KR100956518B1 - A Reinforcing Structure For Improved Transmission Of Slab-Column Joint - Google Patents

Abstract

According to the present invention, the core and the dowel reinforcement are installed at the joint of the slab and the column, so that the load transfer ability from the upper pillar to the lower pillar is improved even when the concrete strength ratio of the pillar and the slab is increased due to the strength of the joint. The present invention relates to a reinforcing structure for transferring load to a joint where a torsion preventing plate is attached to prevent torsion with the concrete and to ensure integral behavior.

Connection, Core, Dowel Rebar, High Strength Concrete

Description

Reinforcing Structure For Improved Transmission Of Slab-Column Joint

1 is a side cross-sectional view showing a conventional junction,

Figure 2a to 2d is a side cross-sectional view showing each embodiment in the present invention,

3A to 3D are plan views illustrating the junctions J in each of the embodiments shown in FIGS. 2A to 2D;

4A-4D are exploded perspective views of each embodiment of the present invention shown in FIGS. 2A-2D,

5 is a perspective view showing a torsion preventing plate,

Fig. 6A shows the experimental apparatus and the member dimensions, and Figs. 6B and 6C are cutaway views showing the reinforcement details of the column and the slab, respectively.

7 is a graph comparing the analysis results of the test specimen NS and PS with the experimental results,

8A to 8D are side cross-sectional analysis diagrams showing the yielding state of reinforcing bars in the ultimate load stage in each test body,

9 is a graph showing the relationship between the axial load and the strain of the slab-column joint specimen.

<Description of the symbols for the main parts of the drawings>

10: upper pillar 20: slab

30: lower pillar 40: longitudinal rebar

50, 60: core 70, 80: dowel rebar

According to the present invention, the core and the dowel reinforcement are installed at the joint of the slab and the column, so that the load transfer ability from the upper pillar to the lower pillar is improved even when the concrete strength ratio of the pillar and the slab is increased due to the strength of the joint. The present invention relates to a reinforcing structure for load transfer to a slab-column joint, in which a torsion preventing plate is attached to prevent torsion with concrete and integral behavior is secured.

In general, structural members subjected to axial force, such as pillar members, have sufficient compressive strength. However, when ordinary concrete is used to reinforce such compressive strength, its cross section becomes too large, which limits the space of the geometry and has disadvantages in terms of construction. have. Therefore, the use of high-strength concrete for such a pillar member can increase the space utilization by reducing the cross section of the pillar while reinforcing sufficient compressive strength, and in recent years, the demand for the use of high-strength concrete as a pillar member for large and high-rise structures is increasing.

However, as shown in FIG. 1, when the pillar member is made of high-strength concrete, the slab between the pillar and the pillar is inevitably economically viable, and when such a construction form is taken, the load of the upper pillar of the slab is increased. The lower pillars reach the lower column. When the ratio of slab and pillar concrete is high, even if the column is reinforced with high-strength concrete, the relatively weak rigid slab underneath the load transfer to the lower column. There is a problem that can not be fully exhibited the advantage of using high-strength concrete in the column can not be fully exhibited.

In addition, even in the case of intensive reinforcement at the joint (J) of the slab and the column to reinforce the load transfer ability from the column to the slab, it is easy to cause torsion due to the joining of dissimilar materials, structural defects due to the difference in deformation amount, etc. there is a problem.

 The present invention has been made to solve the above problems, reinforcing the rigidity of the slab and the joint to strengthen the load transfer capacity, even by this reinforcement slab-pillar can prevent the difference in the amount of twist or deformation Provide reinforcing structures for load transfer at the joints.

In order to achieve the above object, the reinforcing structure for the slab-column junction load transfer of the present invention is the upper column, the slab, and the lower column is composed of the upper column and the lower column and the column junction, the high column and the lower column ; A plurality of longitudinal reinforcing bars penetrating the upper pillar, the slab, and the lower pillar; The slab is characterized by consisting of a core formed of high-strength concrete in the interior surrounded by the longitudinal reinforcement.

The core is characterized in that it is made of high-strength concrete only in the center of the slab height in contact with the upper column.

