Platform Loading and Material Storage
A scaffold platform is designed for a uniformly distributed load of 2.0 kN/m². The platform is 1.2 m wide and 8 m long. A crew is preparing to store 60 concrete blocks, each with a mass of 20 kg, on a 2 m length of the platform. They also plan to place a mortar mixing tub (150 kg) next to the blocks. The scaffold has a single working platform at that level. The competent person notices the proposed storage and must decide whether to permit it.
1. Calculate the load intensity of the proposed storage and compare it with the design load.
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Total mass of blocks = 60 × 20 kg = 1200 kg. Weight = 1200 × 9.81 ≈ 11.77 kN. Mortar tub = 150 kg ≈ 1.47 kN. Total load ≈ 13.24 kN. The load is concentrated on a 2 m length of the 1.2 m wide platform, so the loaded area = 2 m × 1.2 m = 2.4 m². Load intensity = 13.24 kN / 2.4 m² ≈ 5.52 kN/m². This is 2.76 times the design load of 2.0 kN/m². Even if the load were spread over the full 8 m length, the average intensity would be 13.24 kN / (8 × 1.2) = 1.38 kN/m², which is within the design load, but the local intensity over the 2 m length far exceeds it. Therefore, the proposed storage is unsafe as a concentrated load.
2. What should the competent person do, and what alternative storage arrangement could be used?
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The competent person must not permit the proposed storage. The local load intensity of 5.52 kN/m² exceeds the design load of 2.0 kN/m², which could cause platform failure or excessive deflection. The competent person should: (1) instruct the crew to remove the blocks and tub from the scaffold immediately; (2) explain the load limit and the reason; (3) provide an alternative storage area at ground level or in a designated material bay; (4) if some material must be on the scaffold, limit it to a quantity that keeps the load within 2.0 kN/m² over the loaded area, e.g., no more than 2.0 kN/m² × 2.4 m² = 4.8 kN total (about 490 kg), and distribute it evenly; (5) ensure the scaffold is not used for storage beyond the design load. The competent person should also check that the scaffold is not loaded on multiple levels simultaneously without design consideration.