Partal frames 门式钢架理论原理.doc

附录1 专业文献翻译: Partal frames 1. Design and construction 1.1 Portal type and structural action The single-storey clear-span building is in constant demand for warehouses, factories and many other purposes. The clear internal appearance makes it much more appealing than a trussed roof building and it also requires less maintenance and heating. The portal may be of three-pinned, pinned-base or fixed-base construction as show in Figure I.The pinned-base portalis the most common type adopted because of the greater economy in foundation design over the fixed-base type. In plane, the portal resists the following loads by rigid frame action (a).Dead and imposed loads acting vertically. (b).Wind causing horizontal loads on the walls and generally uplift loads on the roof slopes .In the longitudinal direction, the building is of simple design and diagonal bracing is provided in the end bays to provide stability and resist wind load on the gable ends and wind friction on sides and roof. 1.2 Construction The main features in modern portal construction shown in Figure I are: (a).Columns ——uniform universal beam section ; (b).Rafters—— universal beams with haunch usually of sections 30-40% lighter than the columns (c).Eaves and ridge connections ——site-bolted joint using grade 8.8 bolts where the haunched ends of rafters provide the necessary lever arm for design .Local joint stiffening is required . (d).Base —— nominally pinned with two or four holding down bolts. (e) Purlins and sheeting rails——cold-formed sections spaced at not greater than 1.75-2m center； (f).Stays from purlins and rails ——these provide lateral support to the inside flange of portal frame members. (g).Gable frame ——a braced at the gable ends of the buildings； (h).Bracing —— provided in the end bay in roof and walls; Figure I (i).Eaves and ridge ties ——may be provided in larger-span portals, though now replaced by stays from purlins or sheeting rails. 1.3 .Foundations The pinned-base portal is