JP6208090B2 - Temporary support structure for seismic isolation work and seismic isolation method for existing buildings - Google Patents

Description

  The present invention relates to a temporary support structure for seismic isolation work and a seismic isolation method for existing buildings.

  Conventionally, when an existing building is to be seismically isolated, it has been widely practiced to remove a part of a pillar of a layer to be seismically isolated and remove a part, and to install a seismic isolation device in the removed part. In this case, it is necessary to install a temporary support member such as a jack to support the column axial force at least during the period from cutting the column to installing the seismic isolation device.

  In general, a temporary support member is installed from the floor near the column to the upper beam to directly support the upper and lower floors. Although this method can reliably support the column axial force, a load not assumed at the time of design is applied to the upper and lower beams. Therefore, it is necessary to disperse the load by providing temporary support members on the lower floors of the layers to be reinforced or seismically isolated. Therefore, a method for supporting the column axial force by the column itself has been proposed.

  For example, Patent Document 1 describes that a bracket is provided on the outer periphery of a column above and below a column portion to be removed for installing a seismic isolation device, and a jack is installed between the upper and lower brackets.

  In this technique, a column axial force is received from the upper column mainly by the frictional force of the contact surface between the column and the bracket, and transmitted to the lower column via a jack. Since it is necessary to bear the total axial force after cutting the column with frictional force, the opposing bracket is connected by a rod (PC steel bar, etc.), and tension is applied to this rod to reduce the frictional force between the column and the bracket. Increasing. The rods are installed by changing the height in two directions, ie, one direction of the pillar and the direction perpendicular thereto, and the brackets are stacked until the required strength is obtained.

  By the way, as a seismic isolation device for a building, one using laminated rubber is most common. Since the rubber material serves as a support material for the laminated rubber, the cross-sectional area required to support the load of the building is larger than that of a reinforced concrete column. In order to install such a seismic isolation device, it is necessary to increase the outer shape and cross-sectional area by adding concrete to the outer periphery of the existing column.

  Patent Document 2 describes that a jack for supporting a column axial force is installed outside the seismic isolation device by taking a larger hitting portion. Also in this case, a steel material is installed outside the additional striking portion, and the steel material is connected with a PC steel rod that is inserted through the extra striking portion, thereby applying tension.

  Patent Document 3 describes that a jack is installed between brackets provided outside the additional striking part after increasing the installation area by adding concrete to the outer periphery of the pillar. The brackets are provided in one direction with only two members facing each other above and below the planned cutting range, and are connected by a PC steel rod.

JP-A-4-231550 Japanese Patent Laid-Open No. 10-259666 Japanese Patent No. 3725818

  However, in the technique described in Patent Document 2, since not only the seismic isolation device but also the jack is installed between the additional hit portions, the cross-sectional area of the additional hit portion becomes very large. For this reason, even after the earthquake-resistant construction is completed, the additional hitting portion becomes an obstacle and the space that can be used for residence is greatly reduced.

  On the other hand, in the technique described in Patent Document 3, the number of PC steel bars is large in order to increase the frictional force in order to obtain a required yield strength, and there are PC steel bars that penetrate existing columns. However, it is not preferable that a cross-sectional defect occurs in the existing column.

  In view of the above points, the present invention provides a temporary support structure for seismic isolation work that is less likely to reduce the space that can be used for living and the like, and that can ensure strength without losing existing pillars. The purpose is to provide a seismic isolation method for existing buildings.

  The temporary support structure of the seismic isolation work of the present invention is provided on the outer periphery of the pillar above and below the portion where the seismic isolation device of the existing building is inserted, and has an outer shape on which the seismic isolation device can be installed. An additional striking portion, a sheath tube embedded so as to penetrate each of the additional striking portions, a bracket detachably attached to the outside of the additional striking portion, and facing each other in the same direction, and each sheath It is characterized by comprising a tension bar that is inserted through a tube and connected to the opposing brackets and applied with a tension force, and an axial force transmission member installed between the upper and lower brackets.

  According to the temporary support structure for seismic isolation work of the present invention, the axial force transmission member is installed between the upper and lower brackets that are detachably provided on the outer side of the additional striking portion. Compared with the conventional technique, the cross-sectional area of the increased hitting portion can be reduced.

