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Ecological Indicators 97 (2019) 194–203
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Ecological Indicators journal homepage: www.elsevier.com/locate/ecolind
Uneven urban-region sprawl of China’s megaregions and the spatial relevancy in a multi-scale approach
T

Weifeng Li, Weiqi Zhou , Lijian Han, Yuguo Qian Research Center for Eco-environmental Sciences, Chinese Academy of Sciences, Shuangqing Road 18, Beijing 100085, China
A R T I C LE I N FO
A B S T R A C T
Keywords: Coordinated-development Developed land Urban area Rural sprawl
As a global phenomenon, megaregions are now and will continue to be the main form of urbanization, especially in developing countries including China. Although megaregions have been viewed as the most powerful formation to accelerate urbanization, the unprecedented regional growth and the uneven urban-region sprawl between different cities are emerging as critical problems. Despite many concerns about rapid regional growth from social and economic perspectives, not much is known about the multi-scale dynamic of urban-region sprawl in terms of land use. In this study, we examined the two most important megaregions of China, the BeijingTianjin-Hebei region (B-T-H) and the Yangtze River Delta region (Y-R-D), to understand their urban-region sprawl patterns and the relevancy of multiple spatial scales among different types of cities. The analysis included directly identifying the developed land from remotely sensed data collected between 1980 and 2010. The results showed that (1) at the regional scale, although both megaregions expanded rapidly during 1980–2010, the obvious difference existed in their regional sprawl patterns. The sprawling rate of Y-R-D was obviously higher than that of B-T-H, implying the megaregions implemented quite different development strategies. (2) At the city scale, both the dominant and non-dominant cities within the megaregions had distinct contributions to the regional sprawl of the mega cities. The greatest contribution from the dominant cities was the fast expansion of the main urban areas; the greatest contribution of the non-dominant cities was the fast rural sprawl. Overall, the varied spatial differences in the regional sprawl of China’s megaregions highlight that sustainable regional development requires multi-scale joint development plan management, not only considering the synergy of cities with different sizes, but also the synergy between urban and rural areas.
1. Introduction Megaregions are large, densely populated and economically contiguous geographical units that are becoming the most important ways of promoting urbanization to push economic growth globally (Hartmann and Wang, 2014). Recently, the Chinese Government reinforced the importance of the emerging megaregions of China and enormously boosted their rapid development. Although such fast largescale development does bring economic growth, it at the same time increases the conflicts with the environment, such as the aggravation of environmental pollution, degradation of ecosystem health and decline of ecological services (Gao et al., 2014; Han et al., 2015, 2016; Hu et al., 2018; Liu et al., 2013; Mao et al., 2016; Wang et al., 2014). One of the main reasons for these problems is the cumulative effects of urban sprawls from different cities clustered with a multi-hierarch structure. Urban sprawl, as a common phenomenon associated with urbanization, is mostly viewed that if land is consumed at a faster rate than

population growth, then a city can be characterized as sprawling (Davis and Schaub, 2005). Such sprawling urban growth pattern, characterized by the increase of developed land would have serious consequences, particularly in fast developing countries including China, such as fragmentation of landscape, loss of natural habitats, decrease of biodiversity, and so on (Li et al., 2018). Therefore, due to the complex hierarchy structure of megaregions, the phenomenon of urban-region sprawl is highly relevant to the urban sprawls of individual cities within megaregions (Tabuchi and Thisse, 2011; Tian et al., 2011; Cerina and Mureddu, 2014). Thus, to understand the dynamics of urban-region sprawls is critical for finding synergic management actions to support the sustainable regional development. Of great significance to megaregions is that a number of cities closely interact to forma large-scale, but unevenly distributed urban-region, which encompasses not only actual urban areas, but also their surrounding nominally suburban or rural areas (Hagler, 2009). Such rapid growth of megaregions is influenced not only by the densely
Corresponding author. E-mail address: [email protected] (W. Zhou).
https://doi.org/10.1016/j.ecolind.2018.10.004 Received 17 December 2016; Received in revised form 4 September 2018; Accepted 3 October 2018 1470-160X/ © 2018 Elsevier Ltd. All rights reserved.
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2.2. Land cover/land use data
interacting urban areas of different cities but also by their suburban or rural areas. It has been widely noted that a number of megaregions have been evolved in many countries such as the U.S., Canada, some European countries and some developing countries including China (Hamidi and Ewing, 2014; Kasanko et al., 2006; Salvati and Carlucci, 2014;). Although many studies have focused on the growths of megaregions from multi-aspects such as population movement, population density change, or agglomeration economy effect, few studies have quantified the urban-region sprawls (Behrens and Thisse, 2007; Farber, 2013; Garcia-Lopez, 2010; Hasse and Lathrop, 2003; Marull et al., 2013; Salvati and Carlucci,2014; Tabuchi and Thisse, 2011). From the broad sense, “urban sprawl” is a multi-social and complex phenomenon, and has been quantified from varied ways such as growth rates (the ratio between the growth rate of built-up areas and the population growth rate), density (the ratio between a certain urban activities and the area in which it exits), spatial geometry (urban landscape composition and configuration) and accessibility, etc. (Frenkel and Ashkenazi, 2008; Henning et al., 2015; Jaeger et al., 2010; Jaeger and Schwick, 2014; Jaret et al., 2009); from the narrow sense, “urban sprawl”, in terms of land use, is usually referred to low density urban development, exurban and rural development. Most research on urban sprawl has concentrated on single city or metropolitan area, and few studies have examined the urban-region sprawls of megaregions with complex multihierarchy structures (Fallah et al., 2011; Gao et al., 2016; Kuang et al., 2014; Queslati et al., 2015). Research is needed to comprehensively monitor and quantify the urban-region sprawl at large scales and to understand the sprawling mechanism. The objective of this study was to develop a multi-scale approach for investigating the characteristics of urban-region sprawl of megaregions that occurred in China in recent decades. We chose two representative and important megaregions to study, namely the B-T-H (BeijingTianjin-Hebei) and Y-R-D (Yangtze River Delta) regions, with spatial scales ranging from city to regional. First, we used the developed land directly identified from remote sensing imagery as the basic data to measure the land utilization. Second, we developed multi-scale indexes to assess urban-region sprawl. On the regional scale, we used a simple index to evaluate and compare the overall regional sprawl of the two megaregions; on the city scale, we used different indexes to evaluate and compare urban sprawl between urban area and rural area across dominant and non-dominant cities. Finally, we discussed the causes of the uneven urban-region sprawls rom a multi-scale perspective and highlighted the important policy and decision implications.
