Design and construction method of a reverse arch foundation frame bridge

Abstract

The present invention relates to the technical field of bridge structures, and specifically to a design and construction method of an inverted arch foundation frame bridge, comprising the following steps: Step 1: According to the geological survey report of the bridge location, evaluate the geological conditions, hydrological conditions, environmental impacts and adjacent facilities of the bridge construction site. Step 2: Determine the basic parameters and main technical standards of the bridge; including the span, bridge width, highway grade, design load grade, design speed, earthquake zoning, etc. of the bridge; Step 3: Carry out detailed structural design of the bridge, including the size, material type, steel reinforcement and processing details of the top plate, piers and bottom plate; Step 4: Perform mechanical performance analysis and verification on the designed bridge structure to ensure that the design meets the strength, stiffness and stability requirements; The inverted arch foundation frame bridge structure of the present invention has the characteristics of convenient construction, good mechanical properties and convenient maintenance.

Description

Technical Field

[0001] The invention relates to the technical field of bridge structures, and in particular to a design and construction method of an inverted arch foundation frame bridge. Background Art

[0002] For bridge sites located in deep soft soil areas, the engineering properties of soft soil are poor, usually with high compressibility, low strength, poor stability and high water content. Many engineering practices and studies have shown that due to the insufficient bearing capacity of soft soil foundations and large post-construction settlement, when engineering construction is carried out directly on untreated soft soil foundations, it is very easy to cause foundation instability and thus cause safety accidents, or huge settlement during the operation period, resulting in failure to meet operating requirements, causing huge economic losses. On the other hand, the use of inappropriate foundation reinforcement methods often leads to half the result with twice the effort or unsatisfactory economic benefits, causing unnecessary losses.

[0003] Most of the traditional small and medium-sized bridges are prestressed hollow slab beam bridges. The beam height of this scheme is relatively high. If the bridge deck elevation is not raised, the flood discharge space under the bridge will be occupied. In addition, large machinery and equipment are required during the construction process. When constructing on the street site, the working space is easily restricted by ground and aerial pipelines. Therefore, a low-cost, easy-to-construct small and medium-span highway bridge structure and design and construction method in deep soft foundation areas are needed. Summary of the invention

[0004] The purpose of the present invention is to provide a design and construction method of an inverted arch foundation frame bridge. The present application adopts an inverted arch foundation frame bridge because it has the advantages of good integrity, small differential settlement, strong earthquake resistance, strong water-passing capacity, low cost, and convenient construction for small and medium span bridges. It is suitable for complex geological environments such as scattered rural roads, soft soil areas with low load levels, and water level change areas. When designing this type of bridge, it is preferred to fit the riverbed section (the span-rise ratio of the natural riverbed section should be ≤0.22); the arc arch axis bottom plate is selected and the top plate should have a micro-arch; the total span of the bridge should be ≤25m.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A design method for an inverted arch foundation frame bridge structure comprises the following steps:

[0007] Step 1: Based on the geological survey report of the bridge site, evaluate the geological conditions, hydrological conditions, environmental impact and adjacent facilities of the bridge construction site.

[0008] Step 2: Determine the basic parameters and main technical standards of the bridge, including the span, width, highway grade, design load grade, design speed, and earthquake zoning;

[0009] Step 3: Carry out detailed structural design of the bridge, including the size, material type, steel reinforcement and processing details of the top plate, piers and bottom plate;

[0010] Step 4: Use Bridge Doctor software to analyze and verify the mechanical properties of the designed bridge structure to ensure that the design meets the requirements of strength, stiffness and stability;

[0011] The specific operation steps are as follows: input the material properties according to the actual design into the material definition; use structural modeling to establish a three-dimensional model of the inverted arch foundation frame bridge, and input or adjust the geometric parameters and constraints of the structure; set the actual designed steel bar type, diameter, position, and spacing in the steel bar design; input the load data of the bridge in the operation analysis, including dead load and live load, and define the bridge deck positioning line, and then arrange the bridge deck horizontally; the impact coefficient is automatically calculated using the standard method; in the seismic analysis, enter the bridge foundation m-value adjustment coefficient, select the components to be verified, and the support information uses the settings of the construction stage, and then select the highway bridge horizontal response spectrum 2020, and enter the response spectrum parameters of the corresponding area, and select the direction and calculation method of the calculated earthquake and other parameters; view the bending, shear, stress, deflection bearing capacity limit state verification and normal use limit state verification in the result query, and evaluate whether the specification requirements are met and whether the structure is stable and safe based on the calculation results obtained from the result query; in the seismic analysis, view the force, displacement and other response results of the bridge structure under the action of the earthquake in the result query, and evaluate whether the performance of the structure meets the specification requirements based on the structural response obtained from the seismic analysis.

[0012] As a further solution of the present invention: the following steps are also included:

[0013] Step 5: Based on the results of the detailed design phase, draw construction drawings, including a summary of engineering quantities, a bridge site plan, a bridge layout, a reinforcement structure diagram, and construction detail drawings (bridge deck pavement, guardrails, drainage, etc.).

[0014] As a further solution of the present invention: in step 4: obtain the bending bearing capacity, shear bearing capacity, stress allowable value, deflection allowable value, and settlement allowable value, and mark them as M respectively. u 、V u , σ a 、f a , S a ;

[0015] The bridge condition capacity value ZQN is calculated by the formula; among them, a1, a2, a3, and a4 are all partial coefficients, and M d 、V d , σ d 、f d , S dThey are respectively the design bending moment value, the design shear force value, the calculated stress value, the calculated deflection value, and the calculated settlement value;

[0016] If the bridge state capability value ZQN is less than the bridge state capability threshold, a bridge state unqualified signal is generated.

