CN109684764B - Method for calculating reasonable depth of pile foundation embedded in steel pipe column - Google Patents

Method for calculating reasonable depth of pile foundation embedded in steel pipe column Download PDF

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CN109684764B
CN109684764B CN201910001573.9A CN201910001573A CN109684764B CN 109684764 B CN109684764 B CN 109684764B CN 201910001573 A CN201910001573 A CN 201910001573A CN 109684764 B CN109684764 B CN 109684764B
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column
steel pipe
pipe column
bending
rigidity
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陈翰
李明磊
柏林
张先锋
张金伟
贺维国
任玉瑾
张茜珍
邱术来
石斐
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China Railway Liuyuan Group Co Ltd
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Abstract

The invention discloses a method for calculating reasonable depth of a steel pipe column embedded pile foundation, which comprises the following steps: (1) Applying bending moment M and vertical axial force to the top longitudinal beam of the steel pipe column, and obtaining a column foot joint corner theta of the steel pipe column corresponding to different bending moments through numerical simulation; (2) Fitting the applied bending moment M and the column base joint rotation angle theta data to establish a bending moment-column base joint rotation angle relation curve; (3) Establishing a fitting formula according to a bending moment-column base joint corner relation curve to obtain the bending rigidity k of the column base joint θ The method comprises the steps of carrying out a first treatment on the surface of the (4) Bending rigidity k of column foot joint of steel pipe column θ Obtaining the bending rigidity ratio lambda of the parameter column base joint, namely the bending rigidity k of the column base joint θ And the rigidity of the steel pipe column. The method can achieve the beneficial effects of determining the reasonable depth of the embedded pile foundation of the steel pipe column, reducing the space of the steel pipe column which invades the outside of the station outline to the minimum, ensuring the safety of the steel pipe column of the underground excavation station in the construction stage and reserving crossing conditions for the construction of subsequent underground engineering.