We used the medium resolution remote sensing images (30 m) from the Landsat Thematic Mapper to identify the land cover/land use types in 1980, 1990, 2000 and 2010. The data were obtained from the United States Geological Survey. According to the characteristics of the B-T-H and Y-R-D megaregions, the land use/land cover classification system included six classes: forest, grass, water, farmland, developed land and barren land. Developed land is refer to all the types of construction land in both urban and rural area, such as residential, commercial, industrial, transport and public building, etc., whereas barren land mainly includes sand, bare soil, exposed rock and strip mines and quarries. A backdating approach and object-based method were integrated to identify the land cover/land use types (Yu et al., 2016, Ouyang et al., 2016). According to this approach, land cover/use classification is only conducted on a basic reference map for a given year, and based on which the change of land cover/use for other years can be extracted. The land cover/use in 2010 was selected as the basic reference map, based on which the land cover/use in 1980/1990/2000 was extracted. Finally, we selected eight cities (Beijing, Tianjin, Shanghai, Suzhou, Wuxi, Changzhou, Nanjing and Hangzhou) for validating the classification accuracy. We used a stratified random sampling scheme to select locations within the cities and compared the image classification to reference land use data created from the visual interpretation of high spatial resolution SPOT images (2.5 m). For each city, we randomly generated a total number of 300 sample points for each classification map, with at least 30 samples for each land cover/land use category. Therefore, the overall accuracy, Kappa statistic, average producer’s and user’s accuracy exceeded 92%, 0.8, 78% and 93%. 2.3. Analysis frameworks We developed a multi-index approach to comprehensively quantify the urban-region sprawl across the megaregions. The multi-index system included two parts, one part of which evaluated the overall urban-region sprawl at regional scale, and the other part quantified the multi-aspects of urban sprawl of different types of cities at city scale. 2.3.1. Measurement of urban-region sprawl at regional scale On regional scale, we used a simple index (Regional Sprawl Index, ReSI) to measure the overall urban-region sprawl of the megaregion (Eqs. (1) and (2)). The Regional Sprawl Index (ReSI) is a relative measure of regional sprawl, by the comparison of land utilization at two time points. Here, the land utilization is evaluated by the Land Utilization Index (LUI), defined as the ratio between the developed land and total land of the megaregion at the specific spatial scale (Eq. (1)).
2. Data and methods 2.1. Study area The B-T-H and Y-R-D megaregions (Fig. 1) are important urban agglomerations in China. The B-T-H megaregion of northeastern China lies on the shores of Bohai Sea with a total area approximating 22.0 × 106 ha, while the Y-R-D megaregion is located at China’s east coast bordering the East China Sea with the total area of 10.0 × 106 ha. The B-T-H megaregion is composed of 13 cities, and the Y-R-D megaregion contains 15 cities until 2010. Both the two megaregions are the important urbanized and industrialized regions in China and are continuing to exhibit a rapid sprawling tendency. For instance, the average demographic urbanization level of the B-T-H and Y-R-D megaregion was 49.3% and 64.8% respectively in 2010, similar to or obviously higher than the national average of 50% of the same time (National Bureau of Statistics of China, 2011). In the meantime, the average of per capita GDP of the B-T-H and Y-R-D was 35,726 and 68,248 yuan, obviously higher than the national average of 29,992 yuan during the same period (National Bureau of Statistics of China, 2011).
LUI =
DL × 100% TL
(1)
ReSI =
LUIt + 1−LUIt LUIt
(2)
In Eqs. (1) and (2), DL and TL mean, respectively, the developed land and total land at the specific spatial scale and at a particular period; LUIt means the Land Utilization Index at time t. 2.3.2. Measurement of urban sprawl at city scale On city scale, we developed two indexes to quantify urban sprawl from two different aspects, the expansion of urban area and rural sprawl. One index was the Urban-area Sprawl Index (UrSI), being defined as the expansion of the urban area within the total area of a city (Eq. (3)). The other index was the Rural Sprawl Index (RuSI) defined as the increase of developed land within the rural area (Eq. (4)).
UrSI = 195
MUAt + 1−MUAt MUAt
(3)
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Fig. 1. Spatial locations of the Beijing-Tianjin-Hebei (B-T-H) and Yangtze River Delta (Y-R-D) megaregions.
RuSI =
RDL t + 1 −RDL t RDL t
megaregion due to their predominance at social, economic or political status compared with the other non-dominant cities. In China, the territories are organized by the spatial administrative hierarchy, ranking from provinces, prefecture-level cities, counties and towns, among which prefecture-level cities tend to be more like an urban system, and include both urban and rural areas (Bai et al., 2012; Li et al., 2015). From this, there are 2 dominant (Beijing and Tianjin) and the other 11 non-dominant cities of the B-T-H megaregion (The Beijing Government, 2015). Similarly, the Y-R-D megaregion has 6 dominant (Shanghai, Nanjing, Suzhou, Wuxi, Changzhou and Hangzhou) and 9 non-dominant cities (the State Council of China, 2010). Then, we analyzed the difference of urban sprawls between dominant and nondominant cities.
(4)
In Eqs. (3) and (4), MUAt is the size of the urban area of a city at time t; and RDLt is the developed land within the rural area of a city at time t. Herein, we developed a new approach to map urban areas of cities. Traditionally, the urban and rural area of a city is political differentiated by the administrative division such as districts named as urban area, while countries and towns usually as the rural area. In fact, the fast urban expansion particularly such as the landscape urbanization often blurs the administrative boundary between urban and rural area. Some studies have used the remote sensed data to directly map urban area, such as based nighttime light images and land use configuration (Gao et al., 2016; Hu et al., 2015; Small et al., 2005; Zhang et al., 2013). Thus, in this study we divided the urban and rural area directly by land uses and their spatial continuity in the following steps. (1) To delineate the main urban area (Figs. 6 and 7), we created a grid-based thematic map, and calculated the proportions of developed land within each grid cell and its continuity with its adjacent grid cells. Grid cells with proportions of developed lands exceeding 50% and that were contiguous with adjacent grid cells generated from the inner city location were identified as urban areas. The average landscape patch sizes of different sized cities are quite different; specifically, the patch size of developed land in small cities is smaller than that of big cities. Thus, for the 28 cities of both the B-T-H and Y-R-D megaregions, the grid sizes adopted varied from 200 × 200 m to 1200 × 1200 m. (2) Once the urban areas were defined, the rural areas were determined by subtracting the urban area from the whole administrative city area. In addition, to identify the difference in urban sprawl of different types of cities, we divided the cities into two types: dominant and nondominant cities, according to the hierarchy structure of megaregions. The dominant cities are usually characterized as the cores of the
3. Results 3.1. Variation in urban-region sprawl at regional scale Between 1980 and 2010, the overall developed land of both the B-TH and Y-R-D megaregions increased rapidly (Figs. 2 and 3). Compared with the stages of 1980–1990 and 2000–2010, the increase of developed land between 1990 and 2000 was the fastest for both the megaregions. By contrast, the amount of arable land of both megaregions starkly decreased, indicating that most increased developed land was converted from arable land. The arable land of the B-T-H megaregion decreased from 50.59% to 44.37% from 1980 to 2010, the arable land of the Y-R-D megaregion decreased from 59.33% to 37.34% (Table 1). By contrast, the urban-region sprawl of the Y-R-D megaregion was a lot faster than that of the B-T-H megaregion. For instance, the proportion of developed land in the total land area of the B-T-H megaregion increased by 1.84 times from 5.51% to 10.11% during 1980–2010, compared to a 4.37-fold increase (from 4.07% to 21.86%) for the 196
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(a) 1980
(b) 1990
(c) 2000
(d) 2010
Fig. 2. Land cover/land use change in the Beijing-Tianjin-Hebei megaregion, 1980–2010.
