Integrating Plug-in Places making for Sustainable Development: Reimagining Urban Spaces for a Greener Future

A Case Study in Chennai, India

Abstract

Accelerating urbanization worldwide necessitates urgent action towards sustainable development. An essential strategy is in the creation of plug-in places, which involves redesigning urban landscapes to prioritize environmental well-being. By integrating green infrastructure and innovative design, plugin places have the potential to mitigate the adverse effects of urban growth while steering towards a more eco-conscious future. Traditional urban development often exacerbates environmental degradation and social inequalities. However, plugin places offer a promising solution by advocating for sustainable technologies, community engagement, and ecological resilience. The present study emphasizes the growing challenges faced by modern cities due to rapid urbanization. This results in neglected residual spaces that could be strategically repurposed to foster social interaction, recreational activities, and environmental benefits. The study involves a comprehensive analysis of residual spaces within Chennai city, particularly Velachery subarea focusing on their potential for transformation. It involves field study on place making to glean insights into innovative design approaches. The concept of take away plug-in spaces is explored to understand their impact on designated areas. The findings demonstrate the potential of transforming neglected residual spaces into community hubs, incorporating green spaces, mixed-use developments, and infrastructure projects. This contributes to revitalizing urban environments and fostering a more sustainable future for Chennai. The study emphasizes the importance of proactive planning to accommodate future developments and societal needs. It highlights the potential of transforming Chennai's cityscape by strategically utilizing residual spaces to create a more vibrant, inclusive, and sustainable urban environment.

Introduction

As cities are projected to experience rapid population growth, concerns about environmental consequences have urged administrative efforts to improve urban liveability and sustainability (Douglas, Lennon, et al., 2017). The concept of compact, revitalized cities is seen as a potential solution to urban extension. These cities would be characterized by high density, mixed-use development, efficient public transportation (transit-oriented development), and encouragement of cycling and walking (Artmann, Inostroza et al., 2019; Haaland and van den Bosch, 2015; Lennon, 2021; Sharma, Saini, et al., 2023). However, achieving a balance between urban density, quality of life, and environmental benefits remains a challenge. Densification often comes at the cost of green spaces, crucial for urban life and health (Du and Zhang, 2020; Popa, Onose, et al., 2022; Russo and Cirella, 2018).

A 2015 review by Haaland and van den Bosch (2015) highlighted the growing evidence of this trend, supported by subsequent research (Boehnke, Krehl, et al., 2022; Fatiah, Ponrahono, et al., 2021; Yandri, Priyarsono, et al., 2021). This presents a complex issue, as both densification and greening are considered essential for sustainable development (Artmann, Inostroza, et al., 2019; Azmi, 2023; Du and Zhang, 2020; Haaland and van den Bosch, 2015). Finding a way to achieve both goals is crucial for the future of cities. While densification plays a crucial role in safeguarding the environment and landscapes, urban green spaces also serve as vital tools in combating climate change and its impacts. They contribute to enhancing air quality, reducing surface runoff, mitigating the heat island effect, providing habitats for wildlife, and promoting biodiversity (Badiu, Iojă, et al., 2016; Gupta, Kumar, et al., 2012; Saraswat, Pipralia, et al., 2024).

Despite the increasingly recognized benefits of urban green spaces, determining the ideal amount of greenery for urban residents remains a subject of scientific debate (Gupta, Kumar, et al., 2012; Russo and Cirella, 2018). This presents a challenge for urban green space planners and designers, as understanding the relationship between population size and the quality and quantity of green space is essential for the sustainability, health, and resilience of urban areas (Badiu, Iojă, et al., 2016; Escobedo, Giannico, et al., 2019; Gupta, Kumar, et al., 2012; Ha, Kim, et al., 2022; Russo and Cirella, 2018; Wang and Banzhaf, 2018; Wikström, 2005). The complexity of this issue is underscored by the fact that it is not just the total area of green space per unit that matters, but also factors like its quality, accessibility and distribution across the urban landscape (Escobedo, Giannico, et al., 2019; Ha, Kim, et al., 2022; Latasa, Laurenz, et al., 2022; Lauria and Vessella, 2021; Wikström, 2005). Merely adhering to quantitative standards without considering access to green spaces is insufficient at the urban scale, as it can mask deficiencies on other levels (Douglas, Lennon, et al., 2017).

