Sustainable Design for Structural Engineers |
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By Sarah Hodges, Autodesk
Experts agree that buildings are the biggest source of emissions and energy consumption both in the U.S and around the globe. Currently, they account for 40 percent of the world’s energy use.1 As such, early design decisions can lead to significant reductions in building energy consumption and can help to create a more sustainable design. It appears as though sustainable design practices are becoming even more engrained in the design and construction industry than ever before. In fact, according to McGraw Hill’s “2009 Green Outlook”, green building is growing “in spite of the market downturn,” with the value of green construction increasing from $10B in 2005 to $49B in 2008.
Traditionally, architects and more recently MEP engineers have been leading the way to ensure a building’s design is sustainable. In fact, in my role here at Autodesk, I often hear from our MEP engineering customers about ways that they are employing technology to help them make better informed decisions that benefit both the environment and their client’s bottom line. Structural engineers can also play a critical role in this process. However, to take on that role they must be proactive. There are many ways in which a structural engineer can influence a building’s sustainability such as investigating and utilizing the most effective materials, or designing buildings for longevity by considering the design’s adaptability and reuse. Let’s explore these opportunities and explain further how and when these decisions can impact the overall sustainability.
Material Selection
The main design strategy structural engineers can adopt for building sustainability is to minimize embodied energy and maximize design efficiency. Embodied energy can be defined as the total energy consumed in processing, manufacturing, transporting and constructing building materials. Material selection and reuse can go a long way in reducing building waste both for new constructions as well as renovations of existing buildings. During the design process, structural engineers have a direct impact on the committed energy use and embodied carbon footprint of the building. As such they can help to reduce the impact that the buildings have on the built environment prior to construction.
The design phase becomes a critical juncture for the structural engineer to assess how to maximize the use of sustainable materials. There are many factors involved in selecting the most appropriate building material, but many engineers do not consider sustainability when doing so. The predominant choices worldwide for most commercial and institutional structures are reinforced concrete and steel, chosen primarily for availability, strength, and design flexibility. Based on total embodied energy, steel and concrete are comparable and neither offers any significant energy advantages.
But there are alternatives that engineers can explore to reduce the total embodied energy2 of concrete structures. Cement, one of the main components of concrete, is the largest contributor to concrete’s total embodied energy . Utilizing alternatives such as fly ash and slag in concrete mixtures can reduce cement content, and ultimately reduce the concrete’s total embodied energy.
Organizations like WoodWorks--an initiative of the Wood Products Council--promote wood as a viable material for non-residential construction, citing sustainability as one of its many benefits. Wood is the only major building material that is both renewable and sustainable in the long term, and outperforms steel and concrete when measuring global warming potential, resource use, embodied energy, air and water pollution 3.
 Image courtesy of Tocci Building Companies
Structural engineers can also leverage specific building materials that reduce energy consumption and maximize the use of natural daylight for heat gains. For example, structural engineers may look to convince architects to use exposed structural concrete as finishes for floors and walls, maximizing thermal mass and evaluating passive energy systems.
Designing for Longevity and Reuse
Engineers have a unique opportunity to design new buildings for future flexibility and adaptability. Buildings that are renovated and adapted for re-use more often than not need to be retrofitted for new loading requirements. Engineers that investigate structural requirements for increased loading could determine that there is minimal cost and material difference to build the original structure to support future load requirements.
The structural engineer may also be tasked with designing the building for longevity, helping the building owner avoid the need to invest in costly upgrades and continuous maintenance. In terms of minimizing waste, the structural engineer can design a structure using a modular approach, conducive to deconstruction at the end of the building’s life cycle. Hand in hand with designing for deconstruction comes maximizing the use of pre-fabricated systems to help minimize waste in the field.
Technology for Sustainable Design
At Autodesk, we believe that a building information modeling (BIM) process enhances the structural engineer’s workflow and can position them to be actively involved in the sustainable design of a building. We define BIM as an integrated process that allows professionals to explore a project’s key physical and functional characteristics digitally – before it’s built. The Autodesk BIM solutions are based on coordinated, more reliable, high-quality information created with Autodesk Revit-based products and AutoCAD Civil 3D software. By using BIM, design professionals can:
• Design - innovative, intelligent projects from the earliest stages
• Visualize, Simulate, and Analyze - real-world appearance, performance and cost
• Document - projects more accurately and efficiently
• Deliver - projects faster, more economically and with reduced environmental impact
BIM for structural engineers uses this same approach for the entire structural engineering process. The engineer’s virtual structural model can be used for coordination with architects, mechanical, electrical, and plumbing engineers, and civil engineers. That same digital model is integrated with analysis, design, and construction documentation, and is used as the basis for digital design-to-fabrication strategies and construction. Through BIM, structural engineers have the ability to track material quantities and explore design options that ultimately result in a more sustainable design.
At the core of the structural engineering BIM process is the Autodesk Revit Structure software. BIM and Revit Structure enable structural engineers to minimize waste and maximize the re-use of materials. With Revit Structure, structural engineers investigate building design options for long term use and future flexibility, maximizing design efficiency and minimizing waste and overall embodied energy. The rich intelligent information created through a BIM process can also be used for simulation and analysis--enabling structural engineers to make better informed decisions and optimize the structure for durability, flexibility and long term use.
Looking ahead we see industry trends such as BIM, integrated project delivery (IPD), sustainable design and design-to-fabrication continuing to drive the structural engineering market. As the market moves in this direction, it is our hope that sustainability will become a part of the foundation for all successful building projects with every material in the building process selected for its environmental factors and, once the building life ends, all building materials reused or recycled. A sustainable future is one that we can all aspire to.
1World Business Council for Sustainable Development
2BuildingGreen.com
3WoodWorks - http://www.woodworks.org/woodBenefits/sustainableDesign/
Sarah Hodges is the Industry Marketing Manager for Building Engineering at Autodesk.
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| Published 2009-08-17 00:00:00 |
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