Experimental characterization of the constitutive materials composing an old masonry vaulted tunnel of the Paris subway system

A significant proportion of the Paris metro tunnels comprise a masonry vault built out of stone blocks and mortar joints, and sidewalls and slabs made of unreinforced concrete. In order to provide the necessary data for future structural evaluation, an extensive laboratory testing programme has been conducted to characterize the materials of the tunnel separately, i.e., mortar, stone, and concrete. The tests, carried out on specimens taken from cores extracted from a 1930s tunnel, enabled to determine the mechanical properties, including direct tensile, shear strength, and mode I fracture energy, as well as the properties of the stone-mortar interface. Results show that the masonry mortar joints could reach 10 cm in width, and that blocks of stone varied in composition and porosity, thus producing a wide range of mechanical properties. The concrete was composed of large-sized aggregates and showed low stiffness and strength. Based on these experimental results, ratios between mechanical characteristics are hereby proposed. Perspectives on the use of this experimental data in a finite element model are then discussed.     

地铁站点可达性、客流与站点商圈零售商业结构关系研究——以广州市为例

地铁与城市商业地域的结构存在极大关系。实地调查获取广州15个地铁站点商圈零售商业营业面积、地铁网络等数据,利用栅格分析方法计算不同地铁站点的可达性程度的差异性。运用回归模型分析不同地铁站点可达性、客流与站点商圈零售商业空间结构的相关关系。以广州天河市级商业中心为例,微观上分析地铁站点客流对商业中心空间结构的影响。结果表明:地铁站点交通可达性、客流量与站点零售商业营业面积存在较强关联性,但换乘站点的可达优势与客流优势在商业上未能完全体现;地铁客流与较高等级的商业存在较大的相关性,而与低等级的商业相关性小,甚至负相关;客流的增加促进了地铁附近的商业形态从传统零售业向更高级业种演化。     

Identifying metro station types based on transfer purposes: An application of bike-sharing data in Xiamen,China

With the networking of urban rail transit and the large-scale development of bike-sharing, metro and bike-sharing connection has become the preferred way of daily travel for residents of Xiamen. Current studies mainly identify metro station types based on node and place orientation, lacking behaviour-based investigation. To fill this gap, this study aims to explore the classification of metro stations based on transfer purposes by combining bike-sharing and point of interest data in Xiamen, using buffer analysis, kernel density estimation, and DBSCAN clustering algorithm comprehensively. The results indicate the following. (1) Distinct transfer purposes have significant agglomeration characteristics and present poly-centric spatial pattern, an authentic portrayal of Xiamen's land use function. (2) The heterogeneity of connection flow between different transfer purposes and metro stations is apparent. The distribution of flow and flow direction within the same transfer purpose is also in non-equilibrium. (3) Based on traffic connection analysis, metro stations are divided into seven types: transportation hub, employment-oriented, residence-oriented, job-housing balance, school-oriented, traffic-tourism integration, and business connection types. The obtained results assist in improving the transportation connection environment, perfecting urban land use planning, and enhancing low-carbon and green travel.