JP2007051426A - Bridge and construction method of bridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bridge capable of having excellence in wind-resistance efficiency and obtaining a super-huge bridge having a huge center span (3,000 m class) which has not been erected hitherto. <P>SOLUTION: The bridge 1 has a plurality of main towers 2 and 2 installed at an interval and a bridge girder 3 forming parts stretched to both sides through the main towers 2 and 2 in one box girder 31, and, forming the center between both towers in two box girders 32, and is so constituted that the bridge girder 3 in the vicinity of the main towers 2 is supported by a plurality of diagonal tensile cables 4 fixing each one end of them to the main towers and that the center is supported by a plurality of hanger ropes 5a, etc. suspended from two main cables 5 and 5 stretched through the tower tops 2a of the main towers. Each lower end of the hanger ropes 5a, etc. is connected to the outside edge 3a of the bridge girder of the main cable side suspending the hanger ropes 5a. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a bridge such as a suspension bridge having a long center span.

  Conventionally, suspension bridges are used for long bridges with a center span of more than 1000m across the strait, but the height of the main tower increases in proportion to the length of the suspension bridge. In addition to increasing the size of the foundation, various measures must be taken to ensure wind resistance against crosswinds.

  On the other hand, when the center span is up to about 1000 m, a cable-stayed bridge is often constructed with high torsional rigidity of the bridge girder and excellent wind resistance against crosswind.

  Cable-stayed bridges often use a single box girder with a flat box structure for the bridge girder, and suspension bridges employ a two-box girder with a ventilation opening at the center in the width direction of the bridge girder in order to improve wind resistance. Often done.

  Non-Patent Document 1 discloses a cable-stayed suspension bridge having the advantages of such a cable-stayed bridge and a suspension bridge.

  This cable-stayed suspension bridge has a cable-stayed bridge structure in the vicinity of the main tower, a central part between the main towers has a suspension bridge structure, and one box girder is mainly used for the bridge girder of the cable-stayed bridge structure. As the bridge girder, a two-box girder 102 is adopted as shown in FIG.

  In the cable-stayed suspension bridge disclosed in Non-Patent Document 1, the main tower is constructed in accordance with the width of one box girder. Therefore, the interval between the main cables 103 and 103 extending in parallel from the main tower is as shown in FIG. As shown in FIG. 10, it is narrower than the width of the two box girders 102 and equal to the width of the opening 102b between the parallel box girders 102a and 102a.

  In general, in a suspension bridge, a bridge girder (two-box girder 102) is suspended by a hanger rope 104 suspended vertically from the main cable 103. Therefore, the main cable 103, which is stretched at an interval substantially equal to the width of the opening 102b, The hanger ropes 104 and 104 suspended from 103 are connected to the edges of the opening 102b, that is, the inner edges of the single box girders 102a and 102a.

Since a plurality of the hanger ropes 104 are arranged at intervals in the extending direction of the main cable 103, a vertical plane is formed by the group of the hanger ropes 104, and the vertical plane is a road construction on the single box girders 102a and 102a. The limits 106, 106 are not violated.
Jun Murakoshi, 7 others, Survey on superstructure of super-long bridge with excellent economy and wind resistance, JAPAN SOCIETY of CIVIL ENGINEERS 01, P.215-216

  However, in the suspension bridge structure that suspends the inside of the two-box girders 102 as disclosed in Non-Patent Document 1, deformation and torsion tend to increase when exposed to wind speeds close to 80 m / sec. Therefore, the length between the central diameters cannot be made too long.

  In addition, in addition to a static study that examines deformation behavior during a storm, in order to prevent accidents typified by the fall of the Tacomana Rose Bridge in the United States, the extra-long bridge has dynamic wind resistance. Need to be considered.

  This dynamic phenomenon includes a torsional flutter generated at the Tacomana Rose Bridge and a more destructive aerodynamic vibration (coupled flutter) generated at a high wind speed. These are below a predetermined wind speed (for example, 80 m / sec). It is necessary to construct a bridge that does not cause this phenomenon.

  Therefore, an object of the present invention is to provide a bridge that is excellent in wind resistance performance and that can realize a very long bridge with a central span (3000 m class) that has never been constructed.

