Special Issue for Professor Rotter Advances in Structural Engineering 1–11 Ó The Author(s) 2017 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/1369433217742526 journals.sagepub.com/home/ase Effects of different snow load arrangements on steel silo roof structures Eutiquio Gallego, Jose Marı ´a Fuentes, Alvaro Ramı ´rez-Go ´ mez and Francisco Ayuga Abstract Large diameter steel silos usually require a beam structure to support rooftop inspection gangways and resist loads derived from the snow and wind actions. The existence of localized overloads caused by drifted snow on roofs as a consequence of the wind action has been reported in the literature. European standard EN 1991-1-3 also considers the need of taking into account asymmetric patterns for snow loads calculation. However, conical roofs are not included in the specific list of cases considered by this standard. The pres- ent work compares the normal stresses and displacements produced in a conical steel silo roof structure by applying balanced loads distributed on the whole roof and unbalanced loads applied on a roof sector. Experimental measurements and a three-dimensional beam model developed by the authors have been used to predict the stresses and vertical displacements of a metal silo roof structure measuring 18.34 m in diameter. The results show that the existence of an asymmetric load pattern produces higher normal stresses (up to 23%) and vertical displacements (up to 50%) than those derived from balanced loads, for any similar load per beam considered. Keywords drifted snow loads, full-scale tests, roof, silo, steel Introduction Silos have been used as storage facilities in the agricul- tural, mining, chemical and pharmaceutical industries since the end of the 19th century (Ayuga, 2008). Cylindrical silos made of steel are probably the most commonly used for agroindustrial purposes (Gallego et al., 2011). There are many design alternatives that can be employed for this type of silos. However, the installation of many consecutive large-diameter silos forming a ‘silo battery’ is very frequent. In this particu- lar design, an inspection gangway is usually placed over all the silos forming the battery. In addition, silo roofs are exposed to the action of wind and snow, which have to be taken into account in their design. Because of this, the silo roof must have a structure that provides support to rooftop inspection gangways and allows resisting loads derived from the snow and wind actions, covered in Europe by the standards EN 1991-1-3 (2003) and EN 1991-1-4 (2005). Silo roof structure must therefore prevent undesirable stresses on the silo wall, which might result in the denting of the side panels or even their buckling and failure, while allowing all gangways to be held firmly in place (Ayuga, 2008; Briassoulis and Pecknold, 1987; Portela and Godoy, 2005). The loads derived from most of the actions applied on the structures are usually calculated by considering a uniform load arrangement, despite many research works have shown the negative effects caused by asym- metries in the load distribution (Ma et al., 2013; Manko and Beben, 2006; Studzin´ ski et al., 2015; Wang and Li, 2007). Snow loads are responsible of many structural failures in buildings (Wardhana and Hadipriono, 2003). The main cause of structural fail- ures associated with snow loads is the occurrence of exceptional heavy snowfalls that produce snow loads above the limits considered by standards (Krentowski, 2014; Piskoty et al., 2013; Sadovsky´ et al., 2012). However, the existence of localized significant roof overloads caused by drifted snow as a consequence of the wind action occurs frequently. This is the reason why both wind and snow actions are usually combined to design buildings (Wang and Rosowsky, 2013). According to Tsuchiya et al. (2002), the location and ETSIAAB, Universidad Politecnica de Madrid, Madrid, Spain Corresponding author: Eutiquio Gallego, ETSIAAB, Universidad Politecnica de Madrid, Avda. Puerta de Hierro 2-4, Madrid 28040, Spain. Email: eutiquio.gallego@upm.es