[0017] As a further solution of the present invention: the process of obtaining the bending bearing capacity partial coefficient a1 is:

[0018] Obtain the probability distribution type and statistical data of the basic variables related to the flexural bearing capacity (such as material strength, load effect, etc.) and the specified reliability index, calculate and analyze according to the FORM method specified in the specification "Unified Standard for Reliability Design of Highway Engineering Structures" (JTG2120-2020), and combine it with engineering experience and determine it through optimization. When there is a lack of statistical data, the flexural bearing capacity partial coefficient a1 can be determined according to the deterministic method specified in the specification based on the traditional or empirical design method to obtain the flexural bearing capacity partial coefficient a1.

[0019] As a further solution of the present invention: the process of obtaining the shear bearing capacity partial coefficient a2 is:

[0020] Obtain the probability distribution type and statistical data of basic variables related to shear bearing capacity (such as material strength, load effect, etc.) and the specified reliability index, calculate and analyze according to the FORM method specified in the specification "Unified Standard for Reliability Design of Highway Engineering Structures" (JTG2120-2020), and combine engineering experience to determine after optimization. When statistical data is lacking, the shear bearing capacity partial coefficient a2 can be determined according to the deterministic method specified in the specification based on traditional or empirical design methods to obtain the shear bearing capacity partial coefficient a2.

[0021] As a further solution of the present invention: the process of obtaining the stress partial coefficient a3 is:

[0022] Obtain the probability distribution type and statistical data of the basic variables related to stress (such as material properties, geometric dimensions, etc.) and the specified reliability index, calculate and analyze according to the FORM method specified in the specification "Unified Standard for Reliability Design of Highway Engineering Structures" (JTG2120-2020), and combine it with engineering experience and determine it through optimization. When statistical data is lacking, the stress partial coefficient a3 can be determined by the deterministic method specified in the specification based on the traditional or empirical design method to obtain the stress partial coefficient a3.

[0023] As a further solution of the present invention: the process of obtaining the deflection partial coefficient a4 is:

[0024] Obtain the probability distribution type and statistical data of the basic variables related to deflection (such as material properties, geometric dimensions, etc.) and the specified reliability index, calculate and analyze according to the FORM method specified in the specification "Unified Standard for Reliability Design of Highway Engineering Structures" (JTG2120-2020), and combine it with engineering experience and determine it through optimization. When statistical data is lacking, the deflection partial coefficient a4 can be determined according to the deterministic method specified in the specification based on the traditional or empirical design method to obtain the deflection partial coefficient a4.

[0025] As a further solution of the present invention: the process of obtaining the sedimentation partial coefficient a5 is:

[0026] Obtain the probability distribution type and statistical data of basic variables related to settlement (such as foundation characteristics, base plate size, etc.) and the specified reliability index, calculate and analyze according to the FORM method specified in the specification "Unified Standard for Reliability Design of Highway Engineering Structures" (JTG2120-2020), and combine engineering experience to determine after optimization. When statistical data is lacking, the settlement partial coefficient a5 can be determined according to the deterministic method specified in the specification based on traditional or empirical design methods to obtain the settlement partial coefficient a5.

[0027] As a further solution of the present invention: when a signal that the bridge condition is unqualified is obtained, the bending bearing capacity ratio, shear bearing capacity ratio, stress allowable ratio, deflection allowable ratio, and settlement allowable ratio of the designed bridge model are obtained and compared to determine the influencing factors causing the unqualified bridge condition, and the bridge model is modified based on the influencing factors.

[0028] As a further solution of the present invention: the process of obtaining each ratio is:

[0029] The ratio of the design bending moment value to the bending bearing capacity of the ultimate bearing capacity state is calculated to obtain the bending bearing capacity ratio;

[0030] The ratio of the design shear force value to the shear bearing capacity of the ultimate bearing capacity state is calculated to obtain the shear bearing capacity ratio;

[0031] Calculate the ratio of the calculated stress value to the allowable stress value of the normal service limit state to obtain the allowable stress ratio;

[0032] Calculate the ratio of the calculated deflection value to the allowable deflection value of the normal service limit state to obtain the allowable deflection ratio;

[0033] The ratio of the calculated settlement value to the allowable settlement value of the normal use limit state is calculated to obtain the allowable deflection ratio.

[0034] A construction method for an inverted arch foundation frame bridge comprises the following steps:

[0035] Step 1: Build dams and cofferdams to pump water;

[0036] Step 2: Excavation of the anti-arch section;

[0037] Step 3: Throwing rough stones;

[0038] Step 4: Fill the joints with mortar and make cushion;

[0039] Step 5: Construction of the anti-arch bottom plate;

[0040] Step 6: Pier construction;

[0041] Step 7: Top plate construction;

[0042] Step 8: Bridge deck paving construction;

[0043] Step 9: Installation of auxiliary facilities.

[0044] Beneficial effects of the present invention:

[0045] Structural design of the present invention: The inverted arch foundation frame bridge structure of the present invention has the characteristics of convenient construction, good stress-bearing performance and convenient maintenance. Compared with the traditional box-type frame bridge, the inverted arch foundation frame bridge is smaller in size, has less impact on the settlement of the structure, has a bottom plate that fits the riverbed section, and has better stress-bearing performance. Compared with the prestressed hollow slab beam bridge, the inverted arch foundation frame bridge does not require large-scale lifting equipment and pile foundation drilling equipment, which can avoid the removal of the main line; its cast-in-place construction can facilitate the implementation of variable-section beam ends and optimize the plane line shape of the intersection; its beam height is small, which can better guarantee the flood discharge space; the top plate is designed as a micro-arch to facilitate bridge deck drainage. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The present invention will be further described below in conjunction with the accompanying drawings.

[0047] Figure 1 is a flowchart of Embodiment 1 of the present invention;

[0048] Figure 2 It is a flowchart of embodiment 2 of the present invention. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] Example 1

[0051] See also Figure 1As shown, the present invention also provides a design method for an inverted arch foundation frame bridge structure, comprising the following steps:

[0052] Step 1: Based on the geological survey report of the bridge site, evaluate the geological conditions, hydrological conditions, environmental impact and adjacent facilities of the bridge construction site.

