JPS6051222A - Cast-in-place steel tubular concrete pile - Google Patents

Abstract

PURPOSE:To efficiently bond concrete with steel tube against the bending moment of a cast-in-place concrete pile by covering a steel tube having projections formed by rolling on its inner surface on the concrete pile. CONSTITUTION:A steel tube 3 having projections 10 formed by rolling on its inner surface is covered on a cast-in-place concrete pile in order to reinforce the cross section of the pile. By covering the steel tube over whole length of the concrete pile, its strength against the bending moment due to the displacement of the ground at the time of earthquake can be secured, and thereby the number of reinforcing bars to be used can be reduced. The projections 10 of the steel tube 3 serve to increase the bonding strength between the steel tube 3 and concrete and also toughness of the pile. Also, when concrete is ready to separate from the steel tube 3 due to the contraction with time of the concrete, good bonding strength between them can be secured by the projections of the steel tube 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to cast-in-place steel pipe concrete piles.

In the currently practiced cast-in-place reinforced concrete and pile quake installation, we consider the situation in which a horizontal force P acts on the pile head, as shown in Figure 1, and consider the situation in which a horizontal force P acts on the pile head. Pile cross sections are designed for bending moments. As a result, a large bending moment will occur near the pile cap of pile 1 (for example, approximately 10 m from the pile cap for a cast-in-place pile with a pile diameter of 1250+ff1l+), so earthquake resistance design will be performed only near the pile cap. There was virtually no seismic design for the middle and lower part of Pile 1. In Fig. 1, (a) shows the pile structure, and (b) shows the bending moment distribution of the pile.

However, when an earthquake actually occurs, it is beginning to be observed that large bending strains occur in locations other than the vicinity of the pile cap. For example, as shown in Figure 2, the upper part is a soft alluvial layer and the N medium O1 is a diluvial layer with a depth of about 21 m or less, and N>51.
A straight pile 1a with a diameter of 6QQ is placed on the ground with an N value distribution of 1.
rum, a steel pipe pile of JW 9B with a diameter of 60 as the diagonal pile 1b.
A total of 64 steel pipe piles with a wall thickness of Q mm and a wall thickness of 12 mm were driven as shown in Figure 6 (, ).
Insects have been observed on various parts of piles when this occurs.

When the strength of the earthquake is the maximum foundation acceleration of 2.4 yaJ, the strain with respect to the depth of straight pile 1a is shown in Figure 6 (b).
The stop with respect to the depth is as shown in (c).

In other words, in the straight pile 1a, in addition to the bending strain at the pile head, there is also a maximum bending strain of 8.9μ at the upper end of the support layer, and the latter strain cannot be taken into account by the conventional slope design method. It is something. Table 1 shows the estimated strain when the earthquake strength is 200 fa-' and the maximum acceleration of the foundation is estimated from these observation results.

Table 1 In this case, the maximum strain at the top of the support layer of straight pile 1a is 1058μ
However, the problem arises that the yield point of the pile is exceeded.

In this way, based on the observation results when an earthquake actually occurs, it has become clear that the currently used earthquake-resistant design methods for piles are insufficient. A detailed investigation revealed the following: As an experimental model, we considered one consisting of the ground, piles, and superstructure as shown in Figure 4, and created a ground model;

A bow saw consisting of a soft layer and a sand layer with an N value of about 60, a bow saw consisting of a soft layer and a support layer, and a structure in which the actual ground, base tS, and u structure titrate the law of similarity.

Figure 5 shows the above experimental results. (a) shows the bending strain distribution when using a cast-in-place pile model and applying vibrations with an input acceleration of 10 gJ and a ground resonance frequency of 3.3 Hz. (b) shows the bending strain distribution when the steel pipe pile model is subjected to vibrations of 1 history MAL, an input acceleration of 10 f"l, and a ground resonance frequency of 32 Hz σ. At t'; I, the Young's modulus is The value of Em indicates the Young's modulus of each ground layer used as a ground model. Figure 5 (a),
As is clear from (b), a large bending strain -/ which cannot be expressed by the law of σ] and δ is currently occurring.

