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Structural Inspection and Analysis of Outdoor Steel Billboards

Structural Inspection and Analysis of Outdoor Steel Billboards

Structural Inspection and Analysis of Outdoor Steel Billboards

A number of billboard accidents in recent years have highlighted the importance of structural inspection of billboards. At present, there are many problems with billboards. Through the analysis of the problems, we aim to standardize the design and construction of billboards, eliminate safety hazards and protect people’s lives and properties.

Billboard structure inspection
1.1 Content of on-site inspection of advertising facilities
1) Determine the type of advertising facilities: roof truss, steel structure wall type billboard, column mesh frame.
2) Field work exists in the following two situations:

a. On-site mapping when there is no drawing: the size of the panel frame, member models, rivet (bolt ) spacing; the size of the structural frame after the panel, member models, connection mode; the connection mode between the panel frame and structural system, structure and ground roof wall; drawn into a sketch of the frame specific size, model identification clearly.

b. On-site verification when there is a drawing: distinguish between the main load-bearing The main components and secondary components, the actual structure of all the main components of the model, connection method and the drawings to check, the secondary components for random checks, and record the structure and rod that do not match the drawings.

1.2 Testing basis
The technical contents of the calculation and analysis, site inspection and other work carried out on the billboard are carried out according to the current standards.
GB 50009 building structure load code; GB 50010 concrete structure design code; GB50017 steel structure design code; GB50007 foundation design code; GB50011 building seismic design code; GB50204 concrete structure engineering construction quality acceptance code; GB 50205 steel structure engineering construction quality acceptance code; CECS 148 Outdoor Advertising Facilities Steel Structure Technical Regulations; GB50057 Building Lightning Protection Design Code; GB/T50344 Building Structure Inspection Technical Standards.

1.3 Load-bearing capacity calibration
The action applied to outdoor advertising signs can be divided into two categories: action and variable action. The role of the self-weight of the structure, billboard or fixed equipment (lighting facilities) self-weight, operating platform self-weight, floor billboard soil weight, soil pressure and foundation deformation, etc.. Variable loads are wind load, ice load, snow load, installation and maintenance load, common seismic action, temperature change, etc.

In the testing of billboards, wind load and self-weight of the structure are mainly considered.
Based on the site inspection data, a model analysis of the structure was performed using SAP2000, taking into account the importance factor of the structural elements, basic wind pressure, seismic intensity, and the load combinations considered. Based on the analysis results, rectification measures are derived.

2 Problems and Correction Opinions
2.1 The main problems of the billboard are analyzed through testing
1) Structural system: The stiffness and stability of some of the inclined supports and transverse support ties, the length-to-thin ratio does not meet the requirements, the force transmission system is unreasonable, and some of the main load-bearing bars have been deformed; some of the components do not meet the requirements.

2) Connection:

a. The quality of the weld seam is considered at three levels, and does not meet the requirements, there is leakage of welding, not full welding, welding slag is not cleaned up, weld cracking, and the weld has been detached.

b. The panel is connected to the structure by rivets. The rivets are connected with the structure, the rivets are loose and fall off, the spacing is too large, the connection between the rod and the node plate does not meet the specification.

c. The connection between the angle steel and the bolt is improper, and the connection between the angle steel and the steel plate is not standardized. According to the relevant regulations, the roof billboard support is strictly prohibited to use friction type expansion bolts to connect, and some billboards use bolts to connect.

3) Rust prevention: the surface of the rod is rusted, the angle steel and the node at the anti-rust paint is locally peeling. Individual components are seriously corroded.

4) Lightning protection and circuit: No lightning protection grounding; power supply line was partially exposed and entangled with the panel frame, power distribution box was installed on the panel of the billboard, and neon light controller was installed on the panel.

2.2 Suggestions for rectification
1) Structural system: A reasonable method should be used to test the structural system, and unreasonable components should be dealt with, and the components that do not meet the requirements should be replaced or the poles should be increased to make them meet the code requirements.
Make it meet the specification requirements. For the deformed main force members and those that do not meet the requirements, they should be corrected or even replaced.

2) Connection: The welds with obvious defects should be re-welded. Angle and bolt connection using the correct way. Angle steel and steel plate connection using the correct way. According to the relevant provisions, the roof billboard support is strictly prohibited to use friction type expansion bolts connection , should be replaced by chemical anchor bolts of qualified quality, implants. The welding seam between the rod and the node plate with obvious defects should be made up; the distance between the two legs should be welded to fill the plate; the rivet spacing is too large and the case of falling off should be made up.

3) Rust prevention: rustproof paint should be made up if the rustproof paint is off, and the rod should be removed and replaced for the serious rust, and rust prevention measures should be carried out regularly on the components.

4) Lightning protection and circuit: the exposed wires should be protected by additional sleeves; the distribution box should be treated separately, and there are safety hazards when installed on the panel; the neon controller should be protected from moisture.

3 Other problems
Since the management of billboards is confusing and there are multiple management, the following analysis is made from the process of billboards from approval to formation.

1) The approval of the relevant government departments is not carefully studied to prove whether it affects the traffic, whether it affects the aesthetics of the city, and whether it should stipulate the appropriate structural form of the billboard that should be used, the possible hazards caused by the location and shape of the billboard affecting the sight lines of drivers and pedestrians and causing traffic accidents.

2) The owner hired the construction team to carry out the construction and building according to his own conception with little reasonable design.

3) The construction quality of the construction team is not guaranteed, and there is no certificate of induction or technician.

4) Some billboard drawings are designed by formal design institutes, but the construction is not strictly in accordance with the drawings, and the components are missing, causing uneven forces and changing the designed force structure. For the illegal billboard design drawings, strict force analysis should be carried out.

In view of the above management loopholes, I suggest:

1) The relevant departments should strictly approve the location, structural form and advertising area of the billboard, consider its safety, as well as the impact on the surrounding environment. After the billboard is completed, its construction quality and structural form should be strictly accepted, for example, if the area is larger than the area designed, the wind load will increase and the structural force will not match the design , which may

2) For the built billboard without drawings, it should be handed over to relevant departments to test whether it meets the specification requirements and come up with recommendations for rectification.

3) The construction quality should be supervised by relevant departments, and the construction team should be technically competent and construct in strict accordance with the drawings.

4 Conclusion
There are various reasons for the accident, the main reason is that there are few drawings provided by units with design qualification, most of them are designed by advertising companies themselves and given to qualified construction units, there are more serious safety hazards due to the production of billboards without formal design, reasonable construction plan and strict supervision measures. Even if some billboards have construction drawings, they are illegal drawings. Although the structure of the billboard is simple , many advertising companies think it is not important, the accident hazard is still great, so the billboard should be standardized design and construction to eliminate safety hazards and protect people’s lives and property.

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