Evaluation on Spatial Adaptability of Historic Urban Blocks for Commercial Regeneration

In view of the current situation of aging, functional decline and protection difficulties in historic blocks, the feasibility of commercial regeneration is discussed. Referring to the relevant theories of protection and renewal of historic blocks, field investigation and expert consultation, fuzzy evaluation method and analytic hierarchy process are introduced to carry out a research study on the spatial adaptability of historic blocks for commercial regeneration and establish a preliminary evaluation system. An example of Dongguan Street Historic Block in Dalian is used to test the evaluation system. This pro-vides a basis for the formulation of commercial regeneration strategy in the next stage.

considered as an effective strategy for the revival of the existing historic blocks, and it is conducive to the establishment of high-quality business blocks.
There are three types of related researches: 1) the study of the spatial morphology of historic blocks: to systematically analyze the characteristics of historic blocks to provide basic information for the reconstruction [4] [5] [6]; 2) the study of and empirical discussion about the corresponding design methods for different regeneration methods: to figure out the method from the theory and put forward effective reconstruction strategies according to the law [7] [8] [9]; 3) performance evaluation of the built environment of the commercial regeneration of historic blocks: to sort and summarize the actual condition after the completion of the project, analyze the shortcomings and symptoms and figure out the corresponding optimization strategies [10] [11] [12] [13]. In this paper, we try to build an initial evaluation system from the perspective of the research on the spatial adaptability of historic blocks for commercial regeneration that are less mentioned, hoping to explore the various factors that affect the commercial regeneration of historic blocks and promote scientific reconstruction.

Evaluation Index of Spatial Adaptability of Historic Blocks for Commercial Regeneration
The word "adapt" derives from the Latin ad (to) and aptare (fit) [14] and refers to adjustment and change. In the case of historical block, adaptability means the ability to adapt to a new application without compromising the original characteristics of a block. The spatial adaptability of historic blocks for commercial regeneration depends on the coordination among and dynamic development of various elements of the blocks, and restricts the specific modes of the reconstruction and renewal of historic blocks. The idea of introducing adaptability into construction building and planning research is to assist the decision-making process considering the sustainability and suitability for urban regeneration.
In Revitalizing Historic Urban Blocks, Tiesdell Principle of science: the indexes should be scientific, normative and repre-sentative, independent from each other with weak correlation; • Principle of operability: the effectiveness and operability of indexes should be guaranteed in practical application, so that they are easy to collect, sort out, differentiate and quantify; • Principle of hierarchy: the indexes should be classified into different levels from top to bottom according to their relations of juxtaposition or inclusion, so as to avoid logic ambiguity and disorder in subordination relations among the indexes; • Principle of comprehensiveness: the indexes should cover a complete evaluation system and avoid one-sidedness.
According to the research system of Analytic Hierarchy Process [17] [18] [19], in the first level of evaluation indexes, we should list and layer-by-layer subdivide the five types of indexes including external environment, overall situation, internal street and lane space, landscape nodes and markers and internal buildings of historic blocks from macroscopic level to microcosmic level.
• External environment of historic blocks: the historic blocks as part of urban space have undergone long-term development and change. They have a lot to do with the surroundings. The external environment consisting of spatial location, traffic conditions, surrounding conditions. determines the block's commerce carrying capacity and potential commercial value at the city level, and affects the commercial regeneration of the block; • Overall situation of historic blocks: as an internal factor, the situation itself plays a decisive role in the spatial adaptability. The group scale of a historic block is related to the input and output of regeneration, the regeneration method and the corresponding commercial type after the regeneration; the openness of a historic block determines its communication with the outside world and whether it is easy to be perceived by the crowd; the overall spatial layout reflects the spatial organization and order relationship of the building and affects its fit with the commercial functional organization; the internal flow affects the security, orderliness and commercial enjoyment; • Internal street and lane space: the streets and lanes enclosed by the threedimensional interface are the basic skeleton of the historical block, the main carrier of people's behavior and activities after commercial regeneration, and an important index of spatial adaptability. In The Aesthetic Townscape, Yoshinobu Ashihara [20] analyzes the internal street and lane space from the perspectives of the shape (sinuosity), interface, dimensions and scale of street and lane;  (Table 1).

