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Article
Nonlinear Static and Dynamic Analysis of Buildings Considering Soil Structure Interaction

Authors: Ola A. Hussein --- Mohammed J. Hamood --- Ahamed F. Khadum
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2016 Volume: 34 Issue: 9 Part (A) Engineering Pages: 1755-1766
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

An attempt has been made during the present study to understand the behavior of reinforced concrete structures considering soil structure interaction. A multistoried frame building subjected to seismic forces are modeled and analyzed through the finite elements software program (SAP 2000 V14) which are primarily designed according to ACI 318M-11) and ASCE 7-10 Code. Both static and dynamic analysis methods are used, which may be linear and nonlinear. Recorded ground motions are used in nonlinear dynamic (time history) analysis. Analyses of frames are carried out to find the lateral displacements, drift ratios, and time period of free vibration motion of structural systems. The study reveals that soil flexibility has significant effect on the response of structures. Soil flexibility led to increase the storey drift and lateral displacement. In addition, it led to increase in neutral lateral time period of structure vibration of frame buildings especially, with soft soil stiffness. The present study also, presents a methodology to protect the structure against earthquake excitation by using rubber isolators, where decreases in the natural frequency of structure building have been observed and the presence of rubber at a location of each column led to decrease the value of axial force and shear base stress as compared with fixed-base case.


Article
Analyses of Base Isolated Buildings; Nonlinear Modal Time History Versus Codes' Methods

Authors: Haider S. Al-Jubair --- Fareed H. Majeed
Journal: Tikrit Journal of Engineering Sciences مجلة تكريت للعلوم الهندسية ISSN: 1813162X 23127589 Year: 2017 Volume: 24 Issue: 3 Pages: 55-62
Publisher: Tikrit University جامعة تكريت

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Abstract

Multi-story hypothetical reinforced concrete buildings of variable geometric configurations (symmetrical, vertically irregular, horizontally irregular, with and without shear walls); with isolated bases via high damping rubber bearing and friction pendulum systems, are analyzed by using finite element method under seismic load function (North-South component of the ground motion recorded at a site in El Centro, California in 1940) via SAP2000-V16 software. Four methods of analysis are adopted. The accuracy of nonlinear modal time history is compared to that of methods recommended by international codes, namely; nonlinear direct integration, equivalent lateral force, and response spectrum methods. The bilinear hysteretic model of base isolation system and the Rayleigh damping framework for superstructure are adopted. The results support the powerfulness of the nonlinear modal time history analysis, due to the negligible deviations from those predicted by the robust nonlinear direct integration method. The response spectrum method proved to be more reliable than the equivalent lateral force method which over predicts the displacement and rotation profiles for the isolated buildings.


Article
Seismic Analysis Of Liquid Storage Tanks

Authors: AbdulMuttalib I. Said --- Ammar A. AbdulMajeed
Journal: Journal of Engineering مجلة الهندسة ISSN: 17264073 25203339 Year: 2011 Volume: 17 Issue: 3 Pages: 610-619
Publisher: Baghdad University جامعة بغداد

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Abstract

ABSTRACTThis study presents an idealization scheme for the analysis of rectangular storage tanks acted upon by earthquake excitations. Above and below ground tank, uses have been considered. A linear three-dimensional finite element analysis has been used to predict the natural frequencies. Analysis parameters are the ratio of height to length of the tank, the type of soil, level of water in the tank, and also the wall thickness. The results for top displacement and axial force components for a full tankabove ground case have values greater than those in half- full (31%) and empty tank cases (75%). At the opposite of that, the underground tank demonstrates that top displacement and axial force components for an empty tank case have values greater than those in half- full (19%) and full tank cases (40%). The base shear for above ground tank case has values greater than those in underground tank cases (19% to 37%). The shear base for soil type 2 is greater than those in soil type 1(17% to 28%).

تتضمن الدراسة تحليل الخزانات المستطيلة المعرضة الى هزات أرضية بحالتين, الأولى تكون فيها الخزانات مدفونة بشكل كامل تحت الارض والحالة الثانية تكون الخزانات فيها فوق مستوى سطح الارض.أستخدم التحليل الخطي ثلاثي الابعاد بطريقة العناصر المحددة لغرض تحري علاقة كل من الأهتزاز الطبيعي ونسبة ارتفاع الجدران من حيث تغير نوع التربة وكمية الماء الموجودة بالخزان وكذلك علاقتة ايضا بأختلاف سمك الجدران والأزاحة العليا والقوه المحورية لحالة الخزان فوق الارض وهو مملؤ, لها قيم اعظم من الحالة النصف مملؤه بنسبة 31% وبنسبة 75% اعظم من الحالة الفارغة. بعكس ذلك تكون الأزاحة العليا والقوة المحورية لحالة الخزان المدفون اعظم وهو فارغ من ماهو نصف مملؤ بنسبة 19% وبنسبة 40% أعظم من الحاله المملؤه. قوة القص عند الاساس لحالة الخزان فوق سطح الارض لها قيم اعظم من حالة الخزان تحت الارض بنسبة (19% الى 37%). قوة القص عند الاساس في حالة التربة رقم 2 (التربة الضعيفة) تكون اعظم من حالة التربة رقم1 بنسبة (17% الى 28%).


Article
Non linear Vibration Analysis of liquid Storage Tank

Authors: Abdulamir A. Karim --- Thamer hussein amer
Journal: University of Thi-Qar Journal for Engineering Sciences مجلة جامعة ذي قار للعلوم الهندسية ISSN: 26645564/26645572 Year: 2014 Volume: 5 Issue: 1 Pages: 85-100
Publisher: Thi-Qar University جامعة ذي قار

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Abstract

This study presents an idealization scheme for the analysis of rectangular storage tanks acted upon by earthquake excitations. Above and below ground tank, are considered. A linear three-dimensional finite element analysis is adopted to predict the natural frequencies. The analysis parameters are the ratio of height to length of the tank, the type of soil, level of water in the tank, and also the wall thickness. Tanks made from steel as well as from concrete are investigated. A general purpose finite element program (ANSYS 12.0) used to model the analysed system. The tank base and wall are modelled by plane strain shell elements. The contained liquid is represented by a special solid element. Finally, the soil is modelled by simple spring-damper elements. The soil medium is idealized by the elastic half space model, that is, linear springs are assumed to represent the structure-soil interface. Which is then modelled by two-node spring dashpot elements. Forced vibration analysis is conducted on above ground and buried concrete tank. This analysis is carried out by applying the records of the North-South component of the 1940 El Centro earthquake with peak acceleration of 0.32g. It is found that the bending stresses in above ground concrete tank is (74.167) % greater than the stresses in buried tank with the same dimensions.

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