I always worried about cantilever design during my professional practice, mainly because of the totally reliance on ONE support only of the structure. Many factors could go wrong, design, materials, construction, maintenance and overloading. The consequences are always abrupt and often disastrous.
Six students died in US apartment balcony failure on 17th June 2015 News report. That is a nightmare for any Engineer and related parties.
When I was working for a Consulting Firm, my senior Engineer told me, he saw one cantilever balcony collapsed during construction, overloaded with construction materials. Then my former boss also told me, this young engineer designed two 5m long cantilever beams for an Entrance roof beams, both beams failed down after removal of the form-work supports. Luckily no one was hurt. Investigation found that the young engineer used wrong inputs in the commercial computer program and grossly under-designed the beams. My boss had to pay more than RM20,000.
When I was inspecting a 5-storey watch-tower cantilever staircase beam construction, I found that the Contractor put the top main reinforcements at the mid-depth of the beam with the so-called ten years experienced Supervisor did not know what he was supervising (later, I found that his certificate and credentials were all falsified). I immediately asked the Contractor to hack the half cast beam as well as to change the cantilever beam design to simply supported, as hacking or drilling of column was not recommended, despite Architect's unhappiness. Safety was my main concern.
Besides strength, deflection is also a concern which needs to be checked, otherwise cracks will appear on the brickwall sitting on the beams. Higher safety factor is recommended for cantilever design, especially if you are not going down to the field to inspect.
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