JP2009041272A - Construction method for bridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a construction method for a bridge of a continuous girder structure using a precast concrete girder with a small girder height. <P>SOLUTION: The two precast and prestressed concrete girders 2 and 3 composed of high-strength fiber-reinforced mortar are laid across the span of an abutment 110 and a bridge pier 120 by jacking up each of support sections on the bridge piers 120 at the opposed ends of the respective girders by means of a jack 200 so that axially-orthogonal planes of the opposed ends of the precast and prestressed concrete girders 2 and 3 can be formed in an upward-opened V-shape; concrete 60 is placed between the opposed ends of the precast and prestressed concrete girders; after that, the support section is jacked down; and a continuous girder is formed by applying compressive stress to an upper edge of a continuous section of the girder. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for constructing a bridge having a continuous girder structure.

  Conventionally, a concrete girder bridge has a simple girder structure in which a precast concrete girder is installed between the branches, and it has been mechanically clear and easy to construct. Therefore, many bridges have been constructed with a simple girder structure. In such a simple girder structure, expansion joints are required for each span, the expansion joints are easily damaged, the traveling performance is poor, and there is a risk of falling bridges during an earthquake. Etc. For this reason, bridges with a connecting girder structure have recently been developed from the viewpoints of improving the traveling performance of vehicles at high speeds on highways, improving the economy by reducing the number of repairs, and improving earthquake resistance. It is increasing.

  As the bridge of continuous girder structure, cast-in-place concrete is used for the opposite ends of the bridge of continuous girder structure by fixed support work and overhang construction, or the normal pre-cast concrete girder installed between the branches as a simple girder. A bridge having a continuous girder structure is known in which a RC structure or a PC structure is connected in the direction of the bridge axis and a negative bending moment due to an acting load at the connection portion is dealt with. Bridges with a continuous girder structure using precast concrete girder are less subject to restrictions such as support work during construction, although the applicable span length is limited compared to bridges with continuous girder structure by fixed support work or extension work. The construction is relatively simple and the construction period is short (for example, see Non-Patent Document 1).

In recent years, for example, there are cases in which the bridge girder height has to be lowered due to land restrictions, river conditions, construction limit conditions, and the like, and various low girder high bridges have been developed. For example, in a bridge having a prestressed concrete structure, a bridge having a low girder height composed of super high strength mortar and PC steel and having a span ratio to girder height of more than 35 has been proposed (for example, see Patent Document 1).
JP 2004-270382 A “PC Road Bridge Planning Manual”, Prestressed Concrete Construction Association, March 1997, p. 38-41

  Here, when constructing a bridge with a continuous girder structure using a precast concrete girder with a low girder height, the negative bending moment due to the applied load at the above connecting part is a continuous using a precast concrete girder with a normal girder height. Since it acts more greatly than a girder-structured bridge, it is necessary to increase the amount of reinforcing bars and PC cables for forming a continuous girder at the connecting portion. However, when a bridge with a continuous girder structure is constructed using a precast concrete girder with a low girder height, it is necessary to arrange reinforcing bars and PC cables in the limited space with a low girder height at the connecting part. Therefore, the construction may be difficult.

  In view of the above circumstances, an object of the present invention is to provide a method for constructing a bridge having a continuous girder structure using a precast concrete girder having a low girder height.

  The bridge construction method of the present invention that achieves the above-described object is achieved by continuously forming a plurality of precast prestressed concrete girders having a span to girder ratio of 25 or more. Jacking up the support on the bridge pier at the opposite end of each girder so that the plane perpendicular to the axis is open, and laying each girder between successive supports, The concrete is characterized in that concrete is placed in between and then jacked down, and compressive stress is applied to the upper edge of the continuous part of the girder to form a continuous girder.

  According to the bridge construction method of the present invention, the support portions on the bridge piers at the opposite ends of the plurality of precast prestressed concrete girders are respectively jacked up and installed between the continuous supports, and the concrete is driven between the opposite girder ends. This is a construction method in which a continuous girder is formed by jacking down after application and applying compressive stress to the upper edge of the girder continuous part. Moreover, in the state where each of the above-mentioned support portions is jacked up, a V-shape is formed in which the axial orthogonal surfaces of the opposite end portions of each girder are opened upward. Therefore, according to the construction method of the bridge of the present invention, a positive bending moment acts on the portion where the concrete between the opposite beam ends is placed, and this resists the negative bending moment due to the applied load. Therefore, it is possible to reduce the amount of reinforcing bars and PC cables that are placed between the opposite precast prestressed concrete girder ends and reduce the amount of continuous girder using limited space with low girder height. Easy to realize.

