Bivariate Archimedean Copulas to Solve Complex Dependency in Marine Engineering Problems

Climate change has made offshore installations suffer severe consequences from extreme marine hazards. These offshore installations were designed to withstand extreme natural hazards. Marine natural hazards commonly occur interdependently. Thus, a multivariate model to capture this complex dependence structure is necessary. Practically, modelling marine natural hazards is usually assumed to be mutually independent or correlated by a multivariate Gaussian distribution. However, this biased assumption is not relevant to capture the real dependence structure between marine parameters. Copula functions are used to model the complex dependence structure between marine parameters. A simplified case study is selected to illustrate the modelling between wave height and wind speed. Results are compared with the traditional joint probability approach to demonstrate the advantage of copula functions. The use of copula functions provides a better result to model any complex dependence structure between correlated variables

Dependence modelling of marine environmental variables and resilience assessment of offshore structures operating in harsh environments

With increasing global energy demand, energy-related offshore activities continue to increase. As part of this expansion, exploration and operations in harsh ocean environments are becoming more common. Harsh environments are characterized by low temperatures, strong winds, high waves, and ice. These harsher conditions apply increased structural loads and may increase the probability of accidents. Such environmental variables are usually interdependent. Failure to consider these dependencies, when modelling harsh environmental loads, leads to less accurate predictions of design loads and consequently less accurate predictions of offshore structures’ capacity to withstand these loads. This work addresses the dependence issue between environmental variables and seeks to improve predictions of environmental loads and offshore structural capacity. The benefits of considering dependence structures using copula functions are assessed for bivariate and vine-copulas are assessed for multivariate cases of the environmental variables. In each case this is followed by applications to assess offshore structure resilience. Two types of dependence structures are studied: symmetric and asymmetric. Environmental loads are estimated using copula functions to see how significantly the correlation influences the estimation. The copula functions are then applied to assess structural capacity in terms of resilience. A bivariate application case uses copula functions to model two influencing factors that determine the velocity of an iceberg. Results show that the resilience of the offshore structure is mainly dependent on absorptive capacity. Multivariate models are then constructed using Vine Copulas, and a total environmental load is estimated. This multivariate copula model is applied to assess the resilience of an offshore structure subjected to multiple environmental loads. The study concludes that the accuracy of environmental load predictions can be improved using copula functions to model environmental factor dependencies. In addition, the concept of structural resilience provides a better means of considering the overall resistance of a structure subject to harsh and dependent multivariate environmental loads. Applications of the proposed methodologies in this thesis help to develop a robust approach to deal with uncertainties related to dependence structures between marine environmental variables. In addition, this thesis helps to develop safer offshore structures operating in harsh environment by estimating the structure’s capacity in term of resilience in the design stage

PERANCANGAN KEBIJAKAN DAN ANALISIS BIAYA WARRANTY SERTA MENENTUKAN KEBUTUHAN SUKU CADANG PRODUK KANABA TUMBLE DRYER K 16 S DENGAN MENGGUNAKAN PENDEKATAN MODEL KERUSAKAN SATU DIMENSI (Studi Kasus: CV HARI MUKTI TEKNIK)

Dunia industri yang semakin kompetitif dewasa ini menuntut produsen untuk secara terus-menerus memberikan dukungan berupa layanan yang lebih baik kepada konsumen. Warranty telah menjadi salah satu instrumen penting dalam rangka meningkatkan pemasaran dari suatu produk. Warranty dianggap sebagai kontrak antara produsen dengan konsumen.CV Hari Mukti Teknik merupakan salah satu usaha yang bergerak dalam bidang produksi Laundry Equipment yang ada di Yogyakarta dimana salah satu produk unggulannya adalah Kanaba Tumble Dryer K16S. Produk Kanaba Tumble Dryer K16S belum memiliki kebijakan warranty dalam penjualannya dan pihak usaha hanya memberikan garansi perbaikan 1 tahun yang didasarkan pada nota penjualan produk bukan berdasarkan data historis kerusakan produk tersebut.Tujuan dari penelitian ini adalah untuk menentukan durasi warranty yang optimal, estimasi biaya warranty, menentukan kebijakan warranty yang sesuai, menentukan jumlah suku cadang yang dibutuhkan serta penentuan harga jual produk Kanaba Tumble Dryer K16S setelah adanya kebijakan warranty.Hal pertama yang dilakukan untuk mencapai tujuan penelitian adalah dengan mengumpulkan data berupa data komponen penyusun produk dan harga masing-masing komponen serta data Time to Failure produk Kanaba Tumble Dryer K16S. Selanjutnya dilakukan pengolahan data untuk mendapatkan laju kerusakan dan MTTF dari produk. Berdasarkan pertimbangan MTTF dan laju kerusakan dapat ditentukan durasi warranty yang optimal. Selanjutnya dihitung biaya warranty berdasarkan kebijakan Free Replacement Warranty, Pro-Rata Warranty, dan Combination Warranty.Produk Kanaba Tumble Dryer K16S memiliki 3 komponen kritis yaitu komponen blower, motor dan timer. Grafik laju kerusakan setiap komponen kritis menunjukkan probabilitas terjadinya kerusakan meningkat seiring dengan berjalannya waktu. Berdasarkan perhitungan biaya warranty diketahui bahwa biaya Combination Warranty Dari penelitian ini dapat disimpulkan bahwa kebijakan warranty yang sebaiknya diterapkan adalah non-renewing combination dengan durasi 0.75 tahun (9 bulan) dengan masa free replacement sebesar 0,375 tahun atau 5 bulan. Dari kebijakan dan durasi tersebut, diperoleh biaya warranty sebesar Rp 3.067.083,482 dengan jumlah suku cadang 3 buah untuk komponen blower dan timer serta 2 buah untuk komponen motor. Dan harga jual Kanaba Tumble Dryer K16S diketahui sebesar Rp 19.034.703,48. Kebijakan warranty, jumlah suku cadang, harga jual produ