Description

Method for calculating reasonable depth of pile foundation embedded in steel pipe column
Technical Field
The invention belongs to the technical field of building structures, and particularly relates to a method for calculating reasonable depth of a steel pipe column embedded pile foundation.
Background
The urban central area is built with a large amount of infrastructure such as subways, municipal bridges, traffic thoroughfares, municipal pipelines, high-rise buildings and the like in advance, and the newly built subway station has no obvious and cover-excavation construction conditions basically. Meanwhile, in order to reduce the influence of subway construction on traffic, cities such as Beijing and the like are mostly constructed by adopting a hole pile method. For a hole pile method station, a steel pipe column is used as a permanent structure, a middle pile is used as a temporary structure, and in order to ensure that the steel pipe column has enough strength, rigidity and stability, the steel pipe column is embedded into a pile foundation to a certain depth so as to meet the stress requirement. The depth of the steel pipe column embedded into the pile foundation is determined, so that the requirements of various specifications and standards on the embedded depth are generally 2-2.5 times of the diameter of the steel pipe column, but no clear value basis exists.
If the embedding depth is too small, the stress requirement of the steel pipe column cannot be met, and especially the stability of the steel pipe column in the construction stage is difficult to ensure; if the embedding depth is too large, unnecessary waste is caused, and adverse effects are brought to the subsequent underpass of the subway station and the section.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention provides the method for calculating the reasonable depth of the embedded pile foundation of the steel pipe column, which can achieve the beneficial effects of determining the reasonable depth of the embedded pile foundation of the steel pipe column, minimizing the space of the steel pipe column which invades the outside of the station outline, ensuring the safety of the steel pipe column of the underground excavation station in the construction stage and reserving crossing conditions for the construction of subsequent underground engineering.
In order to solve the technical problems, the invention adopts the following technical scheme: the method for calculating the reasonable depth of the embedded pile foundation of the steel pipe column comprises the following steps:
(1) Applying bending moment M and vertical axial force F to the top longitudinal beam of the steel pipe column, and obtaining a corresponding column foot joint corner theta of the steel pipe column under different bending moments through numerical simulation;
(2) Fitting the applied bending moment M and the column base joint rotation angle theta data to establish a bending moment-column base joint rotation angle relation curve;
(3) A fitting formula is established according to a bending moment-column base joint rotation angle relation curve,as shown in FIG. 3, the column shoe joint bending stiffness k is obtained θ ；
(4) Bending rigidity k of column foot joint of steel pipe column θ Obtaining the bending rigidity ratio lambda of the parameter column base joint, namely the bending rigidity k of the column base joint θ The ratio of the rigidity of the steel pipe column to the rigidity of the steel pipe column;
if the bending rigidity ratio lambda of the column base joint is larger than 1, the column base bending rigidity is larger than the column shaft bending rigidity, the column base is not a stress weak point in a structural system, and the embedding depth of the steel pipe column meets the stress requirement;
if the bending rigidity ratio lambda of the column base joint is smaller than 1, the column base bending rigidity is smaller than the column shaft bending rigidity, the column base is still a stress weak point in a structural system, the steel pipe column embedding depth does not meet the stress requirement, and the embedding depth is further increased.
Preferably, in the step (1), finite element software (finite element model diagram is shown in fig. 2) is used to perform numerical simulation on the steel pipe column.
Preferably, in the step (3), a fitting formula established by a bending moment-column shoe joint rotation angle relation curve is as follows:
M＝a+k·θ
wherein: m-bending moment, unit kN.m;
theta-column foot joint rotation angle, unit 10 -3 rad；
a-intercept, which is a fitting coefficient, in kN.m;
k-curve slope, which is the fitting coefficient in units of MN.m/rad;
and the bending stiffness k of the joint is obtained by the following formula θ ：
Figure BDA0001933902900000021
I.e. the joint bending stiffness is equal to the slope of the fitted curve.
Preferably, the flexural rigidity ratio λ of the foot joint in step (4) is calculated as follows:
Figure BDA0001933902900000022
wherein: lambda-column base joint bending rigidity ratio, dimensionless;
k θ -column shoe joint flexural rigidity in mn·m/rad;
d, the diameter of the steel pipe column is equal to the unit m;
EI-rigidity of steel pipe column shaft in MN.m 2 Is a fixed value.
Compared with the prior art, the invention has the following beneficial effects: the invention can determine the reasonable depth of the embedded pile foundation of the steel pipe column, reduce the space of the steel pipe column which invades the outside of the station outline to the minimum, ensure the safety of the steel pipe column of the underground excavation station in the construction stage, reserve crossing conditions for the construction of the subsequent underground engineering, and have better social and economic benefits. The stress requirements of the steel pipe column under different conditions and different boundary conditions are met, and the steel pipe column has stronger pertinence.
Drawings
FIG. 1 is a mechanical model of a steel pipe column and a foundation structure in the present invention;
FIG. 2 is a diagram of a steel pipe column and a basic finite element model according to the present invention;
FIG. 3 is a graph of column shoe joint flexural rigidity in accordance with the present invention;
FIG. 4 is a plot of flexural rigidity versus depth of embedment for a steel pipe column in accordance with the present invention;
FIG. 5 is a plot of bending stiffness ratio versus depth of embedment for a steel column shoe joint in accordance with the present invention.
Detailed Description
The present invention will be described in detail below with reference to the drawings and the specific embodiments, so that those skilled in the art can better understand the technical solutions of the present invention.