Perspectives and Methods of Evaluation
This paper emphasizes on the spatial elements of historic blocks for the evaluation of spatial adaptability. Currently, the research of street-block space and the design of commercial space are all based on mature theories. Therefore, we use the following methods in a specific evaluation process though theoretical judgment combined with an evaluation of a small number of subjects: • For data acquisition, we mainly adopt the method of literature research combined with field research, so as to get the theoretical basis of evaluation standards and accurate data of empirical cases. In a specific survey, the methods including observation, mapping, scaling, summary and induction are adopted;

Determination of Index Weight
Different influence indexes have different influences on the adaptability historic blocks for commercial regeneration. Therefore, determining the weight of influence indexes is the key step to build a scientific and complete model for an  Table 2.

Evaluation Grade and Scoring Criteria
In order to quantify the evaluation indexes, we divide the evaluation indexes into four scores levels (0 -2 points, 3 -5 points, 6 -8 points, 8 -10 points), by referring to the scoring standards of the existing relevant evaluation system and combining with the design theory and the overall characteristics of historic urban blocks, to realize a certain degree of differentiation and ensure the implementation of the evaluation. It's very difficult for China with a vast territory to establish a unified evaluation standard due to its numerous and distinctive historical districts affected by different factors. In this study, we try to establish the reference basis based on its generality (shown in Table 2). During the in-depth study of one specific historic block, we should determine the scoring standard through modification and adjustment according to the characteristics of the historic block.

Application of Evaluation Results
According to the evaluation and quantification results, which theoretically could go from 0 to 1000 aggregate scores, we divide the adaptability levels into Grade A, B, C and D. From A to D, the overall adaptability decreases, and the corresponding methods and strategies of commercial regeneration should be different.  Promiscuous space and disordered arrangement The pattern layout forms include linear arrangement type, the independent centripetal type, the homogeneous structure type, the traditional courtyard type and the group centripetal type and so on, each with its own merits and demerits. Therefore, it is necessary to judge based on the specific conditions.

Internal flow 5
Mixing of pedestrians and vehicles, and crossing between inside and outside Therefore, it is suggested extending the vitality of the historic block through commercial regeneration. For specific implementation, the low-intensity development mode can be also adopted, to preserve the spatial structure and texture of the whole area as much as possible, respect the original appearance of the historical buildings, and conduct local small-scale renovation and progressive renewal to meet the requirements of modern business. If the evaluation result falls in Grade C (Aggregate score: 201 -500), it means that there are many problems in the historic block itself and even some major defects, and it is not suitable for commercial regeneration, from the perspective of commercial requirements. For specific implementation, high-intensity development may be required, which can be achieved through a large-scale restoration or even antique reconstruction while maintaining the same style and features.
If the evaluation result falls in Grade D (Aggregate score: 0 -200), it means that one historic block is basically not suitable for commercial regeneration.
Specifically, it may be due to the quality problem itself (for example, much damage has been done to the urban texture or buildings) or the huge difference between the features of the historic block and the commercial functional requirements and great difficulty in remedy through reconstruction.

Empirical Evaluation of Dalian Dongguan Street Historic Block
In this paper, we try to apply the Spatial Adaptability Evaluation model to Da- The score of overall situation is 190 (280 in total). The Dalian Dongguan Street Historic Block features an appropriate size, high degree of openness and distinct spatial layout is easy to become a reticulate commercial street. Figure 3 1 The total score of each evaluation index is calculated by multiplying the weight by the score. Taking external environment as an example, the weight is 20, and the highest score is 10, the total score of external environment is 200.

Conclusion
Historic blocks unavoidably face challenges from the present and the future. One way out for most historic blocks is to carry out necessary protection, restoration and renovation to embrace new functions. In this paper, we have introduced the method to establish an evaluation system of spatial adaptability of historic blocks for commercial regeneration, both qualitatively and quantitatively on the basis of abundant literature study, consulting interviews and field investigations.
Taking Dalian Dongguan Street as an example, we have discussed the application of the evaluation system from the specific operation level and checked its rationality and operability, with the hope to provide solutions for the issues encountered in the renovation and reconstruction of historic blocks.