Precast concrete solutions for risk management

by Katie Daniel | January 12, 2018 12:22 pm

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By Brian J. Hall
Climate projections by the World Meteorological Organization[2] (WMO) show past and current practices will influence the climate for decades to come. Such projections are usually statements about the likelihood something will happen several decades in the future if certain influential conditions develop in contrast to a prediction. For projections extending well into the future, scenarios are developed over what could happen given various assumptions and judgments. Therefore, in addition to efforts to reduce climate change, design/construction professionals need to prepare for the climate change that cannot be avoided.

After catastrophic flooding in Canada and the United States in recent years, as well as the devastating 2016 wildfires in Fort McMurray, Alberta, people are realizing climate change is one of the biggest challenges facing the planet. For design/construction professionals, part of the task of creating the built environment has now become ensuring structures can safely endure these extreme weather events. In other words, today’s structures need to display resilience.

This term is defined by the globalization-focused Rockefeller Foundation[3] as:

making people, communities, and systems better prepared to withstand catastrophic events—both natural and manmade—and able to bounce back more quickly and emerge stronger from these shocks and stresses.

Increasing resilience is a shared responsibility among citizens, the private sector, and government. It requires bold decisions and investments that often appear to pit short-term thinking against longer-term interests. For example, should we relieve pressure on housing prices by relaxing building codes to allow for cheaper and lighter construction methods at the expense of safety? This article examines the broader implications of resilience in the built environment, and explores how durable materials like precast concrete can help provide the strength and stability needed to weather the coming storm, both literal
and figurative.

Spinning out from the Rockefeller definition, resiliency can be thought of as the adaptability of a system (communities) to maintain functions and structure in the face of turbulent internal and external change. A crucial part of disaster recovery is not only to get essential services back up and running normally, but also to get people back to work. That means buildings must not only resist the damages caused by a disaster, but also remain in a condition that is safe and suitable for occupancy as soon as possible.

Key attributes of enhanced resilience are:

• longevity (i.e. service life);
• robustness (i.e. minimized potential for structural progressive collapse);
• sustainability;
• life safety;
• durability;
• adaptability for reuse; and
• resistance to disasters.

The Community and Regional Resilience Institute[4] (CARRI) considers ‘community resiliency’ to be the “capability of a community to anticipate risk, limit impact, and recover rapidly through survival, adaptation, evolution and growth in the face of turbulent change.” This last phrase can refer to a range of various natural and manmade calamities that include:

• extreme weather events (e.g. snowfall, tornadoes, hurricanes, or flooding);
• geological (e.g. earthquakes, tsunamis, as well as volcanic eruptions);
• man-made crises (e.g. terrorism, war, forest fires, pandemics, or large-scale industrial accidents); and
• economic (e.g. company closing, recession, or depression).

CARRI’s Resilience Loss Recovery Curve is the capacity of hazard-affected bodies to resist loss during disaster and to quickly recover afterward. It helps explain how community function is affected by an acute disturbance and depicts response and recovery curves.

