## 3 Research, Results, and Discussion  
### Design of Model Steel Ordinary Moment Frames with Consideration of the Level of Wind Loads  
In this study, to evaluate the seismic performance of steel OMFs, model office buildings with different structural heights were designed: 9-, 12-, 15-, and 18-story OMFs. Moment frames are economically effective for buildings up to 25 stories, above which their resistance is costly to control. In addition, member sections in OMFs with more than 18 stories could  
Figure 1: Methodology of this study. not be chosen from the section tables provided in the AISC steel construction manual [31]. Thus, this study considered OMFs with 18 or less stories. The W-shaped sections provided in the AISC steel construction manual [31] are used for the OMFs. The plan and elevation of the 15-story model OMF buildings are shown in Figure 2. OMFs are denoted with thick solid lines, which are placed along the perimeter of the building (Figure 2a). The span length is 6.1 m and the height of the first story is 4.6 m, whereas the story height for other stories is 4.0 m. It is assumed that the column splices are located in the middle of the column for every two stories except the first story, as shown in Figure 2b-d. ETABS software [32] is used for the analyses and design. The OMFs were designed according to ASCE/SEI 7-16 [1], ANSI/AISC 360-16 [2], and ANSI/AISC 341-16 [3]. The response modification coefficient (\(R\)), overstrength factor (\(\Omega_{0}\)), and deflection modification factor (\(C_{d}\)) for the steel OMFs are 3.5, 3.0, and 3.0, respectively, according to ASCE/SEI 7-16 [1]. The risk category and importance factor (\(I_{e}\)) are assumed as II and 1.0 according to ASCE 7-16 [1], respectively. Design earthquake spectral response  
Figure 2: Plan and elevation of 15-story steel OMFs: (**a**) plan view; (**b**) elevation of 15-story W0-OMF; (**c**) elevation of 15-story W44-OMF; (**d**) elevation of 15-story W51-OMF. acceleration parameters at short period (\(S_{DS}\)) and 1-s period (\(S_{D1}\)) are defined as 0.499 and 0.199, respectively. The seismic design category (SDC) of the buildings is classified as \(C_{max}\). The dead, cladding, and live loads of typical office buildings are 4.31 kN/m\({}^{2}\), 1.20 kN/m\({}^{2}\), and 2.40 kN/m\({}^{2}\), respectively [12]. The steel material used in the design is ASTM A992 Gr.50 steel, which has a specified minimum yield strength (\(F_{y}\)) of 345 MPa and a specified tensile strength (\(F_{u}\)) of 450 MPa. The seismic loads were determined using the equivalent lateral force (ELF) procedure. To investigate the effect of wind loads on seismic collapse performance and seismic loss for steel OMFs, 9-, 12-, 15-, and 18-story steel OMFs are repeatedly designed for (1) gravity load + seismic load (W0-OMFs), (2) gravity load + seismic load + wind load (wind speed = 44 m/s) (W44-OMF), and (3) gravity load + seismic load + wind load (wind speed = 51 m/s) (W51-OMF). The basic wind speeds of 44 m/s (100 mph) and 51 m/s (115 mph) are the values assigned for most areas over the wind hazard map provided in Section 26.5 of ASCE/SEI 7 [1]. Wind loads were determined using basic wind speed with a mean recurrence interval (MRI) of 700 years, according to Figure 26.5-1B of ASCE 7-16. The exposure category of B was used for the OMF buildings because the model buildings were assumed to be located in urban and suburban flat areas. As seen in Figure 26.5-1B of ASCE 7-16, the basic wind speed for most areas in the USA range from 45 m/s to 51 m/s. In this study, the upper (=51 m/s) and lower bound values (=44 m/s) for the range were considered to assess the effect of wind loads on the seismic performance of OMFs. The exposure category is defined as B, assuming that the model buildings are located in the urban or suburban flat area. Table 1 summarizes the fundamental periods (\(T_{1}\)) of the model OMFs. As expected, \(T_{1}\) tends to increase as the height of OMFs increases.