a stay comprises an inclined casing and a bundle of substantially parallel taut reinforcements lodged in the casing and individually anchored in a first and a second anchoring region . according to the invention , the casing and some of the reinforcements are installed by applying substantially uniform tension values to the reinforcements , then several iterations of the following steps are formed : compacting the installed reinforcements , at least at one end of the casing ; slipping a further group of reinforcements along inside the casing , in a space left available by the compacted reinforcements ; and tensioning each reinforcement of the further group between the first and second anchoring regions so that all the installed reinforcements exhibit substantially uniform tension values .