Tensioning construction method for steep slope photovoltaic flexible support

Abstract

The invention relates to the technical field of mountain photovoltaic support construction and structural engineering mechanics, and discloses an abrupt slope photovoltaic flexible support tensioning construction method. Aiming at the problems of eccentric anchoring stress, mismatched cable system load, insufficient wind vibration resistance and difficulty in assembly transportation and installation in a steep slope scene, anchor point positioning based on a digital elevation model, double-layer expansion cap axis self-calibration anchoring, upper and lower cable asymmetric tension, a wind-resistant cable-stayed stable structure and main cable multiplex cableway installation are adopted; and tension and temperature combined monitoring and hydraulic compensation are set. According to the scheme, eccentric stress of an anchoring area and torsion mismatch of assemblies can be reduced, the wind vibration resistance stability of the structure is improved, and steep slope construction disturbance is reduced.

Description

Technical Field

[0001] This invention relates to the field of construction and structural engineering mechanics of photovoltaic supports in mountainous areas, and particularly to a method for tensioning photovoltaic flexible supports for steep slope scenarios. Background Technology

[0002] As the scale of photovoltaic development in mountainous, hilly, and karst regions continues to expand, traditional photovoltaic support systems that rely on dense pile foundations and rigid beams face challenges such as significant disturbance during foundation construction, difficulties in material transportation, and poor structural adaptability in steep slope scenarios. In construction areas with large slopes, access for heavy machinery is limited. Continuing to use conventional concrete foundations and access roads would not only significantly increase earthwork volume but also easily damage the original vegetation and slope stability.

[0003] Existing flexible cable-net photovoltaic (PV) support technologies, by employing a double-layer cable system and prestressed tensioning, can reduce the number of pile foundations and improve span capacity to some extent. For example, existing technologies disclose double-layer cable-net PV supports and their installation methods. However, these technologies are mainly designed for flat land, water bodies, or general complex terrain, and have not fully addressed the gravity eccentric load mismatch problem unique to steep slope scenarios. Because the equivalent vertical loads on the upper load-bearing cables and the lower stabilizing cables are different, if a symmetrical tensioning method is still used, it is easy to cause inconsistent deflections between the upper and lower cables, resulting in significant torsional mismatch and additional internal forces after the PV modules are installed.

[0004] Furthermore, the wind field in steep slopes and canyons exhibits strong local amplification and high-frequency disturbance characteristics. Traditional flexible cable-stayed structures lack targeted force transmission path reconstruction mechanisms in their wind-induced vibration resistance design, making it particularly difficult to alleviate stress concentration in high-stress knee joint areas. Simultaneously, existing technologies typically treat scaffold erection and material transportation as independent construction phases, failing to fully utilize the pre-tensioned main cables as freight transport channels during construction. This results in low efficiency and high safety risks in transporting components and auxiliary materials in steep slope environments.

[0005] Therefore, it is still necessary to propose a photovoltaic flexible support tensioning construction method and system suitable for steep slope scenarios, so as to simultaneously solve problems such as anchor point topology positioning, asymmetric tensioning of upper and lower cables, wind vibration resistance and high-altitude cableway transportation and installation. Summary of the Invention

[0006] This invention addresses the technical problems existing in the prior art by proposing a method for tensioning and constructing flexible photovoltaic supports on steep slopes.

