JPS6314133B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for assembling a pile cap and a footing in an underwater bridge pier in which the footing of a substructure of the pile foundation type is installed underwater.

In recent years, underwater bridge foundations have been designed with pile cap footings that are either in contact with the seabed or submerged below the seabed in order to achieve rational design and to minimize the reduction in river basin area. Conventionally, when building piles and footings in such a structure, a footing formwork with steel frames and reinforcing bars set in advance was installed on the pile cap, and underwater concrete was poured.

In this case, it is common to cast prepacked underwater concrete, but due to the level control of mortar injection and the arrangement shape of structural members, mortar laitance may accumulate in the large parts of the piles and footings, or may form in layers. It gets stuck and is difficult to securely attach.

The mechanical function of the footing is to transmit vertical loads and horizontal forces acting from the superstructure to the piles. The thickness of the footing is increased to prevent variations in the axial force acting on the pile cap due to bending deformation of the footing. Therefore, the weight of the pile cap footing becomes large, and the horizontal inertia force during an earthquake becomes large, resulting in a structural disadvantage, especially when the sea-based ground is soft. In addition, there is a large amount of concrete, and when prepackaged construction is performed, it is constructed all at once without any breaks.
It is uneconomical.

The present invention was proposed in order to eliminate such problems, and in the construction of underwater piers in which the footing of the substructure in the form of pile foundations is installed underwater,
A footing formwork for underwater concrete placement, which is lined with prestressed steel material, is submerged and set so as to surround the pile head, and the prestressed steel material is also surrounded over the pile head, and then underwater concrete is placed in the footing formwork. This relates to an underwater pile cap construction method characterized by introducing prestress through the prestressed steel material after driving.

In the conventional construction method, underwater concrete is placed between the pile cap and the footing, and the adhesion force is used to stabilize the structure. Management is impossible.

However, according to the present invention, as described above, the PC
A footing formwork for underwater concrete placement with a steel interior was set in a submerged manner so as to surround the pile head, prestressed steel material was surrounded over the pile head, and underwater concrete was placed within the formwork. Later mentioned above
By introducing prestress through the prestressing steel material and tightening the pile head within the footing concrete, the pile head is attached to the footing, so by introducing an appropriate prestress, a reliable structure can be achieved. becomes possible. Furthermore, if the amount of prestress is controlled using a commonly used tension control method, the condition of the pile cap and footing can be adequately controlled.

In addition, by introducing a large prestress, not only can the embedding length of the pile head into the footing be reduced, thereby reducing the footing thickness, but also because the footing itself is a prestressed concrete structure. It is economical because the required footing thickness can be reduced in response to the bending moment that occurs.

In addition, by using a PC cable, you can take advantage of the flexibility of the cable and avoid piles.
PC cables can be placed.

Therefore, in the present invention, by surrounding and arranging the PC steel material in a loop shape over the pile head, sufficient prestress can be introduced to the end pile, and the structural integrity of the end pile can be improved. No problems arise. Furthermore
By using an intermediate movable anchoring tool for tensioning and anchoring the PC steel, the PC steel can be placed continuously.
As the number of anchorage devices is reduced, at the same time the prestress transmission is improved.

The present invention will be described below with reference to the illustrated embodiments.

At the same time as penetrating the pile 1 into the underwater foundation A,
Formwork receiving piles 2 are inserted into the outer periphery of the group. (See Figure 1) On the other hand, the footing formwork 3 is manufactured in the dock. In the same formwork 3, prestressing steel material 4 and reinforcing bars are placed as necessary. Further, a water pressure-resistant work box 5 is attached to the formwork 3. Note that the water pressure-resistant work enclosure 5 may be connected to a part of the main structure of the pier so that workers can enter and exit from the pier and materials can be carried in and out.
(See Figure 2) Next, the formwork 3 is sunk as shown in Figure 3, and the formwork receiving pile 2 is placed so as to surround the pile head of the pile 1.
Set it on top. At this time, the work box 5 is water pressure resistant,
Watertight structure prevents water from entering. When the formwork 3 is set, the prestressing steel material 4 is placed so as to surround each pile head. Next, underwater concrete 6 is poured into the formwork 3. (See Figure 4) Next, in the space inside the work enclosure 5, the prestressed PC steel material 4 is anchored under tension using the intermediate movable anchoring device 7, and the footing and the pile head of the pile 1 are connected to each other. securely anchor. (See Figure 5) Figures 6 and 7 show details of the formwork 3,
An opening 3b into which the pile head of the pile 1 is inserted is bored in the bottom plate 3a. In the figure, reference numeral 8 indicates reinforcing bars arranged within the formwork 3. Note that an auxiliary work canopy may be provided adjacent to the work canopy 5. Furthermore, as shown in FIG. 8, work shelters 5 may be provided at the four corners of the footing. As shown in Fig. 8, large cables are arranged as prestressing steel material 4 in a concentrated manner around the outer periphery of the first group of piles.
By controlling the jacks in several places by remote control,
Prestressing may be introduced from above the water, and this method is advantageous in deep water.

