Mechanism of Tsunami-Induced Erosion of Bridge-Abutment Backfill and Its Countermeasures

Tsunamis can destroy bridges in coastal areas. Studies have attempted to unravel the mechanism of tsunami-induced damage and develop effective countermeasures against future tsunamis. However, the mechanisms of tsunami-induced erosion of bridge-abutment backfill and its countermeasures have not been studied adequately. This study investigates this topic using numerical analysis. The results show that the tsunami flowing down along the downstream wing of the abutment induces bedload sediment transport on the ogive section of the backfill on the downstream side of the abutment, resulting in the onset of backfill erosion. Sediment suspension and bedload sediment transportation occur when the backfill inside the abutment starts to flow out from below the downstream wing. This leads to subsidence of the backfill at the upstream side of the downstream wing. The subsequent backfill erosion is mainly caused by bedload sediment transport. Numerical experiments on countermeasures show that extending the wings downward can prevent the acceleration of backfill erosion in the presence of the abutment. A combination of multiple countermeasures, including extended wings, would be more effective in maintaining the stability of the abutment after a tsunami. This suggests the application of such countermeasures to actual bridges as an effective countermeasure against backfill erosion.

Model of discharge coefficient of crest gate rubber weir at fully closed condition

Crest Gate Rubber Weir is a modification of rubber weir with adding a metal plate or crest gate on the upstream side. The rubber in this weir functioning as a support while the crest gate serves on elevating water. Although many have been implemented, this weir’s discharge coefficient needs be researched considering its unique shape. This study looks for discharge coefficient to determine the discharge that passes through weirs at fully closed conditions. The research was conducted with a hydraulic model resembling part of Tirtonadi Weir in Surakarta with a hydraulic model. The model is made in an angle 53°, which represents the prototype at fully closed condition. Laboratory experiment shows that the discharge coefficient of this weir is greater than the Ogee Weir and Sluice Gate for the same height because of less flow resistance from this weir structural form.

On Dam Failure Induced Seismic Signals Using Laboratory Tests and on Breach Morphology due to Overtopping by Modeling

Dam models were constructed in an indoor flume to test dam breach failure processes to study the seismic signals induced. A simple dam breach model was also proposed to estimate hydrographs for dam breach floods. The test results showed that when the retrogressive erosion due to seepage of the dam continues, it will eventually reach the crest at the upstream side of the dam, and then trigger overtopping and breaching. The seismic signals corresponding to the failure events during retrogressive erosion and overtopping of the dam models were evaluated. Characteristics of the seismic signals were analyzed by Hilbert–Huang transform. Based on the characteristics of the seismic signals, we found four types of mass movement during the retrogressive erosion process, i.e., the single, intermittent, and successive slides and fall. There were precursor seismic signals found caused by cracking immediately before the sliding events of the dam. Furthermore, the dam breach modeling results coincided well with the test results and the field observations. From the test and modeling results, we confirmed that the overtopping discharge and the lateral sliding masses of the dam are also among the important factors influencing the evolution of the breach. In addition, the widening rate of the breach decreases with decreased discharge. The proposed dam breach model can be a useful tool for dam breach warning and hazard reduction.

Environmental Security and Waste Management Aspects of the Tisza Floods

In this article, the author analyses the environmental safety and waste management tasks of the collection, selection and treatment of driftwood and waste accumulated on the upstream side of the Kisköre Dam as a result of floods. It describes separately the work carried out during the floods of 2017 and 2019, which were outstanding in terms of both volume and duration. It covers changes in the amount and proportions of waste and driftwood and analyses changes in work efficiency.

Hydrodynamic Behaviors of Aquaculture Net Cages After the Successive Mooring Lines Failure

This paper aims to study the successive mooring line failure (also known as the domino effect) and the collision between floating collars for aquaculture net cages subjected to currents. The numerical model of this study is developed based on the Morison equation and the lumped-mass scheme in the time domain. This model is then applied to see if the domino effect of moorings will happen after releasing the anchor point #1 on the upstream side. In this study, we adopt four different current speeds (0.5, 1.0, 1.5, 2.0 m/s) and three different safety factors (SF, 1.0, 1.5, 2.0) settings to calculate the number of mooring failures, and to see whether it will cause floating collars collision. The results show that in the case of the SF is 2.0, the domino effect will not be triggered, and the floating collar collision will not occur. When the SF is 1.5, and the current speed is up to 1.0 m/s or higher, only the two anchor points on the upstream side will fail and no collision will occur. However, if the SF is not considered (that is, 1.0), the domino effect will occur under all the four current speeds, and the floating collar collision will all occur. Therefore, we suggest that in order to avoid the domino effect of the mooring system of aquaculture net cages from currents, the SF of the mooring system design must be at least 2 times.

BARRIERS TO ICT ADOPTION BY SMEs IN INDONESIA: HOW TO BRIDGE THE DIGITAL DISPARITY?

The use and utilization of ICT for SMEs attract the attention of many parties. The problems of SMEs in Yogyakarta, Indonesia that is so diverse cannot be simplified on the issue of technology adoption. Moreover, increasing competitiveness is necessary so that ICT can truly be a bridging digital disparity. The action research activity is carried out to close the gap which not only focuses on understanding the pattern of technology adoption alone but also involves action steps in helping SMEs to survive and able to compete. The results showed that the SMEs still had difficulty in utilizing ICT from the upstream side. This is triggered by the limitations of existing human capital in managing technical and operational aspects of ICT. Therefore, the strategies to use of ICT for SMEs is recommended to combine a proactive and reactive approach so that the optimization of resources will be achieved. Accordingly, we suggest that further studies apply the implementation of ICT on proactive and reactive actions to close the knowledge gap between the two in a different setting, context, location, and/or culture.

