Modal Analysis of a Steel Radial Gate Exposed to Different Water Levels

Abstract

With the increase in water retention needs and planned river regulation, it might be important to investigate the dynamic resistance of vulnerable elements of hydroelectric power plants, including steel water locks. The most frequent dynamic loads affecting hydroengineering structures in Poland include vibrations caused by heavy road and railway traffic, piling works and mining tremors. More destructive dynamic loads, including earthquakes, may also occur in our country, although their incidence is relatively low. However, given the unpredictable nature of such events, as well as serious consequences they might cause, the study of the seismic resistance of the steel water gate, as one of the most vulnerable elements of a hydroelectric power plant, seems to be important.In this study, a steel radial gate has been analyzed. As far as water gates are concerned, it is among the most popular solutions because of its relatively small weight, compared to plain gates. A modal analysis of the steel radial gate was conducted with the use of the FEM in the ABAQUS software. All structural members were modelled using shell elements with detailed geometry representing a real structure. Water was modelled as an added mass affecting the structure. Different water levels were used to determine the most vulnerable state of the working steel water gate.The results of the modal analysis allowed us to compare the frequencies and their eigenmodes in response to different loads, which is one of the first steps in researching the dynamic properties of steel water gates and their behaviour during extreme dynamic loads, including earthquakes.

Numerical and Physical Analysis on the Response of a Dam’s Radial Gate to Extreme Loading Performance

“…Radial gates in the closed position can be exposed to a variety of loads, including hydrostatic pressure, ice loads, and hydrodynamic forces, as results of dam-reservoir seismic waves [21]. Additionally, several other loads are developed during the gate operation, including vibration and bending moment, as a result of trunnion pin erosion.…”

Applicability of the Goda–Takahashi Wave Load Formula for Vertical Slender Hydraulic Structures

“…The equivalent-static wave load for cross-sectional force R is defined as the statically applied wave load which would induce the same maximum response as the dynamically applied wave load, that is: f P→R P eq,R = R dyn,max (2) where f P→R (.) represents the mechanical function converting the 'static' wave load P to the 'static' cross-sectional force R, and P eq,R the equivalent-static wave load for cross-sectional force R. Often the equivalent-static wave load is defined by a dynamic load factor (DLF):…”

“…Under certain conditions, the (time-varying) wave loads may cause a dynamic response of the structure, either increasing or decreasing the cross-sectional forces as compared to the static application of the wave loads. For a proper determination of these cross-sectional forces a dynamic assessment needs to be conducted, taking into account the time-histories of the wave load and the dynamic characteristics of the structure, see e.g., [1,2]. A dynamic assessment can however be complex and time-consuming, and requires information that is often not directly available to the engineer (e.g., the time-histories of the design wave load).…”