In other words, the device that generates the bending moment distribution of the pile is the sixth
Pile head σ as shown in Figure (a)] Water'-V-buJ l'
In addition to the strain caused by the earthquake, forced displacement of the pile due to ground displacement during an earthquake as shown in (b) also has a large effect.
Therefore, in the seismic design of piles, <e) + 1
- As shown in (c), it is necessary to consider the bending due to ground displacement: E: 1 and the bending due to the horizontal force of the pile head shown in (d). There is.

Figures 7 to 9 show examples in which the bending moment due to the above-mentioned ground displacement was determined by HtB for cast-in-place reinforced concrete piles, and the influence of ground conditions was investigated.

The calculation method is based on the Japanese National Railways 1-Resistance Construction J1 Guidelines (Draft)
Explanation J (1lsx1.+ 1954 7J:J) pp, 5
Methods 4 to 75 were given out. Death C in Figures 7 to 9
, each (3) is the ground condition, (b) is the pile structure, and (C)
indicates the bending moment due to ground displacement.

Figure 7 shows a shaft diameter D = 1250 mb+ and a length 5 Q tn on the ground with an intermediate sand layer of N = = 30.
Head expansion shift'c Bottom expansion'j A The bending moment distribution due to ground displacement of a pigeon coop with cast-in-place reinforced concrete piles is shown. It has occurred.

? [Figure 48 shows shaft diameter D-1250m+, length 25m
) in Supporting cast iron concrete piles (clear layer ＼ approx. 4
The bending moment distribution due to ground displacement is shown when the joists are thickened. In this case, support j
- A large bending moment occurs near the top end.

Fig. 2 considers the case where there is a supporting layer under the soft layer of N-4 and a depth of 60 m, and shows the result when an expanded cast-in-place reinforced concrete pile with shaft diameter D = 1,250 m is thickened by about 1 m into the supporting layer. The bending moment distribution due to ground displacement is shown. When the soft layer is thick and there is no intermediate sand layer, as is clear from the figure, a large bending moment occurs near the top of the support layer even if the penetration into the support layer is small.

Figure 10 shows the bending moment distribution due to ground movement e when the shaft diameter becomes larger.
) tj: ground condition, (b) shows pile construction, and (C) shows bending moment distribution. Cast-in-place reinforced concrete piles are shaft &
D=250L] nun, length #61J m.

From the above, reinforced concrete piles can be bulky if they have the following problems.

q) It is appropriate for the pile head horizontal force acting on the expanded bottom pile to be thicker than that of a non-expanded pile with the same axis. On the other hand, piles that do not have an enlarged diameter head are often difficult to install, and are usually designed with an enlarged diameter head.

However, as shown in Figure 7, the bending moment due to ground displacement during an earthquake becomes a large value due to the increase in bending rigidity of the pile head due to the wave crest. When this bending moment and the bending moment due to the horizontal force of the pile head are considered together, the reinforcement ratio of the expanded head is often around 6 inches, and due to the high reinforcement ratio, compared to the case where the bending moment due to ground displacement is not considered, Material costs will increase significantly.

■At the middle and lower parts of the pile, where the influence of bending moment due to horizontal force on the pile head is small, as shown in Figures 7 to 10, when the shaft diameter D = 1250 m, the maximum bending moment is approximately 200 km, and the shaft diameter When D=25001an, it is approximately 1700m. The reinforcing bar ratio is 5.5 in both cases.
In many cases, the value is as high as ~6%, and as with the pile head, the material cost increases significantly.The present invention provides a cast-in-place steel pipe concrete pile that solves the above-mentioned problems. The purpose is to

In order to achieve the above object, the cast-in-place steel pipe concrete pile according to the present invention strengthens the cross section by wrapping a steel pipe with projections on the inner surface around the entire length of the cast-in-place steel pipe concrete pile, thereby eliminating the need for reinforcing bars. In addition to decreasing the amount of stress, the degree of adhesion stress between the steel pipe and the concrete portion is increased.

