A combined reinforcement structure using lightweight aggregate concrete to solve the problem of cracked steel bridge decks

Abstract

A composite reinforcement structure for solving the cracked steel bridge deck by using lightweight aggregate concrete, the key points of the technical solution are as follows: It includes a steel bridge deck with fatigue cracks, shear connectors, a fiber-reinforced composite material layer, a steel mesh, and a lightweight aggregate concrete layer. The cracked part of the steel bridge deck with fatigue cracks is paved with a fiber-reinforced composite material layer. The steel mesh is placed on the steel bridge deck with fatigue cracks. Shear connectors are arranged on the fiber-reinforced composite material layer. The lightweight aggregate concrete layer is poured on the steel bridge deck with fatigue cracks and covers the shear connectors, the fiber-reinforced composite material layer, the steel mesh and is connected to the steel bridge deck with fatigue cracks.

Description

Technical Field

[0001] The present invention relates to a bridge structure for strengthening orthotropic steel bridge decks, and more particularly to a composite strengthening structure using lightweight aggregate concrete to solve the problem of cracked steel bridge decks. Background Art

[0002] As an important structural form of steel bridge decks, orthotropic steel bridge decks have been widely used due to their advantages such as light self-weight, high strength, and short construction period. However, with the increase of service time, two types of diseases usually occur in steel bridge decks: fatigue cracking of the steel structure of the steel bridge deck and damage to the bridge deck pavement layer, which seriously affect the normal use of the steel bridge. At present, different degrees of fatigue cracks have been observed in bridges with orthotropic steel bridge decks at home and abroad. The main girders or stiffening girders of important bridge structures such as the Humen Bridge built in China adopt the orthotropic plate structure of steel box girders. After being put into operation, different degrees of fatigue damage, crack diseases and even failures have occurred in the welded parts of the deck, resulting in a significant reduction in the bearing capacity and traffic capacity of the bridge. Measures such as weight limit and speed limit have to be taken, and at the same time, its service life has been greatly shortened. In response to these two major diseases, various strengthening schemes have been proposed. Among them, the patent "A Light Composite Strengthening Structure for Fatigue-Cracked Steel Bridge Decks without Repair" proposes to spot-weld steel plates with welded short studs to the cracked bridge deck, and at the same time weld short studs to the bridge deck, and finally pour ultra-high performance concrete to form a composite strengthening structure to achieve the strengthening effect.

[0003] However, this structure still has many problems: 1. The original bridge deck is not strengthened. The environment where the steel bridge deck is located is harsh, and there is a risk of further cracking and corrosion of the steel bridge deck; 2. The steel strips are spot-welded to the fatigue-cracked steel bridge deck, and they cannot be closely combined with the original bridge deck, and there must be gaps, so they cannot share the force with the original front panel; 3. The densities of the steel strips and ultra-high performance concrete are relatively large, which increases the self-weight of the bridge and reduces the bearing capacity of the bridge. 4. The original bridge deck has already cracked, and then welding short studs will introduce welding residual stress and new cracks, further weakening the bearing capacity of the steel bridge deck. Summary of the Invention

[0004] Different from directly applying concrete to intact orthotropic steel bridge decks (or repairing them to be intact), for fatigue-cracked steel bridge decks, the existence of fatigue cracks will greatly reduce the strengthening effect of the steel panel on the concrete. Therefore, if effective strengthening measures are not taken on the top surface of the cracked steel bridge deck, the tensile strength at the bottom of the concrete layer is extremely low, which will lead to cracking. Therefore, for the application of concrete to cracked orthotropic steel bridge decks, it is necessary to fully consider the adverse effects of steel plate cracks on the stress of the concrete layer, take reasonable strengthening measures, and the key lies in how to strengthen the bottom surface of the concrete layer to prevent the concrete layer from cracking.

[0005] The object of the present invention is to provide a lightweight composite reinforcement structure for a steel bridge deck with fatigue cracks, which has a simple structure, is convenient for construction, and has strong anti-cracking ability at the bottom of the composite bridge deck concrete layer, thereby effectively reducing the fatigue stress amplitude of the steel bridge deck to eliminate fatigue cracking diseases, and ensuring that the bottom of the concrete layer will not be cracked due to the cracks in the steel bridge deck.

[0006] The technical solution adopted by the present invention to solve its technical problems is as follows: It includes a steel bridge deck with fatigue cracks, shear connectors, fiber-reinforced composite material layer, steel mesh, and lightweight aggregate concrete layer. The fiber-reinforced composite material layer is laid on the cracked part of the steel bridge deck with fatigue cracks. The steel mesh is placed on the steel bridge deck with fatigue cracks. Shear connectors are provided on the fiber-reinforced composite material layer. The lightweight aggregate concrete layer is poured on the steel bridge deck with fatigue cracks and covers the shear connectors, fiber-reinforced composite material layer, steel mesh and is connected to the steel bridge deck with fatigue cracks.

[0007] Two or more fiber-reinforced composite material layers are laid on the cracked part of the steel bridge deck with fatigue cracks. Shear connectors are provided on the steel bridge deck between adjacent fiber-reinforced composite material layers, and the spacing between adjacent shear connectors is 100 - 300 mm.

