Atrium installation: load, draught and public access
A Level 1 sculpture student has approval to install a temporary work in the school atrium for three weeks. The space is 3 m wide, 2.5 m deep and 4 m high, with a main door that creates a strong draught and a fire exit route along one side. The student's proposal is a hanging curtain of 120 clear plastic bottles threaded on fishing line from a ceiling beam, with a small fan inside to make it move. The beam has a stated safe working load of 15 kg. The bottles weigh about 25 g each; the line and fittings add 1.2 kg. The fan weighs 0.8 kg and would need a power lead across the floor. The caretaker is worried about access and cleaning. The student has six school days and a budget of NZ$40. They want the work to 'feel immersive and a bit risky'.
1. Calculate the suspended load and evaluate whether the proposal is safe as described. Show your reasoning and identify the assumptions.
Read the worked answer
Load calculation: 120 bottles × 0.025 kg = 3.0 kg. Add line and fittings 1.2 kg and fan 0.8 kg = 5.0 kg total, which is below the beam's 15 kg safe working load. But the calculation is not the whole safety case. The load is dynamic: the fan and door draught will make the curtain swing, adding shock loads to fittings; the fan needs a power lead across the floor, creating a trip hazard on a fire exit route; and the bottles may fall or be pulled by students. The 15 kg rating may be for a static point load, not a swinging distributed load, and the beam's condition is unknown. So the proposal is not safe as described, even though the static number looks comfortable. The student must state assumptions (bottle mass, fitting mass, beam rating, dynamic factor) and have the caretaker or teacher check them.
2. Revise the proposal to keep the immersive idea while meeting safety and access constraints. Give three specific changes.
Read the worked answer
Three changes: (1) Remove the fan and the floor cable; rely on the door draught or gentle air movement, or use a battery fan mounted within the hanging assembly with no trailing lead. (2) Raise the bottom of the curtain to at least 2.1 m above the floor and keep the fire exit route clear by at least 1.2 m, so people do not walk through it. (3) Split the suspension across at least four ceiling anchors with secondary safety lines, use fire-rated or low-risk line, and cap the bottles so they cannot fill with water or fall open. These changes keep the immersive effect - a moving, translucent curtain - while removing the trip, fire and falling-object risks. A 1:10 maquette should be tested first to check density and sightlines.
3. Explain how a 1:10 maquette and a hanging load test would inform the final work. What would each test tell you that calculation alone cannot?
Read the worked answer
A 1:10 maquette tests what calculation cannot: visual density, sightlines from the door, whether 120 bottles read as a curtain or a lump, and how much of the atrium is blocked. It also lets the student test different spacings cheaply. A hanging load test, using sandbags or water weights under supervision, tests what the maquette cannot: how the line stretches, whether the beam deflects, whether fittings slip under swing, and where the weakest point is. Together they connect the design idea to the real structure. The student should record the test results and adjust the final proposal; a test that only confirms the original plan is not a test.