Construction method for rapidly replacing conventional concrete beam with steel-concrete composite beam

Abstract

The invention discloses a construction method for rapidly replacing a conventional concrete beam with a steel-concrete composite beam. The construction method comprises the steps that firstly, the structural form of the steel-concrete composite beam is designed; 2, determining the structural size of the I-shaped steel beam; 3, checking the limit state of the bearing capacity of the steel-concrete composite beam; 4, checking the normal use limit state of the steel-concrete composite beam; and 5, replacing the numerical value and checking again. On the basis of the synergistic deformation principle of the adjacent main beams, the steel-concrete combined bridge is formed, the deformation of the replaced steel-concrete combined beam and the deformation of the original concrete beam are subjected to adaptive fitting, the applicable thickness range of the steel web and the steel bottom plate is calculated, I-shaped steel beams with different size values can be selected in time under different working conditions, and the construction efficiency is improved. A reasonable structure and theoretical system for equivalently replacing an original concrete bridge with the steel-concrete composite beam is formed, and safe and rapid replacement of the main beam of the bridge is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge maintenance construction, and particularly relates to a construction method for quickly replacing a conventional concrete beam with a steel-concrete composite beam. Background Art

[0002] When a bridge encounters disasters such as earthquakes, mudslides, landslides, falling rocks and vehicle collisions, the superstructure of the bridge is prone to excessive deformation, damage, overturning or reinforcement that is difficult to meet regulatory requirements. At the same time, damaged bridges need to be repaired or replaced quickly to buy time for disaster relief after the disaster.

[0003] Usually, when the bridge superstructure is damaged, the traditional beam replacement method is often used to replace the damaged main beam with a concrete beam of the same structure as the original one. The main construction steps include: slotting the main beam top plate, prestressing, lifting the main beam, embedding corrugated pipes, prefabricating the main beam, lifting the main beam, re-tensioning the top plate prestressing tendons, and casting the end beams. However, on the one hand, the traditional replacement method has a long construction period, complex construction procedures, and great damage to the original structure, which cannot meet the basic needs of rapid construction after disasters; on the other hand, after the transverse connection between the new and old structures is completed, the shrinkage and creep are basically completed due to the long service life of the old bridge. In contrast, the concrete age of the new beam superstructure is relatively short, and the shrinkage and creep have just begun. The deformation will continue to develop over time. Therefore, the main problem of the traditional beam replacement method is that the shrinkage and creep of the new and old structures are different, resulting in frequent bridge diseases; in addition, the old beam concrete and steel bars will have a reverse effect of constraint on it, and internal force redistribution will occur between the new and old beams, that is, the shrinkage and creep effect after splicing will cause the new beam concrete to shrink and deform in the horizontal plane, generating longitudinal tensile stress. When the longitudinal tensile stress exceeds the tensile strength of the concrete, cracks will occur, affecting the operation and service life of the structure. At the same time, due to the large constraints and shear stress generated at the wet joints of the old bridge, if it exceeds the shear strength of the concrete, longitudinal cracks will occur.

[0004] In order to solve the adverse effects of shrinkage creep effect on the replaced bridge, the engineering often reduces the adverse effects by delaying the completion time of splicing. However, when the main beam needs to be replaced urgently after a disaster, it is difficult to meet the long-term static requirements of the new beam due to the construction period. In addition, the concrete precast beams of the traditional beam replacement method have a large deadweight and need to be transported to the construction site after prefabrication in the factory, which has high requirements for transportation and lifting equipment; the concrete beams and transverse wet joint casting processes need to go through the aging stage, and the construction period is long; there are many types of small and medium span bridges, which cannot be reserved as safety reserves after prefabrication in the beam yard.