varied among different cities within megaregions, and no obvious regularity was found. For example, the average proportion of developed land in the dominant cities of the B-T-H megaregion increased 1.18 times from 9.4% in 1980 to 20.49% in 2010, faster than that of 0.76 times from 6.4% to 11.69% in the non-dominant cities (Table 2; Fig. 5). Comparatively, the average proportion of developed land in the dominant cities of the Y-R-D increased 5.08 times from 5.42% in 1980 to 25.07% in 2010, lower than that of 6.53 times from 3.6% to 21.86% (Table 2; Fig. 5). Moreover, for each of the three stages, the increase of total developed land of different types of cities was varied without regularity (See Figs. 6 and 7). The average coverage of urban areas in dominant cities was larger than that in non-dominant cities, and the increase of urban area was faster than that of non-dominant cities. For the B-T-H megaregion, the average urban areas of the dominant cities grew from 2.72% in 1980 to 13.89% in 2010, while in the non-dominant cities the urban areas
developed land in the Y-R-D megaregion (Table 1). Moreover, for each of the three stages, the increase of developed land of the Y-R-D megaregion was consistently higher than the B-T-H megaregion. The increase of developed land expansion during 1980–2010 was not uniform in either megaregion. For the B-T-H megaregion, during 1990–2000 developed land increased by 38.00%, which was greater than that from 1980 to 1990 (9.00%) and from 2000 to 2010 (22.00%). For the Y-R-D megaregion, the greatest growth of developed land also occurred during the decade 1990–2000, increasing nearly 89.00%. The second-largest growth occurred in 1980–1990 (increase of 71.00%). By contrast, during the period 2000–2010, the increase of developed land slowed somewhat (66.00%) (Fig. 4). 3.2. Variation in urban sprawl at city scale At city scale, the increase of total developed land of each city was 197
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(a) 1980
(b) 1990
(c) 2000
(d) 2010
Fig. 3. Land cover/land use change in the Yangtze River Delta megaregion, 1980–2010.
expanded from 0.43% to 1.31% over the same period (Table 3). By contrast, for the Y-R-D megaregion, the average urban areas of the dominant cities expanded from 1.78% to 13.58% from 1980 to 2010, while the urban areas of the non-dominant cities expanded from a proportion of 0.29% to 3.61% over the same period (Table 3). In comparison, the urban areas of both dominant and non-dominant cities of the Y-R-D megaregion expanded much faster than that of the B-T-H megaregion, and the expanding speed continued to accelerate from 1980 to 2010. By contrast, although the urban areas of dominant cities in the B-T-H megaregion continued to expand from 1980 to 2010, the expanding speed increased firstly between 1990 and 2000, then decreased between 2000 and 2010 (Fig. 8). Notably, for both the B-T-H and Y-R-D megaregions, the rural sprawl of the non-dominant cities was markedly faster than that of the dominant cities. For the B-T-H megaregion, the average proportion of
Table 1 Composition of land use in the study areas, 1980–2010. Megaregion
Land use
1980
1990
2000
2010
Beijing-Tianjin-Hebei (B-T-H)
Developed land Arable land Forest land Grass land Wetland Others
5.51% 50.59% 32.42% 8.27% 2.90% 0.32%
5.98% 49.61% 33.11% 7.68% 3.40% 0.22%
8.26% 47.15% 32.60% 8.74% 2.95% 0.29%
10.11% 44.37% 33.16% 9.24% 2.79% 0.32%
Yangtze River Delta (YR-D)
Developed land Arable land Forest land Grass land Wetland Others
4.07% 59.33% 23.99% 0.04% 12.37% 0.19%
6.95% 57.68% 23.99% 0.13% 11.10% 0.14%
13.17% 45.79% 25.31% 1.01% 14.68% 0.04%
21.86% 37.34% 25.87% 0.62% 14.29% 0.02%
198
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Increase of developed land in the whole megeregion
500% 450% 400% 350% 300% 250% 200% 150% 100% 50% 0% B-T-H 1980-1990
Y-R-D
1990-2000
2000-2010
1980-2010
Fig. 4. Comparison of the growth of developed land in the Beijing-Tianjin-Hebei (B-T-H) and Yangtze River Delta (Y-R-D) megaregions, 1980–2010.
1980 and 2010, the average increase of developed land in the nondominant cities of the Y-R-D megaregion was 632.54%, quite faster than that of 430.07% in the dominant cities (Fig. 9).
Table 2 Average proportions of developed land in dominant and non-dominant cities of the Beijing-Tianjin-Hebei (B-T-H) and Yangtze River Delta (Y-R-D) megaregions, 1980–2010. 1980
1990
2000
2010
B-T-H
Dominant cities Non-dominant cities
9.40% 6.40%
10.63% 6.88%
14.31% 10.29%
20.49% 11.69%
Y-R-D
Dominant cities Non-dominant cities
5.42% 3.60%
8.35% 6.62%
14.64% 13.65%
25.07% 21.86%
4. Discussion Our study showed that the area of developed lands in two of China’s most important megaregions expanded significantly over the period 1980–2010. However, the increase of developed land is not always consistent with the population and economic growth, indicating the less efficient land utilization of megaregions compared with the demographic and economic urbanization. For instance, the amount of developed land of the B-T-H megaregion increased 1.83 times from 1980 to 2010, while the population grew 1.81 times. During the same period in the Y-R-D megaregion, the amount of developed land grew 5.37 times, much faster than the 1.98 times growth of the population. Furthermore, from 2000 to 2010, the overall proportion of developed land in the B-T-H and Y-R-D megaregions increased by 13.68% and 67.96%, respectively, while during the same period, the GDP grew 4.64 and 4.45 times, respectively. Such urban-region sprawl indicates that even the wealthiest urbanized regions of China are still experiencing an
Increase in developed lands
developed land in the rural areas of the dominant cities grew from 7.67% in 1980 to 10.45% in 2010, while that of the non-dominant cities expanded from 6.12% to 10.69% (Table 4). Between 1980 and 2010, the average increase of developed land in the non-dominant cities of the B-T-H megaregion was 74.47%, faster than that of 34.88% in the dominant cities (Fig. 9). Similarly, the average proportion of developed land in the rural areas of the non-dominant cities in the Y-R-D megaregion grew from 3.39% in 1980 to 19.31% in 2010, while that of dominant cities expanded from 4.03% to 16.28% (Table 4). Between
700% 600% 500% 400% 300% 200% 100% 0%
Dominant cities
Non-dominant cities
B-T-H 1980-1990 1990-2000
Dominant cities
2000-2010
Non-dominant cities
Y-R-D 1980-2010
Fig. 5. Comparison of the average growth of developed land in the dominant and non-dominant cities of the Beijing-Tianjin-Hebei (B-T-H) and Yangtze River Delta (Y-R-D) megaregions, 1980–2010. 199
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Fig. 6. Physical boundary of the main urban areas of the Beijing-Tianjin-Hebei megaregion in 1980, 1990, 2000 from the left to right.
