12 research outputs found
Beban Vertikal Gelombang pada Deck Dermaga di Pelabuhan Marore, Provinsi Sulawesi Utara
No full textAbstrak
Sejumlah literatur menawarkan formulasi untuk memprediksi beban vertikal gelombang pada dermaga, namun terdapat rentang perbedaan hasil yang mengakibatkan tingkat kepercayaan yang berbeda (McConnell, Kirsty, William Allsop, and Ian Cruickshank, 2004). Pada studi ini, simulasi dilakukan dengan model numerik menggunakan ANSYS Fluent 17.2 Academic Release dengan modul Volume of Fluid (VOF), model turbulensi SST k-ω, dan solver PISO. Keluaran model ini berupa seri waktu tekanan total rata-rata pada sisi yang dipilih. Pengaturan model numerik didahului dengan validasinya terhadap model fisik dan numerik dari studi terdahulu. Pengaturan model yang telah divalidasi kemudian digunakan sebagai dasar pemodelan yang diterapkan untuk kondisi perairan dan geometri dermaga yang sebenarnya, dalam empat kondisi tinggi gelombang. Keluaran tekanan total rata-rata maksimum kemudian dibandingkan dengan hasil perhitungan dari formulasi lainnya, untuk melihat kecenderungan studi terdahulu yang mendekati hasil pemodelan. Diperoleh bahwa hasil yang paling mendekati formulasi yang ditawarkan oleh Ito dan Takeda (1967) pada OCDI dengan rentang selisih –12% hingga +29%. Keluaran tekanan maksimum ini juga dibandingkan terhadap peningkatan tinggi gelombangnya, sehingga dapat dibuat hubungan linear sederhana untuk mewakili perhitungan beban akibat gelombang. Diperoleh bahwa beban akibat gelombangnya paling mendekati formulasi yang ditawarkan oleh Elghamry dan Wang (1971) dan Overbeek dan Klabbers (2000) dengan rentang selisih – 32% hingga +6%.
Kata-kata Kunci: Dermaga, ANSYS Fluent, gelombang, beban vertikal, volume of fluid
Abstract
Several literatures offered formulations of vertical wave loads on deck. However, the range of results led to various levels of confidence in the use of these formulations. This study performed simulations using ANSYS Fluent 17.2 Academic Release with Volume of Fluid (VOF) module, SST k-ω turbulence model, and PISO solver. The output was a time series of average total pressure on the selected side. The setting of the numerical model is preceded by validation of the physical and numerical models from previous studies. The validated model was then used as the basis for modeling, which was applied to the actual water conditions and pier geometry in four wave height conditions. The maximum average total pressure was then compared with the results from other formulations to evaluate the trend which was close to previous studies. It was found that the results were closest to the formulation offered by Ito and Takeda (1967) on OCDI, with a difference of –12% to +29%. This maximum pressure output was also compared to the increase in wave height, so a simple linear relationship can be made to represent the wave load. It was found that the load was closest to the formulation offered by Elghamry and Wang (1971) and Overbeek and Klabbers (2000), with a difference of –32% to +6%.
