jnpgroup consulting engineers services provided:
- Structural Design And Detail Of Cantilever Platforms
- Structural Detailing Of Access Ladders
- Structural Detailing Of Fixings
- Existing Stack Structure Investigation And Analysis
- Existing Roof Structure Review And Analysis
- Construction Method Statements
Stack Platforms
The project was to design and detail new lightweight access platforms and ladders to 5 No. Ventilation Stacks on a Laboratory site to enable the stack discharge to be checked at various locations throughout its height. The monitoring points varied in location and some required access ladders or bridge platforms to be installed to assist safe access.
The Site
The 5 No. stacks varied from being integral with buildings and discharging through the roof to external to the building with external duct routes. The stacks also varied in height, diameter and construction thickness, some being steel, some concrete and some steel clad concrete.
The Design
The Client required the monitoring platforms to be installed at a height agreed with the regulatory authority which varied for each stack. Safe egress and access was to be provided to the platform locations. This varied from platform bridges from roofs, to access ladders from the ground.
Stack P was external to the building it served and was of concrete ring construction. The monitoring platform needed to be positioned at approximately 18m above ground level.
The platform was designed as an open grated, lightweight cantilever steel access structure, fixed to the existing concrete structure. Loads were established for fixings and Rawl were consulted with regard to specifying the correct fixing.
The cat ladder access was designed in conjunction with the client’s specific details, providing safety lines and tool lifting equipment. The platform was also provided with safety handrails, mesh infill, safety harness points and a hinged hatch. The ladder was fixed back to the concrete stack following Rawl’s advice.
Stack M protruded through the roof of the building it served. However, the section of roof surrounding the stack was very fragile and not suitable for pedestrian access. Therefore a platform bridge from an adjoining roof had to be designed and installed to assist monitoring of the stack.
The platform would be of a similar specification as above and would also be fixed to the stack. However, the original concrete stack had been provided with an external steel liner with a 30mm gap between the two elements. Rawl were once again consulted with regard to specifying the correct fixing for the loads and construction scenario.
Stack K and L were sited next to each other and protruded through the roof of the building they served, however, the section of roof directly surrounding the stacks was very fragile and not suitable for pedestrian access. Therefore a platform and access ladder had to be detailed to assist access from and adjoining roof.
The platform would be of a similar specification as above and would also be fixed to the stacks. However, both the original concrete stacks had been provided with external steel liners, one with a 30mm gap between the two elements, the other a 130 gap filled with concrete – although the compaction could not be quantified. Rawl were once again consulted with regard to specifying the correct fixing for the loads and construction scenario’s.
The installation required the use of cranes and some minor alterations were required to the proposals were the existing stack rings were out of plumb or not of a true diameter.
New look jnpgroupIn pursuit of providing an overall 'One stop shop' service to our clients, jnpgroup set up a...
'One stop shop' engineeringjnpgroup is committed to providing our clients with a comprehensive 'One Stop'...