Beijing Urban Construction Design & Development Group (China)

China’s rapid urbanization has generated substantial low-strength demolition waste, creating significant environmental and disposal challenges. Recycling this waste as subgrade filler provides a viable solution given the subgrade’s lower strength requirements and high consumption capacity. This study systematically evaluated the feasibility of using unsorted rural demolition waste (URDW) as subgrade filler without separation to improve recycling efficiency. Three gradations (FF20, MF40, and CF80) with maximum particle sizes of 20, 40, and 80 mm were designed based on the characteristics of the raw materials. The composition, compaction behavior, particle breakage mechanisms, and mechanical properties of these fillers were analyzed. The experimental road subgrade employed FF20, with model tests assessing long-term performance under wet–dry (WD) cycles and field evaluations combining quality tests with settlement monitoring. Results showed that increased particle size reduced the combined content of bricks and mortar (CCBM) while raising that of concrete and stones (CCCS) in the raw materials, demonstrating particle size effects on material strength. This explains the decreasing CCBM and increasing CCCS from FF20 to CF80. Heavy compaction produced elevated particle breakage rates (Br) and irregular compaction curves, whereas surface vibration compaction generated standard curves with significantly reduced Br. Although filler compositions varied, particle size and coarse content primarily controlled Br variation during compaction. The FF20 subgrade model exhibited minimal compressive deformation under WD cycling, with transitional deformation progressively diminishing as cycling enhanced the model’s deformation resistance. After cycling, the saturated FF20 model maintained a resilient modulus (MR) above regulatory requirements. Field tests confirmed FF20-filled subgrade complies with specifications for compaction degree, deflection, and MR in both dry and saturated conditions. Forty-month monitoring recorded only 1.64 mm centerline compression, validating satisfactory deformation resistance. This study broadens potential applications for URDW and provides practical guidelines for similar projects.

Urban mental health is increasingly influenced by daily environmental exposures, yet limited empirical evidence exists regarding how the spatial configuration of blue–green environments, rather than their mere quantity, relates to emotional behavior in high-density cities. Guided by restoration theories and a perception-based perspective on landscape integration, this study analyzes the urban core of Shanghai by linking blue–green configurations to emotional states inferred from 20,907 geotagged social media facial photographs. Facial expressions serve to derive indices for emotional valence and arousal. The results demonstrate significant spatial clustering of emotional behavior, where hotspots are concentrated in higher-quality and more open settings, while coldspots cluster in dense areas with sparse vegetation. Emotional behavior also exhibits demographic heterogeneity, as females display higher valence and arousal than males. Furthermore, happiness tends to increase with age across both genders, whereas arousal declines specifically among male age groups. Crucially, emotional outcomes align more consistently with landscape integration and configuration than with isolated blue or green areas. Factors such as high connectivity, superior vegetation condition, and configurations featuring water embedded within green space are associated with favorable emotional responses. Conversely, extensive edge-dominated interfaces and high traffic exposure correlate with less favorable outcomes. These findings suggest a shift in blue–green planning from increasing total area toward optimizing spatial composition. Specifically, priority should be given to embedded and cohesive designs alongside the reduction of ambient stressors to foster emotionally supportive environments in dense urban cores. Methodologically, image-derived behavioral traces provide a scalable and ecologically grounded approach for investigating place-based affect at a city scale.

ABSTRACT This paper presents a distributionally robust tube‐based model predictive control method for nonlinear systems affected by external random disturbances. The reference trajectory is computed by solving a rolling optimization problem for the nominal system, while an auxiliary controller with chance constraints is solved in real time to guarantee that the trajectory of the disturbed system remains within an invariant tube centered on the reference trajectory. Since the distribution information of disturbances is unknown, a distributionally robust ambiguity set is constructed based on disturbance samples collected online to reformulate the chance constraints, thereby ensuring that the state of the disturbed system satisfies the state constraints with a certain probability. It is demonstrated that this method can ensure the disturbed system remains stable, with its state staying near the reference trajectory. Furthermore, its robustness and compliance with constraints have been validated on a nonlinear continuous stirred‐tank reactor.

