Since one of the projects that The Conco Companies have been busy providing a range of concrete services for is the first San Francisco building to be pre-certified LEED Platinum, we will explain some of the criteria. Although the Salesforce Tower is not scheduled for completion until sometime in early 2017, it has already been awarded LEED’s CS Platinum.
LEED certifications are awarded by the U.S. Green Building Council (USGBC), and it is an acronym for Leadership in Energy & Environmental Design. The USGBC defines it as a “green building certification program that recognizes best-in-class building strategies and practices.” Under their rating system there are four certification levels for new construction, certified, silver, and gold with platinum as the highest rating. The categories used to judge a building encompass the following: sustainable sites, water efficiency, energy and atmosphere, materials and resources and indoor environmental quality.
The USGBC explains that Core and Shell (CS) is the green building system used to certify the sustainable design and construction of speculative developments and core and shell buildings. It covers the construction of the base building elements, such as the structure, envelope along with the building-level systems that include things like central HVAC, etc.
The Salesforce Tower’s designation for the pre-certification LEED Core & Shell (CS) Platinum springs from the fact that the skyscraper will in some cases exceed the levels of sustainability that have been established under the most up-to-date, stringent building codes. The Tower is an exceptional example of sustainable design, construction and financial feasibility. Highlights of the new skyscraper will include an under-floor air distribution system, which will greatly reduce the HVAC and fan horsepower energy that is required. Another innovative feature is the comprehensive water recycling system in the tower that will help to reduce water consumption 30% below code inside the building.
Conco is a leading supplier of concrete services for the Western United States. We have built our reputation with superior concrete formwork, reinforcing, place and finish, shotcrete and other ancillary services that benefit from our vast experience. With four regional offices, we serve California, Oregon, Washington, Nevada and Colorado.
Extremely large tower cranes are used in the construction of today’s super tall skyscrapers such as the Wilshire Grand Center in Los Angeles and the Salesforce Tower in San Francisco. Tower cranes assist with lifting heavy loads of steel, concrete, generators and other building materials and can be erected to grow taller as a construction project moves upward. The typical maximum unsupported height of a tower crane is 265 ft. and the maximum reach of the jib is 230 ft. However a tower crane can grow right along with the height of the skyscraper’s construction once it is secured to the building. A tower crane’s maximum lifting strength is generally around 19.8 tons.
Although there are different types of tower cranes, for the most part, the components are the same. The mast is the main supporting tower of the crane and is made from steel trussed sections. The engine that allows the crane to rotate is called the slewing unit and sits on top of the mast with the operating cabin and controls just above that. The jib is the operating arm and is the piece that extends horizontally from the mast. The two common types of jibs are the luffing jib that moves up and down the crane and a fixed jib that is equipped with a trolley to move materials horizontally. The hook is used to connect materials to the crane, and large concrete weights behind the mast are used to counteract the weight of the materials being lifted by the hook.
A tower crane must be stabilized at the jobsite before it is ready for use. This involves constructing a concrete pad equipped with large anchor bolts embedded into the concrete to secure the base of the crane. When the tower crane reaches its maximum height, it can be tied to the side of the structure with steel collars and moved upward to accommodate the upward needs of the project.
The Conco Companies’ mission is to be the best supplier of concrete services in the Western United States and to bring expertise and unsurpassed quality to each project. We continue to upgrade and expand facilities to better serve the growing market for public works projects, commercial, parking structures, educational, and other construction development.
As the most commonly used man-made material in the world, concrete mixes are designed to meet the demands of today’s increasingly complex architectural projects. A structure’s concrete mix must suit the purpose of the structure as well as accommodate any special features and characteristics of the project.
In the early planning stages of a project, a concrete mix is designed to meet the criteria for both strength and appearance of the structure. Additional factors taken into account are local building codes and the kind of weather conditions the structure will be exposed to. Furthermore, standard molded and standard-cured cylinder samples are used to measure the concrete’s compressive strength. Other testing methods may include the Hardened Air Void Systems (AVS), Rapid Chloride Permeability (RCP) and Linear Shrinkage limits.
The slump or consistency of fresh concrete is also considered, and generally there is a trade-off in terms of easy mixing and placement and in achieving the ultimate performance of the concrete. The design process will include discussion on the type, cost and amount of the various additives to be used in addition to the portland cement. It will also be decided if the concrete mix will use fine (small) or coarse (larger) aggregates. Since there is such a wide range of performance requirements for concrete and different types of mixes, sophisticated software programs have been developed to help in the process.