[0008] The fiber-reinforced composite material layer of the present invention is provided with openings and opening steel plate connectors. The fiber-reinforced composite material layer is arranged at intervals along the bridge direction on the steel bridge deck with fatigue cracks through the opening steel plate connectors. The opening steel plate connectors are composed of vertical steel plates with openings in the longitudinal direction of the fiber-reinforced composite material layer, and the longitudinal shear force and uplift force between the fiber-reinforced composite material layer and the lightweight aggregate concrete are resisted by the lightweight aggregate concrete in the holes of the fiber-reinforced composite material layer. The opening steel plate connectors can be connected to the upper flange of the fiber-reinforced composite material layer by two longitudinal steel plates.

[0009] Compared with stud connectors, the connectors of the present invention have less influence on the steel beam. Before reaching the ultimate load, the opening steel plate connectors (PBL connectors) have a greater stiffness. When the slip reaches 15 mm, they can still bear 80% of the ultimate load, while the bearing capacity of the studs begins to decline after the slip reaches 10 mm and some studs are sheared off.

[0010] The fiber-reinforced composite material of the present invention is tightly bonded to the steel bridge deck with fatigue cracks through a cementitious material, and the steel bridge deck is polished.

[0011] The fiber-reinforced composite material layer of the present invention includes fiber-reinforced material strips and metal strips, such as carbon fiber strips and aluminum strips. The fiber-reinforced material strips are located at the bottom end of the fiber-reinforced composite material layer. The metal strips are slightly larger than the fiber-reinforced material strips and are placed on the fiber-reinforced material strips. The length of the fiber-reinforced composite material layer is equal to the width of the fatigue-cracked steel bridge deck. The width range of the fiber-reinforced composite material is 50 - 300 mm. There are metal strips in the fiber-reinforced composite material layer, and the width range of the metal strips is 50 - 200 mm. The metal strips are positioned on the steel bridge deck through connection methods including welding, cementing, and bolting.

[0012] The shear connectors of the present invention include stud bolts, T-shaped steel, angle steel, steel bar connectors, PBL perforated steel plate connectors, and carbon fiber profile shear connectors. The shear keys can be arranged in the gap areas between adjacent reinforced strips.

[0013] The fiber-reinforced composite material layer of the present invention can be made into carbon fiber cloth or carbon fiber strips and used on the fatigue-cracked steel bridge deck.

[0014] The steel bar mesh of the present invention is a multi-layer steel bar mesh. The steel bar mesh is divided into two layers in the longitudinal and transverse bridge directions. Among them, the transverse bridge bars are arranged in the upper layer and the longitudinal bridge bars are arranged in the lower layer. The longitudinal and transverse bridge bars can be tied at the intersection positions. The steel bar mesh is located below and / or above the fiber-reinforced composite material layer. The steel bar mesh is composed of longitudinal bars and transverse bars laid staggeredly with an adjacent bar spacing of 20 - 70 mm, and the bar diameter is 8 - 16 mm.

[0015] The transverse bridge bars and longitudinal bridge bars of the steel bar mesh can be arranged unevenly at intervals, and the closer to the crack, the denser the arrangement.

[0016] The lightweight aggregate concrete layer of the present invention refers to a concrete material composed of water, lightweight aggregates, cement, fine aggregates, silica fume, high-range water reducers, steel fibers, and water-soluble polymers. The components contain steel fibers and use lightweight aggregates that have been treated, with a compressive strength not lower than 50 MPa and a flexural strength not lower than 6.8 MPa. And there is a wear-resistant layer on the lightweight aggregate concrete layer, and the wear-resistant layer includes asphalt concrete and resin.

[0017] The present invention includes a fatigue-cracked steel bridge deck, metal strips or fiber-reinforced composite (FRP) strips connected with shear keys (steel section (angle steel / T-shaped steel) connectors, perforated steel plate connectors (PBL connectors)), and a lightweight aggregate concrete layer. The strips are arranged at intervals along the longitudinal direction of the bridge on the fatigue-cracked steel bridge deck. The lightweight aggregate concrete layer is poured on the fatigue-cracked steel bridge deck and covers the strips and the steel bridge deck.

[0018] Furthermore, the length of the metal strip connected with the shear key (steel (angle steel / T-steel) connector, perforated steel plate connector (PBL connector)) is equal to the width of the steel bridge deck, and the shear key is connected to the center line of the length direction of the metal strip; the width of the metal strip ranges from 50 to 200 mm, and should be determined according to the crack conditions of the steel bridge deck in specific actual bridge applications. The more concentrated the cracks in the steel bridge deck, the wider the metal strip, and the fewer the cracks in the steel bridge deck, the narrower the metal strip. The metal strip is positioned on the steel bridge deck through a reliable connection method.

