A roof BIPV system and a construction method thereof

Abstract

This invention discloses a roof BIPV system and its construction method, relating to the field of photovoltaic power generation technology. The aim is to control the upward deflection of steel beams, improve overall stiffness, and reduce the cross-section and steel consumption of the steel beams. The proposed technical solution includes photovoltaic modules and purlins. The photovoltaic modules are fixed to the purlins, and several steel beams are fixed to the bottom of the purlins. These steel beams are spaced apart along the extension direction of the purlins, and each steel beam extends perpendicular to the extension direction of the purlins. Multiple vertical struts are spaced apart at the top of each steel beam along its length. The top of each vertical strut has a slot, through which prestressed steel strands are threaded. Multiple wire rope clamps are fixed to the prestressed steel strands, with adjacent wire rope clamps located at opposite ends of the slot. The outer diameter of the wire rope clamps is larger than the width of the slot. The prestressed steel strands, vertical struts, and steel beams constitute a combined prestressed steel strand anti-arch structure. This invention can improve overall stiffness and reduce the cross-section and steel consumption of the steel beams.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic power generation technology, specifically to a rooftop BIPV system and its construction method. Background Technology

[0002] Distributed photovoltaic power generation is increasingly being used in the roofs of industrial plants. For existing large-span industrial plants, the roofs are usually portal frame structures with large spans, but the roof panels are mostly thin prestressed concrete slabs, generally only about 30mm thick, with low load-bearing capacity. Moreover, the roof waterproofing layer is quite sensitive to subsequent construction, and once damaged, repair is difficult and costly.

[0003] When installing photovoltaic (PV) brackets on rooftops, it is necessary to address the issues of wind loads, especially the uplift and deflection caused by wind suction. Existing rooftop PV bracket systems mainly adopt the following forms:

[0004] One method is counterweight-type support, which involves installing concrete counterweight blocks on the roof to resist wind suction. This method significantly increases the additional load on the roof, typically by more than 200 kg per square meter, and even more than 400 kg in coastal or high-wind-pressure areas. This far exceeds the allowable load of light industrial plant roofs, often requiring reinforcement of the original structure, increasing costs and affecting production.

[0005] Secondly, there is the chemical anchor bolt anchoring system, which anchors the support base to the roof panel using chemical anchor bolts. This method requires the roof panel to have sufficient thickness, generally over 120mm, to meet the required anchoring depth. However, the prestressed concrete thin slabs commonly used in large-span portal frame factory roofs are only about 30mm thick, which cannot meet the effective anchoring depth of chemical anchor bolts. Furthermore, drilling holes in the roof panel will damage the original waterproofing layer, and even if repairs are made later, leaks are likely to occur.

[0006] Thirdly, steel wire ropes or cables are used to connect the photovoltaic modules to roof fixtures such as parapet walls and louvers. In this method, the steel wire ropes are usually directly connected to the supports or module frames to form a tie system. However, this system has low overall stiffness and is prone to deformation under wind vibration or gusts, making it a flexible system that can easily cause the photovoltaic modules to sway or even be damaged. In addition, the node construction often requires anchors to penetrate the parapet wall or louver wall, which requires high construction precision and is prone to creating water seepage channels; if adhesive or friction fixing is used, long-term reliability is also difficult to guarantee.

[0007] For existing large-span, U-shaped industrial buildings, the roof typically has a central ventilator, with photovoltaic modules installed in the non-ventilator areas on either side. Due to the large span of the building, the steel beams in the shorter span direction are usually over 12 meters long, and under wind suction, the steel beams are prone to significant upward deflection. The existing technologies mentioned above are insufficient to effectively control the upward deflection of large-span steel beams under wind suction without increasing the roof load or compromising the roof waterproofing, while simultaneously ensuring sufficient rigidity and stability of the overall structure. Summary of the Invention

[0008] This invention provides a roof BIPV system and its construction method. The purpose is to effectively control the upward deflection of the steel beams through a steel beam-prestressed steel strand combined inverted arch structure without increasing the additional load on the roof or damaging the roof waterproofing, thereby improving the overall stiffness and reducing the cross-section of the steel beams and the amount of steel used.

