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Numerous transmission towers have collapsed due to experiencing strong winds; therefore, the purpose of this article is to investigate the collapse mechanism and the anti-collapse performance of a long-span transmission tower–line system. The detailed finite element model of a typical tower–line system is established in ABAQUS. A global damage index is proposed to quantitatively estimate the overall damage of the structure and define the collapse criteria. An incremental dynamic analysis is performed to obtain the collapse mechanism and the ultimate capacity of the structure. Subsequently, a fragility analysis for evaluating the anti-collapse performance is conducted due to the uncertainty of wind loads. Eventually, the influence of the wind attack angle and the length of the side spans on the fragility is discussed. The results demonstrate that the proposed global damage index is capable of quantitatively reflecting the overall damage and assessing the ultimate capacity of the structure. In addition, the uncertainty of the wind load has a significant influence on the ultimate capacity and the failure position. Furthermore, the results reveal that the wind attack angle and the length of the side spans have an apparent effect on the fragility of the structure.

Water pollution and water shortage are two of the most important environmental problems in Beijing, China. Water quality of rainfall from July to August 2011 and runoff from a felt roof and an asphalt road were analyzed chemically and further investigated because these are potential sources for augmenting city supplies. Results indicate that chemical oxygen demand (COD Cr ), total phosphorus (TP), total nitrogen (TN), and ammonia nitrogen (NH 4 þ -N) concentrations of initial runoff from roofs and roads all exceeded the Class V surface water quality standard developed by the Ministry of Environmental Protection of the People's Republic of China (MEP). COD Cr concentration from road surfaces was more than 313.55 mg/L at the initial runoff stage, decreasing asymptotically to lower levels with increased rainfall duration. There is strong correlation between COD Cr , TP, TN concentrations and that of total suspended solids in road runoff. Runoff from roofs, after treatment by grid filter, flocculation and sedimentation, can be used as city municipal and domestic water except during the initial runoff stage. However, runoff from road surfaces cannot be directly reused.For city planning, this conclusion may benefit the promotion of rainwater as a renewable water supply, and avoid flooding and water scarcity.