JP2009144410A - Pc bridge closure method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a PC bridge closure method which can shorten the construction period by enhancing construction efficiency in a cantilever erection method, even in the case of any bridge type and even if the front of an abutment has any terrain. <P>SOLUTION: In this first PC bridge closure method, a difference between temperatures of upper and lower floor slabs (21 and 22) of a girder section (2) already cantilevered is set small; deflection of an overhanging end (23) is adjusted; and a web (1) is erected and fixed on a closure section (6) before the construction of floor slab concrete. In the first PC bridge closure method, the web (1) is erected and fixed on the closure portion (6) before the construction of the floor slab concrete, and an auxiliary member (23), which is brought into close contact with regions facing each other across the closure portion, is installed above the web. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a PC bridge closing method constructed by an overhanging construction method in which a bridge is constructed by sequentially projecting blocks in a cantilever manner.

  The overhang construction method of building a bridge by sequentially overhanging blocks from the pier in a cantilever manner has been practiced. The bridge erection work between the piers in this overhanging construction method is completed by the construction of the closing part (the part where the overhanging ends of the blocks protruding from the adjacent piers are finally joined). For this construction work, suspension support facilities are required. Therefore, as in the construction method disclosed in Japanese Patent Laid-Open No. 63-284304 (Patent Document 1), a suspension support facility is installed from below the closing portion.

However, in the case of steep terrain, the suspension support facility cannot be installed from below the closed part. Therefore, in such a case, as shown in Japanese Patent Application Laid-Open No. 2000-45230 (Patent Document 2), a suspension work is performed using an erection work vehicle used for projecting a block. Will be installed.
JP 63-284304 A JP 2000-045230 A

  However, when the above suspension support is installed, the scale of the bridge becomes very large depending on the type of bridge, which increases the number of construction days or increases the construction cost. In addition, the girder part that is overhanged from the pier will be joined to the abutment or the adjacent girder part, but if the terrain in front of this abutment is steep, construction of the cast-in-place support work required for the joining work It becomes difficult. In such a case, a construction method such as installing an intermediate fulcrum such as a deep foundation pile or using a large construction material can be considered, but this construction method also increases the number of construction days or construction costs. There was a problem that increased.

  Therefore, the present invention provides a PC bridge closing method capable of improving the construction efficiency in the overhanging construction method and shortening the construction period regardless of the type of bridge and the topography of the abutment. The purpose is to provide.

  In the first method for closing a PC bridge according to the present invention, the temperature difference between the upper and lower floor slabs in the already-extended girder portion is reduced, the deflection at the overhang end is adjusted, and the web is placed on the closing portion. Install and fix the plate concrete before construction.

  In the present invention, the temperature difference between the upper and lower floor slabs is artificially controlled without being caused by a natural temperature change. For example, the temperature difference can be controlled by watering the surface of the upper floor slab in the already installed main girder.

  The overhang end means the free end of the girder extending over the bridge pier. The closing portion includes not only between the overhanging end portions but also between the overhanging end portion and the end fulcrum portion or the pier head portion. The end fulcrum portion means a portion provided for joining a free end of a girder portion extending from the pier to an abutment where no block is extended. Further, the pier head means a block overhanging portion provided at the upper part of the pier.

  The web is a member that supports the vertical direction in the block, and a corrugated steel plate is preferable. The erection and fixing means that the web is joined to the extent that it forms the structural material of the bridge in the construction stage. Conventionally, the web has become a structural material for the bridge when the upper and lower floor slab concrete has been cast. However, in the present invention, before the floor slab concrete is cast, the web is made of the structural material for the bridge. It will be. When a corrugated steel plate is used as a web component, the joining can be performed by a method such as web welding or bolting. Moreover, when installing over several blocks, you may make it continuous by an attachment board.

  Moreover, it is preferable to provide the corrugated steel plate which comprises a web with the stiffener (flange) on the upper and lower sides.

  Furthermore, you may install a suspension support using this web erected and fixed to this closing part.

  In the second PC bridge closing method according to the present invention, the auxiliary member is installed and fixed to the closing portion before the floor slab concrete is constructed, and is in close contact with the portion facing the closing portion sandwiched above the web. Is installed.