[0019] Furthermore, the length of the fiber reinforced composite (FRP) strip is equal to the width of the steel bridge deck, and the FRP strip is arranged between the shear keys (steel (angle steel / T-shaped steel) connectors, perforated steel plate connectors (PBL connectors)) along the longitudinal direction of the bridge, and is flatly bonded to the steel bridge deck by a reliable bonding method. The width of the FRP strip ranges from 50 to 300 mm, and should be determined according to the crack conditions of the steel bridge deck in specific actual bridge applications. The more concentrated the cracks in the steel bridge deck, the wider the FRP strip, and the fewer the cracks in the steel bridge deck, the narrower the FRP strip.

[0020] Furthermore, shear keys (steel (angle steel / T-steel) connectors, perforated steel plate connectors (PBL connectors)) are arranged on the fatigue cracked steel bridge deck. The aforementioned metal slats or FRP slats connected with the shear keys are laid between the shear keys connected to the steel bridge deck, and the spacing between adjacent shear keys is 100~300mm.

[0021] Furthermore, the connection method between the shear key (steel (angle steel / T-shaped steel) connector, perforated steel plate connector (PBL connector)) and the metal strip, and the connection method between the shear key (steel (angle steel / T-shaped steel) connector, perforated steel plate connector (PBL connector)) and the steel bridge deck can be selected but not limited to continuous welding, intermittent welding, bonding, etc.

[0022] Furthermore, the lightweight aggregate concrete layer is made of ultra-light aggregate concrete, which refers to concrete containing steel fibers and treated lightweight aggregates, with a compressive strength of not less than 50 MPa and a flexural strength of not less than 6.8 MPa.

[0023] A further improvement is that the lightweight composite reinforcement structure also includes a steel mesh arranged in the lightweight aggregate concrete layer, the steel mesh is located below and / or above the metal strips or fiber reinforced composite (FRP) strips connected with shear keys (steel (angle steel / T-shaped steel) connectors, perforated steel plate connectors (PBL connectors)); the steel mesh is composed of longitudinal steel bars and transverse steel bars that are staggered and laid with the spacing between adjacent steel bars being 1.5-5 times their nominal diameters, and the steel bar diameter is 8-12 mm.

[0024] The present invention relates to a lightweight composite reinforcement structure for a steel bridge deck with fatigue cracks. Shear keys (section steel (angle steel / T-shaped steel) connectors, perforated steel plate connectors (PBL connectors)) are arranged on the steel bridge deck with fatigue cracks. Then, metal strips or fiber-reinforced composite (FRP) strips connected with the shear keys (section steel (angle steel / T-shaped steel) connectors, perforated steel plate connectors (PBL connectors)) are arranged between adjacent shear keys (section steel (angle steel / T-shaped steel) connectors, perforated steel plate connectors (PBL connectors)), and are positioned on the cracked steel bridge deck through a reliable connection method, so that the metal strips or fiber-reinforced composite (FRP) strips are arranged longitudinally along the bridge at regular intervals throughout the steel bridge deck and longitudinally across the entire bridge width, forming a lightweight composite reinforcement structure for the steel bridge deck with fatigue cracks, and eliminating the risk of continuous development of cracks in the cracked steel bridge deck.

[0025] The strength and stiffness of the section steel (angle steel / T-shaped steel) connectors of the present invention are higher than those of stud connectors. The section steel (angle steel / T-shaped steel) connectors mainly rely on the local bearing capacity of concrete, and their shear resistance mainly depends on the local compressive strength of concrete. Since the lightweight aggregate concrete used in this patent is incorporated with fibers and is lightweight and high-strength, the section steel (angle steel / T-shaped steel) connectors adopted have high shear resistance.

[0026] Compared with stud connectors, the connectors of the present invention, the perforated steel plate connectors (PBL connectors) have little influence on the steel beam, and have a relatively large stiffness before reaching the ultimate load. After the slip reaches 15 mm, it can still bear 80% of the ultimate load, while the bearing capacity of studs begins to decline after the slip reaches 10 mm and some studs are sheared off. And its fatigue resistance is also better. Fatigue tests show that after 2 million loading cycles under 40% of the ultimate load, the slip of the perforated steel plate connectors (PBL connectors) is only 0.14 mm, while that of the stud connectors reaches 1.5 mm. Under working stress, the deformation of the perforated steel plate connectors (PBL connectors) is small, approaching that of rigid connectors, and the fatigue resistance is better.

[0027] Compared with spot welding, the connection method of the present invention, continuous welding makes the firmness between the two welded parts higher, has better fatigue resistance, can effectively reduce the residual stress after welding, and ensure the welding quality.

[0028] Compared with spot welding, the connection method of the present invention, intermittent welding makes the firmness between the two welded parts higher, has better fatigue resistance, can effectively reduce the residual stress after welding, and ensure the welding quality.

[0029] Compared with spot welding, the connection method of the present invention makes the connection between the metal strip and the already fatigue-cracked steel bridge deck closer by bonding, causing less damage to the original cracked steel bridge deck and improving the reinforcement quality of the reinforcement structure.