  Furthermore, the tension bar is inserted through the sheath tube embedded so as to penetrate the additional hitting portion, and the bracket is connected. Therefore, unlike the technique described in Patent Document 3, the tension bar is inserted. Without missing the pillars of existing buildings. When the column has a quadrangular cross section, the sheath tube is disposed horizontally and parallel to each other along two parallel outer surfaces of the column.

  Furthermore, since the tension bar is inserted through the sheath tube embedded so as to penetrate the additional hitting portion and connects the brackets provided so as to face in the same direction, according to the embodiment of the present invention described below. As will be described in the description, when the upper and lower brackets are provided with multiple brackets, the tension of the tension bar is the same as when the upper and lower brackets are provided to face in different directions. However, the yield strength due to the frictional force generated on the contact surface between the additional striking portion and the bracket is increased. Therefore, when the height of the additional striking part is determined by the height of the bracket, the height of the bracket to secure the required proof strength, and consequently the height of the lower extra striking part, is reduced and can be used for living etc. The space can be expanded. In addition, the load that can be supported is large because the proof stress is larger than that provided to face in different directions, and the work can be performed safely. Furthermore, since the tension force of the tension bar for ensuring the necessary proof stress can be reduced, the burden on the additional hitting portion and the column can be reduced.

In the temporary support structure for seismic isolation work according to the present invention, the tension is applied to the outside of the pillar so as to face the bracket in the same direction on the lower side of the lower additional striking portion. further comprising an auxiliary bracket connected by the auxiliary tension bar, the upper bracket Ru provided vertically multiple stages.

Thereby , the proof stress can be increased by the frictional force generated on the contact surface between the pillar of the existing building and the auxiliary bracket, and the auxiliary bracket is removed after the earthquake-proof construction. Therefore, the space which can be used for residence etc. can be expanded further by reducing the height of the lower additional hitting part. When the shapes of the bracket and the auxiliary bracket are the same, the pillar of the existing building has a smaller contact area and a smaller frictional force because the outer circumference is shorter than the additional hitting portion. In order to obtain a required yield strength, it is desirable to provide a plurality of auxiliary brackets and to face each other in the same direction so as to increase the yield strength.

  The temporary support structure for seismic isolation work according to the present invention preferably further includes an auxiliary support member provided between the lower bracket or the lower surface of the auxiliary bracket and the upper surface of the floor slab.

  In this case, even if it is insufficient to support the column axial force by the frictional force generated on the contact surface between the additional striking part and the bracket, and further on the contact surface between the pillar of the existing building and the auxiliary bracket, It is possible to support the column axial force with the floor slab via the auxiliary support member. The auxiliary support member is desirably provided on the upper surface of the floor slab on the lower floor beam.

  The seismic isolation method for an existing building according to the present invention is reinforced in a state where a sheath tube is embedded in parallel to the outside of the column above and below the portion where the seismic isolation device for the column of the existing building is inserted. A step of forming a portion, and a step of connecting and installing a pair of brackets facing in the same direction by applying a tension force to the outside of the additional striking portion by means of a tension bar member that passes through each sheath tube, and , Installing an axial force transmission member between the upper and lower brackets, applying a load corresponding to a column axial force, removing a portion of the column where the seismic isolation device is inserted, and removing the portion A step of installing the seismic isolation device; a step of removing a load applied by the axial force transmission member; and a step of removing the upper and lower brackets, the tension bar and the axial force transmission member. And

  According to the seismic isolation method for an existing building of the present invention, the axial force transmission member is installed between the upper and lower brackets that are detachably provided on the outside of the additional striking portion. Compared with the conventional technique, the cross-sectional area of the increased hitting portion can be reduced.

  Furthermore, the tension bar is inserted through the sheath tube embedded so as to penetrate the additional hitting portion, and the bracket is connected. Therefore, unlike the technique described in Patent Document 3, the tension bar is inserted. Without missing the pillars of existing buildings.

  Furthermore, since the tension bar is inserted through the sheath tube embedded so as to penetrate the additional hitting portion and connects the brackets provided so as to face in the same direction, according to the embodiment of the present invention described below. As will be described in the description, even if the tension force of the tension bar is the same as when the upper and lower brackets are provided to face each other in different directions, they are generated on the contact surface between the additional striking portion and the bracket. The yield strength due to frictional force increases. Therefore, when the height of the additional striking part is determined by the height of the bracket, the height of the bracket to secure the required proof strength, and consequently the height of the lower extra striking part, is reduced and can be used for living etc. The space can be expanded.

