Civil Engineering and Natural Hazard Mitigation

Civil Engineering and Natural Hazard Mitigation

Civil Engineering and Natural Hazard Mitigation

The National Science Foundation (NSF) leads a $280 million initiative enabling researchers to recreate natural hazards by shaking and rocking full-sized structures. [1] In one experiment, Professor Tara Hutchinson tests steel beam resilience on the device located near San Diego’s outer limits. The earthquake machine utilizes strain gauges and accelerometers numbering in the hundreds to record the many forces that artificially induced seismic activity places on the structure.

New building codes and retrofitting practices have emerged due to the successes achieved at the NSF research site. As a result, $65 million will go toward similar research facilities over the next five years.

Hutchinson’s experiment revealed weaknesses during pretest trials that exerted little force on the test subject. The implication was that small earthquakes might weaken buildings before large events occur, without leaving external clues.

Learning From the Past

Early natural hazard mitigation included massive, expensive and untested hazard deterrents, such as levees and floodgates. [2] After a natural disaster in the 1960’s, engineers discovered that the structures damaged the natural, protective landscape and provided inadequate fortification. Resultantly, engineers now develop mitigation plans incorporating alternative measures, such as land planning, structure relocation and natural land feature preservation.

Today, civil engineers follow design codes established using historical natural hazard data and ever-evolving research. The American Society of Civil Engineers (ASCE), the American Society of Mechanical Engineers (ASME) and the American Petroleum Institute (API) regularly conduct and disseminate research findings as new developments emerge and society’s damage tolerance diminishes.

Earthquake Mitigation

Earthquakes sometimes result in immense property damage and mortal occurrences. For instance, the Northridge Earthquake that occurred in the San Fernando Valley near Los Angeles resulted in $20 billion in property damage.

California State sanctioned the National Earthquake Hazards Reduction Program as early as 1977. Earthquake hazard mitigation encompasses ensuring integrity for critical infrastructure features, such as electric, water and transportation routes, during natural disasters.

The earthquake that occurred in and around the San Fernando Valley consumed several wooden residential structures and more than 70 mobile homes. Because the area suffers earthquakes so frequently, engineers there have continually worked to develop practices that preserve crucial lifeline services.

While federal buildings follow a unified building code, each state follows independent guidelines. In California, civil engineers follow the Unified Building Code, which requires to withstand earthquake activity that occurs once every 475 years. Other municipalities follow more stringent codes derived from the International Building Code, which recommends that engineers reinforce structures against earthquake events that occur once every 2,475 years. However, designers find difficulty accomplishing this with earlier structures.

Flood Preparedness

Floods represent 80-percent of all natural hazard events in the United States. As disasters occur, the civil engineering role evolves to meet current public safety needs. For example, Midwest floods in 1993 were so severe that civil engineers re-examined existing flood hazard policies.

Currently, engineers incorporate sustainable infrastructure planning into flood hazard mitigation. To this end, the United States Army Corp of Engineers (USACE) has published an intensive study titled “Flood Proofing Techniques, Programs and References.”

Landmasses near standing or moving water bodies face added flooding threats. [3] Duly, site selection is the current best defense against flooding. Depending on project specifications, civil engineers design features that allow water in, or wet flood proofing; features that stop water from entering, or dry flood proofing; or features that channel water away from structures.

Wind Hazard Reinforcement

Structures face increased threats from unpredictable hurricane, tsunami and tornado activity along the east coast and the Gulf of Mexico. [2] The Federal Emergency Management Agency (FEMA) reports the 2004 Atlantic Hurricane Season as the most damaging and vigorous storm activity in United States history. Although gale forces occur rarely, the devastating damage that results warrants precautionary measures.

The ASCE publishes hurricane reinforcement codes in the report “Minimum Design Loads for Buildings and Other Structures,” which many municipalities incorporate into uniform building codes. Despite uniform guidelines, some structures still submit to wind damage due to roofing material, doorway and window failure.