[0030] Compared with the connection method of using spot welding between the metal strip and the already fatigue-cracked steel bridge deck, the bonding between the fiber-reinforced composite material (FRP) strip and the already fatigue-cracked steel bridge deck makes the connection between the two closer, causing less damage to the original cracked steel bridge deck and improving the reinforcement quality of the reinforcement structure. The use of the fiber-reinforced composite material (FRP) strip reduces the weight of the reinforcement structure, and it also has a control effect on the cracks on the steel bridge deck, improving the safety of the reinforced bridge.

[0031] Compared with ultra-high performance concrete, the concrete of the present invention, namely lightweight aggregate concrete, has a light self-weight, a low elastic modulus, high toughness, good anti-deformation ability, good anti-seepage performance, and heat preservation and heat insulation. Moreover, it can effectively solve problems such as cracking, pushing, heaving, and waterproofing of the paving layer thereon.

[0032] The present invention may further include an already fatigue-cracked steel bridge deck, a reinforcement strip bonded to the cracked steel bridge deck (shear connectors are bonded to the reinforcement strip), shear connectors welded to the original steel bridge deck, a steel bar mesh, a lightweight aggregate concrete layer, and a wearing course. The reinforcement strip is bonded to the cracked steel bridge deck along the transverse direction of the bridge by an organic structural adhesive. The steel bar mesh is placed on the cracked steel bridge deck. The lightweight aggregate concrete layer is poured on the cracked steel bridge deck and covers the reinforcement strip, shear connectors, and steel bar mesh. The wearing course is poured on the lightweight aggregate concrete layer.

[0033] The reinforcement strip of the present invention can be an aluminum strip and a carbon fiber strip. Shear connectors such as T-shaped, L-shaped steel, or carbon fiber profiles are bonded to the reinforcement strip.

[0034] The reinforcement strip with shear keys of the present invention is bonded to the top surface of the already cracked steel bridge deck along the transverse direction of the bridge by an organic structural adhesive, cooperating with the bottom of the lightweight aggregate concrete in tension to make up for the deficiency of the original steel bridge deck due to fatigue cracking. Through bonding with the organic structural adhesive, it can ensure that the reinforcement strip is closely attached to the original steel bridge deck, avoiding gaps and improving the cooperative stress between the two.

[0035] Shear keys are welded on the already cracked steel bridge deck of the present invention. The shear keys can be in the form of stud bolts, T-shaped steel, L-shaped steel, etc., and the shear keys are arranged in the gap areas between adjacent reinforcement strips.

[0036] The steel bar mesh of the present invention is arranged above the already cracked steel bridge deck and the reinforcement strip, and is staggered from the position of the shear keys. The steel bar mesh is divided into two layers in the longitudinal and transverse directions of the bridge. The steel bar mesh mainly plays a role in strengthening the lightweight aggregate concrete layer. Among them, the transverse steel bars are arranged in the upper layer, and the longitudinal steel bars are arranged in the lower layer. The longitudinal and transverse steel bars can be tied at the intersection positions.

[0037] The lightweight aggregate concrete of the present invention refers to a concrete material composed of water, lightweight aggregate, cement, fine aggregate, silica fume, high-range water reducer, steel fiber and water-soluble polymer. The lightweight aggregate concrete is laid above the steel bridge deck, covering the strengthening bars, shear keys and steel mesh.

[0038] An abrasion layer is laid above the lightweight aggregate concrete of the present invention, and the abrasion layer can be asphalt concrete type and resin type.

[0039] The beneficial effects of the present invention are as follows: small equipment investment, simple operation, easy construction, low requirements for the quality of construction personnel and construction technology, significantly reducing the fatigue stress amplitude of the steel bridge deck, thus eliminating the risk of continuous cracking of the steel bridge deck. At the same time, the existing cracks will not continue to expand, prolonging its anti-fatigue life and improving the durability of the bridge deck system, with great application value and good economic benefits. It is mainly applied to the field of steel bridge construction. Brief Description of the Drawings

[0040] Figure 1 is the schematic structural diagram (I) of the present invention;

[0041] Figure 2 is Figure 1 the side sectional view of

[0042] Figure 3 is the schematic structural diagram (II) of the present invention;

[0043] Figure 4 is Figure 3 the side sectional view (I) of

[0044] Figure 5 is Figure 3 the side sectional view (II) of

[0045] In the figure: 1-fatigued and cracked steel bridge deck, 2-fiber reinforced composite material layer, 3-shear connector, 4-steel mesh, 5-lightweight aggregate concrete layer, 6-abrasion layer. Detailed Embodiment

[0046] The present invention will be further described in detail below with reference to the drawings and embodiments.

[0047] Example 1. The present invention includes a fatigue-cracked steel bridge deck, shear connectors, a fiber-reinforced composite material layer, a steel bar mesh, and a lightweight aggregate concrete layer. Shear connectors are provided on the fatigue-cracked steel bridge deck. The steel bar mesh is placed on the fatigue-cracked steel bridge deck. The fiber-reinforced composite material layer is laid to the cracked part of the fatigue-cracked steel bridge deck. The lightweight aggregate concrete layer is poured on the fatigue-cracked steel bridge deck and covers the shear connectors, the fiber-reinforced composite material layer, the steel bar mesh and is connected to the fatigue-cracked steel bridge deck. Refer to Figures 1 to 5 .

