Load principles for drive mechanisms of Miter gates

Load principles for drive mechanisms of Miter gates: Assessing suitablitliy of current codes and guidelines for drive mechanisms

Gerritse, A.R.

Jonkman, S.N. (mentor)
Molenaar, W.F. (mentor)
Verheij, H.J. (mentor)

Civil Engineering and Geosciences

Hydraulic Engineering

2016-08-14

In recent years, in a number of projects gate drive mechanisms of navigation locks were checked or adapted for a longer service life, during which the reliability, safety and availability of the structure had to be guaranteed for an extended period. Several problems were encountered. When verifying the gate drive mechanism, it was found that the drive mechanisms, which have performed well for years, do not meet the current design criteria. According to the current design criteria the capacity of the drive mechanism would be insufficient. The design force according to the latest criteria exceeds the maximum allowed force on the gate, and cannot be applied without major adaptations to the gate and lock head structure, hence, results in high costs. In coming years a series of approximately 50 locks require replacement or large scale maintenance, it is worth considering the apparent contradiction between drive mechanisms that performed satisfactorily for years against the much higher required capacities by the nowadays codes and guidelines, giving rise to the question; Is the approach as presented in the current codes and guidelines, in specific the ROK 1.3 (Richtlijn Ontwerpen Kunstwerken, issued by Rijkswaterstaat), suitable for the design of drive mechanisms? This study presents a case study in order to answer this question. The case study focuses on a navigation lock containing Miter gates. The original design calculations dating from 1974 are compared to an updated calculation according to ROK 1.3. Both calculations are subsequently compared to a more tailored calculation approach that accounts for site-specific forces. This third approach explained some of the key differences between the fully functioning drive mechanism with the capacity as designed in 1974 and the updated calculation applying ROK 1.3. These differences primarily originate in the schematization of the forces affecting the drive mechanism and the resulting combination of forces. Applying the ROK 1.3 resulted in a conservative estimation. Differences in order of magnitude are mostly explained by the adjusted regulations. In the past external forces were not accounted for in the calculations and the reliability requirements have become more stringent.Furthermore, operational requirements were not accounted for in the design phase. Navigation locks have the following main functions: navigation, water management and flood protection. Not defining properly which main function sets the safety requirement for the construction can result in a misjudgement of the loads that affect the navigation lock. ROK 1.3 builds on principles and guidance for the different main functions separately, and these are not harmonized. The requirements for the different main functions relating the availability and structural reliability all translate into partial load factors that are aggregated into a reliability-index. Where one of the requirements leads to the normative reliability-index It is important to account for the different limit states when increasing availability of the system and, contrary to common practice in calculations for civil components, to increase the partial safety factors in the serviceability limit state. This will increase the safety mechanism of the system leading to higher availability. The regulations in ROK 1.3 are useful in designing drive mechanisms as long as the main function that sets the safety constraint of the construction is taken into account. It is beneficial to include site-specific conditions and to estimate the load components more accurate. Although ROK 1.3 does not explicitly discourage this approach, nor does it elaborate on it. At present another more sophisticated approach is not facilitated by the ROK.

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Student theses

master thesis

(c) 2016 Gerritse A.R.