  In order to achieve the above-mentioned object, the present invention provides a plurality of main towers installed at intervals, and portions projecting on both sides through the main tower are formed in one box girder and between the main towers. A bridge girder having a central portion formed in a two-box girder, the bridge girder in the vicinity of the main tower is supported by a plurality of cable stays fixed at one end to the main tower, and the central portion is a tower of the main tower A bridge supported by a plurality of hanger ropes suspended from two main cables extending through the top, wherein the lower end of the hanger rope is connected to the main cable side where the hanger rope is suspended. The bridge is connected to the outer edge of the bridge girder.

  Here, the interval between the two main cables can be configured such that the interval at the central portion is wider than the interval at the tower top.

  In addition, it is preferable that a fairing having an asymmetric trapezoidal shape in cross section is formed on the outer edge of the two box girder.

  Moreover, it is preferable to arrange | position the space | interval adjustment apparatus which hold | maintains the space | interval of the said 2 main cable in the upper position of the bridge girder formed by the said 2 box girder until construction work of at least 2 box girder is complete | finished. .

  Furthermore, this space | interval adjustment apparatus can be set as the apparatus provided with the beam part and the contact part of the said main cable which can move along the beam part.

  In the bridge construction method of the present invention, a plurality of main towers installed at intervals and a portion projecting on both sides through the main tower are formed in one box girder and the center between the main towers A bridge girder formed in a two-box girder, the bridge girder in the vicinity of the main tower is supported by a plurality of cable stays fixed at one end to the main tower, and the central part is a tower top of the main tower A method for constructing a bridge supported by a plurality of hanger ropes suspended from two main cables extending through the cable, wherein the two main cables are stretched substantially parallel between the main towers. A method for constructing a bridge in which an interval adjusting device for widening the interval between the main cables is installed at a predetermined position, and a lower end of a hanger rope suspended from the main cable is connected to an outer edge of the bridge girder. Features.

  The present invention configured as described above connects the lower end of the hanger rope suspended from the main cable to the outer edge of the bridge girder in the bridge combining the cable-stayed bridge structure and the suspension bridge structure.

  By connecting the hanger rope to the outer edge in this way, it is possible to increase the resistance to lateral deformation as compared to the case where the main cable is connected near the center in the width direction of the bridge girder, and the amount of lateral deflection deformation and The amount of twist deformation can be suppressed.

  Here, the width of the main tower can be narrowed by configuring the distance between the two main cables so that the distance in the central portion is wider than the distance in the main tower.

  If the size of the main tower can be reduced by reducing the width of the main tower in this way, not only can the construction cost of the superstructure of the main tower be reduced, but also the scale of the foundation can be reduced by reducing its weight.

  Further, by forming a fairing having a cross-sectional asymmetric trapezoidal shape on the outer edge of the two-box girder, wind resistance can be improved.

  In addition, at least until the construction work of the two box girders is completed, by disposing an interval adjusting device that holds the gap between the two main cables at an upper position of the bridge girder formed by the two box girders, Excessive stress is not generated in any member of the main cable and the bridge beam connected via the hanger rope.

  Further, the distance adjusting device includes a beam portion and a contact portion of the main cable movable along the beam portion, and the distance between the main cables is desired by moving the contact portion. Can be changed to the width.

  For this reason, the space | interval of the said 2 main cable which spreads gradually toward the center part between the main towers from the said main tower can be hold | maintained to a predetermined space | interval with a space | interval adjustment apparatus.

  In the bridge construction method of the present invention, the distance between two main cables stretched substantially in parallel is expanded to a predetermined width by a distance adjusting device, and then the lower end of the hanger rope is connected to the outer edge of the bridge girder. To do.

  For this reason, when the width | variety of the main cable is directly expanded with a hanger rope, the stress concentration which may generate | occur | produce locally on the main cable does not occur. Moreover, excessive stress is not generated and damaged on the bridge girder side and the hanger rope that draws the hanger rope.

  The best mode for carrying out the present invention will be described below with reference to the drawings. The same or equivalent parts as those in the conventional example will be described with the same reference numerals.

  FIG. 1 is a perspective view showing a schematic configuration of a bridge 1 according to this embodiment, and FIG. 2 is a side view of the bridge 1.

  The bridge 1 according to the present embodiment is stretched to support the main towers 2 and 2 constructed at two positions at intervals, the bridge girder 3 bridged through the main tower 2, and the bridge girder 3. Are composed mainly of two main cables 5, 5 and hanger ropes 5a,.

