Experimental method for earthquake-wave multi-field coordinated generation for offshore anchorless floating bridges

Abstract

The present invention discloses an experimental method for the coordinated generation of earthquake-wave multi-fields for large-scale anchorless floating bridges at sea, belonging to the field of offshore civil engineering safety technology. The method includes the following steps: establishing a numerical finite element model of the curved anchorless floating bridge, giving the maximum heave displacement of each floating foundation during the earthquake duration, obtaining the location where the maximum dynamic response of the target degree of freedom occurs, and releasing all degrees of freedom at the truncation boundary of the floating bridge model; designing a large-scale anchorless floating bridge model; establishing a multi-hazard field input system; and collecting the dynamic response of the large-scale anchorless floating bridge model. The present invention can reproduce actual seismic motion records at the bridge site and simulate the impact of earthquakes transmitted from the shore end of the large floating bridge on the dynamic response of the bridge structure. The present invention can reproduce earthquake-wave coupling effects, providing a method for the coordinated generation of earthquake-wave multi-fields for large floating bridges, and providing equipment support for further exploring the dynamic characteristics of large-scale deep-sea anchorless floating bridges under multiple hazards.

Description

Technical Field

[0001] The present invention relates to the field of offshore civil engineering safety technology, and in particular to an earthquake-wave multi-field coordinated generation experimental method for a large offshore anchor-free floating bridge. Background Art

[0002] In response to the need to build cross-sea channels in deep ocean waters, the concept of a new structural system for deep-water floating bridges has been proposed in recent years and preliminary technical exploration has been carried out, providing a new technical approach for the construction of transportation infrastructure in deep ocean waters. However, the complex marine conditions in deep ocean waters, such as environmental loads such as earthquakes and waves, have greatly increased the difficulty of designing and building floating bridges, and seriously threatened the safety of structural service.

[0003] Currently, research on large floating bridges is primarily focused on fragmented studies of marine environmental loads, dynamic response, and fatigue safety of their structural components or systems. A comprehensive laboratory testing system for engineering construction has yet to be established. Model testing of large floating bridges under multi-hazard field coupling presents challenges in generating multi-physics fields at an experimental scale and in properly truncating large floating bridges within the laboratory, due to their long and flexible structural characteristics and significant multi-field coupling effects. Summary of the Invention

[0004] Based on the above shortcomings, the purpose of the present invention is to provide an experimental method for the coordinated generation of earthquake-wave multi-fields for large-scale anchorless floating bridges at sea, which can reasonably cut off the large-scale anchorless floating bridge in the laboratory and realize the coordinated generation of earthquake-wave multi-fields, thereby reproducing the actual seismic motion records of the bridge site and simulating the influence of the seismic action transmitted from the shore end of the large floating bridge on the dynamic response of the bridge structure.

[0005] The technical solution adopted in this application is as follows: an experimental method for the coordinated generation of earthquake-wave multi-fields for a large-scale anchor-free floating bridge at sea, the steps of which are as follows:

[0006] S1: Reasonable truncation of large anchor-free floating bridge:

[0007] (a) Truncation range: A finite element model of a full-scale reference floating bridge was established in the Mechanical APDL interface of the finite element analysis software ANSYS. The beam element Beam189 was selected to simulate the main beam and piers, and the volume element SOLID 185 and the volume element FLUID 30 were selected to construct the floating foundation and the water body respectively. In order to ensure the equivalence of the buoyancy of the floating foundation, four vertical springs were used on each floating foundation. The spring stiffness K was 1 / 4 of the total waterline stiffness K0. The springs were rigidly connected to specific nodes on the floating foundation determined by the gyration radius in each direction to meet the equivalence of torsional stiffness. Then, a complex buoyancy reconstruction method was obtained that could update the stiffness in real time with the movement of the floating foundation, as shown in Equations (1)-(8).

