General Construction of Steel Buildings

Construction of steel buildings varies in size and scale, but can conjure up images of men balancing on "I-beams" hundreds of feet above a city. In truth, steel construction is a very complex process, involving precise calculations in engineering, architecture and economics. Because steel buildings are generally heavily trafficked areas, even a miniscule chance of structural failure is unacceptable. Due to all of these factors, steel buildings are often very expensive and elaborate ventures.

Physics of Steel Buildings

Steel buildings are generally supported by what is known as the steel frame. The steel frame is best described as a series of small steel boxes contained within a much larger steel box. The John Hancock Tower in Boston is a good example of a steel-framed building. Unlike a brick or cinder block structure, a steel frame supports both the vertical and horizontal load structure by distributing the weight of these forces throughout the steel support system. This allows the steel building to maximize floor space and provide a sleeker, narrower design. The drawback to this structure, however, is that as the vertical load increases (as the building gets taller) the steel supports must be closer together.

Dead Loads

The major load that a steel building must support is known as the "dead load". This is the force of the weight of the materials of the building itself. In practically all steel buildings, the dead load is much greater than the live load--the people and furniture contained inside the building. Logically, it follows that the support structure of the lower levels will need to be much stronger than that of the higher levels, as the dead load is greatest at the base of the steel building. The Empire State Building's tiered design is a good illustration of this theory put into practical construction.

External Forces

Steel construction buildings have to contend with all types of external forces, but the primary concern is nature. Several steel buildings have lightning rods affixed to all of the building's highest points. The rods are attached to a wire cable that runs down the building and into the ground, discharging any electric current that may strike the building. Taller steel buildings also have to contend with wind. The tallest steel skyscrapers can sway several feet back and forth. Engineers and architects must take this variable into account when designing such buildings. They mitigate this force by often employing a system of counterweights, made of steel or even water, to redistribute the weight of the skyscraper back toward the center of the building.

Construction of the Steel Frame

The steel frame is constructed by riveting steel "I-beams" end to end to create vertical columns. All of the vertical columns rise up evenly and are connected to each other using parallel girder beams at each floor level. Often this frame is then supported by diagonal beams as well. The entire structure creates what would appear to be a giant box. The vertical columns are anchored into the ground by a spread footing, which is a series of steel platforms and a row of steel beams stacked on top of each other, all resting on a slab of concrete. The spread footing spreads out like a pyramid, getting wider at the base. This structure is so popular because it requires the outer walls to only support their own weight, which allows them to be very thin--thus maximizing a building's floor space. Glass is often used for the outer walls, giving the building's occupants a fantastic view.

Qualities of Steel

Because of its physical properties, steel continues to be the primary building material for even the most modern buildings. The invention of steel was a revolutionary advancement over iron because it was both lighter and stronger. One of steel's hidden assets however, is that it is also fairly flexible. Architects and engineers continue to experiment with all types of ways to construct new steel buildings and are constantly inventing more innovative and more stylish designs. A recent breakthrough engineers have been experimenting with is the use of wind turbines on taller steel buildings to help generate energy for the building as well as cut down on swaying. There is truly no limit to the advancements and breakthroughs that steel buildings still have locked inside their girders.