  The main tower 2 is constructed in an inverted V shape such that, for example, two pillars support each other on a foundation portion 2b provided on a submarine ground or an island. The main tower 2 is constructed of a steel material such as reinforced concrete or steel plate, and main cables 5 and 5 are inserted side by side at the top 2a of the tower, and cable-stayed cables 4 are provided on both sides facing the bridge girder 3 side. ... one end is fixed.

  Further, in the bridge girder 3, a portion protruding from both sides through the columns of the inverted V-shaped main tower 2 is formed in one box girder 31, and a central portion between the main towers 2, 2 is a two box girder 32. Is formed.

  As shown in the cross-sectional view of FIG. 3, the one-box girder 31 is a flat steel structure, and the inside is hollow, and both side edges in the width direction have fairing 31a, 31a is formed.

  The fairings 31a and 31a are provided to reduce the wind load and suppress the horizontal displacement and rotational displacement of the one box girder 31 due to the cross wind. Further, on the upper surface of the one box girder 31, a central separation band 8 is provided near the center in the width direction, and protective fences 9, 9 such as guard rails are provided on both side edges in the width direction.

  Moreover, as shown in the cross-sectional view of FIG. 4, the two box girder 32 forming the bridge girder 3 in the central portion between the main towers 2 and 2 has two single box girders 32 b and 32 b which are flat steel structures, It is mainly comprised from the opening part 32c formed in the meantime.

  The single box girders 32b and 32b are hollow inside, and asymmetric fairings 32a and 32a having an asymmetric trapezoidal shape in cross section are formed on both side edges in the width direction.

  Further, on the lower surface of the single box girder 32b in the vicinity of the outer edge 3a of the bridge girder 3, a wind shield wall 10 formed of a punching plate, a plate material or the like is continuously or discretely attached in the longitudinal direction of the bridge girder 3, and the lower surface of the bridge girder 3 The flow of wind flowing into the is controlled. In addition to this, a member that improves wind resistance, such as a guide vane (not shown) that rectifies the cross wind, can be installed in the double box girder 32 as necessary.

  In addition, a connecting member 7 is disposed in the opening 32c with a gap in the longitudinal direction of the bridge girder 3. The connecting member 7 connects between the single box girders 32b and 32b arranged in parallel with a gap in the width direction. The

  If the connecting members 7 connect the single box girders 32b and 32b in this way, the two box girders 32 can be made to behave integrally.

  Furthermore, gratings 7a and 7a (not shown in FIG. 1), which are perforated members with excellent ventilation, can be installed on the upper and lower surfaces of the opening 32c for use in a management passage or the like.

  Further, as shown in FIG. 4, protective fences 9,... Are provided on both side edges of the single box girder 32b.

  Between the one box girder 31 and the two box girder 32 is a transition section 33, and as shown in FIG. 1, the interval between the one box girder 32b, 32b branched from the one box girder 31 into two gradually increases. Part.

  Moreover, the introduction parts 34 and 34 provided in the both ends of the bridge 1 connected to the land side may be any form of the one box girder 31, the two box girder 32, and the transition part 33.

  In the bridge 1 of the present embodiment, the one box girder 31 provided in the vicinity of the main tower 2 has a cable-stayed bridge structure, and the two box girder 32 provided in the central portion between the main towers 2 and 2 has a suspension bridge structure. The transition portion 33 can adopt either a cable-stayed bridge structure or a suspension bridge structure, but 3/4 or more of the distance between the main towers 2 and 2 (between the central spans) is between the main towers 2 and 2. When the suspension bridge structure is used, the cross section of the main cable 5 increases, and the anchorage 5b also becomes large and tends to be economically disadvantageous. Therefore, the length of the suspension bridge structure between the main towers 2 and 2 is 1/2 of the center diameter. It is preferable to make the degree.

  The cable-stayed bridge structure is a structure in which one end is fixed to the main tower 2 and the bridge girder 3 is supported by a plurality of cable-cables 4... In this embodiment, as shown in FIG. The other ends of the cable stays 4 are connected to the outer edges 3a, 3a.

