Hat Trick

Building design and construction has experienced few periods of quantum change as significant as today. Three independently developing movements are converging to radically change the manner in which buildings are designed and constructed.

The design-build movement has championed collaborative project development encouraging early integration of every level of the design and construction industry into the project process. Significant cost and schedule savings coupled with enhanced project quality has encouraged project owners to embrace a project delivery methodology outside the design-bid-build comfort zone.

Computer aided design (CAD) has moved from being a simple drafting board substitute to a design tool for intelligent production of 2-D drawings and then 3-D modeling. 3-D modeling proponents then raised the possibility of dissimilar software packages utilized by different segments of the design and construction community exchanging dimensional data electronically. And if dimensional data could be electronically shared, then why not design parameters and intelligence regarding the very components of the building? The embryonic phase of Building Information Modeling (BIM) has already begun to revolutionize project delivery. Virtual design and construction now allows project teams to build a structure twice — once virtually and once physically. Design activities have been horizontally integrated across disciplines while construction activities have been integrated vertically through distinct supply chain stages, resulting in cost savings and shorter schedules, accompanied by enhanced project quality and safety.

Some students of the planet’s ecosystem estimate that the late 20th century was a watershed point that emphasized the earth’s inability to indefinitely sustain itself. While healthy debate swirls around this issue, it is prudent that the built environment today minimizes environmental and energy impacts. The movement toward sustainable development has been championed by numerous organizations around the globe and is in the process of expanding the traditional cost, speed and quality matrix for project evaluation with the addition of sustainable factors. These sustainability factors include concerns related to — but not limited to — green issues of resource utilization, energy and carbon emissions, as well as economic and social impacts.

Each of these three trends, if taken independently, present the possibility of significant change in how buildings are designed and delivered. However, in today’s market these three trends are building upon each other, reinforcing the necessity of change and developing a synergy that is accelerating those changes. Virtual design and construction functions most effectively in a collaborative setting and as such is becoming a catalyst for design-build. Design-build principles form the framework for utilizing 3-D models as contract deliverables.

Inclusion of specialty contractors in the design phase of a project is now recognized as a necessity to gain the benefits of both the horizontal and vertical elements of BIM. And as consideration of sustainable factors becomes more prevalent in project design, the early inclusion of specialty contractors — bringing their unique expertise in materials, products and construction processes — is more critical.

At the same time, BIM presents the opportunity to accurately assess the sustainable impact of a building’s design. This growth in technology will allow economic (cost and speed), social (architectural and safety) and environmental (energy, carbon footprint, resource utilization) factors to be dynamically and accurately assessed during the design phase of a project resulting in a move away from “life cycle assessment” (LCA) estimation, to true LCA calculation.

Without the collaborative structure of design-build attracting every level of construction specialist, and without horizontal and vertical integration of virtual construction, the assessment and determination of sustainable impacts will remain subjective rather than objective.

Optimum sustainable design at the project level will not be accomplished without design-build style collaboration.

Design-Build Trends

The structural steel industry is actively involved in encouraging these changing trends and adapting its design and delivery process to address these changes. Today a growing number of structural steel fabricators are actively engaged as project team members on design-build projects. These specialty contractors are sharing their expertise during the design phases of these projects to optimize the structural steel framing systems from both a cost and schedule perspective. In many cases, structural steel fabricators are leading “steel teams” that assume single-source responsibility for the design, detailing, material acquisition, fabrication and erection of the framing system. Cost savings of nearly 20 percent and schedule compression of 40 percent are typical.

The trend to design-build among steel fabricators continues to grow with American Institute of Steel Construction Inc. (AISC) member fabricators reporting that 25.3 percent of their gross revenue in 2006 was generated on design-build projects, up from 17 percent just five years earlier. But even that trend is a bit understated as these same members report that their integration level into design-build is steadily increasing from merely being consultants on projects to becoming contractual members of the design-build team.

Integrated BIM World

The desire to draw steel fabricators (a.k.a. steel specialty contractors) into a closer working relationship within the design-build team is certainly the result of fabricators’ expertise in optimizing the fabrication and erection of structural steel in harmony with the remainder of the structure. In addition to this traditional expertise, steel specialty contractors are now much in demand as 3-D BIM experts.

