Summary

A carpenter on the 30th floor of a high-rise building under construction was speaking with his supervisor while standing beside the location where wall forms were being flown in and erected. The first wall form had just been set and braced. A steelworker was climbing up the walers to access the work platform so that he could help guide the rebar mat into place. The wall form suddenly fell over, and the steelworker climbing up was able to jump clear. However, the nearby carpenter was crushed by the protruding work platform attached to the wall form and died of his injuries. The supervisor escaped unharmed.

Conclusions

• The wall form became unstable and fell over. It was erected and supported on load blocks with an unequal cantilever at the base at each end. There were no structural elements to prevent lateral movement. As a worker climbed up the walers on the wall form, it kicked out at the south end load block. The braces were not adequately attached to the wall form and therefore were unable to resist the resulting forces to keep the form from falling.

• The engineering drawings for the formwork did not include any instruction or details for erecting and supporting the wall form on load blocks. The bracing could not be installed as shown in the engineering drawings. As a result, these sections were constructed without adequate engineering consideration, relying instead on the experience of the carpenters.
• Climbing the walers to access the work platform was an unsafe practice and was prohibited by the company's safe work procedures. Even though workers had been previously observed and reported, the practice continued. The added weight of the worker climbing on the north end of the wall form was a contributing factor to the wall falling over.
• Nailing was ineffective. Each form aligner brace was nailed with two nails to the end of a waler. Only one nail for each brace could be considered fully engaged. The ends of the walers had been nailed into a number of times previously and were damaged and cracked. The inadequate bracing connections contributed to the wall form's instability.

Link:
Hazard alert