  In addition, as shown in FIGS. 1 and 2, a plurality of cable-stayed cables 4,... Are provided at intervals in the height direction of the main tower 2, and the main tower 2 is centered so that the load is balanced. Arranged symmetrically.

  Such a cable-stayed bridge structure, as shown in FIG. 3, is formed of a substantially triangular truss structure by the cable stays 4 and 4 and the bridge girder 3, so that it has high torsional rigidity and excellent wind resistance against crosswinds. Therefore, one box girder 31 can be adopted.

  In this way, if one box girder 31 is adopted in the cable-stayed bridge structure, the main tower 2 may be constructed according to the width of the one box girder 31, and the scale can be reduced, which is economical.

  The suspension bridge structure is a structure in which the bridge girder 3 is supported by a plurality of hanger ropes 5a,... Suspended from a main cable 5 in which a plurality of steel strands are bundled.

  As shown in FIG. 2, both ends of the main cable 5 are anchored to anchorages 5b and 5b provided near both banks, and the main cable 5 extended from one anchorage 5b has two main towers. It is moored to anchorage 5b on the opposite bank through the top 2a of the second tower.

  And the tension | tensile_strength is given to the main cable 5 by winding up the main cable 5 with the cable drawing-in apparatus etc. with which the anchorage 5b was equipped.

  Here, if the interval between the insertion holes (not shown) provided in the tower top 2a of the main tower 2 that supports the main cable 5 and the interval between the anchorages 5b are the same, the two main cables 5 and 5 are substantially parallel. Is stretched.

  In the present embodiment, a two-box girder 32 is adopted in the central portion between the main towers 2 and 2 having a suspension bridge structure, and the lower ends of the hanger ropes 5a and 5a are provided on the outer edges 3a and 3a of the bridge girder 3 as shown in FIG. Are connected.

  Here, the outer edge 3a of the bridge girder 3 refers to the vicinity of the end of the bridge girder 3 in the width direction, and in the two-box girder 32 of FIG. 4, the periphery including the asymmetric fairing 32a.

  Since the width of the double box girder 32 is wider than the interval between the tower tops 2a through which the two main cables 5 and 5 pass, the hanger ropes 5a and 5a are suspended without damaging the road construction limit 106 (see FIG. 10). Therefore, it is necessary to widen the distance between the main cables 5 and 5 on the double box girder 32.

  Therefore, in the present embodiment, as shown in FIG. 4, the distance adjusting device 6 is disposed between the main cables 5 and 5 to widen the distance between the main cables 5 and 5 to a predetermined width.

  This spacing adjusting device 6 is provided on a beam portion 61 that opposes a force in the width direction in which the main cables 5 and 5 attempt to return to the original position (parallel position), and a lower surface of the beam portion 61. , 5 and the widening tools 63, 63 for moving the contact portions 62, 62 to a predetermined position along the beam portion 61.

  As shown in FIG. 5, the beam portion 61 includes a central beam 61a, adjustment beams 61b and 61b connected to both ends of the beam via hinge portions 64 and 64, and ends of the adjustment beams 61b and 61b. It is mainly comprised from the adjustment beams 61c and 61c connected through the hinge parts 64 and 64, respectively.

  That is, the length of the beam portion 61 can be changed stepwise from the length of only the central beam 61a to the length in which all the adjustment beams 61b, 61b, 61c, 61c are arranged in a straight line.

  When the adjusting beams 61b, 61c,... Are folded as shown in FIG. 5A, for example, a restraining tool 65 such as a steel bar is used in order to limit dropping or falling inward. Is disposed between the beams.

  Further, when the adjusting beams 61b, 61c,... Are extended as shown in FIG. 5 (b), a fixing plate 66,. To fix.

  Further, as shown in FIG. 6, the contact portion 62 includes a side roller 62a that is in contact with the side surface of the main cable 5, a bearing portion 62c of the side roller 62a, and an extrusion portion that attaches the bearing portion 62c. 62f, an upper roller 62b in contact with the upper surface of the main cable 5, a bearing portion 62d of the upper roller 62b, and a plate-like slide mounting portion 62e for mounting the bearing portion 62d and the pushing portion 62f. Is done.

  Since the contact portion 62 is in contact with the main cable 5 via the side roller 62a and the upper roller 62b, the distance adjusting device 6 can be easily moved along the main cable 5.