[0053] Step 2: Determine the basic parameters and main technical standards of the bridge, including the span, width, highway grade, design load grade, design speed, earthquake zoning, etc.

[0054] Step 3: Based on the above information, carry out detailed structural design of the bridge, including the size, material type, steel reinforcement and processing details of the top plate, piers and bottom plate. Bridge design should comply with relevant specifications such as "General Specification for Design of Highway Bridges and Culverts" (JTG D60-2015), "Seismic Design Specification for Highway Bridges" (JTG / T2231-01-2022), and "Durability Design Specification for Concrete Structures of Highway Engineering" (JTG / T3310-2019).

[0055] Step 4: Use the Bridge Doctor software to analyze and verify the mechanical properties of the designed bridge structure to ensure that the design meets the strength, stiffness and stability requirements. The specific steps are: input the material properties of the actual design into the material definition of the Bridge Doctor; use structural modeling to establish a three-dimensional model of the inverted arch foundation frame bridge, and input or adjust the geometric parameters and constraints of the structure; set the actual designed steel bar type, diameter, position, spacing, etc. in the steel bar design; input the bridge load data in the operation analysis, including dead load, live load, etc. (seismic loads are obtained by setting seismic wave parameters and then calculating seismic loads.), and define the bridge deck positioning line, and then arrange the bridge deck horizontally. The impact coefficient is automatically calculated using the standard method; in the seismic analysis, enter the m-value adjustment coefficient of the bridge foundation (usually 2-3), select the components to be verified, and use the support information set in the construction phase. Then select Highway Bridge Horizontal Response Spectrum 2020, and enter the response spectrum parameters of the corresponding area, select the direction of the calculated earthquake and the calculation method and other parameters; in the result query, view the ultimate limit state verification of the bearing capacity such as bending, shear, cracking, stress, deflection and the ultimate limit state verification of normal use, and evaluate whether the calculation results obtained from the result query meet the requirements of the specification and whether the structure is stable and safe; in the seismic analysis, view the force, displacement and other response results of the bridge structure under the action of earthquake in the result query, and evaluate whether the performance of the structure meets the requirements of the specification based on the structural response obtained from the seismic analysis.

[0056] Specifically, obtain the bending bearing capacity, shear bearing capacity, stress allowable value, deflection allowable value, and settlement allowable value, and mark them as M respectively. u 、V u , σ a、f a , S a ;

[0057] The bridge condition capacity value ZQN is calculated by the formula; among them, a1, a2, a3, and a4 are all partial coefficients, and M d 、V d , σ d 、f d , S d They are respectively the design bending moment value, the design shear force value, the calculated stress value, the calculated deflection value, and the calculated settlement value;

[0058] Compare the bridge state capability value ZQN with the bridge state capability threshold;

[0059] If the bridge state capacity value ZQN is greater than or equal to the bridge state capacity threshold, it means that the bridge obtained through model analysis has good structural stability, strong adaptability and high rigidity, and a bridge state qualified signal is generated;

[0060] If the bridge state capacity value ZQN is less than the bridge state capacity threshold, it means that the bridge obtained through the model analysis does not have good structural stability, strong adaptability, and high rigidity, and a bridge state unqualified signal is generated;

[0061] Among them, the process of obtaining the bending bearing capacity partial coefficient a1 is as follows:

[0062] Obtain the probability distribution type and statistical data of the basic variables related to the flexural bearing capacity (such as material strength, load effect, etc.) and the specified reliability index, calculate and analyze according to the FORM method specified in the specification "Unified Standard for Reliability Design of Highway Engineering Structures" (JTG2120-2020), and combine it with engineering experience and determine it through optimization. When there is a lack of statistical data, the flexural bearing capacity partial coefficient a1 can be determined according to the deterministic method specified in the specification based on the traditional or empirical design method to obtain the flexural bearing capacity partial coefficient a1;

[0063] The process of obtaining the shear bearing capacity partial coefficient a2 is as follows:

[0064] Obtain the probability distribution type and statistical data of basic variables related to shear bearing capacity (such as material strength, load effect, etc.) and the specified reliability index, calculate and analyze according to the FORM method specified in the specification "Unified Standard for Reliability Design of Highway Engineering Structures" (JTG2120-2020), and combine engineering experience to determine after optimization. When statistical data is lacking, the shear bearing capacity partial coefficient a2 can be determined according to the deterministic method specified in the specification based on traditional or empirical design methods to obtain the shear bearing capacity partial coefficient a2;

[0065] The process of obtaining the stress partial coefficient a3 is as follows:

[0066] Obtain the probability distribution type and statistical data of the basic variables related to stress (such as material properties, geometric dimensions, etc.) and the specified reliability indicators, calculate and analyze according to the FORM method specified in the specification "Unified Standard for Reliability Design of Highway Engineering Structures" (JTG2120-2020), and combine it with engineering experience and determine it through optimization. When statistical data is lacking, the stress partial coefficient a3 can be determined according to the deterministic method specified in the specification based on the traditional or empirical design method to obtain the stress partial coefficient a3;

[0067] The process of obtaining the deflection partial coefficient a4 is as follows:

[0068] Obtain the probability distribution type and statistical data of the basic variables related to deflection (such as material properties, geometric dimensions, etc.) and the specified reliability indicators, calculate and analyze according to the FORM method specified in the specification "Unified Standard for Reliability Design of Highway Engineering Structures" (JTG2120-2020), and combine it with engineering experience and determine it after optimization. When there is a lack of statistical data, the deflection partial coefficient a4 can be determined according to the deterministic method specified in the specification based on the traditional or empirical design method to obtain the deflection partial coefficient a4;

[0069] The process of obtaining the settlement partial coefficient a5 is as follows:

[0070] Obtain the probability distribution type and statistical data of basic variables related to settlement (such as foundation characteristics, base plate dimensions, etc.) and the specified reliability indicators, calculate and analyze according to the FORM method specified in the specification "Unified Standard for Reliability Design of Highway Engineering Structures" (JTG2120-2020), and combine engineering experience to determine after optimization. When statistical data is lacking, the settlement partial coefficient a5 can be determined according to the deterministic method specified in the specification based on traditional or empirical design methods to obtain the settlement partial coefficient a5;