Modeling of broad crested weirs by using dynamic similarity and CFD

Broad crested weirs and steps are used to regulate the flow in the channel, increase the water level at the upstream side, and measure the discharge. The construction of the broad crested weirs is more practical and also they are more stable compared with the other types of weirs. To serve in accordance with the purpose of their construction, broad crested weirs should be designed and built by considering certain criteria. Before the hydraulic structures are built, model experimental setups are constructed in the laboratory and problems to be encountered are tried to be determined. However, there may be differences between the structure to be built in real life (prototype) and model due to scale effect. These possible differences must be determined and necessary measures must be taken. In this study, the model and prototype of the broad crested weir are constructed in two different open channel systems by using Froude similarity. The geometric similarity between model and prototype is determined as Lr = 4. 44 experimental data were collected from model and prototype. The results obtained from the model and prototype are compared according to hydraulic similarity rules. In addition to the physical experimental setups, numerical models were created using the ANSYS Fluent for the model and prototype separately. By comparing the numerical model and physical experimental setups, optimum mesh size is tried to be determined. According to the results obtained from experimental setups, differences were observed in the position of critical flow depths and downstream water levels due to scale effects.

Velocity and Turbulent flow field at around the cylindrical Pier

This experimental study shows the velocity and turbulence field at vicinity of cylindrical pier with scour hole under clear water condition. The three dimensional velocity data were obtained at 5 cm, 10 cm, 20 cm and 30 cm from the pier with use of Acoustic Doppler Velocimeter at 360 degrees around the pier with 30-degree interval. The flow behaviour were extensively analyzed with the help of time averaged normalized velocity, Turbulent intensity, Turbulent kinetic energy and Reynolds shear stress plots. The study shows the flow behaviour at inside the scour hole, at scour hole ring and outside the scour hole which gives the elusive view of flow at vicinity of pier. An upstream side pier, the flow behaviour almost follows the similar trend but behind a cylinder the flow is asymmetry due to wake vortex and vortex shedding found at the wake region. This study offers an ample cognizance of flow structure at vicinity of circular pier, which is essential in order to design an effective scour control structures like rip-rap, W weir, vanes, slot and etc.,

Perkiraan Tinggi Standar Lantai Jembatan Terhadap Pengaruh Muka Air Banjir

One of the bridge crossing of the Ciliwung River at the upstream side entered DKI-Jakarta area is MT. Haryono Bridge, where the bridge has the heavy and jam traffics. Every rainy season, water level of Ciliwung River flood always increase, where the peak point of the flood was occured on February in 2007, the water level exceeded the bridge deck level. Therefore, it would be necessary to determine a height standard of the bridge deck of MT.Haryono bridge against to the water level of Ciliwung River when the peak flood occured, the existing of the elevation at the below of the bridge deck is + 18.50 meter and the elevation above the bridge deck is + 19.50 meter. Hydrology analysis using Log Pearson type III performed to determine the data of average daily and yearly rainfall around of catchment area of Ciliwung River with using the water level control point near Kalibata Bridge and the flood hydrograf was calculated using synthetic hydrograph method from Nakayasu. Hydraulic analysis utilized the of HEC-RAS software (4.1) using the maximum value of hydrograph unit and consists of two simulations, where the first is simulation of calibration model of Ciliwung River at the upstream side based on the flood occured on February 04th 2007 (called as Q2007) and the second simulation using some scenarios for some return period of 2, 5, 10, 20,50, 100 years. Every result of both simulations generates the height of bridge deck from the water level of flood according to the exsisting requirements. From these results, it could be determined the elevation of bridge deck for return period of flood for the peak flood 2007 and for 2, 5, 10, 20, 50, 100 yearly, and, such as +19.50, +20.50, +21.00, +21.10, +21.80, + 22.10 dan 22.00 meter.

An Experimental Investigation of Streamwise and Vertical Wind Fields on a Typical Three-Dimensional Hill

To study the streamwise and vertical wind fields on a typical three-dimensional hill, wind tunnel tests were performed. The mean values and turbulence intensities of the streamwise and vertical wind speeds of the typical positions above the hill were measured, and they are presented in the form of contour maps for design. Furthermore, the speed-up of the mean wind speeds in the streamwise direction was compared with codes. Finally, the windage yaw of a jumper cable was examined as an example of how to take into account the streamwise and vertical wind field influence on the wind load in the analysis of wind-induced responses. The results show that the most significant speed-up effect in the streamwise direction occurs on the hill crest, and the wind speed-up decreases with the increase of the height. Overall, the wind speed-up along the crosswind center line is larger than that along the along-wind center line of the hill. In the codes, the speed-up effect specified for the structure at half the height of the upstream side of the hill is relatively conservative. With regard to the mean wind speed in the vertical direction, the wind climbing effect located at half the height of the upstream side of the hill is the most significant. The area with the stronger turbulence intensity appears at the foot of the upstream and downstream sides of the hill. The influence of the vertical wind on the jumper cable is remarkable where the wind climbing effect is the most significant, which is worthy of attention in the design of the structure immersed in a hilly terrain-disturbed wind field.