On the other hand, the reinforcing structure for the connection load transfer of the present invention is the slab and the column joint consisting of the upper column, the slab, and the lower column, the upper column and the lower column made of high-strength concrete; A plurality of longitudinal reinforcing bars penetrating the upper pillar, the slab, and the lower pillar; A plurality of dowel bars formed on the joint portion; Characterized in that consisting of; plate-shaped torsion preventing plate attached to the dowel rebar.

In addition, the torsion preventing plate is characterized in that it is composed of a ring inserted into the dowel rebar and the body portion attached to the right angle to the ring.

In addition, the body portion is characterized in that one or more shear rods are attached in a perpendicular direction.

In addition, the dowel reinforcing bar is configured to the junction portion, characterized in that consisting of a transmission portion formed from the upper column to the center of the slab height and a punching portion bent in a centrifugal direction integrally from the transmission portion.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

Figures 2a to 2d is a side cross-sectional view showing each embodiment in the present invention, Figures 3a to 3d is a plan view showing a portion of the junction (J) in each embodiment shown in Figures 2a to 2d, 4A to 4D are exploded perspective views of respective embodiments of the present invention shown in Figs. 2A to 2D, Fig. 5 is a perspective view showing a torsion preventing plate, Fig. 6A shows an experimental apparatus and member dimensions, Figs. 6B and Fig. 6c is a cutaway view showing the details of the reinforcement of the columns and slabs, respectively.

The reinforcing structure for the load transfer of the joint of the present invention is a conventional slab-column structure in the upper column 10, the slab 20, the lower column 30 and a plurality of longitudinal reinforcing bars 40 and the junction (J) through them Reinforcement structure of the core 50, the semi-core 60, the dowel reinforcement 70 and the bent type dowel reinforcement 80 is presented.

The number of longitudinal reinforcing bars 40 can be selected in consideration of the design load and the like, but in FIG.

The upper pillar 10 and the lower pillar 30 is preferably composed of high-strength concrete for reducing the column cross-section and reinforce the compressive rigidity.

Thus, when the upper column 10 and the lower column 30 is composed of high-strength concrete, when the slab 20 is composed of general concrete, the upper column 10 is formed by weakening the rigidity of the slab-column joint J. In order to prevent the load from being transmitted to the lower column 30 and the brittle fracture occurs in the slab 20 portion of the slab-column joint J, the core 50, semi- A core 60, a dowel rebar 70 and a bent dowel rebar 80 are presented.

First, as shown in FIGS. 2A, 3A, and 4A, the core 50 is formed of high strength concrete in a configuration formed inside the slab 20 surrounded by the longitudinal reinforcing bars 40. Thus, bridging fracture can be prevented from occurring at the slab portion of the junction J by reinforcing the load transfer at the junction J by the high-strength concrete constrained laterally by the core 50, that is, the longitudinal rebar 40. It will be possible.

In particular, in the present invention, as shown in Figures 2b, 3b, and 4b to present a semi-core 60, the semi-core 60 is a high-strength concrete only up to the center of the height of the slab 20 in contact with the upper column 10 Characterized in that configured. In other words, the height of the core 60 (semi-core) is to be poured only from the slab 20 in contact with the upper column 10 to the center of the slab 20. This configuration is due to the behavior of the column and slab under load. In other words, under the column load, the joint concrete undergoes greater deformation than the column concrete, but the lateral expansion of the joint is constrained by the perimeter slab. When a load is applied to the slab, the upper part of the joint receives tension and the lower part receives compression. The bending block of the slab constrains the joint at the lower part of the neutral shaft due to bending, but the peripheral slab does not constrain the joint at the upper part of the neutral shaft. Therefore, by configuring the core 60 only in the upper portion from the center of the slab it is possible to reinforce the load transfer in the joint (J).

As such, the strength of the joints J is reinforced by constructing the cores 50 and 60 using the high-strength concrete.