[0071] When a signal indicating that the bridge is in an unqualified state is obtained, the bending bearing capacity ratio, shear bearing capacity ratio, stress allowable ratio, deflection allowable ratio, and settlement allowable ratio of the designed bridge model are obtained and compared to determine the influencing factors causing the unqualified bridge state, and the bridge model is modified based on the influencing factors;

[0072] Specifically, the process of obtaining each ratio is as follows:

[0073] The ratio of the design bending moment value to the bending bearing capacity of the ultimate bearing capacity state is calculated to obtain the bending bearing capacity ratio;

[0074] The ratio of the design shear force value to the shear bearing capacity of the ultimate bearing capacity state is calculated to obtain the shear bearing capacity ratio;

[0075] Calculate the ratio of the calculated stress value to the allowable stress value of the normal service limit state to obtain the allowable stress ratio;

[0076] Calculate the ratio of the calculated deflection value to the allowable deflection value of the normal service limit state to obtain the allowable deflection ratio;

[0077] Calculate the ratio of the calculated settlement value to the allowable settlement value of the serviceability limit state to obtain the allowable deflection ratio;

[0078] Specifically, each ratio is taken and compared with its corresponding prescribed threshold value;

[0079] If the bending capacity ratio is greater than the specified bending capacity threshold, a bending failure signal is generated, and the component with the largest influence on the bending moment in the bridge model is adjusted and modified;

[0080] If the shear bearing capacity ratio is greater than the specified threshold of shear bearing capacity, a shear failure signal is generated, and the component with the greatest impact on shear force in the bridge model is adjusted and modified;

[0081] If the stress allowable ratio is greater than the stress specified threshold, a stress verification failure signal is generated, and the components that have the greatest impact on stress in the bridge model are adjusted and modified;

[0082] If the deflection allowable ratio is greater than the specified deflection threshold, a deflection verification failure signal is generated, and the component with the largest impact on deflection in the bridge model is adjusted and modified;

[0083] If the settlement allowable ratio is greater than the specified settlement threshold, a settlement verification failure signal is generated, and the components that have the greatest impact on settlement in the bridge model are adjusted and modified;

[0084] Step 5: Based on the results of the detailed design phase, draw construction drawings, including bridge site plan, bridge type layout, reinforcement layout, construction detail drawings, etc. Ensure the rationality, safety and feasibility of the design through internal or external review.

[0085] The inverted arch foundation frame bridge first excavates the riverbed base section below the riprap layer, and uses rough stones at the bottom of the riverbed to fill and extrude it densely, and a mortar cushion layer is cast on the riprap layer using a vertical formwork.

[0086] Furthermore, after the cushion layer has formed strength, a formwork is installed on the cushion layer, steel bars are tied, and a base plate is cast, and the base plate and the cushion layer are connected and fixed by concrete bonding and steel bar embedding; the lower beam section steel bars are arranged on the base plate and the formwork is cast, and at the same time, steel bars for extending the bridge piers need to be reserved.

[0087] Furthermore, the top surface of the lower cross beam is roughened to expose the concrete aggregate and the loose materials are cleaned up, and then the steel bars are tied, the formwork is installed, and the bridge piers are cast.

[0088] Furthermore, after the concrete compressive strength of the pier and the bottom plate reaches 70% of the design strength, the top surface of the pier is roughened to expose the concrete aggregate and the loose materials are cleaned up, and then the top plate cast-in-place full-span support can be erected and the erected support is pre-pressed. At the same time, the bridge head foundation is arranged, compacted by a press, and then the mortar cushion layer is cast in a formwork.

[0089] Furthermore, the formwork of the top plate and the upper beam is installed on the bracket, the steel bars are tied, the top plate and the upper beam are cast, and the surface is closed and maintained in time after casting; the formwork can be removed only after the compressive strength of the top plate concrete reaches 75% of the design strength. The top plate bracket is removed according to the principle of removing the rear support first and the front support last.

[0090] Furthermore, after the concrete compressive strength of the top plate and the upper cross beam reaches 90% of the design strength, the construction of auxiliary facilities and the paving of the bridge deck can be carried out.

[0091] Example 2

[0092] Based on the above Example 1, please refer to Figure 2 As shown, the present invention is a construction method of an inverted arch foundation frame bridge, comprising the following steps:

[0093] Step 1: Build dams and cofferdams to pump water;

[0094] In step 1: Since the water level of the river channel at the bridge location is relatively deep, try to clear a dry working platform by building a dam and cofferdam and then pumping out water during the dry season;

[0095] The specific implementation steps are as follows: (1) At an appropriate location 25 meters upstream and downstream of the bridge, a water-retaining earth-rock dam is built to form a construction cofferdam. (2) After the location of the earth-rock dam is selected, rubble stones are dumped on both sides of the axis of the single dam body to form a dike. The top surface of the rubble stone dike can be flush with the water surface. The slope is controlled according to the natural state of the rubble stones. At the bottom of the two dikes, it is necessary to ensure that there is a stone-free space of more than 2 meters. (3) A large area of ​​waterproof geotextile is used to cover the slope between the rubble stone dikes. In order to allow the geotextile to sink smoothly, some clay can be pre-dumped in the stone-free space above the geotextile and between the two rubble stone dikes, and the weight of the clay can be used to press the geotextile to the bottom of the riverbed. (4) After backfilling some clay with water to form a bottom, the water between the rubble stone dikes is pumped out, and then the clay is backfilled. When backfilling, the stone-free space between the two rubble stone dikes should be filled first, and then as the backfill clay rises, it will naturally squeeze toward the slopes of the two dikes; after the clay is backfilled to the top of the rubble stone dike, it should be left to stand for a period of time to allow the clay to settle naturally, and then the clay should be filled intermittently. The top surface of the final backfilled clay should be 0.5m higher than the highest water level during the construction period. (5) After the backfill clay settles basically steadily, the water body in the cofferdam formed by the two earth-rock dams should be drained in stages using a mud pump. If the rubble stone dike is found to be not stable enough, the thickness of the rubble stone dike can be filled wider; if the earth-rock dam is found to be leaking, the water-stopping capacity can be further enhanced by wrapping the water-facing side of the rubble stone dike with waterproof geotextile or plastic film and covering it with clay. (6) It is not allowed to dig riverbed soil on both sides of the dam body for clay backfill to avoid causing the dam body to collapse. (7) Equip with sufficient number and power of pumping equipment to ensure that there is no water accumulation in the cofferdam during operation. (8) The passage formed by the earth-rock dam should be closed and managed, and vehicles and pedestrians are not allowed to pass through.