  Here, the bridge construction method of the present invention preferably uses a high-strength, high-toughness ultra-high strength mortar for the precast prestressed concrete girder.

  Here, the ultra high strength mortar is, for example, a special portland cement premixed with silica fume having a water cement ratio of about 25% or less, and a short fiber reinforcing material such as metal fiber, inorganic fiber, or organic fiber having a particle size of 5 mm. It is a cement-based ultra-high strength material mixed with the following fine aggregates. Such an ultra-high strength mortar has a compressive strength of about 100 MPa to about 180 MPa, a bending strength of about 15 MPa to about 25 MPa, and a tensile strength of about 8 MPa, and has a conventional compressive strength of about 40 MPa to about 60 MPa. It is a high-strength and high-toughness material compared to ordinary concrete having a bending strength of about 6.5 MPa and a tensile strength of about 3.5 MPa.

  Generally, in a bridge with a low girder height, the stress level generated at the upper and lower edges of the girder due to an applied load is larger than that of a normal girder bridge, so it is necessary to introduce a larger prestress. Therefore, when a precast prestressed concrete girder made of ordinary concrete is used in the construction method of the bridge of the present invention, the compressive stress level of the girder upper and lower edges when prestress is introduced and the girder upper and lower edges when designing loads are allowable stresses. May exceed. On the other hand, according to such a preferable form, since the ultra-high strength mortar itself, which is the material of the precast prestressed concrete girder, resists a large degree of compressive stress, it is possible to further lower the digit. It is. Moreover, since this ultra-high-strength mortar is a material that does not use coarse aggregate, it has good flowability and excellent workability.

  Here, in the construction method of the bridge according to the present invention, a steel material is projected from the end portion of the precast prestressed concrete girder, and the steel materials of the opposing precast prestressed concrete girder ends are connected to each other in a jacked up state. It is also a preferred form to cast concrete after having done.

  According to such a preferable form, in addition to the positive bending moment acting on the portion where the concrete between the opposite beam ends is placed, the steel material also resists the negative bending moment due to the applied load. Therefore, it is possible to further reduce the amount of reinforcing bars and PC cables for forming a continuous girder disposed between the opposing precast prestressed concrete girder ends.

  In the bridge construction method of the present invention, the precast prestressed concrete girder is formed by joining a plurality of precast segments provided with recesses facing each other in the joint surface of the joint portion in the bridge axis direction. Is also a preferred form.

  At the joint part of the precast segment, it is common not to allow the generation of tensile stress when prestress is introduced or when the design load is applied. In bridges constructed by the precast segment method, the amount of PC cable is reduced at the joint part of the precast segment. Often decided. Therefore, by providing recesses facing each other in the joint surface of the joint portion of the precast segment in this way, increasing the prestress generated at the upper and lower edges of the joint portion of the precast segment, the recess is formed in the joint surface of the joint portion. The amount of PC cable can be reduced as compared with the case where it is not provided.

  According to the construction method of the bridge of the present invention, a positive bending moment acts on the portion where the concrete between the opposite girder ends is placed, and this resists the negative bending moment due to the applied load. , Can reduce the amount of reinforcing bars and PC cables to be installed between the opposing precast prestressed concrete girder ends, making it easy to use continuous girder using limited space with low girder height Realized.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a side view of a low girder high bridge 1 constructed according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the vicinity of the center of a branch of the low girder high bridge 1 shown in FIG. 3 is a detailed cross-sectional view of the main girder near the center of the span of the low girder high bridge 1 shown in FIG. 1, and FIG. 4 is a cross section of the main girder at the end of the low girder high bridge 1 shown in FIG. FIG.

