Method for improving crack resistance of bridge deck slab in midspan area of main span of composite beam cable-stayed bridge

Abstract

The invention relates to a method for improving the crack resistance of a bridge deck in a main span midspan area of a composite beam cable-stayed bridge, which comprises the following steps of: symmetrically hoisting a first section of steel beam, initially tensioning the tensile force of a stay cable to keep the steel beam horizontal, and pouring a wet joint after hoisting a prefabricated bridge deck; when the strength of the wet joint meets the requirement, the steel beam reaches the level through the pulling force of the two stay cables; symmetrically hoisting the next section of steel beam and aligning the next section of steel beam with the previous section of steel beam, repeating the steps to construct to a mid-span closure section composite beam, pushing the composite beams on the two sides of the closure opening to enable the length of the closure opening to be L + w, heating the closure section steel beam, and enabling the length of the closure section steel beam to be increased by w; a closure section steel beam is hoisted to be connected with the combination beams on the two sides of the closure opening, then a prefabricated bridge deck slab is hoisted, and a wet joint is poured; and after the wet joint strength meets the requirement, the jacking force on the combined beams on the two sides of the closure opening is canceled, the temperature of the closure section steel beam is recovered to the environment temperature, and midspan closure is completed. The anti-cracking performance of the bridge deck slab is improved through the two ways of optimizing the tensioning stay cable and increasing and decreasing the temperature of the closure section steel beam.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge deck construction of a composite beam cable-stayed bridge, and relates to a method for improving the crack resistance of a bridge deck in the middle area of a main span of a composite beam cable-stayed bridge. Background Art

[0002] In composite-girder cable-stayed bridges, the mid-span main girder often experiences significant tensile stress in the concrete deck due to the horizontal force component of the cables running along the bridge, resulting in poor crack resistance. Conventional solutions to this problem include applying large-scale longitudinal prestressing to the deck or employing cross-stay cables within a certain range in the mid-span.

[0003] Problems with applying large-scale longitudinal prestressing: 1. Part of the pressure of the prestressed steel strands is borne by the steel beams, resulting in poor prestressing effect; 2. The amount of prestressed steel strands is large and the cost is high; 3. The prestressed steel strands are large in scale and densely arranged, making construction inconvenient.

[0004] Problems with cross-stay cables: 1. The space required for anchoring the cross-stay cables on the main beam is larger than that of conventional solutions; 2. The construction of cross-stay cables is inconvenient; 3. Before the mid-span closure, the main beam is poorly stressed within the anchoring range of the cross-stay cables. Summary of the Invention

[0005] In response to the above problems, the present invention improves the construction method of the mid-span composite beam, adjusts the initial diagonal cable force to make the steel beam produce the required deformation, erects the prefabricated bridge deck and pours wet joint concrete, and after the concrete strength meets the requirements, the two diagonal cable forces restore the deformation of the steel beam, and provide pressure for the bridge deck through the deformation of the steel beam. When the construction reaches the mid-span joint section, the temperature of the steel beam in the joint section is increased to increase its length. The length of the joint mouth is also increased synchronously by pushing the composite beams on both sides. After the bridge deck of the joint section is erected and wet joint concrete is poured, and after the concrete strength meets the requirements, the temperature of the steel beam in the joint section is restored to be consistent with the environment. The extrusion effect of the composite beams on both sides of the joint mouth and the shrinkage deformation of the steel beam in the joint section are used to provide pressure for the bridge deck in the joint section, thereby greatly reducing the scale of the longitudinal prestressed steel bundles.

[0006] The technical solution adopted in the present invention is: A method for improving the crack resistance of a bridge deck in the mid-span area of a composite beam cable-stayed bridge, characterized by comprising the following steps: (1) The first segment of the steel beam is hoisted symmetrically and the initial tension of the inclined cables on the segment of the steel beam is applied so that the segment of the steel beam remains horizontal under its own weight. The tension of the inclined cables of the segment of the steel beam is S = Ggn / sin(β), where Ggn is the weight of the segment of the steel beam and β is the inclination angle of the inclined cables on the segment of the steel beam. (2) Hoist the precast bridge deck on the steel beam of the segment, constrain the displacement of the precast bridge deck along the bridge direction by temporary matching parts P, pour the wet joint concrete between the precast bridge decks to form an integral connection between the steel beam and the precast bridge deck; (3) After the concrete strength meets the requirements, the two inclined cables on the steel beam of the segment are pulled to the bridge cable force, so that the steel beam of the segment moves upward and reaches the horizontal position; (4) Symmetrically hoist the next segment of steel beam and align it with the previous segment of steel beam, repeat the above steps (1)-(3), when the construction reaches the middle span joint section steel beam, push the combined beams on both sides of the joint mouth to the displacement w / 2 of the joint section steel beam, heat the joint section steel beam to increase the temperature by T degrees, and increase the length of the joint section steel beam by w; (5) Hoist the steel beams of the closure section and connect them with the composite beams on both sides of the closure mouth, then hoist the precast bridge deck of the closure section and pour wet joint concrete; (6) After the concrete strength meets the requirements, the top thrust of the composite beams on both sides of the joint mouth is cancelled, and the temperature of the steel beams in the joint section is restored to the ambient temperature so that the length of the steel beams in the joint section is restored to the initial length L. The shrinkage deformation of the steel beams in the joint section and the squeezing effect of the composite beams on both sides are used to apply pressure to the bridge deck in the joint section to complete the joint of the middle span.