The challenge of green space becomes more acute in compact cities and those undergoing densification processes. Ecosystem services research highlights the need for meticulous planning and a robust knowledge base on the provision of essential ecosystem services within the limited area of green space in compact cities (Douglas, Lennon, et al., 2017; Ekkel and de Vries, 2017; Konijnendijk, 2023; Lähde and Di Marino, 2019). Approaches such as Green Infrastructure (GI) and landscape ecology emphasize connectivity and networked planning (Douglas, Lennon, et al., 2017). Addressing the compact city and sustainability paradox, and managing the trade-offs between compactness and greenery, necessitates integrative approaches that encompass a holistic understanding of the interplay between built and green components, along with their social, economic, and ecological drivers (Haaland and van den Bosch, 2015). Achieving this requires the integration of knowledge from diverse fields, bridging the gap between research and application, and fostering collaboration among government bodies, citizens, universities and research institutes (Konijnendijk, 2023).

The fragmentation of knowledge and research on urban green issues into isolated silos has been a recurring challenge in the field. Escobedo, Giannico, et al. (2019) highlighted this issue, emphasizing the need for integrative transdisciplinary research rather than conceptual segregation. Other similarly noted that the requisite knowledge for effectively managing greenery in compact cities exists across various related fields, emphasizing the need for cohesive integration (Escobedo, Giannico, et al., 2019; Honeck, Sanguet, et al., 2020; Lu, Oh, et al., 2022; Zhang, van den Berg, et al., 2017).

Spatial categories of urban public spaces encompass a diverse range of areas, each with its unique characteristics and functions. Parkland and open green spaces, initially designated for ecological, recreational, and leisure activities, often blur distinctions between formal parks, wildlife corridors, and recreational facilities. These spaces cater to various needs, from ecological conservation to leisure pursuits, managed by multiple stakeholders. Traffic-dominated streets, while essential for vehicular circulation, pose challenges to pedestrian safety and urban aesthetics.

Despite efforts to prioritize pedestrian access, the spatial dominance of vehicles persists, influenced by infrastructure design and regulatory requirements. Residual spaces, stemming from surplus land allocations in new developments or infrastructure projects, often lack intentional design for public use. Instead, they emerge as by-products of planning necessities, offering opportunities for creative repurposing. Building-centred spaces, exemplified by iconic structures, serve as architectural landmarks shaping urban skylines (Escobedo, Giannico, et al., 2019; Gavrilidis, Popa, et al., 2022; Honeck, Sanguet, et al., 2020; Lu, Oh, et al., 2022; Wang and Banzhaf, 2018).

These buildings command significant surrounding areas, resembling sculptural installations, and necessitate careful integration into the urban fabric. Small and large urban spaces, including squares, gardens, and informal areas, play distinct roles in urban life. Large urban spaces serve as focal points for public gatherings and civic activities, while small urban spaces, such as pocket parks and semi-private areas, offer localized amenities and enhance pedestrian experiences. Effective management and intentional design are essential for optimizing the functionality and attractiveness of these spaces, ensuring their contribution to vibrant urban environments (Wikström, 2005; Yandri, Supratikta, et al., 2024).

Rahmoun and Zhao (2024) delineates four distinct categories of residual spaces as shown in Figure 1. First, he identifies Inter zones, emblematic of modernist planning principles, which visibly demarcate spatial autonomy between architectural units. These zones, shaped by surrounding landscapes, act as buffers, accommodating irregularities in built structures, followed by Fringe areas which emerge Fringe areas emerge as transitional spaces where cultivated land converges with wilderness, often fostering clandestine activities along the peripheries of urban areas. Infrastructural border zones, delineated by transportation networks and utility systems, exhibit varied degrees of vegetation and accessibility, occasionally serving as venues for both legal and illicit activities. Lastly, Expansion areas signify prospective development sites, contingent upon planning authorities' foresight and allocation of land. Ranging from undeveloped lots to prepared parcels, these areas may attract illegal dumping when unsecured.

Figure 1. Categories of residual spaces (Rahmoun and Zhao, 2024)

The delineation of a study area is crucial for understanding and analysing various factors that contribute to its dynamics. Major factors influencing the delineation include the presence of main connecting networks, such as transportation routes, which play a pivotal role in determining the accessibility and connectivity within the area. Additionally, existing land use patterns provide valuable insights into the current utilization of space and resources. Anticipated infrastructural developments along major networks are also significant, as they can shape future growth and land use. Nodes within the major network that act as busy transportation hubs further emphasize areas of high activity and potential development. Furthermore, the classification of residual lands within the area is essential for assessing available space for future development.

The total number of identified residual lands, whether along major corridors or elsewhere, provides a foundation for urban planning and land management strategies Understanding the factors influencing changes in land use patterns over time is critical for effective planning and decision-making. The observed increase in mixed-use residences and a decrease in primary residences due to commercialization factors highlight evolving socioeconomic trends. Moreover, the rise in industrial buildings signifies shifts in economic activities within the area. The growing need for leisure activities underscores changing lifestyle preferences, while urbanization emerges as a dominant pattern influencing land use.