In the seismic isolation method for an existing building according to the present invention, a pair of auxiliary brackets facing the same direction as the brackets by auxiliary tension bars on the outside of the pillars on the lower side of the lower additional striking portion. , Ru, further comprising the step of connecting over a period of tension.

Thereby , the proof stress can be increased by the frictional force generated on the contact surface between the pillar of the existing building and the auxiliary bracket, and the auxiliary bracket is removed after the earthquake-proof construction. Therefore, the space which can be used for residence etc. can be expanded further by reducing the height of the lower additional hitting part.

  Moreover, in the seismic isolation method of the existing building of this invention, it is preferable to further provide the process of providing the supporting member for assistance between the lower surface of the said lower side bracket or the said auxiliary bracket, and the upper surface of a floor slab.

  In this case, even if it is insufficient to support the column axial force by the frictional force generated on the contact surface between the additional striking part and the bracket, and further on the contact surface between the pillar of the existing building and the auxiliary bracket, It is possible to support the column axial force with the floor slab via the auxiliary support member.

The front view which shows the temporary support structure of the seismic isolation construction which concerns on embodiment of this invention. (A) is the sectional view on the AA line of FIG. 1, (b) is the sectional view on the BB line of FIG. A graph showing the relationship between tension and maximum strength. It is a front view which shows the seismic isolation construction method of the existing building which concerns on embodiment of this invention, Comprising: (a) shows the state which formed the additional striking part, (b) shows the state which installed the bracket, respectively. It is a front view which shows the seismic isolation method of the existing building which concerns on embodiment of this invention, Comprising: (a) The state in which the part in which a seismic isolation apparatus is installed was removed, (b) Each state is shown.

  A temporary support structure for seismic isolation work according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

  When this existing support structure is to make an existing building seismic isolation, the column A of the layer to be seismic isolation is cut and a part is removed, and the seismic isolation device 30 (FIG. 5B) is removed. This is a structure for supporting the column axial force when installing by inserting a reference).

  The temporary support structure includes an additional striking portion 11, a sheath tube 12, an upper bracket 13, a lower bracket 14, a PC steel rod 15, and a jack 16.

  The additional striking portions 11 are provided on the outer periphery of the existing pillar A above and below the portion A1 that is removed in order to insert the seismic isolation device 30 of the pillar (hereinafter referred to as an existing pillar) A of the existing building. Here, the cross section of the external shape of the existing pillar A and the additional striking part 11 is a rectangle. In addition, the reinforcing bars inside the existing pillar A and the additional striking portion 11 are omitted in the drawing.

  The additional hitting portion 11 has an outer shape on which the seismic isolation device 30 can be installed. The seismic isolation device 30 is an isolator using laminated rubber, for example. The outer shape of the additional striking part 11 is sufficient if the seismic isolation device 30 can be installed, and the cross-sectional area of the extra striking part 11 is minimized, so that the space usable for living etc. It is preferable to suppress the decrease. “The outer shape on which the seismic isolation device 30 can be installed” means that the number of fixing tools 17 for fixing the seismic isolation device 30 can be arranged more than the required number of the opposing surfaces of the additional striking portion 11. The shape which can comprise the structure which can transmit a load with the seismic isolation apparatus 30 is meant. For this reason, the outer shape of the additional striking part 11 may be smaller than the outer shape of the base plate of the seismic isolation device 30.

  In particular, it is sufficient for the lower additional striking portion 11B to have a height that allows the seismic isolation device 30 to be fixed, and it is preferable that the existing column A remains in the lower side. In this way, by reducing the area where the lower additional beating portion 11B is provided as much as possible, when the floor height of the floor where the seismic isolation device 30 is installed is high, the space that can be used for residence etc. is the same as before the construction. If the floor height is low, it can be used as a storage unit.

  Since the upper additional hitting portion 11A does not affect the space that can be used for residence or the like, the range thereof is not limited. The upper additional hitting portion 11A may be provided up to the lower surface of the slab B on the upper floor.

