why does this happen ? I have seen it happen in Canada , the USA , and other venues. Whoever is supplying the construction materials needs to be on the site during the erection to be sure the workmanship and instructions are followed. What is extremely important to know is the weight on the supports and the movement of wind. Wind is the biggest danger.
Suspected Boko Haram suicide bombing kills 38, wounds 51 in Chad village (Reuters)