CONNECTIONS IN PRECAST REINFORCED CONCRETE STRUCTURES

Technical Field

The invention relates to a connection detail for use in moment resisting joints of precast reinforced concrete beam and column elements, which concantrates the structural damage on itself, can be removed, replaced and does not require a short cantilever on the column face.

Prior Art

Depending on the design preference, pinned or moment resisting connection details can be used in the beam-column joints of precast reinforced concrete systems. The following techniques are used in Tiirkiye for moment resisting joints of precast reinforced concrete structural elements.

Wet Column-Beam Connection (MAB1)

Wet connections, which are made to exhibit behavior equivalent to cast-in-place columnbeam connections, are joints where positive and negative moment capacities are provided by cast-in-place concrete and continuity of reinforcement. Beam-column geometric settlement can be formed with or without short cantilever, or with temporary short cantilever.

Full Post-Tensioned Connection (MAB2)

Precast beams can only be connected to columns by post-tensioning to transfer moment. The ducts through which the post-tensioning cables are passed are filled with cement mortar after post-tensioning.

Wet on Top - Welded on Bottom Connections (MAB3)

Joints where the continuity of negative moment capacity is provided by cast-in-place reinforced concrete and the continuity of positive moment capacity is provided by welding. Connections with Sleeve-Pin (MAB4)

In this connection type, the negative moment is carried by cast-in-place reinforced concrete and the positive moment is carried by the shear force capacity of at least 4 pins left in the column cantilever. Negative moment bearing reinforcements are placed into the space left in the column and then topping concrete is casted or by screwing into special sleeves left in the column. Some joint types called dry, wet and hybrid joints for moment transferring joints of precast reinforced concrete structural elements have been studied internationally. While wet joint details are formed by using cast-in-place concrete, dry type joints are defined as joints where only mechanical fasteners and/or welding are used without the use of concrete. Joint types where the properties of these two joint details are utilized in the same joint are referred to as hybrid joints.

One of the details used in the current practice is the wet joint detail called MAB1 in which cast-in-place concrete is used in the joints of precast reinforced concrete elements. In this joint, internal forces are transferred by cast-in-place concrete and reinforcement continuity.

The second joint detail used in practice is known as MAB2 and is named as fully posttensioned connection. In this connection type, precast beams are connected to columns by post-tensioning to transfer moment. The shear force transfer between the beam and the column face is realized by the clamp force created by the post-tensioning cables and friction.

The third method used in the joints is MAB3 which is top wet bottom welded connections. In this method, bending moments are transferred by welding and cast-in-place concrete.

Another method used in practice is MAB4 connections with sleeve-pin. In these connection details, the moment is transferred by using cast-in-place reinforced concrete and the shear force capacity of the pins left in the column cantilever. At the top of the joint, moment bearing reinforcements are placed into the space left in the column and then topping concrete is casted or by screwing into special sleeves left in the column.

The design of existing connection details is based on a strength-based approach that aims to transfer internal forces safely between structural elements. In strength-based approaches, the element capacity is taken into account and no additional precautions are taken to dissipate the earthquake energy between the structural elements.

In practice, wet on top and welded on bottom joint detail (MAB3) is frequently preferred. The connections of the beams and columns that compose the structural system are provided by welding and concrete casting operations on the construction site. Especially the controlled welding process highly effects the joint performance.

The ability to disassembly and/or replace the connections using welded and sleeved joints that remain in the casted concrete is very limited. In practice, serious damage can be caused to the elements during disassembling and replacement operations. The joint zones built by strength-based design do not contain additional mechanisms to absorb earthquake energy. In this case, energy absorption is provided by the formation of damage at a certain distance from the joints of the structural elements.

In the United States patent document numbered US10781582B2 which is in the known state of the art, moment transferring, replaceable and repairable beam-column connection details in precast reinforced concrete buildings are mentioned.

In the Chinese patent document numbered CN106592807A, which is in the known state of the art, a detail containing a replaceable and energy dissipating connection for moment resisting joints of precast reinforced concrete frame is mentioned.

In the international patent document numbered W00220910A1, which is in the known state of the art, an interlocking, energy dissipating and replaceable detail for the connection of structural elements such as columns and beams of a building is mentioned.

