Nonbuilding and Special Structures
It is not uncommon to see in the news alarming headlines about silo failures in the USA and around the world. Sometimes the failure only involves distortion or deformation which, while unsightly, does not pose a safety or operational hazard. In other cases, failure involves complete collapse of the structure with accompanying loss of use and even loss of life. In many cases, lawsuits are inevitable lasting for several years after the incident, which exacerbates the burden already carried by all the parties involved in the failure.
One of the main causes of bin and silo failures is due to inadequate design. Part of the problem lies in the lack of training in this subject at the graduate program level as well as guidance on the literature including standards and codes. Many engineers when faced with the need to analyze a container storing a bulk solid tend to assume theories that may be better known but inapplicable. For example, the wrong assumption that a flowing bulk material behaves like a flowing liquid is commonly made. For those familiar with bulk solids behavior, it is well understood that solid particles can transfer shear stresses between each other and between themselves and silo walls even if there is no relative motion between them. Fluids do not exhibit this behavior. The bulk solids behavior not only has to be in line with the material-induced loads but also with the design of the storage structure. Appropriate theories related to shell structures need to be utilized including their failure modes and critical structural details taking into consideration operation and properties of bulk solids.
Engineers in charge of the structural design and construction of bins and silos as well as industrial facilities will benefit from this presentation as they will be able to better understand the implications of not having a comprehensive standard/code for the design of bulk solids storage structures. Committee members for the loading and structural design of special structures will be able to gather information and discuss how a new standard/code can be beneficial to many industries in the USA.