[0007] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0008] A method for tensioning flexible photovoltaic supports on steep slopes is proposed. S1: For steep slopes with a gradient greater than 30°, digital elevation model data is acquired, slope and aspect features are extracted, a global coordinate system and a local terrain-following coordinate system are established, and a set of spatial coordinates for the foundation anchor points of multiple rows of flexible cable nets is planned along contour lines or a preset oblique normal vector trajectory; S2: Micro-rock anchoring foundations are constructed at the spatial coordinates of the foundation anchor points, cement-based grout is injected into the boreholes, and high-strength steel anchor rods are implanted. A double-layer enlarged cap anchoring device is installed at the exposed end of the anchor rod. The double-layer enlarged cap has a first support surface perpendicular to the preset cable axis direction, so that subsequent tension force is transmitted along the anchor rod axis; S3: In... Upper load-bearing cables and lower stabilizing cables are laid between two adjacent rows of anchor foundations. Based on the difference in equivalent vertical loads between the upper and lower cables caused by gravity eccentricity, snow load, and the normal component of wind pressure, the initial horizontal preload of the upper load-bearing cables and the lower stabilizing cables is calculated, and asymmetric tensioning is implemented to ensure that the maximum deflection of the double-layer cable net at the mid-span position remains consistent after the photovoltaic modules are installed. S4, transverse rigid trusses and inter-row flexible wind-resistant stay cables are installed at the mid-span position of the double-layer flexible cable net and in the knee joint area where the stress concentration factor is greater than 2.0. The installation angle and preload ratio of the front and rear stay cables are adjusted to ensure that the ratio of the absolute average stress of the front stay cable to the total absolute average stress of the front and rear stay cables is equal. Located in the range of 0.95 to 1.05; S5, reuse the upper load-bearing cable and the lower stabilizing cable that have completed asymmetric tensioning in step S3 as an aerial freight cableway, attach the sliding traction trolley carrying photovoltaic modules to the cable, and use the slope top winch to pull the sliding traction trolley from the bottom of the slope to the target span position, and then use locking fasteners with flexible damping pads to fix the photovoltaic modules between the upper load-bearing cable and the lower stabilizing cable.

[0009] Furthermore, in step S3, based on the catenary deformation coordination relationship, the corresponding initial horizontal preload is calculated according to the equivalent uniformly distributed load, target matching deflection, cable span, steel cable elastic modulus and steel cable cross-sectional area of ​​the upper load cable and the lower stabilizing cable, respectively. The calculation process is applicable to steep slope scenarios with a slope of 30° to 60°.

[0010] Furthermore, the sliding traction trolley in step S5 includes a main frame, at least two sets of polyurethane anti-detachment rollers that match the diameter of the steel cable, and a load suspension hook.

[0011] Furthermore, the 2-fold fundamental frequency in step S4 is twice the first natural frequency of the structure, which is determined by finite element modal analysis or field vibration testing.

[0012] Furthermore, this can be achieved by adjusting the preload ratio of the forward and backward stay cables and the installation angle. Regulation.

[0013] Furthermore, the polyurethane anti-detachment roller has a Shore hardness of 80A to 90A, and its static friction coefficient with the galvanized steel cable is less than 0.3.

[0014] Beneficial effects:

[0015] Compared with existing rigid support or conventional flexible cable system construction schemes, this invention firstly enables the tension force of the cable to be transmitted along the anchor rod axis through anchor point topology positioning based on digital elevation model and double-layer enlarged cap axis self-calibration anchoring method, thereby reducing the eccentric force and construction disturbance in the steep slope anchoring area.

[0016] This invention further employs an asymmetric tensioning strategy with differentiated upper and lower cables to ensure consistent mid-span deflection of the double-layer cable net after photovoltaic module assembly, thereby significantly reducing torsional mismatch and additional stress in the modules and improving the structural stability and operational reliability of the flexible support on steep slopes. The constrained wind-resistant cable-stayed topology reconstruction mechanism improves the wind load transmission path under high-frequency dynamic wind loads, alleviates stress concentration in the high-stress knee joint region, and enhances the system's resistance to wind vibration.

[0017] Furthermore, this invention reuses the tensioned main cable as a freight cableway during the construction period, realizing the high-altitude cableway transportation and suspension installation of photovoltaic modules, reducing the need for temporary construction access roads and heavy machinery access, and is suitable for engineering implementation in ecologically sensitive mountainous areas.

