It is common and cost effective to separate the building gravity only steel structure from seismic/wind lateral bracing frames. The gravity structure can then be designed as simple construction in accordance with NZS 3404 Steel Structures Standard. In simple construction the bending members may be assumed to have their ends connected for shear only and to be free to rotate. Examples of such connections are shown in figure 1. In beams and column frames for which simple construction is assumed, there will none the less be bending moments acting on the columns which are caused by eccentricity of the beam reactions.

It is common and cost effective to separate the building gravity only steel structure from seismic/wind lateral bracing frames. The gravity structure can then be designed as simple construction in accordance with NZS 3404 Steel Structures Standard. In simple construction the bending members may be assumed to have their ends connected for shear only and to be free to rotate. Examples of such connections are shown in figure 1. In beams and column frames for which simple construction is assumed, there will none the less be bending moments acting on the columns which are caused by eccentricity of the beam reactions.

Angle sections are commonly used as members in light weight triangulated structures such as trusses and towers. The attraction of angle section is their ease of fabrication, they are however more complex to design than other types of structural sections. The reasons for this is the eccentricity of the common forms of end connections (figure 1) and also because the principal axes of a single angle do not coincide with the axis of the frame or truss of which the angle is a part (Temple et al, 1995).

All steel members which form part of a seismic resisting frame are classified into one of 4 categories for the purpose of seismic design. Category 1 members are capable of sustaining high displacement ductility demands. Category 2 members are capable of sustaining low ductility demands. Category 3 members are capable of developing their nominal section capacity where required to in bending. Category 4 members need not be designed to sustain any displacement ductility demand. Limits are placed on member section geometry for the various categories and this is found in section 12.5 of the Steel Structures Standard (SNZ, 2007). Previous tables have been developed classifying I section members into the appropriate categories (Feeney, 1993). These tables were developed based on the 1992 version of the Steel Structures Standard . Hot rolled steel sections classified were grades 250 and 350. Welded sections classified were limited to WB and WC sections. This article updates the Member ductility category of I sections for seismic design tables for Grade 300 welded sections in accordance with the latest Steel Structures Standard (SNZ, 2007).

All steel members which form part of a seismic resisting frame are classified into one of 4 categories for the purpose of seismic design. Category 1 members are capable of sustaining high displacement ductility demands. Category 2 members are capable of sustaining low ductility demands. Category 3 members are capable of developing their nominal section capacity where required to in bending. Category 4 members need not be designed to sustain any displacement ductility demand. Limits are placed on member section geometry for the various categories and this is found in section 12.5 of the Steel Structures Standard (SNZ, 2007). Previous tables have been developed classifying I section members into the appropriate categories (Feeney, 1993). These tables were developed based on the 1992 version of the Steel Structures Standard . Hot rolled steel sections classified were grades 250 and 350. Welded sections classified were limited to WB and WC sections. This article updates the Member ductility category of I sections for seismic design tables for Grade 300 hot rolled sections in accordance with the latest Steel Structures Standard (SNZ, 2007).

This article provides general guidance on applying the lateral restraint provisions for yielding regions given in Clause 12.6.2 of NZS3404 (SNZ, 2007) to columns and beams of multi-storey buildings. It includes simplification of those provisions which can be made when designing these types of member.

The New Zealand Steel Structures Standard (SNZ, 1997), in keeping with many international design standards has no minimum stiffness requirement for restraints systems preventing flexural-torsional buckling of steel sections bent about their major axis. To account for restraint system flexibility, NZS3404 categorises these systems as providing full or partial restraint. In the commentary to the Steel Structures Standard guidance is provided for roof rafters for the minimum ratio of purlin depth to rafter depth to ensure a lateral restraint system fully restrains the section. No such guidance is provided to allow designers to check that the restraining system is sufficiently rigid to provide at least partial restraint. This is particularly relevant for the bottom critical flanges of deep roof rafters restrained by a flexible tension side system in conjunction with full depth stiffeners (Figure 2). In this paper guidance is provided for structural engineers to help them address this situation.