Holdfast Training Services Trial Blog

I had a rather enlightening conversation a few weeks back and I thought it was time I finally got my act into gear to blog about it – and it is to do with lifts, or more specifically lift shafts.

Australia 108 will be 100 levels, 319m tall.  This will present two significant issues with the serviceability of the lift shafts:

1. Chimney stack effect. The temperature difference between the base of the building and the top of the building will be sufficient to induce an air flow up the lift shafts as the warm air at the bottom rises to the top (see Figure 1). Air is introduced at the base of the lift shaft by being sucked in though the lift doors, creating two undesired effects; firstly, the lift doors will likely jam and secondly, a loud whistling sound (often referred to as a howling).    There are two fundamental options to deal with this problem.  Option A) prevent air being sucked into the shaft (not feasible) or Option B) let the air do what it wants to do but provide an alternative inlet. Surprisingly Option B was the preferred option and we are looking at putting 2No 850 x 1000mm penetrations into the base of each lift shaft.  Without providing additional outlets at the top of the shaft, we are not encouraging an increase in additional air flow to what naturally wants to occur.

Figure 1. Chimney stack effect

2. Piston effect.  Of the 10 lifts, 9 are in banks of 3 and the goods lift is stand alone in its own lift shaft.  The design speed of the goods lift is 5m/s (slower than the remainder) and is of sufficient speed to create a piston-type affect of driving air either up or down depending on the direction of the lift car.  The  displaced air moves around the car at a quicker speed sometimes twice that of the car (see Figure 2) creating undesirable vibration and noise.  The effect is worse at the top, bottom and middle of the shaft (where the counter weights pass the car).  To mitigate these issues, the cars will be made more aerodynamic and a 1000 x 2000mm penetration will be punched into the core walls at a low, middle and high level.

Figure 2. Piston effect

Prima Pearl is a 67 story building that that was completed in Jun 14 by the same management team as A108.  The additional penetrations were not build into the core walls and have since had to be retro fitted to deal with the defects.  Prima is 2/3 the height of A108.

Adding in air-relief penetrations seems like a good fix until you consider these penetrations were not taken into account on the initial design.  In addition to these penetrations, there are also penetrations for the core crane, the hoist, two jump lifts, the jump form as well as embedded power conduit, water, waste water and sewer pipes that also, were not taken into account on the initial design.  This is one core that is working extremely hard.

So what….think the design through to the finish throughout all stages of the life cycle and consult SME contractors to reduce the risk of missing critical elements of the design.  This is not something I would have even thought to consider.  The structural engineers are still struggling to make the core work in the serviceability state and every additional penetration makes this task that much harder.