KR101920223B1 - Efficient Basement Structure by changing connection betwwon piles and footing - Google Patents

Abstract

The present invention relates to a foundation structure and, more specifically, to a foundation structure, in which a steel pipe pile (or a composite pile) and a PHC pile can be efficiently combined with through three-dimensional analysis such that the vertical force, horizontal force and bending moment acting on the foundation can be effectively coped with while maintaining economic efficiency. The present invention provides a foundation structure, comprising: a spread footing modeled by plates or a three-dimensional grid; a steel pipe pile (or a composite pile) having an upper end portion connected to the spread footing by a rigid structure embedded in the lower side of the spread footing so as to be disposed at the lower portion of the spread footing and to resist the vertical force, horizontal force and bending moment acting on the spread footing, and modelled by a three-dimensional beam element such that the side surface and the front end thereof are modelled by spring elements in consideration of the characteristics of the ground layer; and a PHC pile having an upper end portion connected to the spread footing by a hinge structure so as to be disposed at the lower portion of the spread footing and to resist the horizontal force and vertical force acting on the spread footing, and modelled by a three-dimensional beam element hinge-connected to the spread footing such that the side surface and the front end thereof are modelled by spring elements in consideration of the characteristics of the ground layer.

Description

In this paper, we propose a new pile and footing pile foundation,

The present invention relates to a foundation structure, and more particularly, to a pile structure that effectively uses the characteristics of a steel pipe pile (or a composite pile) and a PHC pile through three-dimensional analysis to effectively cope with a normal force, a horizontal force and a bending moment acting on the foundation, To an effective foundation structure.

The foundations supporting the structure are divided into a shallow foundation used for the lower ground and a deep foundation used for the deeper ground.

The piles used for deep foundations are steel pipe piles, PHC piles incorporating prestressing, and reinforced concrete piles. The steel pipe pile and PHC pile are used as piling piles manufactured in the factory because there is little concern about cracking during transportation, and the reinforced concrete pile having a great concern about cracking is mainly manufactured by putting in the field.

The steel pipe pile is about 2 ~ 3 times higher than the PHC pile. The structural performance of the pile material is superior to the PHC pile by the bending moment and the shear resistance capacity of the steel pipe pile by about 7 to 8 times. Therefore, the steel pile pile is mainly used in civil engineering structures with a large influence of lateral force, and the PHC pile is used economically in construction structures having little effect of lateral force.

The bending moment, shear force and axial force act on the pile foundation. As shown in FIG. 1, the bending moment and shear force are generated at the upper end and the size decreases as the depth is deepened. On the other hand, .

The upper end of the pile, which generates moment and shear force based on the characteristics of bending moment and shear force acting on the pile foundation, uses expensive steel pipe pile with excellent resistance to moment and shear force, In the lower part of the pile, a composite pile satisfying economical efficiency and structural safety has been developed and used by combining PHC piles having high axial resistance and economical efficiency.

The composite pile is more economical than the steel pipe pile because it is a combination of steel pipe pile and PHC pile, but it is more expensive than PHC pile because it is necessary to weld the steel pipe pile and PHC pile and to secure the connection part.

The method of connecting the enlarged foundation to the pile can be classified into two types: strong (fixed), hinge, and roller type, and the sectional force acting on the pile is different according to the connection method. However, in the case of bridge foundation, it is specified in the design standard of the bridge for the design of the river which is the method of fixing the head of the pile to the foundation (Commentary on Highway Bridge Design Standard (2008), p. 905) A strong method is applied. The reason why the pile and foundation are designed to be strong in the design standards of the highway bridge is described as "advantageous when the design is controlled according to the horizontal displacement amount and safety of the grounding phase is advantageous because of high number of unsteadiness" This is because it is necessary to examine the pile head hinge joint state when considering the worst conditions in earthquake "and that it is necessary to examine the state of the pile head hinge joint. Are both designed to satisfy both conditions. Therefore, in the design guidelines for highway bridges, only rigid plans are presented without any examples of hinge joints between expansion bases and piles.

According to the above-mentioned design standard, most of the bridge bases are designed and constructed with rigid joints of all piles. In order to ensure safety, only the safety of the pile is examined even in the hinge-coupled state. For this reason, the piles used in most bridge foundations are designed to receive all bending and shear forces. However, it is inevitable to use a composite pile using a steel pipe or a steel pipe as a whole in which a large moment such as an alternating pile is generated. However, in a pier with relatively low moment generation and axial force, The use of piles can be said to be uneconomical.