  Further, the abutting portion 62 can be moved together with the slide mounting portion 62 e by being pushed out by the widening tool 63.

  This widening tool 63 is mainly comprised from the jack part 63a and the reaction force part 63b which attaches the edge part of the jack part 63a.

  Here, the slide mounting portion 62 e of the contact portion 62 and the reaction force portion 63 b of the widening tool 63 can move along a slide guide 67 extending on the lower surface of the beam portion 61.

  The moving method by the widened portion 63 will be described with reference to FIG. 6. FIG. 6A is a view showing a state in which the main cable 5 is held at a predetermined position by the contact portion 62.

  In this state, the slide mounting portion 62e is fixed to the beam portion 61 side by the fixing bolts 68,... When the jack portion 63a is contracted, the reaction force portion 63b is drawn toward the pushing portion 62f side.

  Then, when the reaction force portion 63b is fixed to the beam portion 61 side with fixing bolts 68 and 68, the fixing of the slide mounting portion 62e is released, and the jack portion 63a is extended, as shown in FIG. The part 62 slides and is pushed by the contact part 62, so that the main cable 5 also moves.

  In this manner, the interval between the main cables 5 and 5 can be increased to a desired interval while repeating the state of FIG. 6A and the state of FIG. 6B.

  Next, the construction method of the bridge 1 of this Embodiment is demonstrated, referring FIG.

  First, as shown in FIG. 7 (a), anchorages 5b and 5b are constructed on both banks, and main towers 2 and 2 are constructed between the anchorages 5b and 5b.

  Here, as an example, it is assumed that the distance between the main towers 2 and 2 is 2800 m, the distance between the main tower 2 and the anchorage 5b is 1100 m, the total length is 5000 m, and the bridge 1 has a sag ratio of 1/10. The height of the main tower 2 from the bridge girder 3 is 280 m, and the interval between the insertion holes of the tower top 2 a through which the main cables 5 and 5 pass is 7 m.

  Then, after the main cables 5 and 5 fed out from one anchorage 5b are passed through one tower top 2a, and subsequently the main cables 5 and 5 are extended and passed through the other tower top 2a, the opposite anchorage 5b The ends of the main cables 5 and 5 are moored.

  The main cables 5 and 5 installed in this way are wound up by a cable drawing device or the like provided in the anchorages 5b and 5b to give a tension so that the main cables 5 and 5 are substantially parallel (interval of about 7 m).

  Next, as shown in FIG. 7 (b), the distance adjusting device 6 is installed at a position where the main cables 5, 5 at the substantially center between the main towers 2, 2 hang down most. First, as shown in FIG. 5A, the distance adjusting device 6 is installed in accordance with the initial distance (about 7 m) of the main cables 5 and 5, and the main cables 5 and 5 are moved in the width direction by the widening tools 63 and 63. It moves outside and it is in the state of FIG. 5 (b) (the distance between the main cables 5, 5 is about 31 m).

  As a result, the central part between the main towers 2 and 2 is widened to the width of the double box girder 32 to be hung later (the width between the hanger ropes 5a and 5a in FIG. 4 is about 32 m).

  In the present embodiment, not only the central portion of the suspension bridge structure but also the distance adjusting devices 6 and 6 are installed at both ends of the suspension bridge structure that becomes a boundary with the cable-stayed bridge structure (FIG. 7C).

  As shown in FIG. 1, the distance adjusting devices 6 and 6 installed at both ends of the suspension bridge structure are separated from the bridge girder 3 and the width of the girder is gradually narrowed at the transition portion 33. Even if the distance between the cables 5 and 5 is narrow, the hanger ropes 5a,.

  The distance adjusting devices 6 and 6 are first installed in the most widened state in the vicinity of the central portion where the distance adjusting device 6 is first installed, and are widened while being moved along the main cables 5 and 5 toward the main tower 2. The widening tools 63, 63 are moved inward in the width direction by a procedure reverse to that of time, and are reduced to a desired interval.

  Here, with the outer adjustment beams 61c and 61c folded, the distance between the main cables 5 and 5 is adjusted to be about 23 m.

  In this way, the lower end of the hanger rope 5a hanging from the main cables 5, 5 spread at a predetermined interval is slightly inward from the outer edges 3a, 3a of the two-box girders 32 even in the center. Even if the hanger rope 5a is not pulled with a large force, it can be connected to the outer edges 3a, 3a of the bridge girder 3 as shown in FIG.