  According to the first PC bridge closing method according to the present invention, the web is used as a structural material, and the bridge type has a short pier with a short overhang construction length or the topography in front of the abutment is steep. However, it is possible to improve the construction efficiency of the entire bridge construction work and shorten the construction period.

  More specifically, for example, when the terrain in front of the abutment is steep, the overhanging end of the girder that is overhanging from the pier (in front of the abutment) provided in front of the abutment as viewed from the beam side, and the abutment The web is installed and fixed to the closing part between the provided end fulcrum parts before the floor slab concrete is constructed. Then, it is possible to construct the upper and lower floor slab concrete in a state where the formwork supporting work is directly suspended from the erected and fixed web. Accordingly, a large beam material or girder required between the overhanging end portion and the end fulcrum portion is unnecessary, and the construction period can be shortened even when the front of the abutment is steep.

  General bridge girders are deformed in the vertical and horizontal directions (bridge axis direction) due to differences in temperature, but between the overhang end and the end fulcrum (between the side diameters) and between the overhang ends (center When temporary joining for erection and fixing of corrugated steel sheets or the like is performed at a closing portion), the displacement of the girders is restrained, and force is transmitted to the temporary joining portion to generate stress. And if the stress exceeds allowable stress, a temporary joined part will be broken. Therefore, in order to safely complete the work of erection and fixing the web, the secondary force generated in the temporary joining portion is not generated or the amount generated is reduced from the temporary joining to the completion of the main joining. Is important.

  Normally, at the stage of overhanging construction, the steel wire to which tensile force is applied is placed on the upper floor slab. For improvement, it is generally necessary to place a counterweight or the like at the tip of the overhang to forcibly raise or lower the beam. However, there is a problem that equipment for installing a counterweight or the like becomes a large scale, and cargo handling equipment or the like for that purpose is required separately. With regard to this point, the PC bridge closing method according to the present invention focuses on the outside air temperature (daily air temperature change) and the main girder displacement, and uses the relationship between the temperature difference between the upper and lower surfaces and the displacement so that the deflection of the girder and the stress are reduced. Improvements can be made. More specifically, it is as follows.

  The overhanging girder is deformed due to the temperature difference between the upper and lower surfaces when exposed to sunlight during the day, and is maximized in the evening. The temperature difference generated in the girder with sunset is eliminated and the deformation is reduced. Is recognized as an experience. Therefore, the temporary joining of the web may be performed in a time zone where there is no temperature difference, that is, in the morning. However, the decrease in the outside air and the decrease in the temperature difference on the lower surface do not proceed at the same time, and it takes time until the maximum deflection in the evening converges. This is because there is a time difference between the fluctuation of the outside air and the fluctuation of the concrete temperature due to the properties of the concrete that receives sunlight and stores heat. On the other hand, when temporary joining of the closing part is performed at the site, the work is not necessarily completed only within a time zone in which the deformation of the girder part is small due to the progress of the work. And in that case, it means that work does not necessarily advance to the state where temporary joining is safe. Therefore, by manually reducing the temperature difference between the upper and lower floor slabs and shortening the deflection convergence time, it is possible to secure the work time required for erection and fixing of the web including the temporary joining work.

  As a method for artificially reducing the temperature difference between the upper and lower floor slabs, for example, bridge surface watering is effective. Water is sprayed on the upper surface of the slab (upper slab concrete), and the cooling effect that occurs when the water evaporates can reduce the temperature difference between the upper and lower surfaces, and the amount of displacement can be reduced at the same time. At the same time, the amount of heat stored in the concrete can be controlled quantitatively. Moreover, the same effect can be acquired also by accumulating water in a curing mat.

  However, the temperature management method, which is a feature of the PC bridge closing method according to the present invention, needs to quantitatively grasp the relationship between the girder upper and lower surface temperature difference and the displacement. For example, when using bridge surface watering or curing mats to reduce the temperature difference between the upper and lower surfaces of the girder, the temperature difference parameter is required to understand the relationship between the degree of watering and the deformation due to the amount of accumulated water. Only deformation due to watering events and water accumulation can be grasped only by measuring deformation of the girder part without accompanying. Quantitative evaluations such as how much water is sprayed, how much time is needed, or how much water needs to be accumulated in the curing mat can be done by simultaneously measuring the temperature difference and measuring the displacement. Only possible. And, by such quantitative evaluation, it becomes possible for the first time to quantitatively create the working time of the closed joint temporary joining in which no deformation of the girder occurs.