[0007] The temporary matching parts P in step (2) include the longitudinal reinforcement of the prefabricated bridge deck and transverse plain round steel bars welded to the longitudinal reinforcement, and the transverse plain round steel bars only constrain the displacement of the bridge deck in the longitudinal direction of the bridge.

[0008] After the prefabricated bridge deck is hoisted in step (2), the deformation of the steel beam is not restored by tensioning the cable. Instead, wet joint concrete is directly poured on the deformed steel beam. After the concrete strength meets the requirements, the cable is tensioned for the second time to the cable tension of the completed bridge.

[0009] The jacking displacement w / 2 in step (4) is determined based on the elongation w of the steel beam of the joint section after heating, and the length of the joint mouth after jacking is equal to L+w, where L is the length of the steel beam of the joint section.

[0010] The present invention adjusts the initial tensioning force to cause the steel beam to produce the required deformation, erects the prefabricated bridge deck and pours wet joint concrete. After its strength meets the requirements, the second tensioning force restores the deformation of the steel beam, and provides pressure for the bridge deck through the deformation of the steel beam. When constructing to the mid-span joint section, the temperature of the steel beam in the joint section is increased to increase its length, and the composite beams on both sides of the joint mouth are pushed to adapt to the length of the deformed steel beam in the joint section. After the steel beam in the joint section is connected with the steel beams on both sides, the bridge deck of the joint section is erected and wet joint concrete is poured. After its strength meets the requirements, the temperature of the steel beam in the joint section is restored to be consistent with the environment. The extrusion effect of the composite beams on both sides of the joint mouth and the shrinkage deformation of the steel beam in the joint section provide pressure for the bridge deck in the joint section, thereby greatly reducing the scale of the longitudinal prestressed steel bundles. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a schematic diagram of the construction and hoisting of the n+1 segment steel beam according to the present invention.

[0012] Figure 2 This is a schematic diagram of the hoisting of the prefabricated bridge deck of segment n+1 according to the present invention.

[0013] Figure 3 This is a schematic diagram of pouring wet joint concrete for segment n+1 according to the present invention.

[0014] Figure 4 This is a schematic diagram of the second tensioning of the (n+1) cable according to the present invention.

[0015] Figure 5 It is a schematic diagram of the present invention when hoisting the closure section nhl.

[0016] Figure 6 It is a schematic diagram of the present invention when constructing the nhl steel beam of the joint section.

[0017] Figure 7 This is a schematic diagram of the present invention for hoisting the NHL prefabricated bridge deck at the closure section and pouring wet joint concrete.

[0018] Figure 8 It is a schematic diagram after the implementation of the present invention.

[0019] Figure 9 It is a plan view of the prefabricated bridge deck and temporary matching parts of the present invention.

[0020] Figure 10 This is a schematic elevation diagram of the prefabricated bridge deck and temporary matching parts of the present invention.

[0021] In the figure: P1-1 is the longitudinal reinforcement of the prefabricated bridge deck, and P1-2 is the transverse plain round steel bar welded to the longitudinal reinforcement P1-1. DETAILED DESCRIPTION

[0022] The present invention will be further described with reference to the accompanying drawings and specific embodiments.

