To ensure the safety of dismantling steel supports during high-altitude operations, it is necessary to focus on the four core principles of "preventing falls, preventing collapses, controlling sequences, and strengthening protection", and control risks through a systematic process. Specific measures are as follows:
1、 Preparation and evaluation before demolition
Comprehensive inspection and scheme confirmation
Verify the status of steel support connection nodes (bolt torque, fastener tightness), the degree of component corrosion (wall thickness loss ≤ 10%), and the surrounding environment (such as adjacent buildings, overhead cable distance), mark damaged components (such as bent uprights, broken crossbars), and develop a special dismantling plan.
Clear demolition sequence: Strictly follow the principle of "top-down, non load bearing first, load bearing later", and prohibit vertical cross operation (such as dismantling upper and lower components at the same time). Demolition in the same area should be carried out from the middle to both ends or from one end to the other to avoid local instability of the frame.
Safety protection and tool preparation
Set up a horizontal safety net (mesh density ≥ 2000 mesh/100cm ²) within the 3 floors below the homework level, and securely tie the edges of the net to the components; Set up a 1.2m high guardrail and dense mesh (2000 mesh/100cm ²) near the edge, and a 200mm high toe board at the bottom to prevent components from falling.
Equipped with anti fall tools: Workers wear double hook safety belts (hooks connected to stable nodes and safety ropes respectively), use lifting equipment with anti fall devices (such as electric hoists), and fasten tools (wrenches, pry bars) with anti fall ropes (6mm nylon ropes) fixed on their wrists or frames.
2、 Key controls during the demolition process
Code for Demolition and Lifting of Components
When dismantling bolts and fasteners, use a wrench to loosen them first (do not use a hammer to strike hard), and place the disassembled components into a dedicated cage (volume ≤ 0.5m ³, weight limit 500kg). Throwing is strictly prohibited; Before dismantling long components (>6m), fix both ends with cable wind ropes (12mm steel wire ropes), slowly lay them down to a horizontal position, and then lift them up.
During lifting, the distance between the binding points of the components and both ends should be 1/4~1/3 of the total length to ensure balance. Before lifting, a trial lift should be conducted (pause and check at a height of 30cm from the ground) to confirm that the lifting equipment is not slipping and the components are not shaking before lifting. It is strictly prohibited to stand under the lifted object.
Synchronized uninstallation and real-time monitoring
Before dismantling the load-bearing nodes, slowly unload with a jack (rated load ≥ 2 times the weight of the component) to gradually apply force to adjacent components and avoid collapse caused by instantaneous load transfer; Every time three layers of poles are removed, use a total station to check the verticality of the frame (deviation ≤ 1/200 of the total height). If any tilt is found, immediately stop the operation and add temporary support for correction.
3、 Emergency and Closing Management
Emergency response
In case of severe weather such as strong wind of level 5 or above and rainstorm, the operation shall be stopped immediately, the components that have been removed but not lifted shall be fixed with wind ropes, and the personnel shall be evacuated to the ground safety area; When a component falls or there is abnormal noise from the frame, activate the emergency plan, seal off the scene, and organize professional personnel to evaluate and reinforce it.
On site cleaning and inspection
After the demolition is completed, classify and stack the components (bolts and fasteners should be stored separately to prevent loss), and check whether there are any tools or debris left on the work surface; After conducting a safety inspection of the demolition area and confirming that there are no loose components and protective facilities have been reset, the alert can be lifted.
Through the above measures, risks such as high-altitude falling, object impact, and frame collapse can be effectively avoided, ensuring that the dismantling process of steel supports complies with the requirements of the "Technical Code for Safety of High Altitude Operations in Construction" (JGJ80) and achieves safety and controllability.