Keywords: Pier, ANSYS fluent, wave, uplift, volume of fluidWalaupun ada banyak literatur yang menawarkan formulasi untuk memprediksi beban vertikal gelombang yang mungkin terjadi, namun rentang perbedaan hasil perhitungan membuat tingkat kepercayaan pada formulasi tersebut pun berbeda-beda (McConnell, Kirsty, William Allsop, and Ian Cruickshank, 2004). Pada studi ini, simulasi dilakukan dengan model numerik menggunakan ANSYS Fluent 17.2 Academic Release dengan modul Volume of Fluid (VOF), model turbulensi SST k-ω, dan solver PISO. Keluaran model ini berupa seri waktu tekanan total rata-rata pada sisi yang dipilih. Pengaturan model numerik didahului dengan validasinya terhadap model fisk dan numerik dari studi terdahulu, kemudian hasilnya dibandingkan dengan metode perhitungan dari berbagai formulasi yang ditawarkan studi terdahulu. Pengaturan model yang telah divalidasi kemudian digunakan sebagai dasar pemodelan yang diterapkan untuk kondisi perairan dan geometri dermaga yang sebenarnya, dalam 4 kondisi tinggi gelombang. Keluaran tekanan total rata-rata maksimum tersebut kemudian dibandingkan lagi dengan hasil perhitungan dari formulasi lainnya, untuk melihat kecenderungan studi terdahulu yang mendekati hasil pemodelan. Pada studi ini, diperoleh bahwa hasilnya paling mendekati formulasi yang ditawarkan oleh Ito dan Takeda (1967) pada OCDI dengan rentang selisih -12% hingga +29%. Keluaran tekanan maksimum ini juga dibandingkan terhadap peningkatan tinggi gelombangnya, sehingga dapat dibuat hubungan linear sederhana untuk mewakili perhitungan beban akibat gelombang. Pada studi ini, diperoleh bahwa beban akibat gelombangnya paling mendekati formulasi yang ditawarkan oleh Elghamry dan Wang (1971) dan Overbeek dan Klabbers (2000) dengan rentang selisih -32% hingga +6%. Studi ini hanya mempertimbangkan beban vertikal pada 1 jenis geometri dan 1 jenis kondisi perairan
Seismic Performance of Rail-Counterweight System of Elevator in Buildings
No full textElevators serve a critical function in essential facilities such as hospitals and need to remain operational during and after earthquakes. However, they are still known to malfunction during earthquakes even after several design and sensing improvements required by the current code have been incorporated. Most of the damages were experienced or caused by the rail-counterweight system. Being the heaviest component of an elevator, the counterweight induced strong dynamic effects to the guiding system sometimes even collided and damaged the passenger car.
A realistic analytical model of rail-counterweight system of an elevator that includes details of the supporting system is developed in this study. The nonlinearities caused by closing of the code specified clearances play an important role in determining the dynamic behavior of the system, and are thus included in this study. Also included are the acceleration inputs from different floor of building and the effect of different location of the counterweight along the guide rail. Parametric study is carried out to investigate the effect of different parameters on the seismic responses of the rail-counterweight system.
In order to improve the seismic performance of the rail-counterweight system, several protective schemes are investigated. One simple approach is to increase the damping of the system using additional discrete viscous dampers. However, there is not much space available for installing the devices, and placement parallel to the spring at the roller guide assemblies is not quite effective due to contact between the restraining plate at the roller guide assemblies and the rail that makes the roller guides ineffective.
Another method is to convert the top part of the weights into a tuned mass damper. This method can reduce the maximum stress in the rail if designed properly. The effectiveness of the passive tuned mass damper can be improved further by using it in an active mode by installing an actuator between the mass damper and the counterweight frame. The numerical results that confirm the effectiveness of such an active tuned mass damper are presented. As an alternative to the fully active control scheme, a semi-active control scheme using a magnetorheological damper device between the mass damper and the frame is also studied. This control approach is found to be as effective in reducing the seismic response as a fully active scheme. Since this MR damper can be operated using a simple battery, the external power requirements for implementation of this approach are quite minimal.Ph. D
Beban Vertikal Gelombang pada Deck Dermaga di Pelabuhan Marore, Provinsi Sulawesi Utara
No full textWalaupun ada banyak literatur yang menawarkan formulasi untuk memprediksi beban vertikal gelombang yang mungkin terjadi, namun rentang perbedaan hasil perhitungan membuat tingkat kepercayaan pada formulasi tersebut pun berbeda-beda (McConnell, Kirsty, William Allsop, and Ian Cruickshank, 2004). Pada studi ini, simulasi dilakukan dengan model numerik menggunakan ANSYS Fluent 17.2 Academic Release dengan modul Volume of Fluid (VOF), model turbulensi SST k-ω, dan solver PISO. Keluaran model ini berupa seri waktu tekanan total rata-rata pada sisi yang dipilih. Pengaturan model numerik didahului dengan validasinya terhadap model fisk dan numerik dari studi terdahulu, kemudian hasilnya dibandingkan dengan metode perhitungan dari berbagai formulasi yang ditawarkan studi terdahulu. Pengaturan model yang telah divalidasi