دانلود رایگان مقاله مطالعه بالاآمدگی بارها به علت تاثیر منفذ سونامی بر روی مدل اسکله

Abstract

Tsunamis are unpredictable disasters that have occurred frequently in recent years. An experimental study was conducted to quantify the tsunami bore uplift loads on a deck mounted on a slope, representing a typical wharf structure. Tsunami bores were generated as dam break waves in a flume, and the bore Froude number was approximately 1.6 on the dry bed. Fifty-five tests (11 bore cases, 5 runs each cases) were conducted for detailed measurements of bore height and bore velocity, and 504 tests (7 bore cases, 3 deck heights, 8 wharf slope angles, 3 runs each combination) were conducted for measurements of time-histories of pressure on the soffit of the deck. The effects of bore height, deck height and slope angle on uplift loads were studied. Results show that bore height correlates with bore velocity. The flow motion of the tsunami bore impacting the deck is divided into five stages: front-climbing, front-hitting, run-up, quasi-steady, and recession. The uplift pressure decreases from the deck-slope connection to the deck front edge, and the total uplift load increases with increasing bore height or decreasing deck height. For the front-hitting stage (the maximum pressure), the uplift load increases as the wharf slope angle decreases. However, for the quasi-steady stage (the longest time period), the uplift load is consistent for different wharf slope angles. Based on the experimental data, the equations for predicting the front-hitting and quasi-steady pressures are proposed as functions of bore height, deck height and wharf slope angle, and the predicted values are within ± 20% error.

5. Conclusions

In this study, tsunami bore uplift loads on a wharf model were quantified. The bore characteristics were investigated. Also, the bore height, deck height and slope angle effect on uplift loads were investigated. The main conclusions are summarised below: 1) In our study, the flow motion around the wharf model exhibits five stages, namely front-climbing stage, front-hitting stage, run-up stage, quasi-steady stage, and recession stage. Correspondingly, the time-history of pressure exhibits front-climbing pressure (small fluctuation signals), front-hitting pressure (the largest peak), runup pressure (large fluctuations), quasi-steady pressure (the longest time), and recession pressure (dropping to zero). 2) In the front-hitting stage, the pressure is dominated by dynamic pressure, and the variations of pressure profile along the deck stream-wise centreline occur in this stage. In the quasi-steady stage, the pressure is dominated by hydrostatic pressure, and the pressures are evenly distributed along the stream-wise centreline of the deck. Both front-hitting pressure and quasi-steady pressure reduce from the deck-slope connection to the deck front edge, and are constant in the transverse direction. 3) Both front-hitting pressure and quasi-steady pressure increase as bore height increases or deck height decreases. A smaller wharf slope angle results in a higher front-hitting pressure, but there is little effect of slope angle on quasi-steady pressure. For the 90° wharf slope, a front-hitting pressure was not observed on most of the deck but was observed at the deck-slope joint. 4) From our experimental results, uplift pressure is found to be a function of bore height, deck height and wharf slope angle. The equations for estimating averaged front-hitting pressure and quasi-steady pressure are proposed as Eqs. (12) and (15), respectively. The uplift pressures calculated by the equations agree with the measured pressure within ±20% error.