JP5785476B2 - Reinforcing method and structure of existing foundation - Google Patents

Description

The present invention relates to a method for reinforcing an existing foundation having a footing and a reinforcing structure for an existing foundation .

  For large structures, pile foundations with footings on top of piles placed in the ground are often used. The footing transmits the load of the superstructure to the pile and is often made relatively thick. The existing foundation is designed to have sufficient strength against the weight of the structure and the load during earthquake at the beginning of the design, but due to the increase in the load of the superstructure and the revision of the seismic design standards after use. It may be difficult to secure the required earthquake resistance. In such a case, it is necessary to reinforce the existing foundation.

  However, in the case of a foundation having a footing, it is difficult to provide a new pile below the footing. Therefore, a reinforcing structure in which an additional pile is constructed around the existing footing and the additional pile is connected to the existing footing by an extension footing constructed on the outer periphery of the existing footing may be employed (see the prior art in Patent Document 1). ).

  In addition, as a reinforcing method of the footing foundation, the outer peripheral part of the existing footing is connected with a water jet or the like to expose the tip of the lateral main reinforcing bar, and an additional pile is placed on the outer periphery of the existing footing and load transmission is possible In this way, an invention has been proposed in which an additional foot is arranged on the outer periphery of an existing footing so as to cover the additional pile from above after arranging the additional reinforcing bar in the lateral main reinforcing bar (see Patent Document 2).

JP 2004-339894 A JP-A-8-296209

  However, in the conventional reinforcement structure that connects the additional pile and the existing footing by the extension footing, in order to join the existing footing and the extension footing, a shear bearing material such as many anchor bars is provided on the side of the existing footing. It is necessary and construction takes time. Further, in order to connect the additional pile and the existing footing, an additional footing is essential.

  Further, in the invention of Patent Document 2, not only the extension footing is essential, but also the lifting work takes time. In particular, in order to expose the lateral main reinforcing bar so that load transmission is possible, it is necessary to hang the side surface of the existing footing over the entire circumference with a considerable thickness, so that a great deal of time is required for the construction.

  The present invention has been made in view of such a background, and an additional footing is not indispensable, does not take time for construction, and provides a reinforcing structure for an existing foundation that can shorten the construction time. Its main purpose.

  In order to solve the above problems, the present invention is a reinforcing structure (1) of an existing foundation (10) having a footing (12), which is constructed on the outer periphery of the footing, and has pile head concrete (23) on the head. A plurality of additional piles (21) made of steel pipe piles filled with a horizontal beam (24) joined to the side surface (12s) of the footing with a plurality of joints (30), and an upper surface (21u) of the additional piles And a connecting member (25) that is embedded in the pile head concrete, integrated with the additional pile, and joined to the cross beam.

  By setting it as such a structure, an additional pile and a footing can be directly joined via a connection member and a horizontal beam, without making an extension footing essential. And even if the construction position of the additional pile is slightly shifted, if the construction error is within the range where the connecting member fits in the steel pipe, just place the pile head concrete with the connecting member joined to the installed horizontal beam. Since construction errors can be absorbed, construction does not take time and construction time can be shortened.

  Further, according to one aspect of the present invention, the transverse beam is inserted into a through hole (33) provided substantially horizontally in the footing at at least two of the joint portions (30b), and an end portion (32a) thereof is provided. The PC steel material (32) fixed to the cross beam was friction bonded to the side surface of the footing, and both ends of the PC steel material were fixed to the pair of joint portions (30b) located on opposite side surfaces of the footing. It can be configured.

  According to this configuration, it is possible to reliably join the cross beam to the side surface of the footing with a small number of joints by friction welding using PC steel. Moreover, since prestress is introduce | transduced into a footing because PC steel materials give the compressive force of a horizontal direction to a footing, the reinforcing bar stress degree of a footing can be reduced.

  Further, according to one aspect of the present invention, the transverse beam is fastened to the side surface of the footing by an anchor bolt (31) provided substantially horizontally on the footing at a joint portion (30a) in the vicinity of the connecting member. The connecting member may be configured to be fastened to the cross beam by a bolt (26).