CONCRETE POTENTIAL

Whether cast-in-place or precast, properly designed concrete assemblies offer a robustness making them inherently resistant to wind, hurricanes, flooding, and fire. Plant-cast precast systems offer even greater risk enhancement because of the superior quality control and protection from the environment during fabrication. Since 2004, this has been recognized by CSA A23.3, Design of Concrete Structures, which allows for an increased resistance factor for precast concrete produced in a precast plant that is certified in accordance to CSA A23.4, Precast Concrete−Materials and Construction. The resistance factor is increased from 0.65 for cast-in-place concrete to 0.70 for precast from a certified facility.As a structural material and as a building exterior skin, precast concrete has the ability to withstand nature’s normal deteriorating mechanisms as well as natural disasters. One example of a resilient structure is Winnipeg’s Grosvenor House, a 33-suite total precast apartment building constructed in 1960 and designed by Libling Michener and Associates. The form of this apartment building resulted from studies of the site, the living patterns of the anticipated market, and most particularly, of the structural system. Precast concrete can differ from traditional poured-in-place concrete in several important respects. It is possible to obtain a high-quality of finish and colour control in the structural elements, allowing the use of the materials as both structure and finish. The natural method of ‘joinery’ of precast beams to spandrels and to columns produces an articulation of the structural elements unlike the monolithic nature of poured-in-place concrete. Each element of the building is joined in a precise and definitive manner; from this, develops the architectural form. At 57 years old, the building is an attractive showcase of precast concrete resiliency with a life expectancy of well over a century. Looking further west, the country’s first prestressed, precast concrete bridge can be found in North Vancouver. The Mosquito Creek Bridge, originally completed in 1953 and located near the intersection of Marine Drive and Fell Avenue in North Vancouver, represents the first use of prestressed concrete technology on bridge stringers in Canada and is still in use today. This significant advancement in civil engineering technology is now one of the most widely used methods of bridge construction worldwide. In the summer of 2017, it was recognized during a historic site dedication ceremony held by the Canadian Society for Civil Engineering (CSCE). The bridge and the Grosvenor House are two of many examples of Canadian projects showcasing the ability of precast concrete to endure. With the renewed push for resilience, future projects can also benefit from the material’s long-term structural strength and performance.

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How resilient communities differ from the current situation
It is clearly in the public interest to reduce property losses (and injuries and fatalities) associated with natural disasters, and to encourage the development of resilient communities through sustained efforts involving mitigation, preparedness, response, and recovery. These efforts include improved land-use decisions and building code implementation, as well as construction of a built environment that includes resilient buildings and infrastructure. (True community resilience also requires improved business and household planning to minimize loss, as well as  better orchestrated response of both citizens and local agencies.)

A resilient community can more quickly restart local services (e.g. utilities, businesses, and schools) and chart a path to a ‘new normal.’ A more resilient community incurs some losses, but avoids additional ones because it has taken informed measures—such as anticipating threats, disaster response plans, and recovery strategies—to minimize the impact of the disturbance.

The key to disaster recovery is not only to get essential services back up and running, but also to allow people to return to their homes and workplaces. This means structures must not only resist the damages caused by an adverse event, but also be in a condition suitable to occupancy as soon as possible after the event. The choice of building materials can play an important role in this regard.

The missing link
Canada’s model codes are a set of minimum requirements for building design, construction, and operation to protect public health, safety, and natural resources. The codes can now offer enhanced protection to make communities more resilient, sustainable, and livable for generations to come, lowering the price of mitigation for business and building owners. Excessively damaged buildings may slow or even prevent recovery for some neighbourhoods and businesses.

Climate change is already damaging the global economy. Until recently, the usual thinking among macroeconomists has been that short-term weather fluctuations do not matter much for economic activity. However, recent events have prompted this view to be rethought. (For more, see the October 17 World Economic Outlook article, “Seeking Sustainable Growth: Short-term Recovery, Long-term Challenges[6].”)

Extreme weather certainly throws a ringer into key short-and long-term macroeconomic statistics[7]. With the ability to add or subtract 110,000 jobs to monthly North American employment data, it is now the single most-watched economic statistic in the world, and generally thought to be one of the most accurate.

The global insurance industry tracks the number of natural catastrophes worldwide. The trend in catastrophes caused by weather, water, or climate has increased over the last 30 years. A 2012 report[8] from the Insurance Bureau of Canada states “climate change is likely responsible for the rising frequency and severity of extreme weather events, such as floods, storms, and droughts, since warmer temperatures tend to produce more violent weather patterns.”

Payouts from Canadian insurance companies for damages caused by natural disasters—including those related to weather and water—have doubled every five years since 1983. The extreme weather events of greatest concern in Canada include heavy rain and snowfall, heat waves, and drought, which are linked to flooding and landslides, water shortages, forest fires, and reduced air quality.