  The sheath tube 12 is embedded in each of the additional striking portions 11A and 11B so as to penetrate in the same direction. A plurality of sheath tubes 12 are provided in each of the additional striking portions 11A and 11B, avoiding the existing column A. Here, one sheath tube 12 is placed on the outer side in the vertical direction of FIG. 2A of the existing column A, so that the sheath tube 12 is positioned horizontally and parallel to each other along two parallel outer surfaces of the existing column A. As shown in FIG. 1, the upper additional striking portion 11A is provided with four steps in the vertical direction, and the lower additional striking portion 11B is provided with two steps in the vertical direction. The sheath tube 12 is made of a resin such as vinyl chloride, for example.

  Further, a fixing tool 17 for fixing the seismic isolation device 30 is also embedded in each of the additional hitting portions 11A and 11B. The fixture 17 is, for example, a cap nut.

  The upper bracket 13 is detachably installed on the outer side of the upper additional portion 11A. The lower bracket 14 is detachably installed on the outer side of the lower additional beating portion 11B. Here, the brackets 13 and 14 are made of a steel plate, and are formed by combining, for example, H-shaped steel by welding.

  The upper bracket 13 and the lower bracket 14 are composed of one pair of two pairs of brackets connected by PC steel rods 15 that respectively pass through the existing pillar A in the vertical direction outside in FIG. The PC steel bar 15 corresponds to the tension bar of the present invention.

  Steel plates are fixed to the four corners of the lower surface of the upper bracket 13 and the upper surface of the lower bracket 14 by welding or the like in order to install the jacks 16 respectively.

  The brackets 13 and 14 are connected to each other by a PC steel rod 15 that penetrates the increased striking portions 11A and 11B while avoiding the existing pillar A. A nut 18 is screwed and fixed to the tip of the PC steel rod 15 protruding from the brackets 13 and 14 outward in the left-right direction in FIG. Thereby, tension force is applied to the PC steel bar 15 and compressive force is applied to the additional striking portions 11A and 11B via the pair of brackets 13 and 14, respectively.

  This compressive force generates a frictional force on the contact surface between the increased striking portions 11A and 11B and the brackets 13 and 14, so that a vertical load (column axial force) applied to the existing column A can be supported.

  Thus, in order to ensure the column axial force, a large frictional force is required, and the brackets 13 and 14 are preferably provided in a plurality of upper and lower stages. However, it is not preferable to increase the number of steps of the lower bracket 14 because the height of the lower increased hitting portion 11B increases and the space usable for living or the like decreases.

  The upper bracket 13 and the lower bracket 14 are provided so as to face each other in the same direction at all stages. This is an experiment of the relationship between the tension force applied to the PC steel bar 15 and the maximum proof stress when the brackets are provided in two steps in the same direction and when the brackets are provided in two steps in a direction perpendicular to each other. Based on the results. Specifically, as shown in FIG. 3 showing an example of the experimental results, the black circle in which the brackets are indicated by X having two stages in the same direction and the brackets are provided in one stage in a direction orthogonal to each other. This is because it has been found that the maximum proof stress is larger than the case indicated by.

  Furthermore, since the brackets 13 and 14 are in the same direction and not in different directions, the upper and lower stages can be integrated, the configuration is simplified, and no gaps are created between the stages, so that all stages are effective. Therefore, it is possible to expect the proof stress as designed.

  Furthermore, since the brackets 13 and 14 are in the same direction, it is possible to select a direction in which the installation is easy, such as avoiding the direction in which the seismic wall is present, and installation of a device for applying tension to the PC steel bar 15 There is also an advantage that movement becomes easy.

  The jack 16 is disposed between the upper bracket 13 and the lower bracket 14. The jack 16 corresponds to the axial force transmission member of the present invention. Here, four jacks 16 are disposed at the four corners of the brackets 13 and 14 to transmit the vertical load of the upper structure to the lower structure.

Furthermore, temporary support structure, as shown in FIG. 1 and FIG. 2 (b), that has an additional bracket 21 provided on the outer periphery of the lower existing column A of the lower bracket 14.