In the Turkish patent document numbered 2020/00839, which is in the known state of the art, a joint detail with energy dissipating resistance rods mounted on the beam end and column surface for beam-column joints is mentioned.

In the Chinese patent document CN110700404A, which is in the known state of the art, an energy dissipating column and beam joint detail is mentioned. The joint detail consists of moving elements, hinge seat, boundary plate, energy dissipating element, groove, pin, column and beam connectors.

In the United States patent document numbered US8375652B2, which is in the known state of the art, a joint detail that can be used for the connection of beam and column elements is mentioned.

With this joint detail, shear force is transferred by steel plates that were welded to the end plates on the faces of columns and beams. Concrete is not used in the joint region. The bending moment is converted into a force pair and transferred to the element series in which the fuse type elements are located. The mace screw used for the connection of the fuse-type elements and the spherical shape of the main coupler enable sufficient tolerance for the joint. Therefore, the invention is capable of creating greater assembly tolerances. The elements transferring the bending moment as a force pair are connected to the end plates by means of sleeves. This will allow the elements to be easily removed and replaced with the new ones if necessary. Therefore, it is necessary to develop a replaceable joint detail that does not require a short cantilever for moment resisting beam-column connections in precast reinforced concrete structures.

Objectives of the Invention

The objective of the present invention is to provide a joint detail that transfers moment in precast reinforced concrete structures, where the shear force and bending moment are transferred separately, where energy dissipation is realized in the elements that convert the bending moment into a force pair, the parts that transfer the bending moment and shear force can be disassembled and/or replaced, and which does not require short cantilevers on the column faces.

Detailed Description of the Invention

In order to achieve the objectives of the present invention, an energy dissipating, replaceable joint detail, which does not require short cantilevers, for application in moment resisting beam-column connections of precast reinforced concrete structures, is shown in the attached figures.

These figures;

Figure 1: A view of the detail of a replaceable joint that does not require a short cantilever for moment transferring beam-column connections in precast reinforced concrete structures.

Figure 2: a. Front b. Rear perspective views showing column end plate and column shear force plate parts.

Figure 3: Front perspective view of beam end plate and beam shear force plate a. with inbeam sleeve and b. without in-beam sleeve. Figure 4: Rear perspective view of beam end plate and beam shear force plate a. with inbeam sleeve and b. without in-beam sleeve.

Figure 5: Rear perspective view of precast reinforced concrete beam with beam end plate and beam shear force plate connected.

Figure 6: Front perspective view of precast reinforced concrete beam with beam end plate and beam shear force plate connected.

Figure 7: Exploded perspective view showing the shear force plates of the precast reinforced concrete beam and precast reinforced concrete column being assembled with the connecting shaft and nut.

Figure 8: Exploded side view showing the shear force plates of precast reinforced concrete beam and precast reinforced concrete column being assembled with connecting shaft and nut.

Figure 9: Perspective view showing the connection of shear force plates of precast reinforced concrete beam and precast reinforced concrete column with connecting shaft and nut.

Figure 10: The view of the mace screw, mace nut and fastener nut, which are the elements that enable the moment to be transferred by converting the moment into a force pair, before the connection.

Figure 11: Perspective view showing the mace screw, mace nut and fastener nut, which are the elements that transform the moment into a force pair, connected to the precast reinforced concrete beam.

Figure 12: Side view showing the mace screw, mace nut and fastener nut, which are the elements that transform the moment into a force pair, connected to the precast reinforced concrete beam.

Figure 13: View showing the mace screw, mace nut and fastener nut connected to the beam and before the connection of the main coupler, column sleeve and fuse element.

Figure 14: View of main coupler, column sleeve and fuse element before connection. Figure 15: View of the main coupler, column sleeve and fuse element before connection to the joint assembly.

Figure 16: Partial cross-sectional view of the main coupler, column sleeve and fuse element before connection to the joint assembly.

Figure 17: View of the elements that transform the moment into a force pair on the joint assembly before tightening the main coupler and column sleeve.

Figure 18: Partial cross-sectional view of the elements that transform the moment into a force pair on the joint assembly before tightening the main coupler and column sleeve.

