@article { author = {Golafshani, A. A. and Gholizad, A.}, title = {Passive Vibration Control for Fatigue Damage Mitigation in Steel Jacket Platforms}, journal = {International Journal of Engineering}, volume = {21}, number = {4}, pages = {313-324}, year = {2008}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {Considering the stress cycles in the joints and members due to wave induced forces on offshore platforms, fatigue analysis is therefore one of the most important analyses in the offshore platforms design. Although most of the steel jacket type platforms are designed and located in areas with relatively high ratios of operational sea-states, for maximum environmental events, would have acceptable safety margin in an in-place and seismic analyses; but for fatigue analyses it faces critical condition. Therefore it seems utilizing control mechanisms with the aim of increasing fatigue life in such platforms will be more preferable, to merely deck displacement control. Investigation of tuned mass damper parameters optimality for vibration control of wave excited systems, implies that optimum tuning and damping ratios are strongly dependent on sea-state, in addition to system parameters. The efficiency of optimally designed tuned mass damper for fatigue damage mitigation in real steel jacket platforms has been evaluated using full stochastic spectral analysis method and the results have shown a great performance for TMDs in this application. Sea-state conditions are predictable through weather forecasting methods and this can be benefited also to increase the efficiency of TMDs with variable tuning parameters which have been optimally adjusted for each sea-state. In a case study, utilization of this auxiliary device resulted in 26.6 % reduction in maximum fatigue damage. This efficiency can be increased to 36.7 % using different tuning parameters for each sea-state.}, keywords = {Steel Jacket Platforms,Tuned mass damper,Fatigue Damage,vibration control}, url = {https://www.ije.ir/article_71734.html}, eprint = {https://www.ije.ir/article_71734_a63bf1ddc605ef19eddb2791e290cf27.pdf} } @article { author = {Mohammadi, M.}, title = {Local and Global Friction Factor in a Channel with V-Shaped Bottom}, journal = {International Journal of Engineering}, volume = {21}, number = {4}, pages = {325-336}, year = {2008}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {This paper presents an experimental research on the distribution of local friction factor, fb, and global friction factor, f, over the cross-section of a channel with V-shaped bottom, which typically occurs in sewers and culverts. Several series of experiments were conducted for measuring velocity and boundary shear stress. It is found that, Darcy-Weisbach, f, is more sensitive than other resistance coefficients such as Manning, n. Local boundary shear stress around wet perimeter, τb, and depth-averaged velocity, Ud, data are used to evaluate fb. The results illustrate that, the friction factor is shown to be a function of flow depth as well as being dependent upon the Froude number, Fr. Therefore, the local friction factor does not remain constant across the channel. Meanwhile, the common technique of assuming a constant friction factor over the entire section of the channel has been found to have theoretical justification. The results indicate that the global friction factor decreases as flow discharge increases and channel bed getting steeper in the experiments including subcritical and supercritical flow conditions. However, it can be seen that the effects of walls are very high at low Froude numbers. In general, the results indicate that the perturbations in the distribution of local friction factor are quite considerable in steeper channels as Froude number increases.}, keywords = {V,shaped channel,2D Isovels,Depth,Averaged Velocity,Boundary Shear Stress,Local Friction Factor}, url = {https://www.ije.ir/article_71736.html}, eprint = {https://www.ije.ir/article_71736_b144b81c5efaf941cfeeebb6e06d1915.pdf} } @article { author = {Tabnak, A. and Dehghani, A. and Nateghi, F.}, title = {Seismic Damage and Disaster Management Maps (A Case Study)}, journal = {International Journal of Engineering}, volume = {21}, number = {4}, pages = {337-344}, year = {2008}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {There are many cities in developing countries that are built with minimal seismic considerations. Also, due to the expenses involved regarding detailed and analytical identification of such vulnerable buildings and structures in these cities, is very difficult and also time consuming. It is necessary and much needed to have a quick and inexpensive solution for such assessment in cities with the above mentioned criterion, for disaster management planning. Therefore this paper offers a study of a simplified evaluation form which was developed in order to assess the key seismic vulnerability parameters of buildings and structures in the city of Gachsaran located along the Zagrous mountain range in Iran. Based on the gathered information, a data bank was created and using the generalized physical vulnerability functions which was developed for typical Iranian buildings, a series of scenario based damage maps for the city was created. Using these maps and available resources, a series of disaster management planning maps were created for different levels of potential hazard. These simplified procedures are used for underdeveloped cities such as Gachsaran to establish preliminary needs for planners, while more sophisticated methods can be utilized. The method used in this paper will be discussed and results obtained will be presented. It also is believed that, this simple solution can be utilized in similar cases throughout the world.