This paper is aimed at those responsible for and concerned with the quality of the urban environment in cities, and more specifically those involved in the planning, design and management of the outdoor spaces to bring about viable solutions in existing urban open spaces with sustainable recommendations for transforming residual spaces into successful urban public spaces. The paper prospects that transformation demonstrated herein shall direct the stakeholders and the community to implement in the existing and the future design of urban spaces. This paper aims to analyse urban growth patterns and their impact on urban blight. It identifies and categorizes residual spaces for regeneration to restore community vitality through place making. The study promotes diverse, need-based use of these spaces via temporary plug-in architecture.

Significance of The Study

The unchecked urbanization and haphazard development in Chennai have led to widespread congestion and urban sprawl, resulting in the emergence of residual void spaces scattered throughout the city. These neglected areas, often overlooked in the planning process, represent missed opportunities for the creation of vibrant public spaces. Consequently, the lack of utilization of these public spaces has had a detrimental effect on the dynamism and liveliness of the surrounding urban environment. Residents and visitors alike find themselves deprived of valuable leisure opportunities, as there are insufficient considerations for fostering community interaction and recreational activities. This issue underscores the urgent need for comprehensive work and analysis to address the shortages in urban planning and design, aiming to revitalize these neglected spaces and enhance the overall quality of life for Chennai's inhabitants.

Concerning urban planning, underutilized spaces present opportunities for temporary occupation, fostering social interaction and enriching the urban experience. The concept of take away plug-in spaces emphasizes the importance of activating vacant or underused areas for short-term uses, contributing to the vitality of the city. This approach acknowledges the significance of temporary interventions in urban design, offering a means to explore the city's potential and create convivial urban environments. By integrating formal and informal elements, take away plug-in spaces challenge conventional urban development paradigms, embracing diversity and alternative viewpoints. Additionally, understanding people's behaviour in urban environments is crucial. Take away plug-in spaces respond to the desire for adaptable urban spaces, aligning with the practice of urban wandering and exploring the psycho geographical aspects of the cityscape. This approach emphasizes the dynamic interaction between individuals, social dynamics, and the built environment, shaping a more responsive and inclusive urban fabric.

Study Area and Methodology

Chennai, the capital city of Tamil Nadu, lies on the south-eastern coast of India, along the shores of the Bay of Bengal. The city is known for its rich cultural heritage, vibrant traditions, and rapid urbanization. Geographically, Chennai sits on the Coromandel Coast, a narrow coastal plain bordered by the Eastern Ghats to the west and the Bay of Bengal to the east. The city is built on flat terrain with the Adyar and Cooum rivers flowing through its boundaries. Chennai's coastline stretches for approximately 19 kilometres, with Marina Beach being one of the longest urban beaches in the world. Driven by the presence of prominent IT establishments along the OMR and GST Road, Velachery (Figure 2) has witnessed a surge in residential growth and demand. Professionals working in these hubs are increasingly choosing Velachery as their home base, attracted by its excellent facilities, efficient connectivity, and proximity to their workplaces.

This rapid development is directly linked to the booming IT sector, with new housing projects sprouting to meet the rising demand for quality accommodation. Connectivity plays a crucial role in the Velachery area. It boasts all-in-one access to Chennai International Airport via the Inner Ring Road, while a network of bus routes and railway stations offer convenient public transportation options. Residents have easy access to buses, and the MRTS railway system connects Velachery to key areas like OMR, ECR, Besant Nagar, and Marina Beach. Velachery's strategic location adds to its attractiveness. Surrounded by established IT hubs and offering a variety of residential options, it has become a preferred choice for both homebuyers and investors. The surrounding areas like Thiruvanmiyur, Guindy, Adyar, Perungudi, Taramani, and Madippakkam are also witnessing significant residential growth. This coupled with ongoing infrastructural developments, good connectivity, and a plethora of commercial establishments paints a promising picture for future growth. Velachery is poised to attract even more residents seeking a convenient, well-connected, and vibrant living environment.

Figure 2. GPS image and Delineation of study area, Velachery, Chennai, India

The scope of this study includes a comprehensive exploration of residual spaces, primarily focusing on their classification. Specifically, the work explores the analysis and categorization of negative residual public spaces within Velachery, Chennai, employing a systematic classification framework. The study extends to a thorough examination of existing work and case studies related to place making, shedding light on innovative approaches and strategies. Additionally, the study incorporates an in-depth exploration of transformative takeaway plug-in spaces, aiming to identify and understand their impact on the designated areas.