According to the Portland Cement Association (PCA), “The key to achieving a strong, durable concrete rests in the careful proportioning and mixing of the ingredients. A mixture that does not have enough paste to fill all the voids between the aggregates will be difficult to place and will produce rough surfaces and porous concrete. A mixture with an excess of cement paste will be easy to place and will produce a smooth surface; however, the resulting concrete is not cost-effective and can more easily crack.” They suggest that a common concrete mix is approximately “10 to 15 percent cement, 60 to 75 percent aggregate and 15 to 20 percent water.” For concrete mixes with entrained air, it can account for another 5 to 8 percent of the mix.
The Conco Companies are one of the leading concrete contractors in the Western U.S. and offer a wide range of quality services and products. Our experience includes providing services for commercial, educational, parking and other construction development as well as public works projects. We proudly serve California, Washington State, Oregon, Colorado and Nevada.
At Conco we have been busy providing concrete services for the Wilshire Grand Center in Los Angeles that is one of the tallest buildings to be constructed in a seismic hot zone. The building’s design has been put through extensive scrutiny and has the benefit of top experts in the field guiding the process to ensure safety.
Across the globe we have other examples of skyscrapers built in earthquake prone areas where experts have carefully designed and implemented the best practices of earthquake engineering. One such building is the Zifeng Tower (formerly the Nanjing Greenland Financial Center) in Nanjing, China that was completed in 2010 and is 1,476 ft. tall. Built in an area known for seismic activity, the skyscraper was designed to withstand earthquake forces that are “between two and six times stronger than those that are normally required by Chinese building codes.”
Another area in China that has had its share of earthquakes is Shanghai. There the Shanghai World Financial Center (SWFC) is one of three super tall skyscrapers that are grouped together in the Lujiazui Financial District in Pudong, Shanghai, China. In addition to the SWFC, the Shanghai Tower is under construction and will replace the SWFC as the tallest building in China. The third skyscraper in the group is the Jin Mao Tower. At 1,614 ft. tall with 101 floors, the SWFC’s “steel trusses are designed to tighten against typhoon strength winds and earthquakes, which allowed the skyscraper to be built using less steel and helped it to earned points for sustainability.”
The Taipei 101 in Xinyi District, Taipei, Taiwan opened in 2004 and stands at 1,671 ft. tall. It was designed to withstand adverse conditions that are known to occur in the area such as typhoon strength winds and earthquakes. The goal was to construct “a structure that could withstand gale winds of 134 mph and the strongest earthquakes likely to occur in a 2,500 year cycle.” By using strong reinforced concrete supports and an extremely solid foundation, the Taipei 101 is believed to be one of the most stable buildings ever constructed.
The Conco Companies are a leading supplier of concrete services for the Western U.S. and got our start in the Bay Area in 1959 by offering clients the best value on a wide range of concrete services and products. Since that time, we have taken a leading role as one of the top concrete contractors in the region. We currently serve California, Washington, Oregon, Nevada and Colorado.
Sources:en.wikipedia.org/wiki/Zifeng_Tower, en.wikipedia.org/wiki/Shanghai_World_Financial_Center, en.wikipedia.org/wiki/Taipei_101
In an article about earthquakes published by Scientific American, they explain that, “Lateral shaking is the force that can cause the most damage to a building during an earthquake.” Since the force usually occurs in a direction parallel to the ground, skyscrapers in earthquake prone areas need to have lateral resistance to prevent quake damage and to protect against other lateral forces such as wind.
The Conco Companies are providing concrete services on the new Wilshire Grand Center in downtown Los Angeles, which when finished, will be the tallest structure built in a “seismic hot zone.” For this reason, the building’s design has been put through some of the most advanced and sophisticated earthquake modeling available.
The skyscraper’s earthquake resistance is further complicated by the fact that architect, David Martin, designed the building with large windows on every floor that required the construction of a concrete core. Since the core is 33 feet wide along its narrowest side for a building that will be 1,100 feet tall, the geotechnical firm, AMEC, was hired to ensure the building’s resistant to damage from a quake. Their job was to create simulated earthquakes to test the tower design and to evaluate “the maximum acceleration — the greatest jolt — that the building could experience.”
After a series of numerous tests and studying damage from past earthquakes in Southern California, the engineers refined the size and depth of the foundation to resist as much as “13.2 million pounds of force pulling up and 25 million pounds of force pushing down on each of the 20 perimeter columns as the tower swayed during an earthquake.” However the test still simulated some buckling so rather than increase the amount of concrete, AMEC’s solution was to add devices called buckling-restrained braces. The devices are long steel bars encased in a steel box filled with grout that allows the bars to compress or stretch when the building moves. The redesign of the Wilshire Grand will now include 170 of these devices.