The method of structural analysis of piles proposed in the design guidelines for highway bridges is the displacement method (see the foot bridge design guide (2008), 889). The displacement method is based on the equation proposed by Chang in 1930, The method of obtaining the spring constant (k) in the axial direction and the direction perpendicular to the axis of the pile, which is used to solve the above equation, is a method of obtaining the solution of the equation obtained by idealizing the pile and the ground by one spring, (2008), pp. 885 to 999, which is incorporated herein by reference.

Therefore, similar piles with the same stiffness were used in general bases and the tofu of the pile was designed to be combined with an expansion base and rigid or hinged. In order to improve the economical efficiency, it is one of the major factors to use the piles with different stiffness on the basis of the same bridge or to attempt to change the connection conditions of the pile head.

Chang 's equation presented in the design guidelines for the highway bridge was proposed in the 1930' s and is an idealized equation to solve the solution by numerical calculation. Considering the fact that computer and analysis methods are developed remarkably in comparison with that time, it is somewhat complicated to use piles with different stiffnesses on the same foundation or to modify the connection conditions of the pile head to simulate it in close proximity to reality It is necessary to make the effective design possible by considering the load acting on the pile coupled with the foundation by the three-dimensional analysis method similar to the actual one.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems raised in the background art, and it is an object of the present invention to solve the above problems by arranging a steel pipe or a composite pile and a PHC pile according to the magnitude of moment and shear force, To thereby provide a foundation structure that can be constructed with the above structure.

As a means for solving the above-mentioned problems,

An enlarged base modeled as a plate or a three dimensional grid;

The upper portion is connected to the lower frame of the enlarged base so as to be able to withstand the vertical force, the horizontal force and the bending moment acting on the enlarged frame, and is modeled as a three-dimensional beam element, And the tip is a steel pipe pile modeled as a spring element considering the characteristics of strata;

The upper portion is connected to the enlarged base by a hinge structure so as to be able to resist a horizontal force and a vertical force acting on the enlarged base and is modeled as a three dimensional beam element connected to the enlarged base by a hinge, And a PHC pile modeled as a spring element considering the characteristics of the stratum.

It is preferable that the steel pipe pile is disposed at the outer periphery of the expansion base relatively to the PHC pile.

Further comprising a connecting rod including a reinforcing concrete disposed in an upper side of the PHC pile, a steel band surrounding the upper end of the PHC pile, and a rod or a bar made of a steel in one direction, the lower end of which is inserted into the reinforcing concrete,

It is preferable that the enlarged base and the PHC pile are coupled in such a manner that a portion of the connecting rod exposed on the upper portion of the PHC pile is embedded in the enlarged base.

In addition,

An enlarged base modeled as a plate or a three dimensional grid;

A rigid structure that is disposed at a lower portion of the enlarged foundation and has an upper end embedded in a lower portion of the enlarged foundation so as to resist a vertical force, a horizontal force, and a bending moment acting on the enlarged foundation, A composite pile modeled as a dimension beam element whose side and tip are modeled by spring elements taking into account the characteristics of strata;

The upper portion is connected to the enlarged base by a hinge structure so as to be able to resist a horizontal force and a vertical force acting on the enlarged base and is modeled as a three dimensional beam element connected to the enlarged base by a hinge, And a PHC pile modeled as a spring element considering the characteristics of the stratum.

Preferably, the composite pile is disposed on the outer periphery of the expansion base relatively to the PHC pile.

Further comprising a connecting rod including a reinforcing concrete disposed inside the upper side of the PHC pile, a steel band surrounding the upper end of the PHC pile, and a rod or bar made of one-directionally long steel in which the lower end is inserted into the reinforcing concrete,

It is preferable that the enlarged base and the PHC pile are coupled in such a manner that a portion of the connecting rod exposed on the upper portion of the PHC pile is embedded in the enlarged base.

According to the present invention, a steel pipe pile (or a composite pile) and a PHC pile are efficiently disposed through a three-dimensional analysis, and the type of coupling with the expansion base is controlled to provide an economically excellent foundation structure can do.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a bending moment, a shearing force and an axial force acting on a pile coupled to a foundation; FIG.
Fig. 2 is a view showing a method of joining a pile and a foundation on a design standard of a highway bridge; Fig.
Fig. 3 is a view showing a three-dimensional modeling of a combination of an enlarged base and a pile. Fig.
Fig. 4 is a view for explaining a three-dimensional modeling analysis method when the enlarged base and the pile are coupled by a rigid coupling or a hinge structure; Fig.
5 is a view for explaining the hinge structure coupling of the PHC pile and the enlarged base;
6 is an assembled sectional view of Fig.
7 and 8 are views for explaining the arrangement of a steel pipe pile (or a composite pile) and a PHC pile.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings, and specific details for carrying out the present invention will be provided.

