Poor -quality project
Sometimes the cause of the collapse is a poor -quality project, the absence of CMD drawings in the manufacture of structures.
In 1961. In. Baku, a collapse of a 54 m with a span of 27 m. The coverage of the workshop was made of steel rafter farms and prefabricated reinforced concrete panels with a length of 6 m, laid on the upper belts of the farms. Farms were made in the workshops of the construction trust. In the manufacture of rafter farms, a number of deviations were allowed from the “technical conditions for the manufacture and installation of steel structures” (CH 95-60). The manufacture of farms was carried out according to the drawings of km. CMD detailed drawings were not developed. In the project (drawings of KM), the lengths and cross -section of the welds were not set. The sections of the elements of the farms in the workshop changed arbitrarily, a number of elements were unreasonably weighted, while other elements were significantly weakened. In the manufacture of farms, steel without certificates was used. Low quality welding with a large number of non -carriers and cuts aggravated the condition of the farms. The share of guilt also lies with the installation organization, which, without the relevant documentation guaranteeing the quality of the structures, mounted the farm.
One of the reasons for the collapse of steel structures is the use of poor -quality material.
In 1950. The lower belt of a steel rod run over the ceiling of the industrial building of one plant in Kyiv exploded. When investigating the reasons, a crack in the lower belt of a run, made of square steel with a cross section of 30×30 mm, was found at the gap. They did not pay no attention to this crack in the manufacture of a rod. The crack loosened the cross -section of the lower belt in the most stressful place by 60%.