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Step 2: Structural modeling. Each column is modeled with one element and beam with two elements. The distributed gravity loads are converted to equivalent concentrated loads on the beam, as shown in Figure 5.45. In explicit imperfection modeling, the geometric imperfection is obtained by multiplying the column height by 0.002. In the equivalent notional load method, the notional load is 0.002 times the total gravity load plus the lateral load. In the further reduced tangent modulus method, the program automatically accounts for geometric imperfection effects. Although users can choose any of these three models, the further reduced tangent modulus model is the only one presented herein. The incremental loads are computed by dividing the concentrated load by the scaling factor of 20.

Step 3: Analysis. The three parameters of the connections can be computed by the use of the computer program 3PARA. Corresponding to the input format in Table 5.2, the input data, CONN.DAT, may be generated, as shown in Table 5.10.

Referring to the input instructions (Section 5.5.4), the input data are written in the form shown in Table 5.11. Programs DATAGEN, INPUT, and PAAP are executed sequentially by typing "RUN." The program will continue to analyze with increasing load steps up to the ultimate state.

Step 4: Check of load-carrying capacity. As shown in output file, P.OUT2, the ultimate load-carrying capacities of the load combinations 1 and 2 are 46.2 and 42.9 kip, respectively, at nodes 7-13 (Figure 5.45). Compared to the applied loads, 45.5 and 31.75 kip, the initial member sizes are adequate.

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