Investigation of uplift impact forces on a vertical wall with an overhanging horizontal cantilever slab

A vertical wall with an overhanging horizontal cantilever slab is tested in a small scale test set-up under wave impact (impulsive) loads. Tested waves are regular and irregular. A single approaching wave creates two individual impacts which occur sequentially on the wall and slab of the structure. Results from wave impact tests are used to analyze the uplift impact forces under breaking waves. Then, a set of parameters which is responsible for the uplift impact forces is investigated under regular waves and results are compared with the results of irregular wave tests. Incident wave height at the toe of the foreshore (H-1), water depth at the structure toe (hs) and incident wave period (T) are the main parameters governing the uplift impact forces. In addition, the influence of different geometric properties, described by dimensionless ratios like c'/h(s) (c' is the clearance between still water level and slab of the structure) should be taken into account. Based on the experimental investigations on breaking wave kinematics and impact loads, a new prediction model for uplift impact forces, occurring on the overhanging horizontal cantilever slab, has been derived as a function of the rise time t(r). t(r) is the time duration between points t(1) and t(2), see Fig. 2. The formula is tested within the range 0.45 <= H-1/h(s) <= 1.2, 2.0 s <= T <= 2.8 s and 0.75m <= h(s) <= 1.65m. The formula is developed based on the scaled test results. Therefore, a correction of the formula is required for the prototype dimension. In addition, the formula considers the maximum uplift impact forces which are more intense but shorter lasting. Thus, the structural response of the cantilever should be taken into account in design process. This paper is a completion of previously published works (Kisacik et al., 2012a and Kisacik et al., 2012b) on this type of structure. (C) 2014 Elsevier B.V. All rights reserved.