kemudian digunakan sebagai dasar pemodelan yang diterapkan untuk kondisi perairan dan geometri dermaga yang sebenarnya, dalam 4 kondisi tinggi gelombang. Keluaran tekanan total rata-rata maksimum tersebut kemudian dibandingkan lagi dengan hasil perhitungan dari formulasi lainnya, untuk melihat kecenderungan studi terdahulu yang mendekati hasil pemodelan. Pada studi ini, diperoleh bahwa hasilnya paling mendekati formulasi yang ditawarkan oleh Ito dan Takeda (1967) pada OCDI dengan rentang selisih -12% hingga +29%. Keluaran tekanan maksimum ini juga dibandingkan terhadap peningkatan tinggi gelombangnya, sehingga dapat dibuat hubungan linear sederhana untuk mewakili perhitungan beban akibat gelombang. Pada studi ini, diperoleh bahwa beban akibat gelombangnya paling mendekati formulasi yang ditawarkan oleh Elghamry dan Wang (1971) dan Overbeek dan Klabbers (2000) dengan rentang selisih -32% hingga +6%. Studi ini hanya mempertimbangkan beban vertikal pada 1 jenis geometri dan 1 jenis kondisi perairan
Shock and Vibration
No full textBased on the observations in the past earthquake events, the traction elevators in buildings are known to be vulnerable to earthquake induced ground motions. Among several components of an elevator, the counterweight being heaviest is also known to be more susceptible than others. The inertial effects of the counterweight can overstress the guide rails on which it moves. Here we investigate to use the well-known acceleration feedback-based active and semi-active control methods to reduce stresses in the rails. The only way a control action can be applied to a moving counterweight-rail system is through a mass damper placed in the plane of the counterweight. For this, a part of the counterweight mass can be configured as a mass damper attached to a small actuator for an active scheme or to a magneto-rheological damper for a semi-active scheme. A comprehensive numerical study is conducted to evaluate the effectiveness of the proposed configuration of control system. It is observed that the two control schemes are effective in reducing the stress response by about 20 to 25% and improve the system fragility over a good range of seismic intensities.Published versio
Design and reliability analysis of accommodation work barge mooring configuration at a tension leg platform in Makassar Strait, Indonesia
No full textAn Accommodation Work Barge in Makassar Strait attaches to a Tension Leg Platform (TLP), a floating offshore platform operating in deep-water oil and gas field for a well intervention project. The mooring system are tied up to the north mooring lines of the vessel, whilst hawsers from the TLP connected to the south lines of the vessel. The TLP is fitted with two “TH” lines on its south side. However, these “TH” lines fail due to the unknown reason. The purpose of this study is to evaluate mooring performances to support the TLP operation by using API RP2SK recommendation, which suggests line tension limit, TLP offset, and minimum clearance between facilities. This study assesses reliability index (β) of the recommended design to evaluate whether the TH lines are required or could be eliminated. Mooring analysis is performed using ORCAFLEX for intact and damaged condition, while Monte Carlo simulation is performed to get system failure probability with minimum breaking strength ratio (%MBS) as required parameter. From the results, it is found that TH lines could be eliminated, as they do not affect significantly to the system. The analysis delivers a very secure index (β=14.676) with probability of failure below 10-5
DESIGN AND CONSTRUCTION OF COMMUNITY BASED FLOATING DOCK IN PARIT ISLAND, KARIMUN DISTRICT, RIAU ISLANDS, INDONESIA
No full textMany Indonesian islands lack essential inter-island crossing facilities, posing challenges for small island communities' livelihoods. This study addresses the need for accessible docking facilities in Parit Island, Riau Islands, using a community-based floating dock approach. It is chosen due to relatively high tides conditions onsite. The project began with site-specific metocean analysis and extensive stakeholder consultations, ensuring alignment with community aspirations. Eco-friendly materials like wooden frames and plastic drums were used for simplicity and sustainability in dock construction. Local artisans and laborers were engaged, promoting community involvement and economic empowerment. This paper delves into dock design, stability, piling systems, and accessibility. The completed community-based floating dock enhances local living standards and regional trade. It serves as a model for straightforward infrastructure development in island communities, emphasizing community engagement, environmental responsibility, and socioeconomic progress
Acceleration Feedback-Based Active and Semi-Active Seismic Response Control of Rail-Counterweight Systems of Elevators