In the late 1990s, the structural steel industry invested heavily in the development of the CIS/2 standard to define data transfers between dissimilar software packages used for structural design, detailing, material management and shop floor equipment control. The result has allowed the importation of 3-D structural design models produced by structural engineers into the software packages utilized by detailers. The imported model contains not only geometric information, but also analytic data relative to member sizes, loads and reactions. Prior to these transfers taking place, the detailer was forced to rebuild the structural model from 2-D drawings generated from the 3-D structural model. The detailing software properly dimensions the beams and columns while developing the connections used to construct the structure in the field.

From the detailed model, either shop drawings are generated for approval, or the detailed model is passed back to the structural engineer for approval of the elements and connections. The vertical integration of the structural steel supply chain is completed by moving the model to both the shop management system and extracting information used to program automated fabrication equipment for the actual cutting and drilling of the steel.

As the leader in the practical application of BIM and virtual construction, the structural steel industry has demonstrated the viability of BIM in today’s marketplace. The accomplishment of vertical integration has motivated other specialty contractors to begin replicating these successes in their vertical project supply chain. At the same time, the marketplace continues to move toward horizontal integration of design software where the sharing of coordinated 3-D design models between architects and engineers brings further advantages.

Effective BIM utilization, in both a horizontal and vertical manner through industry standard exchange protocols and data structures, optimizes a building project by forcing early decisions and engaging all members of the project team in a true value engineering process. The end result is a virtual building that will be replicated in the physical construction process.

The structural steel industry then benefits the physical construction process through offsite fabrication of building elements that can be rapidly assembled in the field.

Sustainable Construction

The U.S. movement toward sustainable construction is transitioning from infancy to early adolescence. As in the early stages of any movement, the focus has been to identify issues, raise the level of concern in the overall building design and construction industry for sustainability and encourage sustainable practices in building design and construction.

During this same period, the structural steel industry was engaged in significant environmental improvements related to structural steel production. These included improved recycled content, embodied energy and reduction of carbon footprint.

In the 1980s the structural steel industry moved away from the traditional iron ore based, blast furnace technology — basic oxygen furnace (BOF) — for production. Instead, structural steel mills utilized the electric arc furnace (EAF) process, using ferrous scrap rather than iron ore as the primary feedstock material. In reality this decision moved the structural steel industry from a consumer of natural resources (iron ore) to a recycler of discarded materials (steel and iron scrap). Today’s structural steel mills are, in effect, the nation’s largest recycling plants, consuming automobiles, appliances, steel from demolished buildings, industrial scrap and steel scrap from curbside recycling programs.

The implications of these changes are significant. The use of structural steel does not require the mining or quarrying of its major source of material, therefore land utilization and scarring is minimized. In fact, the recycling rate — the percentage of scrapped material being utilized rather than disposed of in landfills — for automobiles in the United States currently stands at 104 percent, which indicates that the number of vehicles in junk yards is actually decreasing (see chart).

Adopting the EAF process has resulted in the recycled content (the percentage by mass of recycled material in a product) of domestically produced structural steel to average more than 90 percent over the past decade. It is not a surprise that structural steel has long been considered by building designers and owners as the premier green building material.

The structural steel industry does not rely on recycled content alone to address the sustainable challenges of the 21st century, however. The industry is continuing to improve its environmental performance by reducing greenhouse gas emissions. While numerous efforts have targeted emissions, energy efficiency and related environmental concerns in recent years, the structural steel industry has proactively pursued measures that typically exceed regulatory requirements.

The iron and steel industry, in fact, has reduced carbon emissions well below those recommended worldwide. The Environmental Protection Agency’s recent greenhouse gas findings show a 47 percent drop in carbon emissions by the iron and steel industry from 1990 to 2005. This figure is more than eight times the standards set forth by initiatives such as the Kyoto Protocol, which has emission reduction goals of 5.2 percent by 2012. The industry is also adopting standards set forth by the Climate Vision program, with goals to reduce energy use by an additional 10 percent over the next four years.

The sustainability movement also extends beyond new building construction and focuses on deconstruction at the end of a building’s useful life. Structural steel can be either reused in a new structure or recycled into new structural steel components. With the current recycling rate for structural steel from old buildings at 98 percent, market demand and compensation for scrap steel results in firms often willing to pay owners for a steel structure demolition, while charging owners for demolishing and land filling their concrete and wood structures. While varying by geographic region, typical demolition and landfill costs for concrete structures range around $3 per square foot and $10 per square foot for wood structures.

But as the sustainability movement transitions to early adolescence, the mere material selection with strong sustainable characteristics will no longer be adequate. Rather, project level decisions will be required that optimize the project’s design against analytically definable criteria. This will be true not only for building systems, such as heating, ventilation, air conditioning, water utilization and lighting, but for materials and processes used in construction.

