Experimental Study On The Influence Of The Cushions For Touchdown Vibration On Collapsing Of Water Tower

Building collapse touchdown vibration becomes larger than blasting vibration. Touchdown vibration becomes the main harm factors to surrounding buildings. The characteristics and development status of the touchdown vibration are introduced. Two methods are often used to control the touchdown vibration:control sourse of vibration and control the route of transmission of the vibration.Crumbing body touchdown process is very complex. It connects with crumbing body shape, material and mechanical characteristic. The touchdown process was simpfied to collision of physical mechanics. The impact dynamics theory was used to study effect of touchdown vibration. The shock load of building collapse touchdown was analyzed. The problem of above ground buildings responsed to vibration and force situation of shallow pipes was analysised. Reducing impulse and covering the cushions could protect shallow pipe effectively.The touchdown vibration velocity formula and main vibration frequency formula was studied by dimensional analysis. Dimensional formula of touchdown vibration velocity was verified by analogue experiment. Do simulation experiments for vibration caused by tank of water tower collapse. Researched on damping effect of cushioning, some conclutions are gained as below:(1) Vibration velocity becomes smaller as the distance becomes larger. By the regression analysis, we found that the vertical sites velocity reduces faster than horizontal radial sites. And its duration is shorter. If the thickness of sand cushion was no changes, only changed the hight of the hammer, the variation of "K" and "α" of vertical sites and horizontal radial sites changed smalless. This mean, we could confirm the "K" and"α" by the test in advance.(2) With the thickness of sand cushion increase, touchdown vibration was reduced obviously. The damping rate could reach 92%. But when the thickness got a numerical value, the damping became gently. This mean, there was a critical value. If the thickness of sand cushion reached the critical value, the damping effect will not increase.