[0018] Finally, the present invention forms a closed-loop regulation mechanism by combining tension and temperature monitoring and hydraulic compensation actuator, which can provide early warning and compensation when changes in ambient temperature cause tension attenuation or tension increase, thereby improving safety and maintenance convenience during long-term service. Attached Figure Description

[0019] Figure 1 This is the main flowchart of the present invention. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0021] Example 1:

[0022] like Figure 1As shown, for steep slope areas with a gradient greater than 30° to be constructed, digital elevation model data is acquired, slope and aspect features are extracted, a global coordinate system and a local terrain-following coordinate system are established, and a set of spatial coordinates for the foundation anchor points of multiple rows of flexible cable nets is planned along contour lines or a preset oblique normal vector trajectory. Specifically, before construction, digital elevation model data is first collected for steep slope areas with a gradient greater than 30°. Preferably, three-dimensional point cloud data of the construction area can be acquired through UAV laser mapping or ground mapping equipment, and a global coordinate system and a local terrain-following coordinate system are established accordingly. Combining slope features, aspect features, and array shading requirements, a set of spatial coordinates for the foundation anchor points is generated along contour lines or a preset oblique normal vector trajectory. For steep slope areas with a gradient of 30° to 60°, it is preferable to stagger adjacent rows of anchor points according to the contour line direction to balance anchoring efficiency and component light exposure conditions.

[0023] Miniature rock anchoring foundations are constructed at each anchor point. At the spatial coordinates of the foundation anchor points, miniature rock anchoring foundations are constructed by injecting cement-based grout into the borehole and inserting high-strength steel anchor rods. A double-layer enlarged cap anchoring device is installed at the exposed end of the anchor rod. The double-layer enlarged cap has a first support surface perpendicular to the preset cable axis direction, so that subsequent tension force is transmitted along the anchor rod axis. Specifically, a small drilling device is used to penetrate the surface loose soil layer and enter the stable rock layer. Cement-based grout is injected into the hole and high-strength steel anchor rods are inserted. A double-layer enlarged cap is installed at the exposed end of the anchor rod. The double-layer enlarged cap consists of a lower enlarged cap and an upper enlarged cap. The upper enlarged cap has a first support surface perpendicular to the preset cable axis direction. A spherical self-aligning washer and a hydraulic self-locking nut are also provided on the first support surface to compensate for the installation normal deviation caused by the irregular surface of the steep slope and to transmit the output force of the tension jack along the anchor rod axis.

[0024] Upper load-bearing cables and lower stabilizing cables are laid between two adjacent rows of anchor foundations. Based on the difference in equivalent vertical loads between the upper and lower cables caused by gravity eccentricity, snow load, and the normal component of wind pressure, the initial horizontal preload of the upper load-bearing cables and the lower stabilizing cables is calculated, and asymmetric tensioning is implemented to ensure that the maximum deflection of the double-layer cable net at the mid-span remains consistent after the photovoltaic modules are assembled. Specifically, upper load-bearing cables and lower stabilizing cables are laid between two adjacent rows of micro-rock anchor foundations. Since the main load after the photovoltaic modules are installed initially acts on the upper load-bearing cables, the equivalent uniformly distributed loads borne by the upper load-bearing cables and the lower stabilizing cables are different. To reduce torsional mismatch of the modules, the initial horizontal preload of the upper load-bearing cables and the lower stabilizing cables needs to be calculated separately.

[0025] In this embodiment, the catenary deformation compatibility relationship is preferably used for back calculation. Let the cable span be... The horizontal cable force component after deformation is The equivalent uniformly distributed vertical load is The maximum deflection at mid-span is Then the approximate relationship of deflection can be expressed as:

[0026]

[0027] When considering the arc length increment caused by geometric nonlinearity and the elastic elongation of the material, an equilibrium relationship can be established.

[0028]

[0029] in, The initial horizontal preload, , The elastic modulus of the steel cable. This represents the cross-sectional area of ​​the steel cable.

[0030] In this embodiment, the equivalent uniformly distributed load of the upper load-bearing cable is respectively... Equivalent uniformly distributed load of the lower stabilizing cable Substituting the above relationships, we can match the deflection based on the same target. Find them separately and Then, differentiated tensioning is implemented based on the back-calculation results. This ensures that the maximum deflection of the double-layer cable net at the mid-span position remains consistent after the photovoltaic modules are installed. The small inclination angle approximation mentioned here refers to the inclination angle of the cable mid-span tangent relative to the horizontal line being within the approximate range of small deflection in engineering, rather than the terrain slope itself being small; when the slope exceeds 60° or the cable-to-span ratio exceeds the preset range, a precise catenary model or a geometrically nonlinear finite element model can be used for correction.