[0008] K0=ρ water ·g·S pon (1)

[0009]

[0010]

[0011]

[0012]

[0013]

[0014]

[0015]

[0016] Where S pon is the waterplane area, is the displacement, GM T and GM L are the lateral and longitudinal metacentric heights, L P and B P are the length and width of the floating foundation, ρ water is the density of water, g is the acceleration due to gravity, L0 and B0 are the longitudinal and lateral gyration radii respectively, F B It is the buoyancy of the floating foundation when it is in static equilibrium. It is the average surface load generated by the buoyancy of the floating foundation in the static equilibrium position;

[0017] The equation of motion of the floating bridge is expressed as follows using the Galerkin method:

[0018]

[0019]

[0020] Where x, y, and z are the coordinates in the finite element model, u, v, and w correspond to the displacement components in the x, y, and z directions, n is the number of nodes of the fluid unit, and p is the displacement component of the fluid unit. e is the solid point pressure vector of the unit, N i and is the interpolation function corresponding to node i, x e is the nodal displacement vector of the element. By integrating and iterating the basic equations and boundary conditions of the fluid and solid domains, the final finite element equation of the fluid-solid interaction of the floating foundation is obtained, as shown in the following equation:

[0021]

[0022] Where Q is the fluid-structure coupling matrix of the floating foundation, M F and K F are the mass and stiffness matrices of the fluid, M S and K S are the mass and stiffness matrices of the solid, F S is the external load on the solid caused by earthquake action, assuming the fluid is an ideal fluid and ignoring the mass matrix caused by fluid compressibility and free surface fluctuations;

[0023] Furthermore, the modal analysis results of the floating bridge with fluid-structure interaction were obtained. Based on the AQWA (Advanced Quantitative Wave Analysis) software, the added mass of the floating foundation in still water was obtained, and the fluid-structure interaction problem of the floating bridge was further simplified to a solid dynamic analysis problem with added mass.

[0024] At this point, the finite element numerical model of the large-scale anchorless floating bridge has been constructed. To ensure the integrity of the dynamic analysis of the truncated model, a floating foundation is selected backwards according to the location where the maximum response of the full-scale floating bridge occurs.

[0025] (b) Truncation boundary: Through the modal analysis of the full-scale floating bridge, it is found that the lateral period of the large-scale unanchored floating bridge is 100±40s, and all degrees of freedom at the truncation boundary are released;

[0026] S2: Design of a large-scale anchorless floating bridge model: The model design uses the Froude similarity criterion and is divided into 12 sections along the longitudinal direction of the bridge. The rigidity of the floating bridge is provided by internal steel pipes and the exterior is covered with geometrically shaped organic glass. Foam plastic is filled in between to prevent fluid leakage. Aluminum piers and aluminum floating foundations serve as rigid bodies.

[0027] S3: Establishing an earthquake-wave multi-field input system: This system consists of a wave action input system and an earthquake action input system. The wave action input system is a mechanical wave generator installed at one end of the wave tank. By adjusting the hydrodynamic input parameters, it is used to reproduce the complex wave loads in the deep sea area, including regular waves and irregular waves. A wave absorbing device is placed at the other end of the tank. The earthquake action input system is realized by an electric actuator installed in the model placement area. By adjusting the earthquake action dynamic parameters, the original ground motion is simulated.

[0028] S4: Acquisition of dynamic response of large-scale anchorless floating bridge model:

[0029] (a) Use a wave height meter to measure the liquid level around the model;

[0030] (b) Based on the 3D optical motion capture system and Qualisys Track Manager software, the displacement response of the floating bridge model is obtained in real time by sticking QTM markers on the model surface;

[0031] (c) A three-axis waterproof accelerometer is used to measure the real-time acceleration of the floating bridge model. A unidirectional accelerometer is placed at the connection point between the electric actuator and the model to measure the actual ground motion generated by the electric actuator.

