• Energy Research

Wind characteristics (e.g., mean wind speed, gust factor, turbulence intensity and integral scale, etc.) are quite scattered in different measurement conditions, especially during typhoon and/or hurricane processes, which results in the structural engineer ambiguously determining the wind parameters in wind-resistant design of buildings and structures in cyclone-prone regions. In tropical cyclones (including typhoons and hurricanes), the inconsistent wind characteristics may be in part ascribed to the complex flow structure with the coexistence of both mechanical and convective turbulence in the boundary layer of tropical cyclones. Another significant contribution to the scattered wind characteristics is due to various measurement conditions (e.g., terrain exposure and height) and data processing schemes (e.g., averaging time). The removal of the inconsistency in the field-measurement system may offer a more rational comparison of measured wind data from various observation platforms, and hence facilitates a better identification scheme of the wind characteristics to guide the urban planning design and wind-resistant design of buildings and structures. In this study, an analytical framework was firstly proposed to eliminate the potential observation-related effects in wind characteristics and then the wind characteristics of seven field measured tropical cyclones (four typhoons and three hurricanes) were comparatively investigated. Specifically, field measurements of wind characteristics were converted to a standard reference station with a roughness length of 0.03 m, observation duration of 10 min for mean wind and averaging time of 3 s for gusty wind at a 10 m height. The differences of the measured wind characteristics between the typhoons and hurricanes were highlighted. The standardized turbulent wind characteristics under the analytical framework for typhoons and hurricanes were compared with the corresponding recommendations in standard of American Society of Civil Engineers (ASCE 7-10) and Architectural Institute of Japan Recommendations for Loads on Buildings (AIJ-RLB-2004).

Heavy-duty diesel truck (HDDT) is one of the major sources of air pollution and energy consumption. To reduce the estimation bias and improve the interpretability, the random parameters logit (RPL) model was employed to examine the effects of influencing factors on fuel consumption of HDDTs in the real world. The unobserved heterogeneity effects varying across the samples on fuel efficiency were extracted from the long-term daily trip-based data. In order to further illustrate the advantages of the RPL model in explaining the impacts of factors, a fixed parameters logit model with twenty parameters was constructed and compared. The Akaike information criterion and the Bayesian information criterion were used to select a more reasonable model structure. The findings show that the RPL model performs better and the unobserved heterogeneity would affect the effects of factors of rolling without engine load proportion and temperature and, consequently, map the level of fuel consumption. This reveals the variability of the fuel consumption among the samples. Driving compensation effects were also identified in this study (i.e., the drivers tend to perform the fuel-saving operations in adverse driving circumstances and vice versa). The methodology proposed in this paper can provide a new insight for researchers to identify the instability of energy-related factors under real road conditions. Future research could be implemented to assess the similar effects of alternative fuel vehicles.

Abstract To ensure acceptable performance for survivability, serviceability and habitability of the mega-tall buildings, it is necessary to study their wind-induced response characteristics and vortex-induced resonance mechanism. In this study, the wind-induced responses of a thousand-meter-scale four-tower-connected mega-tall building are investigated using the aeroelastic model test in a boundary layer wind tunnel. The results show that the root mean square across-wind tip displacement increases dramatically within a certain wind velocity range at 60°wind direction, which indicates that the vortex-induced resonance occurs. Accordingly, the relation between the aerodynamic damping ratio and reduced wind velocity is further studied at this wind direction. Furthermore, the underlying mechanism of vortex-induced vibration (VIV) is comprehensively discussed based on the amplitude spectra of the across-wind tip displacements, which facilitates the identification of corresponding lock-in region. The identified critical reduced wind velocity for vortex-induced resonance for the mega-tall building is 10.19, with a lock-in region from 10.19 to 11.70. In addition, the VIV-like phenomenon occurred in the along-wind direction for this complex mega-tall building, associated with VIV in the across-wind direction. This observation indicates that there is aerodynamically coupled vortex shedding of the mega-tall building in the two directions. This study contributes to a detailed insight of the VIV phenomenon for the thousand-meter-scale four-tower-connected mega-tall building, and hence facilitates the wind-resistance design of this type of flexible structures.