Structure Strengthening Method for Enhancing Seismic Behavior of Soft Tunnel Portal Section

Table 1

Test cases.

Test case	Concrete grade	Ec (×10^4 N/mm^2)	ft (N/mm^2)	fc (N/mm^2)
1	C25	28	1.27	11.9
2	C30	30	1.43	14.3
3	C35	31.5	1.57	16.7
4	C40	32.5	1.71	19.1

E_c is the elastic modulus, f_t is the axial tensile strength, and f_c is the axial compressive strength.