How Skyscrapers Are Anchored
April 9, 2010
When peering up from the ground, skyscrapers seem to go on forever. The view from the upper floors is usually stunning, and it can feel a little strange to see how small everything on the ground appears. While enjoying the views, most people do not consider how these marvels of modern engineering are built. After construction is complete, it appears that a skyscraper simply sits on a normal foundation much like any other building. The reality is that a well-planned anchoring structure deep within the ground prevents these towering buildings from toppling over.
A low center of gravity is the secret to making sure skyscrapers are stable. If a skyscraper was built on a standard foundation, its center of gravity would be somewhere around the middle floor. This would make it very easy to tip over for the slightest reason. For maximum stability, the center of gravity is positioned deep within the ground. To achieve that goal, the building site is excavated until stable soil or bedrock is found. Next, a deep foundation is created that will anchor the structure to the ground.
If the bedrock is close to the surface of the soil,drilling rigs are brought in to create deep footings within the bedrock. The drill rigs are very similar to the equipment used to drill for oil, but are usually mounted on a truck for easy transport. Large drill bits, similar to a power drill, are used to cut through the bedrock. Steel or reinforced concrete pillars are inserted into the footings. Once the construction of the building begins, it is secured to these sturdy columns.
Pile driving equipment is used where the bedrock is much deeper. Vertical beams, or piles, are driven through the soil and into the bedrock. The pile driving process involves dropping a heavy weight on top of the piles repeatedly until they sink as deep as necessary to stabilize the skyscraper. The pile driver is a tall, upright device that holds the pile in a secure, vertical position. The hammer or weight used to drop on top of the pile is positioned near the top. A cushion sits between the hammer and the pile to prevent damage, while leads make sure that the hammer is under control. The entire device is held in place by a large crane.
Regardless of which method is used, the foundation makes the skyscraper even more stable than a normal building. As the foundation and building become one structure, the center of gravity is much lower than where it would be without the deep, underground infrastructure.
Various Uses for Pile Drivers
April 24, 2010
Various Uses for Pile Drivers
Commercial pile drivers are leverage by construction firms to cover a wide variety of applications. The various product lines that are available have resulted in these machines becoming an intricate part of project planning stages for the foundation construction industry. Due to their versatility and nearly unlimited application ability, pile driving equipment now affords architects new opportunities in design.
When thinking about pile driving equipment, loud and dirty machines typically come to mind. These visual images are likely the result of years of hearing “hammering” sounds when passing by large commercial construction sites. The manufacturers of pile driving equipment have been very busy over the last few years enhancing their existing piling stalwarts, and developing new and creative ways to support structures while minimizing the collateral effects that are noticeable during their operations. These machines are large in nature and are often attached to a large crane to be fully effective.
An invention that has benefited both the construction crews and those in the immediate area of a large construction project is the vibratory pile driver/extractor. This machine is heavily utilized in areas where noise tolerances are very low; such as near hospitals or recording studios. The pile driver leverages eccentric weights to create a vibration that inserts the pile into the ground without the need of direct force which results in a “hammering” sound. The extractor element also allows piles that were place for temporary purposes to be removed with the same low volume effort. Project managers also leverage this machinery when they are concerned that the repetitive resonations from a diesel hammer pile driver may negatively affect the foundations of existing structures adjacent to the job site.
Micropiling machines were developed out of the need for crews to work in areas with limited access or limited operating space. These machines come in a variety of sizes, and as their name indicates, they are much smaller than traditional piling machines. Micropile machines have proven to be invaluable in certain situations and their effectiveness has almost no parallel. For instance older buildings may often experience foundational issues, but the ability to access these lower level areas may be prohibited by adjacent buildings or may not be permissible at all due to restricted access paths. Micropile machines can be leveraged to nimbly navigate areas in a building’s basement or parking deck. Some of the machines require only 6 feet of overhead working clearance, yet their abilities can shore up foundations as well as traditional larger methods.
Some of the micropile machines utilize a boring/drilling technique that mitigates vibrations to the existing and/or adjacent structure to prevent unwanted noise and damage. These piling applications have resulted in extraordinary benefits to building owners who may have had to consider abandoning structures in the past.
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