Structural Steel and AESS - Blog 10 - Yukta Yogeesh

 

01/September/2020


Today’s session is clearly a continuation of my previous blog. Sections were already a part of the evolution and today's session made it clear that certain things, even though evoloving, does not lose its originality and they do have their own importance because of which it becomes irreplacable. So, today was about learning the different types of sections available in standard structural steel and about a more complex steel strata called AESS. The details are as follows :-

 

Market forms of steel

Angle sections - Equal and unequal angles of sizes (200x200x25) mm - 736N/m length, 30x20x3mm -11N per m length. Usage - Filler joist flooring, structural steel roof trusses, bridges, etc

Channel sections - 2 flanges and 1 web section, Types - ISJC (Jr.), ISLC (Light), ISMC (Medium) and of sizes 100x45 per metre length - 58N

Corrugated - Formed by passing steel sheets through grooves and its market form is GI sheets - used as roof covering material

Expanded metal - Prepared from sheets of mild steel, machine cut and drawn out. It’s used in Partitions, reinforcement in foundations metal lighting materials.

Flat bars come in sizes 10mm - 400mm thick, and 3mm - 40mm thickness and is used in steel grill work for windows, gate sections, etc

I section - Rolled steel joists/beams - 2 flanges and 1 web - if rotated, becomes H sections. Comes in sizes 75x50 - 61N, max 600x210mm - 995N and of types ISJB, ISLB, ISMB, ISWB ISHB

Plates - Comes in sizes 5mm thick - 392N/sqm, 50mm thick - 3925 N/sqm and its used to connect steel beams for length extension, as tension members for steel trusses.

Ribbed Torsteel bars - 6mm dia at 2.22N/m and is used - bridges, harbour, roads, foundation, piles foundation, pre-cast concrete works. This is produced by cold twisting of hot rolled bars.

Round bars - round in shape, comes in different diameters with varying strengths based on the type of section.

Square bars - 5mm-250mm, 5mm width - 2N/m and 25mm width - 49N/m

T sections - Flange, Flange thickness, Web, Web thickness - 20x20x3 at 9N/m 


Market forms of steel - other than Standard sections:

1.      Acute - less than 90 deg. 

2.      Obtuse - more than 90 deg. 

3.      Rail sections - used for railway tracks 

4.      Trough sections - similar to a box section 

5.      Z sections - An inclined I section 

Hollow Structural Sections

They can be used in construction of sheds, shelters, parking, roof panels, shelter panels, support systems, roof casing frames, frames for tile roofs, fences and doors, storage systems, agricultural applications, house doors and windows. It can be composed with other steel sections as well. They come in square, rectangular and circular shapes. Black sections are hot rolled sections. Galvanised sections are coated sections.  Advantages of Structural steel - Avoids failure, carbon steel composition, carries high load. 

AESS – Architecturally Exposed Structural Steel

·        Examples - International Airport, Portugal - skylight and Pedestrian bridge in Canada designed by SOM

·        Criteria to check while installing AESS- services, client views, electrical fixtures, etc

·        Major features of AESS - Creating joints between the members - Extensive details of fabrication, design - balance, form, symmetry, economy. 

·        Opportunities using AESS - Design strategy, aesthetic, new language, collaboration between architect-engineer-fabricator, visual points and distances. 

·        Challenges - craftsmanship, design, cost, connection joints, detailing required.

·        Differences between AESS and Structural Steel - The differences are based on - Aesthetics and functionality, corrosion, concealed and exposed, joints and details, scale, cost, design requirements. 


 Although steel comes in different sizes and different compositions, each steel type has its own purpose to resolve. Even though AESS is more stable and aesthetic, Structural steel is used in large quantity when compared to AESS because of the cost, based on the scale of the project. So, what is it that matters the most? Stability and strength or design and aesthetics or the cost? Then, where exactly does sustainability play its role? 

 

Yukta Yogeesh

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