Yoyok Setyo Hadiwidodo

Development of Scilab-based structural reliability analysis software using Monte Carlo Simulated Finite Element Method

So far, the calculation of structural reliability using common methods always demands a closed form equation of performance function. This necessitates distribution information of loads and strength. Monte Carlo FEM method for structural reliability analysis was proposed by Guoliang et.al. However the proposed method tries to avoid simulation. Its result have some serious error. Whereas, simulation is a very powerful to analyze structural reliability. Improving the Guoliang method, this research presents how Finite Element Methods can be incorporated into Monte Carlo Simulation and develops a software based on open source code Scilab, to analyze the reliability of Plane Truss structure. This paper describes a technique based on simulations that reliability analysis of complex structure are not of a problem and of low effort. In the first step of this research, an algorithm is established by applying Monte Carlo Simulation into Finite Element Method. Then software functions in Scilab are developed based on it. For the validation, the software is used to calculate responses of simple Plane Truss structure. The results are compared to manual calculation using basic structural analysis. This research have produced a fresh procedure and simple software to analyze the Plane Truss reliability based on the incorporation of Monte Carlo Simulation with Finite Element Method.

Stress concentration factor distribution of inclined brace in multiplanar offshore tubular double kt joints

The majority of tubular joints commonly found in offshore structures are in the form of multi-planar tubular joints, but very few investigations have been reported due to the complexity and high cost involved. The majority of research have been focused on the study of stress distribution at certain position such as saddle and crown points, and the hot spot stress (HSS) at other position along the weld toe of brace/chord intersection have been ignored. In this paper a 60° two-planar double KT (DKT) tubular joint is modelled as a finite element model from an offshore jacket platform. The effect of dimensionless geometrical parameters on the geometrically stress distribution and SCF distribution along the weld toe of inclined brace in axially loaded on the joint are investigated. Non-dimensional parameters that are varied include β, τ, γ and θ. Validation of the finite element model shown a good agreement to the global structural analysis results. The results of parametric studies show that the increase of the β leads to decrease of SCF. While the increase of the τ, γ and θ leads to increase of SCF. The peak SCF mostly occurs at the outer saddle point. The effect of parameters β, γ and θ on the SCF are greater than the effect of parameters τ.

Strength Analysis and Sea-Fastening Design of Container Crane Structure for Heavy Lifting Sea Transportation

This paper discusses heavy-lifting sea-transportation of 831-ton container-crane in Indonesia from Surabaya to Kupang. Structural strength analysis is carried out to ensure the safety of the crane during the transportation process. The purpose of this analysis is to design the sea-fastening construction capable of redistributing the excessive stress that might occurred, to avoid structural failure. The first step is to model the crane structure and barge under certain various drafts. This is important because selection of the proper draft will determine the suitable righting moments of barge and hence to ensure good stability. The selected drafts under investigation are taken between 0.25 T to 0.75 T. The result of the structural strength calculation shows that the static load is found around 8150 kN. Loads due to motion of barge for heave, roll, and pitch motions are 116 kN, 7424 kN, and 232kN, respectively. Location of the high stress due to the motion is identified at the bottom of the crane structure so that the design of sea-fastening constructions will be concentrated in the vicinity of this position. The values of Unity Check after fitting the sea-fastening construction are reduced to 0.940, 0.704, and 0.702, respectively. It is concluded that the structure of container crane under such sea-fastening design is proven to be capable of overcoming the loads during transportation process.

Analisa Pemasangan Loop Ekspansi Akibat Terjadinya Upheaval Buckling pada Onshore Pipeline

Pada pipa yang dipendam didalam tanah sering terjadi kegagalan deformasi. Kegagalan deformasi global yang menyebabkan pipa menekuk vertikal ke atas yang disebut sebagai upheaval buckling. Lengkungan awal pada pipa penyalur yang terpasang bisa terjadi akibat kombinasi dari kenaikan temperatur saat operasional dan gaya friksi tanah akan menghasilkan gaya tekan aksial efektif pada pipa. Salah satu cara yang akan dibahas pada penelitian ini jika terjadi upheaval buckling adalah pemasangan loop ekspansi pada daerah yang mengalami upheaval buckling. Loop ekspansi akan divariasikan dengan 2 tipe yaitu tipe loop horizontal dan tipe loop vertical. Pada penelitian ini terlebih dahulu pipa dimodelkan dengan panjang pipa tertentu kemudian ujung-ujungnya diberi tumpuan sehingga didapatkan besar tegangan longitudinal sebesar 41366,563 Psi. Tegangan tersebut melebihi tegangan ijin sehingga pipa mengalami ekspansi termal atau elongasi yang membentuk lengkungan keatas dengan tinggi 0.259 meter. Maka dilakukan pemodelan loop ekspansi untuk meredam elongasi tersebut dengan panjang loop 5.3 meter. Kedua loop tersebut mampu meredam tegangan aksial menjadi 3662 Psi untuk tipe loop horizontal dan 3670 Psi untuk tipe loop vertikal. Dari kedua tipe loop tersebut kemudian juga dilakukan perbandingan besar tegangan yang terjadi pada bagian elbow. Maka didapatkan bahwa tipe loop horizontal mengalami tegangan relatif lebih kecil dari pada tipe loop vertikal sehingga sebagai bahan rekomendasi maka pemasangan loop horizontal lebih diutamakan.

Slump Flow Modeling of Self-Compacting Concrete Using Smooth Support Vector Regression (SSVR)

A new method of prediction based on smooth support vector regression (SSVR) is introduced to resolve the slump flow modelling of self-compacting concrete (SCC). The slump flow is a function of the content of all concrete ingredients, including cement, silica fume, water, superplasticizer, coarse and fine aggregate. In this paper, the basic ideas underlying SSVR are reviewed, and the potential of the SSVR for multiple regression (modelling) problems is demonstrated by applying the method to model of slump flow from experimental data. The results of experimentation indicate that SSVR has excellent performance on slump flow prediction. Compared with traditional prediction method such as second order regression, SSVR has much more accurate and effective to prediction of slump flow and it is very promising result.