  FIG. 7D is a diagram showing the width of the double box girder 32 below the unfolded main cables 5 and 5 by a one-dot chain line.

  In FIG. 7 (d), the difference between the distance between the main cables 5 and 5 and the width of the two box girders 32 is large near the end of the suspension bridge structure. 5 and 5 and the bridge girder 3 are separated from each other, and the girder width gradually becomes a transition portion 33 that approaches the width of the one box girder 31, so that the bridge girder 3 can be obtained without excessively pulling the hanger ropes 5a,. Can be connected to the outer edges 3a, 3a.

  In addition, after the connection of all the hanger ropes 5a,... And the bridge girder 3 is completed and the structure is stable, the distance adjusting device 6 can be removed.

  Next, the analysis result performed in order to confirm the behavior at the time of a wind acting on the bridge 1 of this Embodiment is demonstrated.

  Since the behavior when the wind load is applied to the bridge 1 is a result of overlapping various factors, it is very difficult to predict the behavior just by looking at the designed structure. In particular, the longer the center span, the more difficult it is to predict, so the behavior of the bridge 1 is confirmed by wind tunnel experiments or numerical analysis using a computer.

  FIG. 8 is a comparison of the analysis results of the bridge 1 (external suspension structure) of the present invention and the inner suspension structure in which the edge of the opening 102b of the two-box girder 102 shown in FIG. 10 is suspended. .

  Here, in order to clarify the difference due to the difference in the suspension position between the outer suspension structure and the inner suspension structure, the shape of the two-box girder 32 of the present invention matches the shape of the two-box girder 102 of FIG. The same analysis was performed.

  As a result, it was found that the outer suspension structure is smaller than the inner suspension structure in both vertical displacement and torsional displacement. Here, even when a wind speed of 80 m / sec is applied at the actual bridge conversion wind speed, it is desired that the deformation is suppressed to an allowable deformation or lower, that is, the flutter expression wind speed is 80 m / sec or more. If it is (outside suspension structure), deformation can be suppressed within an allowable range.

  Next, FIG. 9 shows the result of investigation on the shape of the fairing formed on the outer edge 3a of the bridge girder 3.

  Here, an isosceles triangular section having an isosceles triangular section like the triangular fairings 102c and 102c in FIG. 10, and an asymmetric trapezoid having an asymmetric trapezoidal section like the asymmetric fairings 32a and 32a in FIG. The cross section was compared.

  These fairings were applied to the two-box girders 32, respectively, and the other structures were analyzed in accordance with the configuration of the present embodiment described above.

  The shape used for this analysis is 25.6m wide (including 7m width of the opening 32c) excluding the fairing of the double box girder 32, 2.76m thick, the width direction vertex of the isosceles triangle section of the fairing The height of the trapezoid is 2m, the top of the asymmetric trapezoidal cross section is 1.01m from the bottom of the girder to 1.41m (the bottom is 2.76m, the same as the thickness), and the height of the trapezoid is 1m.

  As a result of analysis under such conditions, it can be seen that the vertical displacement and the torsional displacement when the wind load is applied are smaller in the asymmetric trapezoidal cross section as shown in FIG.

  From the above results, when the lower ends of the hanger ropes 5a,... Are connected to the outer edges 3a, 3a of the two-box girders 32 and the asymmetric fairings 32a, 32a are provided, the best wind resistance performance is obtained. I can say that.

  Next, the operation of the bridge 1 in the present embodiment will be described.

  The present invention configured as described above is the bridge 1 combining the cable-stayed bridge structure and the suspension bridge structure, and the lower ends of the hanger ropes 5a suspended from the main cables 5, 5 are connected to the outer edges 3a, Connect to 3a.

  By connecting the hanger ropes 5a,... To the outer edges 3a, 3a in this way, the resistance against lateral deformation can be increased compared to the case where the main cables 5, 5 are connected near the center in the width direction of the bridge girder 3. While being able to increase, lateral deflection deformation amount and twist deformation amount can be suppressed.

  As a result, the flutter expression wind speed can be set to 80 m / sec or more, and the wind speed below that can be suppressed to a fluctuation in an allowable range both statically and dynamically.