[0032] Compared with the existing technology, the advantages and beneficial effects of the present invention are: the present invention can reproduce the actual seismic motion records of the bridge site area and simulate the influence of the earthquake action transmitted from the shore end of the large floating bridge on the dynamic response of the bridge structure; the present invention can reproduce the earthquake-wave coupling effect and provide a method for the coordinated generation of earthquake-wave multi-fields for large floating bridges. At the same time, the present invention provides a model design and truncation method for a large anchorless floating bridge at the laboratory scale, as well as a means of measuring the dynamic response of the structure during the test, providing equipment support for further exploring the dynamic characteristics of large deep-sea anchorless floating bridges under multiple disasters. In addition, the present invention has high measurement accuracy and can be effectively used for the engineering characteristics evaluation of large anchorless floating bridges under earthquake-wave coupling. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A top-down schematic diagram of the complex buoyancy reconstruction of the floating foundation;

[0034] Figure 2 Reconstruct the elevation diagram for the complex buoyancy of the floating foundation;

[0035] Figure 3 Schematic diagram of the heave displacement of a floating foundation under earthquake action;

[0036] Figure 4 This is a schematic diagram of the cutoff range of a large-scale anchor-free floating bridge;

[0037] Figure 5 A top view schematic diagram of the measurement point arrangement of the floating bridge model provided in an embodiment of the present application;

[0038] Figure 6 A schematic elevation diagram of the arrangement of measurement points for a floating bridge model provided in an embodiment of the present application;

[0039] Figure 7 Schematic diagram of an indoor test platform for simulating earthquake-wave coupling provided in an embodiment of the present application;

[0040] Among them, 1-main beam; 2-bridge pier; 3-floating foundation; 4-electric actuator; 5-wave height meter; 6-QTM marker point; 7-three-axis waterproof acceleration sensor; 8-unidirectional acceleration sensor; 9-horizontal plane; 10-programmable wave maker; 11-wave breaking device; 12-high-sensitivity camera. DETAILED DESCRIPTION

[0041] The present invention is further described below with reference to the accompanying drawings. The steps of the earthquake-wave multi-field coordinated generation experimental method for an offshore anchorless floating bridge provided by the present invention are as follows:

[0042] Example 1

[0043] An experimental method for the coordinated generation of earthquake-wave multi-fields for a large-scale anchorless floating bridge at sea is described as follows:

[0044] S1: Reasonable truncation of large anchor-free floating bridge:

[0045] (a) Truncation range: A finite element model of a full-scale reference floating bridge was established in the Mechanical APDL interface of the finite element analysis software ANSYS. The beam element Beam189 was selected to simulate the main beam 1 and the pier 2, and the volume element SOLID 185 and the volume element FLUID 30 were selected to construct the floating foundation 3 and the water body, respectively. Figure 1-2 As shown in FIG, for the equivalence of the buoyancy of the floating foundation 3, it is decided to use four vertical spring units on each floating foundation 3. The spring stiffness K is 1 / 4 of the total waterline stiffness K0. The springs are rigidly connected to specific nodes on the floating foundation 3 determined by the gyration radius in each direction to meet the equivalence of torsional stiffness. Then, a complex buoyancy reconstruction method that can update the stiffness in real time with the movement of the floating foundation 3 is obtained, as shown in Equations (1)-(8).

[0046] K0=ρ water ·g·S pon (1)

[0047]

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054] Where S pon is the waterplane area, is the displacement, GM T and GM L are the lateral and longitudinal metacentric heights, L P and B P are the length and width of the floating foundation, ρ water is the density of water, g is the acceleration due to gravity, L0 and B0 are the longitudinal and lateral gyration radii respectively, F B It is the buoyancy of the floating foundation when it is in static equilibrium. It is the average surface load generated by the buoyancy of the floating foundation in the static equilibrium position;

[0055] The equation of motion of the floating bridge is expressed as follows using the Galerkin method:

[0056]

[0057]

[0058] Where x, y, and z are the coordinates in the finite element model, u, v, and w correspond to the displacement components in the x, y, and z directions, n is the number of nodes of the fluid unit, and p is the displacement component of the fluid unit. e is the solid point pressure vector of the unit, N i and is the interpolation function corresponding to node i, x e is the nodal displacement vector of the element. By integrating and iterating the basic equations and boundary conditions of the fluid and solid domains, the final finite element equation of the fluid-solid interaction of the floating foundation is obtained, as shown in the following equation:

[0059]

[0060] Where Q is the fluid-structure coupling matrix of the floating foundation, M F and K F are the mass and stiffness matrices of the fluid, M S and K S are the mass and stiffness matrices of the solid, F S is the external load on the solid caused by earthquake action, assuming the fluid is an ideal fluid and ignoring the mass matrix caused by fluid compressibility and free surface fluctuations;

[0061] Furthermore, the modal analysis results of the floating bridge with fluid-structure interaction were obtained. Based on the AQWA (Advanced Quantitative Wave Analysis) software, the added mass of the floating foundation in still water was obtained, and the fluid-structure interaction problem of the floating bridge was further simplified to a solid dynamic analysis problem with added mass.

[0062] At this point, the finite element numerical model of the large-scale anchorless floating bridge has been constructed. To ensure the integrity of the dynamic analysis of the truncated model, a floating foundation is selected backwards according to the location where the maximum response of the full-scale floating bridge occurs.

[0063] (b) Truncation boundary: Through the modal analysis of the full-scale floating bridge, it is found that the lateral period of the large-scale unanchored floating bridge is 100±40s, and all degrees of freedom at the truncation boundary are released;

[0064] S2: Design of a large-scale anchorless floating bridge model: The model design uses the Froude similarity criterion and is divided into 12 sections along the longitudinal direction. The rigidity of the floating bridge is provided by internal steel pipes and covered with geometrically shaped organic glass on the outside. Foam plastic is filled in between to prevent fluid leakage. Aluminum piers and aluminum floating foundation 3 serve as rigid bodies.

[0065] S3: Establishing a multi-hazard field input system: This system consists of a wave action input system and an earthquake action input system. The wave action input system is a programmable wave generator 10 installed at one end of the wave tank. By adjusting the hydrodynamic input parameters, it is used to reproduce the complex wave loads in the deep sea area, including regular waves and irregular waves. A wave absorbing device 11 is placed at the other end of the tank. The earthquake action input system is realized by an electric actuator 4 installed in the model placement area. By adjusting the earthquake action dynamic parameters, the original ground motion is simulated.

[0066] S4: Acquisition of dynamic response of large-scale anchorless floating bridge model:

[0067] (a) Use a wave height meter to measure the liquid level around the model;

[0068] (b) Based on the 3D optical motion capture system and Qualisys Track Manager software, the displacement response of the floating bridge model is obtained in real time by sticking QTM markers on the model surface;

[0069] (c) A three-axis waterproof accelerometer is used to measure the real-time acceleration of the floating bridge model. A unidirectional accelerometer is placed at the connection point between the electric actuator and the model to measure the actual ground motion generated by the electric actuator.

[0070] Example 2

[0071] (1) Select the “E39” project planned by the Norwegian Public Roads Administration (NPRA) to cross A conceptual curved anchorless floating bridge in the fjord is used as an example. First, a numerical finite element model of the curved anchorless floating bridge is established based on a magnitude of 7.4 and a peak acceleration of 103.9 cm / s. 2The maximum heave displacement of each floating foundation during the earthquake was given by the Tabas earthquake action, and it was found that the maximum heave displacement of the floating foundation appeared at the 3# floating foundation near the fixed end (such as Figure 3 Then, the position where the maximum dynamic response of the target degree of freedom occurs is obtained. Taking the 3# floating foundation as the benchmark, a floating foundation is selected backward to ensure the integrity of the dynamic analysis of the bridge model, as shown in Figure 4 As shown. Through modal analysis of a full-scale bridge, it was found that the first-order transverse modal period of the embodiment was approximately 65s. Due to the large natural period of the structure and the very small stiffness provided at the truncation boundary, it cannot be reproduced on a laboratory scale. At the same time, considering that the additional stiffness at the truncation boundary may cause changes in the initial deformation of the floating bridge model and increase the overall stiffness of the structure. In summary, all degrees of freedom at the truncation boundary of the floating bridge model are released.