  In the vicinity of the connecting member in the cross beam, it is difficult to install the PC steel material to join the connecting member. However, according to this configuration, the joint bolt is also provided in the vicinity of the connecting member by using the anchor bolt, and the load of the footing is efficiently performed. It can be transmitted to the connecting member well. Further, since it is sufficient to join the connecting member and the cross beam with bolts, the connecting operation is easy and the construction time can be shortened.

  Moreover, according to one aspect of the present invention, the PC steel material further includes an additional footing (22) that is constructed on an outer periphery of the footing so as to cover the additional pile from above, and that embeds the transverse beam and the connecting member. The extended PC steel material (36) connected to the end portion of the additional footing and fixed in the vicinity of the side surface (22s) of the additional footing.

  According to this configuration, since the transverse beam and the connecting member are embedded in the extension footing, it is possible to prevent such corrosion and damage. In addition, since the extended PC steel is also provided in the extension footing, prestress is introduced to the connecting surface between the existing footing and the extension footing, so the shear transmission resistance is improved and the existing footing and extension footing are securely connected. Can be integrated.

  Further, according to one aspect of the present invention, the additional footing can be constructed above the footing.

  The additional pile increases the bearing capacity, and the distance from the footing center to the support position (increased pile) increases, so the stress generated in the footing increases. According to this configuration, the shearing capacity and bending capacity of the footing are increased. Can be strengthened.

  As described above, according to the present invention, it is possible to provide a reinforcing structure for an existing foundation that does not require additional footing, does not require time for construction, and can shorten the construction time.

The top view of the reinforcement structure of the existing foundation which concerns on this invention II-II sectional view in FIG. III-III sectional view in FIG. Partial enlarged view of FIG. VV cross-sectional enlarged view in FIG.

  Hereinafter, with reference to drawings, the embodiment of reinforcement structure 1 of existing foundation 10 and the reinforcement method of existing foundation 10 concerning the present invention is described in detail. In addition, in order to avoid complexity, the hatching of the concrete structure portion is omitted in each drawing, and in FIG. 1, the additional footing 22 is shown in a transparent state. Also, in the following explanation, in order to distinguish existing ones from those to be added, “existing”, “addition” or “addition” is added before each name such as piles and footings, respectively, and existing ones are added. In the case of indicating generically including “”, “footing 2” or the like is simply written without attaching anything to the name.

  As shown in FIGS. 1 to 3, the existing foundation 10 is a foundation of the pier 4 that is an upper structure, and here, four existing piles 11 and the heads of these existing piles 11 are connected to each other. It has the existing footing 12 provided. The existing footing 12 has a substantially rectangular parallelepiped shape with a square shape in plan view, and the pier 4 is integrally constructed at the center of the figure on the plane. Each existing pile 11 is arranged near the four corners of the existing footing 12. In addition, the existing foundation 10 should just have the existing footing 12, and does not need to have the existing pile 11. FIG.

  The reinforcing structure 1 according to the present invention is expanded to reinforce the existing foundation 10, and is constructed on the outer periphery of the existing footing 12, and the head is filled with pile head concrete 23 (see FIG. 4). A plurality (20 in this case) of additional piles 21 (21C and 21S) and a plurality (here, 10 points each on the surface facing the bridge axis direction, perpendicular to the bridge axis direction) on the four side surfaces 12s of the existing footing 12 Embedded in pile head concrete 23 in such a manner that it protrudes from the upper surface 21u of the additional pile 21 and four transverse beams 24 made of grooved steel joined with joint portions 30 (30a and 30b) of 8 faces on each side. In addition to being integrated with the additional pile 21, the connecting member 25 made of H-shaped steel joined to the cross beam 24 and the outer periphery of the existing footing 12 so as to cover the additional pile 21 from above are constructed. And a additional footings 22 for burying the fine connecting member 25.

  The increased pile 21 has a lower end (not shown) that enters the support ground with a predetermined penetration length, and the upper end is set to a length that is slightly higher than the lower surface 12 l of the existing footing 12 in the same manner as the existing pile 11. Here, in order to make the expansion dimension of the footing 2 by reinforcement as small as possible, the cross-sectional dimension of the additional pile 21 is made smaller than the cross-sectional dimension of the existing pile 11, and the number of the additional piles 21 is relatively large. There have been many. The additional piles 21 are arranged at equal intervals along the outer periphery (side surface 12s) of the existing footing 12 so as to form a square in a plan view and surround the existing footing 12, and four additional piles arranged at the four corners. 21 (hereinafter referred to as a corner pile 21C) and 16 additional piles 21 (hereinafter referred to as side piles 21S) other than the corner pile facing the side surface 12s of the existing footing 12.