[0009] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0010] A building-integrated photovoltaic (BIPV) roofing system is applied to a factory roof. The roof has a central louver and a parapet wall around its perimeter. The system includes photovoltaic modules and purlins. The photovoltaic modules are fixed to the purlins, and several steel beams are fixed to the bottom of the purlins. These steel beams are spaced apart along the extension direction of the purlins, and each beam extends perpendicular to the extension direction of the purlins. One end of each steel beam is fixedly connected to a louver column, and the other end is fixedly connected to a parapet wall structural column. At the top of each steel beam, along its length... Multiple vertical struts are installed at intervals; the top of each vertical strut has a slot, through which a prestressed steel strand extending perpendicular to the purlin extends. One end of the strand is anchored to the louver column, and the other end is anchored to the parapet column. Multiple wire rope clamps are fixed to the prestressed steel strands, with two adjacent clamps located at opposite ends of the slot. The outer diameter of the clamps is larger than the width of the slot. The prestressed steel strands, vertical struts, and steel beams constitute a combined prestressed steel strand anti-arch structure.

[0011] Furthermore, the steel beams are welded to the ventilator columns, and stiffening plates are installed on the opposite side of the weld. The ventilator columns are fixed to the top of the original steel frame structure support beams of the factory building with bolts.

[0012] Furthermore, end columns are installed between the steel beam and the parapet wall structural column; one side of the end column is anchored in the parapet wall structural column, and the other side is fixed to the gutter sidewall by tie bolts; the connection between the end column, the parapet wall structural column and the gutter sidewall is filled with secondary fine stone concrete, and the surface of the secondary fine stone concrete is coated with an epoxy asphalt waterproof layer.

[0013] Furthermore, the parapet wall structural column sidewall is fixed with channel steel stiffening ribs, and the end of the prestressed steel strand is fixed to one end of the first turnbuckle tightener through the first U-shaped combination lock head, and the other end of the first turnbuckle tightener is fixed to the channel steel stiffening ribs.

[0014] Furthermore, the column of the air vent is pre-welded with a fixed steel plate stiffening rib, and a U-shaped buckle is fixed on the fixed steel plate stiffening rib. The end of the prestressed steel strand is fixed to one end of the second turnbuckle tightener through the second U-shaped combination lock head. The other end of the second turnbuckle tightener is connected to the U-shaped buckle, and the U-shaped buckle is fixed to the fixed steel plate stiffening rib.

[0015] Furthermore, the louver column is also equipped with end steel beams that extend along the extension direction of the purlins. One end of the beam is anchored to the louver column, and the other end is anchored to the end parapet wall. A vertical strut is installed on the top of the end steel beam, and a prestressed steel strand extending perpendicular to the extension direction of the purlins passes through the top of the vertical strut. The two ends of the prestressed steel strand are anchored to the side parapet walls on both sides of the louver, forming a closed structure on both sides of the louver.

[0016] A method for constructing a roof BIPV system includes the following steps:

[0017] S1: Fix one end of the steel beam to the louver column and the other end to the parapet wall structural column;

[0018] S2: Install multiple vertical struts on the top of the steel beam;

[0019] S3: Pass the prestressed steel strands through the slots at the top of each vertical strut and temporarily fix them with wire rope clamps, allowing the prestressed steel strands to slip slightly along the short span direction;

[0020] S4: Anchor one end of the prestressed steel strand to the louver column and the other end to the parapet wall structural column.

[0021] S5: Tensile prestressed steel strands to induce downward camber in the steel beam, and monitor the downward camber value;

[0022] S6: When the downward pre-camber value reaches the preset value, stop tensioning and lock the wire rope clamps at the top of each vertical strut.