[0023] like Figure 1-10 As shown, the present invention provides a method for improving the crack resistance of the bridge deck in the middle area of the main span of a composite beam cable-stayed bridge, which is characterized by comprising the following steps: (1) The first segment of the steel beam is hoisted symmetrically and the initial tension of the inclined cables on the segment of the steel beam is applied so that the segment of the steel beam remains horizontal under its own weight. The tension of the inclined cables of the segment of the steel beam is S = Ggn / sin(β), where Ggn is the weight of the segment of the steel beam and β is the inclination angle of the inclined cables on the segment of the steel beam. Figure 1The figure shows the hoisting of the n+1 segment steel beam, where n is a natural number greater than 1, and the first tensioning of the n+1 inclined cable to ensure that the n+1 segment steel beam is horizontal. At this time, the inclination angle of the n+1 cable is a; (2) The precast bridge deck is hoisted on the steel beam of the segment, and the displacement of the precast bridge deck along the bridge direction is constrained by the temporary matching parts P. The wet joint concrete of the precast bridge deck is poured to form an integral connection between the steel beam and the precast bridge deck. The temporary matching parts P include the longitudinal steel bars P1-1 of the precast bridge deck and the transverse round steel bars P1-2 welded to the longitudinal steel bars P1-1. The transverse round steel bars only constrain the displacement of the bridge deck along the bridge direction, as shown in FIG. Figure 9 、 Figure 10 As shown; Figure 2 The figure shows the hoisting of the precast bridge deck of segment n+1. At this time, the inclination angle of the n+1 cable increases to b, and the displacement of the precast bridge deck along the bridge direction is constrained by the temporary matching part P. Figure 3 The figure shows the pouring of wet joint concrete of segment n+1. At this time, the inclination angle of the n+1 cable-stayed cable increases to c, where s is the wet joint. After the prefabricated bridge deck is hoisted in step (2) of the present invention, the deformation of the steel beam is not restored by tensioning the cable-stayed cable. Instead, the wet joint concrete is directly poured on the deformed steel beam. After the concrete strength meets the requirements, the cable-stayed cable is tensioned for the second time to the completed bridge cable force.

[0024] (3) After the concrete strength of the wet joint meets the requirements, the two inclined cables on the steel beam of the segment are pulled to the bridge cable force, so that the steel beam of the segment moves upward and reaches the horizontal position; Figure 4 The figure shows the second tensioning of the No. n+1 inclined cable. At this time, the No. n+1 segment steel beam is close to horizontal, and the inclination angle of the No. n+1 inclined cable is d; (4) Symmetrically hoist the next segment of steel beam and align it with the previous segment of steel beam, repeat the above steps (1)-(3), and when the construction reaches the middle span joint section steel beam, push the combined beams on both sides of the joint mouth to the displacement w / 2 of the joint section steel beam respectively, heat the joint section steel beam to increase the temperature by T degrees, and increase the length of the joint section steel beam by w; the pushing displacement w / 2 is determined according to the elongation w of the joint section steel beam after heating, and the length of the joint mouth after pushing is equal to L+w, where L is the initial length of the joint section steel beam; Figure 5 The figure shows that when the construction reaches the joint section steel beam nhl, the composite beams on both sides of the joint mouth are pushed up, the pushing distance is w / 2, and the joint section steel beam is hoisted. At this time, the length of the joint section steel beam is L; (5) Hoist the steel beams of the closure section and connect them with the composite beams on both sides of the closure, then hoist the precast bridge deck and pour wet joint concrete; Figure 6 The figure shows the hoisting of the joint section steel beam nhl, and the use of industrial electric blanket to heat the joint section steel beam until the temperature of the joint section steel beam is higher than the ambient temperature T degrees. At this time, the joint section steel beam stretches w, and the length becomes L+w, and the joint section steel beam is connected to the steel beams on both sides; Figure 7The figure shows that the temperature of the steel beams in the closure section is kept higher than the ambient temperature T, the precast bridge deck of the steel beams in the closure section nhl is hoisted, and the wet joint concrete is poured; (6) After the concrete strength of the wet joint meets the requirements, the thrust force on the composite beams on both sides of the joint mouth is cancelled, and the temperature of the steel beams in the joint section is restored to the ambient temperature so that the length of the steel beams in the joint section is restored to the initial length L. The shrinkage deformation of the steel beams in the joint section and the extrusion effect of the composite beams on both sides are used to apply pressure to the bridge deck in the joint section to complete the joint of the middle span. Figure 8 The figure shows that the jacking force of the composite beams on both sides of the joint is cancelled, and the temperature of the steel beams in the joint section is restored to be consistent with the environment. At this time, the nhl length of the steel beams in the joint section is restored to L, and the mid-span joint is completed.

[0025] Beneficial effects of the present invention: principle: (1) After the crane hoists the steel beam, the steel beam segment n+1 is connected to the installed segment n as a whole. The initial tensioning cable n+1 is used to ensure that the steel beam segment n+1 is horizontal under the action of its own weight; (2) After the prefabricated bridge deck is hoisted, the cables stretch under the action of the bridge deck's gravity, and the steel beam segment n+1 bends downward, causing the end to have a downward vertical displacement. The steel beam is long (relatively small in stiffness) and the bridge deck is short (relatively large in stiffness), resulting in a relative rotation angle between the steel beam and the bridge deck.

[0026] (3) After pouring the wet joint concrete, the precast bridge deck on the steel beam segment n+1 is connected to the steel beam segment n+1 as a whole. Before the strength of the wet joint concrete is formed, it adapts to the relative displacement between the steel beam and the precast bridge deck. The wet joint and the precast bridge deck form a concrete bridge deck with a certain curvature.