[0005] In summary, when the traffic pressure of the bridge that needs to be replaced urgently is small and the construction process has little impact on traffic, concrete beams can be used to replace the damaged structure. However, during the rapid replacement of concrete main beams, there is not enough time to age the concrete, which is greatly affected by shrinkage and creep, and it cannot be stored in the factory. The construction period is long, and the heavy weight makes transportation inconvenient. It is not suitable for the timeliness requirements of rapid replacement of bridges after disasters. Therefore, for bridges with high commuting pressure and tight construction period requirements, a new steel-concrete composite beam design method needs to be designed to achieve safe and rapid main beam replacement. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a construction method for quickly replacing conventional concrete beams with steel-concrete composite beams in view of the deficiencies in the above-mentioned prior art. The present invention is based on the principle of coordinated deformation of adjacent main beams to form a T-shaped steel-concrete composite bridge, and adapts the deformation of the replaced steel-concrete composite beam to the original concrete beam, and calculates the applicable thickness range of the steel web and steel bottom plate, so as to facilitate timely selection of I-shaped steel beams of different size values ​​under different working conditions, and form a reasonable structure and theoretical body for equivalently replacing the original concrete bridge with a set of steel-concrete composite beams, thereby realizing safe and rapid replacement of the bridge main beam and facilitating popularization and use.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a construction method for quickly replacing conventional concrete beams with steel-concrete composite beams, characterized in that the method comprises the following steps:

[0008] Step 1: Design a steel-concrete composite beam structure: the steel-concrete composite beam comprises an I-shaped steel beam and a concrete top plate arranged on the I-shaped steel beam, wherein the I-shaped steel beam comprises a steel top plate, a steel web plate and a steel bottom plate;

[0009] An I-shaped steel beam is arranged between two adjacent main beams, and then a concrete top plate is constructed on the I-shaped steel beam, and the upper surface of the concrete top plate is made flush with the upper surface of the adjacent main beams;

[0010] Step 2: Determine the structural dimensions of the I-shaped steel beam:

[0011] Step 201: Determine the fitting formula of the steel web and the steel bottom plate at the upper limit y' of the fitting function according to the deflection requirement of the I-shaped steel beam section. And the fitting formula of the steel web and steel bottom plate at the lower limit y" of the fitting function Then determine the thickness x of the steel web and the thickness y of the steel bottom plate;

[0012] Among them, y0, y1, A1, A2, A3, A4, t1, t2, t3, t4 are all coefficients;

[0013] Step 202, obtaining a value range of the thickness x of the steel web as d1-d2, and a value range of the thickness y of the steel bottom plate as d3-d4, wherein d1, d2, d3, and d4 are all positive numbers;

[0014] Step 3: Check the ultimate bearing capacity of the steel-concrete composite beam:

[0015] Step 301, select a value from d1 to d2 as the thickness of the steel web, select a value from d3 to d4 as the thickness of the steel bottom plate, and then execute step 302;

[0016] Step 302: According to the formula Calculate the bending bearing capacity σ of the steel-concrete composite beam. When γ0σ≤f, execute step 303. When γ0σ>f, execute step 5.

[0017] Among them, i is a different stress calculation stage, i=Ⅰ represents the stress calculation stage before the steel-concrete composite beam is formed, and i=Ⅱ represents the stress calculation stage after the construction of the steel-concrete composite beam is completed. In different stress calculation stages, M d,i is the design value of the bending moment acting on the steel-concrete composite beam, W eff,i is the flexural modulus of the corresponding steel-concrete composite beam, and I' is the moment of inertia of the steel-concrete composite beam section, is the centroid height of the steel-concrete composite beam section, γ0 is the structural importance coefficient, and f is the strength design value of the steel-concrete composite beam;

[0018] Step 303: According to formula V u =f vd A W , calculate the shear capacity V of the steel-concrete composite beam u , when γ0V d ≤V u When γ0V d >V u When , execute step 5;

[0019] Among them, V d is the shear design value of the steel-concrete composite beam, f vd is the design value of the shear strength of the steel web, A W is the cross-sectional area of ​​the steel web;

[0020] Step 304: Based on the influence of bending moment and shear force on the steel-concrete composite beam, use the formula Calculate the maximum reduced stress of the steel web;

[0021] Among them, σ1 and τ1 are the normal stress and shear stress generated simultaneously at the same point on the steel web, respectively, and f d is the design value of tensile strength of steel web;

[0022] Step 4: Check the limit state of normal use of the steel-concrete composite beam: Use finite element analysis software to load the standard combination and quasi-permanent combination of loads, and consider the reduced stiffness B of the composite beam slip effect to calculate the deflection value ω of the steel-concrete composite beam, that is, through the formula Calculate, when When the final thickness of the steel web and the thickness of the steel bottom plate are obtained, When , execute step 5;

