Structural Loads in Buildings

Structural Loads in Buildings

• Loads are forces acting on a structure.
• Gravity loads act downwards.
• Lateral loads act horizontally.
• Other loads include fluid pressure, lateral soil pressure, ponding load, and self-straining forces.

Gravity Loads

• Dead Load: Weight of all building materials.
• Live Load: Weight of occupants, furniture, and movable objects.
• Roof Live Load: Weight of things on the roof.

Lateral Loads

• Earthquake Load: Force from earthquakes.
• Wind Load: Force from wind.

Other Loads

• Fluid Pressure: Force from fluids (e.g., water).
• Lateral Soil Pressure: Force from the soil on the structure.
• Ponding Load: Water accumulation on a roof.
• Self-straining Forces: Forces related to temperature changes, shrinkage, and creep.

Design Codes/Standards

• National Structural Code of the Philippines (NSCP 2015)
• ASCE 7-22 (Minimum Design Loads for Buildings and Other Structures)

Dead Load

• Weight of all materials incorporated in a building.
  • Materials include walls, floors, ceilings, plumbing fixtures, and more.
• Different materials have different densities.

Dead Load per Unit Area

• Material densities are prescribed by NSCP 2015. Examples include Concrete, cinder, slag, copper, cork, earth.
• These densities determine the dead load per unit area for various building components such as ceilings, floor partitions etc..

Dead Load due to Weight of Floor System

• Parameters like beam width, beam depth, column width, slab thickness, and concrete density are needed to calculate the total floor weight
• Measurements and calculations are provided

Dead Load due to Weight of Walls

• Calculations related to wall weights are provided

Live Loads

• Gravity loads that are not permanently attached to the structure e.g., occupants, furniture, etc.
• Different loads apply to different areas and occupancies (e.g., offices, residential areas, assembly areas).

Live Load Reduction

• The maximum reduction for live load is usually 40%.
• There shall not be any reduction on live loads over 4.8 kPa.
• Storage loads exceeding 4.8 kPa shall not be reduced.
• Reduction in live load can be calculated based on area, dead load, and live load

Earthquake

• Earthquake is a shaking of the ground caused by sudden movements of rock materials beneath the Earth's surface.
• Earthquakes originate at tectonic plate boundaries.
• Hypocenter/Focus: The point where the earthquake originates inside the Earth.
• Epicenter: The point on the surface of the Earth directly above the hypocenter.

Earthquake Magnitude

• Magnitude is proportional to the energy released during an earthquake.
• Seismograph is used to record earthquakes and calculate their magnitude.
• Magnitude is represented by Arabic numbers (e.g., 4.8, 9.0).

Earthquake Intensity

• Earthquake intensity is how strongly people feel an earthquake.
• Intensity is generally higher closer to the epicenter.
• Intensity is represented by Roman numerals (e.g., II, IV, IX).

Earthquake Hazards

• Fault and Ground Rupture: Ground surface breakage
• Ground Shaking: Movement of ground surfaces
• Earthquake-Induced Landslides: Movements of soil on slopes
• Liquefaction: Soils behaving as liquids
• Tsunami: Large waves in oceans caused by earthquakes
• Coastal Uplift or Subsidence: Changes in ground level

Past Earthquakes

• The document mentions past significant earthquakes in the Philippines.
•   1976 Moro Gulf Earthquake is one example

Earthquake Load

• Occupancy category (importance of building)
• Distance to the nearest seismic source
• Soil type
• Seismic zone
• Natural period of the structure

Occupancy Category (NSCP 2015)

• Classifications of structures are listed for earthquake design purposes.

Distance to Nearest Seismic Source

• Tools for determining distance to nearest seismic source

Soil Type

• Soft or loose soil leads to higher earthquake loads.
• Hard or dense soil leads to lower earthquake loads.

Seismic Zone

• Maps illustrate seismic zones in the Philippines.

Natural Period of the Structure

• Time required for the structure to complete one cycle of free vibration.
• Examples are presented for calculations.

Wind Load

• Basic wind speed of area
• Exposure category classifying the terrain (B,C,D) as per given standards.
• Topographic effect on wind conditions.
• Gust effect based on the structure's flexibility
• Enclosure classification (open or enclosed buildings)

Fluid Pressure

Lateral Soil Pressure

Ponding Load

• Water accumulating on a roof.

Self-straining Forces and Effects

• Forces from temperature changes, creep, shrinkage, and differential settlement.

References

• Documents referencing the NSCP, ASCE codes, and specific Philippine organizations like PHIVOLCS.