The research methodology involves rigorous data collection and site analysis of the targeted geographic region, providing a foundational understanding of the local context. Finally, the study aims to propose design solutions tailored to address the challenges and opportunities presented by plug-in spaces as seen in Figure 3 in the identified main area, contributing valuable insights to the enhancement of public spaces in Velachery, Chennai. Despite the comprehensive scope, it is important to acknowledge certain limitations inherent to the study, such as potential constraints in data availability, resource limitations, and external factors that may impact the feasibility of certain design interventions.

Figure 3. Solution for plug-in place making

It is challenging to envision the contemporary cityscape, which has expanded significantly. Despite the addition of numerous commercial and institutional buildings, there is a noticeable absence of new public spaces apart from a handful of memorials. Moreover, the perception of leisure and communal gathering has evolved, intertwined closely with consumerism. Many air-conditioned malls, despite resembling streets or plazas, remain privately owned, exemplified by the design of places like Phoenix Market City (Phoenix Mall), Express Avenue which lacks seating and encourages constant movement. Unfortunately, the streets, once bustling with activity including vibrant street vendors, now feel exclusive to a select few, leaving the hawkers marginalized. Unexpected urban developments, like the growth of south Chennai, have shifted the city's dynamics, privileging certain areas over others. Economic liberalization has favoured south Chennai, attracting software parks and international companies, transforming places like Elliots Beach into trendy destinations. Conversely, north Chennai is predominantly industrial and commercial.

Residual spaces, as observed in their current land use pattern often exhibit fragmented and underutilized areas within urban landscapes, characterized by ad hoc activities and neglected infrastructure. However, with a proposed land use pattern, these residual spaces could be transformed into vibrant community hubs, incorporating mixed-use developments, green spaces, and innovative infrastructure projects, thus revitalizing urban environments and enhancing quality of life for residents. By repurposing these spaces with strategic planning and community engagement, cities can unlock their potential to foster social cohesion, economic growth, and environmental sustainability. In discussing the typology of residual spaces, it becomes evident that these areas encompass a spectrum of functions and characteristics, including fringe areas, infrastructural border zones, and expansion areas. Each type reflects distinct spatial relationships and planning dynamics within urban environments. Furthermore, exploring the ownership of residual lands unveils a complex interplay between public and private entities, with implications for future development, resource allocation, and the mitigation of urban blight.

The flowchart as provided in Figure 4 outlines a systematic approach to repurposing residual spaces through place making. It begins with identifying the causes behind residual spaces, such as urban sprawl, land use patterns, and infrastructural changes, followed by understanding their typologies like fringe areas or interstitial zones. Portable or modular structures are then explored for plug-in place making, emphasizing flexibility and sustainability. Specific residual spaces within the study area are identified through mapping and analysis, with attention to their typology, ownership, site area and current condition. Site ownership and site area are verified to ensure sustainable use, and spatial needs are assessed based on social behaviour and site context. Finally, modular takeaway structures are implemented to transform these spaces into functional, green, and vibrant community hubs, enhancing urban ecology and public well-being.

Figure 4. Framework for transforming residual spaces into vibrant community hubs through place-making

Proposed Structural Elements and Materials

Different types of modules haves been proposed in the present study for plug-in place making and depend on the adaptability and the movability of the structure for a particular use. The V-Fold module is a structural design element commonly used in various applications, including partitions, façades, and decorative features. Its distinctive V-shaped profile provides both structural integrity and aesthetic appeal. The module typically consists of a series of interconnected panels arranged to form a flexible and modular system. Additionally, the panels can be fabricated with perforations or patterns to enhance visual interest and control light penetration. The V-Fold module's adaptability extends to its installation methods, which can vary depending on the specific application and desired aesthetic. It can be installed as a standalone feature or integrated into larger architectural assemblies. Furthermore, the modular nature of the V-Fold system enables easy disassembly and reconfiguration, facilitating maintenance and future modifications.

The T-Fold module features a distinctive T-shaped profile, which provides both structural stability and visual interest. The module consists of interconnected panels arranged in a perpendicular configuration. This arrangement allows for flexibility in design and adaptability to different spatial requirements. The T-Fold module offers a balance of structural integrity and aesthetic appeal, making it suitable for a wide range of architectural applications. The panels are designed to fold along predefined hinge points, enabling dynamic configurations and easy installation.

The X-Fold module is characterized by its X-shaped profile, which lends itself to intricate and dynamic architectural forms. The X-Fold module consists of interconnected panels arranged in a cross-shaped configuration. This configuration allows for multidirectional folding and articulation, enabling the creation of complex spatial geometries and sculptural elements. It offers a versatile and visually striking solution for architectural expression, suitable for both interior and exterior applications.