extensive land resource dependent growth pattern (Bai et al., 2014). On the one hand, the rapidly increased population needs more residential area, basic infrastructure and support for other human activities, which has stimulated land development. On the other hand, under the specific land use policies (i.e. land is state owned and the governments could raise enormous revenue from leasing lands), China’s governments have been able to raise large revenues from selling lands (Bai et al., 2012). Thus, the critical question facing the planners and decision-makers is how to change the growth pattern from extensive to intensive to realize regional synergetic development. Although the urban-region sprawl was varied between and within the megaregions, it had similar regular patterns. On the regional scale, the overall developed land in the Y-R-D megaregion has increased by a factor of 4.37, quite a lot faster than 84% increase of the B-T-H megaregion. This implied that the multi-nuclei development mode such as the Y-R-D megaregion with 6 dominant cities would be apt to be more sprawling than the dual-nuclei development mode such as the BT-H megaregion with 2 dominant cities. In addition, on the city level, the dominant cities contributed to the urban-region sprawl mainly through expansion of urban areas, while the non-dominant cities contributed to sprawl through fast rural sprawl, suggesting that cities in different urban hierarch ranks had distinct impacts on urban sprawl. For instance, the main urban areas of the dominant cities of both the BT-H and Y-R-D megaregions grew 4.48 and 11.84 times, faster than the 1.86- and 11.18-fold increases of the non-dominant cities accordingly. The main reason is that the dominant cities usually are the economic centers of the megaregions and have many advantages over the nondominant cities, such as better infrastructure, healthcare and education, which attract more people to reside and work in the urban centers of these cities. As a consequence, the dominant cities promote fast urban expansion. By contrast, non-dominant cities contributed to urban-region sprawl by the fast expansion of suburban areas, probably because
Table 3 Main urban area as a proportion of the dominant and non-dominant cities in the Beijing-Tianjin-Hebei (B-T-H) megaregions, 1980–2010. 1980
1990
2000
2010
B-T-H
Dominant cities Non-dominant cities
2.72% 0.43%
3.09% 0.47%
6.13% 0.95%
13.89% 1.31%
Y-R-D
Dominant cities Non-dominant cities
1.78% 0.29%
2.33% 0.42%
4.83% 1.08%
13.58% 3.61%
of the policies that have specific legacy-based Chinese characteristics. For example, in China, there was a strict household (Hukou) registration policy to constrain population migration between rural and urban areas. As a result, although many migrant workers “temporarily” live in urban areas, their official hometowns are still in the rural areas of small cities, and they improve their living conditions by expanding their hometown houses using the money earned in cities. In addition, during the 1990 s the national government implemented the policy of “strictly controlling the scale of big cities, rationally developing medium cities, and actively encouraging the development of small cities”, which pushed the fast development of the non-dominant cities, such as by the relocations of many industries from large cities particularly in eastern China including B-T-H and Y-R-D, where urban land is almost exhausted and land price is extremely expensive (Liu et al., 2013; Dang et al., 2016). Thus, better understanding the rules and causes of urban sprawl across the multiple scales is critical to the sustainability of China’s megaregions. Notably, for both megaregions, arable land was the major land use type that covered more than half of total area at the beginning period, but it obviously decreased corresponding to the dramatic increase of developed land. This finding indicated that the developed land increased was mainly created by the conversion of arable lands, and
Fig. 7. Physical boundary of the main urban areas of the Yangtze River Delta megaregion in 1980, 1990, 2000 from the left to right. 200
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Growth of the main urban area
W. Li et al.
1400% 1200% 1000% 800% 600% 400% 200% 0% Dominant cities
Non-dominant cities
Dominant cities
B-T-H 1980-1990
Non-dominant cities Y-R-D
1990-2000
2000-2010
1980-2010
Fig. 8. Comparison of the average growth of the main urban area in dominant and non-dominant cities in the Beijing-Tianjin-Hebei (B-T-H) and Yangtze River Delta (Y-R-D) megaregions, 1980–2010.
urban-region sprawl over the large-scale megaregions of China from the multi-scale perspective. Despite as the most urbanized region, the fast sprawl leads to tension between regional development, natural resources and environmental quality. Recently, to push development further, the Chinese Government issued the planning framework of the B-T-H synergetic development and the regional plan of the Y-R-D megaregion, of which the critical question is how to coordinate the development of the large, medium and small cities. Our results illustrate what important information can help guide the planning and decisions about efficient and rational land utilization to support the synergetic regional development: 1) on the regional scale, setting the explicit land utilization intensity targets for different kinds of megaregions due to their distinct objectives and functions; 2) On the city scale, for the dominant cities, prioritizing strictly controlling the overly rapid expansion of urban area, while for the non-dominant cities curbing the excessive land development of the rural area by improving
Table 4 Proportion of developed land in the rural area of dominant and non-dominant cities in the Beijing-Tianjin-Hebei (B-T-H) and Yangtze River Delta (Y-R-D) megaregions, 1980–2010. 1980
1990
2000
2010
B-T-H
Dominant cities Non-dominant cities
7.67% 6.12%
8.30% 6.54%
9.49% 8.81%
10.45% 10.69%
Y-R-D
Dominant cities Non-dominant cities
4.03% 3.39%
6.56% 6.34%
11.14% 12.88%
16.28% 19.31%
reinforced that the contradictions between urban-region sprawl and cultivated land protection was still outstanding in China’s most welldeveloped megaregions (Tan et al., 2005; Bai et al., 2014; Jiang et al., 2016; Tan et al., 2014; Zeng et al., 2015). This study provides a simple way to comprehensively monitor
Increase in developed lands in rural area
700% 600% 500% 400% 300% 200% 100% 0% Dominant cities
Non-dominant cities
Dominant cities
B-T-H 1980-1990
Non-dominant cities
Y-R-D 1990-2000
2000-2010
1980-2010
Fig. 9. Comparison of the average growth of developed land in the rural areas of dominant and non-dominant cities in the Beijing-Tianjin-Hebei (B-T-H) and Yangtze River Delta (Y-R-D) megaregions, 1980–2010. 201
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the land utilization efficiency.