[0023] Furthermore, the tensioning process in step S5 is divided into three stages:

[0024] Initial tensioning stage: Apply small tension force to eliminate steel strand slack, anchor deformation and gaps;

[0025] Staged loading phase: Hold the load for 2 minutes after each loading stage to allow the tension to stabilize before proceeding to the next stage;

[0026] Final load holding stage: After reaching the design tension, hold the load for 5 minutes, and lock the anchor after confirming that the tension is stable and has no attenuation.

[0027] Furthermore, in step S5, the downward pre-camber value is monitored using the wire pulling method: thin steel wires are pulled taut at both ends of the steel beam, the vertical distance between the steel wire at the mid-span position and the upper surface of the steel beam is measured, and the mid-span camber value is calculated in combination with the height difference at the ends; the preset downward pre-camber value is 15mm.

[0028] Furthermore, after step S6, a supplementary tensioning step is also included: supplementary tensioning is carried out on the same day after tensioning and anchoring, and the compensation tension is calculated based on the anchor retraction amount and the slack loss of the steel strand. The steel strand is tensioned to the design tension plus the compensation value and then re-anchored.

[0029] The present invention has the following beneficial effects:

[0030] This invention utilizes a rigid composite anti-arch structure formed by steel beams, vertical struts, and prestressed steel strands: initial tensioning of the prestressed steel strands causes the steel beams to arch downwards, directly offsetting some of the wind-induced upward deflection; as wind suction increases, the upward deflection tendency of the steel beams drives the displacement of the vertical struts, causing the prestressed steel strands to passively elongate and their tension to automatically increase, thus confining the upward deflection deformation of the steel beams and forming an adaptive wind-resistant stress mechanism. Compared to pure steel beam schemes or flexible steel wire rope tie systems, the overall vertical stiffness is significantly improved, the upward deflection deformation of the steel beams can be stably controlled within the allowable range specified in the code, and the cross-sectional dimensions of the steel beams can be significantly reduced, resulting in a substantial reduction in the amount of steel used in the structure.

[0031] This invention anchors the two ends of the steel beam to the ventilator column and the parapet wall column respectively. All the self-weight and wind load of the system are directly transferred to the original main steel frame of the factory building through the vertical components at both ends. The roof panel does not bear any additional concentrated load or counterweight load, completely avoiding the need for reinforcement and modification of the original roof structure, saving reinforcement costs and not affecting the normal production and operation of the factory building.

[0032] All load-bearing anchoring nodes in this invention are set on existing vertical components such as louver columns and parapet wall structural columns, without drilling holes or installing reinforcement bars on the roof panel, thus not damaging the roof waterproof membrane itself; the parapet wall nodes only partially treat the sidewalls and are sealed with secondary concrete to overlap with the waterproof membrane, thus fully integrating with the original roof waterproof system and fundamentally eliminating the risk of roof leakage. Attached Figure Description

[0033] Figure 1 This is a planar schematic diagram of the present invention;

[0034] Figure 2 This is a schematic diagram of the installation of prestressed steel strands, vertical struts, and steel beams;

[0035] Figure 3 This is a schematic diagram of the installation of prestressed steel strands, steel beams, and parapet wall structural columns.

[0036] Figure 4 This is a schematic diagram of the installation of prestressed steel strands, steel beams, and ventilator columns;

[0037] Figure 5 This is a schematic diagram comparing the displacement cloud diagrams of the present invention and the pure steel beam scheme under the action of wind suction.

[0038] Figure 6 This is a schematic diagram comparing the stress cloud diagrams of the present invention and the pure steel beam scheme under wind suction.