  As described above, the deflection of the girder part begins to occur in the morning and increases in the evening when the temperature difference between the upper and lower sides becomes large. Accordingly, the cross-sectional force (stress) generated in the web of the closing portion varies depending on the time period in which the installation and fixing work is completed. For example, when watering a bridge surface during the day, if the web of the closing portion is joined with the temperature difference being large and the girder being deformed downward, the upper edge of the closing portion web is removed in the state where the temperature difference is eliminated. A tensile force is generated on the upper flange if the flange is provided, and a compressive force is generated on the lower edge if the flange is provided. Further, if the closed portion is joined to the web in a state where there is no temperature difference, during the day when deformation occurs, compressive stress acts on the upper edge of the closed portion web and tensile stress acts on the lower edge.

  On the other hand, in the PC bridge closing method according to the present invention, since the web is installed and fixed to the closing portion and used as a structural material, when concrete is placed in the closing portion, the compressive force is applied to the upper edge of the web due to the concrete load. A tensile force acts on the lower edge. Therefore, when the web is joined in a state where the girder is deformed downward, the stress generated in the web due to the concrete load can be reduced. In other words, when the bridge is completed, if a compressive force is applied to the lower floor slab and a tensile force is applied to the upper floor slab, the force is in the opposite direction to the dead load and live load applied to the bridge. Omission of structural members such as steel can be expected.

  It should be noted that the deformation of the girder starts to deform at the same time as the temperature difference begins to occur due to sunlight, but the deformation recovery speed is slowed down due to the heat storage effect of the concrete even after the evening sunlight is finished, as described above. . Therefore, when performing web joining using a time zone in which the deformation of the girder occurs downward, it is necessary to match the height with the existing web. By combining the temperature difference measurement, the displacement measurement data, and the control by watering, it becomes possible to make a web-friendly joint while making the web joint height match.

  A corrugated steel sheet is suitable as a constituent material of the web, but it is more preferable to provide stiffeners (flanges) above and below the corrugated steel sheet. In this case, since the web comprised with this corrugated steel plate can transmit the force of adjacent girder parts, it will have a function as a reinforcing material when placing concrete.

  According to the second PC bridge closing method according to the present invention, in the closing portion, the auxiliary member that is in close contact with the opposite portion across the closing portion is installed above the erected and fixed web. The axial force and rotation resulting from the deformation are restrained, the deformation of the closing portion at the time of floor slab concrete construction is suppressed, the structure of the support work is simplified, or the web steel plate can be made thin. And since it is a simple structure made close to the part which opposes on both sides of a closing part, it does not affect a construction period.

  An embodiment of a PC bridge closing method according to the present invention will be described with reference to FIGS. FIG. 1: shows the general | schematic process at the time of constructing the closing part between the overhang | projection edge part and an end fulcrum part in the construction method, (a) is a side view of the state before a web is constructed in a closing part, (b) ) Is a side view of a state where a web is erected in the closed part and a suspension support is installed, (c) is a side view of a state where the lower floor slab concrete is placed in the closed part, and (d) is an upper floor of the closed part. It is a side view in the state where slab concrete was laid. FIG. 2 is a side view showing a partial overview of the pier in which the construction method is implemented. FIG. 3 shows a schematic process of overhang construction from a bridge pier, and (a) is a perspective view in a state where a lower floor slab concrete is placed in a construction target area and a moving work vehicle is moved onto a web in the next area. b) is a perspective view in a state in which precast ribs are temporarily installed in a construction target area, and (c) is a perspective view in a state in which upper floor slab concrete is placed in the construction target area.