The present invention will be explained below based on Examples.

FIG. 11(a) is a cross-sectional view of the embodiment of the present invention, and FIG. 11(b) is a cross-sectional view of the peak along line A-A.
), 3 is a steel pipe with protrusions on the inner surface wrapped in concrete.

[Example 1] In the cast-in-place steel pipe concrete pile of the present invention shown in Fig. 11, all the constant electric charge is supported by the concrete part, and the white part due to ground displacement during an earthquake is handled by the outer shell steel pipe. think of.

First, we will explain the advantages of using steel and concrete, and then explain the necessity of using a steel plate with protrusions instead of a flat steel plate for this steel pipe.

Regarding the advantages of using steel pipe concrete, we will consider the general area excluding the vicinity of the pile head. For example, shaft diameter 12
As is clear from FIGS. 7 to 9, the bending moment of a 50 n+m cast-in-place reinforced concrete pile due to ground displacement is often 150 to 2 U Ot-m. The reinforcing bar ratio at this time is 4 to 6 inches, compared to about 0.4 inches when the current ground displacement is not considered.
Very dense reinforcement is required, and the old construction cost for reinforcing bars becomes very large. Figure 12 shows the unit long-term axial force (1) and unit length 6-n for the bending moment generated by ground displacement for the cast-in-place steel pipe concrete pile according to the present invention and the conventional cast-in-place reinforced concrete pile with a shaft diameter of 1250M. ) The construction costs of the construction companies are reported in the magazine “Construction Prices”.
This is an example calculated based on (6J1, 1988). The approximate price for steel plates with protrusions is that of flat steel plates. In FIG. 12, (a) shows the material cost for the cast-in-place steel pipe concrete pile according to the present invention, the material cost for the conventional cast-in-place reinforced conocrete pile, and the material cost for the conventional cast-in-place reinforced concrete pile. This figure shows the ratio of the material cost (a) for the cast-in-place steel pipe concrete pile according to the present invention to the construction cost (b).As is clear from Figure 12 (c), the material cost for the pile according to the present invention is , compared to the material cost for conventional piles, the larger the bending moment of ground displacement becomes, the more advantageous the material cost F when the bending moment is 200 t-m.
i, it will be about 80chi.

Table 2 shows the range of steel pipe plate thickness in areas where the influence of the bending moment caused by the horizontal force of the pile cap is small (portions other than the vicinity of the pile cap). However, the plate thickness includes one layer of corrosion type.

Table 2 Next, consider the vicinity of the pile head in this example. As shown in the above problem (■), in ordinary cast-in-place reinforced concrete piles, f? Because the wave crest is formed and the bending rigidity of the expanded head increases, the bending moment due to ground displacement becomes extremely large. In the following, the diameter of the head pile is assumed to be approximately the same as that of the general section at the bottom, and instead of using reinforced concrete IJ with an enlarged diameter head, this section will be made of steel pipe concrete with a pipe wrapped around it. State the superiority.

H' = Fig. 13 (a) K oil, (a) diameter Dz of enlarged head shown in (b) = 1750 mm, length 13 m, - collection part (1) diameter Da"" 1250 pus wave crest in place This figure shows the bending moment distribution caused by ground displacement in a reinforced concrete pile. In ol), the pile diameter of the head shown in (c) is kept as 1250ff1m, a steel pipe 61 with a wall thickness of 23mm is wrapped around the head for 8m, and a steel pipe 62 with a wall thickness of 10f1m is placed below it.
Similarly, the bending moment distribution is shown for cast-in-place steel pipe coil piles sown with , -) piles. Both piles have a pile length of 19m1, a diameter of the expanded bottom part of 2000mm, a constant shaft cuff of 30t,
It was designed to support an axial force of 146°t1 and a horizontal force of 14Ut during an earthquake, and to resist the bending moment caused by ground displacement. The pile head is fixed. The ground on which the piles were installed is shown in (d). From this figure, it can be seen that by using steel pipe concrete, the bending moment due to ground displacement can be kept small at the pile head. Well, the construction cost for this 1 tsubo 1 m2 head is 150.380 yen for steel pipe concrete piles, and 228.490 yen for expanded head reinforced concrete piles, so I decided to make the head of steel pipe concrete IJ-. Yes, we can see great economic efficiency. This material cost was calculated based on the above-mentioned magazine "Construction Prices" (June 1982), and the price of a flat steel plate is used as an approximation of the price of a steel plate with a protrusion.