spatial structure changing? J. Hous. Econ. 19, 119–132. https://doi.org/10.1016/j. jhe.2010.04.002. Hagler, Y., 2009. Defining U.S. Megaregions. America 2050. Hamidi, A., Ewing, R., 2014. A longitudinal study of changes in urban sprawl between 2000 and 2010 in the United States. Landscape Urban Plann. 128, 72–82. https://doi. org/10.1016/j.landurbplan.2014.04.021. Han, L.J., Zhou, W.Q., Li, W.F., 2015. City as a major source area of fine particulate (PM2.5) in China. Environ. Pollut. 206, 183–187. https://doi.org/10.1016/j.envpol. 2015.06.038. Han, L.J., Zhou, W.Q., Li, W.F., 2016. Fine particulate (PM2.5) dynamics during rapid urbanization in Beijing. Sci. Rep. 6, 1–5. https://doi.org/10.1038/srep23604. Hartmann, R., Wang, J.A., 2014. A comparative geography of China and the U.S. Springer, New York. Hasse, J.E., Lathrop, R.G., 2003. Land resource impact indicators of urban sprawl. Appl. Geogr. 23, 159–175. https://doi.org/10.1016/j.apgeog.2003.08.002. Henning, E.I., Schwick, C., Soukup, T., Orlitova, E., Kienast, F., Jaeger, J.A.G., 2015. Multi-scale analysis of urban sprawl in Europe: towards a European de-sprawling strategy. Land Use Pol. 49, 483–498. https://doi.org/10.1016/j.landusepol.2015.08. 001. Hu, S., Tong, L., Frazier, A.E., Liu, Y., 2015. Urban boundary extraction and sprawl analysis using Landsat images: a case study in Wuhan, China. Habitat Int. 47, 183–195. https://doi.org/10.1016/j.habitatint.2015.01.017. Hu, T.F., Mao, J.Q., Pan, S.Q., et al., 2018. Water level management of lakes connected to regulated rivers: an integrated modeling and analytical methodology. J. Hydro. 562, 796–808. https://doi.org/10.1016/j.jhydrol.2018.05.038. Jaeger, J.A.G., Betiller, R., Schwick, C., Kienast, F., 2010. Suitability criteria for measures of urban sprawl. Ecol. Indic. 10, 397–406. https://doi.org/10.1016/j.ecolind.2009. 07.007. Jaeger, J.A.G., Schwick, C., 2014. Improving the measurement of urban sprawl: Weighted Urban Proliferation (WUP) and its application to Switzerland. Ecol. Indic. 38, 294–308. https://doi.org/10.1016/j.ecolind.2013.11.022. Jaret, C., Ghadge, D., Reid, L.W., Adelman, R.M., 2009. The measurement of suburban sprawl: an evaluation. City Commun. 8 (1), 65–84. https://doi.org/10.1111/j.15406040.2009.01270.x. Jiang, G.H., Ma, W.Q., Qu, Y.B., et al., 2016. How does sprawl differ across urban built-up land types in China? A spatial-temporal analysis of the Beijing metropolitan area using granted land parcel data. Cities 58, 1–9. https://doi.org/10.1016/j.cities.2016. 04.012. Kasanko, M., Barredo, J.I., Lavalle, C., et al., 2006. Are European cities becoming dispersed? A comparative analysis of 15 European urban areas. Landscape Urban Plann. 77, 11–130. https://doi.org/10.1016/j.landurbplan.2005.02.003. Kuang, W.H., Chi, W.F., Lu, D.S., Dou, Y.Y., 2014. A comparative analysis of megacity expansions in China and the U.S.: patterns, rates and driving forces. Landscape Urban Plann. 132, 121–135. https://doi.org/10.1016/j.landurbplan.2014.08.015. Li, H., Wei, Y.D., Liao, F.H., Huang, Z., 2015. Administrative hierarchy and urban land expansion in transitional China. Appl. Geogr. 56, 177–186. https://doi.org/10.1016/ j.apgeog.2014.11.029. Li, W.F., Zhou, W.Q., Bai, Y., Pickett, S.T.A., Han, L.J., 2018. The smart growth of Chinese cities: opportunities offered by vacant land. Land Degrad. Dev. https://doi.org/10. 1002/ldr.3125. Liu, Y.S., Lu, S.S., Chen, Y.F., 2013. Spatio-temporal change of urban-rural equalized development patterns in China and its driving factors. J. Rural Stud. 32, 320–330. https://doi.org/10.1016/j.jrurstud.2013.08.004. Mao, J.Q., Zhang, P.P., Dai, L.Q., et al., 2016. Optimal operation of a multi-reservoir system for environmental water demand of a river-connected lake. Hydrol. Res. 47, 206–224. Marull, J., Galletto, V., Domene, E., et al., 2013. Emerging megaregions: a new spatial scale to explore urban sustainability. Land Use Pol. 34, 353–366. https://doi.org/10. 1016/j.landusepol.2013.04.008. National Bureau of Statistics of China, 2011. China City Statistical Year Book. Statistical Press, Beijing, China. Ouyang, Z.Y., Zheng, H., Xiao, Y., et al., 2016. Improvements in ecosystem services from investments in natural capital. Science. 352 (6292), 1455–1459. https://doi.org/10. 1126/science.aaf2295. Queslati, W., Alvanides, S., Garrod, G., 2015. Determinants of urban sprawl in European cities. Urban Stud. 52 (9), 1594–1614. Salvati, L., Carlucci, M., 2014. Urban growth and land-use structure in two mediterranean regions: an exploratory spatial data analysis. SAGE Open. 10–12, 1–13. https://doi. org/10.1177/2158244014561199. Small, C., Pozzi, F., Elvidge, C.D., 2005. Spatial analysis of global urban extent from DMSP-OLS night lights. Remote Sens. Environ. 96, 277–291. https://doi.org/10. 1016/j.rse.2005.02.002. Tabuchi, T., Thisse, J.F., 2011. A new economic geography model of central places. J. Urban Econ. 69, 240–252. https://doi.org/10.1016/j.jue.2010.11.001. Tan, M.H., Li, J.B., Xie, H., et al., 2005. Urban land expansion and arable land loss in China—a case study of Beijing–Tianjin–Hebei region. Land Use Policy 22, 187–196. https://doi.org/10.1016/j.habitatint.2014.07.005. Tan, R.H., Liu, Y.L., Liu, Y.F., et al., 2014. Urban growth and its determinants across the Wuhan urban agglomeration, central China. Habitat Int. 44, 268–281. https://doi. org/10.1016/j.habitatint.2014.07.005. The Beijing Government, 2015. Planning outline of coordinated development of Beijing, Tianjin and Hebei. Available from: http://zhengwu.beijing.gov.cn/zwzt/jjjyth/. The State Council of China, 2010. Regional planning of the Yangtze River Delta. Available from: http://www.gov.cn/gzdt/2010-05/24/content_1612730.htm. 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5. Conclusions Today in China, the sustainable development of the megaregions is closely related to the overall national urbanization, and the grand challenge confronting decision-makers is to find the most effective and efficient way to minimize the contradiction between economic growth and environmental protection. In this study, we suggest a new approach to comprehensively measure urban-region sprawl of two important megaregions of China from a multi-scale perspective, and find the potential the causes. Our example revealed that the increase of developed land of the megaregions outpaced the population growth. The characteristics of urban-region sprawl were relevant to the multi-hierarchy structure of megaregions. The major contribution from the dominant cities is the expansion of the urban areas, while the primary contribution of the non-dominant cities is the rapid increase of developed land in rural areas. The findings have important policy implications. Currently, China’s government has set important state policy “promoting coordinated development of large, medium cities and small towns” to push the fast development of megaregions. The implementation of this policy needs to pay extra attention to the over-fast sprawl of nondominant cities. The rapid increase of developed land and the unbalanced growth patterns between and within the two most important of China’s megaregions resemble those occurring in other megaregions in China. Thus, our analytic framework could be applied to other megaregions as the standard and effective practice for comprehensively understanding the complex dynamics and mechanisms of urban-region sprawl. Acknowledgements The authors are grateful to the funding support from the National Key Research and Development Program of China (Grant 2017YFC0505701) and the National Natural Science Foundation of China (Grant 41590841). References Bai, X.M., Chen, J., Shi, P.J., 2012. Landscape urbanization and economic growth in China: positive feedbacks and sustainability dilemmas. Environ. Sci. Technol. 