  The auxiliary bracket 21 is also formed with a through hole through which the PC steel rod 22 is inserted. The PC steel bar 22 corresponds to the auxiliary tension bar of the present invention. The auxiliary bracket 21 faces the same direction as the brackets 13 and 14, the left-right direction in FIG. 1, and the up-down direction in FIG. A nut 18 is screwed and fixed to the tip of the PC steel rod 15 protruding outward from each auxiliary bracket 21. Thereby, the PC steel rod 22 is disposed horizontally and parallel to each other along two parallel outer surfaces of the existing pillar A. A tension force is applied to the PC steel rod 22 and a compressive force is applied to the existing column A via the pair of auxiliary brackets 21.

This compressive force generates a frictional force on the contact surface between the existing column A and the auxiliary bracket 21 and can support the vertical load (column axial force) applied to the existing column A. The proof stress can be increased by the frictional force of the contact surface between A and the auxiliary bracket 21, and the auxiliary bracket 21 is removed after the seismic work. Therefore, the space which can be used for a residence etc. can be expanded further by reducing the height of the lower additional striking part 11B.

  Further, as shown in FIG. 1, the temporary support structure may include an auxiliary support member 23 between the lower surface of the auxiliary bracket 21 and the upper surface of the floor slab C of the seismic isolation layer. In the case where the auxiliary bracket 21 is not provided, an auxiliary support member 23 may be provided between the lower surface of the lower bracket 14 and the upper surface of the floor slab C of the seismic isolation layer.

  If the frictional force between the additional striking portion 11 and the brackets 13 and 14 and further between the existing pillar A and the auxiliary bracket 21 is insufficient, the brackets 13 and 14 are displaced from a predetermined position, and the existing building Will tilt. When the frictional force is insufficient to support the axial load in this way, the auxiliary support member 23 transmits the insufficient load to the lower floor pillar via the floor slab and the lower beam. To do. Therefore, if the frictional force is sufficient to support the axial load, the load is not borne, and the upper end of the auxiliary support member 23 may not be in contact with the lower surface of the lower bracket 14.

  The auxiliary support member 23 may be a simple steel bar. However, the auxiliary support member 23 is preferably extendable to adjust the height of the upper end.

  Hereinafter, the seismic isolation method for an existing building according to the embodiment of the present invention using the above-described temporary support structure will be described with reference to FIGS. 1 to 2, 4, and 5.

  First, as shown to Fig.4 (a), it adds to the outer periphery of the existing pillar A, respectively, at the upper and lower sides of the part A1 in which the seismic isolation device 30 (refer FIG.5 (b)) of the existing pillar A is inserted, respectively. , 11B is performed.

  Each of the additional punching portions 11A and 11B is formed by placing a formwork (not shown), performing reinforcement, and placing concrete in a state where the sheath tube 12 and the fixture 17 are embedded.

  Next, as shown in FIG. 4B, the pair of opposing brackets 13 and 14 are tensioned by the PC steel rods 15 that pass through the respective sheath tubes 12 outside the upper and lower increased portions 11A and 11B. The process of connecting and installing with force is performed.

  Further, a step of connecting and installing the auxiliary bracket 21 under tension with a PC steel rod 22 on the outside of the existing pillar A on the lower side of the lower increased portion 11B is performed.

  Further, a step of providing an auxiliary support member 23 between the lower surface of the lower bracket 14 and the upper surface of the floor slab C is performed.

  Next, as shown in FIG. 1, the jack 16 is installed between the upper and lower brackets 13 and 14, and a step of applying a load corresponding to the column axial force is performed.

  Next, a step of cutting and removing the portion A1 into which the seismic isolation device 30 of the existing pillar A is inserted is performed as shown in FIG.

  Next, with reference to FIG.5 (b), the process of installing the seismic isolation apparatus 30 in the removed part is performed. At this time, the seismic isolation device 30 is fixed by using the fixing tool 17 embedded in the additional striking portion 11.

  Next, a process of removing the load applied to the jack 16 is performed.

  Finally, a process of removing the brackets 13 and 14, the PC steel bars 15 and 22, the jack 16, the auxiliary bracket 21 and the auxiliary support member 23 is performed to obtain the state shown in FIG.

  As described above, according to the embodiment of the present invention, the seismic isolation device 30 is installed on the outer periphery of the existing column A above and below the portion A1 where the seismic isolation device 30 of the existing column A is inserted. The seismic isolation device 30 using the laminated rubber can be installed because the installation area is larger than the cross-sectional area of the existing pillar A because it has the increased hitting portions 11A and 11B having possible outer shapes.

