A structure comprising at least one layer comprising a BACT/XT copolyamide wherein: - BACT is a unit with an amide motif present at a molar content ranging from 20 to 70%, preferably from 25 to 60%, more preferably from 35 to 55%, where BAC is chosen from among 1,3-bis(aminomethyl)cyclohexane (1,3-BAC), 1,4-bis(aminomethyl)cyclohexyl (1,4-BAC) or a mixture thereof, and T is terephthalic acid, - XT is a unit with an amide motif present at a molar content ranging from 30 to 80%, preferably from 40 to 75%, more preferably from 45 to 65%, where X is a C9 to C18 linear aliphatic diamine, preferably C9, C10, C11 or C12, and where T is terephthalic acid, preferably C10, C11 or C12. - in the BACT and/or XT units, independently of each other, up to 30 mol%, preferably 20 mol%, particularly up to 10 mol% of terephthalic acid, relative to the total quantity of dicarboxylic acids, can be replaced by other diaromatic, dialiphatic or di(cyclo)aliphatic acids comprising 6 to 36 carbon atoms, particularly 6 to 14 carbon atoms, and - in the BACT and/or XT units, independently of each other, up to 30 mol%, preferably 20 mol%, particularly up to 10 mol%, of the BAC and/or if applicable X, relative to the total diamine quantity, can be replaced by other diamines comprising from 4 to 36 carbon atoms, particularly 6 to 12 carbon atoms, and - in the copolyamide, not more than 30 mol%, preferably not more than 10 mol%, relative to the total quantity of the monomers, can be formed by lactams or aminocarboxylic acids, and - provided that the sum of the monomers that replace terephthalic acid, BAC and X does not exceed a concentration of 30 mol%, preferably 10 mol%, relative to the total quantity of the monomers used in the copolyamide, and - provided that BACT and XT units are still present in said polyamide polymer, said structure being devoid of strengthening fibers. - BACT is a unit with an amide motif present at a molar content ranging from 20 to 70%, preferably from 25 to 60%, more preferably from 35 to 55%, where BAC is chosen from among 1,3-bis(aminomethyl)cyclohexane (1,3-BAC), 1,4-bis(aminomethyl)cyclohexyl (1,4-BAC) or a mixture thereof, and T is terephthalic acid, - XT is a unit with an amide motif present at a molar content ranging from 30 to 80%, preferably from 40 to 75%, more preferably from 45 to 65%, where X is a C9 to C18 linear aliphatic diamine, preferably C9, C10, C11 or C12, and where T is terephthalic acid, preferably C10, C11 or C12. - in the BACT and/or XT units, independently of each other, up to 30 mol%, preferably 20 mol%, particularly up to 10 mol% of terephthalic acid, relative to the total quantity of dicarboxylic acids, can be replaced by other diaromatic, dialiphatic or di(cyclo)aliphatic acids comprising 6 to 36 carbon atoms, particularly 6 to 14 carbon atoms, and - in the BACT and/or XT units, independently of each other, up to 30 mol%, preferably 20 mol%, particularly up to 10 mol%, of the BAC and/or if applicable X, relative to the total diamine quantity, can be replaced by other diamines comprising from 4 to 36 carbon atoms, particularly 6 to 12 carbon atoms, and - in the copolyamide, not more than 30 mol%, preferably not more than 10 mol%, relative to the total quantity of the monomers, can be formed by lactams or aminocarboxylic acids, and - provided that the sum of the monomers that replace terephthalic acid, BAC and X does not exceed a concentration of 30 mol%, preferably 10 mol%, relative to the total quantity of the monomers used in the copolyamide, and - provided that BACT and XT units are still present in said polyamide polymer,