[0039] Figures 1 to 4 The reference numerals in the attached drawings represent: 1. Factory roof; 2. Photovoltaic module; 3. Purlin; 4. Gas vent column; 4. Stiffening plate; 41. Fixed steel plate stiffening rib; 42. U-shaped buckle; 43. Parapet wall structural column; 5. End column; 51. Gutter; 52. Channel steel stiffening rib; 53. Steel beam; 6. End steel beam; 61. Vertical strut; 7. Prestressed steel strand; 8. Wire rope clamp; 81. First U-shaped combination lock head; 82. First turnbuckle tightener; 83. Second U-shaped combination lock head; 84. Second turnbuckle tightener; 85. Support beam; 9. Detailed Implementation

[0040] The specific embodiments of this application will now be described with reference to the accompanying drawings. It should be noted that, in this embodiment, for ease of description, the long span direction is used to represent the direction of extension along the purlin 3; the short span direction is used to represent the direction perpendicular to the direction of extension of the purlin 3.

[0041] Please refer to Figure 1-4 This embodiment describes in detail a roof BIPV system applied to the roof 1 of an existing large-span, U-shaped industrial plant. A louver is located in the middle of the roof 1, and parapet walls surround the louver. The parapet walls at both ends along the extension direction of the louver are end parapet walls, and the parapet walls at both ends along the width direction of the louver are side parapet walls. The roof BIPV system includes photovoltaic modules 2, purlins 3, and a support structure. The photovoltaic modules 2 are fixed to the purlins 3.

[0042] Several steel beams 6 are fixed to the bottom of the purlin 3, and these steel beams 6 are spaced apart along the extension direction of the purlin 3. Each steel beam 6 extends perpendicular to the extension direction of the purlin. The steel beams 6 are H-shaped steel beams, with one end fixedly connected to the louver column 4 and the other end fixedly connected to the parapet wall structural column 5. The purlin 3 extends along the long span and is fixed to the top of the steel beams 6. The photovoltaic modules 2 are fixed to the purlin 3 by clamps or bolts. At the top of each steel beam 6, multiple vertical struts 7 are spaced apart along the beam length. The vertical struts 7 are vertically welded or bolted to the steel beams 6.

[0043] The top of the vertical strut 7 has a slot for the prestressed steel strands 8 to pass through. Multiple prestressed steel strands 8 are arranged along the short span direction and pass through the slots of the vertical strut 7 at the top of each steel beam 6. The prestressed steel strands 8 are limited by wire rope clamps 81, which are sleeved on the prestressed steel strands 8 and located on both sides of each slot of the vertical strut 7, restricting the displacement of the prestressed steel strands 8 only in the long span direction. In this way, the prestressed steel strands 8 can expand and contract along the short span direction at the top of the vertical strut 7, while being confined within the slots and preventing them from coming out.

[0044] One end of the prestressed steel strand 8 is anchored to the parapet wall structural column 5, and the other end is anchored to the louver column 4. By tensioning the prestressed steel strand 8, pretension is generated. A downward vertical force is applied to the steel beam 6 through the vertical strut 7, causing the steel beam 6 to arch downwards, forming a combined anti-arch structure of steel beam and prestressed steel strand. Under wind suction, when the steel beam 6 tends to deflect upwards, the top of the vertical strut 7 moves upwards, causing the prestressed steel strand 8 to elongate, increasing its internal tension. This increases the downward constraint force on the steel beam 6, limiting its upward deflection and forming an adaptive wind-resistant constraint mechanism. Thus, even with strong wind suction, the deflection of the steel beam 6 can be controlled within the allowable range specified in the code.

[0045] To improve node stiffness and load-bearing capacity, the ventilator column 4 is made of steel. The steel beam 6 is connected to the ventilator column 4 via butt welds, and stiffening plates 41 are installed on opposite sides of the weld. The ventilator column 4 is fixed to the top of the existing steel frame support beam 9 of the factory building using four high-strength bolts. The support beam 9 is a long-span component of the original factory building's steel frame, and the bottom of the ventilator column 4 is bolted to it, thereby transferring the wind load and self-weight from the steel beam 6 to the main structure of the original factory building, avoiding the need for direct supports on the roof panel. After welding, the weld and heat-affected zone are ground and treated with anti-corrosion measures to prevent rust.

