JPH07229133A - Precast underground multi-purpose duct construction method - Google Patents

Abstract

PURPOSE:To provide a precast underground multi-purpose duct construction method where a rational prestress on the basis of a economical and reasonable design technique is introduced. CONSTITUTION:In order to cope with the axial elongation and contraction deformation action force such as earthquake wave motion or the like and bending deformation action force perpendicular to the axis, a designated number of precast concrete building frames are disposed to give prestress by a post tension method, and if the axial elongation and contraction deformation action force is within the stress of prestress of a PC steel material, a joint part between the concrete building frames will not be opened. If the axial elongation and contraction deformation action force exceeds the initial introduction stress, the opening amount is obtained by the expression 1, and the stress of PC steel material is obtained by the expression 2. If the bending deformation action force perpendicular to the axis exceeds prestress, the opening amount is obtained by the expressions 3, 4, and the stress of PC steel material is obtained by the expression 5. The allowable value of PC steel material is confirmed, and the allowable value of the opening amount of the joint part of the precast concrete building frames is set 20mm or below, whereby the amount of PC steel material used can be decreased. A waterproof joint material according to the performance of a joint material to be required in the joint part for waterproofness and expansible performance is selected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precast joint ditch construction method for forming a cavern in the underground of a road surface in an urban area.

[0002]

2. Description of the Related Art Generally, since a gas pipe, a cable such as an electric wire and a telephone are stored together, a joint groove may be buried under the road surface underground in an urban area. In-situ construction method to form a reinforced concrete box by in-situ casting using a frame, and box blocks of a specified standard are laid out in a line in the excavated underground trench, and are integrally connected with PC steel etc. There are two methods, namely, the precast joint groove construction method for forming.

A seismic resistant structure is required for the joint groove, but for this seismic resistant design, design guidelines have already been established for the field casting method. However, there is still no design guideline for the precast joint groove construction method.
The current situation is that it complies with the design guidelines of the in-situ construction method.

Further, the common groove is required to be watertight because it causes inconvenience if groundwater or the like enters, but the design guideline shows that a joint is used between the common grooves of a predetermined length in this design and construction. ing. However, even in this joint, a flexible joint is used as an example of an earthquake-resistant structure.

By the way, as shown in FIG. 3, the precast joint groove has a predetermined shape in which a plurality of box blocks 1 having a predetermined shape are laid out in a row and the PC steel material 2 is axially inserted and integrally connected. A box 3 having a length is formed, and a plurality of the boxes 3 are connected by flexible joints 6, respectively.

The box block 1 is a tubular body made of reinforced concrete or prestressed concrete and having a rectangular cross section, and is often manufactured as a precast concrete skeleton at a factory or the like and transported to the site. Is.

The box blocks 3 are integrally connected with the PC steel material 2 to form the box paths 3. The box blocks are connected vertically in consideration of prevention of differential sinking and leakage of water. This is for the purpose of performing the integration of each box block 1.

Referring to the conventional amount of PC steel used, about 32 PC steels (steel rods) 2 are inserted in the cross section of the box block 1 in the example shown in FIG. Conventionally, the diameter of the PC steel rod 2 is 26 mm or the like.

In order to secure the watertightness of Hakoji 3,
As shown in FIG. 5, a flexible material made of synthetic rubber or the like is used between the boxes 3 having the joints 1a formed between the box blocks 1 and having the length L of about 30 m. The joint 6 is used. At both ends of the flexible joint 6, bolts 10 are inserted into the anchor bolts 7 fixed to the inner ends of the box block 1 and the nuts 8 or the inserts 9 are fastened to push the plate 11.
It is fixed watertightly.

[0010]

However, when the design guideline of the in-situ construction method is applied to the design of the precast joint groove construction method, the joint 1a between the box blocks 1 is opened against the sectional force generated by the earthquake. It is necessary to introduce a huge prestress in order to prevent the occurrence of

Therefore, it is necessary to previously provide a large number of PC steel material insertion holes in the precast concrete frame (see FIG. 4), which causes an increase in manufacturing cost.
A large amount of input of the PC steel material 2 and the flexible joint 6 and its cost and work are required.

This can be said to be an irrational design concept if attention is paid to the characteristics of the precast joint groove. Therefore, in contrast to the conventional irrational design concept, by paying attention to the characteristics of the precast joint groove and allowing this after considering the opening of the joint 1a between the box blocks 1, a rational introduction of prestress is introduced. Is possible.

By the introduction of this rational prestress,
The size (required diameter and number) of PC steel 2 can be reduced, and the conventional flexible joint 6 against seismic force on the same ground
It is also possible to extend the interval between, and therefore, it is expected that a very economical and rational design method will be established.

