Dynamic Characteristics Identification of an Arch Dam Model via the Phase-Based Video Processing

Qi Li,Gaohui Wang,Aral Sarrafi,Xinqiang Niu,Wenbo Lu,Zhu Mao 대한토목학회 2021 KSCE Journal of Civil Engineering Vol.25 No.1

In recent years, the extraction of structural dynamic characteristics by using phase-based video processing has attracted considerable attention. Edge detection routine is oftentimes employed to obtain the quantified operational deflection shape (ODS) vectors of structures. However, this approach is unreliable because of intensive human supervision and correction. To reduce operational uncertainty, a hybrid computer-vision-based approach called edge detection-region labeling, which involves vision sensor preparation, bottom-hat filtering, edge detection, hole filling, and region labeling, was presented in this work to extract the quantified ODS’s. The performance of this method was firstly evaluated by conducting a lab-scale cantilever beam test and subsequently the phase-based video processing was applied to extract the dynamic characteristics of an arch dam model. The operational modal analysis (OMA) test was conducted on the benchmark dam model. In-plane motions of the dam were captured and processed to identify the natural frequencies of the dam. The structural ODS’s were quantified using the proposed method. A comparison of the modal parameters of the dam identified from the video data with those obtained in the OMA test revealed that the two sets of results were consistent, and the video processing approach was able to bypass the requirement of human supervision, which facilitates the application of the phase-based video processing for complex structures.

A SPH-Lagrangian-Eulerian Approach for the Simulation of Concrete Gravity Dams under Combined Effects of Penetration and Explosion

Guangdong Yang,Gaohui Wang,Wenbo Lu,Peng Yan,Ming Chen,Xinxia Wu 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.8

The damage prediction of high dams under the attacks of earth-penetrating weapons has gained significant importance in recentyears. For this purpose, a SPH-Lagrangian-Eulerian coupled approach is proposed to describe the damage processes of concretegravity dams subjected to the combined action of the penetration and explosion. The SPH method is used to model the concretematerial with the large deformation near the penetration and explosion regions. The Lagrangian algorithm is adopted to simulate thehigh-velocity projectile and dam body with the small distortion. And the Eulerian algorithm is employed to describe the dynamicbehavior of the water and air media. The validity of the penetration model is calibrated against a previous penetration test. Meanwhile, the SPH-Lagrangian-Eulerian coupled method is verified by implementing an underwater explosion test in a concretecube. The computed distribution of cracking damage is consistent with the result of the experimental test, which validates the validityof the proposed SPH-Lagrangian-Eulerian coupling method. Subsequently, the penetration processes of a concrete gravity dam underthe high-velocity projectile are presented. After the rapid penetration, the explosives are detonated in the dam with the initialpenetration damage. The shock wave propagation characteristics in the dam and reservoir water are discussed. The failure processesand dynamic responses of the dam subjected to the combined action of the penetration and explosion are investigated. The influenceof the initial penetration damage and the reservoir water on the failure processes of the dam subjected to the internal blast loading is alsodiscussed. The results show that the penetration of the high-velocity projectile only causes a local damage to the concrete gravity dam. However, the combined effects of the penetration and explosion cause significantly more damage to the upper region of the dam.

Effects of Strain Energy Adjustment: A Case Study of Rock Failure Modes during Deep Tunnel Excavation with Different Methods

Liang-Tao Xie,Peng Yan,Wenbo Lu,Ming Chen,Gaohui Wang 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.10