[0023] Where E is the elastic modulus of the steel-concrete composite beam, I eq is the converted section inertia moment of the steel-concrete composite beam, ξ is the stiffness reduction factor, and l is the calculated span of the bridge;

[0024] Step 5: Replace the value and recalculate: reselect a value from d1 to d2 as the thickness of the steel web, reselect a value from d3 to d4 as the thickness of the steel bottom plate, and then execute step 302.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 1. Based on the cooperative deformation principle of adjacent main beams, the present invention designs a method for quickly replacing main beams after a disaster. By adopting I-beams of standard size and cooperating with concrete top plates, steel-concrete composite beams are formed to replace the original bridge structure that has been severely damaged or fallen. This solves the problems of traditional reinforcement methods, such as long construction period, complex construction procedures, difficult lifting, great damage to the original structure, and inability to meet the needs of rapid replacement after a disaster. In addition, I-beams are fast to construct, can realize rapid replacement of main beams, and have strong emergency response capabilities.

[0027] 2. The present invention adopts multivariate linear regression analysis to adapt and fit the deformation of the replaced steel-concrete composite beam and the original concrete beam, and calculates the applicable thickness range of the steel web and the steel bottom plate. After multiple verifications of the ultimate bearing capacity state and the normal use limit state, the most suitable thickness values ​​of the steel web and the steel bottom plate are selected, which is convenient for timely selection of I-shaped steel beams of different size values ​​under different working conditions, forming a reasonable structure and theoretical system for equivalent replacement of the original concrete bridge by a set of steel-concrete composite beams. The system is reliable and stable, and has good use effect.

[0028] 3. The I-beam steel beam used in the present invention has a fast construction speed, and the steel-concrete composite beam has the advantages of small weight, convenient transportation and lifting compared to the concrete beam. The I-beam steel beam is connected to the concrete top plate by welding nails, and the welding nails can transmit deformation and stress, so that the I-beam steel beam and the concrete top plate form a synergistic force-bearing structure, which can give full play to the material properties of concrete and steel structure and is easy to promote and use.

[0029] In summary, the present invention forms a steel-concrete composite bridge based on the cooperative deformation principle of adjacent main beams, and adapts the deformation of the replaced steel-concrete composite beam to the original concrete beam, and calculates the applicable thickness range of the steel web and steel bottom plate, so as to facilitate timely selection of I-shaped steel beams of different size values ​​under different working conditions, form a set of reasonable structure and theoretical body of steel-concrete composite beams that are equivalent to the original concrete bridge, realize safe and rapid replacement of the bridge main beam, and facilitate popularization and use.

[0030] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a flowchart of the construction method of the present invention.

[0032] Figure 2 It is a schematic diagram of the structure of the present invention.

[0033] Figure 3 The figure is a relationship diagram between the steel web thickness and the deflection of the I-shaped steel beam of the present invention.

[0034] Figure 4 The figure is a relationship diagram between the steel bottom plate thickness and the deflection of the I-shaped steel beam of the present invention.

[0035] Figure 5 This is a graph showing the relationship between the thickness of the steel web and the thickness of the steel bottom plate of the present invention.

[0036] Figure 6 It is a fitting function interval diagram of the steel web thickness and the steel bottom plate thickness of the present invention.

[0037] Description of reference numerals:

[0038] 1-adjacent main beams; 2-concrete top plate; 3-steel top plate;

[0039] 4-Steel web; 5-Steel bottom plate. DETAILED DESCRIPTION

[0040] like Figures 1 to 6 As shown, a construction method of the present invention for quickly replacing conventional concrete beams with a steel-concrete composite beam comprises the following steps:

[0041] Step 1: Design a steel-concrete composite beam structure: The steel-concrete composite beam includes an I-shaped steel beam and a concrete top plate 2 arranged on the I-shaped steel beam, and the I-shaped steel beam includes a steel top plate 3, a steel web plate 4 and a steel bottom plate 5.

[0042] An I-shaped steel beam is arranged between two adjacent main beams 1 , and then a concrete top plate 2 is constructed on the I-shaped steel beam, and the upper surface of the concrete top plate 2 is made flush with the upper surface of the adjacent main beams 1 .