  Further, since the suspension load can be reduced by combining the cable stayed bridge structure and the suspension bridge structure, the diameter of the main cable 5, the size of the anchorage 5b, and the scale of the main tower 2 can be made economical.

  Here, the interval between the two main cables 5 and 5 is configured such that the interval at the center portion is wider than the interval when passing through the top 2a of the main tower 2, so that the main tower 2 Can be narrowed.

  If the scale can be reduced by narrowing the width of the main tower 2 in this way, not only the construction cost of the upper structure of the main tower 2 can be reduced, but also the foundation 2b supporting the upper structure can be reduced in size by reducing its weight. Construction costs can be reduced.

  Further, by forming the asymmetric fairing 32a, 32a having a cross-sectional asymmetric trapezoidal shape on the outer edges 3a, 3a of the double box girder 32, the vertical displacement and the torsional displacement can be greatly reduced as can be seen from the above-described analysis results. Wind resistance performance can be improved.

  Further, at least until the construction work of the two box girders 32 is completed, the gap adjusting device 6 that holds the gap between the two main cables 5, 5 is attached to the bridge girder 3 formed by the two box girders 32. By arranging in the upper position, the hanger ropes 5a,... Can be connected to the outer edges 3a, 3a of the bridge girder 3 without being pulled with an excessive force.

  That is, the main cables 5 and 5 stretched substantially in parallel at intervals of about the width of the opening 32c of the two box girders 32 are moved to the position of the outer edge 3a of the bridge girder 3 just by pulling the hanger ropes 5a. If it is moved, excessive stress is applied to the hanger rope 5a and the outer edge 3a through the intersection of the hanger rope 5a and the main cable 5, and winches installed on the outer edge 3a of the bridge girder 3 to attract the hanger rope 5a. May occur.

  Further, even if the hanger rope 5a is connected to the outer edge 3a, in the state where the hanger rope 5a is partially connected, the restoring force for returning the main cable 5 to the original position is larger, and the hanger rope There is a possibility that concentrated stress is generated at 5a, the intersection of the main cable 5, the outer edge 3a, and the like.

  On the other hand, if the lower end of the hanger rope 5a is connected to the outer edge 3a of the bridge girder 3 while the distance between the main cables 5 and 5 remains narrow, the road building limit 106 is affected by the hanger rope 5a that is slanted. Become.

  On the other hand, in the bridge 1 of the present invention, the distance between the main cables 5 and 5 is expanded to a predetermined width by the distance adjusting device 6, and then the lower end of the hanger rope 5 a is connected to the outer edge 3 a of the bridge girder 3. For this reason, excessive stress is not generated even on the hanger rope 5a temporarily, and excessive stress is not generated on the members connected thereto to be damaged.

  Further, the distance adjusting device 6 includes a beam portion 61 and a contact portion 62 of the main cables 5 and 5 that can move along the beam portion 61. The distance between the cables 5 and 5 can be changed to a desired width.

  For this reason, the interval between the two main cables 5, 5 that gradually spread from the main tower 2 toward the central portion between the main towers can be maintained at a predetermined interval by the interval adjusting device 6.

  Although the best embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes that do not depart from the gist of the present invention are possible. Are included in the present invention.

  For example, in the present embodiment, the case where the main tower 2 is constructed in accordance with the width of the one box girder 31 has been described. However, the present invention is not limited to this, and is wider than this and has a gate shape or a front view rectangle. By constructing a truss-shaped main tower and projecting the main cables 5 and 5 therefrom, the main cables 5 and 5 can be stretched in a form close to parallel over the entire length between the main towers.

  As described above, when the main cables 5 and 5 can be arranged in the vicinity of just above the outer edges 3a and 3a of the two-box girder 32 from the beginning, the distance adjusting device 6 need not be arranged.

  In addition, the shape of the fairing provided in the one box girder 31 and the two box girders 32 in the present embodiment is not limited to the above shape, and the cross-sectional view may vary depending on the behavior when a wind load is applied. An optimum shape may be selected from shapes such as equilateral triangles, trapezoids, asymmetric trapezoids, and semicircles.

  Furthermore, in the present embodiment, the case where the distance adjusting device 6 is provided at the central portion and both end portions of the suspension bridge structure has been described. However, the present invention is not limited to this. What is necessary is just to set the optimal number of installations by installation range.