The embodiment of the invention discloses a method for calculating reasonable depth of a steel pipe column embedded pile foundation, which comprises the following steps:
(1) Applying bending moment M and vertical axial force F to a top longitudinal beam of the steel pipe column, and carrying out numerical simulation on the steel pipe column by adopting finite element software (a finite element model diagram is shown as figure 2) to obtain a column foot joint corner theta corresponding to the steel pipe column under different bending moments;
(2) Fitting the applied bending moment M and the column base joint rotation angle theta data to establish a bending moment-column base joint rotation angle relation curve;
(3) A fitting formula is established according to a bending moment-column base joint rotation angle relation curve,
M＝a+k·θ
wherein: m-bending moment, unit kN.m;
theta-column foot joint rotation angle, unit 10 -3 rad；
a-intercept, which is a fitting coefficient, in kN.m;
k-curve slope, which is the fitting coefficient in units of MN.m/rad;
and the bending stiffness k of the joint is obtained by the following formula θ ：
Figure BDA0001933902900000041
I.e. the joint bending stiffness is equal to the slope of the fitted curve. As shown in fig. 3;
(4) Bending rigidity k of column foot joint of steel pipe column θ Obtaining the bending rigidity ratio lambda of the parameter column base joint, namely the bending rigidity k of the column base joint θ The ratio of the rigidity of the steel pipe column to the rigidity of the steel pipe column;
the calculation formula is as follows:
Figure BDA0001933902900000042
wherein: lambda-column base joint bending rigidity ratio, dimensionless;
k θ -column shoe joint flexural rigidity in mn·m/rad;
d, the diameter of the steel pipe column is equal to the unit m;
EI-rigidity of steel pipe column shaft in MN.m 2 Is a fixed value
If the bending rigidity ratio lambda of the column base joint is larger than 1, the column base bending rigidity is larger than the column shaft bending rigidity, the column base is not a stress weak point in a structural system, and the embedding depth of the steel pipe column meets the stress requirement;
if the bending rigidity ratio lambda of the column base joint is smaller than 1, the column base bending rigidity is smaller than the column shaft bending rigidity, the column base is still a stress weak point in a structural system, the steel pipe column embedding depth does not meet the stress requirement, and the embedding depth is further increased.
Taking a subway station as an example, the diameter of a steel pipe column is 1m, the length is 16.5m, and the diameter of a middle pile foundation is 1.8m; the concrete poured in the steel pipe column adopts C50 micro-expansion concrete, the design value of compressive strength is 23.1MPa, the standard value of compressive strength is 32.4MPa, the elastic modulus E=34.5 GPa, and the Poisson ratio is 0.2; the middle pile foundation concrete adopts C30 concrete, the design value of compressive strength is 14.3MPa, the standard value of compressive strength is 20.1MPa, the elastic modulus E=30GPa, and the Poisson's ratio is 0.2; the steel pipe column adopts Q235 steel bars, the yield strength is 235MPa, the ultimate strength is 310MPa, the elastic modulus E=210 GPa, and the Poisson's ratio is 0.3.
And obtaining the bending rigidity of the joint of the steel pipe column base under the condition of different embedding depths through finite element calculation, and comparing the bending rigidity with the bending rigidity of the steel pipe column. Firstly, obtaining the embedding depth of the steel pipe column corresponding to the reasonable section of the bending rigidity of the column base joint through trial calculation, then taking the embedding depths of 50mm, 200mm, 300mm and 500mm as examples, calculating structural deformation and stress, and analyzing the change condition of the bending rigidity of the steel pipe column base joint along with the embedding depth, as shown in figure 4. When the embedding depth of the steel pipe column is smaller, the column foot embedding part is used as the only stressed fulcrum for resisting external bending moment in the structural system, and the bending rigidity of the joint is sensitive to the embedding depth and is shown as the larger slope of the column foot bending rigidity in the initial stage in the figure 4; with the increasing depth of embedding, the joint at the column foot has gradually changed from a weak point of stress in the structural system to a region with larger rigidity, and the sensitivity to the depth of embedding gradually decreases, which is shown by the gradual decrease of the slope of the column foot bending rigidity in the later stage in fig. 4. The bending rigidity of the steel pipe column shaft is a fixed value, and when the embedding depth reaches 200mm, the bending rigidity of the column foot joint is larger than the bending rigidity of the column shaft.
To more intuitively represent the relationship between column shoe stiffness and column shaft stiffness, fig. 4 is arranged as a column shoe joint bending stiffness ratio λ versus insertion depth curve, as shown in fig. 5. The bending rigidity ratio lambda of the steel pipe column base joint has a nonlinear variation trend along with the embedding depth, and the relative rigidity of the column base is increased in a nonlinear manner. When the embedding depth reaches 200mm and continues to be increased, the bending rigidity ratio lambda of the column base joint is larger than 1, which indicates that the bending rigidity of the column base is larger than the bending rigidity of the column shaft at the moment, the column base is not a stress weak point in a structural system, and the embedding depth can meet the stress requirement. The minimum theoretical embedding depth of the steel pipe column with the diameter of 1m is 200mm.
The present invention has been described in detail by way of examples, but the description is merely exemplary of the invention and should not be construed as limiting the scope of the invention. The scope of the invention is defined by the claims. In the technical scheme of the invention, or under the inspired by the technical scheme of the invention, similar technical schemes are designed to achieve the technical effects, or equivalent changes and improvements to the application scope are still included in the protection scope of the patent coverage of the invention. It should be noted that for clarity of presentation, descriptions of parts and processes known to those skilled in the art that are not directly apparent to the scope of the present invention have been omitted from the description of the present invention.