[0048] Example 2. The shear connectors of the present invention are connected to the fiber-reinforced composite material layer. The fiber-reinforced composite material arranges shear connectors along the direction of the fatigue-cracked steel bridge deck. Shear connectors are provided on the fatigue-cracked steel bridge deck. The fiber-reinforced composite material layer connected with the shear connectors is laid between the shear connectors connected to the steel bridge deck. The spacing between adjacent shear connectors is 100 - 300 mm. Refer to Figures 1 to 5 , and the rest is the same as any one of the above embodiments or a combination of more than 2 embodiments.

[0049] Example 3. The fiber-reinforced composite material layer of the present invention is provided with openings and opening steel plate connectors. The fiber-reinforced composite material layer is arranged on the fatigue-cracked steel bridge deck at intervals along the bridge direction through the opening steel plate connectors. The opening steel plate connectors are composed of vertical steel plates with openings in the longitudinal direction of the fiber-reinforced composite material layer, and the longitudinal shear force and uplift force between the fiber-reinforced composite material layer and the lightweight aggregate concrete are resisted by the lightweight aggregate concrete in the holes of the fiber-reinforced composite material layer. The opening steel plate connectors can be connected to the upper flange of the fiber-reinforced composite material layer by two longitudinal steel plates. Refer to Figures 1 to 5 , and the rest is the same as any one of the above embodiments or a combination of more than 2 embodiments.

[0050] Example 4. Compared with stud connectors, the opening steel plate connectors (PBL connectors) of the present invention have less influence on the steel beam. Before reaching the ultimate load, the stiffness of the opening steel plate connectors (PBL connectors) is relatively large. When the slip reaches 15 mm, it can still bear 80% of the ultimate load, while the bearing capacity of the studs begins to decline after the slip reaches 10 mm and some studs are sheared off. Refer to Figures 1 to 5 , and the rest is the same as any one of the above embodiments or a combination of more than 2 embodiments.

[0051] Example 5. The fiber-reinforced composite material of the present invention is closely bonded to the fatigue-cracked steel bridge deck through a cementing material, and the steel bridge deck is polished. Refer to Figures 1 to 5 , and the rest is the same as any one of the above embodiments or a combination of more than 2 embodiments.

[0052] Example 6. The fiber-reinforced composite layer of the present invention includes fiber-reinforced material strips and metal strips, such as carbon fiber strips and aluminum strips. The fiber-reinforced material strips are located at the bottom end of the fiber-reinforced composite layer. The metal strips are slightly larger than the fiber-reinforced material strips and are placed on the fiber-reinforced material strips. The length of the fiber-reinforced composite layer is equal to the width of the fatigue-cracked steel bridge deck. The width range of the fiber-reinforced composite is 50 - 300 mm. Metal strips are provided in the fiber-reinforced composite layer, and the width range of the metal strips is 50 - 200 mm. The metal strips are positioned on the steel bridge deck by connection methods including welding, cementing, and bolting. Refer to Figures 1 to 5 , and the rest is the same as any one of the above embodiments or a combination of two or more embodiments.

[0053] Example 7. The shear connectors of the present invention include stud bolts, T-shaped steel, angle steel, steel bar connectors, PBL perforated steel plate connectors, and carbon fiber shear connectors. The shear keys can be arranged in the gap areas between adjacent reinforcement strips. Refer to Figures 1 to 5 , and the rest is the same as any one of the above embodiments or a combination of two or more embodiments.

[0054] Example 8. The fiber-reinforced composite layer of the present invention can be made into carbon fiber cloth or carbon fiber strips and used on the fatigue-cracked steel bridge deck. Refer to Figures 1 to 5 , and the rest is the same as any one of the above embodiments or a combination of two or more embodiments.

[0055] Example 9. The steel bar mesh of the present invention is a multi-layer steel bar mesh. The steel bar mesh is divided into two layers in the longitudinal and transverse bridge directions, where the transverse bridge steel bars are arranged in the upper layer and the longitudinal bridge steel bars are arranged in the lower layer. The longitudinal and transverse bridge steel bars can be tied at the intersection positions. The steel bar mesh is located below and / or above the fiber-reinforced composite layer; the steel bar mesh is composed of longitudinal steel bars and transverse steel bars laid alternately with an adjacent steel bar spacing of 20 - 70 mm, and the steel bar diameter is 8 - 16 mm. The transverse bridge steel bars and longitudinal bridge steel bars of the steel bar mesh can be arranged unevenly at intervals, and the closer to the crack, the denser the arrangement. Refer to Figures 1 to 5 , and the rest is the same as any one of the above embodiments or a combination of two or more embodiments.