[0046] To ensure reliable anchoring and avoid damage to the roof slab and gutter waterproofing layer, end columns 51 are installed between the steel beam 6 and the parapet wall structural column 5. The end columns 51 can be made of square steel pipe or H-beams and are installed vertically. One side of the end column 51 is anchored to the parapet wall structural column 5 using chemical anchors or rebar, and the other side is fixed to the sidewall of the gutter 52 using tie bolts. The tie bolts penetrate the sidewall of the gutter 52, and a pad is placed on the outer side of the sidewall. During construction, only a portion of the concrete on the parapet wall sidewall is removed; the gutter concrete is not removed. After the end columns 51 are installed and the prestressed steel strands are tensioned, secondary fine aggregate concrete is filled at the connection between the end columns 51, the parapet wall structural column 5, and the sidewall of the gutter 52 to cover the joint. After the secondary fine aggregate concrete hardens, an epoxy asphalt waterproofing layer is applied to its surface, overlapping with the original roof waterproofing system to form a complete waterproof layer. Gutter 52 is a longitudinal drainage component installed at the junction of the parapet wall and the roof, used to collect rainwater from the roof and guide it to the downpipe for discharge.

[0047] The prestressed steel strand 8 is anchored at the parapet wall structural column 5 as follows: A channel steel stiffening rib 53 is fixed to the side wall of the parapet wall structural column 5 using chemical anchors, and through holes are opened in the channel steel stiffening rib 53. The end of the prestressed steel strand 8 is fixed to one end of the first turnbuckle tightener 83 via a first U-shaped combination lock head 82, and the other end of the first turnbuckle tightener 83 is fixed to the channel steel stiffening rib 53. The first turnbuckle tightener 83 is used to adjust the tension of the prestressed steel strand 8.

[0048] The prestressed steel strand 8 is anchored at the louver column 4 as follows: a fixing steel plate stiffening rib 42 is pre-welded onto the louver column 4, and holes are made in the fixing steel plate stiffening rib 42. A U-shaped buckle 43 passes through the holes in the fixing steel plate stiffening rib 42, and the other end of the U-shaped buckle 43 is connected to one end of the second turnbuckle tightener 85. The end of the prestressed steel strand 8 is fixed to the other end of the second turnbuckle tightener 85 through a second U-shaped combination lock head 84. The tension of the prestressed steel strand 8 can be adjusted by rotating the second turnbuckle tightener 85.

[0049] To improve the overall structural stability, end steel beams 61 are installed at both ends of the gas tower 4 along its long span. The end steel beams 61 extend along the long span, with one end fixedly connected to the end column 51 and the other end fixedly connected to the end parapet wall. Vertical struts 7 are also spaced at intervals along the length of the end steel beams 61. Prestressed steel strands 8 extending along the short span are threaded through the top of the vertical struts 7, with both ends of the prestressed steel strands 8 anchored to the parapet walls on both sides of the long side of the building. In this way, the BIPV structural systems on both sides of the gas tower are connected as a whole through the end steel beams 61 and the prestressed steel strands 8, forming a closed load-bearing system, enhancing the overall wind resistance and spatial coordination performance.

[0050] This embodiment also provides a construction method for the above-mentioned roof BIPV system, including the following steps:

[0051] S1: One end of the steel beam 6 is fixedly connected to the louver column 4, and the other end is fixedly connected to the parapet wall structural column 5. The steel beam 6 on the louver side is welded to the louver column 4 and stiffening plate 41 is added. Then the louver column is fixed to the support beam 9 with bolts. The steel beam 6 on the parapet wall side and the parapet wall structural column 5 are provided with end columns 51. One side is anchored to the parapet wall structural column 5, and the other side is fixed to the side wall of the gutter 52 with tie bolts. Then, secondary fine stone concrete sealing and waterproofing treatment are carried out.