The Zig Zag module features a zigzagging profile, which adds visual interest and texture to architectural surfaces. Comprising interconnected panels arranged in a series of alternating folds, the Zig Zag module creates a rhythmic pattern that can be customized to suit different design aesthetics. It offers a dynamic and adaptable solution for partitioning, screening, and decorative applications. Its modular design allows for easy installation and reconfiguration, making it ideal for temporary or movable structures. A detailed structural configuration and the specification has been provided in Annex 1.

Similarly, materials were also studied for their different structural configuration and compatibility with the structure. Some of the suggested materials are: Ethylene Tetra Fluoro Ethylene (ETFE), Smart Wrap, Aluminium Composite Panels (ACP), Polycarbonate twin-wall sheets, Glass Reinforced Plastic (GRP). ETFE, available in both single-ply membranes and cushion panels, offers a lightweight and versatile solution for architectural applications. Single-layer installations, reinforced by wire cables or lightweight metals, provide thermal resistance and stability to structures. ETFE's low load-bearing capacity reduces strain on supporting frameworks, making it an efficient choice. During the day, it allows natural light to penetrate interiors, while at night, it can provide a vibrant display with interior or exterior lighting. Its recyclable nature contributes to sustainability, and its insulation properties improve with multiple layers. Despite its advantages in flexibility, portability, and the possibility of multi-color applications, ETFE's plastic composition may pose drawbacks for some, though workarounds like adding extra layers can mitigate issues like rain noise. Overall, ETFE presents a modern and adaptable alternative to traditional glazing systems, offering ease of installation and dismantling for various architectural designs.

Smart Wrap presents a cutting-edge solution for building facades by combining climate regulation, energy generation, lighting, and information display into one lightweight material. This is achieved through the use of deposition-printed organic photovoltaics (OPV) and organic light-emitting diodes (OLED) on thin PET films. It is not only energy-efficient but also customizable and sustainable. Its assembly and dismantling process are simple and eco-friendly, with virtually no waste generated during removal. While its high-tech manufacturing process may limit availability initially, its lightweight nature and rapid installation make it a promising solution, particularly for projects in developing regions. With the ability to change color and appearance while providing shelter and controlling interior climates, Smart Wrap represents a versatile and forward-thinking option for modern architecture.

ACPs serve as versatile solutions for both external and internal architectural needs, requiring minimal maintenance over extended periods, often a decade or more. These panels, known for their durability, are corrosion-resistant, making them ideal for a range of applications. ACP panels, essentially sandwich panels, offer a combination of high structural rigidity and low weight, making them suitable for portable structures and applications where strength and lightweight properties are essential. Polycarbonate twin-wall sheets offer a lightweight and easy-to-install solution for various construction projects. Its stiffness allows for the design of structures with greater spans, while their flexibility enables them to be cold bent for use in curved and cube applications, making them versatile for diverse designs. With a high light transmission capacity of around 85%, these sheets minimize condensation and dripping from overhead, enhancing comfort in enclosed spaces.

Overall, polycarbonate twin-wall sheets combine durability, flexibility, and excellent light transmission, making them a preferred choice for architectural and construction applications where ease of handling and aesthetic considerations are essential. GRP offers a durable and versatile solution for portable structures, consisting of a composite material where plastic is reinforced by fine glass fibers. The strength and weight of GRP are determined by the pattern of weave, which varies according to different practical applications. Once resin is added, the polyester in GRP becomes thermosetting, providing high temperature resistance and UV protection. A detailed comparison of materials with various parameters are provided in Annex 2.