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These events also have impacts related to property and infrastructure damage, business disruptions, and illness or mortality. Such costs are borne by individuals, businesses, and governments. Science links recent climate change to the greenhouse gases (GHG) released to the atmosphere through human activities over the past century. Based on historic emissions, further changes are unavoidable. (To read WMO’s “Statement on the State of the Global Climate in 2017 Provisional Release,” visit http://bit.ly/2AzaGzp[10].)

A key component to economic, societal, and environmental viability, the need for enhanced resiliency of buildings and structures, is becoming increasingly important, both nationally and globally. A 2011 United Nations report[11] on risk reduction identified losses from disasters are rising faster than gains made through economic growth across all regions, threatening the economies of low- and middle-income countries, as well as outpacing wealth gains across many of the world’s more affluent nations.

Recent major natural disasters and their impacts on national and global economies have heightened awareness and spurred activity to improve the nation’s infrastructure. The National Research Council’s (NRC’s) new Climate-Resilient Buildings and Core Public Infrastructure program will help develop new building codes to reflect the fact Canada is seeing more heavy rain, floods, high winds, snow, ice, temperature swings, and all-around extreme weather conditions. NRC has received $40 million from Infrastructure Canada to make updates to its model codes. The money is also being used to improve the resilience of core public infrastructure—such as buildings, bridges, sewage systems, and roadways—by developing new guides, risk-assessment tools, and life-cycle modelling tools.

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Design for resilience
A town or city featuring stronger, better built buildings, and roads and services to support them is truly resilient. Its leadership recognizes the value of planning for potential disasters and has taken steps to ensure the community has the ability to survive such events with less loss of housing, employment, and critical services. Resilient building materials like concrete and other products can play a vital role in creating stronger and safer communities.

There are various ways to incorporate precast concrete to make projects more durable and disaster-resistant. Precast concrete underground products, wall, floor, and roof systems, along with bridges, offer an unsurpassed combination of structural strength and resistance against wind and blast forces. Builders, architects, and designers have come to recognize more durable underground infrastructure, public buildings, residences, and businesses, often built with precast concrete, resist damage from natural and manmade disasters and can greatly reduce the impact the built environment has on the planet.

These built-to-last communities begin with comprehensive planning, including stricter building codes producing robust structures with long service lives. More durable buildings with high-performance features help promote community continuity, making cities and towns stronger, and better able to successfully weather any challenge.

The residents of more robust cities and towns experience major benefits from the overall improvement of building resilience. These range from fewer burdens on local services and a more stable local economy providing consistent sources of money to run the municipality to a more enduring legacy for future generations.

Conclusion
Climate change is getting attention from decision-makers and citizens around the world. Recent natural disasters and their devastating impacts on communities and the global economy have heightened everyone’s concern. Building resilient and durable structures are becoming more important than ever as we try to adapt to new and extreme changes in weather patterns.

Communities that are being proactive and effectively planning ahead will be in a better position to build stronger, safer buildings and see the long-term benefits. Precast concrete is a reliable building material that can help communities become more resilient to natural and manmade disasters. We need to act now to build a stronger tomorrow.