}, keywords = {disaster,Management,Earthquake,Structures,Map,vulnerability}, url = {https://www.ije.ir/article_71738.html}, eprint = {https://www.ije.ir/article_71738_7103127da616d5f8d2268934bb92ce42.pdf} } @article { author = {Abbasnejad, Alireza and Sadr Karimi, Jamshid}, title = {An Experimental Investigation into the Arching Effect in Fine Sand}, journal = {International Journal of Engineering}, volume = {21}, number = {4}, pages = {345-360}, year = {2008}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {In the current paper results of a well instrumented experimental procedure for studying the arching effect in loose and dense sand are presented. The apparatus comprises concentric circular trapdoors with different diameters that can yield downward while stresses and deformations are recorded simultaneously. As the trapdoor starts to yield, the whole soil mass deforms elastically. However, after an immediate specified displacement, depending on the diameter of the trapdoor and relative density of the soil, the soil mass behaves plastically. This behavior of sand occurs due to flow phenomenon and continues until the stress on trapdoor is minimized. Then the failure process develops in sand and the measured stress on the trapdoor shows an ascending trend. This indicates gradual separation of the yielding mass from the whole soil body. Finally, the flow process leads to establish a stable vault of sand called arching mechanism. Depending on the trapdoor diameter there is a critical relative density at/above which the test leads to form a stable arch. A mathematical method to establish the shape of the sand vault is introduced and the results obtained from experimental investigations are compared to this method. The results are also, compared to Terzaghi's theory and the assumption of upper boundary solution is discussed.}, keywords = {Arching Effect,embankment,Relative Displacement,Stress Distribution}, url = {https://www.ije.ir/article_71739.html}, eprint = {https://www.ije.ir/article_71739_f234eaf382294b13af2e2a3f0be0bc3e.pdf} } @article { author = {Abbaszadeh, R. and Vafaeian, M.}, title = {Laboratory Model Tests to Study the Behavior of Soil Wall Reinforced by Weak Reinforcing Layers}, journal = {International Journal of Engineering}, volume = {21}, number = {4}, pages = {361-374}, year = {2008}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {In this paper we suggest a method to calculate the first integrals of a special system of the first order of differential equations. Then we use the method for finding the solutions of some differential equations such as, the differential equation of RLC circuit}, keywords = {Reinforced Soil,External Load,Failure,Safety factor}, url = {https://www.ije.ir/article_71742.html}, eprint = {https://www.ije.ir/article_71742_393902254656c395444c13ebf4d5918b.pdf} } @article { author = {Hejazi, S. R. and Nadjafikhah, M.}, title = {First Integrals of a Special System of Odes (TECHNICAL NOTE)}, journal = {International Journal of Engineering}, volume = {21}, number = {4}, pages = {375-383}, year = {2008}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {In this paper we suggest a method to calculate the first integrals of a special system of the first order of differential equations. Then we use the method for finding the solutions of some differential equations such as, the differential equation of RLC circuit.}, keywords = {Distribution,First Integral,RLC Circuit,Heat Capacity}, url = {https://www.ije.ir/article_71744.html}, eprint = {https://www.ije.ir/article_71744_68e01da85c9e0e42660f64e242a3823b.pdf} } @article { author = {Jalili, Mohamad Mahdi and Durali, Mohammad}, title = {Investigation of Wagon Derailment Moving on Random Rail Irregularities using Nonlinear 3-Dimentional Model (RESEARCH NOTE)}, journal = {International Journal of Engineering}, volume = {21}, number = {4}, pages = {385-400}, year = {2008}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {Rail irregularity is one of the most effective factors in train derailment. theste irregularities have generally random distribution that are assumed to be stationary random and ergodic processes in space, with Gaussian amplitude probabiliy densities and zero mean values. The quality of irregularities, their distribution along the rails and wagon speed are the main factors for train derailment which is investigated in this article. The car model is nonlinear and three-dimensional with 48 DOF. Using simulation results, the safe speed for moving wagon on different types of random rail irregularities is also determined.}, keywords = {3,D Train Model,Nonlinear Train Model,Random Rail Irregularities,derailment,Simulation}, url = {https://www.ije.ir/article_71745.html}, eprint = {https://www.ije.ir/article_71745_9f0399d0589f01262efb0e33f50b3c4d.pdf} } @article { author = {Fazelpour, Mohammad and Shojaefard, M. H. and Goudarzi, Koorosh}, title = {Effect of Contact Pressure and Frequency on Contact Heat Transfer Between Exhaust Valve and its Seat}, journal = {International Journal of Engineering}, volume = {21}, number = {4}, pages = {401-408}, year = {2008}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {The hot gases produced by the internal combustion engines passes through the exhaust valve and causes high temperatures in the exhaust valve and its seat. To avoid damaging the exhaust valve, heat must be transferred from the valve to its seat during the contact they make at the opening and closing cycle. Heat transfer rate from the exhaust valve to its seat is a function of many factors. One of the most important factors is the thermal contact conductance (TCC) between the exhaust valve and its seat. Very few researches have been done about estimation of the TCC between the exhaust valve and its seat in the past. An experimental study has been conducted to determine the TCC between two co-axial cylinders, as the exhaust valve and its seat. Furthermore, the influence of contact pressure and frequency of contact upon the TCC is studied. The results show that the TCC decreases as the frequency of contact increases. The experimental results obtained from the present work are in good agreement with the previous published data.}, keywords = {Thermal Contact Conductance,Exhaust Valve,Contact pressure,Frequency of Contact}, url = {https://www.ije.ir/article_71747.html}, eprint = {https://www.ije.ir/article_71747_e8709bc9147522f17813f94d8bfbcc97.pdf} }