[0043] In actual design, when replacing the concrete beam, the beam height, bottom plate width and web height of the steel-concrete composite beam are all kept consistent with the height and width of the original concrete beam to be removed, that is, the size of the concrete top plate 2, the thickness of the steel top plate 3, the height of the steel web 4 and the width of the steel bottom plate 5 cannot be changed, and only the thickness of the steel web 4 and the thickness of the steel bottom plate 5 can be changed. Finite element analysis software was used to replace one of the original concrete beams with a steel-concrete composite beam. The main beam was replaced considering its compatibility with the original structure. The thickness of the steel web 4 and the thickness of the steel bottom plate 5 were set in multiple groups of working conditions in an arithmetic manner. The thickness of the steel web 4 and the thickness of the steel bottom plate 5 of the steel-concrete composite beam were changed respectively for finite element calculation. The relationship between the thickness of the steel web 4 and the thickness of the steel bottom plate 5 and the deflection of the steel-concrete composite beam was analyzed using a scatter plot. That is, the deflection of the original concrete bridge was taken as the standard value. The thickness of the steel web 4 and the thickness of the steel bottom plate 5 of the steel-concrete composite beam with a deflection change within the range of ±0.005cm were statistically analyzed, and a scatter plot was made to obtain Figures 3 to 5 The relationship diagram shown in Figure 5 get Figure 6 The fitting function interval diagram shown in Figure 2 is shown in Figure 2; Figures 3 to 5 The solid black dots in the graph indicate that the deflection variation is within the range of ±0.005 cm.

[0044] Step 2: Determine the structural dimensions of the I-shaped steel beam:

[0045] Step 201: Determine the fitting formula of the steel web 4 and the steel bottom plate 5 at the upper limit y' of the fitting function according to the deflection requirement of the I-shaped steel beam section. And the fitting formula of the steel web 4 and the steel bottom plate 5 at the lower limit y" of the fitting function The thickness x of the steel web 4 and the thickness y of the steel bottom plate 5 are then determined.

[0046] Among them, y0, y1, A1, A2, A3, A4, t1, t2, t3, and t4 are all coefficients.

[0047] In actual construction, y0=-0.67347, y1=-1.29835, A1=2.21415,

[0048] A2=2.21415, A3=2.28153, A4=2.28153, t1=1.66475, t2=2.0347,

[0049] t3=2.2183, t4=2.71126.

[0050] Step 202: The value range of the thickness x of the steel web 4 is obtained to be d1-d2, and the value range of the thickness y of the steel bottom plate 5 is obtained to be d3-d4, wherein d1, d2, d3, and d4 are all positive numbers.

[0051] When the present invention is used, when selecting the thickness of the steel web 4 and the steel bottom plate 5 under the same span, the greater the thickness of the steel web 4 and the steel bottom plate 5, the greater the bending moment of inertia Iyy and the torsional moment of inertia Ixx of the I-shaped steel beam, the smaller the deflection change of the adjacent main beam 1, the better the coordinated deformation of the two, the smaller the deflection change ratio, and the stiffness match with the original concrete bridge will be as close as possible.

[0052] Step 3: Check the ultimate bearing capacity of the steel-concrete composite beam:

[0053] Step 301 , select a value x1 from d1 to d2 as the thickness of the steel web 4 , select a value from d3 to d4 as the thickness of the steel bottom plate 5 , and then execute step 302 .

[0054] Step 302: According to the formula The bending bearing capacity σ of the steel-concrete composite beam is calculated, that is, the bending bearing capacity σ of the steel-concrete composite beam under the coordinated deformation of the adjacent main beams after replacing the original concrete main beam. When γ0σ≤f, execute step 303; when γ0σ>f, execute step five.

[0055] Among them, i is a different stress calculation stage, i=Ⅰ represents the stress calculation stage before the steel-concrete composite beam is formed, and i=Ⅱ represents the stress calculation stage after the construction of the steel-concrete composite beam is completed. In different stress calculation stages, M d,i is the design value of the bending moment acting on the steel-concrete composite beam, W eff,i is the flexural modulus of the corresponding steel-concrete composite beam, and I' is the moment of inertia of the steel-concrete composite beam section, is the centroid height of the steel-concrete composite beam section, γ0 is the structural importance coefficient, which is taken as 1.2, and f is the strength design value of the steel-concrete composite beam.

