## 4 Discussion  
### Interference Effects of Wind Loads  
To investigate the interference effect, container cranes were arranged in a line, similar to their arrangement in ports and terminals. To study the interference effect more quantitatively, we introduced the interference factor [38] (IF, also known as buffeting or shielding factor) to assess the interference effects imposed by the surrounding structures quantitatively:  
\[IF=\frac{F_{\mathrm{g}}}{F_{\mathrm{i}}} \tag{15}\]  
where \(F_{\mathrm{g}}\) and \(F_{\mathrm{i}}\) represent the force on a group-arranged building considering the IE and force on an isolated building, respectively. IF < 1 means that the IE will reduce the wind load of the crane. IF > 1 means that the IE will increase the wind load. We calculated the mean interference factor (MIF), dynamic interference factor (DIF), and extreme interference factor (EIF) by force or moment coefficients \(\overline{C}_{\lambda}\), \(\widetilde{C}_{\lambda}\), and \(\hat{C}_{\lambda}\) defined previously. The _MIF_ of the group-arranged cranes with \(S/H\) = 0.484-1.211 for both states are demonstrated in Figures 13 and 14. It was found that the minimum _IF_ is 0.6 and 0.7 when \(\alpha\) = 90\({}^{\circ}\) with minimum spacing for boom-down and boom-up states, respectively. A more significant and larger influence range was found in boom-down cranes compared with the corresponding cases of boom-up cranes, noting the factor is always smaller in the boom-down state. The IE is more dominant on crane 3# as compared to crane 2# because of the presence of one more upstream structure. The factor reduces by 13% and 18% as a windward shielding crane locates when \(\alpha\) = 90\({}^{\circ}\) with minimum spacing. This influence becomes less dominant as wind direction deviates 90\({}^{\circ}\). In addition, as the spacing changes larger, the influence range of the interference effect became smaller and less dominant. As for crane 2#, an interference effect can be observed in \(\alpha\) = 30\({}^{\circ}\)-150\({}^{\circ}\) when \(S/H\) = 0.484, while the range shrinks to about 60-120\({}^{\circ}\) for the boom-down crane. A similar tendency can also be determined in crane 3# and boom-up state. However, crane 1#, the upstream one, is not affected by the interference effect regardless of the nondimensional spacing and crane state. The IF of these cases is always around 1.0. Tables 5-7 provide the maximum values of MIF, DIF, and EIF as well as the occurrence cases under different nondimensional spacings. The following findings can be observed:  
1. For the mean wind load, the maximum interference factor occurred in boom-down crane 1# for \(S/H\) = 0.484. The amplification of the mean wind load is not dominant in the case of group-arranged cranes, indicating that the influence of the interference effect on the mean wind load can be neglected;  
Figure 12: Validation of the simulated base shear force. For the dynamic wind load, the DIF of the boom-down cranes is always high, which is similar to the distribution of EIF values. In addition, the maximum DIF always occurred when \(\alpha=165^{\circ}\). Amplification of the wind loads is observed in some cases of boom-down cranes, especially for crane 3#, and the effect became more dominant as the spacing became smaller. However, the IE is negligible among boom-up cranes;
3. The interference effect is more obvious in the DIF and MIF. Values of the three IF exhibited different distributions. The value of the DIF is higher and the maximum is 1.24, indicating fluctuating wind loads may increase more than 20% for the boom-down crane 3#;
4. Though the RMS and peak wind forces are amplified in some cases, the most unfavorable case in terms of the peak wind force coefficients do not change significantly. It attributes that the most unfavorable cases are always the cases in which IE reduces the wind loads. To explain the phenomenon and mechanism of IE on the group-arranged cranes, two cases of \(\alpha=30^{\circ}\) and \(90^{\circ}\) with minimum spacing are shown in this section.