No full textBased on the observations in the past earthquake events, the traction elevators in buildings are known to be vulnerable to earthquake induced ground motions. Among several components of an elevator, the counterweight being heaviest is also known to be more susceptible than others. The inertial effects of the counterweight can overstress the guide rails on which it moves. Here we investigate to use the well-known acceleration feedback-based active and semi-active control methods to reduce stresses in the rails. The only way a control action can be applied to a moving counterweight-rail system is through a mass damper placed in the plane of the counterweight. For this, a part of the counterweight mass can be configured as a mass damper attached to a small actuator for an active scheme or to a magneto-rheological damper for a semi-active scheme. A comprehensive numerical study is conducted to evaluate the effectiveness of the proposed configuration of control system. It is observed that the two control schemes are effective in reducing the stress response by about 20 to 25% and improve the system fragility over a good range of seismic intensities
Design and reliability analysis of accommodation work barge mooring configuration at a tension leg platform in Makassar Strait, Indonesia
No full textAn Accommodation Work Barge in Makassar Strait attaches to a Tension Leg Platform (TLP), a floating offshore platform operating in deep-water oil and gas field for a well intervention project. The mooring system are tied up to the north mooring lines of the vessel, whilst hawsers from the TLP connected to the south lines of the vessel. The TLP is fitted with two “TH” lines on its south side. However, these “TH” lines fail due to the unknown reason. The purpose of this study is to evaluate mooring performances to support the TLP operation by using API RP2SK recommendation, which suggests line tension limit, TLP offset, and minimum clearance between facilities. This study assesses reliability index (β) of the recommended design to evaluate whether the TH lines are required or could be eliminated. Mooring analysis is performed using ORCAFLEX for intact and damaged condition, while Monte Carlo simulation is performed to get system failure probability with minimum breaking strength ratio (%MBS) as required parameter. From the results, it is found that TH lines could be eliminated, as they do not affect significantly to the system. The analysis delivers a very secure index (β=14.676) with probability of failure below 10-5
Experimental Study on Wall-Frame Connection of Confined Masonry Wall
No full textAbstractFour full-scale (3m×3m) confined masonry wall specimens that represented simple house wall panels in Indonesia were subjected to cyclic in-plane lateral load. The construction of the specimens, including reinforcement assemblies, concreting, and brick-laying, followed the common construction practice in Indonesia. A specimen with no anchorage between the wall and the reinforced concrete frame was chosen as a benchmark model. The other specimens were varied in the details of wall-frame connection, i.e. zigzag (toothing) connection, short anchor between column and wall, and continuous anchorage from column to column. The models were then subjected to cyclic in-plane lateral loads, which represents earthquake loads, with increasing amplitude until collapsed. The behavior of these specimens was then evaluated and compared. The parameters evaluated were crack patterns and failure mechanism of the wall panel, loading capacity, and energy dissipation. The study revealed that zigzag connection and short anchor did not improve the performance of the confined masonry wall; instead they were more likely to reduce the performance of the wall. Cracks and failures of the two specimens were initiated by vertical crack on the face of the wall-frame connection, which then reduced the confinement of the wall. Therefore, the final failure mode followed sliding shear patterns on the bed joint of brick-mortar, which produced more brittle failure. Conversely, continuous anchorage strengthened the confinement, thus the diagonal crack patterns were observed on the wall and the strut and tie mechanism between the wall and the confining column was developed. Therefore, this specimen shows more ductile behavior as well as higher lateral load capacity. In conclusion, the study shows that installing proper wall-frame connection strategies is crucial in improving the structural performance
Seismic Behavior of Rail Counterweight Systems of Elevators in Buildings
No full textThis report describes an investigation of the seismic performance of elevator systems. The report begins with an overview of elevator systems used in buildings, including various components of the system and their functions. Because counterweights are the most vulnerable components to earthquake induced ground motion, the focus of this study is on the development of comprehensive analytical models of the rail-counterweight systems, including details of their guidance systems. The authors develop both linear and nonlinear models to evaluate the seismic performance of the rail-counterweight system. Several sets of numerical results are presented for different buildings, earthquake motions, rail sizes, flexibilities, and gap sizes. Current code provisions for the design of guide rails are also discussed. The analytical models and approach described in the report can aid in the seismic evaluation of critical facilities, such as hospitals, that are equipped with elevators. This study can also help designers and manufacturers of elevator systems understand why elevators behave as they do in earthquakes and how to evaluate modification and design changes that may be necessary to improve their seismic performance.This research was conducted at Virginia Polytechnic Institute and State University and was supportedprimarily by the Earthquake Engineering Research Centers Program of the National ScienceFoundation under award number EEC-9701471
