ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.
Issue link: http://www.aspiremagazinebyengineers.com/i/306882
Rehabilitation of the Benton Boulevard Bridge in Kansas City, Mo., allowed preservation of an existing arch bridge originally constructed in 1923. Photo: Harrington & Cortelyou Inc. 16 | ASPIRE , Spring 2008 P E R S P E C T I V E Is sustainability merely a fad or a concept whose time has come? At every turn, we are exposed to print media, industry dialog, political stumping, and even Hollywood celebrities promoting sustainability and the value of going green. What is this all about, and how does the concrete bridge industry relate? And perhaps of greater significance, why should we care? This issue of ASPIRE™ focuses on the social benefits of sustainable concrete bridges. Social benefits, including life-safety issues, accelerated bridge construction, context-sensitive designs, and aesthetics are just one aspect of the overall theme of sustainable design as it relates to highway bridges. Future issues of ASPIRE will delve into the economic and ecologic aspects of sustainable concrete bridges. In this article, we will examine the social benefits of sustainable concrete bridges and how we can balance the impact of our choices on society. What is a Sustainable Structure? For a better understanding of the subject, some definitions are in order. To the casual observer, a sustainable structure will last a long time and have minimal negative impact on our environment. However, to the environmental advocate, sustainability connotes a much deeper intent. To be truly sustainable, all aspects associated with a structure including design, location, materials utilized, construction techniques, maintenance, impact on the environment, overall energy consumption, and effect on future generations must be considered. All elements should be coordinated in a manner to benefit society. The consequences of our decisions now may affect our children's future. To put it another way, a sustainable bridge design accomplishes our needs now without compromising the ability of future generations to meet their own needs. Much of the concern in the field of going green relates to carbon emissions in the atmosphere. A reported three- fold increase in carbon dioxide in the atmosphere since 1977 prompts the global warming concern. One aspect of sustainability is the minimization or elimination of carbon emissions to reduce the portion of climate change that may be caused by this phenomenon. Locating bridges where drive times and travel distances are minimized can reduce overall carbon emissions from vehicles. Social Benefits of Sustainable Concrete Bridges Society is the benefactor when our industry provides safe, long-term, dur- able structures. Even more so when economical, attractive, and low-main- tenance describes our bridge. Sound familiar? Additional benefits occur when construction minimizes site disruption, environmental impact, and traffic congestion, again, all common benefits inherent to current bridge construction. Let's look at various social benefits of concrete bridges as they relate to sustainability. Life Safety Concrete bridges, with their typically redundant structural systems, are safe bridges. The excellent fire and seismic resistance characteristics of these structures further ensures the public well- being. In seismic zones, confinement and corresponding ductile behavior in plastic hinge regions provides for minimal earthquake damage, low repair costs, and immediate post-earthquake use. With accelerated bridge construction, rapid replacement of other bridges that may have been damaged is also beneficial. Concrete bridges also demonstrate outstanding performance when exposed to fire as illustrated by other articles in this issue. The necessity of safe bridges is fundamental to our industry. Accelerated Bridge Construction P re c a s t c o m p o n e n t s a l l o w r a p i d construction of bridges to occur. With the advancement of rapid construction techniques, construction time previously measured in weeks and months is now measured in hours and days. Minimal lead times, locally manufactured products, and standard shapes make this method economically feasible. Deck formwork for cast-in-place concrete can be eliminated when adjacent precast members are used. Combined with the reduced disruption to traffic, shorter detour times, and minimal site impact afforded, the social benefits are significant. Context-Sensitive Design A context-sensitive design utilizes a by Kevin R. Eisenbeis SUSTAINABILITY Social Benefts of Concrete Bridges— How Green is Our Valley? The excellent fire and seismic resistance characteristics of these structures further ensures the public well-being. ASPIRE_spring08.indb 16 3/24/08 1:32:12 PM