BSF News

What’s been going on

The steel frame is now complete. This week we have fixed the safety nets below the remaining suspended floor slabs and started placing the metal decking to Section 3.

The metal decking sheets are designed to span between the steel beams and take the load of wet concrete and construction operatives without the need for any temporary propping to the deck whilst the concrete gains strength. The galvanised steel in the deck sheets is only 1mm thick but because it is bent into a trapezoidal profile the ability of the decking to resist bending is greatly increased. You can do a simple experiment to demonstrate this principle. Lay a sheet of paper between to blocks to form a bridge. Almost any load makes the bridge collapse. Now fold the paper backwards and forwards to make corrugations and place between the same blocks; the bridge will now take a real load. The ‘Section Modulus’ is the property that defines how strong a material is when acting in bending. The Section Modulus is proportional to square of the height of a profile. Hence a 55mm profiled metal deck will be approximately 3000 times stronger than the 1mm sheet the profile is bent from. The bending force on a member increases with the distance it spans. The greater Section Modulus is why deeper sections can span longer distances.

The ground floor slab preparation works continue to progress. Photograph 6 (below) shows the insulation and mesh reinforcement delivered ready for placing to the Section 1 Slab. Photograph 7 shows the final preparation of the Section 1 slab. The top of the stone is being blinded with sand to ensure that no stones can project up and puncture the damp proof membrane when the concrete is poured. This week we have also been erecting timber shutters to form the perimeter of the slab.

Photograph 8 shows work progressing to the Section 3 under slab drainage ahead of programme. Whenever there is an opportunity with no work ongoing above, we have been allowing the drainage gang to carry on working in this area. To ensure the safety of the operatives laying the deck sheets, all machinery must be removed from under the nets prior to the works above restarting. This ensures that should there be a fall into the net there are no obstructions below which someone in the net could strike before their fall is arrested. The segregation of works above and below is maintained by controlling access to the pre-cast concrete stairs to Section 3 upper floor levels.

Another team of netters have been busy this week erecting safety nets below the steel work to the Section 2 roof. They will continue on to net out the Section 1 roof, working off the concrete slab, next week. A scaffold hand rail will also be erected around the perimeter of the section 2 roof to allow safe access to install deck sheets week commencing 5th July.

To lift these sheets into place a different type of crane will need to be used. Although the sheets are comparatively lightweight, the distance that they will have to be lifted from the hard standing on the old playground to the Section 2 roof is in excess of 50m. To carry out this lift a mobile tower crane will be used. These cranes are lorry mounted so the can travel to site under their own power. The crane then self erects to form a tower crane assembly like the fixed ones you may have seen on large buildings in Manchester and recently on developments in Bury. Unlike the mobile cranes we have used so far on this project, this crane will be able to lift vertically adjacent to the new structure and then distribute the sheets horizontally on to the roof of the new Dance/Drama auditorium.

Over at the boundary of the sports pitches our contractor has been completing the second (and last) of the new outfalls taking the sports pitch drainage into the Butterworth Brook.

Coming soon

• Upper floor slabs

  All works including concrete to the decks will be completed by the start of the College Summer Holidays.

• Ground floor slabs.

  Ground floor slab construction will continue into the Summer Holidays. All slabs will be cast before your return in September.

• Roof

  Works will continue into September to lay the roof sheets. When this is complete the roof lights will be fitted.

• Envelope.

  The construction of the envelope will be ongoing for the rest of this year.

• Stair enclosure behind the existing Sports Hall

  Works will continue to place the ground slab to the stairs over the next week so that the foundation is ready for stair installation over the summer holiday.

Regards,
John England – Carillion Project Manager