[0056] Example 10. The lightweight aggregate concrete layer of the present invention refers to a concrete material composed of water, lightweight aggregate, cement, fine aggregate, silica fume, high-range water reducer, steel fiber, and water-soluble polymer. The components contain steel fiber and use concrete with treated lightweight aggregate, a compressive strength not lower than 50 MPa, and a flexural strength not lower than 6.8 MPa. And a wear-resistant layer is provided on the lightweight aggregate concrete layer, and the wear-resistant layer includes asphalt concrete and resin. Refer to Figures 1 to 5 , and the rest is the same as any one of the above embodiments or a combination of two or more embodiments.

[0057] Example 11, the present invention includes a steel bridge deck with fatigue cracks, metal strips or fiber-reinforced composite (FRP) strips connected with shear keys (section steel (angle steel / T-shaped steel) connectors, perforated steel plate connectors (PBL connectors)), and a lightweight aggregate concrete layer. The strips are arranged at intervals along the longitudinal direction of the bridge on the steel bridge deck with fatigue cracks. The lightweight aggregate concrete layer is poured on the steel bridge deck with fatigue cracks and covers the strips and the steel bridge deck.

[0058] Furthermore, the length of the metal strip connected with shear keys (section steel (angle steel / T-shaped steel) connectors, perforated steel plate connectors (PBL connectors)) is equal to the width of the steel bridge deck. The shear keys are connected on the center line in the length direction of the metal strip. The width range of the metal strip is 50 - 200 mm, which should be determined according to the crack conditions of the steel bridge deck in actual bridge applications. The more concentrated the cracks on the steel bridge deck, the wider the metal strip; the fewer the cracks on the steel bridge deck, the narrower the metal strip. The metal strip is positioned on the steel bridge deck through a reliable connection method.

[0059] Furthermore, the length of the fiber-reinforced composite (FRP) strip is equal to the width of the steel bridge deck. The FRP strips are arranged along the longitudinal direction of the bridge between the shear keys (section steel (angle steel / T-shaped steel) connectors, perforated steel plate connectors (PBL connectors)) and are smoothly adhered to the steel bridge deck through a reliable bonding method. The width range of the FRP strip is 50 - 300 mm, which should be determined according to the crack conditions of the steel bridge deck in actual bridge applications. The more concentrated the cracks on the steel bridge deck, the wider the FRP strip; the fewer the cracks on the steel bridge deck, the narrower the FRP strip.

[0060] Furthermore, shear keys (section steel (angle steel / T-shaped steel) connectors, perforated steel plate connectors (PBL connectors)) are arranged on the steel bridge deck with fatigue cracks. The aforementioned metal strips or FRP strips connected with shear keys are laid between the shear keys connected to the steel bridge deck, and the spacing between adjacent shear keys is 100 - 300 mm.

[0061] Furthermore, the connection method between the shear keys (section steel (angle steel / T-shaped steel) connectors, perforated steel plate connectors (PBL connectors)) and the metal strip, and the connection method between the shear keys (section steel (angle steel / T-shaped steel) connectors, perforated steel plate connectors (PBL connectors)) and the steel bridge deck can be selected but are not limited to continuous welding, intermittent welding, bonding, etc.

[0062] Furthermore, the lightweight aggregate concrete layer is made of ultra-lightweight aggregate concrete. The ultra-lightweight aggregate concrete refers to concrete containing steel fibers in its components and using treated lightweight aggregates, with a compressive strength not less than 50 MPa and a flexural strength not less than 6.8 MPa.

[0063] A further improvement is that the lightweight composite reinforcement structure further includes a steel mesh arranged in the lightweight aggregate concrete layer, and the steel mesh is located below and / or above the metal strip or fiber-reinforced composite (FRP) strip connected with shear keys (section steel (angle steel / T-shaped steel) connectors, perforated steel plate connectors (PBL connectors)); the steel mesh is composed of longitudinal steel bars and transverse steel bars laid staggeredly with the adjacent steel bar spacing being 1.5 - 5 times its nominal diameter, and the diameter of the steel bars is 8 - 12 mm. Refer to Figures 1 to 5 , and the rest is the same as any one of the above embodiments or a combination of two or more embodiments.

[0064] Embodiment 12: The present invention is a lightweight composite reinforcement structure for a steel bridge deck with fatigue cracks. Shear keys (section steel (angle steel / T-shaped steel) connectors, perforated steel plate connectors (PBL connectors)) are arranged on the steel bridge deck with fatigue cracks; then, metal strips or fiber-reinforced composite (FRP) strips connected with shear keys (section steel (angle steel / T-shaped steel) connectors, perforated steel plate connectors (PBL connectors)) are arranged between adjacent shear keys (section steel (angle steel / T-shaped steel) connectors, perforated steel plate connectors (PBL connectors)), and are positioned on the cracked steel bridge deck through a reliable connection method, so that the metal strips or fiber-reinforced composite (FRP) strips are arranged longitudinally along the bridge direction at regular intervals throughout the steel bridge deck and transversely along the entire bridge width, forming a lightweight composite reinforcement structure for the steel bridge deck with fatigue cracks, eliminating the risk of continuous development of cracks in the cracked steel bridge deck. Refer to Figures 1 to 5 , and the rest is the same as any one of the above embodiments or a combination of two or more embodiments.

