JPS59145825A - Reinforcement of vertical joint of underground continuous wall - Google Patents

Abstract

PURPOSE:To raise the safeness of a structure by a method in which when an iron bar cage is installed on the basal end of coupling iron bars, reinforcing iron bars set in parallel with the outside of the tips of coupling iron bars on the following wall of the preceding wall are attached through width-limiting iron bars. CONSTITUTION:A reinforcement member 4 of a ?-shaped bent form is set in a multi-stage ladder form and welded to the basal end portion of the coupling iron bars 2'b of the end of the preceding wall side of iron bar cage 2'. The right- angled portion of the ends of the member 4 is formed into reinforcing iron bars 4a in parallel with the coupling iron bars 2'b on the side of the iron bar cage 2' and fixed with vertical iron bars 4e, and the intermediate portion is formed into width-limiting iron bars 4b serving shear reinforcement. Even when the pressures of soil and water (not illustrated) are applied to the vertical coupling so reinforced, abrupt development of bending cracking to bond cracking in the lap coupling does not occur and no breakage of the lap coupling takes place, and therefore, cracking caused by the pressures of soil and water can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for reinforcing vertical joints of reinforced concrete cast-in-place walls, that is, underground continuous walls.

Between each unit wall of an underground continuous wall constructed by repeatedly excavating a trench, suspending a reinforcing bar cage, and pouring concrete,
Normally, as shown in Fig. 1, horizontal main reinforcements are penetrated and protruded through the weir plate 3 of the leading wall, which is buried on the trailing wall side and becomes the joint surface, to form the joint reinforcing bars 2a. At that time, on the trailing wall side of the weir plate 3, that is, at the vertical joint, the reinforcing bar cage inserted in the groove /' for the trailing wall shown in Figure 1 is The joint reinforcing bar λ'b of λ' and the joint reinforcing bar 2a of the leading wall are combined into a lap joint when concrete is poured into the trailing wall.

However, in order to facilitate the insertion of the reinforcing bar cage, the reinforcing bars are arranged so that the joint reinforcing bars λ'b on the leading wall side are inside the joint reinforcing bars 2a on the trailing wall side of the leading wall, as shown in Figure 1. There must be. This results in the following structural defects.

That is, when an out-of-plane force P such as earth water pressure is applied to a joint structure in which the joint reinforcing bar λ'b on the leading wall side of the trailing wall is inside, as shown in FIGS. 3 and 9, first, A bending crack Cm occurs at the tip of the reinforcing bar of the leading wall joint, that is, the base end of the reinforcing bar of the trailing wall joint, and further develops into an adhesion crack cb between the reinforcing bars of the lap joint and a shear crack 08 at the center of the joint, causing the lap joint to fail. There is great danger.

However, if the joint reinforcing bars 2'b of the trailing wall are placed outside of the leading wall joint reinforcing bars Ua, the joint reinforcing bars 2'b will swing when the trailing wall reinforcing bar cage is lifted, and the joint reinforcing bars of the leading wall will It is difficult to insert the reinforcing bar 2a because the space between the reinforcing bar 2a and the groove wall surface is narrow.

Of course, this problem would not occur if the lap joints were made longer or if shear reinforcing bars were installed that intersected the lap joints, but
The former is uneconomical, and the latter involves the work of moving the reinforcing steel in the stabilizing liquid underground, and neither is an effective solution.

The present invention has been made in view of these drawbacks, and the above-mentioned drawbacks are overcome by attaching a reinforcing member to the outside of the base end of the leading wall side joint reinforcing bar 2'b of the trailing wall reinforcing bar cage. It is something to be solved.

Hereinafter, the present invention will be described in detail with reference to the drawings again.

As shown in the perspective view of FIG. 3, the first embodiment is a reinforcing member bent into a U-shape at the base end of the joint reinforcing bar λ'b at the leading wall side end of the reinforcing bar cage. The vertical reinforcing bars 9a are arranged on the side of the reinforcing bar cage and parallel to the joint reinforcing bars x'b, and the vertical reinforcing bars Fixed.

And in the middle part is the stopper reinforcing bar 41 which also serves as a shear reinforcing bar.
form b. When the reinforcing bar basket is dropped into the groove, the reinforcing reinforcing bars 11a are set parallel to the outside of the tip of the joint reinforcing bars of the preceding wall, as shown in FIG.

Even when earth water pressure P is applied to the vertical joints reinforced in this way, there is no rapid development of adhesive cracks from bending cracks to the lap joints as shown in Figure 7, and it has been confirmed through experiments that the lap joints will not fail. .

The first embodiment is shown in a perspective view in Fig. g. Troughs placed vertically at both ends of a large number of suspended reinforcing bars +b welded to the base end of each stage of the joint reinforcing bars ko'b on the leading wall side of the trailing wall via angle steel lId placed vertically. A large number of reinforcing reinforcing bars lIa are arranged and welded in parallel to the joint reinforcing bars j'b via the angle steel 'lc', and are manufactured integrally with the reinforcing bar cage λ'.