Further, as shown in FIG. 9, the prestressing steel materials 4 may be arranged concentrically to introduce prestress from a plurality of work boxes 5.

Note that tension anchoring of the PC steel material 4 is performed using an intermediate movable anchoring device 7.

FIG. 10 to FIG. 13 show an example thereof,
A movable anchor 7 arranged in the work space of the work box 5
A center hole type jack 11 is connected to the center hole jack 11 via a curb chain air 9 and a jack jack air 10, one end of the loop-shaped PC steel material 4 is wedged to the anchor anchor 7 with a wedge 12, and the other end is connected to the anchor anchor 7, Each of the chairs 9, 1
0, tensioned with the jack 11, wedged to the anchoring tool 7 via a wedge 13, and then concrete 14 is poured into the work space. In addition
Grouting between the PC steel material 4 and the sheath in the footing concrete 6 is the same as in the conventional method.

Note that FIGS. 14 and 15 show cases in which the PC steel material 4 is in the work enclosure 5 and cases in which it is not, respectively.

FIGS. 16 to 19 show another embodiment of the intermediate movable anchoring device, which includes a bearing plate 17 having a notch 15 on the outer periphery and a PC steel anchoring hole 16 arranged in the inner center,
A small bearing plate 19 with a row of notches 18 on the outer periphery
A jack 20 is interposed between both bearing plates 17 and 19, and the jack main body 20a is attached to the anchoring plate 1.
9, and the jack cylinder 20b.
is fixed to the anchoring plate 18, and one end of the loop-shaped PC steel material 4 is attached to the anchoring grip 2 in the notch 15 of the anchoring plate 17.
1, the other end is inserted into the anchoring hole 16 of the anchoring plate 17, and the anchor is anchored in the notch of the anchoring plate 19 via the anchoring grip 22.
Prestress is introduced by tensioning the PC steel material 4 and anchoring it in the anchoring hole 16 via the anchoring wedge 23.

Although the present invention has been described above with reference to embodiments, the present invention is, of course, not limited to such embodiments, and can be modified in various ways without departing from the spirit of the present invention. .

[Brief explanation of the drawing]

1 to 5 are longitudinal cross-sectional views showing an embodiment of the underwater pile cap construction method according to the present invention; FIG. 6 is a longitudinal cross-sectional view showing the arrangement of PC steel materials and reinforcing bars in the footing form; Figure 7 is the arrow view of Figure 6, Figure 8.
Figures 1 and 9 are plan views showing the arrangement of PC steel materials and piles inside the work enclosure, Figures 10 to 13 show the tension anchoring work process for PC steel materials, and Figures 10 and 12 are longitudinal side views. Figures 11 and 13 are plan views;
Figures 14 and 15 are vertical side views showing the state of tension anchoring work for prestressed steel. Figure 14 shows the case where the prestressed steel is in the work box, and Figure 15 shows the case where the prestressed steel is not in the work box. Fig. 16 is a plan view showing another example of tension anchoring work for prestressed steel material, Fig. 17 shows the case.
Figures 18 and 19 are taken in the direction of arrows XI in Figure 16, respectively.
-Figure XI. 1...Pile, 3...Footing formwork, 4...PC steel material,
6...Underwater concrete.

Claims (1)

[Claims] 1. In the construction of an underwater pier in which the footing of a pile foundation-type substructure is installed underwater, the footing formwork for underwater concrete placement, which is lined with prestressed steel, is set to subside so as to surround the pile head, and the Surround the pile head with steel material,
A method for constructing an underwater pile cap, characterized in that, after submerged concrete is placed in the footing formwork, prestress is introduced through the prestressing steel material.