# Exercise 1: dead and live load on a footbridge deck
# 20 m x 3 m deck, 0.2 m of concrete (2400 kg/m3), live load 4 kN/m2, two supports.

G = 9.81  # m/s2

def kn(kg):
    """Convert a mass in kg to a weight in kN."""
    return kg * G / 1000

length, width, thickness = 20, 3, 0.2
area = length * width                       # 60 m2
slab_mass = area * thickness * 2400         # 28800 kg
dead = kn(slab_mass)
live = 4 * area
total = dead + live

print(f"area {area} m2, slab mass {slab_mass:.0f} kg")
print(f"dead {dead:.1f} kN, live {live:.1f} kN, total {total:.1f} kN")
print(f"each support carries {total / 2:.1f} kN")

# Output (as run):
# area 60 m2, slab mass 28800 kg
# dead 282.5 kN, live 240.0 kN, total 522.5 kN
# each support carries 261.3 kN
#
# Note: the dead load is already larger than the live load, and it is always there.