Formwork Blog

Posts Tagged ‘High Rise’

Location: A Surfers Paradise High-Rise Construction Site, Gold Coast Australia

There is nothing more disappointing than stripping the formwork from columns or walls and discovering that there is absolutely no cover from the edge of the concrete to the reinforcement steel.

No Cover Concrete Column

Experienced formworkers will see this problem in advance and therefore ensure that the steel has the specified cover before closing up the formwork. This either means fixing it yourself, or organizing it to get fixed.

Obviously this is just another one of those dodgy high-rise construction projects on the Gold Coast where there is no quality control in place. Yes, there must be a Work Method statement in place, but it seems that on this job it is only good to wipe your arse with.

What is more disturbing to think about is how many of the columns on this 50+ storey appartment tower have the steel just 5mm under the surface of the concrete and therefore not detected? If it was not detected, is was probably never repaired.

Tip: before placing the Column Steel Cage onto the Column Starters, mark out all the columns on that floor in order to see in advance how much cover there is. Then, reposition any Starter Bars that are in the wrong position.

It is extremely rare to find Starter Steel in the correct position 100% of the time. Marking out the columns before the cage is placed will make it easier to reposition the starters into the correct position. In the long-run, this is quicker, cheaper and easier than making concrete repairs.

Location: A High-Rise Construction Site at Edward Street Brisbane Queensland Australia

Formworkers Dino, Chewy and Marco cram inside the Personel Hoist at smoko time.

Formworkers Dino, Chewy and Marko

Location: Surfers Paradise Gold Coast Australia

While I was briefly associated with the Formwork Company at the Circle on Cavil high-rise construction site, the project was visible from the apartment building where I was staying. It took seven minutes to walk there eliminating the need to battle the traffic and pay for car parking.

Circle On Cavil

Circle On Cavil

Location: A Surfers Paradise High-Rise Construction Site, Gold Coast Australia

A Formworker built this work platform on top of a dodgy Guardrail around a Crane Base Penetration in order to do some Stripping and Back-Propping. Obviously he does not have the level of awareness required to work safely on high-rise construction sites. This is the result of poor training and supervision on behalf of the formwork company.

Dodgy Scaffolding and Guardrail Combination

What’s Wrong With This Scaffolding?

Firstly, some bloke comes along and erects a dodgy guardrail to prevent people and objects falling down the Crane Base Penetration, then some other guy comes along and builds a dodgy Work Platform on top of it. Criiiikey!

It is dodgy because the top Scaffolding Tube has a join with only one Post at each end and the Posts “wobble” because they are not anchored securely. This combination represents the danger of the two Scaffold Tubes separating at the join.

The Top-Rail in this situation should be one piece without any joins. When this is done on all four sides of the penetration, it makes a strong, rigid Guardrail protection for any square shaped penetration even if the posts are a bit wobbly (which they shouldn’t be).

Furthermore, the Sleeve-Coupler used to join the two pieces of Scaffold Tube is upside down. This type of Sleeve-Coupler should always be attached with the opening facing up and the bolts facing away from the user. The reason?

• Because the Sleeve Coupler is designed to be used that way.
• Because the Sleeve Coupler is stronger that way.
• The opening facing upwards provides a visual check-point to see if the Scaffold Tube is in fact inserted all the way into the Coupler.
• The bolts facing away from the user minimizes injuries.

Even if all the above corrections were made to this Guardrail, work platforms should not be built on top of guardrails anyway.

Location: A Surfers Paradise High-Rise Construction Site, Gold Coast Australia

After reading about a killed worker as a result of being buried under wet concrete after a suspended slab collapsed, I wandered if some of us too relaxed with our attitude towards Back-Propping.

The Do It Later Attitude

The photo below shows a small part of a formwork deck which in my opinion was done in a hurry due to the large number of incomplete Back-Propping assignments. This can only be the result of a flawed Work Method Statement.

Unsafe Back-Propping

You’ll notice that the Props are sitting on a flat timber which also needs to be propped before the concrete pour. The attitude here is “we’ll do it later”, or worse, “it’s okay” as it is. The problem with this attitude is that inside this maze of formwork frames, it can be very difficult to remember or spot all these important do-it-later jobs.

Often this do-it-later job is allocated to a Formworker experienced with spotting danger areas of a deck and back-propping accordingly. Too often this job is allocated too late only allowing time to insert the props, but not to tie them off with Scaffold Tube and Clamps (Fittings).

Top is Back Propped, bottom is Not

The other reason that this finish-it-just-before-the-concrete-pour attitude is flawed is because the deck will continue to be loaded with additional bundles of plywood, timber and steel well before the concrete pour day. Heavy compressors could also be landed on the deck along with big bundles of pipes for the concrete pump.

What this means is that it is possible to overload and collapse parts of the deck even before the concrete pour day if the Back-Propping is incomplete.

Do It Now

Never leave these Back-Propping jobs incomplete. Do them immediately and completely as you go. This procedure should be placed in the companies Work Method Statement in order to ensure that your supervisor or leading hand can not take you to another job before the Back-Propping is 100% complete.

Communicate

You should also communicate with the Deck Head informing them of the areas where construction materials should not be placed. Deck heads should also inform Doggers the correct way to lay the Dunnage/Gluts.

For example, the Dunnage should always go across several Joist timbers instead of longways in between the Joists where the loaded Dunnage could easily penetrate through the plywood. This mistake is made very often so keep an eye on beginner doggies with no formwork experience.

Secure Those Props

Too often props are not nailed at the top because there is simply no way to reach up there safely. A single prop on it’s own falling over can threaten life or limb as well as be responsible for the collapse of a formwork deck.

Even if the props are nailed to the Header, there is no guarantee that the Header is nailed properly to the Joists. For this reason, props should be secured with scaffold tube and clamps back to the frames which will ensure the props remain in the desired position.

Plan To Minimize Back-Propping

A lot of Back-Propping in the above pictured deck could have been eliminated altogether by planning the layout of the frames better. If frames are erected at the minimum required span or less, the need for Back-Propping will be reduced to a minimum.

Of course this method assumes that the formwork company does not take short-cuts by deliberately using lots of unnecessary props because there is a shortage of Frames. The general rule for this should be if a Frame can fit, put it in there.

Cause And Effect

Because