test process to maintain the certified composition of carbon, Sulfur and phosphorus in the rebar sections which makes them the best choice for construction. These are essential for being in compliance with tolerance parameters and high dimensional accuracy. Model Steel Mills fitted to utilized cast billets to be hot rolled. The process is controlled by monitoring devices, in an all mechanized technical operational environment. This enables the production of rebar’s with perfect shape, uniform thickness and equal standard length. The rolling mills, operating in constant billet temperature, help reduce the material throughput time and ensures excellent dimensional tolerance and surface finish.
SEISMIC ZONES OF PAKISTAN
The design and building codes divide various localities in to six zones based on the expected severity of the earthquake, that is, Zones 0, 1, 2A, 28, 3 and 4. Zone 0 is that region where the effect of the earthquake is insignificant and Zone 4 is a region close to the faults in the earth's surface. Seismic provisions of the Pakistan Building Code issued in 2007 give zones of various cities of Pakistan.
Pakistan Earthquake Zone Map
Advance High Strength Steel (AHSS) and Ultra High Strength Steel (UHSS) by Model Steel:
Steel Billets – A615
Grade 60 reinforcing bars conforming to A615 are the most widely used type and grade of reinforcing steel. A major revision in 1981 editions of A615 standard is the deletion of grade 40 bar size # 7 through number 11, the standard now covers grade 40 bars only in sizes # 03 through # 06
HISTORY OF Earthquake Resistant Steel Bar A 706
The first version of ASTM was published by ASTM international in 1974.An interesting description of its background and development is included in a 1973 report by ACI committee. The specification was developed in response to the engineering communities’ requirement for reinforcing bars with controlled tensile properties for earthquake-resistant structures and controlled chemical composition for weld ability.
In 1986, the specification was revised into a combined standard containing both in –Ib and Sl units, and the new designation became ASTM 706/A Reinforcing Bars Technical Information with Commentary on Usage and availability.
Prepared by the CRSI technical staff, this report was a response to questions raised by architects, engineers, contractors and state and federal governments’ agencies. The 1991 article titled “Questions and answers on ASTM A 706 reinforcing Bars” was based on this CRSI publication and reported that the demand for weld able Bars in cast-in-place construction had never fully materialized.
Starting in January in 1995, however the California Department of transportation (Caltrans) initiated a policy of requiring A 706 Bars for virtually all of their reinforced concrete structures. Carbon-steel reinforcing Bars conforming to ASTM A 615/A615M would only be permitted for use in slope and channel paving, minor structures, signs and signal foundations (pile and spread footing types), road side rest facilities, certain types of concert barriers, and temporary railing. In November 2005, the Illinois Department of Transportation (IDOT) implemented a policy requiring the exclusive use of A 706 Bars for all reinforced concrete construction.
IDOT’S requirements are even broader than those of Caltrans. For example, IDOT requires A 706 Bars for continuously reinforced concrete pavement.
Other idots, including those in Nevada, Alaska, South Carolina, Tennessee and Virginia are requiring or currently considering requiring the use of A 706 bars.
Bars Comparison Because A 706 bars are produced to only one strength level with a minimum yield strength f^ sub y^ of 60,000 psi (420 mpa). The following comparisons are made to Grade 60 (420 bars) in ASTM 615/A615M does not include comparable requirement.
Tensile properties ASTM A 706/A 706/M like others specification of non-pre stressed steel reinforcement, prescribed a minimum f^ sub Y^ of 60,000 PSI (420 mpa and a minimum tensile strength F^ sub U^ of 80,000 PSI (550 mpa) the specification however the 80,000 PSI
If the laboratory tension tests of reinforcing bars resulted in measured yield strength ranging from slightly above 64000 PSI (440mpa) to the maximum permitted value of 78000 Psi (540 mpa). The corresponding tensile strength would have to range from slightly above 80,000 to 97,500 Psi (550 to 675 mpa)
Earthquake Resistant Steel Bars Grades Produced by Model Steel:
Cost of Construction Comparison:
Determination of Concrete and Steel Volume for Flat plate slab (Using ACI Code)
For estimation purpose of total steel, Negative reinforcements at column strips are provided up to 0.3L from column supports and 25% of total negative steel are assumed continuous for seismic resistance. Negative reinforcements at middle strips are provided up to 0.22L from column supports.
Advantages of Earthquake Resistant Steel Bars ASTM G615 - ASTM G706
Model Steel approved Bars manufactured by Model Steel, possess a higher elongation from other brands thus giving Model Steel constructions an edge over other sites.
Model Steel bars exhibit consistent superior strength and high ductility which ensures superior structure.
They support seismic design due to the its unique combination of strength, ductility and stress ratio.
The unique feature of model Steel TMT bars have high Fatigue Resistance on dynamic loading on account of the high strength of the surface layer.
Controlled Chemical Compositions:
Hot rolled from superior billets, which have uniform chemical compositions like low carbon content and high manganese content.
Use of Model Steel bars results in saving of 20 to 30% compared to CTD and other commercial bars. This is due to the fact that the bars have higher tensile strength and better elongation value then CTD rother commercial bars.
Size reduction from billet to the bars is done gradually in multiple stages (in one single for better and consistent grain structure. Refi¬ned grain structure gives better metallurgical properties to the bars and give a longer life.
Bars have an edge over other bars in terms of superior welding forming stronger bonds. Model bars at have a low carbon equivalent making them convenient to use, and superior to conventional CTD and other commercial bars. Produced only from MS Steel Billets that make the bars free of impurities and balanced in chemical composition.
The higher thermal stability of the bars ensures that they can be used at temperatures touching 600° C without any drop in strength. This quality of the bars enables utility in withstanding damage that may be caused due to ¬fire.
Consistent Quality and Accuracy:
Continuous research and development is undertaken to offer only excellent quality products to customers. Each and every bar undergoes numerous quality checks and has accurate chemical properties to enable stability of the structures even in environmental strains.
Due to the ease of usability of the bars, Model Steel saves a lot of time on the construction site. They also help in saving money and labor hours leading to faster and better constructions. Formability easy to send in any angle or shape.
Better Corrosion Resistance:
- Reinforcement bars of wire rods are used in conjunction with cement concrete to build up a reinforced concrete structure which has a much higher strength, However, corrosion of reinforcement bars arises due to the presence of chloride ions in the concrete and cement which contains calcium hydroxide produces calcium carbonate in the presence of carbon dioxide and moisture in the environment.
- The Model Steel bars are produced with utmost care and with adequate addition of corrosion resistance elements such as Copper, Chromium and phosphorous. All process-controlled parameters are adhered to strictly at Steel Melting shop and at rolling mill.
- The controlled Thermo Mechanical Treatment results in a uniform and thick tempered martensitic rim, completely free from internal stress. The martensitic rim improves the corrosions resistance as well as fatigue strength.
Greater Bond Strength Due to the State of Art Vertical and fish Ribs Technology:
- Model Steel bars are rib-patterned enabling better strength between the bars and the adjacent concrete. It enhances the strength of the structure thus giving it a better and longer life attaches with better ribs.
- The strength of a construction depends on the quality of Model Steel bars used in it and most importantly the ribs on these bars.
- Model Steel bars bear very prominent ribs that give them improved adhesiveness, and provide the construction with higher strength and a longer life.