A Calculation Method for Bearing Capacity of Vertical Support Columns in the Construction Environment of Upside-Down Method

Abstract

A method for calculating the bearing capacity of a vertical support column under an upside-down construction environment, the vertical support column is a steel pipe concrete column and used as an equivalent pile, the pile body of the vertical support column is used as an actual pile, and the calculation method for the bearing capacity is to obtain The slenderness ratio λ of the steel tube concrete column, the calculation formula of the slenderness ratio λ is: l c is the calculated length of the CFST column, and i is the converted radius of gyration. According to the principle of pile-soil interaction, this method reflects the difference of pile hole filling and foundation soil type through the m value, and derives the calculation length formula of the steel column under the reverse construction condition. Through numerical analysis, simulation test and engineering practice test, this formula is more comprehensive, reasonable and reliable than the calculation formula of increasing geometric length method. The converted radius of gyration i is a standard calculation value, so according to the formula for calculating the length of steel columns under reverse construction conditions, the formula for the slenderness ratio of steel columns under reverse construction conditions is also more reasonable and reliable.

Description

technical field [0001] The invention relates to the technical field of building construction tests, in particular to a calculation method for the bearing capacity of a vertical support column under the construction environment of the reverse method. Background technique [0002] With the leap-forward development of China's urban construction, the construction of large-scale high-rise building foundations and basements, large underground shopping malls, underground parking lots, underground stations, underground transportation hubs, and underground substations are all faced with deep foundation pit construction. problem. Since the engineering geology and hydrogeological conditions of the construction site are often complex and changeable, and the foundation pit construction is often in a super large area and deep construction situation, under the condition of ensuring a series of requirements such as construction schedule, resource conservation and environmental protection, t...

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Problems solved by technology

The section of most vertical supporting columns in the actual reverse engineering is controlled by the slenderness ratio structure requirements. How to calculate the calculated length of the steel column by considering the restraint effect of different backfill materials in the pile hole, and then further calculate the slenderness ratio of the steel column, the national standard does not No specific regulations have been made, and only a local standard in China has adopted the method of increasing the geometric length to determine the calculated length of the vertical support column, but the influence of the difference in backfill materials between the vertical support column and the pile on the calculated length has not been considered

The method of enlarging the geometric length does not take into account the difference of the foundation soil around the pile hole, and it is unsafe for the foundation soil around the pile hole to be mainly composed of poor flow-plastic clay layer, silt and loose filling layer; and the method of enlarging the geometric length It is required that the backfilling material for the gap between piles and columns must be sand and gravel and the grouting is dense, and other backfilling materials or the situation that the grouting is not dense are not considered

[0007] At present, in the existing engineering design in Anhui Province, the calculation length is often calculated according to the total length of the steel column combined with the constraints of the upper and lower ends, and the constraint effect of the surrounding soil is not considered at all. The designed steel column is often too large in section, resulting in The cross-section of the frame column formed by the outsourcing reinforced concrete is too large, which affects the use function and wastes resources

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