Fig. 3 is a view showing a three-dimensional modeling of a combination of an enlarged base and a pile. Fig. Fig. 4 is a view for explaining a three-dimensional modeling analysis method when the enlarged foundation and the pile are coupled by a steel hull structure or a hinge structure, Fig. 5 is a view for explaining the hinge structure combination of the enlarged foundation and the PHC pile, 5 and FIGS. 7 and 8 are views for explaining the arrangement of a steel pipe pile (or a composite pile) and a PHC pile.

The foundation structure according to the present embodiment comprises an enlarged foundation 10, a steel pipe pile 20, and a PHC pile 30.

The enlarged base 10, the steel pipe pile 20 and the PHC pile 30 are analyzed by a three-dimensional model as shown in Fig.

The displacement method on the design basis of the highway bridge which is used to examine the structure of the foundation and the pile is advantageous in that the calculation method is simple and easy to apply. However, since the displacement method assumes that there is no change in the ground and that the stiffness of the pile is the same, the pile is sufficiently inserted into the ground having a certain ground condition, and the pile of the same kind, This is an analysis method that can be applied only when it is combined by a strong structure. If there is a change in strata, or if a combination of different types of piles with different stiffnesses in the same foundation is used, or if the combination conditions of the enlarged foundation and the pile are changed, it is contrary to the basic assumption of the equation derived from the displacement method. I will not.

Therefore, it is difficult to apply displacement method, which is a conventional analysis method, when using various piles in combination to improve structural efficiency and economical efficiency in bridge foundation. When using various piles in combination, it is necessary to analyze the three-dimensional structure in order to simulate the behavior of the foundations close to the actual condition, and the concrete method can be solved by the following method.

- Enlarge foundation applied plate or 3D grid model

- 3-dimensional beam element considering pile characteristics

- Application of spring element for each layer considering ground change

- Boundary conditions such as steel structure (steel pipe pile) and hinge structure (PHC pile) are applied to the connection between the enlarged foundation and the upper end of the pile

In the present invention, the three-dimensional structure analysis according to the four criteria described above is applied. The enlarged base 10 is a reinforced concrete structure modeled and analyzed by a plate or a three-dimensional beam element.

The steel pipe pile 20 is disposed under the enlarged base 10 and is modeled by a three-dimensional beam element. As shown in FIG. 4, the side and the tip of the steel pipe pile 20 are modeled by a spring element, .

The steel pipe pile 20 is connected to a steel structure buried in the lower portion of the enlarged base 10 so as to resist a vertical force, a horizontal force and a bending moment acting on the enlarged base 10. Since the method of connecting the steel pipe pile 20 to the enlarged base by a steel structure is a commonly used method, it can be sufficiently known that a person having an average degree of knowledge in the field to which the present invention belongs. Therefore, And further explanation will be omitted.

The PHC pile 30 is disposed under the enlarged base 10 and is modeled as a three-dimensional beam element, like the steel pipe pile 20. In the present embodiment, the PHC pile 30 is connected to the enlarged base 10 in a hinge structure so as to resist a horizontal force and a vertical force acting on the enlarged base 10, At the time of modeling, the expansion base 10 is hinged and its side and tip are modeled and analyzed by a spring element taking into account the characteristics of the stratum.

A configuration for hinge connection between the enlarged base 10 and the PHC pile 30 will be described.

5 and 6, the filling concrete 35 and the reinforcing bars 36 are disposed inside the upper portion of the PHC pile 30, and the steel band 32 surrounding the outside is provided at the upper end of the PHC pile 30 . The steel band 32 is composed of two pieces. Each of the sections is provided with a wing plate 33. The high strength bolt 34 and the nut (not shown), which are fastened to the wing plate 33, So that the upper end of the pile 30 is engaged while being wrapped.

The lower end of the connecting rod 31, which is a long steel rod having a circular cross-section in one direction, is coupled to the concrete 35 in a state of being buried. As the joining rods 31, steel rods having a circular cross-section shown in Fig. 5, bundle reinforcing rods 31 'shown in Fig. 9, bent reinforcing bars 31' arranged to cross in an X- (31 ") or the like may be used.

The exposed portion of the coupling rod 31 and the upper end of the PHC pile 30 are embedded in the enlarged base 10 as shown in FIGS. 6, 9 and 10, The coupling rod 31 is fixed to the enlarged base 10, but the upper end of the PHC pile 30 is fixedly engaged with the enlarged base. Due to this coupling structure, the displacement of the PHC pile 30 in the horizontal direction is constrained, but the rotational displacement is allowed to be a hinge structure.