Aiming to address the limitations associated with conventional cut-and-cover metro stations that utilize cast-in-situ reinforced concrete structures, this study proposes an optimized design method for a semi-prefabricated UHPC-RC metro station structure, which integrates ultra-high performance reinforced concrete (UHPC) as permanent formwork with conventional cast-in-situ reinforced concrete (RC). The optimization scheme and construction method of the semi-prefabricated UHPC-RC metro station are elaborated. Finite element analysis (FEA) was employed to evaluate the stress, damage, and deformation of the longitudinal beams, floor slabs, and sidewalls of the prefabricated UHPC-RC structure under various loading conditions. Furthermore, bending and shear capacity, as well as crack resistance, were verified for the longitudinal beams, slabs, and side walls. The results demonstrate that, compared to conventional cast-in-situ RC metro stations, the proposed semi-prefabricated UHPC-RC metro station features reduced structural dimensions, the thickness of the roof and the middle plate is reduced by 11.8% and 12.5% respectively, the overall project scale is reduced by 1.8%, and the space utilization rate is increased by 0.8%. In the finite element calculation of the design load in the construction stage and operational stage, the UHPC-RC shell structure exhibits minimal plastic damage, and the maximum settlement is 4.62 mm. The main structural components meet the requirements of the specification, and the structural safety reserve is about 1.2 ~ 1.8 times that of the conventional cast-in-situ RC station structure. The proposed semi-prefabricated UHPC-RC metro station offers an innovative and viable solution for metro station construction.

Urban renewal is profoundly reshaping the appearance and social role of historic districts. How to achieve rational utilization while protecting them has become a core issue for sustainable development. Traditional single-mode protection focuses on static maintenance, which is insufficient to meet the real-world needs of the diversified transformation of district functions. By establishing a comprehensive value assessment framework for historic districts, researching effective strategies for revitalizing their physical spaces under the premise of protection, and exploring innovative new models for sustainable cultural and ecological development, we can achieve the dual benefits of effective inheritance of heritage value and revitalization of regional space.

Against the backdrop of global rural decline and China’s Rural Revitalization Strategy (2017–2050), this study examines the spatial form evolution and development mechanism of Central Village in Huotong Town, Ningde. To achieve this, it employs field surveys, spatial mapping, and hierarchical element analysis to analyze the village’s scale, architectural texture, street interfaces, and landscape nodes. Results show three evolutionary stages: pre-2017 traffic-guided disorderly expansion, 2017–2020 policy-driven orderly planning, and post-2020 stock optimization, forming an “oval radial” structure constrained by the southern hills and Huotong River. The spatial structure shifted from a “kinship-based agglomeration” to a multi-center model, yet contradictions like historical texture damage and excessive street commercialization emerged. Its development is driven by four linked factors: policy, the market, socio-culture issues, and nature. This study offers references for similar rural settlements’ spatial planning and sustainability.

Due to the discrete deterioration characteristics of timber sleepers on open bridge deck, continuous replacement is difficult. New bamboo-based composite sleepers (BCSs) offer excellent performance at a low price, making them an ideal alternative to timber sleepers. Therefore, this study focuses on the mechanical properties and safety of the interspersed replacement of timber Sleepers with BCSs. A static model of the open deck track and a vehicle-track coupling dynamic model were established to precisely analyze the influence of 1 in 2, 1 in 3, and 1 in 4 interspersed replacement, as well as full replacement with BCSs on the force and deformation of the track structure and the dynamic characteristics of the vehicle-track system. After the interspersed replacement of timber sleepers with BCSs, the sleeper compression, sleeper vertical displacement, and gauge reduction were decreased; however, the sleeper bending moment, vehicle acceleration, wheel-rail force, and bridge deck acceleration were slightly increased. At the longitudinal beam support, the BCSs showed a negative bending moment, with compression at the bottom and tension at the top. The maximum tensile and compressive stresses were 4.87 MPa and 7.97 MPa, respectively, which are both below the allowable stress of the material—meeting the strength requirements for BCSs. Although the interspersed replacement of timber sleepers with BCSs leads to uneven track stiffness, the track deformation, stress distribution and dynamic response remain within acceptable limits. This research provides new ideas for track structure upgrades and maintenance strategies.