[0027] (4) After the strength of the wet joint concrete is formed, the two inclined cables and the steel beam segment n+1 produce an upward displacement under the action of the cable force, and the main beam segment n+1 produces an overall rotation. The internal force is redistributed between the steel beam and the bridge deck. Under this distribution result, the steel beam bears a certain tensile force and the bridge deck bears a certain compressive force.

[0028] (5) When the construction reaches the joint section, the thermal expansion and contraction characteristics of steel are used. Before the joint is completed, the steel beams of the joint section are heated to T degrees, and the length of the steel main beam is increased. At this time, the composite beams on both sides need to be pushed to make the length of the joint mouth match the length of the steel beams of the joint section after heating. After the steel beams of the joint section are connected with the steel beams on both sides, the concrete bridge deck of the joint section is laid. After the wet joint concrete is poured, when the concrete strength meets the requirements, the pushing force of the composite beams on both sides of the joint mouth is cancelled, and the heating facilities are removed. The temperature of the steel beams of the joint section gradually drops to the ambient temperature, and the length of the steel beams of the joint section is reduced accordingly. The composite beams on both sides squeeze the composite beams of the joint section (including steel beams and bridge deck) toward the middle. At the same time, the shortening of the steel beams of the joint section will also exert pressure on the corresponding bridge deck. The two work together to make the steel beams and bridge deck of the joint section bear enough pressure to offset the tension brought by the horizontal component of the cables on both sides, thereby increasing the pressure reserve of the bridge deck and enhancing its crack resistance. The configuration scale of the longitudinal prestressed steel strands of the composite beams in the mid-span is reduced, the construction cost is reduced, and the construction is convenient.

Claims

1. A method for improving the crack resistance of the bridge deck in the middle area of the main span of a composite beam cable-stayed bridge, characterized in that: The following steps are involved: (1) The first segment of the steel beam is hoisted symmetrically and the initial tension of the inclined cables on the segment of the steel beam is applied so that the segment of the steel beam remains horizontal under its own weight. The tension of the inclined cables of the segment of the steel beam is S = Ggn / sin(β), where Ggn is the weight of the segment of the steel beam and β is the inclination angle of the inclined cables on the segment of the steel beam. (2) The precast bridge deck is hoisted on the steel beam of the segment, and the displacement of the precast bridge deck along the bridge direction is constrained by temporary matching parts P. The wet joint concrete of the precast bridge deck is poured to form an integral connection between the steel beam and the precast bridge deck; (3) After the concrete strength of the wet joint meets the requirements, the two inclined cables on the steel beam of the segment are pulled to the bridge cable force, so that the steel beam of the segment moves upward and reaches the horizontal position; (4) Symmetrically hoist the next segment of steel beam and align it with the previous segment of steel beam, repeat the above steps (1)-(3), and when the construction reaches the composite beam of the middle span joint section, push the composite beams on both sides of the joint mouth to a distance of w / 2 from the joint section steel beam, heat the joint section steel beam to increase the temperature by T degrees, so that the length of the joint section steel beam increases by w; (5) Hoist the steel beams of the closure section and connect them with the composite beams on both sides of the closure, then hoist the precast bridge deck and pour wet joint concrete; (6) After the concrete strength of the wet joint meets the requirements, the thrust on the composite beams on both sides of the joint is cancelled, and the temperature of the steel beams in the joint section is restored to the ambient temperature to complete the mid-span joint.

2. The method for improving the crack resistance of the bridge deck in the middle area of the main span of a composite beam cable-stayed bridge according to claim 1, characterized in that: The temporary matching parts P in step (2) include the longitudinal reinforcement of the prefabricated bridge deck and transverse plain round steel bars welded to the longitudinal reinforcement, and the transverse plain round steel bars only constrain the displacement of the bridge deck in the longitudinal direction of the bridge.

3. The method for improving the crack resistance of the bridge deck in the middle area of the main span of a composite beam cable-stayed bridge according to claim 1, characterized in that: After the prefabricated bridge deck is hoisted in step (2), the deformation of the steel beam is not restored by tensioning the cable. Instead, wet joint concrete is directly poured on the deformed steel beam. After the concrete strength meets the requirements, the cable is tensioned for the second time to the cable tension of the completed bridge.

4. The method for improving the crack resistance of the bridge deck in the middle area of the main span of a composite beam cable-stayed bridge according to claim 1, characterized in that: The jacking displacement w / 2 in step (4) is determined according to the elongation w of the steel beam of the joint section after heating, and the length of the joint mouth after jacking is equal to L+w, where L is the initial length of the steel beam of the joint section.

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