Therefore, the present invention provides a precast joint groove construction method in which a rational prestress is introduced based on an economical and rational design method.

[0015]

According to the first aspect of the present invention, the precast joint groove construction method is adapted to deal with the axial expansion / contraction deformation force and the axis-perpendicular bending deformation action force such as seismic waves. , A predetermined number of precast concrete skeletons are arranged and prestressed by the post-tension method, and the joint between concrete skeletons shall not be opened when the axial expansion / contraction deformation force is within the stress due to the prestress of the PC steel material, When the axial stretching deformation acting force exceeds the initial introduction stress, the opening amount is calculated by the formula 1 and PC is calculated by the formula 2.
In addition to obtaining the stress of the steel material, when the bending deformation acting force in the direction perpendicular to the axis exceeds the prestress, the opening amount is obtained by the equations 3 and 4, and the stress of the PC steel material is obtained by the equation 5, and
By checking the allowable value of PC steel and setting the allowable value of the opening of the joint of the precast concrete frame to 20 mm or less, the amount of PC steel used is reduced, and the waterproof and stretchable joint used for the joint The feature is that a waterproof bonding material is selected according to the performance of.

According to claim 2, a predetermined number of precast concrete skeletons are provided in order to deal with the axial action force such as seismic waves and the bending deformation action force in the direction perpendicular to the axis,
Pre-stressed by PC steel material by post-tension method to form a bar-shaped beam, the opening and displacement due to the axial expansion and contraction deformation acting force between the connecting beams are seismic waves, the length of the bar-shaped beam, and the buried ground The optimum flexible joint spacing according to the joint material performance is calculated according to the type according to the type, and the opening amount and displacement amount due to the bending deformation acting force between the connecting beams in the direction perpendicular to the axis are the seismic wave length・ Determined by equations 7 and 8 according to the type of buried ground, and the displacement amount due to the shear deformation action force in the direction perpendicular to the axis between the connecting beams is determined by equation 9 to find the optimum flexible joint spacing according to the joint material performance. , Installation interval
Select a flexible joint material according to the amount of elongation.

[0017]

[Function] The scale (required diameter and number) of PC steel can be reduced, and the flexible joint space can be extended against seismic force on the same ground.

Therefore, by manufacturing the precast concrete frame, reducing the PC steel material and the flexible joint, and facilitating the workability, a very economical and rational precast joint groove can be obtained.

[0019]

[Example] The main purpose of the seismic design in the longitudinal direction of the precast joint groove is to optimize the optimum flexible joint spacing and rational prestress initial stage according to the strength of earthquake motion, ground type, presence or absence of liquefaction, and structural dimensions. It is to decide the introduction power.

In the seismic design, ground displacement due to propagation of seismic waves and uplifting, subsidence, and lateral movement due to liquefaction are taken into consideration as the influence of the earthquake, but stress and strain of concrete and PC steel and flexible joints and general joints are considered. Check the following items for displacement.

(1) The concrete skeleton stress is less than the allowable stress or the critical stress (2) The stress of the PC steel material is less than the allowable stress or the critical stress, or the strain is less than the critical strain (3) The amount of opening of the flexible joint in the longitudinal direction and the amount of opening due to horizontal / vertical bending are less than the allowable displacement or the limit displacement. (4) The amount of opening of the general joint in the longitudinal direction and the amount of opening due to horizontal / vertical bending are The allowable displacement is not more than the allowable displacement or the limit displacement.The limit displacement of the flexible joint is not restricted by the product standard, and the limit elongation of the flexible joint and the durability and safety of the joint in a deformed state can be determined. It must be decided in consideration.

Further, it is necessary to set the limit displacement of the general joint in consideration of the inflow amount of earth and sand due to the joint opening and the difficulty of recovery after the earthquake.

The above is the purpose and flow of the seismic design in the content shown as the guideline for the seismic design of the precast joint groove having the flexible joint upon the construction of the precast joint groove.

Accordingly, in accordance with this, a new seismic design of the precast joint groove is performed as follows.

A. Basics of seismic design In order to calculate the cross-sectional force due to an earthquake, it is the first step to know the nature of seismic waves. This is the current situation in terms of using the "response displacement method" that has been theoretically engineered from many years of research. It is no different from the seismic design standard.

B. Conditions for seismic design 1. Set cross-sectional shape The shape shown in FIG. 1 was used, and necessary dimensions are shown in the drawing.

