9.11 Archives - Standards Michigan

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Structures

9-11 Commission

Today we examine best practice literature for education building structures developed by accredited and consortia standards developers such as ASCE, ACI, AISC, ASTM, AWS, CRSI, ICC, NFPA and IEEE. The US education industry among the top three largest building construction markets; with annual new and renovated building construction running close to $100 billion annually.

We limit our coverage to low-risk regions in the US, such as areas with minimal seismic activity, low risk of flooding and moderate weather conditions. Another huge topic which we will likely break up into separate modules in the fullness of time. For now, we sweep through the basics:

Foundation

Site Analysis:
- Conduct soil testing to determine its bearing capacity and composition.
- Ensure the site is properly graded and drained to prevent water accumulation.
Foundation Type:
- Slab-on-Grade: Common in residential buildings. A concrete slab is poured directly on the ground.
- Basement: Provides additional living space and storage, common in residential buildings.
Design and Preparation:
- Use rebar reinforcement to strengthen the concrete.
- Install vapor barriers to prevent moisture from seeping through the foundation.
- Properly compact the soil to prevent settling and shifting.
Concrete Pouring:
- Use high-quality concrete mix suitable for the local climate.
- Ensure proper curing of the concrete to achieve maximum strength.
- Use expansion joints to accommodate temperature changes and prevent cracking.
Waterproofing and Insulation:
- Apply waterproofing membranes or coatings to protect the foundation from water damage.
- Insulate the foundation to improve energy efficiency and prevent frost heave in colder climates.

Ironwork

Materials:
- Use high-quality steel that meets industry standards (e.g., ASTM specifications).
- Ensure the steel is properly treated to resist corrosion, especially in humid or coastal areas.
Design:
- Follow structural engineering guidelines and building codes for the specific type of building.
- Use appropriate load calculations to determine the size and placement of steel beams, columns, and reinforcements.
Fabrication and Assembly:
- Ensure precision in cutting, welding, and assembling steel components.
- Use certified welders and follow welding standards (e.g., AWS D1.1/D1.1M).
- Pre-fabricate components where possible to ensure quality control and reduce on-site labor.
Erection:
- Use proper lifting equipment and techniques to safely erect steel structures.
- Align and level steel components accurately before final fastening.
- Use bolted connections where possible for ease of assembly and future maintenance.
Inspection and Quality Control:
- Conduct regular inspections throughout the construction process to ensure compliance with design specifications and building codes.
- Perform non-destructive testing (e.g., ultrasonic testing) on critical welds and connections.
Protective Coatings:
- Apply protective coatings (e.g., galvanization, epoxy paint) to steel components to prevent corrosion.
- Maintain the protective coatings over the lifespan of the building.

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Post 9-11 Standards

Following the September 11, 2001 attacks on the World Trade Center, U.S. standards developers — the International Code Council (ICC) and the National Fire Protection Association (NFPA) topmost among them — responded with revisions to technical standards based on thirty findings of the National Institute of Standards and Technology (NIST). These changes aimed to enhance structural integrity, fire safety, and evacuation procedures in high-rise buildings.

Increased Structural Robustness: Codes were updated to improve resistance to progressive collapse, where the failure of one structural element spreads to others. This included increasing the minimum thickness of steel beams and columns and adding more connections between structural elements.

Concrete Reinforcement: Structures like One World Trade Center adopted reinforced concrete cores and thicker structural elements to withstand extreme events.

Fire SafetyEnhanced Fire Resistance: Higher standards for fire-resistant materials were introduced, including mandates for fire sprinklers and smoke alarms in high-rise buildings.

Fire Protection Systems: Improved requirements for active fire protection systems, such as sprinklers, to mitigate fire spread.

Egress and EvacuationElevator Requirements: Elevators are now required in high-rise buildings over 120 feet tall to aid firefighters in accessing upper floors without climbing stairs with heavy equipment.

Additional Stairways: High-rises over 420 feet must include an extra stairway to ensure multiple egress paths.

Exit Path Markings: Self-luminous or photoluminescent exit path markings were mandated to guide occupants to exits during low-visibility emergencies, applied to both new and existing high-rise buildings.

Increased Exit Spacing: Exit enclosures must be spaced farther apart to prevent a single event, like a fire, from blocking multiple exits.

Emergency Communication and PreparednessImproved Communication Systems: Codes now require better communication systems for emergency responders to coordinate during crises, addressing the breakdown in communication during 9/11.

Evacuation Procedures: Elevators can now be used for evacuation in some fire scenarios, a shift from the traditional reliance on stairs, improving evacuation efficiency.

Blast-Resistant Features: Designs for high-profile buildings, like One World Trade Center, incorporated blast-resistant bases (e.g., a 185-foot concrete base) to protect against street-level attacks.

Changes were debated to balance safety with construction costs, with some measures (like exit markings) having minimal cost but significant benefits. Not all proposals were adopted due to cost concerns or feasibility, but they spurred further structural design advancements. These changes reflect a shift toward designing buildings to withstand extreme, unpredictable events like terrorist attacks, beyond traditional natural disaster scenarios.

Our work in the NFPA catalog | Our work in the ICC catalog | Our work in the ASCE catalog