rectangular construction composed of top plate 36 bottom plate 38 and side plates 40 end portion 34 of beam assembly 18 has resilient bushing 33 which is integral with beam assembly 18 and is comprised of outer shell 46 elastomeric device 44 and inner tube 42 outer shell 46 is integral with and constructed of the same material as the beam such as metal or iron inner tube 42 is disposed longitudinally across the entire width of beam assembly 18 within shell 46 and its ends 43 further extend a distance outwardly away from beam assembly 18 beyond side plates 40 as well as beyond side plates 30 and 32 inner tube 42 is of a hollow rigid construction of metal or similar material inner tube 42 is positionally stabilized in substantially the center of shell 46 by resilient elastomeric device 44 which is disposed between shell 46 and tube 42 in concentric relation elastomeric device 44 is constructed of natural rubber or a similar elastomeric compound that has a high degree of resistance to climatic conditions and exhibits resilient properties elastomeric device 44 is provided with cavities 45 which give markedly different deflections beam wise than hanger wise and spring rates in.