[0031] Transverse rigid trusses and inter-row flexible wind-resistant stay cables are assembled at the mid-span location and knee joint area where the stress concentration factor is greater than 2.0 in the double-layer flexible cable net. By adjusting the installation inclination angle and preload ratio of the front and rear stay cables, the ratio of the absolute average stress of the front stay cable to the total absolute average stress of the front and rear stay cables is adjusted. Located within the range of 0.95 to 1.05. Specifically, transverse rigid trusses and flexible wind-resistant stay cables are installed at the mid-span and knee joint areas of the double-layer flexible cable net. The knee joint area, as referred to in this paper, refers to a node or its vicinity where the stress concentration factor is greater than 2.0 in structural analysis. The flexible wind-resistant stay cables include forward and backward stay cables. By adjusting the preload ratio and installation angle of both, the ratio of the absolute average stress of the forward stay cable to the total absolute average stress of the forward and backward stay cables is made... It falls within the range of 0.95 to 1.05.

[0032] when When the value approaches 1, it indicates that the forward cable bears the main tension under the prevailing wind direction, and the system can switch from a symmetrical distributed force transmission mode to a wind load transmission mode dominated by a single cable, thereby alleviating local torsion and stress concentration in the knee joint area. The "2 times the fundamental frequency" mentioned in step S4 refers to twice the first natural frequency of the structure, which can be determined through finite element modal analysis or on-site vibration testing. In engineering implementation, the stress state of the forward and backward cables can be checked separately for the prevailing wind direction to improve wind vibration resistance.

[0033] After completing the asymmetric tensioning described in the embodiment, the upper load-bearing cable and the lower stabilizing cable, which underwent asymmetric tensioning in step S3, are reused as an aerial freight cableway. A sliding traction trolley carrying photovoltaic modules is mounted on the cable, and the trolley is lifted from the bottom of the slope to the target span position by a winch at the top of the slope. Then, the photovoltaic modules are fixed between the upper load-bearing cable and the lower stabilizing cable using locking fasteners with flexible damping pads. Specifically, the upper load-bearing cable and the lower stabilizing cable are used as an aerial freight cableway. The sliding traction trolley, mounted on the cable, includes a main frame, at least two sets of polyurethane anti-detachment rollers, and a load suspension hook. Preferably, the polyurethane anti-detachment rollers have a Shore hardness of 80A to 90A, and their static friction coefficient with the galvanized steel cable is less than 0.3, to balance stable rolling and protection of the anti-corrosion layer on the steel cable surface.

[0034] During actual installation, a winch and traction steel cable positioned at the top of the slope are used to lift the sliding trolley carrying the photovoltaic modules from the bottom of the slope to the target span position. Construction workers unload the photovoltaic modules at the target position and secure them between the upper load-bearing cable and the lower stabilizing cable using locking fasteners with flexible damping pads. The flexible damping pads, made of weather-resistant elastic material, allow the modules to undergo slight energy-dissipating deflection under strong winds, thereby reducing the adverse effects of high-frequency vibrations on the modules and connectors.

[0035] In step S3, based on the catenary deformation coordination relationship, the corresponding initial horizontal preload is calculated according to the equivalent uniformly distributed load, target matching deflection, cable span, steel cable elastic modulus and steel cable cross-sectional area of ​​the upper load cable and the lower stabilizing cable. The calculation process is applicable to steep slope scenarios with a slope of 30° to 60°.

[0036] like Figure 1As shown, the dynamic monitoring feedback subsystem collects monitoring data from the tension sensor and temperature sensor in real time, and the logic control unit determines whether to activate the hydraulic compensation actuator. When the ambient temperature rises, causing the cable mid-span deflection to increase and the horizontal tension to decrease by more than 5% of the initial tension setting, the logic control unit triggers an alarm and starts an automatic or semi-automatic hydraulic compensation tensioning program. The 5% threshold can be determined based on the cable fatigue life curve and structural reliability analysis, or alternatively, it can be set to 3% to 8% of the initial tension setting.

