hola yo lo hago de esta manera y me funciona bien

CALL FUNCTION 'REUSE_ALV_GRID_DISPLAY'
EXPORTING
i_callback_program = g_repid
i_structure_name = 'TI_ORDENES' ---> te falta esto
is_layout = gs_layout
it_fieldcat = gt_fieldcat[]
i_save = g_save
* is_variant = g_variant
it_events = gt_events[]
is_print = gs_print
TABLES
t_outtab = TI_ORDENES
EXCEPTIONS
program_error = 1
OTHERS