1 and above showed the advantage of using copper pipe concrete in the vicinity of the pile cap and in the general area excluding the vicinity of the pile cap.

Next, the necessity of providing protrusions on the inner surfaces of these steel pipes will be explained. First, I will talk about the vicinity of the pile head.

In the extreme design, the adhesion strength required between the steel pipe and the concrete will be examined at the next entrance 1.

The collapse mechanism near the head of a concrete section wrapped around a steel pipe differs depending on whether it is due only to the horizontal force of the pile head, only to ground displacement, or when both act simultaneously. Regarding the bond strength of 8 layers, the value for the collapse mechanism when only horizontal force acts on the pile (b'1) is the largest value. Therefore, let us consider the state where only horizontal force acts on the pile head. The bending moment in the extreme state due to the horizontal loading of the pile head and the
Calculate the force distribution using the BROMS method 1, for example N = 3UO) on sandy ground (surface layer) with a diameter of 150 (Jm + u,
Wall thickness 14, concrete Fi:, shrinkage strength Fe, 24
Figure 14 shows the distribution of bending moment and shearing force of []kWlcrl tli St-wound concrete. h'> In Figure 14, (a) shows the shear force distribution with respect to the depth of the pile, and (b) shows the moment distribution with respect to the pile floor type.

With this Promus method, table M is N=]10 or N=
31J OD e Earth gt K, a Ka 1 [IL) Ow
n, 15 () Om.

Pile head bending 7-ment Mp when 2000 pieces are made.

Pay attention to the depth at which the shearing force Qu and the bending force Qu and the bending force /1 are zero, and calculate the required bond stress tb from these values.
, resho is shown in Table 6.

and ζ, the degree of adhesion stress τ between the steel pipe 6 and the reinforced concrete 2
b and re1p can be determined under the conditions shown in FIG. In Figure 15, (a) is a front view of the steel pipe-wrapped concrete part, (b) is a plan view of the steel pipe-wrapped concrete part at 1ThJ, (C) is a distribution diagram of the bending moment Mp, and (d) is the compressive force It shows the stress distribution of concrete when the stress is applied. Note that 41- is the cross-sectional area of the concrete on which compressive stress is applied, and 5 is the neutral axis.

bending moment) 1,41'i4j until Mp becomes zero
In A, assume that the bending moment distribution is a linear distribution as shown in FIG. 15(c), the shear distribution is -W, and, for example, the axial force during an earthquake is (constant axial force x (1±1)).

Under these conditions, the adhesion stress ``b'' and tel necessary for the steel pipe and the cock IJ-to part to be integrated are calculated as follows.

c Ac τb , r e g--, -(ky/cnl) ・
・・・・・・・・・・・・・・・・・・(1φ stone Here, Fc is the compressive strength of the concrete, AC is the cross-sectional area of the concrete IJ-t on which compressive stress is applied, and φ is The length of the contact area between the concrete part and the steel pipe, where compressive stress is applied, is the depth at which the bending moment becomes zero.The above pile diameter is 100 Qwm.

Regarding the case of 1500++rffl, 2000 fermentation (1
) Table 6 shows the required adhesion stress degree calculated by applying the formula.