[0056] In actual calculation, when γ0σ>f, when executing step 5, in step 301, a value larger than the first value is selected as the thickness of the steel web 4, and a value larger than the first value is selected as the thickness of the steel bottom plate 5, which is beneficial to directly affect W eff,i The numerical value is convenient for satisfying the bending bearing capacity verification.

[0057] In actual calculation, the moment of inertia of the steel-concrete composite beam section is in, A s =ax+2by, moment of inertia of I-beam a and b are both constants. Each time, a set of thickness x of the steel web 4 and thickness y of the steel bottom plate 5 are used for calculation. c is the moment of inertia of the concrete top plate 2, d c is the distance between the centroid of the I-shaped steel beam and the centroid of the concrete top plate 2; the centroid height of the steel-concrete composite beam section Among them, h s h is the distance from the centroid of the I-beam to the bottom of the I-beam. c is the distance between the centroid of the concrete top plate 2 and the bottom surface of the I-shaped steel beam, α E It is the ratio of the elastic modulus of the concrete top plate 2 and the I-shaped steel beam.

[0058] In actual construction, the concrete top plate 2 uses C50 concrete, whose elastic modulus is E c =3.45×10 4 MPa, the steel top plate 3, steel web plate 4 and steel bottom plate 5 are all made of Q345c steel, and its elastic modulus is E S =2.06×10 5 MPa, at this time, the elastic modulus ratio of the concrete top plate 2 and the I-shaped steel beam is

[0059] Step 303: According to formula V u =f vd A W , calculate the shear capacity V of the steel-concrete composite beam u , that is, after replacing the original concrete main beam, the shear bearing capacity V of the steel-concrete composite beam under the coordinated deformation of the adjacent main beams u , when γ0V d ≤V u When γ0V d >V u , execute step 5.

[0060] Among them, V d is the shear design value of the steel-concrete composite beam, f vd is the design value of the shear strength of the steel web 4, A W is the cross-sectional area of ​​the steel web 4.

[0061] In actual calculation, when γ0V d >V u When executing step 5, in step 301, a value larger than the previous value is selected as the thickness of the steel web 4, which is beneficial to increase the cross-sectional area A of the steel web 4. W , which is convenient for satisfying shear bearing capacity verification.

[0062] Step 304: Based on the influence of bending moment and shear force on the steel-concrete composite beam, use the formula Calculate the maximum reduced stress of the steel web 4.

[0063] Among them, σ1 and τ1 are the normal stress and shear stress generated simultaneously at the same point of the steel web 4, respectively, and f d is the design value of the tensile strength of the steel web 4.

[0064] By calculating the maximum reduced stress of the steel web 4 under the combined action of bending moment and shear force, it is convenient to determine the maximum bearing capacity of the steel web 4, thereby facilitating determination of whether the thickness values ​​of the selected steel web 4 and the steel bottom plate 5 meet the design requirements, thereby enabling replacement of the original concrete main beam structure.

[0065] Step 4: Check the limit state of normal use of the steel-concrete composite beam: Use finite element analysis software to load the standard combination and quasi-permanent combination of loads, and consider the reduced stiffness B of the composite beam slip effect to calculate the deflection value ω of the steel-concrete composite beam, that is, through the formula Calculate, when When the final thickness of the steel web 4 and the thickness of the steel bottom plate 5 are obtained, , execute step 5.

[0066] Where E is the elastic modulus of the steel-concrete composite beam, I eq is the converted section inertia moment of the steel-concrete composite beam, ξ is the stiffness reduction factor, and l is the calculated span of the bridge.

[0067] Step 5, replace the value and recalculate: reselect a value from d1 to d2 as the thickness of the steel web 4, reselect a value from d3 to d4 as the thickness of the steel bottom plate 5, and then execute step 302.

[0068] In actual calculation, when the standard combination of loads is applied, the effective width of the concrete top plate 2 is first divided by the elastic modulus of the steel-concrete composite beam to obtain the width of the concrete top plate 2 when converted to a steel section, and then the converted width is used to calculate the moment of inertia of the steel-concrete composite beam; when the quasi-permanent combination of loads is applied, the effective width of the concrete top plate 2 is divided by 2α E , and obtain the converted cross-sectional width.