[0072] (2) In order to study the influence of earthquake motion transmitted from the anchor end on the dynamic response of the floating structure, the geometric scale ratio of the model design in this embodiment is set to 1:100, taking into account the actual test site and the requirements of the hydrodynamic test. The truncated model of the floating bridge can be designed to consist of three full spans and two half spans. The model is shown in Figure 5-6 As shown. The model is 4.0m long and has four floating foundations. The beam is 31cm wide and 5cm high, with a box beam section. In order to consider the elastic deformation of the main beam under the combined action of earthquakes and waves, the floating bridge model is divided into 12 parts along the longitudinal bridge direction, and the model is constructed using steel, foam plastic, organic glass, etc. The rigidity of the main beam is provided by the internal steel plate, the external geometry is achieved by organic glass, and foam plastic is filled between the two to prevent fluid leakage. For the floating foundation and piers, both can be assumed to be rigid bodies. The piers are constructed using aluminum tubes and fixed to the floating foundation and main beam with screws. The floating foundation is made of aluminum plates, and two screws are welded at the bottom to install the aluminum counterweight plate to achieve the target draft.

[0073] (3) Figure 7 As shown, the earthquake-wave multi-field input system consists of a wave action input system and an earthquake action input system. The wave action input system is a mechanical wave generator installed at one end of the wave tank. By adjusting the hydrodynamic input parameters, it is used to reproduce the complex wave loads in the deep sea area, including regular waves and irregular waves. A wave absorbing device is placed at the other end of the tank. The earthquake action input system is realized by an electric actuator installed in the model placement area. By adjusting the earthquake action dynamic parameters, the original ground motion is simulated.

[0074] (4) In this embodiment, a wave height meter 5, a 3D optical motion capture system and an acceleration sensor are used to measure the wave field, motion state and acceleration of the test model respectively. Figure 5-7). The details are as follows: Water surface elevation: Three wave height meters 5 are installed upstream of the test model to measure the elevation change of the water surface. The second wave height meter is located in the center of the model, 2.5m away from the water tank wall and 40cm horizontally from the center of the model. The first wave height meter and the third wave height meter are located on both sides of the second wave height meter, both 1.0m away from the second wave height meter. Motion state: The motion state of the main beam and floating foundation is measured based on a 3D optical motion capture system with six high-sensitivity cameras 12. In order to capture the movement of structural components, a total of 52 QTM markers 6 were used for model testing. Among them, 28 QTM markers 6 were installed in 7 areas 50cm apart along the longitudinal axis on the upper part of the main beam. For each floating foundation, a total of 6 QTM markers 6 were installed on the upper surface of the two semicircles. The captured signals of the markers are processed using the supporting software Qualisys TrackManager (QTM) to obtain the displacement response of the model. Acceleration: The acceleration response of the test model was measured using three-dimensional waterproof accelerometers 7 mounted on top of four floating foundations 3. A single unidirectional accelerometer 8, located at the connection between the test model and the actuator, measured the actual ground motion generated by the actuator. Furthermore, test data from all sensors was synchronously collected using the NIPXI real-time data acquisition system. Water surface elevation and acceleration response were measured at a sampling frequency of 1000 Hz, and the kinematic state of the test model was extracted at a sampling frequency of 200 Hz.

[0075] (5) Finally, the dynamic response of the floating bridge model under wave action, earthquake action, and earthquake-wave coupling action can be obtained, including displacement, velocity, and acceleration.

