Evaluation Of Sustainable Urban Form Based On Complex Adaptive System

Since the concept of sustainable development was put forward in the 1980 s,although the relationship between cities and sustainability has received extensive attention from countries and regions around the world,our cities are still facing such issues as climate change,population skyrocketing,traffic congestion,environmental degradation,and other issues that threaten the safety of the ecosystem and human health.After entering the new century,the accelerated process of urbanization in my country has brought about complex urban problems that have seriously affected the healthy and orderly development of cities.In particular,the complicated problems brought about by the process of urbanization in our country have affected the healthy development of cities.Urban form is the root cause of urban problems which scholars have widely agreed with and point out its importance to the construction of sustainable urban.Therefore,the shaping of a sustainable urban form as an important spatial means of building a sustainable city has been extensively discussed.Based on the original intention of not forgetting to design a beautiful city and keeping in mind the mission of achieving sustainable urban development.This paper conducts research on the nature,evaluation,and optimization of sustainable urban forms,and takes Tianjin as a case city for empirical analysis.The research in this article consists three parts.The first part is the discussion of the essence of sustainable urban form,which is to clarify the core connotation of sustainable urban form and provide a basis for evaluation and optimization.First,analyze the transformation of sustainable urban values in the new era and clarify the fundamental value orientation for current urban research.Secondly,adopt philosophical thinking to analyze the philosophical values contained in sustainable urban form;then,on the base of defining the elements of sustainable urban form and analyzing its sustainable effects,establish the internal relationship between philosophical views and form elements,and use form elements as implementation object of philosophical views;finally,made the above analysis as foundation,the essence of sustainable urban form is obtained and analysis its enlightenment on the evaluation content and optimization strategy of sustainable urban form.The second part is the theoretical and empirical discussion on the evaluation content and quantitative methods of sustainable urban form.As the core research contents of this article,it is to clarify the sustainability performance of urban form.Taking the theory of complex adaptive systems(CAS)as the theoretical basis for the evaluation,and on the base of analyzing the applicability of the theory to the evaluation of sustainable urban form,this paper proposes the evaluation content,quantification method and result judgment of sustainable urban form.The evaluation content includes five aspects: evaluation of non-linear characteristics of sustainable urban form,assessment of form spatial mobility,assessment the form coordination of partial and overall,assessment of form diversity,and assessment of advantages of form element identification.The quantitative methods determined are as follows:(1)Using fractal theory as a technical method to evaluate the non-linear characteristics of morphology,and on the base of elaborating the technical applicability,using a method that combines the difference with the ideal fractal dimension value and the significance test of the actual fractal dimension value to evaluate the non-linear characteristics of the sustainable urban form;(2)Based on the spatial syntax technology,on the basis of elaborating the technical applicability,using the concept of spatial efficiency based on the degree of integration and selectivity to evaluate the spatial mobility,and explain the principles and calculations method in a detail way;(3)Based on the connotation of the integration degree of spatial syntax parameters,the local and global integration point sets representing the local and the whole are placed in the same scatter diagram,and analysis the linear characteristics and positions of the point sets representing the local area in the entire and use it to assess the coordination of the partial and overall,at the same time,systematically expounds the assessment principles,judgment standards and methods;(4)Propose three types of sustainable urban form diversity,and determine each type of quantitative method based on the biodiversity measurement method;propose a quantitative method to analyze the fit of diversity and space efficiency to evaluate the spatial efficiency of diversity,as important aspects of regional morphological diversity assessment;(5)Establish an indicator system from three aspects: adaptability,connectivity,and complexity of morphological elements to evaluate the advantages of identification,and elaborate on indicators step that using path network analysis to quantify connectivity and complexity.On this basis,use the evaluation content and quantitative methods an empirical analysis in 85 streets in the central city of Tianjin,the result shows that:(1)In terms of the evaluation of the non-linear characteristics of the sustainable urban form,the current central city form dimension is far from the ideal dimension and tends to be rigid and the fractal dimension of land for different functions has changed significantly.(2)In terms of the assessment of morphological spatial fluidity,with the increase of the spatial scale radius,the spatial efficiency tends to be concentric,with the highest spatial efficiency in the center and gradually decreasing toward the periphery.(3)In terms of local and overall coordination assessment,most of the streets in the six central districts are well coordinated,while the central urban fringe areas have poor coordination,and the overall coordination between the historical cultural blocks and the urban area is perfect.(4)In terms of morphological diversity assessment,the streets of Santiaoshi,Da Hutong,Quan yechang,Nanshi,Xinxing in the urban area are poor,other streets are better,and the streets in the old city,the northeast and west edges of the central city and the lower reaches of the Haihe River is poor in the fit of diversity and space efficiency.(5)In terms of the advantages of the form element identification,the form element identification of the old city area has the best advantage,while the outer ring West Road and North Road first-line streets in the central city have poor advantages.At the same time,conduct spatial correlation analysis of the evaluation results to grasp its spatial distribution characteristics,and combine field investigations to verify the evaluation results and perform detailed interpretations to confirm the validity of the evaluation results.The third part is the optimization strategy of sustainable urban form,which is to clarify how to realize the sustainability of form.First proposed the "local compactoverall reachable" form optimization model,expounding the mechanism of the optimization model to eliminate the disadvantages of compact cities to enhance the effectiveness of the model,and finally proposed form optimization based on the analysis the relationship among the evaluation content,the optimization model and the form elements,to point out the optimization strategy of sustainable urban form and.In terms of planning and design strategies:(1)Propose regional form optimization ideas to provide a good environment for the city;(2)Propose optimization strategies that reflect the evaluation content based on form elements such as land parcels,roads,and open spaces;(3)Propose the method to construct the green infrastructure ecological network and optimization strategy of detailed structure design.In terms of optimization support strategy: the strategy is mainly proposed from two aspects: technology and policy guarantee.Finally,based on the evaluation results of the central urban area of Tianjin,an optimization strategy for the urban form is proposed:(1)Actively revitalize the existing urban construction land,reduce the fractal dimension and optimize the fractal structure of the urban area;(2)Take the morphological elements as the object,clarify the optimization ideas,and respectively propose shape optimization strategy for 85 Street;(3)The strategy of building an ecological network based on the urban natural landscape and enhancing the urban living environment base;(4)With residential buildings as the starting point,daily service facilities as the end point,and roads as the network,the Rhino technology platform is used to simulate the roads suitable for slow travel in each street and point out the key points of travel environment optimization;(5)Put forward the strategy of government-led and residents’ active participation in optimization to regulate the behavior of form subject.Based on philosophical thinking,this paper reflects on the nature of sustainable urban form and proposes form assessment content and quantitative methods based on the theory of complex adaptive systems,which enriches the research theory of sustainable urban form;at the same time,based on the empirical analysis of Tianjin,it proves the validity of the research content.So,it has a certain meaning in theory and practice.