  Each cross beam 24 is made of channel steel made of steel such as SS400, and has the same height position in the vicinity of the center line Ch in the height direction of the existing footing 12 (here, the center of the cross beam 24 in the height direction is the existing footing 12). Are arranged horizontally at positions slightly lower than the center line Ch in the height direction. The horizontal beams 24 are slightly shorter than the horizontal length of the side surface 12s of the existing footing 12 so as not to interfere with each other at the corners of the existing footing 12.

  The cross beam 24 is bonded to the side surface 12s of the existing footing 12 with four first joint portions 30a disposed in the vicinity of the additional pile 21 corresponding to the additional pile 21 and six other second joint portions 30b. Has been. As shown in FIG. 4, in the first joint portion 30 a, the cross beam 24 is fastened to the existing footing 12 by four anchor bolts 31 having male threads driven on the existing footing 12.

  On the other hand, in the second joint portion 30b, as shown in FIG. 5, the cross beam 24 is frictionally joined to the side surface 12s of the existing footing 12 by a PC steel rod 32 orthogonal to the side surface 12s of the existing footing 12. The PC steel bar 32 is inserted into a through hole 33 horizontally drilled by a core drill or the like so as to open perpendicularly to a pair of parallel side surfaces 12s of the existing footing 12 and is strained by a predetermined tension tool. In this state, the end 32 a is fixed to the horizontal beam 24 by the fixing tool or the fixing tool 34, so that prestress of compression is introduced to the existing footing 12 via the horizontal beam 24.

  Here, since the existing footing 12 has a square shape in plan view, the extending direction of the PC steel bar 32 is two directions, ie, the bridge axis direction and the bridge axis perpendicular direction. The PC steel bar 32 extending in the bridge axis direction and the PC steel bar 32 extending in the direction perpendicular to the bridge axis have different heights so that the through-holes 33 do not contact each other so as to intersect each other in a plan view. Arranged in two stages.

  As shown in FIGS. 1 and 4, the connecting member 25 has a cross-sectional dimension that can be inserted into the additional pile 21, and is installed on the side pile 21 </ b> S in which the horizontal beam 24 is positioned above the additional pile 21. . Each connecting member 25 is arranged in the center of the pile 21 in a plan view, and the lower portion is increased and embedded in the pile head concrete 23 of the pile 21, and the upper portion includes a plurality of (four sets here) bolts. -It is fastened to the cross beam 24 by a nut 26. The transverse beam 24 is welded with a connecting plate 24a formed with a bolt insertion hole at a position corresponding to the connecting member 25 (the additional pile 21) to close the groove of the grooved steel, and the width direction of the connecting plate 24a. A stiffener 24b having a shape that fits the inner surface (groove) of the cross beam 24 is welded to the center portion of the beam.

  The pile head concrete 23 of the additional pile 21 is constructed from a position deeper than the lower end of the connecting member 25 to the upper surface 21u of the additional pile 21, and the load of the existing footing 12 transmitted from the connecting member 25 causes the pile head concrete 23 to be loaded. Thus, it is transmitted to the additional pile 21 with certainty. Note that resistance means such as stud bolts may be provided on the lower outer surface of the connecting member 25 and the inner surface of the additional pile 21.

  In the corner pile 21C in which the cross beam 24 is not positioned above the additional pile 21, although detailed illustration is omitted, the pile with a general reinforcing bar rod protruding from the upper surface 21u of the corner pile 21C installed on the pile head Head concrete 23 is cast and integrated with the extension footing 22.

  The extension footing 22 is constructed from the same height as the lower surface 12 l of the existing footing 12, so that the head of the additional pile 21 is rolled up and the footing 2 is constructed to a position higher than the upper surface 12 u of the existing footing 12. The height of is made larger. The side surfaces 12s and the upper surface 12u of the existing footing 12 and the lower side surface of the bridge pier 4 which are joint surfaces with the additional footing 22 are roughened by chipping or the like.

  Of the side surface 12 s of the existing footing 12, the surface of the portion to be joined to the cross beam 24 is not subjected to surface treatment in order to directly contact the cross beam 24, but the surface is roughened in order to increase the degree of adhesion with the cross beam 24. In addition, the non-shrinkable mortar or the like may be filled in the gap with the cross beam 24.

