(4/4) Codes and Classes of Loadings – An Introduction to Structural Theory | Structural Theory

Main ideas / concepts covered

• Purpose of structural design (structural theory): A structural engineer designs a structure to withstand all loads it will experience over its intended lifespan, while also meeting serviceability requirements (e.g., the structure should not collapse or otherwise fail during use).
• Role of codes in design: Design loads are commonly specified in engineering codes, which guide how to determine required load effects and calculations.
• Two categories of codes used by structural engineers:
  1. General building codes (government/legal minimum requirements)
  2. Design codes (technical guides/standards for calculations; generally not “laws,” but essential for correct design)

The lecture then transitions from codes to the classes of structural loadings.

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Codes

General building codes (government requirements / minimum loads + construction standards)

Definition / meaning

• These codes specify:
  • Minimum design loads for structures
  • Minimum construction standards
• They act as legal requirements enforced by government bodies.
• The presenter references the Office of the Building Official as the permit-evaluating authority.

Types mentioned

• International codes (model codes adopted by countries)
  • Example: IBC — International Building Code
    • A model code that may be adopted by other countries (e.g., the Philippines).
  • Another example: ASCE/SEI 7-16 — Minimum Design Loads for Buildings and Other Structures
    • Includes minimum loads for:
      • Dead loads
      • Live loads
      • Code-based formulations for wind and earthquake loads
    • The presenter states it is used as a basis for Chapter 2 of the National Structural Code of the Philippines (NSCP).
• Local codes
  • Example: NBCP — National Building Code of the Philippines
    • Used by government authorities (Office of the Building Official) for building/construction permit evaluation.

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Design codes (technical calculation standards / not strictly laws)

Definition / meaning

• Design codes provide detailed standards, such as:
  • reinforcement detailing rules
  • design equations
• While they are not necessarily legal requirements, they are important to ensure correct computations.

Design codes listed (and their typical applications)

1. ACI — American Concrete Institute
   • For reinforced concrete design
   • Presenter notes NSCP is based on ACI for reinforced concrete.
2. AISC — American Institute of Steel Construction
   • For steel design
   • Presenter notes NSCP is based on AISC for steel design (referenced as likely around Chapter 5).
3. AASHTO — American Association of State Highway and Transportation Officials
   • For highway bridge design
4. AFPA — American Forest and Paper Association
   • For wood/timber design
5. AREA — American Railway Engineering Association (as stated in subtitles)
   • For railway engineering design
6. NSCP — National Structural Code of the Philippines (local design code)
   • Presenter indicates the latest edition discussed is 2015.

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Classes of loadings (lecture focus next)

The lecture identifies three classes of loadings:

1. Dead loads
2. Live loads
3. Environmental loads

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1) Dead load

Core definition

• Gravity loads with constant magnitude and fixed position that act permanently on the structure.
• Direction: always downward (because they are gravity loads).

Subclasses of dead load

• Self-weight (dead load)
  • The weight of structural members themselves.
• Superimposed dead load
  • The weight of materials attached to the structure, such as:
    • Ceiling under a slab
    • Electrical wirings / lighting
    • Pipes (for electrical or other services) under a slab

Example used to clarify (slab design)

• Self-weight = slab’s own weight
• Superimposed = ceiling, lighting, pipes attached beneath/under the slab

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2) Live load

Core definition

• Loads with varying magnitude and/or varying position due to use of the structure.

What makes something “live” (as described)

• If it changes position and/or changes amount, it is treated as a live load.

Examples mentioned

• People walking/standing on a slab (weight and position vary)
• Tables and chairs
  • Treated as live loads because they can be moved/arranged
• Shelves, dividers, etc.
  • Treated as live loads if they can change how/where loads are applied

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3) Environmental loads

Core definition

• Loads caused by the environment.

Examples mentioned

• Wind load
• Snow load (for countries where snow exists)
  • Presenter notes that in the Philippines, it is typically rain instead, so the relevant consideration is rain load.
• Earthquake load
  • Described as lateral (horizontal direction) due to earth movement
  • The presenter says earthquake load will be discussed in a future video

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Speakers / sources featured

Speaker(s)

• Sir Mars (presenter; subtitles repeatedly refer to “sir mars” and “this is Sir mars”)

Source organizations / codes mentioned

• International Building Code (IBC)
• ASCE/SEI 7-16 — Minimum Design Loads for Buildings and Other Structures
  • American Society of Civil Engineers
• NBCP — National Building Code of the Philippines
• NSCP — National Structural Code of the Philippines (latest edition referenced: 2015)
• ACI — American Concrete Institute
• AISC — American Institute of Steel Construction
• AASHTO — American Association of State Highway and Transportation Officials
• AFPA — American Forest and Paper Association
• AREA — American Railway Engineering Association (as written in subtitles)