EG-2008

Wind Loading on Buildings

• Storm Events

  • Definition: A "one in 50 years" storm event
  • Key Features: Highly unpredictable, varies depending on surroundings.

• Impact of Urban Design

  • Wind loading can change based on surrounding structures.
  • Initial design may be in open spaces, but future urban environment must be considered.
  • Wind effects can funnel through corridors of buildings, concentrating forces.

• Usability of Spaces

  • Urban design should consider not just aesthetics but functionality.
  • Avoiding wind funnels and ensuring safety from hazardous wind levels around building corners.

• Factors Affecting Wind Load

  • Wind loading changes based on a building's height, location, and surroundings in the UK.
  • Maps exist to calculate basic wind levels, analogous to snow loads.

• Simplifying Wind Calculations

  • Characteristic Load Calculation: Similar to snow load, multiple factors affect wind severity.
  • Focus on calculating horizontal wind loads primarily.

• Wind as Pressure

  • Wind acts against buildings as a pressure rather than a point load.
  • Pressure variations: For taller buildings, pressure varies with height.

• Assumptions in Calculations

  • Assume wind acts normally to the vertical surfaces of buildings (90 degrees).
  • For buildings with irregular shapes, consider additional factors, including friction and suction on the windward and leeward sides, respectively.

• Building Design Considerations

  • Adequate bracing is crucial to ensure the structural integrity against wind forces.
  • Importance of serviceability in design considerations.

• Calculation Flowchart

  • A flowchart outlines methods for calculating wind effects, indicating systematic calculations to be followed.

• UK National Annex Reference

  • Focus on determining the characteristic value of wind force to ensure building safety.

• Basic Wind Velocity Calculation

  • VB0 (Fundamental basic wind velocity) determined from wind maps.
  • Altitude factor: $C_{L}$ accounts for location and building altitude.
  • Mapping details included dependency on geographic location (e.g., London, Swansea).

• Basic Wind Velocity

  • Fundamental basic wind velocity imported into further calculations with altitude correction.

• Directional and Seasonal Factors

  • Directional factor in the UK set to 1 due to uniform wind behavior.
  • Seasonal factors also set to 1 for similar reasons.

• Peak Velocity Pressure Calculation

  • Converts basic wind velocity into pressure based on density.
  • Differences between country and town terrains affect the calculation methodology.

• Displacement Height Calculation

  • Wind behavior near structures is affected by neighboring buildings; hence, displacement should be calculated based on relative heights and proximities.
  • In the countryside, displacement height is effectively zero, leading to full wind pressure acting on the building.

• Distance from Shoreline

  • Wind intensity decreases as one moves away from the shoreline.

• Scaling Parameters

  • Terrain affects wind speed and displacement calculations using scaling coefficient ($C_{EZ}$).

• Combination of Parameters for Final Calculation

  • The various co-efficient values are combined to determine the horizontal wind force on the structure.

• Worked Example

  • Example: Building dimensions are 5m x 5m and height is 10m in a rural setting.
  • Characteristic Value Calculation: Inputs include height, building sizes, and location-exposed contour maps.

• Final Horizontal Load Calculation

  • The comprehensive calculation includes all parameters to determine the characteristic horizontal load for bracing design.

• Safety Considerations

  • Discussion on how building designs account for sustained wind via appropriate bracing structures, including zigzag bracing examples.

• Key Calculations & Parameters

  • Overall horizontal force is determined by compiling the individual wind pressures multiplied by reference areas, yielding a single force value.

• Reflection on Wind Calculations in Practice

  • Importance of clear definition and consideration when calculating wind effects on buildings.

Concrete Design Overview

• Materials and Design Philosophy

  • Concrete, especially reinforced concrete, is critical for robust structures.
  • Steel is an essential reinforcement component because of its superior tensile strength compared to concrete alone.

• Reinforcement Techniques

  • Commonly employed techniques include using rebar strategically in tension regions of structural elements.

• Concrete Behavior

  • Concrete exhibits minimal tensile strength and functions mainly in compression.
  • Properties become problematic if excessive tensile stresses are imposed.

• Graph Understanding

  • Graphs illustrate how concrete behaves under compression: linear phases followed by failure stages.

• Partial Safety Factors and Characteristic Strength

  • Characteristic strength (C4_FK) is fundamental for design and revolves around ensuring safety with partial factors.

• Design Implications for Durability

  • Concrete strength ratings define how concrete must be designed. Exposure classes dictate the properties and protection required in diverse environments.

• Crack Assessment in Existing Structures

  • Discussions around visual inspections for detecting flexural cracks indicate the performance of existing constructions in service.

• Examples of Application and Application in Practice

  • Various applications of concrete are presented, demonstrating its versatility in contrasting environments.

• Combination of Material Strengths

  • Emphasis on harmonious load-taking capacities between steel and concrete to ensure longevity and performance.