Experimental Analysis of Hydraulic Jump at High Froude Numbers

The hydraulic jump is a rapid transition state from supercritical to subcritical flow that occurs commonly in rivers, prismatic channels and downstream of spillways. In this study, the characteristics of the hydraulic jump in a stilling basin downstream of the spillway chute channel with the slopes of α = 12o and 30o were investigated experimentally for different Froude numbers of incoming flow, Fr1 = 7, 7.5, 8, 9, 10 and 12, and relative heights of sill in the range of 4 < hs/h1 (S) < 13 (S relative height). In the experiments, in which velocity field measured by laser Doppler Anemometry, it was particularly focused on the effects of both different structural configuration and flow conditions on the hydraulic jump and energy dissipation ratio. Experimental measurements showed that the length of hydraulic jump and the roller zone increases with the decrease of the sill height for α = 12o and 30o. In addition, the length of the hydraulic jump and roller zone increased with decreasing Froude numbers. The turbulence intensity in the jump region was determined to be greater than the turbulence intensity in the region near the bottom of stilling basin. The turbulence intensity, in general, tended to decrease with decreasing Froude number.

Damage localization based on modal strain energy index and evidence theory

A damage localization approach based on modal strain energy index and evidence theory is proposed in this paper. First, the modal strain energy change ratio (MSECR) method and modal strain energy dissipation ratio (MSEDR) method are used to preliminarily detect the damage locations, respectively. Then, the evidence fusion technique is applied to integrate these results and determine the damage locations of structures. To investigate the effectiveness of the proposed method, a numerical example is considered. The numerical results show that the proposed method achieves a better performance in determining the damage locations of structures.

Structural damage identification based on gray cloud rule generator algorithm

It is difficult for the traditional methods to identify uncertain damage problems caused by noise. Therefore, a gray cloud rule generator algorithm based on cloud model and modal strain energy is presented to solve the problems. Cloud model can simulate both randomness and fuzziness with fixed parameters. Therefore, it is applicable for the uncertain damage problems. First, modal strain energy and modal strain energy dissipation ratio index are introduced. Then, numerical characteristics of a cloud model are described and some cloud generators are analyzed. Finally, a gray cloud rule is proposed and the gray cloud rule generator algorithm based on the gray cloud rule generator and modal strain energy is developed. The interference of uncertain noise is reduced through a large number of cloud droplets. A two-dimensional truss structure model has been used to verify the effectiveness of the algorithm. The results indicate that the proposed gray cloud rule generator algorithm is applicable to identify the uncertain damage caused by noise, and the identification results of the proposed method are relatively better than those of modal strain energy dissipation ratio index.

The Effect of Infill Steel Plate Thickness on the Cycle Behavior of Steel Plate Shear Walls

The effect of changing in the bed slope of stilling basins produces changing in characteristics of the hydraulic jump such as sequent depth ratio, length of jump ratio, length of the roller and energy dissipation ratio, consequently the dimensions of stilling basin changed. In this study hydraulic jump investigated on smooth bed (without any appurtenances) for three adverse slopes (- 0.03, - 0.045, - 0.06) in addition to horizontal bed slope, the experiments were applied for the range of Froude number (Fr1) between 3.99 and 7.48. The results showed a reduction about10 % in sequent depth ratio, 22.1 % in length of jump ratio, 20.51 % in length of roller ratio and 13.87% in the energy dissipation ratio when the adverse slope (- 0.06) used instead of horizontal bed for the same Froude numbers. Empirical equations for the sequent depth ratio, length of roller ratio and the energy dissipation ratio were obtained from the experimental data

Hydraulic shape memory alloy shock absorber: Design, analysis, and experiments

In this article, a new hydraulic shape memory alloy shock absorber is introduced. The shape memory alloy bars are used as the kernel components for energy dissipation and restoration in the stress mode of pure tension, and their initial deformation is enlarged by a hydraulic system with two pistons of different sizes. This particular arrangement yields high shape memory alloy material utilization and large displacement–length ratio simultaneously. A prototype device was fabricated and tested. The specific input energy (input energy/mass of shape memory alloy) and energy dissipation ratio (dissipated energy/input energy) in the experiments were about 2 J/g and 30%, respectively, at the full stroke. Based on this hydraulic shape memory alloy shock absorber, a combined device including viscous damping was theoretically investigated. According to the calculation results, the maximum specific input energy and energy dissipation ratio can increase by onefold from the initial model without viscous damping. Based on the works and results of this study, the three guidelines in the designing of shape memory alloy–based shock absorbers have been brought up: (1) keep the shape memory alloy parts in the pure tension state to increase the material utilization, (2) introduce deformation or displacement enlargement structures to amplify the work stroke, and (3) combine with other energy dissipation mechanisms.

Effect of baffle block configurations on characteristics of hydraulic jump in adverse stilling basins

The construction of stilling basin with adverse slope change the characteristics of hydraulic jump such as sequent depth ratio, length of jump ratio, length of roller and energy dissipation ratio, consequently the dimensions of stilling basin are changed, also using baffle blocks with different configurations develop these characteristics. In this study different shapes of baffle block (models (A), (B), (C) and (D)) installed in the stilling basins at adverse slopes (- 0.03, - 0.045, - 0.06) in addition to horizontal bed, all these models are tested in the stilling basin to show their effects on the characteristics of hydraulic jump, the experiments applied for the range of Froude number (Fr1) between 3.99 and 7.48. The baffle block model (D) showed good results when compared with models (B) and (C), therefore it used with arrangement of (single and double row) and compared with baffle block model (A) at slopes (0, - 0.03, - 0.045, - 0.06) to study the effects of baffle blocks on hydraulic jump when bed slopes are changed. In general using baffle block caused a reduction in sequent depth ratio, length of jump ratio and the length of the roller, but the energy dissipation ratio increased.

Characterizing Seismic Resiliency Using an Energy Dissipation-Recentering Correlation Diagram

For a structural system, the potential to dissipate energy and recenter during an earthquake are two important characteristics that support seismic resiliency. This paper proposes two dimensionless parameters, namely, an energy dissipation ratio ( R ED) and a recentering ratio ( R RC), to quantify the potential of an inelastic mechanism to dissipate hysteretic energy and recover from inelastic deformations, respectively. For most mechanisms used in seismic design, these two parameters are not independent, but rather, they are inherently related. In this work, an R ED- R RC correlation diagram is established by placing each parameter within a two-dimensional plot. Importantly, four different zones with varying seismic response attributes are identified. Numerical studies considering various idealized inelastic systems coupled with experimental data are then utilized to demonstrate the utility of the R ED- R RC correlation diagram as a simple design tool for estimating the seismic resiliency of a system.

Design of SMA Damper and Analysis on Seismic Control of Frame Structure

With the SMA (Shape Memory Alloy) banner model, the effect of pre-stressing and displacement, stiffness and length to the energy dissipation ratio is studied. The two equations, which are of pre-stressing and displacement to the energy dissipation ratio are proposed. The method are put forward to confirm the stiffness and length of SMA . Based on the above analysis, a new pull-press SMA damper is designed. The simulation analysis on seismic response of five-floor frame with SMA damper shows that the displacement and acceleration of the top floor are reduced by 50﹪at least. It verifies that this kind of SMA damper can availably suppress the seismic response of structure.