[0065] Embodiment 13: The strength and stiffness of the section steel (angle steel / T-shaped steel) connectors of the present invention are higher than those of stud connectors. The section steel (angle steel / T-shaped steel) connectors mainly rely on the local bearing capacity of concrete, and their shear resistance mainly depends on the local compressive strength of concrete. Since the lightweight aggregate concrete used in this patent is incorporated with fibers and is lightweight and high-strength, the section steel (angle steel / T-shaped steel) connectors adopted have high shear resistance. Refer to Figures 1 to 5 , and the rest is the same as any one of the above embodiments or a combination of two or more embodiments.

[0066] Example 14. Compared with stud connectors, the connector of the present invention has less influence on the steel beam for the perforated steel plate connector (PBL connector). Before reaching the ultimate load, the stiffness of the perforated steel plate connector (PBL connector) is relatively large. When the slip reaches 15 mm, it can still bear 80% of the ultimate load, while the bearing capacity of the stud starts to decline after the slip reaches 10 mm and some studs are sheared off. And its fatigue resistance is also better. Fatigue tests show that after 2 million loading cycles under 40% of the ultimate load, the slip of the perforated steel plate connector (PBL connector) is only 0.14 mm, while that of the stud connector reaches 1.5 mm. Under working stress, the perforated steel plate connector (PBL connector) has small deformation, is close to a rigid connector, and has better fatigue resistance.

[0067] Compared with spot welding, the connection method of the present invention makes the connection between the two welded parts more firm and has better fatigue resistance by continuous welding. It can effectively reduce the residual stress after welding and ensure the welding quality.

[0068] Compared with spot welding, the connection method of the present invention makes the connection between the two welded parts more firm and has better fatigue resistance by intermittent welding. It can effectively reduce the residual stress after welding and ensure the welding quality.

[0069] Compared with spot welding, the connection method of the present invention makes the connection between the metal strip and the fatigue-cracked steel bridge deck closer by bonding, causes less damage to the original cracked steel bridge deck, and improves the reinforcement quality of the reinforcement structure.

[0070] Compared with the connection method of spot welding between the metal strip and the fatigue-cracked steel bridge deck, the connection between the fiber-reinforced composite material (FRP) strip and the fatigue-cracked steel bridge deck is closer by bonding, causes less damage to the original cracked steel bridge deck, and improves the reinforcement quality of the reinforcement structure. The use of the fiber-reinforced composite material (FRP) strip reduces the weight of the reinforcement structure, and it also has a control effect on the cracks on the steel bridge deck itself, improving the safety of the reinforced bridge. Refer to Figures 1 to 5 , and the rest is the same as any one of the above embodiments or the combination of two or more embodiments.

[0071] Example 15. The present invention may further include a fatigue-cracked steel bridge deck, a strengthening strip bonded to the cracked steel bridge deck (shear connectors are bonded to the strengthening strip), shear connectors welded to the original steel bridge deck, a steel mesh, a lightweight aggregate concrete layer, and a wearing course. The strengthening strip is bonded to the cracked steel bridge deck along the transverse direction of the bridge by an organic structural adhesive. The steel mesh is placed on the cracked steel bridge deck. The lightweight aggregate concrete layer is poured on the cracked steel bridge deck and covers the strengthening strip, shear connectors, and steel mesh. The wearing course is poured on the lightweight aggregate concrete layer.

[0072] The strengthening bars of the present invention can be aluminum alloy bars and carbon fiber bars. Shear connectors such as T-shaped, L-shaped steel or carbon fiber profiles are bonded to the strengthening bars.

[0073] The strengthening bars with shear keys of the present invention are adhesively bonded to the top surface of the cracked steel bridge deck along the transverse direction of the bridge by an organic structural adhesive, and cooperate with the light-aggregate concrete to be tensioned at the bottom to make up for the deficiency of fatigue cracking of the original steel bridge deck. Through the bonding of the organic structural adhesive, it can ensure that the strengthening bars are closely attached to the original steel bridge deck, avoid gaps, and improve the cooperative force between the two.

[0074] Shear keys are welded on the cracked steel bridge deck of the present invention. The shear keys can be in the form of stud bolts, T-shaped steel, L-shaped steel, etc., and the shear keys are arranged in the gap areas between adjacent strengthening bars.

[0075] The steel bar mesh of the present invention is arranged above the cracked steel bridge deck and the strengthening bars, and is staggered from the positions of the shear keys. The steel bar mesh is divided into two layers in the longitudinal and transverse directions of the bridge. The steel bar mesh mainly plays a role in strengthening the light-aggregate concrete layer. Among them, the transverse steel bars are arranged in the upper layer, the longitudinal steel bars are arranged in the lower layer, and the longitudinal and transverse steel bars can be tied at the intersection positions.

[0076] The light-aggregate concrete of the present invention refers to a concrete material composed of water, light aggregates, cement, fine aggregates, silica fume, high-range water-reducing agent, steel fibers and water-soluble polymers. The light-aggregate concrete is laid above the steel bridge deck, covering the strengthening bars, shear keys and steel bar mesh.