2. Structural section specifications

[0028]

[Table 1]

3. Area classification A area 4. Soil condition

[0030]

[Table 2]

5. From ground type T _G ≧ 0.6 [S] 4
Seed ground C. Properties of seismic waves

[0032]

[Table 3]

D. Amplitude of seismic waves used for seismic design 1) Superposition of axial expansion and contraction in seismic calculation

[0034]

[Equation 10]

2) Amplitude in the seismic calculation of bending deformation Propagation in the axial direction of the common groove and the vibration direction is the axis orthogonal direction in the horizontal plane a = U _h Propagation in the axial direction of the common groove and the vibration direction is the direction orthogonal to the axis in the vertical plane a = U _V E. Arrangement of PC steel material Arrangement and sectional view of PC steel material are set as shown in Fig. 2. F. Seismic design of axial expansion and contraction 1. Calculation of box stress

[0036]

[Equation 11]

The box stress is positive for compression. Since a negative value (tensile stress) is generated from the calculation result, joint opening occurs. Therefore, the joint opening amount and P when the joint is opened next
Calculate the stress of C steel bar and consider safety.

2. Calculation of joint opening amount The joint opening amount δ _jG of the general joint is calculated by the above formula 1. 3. Stress of PC steel material when joint of general joint opens When stress of PC steel material when joint of general joint opens is calculated by the previous formula 2. Calculation of Opening Amount of Flexible Joint The opening amount δ _jF of the flexible joint is calculated by the above equation 6.

G. Seismic design for bending deformation in the direction perpendicular to the axis 1. Calculation of box stress 1) In horizontal plane

[0040]

[Equation 12]

2) Within the vertical plane

[0042]

[Equation 13]

The maximum bending moment in the horizontal / vertical plane is given by the following equation.

[0044]

[Equation 14]

For the box stress, compression is positive. From the calculation results, a negative value (tensile stress) is generated, which causes joint opening. Therefore, the joint opening amount and the stress of the PC steel bar when the joint is opened are calculated next, and safety is checked.

2. Calculation of joint opening amount The joint opening amount δ _jG of a general joint is calculated by the following formula.

1) in the horizontal plane δ _JG = h · θ where h: box width (625 cm) θ: opening angle (rad) 2) in the vertical plane δ _JG = h · θ, where h: box width (330 cm) θ: Opening angle (rad) The opening angle of the box is

[0048]

[Equation 15]

Here, e: length of one box (m) L: wavelength of seismic wave (m) a: ground displacement amplitude (m) a ": concrete edge stress and tensile stress due to bending deformation equal to prestress Ground displacement amplitude (m)

[0050]

[Equation 16]

Here, E _c : Young's modulus of concrete (t / m ² ) A _c : Total cross-sectional area of concrete (m ² ) P: Prestressing force (t) 3. Stress of PC steel when joint of joint is opened Calculate stress of PC steel when joint of joint is opened by the following formula 1) In horizontal plane

[0052]

[Equation 17]

2) Within the vertical plane

[0054]

[Equation 18]

Where σ _p1 : initial stress of PC steel δ ^v _jg : opening of general joint in vertical plane δ ^h _JG : opening of general joint in horizontal plane E _p : Young's modulus of PC steel M ” _v : vertical Bending moment due to ground displacement amplitude a "at which stress due to in-plane bending deformation equals prestress M" _h : Bending moment due to ground displacement amplitude a "at which stress due to bending deformation in the horizontal plane becomes equal to prestress

[0056]

[Formula 19]

4. Calculation of the opening amount of the flexible joint The opening amount δ _jF of the flexible joint is calculated by the following formula: 1) In the horizontal plane δ _JF = h ・ θ _max where h: Box width (625 cm) θ _max : Opening Angle (rad) 2) In the vertical plane δ _JF = h · θ _max where, h: height of the box (330 cm) θmax: opening angle (rad)

[0058]

[Equation 20]

From the above calculation results, the following settings are stable: Flexible joint spacing 30 m PC steel rod φ23 mm-6 used Here, in the next step, the settings are changed as follows:
Calculate again.

Flexible joint spacing 60 m or less The numerical values of the main design calculation results are shown below.

H. Optimal flexible joint spacing setting Numerical result of main design calculation 1) Box stress

[0062]

[Table 4]

2) Flexible joint-Axial displacement δj _F = 9.11 cm-Maximum rotation angle: Horizontal section θhmax = 0.0008rad Vertical section θvmax = 0.0002rad 3) General joint-Joint opening: Axial δj _G = 0.15cm Bending direction horizontal section δhj _G = 0.02cm Bending direction vertical section δvj _G = 0.00cm By the above calculation, it will be stable even in the reset state,
Regardless of the joint distance of 30 m, it is decided to be 60 m.