46, 132–139. https://doi.org/10.1021/es202329f. Bai, X.M., Shi, P.J., Liu, Y.S., 2014. Realizing China’s urban dream. Nature 509, 158–160. Behrens, K., Thisse, J.F., 2007. Regional economics: a new economic geography perspective. Reg. Sci. Urban Econ. 37, 457–465. https://doi.org/10.1016/j.regsciurbeco. 2006.10.001. Cerina, F., Mureddu, F., 2014. Is agglomeration really good for growth? Global efficiency, interregional equity and uneven growth. J. Urban Econ. 84, 9–22. https://doi.org/10. 1016/j.jue.2014.08.006. Dang, S., Yuan, D.C., Kong, W.Y., 2016. Land cooperatives as an approach of suburban space construction: under the reform of Chinese land transfer market. Front. Arch. Res. 5, 425–432. https://doi.org/10.1016/j.foar.2016.09.002. Davis, C., Schaub, T., 2005. A transboundary study of urban sprawl in the Pacific Coast region of North America: The benefits of multiple measurement methods. Int. J. Appl. Earth Obs. Geoinf. 7, 268–283. https://doi.org/10.1016/j.jag.2005.06.007. Fallah, B.N., Partridge, M.D., Olfert, M.R., 2011. Urban sprawl and productivity: evidence from US metropolitan areas. Pap. Reg. Sci. 90 (3), 451–472. https://doi.org/10. 1111/j.1435-5957.2010.00330.x. Farber, S.L.X., 2013. Urban sprawl and social interaction potential: an empirical analysis of large metropolitan regions in the United States. J. Transp. Geogr. 31, 267–277. https://doi.org/10.1016/j.jtrangeo.2013.03.002. Frenkel, A., Ashkenazi, M., 2008. The integrated sprawl index: measuring the urban landscape in Israe. Ann. Reg. Sci. 42 (1), 99–121. https://doi.org/10.1007/s00168007-0137-3. Gao, B., Huang, Q.X., He, C.Y., Sun, Z.X., Zhang, D., 2016. How does sprawl differ across cities in China? A multi-scale investigation using nighttime light and census data. Landscape Urban Plann. 148, 89–98. Gao, Y., Feng, Z., Li, Y., et al., 2014. Freshwater ecosystem service footprint model: a model to evaluate regional freshwater sustainable development—a case study in Beijing–Tianjin–Hebei, China. Ecol. Indic. 39, 1–9. https://doi.org/10.1016/j. ecolind.2013.11.025. Garcia-Lopez, M.A., 2010. Population suburbanization in Barcelona, 1991–2005: Is its
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SETTLEMENT N.
JOINTS V.
Kuznetsov
IN and
BUILDINGS A.
N.
Pechenov
UDC 624.012.43
In o r d e r to p r e c l u d e the f o r m a t i o n of c r a c k s and o t h e r d e f o r m a t i o n s caused by uneven foundation s e t t l e m e n t , buildings a r e d i s s e c t e d by s e t t l e m e n t d e f o r m a t i o n joints which p r e v e n t c r a c k s developing either c o m p l e t e l y or to a substantial degree. The c o r r e c t design and c o n s t r u c t i o n of d e f o r m a t i o n joints have a c o n s i d e r a b l e effect on the strength and durability of buildings, but data on this subject a r e v e r y m e a g e r , and a r e s c a t t e r e d a m o n g d i v e r s e j o u r n a l s . T h e r e f o r e , both design and c o n s t r u c t i o n e n g i n e e r s do not always b e a r in mind the consequences of d i s r e g a r d i n g such s e e m i n g l y u n i m p o r t a n t details as d e f o r m a t i o n joints. P a r t i c u l a r l y t r o u b l e s o m e a r e the phenomena which o c c u r when new buildings a r e c o n s t r u c t e d i m m e d i a t e l y adjacent to existing r e s i d e n c e s , when the l a t t e r suffer s e r i o u s d e f o r m a t i o n s . In Kiev alone, one could compile a long list of such p r e m a t u r e l y d a m a g e d buildings. All t h i s n e c e s s i t a t e s drawing the attention of design and construction e n g i n e e r s once again to the question of c o r r e c t l y d i s s e c t i n g buildings by d e f o r m a t i o n joints. D e f o r m a t i o n joints a r e c l a s s i f i e d into t h r e e t y p e s , a c c o r d i n g to t h e i r p u r p o s e and constructional f e a t u r e s : s e t t l e m e n t t e m p e r a t u r e and contraction. The type examined below will, in the main, be the s e t t l e m e n t joints. A s e t t l e m e n t joint in one v e r t i c a l plane should d i s s e c t the foundations and all i t e m s of the a b o v e ground s t o r i e s of the building {walls, floors, f r a m e e l e m e n t s , etc.). Also, the s e t t l e m e n t joints in the wails and the foundations should coincide, and those in the floors and other i t e m s should m a t c h each other. Settlement joints should be provided in all c a s e s where uneven s e t t l e m e n t of the building foundation is anticipated: a) at the junctions of building components located on d i s s i m i l a r soils or c o n s t r u c t e d at different times; b) when a building is c o n s t r u c t e d adjacent to an existing s t r u c t u r e ; c) when the difference in height of individual p a r t s of a building e x c e e d s 10 m; d) when the foundations of adjoining walls have a c o n s i d e r a b l e difference in b a s e width and e m b e d m e n t depth, and likewise if the t y p e s of foundation under v a r i o u s p a r t s of the building a r e different, viz. s t r i p footings, piled foundations, continuous slab, individual supports, etc. The e m b e d m e n t of the adjoining foundations of two p a r t s of a building s e p a r a t e d by a s e t t l e m e n t joint should be maintained at the s a m e level. When constructing a s t r u c t u r e adjacent to an existing building, one must take into account the soil p r e s s u r e distribution under the foundations. The s t r e s s e s which a r e g e n e r a t e d in the soft by the weight of the building, and which cause its s e t t l e ment, a r e d i s t r i b u t e d not only v e r t i c a l l y with depth but also l a t e r a l l y beyond the foundation boundaries. T h e r e f o r e , even with the p r o v i s i o n of a s e t t l e m e n t joint and the e mbedment of the new foundations to the level of the foundation of the existing building, c r a c k s a r e often f o r m e d in the walls of the l a t t e r , t h e s e being the r e s u l t of subsequent s e t t l e m e n t of the end-wall foundation of the old building, caused by the supp l e m e n t a r y consolidation of the foundation soil by the weight of the new building constructed alongside. Kiev. T r a n s l a t e d f r o m Osnovaniya, Fkmdamenty [ Mekhanika Gruntov, No. 3, pp. 16-17, M a y - J u n e ~1972.