[0069] In actual use, when the final thickness of the steel web 4 and the thickness of the steel bottom plate 5 are determined, the size of the I-beam steel beam suitable for the bridge span can be determined, which is convenient for prefabricating the I-beam steel beam directly in the factory, thereby speeding up the construction process of replacing the bridge on site.

[0070] In this embodiment, the thickness of the steel web 4 is x=1 cm, and the thickness of the steel bottom plate 5 is y=1.8 cm. At the same time, the concrete top plate 2 uses C50 concrete, and the width b of the concrete top plate 2 is e=150cm, the thickness of the concrete top plate 2 h c =18cm, the elastic modulus of the concrete top plate 2 is E c =3.45×10 4 MPa; the steel top plate 3, steel web 4 and steel bottom plate 5 are all made of Q345c steel, among which the width of the steel top plate 3 is 30 cm, and the thickness of the steel top plate 3 is 1.8 cm; the width of the steel bottom plate 5 is 30 cm, and the thickness of the steel bottom plate 5 is 1.8 cm; the thickness of the steel web 4 is 1.0 cm, and the height of the steel web 4 is 130 cm.

[0071] At this time, the conversion width calculation formula of the concrete top plate 2 is: Right now Convert the moment of inertia of the cross section Among them, I s ,I c are the moments of inertia of the steel beam and the concrete top plate 2, d c It is the distance from the centroid of the steel beam to the centroid of the concrete bridge deck.

[0072] In actual design,

[0073]

[0074] It can be calculated at this time,

[0075] A s =hx+2b+y=130×1+2×30+1.8=191.8cm 2 ,

[0076] A c =b eq h c =25.1×18=451.8cm 2 , we can calculate and Then the centroid height after the converted section is obtained

[0077] Among them, y s and c Respectively represent the distance from the centroid of the I-shaped steel beam and the concrete top plate 2 to the bottom surface of the I-shaped steel beam, and then calculate Among them, W eff is the bending modulus of the steel-concrete composite beam, I is the moment of inertia of the converted section, is the centroid height of the converted section.

[0078]

[0079] Then in step 302, according to the formula Calculate the bending capacity σ of the steel-concrete composite beam. At this time, W eff =5919.9cm 3 , M d Calculated based on the actual condition of the bridge.

[0080] In step 303, according to formula V u =f vd A W , calculate the shear capacity V of the steel-concrete composite beam u ; Among them, f vd =150MPa, the cross-sectional area A of the steel web 4 W =130cm 3 , V u =150×130=1950kN, then compared with the shear bearing capacity V of the steel-concrete composite beam under actual working conditions u For comparison, if γ0V d ≤V u , the thickness of the steel web 4 in this embodiment is x=1 cm, and the thickness of the steel bottom plate 5 is y=1.8 cm, which meets the design requirements and can be used in the construction of steel-concrete composite beams to quickly replace conventional concrete beams under the above engineering conditions.

[0081] In response to the demand for rapid replacement after a disaster, the present invention designs a method that meets the demand for rapid replacement of main beams after a disaster based on the principle of coordinated deformation of adjacent main beams. By adopting I-beams of standard size and cooperating with concrete top plates 2, a steel-concrete composite bridge is formed to replace the original bridge structure that has fallen beams or is severely damaged. This solves the problems of traditional reinforcement methods such as long construction period, complex construction procedures, difficult lifting, large damage to the original structure, and inability to meet the demand for rapid replacement after a disaster. In addition, I-beams are fast to construct, and rapid replacement of main beams can be achieved, with strong emergency response capabilities.

[0082] The present invention adopts multiple linear regression analysis to adapt and fit the deformation of the replaced steel-concrete composite beam and the original concrete beam, calculates the applicable thickness range of the steel web 4 and the steel bottom plate 5, and selects the most suitable thickness values ​​of the steel web and the steel bottom plate after multiple calculations of the ultimate bearing capacity limit state and the normal use limit state, so as to facilitate the timely selection of I-shaped steel beams with different size values ​​under different working conditions, and form a reasonable structure and theoretical system for equivalent replacement of the original concrete bridge by a set of steel-concrete composite beams. The system is reliable and stable, and has good use effect.

[0083] It should be noted that the I-beam steel beam used in the present invention has a fast construction speed, and the steel-concrete composite beam has the advantages of light weight, convenient transportation and lifting compared to the concrete beam. The I-beam steel beam is connected to the concrete top plate 2 by welding nails, and the welding nails can transmit deformation and stress, so that the I-beam steel beam and the concrete top plate 2 form a whole that is synergistically stressed, which can give full play to the material properties of concrete and steel structure and is easy to promote and use.