Potential Sites: Needs and Solutions

For site selection in the Inter zones several factors of residual lands have been considered, including the land area, typology, and ownership of the residual land as shown in Figure 5. Given the existing scenario where most of these site locations consist of unused or underutilized parks, dump yards, or spaces between buildings, there is a clear need for the development of recreational spaces and community facilities as demonstrated by these pictures, (as provided in Figure 10 taken during 2018 and 2019). To address this, a comprehensive solution program is proposed, including the installation of seating areas, sheltered gathering spaces, libraries, gyms, children's play areas etc. (Annex 3) The typology of the residual land, which often lies between buildings or serves as vacant lots, presents an opportunity for creative urban re development. By leveraging these spaces, the community can benefit from new amenities and gathering places that enhance quality of life. However, it's crucial to consider the ownership status of these lands to ensure proper permissions and collaboration with relevant stakeholders for successful implementation. Moving to the Vijaya nagar (Junction Site 3), which spans three acres and experiences significant traffic due to its status as a nodal point and the presence of the Vijaya nagar bus stand, has an evident need for crowd management and the creation of visually pleasing, refreshing spaces. To address this, a solution program featuring pavilions and community gathering spaces is proposed. However, existing traffic congestion poses a significant challenge that must be addressed to optimize the functionality and safety of the area. Finally, the MRTS (Site 6), with its oversized infrastructure and abundant surrounding land, presents an opportunity for multifunctional development. The need for amenities such as play areas for children, exercise spaces, walking pavements, and social gathering spots is clear. Additionally, the potential relocation of offices under the flyover to these spaces can further optimize land use. A solution program encompassing children's play areas, pavilions, gyms, yoga centres, libraries, seating areas, parking shelters, and planters is proposed. However, accessibility and parking facilities must be addressed to accommodate increased socializing activities and ensure the usability of the space by all members of the community. Overall, by carefully considering the land characteristics, community needs, and potential challenges, these sites can be transformed into vibrant, inclusive spaces that enrich the lives of residents and visitors alike. Upon the location, 160 residual lands of various sizes, ownership and typology have been identified, in which six sites locations have been selected as potential sites to implement the proposed solutions for plug-in place-making based on the typology of the residual spaces, sufficient plot area to accommodate the plugin place making and ownership of the particular site which in turn enhances the benefits for stakeholders. Figure 6 through Figure 15 provides the detailed topography and ownership of the sites.

Figure 5. Identifying 160 residual lands in the delineated study area

Figure 6. Understanding the typology of the identified residual spaces.

Figure 7. Understanding the ownership of the identified residual spaces.

Figure 8. Understanding the plot area of the identified residual spaces

to understand the spatial accommodation of the plugin structures.

Figure 9. Location of identified six potential sites for the application of plug-in place making as a sustainable solution.

The sites 1, 2, 4, and 5, although not visible from major connectivity routes, are accessible via a minor road. However, it lacks a compound wall or any restrictions, and there are no hospitals or clinical centres nearby. Surrounding constructions are predominantly wall-to-wall. Despite this, there is a bus stop within walking distance, facilitating accessibility. To address micro-level impacts, facilities such as gyms, yoga centres, seating areas, canopies, play spaces, mobile toilets, and after-classrooms are proposed. For macro-level impacts, the inclusion of clinical centres, exhibitions, and pavilions with stages can enhance the site's functionality and community engagement. The sites 1, 2, 3, 4 and 5 as seen in Figure 9, exhibit strength in their potential for generating micro-level impacts, offering opportunities for various activities. Additionally, they provide a platform for fostering socio-cultural engagement through temple festivals. However, their weaknesses lie in the small access road, which may hinder accessibility and transportation. Despite this, opportunities abound for development, including the creation of after-classrooms, market spaces, seating areas, canopies and pavilions with stages, exhibit halls, libraries, gyms, yoga centres, and clinical centres. Nevertheless, the threat of increased crowds and people movement poses a challenge to be managed effectively to ensure a site's functionality and safety.

Figure 10. Site 1

Figure 11. Site 2

Figure 12. Site 3

Figure 13. Site 4

Figure 14. Site 5

Figure 15. Site 6

The Site 6 enhances its strength as a transit hub, with a bus stop conveniently located at the MRTS station, facilitating easy access for people from across Chennai. This accessibility ensures that the site can serve as a focal point for a wide range of activities. Furthermore, the presence of residences and offices beneath the flyover presents an opportunity for the integration of macro-level impacts into the site's development. Cultural festivals and leisure activities can enhance its socio-cultural significance. However, the challenge lies in designing the site while considering existing parking arrangements without disrupting them. Despite this, opportunities abound for the creation of after-classrooms, seating areas, canopies, pavilions with stages, exhibit halls, and clinical centres. Nonetheless, the potential increase in footfalls poses a threat that must be carefully managed to maintain the site's functionality and safety.

Proposed suitable plugin placing making structures as sustainable solution for the sites 1 to 6 by understanding the connecting network, surrounding land use, site observation and user analysis (Figure 10, Figure 11, Figure 12, Figure 13, Figure 14, Figure 15).