WHY CERTIFICATION IS IMPORTANT TO RESILIENT CONSTRUCTION

Infrastructure resilience has become a primary objective for governments and national security organizations over the past decade. Recent initiatives have focused on resilient building design, and one approach under consideration is a voluntary certification program for commercial and residential buildings. There are three credits in the new Leadership in Energy and Environmental Design (LEED) v4 program centred on resilient design. In a nutshell, these three credits are designed to ensure a design team is aware of vulnerabilities and addresses the most significant risks in the project design, including functionality of the building in the event of long-term interruptions in power or heating after human-caused and natural disasters. The intent of these types of programs is to encourage the adoption of resilient design practices in construction and planning of the buildings. Stringent certification programs like that of the Canadian Precast/Prestressed Concrete Institute (CPCI) can help in ensuring quality assurance of these projects. The CPCI certification program was developed, and is continually updated, by a team representing all industry stakeholders. Further, the program is backed by CPCI’s network of committees, research and development, education, codes and standards initiatives, and integrated programs and relations throughout the industry. The program ensures each plant has developed and documented an in-depth, in-house quality system based on time-tested, national industry standards. To become ‘CPCI Certified,’ plants must demonstrate they have appropriate experience and training in manufacturing precast concrete, have quality systems and procedures in place, and be committed to quality throughout the organization. Each plant is required to develop a site-specific quality systems manual (QSM) that defines in detail how its operations work; this is then reviewed and approved by CPCI. After the QSM is completed, an initial unannounced audit takes place. On passing its first audit, a plant is certified. Twice annually, certified plants undergo a thorough, unannounced two-day audit conducted by third-party engineers who follow criteria specifically targeted to the products being manufactured at that location. Quality assurance ensures certified plants produce materials that are durable and can help ensure a long lifespan of structures and buildings. Additionally, when quality products are used in projects, they are more resilient and have the ability to withstand some of the harsh climate conditions expected in the future. CPCI Certified plants are audited in accordance with standards published in the requirements of CAN/CSA-A23.4-16, Precast Concrete−Materials and Construction, including Annexes A and B, together with: Precast/Prestressed Concrete Institute (PCI) MNL-116, Manual for Quality Control for Plants and Production of Precast and Prestressed Concrete Products; and PCI MNL-117, Manual for Quality Control for Plants and Production of Architectural Precast Concrete Products. How to specify CPCI certification In the CSA standard, precast concrete products are divided into the following five categories, with further subcategories.* Manufacturers may be prequalified in any or all of the product group classifications: Group A−Architectural Products (AT−Architectural Trim Units, Architectural Products); Group B−Bridges (B1−Precast Bridge Products, B2−Prestressed Miscellaneous Bridge Products, B3−Prestressed Straight Strand Bridge Members, B4−Prestressed Deflected Strand Bridge Members, BA1, BA2, BA3, BA4−Bridge Products with an Architectural Finish); Group C−Commercial [Structural] (C1−Precast Concrete Products, C2−Prestressed Hollow-core and Repetitive Products, C3−Prestressed Straight Strand Structural Members, C4−Prestressed Deflected Strand Structural, CA1, CA2, CA3, CA4−Commercial Products with an Architectural Finish); Group D−Drainage Products (D1–Standard Precast Concrete Drainage Products); and Group S−Standard Products. The following language can be helpful in specifying CPCI precast plant certification: Precast concrete manufacturers to be certified to Canadian Precast/Prestressed Concrete Institute (CPCI) Plant Certification Program in [Architectural Precast Concrete Products, A1,] [Subcategory AT], [Precast and Prestressed Bridge Products, B,] [Subcategory] [B1] [BA1] [B2] [BA2] [B3] [BA3] [B4] [BA4] [Commercial Precast and Prestressed Concrete Products (Structural), C,] [Subcategory] [C1] [CA1] [C2] [CA2] [C3] [CA3] [C4] [CA4] [Precast Concrete Drainage Products, D,] [Subcategory] [D1] [Standard Products, S] prior to the time of bid. Only precast elements fabricated under the CPCI plant certification program to be acceptable, and plant certification is to be maintained for the duration of fabrication, [erection,] and until warranty expires. Precast fabrication to meet the requirements of CAN/CSA-A23.4-16, including Annexes A and B, together with PCI MNL-116 and 117 and CPCI certification requirements. *  Visit www.precastcertification.ca/en/certified_plants[13].

Brian J. Hall, BBA, MBA, is the managing director of the Canadian Precast/Prestressed Concrete Institute (CPCI), the vice-chair of the Royal Architectural Institute of Canada Foundation, and a board member of the Athena Sustainable Materials Institute. In 1998, Hall joined CPCI as its national marketing director. He is one of the authors of the institute’s sustainability strategy, which includes the development of the CPCI Precast Concrete Life Cycle Assessment, the Sustainable Plant Program, and the CPCI North American Environmental Product Declaration for precast concrete. Hall can be reached via e-mail at brianhall@cpci.ca[14].

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