[0096] Step 2: Excavation of the anti-arch section;

[0097] In step 2, (1) excavation of the riverbed anti-arch section should be carried out in a top-down order, that is, the bridgehead slope should be excavated first, and then the riverbed bottom space should be cleared. (2) The riverbed slope should be cleared as far as possible to ensure a 50 cm thick rubble backfill space to avoid large differences in base modulus.

[0098] Step 3: Throwing rough stones;

[0099] In step 3, (1) after the excavation of the base section is completed, the rubble stones at the bottom of the riverbed are dumped and squeezed as soon as possible to prevent the base from silting up and affecting the construction work. (2) A long-arm excavator is used to pat and preliminarily shape the stones dumped at the bottom of the riverbed so that the stones can squeeze out the silt as much as possible and form a plate-like body, and then further stack them with manual labor. (3) After the stones at the bottom of the riverbed are dumped, a long-arm excavator is used in combination with manual labor to stack the rubble stones on the riverbed slope. The slopes must be stacked tightly and densely, with no loose large-size stones, the connecting surfaces between the stone blocks are inclined inward, the slope is smooth, and larger holes on the surface are filled with stones of appropriate size;

[0100] Step 4: Fill the joints with mortar and make cushion;

[0101] In step 4, (1) M10 cement mortar is mixed according to the standard of "Premixed Mortar" (GBT 25181-2019). The mortar consistency is 50-90m. A higher value can be used when the evaporation on site is large, and a lower value can be used when the mortar needs to harden as quickly as possible. (2) The formwork is constructed in a vertical operation mode to ensure that a 10cm thick mortar cushion layer (excluding the amount of grouting) is formed. The relevant technical indicators of the formwork are implemented in accordance with the "Technical Specifications for Highway Bridge and Culvert Construction" (JTGT 3650-2020). If a wooden formwork is used, it needs to be pre-processed and formed according to the curvature of the structure; if a standard steel formwork is used, considering that the curved formwork is not very versatile, a straight formwork with a length of no more than 1 meter can be used to replace the curve. Note: The middle part of the fold line is at the same elevation as the curve, and the end is lower than the curve elevation to avoid insufficient protective layer. (3) After the formwork is completed, the mortar is placed and short steel bars are used to tamp and fill the joints as densely as possible; the mortar in the cushion layer should be compacted and smoothed. (4) The construction sequence of the mortar cushion is symmetrical from low to high, that is, first lay the mortar of the riverbed section at the bottom of the inverted arch, and then lay the mortar of the riverbed slope section in time according to the progress of the mortar hardening until the top of the bottom plate, and ensure that the mortar cushion does not slide and collapse. Note: Multiple control points should be arranged for the elevation in the cross-section direction, at least 7 rows.

[0102] Step 5: Construction of the anti-arch bottom plate;

[0103] In Step 5: The inverted arch slab construction is divided into two stages, first installing the slab formwork and reinforcement, and then pouring the slab concrete.

[0104] The specific construction steps for installing the bottom plate formwork and steel bars are as follows: (1) After the mortar cushion layer has formed strength, the formwork is installed on the top surface of the cushion layer. The relevant technical requirements of the formwork shall be implemented in accordance with the "Technical Specifications for Highway Bridge and Culvert Construction" (JTGT 3650-2020). If a wooden formwork is used, it needs to be pre-processed and formed according to the structural curvature; if a standard steel formwork is used, a straight formwork with a length of no more than 1 meter can be used to replace the curve with a fold, but the formwork gap must be properly sealed to avoid leakage when pouring concrete. (2) The reinforcement is planted in the cushion layer according to the design, and then the reinforcement processing equipment is used to cut and process the reinforcement segments according to the designed line shape, and then sent to the cushion layer for layout. The relevant technical requirements for reinforcement processing, connection, binding and installation, as well as the protective layer pads, shall be implemented in accordance with the "Technical Specifications for Highway Bridge and Culvert Construction" (JTGT3650-2020). (3) When laying the reinforcement of the crossbeam section under the bottom plate, the bridge pier extension reinforcement should be pre-embedded.

[0105] The specific construction steps for pouring the bottom slab concrete are as follows: (1) The bottom slab concrete is poured by pumping. The pouring sequence should be symmetrical from low to high in the longitudinal direction of the bridge and symmetrical on both sides of the entire section in the transverse direction of the bridge; that is, the concrete at the bottom of the inverted arch (the section between the two lower beams) is poured first, and then the concrete at the lower beam is poured continuously and symmetrically, and finally the concrete at the riverbed slope section is poured continuously and symmetrically until the top of the bottom slab. For the concrete at the bottom of the inverted arch poured first, whether to take counterpressure measures (or use a scraper to cooperate with finishing) depends on its hardening condition. The joint surface of the segmented pouring should be completed before the concrete of the first pouring section begins to set or can be reshaped, and no construction joints or cold joints are set. The relevant technical indicators and requirements shall be implemented in accordance with the "Technical Specifications for Highway Bridge and Culvert Construction" (JTGT 3650-2020). (2) The concrete at the lower beam section is relatively thick and should be poured in layers at the same time. (3) After pouring, the surface should be closed and maintained in a timely manner in accordance with the specifications. (4) The non-load-bearing side formwork may be removed only when the concrete compressive strength reaches more than 70% of the design strength and its surface and edges are guaranteed not to be damaged by formwork removal.