[0052] S2: Install multiple vertical struts 7 on the top of each steel beam 6. The vertical struts 7 can be pre-welded to the steel beam 6 or bolted on site.

[0053] S3: Pass the prestressed steel strand 8 through the slots at the top of each vertical strut 7 and temporarily fix it with wire rope clamps 81. At this time, the wire rope clamps 81 are not locked, allowing the prestressed steel strand 8 to slide slightly along the short span direction for adjustment during subsequent tensioning.

[0054] S4: Anchor one end of the prestressed steel strand 8 to the louver column 4 and the other end to the parapet wall structural column 5. Specifically, a U-shaped combination lock head and a turnbuckle tightener are used for connection.

[0055] S5: The prestressed steel strands 8 are tensioned by rotating the turnbuckle tightener, causing the steel beam 6 to camber downwards. During tensioning, the downward camber value is monitored using the wire pulling method. Specifically, a thin steel wire is pulled taut at both ends of the steel beam 6, and the vertical distance between the wire at the mid-span position and the upper surface of the steel beam is measured. The actual camber value at the mid-span is calculated based on the height difference at the ends. In this embodiment, the preset downward camber value is 15mm.

[0056] S6: When the downward pre-camber value reaches the preset value, stop tensioning and lock the wire rope clamps 81 at the top of each vertical strut 7 to form a fixed connection between the prestressed steel strand 8 and the vertical strut 7, and maintain the pretension.

[0057] In step S5, tensioning can be divided into three stages:

[0058] Initial tensioning stage: Apply a small tension force, such as 20%-30% of the design tension force, to eliminate slack in the steel strands, deformation of the anchorages, and gaps between the steel strands and the groove, so that the system enters the stress state.

[0059] Staged loading: Hold the load for 2 minutes after each loading stage to allow the tension to stabilize before proceeding to the next loading stage, in order to avoid damage to the steel strand and anchorage end caused by impact load.

[0060] Final load holding stage: After reaching the design tension, hold the load for 5 minutes, and lock the anchor after confirming that the tension is stable and has no attenuation.

[0061] Following step S6, a supplementary tensioning step is also included. Since anchor retraction and strand slack can lead to pretension loss, supplementary tensioning is performed on the same day as the initial tensioning and anchoring. The compensating tension force is calculated based on the anchor retraction and strand slack loss. The strands are then tensioned to the design tension plus the compensation value and re-anchored to ensure that the anti-camber effect is not reduced during long-term use.

[0062] In one specific embodiment, the factory building is an existing large-span U-shaped industrial building, with a distance of 15m from the ventilator to the parapet wall and a basic wind pressure of 0.8kN / m². 2 The design value for wind suction is 2.5 kN / m. 2Without prestressed steel strands, the steel beam is H500×200×4.5×8.0, with a maximum mid-span deflection of 40.8 mm and a steel consumption of 42.22 kg / m. Using the combined steel beam-prestressed steel strand inverted arch structure of this embodiment, the steel beam cross-section can be reduced to H200×100×3.2×4.5. The prestressed steel strands adopt a 1×7 structure with an equivalent diameter of 12.7 mm and a tensile strength of 1860 MPa. The total prestress is controlled within 10 kN, and the initial prestress in this embodiment is 5 kN. Finite element analysis shows that after applying a 5 kN prestress, the steel beam produces a downward pre-arch of approximately 15 mm. Under wind suction, the maximum upward deflection of the steel beam can be controlled within 50 mm, meeting the deflection requirement of L / 250. The amount of steel used was reduced to 11.86 kg / m, which is about 72% less than the pure steel beam scheme. Furthermore, no counterweights or holes were installed on the roof panels, so as not to damage the roof waterproofing.