© 1972 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West I7th Street, New York, N. Y. 10011. All rights reserved. This article cannot be reproduced for an 7 purpose whatsoever without permission of the publisher, d copy of this article is available from the publisher for $15.00.
169
As an example of an u n s u c c e s s f u l foundation design when c o n s t r u c t i n g a building adjoining an e x i s t ing s t r u c t u r e , one can cite the f i v e - s t o r y b r i c k r e s idential building c o n s t r u c t e d in 1959 at 57 Shevchenko Boulevard, c o r n e r of Vozdukhoflotsk P r o s p e c t , Kiev, using r e i n f o r c e d c o n c r e t e piles. The p i l e s p e n e t r a t e d through a highly p e a t y soil 3 to 4 a~ thick located at a depth of 5 to 6 m, and were driven ] to 2 m into the underlying sand deposit. In 1961, a s i m i l a r r e s i d e n tial building was e r e c t e d adjacent to it, its foundation c o m p r i s i n g a continuous ribbed slab.
Fig. 1. Damage to a r e s i d e n t i a l building, caused by the construction of a new building alongside. a) Old building, damaged; b) new building. AB z~, As
AI
'-B e~%'~///2/h=
Fig. 2
Fig. 3
Fig. 4
Fig. 2. Schematic d i a g r a m of settlement joint. Fig. 3. Construction of walls on c a n t i l e v e r wall b e a m s . 1) C a n t i l e v e r b e a m s of wall A; 2) cantile v e r b e a m s of wall B. Fig. 4. Schematic d i a g r a m of a joint which p r e vents drafts.
The consolidation and settlement of the soil caused by the weight of the new building, extended to a c o n s i d e r a b l e depth and in all d i r e c t i o n s outside the slab, and consequently enveloped a zone under the p r e viously constructed building alongside. Thus, a thick soil l a y e r and the p i l e s under p a r t of this building adjoining the slab settled w h e r e a s the r e m a i n d e r of the building suffered no s e t t l e m e n t . As the result of the uneven s u p p l e m e n t a r y s e t tlement of s o m e of the piles, the building at No. 57 was split by c r a c k s o v e r its full height, the c r a c k s widening with elevation and reaching a m a x i m u m opening of 15 c m at the top (Fig. 1). The c r a c k s w e r e r e peatedly stopped up, but they n e v e r t h e l e s s opened again a f t e r a t i m e , indicating the continuation of deformations° In this c a s e , the inevitability d uneven s e t t l e ment was not recognized and it was wrong to adopt a slab foundation under the new building, which should have been e r e c t e d on p i l e s also. To avoid damaging the existing building by the blows d e l i v e r e d by p i l e driving equipment, the piles could have been sunk a f t e r p r e l i m i n a r y boring, o r c o n c r e t e d - i n - p l a c e b o r e d p i l e s used.
To eliminate d e f o r m a t i o n s in the existing building, the new building being designed for construction alongside should be positioned to provide an a p p r o p i r a t e intervening space. When constructing the new building adjoining the existing s t r u c t u r e , it is s o m e t i m e s p o s s i b l e to move the foundation of the new end wall an a p p r o p r i a t e distance away f r o m the existing end wall, and to e r e c t the a b o v e - g r o u n d end e l e m e n t s of the new building on c a n t i l e v e r e d wall b e a m s . If the foundations have to be positioned side by side, then, before e r e c t i n g the whole new building, it is n e c e s s a r y to d r i v e a row of t i m b e r or steel sheet piling between the old and new foundations, a s this substantially r e d u c e s the additional s t r e s s e s under the existing foundation due to the weight of the new building. If the v i b r a t o r y method of sinking the sheet piling is adopted, the v i b r a t o r should be worked in short b u r s t s so as to p r e c l u d e a d e s t r u c t i v e build-up of v i b r a t i o n s in the s t r u c t u r a l e l e m e n t s of the existing building, should t h e i r frequency coincide with that of the v i b r a t o r . B r i c k buildings should be dissected by s e t t l e m e n t joints through the blank portions of the walls; or through dividing walls, at the t r a n s v e r s e walt. The settlement joint should be designed to e n s u r e that both p a r t s of the building and t h e i r s t r u c t u r a l e l e m e n t s will r e t a i n t h e i r strength and stability; and that the int e r i o r r o o m s will be p r o t e c t e d f r o m rainfall and drafts, in the event of substantial d i f f e r e n c e s in the s e t t l e ment of the two p a r t s of the building o r of l a r g e angles of tilt.
