Ductile design considerations

Eurocode 8 (EC8) follows three general design concepts based on the ductiUty requirements and capacity design considerations of steel buildings the concept of the low-dissipative structural behavior of DCL structures, the concept of dissipative stmctural behavior of DCM and DCH stmctures satisfying the ductility and capacity design requirement, and the concept of dissipative structural behavior with steel dissipative-controUed zones. In the latter case, when composite action may be considered from Eurocode 4 (EC4) in the presence of the steel and concrete (slab) interaction, specific measures have been stipulated to prevent the contribution of concrete under seismic conditions, hence apply general rules for steel frames. 

A fatal accident and some other disasters, which were caused by small cracks, lead to a more strict consideration of the security of these steam drums. Parallel to these the economical pressure, due to the globalisation of the today s industry, lead to the increase of the pressure and the rotation speed of the paper production machines for a higher output of the production, which means, that all safety aspects from the design and the material will be exploited totally. On the other hand cast iron is also not a ductile and comfortable material, like the most steels for the pressure equipment. 

The ranges of properties in plastics encompasses all types of environmental and load conditions, each with its own individual, yet broad, range of properties (Fig. 1-9). These properties can take into consideration wear resistance, integral color, impact resistance, transparency, energy absorption, ductility, thermal and sound insulation, weight, and so forth. There is unfortunately no one plastic that can meet all maximum properties. Therefore, the designer has different options, such as developing a compromise because many product requirements provide options, particularly if cost is of prime importance. 

This type of construction uses precast concrete walls with steel or concrete frames (Figure 4.2). The frame resists all vertical loads and precast shear walls resist lateral loads. Ductile connections for precast panels are an important consideration. Precast panels are made with embedded steel connection devices attached to the building frame by bolting or welding. The roof is usually a concrete slab on metal deck. The metal deck is attached to steel framing by studs or puddle welds. Tins type of construction can be economically designed to withstand blast loading on the order of 7 to 10 psi (48 to 69 kPa) side-on overpressure. 

Slenderness considerations are of particular importance to the ductility of structural steel members, Steel, as compared to other building materials used in blast design, is considerably thinner, both in terms of the overall structure anc the components of a typical member cross section. As a result, the effect of ovcratl and local instability upon the ultimate capacity is an important consideration. Width-thickness provisions must be applied not only to the extent that a full plastic capacity can be achieved, but to the extent that higher ductility ratios can also be safely reached. The width-thickness ratios, from Table 8-1 of Seismic Provisions for Structural Steel Buildings (AISC 1992) are used for this purpose. 

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