Vol 2 No 1 (2023)

• Research on air pollution characteristics and planning strategy of urban street environment

  Shen Yang, Qingming Zhan, Liu Wen

  Dense buildings in modern cities make street pollutants more and more difficult to disperse, and the exposure level of urban residents to pollutants has increased significantly. This study focuses on the spatial and temporal distribution of ambient air pollution in urban streets and the relationship between street morphology and pollutant dispersion, and explores ways to reduce ambient air pollution in streets through spatial design. The study used the CityGrid urban grid data monitoring station to conduct an empirical study on an urban trunk road in Wuhan during the winter of 2020 to 2021, monitoring pollutants including NO₂, O₃, PM_2.5, and PM₁₀. The results showed that pollutant concentration changes in the near-road environment are affected by a combination of meteorological elements and traffic flow characteristics. The wind parallel to the road is more favorable to evacuate pollutants inside the street canyon, and the ambient wind above the canyon perpendicular to the road causes vortices in the canyon that cause gaseous pollutants to accumulate on the leeward side of the canyon. The distribution of particulate pollutants is mainly related to the distance of road pollutant sources. Building access ventilation can effectively evacuate street pollutants, and NO₂ and O₃ decay to stable levels in shorter distance from the road than PM_2.5 and PM₁₀ in downwind direction. The future urban street planning can effectively alleviate street pollution levels through strategies such as street canyon morphology control, green landscape facilities arrangement, increasing the building interface opening, and building bottom overhead.

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• Verification of seismic enforced-displacement pushover procedure on torsionally flexible, asymmetric, multi-storey r/c buildings

  Triantafyllos Makarios, Athanasios Bakalis

  A recently proposed direct Displacement-based procedure of nonlinear static (pushover) analysis on multi-storey reinforced concrete (r/c) buildings is verified here against the results of Nonlinear Response History Analysis. An asymmetric, regular in elevation, torsionally flexible, multi-storey r/c building designed according to Eurocode EN 1998 is investigated. Taking fully into account the inelastic torsion and the higher mode effects, as well as the P-Delta effects, the proposed procedure applies a pattern of seismic floor enforced-displacements along on the “Capable Near Collapse Principal Axes of the building”, aiming at Near Collapse state.  The envelope of the results of sixteen final non-linear static analyses on the investigated building shows that the main aspects of the spatial seismic action effects can be safely captured by the proposed procedure, especially regarding the inelastic interstorey drift ratios, as well as the plastic mechanism of the building.

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• Tutorial on the use of Finite Element Modelling with Abaqus and Tosca for Topology Optimization of Steel

  Tiago Ribeiro, Luís Bernardo, Ricardo Carrazedo

  Finite Element Method (FEM) is widely employed for solids and multiphysics problems analysis in practically all engineering and science fields. Yet, when it comes to Topology Optimization (TO), significant issues arise concerning the geometry, hence the mesh, and non-stationary condition. Contrarily to broader Finite Element Modelling, FEM for TO has much less bibliographic support and research. Herein we depict, apply and discuss the major challenges and options concerning modelling with finite elements within TO problems. It is shown that, for the optimization of a steel connection part, mesh refinement is critical for effective yet computationally efficient analysis. Moreover, a case-based and user-friendly approach, in the form of tutorial, is proposed to address the practical FE meshing for TO.

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• Comparison between the life cycle carbon footprint of refurbished and new buildings: A case study of Community centre

  Fadoua Zhour, Mawada Abdellatif, Yassin Osman, Denise Lee

  Buildings are a huge carbon emitter. Efforts are being made to cut both embodied and operational carbon emissions to reduce the impact on the built environment. This study aims to compare the Life Cycle Carbon Footprint (LCCF) and LCC of two alternatives: refurbishment and radical replacement of an existing community centre building in Liverpool to identify options that could achieve significant CO2 emission reductions in an economically viable way. The calculation methods are standardised by the UK's RICS (Royal Institute of Chartered Surveyors) to overcome the limitations of LCAs undertaken in previous research. This refers to the Inventory of Carbon and Energy (ICE) database from which embodied calculation factors were extracted to get the greenhouse gases. While the operational emissions data were obtained from a thermal simulation through IES software. The results of this study showed that the refurbishment scenario is the best option since it emits 50% less GHG and reaches 64% lower costs compared to the new build case throughout the building’s life cycle. Such that the LCCF of the refurbishment scenario was 215,084.36 kgCO2e/m2 and its LCC £ 88,135.32, while the replacement scenario achieved 429,397.44 kgCO2e/m2 and £ 246,213.59. It can be deducted that to reach significant reductions in carbon emissions rates with a lower economic impact, refurbishment is preferable to demolition and new construction, even if the building shows several damages and defects, which suggests that the UK government should incentivise and encourage re-use for faster environmental rehabilitation.

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