170
The most r e l i a b l e design of a s e t t l e m e n t joint is s h o w n i n F i g . 2, where p r o v i s i o n is made for closing t r a n s v e r s e walls, one b r i c k in t h i c k n e s s , in both p a r t s of the d i s s e c t e d building. This design e n s u r e s both stability and t h r e e - d i m e n s i o n a l rigidity of both sections, even if t h e i r s e t t l e m e n t s or the tilt, a r e conside r a b l e , which can o c c u r with weak foundation soils. The foundations of the p a i r e d t r a n s v e r s e walls in this case can be made discontinuous with a p r o j e c t i o n of the n e c e s s a r y c a n t i l e v e r development under the wall b e a m of the adjoining t r a n s v e r s e wall (Fig. 3). A i r t i g h t u e s s of s e t t l e m e n t joints can also be e n s u r e d by the design shown in Fig. 4, which p r o v i d e s f o r the c o n s t r u c t i o n of a m a s o n r y t r a n s v e r s e wall 1 alongside the joint, in one p a r t of the building only, closing in the g r e a t e s t segment of the longitudinal walls, f r o m the joint to the next t r a n s v e r s e m a s o n r y wall. Instead of a second wall, a p a r t i t i o n 2 is provided. T h i s design c a n be sufficiently r e l i a b l e where the foundation soils under the bulding a r e m o r e c o m p a c t . At the abutting plane of the longitudinal m a s o n r y walls of both p a r t s of the building, it is usual to i n c o r p o r a t e g r o o v e s 3, with the tongue 4 one h a l f - b r i c k wide. The s e t t l e m e n t joints f o r l a r g e - p a n e l buildings a r e of s i m i l a r design as those f o r b r i c k buildings. Both p a r t s of such buildings a r e closed in at the s e t t l e m e n t joint by blank, smooth, p a r a l l e l t r a n s v e r s e wall panels. A t o n g u e - a n d - g r o o v e detail is not provided at joints in l a r g e - p a n e l buildings. The s e t t l e m e n t joints of buildings made up of s p a c i o u s - m o d u l a r r o o m s have the s a m e flush joint. The s e t t l e m e n t joints in f r a m e w o r k buildings a r e effected by one of the following two methods: 1. The two adjoining t r a n s v e r s e rows of columns a r e a r r a n g e d to f o r m a s e t t l e m e n t joint and to close in each p a r t of the building at the joint. This, the m o s t reliable method of c o n s t r u c t i o n a l lows both p a r t s of the d i s s e c t e d building to settle independently of each other. 2. The longitudinal e l e m e n t s of the f l o o r s and suspended wall panels a r e laid in an a r t i c u l a t e d p a t t e r n , onto t r a n s v e r s e c o l l a r b e a m s and columns at one of the middle spans of the building (where a s e t t l e m e n t joint is required), which allows e a c h p a r t of the building to settle independently. Howe v e r , this method can be adopted only where the anticipated r e l a t i v e s e t t l e m e n t between the two p a r t s of the building is v e r y s m a l l , as o t h e r w i s e even an insignificant rotation of the hinges can lead to the f o r m a t i o n of c r a c k s . F o r all designs of s e t t l e m e n t joints, and f o r any type of building construction and of m a t e r i a l s , the design of the spanning of the building in the roofing details r e q u i r e s special attention: The spanning a r r a n g e m e n t should be flexible and f r e e to move, able to ' b r e a t h e ~ and to a c c o m m o d a t e all p o s s i b l e rotations, tilting and s e t t l e m e n t of both p a r t s of the building, and to p r o t e c t t h e m r e l i a b l y f r o m the infiltration of r a i n s t o r m and s n o w - m e l t w a t e r s .
,~?F~ti~iri~'il~l~lti~ll~ill.~l,
il~r ~
i~li~lz,~li~lil~iii. .I
Fig. 5. D e t e r m i n a t i o n of the dimensions of zone of p o s s i b l e def o r m a t i o n s , a) S e c o n d - s t a g e c o n s t r u c t i o n of building; b) f i r s t stage construction of building; Z.D. (zone of possible d e f o r m a tion); 1) s e t t l e m e n t joint; 2) r e inforced c o l l a r s .
In p a r t s of buildings sectionalized by s e t t l e m e n t joints which a r e being c o n s t r u c t e d above underground m i n e s , on soils p r o n e to s l u m p type s e t t l e m e n t , o v e r the r o u t e s of underground r a i l w a y s , etc., t h e r e can occur, in addition to uneven settlement, horizontal f o r c e s a r i s i n g f r o m horizontal d e f o r m a t i o n s of the soil in the specific conditions cited. In t h e s e c a s e s , whatever the s t r u c t u r a l design adopted, the buildings should i n c o r p o r a t e e l e m e n t s which can a b s o r b t h e s e f o r c e s (closed c o l l a r s of monolithic r e i n f o r c e d c o n c r e t e or of p r e f a b r i c a t e d r e i n f o r c e d - c o n c r e t e e l e m e n t s ) . T h e s e e l e m e n t s a r e laid along blocks of the s t r i p footings of both p a r t s of the building, whether of brick, l a r g e - p a n e l or l a r g e - b l o c k type, which is d i s s e c t e d by a s e t t l e m e n t joint, and also in the a b o v e - g r o u n d s t o r i e s of b r i c k buildings. In such c a s e s , s u p p l e m e n t a r y r e i n f o r c i n g m e s h can be placed at an u p p e r level in the opening in the a b o v e - g r o u n d p a r t s of l a r g e - p a n e l buildings, and this m a r k e d l y i n c r e a s e s the general t h r e e - d i m e n s i o n a l stiffness of the f r a m e w o r k of each p a r t of t h e building. In addition, the joint width in many c a s e s should be i n c r e a s e d .
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When constructing a building in two stages, both p a r t s should likewise be divided by a settlement joint, insofar that the second part during its erection should be regarded as an addition to an existing building. Consequently, in this case also, it is desirable to provide a gap between the two p a r t s of the building, even if this is only between t h e i r foundations. If it is n e c e s s a r y to locate the foundations of the two p a r t s of a building alongside each other, a row of sheet piling should be driven between them, before c o n s t r u c t i n g the second stage. If it is not possible to drive such piling, it is n e c e s s a r y to provide r e i n f o r c e d - c o n c r e t e c o l l a r s at e v e r y s t o r y of the building at its end wall. These c o l l a r s must be laid on the end wall and extended along all the longitudinal wall for a distance which exceeds by 3 to 4 m the length of the zone of possible deformations in the longitudinal walls caused by supplementary settlements of the end-wall foundation of the second-stage of the building. The length of the zone of possible deformation in the longitudinal walls of the f i r s t - s t a g e building is difficult to determine accurately. On the strength of observations made on old buildings when e r e c t i n g new buildings alongside them, this length is determined approximately by a line drawn on the facade of the building at an angle of 30 ° to the vertical, starting f r o m the base level of the end-wall foundation at the settlement joint, as indicated by the hatched a r e a in Fig. 5. The design of the r e i n f o r c e d c o l l a r s is determined with due r e g a r d for the slumping-settlement c h a r a c t e r i s t i c s of the soils c o m p r i s i n g the building foundation at the specific site, f o r the type of c o n s t r u c tion of the building, and other conditions. Thus, where a significant settlement of the second-stage p a r t of a building is expected, the f i r s t - s t a g e part - a s s u m e d constructed of b r i c k - should be provided with r e i n f o r c e d - c o n c r e t e c o l l a r s having a thickness of two or three c o u r s e s (15 o r 22 cm), located at each story, reinforcing them with four rods of 16-mm diam. in the upper and lower zone, with 6 - m m diam. s t i r r u p s at 2 0 - c m centers. Where a small settlement is expected, in o r d e r to strengthen a l a r g e - p a n e l building in its first stage, reinforced joints can be adopted, a r r a n g e d at the horizontal butt junction of wall panels, c o m prising a mesh of four o r five longitudinal rods of 3 or 4 m m diam. and lateral rods of the same diameter spaced 15 to 20 cm apart, using a h i g h - s t r e n g t h cement m o r t a r .
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