{Experimental Example 1}

In this experiment, four slab-column specimens were fabricated to help understand the slab-column joint behavior under failure load. Specimen NS was constructed from 90 MPa high-strength concrete columns above and below 45 MPa general-strength concrete slabs with a thickness of 150 mm, with the structure shown in FIG. It became. In other words, PS is a test specimen in which high-strength concrete is poured on the slab so that it has a larger area than the contact with the slab of the column. Both specimens were fabricated from 150 mm thick 1350 mm square slabs and 250 mm square columns of 675 mm height above and below the slab. Each specimen was placed in three stages: the first lower column placing, the slab casting two days later, and the upper column placing on the day of slab placing, taking into account the actual construction order. In the case of the extruded part of the test body PS (high-strength concrete part in the slab formed wider than the area in contact with the slab of the column), on the day of placing the slab, high-strength concrete is first placed in the vicinity of the column, and then the rest of the slab is placed in general strength. It was poured into concrete. The high strength concrete in the extruded section then merged well with the general strength slab concrete. In order to improve the load shear force at both ends of the column, the upper and lower column ends were completely restrained by using a steel clamp. FIG. 6A shows the experimental apparatus and the member dimensions, and FIGS. 6B and 6C show the reinforcement details of the column and the slab, respectively. The coating thickness of the slab was 20 mm, and the effective depth d was 120 mm. The longitudinal reinforcement of the column was designed to have continuity for the entire height of the member.

To account for the actual restraint of the slab-column joint, four hydraulic jacks were connected to one hydraulic pump and loads were applied to the four corners of the slab. The slab load was manually operated and measured by load cells installed in each hydraulic jack. Column loads were computerized displacement controlled using a 11,000 kN Universal Testing Machine (UTM) and applied as forged loads. Loads and displacements were also recorded automatically via UTM.

Three LVDTs were installed on each of the two sides of the opposing columns to measure the average strain for the 150 mm slab thickness and 300 mm above and below the slab surface. Small holes were drilled in the slab, allowing the LVDT to measure the average strain of the slab. In addition, strain gauges were installed on the slab and column reinforcement of each specimen. Four were attached to the upper slab reinforcing bar in contact with the column, four were attached to the upper slab reinforcing bar located at the center of the column, and eight were attached to the longitudinal bars of the column. Sixteen strain gauges were embedded.

A column load of 400 kN was applied to fix each test specimen to the UTM. The slab load was then slowly applied, and after applying up to the total slab load, the column load was gradually increased while maintaining the slab load. The total slab load of the specimen NS is the load when the average of the four strain gages at the position intersecting the column face among the strain gages attached to the slab rebar is 2,000 με. In a typical slab-column structure, the strain of 2,000 με around the column corresponds to the full service load. The total slab load applied to the specimen NS was 132 KN, and to observe the effect of the expansion of high-strength concrete, the specimen PS was applied with the same size of the total slab load applied to the specimen NS regardless of the strain of the slab reinforcement. .

In this experiment, three-dimensional nonlinear finite element analysis was performed on slab-column specimens. Since the three-dimensional nonlinear finite element analysis evaluates the stress and deformation of the structure more completely than the experiments, it can help to understand the mechanical behavior of the structure up to the breaking load.

In order to compare the analysis results with the experimental results, the test specimens used in the analysis were to have the same size and the same reinforcement details as the test specimens used in the experiment. In addition, in order to study alternative methods for improving the performance of slab-column joints, the analysis of other test specimens was performed.

Test specimen NS using a plain-strength concrete slab was used as a benchmark specimen to compare the behavior of slab-column specimens reinforced with various methods. One way to transfer axial loads from high strength concrete columns is to "puddled" concrete with high strength concrete at the joints of the slab and around the column. In this experiment, in the case of test specimen PS, high-strength concrete was cast to the slab 2d ('d' is the effective depth of slab) from the column surface during the experiment and finite element analysis.

Test specimens NS-HC and NS-FC were analyzed with high-strength concrete cores constrained by longitudinal bars. Under column loads, the joint concrete undergoes greater deformation than the column concrete, but the lateral expansion of the joint is constrained by the perimeter slab. When a load is applied to the slab, the upper part of the joint receives tension and the lower part receives compression. The bending block of the slab constrains the joint at the lower part of the neutral shaft due to bending, but the peripheral slab does not constrain the joint at the upper part of the neutral shaft. Therefore, the specimen NS-FC was analyzed with the high strength concrete core throughout the joint, whereas the specimen NS-HC had the high strength concrete core only at the upper part of the joint.

In order to verify the applicability of the analysis model to the test body, as shown in FIG. 7, the analysis results of the test body NS and the PS were compared with the test results. The results of the finite element analysis were in good agreement with the experimental results, showing similar behavior in maximum load capacity, ultimate mean strain of the column, and stiffness. In addition, the types of failures presented in the analysis were very consistent with those observed in the experiments.