Discussion

Over time, urban settlements undergo significant changes due to the passage of time and interactions between different neighbourhoods, leading to transformations in various elements of the urban form, such as plotted land, built spaces, unbuilt spaces, streets, open spaces, and residual spaces. In this context, takeaway architecture—known globally for its innovative and flexible designs—has inspired designers worldwide by reimagining the potential of mobile structures. When these structures are strategically placed in residual spaces, they not only make these underutilized areas more memorable and functional but also serve as temporary landmarks that enhance the surrounding urban fabric (Çalışkan, 2024; Kim and Kwak, 2022). This concept aligns with the broader place making approach, a dynamic tool that positively impacts society by transforming cultural, leisure, and daily life activities into notable urban experiences. This research focuses on identifying the residual lands and their challenges in Velachery, an area in Chennai shaped by continuous urban transformations. The goal is to repurpose these neglected spaces into vibrant public areas using takeaway spaces as plug-in place making elements. By doing so, these spaces can serve as temporary breathing zones, contributing to a greener and more sustainable urban future.

Conclusion

Based on the present study the following conclusion have been drawn:

Residual spaces, though underutilized and fragmented, can be transformed into active community hubs through strategic land use. Proposed uses include mixed-use development, green areas, and innovative infrastructure to revitalize urban areas and enhance liveability.

Strategic repurposing of residual spaces through planning and community engagement fosters social, economic, and environmental benefits. Residual space typologies—such as fringes, infrastructural edges, and expansion zones—demand tailored spatial planning strategies.

Folded structural modules like V-Fold, T-Fold, X-Fold, and Zig-Zag enable flexible, adaptable, and visually engaging plug-in placemaking. Materials such as ETFE, SmartWrap, ACP, polycarbonate sheets, and GRP enhance durability, sustainability, and design versatility in architectural applications.

Plugin place-making sites must be selected based on land characteristics, community needs, and implementation challenges. Proposed interventions target both micro- and macro-level impacts, promoting community engagement, socio-cultural activity, and economic growth while addressing accessibility. Transforming residual spaces into active hubs supports inclusive, sustainable urban development.

Author Contributions

Conceptualization, P.H, T.S and A.G.; methodology, P.H, and A.G.; investigation, P.H; resources, P.H, and A.G.; data curation, P.H, and A.G.; writing—original draft preparation, P.H, T.S and A.G.; writing—review and editing, P.H, and T.S; supervision, P.H, T.S and A.G. All authors have read and agreed to the published version of the manuscript.

Ethics Declaration

The authors declare that they have no conflicts of interest regarding the publication of the paper.

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Appendices

 

Annex 1. Process of assembling the takeaway structures as a plug-in placemaking solution for the selected potential sites

V FOLD MODULE STRUCTURAL DETAILS

T FOLD MODULE STRUCTURAL DETAILS

X FOLD MODULE STRUCTURAL DETAILS

Zig Zagmodule Structural Details

 

Annex 2. Proposed suitable plug-in placemaking structures as a sustainable solution for Sites 1 to Site 6. understanding the connecting network, surrounding land use, site observation and user analysis

Annex 3 . Understanding of various materials based on parameters of use for the takeaway plug-in placemaking structures