  As shown in FIG. 5, a coupler 35 is connected to the end portion 32a of the PC steel rod 32, and the coupler 35 extends on the opposite side of the side to which the PC steel rod 32 is connected. One end of the existing extended PC steel rod 36 is connected. The other end of the extended PC steel rod 36 is fixed to the extension footing 22 by the fixing body 37 in the vicinity of the side surface 22s thereof, thereby introducing compression prestress into the extension footing 22.

  The reinforcing method of the existing foundation 10 having the above-described configuration is as follows. First, a steel pipe pile is driven into the ground on the outer periphery of the existing footing 12 by the Nakabori method or the like so as not to affect the existing foundation 10, and the pile 21 is constructed. Further, a through hole 33 is formed in the existing footing 12 by core boring or the like, and a PC steel rod 32 is set in the through hole 33. The side surface 12s and the upper surface 12u of the existing footing 12 are roughened by chipping or the like, and the anchor bolt 31 is fixed by drilling holes in the side surface 12s of the existing footing 12. Next, the cross beam 24 is fastened to the side surface 12 s of the existing footing 12 with the anchor bolt 31. Further, the PC steel rod 32 is tensioned and its end portion 32 a is fixed to the cross beam 24 by the fixing tool 34, and horizontal prestress is introduced into the existing footing 12. Further, the upper part of the connecting member 25 is fastened to the cross beam 24 with bolts and nuts 26 with the lower part of the connecting member 25 inserted into the pile head of the additional pile 21, and the pile head concrete 23 is placed. Thereafter, the coupler 35 and the extended PC steel rod 36 are connected to the end 32a of the PC steel rod 32 to construct the extension footing 22, and after the concrete of the extension footing 22 is hardened, the extension PC steel rod 36 is tensioned and fixed. The body 37 is fixed in the vicinity of the side surface 22 s of the extension footing 22, and horizontal prestress is introduced into the extension footing 22.

  According to the reinforcing structure 1 and the reinforcing method of the existing foundation 10 thus configured, the additional pile 21 and the existing footing 12 are directly joined via the connecting member 25 and the cross beam 24. Therefore, the existing foundation 10 can be reinforced without requiring the additional footing 22. And since it is the form which joins the additional pile 21 and the existing footing 12 directly, since the additional pile 21 can be arrange | positioned close to the existing footing 12, the expansion dimension of the existing foundation 10 by reinforcement is small, and a site cannot be ensured. The present invention can also be applied to cases and cases where structures or the like exist in close proximity.

  In addition, even if the construction position of the additional pile 21 is slightly shifted, if the construction error is within a range where the connecting member 25 can be accommodated in the steel pipe, the pile head concrete 23 is attached in a state where the connecting member 25 is joined to the installed lateral beam 24. Construction errors can be absorbed simply by placing, so that construction does not take time and construction time can be shortened.

  Further, since the transverse beam 24 is frictionally joined to the side surface 12s of the existing footing 12 by the PC steel bar 32 at the plurality of second joining portions 30b, the transverse beam 24 is reliably joined to the side surface 12s of the existing footing 12 at a small number of joints. The And the both ends of PC steel bar 32 are fixed to cross beam 24 by a pair of 2nd joined parts 30b, and the prestress of compression is introduced into existing footing 12, and the rebar stress degree of existing footing 12 is reduced.

  Further, in the vicinity of the connecting member 25 in the cross beam 24, it is difficult to install the PC steel rod 32 in order to join the connecting member 25. Fastened to the footing 12 and the connecting member 25 is fastened to the cross beam 24 by bolts and nuts 26, so that a joint 30 between the cross beam 24 and the existing footing 12 is also provided in the vicinity of the connecting member 25. The load is efficiently transmitted to the connecting member 25. Further, since the connecting member 25 and the cross beam 24 are joined by the bolt / nut 26, the connecting work can be easily performed in a short construction time.

  Further, since the additional footing 22 is constructed on the outer periphery of the existing footing 12, the cross beam 24 and the connecting member 25 are covered with concrete and are not corroded or damaged. Since the extension PC steel rod 36 is fixed in the vicinity of the side surface 22 s of the extension footing 22, prestress is introduced into the connecting surface between the existing footing 12 and the extension footing 22, thereby improving the shear transmission resistance. The existing footing 12 and the extension footing 22 are reliably integrated.