  In front of the bridge abutment 3 where this PC bridge closing method is implemented, the terrain is steep and difficult to perform in-situ support. Therefore, the construction period can be shortened by implementing the following processes without adopting a construction method that prolongs the construction period, such as installing an intermediate fulcrum such as a deep foundation pile or using a large construction material. It has been. In addition, although the process demonstrated below is the case where both the closing method of the 1st and 2nd PC bridge which concerns on this invention is constructed simultaneously, it is also possible to perform these methods separately, respectively.

  First, the girder 2 is extended from the bridge pier 4a (hereinafter referred to as the front pier 4a) provided in front of the abutment 3 as viewed from the beam side toward the abutment 3. In this overhang construction process, as shown in FIG. 3, first, the web 1 is erected in the construction target region n, and the lower floor slab concrete is placed to construct the lower floor slab 22. In addition, the corrugated steel plate is used for the structure of the web 1 in this Example including the following processes. Subsequently, the web 1 is installed in the next construction area n + 1, and the mobile work vehicle 5 is moved to the next construction area, so that the state shown in FIG. Then, after precast ribs 24 are temporarily installed in the construction target region n to obtain the state shown in FIG. 3B, the upper floor slab concrete is placed, the upper floor slab 21 is constructed, and a block is formed (FIG. 3 ( c)). Thereafter, the blocks can be sequentially formed by performing the same construction in the next construction area n + 1. However, either the upper or lower floor slab concrete may be placed first, and the upper and lower floor slabs may be simultaneously applied according to the girder length. Further, the corrugated steel sheet 1 may be constructed at a time for several construction areas.

  The end 23 (corresponding to the overhang end of the present invention) of the girder 2 overhanging from the front bridge pier 4a approaches the end fulcrum 31 provided in advance on the abutment 3 to some extent, and is in the state shown in FIG. Then, the web 1 is constructed and fixed to the closing portion 6 between the end portion 23 and the end fulcrum portion 31. A crane or the like may be used to construct the web 1.

  Since the girder part 2 that is extended from the front pier 4a is deformed in the vertical direction and the horizontal direction (bridge axis direction) due to the difference in temperature, when the web 1 is erected and fixed to the closing part 6, The displacement is constrained and a force is transmitted to the temporarily joined portion to generate a stress. And if the stress exceeds allowable stress, a temporary joined part will be broken. Therefore, this erection and fixing work is performed in the morning where the deflection due to the deformation of the girder 2 is minimized. Further, in order to secure a sufficient work time, the temperature difference between the upper and lower floor slabs 21 and 22 is artificially reduced by watering the bridge surface from the day before the work, and the convergence time of the deflection is shortened.

  When the erection and fixing work is finished, next, an auxiliary member 23 is installed above the erected and fixed web 1 so as to be in close contact with the part facing the closing part 6. The support work 7 is directly hung to a state shown in FIG. Then, in this state, the lower floor slab concrete is placed, the lower floor slab 22 is closed, and the state shown in FIG. Next, after prestressing the lower floor slab 22 to form a cross section integrated with the web 1, the upper floor slab concrete is placed, prestress is introduced, the upper floor slab 21 is closed, and the closing operation is completed. It becomes. However, the construction of the upper and lower floor slabs 21 and 22 may be preceded in the same manner as the overhang construction from the near bridge pier 4a, and the upper and lower floor slabs 21 and 22 may be simultaneously constructed according to the closing length. Alternatively, the mobile work vehicle 5 may be moved and installed directly on the web 1 and used as a support work.

  For the auxiliary member 23, a normal H-section steel is used. A jack (not shown) is interposed between one end of the H-shaped steel and one of the existing upper floor slabs 21 facing each other with the closing portion interposed therebetween. By adjusting the length of the jack, the closing portion is It is set as the state made to contact | adhere to the existing upper floor slab 21 which opposes on both sides. However, there is no limitation on the material and installation method of the auxiliary member 23, and other materials may be used as appropriate as long as the axial force and rotation caused by deformation due to temperature difference can be restrained until the floor slab concrete construction. Good.

  In addition, although the Example shown in FIGS. 1-3 is in the closing part between the overhanging end part and the end fulcrum part provided in the abutment, the closing method of the PC bridge of the present invention is the overhanging end part 23. It is also possible to implement in the closed part between each other or the overhanging end part 23 and the pier head part 41.