[0063] To verify the effect of the steel beam-prestressed steel strand combined inverted arch structure of the present invention on the control of steel beam deflection, finite element software was used to conduct a comparative analysis of two cases: one is the system of the present invention using H200×100×3.2×4.5 steel beams and prestressed steel strands, and the other is the pure steel beam system using H500×200×4.5×8.0. Both systems were simulated under the action of wind suction design value.

[0064] Figure 5 The images show the mid-span upper deflection displacement cloud diagrams of the beam under wind suction. The upper diagram shows the displacement cloud diagram of the steel beam-prestressed steel strand combined inverted arch structure of this invention, while the lower diagram shows the displacement cloud diagram of the pure steel beam system. Figure 5 It can be seen that the maximum upward deflection of the steel beam at mid-span of the combined anti-arch structure of the present invention is significantly smaller than that of the pure steel beam system, and the deflection is controlled within the allowable range of L / 250 in the specification; while the pure steel beam system, although using a larger cross section, still has a greater upward deflection than the scheme of the present invention. This indicates that the anti-arch structure formed by the prestressed steel strands and vertical struts of the present invention can effectively improve the vertical stiffness of the steel beam and control the upward deflection due to wind suction.

[0065] Figure 6 These are stress cloud diagrams of the steel beams under wind suction. The upper diagram shows the stress cloud diagram of the combined anti-arch structure of this invention, and the lower diagram shows the stress cloud diagram of the pure steel beam system. Figure 6 It can be seen that the tensile and compressive stresses of the steel beams in both schemes are within the allowable range of material strength. The cloud diagram on the right shows that the stress range is from -240MPa to 240MPa, indicating that while reducing the cross-section of the steel beam and the amount of steel used, the strength of the steel beam can still meet the design requirements, and the structure is safe and reliable.

[0066] The above comparative analysis shows that, without increasing the additional load on the roof or damaging the roof waterproofing, the present invention, through the combination of steel beams and prestressed steel strands in the inverted arch structure, can effectively control the upward deflection of the steel beams under wind suction and significantly reduce the cross-section of the steel beams and the amount of steel used.

Claims

1. A roof BIPV system applied to a factory roof (1), wherein a ventilator is provided in the center of the factory roof (1), and a parapet wall is provided around the perimeter of the factory roof (1), characterized in that, The system includes a photovoltaic module (2) and a purlin (3). The photovoltaic module (2) is fixed to the purlin (3). Several steel beams (6) are fixed to the bottom of the purlin (3). The steel beams (6) are arranged at intervals along the extension direction of the purlin (3). Each steel beam (6) extends in a direction perpendicular to the extension direction of the purlin (3). One end of the steel beam (6) is fixedly connected to the louver column (4), and the other end is fixedly connected to the parapet wall structural column (5). Multiple vertical struts (7) are arranged at intervals along the length of each steel beam (6). The top of the vertical struts (7) The prestressed steel strand (8) is provided with a slot, and a prestressed steel strand (8) extending in a direction perpendicular to the extension of the purlin (3) is inserted into the slot. One end of the strand is anchored to the louver column (4), and the other end is anchored to the parapet wall structural column (5). Multiple wire rope clamps (81) are fixed on the prestressed steel strand (8). Two adjacent wire rope clamps (81) are located at the two ends of the slot, and the outer diameter of the wire rope clamp (81) is larger than the width of the slot. The prestressed steel strand (8), the vertical strut (7), and the steel beam (6) constitute a steel beam prestressed steel strand combined anti-arch structure.

2. The roof BIPV system according to claim 1, characterized in that, The steel beam (6) is welded to the ventilator column (4), and a stiffening plate (41) is set on the opposite side of the weld. The ventilator column (4) is fixed to the top of the original steel frame structure support beam (9) of the factory building by bolts.