The Conco Companies are a leading supplier of concrete services for the Western United States. We have built our reputation with superior concrete formwork, reinforcing, place and finish, shotcrete and other ancillary services that benefit from our vast experience. With four regional offices, we serve California, Oregon, Washington, Nevada and Colorado.
graphics.latimes.com/wilshire-grand-earthquakes/ - Sources: Leonard Joseph, Thornton Tomasetti; Tammy Jow, Joseph Varholick, Carey McLeod and Noel Moreno, A.C. Martin; Steve Carroll, Schuff Steel; Ian Aiken, SIE Inc.; Nippon Steel Engineering USA; G.G. Schierle, USC School of Architecture; Dave Eichten, Pankow.
Twenty-five years ago North America was home to 80 percent of the tallest skyscrapers in the world. Now it stands at just 20 percent. Statistics from the Council on Tall Buildings and Urban Habitat (CTBUH) reports that of the 20 tallest skyscrapers constructed in 2014 across the globe, only 4 of them were built in the U.S. The majority are located in Asia or the Middle East.
Antony Wood, executive director of the CTBUH said, "If you predicted the world's tallest building 30 years ago you'd have said three things with certainty: You'd have said number one, it'll be in North America; number two, it will be an office building; and number three, it'll be built out of steel. Now the exact opposite is true. It'll probably be in Asia or the Middle East. It'll be residential or mixed-use, and it'll probably be concrete construction."
Winners of the CTBUH’s 2014 Awards were One Central Park in Sydney Australia for the “Best Tall Building Worldwide.” The “Best Tall Building - Americas” award went to the Edith Green-Wendell Wyatt Federal Building in Portland, USA. The award for the “Best Tall Building in Europe” went to the De Rotterdam in Rotterdam, Netherlands. For the “Best Tall Building - Middle East & Africa” the award went to the Cayan Tower in Dubai, UAE. Visit their website for information on the criteria used and to see other award winners.
The Conco Companies are providing our vast expertise to structural concrete work for the new Wilshire Grand Center, a mixed-use skyscraper currently under construction in Downtown Los Angeles. The Grand will be the tallest building west of the Mississippi once it opens in 2017. The mixed-use building will have 900 luxury hotel rooms, 18 floors of office space totaling 365,000 RSF, and 45,100 square feet of restaurants and retail shops.
When your project demands exceptional services and the best value, Conco can deliver. We partner with clients on every project from the pre-construction stage right through to final completion offering cost-effective solutions to meet the ever-changing demands of the industry. We have four regional offices serving California, Oregon, Washington, Nevada and Colorado.
Another one of The Conco Companies’ projects is the Salesforce Tower currently under construction in downtown San Francisco. Cesar Pelli of Pelli Clarke Pelli Architects, the lead architect on the project noted that, “The tower will be an elegant and exciting line on the skyline of a great city.” For our part, we are providing extensive concrete services for the Tower, which, after the Wilshire Grand Center in L.A., will be the second tallest building west of the Mississippi when it opens in 2017.
The Tower has already been given the U.S. Green Building Council’s highest rating, the LEED Core and Shell Pre-Certified Platinum, and meets or exceeds the levels of sustainability set by the new, more stringent building codes. Features of the 61-story Tower include an innovative air system that brings outside air to every floor to provide occupants with outdoor-fresh air. In addition special glass and sunshades will allow natural light in but control the amount of solar heat.
Pedestrian friendly, the Tower is within walking distance to restaurants and several forms of public transportation. Located just blocks from a BART Station and the freeway, it is adjacent to the new San Francisco Transbay Transit Center that is scheduled to be completed in 2017. The Transit Center will connect 11 transit systems to eight counties throughout the Bay Area as well as connect the planned high speed rail system from San Francisco to Los Angeles.
As part of the Transbay Transit Center Project, the Transbay neighborhood will have more than 6 million square feet of office space; over 4,000 units of new housing; and almost 1,000 new hotel rooms in addition to the Salesforce Tower. Another interesting aspect of the project is a proposed 5.4 acre public rooftop park that sits atop the Transit Center. The park will feature amenities such as an amphitheater, water features, a restaurant, gardens and more.
At The Conco Companies, we are one of the leading concrete contractors in the Western U.S. and offer a wide range of quality services and products. Our experience includes providing services for commercial, educational, parking and other construction development as well as public works projects. We serve California, Washington State, Oregon, Colorado and Nevada.