Analysis of rooftop distributed photovoltaic structure carrying capacity
Foreword
Rabbit King recently received a lot of consulting messages. Everybody mainly wants to know whether the roof capacity meets the construction requirements. Indeed, for roof distributed photovoltaic projects, the bearing capacity is one of the decisive factors for the construction. Today Rabbit King is popular for everyone. The bearing capacity of various types of connections under the roof.
According to the use requirements of the roof, the roof forms are generally divided into accessible roofs and inaccessible roofs.
The analysis of roof load includes permanent load and variable load, among which variable load includes live load, wind load, snow load, ash load and so on.
Discussion on roof types and connection forms
At present, the roof forms used in distributed photovoltaic projects on the roof mainly include reinforced concrete roofs and colored steel tile roofs. Reinforced concrete roofs are generally arranged on the roof using a weight block connection. In general, the bearing capacity of reinforced concrete roofs will not have any problems, so this article focuses on the analysis of the bearing capacity of the three connection forms of color steel tile roofs. Depending on the roof structure, the color steel tile roof generally adopts two types of connection: clamps and connectors. The outermost layer of the roof structure is generally in the form of a clamp if the profiled steel plate is used. If the Tpo flexible waterproof membrane is generally connected to the substructure through a thermal insulation layer.
Fixture
1. The common profiled steel plates can be divided into overlap type, snap-type, and bite type (Angle Chi, upright hemming) from the plate type. There are different fixing fixtures for different plate types. There are holes in the profiled steel plate, so it does not affect the waterproof ability of the original roof.
2. Installation method: The general fixture is located on the roof purlin, the primary and secondary keels are connected to the fixture, and the photovoltaic panel is placed on the keel.
3. Load analysis
(1) Permanent load
Self-weight of the photovoltaic system, self-weight of the roof system, self-weight of grid structure: 0.25kN / m².
(2) Variable loads (live load, wind load, snow load, ash load, etc.)
Standard values for wind loads, standard values for snow loads, and live roof loads.
The standard value of the live load and the combined value coefficient of the roof of a house building on its horizontal projection surface.
Ash load:
The components are cleaned regularly so it can be disregarded. The effect of temperature is also not considered.
(3) Compared with the original design
The original design value of the roof load is compared with the value after the addition of the photovoltaic system. The value after the increase is less than the original design value to meet the requirements. The values to be compared are permanent load, live load, wind load, and snow load. For tiled projects, only the permanent load is usually different from the original design.
The permanent load is divided into the permanent load of the grid and the permanent load of the purlin. The increased permanent load of the grid includes the self-weight of the system, the roof, and the grid structure; the increased permanent load of the purlin includes the self-weight of the system and the roof structure.
The value of the original design and the addition of the photovoltaic system is compared through the load combination. The original design is greater than the actual load after the increase, and the condition is satisfied. If the actual load is greater than the original design, the unsatisfied items need to be reviewed.
Connector
1. Installation method: The connecting member passes through the roof system and is connected with the steel roof truss or roof steel beam.
2. Advantages: This connection method transmits force directly, and has no effect on the mechanical performance of the steel bearing plate and purlin.
3. Disadvantage: It will damage the original roof waterproof layer, but connection with steel roof trusses or roof steel beams can reduce the number of openings.
4.Load
The analysis method is the same as the fixture, the difference is that the self-weight of this type of roof photovoltaic system is generally higher than that of the roof using the fixture, for example, the load of the self-weight component of the photovoltaic system is 0.12kN / m², and the load of the supporting system is 0.08kN / m², totaling 0.20kN / m².