JP2870439B2 - Mortar-filled rebar joint sleeve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mortar-filled reinforcing joint sleeve for use in precast concrete building materials.

[0002]

2. Description of the Related Art A mortar-filled rebar joint sleeve for joining rebar of precast concrete building materials is disclosed in
It is publicly known, for example, from JP-A-3-7453. This known sleeve is made of cast iron, and has a tubular body whose axial direction is the same as or smaller than the center, a plurality of inner peripheral projections formed on the inner periphery of the main body, and mortar provided at both ends. The main body had the same radial thickness over its entire length except for the inner peripheral projections. This thickness was determined based on the allowable stress and safety factor of the cast iron and the specified load.

[0003]

The inventor of the present application attached a strain gauge to the outer peripheral surface of a known sleeve body,
Reinforcing bars were passed through the main body from both sides, and mortar was filled inside to join the reinforcing bars on both sides, and then a tensile force was applied to the reinforcing bars on both sides. At this time, the axial distribution of the tensile stress acting on the main body was measured. The results are as shown in FIG. 3, and it was found that the tensile stress σ was the largest at the central portion of the main body and gradually decreased toward both ends. This is because, other than at the central portion of the main body, the rebar inserted into the main body also bears the tensile load applied to the joint by the interposition of the mortar, and the rebar burden increases toward the end of the main body.

[0004] The present invention has been made based on the above findings, and an object of the present invention is to reduce the wall thickness of a sleeve main body in a portion where a rebar bears a part of a tensile load, thereby reducing the weight of a sleeve which is lighter than a conventional sleeve. Is to provide.

[0005]

Means for Solving the Problems In order to achieve the above object, means adopted by the present invention is to gradually increase the thickness of the sleeve body in the radial direction from the central portion to both end portions, except for the inner peripheral projection portion. Or that it has been continuously reduced. The radial thickness of the body is set such that the tensile stress acting thereon is equal to or slightly less than the tensile stress of the central part. It is desirable that the outer peripheral surface of the sleeve has the same shape and dimensions as before, and that the inner diameter of the portion of the inner peripheral surface other than the inner peripheral projections is made larger than before to reduce the thickness.

[0006]

The sleeve of the present invention has the same radial thickness at the central portion as that of the conventional body having the same thickness in the radial direction, but has the same thickness as that of the conventional body except at the central portion. Since it is thinner than the conventional one, the weight is reduced accordingly. Thereby, the operation of transporting the sleeve and the operation of attaching it to the formwork are easier than before. Although the tensile stress generated in portions other than the central portion of the main body becomes larger than before, it does not exceed the allowable value, so that the safety of the sleeve can be sufficiently ensured.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A sleeve according to the present invention will be described based on an embodiment shown in the drawings. A cylindrical main body 10 shown in FIG. 1 has a portion having left and right inner peripheral projections 11, 12, 13, and 14, and a left and right first inner peripheral projection 11,
Except for the central portion between 11, the radial thickness decreases continuously as it approaches the left and right ends. The wall thickness of the part thinner than the center of the main body is set so that the tensile stress at that part is equal to or smaller than the tensile stress at the center of the main body.

The cylindrical body 10 shown in FIG. 2 has a thickness in the radial direction that exceeds the left and right inner peripheral projections from the center, except for the portions where the left and right inner peripheral projections 11, 12, 13, and 14 are present. Decrease step by step. The thickness of the central portion located between the left and right first inner peripheral projections 11 and 11 is maximum, and the thickness of the portions located at the left and right ends is minimum. The thickness of the part thinner than the central part is set so that the tensile stress in that part is equal to or smaller than the tensile stress in the center of the main body 10.

The main body 10 shown in FIGS. 1 and 2 has the same thickness at the central portion and the inner peripheral projection as that of the conventional body having the same tensile strength and a constant thickness. Since the thickness of the other parts is thinner than the conventional one, the weight is reduced accordingly. This simplifies the task of transporting the sleeve and attaching it to the formwork, and saves material, thereby reducing costs.

Although a cylindrical body having a constant outer diameter has been shown as an embodiment, it goes without saying that the present invention can be applied to a sleeve having a body having a truncated cone on one or both sides in the axial direction. As in the case of the conventional sleeve, a reinforcing bar is passed through the sleeves of FIGS. When a tensile load is applied to the sleeve, the tensile stress generated in the portion thinner than the central portion does not become larger than the tensile stress generated in the center.

[0011]

As described above, the sleeve of the present invention is different from the conventional body in which the radial thickness of the main body is constant.
The thickness of the central part of the main body is the same as that of the conventional one, but the thickness of the sleeve decreases continuously or stepwise toward the both ends, thereby reducing the weight compared to the conventional one. This provides an excellent effect that the work of attaching to the formwork is facilitated and the cost for producing the sleeve is reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a first embodiment of the present invention,

FIG. 2 is a longitudinal sectional view of a second embodiment,

FIG. 3 is a graph showing an axial distribution of tensile stress measured by applying a tensile load to a conventional sleeve,

[Explanation of symbols]

 10: body, 11, 12, 13, 14: inner projection

Claims (1)

(57) [Claims] 1. A cylindrical main body (10) having a constant outer diameter and a plurality of inner peripheral projections (11, 12, 13, 1) formed on the inner periphery of the main body.
4), the radial thickness of the main body excluding the inner peripheral projection portion is such that the tensile stress acting thereon is equal to or slightly smaller than the tensile stress of the central portion. Thus, the mortar-filled reinforcing joint sleeve is characterized in that the central portion in the axial direction is maximum, and the radial thickness of the outer portion is continuously or gradually reduced.