Figure 19: The view of the elements that transform the moment into a force pair after assembly.

Figure 20: Partial cross-sectional view of the elements that transform the moment into a force pair after assembly.

Figure 21: Perspective view of the elements that transform the moment into a force pair after assembly.

Figure 22: Side view of the joint detail during the installation of the jacket.

Figure 23: Perspective view of the joint detail during the installation of the jacket.

Figure 24: Side view of the joint detail after the installation of the jacket.

Figure 25: Partial section view of the joint detail from the side after the installation of the jacket.

Figure 26: Perspective view of the joint detail.

Figure 27: Perspective view of the joint detail with invisible lines.

Figure 28: Exploded perspective view of the joint detail.

Figure 29: Exploded perspective view of the joint detail with invisible lines. The parts in the figures are individually numbered and the corresponding numbers are given below.

1. Precast reinforced concrete beam

2. Precast reinforced concrete column

3. Beam end plate

4. Column end plate

5. Beam shear force plate

6. Column shear force plate

7. In-beam sleeve

8. Shear force plates connection bolt

9. Shear force plates connection nut

10. Mace screw

11. Mace nut

12. Fastener nut

13. Main coupler

14. Column sleeve

15. Fuse element

16. Jacket

The invention is a replaceable joint detail for moment transferring beam-column connections in precast reinforced concrete structures which does not require short cantilevers on the column face and comprises;

- a precast reinforced concrete beam (1) that carries the vertical and lateral loads acting on the structural system and transfer the force through beam-column joints,

- a precast reinforced concrete column (2) that carries the vertical and lateral loads acting on the structural system and the forces transferred from precast reinforced concrete beams (1) and transfers them to subfloor columns and/or foundations,

- a beam end plate (3), which is attached to the face of the precast reinforced concrete beam (1) and enables the parts to be connected,

- a column end plate (4) attached to the face of the precast reinforced concrete column (2) and enables the parts to be connected,

- a beam shear force plate (5) which is connected to the beam end plate (3) and where the shear force will be transferred, - a column shear force plate (6), which is connected to the column end plate (4) and where the shear force will be transferred,

- an in-beam sleeve (7), which is connected to the beam end plate (3) and allows the members to be connected to each other without welding,

- a shear force plate connection bolt (8) connecting the beam shear force plate (5) and the column shear force plate (6),

- a shear force plate connection nut (9), which is screwed to the shear force plate connection bolt (8) and holds the beam shear force plate (5) and column shear force plate (2) together,

- a mace screw (10), which is connected to the beam end plate (3) and is one of the elements that allows the bending moment to be transformed into a force pair and transferred,

- a mace nut (11), where the knob part of the mace screw (10) is located and which is one of the elements that allows the bending moment to be transformed into a force pair and transferred,

- a fastener nut (12), which is connected to the mace nut (11) and is one of the elements that allows the bending moment to be transformed into a force pair and transferred,

- a main coupler (13) connected to the mace nut (11), where the knob part of the mace screw (10) is located, and which is one of the elements that allows the bending moment to be transformed into a force pair and transferred,

- a column sleeve (14), which is connected to the column end plate (4) and is one of the elements that allows the bending moment to be transformed into a force pair and transferred,

- a fuse element (15) placed between the main coupler (13) and the column sleeve (14), the element where the plastic deformation will occur,

- a jacket (16) positioned over the bearings in the column sleeve (14) and main coupler (13), used to prevent buckling of the fuse element (15).

As is known, the joints of precast reinforced concrete elements can be designed as moment resisting or pinned. This depends on the design preference and the present invention aims to be a moment resisting joint. Although designing the beam column joints as moment resisting is important in terms of lateral stiffness of the structure, it is inevitable that the structural elements will suffer certain damage under large earthquake forces. On the other hand, the connection of the prefabricated structural elements transported to the construction site with a monolithic joint detail is very difficult and requires meticulous workmanship under construction site conditions. With the proposed invention, beam-column joints can be assembled quite practically. Since the joint details used in the application include casting concrete and/or welding processes, it is extremely important to ensure the continuity of material and workmanship quality under construction site conditions. Since the components used in this joint detail will be manufactured like the structural elements, it is predicted that the quality of the connection will not be below the quality of the structural elements.