[0084] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A construction method for quickly replacing conventional concrete beams with steel-concrete composite beams. It is characterized in that The method comprises the following steps: Step 1: Designing a steel-concrete composite beam structure: the steel-concrete composite beam comprises an I-shaped steel beam and a concrete top plate (2) arranged on the I-shaped steel beam, and the I-shaped steel beam comprises a steel top plate (3), a steel web plate (4) and a steel bottom plate (5); An I-shaped steel beam is arranged between two adjacent main beams (1), and then a concrete top plate (2) is constructed on the I-shaped steel beam, so that the upper surface of the concrete top plate (2) is flush with the upper surface of the adjacent main beams (1); Step 2: Determine the structural dimensions of the I-shaped steel beam: Step 201: According to the deflection requirement of the I-shaped steel beam section, determine the fitting formula of the steel web (4) and the steel bottom plate (5) at the upper limit y' of the fitting function. And the fitting formula of the steel web (4) and the steel bottom plate (5) at the lower limit y" of the fitting function is: Then, the thickness x of the steel web (4) and the thickness y of the steel bottom plate (5) are determined; Among them, y 0 ,y 1 , A 1 , A 2 , A 3 , A 4 ,t 1 ,t 2 ,t 3 ,t 4 All are coefficients; Step 202: The value range of the thickness x of the steel web (4) is d 1 ~d 2 , and the thickness y of the steel bottom plate (5) ranges from d 3 ~d 4 , where d 1 ,d 2 ,d 3 ,d 4 All are positive numbers; Step 3: Check the ultimate bearing capacity of the steel-concrete composite beam: Step 301: 1 ~d 2 Select a value from the table as the thickness of the steel web (4) and 3 ~d 4 Select a value as the thickness of the steel bottom plate (5), and then execute step 302; Step 302: According to the formula Calculate the bending capacity σ of the steel-concrete composite beam, when γ 0 When σ≤f, execute step 303. 0 When σ>f, execute step 5; Among them, i is a different stress calculation stage, i=Ⅰ represents the stress calculation stage before the steel-concrete composite beam is formed, and i=Ⅱ represents the stress calculation stage after the construction of the steel-concrete composite beam is completed. In different stress calculation stages, M d,i is the design value of the bending moment acting on the steel-concrete composite beam, W eff,i is the flexural modulus of the corresponding steel-concrete composite beam, and I' is the moment of inertia of the steel-concrete composite beam section, is the centroid height of the steel-concrete composite beam section, γ 0 is the structural importance coefficient, f is the strength design value of the steel-concrete composite beam; Step 303: According to formula V u =f vd A W , calculate the shear capacity V of the steel-concrete composite beam u , when γ 0 V d ≤V u When γ 0 V d >V u When , execute step 5; Among them, V d is the shear design value of the steel-concrete composite beam, f vd is the design value of the shear strength of the steel web (4), A W is the cross-sectional area of ​​the steel web (4); Step 304: Based on the influence of bending moment and shear force on the steel-concrete composite beam, use the formula Calculate the maximum reduced stress of the steel web (4); Among them, σ 1 and τ 1 are the normal stress and shear stress generated simultaneously at the same point on the steel web (4), f d is the design value of the tensile strength of the steel web (4); Step 4: Check the limit state of normal use of the steel-concrete composite beam: Use finite element analysis software to load the standard combination and quasi-permanent combination of loads, and consider the reduced stiffness B of the composite beam slip effect to calculate the deflection value ω of the steel-concrete composite beam, that is, through the formula Calculate, when When the thickness of the steel web (4) and the thickness of the steel bottom plate (5) are obtained, When , execute step 5; Where E is the elastic modulus of the steel-concrete composite beam, I eq is the converted section inertia moment of the steel-concrete composite beam, ξ is the stiffness reduction factor, and l is the calculated span of the bridge; Step 5: Change the value and recalculate: 1 ~d 2 Select a new value as the thickness of the steel web (4) in d 3 ~d 4 A value is reselected as the thickness of the steel bottom plate (5), and then step 302 is executed.

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