8a to 8d show the yielding of reinforcing bars in the ultimate loading stage of all test specimens. The thick line indicates the yield of the rebar. The longitudinal reinforcing bars of the specimen NS column yielded in the order of the upper column, the lower column, and the joints, and all other specimens were yielded in the same order as that of the specimen NS. However, the specimen PS expanded from high-strength concrete and NS-HC and NS-FC cored from high-strength concrete did not yield longitudinal reinforcing bars at the joint. This means that the joint can effectively transfer the column load up to the ultimate load by the expansion of the high-strength concrete and the core formation.

Figure 9 shows the relationship between the axial load and the strain of the slab-column joint specimen under the influence of several variables. In the slab-column joint test specimen, the high-strength concrete expansion pour shows the relationship between the axial load and the average strain of the joint, and the high-strength concrete expansion pour increases the strength and stiffness. Also noteworthy here is that the ACI Code requires that the concrete be cast to a slab at least 600 mm (500 mm in the CSA Standard) from the column surface when the column concrete is to be expanded. )) In particular, the specimen NS-FC having a high-strength concrete core over the entire slab thickness showed an extreme load similar to that of the specimen PS, although the cross-sectional area of the core corresponds to 16% of the column cross-sectional area. In addition, the test specimen NS-HC in which the high-strength concrete core was placed only at the upper portion of the joint was similar to the PS, as in the case of the test specimen NS-FC having the high-strength concrete core.

Therefore, a new design of expanded casting of high strength concrete, full placing of high strength concrete core and half casting was proposed as a method for improving the column load transfer performance of slab-column joint. An analysis was performed. The finite element analysis results are consistent with the experimental results, and the nonlinear three-dimensional finite element analysis method for the slab-column joint behavior proposed in this study is found to be reliable.

Experimental and analytical results show that the expanded casting method of high-strength concrete (PS) for slabs around columns shows excellent performance improvements such as increased axial compressive strength, increased stiffness, and prevention of reinforcing bars of slab-column joints. In the case of the NS-FC method, the stiffness and the joint reinforcement prevention performance were as good as the high-strength concrete expansion. Especially, the core is formed only on the upper part of the slab (NS-HC). In the case of, it shows the ultimate load and yield resistance similar to the core forming method (NS-FC).

As a result, by constructing the core for joint strength reinforcement, the result is almost the same as that of reinforcing the slab with high strength concrete. It can be concluded that it can be configured only in the upper part of the center.

On the other hand, the reinforcing structure for the load transmission of the joint of the present invention by the upper pillar 10 and the lower pillar 30 in another embodiment by constructing a high-strength concrete, when the slab 20 is composed of ordinary concrete ( In the present invention, the load transmitted from the upper pillar 10 due to the weakening of J) is not sufficiently transmitted to the lower pillar 30 and brittle fracture is prevented from occurring at the slab 20 portion of the joint J. As a structure, the dowel reinforcing bar 70 and the bent dowel bar 80 are presented.

First, the dowel rebar 70 is a reinforcing bar extending through the slab 20 at the joint portion J and extending to a predetermined portion of the upper column 10 and the lower column 30, as shown in FIGS. 2C, 3C, and 4C. As shown in the reinforcement between the longitudinal reinforcing bar 40 as described above is to be welded to the band reinforcing bar 41 together with the longitudinal reinforcing bar 40 to reinforce the ductility and strength of the joint (J). The number of the dowels 70 may be selectively configured in consideration of the strength ratio of the high strength concrete of the column and the general concrete of the slab, etc. In FIG. 3C and 4C, for example, each longitudinal rebar 40 is used. 8 shows a case in which a total of eight are configured between two.

In addition, the torsion bar 70 is provided with a torsion preventing plate 71 is installed in the junction of the slab 20 and each of the pillars (10, 30) to prevent the torsion that may be caused by heterogeneous materials Preferably configured.

That is, the torsion preventing plate 71 is attached to the dowel rebar 70, but attached to each position where the upper pillar 10 and the lower pillar 30 and the slab 20 in contact with the torsion in this case It is reasonable that the plate 71 is attached to the dowel rebar 70 by welding, so that the strength of the attachment portion is maintained at or above the strength of the dowel reinforcing bar 70 and the torsion preventing plate 71. It is advisable to prevent brittle fractures.

