Principle of Load Transfer (Descente de Charge)
📌 Building structures transfer additional loads (snow, wind, user occupancy) from the roof down to the foundations, moving from spanning elements to load-bearing elements.
⚙️ Understanding this load transfer principle (descente de charge) is essential for accurately sizing structural components.
🧱 The transfer path moves sequentially from the roof structure down through the spanning elements, load-bearing elements, and finally to the foundations.

Mass, Weight, and Units
⚖️ Weight ($F$) is the vertical force of gravity proportional to mass ($m$), defined by Newton's formula: $F=mg$.
🌍 In Earth's gravitational field ($g \approx 9.81 \text{ m/s}^2$), 1 Newton (N) roughly corresponds to a mass of 100 grams.
🔗 Key metric conversions: 1 decaNewton (daN) equals 1 kg, and 1 KiloNewton (kN) equals 100 kg (or 10 kN for 1 ton).

Types of Structural Loads and Calculation
🏋️ Volumetric loads ($P$) are calculated as volumetric weight ($\gamma$) times volume ($V$): $P=\gamma V$.
🏗️ Examples of volumetric weights ($\gamma$): Reinforced concrete is $25 \text{ kN/m}^3$, and steel is $60.18 \text{ kN/m}^3$.
📉 Surface load ($p$) is derived by relating the total load ($P$) to a unit area, resulting in units of $\text{kN/m}^2$ ($p = \gamma \times \text{thickness}$).
📊 Applied surface loads include dead loads (self-weight) and live loads (occupancy, snow, wind), which are regulated by building codes.

Load Distribution Forms
〰️ Loads can be distributed linearly along a line (e.g., loads on beams), measured in kN/m (kiloNewtons per meter).
📍 Forces can also be punctual (applied at a single point), typically representing loads from columns, measured in Newtons (N) or KiloNewtons (kN).

Key Points & Insights
➡️ Rigorous unit handling in the $\text{kN/m}^3$, $\text{kN/m}^2$, and $\text{kN/m}$ range is crucial for accurately understanding the physical phenomena in structural design.
➡️ Live loads, such as those for a library floor, are mandated by regulation (e.g., requiring $4\times$ the surface load of a typical dwelling due to book weight).
➡️ The concept of volumetric weight ($\gamma$) is a material characteristic expressed in $\text{kN/m}^3$ which allows for direct calculation of self-weight loads.

📸 Video summarized with SummaryTube.com on Nov 25, 2025, 22:30 UTC