  The low girder high bridge 1 shown in FIG. 1 to FIG. 4 is a continuous bridge with two spans in which two precast prestressed concrete girders 2 and 3 made of high strength fiber reinforced mortar are made continuous. Moreover, the precast prestressed concrete girder 2 is formed by joining three precast segments 21, 22, and 23 in the bridge axis direction as shown in FIG. The precast prestressed concrete girder 3 is also formed by joining three precast segments 31, 32, and 33 in the bridge axis direction, as shown in FIG. In addition, in FIG. 1, the abutment 110 and the pier 120 are also shown in addition to the continuous girder in which the two precast prestressed concrete girders 2 and 3 are made continuous.

  Here, this high-strength fiber reinforced mortar is made of steel fiber, which is a short fiber reinforcing material, into silica fume cement (manufactured by Mitsubishi Materials Corporation) having a water cement ratio of about 20% or less, and a fine bone having a particle size of about 5 mm or less. It is a cement-based ultra-high strength material mixed with the material. This high-strength fiber reinforced mortar has, for example, a compressive strength of about 150 MPa, a bending strength of about 20 MPa, a tensile strength of about 8 MPa, a conventional compressive strength of about 40 MPa to about 60 MPa, a bending strength of about 6.5 MPa, Compared to ordinary concrete with a tensile strength of about 3.5 MPa, it is a material with high strength and toughness. Therefore, the high-strength fiber reinforced mortar that is the material of the precast prestressed concrete girders 2 and 3 itself resists the large compressive stress of the upper and lower edges of the girders when prestress is introduced and the upper and lower edges of the girders when the design load is applied. Therefore, it is possible to further increase the digit. Moreover, since this high-strength fiber reinforced mortar is a material that does not use coarse aggregate, it has good fluidity and excellent workability. The high-strength fiber reinforced mortar shown here is one design example of the ultra-high-strength mortar referred to in the present invention, and the ultra-high-strength mortar referred to in the present invention is not limited thereto.

  An example of the low girder high bridge 1 is, for example, a low girder PC (prestressed concrete) bridge having a bridge length of 62.8 m, a span length of 30.9 m, and a girder height of 1.0 m. The total width of the low girder high bridge 1 is, for example, 8.2 m. As shown in FIG. 2, for example, six main girders 10 are arranged in parallel, and the road surface is covered by the pavement 20. ing. The space between adjacent main girders 10 is tightened by a laterally tightened PC steel material (not shown).

  As shown in FIG. 3, the main girder 10 near the center of the span is an I-shaped concrete girder having upper and lower flanges, and has four PC steel material insertion sheaths 11 built in the lower flange. Further, as the tensile force, for example, a “19S15.2” PC steel material in which 19 strands (7 strands) of PC steel having an outer diameter of 15.2 mm are bundled is used.

  As shown in FIG. 4, the main girder 10 at the end has a substantially rectangular cross section, and each of the four PC steel material insertion sheaths 11 has a predetermined edge distance and a predetermined center distance defined for the PC steel material fixing tool. Arranged to satisfy. Here, for example, the edge distance is 235 mm or more, and the center interval is 375 mm or more.

  Next, the construction method of the low girder high bridge 1 which is 1st Embodiment of the construction method of the bridge of this invention is demonstrated.

  FIG. 5 is an explanatory diagram showing a first step in the first embodiment. FIG. 6A is an explanatory diagram for explaining a precast segment joint portion in the precast prestressed concrete girders 2 and 3 shown in FIG. 5, and FIG. 6B is an explanation for explaining a conventional precast segment joint portion. FIG.

  First, three precast segments 21, 22, 23 made of high-strength fiber reinforced mortar are joined in the bridge axis direction to produce precast prestressed concrete girder 2 on the ground, and three precast segments 31, made of high-strength fiber reinforced mortar, 32 and 33 are joined in the direction of the bridge axis, and the precast prestressed concrete girder 3 is manufactured on the ground.

  Next, as shown in FIG. 5, for example, a “19S15.2” PC steel material 40 is inserted into each of the PC steel material insertion sheaths 11 provided in each of the main beams 10 of the precast prestressed concrete beams 2 and 3. Then, this PC steel material 40 is fixed in tension.