Parameters / Materials		EFTE	Smart wrap	ACP panels	Polycarbonate twin wall	Glass reinforced plastic
1	Flexibility	It can be used as shelter for semi open structure, or facade system for fully closed structure with more transparency films or panel form.	As shelter for semi open structure, or facade system for fully closed structure with more transparency.	Well suited for enclosed structures where privacy is more necessary.	Based on the openness and closeness of the structure it can either be transparent or opaque.	Maximum used for fully closed structure.
2	Movability	Since it is light in weight it is easily transportable. Easily foldable while transporting since it is a fabric material.	Since it is a feasible portable material and light weight, it is easily transportable. It is in panel form so can be transported in piles.	Available in panel forms so it is transported in piles to the site.	Available in panel forms, so it is transported in the form of piles.	Available in panel forms, so it is transported in the form of piles.
3	Interactivity	The material is more transparent in nature, allowing interaction between internal and external environments. Presence of this material invites more people.	Due to transparency of the material, it allows interaction between the internal and external environment.	Since it is a solid panel, there is no interaction between the internal and external environment.	It allows visual interaction between inside and outside based on the transparency rate.	The material is opaque in nature and does not allow interaction between interior and exterior. The presence of this material invites more people.
4	Adaptability	Used as a single structure or single element. Either a building as a whole or for roofing alone, or for wall alone. Maximum is not used for internal partitioning because of its transparency.	Used as an exterior wall. Maximum not used for internal partitions because of its transparency	Used as external wall. Used for internal partitioning. More adaptable for changing function within the interior.	Used as external wall as a transparent structure or an opaque structure. Can be used as internal partitioning and is adaptable for changing functions within the interior.	Used as external wall. Used for internal partitioning. More adaptable for changing functions within the interior.
5	Mechanical Resistance	ETFE films are very elastic (up to 600% at breaking point), but still structurally resistant. It can be screwed on once the structure is erected on the site.	It can be easily fixed to aluminum frames.	It can be easily screwed onto aluminum or steel frames. It allows rotation, sliding, folding, and unfolding movement	It supports rotation, translation, folding, and unfolding movements.	It supports actions like rotating, moving, folding, and unfolding.
6	Transparence or opacity	ETFE films are highly transparent (from 90% to 95%).	It is more transparent in nature.	Since it is a solid panel, no rate of transparency is seen.	High light transmission thus it allows 80% of visible light to pass through. Opaque shades are also available for private, enclosed structures.	Both transparent and opaque panels are available.
7	Fire resistance	International tests for fire resistance are carried out and fire resistance has been proven. Fire ignites only above 800 degrees.	It has good fire resistance properties.	It is not self-combustible, but once there is fire from an external source the resistance of the material is based on the core material used like polyurethane or mineral wool.	Completely protected against fire and does not give off any kind of toxic gases.	It has good fire resistance properties.
8	Waterproof	ETFE does not allow water to penetrate inside and interiors are safe from the waterproofing aspect.	Does not allow water to penetrate inside and interiors are safe from the water proofing aspect.	The structure with ACP panels are watertight and some waterproof coats are to be added during manufacturing.	The material is waterproof and watertight given it is made of plastic.	The material forms an enclosure with watertight and airtight. No waterproof coating has to be provided.
9	Building Component s	Mostly suitable as roofing material. It can be used as wall element where the structure is to be more transparent in nature based on the function.	The material incorporates all of the functionality of a regular wall (insulation, security, electricity, windows).	Can be used as wall components, internal partitions, ceilings.	Overhead covers and wall components.	Roofing elements, doors and windows, sanitary ware, wall cladding, partition and paneling.
10	Self-cleaning	ETFE is self-cleaning due to its non-stick surface.	Has self-cleaning properties.	Have no self-cleaning properties and the cleaning has to be done manually.	Have no self-cleaning properties and the cleaning has to be done manually.	Have no self-cleaning properties and the cleaning has to be done manually.
11	Thermal insulation	ETFE has the advantage of self-venting. This would prevent heat buildup within the structures, which may further cause an explosion or building collapse. Does not allow external heat to penetrate inside.	The nature of the material itself allows natural thermal insulation, thereby reducing the heat penetration inside.	Different thermal insulation is achieved with various core materials like polyurethane or mineral wool.	Air layer is provided in-between for insulation.	Has good thermal insulation properties.
12	Acoustic insulation	ETFE film has approximately 70% acoustic transmission.	The acoustic performance is poor, as it transmits sound easily.	The assessed sound reduction measurement lies at approx. 25db for polyurethane elements and at approx. 30 db for mineral wool elements.	Acoustically good.	Acoustically good.
13	Micro-climate	Supports local climate because it is heat resistant, light trap quality can withstand temperature of −185 °C to +150 °C.	Controlled interior climate.	Suits the climate since more ACP panels are used for permanent buildings.	Can withstand temperature range in excess of 120 °C (-51 °C to 71 °C). Ideally made in polycarbonate material.	Can withstand microclimates.
14	Recycling	Easily recyclable, waste from the manufacturing process or even old ETFE elements can be remolded into new ETFE products such as tubing components, wires or castings.	Infinitely reusable.	Aluminum is the most recyclable construction material.	It has the ability to be recycled at the end of its service life, which is highly beneficial.	Can be reused.
15	Durability	Under exposure to environmental pollution, UV light, harsh chemicals or extreme temperature variations, ETFE does not degrade and has long life; life span in excess of 40 years.	Long-life but very much suitable as a temporary material.	Durable and long life and offers high load performance.	Twin wall Polycarbonate exhibits high degree of durability and toughness.	Durable for a long time, but some maintenance has to be carried out.
16	Cost	Higher initial cost and operational cost is less due to less maintenance being required.	High initial cost, because it is now trending in the market.	High initial cost that limits the number of uses.	High cost is one of its major disadvantages.	High initial cost.
17	Availability	It is easily available in the market.	Have to be imported from foreign countries.	It is easily available on the market.	It is easily available on the market.	It is easily available on the market.
18	Suitability to programs	Sport stadium, exhibit halls, market spaces, sheltered canopies.	Library, market spaces, shops.	Classrooms, library, housing, shops, clinical areas, sheltered canopies, mobile toilets.	Sport stadium, exhibit halls, market spaces, sheltered canopies, library, shops, classrooms.	Sport stadium, exhibit halls, market spaces, sheltered canopies, library, shops, classrooms.