[0106] Step 6: Pier construction;

[0107] In step 6, after the concrete strength of the bottom plate and the lower crossbeam reaches more than 70% of the design strength or the curing period reaches 7 days, the pier reinforcement and formwork are installed. (2) The contact surface between the lower crossbeam and the pier should be roughened to expose the concrete aggregate and the loose materials should be removed and then cleaned. (3) The technical requirements for the processing, connection, binding and installation of reinforcement and protective layer pads shall be implemented in accordance with the "Technical Specifications for Highway Bridge and Culvert Construction" (JTGT 3650-2020). (4) The technical indicators and requirements for formwork and brackets shall be implemented in accordance with the "Technical Specifications for Highway Bridge and Culvert Construction" (JTGT 3650-2020). The piers should use standardized steel formwork, and ensure the strength and rigidity of the formwork, as well as the stability of the installation, to prevent the formwork from collapsing during the pouring process. Construction work steps and platforms are set up simultaneously. (5) The pier concrete is poured by pumping. The concrete of the entire length of the pier should be poured in one step. The continuous pouring of multiple piers should be carried out in a symmetrical order. (6) When the compressive strength of the pier concrete reaches more than 70% of the design strength and its surface and edges are guaranteed not to be damaged by formwork removal, the formwork shall be removed from top to bottom. After formwork removal, maintenance shall be carried out in accordance with the specifications.

[0108] Step 7: Top plate construction

[0109] In step 7, the top slab construction is divided into five stages. The first is to prepare the bridge head foundation, then set up the cast-in-place support for the suspended section of the top slab and pre-press it, install the top slab and upper beam formwork and steel bars and pour concrete, and finally remove the formwork and support.

[0110] The specific construction steps for the bridgehead foundation are as follows: (1) Use small excavators or manual methods to excavate and tidy up the bridgehead foundation, and ensure that the backfill thickness of the mountain gravel soil below the bottom surface of the cantilever section top plate is not less than 50 cm. (2) Backfill the mountain gravel soil, the single-layer filling thickness should be less than 30 cm, large-size stones should be evenly dispersed in the filler, and the gaps between the stones should be filled with small-size stones and soil. Use small compaction equipment such as vibrating plate tampers with an excitation force of 1.5 to 3.0 tons to roll in layers. If a small roller with a deadweight of about 2.0 tons is used for rolling, static pressure should be adopted. Large-scale compaction equipment is not allowed to be used for rolling to avoid adverse effects on the anti-arch bottom plate and riverbed slope. The compaction quality is based on the absence of rolling marks on the surface after rolling. (3) Mix M10 cement mortar according to the standard of "Premixed Mortar" (GBT 25181-2019). The mortar cushion layer should be constructed using a vertical formwork method to ensure that a 10 cm thick mortar cushion layer is formed.

[0111] The specific construction steps for erecting cast-in-place supports for the suspended section of the top slab and preloading are as follows: (1) After the concrete strength of the pier reaches more than 70% of the design strength or the curing period reaches 7 days, the cast-in-place supports for the top slab can be erected based on the bottom slab and the piers. This type of bridge is suitable for full-bridge supports, and most of the load should not be concentrated on the piers that have not yet formed an overall frame structure. (2) The erected supports should have sufficient strength, rigidity and stability, and ensure safety and applicability during construction, and should not cause deformation that affects normal use. The elastic deflection of the supports after being loaded should not be greater than 1 / 400 of the calculated span of the structure. Relevant technical standards shall be implemented in accordance with the "General Specifications for Construction Scaffolding" (GB 55023-2022), "Uniform Standards for Safety Technology of Construction Scaffolding" (GB51210-2016), "Technical Specifications for Highway Bridge and Culvert Construction" (JTGT 3650-2020) and other series of specifications. (3) Preload the erected supports. This type of bridge support foundation uses an inverted arch bottom plate, which is a rigid foundation, so there is no need to preload the support foundation, but the support itself needs to be preloaded to test the safety of the support, eliminate non-elastic deformation, and obtain elastic deformation data (for setting the pre-arch degree). The distribution of the preload load should simulate the structure and construction load of the top plate construction stage. The relevant technical indicators of preloading shall be implemented in accordance with the "Technical Specifications for Preloading of Steel Pipe Full-Span Supports" (JGJT194-2009), "Technical Specifications for Highway Bridge and Culvert Construction" (JTGT 3650-2020) and other series of specifications.

[0112] The specific construction steps for installing the top plate and upper crossbeam formwork and steel bars and pouring concrete are as follows: (1) Install the cast-in-place formwork for the top plate. The relevant technical requirements of the formwork shall comply with the "Technical Specifications for Highway Bridge and Culvert Construction" (JTGT3650-2020). It is recommended to use standardized steel formwork. (2) Use steel bar processing equipment to cut materials and process steel bar segments according to the designed line shape, and then lay them out. The relevant technical requirements for steel bar processing, connection, binding and installation, as well as protective layer pads, shall comply with the "Technical Specifications for Highway Bridge and Culvert Construction" (JTGT3650-2020). (3) The contact surface between the pier and the upper crossbeam should be roughened to expose the concrete aggregate and cleaned after removing the loose materials. (4) When laying the top plate steel bars, the anti-collision guardrail, embedded steel bars or other ancillary facilities should be pre-embedded. (5) The top slab concrete shall be poured by pumping. The pouring sequence shall be symmetrical from the middle of the span to both ends in the longitudinal direction and symmetrical on both sides of the entire section in the transverse direction. The relevant technical indicators shall be implemented in accordance with the Technical Specifications for Highway Bridge and Culvert Construction (JTGT3650-2020). (6) The concrete of the upper crossbeam section is relatively thick and shall be poured in layers at the same time. (7) After pouring, the surface shall be closed and maintained in a timely manner in accordance with the regulations. Note: The top slab is a micro-arch slab. Multiple control points should be arranged for the elevation in the cross section, at least 7 rows.

