0 1.0 2.0 FIGURE 5.26 Stress-strain relationships for Vogel's frame.

5.3.4 Semirigid Frame

In the open literature, no benchmark problems solving semirigid frames with geometric imperfections are available for a verification study. An alternative is to separate the effects of semirigid connections and geometric imperfections. In the previous sections, the geometric imperfections were studied and comparisons between proposed methods, plastic-zone analyses, and conventional LRFD methods were made. Herein, the effect of semirigid connections will be verified by comparing analytical and experimental results.

Stelmack [36] studied the experimental response of two flexibly connected steel frames. A two-story, one-bay frame in his study is selected as a benchmark for the present study. The frame was fabricated from A36 W5 x 16 sections, with pinned base supports (Figure 5.28). The connections were bolted top and seat angles (L4 x 4 x 1) made of A36 steel and A325 |in.-diameter bolts (Figure 5.29). The experimental moment-rotation relationship is shown in Figure 5.30. A gravity load of 2.4 kip was applied at third points along the beam at the first level, followed by a lateral load application. The lateral load-displacement relationship was provided in Stelmack.

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