Claims (2)

1. The method for calculating the reasonable depth of the embedded pile foundation of the steel pipe column is characterized by comprising the following steps of:
(1) Applying bending moment M and vertical axial force F to the top longitudinal beam of the steel pipe column, and obtaining a corresponding column foot joint corner theta of the steel pipe column under different bending moments through numerical simulation;
(2) Fitting the applied bending moment M and the column base joint rotation angle theta data to establish a bending moment-column base joint rotation angle relation curve;
(3) Establishing a fitting formula according to a bending moment-column base joint corner relation curve to obtain the bending rigidity k of the column base joint θ ；
In the step (3), a fitting formula established by a bending moment-column foot joint rotation angle relation curve is as follows:
M＝a+k·θ
wherein: m-bending moment, unit kN.m;
theta-column foot joint rotation angle, unit 10 -3 rad；
a-intercept, which is a fitting coefficient, in kN.m;
k-curve slope, which is the fitting coefficient in units of MN.m/rad;
and the bending stiffness k of the joint is obtained by the following formula θ ：
Figure FDA0004065609380000011
(4) Bending rigidity k of column foot joint of steel pipe column θ Obtaining the bending rigidity ratio lambda of the parameter column base joint, namely the bending rigidity k of the column base joint θ The ratio of the rigidity of the steel pipe column to the rigidity of the steel pipe column;
if the bending rigidity ratio lambda of the column base joint is larger than 1, the column base bending rigidity is larger than the column shaft bending rigidity, and the steel pipe column embedding depth meets the stress requirement;
if the bending rigidity ratio lambda of the column base joint is smaller than 1, the column base bending rigidity is smaller than the column shaft bending rigidity, and the steel pipe column embedding depth does not meet the stress requirement;
in the step (4), the calculation formula of the bending stiffness ratio lambda of the column foot joint is as follows:
Figure FDA0004065609380000012
wherein: lambda-column base joint bending rigidity ratio, dimensionless;
k θ -column shoe joint flexural rigidity in mn·m/rad;
d, the diameter of the steel pipe column is equal to the unit m;
EI-rigidity of steel pipe column shaft in MN.m 2 Is a fixed value.
2. The method for calculating the reasonable depth of the embedded pile foundation of the steel pipe column according to claim 1, wherein in the step (1), finite element software is adopted to conduct numerical simulation on the steel pipe column.
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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102995667A (en) * 2012-12-27 2013-03-27 长安大学 Slippage shock insulation pile foundation top bending moment releaser

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* Cited by examiner, † Cited by third party
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CN104484573B (en) * 2014-12-30 2017-09-15 中国石油天然气股份有限公司 A kind of method of determination stratum stiffness coefficient

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102995667A (en) * 2012-12-27 2013-03-27 长安大学 Slippage shock insulation pile foundation top bending moment releaser

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* Cited by examiner, † Cited by third party
Title
钢管混凝土柱-梁连接节点弯矩-转角关系计算方法;曲慧等;《工程力学》;20100531;第106-115页 *

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