Experimental work carried out on automotive bolted joints to investigate the modal damping and energy dissipation capacity in jointed structures in a certain range of frequency are detailed in this paper. Single-lap bolted joints are assembled from aluminium beams, and five different bolt sizes are used to explore the contribution of bolt size have in dissipating energy in engineering structures. An analogous monolithic solid piece beam is sculpted from the same aluminium material to isolate the joint effects and directly compare the structural and joint damping data acquired for the bolted single-lap joints. The common modes of the jointed structures and analogous monolithic beam captured under free-free boundary conditions due to forced excitation are analysed to recognize the contribution and primary source of damping in the same sampling frequency range. The detailed research results of the experimental modal analysis on jointed structures are used to create a simplified but precise analytical model that can be used at a preliminary design stage to estimate the modal behaviour of the jointed structure and the energy loss due to dynamic loading for specific modes of vibration.