18 Foot Thick Foundation

Posted by OfficeManager on Feb 28, 2014 in General Interest | 0 comments

Now That’s a Foundation

The new LA skyscraper will be taller than this Houston landmark

Recently a Korean company began construction on what will become the tallest building west of the Mississippi River. Los Angeles will be the home of this skyscraper that will offer 900 hotel rooms, offices, and convention space. Its 18 foot thick foundation also boasts the longest continuous concrete pour in history as verified by Guinness World Records.

This massive foundation required 2,200 truckloads of concrete for the New Wilshire Grand, as the new building will be named. It was a process that was carefully coordinated and completed in 26 hours because the high strength concrete must be poured within 90 minutes of being mixed. The structural engineers included 7 million pounds of steel rebar that was part of the 18 foot thick concrete foundation – a massive amount. The weight of the concrete is about 84 million pounds. The new skyscraper will be 1100 feet tall and will cost more than $1 billion.

Curing

After the concrete pour is completed the curing process begins, which is the hardening of the concrete. The curing process will require about two weeks and the size of the foundation will necessitate a cooling process.  If a concrete foundation becomes too hot during the cure it could compromise the integrity of the concrete. Therefore the engineers have laid out 100,000 feet of polyethylene hoses with will carry 45 degree water for cooling the massive foundation. They expect the foundation to cure between a range of 120 to 160 degrees.

Why 18 feet Thick?

There are numerous considerations the structural engineers must consider when designing a foundation. All concrete slab foundations rest on soil and soils can move. Clay soils are notorious for expanding when wet and shrinking when dry. The 18 foot thickness will have to support the weight of a 1100 foot tall building, resist soil movement, and resist earthquake movement.

The structural engineers also include a safety factor into the design of the foundation. That is, they calculate the greatest expected or possible stresses on the foundation and then design it to withstand 2 or 3 or 4 times the worst possible stress.

How does this compare to Your Home Foundation in Texas?

There are several significant differences in the approach and design of this commercial foundation and your home foundation in Texas.

1) If the structural engineers make a mistake with this commercial foundation they and their companies will be sued by the building owner. A person who purchases a new home in Texas does not have this option because he/she/they “signed it away” in their purchase contract. A Texas homeowner is stuck with Mandatory Arbitration which has historically found in favor of the business owner between 90% and 97% of the time.

2) The foundation of this new skyscraper is designed to perform for hundreds of years. A new home concrete slab foundation in Texas rarely makes it to 10 years without significant cracks. New home foundations in Texas use a minimum amount of concrete because increasing the thickness would reduce the contractors’ profits.

Should you see any warning signs of foundation damage with your home then give us a call or send an email.

Leaning Tower of Pisa

Posted by OfficeManager on Feb 15, 2014 in General Interest | 0 comments

Tower of Pisa – Foundation Problems?

The Tower of Pisa is one of the most famous buildings in the world because it has been leaning at a gravity-defying angle for over 800 years. The world wonders when it will collapse because in 1989 a similar leaning bell tower in the town of Pavia, Italy collapsed without warning. When this happened the civic officials closed the Tower of Pisa to the public fearing its imminent collapse.

Why does the Tower of Pisa lean?

All man-made structures are supported by the ground (soil) underneath. If the soil (or rock) is strong and durable then the building or structure should have few or no problems during its lifetime. However, if the soil is soft, easily compressed, and/or shrinks/swells then the structures built on top will experience movement.

The Tower of Pisa, and its foundation, is built on soft soil that is primarily sand, mud, and clay. The original builders realized they had a problem by the time the third story was being built. Their solution was to build the arches and columns on one side of the third story taller to compensate for the lean. Later both the fifth and final (eighth) stories were also built with slightly taller arches and columns on one side of the building. Unfortunately, these uneven floors did not solve the problem, which was soft and unstable soil.

The Stabilization

Modern technology and engineering were finally applied to the Tower of Pisa a few decades ago. Basically, the engineers wrapped the lower floors with steel bands while they removed some soil under one side of the building. They also used cables and over 800 tons of lead weights to try and pull the tower closer to a vertical orientation. Over a period of years their efforts were considered successful and the angle of lean was reduced from over 5 degrees to 3.97 degrees. The overall decrease in the lean was 19 inches.

The engineers think that the Tower of Pisa is now stable enough to survive the next 200 years barring any severe earthquakes. And the Tower of Pisa is now open to the public once again.

The Leaning Tower of Pisa is a great example of the importance of stable soil for any building or home. More information about the Leaning Tower of Pisa can be found at its Wikipedia web page.