Table 3 As a result, the l9iff layer stress between the steel pipe and the concrete part is 20 to 30 kf/Crl. Including the above required adhesive strength, the following six conditions must be satisfied regarding adhesive stress.

■Required adhesion strength is 3' (3 kg/CI& or more).

■In the event of a severe earthquake, which is subject to secondary design, see Figure 16 (,
), the adhesion stress occurs when the strength is reached, but in this state, the strength does not deteriorate as shown in (b) of the same figure, and the strength increases as shown in (C). It is necessary to maintain it.

■Due to the shrinkage of concrete over time, detachment between the concrete and steel pipes may occur, so prevent the deterioration of bond strength due to this.

The adhesion strength between a regular flat steel plate and a round steel pipe and concrete is 2 to 10 kg/d. Moreover, it is presumed that the properties shown in FIG. 16(b) will be exhibited when subjected to repeated loading after reaching the strength. Furthermore, unless special measures such as expanded concrete are taken, it is difficult to prevent the adhesive strength from deteriorating due to shrinkage of concrete over time.

On the other hand, it will be shown below that the above conditions can be solved by using a steel plate with projections. The adhesion stress between the protruded steel pipe and the concrete 17 was determined to be 950 kg/d by the steel pipe-concrete adhesion strength test shown in FIG. 17 as an experimental value. That is, the adhesion strength of 30 kg/d required under condition (2) is fully satisfied.

In FIG. 17, reference numeral 2 is a reinforced concrete, a reed, 3 is a steel pipe, and 6 is a portion where the reinforced concrete 2 and the steel pipe 66 are attached. In this case, the pulling force increases monotonically.

Next, we will talk about maintaining strength in the combed state, which is required under condition (①). Reinforced concrete 2 as shown in Figure 18
Steel plate with protrusions inside? FIG. 19 shows the degree of adhesion stress when repeatedly applying a pulling force to the steel plate 9 with projections in the test block 8 provided with the above. In FIG. 19, δp represents the amount of slippage at the top of the test block shown in FIG. 18, and δf represents the amount of slippage at the bottom. In Fig. 18, the reinforcing bars 7 are vertical bars.

Both hoop muscles were 5R24 and had a diameter of 6 mm.

As shown in FIG. 19, the adhesion stress between the protruded steel plate and the concrete does not deteriorate even under repeated loads.

Although this test was not a test for both types as shown in FIG. 16, but was for oscillation, it can be easily expected that the same strength could be maintained for both types.

Next, we will discuss the prevention of adhesive strength deterioration due to shrinkage of concrete over time, which is necessary in the last condition (①).

Although the amount of shrinkage over time varies depending on various conditions such as the cement Wr, it is sufficient to consider 4×10′ as the maximum volumetric strain. As an example, if we consider a pile with a diameter of 2000M, the 20th
As shown in Figure (,), when the steel pipe shrinks uniformly toward the center, the gap between the steel pipe and concrete is 0.41MR1 Figure (
As shown in b), the clearance when the side stones are contracted is 0.
8 It becomes pus. If the height of the protrusion is set to be greater than or equal to these values, deterioration of adhesive strength due to shrinkage over time can be prevented.

Next, we will discuss the necessity of adding protrusions to the inner surface of the steel pipe in the general area, excluding the vicinity of the pile cap.

In a cast-in-place pile with a shaft diameter of 12501+o+l, which is not shown in FIGS. 7 to 9, a maximum shear force of about 80 t is generated. When a steel pipe with a thickness of 9 tm is used, the adhesion stress required to maintain the integrity between the steel pipe and concrete against this shear force is about 10 kg/crl. The maximum acceleration in these values supporter is 200yak! , but in consideration of severe earthquakes, the maximum acceleration at the support layer is 4.
In the case of 00 fcLJ-, it is estimated to be around 16ot and 20y/cd, which is twice the shearing force and the required adhesion stress #'i. Therefore, if the maximum acceleration in the support layer is 200 yaJ-, the safety factor is set to 2, and 400? -1, the required adhesion strength is 20 to 9 I/d, assuming the safety factor is 1. The six conditions (1), (2), and (3) necessary for bond stress described in the vicinity of the pile head also hold true in the -crotch section by rewriting the required bond strength of 30k17/d as 20#/ffl. Therefore, the need to use a steel plate with protrusions mentioned in the vicinity of the pile head can also be applied to the general part.