[0077] An abrasion layer is laid above the light-aggregate concrete of the present invention. The abrasion layer can be asphalt concrete and resin, refer to Figures 1 to 5 , and the rest is the same as any one of the above embodiments or a combination of two or more embodiments.

Claims

1. A combined reinforcement structure using lightweight aggregate concrete to solve the problem of cracked steel bridge decks, characterized in that: It includes a steel bridge deck with fatigue cracks, shear connectors, a fiber-reinforced composite material layer, a steel bar mesh, and a lightweight aggregate concrete layer. The fiber-reinforced composite material layer is laid on the cracked part of the steel bridge deck with fatigue cracks. The steel bar mesh is placed on the steel bridge deck with fatigue cracks. Shear connectors are provided on the fiber-reinforced composite material layer. The lightweight aggregate concrete layer is poured on the steel bridge deck with fatigue cracks and covers the shear connectors, the fiber-reinforced composite material layer, the steel bar mesh and is connected to the steel bridge deck with fatigue cracks. Openings are provided on the fiber-reinforced composite material layer and opening steel plate connectors are provided. The fiber-reinforced composite material layer is arranged at intervals along the bridge direction on the steel bridge deck with fatigue cracks through the opening steel plate connectors. The opening steel plate connectors are composed of vertical steel plates with openings longitudinally in the fiber-reinforced composite material layer, and the lightweight aggregate concrete in the holes of the fiber-reinforced composite material layer is used to resist the longitudinal shear force and uplift force between the fiber-reinforced composite material layer and the lightweight aggregate concrete. The opening steel plate connectors can be connected to the upper flange of the fiber-reinforced composite material layer by two longitudinal steel plates.

2. The combined reinforcement structure for solving the cracked steel bridge deck by using lightweight aggregate concrete according to claim 1, wherein: More than 2 fiber-reinforced composite material layers are laid on the cracked part of the steel bridge deck with fatigue cracks. Shear connectors are provided on the steel bridge deck between adjacent fiber-reinforced composite material layers, and the spacing between adjacent shear connectors is 100 - 300 mm.

3. The combined reinforcement structure for solving the cracked steel bridge deck by using lightweight aggregate concrete according to claim 1, characterized in that: The fiber-reinforced composite material is tightly bonded to the steel bridge deck with fatigue cracks through a cementitious material, and the steel bridge deck is polished.

4. The combined reinforcement structure for solving the cracked steel bridge deck by using lightweight aggregate concrete according to claim 1, characterized in that: The fiber-reinforced composite material layer includes fiber-reinforced material strips and metal plate strips. The fiber-reinforced material strips are located at the bottom end of the fiber-reinforced composite material layer. The metal plate strips are slightly larger than the fiber-reinforced material strips and are placed on the fiber-reinforced material strips. The length of the fiber-reinforced composite material layer is equal to the width of the steel bridge deck with fatigue cracks. The width range of the fiber-reinforced composite material is 50 - 300 mm, and the width range of the metal plate strips is 50 - 200 mm. The metal plate strips are positioned on the steel bridge deck through connection methods including welding, cementing, and bolting.

5. The combined reinforcement structure for solving the cracked steel bridge deck by using lightweight aggregate concrete according to claim 1, characterized in that: The shear connectors include stud bolts, T-shaped steel, angle steel, steel bar connectors, PBL opening steel plate connectors, and carbon fiber profile shear connectors.

6. The combined reinforcement structure for solving the cracked steel bridge deck by using lightweight aggregate concrete according to any one of claims 1, 2, 3, 4, and 5, characterized in that: The steel bar mesh is a multi-layer steel bar mesh. The steel bar mesh is divided into two layers in the longitudinal and transverse bridge directions. Among them, the transverse bridge direction steel bars are arranged in the upper layer and the longitudinal bridge direction steel bars are arranged in the lower layer. The longitudinal and transverse bridge direction steel bars can be tied at the intersection positions. The steel bar mesh is located below and / or above the fiber-reinforced composite material layer. The steel bar mesh is composed of longitudinal steel bars and transverse steel bars laid alternately with an adjacent steel bar spacing of 20 - 70 mm, and the steel bar diameter is 8 - 16 mm.

7. The combined reinforcement structure for solving the cracked steel bridge deck by using lightweight aggregate concrete according to claim 6, wherein: The transverse bridge direction steel bars and longitudinal bridge direction steel bars of the steel bar mesh can be arranged at uneven intervals, and the closer to the crack, the denser the arrangement.

8. The combined reinforcement structure for solving the cracked steel bridge deck by using lightweight aggregate concrete according to any one of claims 1, 2, 3, 4, and 5, characterized in that: The lightweight aggregate concrete layer refers to a concrete material composed of water, lightweight aggregate, cement, fine aggregate, silica fume, high-range water reducer, steel fiber and water-soluble polymer. The component contains steel fiber and uses concrete with treated lightweight aggregate, a compressive strength of not less than 50 MPa and a flexural strength of not less than 6 MPa. And a wearing course is provided on the lightweight aggregate concrete layer, and the wearing course includes asphalt concrete type and resin type.

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