20826Structural Steel Design Requirements Guide [36

20.8.2.6.1 Limiting Width-to-Thickness Ratios

For capacity-protected components, width-thickness ratios of compression elements shall not exceed the limiting value 1r as specified in Table 20.13. For ductile components, width-thickness ratios shall not exceed the 1p as specified in Table 20.13. Welds located in the expected inelastic region of ductile components are preferably complete penetration welds. Partial penetration groove welds are not recommended in these regions. If the fillet welds are only practical solution for an inelastic region, quality control and quality assurance inspection procedures for the fracture critical members shall be followed (Figure 20.27).

20.8.2.6.2 Limiting Slenderness Ratio

The slenderness parameter 1c for compression members and Ab for flexural members shall not exceed the limiting values, Acp and !bp, as specified in Table 20.14, respectively.

20.8.2.6.3 Limiting Axial Load Ratio

High axial load in a column usually results in the early deterioration of strength and ductility. The ratio of factored axial compression due to seismic load and permanent loads to yield strength (AgFy) for columns in ductile moment-resisting frames and single-column structures shall not exceed 0.3.

20.8.2.6.4 Shear Connectors

Shear connectors shall be provided on the flanges of girders, end cross-frames, or diaphragms to transfer seismic loads from the concrete deck to the abutments or pier supports. The cross-frames or diaphragms at the end of each span are the main components to transfer the lateral seismic loads from the deck down to the bearing locations. Recent tests on a 0.4 scale experimental steel girder bridge (18.3 m long) conducted by University of Nevada, Reno [69] indicated that too few shear connectors between the girders and deck at the bridge end did not allow the end cross-frame to reach its ultimate capacity.

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