1. Theodore P. Zoli, PE 2. Supriya Gupte
The proposal suggests using synthetic hand made ropes for the construction of rope foot bridges which serve the dual purpose of enhancing the cottage industry of the rural mountainous regions and providing a sustainable solution to the use of recycled plastic which would have otherwise gone into landfills.
Stunted economic development of rural mountainous regions is attributed to inadequate infrastructure. Basic heath care and education are denied due to limited means of transport to hospitals and centers of learning. These areas are also inaccessible to relief measures during natural calamities.
Main idea behind the project is to apply concepts of bridge engineering at a level from where it evolved: to meet critical needs of transportation. However, they thrives on bare minimal to the extent of being away from basic health support even at times of natural disasters.
First stage was devoted to studying the rope bridges built by hand by the Ancient Inca Empire in Peru, South America. The process of community bridges was looked at and parallels were drawn with the programs run by the Swiss Development Cooperation and Helvetas in Nepal and by a Non Profit Organization called Bridges to Prosperity in Guatemala and Ghana.
Technical aspects of the project involve developing a stress ribbon bridge in contrast to the regular suspension bridge, which is the preferred structural type for these bridges. The motivation for this structural type comes from the initiative of using recycled plastic ropes in the deck, for suspenders and handrail. Primary applications of these ropes in the off-shore mooring industry exhibit its resistance to unfavorable climatic conditions and load capacities. Thus life cycle analysis of the stress ribbon structure should yield positive results. Further, since this bridge is to be hand made by the locals, our aim is to use least amount of industrial products. So clamps connecting the suspenders to the main cable have been replaced by knots and may other similar green changes have been adopted.
An innovative approach to the critical problems has come in the form of community bridges. This methodology helps meet the demand for bridges on the remote trails and also mobilize the locally available manpower. It is them who make decisions regarding the requirement and location of the bridge. The project seeks to provide employment to specific percentage of ethnic, women and dalits (belonging to the lower class). The key aspect of the policy is to improve the livelihood of locals. The program will make it possible to reach marginalized people in the remotest parts of the world. The community bridge will not only contributed towards bridging gaps between lands but also greatly abate the social divide between the elite and the dalits as they work together. The cottage industry of the region will receive further out reach in terms of patrons as a result of the installation of the bridge. The process of making ropes from synthetic fibers at the household level is studied to predict the success of rope making as a cottage industry. Apart from these social and economic issues, the major problem of plastic disposal is also countered, since these ropes are made from recycled plastic. Technologically, the proposal hopes to generate renewed interest in stress ribbon structures and open it for future research by changing various parameters to come up with similar bridges even for motorized traffic. Currently, only Japan has a recycling plant which deals with manufacturing the desired end product of recycled plastic that can be used for our purpose. Other such plants can be set up thereby considerably reducing the amount of plastic that goes into landfills each year. This proposal is a breakthrough since it resolves numerous global problems through just one approach.
Global developmental programs aim at providing employment and infrastructure to undeveloped regions through innovative schemes. Like the Swiss Development Cooperation is involved in building community bridges in Nepal. These organizations in collaboration with the local government draw attractive benefits for the people. The proposed initiative runs on the same lines in providing social, cultural and economic advantages. It differs at the point where this solution can be made sustainable/green. Using plastic instead of steel for the ropes, makes them easier to handle and risk free for people who will be working on building the bridge.
Another contrasting feature of this project is the structural type. It explores one of the most efficient structural forms with regard to a suspension bridge. It is interesting to note that a stress ribbon bridge is special type of suspension bridge where the cables in the deck support the loads through their natural tendency to be under tension. Various patterns of suspenders are studied to arrive at the form which further puts the deck into camber. In a regular suspension bridge cables only support the loads through the suspenders and the main cable. Hence once the proposed stress ribbon bridge is designed for pedestrian loads, scope for further research lies in studying the structural form, which can withstand motorized loads.
Theodore P. Zoli, PE: He is the vice president at HNTB Corporation and serves as technical director of HNTB’s bridge practice worldwide. He led the design team for various challenging and award winning projects during his 17 years at HNTB. Some of these landmark bridges include the Leonard P. Zakim Bunker Hill Bridge in Boston; and the Missouri River Pedestrian Bridge in Omaha. Recently, he was declared the MacArthur Fellow for the year 2009.
Supriya Gupte, student Columbia University: She is a student at Columbia University pursuing Master of Science in Structural Engineering. This project is her Masters thesis. She has taken courses in bridge design, structural dynamics and other relevant subjects. She has written papers relating to this project and presented them at conferences.
Support for our project has come in the form of paper publication and abstract selection. At the American Society for Engineering Education Conference in April ’09 the paper was nominated for the Best Student Paper Award. Additionally, the abstract has received appreciation and a request for submission of complete paper for the International Association for Bridge Maintenance And Safety 2010 in July ’10. Apart from this one of the non profit organizations, Bridges to Prosperity has agreed to construct the bridge for one of their projects as soon as it is design and evaluated.
Initially, the marco-level study will be conducted. This involves designing the stress ribbon for pedestrian loads and other external loading like wind. The efficiency of the structure is governed by the arrangement of suspenders and their point of attachment to the main cable. Since clamps are going to be avoided, various types of knots will be studied in order to have similar performance. Based all these results, an optimized structural design will be arrived at which uses minimum amount of material and least complicated design. This will be the first milestone for the project. Next step will be, to make a working demonstration model which can be built for public review. It will be scale down version of the original bridge and can be walked upon and tested physically. For the purpose of this model, rope manufacturing companies will be negotiated with to donate some samples of ropes. We hope to receive a positive response from these companies since the success of the project will open new markets for their products [currently only used for off-shore mooring]. Life cycle analysis will be performed where micro-level study involving the internal friction, angle of twist and other details of the rope will be carried out. Final milestone is to find a project and consent of one of the organizations to go ahead and build these bridges for their program. A project can also be obtained from the US National Parks and a pedestrian bridge can be built in one of their developing parks
The only obstacle that the team forsees is popular acceptance that fiber ropes have comparable strength to the steel ropes. In order to put the message across strongly, a demonstration model during the developmental stages of the project and later a full scale project in collaboration with Organizations like the Swiss Development Cooperation, Helvetas or Bridges to Prosperity will serve the purpose. After the initial success it will be interesting as well as challenging to design a similar bridge for motorized traffic. Other than this the team does not expect to come across any major hurdles during the various stages of development of the project.
Project requires support in the form of donations from rope manufacturing companies, initially for the demonstration bridge and later for the developmental program by Swiss Development Cooperation or Bridges to Prosperity. We are positive that these companies will be extremely interested since the success of the project will significantly raise the demand for their products as bridge design will go greener soon. This project is also aimed at dealing with large amounts of plastic waste which is a global concern today. Thus numerous other organizations are expected to come forth and sustain the project during its developmental stages. Also, the Swiss Development Cooperation who currently purchase steel ropes, if convinced of the viability of the project, should be willing to support it for one of their programs. Similarly, other developmental organizations like the World Bank and the US National Parks may also be interested.
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