  In addition, the supporting force of the footing 2 is increased by the additional pile 21 and the stress generated in the footing 2 is increased. However, since the additional footing 22 is constructed above the existing footing 12, the shear strength of the footing 2 and Increased bending strength.

  This is the end of the description of specific embodiments, but the present invention is not limited to these embodiments. For example, in the said embodiment, although this invention is applied to the existing foundation 10 of the pier 4, you may apply to the foundation of the lower structure of another structure. In the above embodiment, the extension footing 22 is constructed. However, if there is no problem of corrosion or damage to the cross beam 24 or the connecting member 25, the extension footing 22 may not be constructed. Moreover, in the said embodiment, although the existing footing 12 is exhibiting the planar view square, different shapes, such as a rectangle, a polygon, a circle | round | yen, track shape, may be sufficient. In addition, the specific shape, arrangement, quantity, and the like of each member can be changed as appropriate without departing from the spirit of the present invention. In addition, the constituent elements of the reinforcing structure 1 of the existing foundation 10 and the steps of the reinforcing method of the existing foundation 10 according to the present invention shown in the above embodiment are not necessarily all necessary, and at least do not depart from the spirit of the present invention. It is possible to make appropriate selections as long as possible.

DESCRIPTION OF SYMBOLS 1 Reinforcement structure 10 Existing foundation 12 Existing footing 12s Side surface 21 Additional pile 21u Upper surface 22 Additional footing 22s Side surface 23 Pile head concrete 24 Horizontal beam 25 Connecting member 26 Bolt / nut 30 Joint portion 30a First joint portion 30b Second joint portion 31 Anchor bolt 32 PC steel bar 33 Through hole 36 Extended PC steel bar

Claims (5)

A method of reinforcing an existing foundation for constructing a reinforcing structure of an existing foundation having a footing,
A step of constructing a plurality of increasing piles made of steel pipe pile on the outer periphery of the footing,
And bonding a crossbeam with a plurality of joint portions on the side surface of the footing,
A step of joining the upper part of the connecting member protruding from an upper surface of the widening pile in a state of inserting the lower portion of the connecting member to the pile head of the widening pile to said cross beam,
And Da設the pile head concrete head of the widening pile so that the bottom is embedded in the connecting member, and wherein said connecting member having a <br/> the step of integrating the widening pile method for reinforcing the existing basis for. A reinforcing structure for an existing foundation having a footing,
A plurality of additional piles constructed of steel pipe piles constructed on the outer periphery of the footing and filled with pile head concrete in the head;
A lateral beam joined to the side surface of the footing with a plurality of joints;
The widening in a manner to protrude from the upper surface of the pile is embedded in the pile concrete is integrated into the widening pile, have a connecting member joined to the cross beam,
The transverse beam is frictionally joined to the side surface of the footing by a PC steel material that is inserted into a through-hole provided substantially horizontally in the footing and has an end fixed to the transverse beam in at least two of the joining portions,
The PC steel material, the reinforcing structure already set basic you characterized in that both ends to a pair of the joint portion located on the opposite side of the footing is fixed. A reinforcing structure for an existing foundation having a footing,
A plurality of additional piles constructed of steel pipe piles constructed on the outer periphery of the footing and filled with pile head concrete in the head;
A lateral beam joined to the side surface of the footing with a plurality of joints;
The widening in a manner to protrude from the upper surface of the pile is embedded in the pile concrete is integrated into the widening pile, have a connecting member joined to the cross beam,
The lateral beam is fastened to the side surface of the footing by an anchor bolt provided substantially horizontally on the footing at a joint near the connecting member.
The coupling member, the reinforcing structure already set basic by bolts characterized in that it is fastened to the crossbeam. It is constructed on the outer periphery of the footing so as to cover the additional pile from above, and further has an additional footing for burying the transverse beam and the connecting member,
The reinforcing structure for an existing foundation according to claim 2, further comprising an extended PC steel material connected to an end of the PC steel material and fixed in the vicinity of a side surface of the additional footing. The reinforcing structure for an existing foundation according to claim 4, wherein the additional footing is also constructed above the footing.

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