In structural engineering, dead load refers to the intrinsic weight of the structure itself. Unlike live loads (occupants, furniture, or traffic), dead loads are permanent and remain constant throughout the life of the building.
How Dead Load is Calculated
The formula for calculating the dead load of a structural element is based on its volume and the density of the material used. The basic physics equation used is:
Dead Load (Mass) = Volume (Length × Width × Thickness) × Material Density
To convert this mass into a force (Load in kilonewtons), we multiply the mass by gravity (approximately 9.81 m/s²) and divide by 1000.
Common Material Densities
Material
Typical Density (kg/m³)
Reinforced Concrete
2400 – 2500
Structural Steel
7850
Brickwork
1800 – 2000
Glass
2500
Practical Example
Suppose you are calculating the weight of a concrete floor slab that is 6 meters long, 4 meters wide, and 0.2 meters thick. Using the density of reinforced concrete (2400 kg/m³):
Volume: 6m × 4m × 0.2m = 4.8 m³
Mass: 4.8 m³ × 2400 kg/m³ = 11,520 kg
Dead Load: (11,520 kg × 9.81) / 1000 = 113.01 kN
Architects and engineers use these calculations to ensure that the foundations, columns, and beams can safely support the cumulative weight of the building's components before any people or equipment even enter the space.
function calculateDeadLoad() {
var length = parseFloat(document.getElementById('dl_length').value);
var width = parseFloat(document.getElementById('dl_width').value);
var thickness = parseFloat(document.getElementById('dl_thickness').value);
var density = parseFloat(document.getElementById('dl_density').value);
var resultArea = document.getElementById('dl_result_area');
if (isNaN(length) || isNaN(width) || isNaN(thickness) || isNaN(density) || length <= 0 || width <= 0 || thickness <= 0 || density <= 0) {
alert('Please enter valid positive numbers for all fields.');
return;
}
// Calculations
var volume = length * width * thickness;
var mass = volume * density;
var gravity = 9.80665;
var forceKn = (mass * gravity) / 1000;
// Displaying results
document.getElementById('res_volume').innerText = volume.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 4}) + ' m³';
document.getElementById('res_mass').innerText = mass.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}) + ' kg';
document.getElementById('res_force').innerText = forceKn.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}) + ' kN';
resultArea.style.display = 'block';
resultArea.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}