The removable and/or replaceable feature of the joint detail allows the structural elements to be replaced and used for different purposes and creates a practical and economical solution by allowing an application without a short cantilever on the column face.

Unlike the joint details required by the codes, the developed joint detail aims to absorb the earthquake energy in attenuated dry joint zones with an innovative approach. Energy dissipation is realized by utilizing the elongation deformation of the fuse elements (15) in the joint, and these elements can be replaced with new ones to be used again in the oncoming earthquake.

It is extremely important to have sufficient tolerance in terms of distance during the installation of structural elements. Because if there is not enough tolerance, the joint may not be applied as designed due to site conditions, assembly workmanship, etc. At this point, the fact that the joint has a feature that enables sufficient tolerance will allow the assembly of the structural elements.

The developed joint detail consists of beam shear force plate (5) and column shear force plate (6), shear force plate connection bolt (8), shear force plate connection nut (9), mace screw (10), mace nut (11), fastener nut (12), main coupler (13), column sleeve (14), jacket (16) and replaceable fuse element (15) that concentrate the damage, which connect the precast reinforced concrete beam (1) and precast reinforced concrete column (2) in such a way as to transfer moment to each other. The developed joint detail also includes beam end plate (3) and in-beam sleeves (7) integrated into the precast reinforced concrete beam (1), and column end plate (4) integrated to precast reinforced concrete column (2) to enable connection assembly.

In the connection preparation phase, threaded holes were formed in the column end plate (1) and beam end plate (3). Column shear force plates (6) are welded to the column end plate (1) and beam shear force plates (5) are welded to the beam end plate (3). In addition, inbeam sleeves (7) are mounted to the reinforcement bars which the ends are threaded, and connected to the beam end plate (3). Steel elements are placed at the end of the precast reinforced concrete beam (1) and the face of the precast reinforced concrete column (2) and concrete casting is realized.

The precast reinforced concrete beam (1) and precast reinforced concrete column (2), whose concrete hardening is completed, are fixed in the construction site by inserting the shear force plate connection bolt (8) through the unthreaded holes of the beam shear force plate (5) and column shear force plate (6) and fastening the shear force plates with the connection nut (9).

The mace nut (11) is threaded into the mace screw (10). The fastener nut (12) is connected by means of threads. This assembled part is connected to the in-beam sleeves (7) also by means of threads. The mace nut (11) and fastener nut (12) are slid on the mace screw (10) up to the beam end plate (3).

The main coupler (13) is connected to the fuse element (15) and the column sleeve (14) by means of threads. The appropriate end of the main coupler (13) and the mace screw (10) are connected. The mace nut (11) and fastener nut (12) are connected to the main coupler (13) by means of threads. The fuse element (15) are slid from the main coupler (13) by means of a wrench and the column sleeve (14) are connected to the column end plate (4) by means of threads.

The connection of the precast reinforced concrete beam (1) to the precast reinforced concrete column (2) is completed by installing the jacket (16) on the bearings of the main couplers (13) and column sleeves (14). The assembly of the jacket (16) is made using alien head bolts.

The joint detail has been developed to be applied in the construction industry, especially in the construction of multi-storey residential buildings where precast reinforced concrete elements are used. The developed joint detail ensures the structural integrity of reinforced concrete beams in a moment resisting manner and prevents damage to the structural elements with dissipating earthquake energy by concentrating the plastic deformation on itself.

The advantages obtained with the developed joint detail are listed below. With the proposed joint method, earthquake energy is dissipated by the elements in the joint details of the structural elements. Thus, damage to the structural elements is prevented. - Since welding and concrete casting are not adopted in the joint and the components are produced in the workshop, the quality standard can be maintained and a joint without material uncertainties can be formed.

The joint detail provides the tolerance to eliminate the difficulties encountered during assembly and provides a practical and economical solution by allowing an application without the need of short cantilever on the column face.

The joint detail has a feature that allows the joints of precast column and beam elements to be removed and/or replaced in a practical way. This feature also allows the structural elements to be replaced if necessary. Thus, damage to the structural elements during the disassembly of the components in the joint is prevented.