The prevention strategies for strengthening the resilience of urban high-rise and high-density built environment based on multi-objective optimization: An empirical study in Guangzhou, China

The effective resistance and rapid recovery from external environmental risks has risen to be a social challenge in the accelerated urbanization process of China. However, the current measures for urban high-rise and highdensity core area with high-volume pedestrians and high pollution are often focused on one-dimensional means, which cannot meet the multi-objective demands simultaneously. Therefore, this paper is aimed to explore a prevention-oriented route - a vertical pedestrian system for high-rise buildings based on scheme phase, with multiple objectives optimization of strengthening the ability of ecological order restoration and assisting occupants in recovering psychological and physiological injury from high-density environment in a relative fast speed. The feasibility and effectiveness have been verified by a complete technology route of scheme selection, numerical simulation and field measurements. The results show that, first, after the integration of secondary ground pedestrian system (SGPS) basic unit, the average predicted mean vote (PMV) improves 75.45%, the average air temperature declines 2.75 degrees C, and the average spatial integration increases 35.35%. Second, the optimal range of unit height difference in SGPS under hot-humid climate condition is suggested to be 6-9 storeys. Third, compared with single-sided "E-type" connection, the thermal comfort improves 70.49% and the indoor average PMV is optimized by 2.56%, with a more stable wind speed by using bilateral alternating "S-type" connection. Finally, compared with connections among low-integrated secondary ground units, the average integration is up to 6.98% with visual and path links of high-integrated-orientation. This paper objectively answers the question of whether and to what extent the combination of vertical greening and walking system contributes to ecological order restoration, which provides a new orientation for exploring the routes of maintaining urban ecological stability and optimizing environmental structure.