Does function align with expansion? Revisit urban sprawl by comparing the morphological and functional concentricity of 35 major cities in China

Conventional metrics of urban sprawl, largely derived from low-density suburbanization, fail to capture an emerging pattern in China characterized by compact expansion with limited functional utilization. Addressing this gap, this study reconceptualizes urban sprawl as a spatial accumulative decoupling between urban morphology and urban function along the urban–rural gradient. Using a concentric partitioning framework, we quantify and compare morphological and functional concentricity across 35 major Chinese cities based on multiple cross-sectional datasets. Results show that functional concentricity is stronger and more robust than morphological concentricity, indicating a systematic decoupling between physical expansion and socio-economic activity on urban–rural gradient. This mismatch gradually intensified toward urban peripheries in most cities, revealing an accumulation of underutilized built space. Nevertheless, the utility efficiency of buildings does not show a robust decline on the urban–rural gradient. These findings reveal a distinctive pattern of sprawl in contemporary China characterized by high-density development coupled with functional insufficiency, fundamentally different from low-density sprawl in the context North America. By reframing sprawl as a morphology–function mismatch rather than a density-based phenomenon, this study provides a conceptually grounded and comparable metric for diagnosing excessive expansion, with implications for land supply regulation, infill prioritization, and fiscal risk management in excessive urban expansion.