In addition, the torsion plate 71 as shown in Figure 5 to easily attach the torsion prevention plate 71 to the dowel rebar 70 and the ring 71a is inserted into the dowel rebar and the It may be composed of a body portion 71b attached to the ring at a right angle. By this configuration, the ring 71a may be inserted into the dowel rebar 70 to facilitate welding, and the number of the rings 71a may be selectively configured in consideration of formability.

In addition, the torsion preventing plate 71 may have a difference in deformation amount due to load due to different materials of concrete and high-strength concrete in contact with the dowel reinforcement 70 and its outer circumference. In order to correct, a plurality of rod-like shear bars 71c may be configured in a direction perpendicular to the body portion 71b. More specifically, as shown in FIG. 5, the shear rod 71c is integrally attached to the body portion 71b and integrally connected with the dowel reinforcing steel 70 and the outer circumferential edge thereof. It is to be able to secure.

On the other hand, as another embodiment of the present invention as a reinforcing structure for the load transmission of the joint as shown in Figure 2d, 3d, and 4d dowel rebar 80 is presented. The dowel reinforcement 80 is configured in the junction (J), the centrifugal direction integrally from the transmission portion 81 and the transmission portion 81 formed from the upper column 10 to the center of the height of the slab 20 It is characterized by consisting of a punching portion 82 bent to. In other words, the bent dowel reinforcement 80 is formed of a "b" shape for the transfer of load of the joint by the transfer portion 81 is formed from the upper column 10 to the center of the slab 20 height The reinforcement is to be reinforced, and the bent punching portion 82 is used to reinforce the fracture by the punching shear that may occur at the junction J of the slab column.

The formation of the transfer part 81 from the upper pillar 10 to the center of the slab 20 height is also attributable to the behavior generated under load load at the joint as mentioned above. In other words, under the column load, the joint concrete undergoes greater deformation than the column concrete, but the lateral expansion of the joint is constrained by the perimeter slab. When a load is applied to the slab, the upper part of the joint receives tension and the lower part receives compression. Due to the deflection, the compression block of the slab restrains the joint at the lower part of the neutral shaft, but the peripheral slab does not restrain the joint at the upper part of the neutral shaft. Therefore, even if the transmission part 81 is comprised only in the upper part in the center of a slab, it will be sufficient reinforcement for load transmission in the junction part J. As shown in FIG.

The reinforcing structure for the load transfer of the joint according to the present invention is provided with a core and a dowel reinforcement at the joint, whereby the strength is reinforced at the joint, in particular, the slab portion cast in general concrete, thereby providing sufficient rigidity for the load transfer from the upper pillar. There is an advantage.

In addition, the torsion prevention plate is attached to the joint with the dowel reinforcement to prevent torsion due to heterogeneous materials, there is an advantage that the integral behavior with the concrete is secured.

In the detailed description of the present invention described above with reference to the preferred embodiment of the present invention, those skilled in the art or those skilled in the art having ordinary knowledge of the present invention described in the claims It will be understood that various modifications and changes can be made in the present invention without departing from the spirit and scope of the invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (6)

delete delete In the slab-column junction consisting of an upper column, a slab, and a lower column, An upper pillar and a lower pillar composed of high-strength concrete; A plurality of longitudinal reinforcing bars penetrating the upper pillar, the slab, and the lower pillar; A plurality of dowel bars formed on the joint portion; Reinforcing structure for slab-column joint load transfer, characterized in that consisting of; plate-shaped torsion preventing plate attached to the dowel rebar. The method of claim 3, The torsion preventing plate is a reinforcing structure for the slab-column joint load transfer, characterized in that consisting of a ring inserted into the dowel rebar and a body portion attached to the ring at right angles. The method of claim 4, wherein Reinforcing structure for the slab-column junction load transfer characterized in that the body portion is attached to one or more shear rods. The method of claim 3, The dowel reinforcement is configured to the junction portion, the slab-column junction load transfer characterized in that it consists of a transmission portion formed from the upper pillar to the center of the slab height and a punching portion bent in a centrifugal direction integrally from the transmission portion Reinforcement structure.

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