  Here, in the joint portion of the precast segment, it is common not to allow the generation of tensile stress when prestress is introduced or when the design load is applied. In the bridge constructed by the precast segment method, the joint portion of the precast segment is PC. The amount of steel is often determined. In this embodiment, the precast segments 21, 22, 23, 31, 32, 33 constituting the precast prestressed concrete girders 2, 3 are opposed to each other within the joint surface of the joint portion as shown in FIG. 6 (a). A recess 50 is provided. Accordingly, since the prestress generated at the upper and lower edges of the joint portions of the precast segments 21, 22, 23, 31, 32, and 33 can be increased, like the conventional precast segment joint portion shown in FIG. The amount of the PC steel material 40 can be reduced as compared with the case where no recess is provided in the joint surface of the joint portion.

  FIG. 7 is an explanatory diagram showing a second step in the first embodiment.

  The two precast prestressed concrete girders 2 and 3 manufactured in the first step are used as shown in FIG. 7 by using jacks 200 on the pier 120 at the opposite ends of the precast prestressed concrete girders 2 and 3. For example, it is jacked up by 200 mm and installed between the abutment 110 and the pier 120. Thus, in the state which jacked up the said support part, it makes V shape where the axis orthogonal surface of the edge part which each girder opposes opened upwards. After that, in a jacked up state, the concrete 60 is placed between the two precast prestressed concrete girders 2 and 3 facing each other.

  FIG. 8 is an explanatory diagram showing a third step in the first embodiment.

  The support part jacked up in the second step is jacked down by 200 mm, and a compressive stress is applied to the upper edge of the girder continuous part to form a continuous girder. Here, a compressive stress of 11 MPa is applied to the upper edge of the girder continuous part.

  According to the first embodiment, a positive bending moment of 1823 kN · m is applied to each of the six main beams 10 arranged in parallel in the portion where the concrete 60 between the two precast prestressed concrete beams 2 and 3 is placed in parallel. Since this acts and resists negative bending moments due to working loads, the amount of rebar and PC steel for continuous girders placed between the two precast prestressed concrete girders 2 and 3 is reduced. Therefore, continuous digitization can be easily realized using a limited space with a low digit height.

  Above, description of 1st Embodiment of this invention is complete | finished and 2nd Embodiment of this invention is described.

  In the second embodiment described below, attention is paid to differences from the first embodiment described above, and the same elements are denoted by the same reference numerals and description thereof is omitted.

  FIG. 9 is an explanatory view showing a steel material projecting step in the second embodiment.

  The two precast prestressed concrete girders 2 and 3 manufactured in the first step are used as shown in FIG. 9 by using jacks 200 on the pier 120 at the opposite ends of the precast prestressed concrete girders 2 and 3. For example, 200 mm jack-up is carried out, and it spans between the support of the abutment 110 and the bridge pier 120, and the steel material 70 protrudes in the edge part which these two precast prestressed concrete girders 2 and 3 oppose. The steel material 70 may be projected before the precast prestressed concrete girders 2 and 3 are installed between the supports.

  FIG. 10 is an explanatory view showing a steel material connecting step in the second embodiment.

  Next, as shown in FIG. 10, the steel materials 70 at the opposite ends of the precast prestressed concrete girders 2 and 3 are connected. Thereafter, in the same manner as the second step described with reference to FIG. 7, the concrete 60 is placed between the opposite ends of the precast prestressed concrete girders 2 and 3 while being jacked up.

  According to the second embodiment, in addition to the positive bending moment acting on the portion where the concrete 60 between the opposite precast prestressed concrete girders 2 and 3 is placed, the connected steel material 70 also has a negative bending moment due to the applied load. Therefore, it is possible to further reduce the amount of reinforcing bars and PC steel materials for forming continuous girders disposed between the ends of the precast prestressed concrete girders 2 and 3 facing each other.

  Above, description of 2nd Embodiment of this invention is complete | finished and 3rd Embodiment and 4th Embodiment of this invention are described.

  In the third and fourth embodiments described below, attention is paid to differences from the first embodiment described above, and the same components are denoted by the same reference numerals and description thereof is omitted.

  FIG. 11 is an explanatory diagram showing a second step in the third embodiment.

  As shown in FIG. 11, the third embodiment is a method for constructing an inclined low girder high bridge in which the heights of the upper surfaces of the abutment 110 and the pier 120 are different. Even in such a case, similarly to the second step in the first embodiment, the two precast prestressed concrete girders 2 and 3 are connected to the axis orthogonal planes at the opposite ends of the precast prestressed concrete girders 2 and 3. So that the support portions on the bridge piers 120 at the opposite ends of each girder are jacked up using the jacks 200 so as to be bridged between the abutments 110 and 120, Concrete 60 is laid between the opposite precast prestressed concrete beam ends.