Both the selection among construction materials and their optimal use will need to be measured using verifiable industry data. And these factors must take into account not just the production of the material but all stages of the construction process.

A growing amount of research compares the relative impacts of structural steel, concrete and wood with respect to embodied energy, carbon impacts and resource depletion. At the same time, a new generation of life cycle analysis estimators are being developed to provide a comparison of the sustainable impact of various design choices.

Clark Hyland and Xiao Huantian note in “Comparative Embodied CO2 Emissions Assessments of New Zealand Multi-Storey Buildings,”

A review of three competitive structural construction options for a 10-story building has shown that the steel construction option had the lowest carbon footprint compared to the hybrid steel and concrete option and the full concrete option. The reason appears to be that the higher strength to weight ratio of steelwork leads to less material intensive design solutions.

Hyland and Huantian were conservative in their use of impact metrics based on studies performed by the International Iron and Steel Institute (IISI) that utilize global production factors for structural steel combining both BOF and EAF production. Had they considered production based solely on EAF methods utilized in the domestic structural steel industry, their findings would be even more significant.

A similar study by Timothy Johnson, “Comparison  of Environmental Impacts of Steel and Concrete as Building Materials Using the Life Cycle Assessment Method,” concluded:

Without question sustainability is now a decision making tool in the construction and design industry. ... The conclusion of the study is that steel is “better,” but that conclusion is based on an un-weighted comparison across only three environmental impacts narrowly defined by the functional unit and MWU method. This definitive conclusion can also be made because in the case of this study, steel either has less or equivalent impact of concrete in all impact areas.

The key here is not simply answering the question, “Which material should I choose?” but the development of both verifiable metrics for construction materials, an analytical framework for the assessment of the materials and a mode for optimizing the utilization of those materials within the context of the project.

The structural steel industry is working to quantify all energy inputs, carbon impacts and resource utilization factors for structural steel from harvesting and transporting of scrap through mill production, material delivery to a fabricator, fabrication operations, material delivery to the project site and structural steel erection. At the same time analogous studies are being performed to quantify the secondary impacts resulting from offsite fabrication versus onsite construction (worker travel distances, project efficiencies, number of workers required), construction site waste elimination versus construction site waste management (i.e. current sustainable guidelines address how construction waste is managed, not how construction waste is minimized) and secondary impacts to other aspects of the project (i.e. lighter steel frames reduce foundation requirements reducing the environmental impact of foundation construction).

Three-Way Convergence

As these studies become available it will be possible not only to determine the optimum framing material for selection, but to optimize the design of the structure utilizing that material. In a very real sense this decision process will be parallel to that of optimizing a project’s design based on cost and schedule. It is at that point when the three distinct movements (Design-Build, Building Information Modeling and Sustainability) will become fully complementary and become the preferred approach for building design and construction.

The information within a building information model defining material quantities, number of pieces, types of connections and other related factors will be able to be extracted to an impact calculator, just as these same factors are extracted today to form the basis of a cost estimate. (The AISC Steel Solutions Center currently provides a complementary SteelTool, The RAM Estimator, on the AISC Web site, www.aisc.org, to extract these factors.) Rather than simply estimating impacts based on selected assemblies, the actual design of the structure can be optimized to minimize energy, carbon impacts and other sustainable factors. When this occurs the world of sustainability will move from concepts and estimates to an accurate assessment of a specific project design.

At the same time the collaborative input of a steel specialty contractor early in the design life of the structure will be beneficial in suggesting ways to reduce the sustainable impact of the project. The steel fabricator is well prepared to give guidance on minimizing weld requirements to reduce electric consumption, delivery scheduling to reduce wait times, balancing the trade-offs between additional material and the use of cambering, doublers and stiffeners, optimizing the project flow based on shop configuration, enhanced erection efficiencies and evaluating various framing and bracing options from an environmental impact perspective.

It is only in the context of design-build and BIM that sustainability will reach the goal of broad based, optimally sustainable structures. It is only in the context of design-build and sustainability that BIM will become an indispensable tool for building design and construction. And it is only within the context of BIM and sustainability that design-build will become the project delivery methodology of preference.

History has demonstrated that whatever the challenge, there has always been a solution in structural steel. Today’s structural steel industry has demonstrated that it stands prepared to innovatively address the challenges of design-build, BIM and sustainability with that same confidence.

John Cross is vice president of marketing with the American Institute of Steel Construction.