Claims

1. An experimental method for earthquake-wave multi-field coordinated generation for a large-scale anchorless floating bridge at sea, characterized by: The steps are as follows: S1: Reasonable truncation of large anchor-free floating bridge: (a) Truncation range: A finite element model of a full-scale reference floating bridge was established in the Mechanical APDL interface of the finite element analysis software ANSYS. The "Beam 189" was selected to simulate the main beam and piers, and the "Volume Element SOLID185" and "Volume Element FLUID 30" were selected to construct the floating foundation and water body respectively. In order to ensure the equivalence of the buoyancy of the floating foundation, four vertical springs were used on each floating foundation. The spring stiffness K was 1 / 4 of the total waterline stiffness K0. The springs were rigidly connected to specific nodes on the floating foundation determined by the gyration radius in each direction to meet the equivalence of torsional stiffness. Then, a complex buoyancy reconstruction method was obtained that could update the stiffness in real time with the movement of the floating foundation, as shown in Equations (1)-(8). K0=ρ water ·g·S pon (1) Where S pon is the waterplane area, is the displacement, GM T and GM L are the lateral and longitudinal metacentric heights, L P and B P are the length and width of the floating foundation, ρ water is the density of water, g is the acceleration due to gravity, L0 and B0 are the longitudinal and lateral gyration radii respectively, F B It is the buoyancy of the floating foundation when it is in static equilibrium. It is the average surface load generated by the buoyancy of the floating foundation in the static equilibrium position; The equation of motion of the floating bridge is expressed as follows using the Galerkin method: Where x, y, and z are the coordinates in the finite element model, u, v, and w correspond to the displacement components in the x, y, and z directions, n is the number of nodes of the fluid unit, and p is the displacement component of the fluid unit. e is the solid point pressure vector of the unit, N i and is the interpolation function corresponding to node i, x e is the nodal displacement vector of the element. By integrating and iterating the basic equations and boundary conditions of the fluid and solid domains, the final finite element equation of the fluid-solid interaction of the floating foundation is obtained, as shown in the following equation: Where Q is the fluid-structure coupling matrix of the floating foundation, M F and K F are the mass and stiffness matrices of the fluid, M S and K S are the mass and stiffness matrices of the solid, F S is the external load on the solid caused by earthquake action, assuming the fluid is an ideal fluid and ignoring the mass matrix caused by fluid compressibility and free surface fluctuations; Furthermore, the modal analysis results of the floating bridge with fluid-solid coupling effect were obtained. Based on the AQWA software, the added mass of the floating foundation in still water was obtained. The fluid-solid coupling problem of the floating bridge was further simplified into a solid dynamic analysis problem with added mass. At this point, the finite element numerical model of the large-scale anchorless floating bridge has been constructed. To ensure the integrity of the dynamic analysis of the truncated model, a floating foundation is selected backwards according to the location where the maximum response of the full-scale floating bridge occurs. (b) Truncation boundary: Through the modal analysis of the full-scale floating bridge, it is found that the lateral period of the large-scale unanchored floating bridge is 100±40s, and all degrees of freedom at the truncation boundary are released; S2: Design of a large-scale anchorless floating bridge model: The model design uses the Froude similarity criterion and is divided into 12 sections along the longitudinal direction of the bridge. The rigidity of the floating bridge is provided by internal steel pipes and the exterior is covered with geometrically shaped organic glass. Foam plastic is filled in between to prevent fluid leakage. Aluminum piers and aluminum floating foundations serve as rigid bodies. S3: Establishing an earthquake-wave multi-field input system: This system consists of a wave action input system and an earthquake action input system. The wave action input system is a mechanical wave generator installed at one end of the wave tank. By adjusting the hydrodynamic input parameters, it is used to reproduce the complex wave loads in the deep sea area, including regular waves and irregular waves. A wave absorbing device is placed at the other end of the tank. The earthquake action input system is realized by an electric actuator installed in the model placement area. By adjusting the earthquake action dynamic parameters, the original ground motion is simulated. S4: Acquisition of dynamic response of large-scale anchorless floating bridge model: (a) Use a wave height meter to measure the liquid level around the model; (b) Based on the 3D optical motion capture system and Qualisys Track Manager software, the displacement response of the floating bridge model is obtained in real time by sticking QTM markers on the model surface; (c) A three-axis waterproof accelerometer is used to measure the real-time acceleration of the floating bridge model. A unidirectional accelerometer is placed at the connection point between the electric actuator and the model to measure the actual ground motion generated by the electric actuator.

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