[0113] The specific construction steps for removing the formwork and support are as follows: (1) The non-load-bearing side formwork should be removed only when the concrete compressive strength reaches 70% of the design strength and its surface and edges are not damaged by formwork removal. (2) The load-bearing formwork and support should be removed only after the concrete strength reaches more than 75% of the design strength and is not less than 7 days old. (3) The removal of the load-bearing formwork should be carried out simultaneously in the horizontal direction and symmetrically in the vertical direction, that is, the middle span should be removed first and then the side span, and it is advisable to remove it in a cyclic manner from the middle of the span to the pier. The formwork should be removed in two times. The first time is to slightly loosen and remove the main supporting force, and the second time is to completely remove all the supporting force to prevent excessive impact. (4) The support removal should follow the principle of removing the rear support first and the front support last. The removal order is from top to bottom layer by layer, and the same layer should be removed in the order of outside first and inside later. Reinforcements such as scissor braces and diagonal braces should be removed when the rods at that location are removed, and the wall connecting parts should be removed synchronously with the frame layer by layer.

[0114] Step 8: Bridge deck paving construction (concrete pavement);

[0115] In step 8, (1) the concrete slag particles on the top plate base surface should be chiseled out, and impurities such as floating blades and mud skin should be removed, and the concrete should be cleaned and made rough. (2) On the top plate base surface, use an impact drill to drill holes at a spacing of 1 meter in the vertical and horizontal directions, with a hole diameter of 12 mm and a hole depth of about 4 cm. Wedge the C12 steel bar head into the hole. The length of the steel bar head is determined by calculating the cross slope of the bridge deck and the thickness of the protective layer. (3) Weld 15 cm long C12 horizontal short bars on the steel bar head to form steel mesh frame positioning bars. (4) Then lay the steel mesh and spot weld it on the frame positioning bars to ensure that the steel mesh does not shift when pouring concrete. The longitudinal bars of the steel mesh are placed on the upper layer, the thickness of the protective layer is 4 cm, and the transverse bars are placed under the longitudinal bars. (5) The bridge deck paving concrete is laid by pumping, and leveling, finishing, grooving or pressing are carried out in time, and covering measures are used for moisture retention and maintenance. (6) After 7 days of moisturizing and curing, use a circular saw to cut a groove with a depth of 3 cm and a width of 5 mm to form a plate gap. (7) After cleaning the groove, fill it with a sealant. The sealant can be asphalt, silicone or polyurethane. The relevant technical indicators are in accordance with "Highway Cement Concrete Pavement Joint Materials" (JTT203-2014).

[0116] Step 9: Installation of auxiliary facilities

[0117] In step 9, the specific construction steps of the concrete guardrail are as follows: (1) The guardrail reinforcement should be reliably connected to the pre-embedded reinforcement of the top plate, and the formwork should use a standardized steel formwork. (2) When there is a conflict between the installation of the bridge deck drain hole pipe and the guardrail reinforcement, avoidance measures should be taken and the reinforcement should not be cut. (3) The guardrail concrete should be poured in layers by pumping, and the process should be carried out symmetrically on both sides of the bridge deck. (4) After the guardrail is demolded, a false seam should be cut at the bridge pier with a seam width of 3 mm and a seam depth of 20 mm.

[0118] The specific construction steps of the lighting system are as follows: (1) Install the bridge lighting facilities, including lamp posts and lamps, by fixing the embedded parts on the top plate. (2) Pull the cable from the nearest power point to the light pole location and connect the cable to the electrical facilities inside the light pole, including circuit breakers, junction boxes, etc. (3) Check whether the switch function of the lamp is normal. Adjust the direction and angle of the lamp to ensure that the lighting effect meets the design requirements and that all electrical installations meet safety standards.

[0119] The specific construction steps for signs and markings are as follows: (1) Use a high-pressure water gun or other cleaning equipment to thoroughly clean the bridge deck to remove dust, oil, etc., and ensure that the road surface is dry. (2) According to the design drawings, use measuring tools to mark the specific location of the markings on the bridge deck. (3) In some specific cases, such as when using thermoplastic marking paint, it may be necessary to apply a layer of primer first to enhance adhesion, which needs to be heated to an appropriate temperature first. (4) Use a marking machine to carry out construction according to the predetermined markings. During the construction process, the speed of the marking machine and the flow of paint need to be controlled to ensure that the markings are uniform and neat. (5) If the sign requires an independent column, the column should be installed first. Fix the sign in the preset position to ensure that it is stable and clearly visible.

[0120] Since the top plate of the drainage system adopts a micro-arch design, the longitudinal slope can be used to drain water to both sides without any additional drainage design.

