“…F slab = ε slab E S A slab (25) where F UHPC is the resulting force of the UHPC layer, E UHPC is the elastic modulus of UHPC, ε UHPC is the strain of UHPC, A UHPC is the area of the UHPC layer, F top−steel is the resulting force of the top steel reinforcements, ε top−steel is the strain of the top steel reinforcements, E S is the elastic modulus of the steel reinforcements, A top−steel is the area of the steel reinforcements in the UHPC, F mid−steel is the resulting force of the steel reinforcements in the concrete, ε mid−steel is the strain of the steel reinforcements in the concrete, A mid−steel is the area of the steel reinforcements in the concrete, F f lange is the resulting force of the flange of the steel ribs, ε f lange is the strain of the flange of the steel ribs, A f lange is the area of the flange of the steel ribs, F web−1 is the resulting force of the web of steel ribs above the neutral axis, ε web−1 is the maximum strain of the web of steel ribs above the neutral axis, A web−1 is the area of the web of steel ribs above the neutral axis, F web−2 is the resulting force of the web of steel ribs below the neutral axis, ε web−2 is the strain of the web of steel ribs below the neutral axis, A web−2 is the area of the web of steel ribs below the neutral axis, F concrete is the resulting force of the compressive concrete, ε concrete is the maximum strain of the compressive concrete, and A concrete is the area of the compressive concrete. The height of the neutral axis can be determined according to the force equilibrium (Equation ( 26)).…”