Civil engineers primarily work to reduce hurricane related mortality and property damage by designing structures that withstand gale forces that occur commonly in a particular region. Precipitation increases the structural threat imposed by wind. During Hurricane Andrew, most reported damage was due to elements penetrating structural features. Therefore, civil engineers design walls and roofs that shed precipitation and resist moisture saturation.

Slope Hazard Reinforcement

Every American state faces landslide threats, and almost 75-percent of all states contain high-risk landslide zones. Each year, property owners incur one to three billion dollars in landslide damage, while 25 to 50 individuals succumb to landslide related fatalities.

The United States Geological Survey (USGS) serves as a clearinghouse for landslide information. Earthquakes, floods, hurricanes and volcanic activity typically occur in unison with this threat, which civil engineers manage with strategies such as:

  • Data gathering and interpretation
  • Educational initiatives
  • Emergency management
  • Hazard mapping
  • Loss Assessment
  • Real-time monitoring

Civil engineers use both traditional and alternative solutions to mitigate landslide threats. Remedies include, but are not limited to:

  • Drainage systems
  • Fill slope re-compacting
  • Hydro-seeding
  • Reinforced concrete grids
  • Retaining walls
  • Sprayed concrete

Tunnels are also an effective, but costly, solution. To date, civil engineers do not share common practices for landslide mitigation but determine the best way to reinforce unstable slopes on a case-by-case basis.

Drought and Famine Recovery

The Army Corps of Engineers estimates that the United States suffered $8 billion in drought damage in 1995 alone. Despite advancements in weather forecasting, hazardous droughts remain unpredictable. Because the condition develops gradually, it is difficult to pinpoint. As such, drought hazard mitigation encompasses unique famine prevention and recovery planning for each afflicted region.

The unpredictable circumstances presented by drought conditions necessitate that engineers rely on ingenuity and technical skills to recover famine stricken regions. This might involve developing creative solutions to replenish critical water sources and educating local stakeholders on water conservation.

An Innovative Natural Hazard Mitigation Tool

Civil engineers use a comparatively new technology, building information modeling (BIM), to design secure buildings. BIM allows designers to uncover building feature interaction during seismic events or accidental blasts and allows designers from varying disciplines to collaborate in producing structures that withstand atypical forces. Building information modeling software also allows property owners to monitor and track mechanical systems for the entire structure life cycle.

Improving the Safety of Contemporary Roofing Design

In a study that testifies to the civil engineer’s relentless quest to protect public safety, researcher Korah Parackal examined how effectively contemporary building codes protect against wind suction roof hazards. [4] He concluded that nontraditional roof designs are ineffective against suction pressure created by high force winds.

To compare performance between traditional and contemporary roofs, the researcher – along with fellow Mitchell Humphreys – constructed miniature mock-ups and exposed them to varying gale forces. The modern designs performed differently than traditional box-shaped rooftops.

While newer roofs designs do not place building occupants in immediate danger, they do allow unwanted elements to seep into joints and edges previously weakened by wind. The researchers warn current and future engineers that it only takes the slightest error to design a roof that cannot withstand the elements over time.

Learn More

Civil engineers play a crucial role in engineering the structural solutions of tomorrow and plan, design, construct, and operate the infrastructure essential to our modern lives. As a student in the online Master of Science in Civil Engineering program, you can enhance your quantitative decision-making skills and learn how to justify managerial decisions with data. You will also explore the capabilities of modern management technologies and discover how to successfully leverage these tools to maximize efficiencies in your projects and on your teams.

Sources:

[1] http://www.sciencemag.org/news/2016/07/these-disaster-machines-could-help-humanity-prepare-cataclysms
[2] https://training.fema.gov/hiedu/docs/emt/engineering%20contribution.pdf
[3] https://www.wbdg.org/design-objectives/secure-safe/natural-hazards-mitigation
[4] http://www.upi.com/Science_News/2016/10/13/Scientists-pit-modern-roof-shapes-against-high-speed-winds/7971476366447/
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