Then, reinforcing reinforcing bars 4Za are placed outside the joint reinforcing bars 2a of the preceding wall.
(Fig. 9), and even if an out-of-plane force is applied to the completed joint, there will be little adhesion cracking in the lap joint (Fig. 9).
θ diagram) is the same as in the first embodiment.

The diameter of the reinforcing reinforcing bar is preferably the same as or larger than that of the joint reinforcing bar, and the overlapping length thereof is preferably approximately /θ times the diameter of the reinforcing bar λ'.

Next, if we consider the effects of reinforcing members on the structural performance, firstly, reinforcing reinforcing bars +a delay the occurrence of bending cracks Cm, and second, stopper reinforcing bars llb and joint reinforcing bars 2a of the preceding wall
By restraining the tip of the overlap joint reinforcing bars cb
As a result, the strength of the joint against shear force is maintained.

As described above, the present invention is easy to implement because a predetermined reinforcing member is attached to a predetermined position of a reinforcing bar cage.
In addition, it has the advantage of improving the structural performance of the joint, such as strength, rigidity, and toughness. Thermal theory: The length of the reinforcing member is shorter than that of the joint reinforcing bar, so it won't swing when the reinforcing bar cage is hung and cause problems with insertion.

〔Example〕

As already quoted in part, an experiment was conducted in which a concentrated load was applied in an out-of-plane direction to the joint or its vicinity.

That is, a part of the wall with the joint in the center is horizontally suspended to form a simple beam, and a centrally concentrated load is applied to it. As explained above, the test specimens shown in FIGS. 7 and 10, which are joints, had cracks as shown in the respective figures.

The effect brought about by this difference in cracks is
This appears in the load-deformation curves shown in FIG. That is, in the test specimens according to the prior art (Bs3 (Fig. 3) and B S , ?' (Fig. 9)), the lap joints failed all at once before yielding of the main reinforcement on the tension side, whereas the test specimens according to the present invention The structural performance such as strength, rigidity, and toughness of the joint members of the body (BS, ?-1 (Fig. 7) and BS, ?'-2 (Fig. 1O)) has been greatly improved, and after plastic deformation, the structure It makes a huge contribution to the safety of things.

Incidentally, the design values for the specimen in this experiment are shown below.

size ! 00xk00x2300 (cl-,?rij
lm) Reinforcing bar (SD-30) Upper bar ff-DIJ lower bar g-D/A Shear connector 6-D/B overlap joint length t-, 74+tφ (S 2B)

[Brief explanation of the drawing]

FIGS. 1 and 2 are plan views showing a general construction method for a joint part of an underground continuous wall in the order of construction, in which conventional reinforcing bars are used. 3 and 9 are side views of a test specimen showing cracks when an out-of-plane force is applied to a conventional unreinforced joint. FIG. 5 is a perspective view showing the first embodiment of the present invention, and FIG. 6 is a plan view showing the state in which the first embodiment is sunk into a groove. FIG. 7 is a side view of the test specimen showing cracks in the joint due to out-of-plane force. Figures 1 to 1O are explanatory diagrams of the first embodiment, and each figure is a This corresponds to Figures r to 7. Figures 1/1 and 12 are similar to Figures 3, 7, and 9.
FIG. 1 is a graph showing the load-deformation curve of the test specimen shown in FIG. 11/'...Groove, -'...Reinforcing bar Basket 2a...Joint reinforcing bar on the trailing wall of the leading wall λ'b...Joint reinforcing bar on the leading wall of the trailing wall 3...Se
Plate... Reinforcement member lIa... Reinforcement reinforcing bar b... Canceled reinforcing bar lIc... Angle steel bars attached to both ends of the discontinued reinforcing bar d.
・・Angle steel da e that connects the joint reinforcing bar B and the suspended reinforcing bar +b
... Vertical reinforcing bars 5 connecting reinforcing bars 4Za... Partition plate 6 ... Shear connector Figure 1 Figure 6 Figure 9 Figure 11

Claims (1)

[Claims] With respect to the joint reinforcing bars on the trailing wall of the leading wall that protrudes from the joint surface of the leading wall of the underground continuous wall, there are joint reinforcing bars on the leading wall arranged to form a lap joint located inside the joint reinforcing bars on the trailing wall. In the trailing wall reinforcement section, when the reinforcing bar basket is installed at the predetermined position at the base end of the joint reinforcing bar, the reinforcing reinforcing bar is placed parallel to the outside of the tip of the joint reinforcing bar on the trailing wall side of the leading wall. A method for reinforcing vertical joints of underground continuous walls, characterized in that the vertical joints are installed through reinforcing bars.