  In constructing the Akabanegawa Bridge down line of the Second Tomei Expressway, the PC bridge merge method according to the present invention was implemented. In the target bridge, it was found from prior measurements that the girder that was built on the abutment and extended from the front pier was long and that the variation due to the temperature difference between the upper and lower decks was large. Therefore, the bridge surface watering from the previous day was carried out to shorten the deflection convergence time. 4 to 6 show changes in temperature difference and deflection between the upper and lower floor slabs. A data logger and a thermocouple are used to measure the temperature difference between the upper and lower floor slabs. As shown in FIG. 7, the thermocouple is located at two locations (91, 92) above the corrugated steel plate of the upper floor slab, the lower floor slab. Were installed at one location (93) in the center in the width direction, 1 location (94) inside the block, and 1 location (95) outside the block. In addition, in FIGS. 4-6, the circle mark has shown the visual result. Moreover, the broken line which cross | intersects the time axis in FIG. 6 has shown 8:30 which is the start time of bridge surface watering, and 16:00 which is an end time. Further, in FIG. 7, the same reference numerals are given to substantially the same places as in the embodiment shown in FIGS.

  As shown in FIG. 4 to FIG. 6, it was found that the deflection due to the floor slab temperature difference became large during fine weather, and the deflection in that case occurred around 8 o'clock in the morning. In addition, it was found that the deflection convergence time can be shortened by controlling the temperature difference between the upper and lower floor slabs when watering the bridge surface. Therefore, the bridge surface watering was carried out from the previous day to shorten the deflection convergence time, and ensured the work time to finish the closing work by 8:00 am. As a result, the difference in deflection during the closing operation was suppressed to about 5 mm, and the secondary stress generated during the upper and lower flank could be greatly reduced.

The rough process at the time of constructing the closing part between the overhang | projection edge part and an end fulcrum part in the Example of the closing method of the PC bridge which concerns on this invention is shown, (a) is the state before a web is constructed in a closing part (B) is a side view of a state in which a web is installed in a closed portion and a suspension support is installed, (c) is a side view of a state in which lower floor slab concrete is placed in the closed portion, (d ) Is a side view of a state in which the upper floor slab concrete of the closing portion is placed. It is a side view which shows the one part outline of the pier in which the closing method of the PC bridge is implemented. (A) is a perspective view of a state where a lower floor slab concrete is placed in a construction target area and a moving work vehicle is moved on a web in the next area. b) is a perspective view in a state in which precast ribs are temporarily installed in a construction target area, and (c) is a perspective view in a state in which upper floor slab concrete is placed in the construction target area. The temperature difference between the upper and lower floor slabs and the time transition of the deflection in fine weather are shown, (a) is the transition graph of the temperature difference between the upper and lower floor slabs, and (b) is the transition graph of the deflection. The temperature difference between the upper and lower floor slabs and the time transition of deflection during rainy weather are shown. (A) is a transition graph of the temperature difference between the upper and lower floor slabs, and (b) is a transition graph of the deflection. The transition of the temperature difference and deflection of the upper and lower floor slabs when the bridge surface watering is performed in fine weather, (a) is a transition graph of the temperature difference of the upper and lower floor slabs, (b) is a transition graph of the deflection. It is a schematic cross-sectional view of a block showing the installation location of a thermocouple.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Web 2 Girder part 3 Abutment 6 Closure part 7 Suspension support work 21 Upper floor slab 22 Lower floor slab 23 Auxiliary member 31 End fulcrum part 41 Pier head

Claims (3)

  Reduce the temperature difference between the upper and lower floor slabs (21, 22) in the already stretched girder (2), adjust the deflection at the stretched end (23), and place the web (1) in the closing part (6), A method of closing a PC bridge, characterized in that it is erected and fixed before construction of floor slab concrete.   The method for closing a PC bridge according to claim 1, wherein the suspension support (7) is installed using the web (1) erected and fixed to the closing portion (6).   Prior to construction of floor slab concrete, the web (1) is erected and fixed to the closing part (6), and is closely above the web (1) to the opposite part across the closing part (6). A method for closing a PC bridge, characterized by installing an auxiliary member (23).

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