High & Mid Rise
Black Diamond Nationwide (BDN) has been commercial contracting and subcontracting Mid-Rise and High-Rise commercial and mixed-use buildings for over 25 years. We are proud of the unique, innovative and iconic structures that we have been a part of building from California to New York and many notable buildings in between. It takes a certain size and kind of commercial contractor to be able to build these structures effectively and efficiently. A contractor must be able to provide the proper level of services to form and install the basement and all sub-surface infra-structure as well as provide the service and material delivery for the superstructure.
BDN is more than capable of performing all levels of required concrete and steel services for the structural walls and sub-floors that may support a 50+ story building. Also, a qualified contractor like BDN must have the proper manpower, knowledge base and experience level to brace, form and pour and finish each and every floor in a safe manner and on a schedule mandated by the owner and General Contractor. Also, at the same time, our seasoned crews are erecting the structural steel columns that it takes to support the entire structure from the ground floor to the roof. You will not have to worry when you select BDN as your concrete and Steel Erection partner.
BUILDING DATA & MiSC INFORMATION
The size of buildings in the commercial, institutional, and industrial market segment ranges from a few hundred to as much as 45,000 square metres (500,000 square feet). The unit costs are generally higher than those for dwellings (although those of simple industrial buildings may be lower), and this type includes buildings with the highest unit cost, such as hospitals and laboratories. Residential buildings are fairly static in their function, changing only at long intervals.
By contrast, most commercial, institutional, and industrial buildings must respond to fairly rapid changes in their functions, and a degree of flexibility is required in their component systems. In addition, these buildings are built by contractors who utilize heavy mechanized equipment not only for foundations (pile drivers and caisson augers) but also for lifting heavy components (a wide variety of cranes and hoists). Semimanual machines such as cement finishers, terrazzo grinders, and welding generators are also used, but a large percentage of the work is done manually; the human hand and back remain major instruments of the construction industry, well adapted to the nonrepetitive character of the building.
The foundations in these buildings support considerably heavier loads than those of residential buildings. Floor loadings range from 450 to 1,500 kilograms per square meter (100 to 300 pounds per square foot), and the full range of foundation types is used for them. Spread footings are used, as are pile foundations, which are of two types, bearing and friction. A bearing pile is a device to transmit the load of the building through a layer of soil too weak to take the load to a stronger layer of soil some distance underground; the pile acts as a column to carry the load down to the bearing stratum. Solid bearing piles were originally made of timber, which is rare today; more commonly they are made of precast concrete, and sometimes steel H-piles are used. The pile length may be a maximum of about 60 meters (200 feet) but is usually much less. The piles are put in place by driving them into the ground with large mechanical hammers. Hollow steel pipes are also driven, and the interiors are excavated and filled with concrete to form bearing piles; sometimes the pipe is withdrawn as the concrete is poured.
An alternative to the bearing pile is the caisson. A round hole is dug to a bearing stratum with a drilling machine and temporarily supported by a steel cylindrical shell. The hole is then filled with concrete poured around a cage of reinforcing bars; and the steel shell may or may not be left in place, depending on the surrounding soil. The diameter of caissons varies from one to three metres (three to 10 feet). The friction pile of wood or concrete is driven into soft soil where there is no harder stratum for bearing beneath the site. The building load is supported by the surface friction between the pile and the soil.
When the soil is so soft that even friction piles will not support the building load, the final option is the use of a floating foundation, making the building like a boat that obeys Archimedes’ principle—it is buoyed up by the weight of the earth displaced in creating the foundation. Floating foundations consist of flat reinforced concrete slabs or mats or of reinforced concrete tubs with walls turned up around the edge of the mat to create a larger volume. If these buildings do not have basements, in cold climates insulated concrete or masonry frost walls are placed under all exterior nonbearing walls to keep frost from under the floor slabs. Reinforced concrete foundation walls for basements must be carefully braced to resist lateral earth pressures. These walls may be built-in excavations, poured into wooden forms. Sometimes a wall is created by driving interlocking steel sheet piling into the ground, excavating on the basement side, and pouring a concrete wall against it.
Deeper foundation walls can also be built by the slurry wall method, in which a linear series of closely spaced caisson-like holes are successively drilled, filled with concrete, and allowed to harden; the spaces between are excavated by special clamshell buckets and also filled with concrete. During the excavation and drilling operations, the holes are filled with a high-density liquid slurry, which braces the excavation against collapse but still permits the extraction of excavated material. Finally, the basement is dug adjoining the wall, and the wall is braced against earth pressure.
