JP2536222Y2 - Damping steel pile - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a damping steel pile capable of exhibiting a reliable damping performance even for small to medium-sized earthquakes.

[0002]

2. Description of the Related Art Conventional steel piles include steel pipe piles and H-shaped steel piles made of ordinary steel.

[0003]

[Problems to be solved by the present invention] Since conventional steel piles are designed to have a predetermined bending strength so as to be able to withstand a large earthquake, the steel pile is used when a large earthquake occurs. There is no problem with the ability to absorb and attenuate the energy of the steel pile, but when a small or medium-sized earthquake occurs, it is within the elastic range and the damping performance is weak. As a result, the amplitude of the upper structure increases, and there is a problem that a sufficient energy absorbing effect cannot be obtained.

An object of the present invention is to solve the above-mentioned problems and to provide a damping steel pile capable of exhibiting a reliable damping performance not only for a large earthquake but also for a small earthquake.

[0005]

In order to achieve the above object, in the present invention, the whole or a part of the surface of the pile head of the pile body made of ordinary steel is provided with a ring shape or a plate shape made of extremely mild steel. In the event of an earthquake, the end member of the pile body and the end member reaches the yield point earlier and is provided with a damping performance by plastic deformation of the end member. .

[0006] The principle of the mechanism by which the damping steel pile having the above structure absorbs seismic energy will be described. (1) In the case where both the ordinary steel pile main body and the extreme mild steel end member yield in bending, the relationship between the bending moment M and the curvature φ of the ordinary steel pile main body and the extreme mild steel end member yields as shown in FIG. The curvatures when the moments M _M and M _S act are φ _M and φ _S , and when a bending moment exceeding the yield moments M _M and M _S occurs, plastic deformation occurs. (EI) _M , (EI) in FIG.
_S is the bending stiffness, E is Young's modulus, and I is the second moment of area. The relationship between the bending moment and the curvature obtained by combining the two forms a hysteresis loop as shown in FIG. 2, in which the extreme mild steel end member reaches the yield point before the ordinary steel pile body yields.

Therefore, when a large earthquake occurs in which both the ordinary steel pile main body and the extremely mild steel end member yield,
The hatched portion in FIG. 2 is given as an energy absorbing effect due to plastic deformation of the extreme mild steel end member, thereby more effectively damping the vibration of the superstructure. (B) When only the extreme mild steel end member yields by bending The relation between the stress σ and the strain ε between the ordinary steel pile main body and the extreme mild steel end member is the straight line in FIG. 3A and the history in FIG. as indicated by the loop, but ordinary steel pile body is deformed in the elastic region, the pole when mild steel end member are plastically deformed beyond the yield point, when restoring stress σ to zero residual strain epsilon ₁ occurs.

Considering the relationship between the stress and the strain when the two are combined, the residual strain when the stress σ returns to zero is an intermediate value ε ₂ (0 <ε ₂ <) between zero and ε _1. ε ₁ ), the extremely mild steel end member is loosened corresponding to (ε ₁ −ε ₂ ) and does not contribute to the bending rigidity. Therefore, looking at the relationship between the bending moment M and the curvature φ, when the bending moment M is close to zero as shown in FIG. 4, only the bending rigidity (EI) _M of the ordinary steel pile main body is effective, and the bending moment M Is slightly increased and the looseness of the extreme mild steel end member disappears, the sum of the bending stiffness of the ordinary steel pile body and the extreme mild steel end member (E
I) _M + (EI) _S now contributes as stiffness,
When the bending moment M further increases and the extremely mild steel end member bends and yields, a hysteresis loop is drawn in which only the bending rigidity (EI) _{M of the} ordinary steel pile main body contributes.

Since the hysteresis loop shown in FIG. 4 has a slip-shaped bilinear shape, when a small-to-medium-sized earthquake occurs in which only the extremely mild steel end member yields without yielding the ordinary steel pile body, As a seismic energy absorbing effect of the hysteresis loop, a vibration damping force for attenuating the vibration of the upper structure is applied, and a vibration damping force similar to that of a slippery type due to slip is also applied.

[0010]

FIG. 5 shows a steel pile 10 installed underground and a steel pile 1
FIG. 6 and FIG. 7 are schematic views showing an upper structure 1 supported by a steel pipe 0 and FIGS. 6 and 7 show an embodiment in which the present invention is applied to a steel pipe pile. FIG. 6 shows a ring-shaped end member 10b made of extremely mild steel on an outer peripheral surface of a pile head of a pile body 10a made of ordinary steel.
And the upper edge is aligned with the end face of the pile body 10a and fixed by welding.

FIG. 7 shows an elongated plate-like end member 10 made of extremely mild steel on an outer peripheral surface of a pile head of a pile body 10a made of ordinary steel.
b is arranged in parallel with the length direction at an appropriate interval in the circumferential direction, and is fixed by welding so that the upper end edge coincides with the end face of the pile main body 10a.

[0012]

[Effects of the Invention] As described above, according to the present invention, an extremely mild steel end member having a lower yield point is welded to the pile head of the ordinary steel pile main body, and when an earthquake occurs, the ordinary steel and the pole are welded. The vibration damping function is provided based on the principle of energy absorption by the hysteresis loop that combines the characteristics of mild steel with each other, so resonance occurs not only when a large earthquake occurs but also when a small earthquake occurs. A vibration damping steel pile exhibiting reliable damping performance without inducing a phenomenon can be obtained.

Further, according to the present invention, a desired vibration damping effect can be obtained by a very simple structure in which an extremely mild steel end member is welded to the pile head of the ordinary steel pile. There is an advantage in that there is no need to install a device, and maintenance and management of vibration damping devices are not required at all.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a moment and a curvature at the time of bending yield of a normal steel pile main body and an extremely mild steel end member.

FIG. 2 is a diagram showing a relationship between a bending moment and a curvature obtained by combining the ordinary steel pile main body and the extreme mild steel end member of FIG. 1;

FIG. 3 is a diagram (A) showing the relationship between stress and strain in the elastic region of the ordinary steel pile main body, and the stress and strain until the stress returns to zero after the extremely mild steel end member undergoes plastic deformation due to bending yield. FIG. 3B is a diagram (B) showing the relationship.

FIG. 4 is a hysteresis loop diagram showing a relationship obtained by combining FIGS. 3A and 3B with a relationship between bending moment and curvature.

FIG. 5 is a schematic side view showing an upper structure and a pile supporting the upper structure.

FIG. 6 is an end view (A) and a side view (B) of a pile head showing an embodiment of the damping steel pile of the present invention.

FIG. 7 is an end view (A) and a side view (B) of a pile head showing another embodiment of the damping steel pile of the present invention.

[Explanation of symbols]

 Reference Signs List 10 steel pile 10a ordinary steel pile main body 10b extremely mild steel end member

Claims (1)

(57) [Scope of request for utility model registration] 1. A ring-shaped or plate-shaped end member made of extremely mild steel is welded to the whole or a part of the surface of a pile head of a pile body made of ordinary steel. A vibration damping steel pile, wherein the end member reaches the yield point earlier, and a damping performance due to plastic deformation of the end member is provided.