[0121] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A design method for an inverted arch foundation frame bridge structure, characterized in that: The following steps are involved: Step 1: Based on the geological survey report of the bridge site, evaluate the geological conditions, hydrological conditions, environmental impact and adjacent facilities of the bridge construction site; Step 2: Determine the basic parameters and main technical standards of the bridge, including the span, width, highway grade, design load grade, design speed, and earthquake zoning; Step 3: Carry out detailed structural design of the bridge, including the size, material type, steel reinforcement and processing details of the top plate, piers and bottom plate; Step 4: Use Bridge Doctor software to analyze and verify the mechanical properties of the designed bridge structure to ensure that the design meets the requirements of strength, stiffness and stability; The specific operation steps are as follows: input the material properties according to the actual design into the material definition; use structural modeling to establish a three-dimensional model of the inverted arch foundation frame bridge, and input or adjust the geometric parameters and constraints of the structure; The actual designed steel bar type, diameter, position and spacing are set one by one in the steel bar design; in the operation analysis, the load data of the bridge, including dead load and live load, is input, and the bridge deck positioning line is defined, and then the bridge deck is arranged horizontally; the impact coefficient is automatically calculated using the standard method; in the earthquake analysis, the bridge foundation m-value adjustment coefficient is input, the components to be verified are selected, and the bearing information is set according to the construction stage. Then, the highway bridge horizontal response spectrum 2020 is selected, and the response spectrum parameters of the corresponding area are input, and the direction and calculation method parameters of the calculated earthquake are selected; in the result query, the ultimate limit state verification of bending, shear, stress and deflection bearing capacity and the ultimate limit state verification of normal use are checked, and the calculation results obtained from the result query are evaluated to see whether the requirements of the standard are met and whether the structure is stable and safe; In the result query of seismic analysis, check the stress and displacement response results of the bridge structure under earthquake action, and evaluate whether the performance of the structure meets the requirements of the specification based on the structural response obtained by seismic analysis; In step 4: obtain the bending bearing capacity, shear bearing capacity, stress allowable value, deflection allowable value, and settlement allowable value, and mark them as M respectively. u 、V u , σ a 、f a , S a ; By formula The bridge status capacity value ZQN is calculated; Among them, a1, a2, a3, a4, and a5 are all partial coefficients, M d 、V d , σ d 、f d , S d They are respectively the design bending moment value, the design shear force value, the calculated stress value, the calculated deflection value, and the calculated settlement value; If the bridge state capability value ZQN is less than the bridge state capability threshold, a bridge state unqualified signal is generated.

2. The design method of a reverse arch foundation frame bridge structure according to claim 1 is characterized in that: The following steps are also included: Step 5: Based on the results of the detailed design phase, draw construction drawings, including a summary of engineering quantities, a bridge site plan, a bridge layout, a reinforcement structure diagram, and construction detail drawings.

3. The design method of a reverse arch foundation frame bridge structure according to claim 2 is characterized in that: The process of obtaining the bending bearing capacity partial coefficient a1 is as follows: Obtain the probability distribution type and statistical data of the basic variables related to the flexural bearing capacity and the specified reliable indicators, calculate and analyze them according to the FORM method, and determine them after optimization in combination with engineering experience; when there is a lack of statistical data, determine the flexural bearing capacity partial coefficient a1 according to the deterministic method specified in the code based on the traditional or empirical design method to obtain the flexural bearing capacity partial coefficient a1.

4. The design method of a reverse arch foundation frame bridge structure according to claim 3 is characterized in that: The process of obtaining the shear bearing capacity partial coefficient a2 is as follows: Obtain the probability distribution type and statistical data of the basic variables related to the shear bearing capacity and the specified reliable indicators, calculate and analyze them according to the FORM method, and determine them after optimization in combination with engineering experience; when there is a lack of statistical data, determine the shear bearing capacity partial coefficient a2 according to the deterministic method specified in the code based on the traditional or empirical design method to obtain the shear bearing capacity partial coefficient a2.

5. The design method of a reverse arch foundation frame bridge structure according to claim 4 is characterized in that: The process of obtaining the stress partial coefficient a3 is as follows: Obtain the probability distribution type and statistical data of the basic variables related to stress and the specified reliable indicators, calculate and analyze them according to the specification FORM method, and determine them after optimization in combination with engineering experience; when there is a lack of statistical data, determine the stress partial coefficient a3 according to the deterministic method specified in the specification based on traditional or empirical design methods to obtain the stress partial coefficient a3.

6. The design method of a reverse arch foundation frame bridge structure according to claim 5 is characterized in that: The process of obtaining the deflection partial coefficient a4 is as follows: Obtain the probability distribution type and statistical data of the basic variables related to deflection and the specified reliable indicators, calculate and analyze them according to the FORM method, and determine them after optimization in combination with engineering experience; when there is a lack of statistical data, determine the deflection partial coefficient a4 according to the deterministic method specified in the specification based on traditional or empirical design methods to obtain the deflection partial coefficient a4.

7. The design method of a reverse arch foundation frame bridge structure according to claim 6 is characterized in that: The process of obtaining the settlement partial coefficient a5 is as follows: Obtain the probability distribution type and statistical data of basic variables related to settlement and the specified reliable indicators, calculate and analyze them according to the FORM method, and determine them after optimization in combination with engineering experience; when there is a lack of statistical data, determine the settlement partial coefficient a5 according to the deterministic method specified in the code based on traditional or empirical design methods to obtain the settlement partial coefficient a5.

8. The design method of a reverse arch foundation frame bridge structure according to claim 7 is characterized in that: When a signal that the bridge condition is unqualified is obtained, the bending bearing capacity ratio, shear bearing capacity ratio, stress allowable ratio, deflection allowable ratio, and settlement allowable ratio of the designed bridge model are obtained and compared to determine the influencing factors causing the unqualified bridge condition, and the bridge model is modified based on the influencing factors.

9. The design method of a reverse arch foundation frame bridge structure according to claim 8 is characterized in that: The process of obtaining each ratio is as follows: The ratio of the design bending moment to the bending bearing capacity at the ultimate bearing capacity state is calculated to obtain the bending bearing capacity ratio; The ratio of the design shear force to the shear bearing capacity of the ultimate bearing capacity state is calculated to obtain the shear bearing capacity ratio; Calculate the ratio of the calculated stress to the allowable stress value of the service life limit state to obtain the allowable stress ratio; Calculate the ratio of the calculated deflection to the allowable deflection of the normal service limit state to obtain the allowable deflection ratio; The ratio of the calculated settlement to the allowable settlement of the service life limit state is calculated to obtain the allowable deflection ratio.

10. A construction method for an inverted arch foundation frame bridge, the inverted arch foundation frame bridge being designed by the design method of claim 1, characterized in that: The following steps are involved: Step 1: Build dams and cofferdams to pump water; Step 2: Excavation of the anti-arch section; Step 3: Throwing rough stones; Step 4: Fill the joints with mortar and make cushion; Step 5: Construction of the anti-arch bottom plate; Step 6: Pier construction; Step 7: Top plate construction; Step 8: Bridge deck paving construction; Step 9: Installation of auxiliary facilities.

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