The most commonly used single-column basis billboard type are: reinforced concrete foundations (including the cutting of reinforced concrete or reinforced concrete slab foundation pier foundation), pile cutting base and hand-dug pile foundation of the three basic types of weight. Yarn cutting board basis
On the basis of the yarn cutting board, including the cutting of reinforced concrete and reinforced concrete slab foundation pier foundation, three sides through large areas of excavation (typically 2-3M deepening), then pouring a large volume of reinforced concrete, and the column via embedded parts , by reinforced concrete slab and the weight of the overlying soil to resist the effects of wind from the surface of the billboard. The biggest advantage is the foundation for building a simple, convenient and does not require heavy construction equipment, it is widely used, is a single-column forms the main basis for billboards.
The most commonly used basic dimensions: 6 m × 6 米 × 3 (or 4) M, 8M × 6 米 × 2 (3) m, 12 m × 6 m × 2 m. Based on this the biggest drawback is the wind resistance is small, very affordable, basic expensive and large-scale use.
This laid the foundation for the currently used single-column design billboards biggest question is: due to high cost, the basic design is too small, and its wind power capacity generally can not meet the specifications agreed upon design requirements, low drag, resulting in May encountered strong winds capsized, 2004 Wenzhou capsized in the typhoon large billboards along a single column primary underlying type. The reasons are mainly the following four aspects:
1) on the basis of cost, the owner generally not acceptable bases, in order to meet the design requirements;
2) based on specifications and design calculations involving overthrow extensive knowledge, designers often difficult to fully grasp the wind load calculations, the buoyancy of water calculated wind resistance and bearing capacity calculations, based on calculations and many other aspects of knowledge, lead to the design calculations consideration is not enough to make the basic design is unreasonable.
3) foundation design is not only a regional billboard wind loads, but lower on the basis of the foundation soil characteristics, but also has a close relationship, the general unipole billboard difficult to provide an accurate report of geotechnical engineering investigation and design most basic type of application, based on the complex nature of the soil, and one of the main basic design is unreasonable.
4) The current design basis, in the past the design is often based on past design billboards, single column does not mean you can not overturn meet the design requirements, because any one designed to be long-term test and a certain safety margin.
Cut pile foundation structure mainly by withdrawal, available in a small pile of reinforced concrete cutting board to produce torque to resist wind loads compressive bearing capacity of the pile. The pile substantially symmetrically distributed form, generally not less than the number of the pile 4. Formed on the basis of one of the biggest advantages is the strong wind resistance. The most common type of bored piles, precast piles, the biggest drawback is the large construction equipment, the high cost of entry and exit, combined with the construction site for high pile pullout capacity of the flatness of the small, and thus reducing the project be used. Identified in 2005 by the Shanghai umbrella to expand self-anchored belled pile of new technologies to compensate for this deficiency, on the basis of a single column cutting pile billboard design application has opened up new ideas, has broad application prospects.
Umbrella is a new self-expanding anchor pulled form the basis of, the principle is the same way, you can be like an umbrella distraction, stowed state body buried in the soil surface by drawing equipment anchors, anchor in the soil can As far umbrella distraction, thus providing a huge bulge under pressure.
Self-expansion anchor umbrella structure and tectonics
Umbrella to expand self-anchored pedestal pile due to its unique creativity, novelty and practicality, the research and application of results, "civil engineering", "Journal of Geotechnical Engineering" and other authoritative publications, reports, there is a single column with billboards based applications. Lightweight umbrella base anchor piles of construction machinery, construction, simple operation, and thus its adaptability, appearance fees expanded into the bottom, time fast, high carrying capacity, thereby reducing construction costs, the cost basis under the same conditions, the general weight type base cutting board 40% to 60%. In Shanghai and other coastal areas of wind, soft place, structural height is particularly large billboard affordable. A pile billboard 3-4 million range, the average cost of wind torque is available between 4000kN.m ~ 6000kN.m.
Hand-dug pile foundation
Manual hole digging pile construction, low construction cost, in recent years in the north of the land area less equipment, because some hard to use. The underlying type generally include hand-dug piles, pile top casting has a lid to resist wind loads, this type is generally based on the application of pure lack of calculation basis. Geotechnical engineers work is generally known, pile bending resistance is very low, the use of single pile overturning design principle is unreasonable, basic types of land area in the northern disk reason why you can use two main reasons , one of which is the soil strength is high, and the second is only a small area of the wind. This basic type should have strict conditions of use, in the following cases, you can not use:
1) Do not use the soft soil, mainly because on the one hand can not be soft soil manual hole digging pile construction, the second is the low soil strength, hand-dug pile bending capacity is too small.
2) a large area of the wind can not be used, primarily the mono pile does not provide sufficient air at the moment.
3) At higher billboards can not be used, mainly due to higher wind overturning cards require high pile capacity can not meet the design requirements.