  FIG. 12 is an explanatory diagram showing a second step in the fourth embodiment.

  As shown in FIG. 11, 3rd Embodiment is a construction method of the continuous bridge of 3 spans formed by making three precast prestressed concrete girders 2, 3, and 4 continuous. Even in such a case, the three precast prestressed concrete girders 2, 3 and 4 are formed in a V shape in which the axial orthogonal surfaces of the opposing ends of the precast prestressed concrete girders 2 and 3 are opened upward. Thus, the support part on the pier 120 at the opposite end of each girder is jacked up by, for example, 200 mm using the jack 200, and installed between the abutment 110 and the pier 120, and each precast prestressed concrete girder end facing each other. Concrete 60 is placed between them.

  Also in the third embodiment and the fourth embodiment, as in the first embodiment described above, the support portion that has been jacked up at the time of erection is jacked down after the concrete is placed, and compressive stress is applied to the upper edge of the girder continuous portion. By forming a continuous girder, a positive bending moment acts on the portion where the concrete between the opposite girder ends is placed, and this resists the negative bending moment caused by the applied load.

  In each of the above-described embodiments, the precast prestressed concrete girder is described as an example of a high-strength fiber reinforced mortar. However, the precast prestressed concrete girder is not limited thereto, and the span of the girder height is not limited. Applies to concrete girders with a ratio of 25 or more.

  Further, in each of the above-described embodiments, a continuous bridge between two diameters formed by continuous two precast prestressed concrete girders 2 and 3 and a three diameter formed by continuous three precast prestressed concrete girders 2, 3 and 4 Although the continuous bridge construction method has been described, the bridge construction method of the present invention is not limited to this, and can also be applied to a bridge construction method of four or more spans.

It is a side view of the low girder high bridge constructed by one Embodiment of this invention. It is a cross-sectional view near the center of the span of the low girder high bridge shown in FIG. FIG. 2 is a detailed cross-sectional view of the main girder near the center of the span of the low girder high bridge shown in FIG. 1. FIG. 2 is a detailed cross-sectional view of the main girder at the end of the low girder high bridge shown in FIG. 1. It is explanatory drawing which shows the 1st process in 1st Embodiment. It is a comparison figure of the precast segment joint part in the precast prestressed concrete girder shown in Drawing 5, and the conventional precast segment joint part. It is explanatory drawing which shows the 2nd process in 1st Embodiment. It is explanatory drawing which shows the 3rd process in 1st Embodiment. It is explanatory drawing which shows the steel material protrusion process in 2nd Embodiment. It is explanatory drawing which shows the steel material connection process in 2nd Embodiment. It is explanatory drawing which shows the 2nd process in 3rd Embodiment. It is explanatory drawing which shows the 2nd process in 4th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Low girder high bridge 110 Abutment 111 Parapet 120 Bridge pier 2,3,4 Precast prestressed concrete girder 21,22,23,31,32,33 Precast segment 10 Main girder 11 PC steel penetration sheath 20 Pavement 40 PC steel 50 Recess 60 Concrete 70 Steel 200 Jack

Claims (4)

  When a plurality of precast prestressed concrete girders having a span ratio to a girder height of 25 or more are serialized, the axial orthogonal surfaces of the opposing ends of the plurality of precast prestressed concrete girders are formed in a V shape. In addition, the support on the pier at the opposite end of each girder is jacked up, and each girder is installed between successive supports, and concrete is placed between the opposite girder ends, then jacked down, and the girder is continuous A construction method for a bridge characterized in that a continuous girder is formed by applying compressive stress to the upper edge of the part.   The bridge construction method according to claim 1, wherein the precast prestressed concrete girder is made of ultra high strength mortar.   A steel material is protruded from an end portion of the precast prestressed concrete girder, and the concrete is cast after connecting the steel materials of the opposing precast prestressed concrete girder ends in a jacked-up state. Item 3. A bridge construction method according to item 1 or 2.   4. The precast prestressed concrete girder is formed by joining a plurality of precast segments provided with concave portions facing each other in a joint surface of a joint portion in a bridge axis direction. How to construct a bridge.

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