[Example 2] As another example of the cast-in-place steel pipe concrete pile shown in Figure 11, if part of the constant load is held by concrete and part by steel pipe, the steel pipe concrete pile The shaft diameter of the reinforced concrete pile is smaller than that of the reinforced concrete pile. For example, for a constant vertical load of 70m, the shaft diameter of an expanded cast-in-place reinforced concrete pile must be 125m in diameter, but in the case of the steel pipe concrete pile in place according to the present invention, the shaft diameter is 900m+, steel pipe wall thickness 12fl
(corrosion 14). This also reduces the bending rigidity of the pile.

When the bending rigidity of a pile decreases, the bending moment of the pile shaft, which often occurs due to ground displacement during an earthquake, also decreases. 21st
- shows the bending moment distribution of the expanded-bottom cast-in-place reinforced concrete pile and the expanded-bottom cast-in-place steel pipe concrete pile according to the present invention when the constant vertical load is 730 t. In Fig. 21, (a) #'i shaft diameter D1250fi, expanded bottom diameter 19
0 [3111111, a conventional expanded bottom cast-in-place reinforced concrete pile with a pile length of 19 m, and (b) a shaft diameter of D1900.
Area, steel pipe wall thickness 124, expanded bottom diameter 1900mm, pile length 19m
1 shows an expanded cast-in-place steel pipe concrete pile according to the present invention. Furthermore, as shown in (d), (c) ti ground conditions,
Ground displacement during an earthquake when the piles shown in (a) and (b) are driven into fine sand with N=7 as the surface layer, silt with N=5 as the middle layer, and gravel with N=50 as the supporting layer. An example of the bending moment distribution generated by force is shown. In (e), (In is the conventional cast-in-place reinforced concrete pile with an expanded bottom!J-) In the case of (a), ←) shows the case of the expanded-bottom cast-in-place steel pipe concrete pile (b) according to the present invention.

In Fig. 21, when comparing the value of the typical bending moment of the pile at a depth of 8rn with that of the conventional cast-in-place reinforced concrete pile with an expanded bottom, the generated moment is 9.5 t-m, whereas the moment generated with the expanded-bottom cast-in-place reinforced concrete pile of the present invention is The generated moment of the steel pipe concrete pile is 45 t-m, which is about 1/2 of that of the steel pipe concrete pile. The pile was designed by taking into account the axial force during the earthquake in addition to the generated moment, and published in the magazine "Construction Price" (June 1982).
Considering the material cost based on the above, the general part excluding the vicinity of the pile head is approximately 47,000 yen/ns for steel pipe concrete, and 55,000 yen/ns for reinforced concrete.
Material costs can be reduced. Note that the price of a flat steel plate is used as an approximate value for the price of a steel plate with projections.

The embodiment of the steel pipe with protrusions according to the present invention described above is shown in the 22nd embodiment.
As shown in the figure. Lo is a steel pipe with a protrusion, and 1o is a protrusion.

As is clear from the above description, according to the present invention, by wrapping the steel pipe around the entire length of the cast-in-place concrete pile,
The bending moment of the pile due to ground displacement during an earthquake can be coped with, and the pile can be reinforced economically, so the need for reinforcing bars can be eliminated or reduced. Furthermore, by making the steel pipe with protrusions, the adhesion strength and toughness between the steel pipe and the concrete are increased, and even if the concrete and the steel pipe come apart due to shrinkage of the concrete over time, the protrusions on the steel pipe will provide good support. You can expect good adhesion. Therefore, the effect is significant when applied to cast-in-place piles designed for earthquake resistance.

