.3.1 Requirements of structural system 干有 idimuk-b Figure 8.21 Transverse frames h ste 女然时 axis 5.Th 2 12 1、 The structural systems for one storey factory can be generally divided as transverse frame and longitudinal frame. The transverse frame is composed of column and beam or column and truss, while the longitudinal frame is composed of column, linking member (truss) and braces. In the large span workshop, the grid structure is also used nowadays. Here, only the points of frame structures are explained. Figure 8.21 and 8.22 shows examples of frame structures. 8.3.1 Requirements of structural system (a) framed bent (b) rigid frame (c) multi-bay frame with same height (d) multi-bay frame with different heights Figure 8.21 Transverse frames Figure 8.22 Longitudinal frames truss support truss vertical brace brace between lower columns brace between upper columns crane beam tie bar 2、Earlier than 1990s, most of the industrial workshop adopted purlinless roof structures, by using the pre-cast concrete roof slab, and in many cases with the skylight truss out of roof. Now the roof structures commonly use purlin system in which steel deck replaces the concrete slab that the roof weight becomes light. Instead of skylight truss small ventilator are widely used. These changes are advantageous to seismic design due to the decrease of roof mass therefore the inertial load caused by ground motion. 3、 In the view of seismic design the arrangement of structural system for industry workshop, the following should be paid attention. (1) The height of multi-bay frame had better been designed same. If this requirement can not be satisfied, the lateral force at the column due to the lower roof mass should be fully considered. . (2) The layout of the plan shall be arranged regular as possible. For example, two bays have different longitudinal sizes, thus the displacement, vibration velocity and acceleration of transverse frame in axis 4 will the different from those of frame in axis 5. The connection will be easily damaged. (3) If the layout is complicated and the structural engineers have no way to avoid the irregularity, expansion joint should be set referring to Figure 8.24 5 Figure 8.23 Irregular plan Location of expansion point Figure 8.24 Workshops have perpendicular longitudinal layout