The precast joint groove based on the above design is
As shown in FIG. 2, it suffices to insert at least six PC steel materials (steel rods) 12 having a diameter dimension of 23 mm into the cross section of the precast concrete skeleton 11, for example, and the flexible joint also has a conventional It is sufficient to install them twice, that is, at intervals of about 60 m.

By appropriately selecting the diameter of the PC steel rod 12, six or more PC steel rods 12 are arranged within the cross section of the precast concrete skeleton 11, or 4
It may be sufficient to insert the PC steel rod 12 of the book.

Therefore, when the pre-cast joint groove is constructed based on the above design concept, the amount of PC steel material is about 1/5 of the conventional amount, and the amount of flexible joint material is about 1 of the conventional amount.
Even if each is reduced to about 1/2, it is possible to construct a precast joint groove with a reasonable seismic design that satisfies the design guidelines of the existing in-situ construction method.

Although the present invention has been described with respect to the precast common groove, the present invention is not limited to this, and the precast concrete skeleton includes box culverts, arch culverts, oval shapes, and other underground conduits buried in the ground.

[0068]

According to the present invention described above, the amount of PC steel material is about 1/5 of the conventional amount, and the amount of flexible joint material is about 1 of the conventional amount.
Even if it is reduced to about 1/2, it is possible to construct a precast joint groove with a rational seismic design that satisfies the existing design guidelines for the in-situ casting groove method. Therefore, the material cost and cost for precast joint groove construction can be reduced. It is a very economical and rational precast joint ditch construction method that is simple, quick and easy, and can shorten the construction period.

[Brief description of drawings]

FIG. 1 is a sectional view of a set shape of a precast joint groove.

[Fig. 2] PC steel material arrangement cross section

[Fig. 3] Plan view of precast joint groove

[Fig. 4] Conventional PC steel material arrangement cross-sectional view

5 (A), (B), and (C) are cross-sectional views of a flexible joint having a precast joint groove.

[Explanation of symbols]

 11 ... Precast concrete frame 12 ... PC steel

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideto Tabata 1-6-14 Akebono, Kashiwa City, Chiba Prefecture (72) Inventor Hiroaki Tsuchiya 1-8-22-305 (72) Invention, Kamimiya Tsurumi Ward, Yokohama City, Kanagawa Prefecture Person Kiyoshi Morinaga 2555-26 Sunadata, Kawagoe City, Saitama Prefecture (72) Inventor Jiro Kondo 4-8-18-206 Kanno, Ichikawa City, Chiba Prefecture (72) Hideaki Morita 1623-4 Yamazaki, Noda City, Chiba Prefecture

Claims (2)

[Claims] 1. A predetermined number of precast concrete skeletons are provided to pre-stress by a post-tensioning method in order to deal with axial stretching deformation acting force such as seismic waves and bending deformation acting force in a direction perpendicular to the axis. It is assumed that the joint between the concrete frames does not open when the directional elastic deformation acting force is within the stress due to the prestressing of the PC steel material, and when the axial extensible deformation acting force exceeds the initial introduction stress, the opening amount is calculated by Equation 1. When the stress of the PC steel is calculated by the formula 2, when the bending deformation acting force in the direction perpendicular to the axis exceeds the prestress, the opening amount is calculated by the formulas 3 and 4, and the opening amount is calculated by the formula 5
By determining the stress of the C steel material, checking the allowable value of the PC steel material, and setting the allowable value of the opening amount of the joint portion of the precast concrete frame to 20 mm or less, the usage amount of the PC steel material can be reduced and used for the joint portion. A precast joint groove construction method characterized in that a waterproof type joint material is selected according to the performance of a waterproof type and stretchable joint material. [Equation 1] [Equation 2] [Equation 3] [Equation 4] [Equation 5] 2. A predetermined number of precast concrete skeletons are provided and prestressed with a PC steel material by a post-tension method in order to cope with the axial action force such as seismic waves and the bending deformation action force in the direction perpendicular to the axis. Without a bar-shaped beam, the amount of opening due to the axial stretching deformation acting force between the connecting beams,
The amount of displacement is calculated based on the seismic wave, the length of a bar-shaped beam, and the type of buried ground, using Equation 6 to find the optimum flexible joint spacing according to the joint material performance, and the bending deformation action between the connecting beams in the direction perpendicular to the axis. The amount of opening and the amount of displacement due to the force are determined by the formulas 7 and 8 according to the seismic wave, the length of the bar-shaped beam, and the type of the buried ground, and the amount of displacement due to the shear deformation acting force between the connecting beams is expressed by the formula. The precast joint groove construction method characterized in that the optimum flexible joint spacing according to the joint material performance is obtained according to 9, and the flexible joint material is selected according to the installation spacing and the amount of extension. [Equation 6] [Equation 7] [Equation 8] [Equation 9]