[Brief explanation of the drawing]

Figure 1 (,) is a schematic diagram of a pile in place based on the conventional seismic design method, (b) is its bending moment distribution diagram, and Figure 2 is a diagram of the ground conditions when strain on the pile was observed during an earthquake. , 3rd
Figures (,) are pile structure diagrams when strain on piles was observed during an earthquake, (b) U bending strain distribution diagram of straight piles at that time, (C) bending strain distribution diagram of slanted piles, Figure 4 The figure is a model diagram of a model vibration experiment, Figures 5 (,) and (h) are bending strain distribution diagrams of piles in a model vibration experiment, Figure 6 (,) is a schematic diagram of a cast-in-place pile,
(b) is a ground displacement diagram, (C) is a bending moment distribution diagram due to ground displacement, (d) is a bending moment distribution diagram due to horizontal force on the pile head, (e) is a bending moment distribution diagram that combines both. Figures 7 ('), (I + Le (c) to Figures 10 (a), (b), and (c) are respectively a ground condition diagram, a pile structure diagram, and a bending moment distribution diagram due to ground displacement; Figure 11 (
,) is a vertical cross-sectional view of an embodiment of the present invention, (b) is a cross-sectional view taken along the line A-A, FIG. 12 is a material cost distribution map, and FIG. Bending moment distribution diagram generated due to ground displacement of cast-in-place steel pipe concrete piles, (b) is a front view of the wave crest cast-in-place reinforced concrete pile, (c) h is a front view of cast-in-place steel pipe concrete piles, (d) is the ground condition Figures 14(a) and 14(b) are shear force distribution diagrams and bending moment distribution diagrams using the Proms method, Figure 15(a) is a front view of steel pipe-wrapped concrete, and (b) is a plan view. C) is a bending moment distribution diagram,
(d) is a stress distribution diagram of concrete, Figure 16 is an adhesive stress distribution diagram, (&) is a distribution diagram where adhesive stress changes over time, (b) strength is Distribution diagram when the strength deteriorates, (e) Distribution diagram when the strength does not deteriorate, Figure 17 is a configuration diagram of the steel pipe-concrete adhesive strength test block, Figure 18 (a) shows the adhesive stress between the steel plate with protrusions and concrete Figure 19 is a plan view of the strength test block, (b) is a side view, Figure 19 is an adhesion stress distribution diagram when repeated pulling force is applied to the block in Figure 18, Figure 20 (a),
(b) and (e) are state diagrams of shrinkage over time of concrete with a diameter of 2,000 fins, Figure 21 (a) is a front view of a conventional cast-in-place reinforced concrete pile with a constant vertical load of 7000, and (b) is a A front view of the expanded cast-in-place steel pipe concrete pile according to the present invention, (C) is a bending moment distribution diagram due to ground displacement, (d) is a ground condition diagram, and Figures 22 (a) and (b)
is a configuration diagram of a steel pipe with projections. 1: Pile, 2: Reinforced concrete, 6: Steel pipe with protrusions. Representative Patent Attorney Sanro Kimura Fig. 4 2 (1) mm Fig. 6 Fig. 5 (a) ■・Dinghuan (P) 2004■ 600 Fig. 5 (b) 1.1・-'i(/ ”) Fig. 7 (a) (b) (c) ) (c) N A direct bending size 'Leech-me>v (t, m) Fig. 10 (a) (c) (b) N 6i wlTi-me>%-(t, m) Fig. 11 Fig. 13 Figures (a) (b) (c) (d) N pigeon Figure 21 (o) (b) (c) 1++1'' main-men ■ (f, m) (m) Figure 22 (b)

Claims (1)

[Claims] A cast-in-place steel pipe concrete IJ-concrete pile characterized in that cross-sectional reinforcement is achieved by wrapping a steel pipe having projections formed by rolling on the inner surface over the entire length of the cast-in-place conocrete pile.