Thanh Ngo, Jaehak Park, Seongbaek Park and Yujin Lim
International Journal of Railway, vol. 10, no. 1, pp.15-19, 2017

Abstract : In this study a new detection technique based on Wave Activated Stiffness concept is introduced that can be used for identifying gap presence under the concrete slab track by triggering activated waves on surface of the concrete slab. If a gap exists immediately below the concrete slab, unstable condition is generated to the track. Wave Activated Stiffness K of the concrete slab track with a gap can be lower than that of the concrete slab track without a gap. The concrete slab is assumed as a single degree of freedom system (SDOF). The Wave Activated Stiffness K can be obtained by iteration with changing mass (m), stiffness (k) and damping coefficient (c) of SDOF system. Those parameters are used to specify the slab condition underneath the slab. Typical test results using a small slab model test constructed in a backyard are summarized and explained for proof of effectiveness of the impact test for identifying gap under the railway concrete slab based on Wave Activated Stiffness K.

Keyword : Track, Track stiffness, Gap, Wave Activated Stiffness, Nondestructive test