  Moreover, the structure of the space | interval adjustment apparatus 6 is not limited to the said embodiment, What is necessary is just a structure which can expand and hold | maintain the space | interval of the main cables 5 and 5. FIG.

  Furthermore, in the said embodiment, although the bridge 1 provided with the two main towers 2 and 2 was demonstrated, it is not limited to this, When three or more main towers 2, ... are provided A similar configuration of the present invention can be applied.

It is a perspective view explaining the schematic structure of the bridge of the best embodiment of this invention. It is a side view explaining the structure of the bridge of the best embodiment of this invention. It is sectional drawing explaining the structure of the part which supports one box girder with a cable-stayed bridge structure. It is sectional drawing explaining the structure of the part which supports a two box girder with a suspension bridge structure. (A) The side view explaining the structure of the state where the space | interval adjustment apparatus was folded, (b) The side view explaining the structure of the state where the space | interval adjustment apparatus was extended. It is a figure explaining the movement method of the contact part of a space | interval adjustment apparatus, (a) is explanatory drawing which shows the state in which the contact part is being fixed, (b) is the state in which the contact part is moving. It is explanatory drawing shown. It is a figure explaining the construction method of a bridge, (a) is a top view explaining the state where the main cable was stretched substantially in parallel, (b) shows the state where the interval adjusting device is arranged in the central part of the suspension bridge structure. A plan view to explain, (c) is a plan view illustrating a state in which a distance adjusting device is disposed at both ends of the suspension bridge structure, and (d) is a plan view showing an outer shape of a two-box girder suspended from the suspension bridge structure. is there. It is the figure which compares the analysis result of the behavior to the wind load of the inner suspension structure and the outer suspension structure, (a) is the figure which showed the relationship between actual bridge conversion wind speed and vertical displacement, (b) is the actual bridge conversion wind speed and It is the figure which showed the relationship of the twist displacement. It is a figure which compares the analysis result of the behavior with respect to the wind load of an asymmetric trapezoidal section and an isosceles triangle section, (a) is a figure showing the relation between an actual bridge conversion wind speed and vertical displacement, and (b) is an actual bridge conversion wind speed. It is the figure which showed the relationship between and torsional displacement. It is sectional drawing explaining the structure of the part which supports a two box girder with the conventional suspension bridge structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bridge 2 Main tower 2a Tower top part 3 Bridge girder 3a Outer edge 31 One box girder 32 Two box girder 32a Asymmetric fairing 4 Cable cable 5 Main cable 5a Hanger rope 6 Spacing adjustment device 61 Beam part 62 Contact part

Claims (6)

A plurality of main towers installed at intervals, and a bridge girder in which a portion projecting on both sides through the main tower is formed in one box girder and a central portion between the main towers is formed in two box girder The bridge girder in the vicinity of the main tower is supported by a plurality of cable-stretched cables having one end fixed to the main tower, and the central portion is extended through two tower tops of the main tower. A bridge supported by a plurality of hanger ropes each suspended from a cable,
The bridge characterized by connecting the lower end of the said hanger rope to the outer edge of the said bridge girder by the side of the main cable which suspended the hanger rope.   2. The bridge according to claim 1, wherein the interval between the two main cables is wider at the central portion than at the tower top.   The bridge according to claim 1 or 2, wherein a fairing having a cross-sectional asymmetric trapezoidal shape is formed on an outer edge of the two-box girders.   The distance adjusting device for maintaining the distance between the two main cables is disposed above a bridge beam formed by the two box beams. Bridge.   The bridge according to claim 4, wherein the distance adjusting device includes a beam portion and an abutting portion of the main cable movable along the beam portion. A plurality of main towers installed at intervals, and a bridge girder in which a portion projecting on both sides through the main tower is formed in one box girder and a central portion between the main towers is formed in two box girder The bridge girder in the vicinity of the main tower is supported by a plurality of cable-stretched cables having one end fixed to the main tower, and the central portion is extended through two tower tops of the main tower. A method of building a bridge that is supported by a plurality of hanger ropes each suspended from a cable,
Two main cables are stretched substantially parallel between the main towers, a distance adjusting device for widening the distance between the main cables is installed at a predetermined position, and the lower end of the hanger rope suspended from the main cable Is connected to the outer edge of the bridge girder.

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