3. The roof BIPV system according to claim 1, characterized in that, An end column (51) is provided between the steel beam (6) and the parapet wall structural column (5); one side of the end column (51) is anchored in the parapet wall structural column (5), and the other side is fixed to the side wall of the gutter (52) by tie bolts; the connection between the end column (51) and the parapet wall structural column (5) and the side wall of the gutter (52) is filled with secondary fine stone concrete, and the surface of the secondary fine stone concrete is coated with an epoxy asphalt waterproof layer.

4. A roof BIPV system according to claim 1, characterized in that, The parapet wall structural column (5) has a channel steel stiffening rib (53) fixed on its side wall. The end of the prestressed steel strand (8) is fixed to one end of the first turnbuckle tightener (83) through the first U-shaped combination lock head (82). The other end of the first turnbuckle tightener (83) is fixed to the channel steel stiffening rib (53).

5. A roof BIPV system according to claim 1, characterized in that, The column (4) of the air tower is pre-welded with a fixed steel plate stiffening rib (42), and a U-shaped buckle (43) is fixed on the fixed steel plate stiffening rib (42). The end of the prestressed steel strand (8) is fixed to one end of the second turnbuckle tightener (85) through the second U-shaped combination lock head (84). The other end of the second turnbuckle tightener (85) is connected to the U-shaped buckle (43), and the U-shaped buckle (43) is fixed to the fixed steel plate stiffening rib (42).

6. A roof BIPV system according to claim 1, characterized in that, The column (4) of the air tower is also provided with an end steel beam (61) which extends along the extension direction of the purlin (3). One end of the beam is anchored to the column (4) of the air tower and the other end is anchored to the end parapet wall. The top of the end steel beam (61) is provided with a vertical support rod (7). The top of the vertical support rod (7) is provided with a prestressed steel strand (8) extending along the extension direction perpendicular to the purlin (3). The two ends of the prestressed steel strand (8) are respectively anchored to the side parapet walls on both sides of the air tower, and the two sides of the air tower form a closed structure.

7. A construction method for a roof BIPV system, characterized in that, Includes the following steps: S1: Fix one end of the steel beam (6) to the ventilator column (4) and the other end to the parapet wall structural column (5). S2: Install multiple vertical struts (7) on the top of the steel beam (6); S3: Pass the prestressed steel strand (8) through the slot at the top of each vertical strut (7) and temporarily fix it with a wire rope clamp (81), allowing the prestressed steel strand 8 to slide slightly along the short span direction; S4: Anchor one end of the prestressed steel strand (8) to the louver column (4) and the other end to the parapet wall structural column (5). S5: Tension the prestressed steel strands (8) to cause the steel beam (6) to camber downwards, and monitor the downward camber value; S6: When the downward pre-arch value reaches the preset value, stop tensioning and lock the wire rope clamps (81) at the top of each vertical strut (7).

8. A construction method for a roof BIPV system according to claim 7, characterized in that, The tensioning process in step S5 is divided into three stages: Initial tensioning stage: Apply small tension force to eliminate steel strand slack, anchor deformation and gaps; Staged loading phase: Hold the load for 2 minutes after each loading stage to allow the tension to stabilize before proceeding to the next stage; Final holding phase: After reaching the design tension, hold the load for 5 minutes, and lock the anchor after confirming that the tension is stable and has no attenuation.

9. A construction method for a roof BIPV system according to claim 7, characterized in that, In step S5, the downward camber value is monitored by the wire pulling method: a thin steel wire is pulled taut at both ends of the steel beam (6), the vertical distance between the steel wire at the mid-span position and the upper surface of the steel beam (6) is measured, and the mid-span camber value is calculated by combining the height difference at the ends.

10. A construction method for a roof BIPV system according to claim 7, characterized in that, After step S6, a supplementary tensioning step is also included: supplementary tensioning is carried out on the same day after tensioning and anchoring. The compensation tension is calculated based on the anchor retraction and the slack loss of the steel strand. The steel strand is tensioned to the design tension plus the compensation value and then re-anchored.

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