[0037] In this embodiment, the compensation stroke of the hydraulic compensation actuator It can be calculated using the following formula:

[0038]

[0039] in, The coefficient of linear expansion of the steel cable is _____. The length of the cable segment. The change in temperature The initial horizontal preload, For the current horizontal tension, The elastic modulus of the steel cable. Let be the cross-sectional area of ​​the steel cable. Through this compensation relationship, the thermal expansion and contraction effect caused by temperature and the tension deviation correction amount can be uniformly mapped into the displacement control amount of the actuator.

[0040] For those skilled in the art, without departing from the principles of this invention, equivalent substitutions or conventional adjustments can be made to the structural form, parameter values, and control methods of each subsystem, and such equivalent substitutions or adjustments should all fall within the protection scope of this invention.

Claims

1. A method for tensioning a flexible photovoltaic support structure on a steep slope, characterized in that, The process includes the following steps: S1, for steep slope areas with a gradient greater than 30° to be constructed, acquire digital elevation model data, extract slope and aspect characteristics, establish a global coordinate system and a local terrain-following coordinate system, and plan a set of spatial coordinates for the foundation anchor points of multiple rows of flexible cable nets along contour lines or a preset oblique normal vector trajectory; S2, construct micro-rock anchor foundations at the spatial coordinates of the foundation anchor points, inject cement-based grout into the boreholes and implant high-strength steel anchor rods, and install double-layer enlarged cap anchoring devices at the exposed ends of the anchor rods. The double-layer enlarged caps have a first support surface perpendicular to the preset cable axis direction, so that subsequent tension force is transmitted along the anchor rod axis; S3, on the two adjacent upper and lower... Upper load-bearing cables and lower stabilizing cables are laid between the anchorage foundations. Based on the difference in equivalent vertical loads between the upper and lower cables caused by gravity eccentricity, snow load, and wind pressure normal components, the initial horizontal preload of the upper load-bearing cables and the lower stabilizing cables are calculated and asymmetric tensioning is implemented to ensure that the maximum deflection of the double-layer cable net at the mid-span position remains consistent after the photovoltaic modules are installed. S4, transverse rigid trusses and flexible wind-resistant cable stays between rows are installed at the mid-span position of the double-layer flexible cable net and in the knee joint area where the stress concentration factor is greater than 2.

0. By adjusting the installation inclination angle and preload ratio of the front and rear cable stays, the ratio of the absolute average stress of the front cable stay to the total absolute average stress of the front and rear cable stays is adjusted. Located in the range of 0.95 to 1.05; S5, reuse the upper load-bearing cable and the lower stabilizing cable that have completed asymmetric tensioning in step S3 as an aerial freight cableway, attach the sliding traction trolley carrying photovoltaic modules to the cable, and use the slope top winch to pull the sliding traction trolley from the bottom of the slope to the target span position, and then use locking fasteners with flexible damping pads to fix the photovoltaic modules between the upper load-bearing cable and the lower stabilizing cable.

2. The method for tensioning and constructing a flexible photovoltaic support on a steep slope according to claim 1, characterized in that, In step S3, based on the catenary deformation coordination relationship, the corresponding initial horizontal preload is calculated according to the equivalent uniformly distributed load, target matching deflection, cable span, steel cable elastic modulus and steel cable cross-sectional area of ​​the upper load cable and the lower stabilizing cable. The calculation process is applicable to steep slope scenarios with a slope of 30° to 60°.

3. The method for tensioning and constructing a flexible photovoltaic support on a steep slope according to claim 1, characterized in that, The sliding traction trolley in step S5 includes a main frame, at least two sets of polyurethane anti-detachment rollers that match the diameter of the steel cable, and a load suspension hook.

4. The method for tensioning and constructing a flexible photovoltaic support on a steep slope according to claim 1, characterized in that, The 2-fold fundamental frequency in step S4 is twice the first natural frequency of the structure, which is determined by finite element modal analysis or field vibration test.

5. The method for tensioning and constructing a flexible photovoltaic support on a steep slope according to claim 1 or 4, characterized in that, This is achieved by adjusting the preload ratio of the forward and backward stay cables and the installation angle. Regulation.

6. The method for tensioning and constructing a flexible photovoltaic support on a steep slope according to claim 3, characterized in that, The polyurethane anti-detachment roller has a Shore hardness of 80A to 90A, and its static friction coefficient with the galvanized steel cable is less than 0.3.

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