  Further, since the jack 16 is installed between the brackets 13 and 14 that are detachably provided on the outer sides of the additional hitting portions 11A and 11B, respectively, the additional hitting portion 11A is compared with the technique described in Patent Document 2. , 11B can be reduced in cross-sectional area.

  Furthermore, since the PC steel bar 15 is inserted through the sheath tube 12 embedded so as to penetrate the increased punching portions 11A and 11B and connects the brackets 13 and 14, the technique differs from the technique described in Patent Document 3 above. In order to insert the PC steel rod 15, the existing pillar A is not lost.

  Further, since the PC steel rod 15 is inserted through the sheath tube 12 embedded so as to penetrate the additional punching portions 11A and 11B and connects the brackets 13 and 14 provided so as to face in the same direction, Compared to the case where the brackets 13 and 14 are provided so as to face each other in a different direction as in the technique described in Patent Document 1, even if the tension force of the PC steel bar 15 is the same, the increased hitting portion The proof stress by the frictional force between 11A, 11B and the brackets 13, 14 increases. Therefore, it is possible to reduce the height of the lower bracket 13 for ensuring the necessary proof stress, and hence the height of the lower additional hitting portion 11B, thereby expanding the space that can be used for living.

  As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to this. For example, the fixing tool 17 is not embedded in the additional hitting portions 11A and 11B, but a bag for fixing a base for fixing the seismic isolation device 30 after cutting and removing the portion A1 is embedded in the additional hitting portions 11A and 11B. A nut 17 or the like may be used to form the concrete, and the fixture 17 may be embedded in this pedestal.

DESCRIPTION OF SYMBOLS 11 ... Additional punching part, 11A ... Upper additional punching part, 11B ... Lower additional punching part, 12 ... Sheath pipe, 13 ... Upper bracket (upper bracket), 14 ... Lower bracket (lower bracket), 15 ... PC steel bar (tension bar), 16 ... Jack (axial force transmission member, 17 ... fixing tool, 18 ... nut, 21 ... auxiliary bracket, 22 ... PC steel bar (auxiliary tension bar), 23 ... auxiliary Support member 30 ... Seismic isolation device flat plate A ... Existing building column, existing column A1 ... Part to be removed B ... Upper slab C ... Floor slab.

Claims (4)

An additional striking part having an outer shape on which the seismic isolation device can be installed on the outer periphery of the column above and below the part where the seismic isolation device of the pillar of the existing building is inserted
A sheath tube embedded so as to penetrate each of the additional striking portions;
A bracket provided so as to be detachable on the outside of the additional striking portion and facing each other in the same direction;
A tension bar that is inserted through each sheath tube and connected to the opposing bracket,
An axial force transmission member installed between the upper and lower brackets ;
Auxiliary bracket, which is provided on the outer side of the pillar on the lower side of the lower additional striking portion so as to face the bracket in the same direction and is connected by an auxiliary tension bar to which tension is applied. Prepared ,
The upper support bracket is provided with a plurality of upper and lower stages in the same direction as the tension bar, and is a temporary support structure for seismic isolation work. The temporary support structure for seismic isolation work according to claim 1 , further comprising an auxiliary support member provided between a lower surface of the lower bracket or the auxiliary bracket and an upper surface of the floor slab. A seismic isolation method for existing buildings,
Forming an additional striking portion in a state where a sheath tube is embedded in parallel to the outside of the column above and below the portion where the seismic isolation device of the column of the existing building is inserted;
A step of connecting and installing a pair of brackets facing in the same direction with tension bars inserted through the sheath tubes on the outside of the additional striking portion, applying tension force, and
A step of connecting a pair of auxiliary brackets opposite to the bracket in the same direction by applying a tension force to the outer side of the column on the lower side of the lower additional striking portion,
Installing an axial force transmission member between the upper and lower brackets and applying a load corresponding to a column axial force;
Removing the portion of the pillar where the seismic isolation device is inserted;
Installing the seismic isolation device in the removed portion;
Removing the load applied by the axial force transmission member;
And a step of removing the upper and lower brackets, the tension bar and the axial force transmission member. The seismic isolation method for an existing building according to claim 3 , further comprising a step of providing an auxiliary support member between the lower bracket or the lower surface of the auxiliary bracket and the upper surface of the floor slab.