The mechanism of block form diversification in urban morphological transformation: Case study of grid blocks in Beijing, China

Beijing is a typical traditional city in China, originating from the uniform and conventional grid plan, but transformed diversely, either on purpose or spontaneously. This research took the diversification process of grid blocks as an angle to understand the transformation process of Beijing's urban morphology. It took 194 grid blocks within the 3rd Ring Road of Beijing as research objects. First, the paper proposed a whole view of Beijing's grid blocks by 1) visualizing their construction process, 2) classifying 5 morphological clusters by 7 indicators (Block size, Block shape regularity, Intensity, Coverage, Network density, Plot shape regularity, Standard deviation of plot size), and 3) investigating their distribution. Second, the diversification process of grid blocks was clarified from two layers: the block-boundary layer and the inner-space layer. Finally, the mechanism of block form diversification was clarified by exploring the connections between elements in each layer, and the influence of urban development on block form transformation. The study re-defined the diversification process in a more quantitative way from both time and spatial dimension. It concluded that the diversification is influenced by changes in urban planning principles and locations, and emerged thorough the long-term transformation and re-subdivision. The interaction between the boundary and the inner space stimulates the diversification. And based on these, it concluded with a discussion of limitations and potentials on grid blocks' construction and renovation.