A gas turbine joint assembly

A joint assembly (40) for securing the flanges (42, 44) of two casings (26, 38) comprising a plurality of bolts (50), a plurality of collars (52) and a plurality of nuts (54). Each bolt (50) extends through an aperture in the first flange (42) and an aperture in the second flange (44), each collar (52) being arranged around a shank of a respective bolt (50) and each nut (54) being secured on a respective one of the bolts (52). Each collar (52) being arranged between one of the flanges (42, 44) and a nut (54) or a head of a bolt (50). Each collar (52) comprises a first member (62) and a second member (64), the second member (64) being arranged at a first end of the first member (62). The second member (64) being substantially U-shaped in cross-section, the second member (64) having a first and second radially inner ends (70,74) and a radially outer mid portion (72,76) and an axial space (78) is defined between the first radially inner end (70) and the second radially inner end (74) of the second member (64).