Since the bending moment and the horizontal force acting on the enlarged base 10 are sufficiently supported by the steel pipe pile 20, the PHC pile 30 is designed to share only the normal force, so that the enlarged base 10 and the PHC pile 30 are hinge- There is no problem in resisting the load acting on the enlarged base 10.

7, the PHC pile 30 is disposed on the outer side of the enlarged base 10, and the PHC pile 30 is disposed on the inner side of the enlarged base 10, This is because the bending moment and the shearing force due to the horizontal force acting on the outer frame portion are relatively large and the steel pipe pile 20 is arranged on the outer frame portion can more effectively resist the bending moment and the shearing force. Of course, the number of the steel pipe pile 20 and the PHC pile 30 to be disposed and the arrangement shape thereof are determined by the above-described three-dimensional modeling analysis.

As pointed out in the problems of the background art, conventionally, the same kind of pile is used in one foundation, and therefore, the horizontal force is not acted largely so that the pile foundation having a relatively small bending moment and shear force, There is a problem in that the pile is used and it is economically inefficient. In the present invention, a three-dimensional model analysis is introduced in order to design the type and arrangement of the pile economically, thereby enabling a more accurate structural analysis, and a bending moment or a shear force due to the horizontal force It is possible to design an economically efficient pile by efficiently arranging the pile so as to be resisted by the steel pipe pile 20 and supported by the PHC pile 30, which is relatively less expensive than the steel pipe pile 20 with a normal force.

Hereinafter, a second embodiment of the present invention will be described.

The foundation structure according to the present embodiment comprises an enlarged foundation 10, a composite pile 20 'and a PHC pile 30.

The construction of the enlarged base 10 and the PHC pile 30 is substantially the same as that of the enlarged base 10 and the PHC pile 30 of the embodiment described above and thus the description thereof is omitted.

The composite pile 20 'is also the same as the steel pipe pile 20 except that the steel pipe pile 20 is a pile composed of a steel pipe and the composite pile 20' is a combination of a steel pipe and concrete. The configuration related to the connection with the expansion base 10 and the relative arrangement with respect to the PCH pile 30 are the same as those of the steel pipe pile 20 of the embodiment described above and will not be described further Also in the drawing, the steel pile pile is indicated by 20 and the composite pile is indicated by 20 'in the same drawing.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, As shown in FIG.

10: Expanding foundation 20: Steel pipe pile
30: PHC pile 20 ': Composite pile

Claims (6)

An enlarged base modeled as a plate or a three dimensional grid;
The upper portion is connected to the lower frame of the enlarged base so as to be able to withstand the vertical force, the horizontal force and the bending moment acting on the enlarged frame, and is modeled as a three dimensional beam element, And the tip is a steel pipe pile modeled as a spring element considering the characteristics of strata;
The upper portion is connected to the enlarged base by a hinge structure so as to be able to resist a horizontal force and a vertical force acting on the enlarged base and is modeled as a three dimensional beam element connected to the enlarged base by a hinge, And a PHC pile modeled as a spring element considering the characteristics of strata,
Wherein the steel pipe pile is disposed at an outer portion of the enlarged foundation relatively to the PHC pile.
delete The method according to claim 1,
Further comprising a reinforcing concrete disposed in an upper side of the PHC pile, a steel band surrounding the upper end of the PHC pile, and a connecting rod including a rod or a bar made of a steel material having a one-
Wherein the enlarged base and the PHC pile are coupled in such a manner that a portion of the connecting rod exposed on the upper portion of the PHC pile is embedded in the enlarged base.
An enlarged base modeled as a plate or a three dimensional grid;
A rigid structure that is disposed at a lower portion of the enlarged foundation and has an upper end embedded in a lower portion of the enlarged foundation so as to resist a vertical force, a horizontal force, and a bending moment acting on the enlarged foundation, A composite pile modeled as a dimension beam element whose side and tip are modeled by spring elements taking into account the characteristics of strata;
The upper portion is connected to the enlarged base by a hinge structure so as to be able to resist a horizontal force and a vertical force acting on the enlarged base and is modeled as a three dimensional beam element connected to the enlarged base by a hinge, And a PHC pile modeled as a spring element considering the characteristics of strata,
Wherein the composite pile is disposed on the outer periphery of the enlarged foundation relative to the PHC pile.
delete 5. The method of claim 4,
Further comprising a reinforcing concrete disposed in an upper side of the PHC pile, a steel band surrounding the upper end of the PHC pile, and a connecting rod including a rod or a bar made of a long steel material inserted into the reinforcing concrete at a lower end thereof,
Wherein the enlarged base and the PHC pile are coupled in such a manner that a portion of the connecting rod exposed on the upper portion of the PHC pile is embedded in the enlarged base.

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