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Introduction to Sustainable Bridge Design

What is sustainable bridge design and why do we need it?

Sustainable design, like the term “organic” in the food industry, is a hot topic in the bridge world. Everybody wants the term applied to their project but few actually meet the requirements for a sustainable bridge design.

The American Society of Civil Engineers (ASCE) actually mandates sustainable development in its first ethical Canon.

“Canon 1. Engineers shall hold paramount the safety, health and welfare of the public and shall strive to comply with the principles of sustainable development in the performance of their professional duties. “

ASCE defines sustainable development as the following:

“Sustainable Development is the process of applying natural, human, and economic resources to enhance the safety, welfare, and quality of life for all of society while maintaining the availability of the remaining natural resources.”

Obviously engineers protect the safety of the traveling public with their bridge designs but do they consider the remaining goals in that definition?

The welfare and quality of life of the public can be greatly improved with a modern bridge but it can also be negatively affected by the presence of huge unattractive structures in their neighborhood. Bridges and roads take an enormous amount of land and energy, while new projects, in established areas, can create a divide between winners and losers.
To produce a sustainable design we must first provide a definition and then develop the steps required to achieve and test a sustainable bridge design.

Sustainable Bridge Design (SBD) Definition (TBG version)

“Sustainable Bridge Design is the philosophy of designing bridges, to comply with the principles of social, economic, and ecological sustainability.”

Social sustainability can be described by the Western Australian Council of Social services as follows:

“Social sustainability occurs when the formal and informal processes; systems; structures; and relationships actively support the capacity of current and future generations to create healthy and livable communities. Socially sustainable communities are equitable, diverse, connected and democratic and provide a good quality of life.”

Obviously, the definition does not mean structures in the sense of bridge structures but it does give a meaningful overview of the goals of social sustainability.

Economic sustainability has been described as using available resources in an efficient and responsible way. Typically, this is based on a monetary analysis of the project and often shown in terms of a benefit – cost ratio. It is critically important that the relevant factors are used in determining the economic cost of a project, so as not to skew the results.

Finally, ecological sustainability is described as the prevention of environmental degradation. If fact, it should be looked as a goal of improving the current state of the environment and ensuring the future “health, diversity and productivity of the environment is maintained or enhanced for the benefit of future generations.”

In the past bridge designers have typically focused on providing the safest structure for the lowest cost. With today’s goal of sustainable design, engineers should be looking at bridge design in a holistic manner, with concern for all aspects of the life cycle of a bridge.

This “whole” bridge approach will strengthen the knowledge of engineers, enhance the status of engineering and provide the best outcomes for society.

Future post:

Steps to a Sustainable Bridge Design