The selection of structural steel for a building's framing system brings numerous benefits to a
project. All other materials are measured against the standard of structural steel and structural
steel is still the material of choice.
These benefits include:
Other materials may be able to start field work sooner, but the rapid design, fabrication and erection cycle with structural steel will allow the framing system to finish sooner and be available earlier to other trades. Structural steel enhances construction productivity because of its shop fabrication while maintaining tight construction tolerances. Field placed material will always lag behind the productivity curve. Productivity enhancements for construction will occur not in labor based field activities, but in shop based technology enhancements. Technology exists today in the form of 3-D interoperability and Building Information Modeling to allow the close cooperation between designers and steel specialty contractors in the design, fabrication and erection of building structures. This technology allows designs to save both time and dollars in the construction process by integrating fabricating and erection efficiencies in the design and passing design models between analysis, detailing and fabricating operations. This is full integration is process unique to structural steel generating significant cost savings. Rapid erection in all seasons with close tolerances being maintained for integration with other building systems and minimal construction site waste is achievable only with structural steel. Other materials may be able to start field work sooner, but the rapid design, fabrication and erection cycle with structural steel will allow the framing system to finish sooner and be available earlier to other trades.
Today, when competing framing systems are evaluated for projects using comparable, current cost data, structural steel remains the cost leader for the majority of construction projects. Comparative studies indicate that a structural steel framing system including decking and fire protection will typically cost 5% to 7% less than a concrete framing system on a national basis.And that is not surprising; structural steel has remained the cost leader for construction materials over the past 30+ years. According to the Bureau of Labor Statistics the price for fabricated structural steel prices for commercial buildings increased 62% from their base date of 1980. Today that same ton of structural steel requires substantially less than a single manhour. While not as dramatic, similar productivity enhancements have impacted the cost of detailing and fabrication. The end result is that the structural steel component of the construction industry is one of the few segments where significant productivity increases have occurred.
Architects praise the natural beauty of steel and are excited about exposing it in the design of their structures to emphasize grace, slenderness, strength and transparency of frame. Structural steel allows the project architect a greater degree of expression and creativity in their design than any other construction material as they address both the functional demands of the building and unique identity of their client.
From the simplest, functional structure to the complex, signature design structural steel can be readily used to accomplish the design intent of the architect and structural engineer. No other framing material comes close to structural steel in the ability to encourage freedom of expression and design creativity. The range of submissions highlight the innovation and creative of project architects and structural engineers in their use of structural steel.
All other materials talk about high strength, but their strength is still less than that of structural steel even when enhanced by steel reinforcing. In fact, the increase in the standard strength of steel used in buildings today compared to 10 years ago is greater than the total strength of competing “high strength” materials. Structural steel is typically 50 ksi material indicating that the steel has a yield stress of 50,000 pounds per square inch in both compression and tension. By comparison, a normal concrete mix has a yield stress of 3 to 5 ksi in compression only and “high strength” concrete may have a compressive yield stress of 12 to 15 ksi. Not only is structural steel a stronger material, it also has a much higher strength to weight ratio than other materials. This results in the building being lighter and lighter buildings require less extensive and costly foundations.
Structural steel remains the most desirable material for the structural engineer to design in. Tools for structural steel design abound and are a quantum step ahead of tools for other systems. Full integration between analysis, design, detailing and fabricating software is in use today. The structural steel industry is the poster child for collaborative Building Information Modeling. This innovative blending of technology is not just for simple boxes, but also for complex structures requiring innovative design approaches and the cost saving techniques of 3-D modeling with full steel specialty contractor involvement in the design process.
Sustainability is structural steel's middle name. Structural steel is the most recycled material on our planet – today's structural steel is made of 88% recycled product, is fully recyclable in the future and can be reused without further processing. The carbon footprint of structural steel has been reduced by 47% since 1990. Energy used in the production of structural steel has been reduced by 9% in the past 10 years and over 30% in the past three decades. The production of structural steel conserves our most valuable resource: water. The only water used in the production of structural steel is make-up water added to a closed loop recycling process. Structural steel mills discharge no water to the environment. Water is not used in the fabrication process and no water is used or discharged at the project site. The recycling rate of structural steel and automobiles at the end of their life is greater than 100%. Rather than utilizing land for quarrying operations to provide aggregates or as landfills for construction material waste, structural steel is emptying salvage yards allowing that land to be used for other purposes.
Structural steel buildings can be modified in the future for new applications, loading conditions, vertical expansions and changes in owner desires in ways that other framing systems can never accomplish. Building owners and managers are always faced with changing requirements and a composite steel frame can be easily modified to satisfy existing or new tenant changing requirements such as increased floor loads for storage and equipment, new openings for mechanical equipment and vertical shafts for floor-to-floor staircases. Existing steel columns and beams can be strengthened through the attachment of steel plate to the flanges or web of sections allowing for greater loads. New stairways can be added to existing steel framed buildings by removing a portion of the floor decking, bracing a single bay and adding the desired stair structure. These types of changes can be accomplished with little disruption while the building is still occupied. It is not unusual for a structural steel building to have additional floors added even years after the building was originally completed. During 2008 and 2009 the existing 32 story Blue Cross Blue Shield building in Chicago is being enlarged by adding 24 stories to the structure. The construction is proceeding while the existing building is still occupied.
Structural steel buildings optimize building space efficiency through the use of slender columns maximizing useable floor space, longer spans for open, column-free spaces and the integration of HVAC systems into structural spaces allowing reduction of floor-to-floor heights. The typical steel column occupies 75% less floor space than an equivalent concrete column. At the same time structural steel allows longer spans that eliminate intermediate columns creating open floor areas ideal for today's office layouts. Parking structures benefit from smaller structural steel columns and longer spans as well. Structural steel framing systems for parking structures will typically span 60 feet allowing for a drive lane and 2 parking bays without any intervening columns. The use of the smaller footprint steel columns at the front of the parking bays create less intrusion into the parking space thanlarger concrete columns. In fact, because of the smaller footprint of the columns, steel framed garages can provide one level of service above the standard level of service for parking garages of similar dimensions framed in concrete.