The strain energy adjustment processes and rock failure modes corresponding to different excavation methods, such as Tunnel Boring Machine (TBM) or blasting, are quite different during construction of deep tunnel. Based on the diversion tunnel excavation of Jin-Ping II hydropower station (JPII) in southwestern China, the distribution characteristics of damage zones and adjustment process of rock strain energy under different excavation methods are analyzed and discussed, and the occurrences of rock bursts in the diversion tunnels are also monitored and analyzed. Research reveals that, the adjustment process of rock strain energy and the distribution of damage zones are obviously different under different excavation methods, and the depth and distribution of damage zone are positively correlated with the accumulation depth of rock strain energy. For blasting excavation, due to the combined effects of blast loading and in situ stress transient unloading, the surrounding rock is damaged seriously. The accumulation depth of rock strain energy is significantly larger than that by TBM excavation, while the accumulation peak of rock strain energy is smaller. For TBM excavation, the strain energy releases smoothly and slowly, and much more strain energy is accumulated in the vicinity of excavation face. Under similar geological conditions in the JPII, the rock bursts of intensive and mediate grades can be more frequently observed after blasting for the impact of severe excavation disturbance, and the strain energy transient adjustment may be the main disturbance contributor. While during TBM excavation, due to the smooth adjustment process of rock strain energy, the disturbance to surrounding rock is limited, and the accumulation peak of rock strain energy is higher and closer to the excavation face, which may result in more spalling events or minor rock bursts.

Numerical Simulation on Energy Concentration and Release Process of Strain Rockburst

Ang Lu,Peng Yan,Wenbo Lu,Ming Chen,Gaohui Wang,Sheng Luo,Xiao Liu 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.10

Rockburst mechanism has been a hot topic in the stability analysis of underground carven excavation, and the accurate description of energy evolution process is very critical to rockburst prediction. To study the evolution process of rockburst, such as V-shaped rockburst pit, theoretical formula derivation and numerical simulation are adopted to research the dynamic response characteristics during the formation process of rockburst pits quantitatively. The results show that rockburst intensity distribution varies with failure depth. It can be divided into three zone: slow-increase, rapid-increase and slow-decrease. For a circular tunnel with radius R, the strain energy release rate and vibration response of surrounding rock increases gradually within (0 − 0.06) R; reaches the peak value around (0.06 − 0.1) R and drops to a balance beyond 0.1R. Due to the same law of them, the rockburst risk can be conveniently predicted by monitoring vibration of surrounding rock with a certain depth. This work is beneficial to provide a good reference for rockburst prediction.

NADH oxidase from <i>Lactobacillus reuteri</i>: A versatile enzyme for oxidized cofactor regeneration

Gao, Hui,Li, Jinglin,Sivakumar, Dakshinamurthy,Kim, Tae-Su,Patel, Sanjay K.S.,Kalia, Vipin C.,Kim, In-Won,Zhang, Ye-Wang,Lee, Jung-Kul Elsevier 2019 INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES Vol.123 No.-

<P><B>Abstract</B></P> <P>Pyridine nucleotide cofactors play important roles in biocatalytic processes that generate value-added chemicals for the pharmaceutical and food industries. Because of the high price of these pyridine cofactors, cofactor regeneration is highly desirable. However, recycling the oxidized form of cofactors, especially NADP<SUP>+</SUP>, remains a challenge. Here, we cloned and characterized an NADH oxidase from <I>Lactobacillus reuteri</I> (LreNox) which can oxidize both NADH and NADPH. Unlike many other Noxs, LreNox showed equal catalytic efficiency towards NADH and NADPH. To the best our knowledge, LreNox has the highest activity towards NADPH as a substrate compared to other wild type Noxs. Homology modeling and substrate docking studies provided insights into the dual substrate specificity of LreNox. Gly155, Ser179, and His184 in the LreNox substrate binding pocket, which are absent in other Noxs structures, are crucial for NADPH recognition, providing more space for interactions with the additional phosphate group present in NADPH. We also explored the utility of LreNox for NADP<SUP>+</SUP> regeneration in <SMALL>L</SMALL>-sorbose production by coupling it with a sorbitol dehydrogenase. The turn over number (TTN) improved ~53-fold after using LreNox as the NADP<SUP>+</SUP> recycling enzyme. This study demonstrates that LreNox could potentially be used for the regeneration of NAD(P)<SUP>+</SUP> in commercial applications.</P>