The structural design requirements of an offshore platform subjected to wave induced forces and moments in the jacket can play a major role in the design of the offshore structures. For an economic and reliable design; good estimation of wave loadings are essential. A nonlinear response analysis of a fixed
offshore platform under structural and wave loading is presented, the structure is discretized using the finite
element method, wave plus current kinematics (veloc
ity and acceleration fields) are generated using 5th order Stokes wave theory, the wave force acting on the member is calculated using Morison’s equation. Hydrodynamic loading on horizontal and vertical tubular members and the dynamic response of fixedoffshore structure together with th e distribution of displacement, axial force and bending moment along the leg are investigated for regular and extreme cond
itions, where the structure should keep production
capability in conditions of the 1-yr return period wave and must be able to survive the 100-yr return period
storm conditions. The result of the study shows that the nonlinear response investigation is quite crucial for
safe design and operation of offshore platform.
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OPTIMUM DESIGN OF PIN-JOINTED 3-D DOME STRUCTURES USING GLOBAL OPTIMIZATION TECHNIQUES
Author: YAVUZ SARAÇ | Size: 9.31 MB | Format:PDF | Quality:Unspecified | Year: November 2005, | pages: 204
Difficult gradient calculations, converging to a local optimum without exploring the design space adequately, too much dependency on the starting solution, lacking capabilities to treat discrete and mixed design variables are the main drawbacks of conventional optimization techniques. So evolutionary optimization methods received significant interest amongst researchers in the optimization area. Genetic algorithms (GAs) and simulated annealing (SA) are the main representatives of evolutionary optimization methods. These techniques emerged as powerful and modern strategies to efficiently deal with the difficulties encountered in conventional techniques, and therefore rightly attracted a substantial interest and
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Article/eBook Full Name: Construction Technology For Tall Buildings
Author(s): Yit Lin Chew, Michael
Edition: 3 rd
Publish Date: 2009
ISBN: 978-981-281-861-4
Published By: worldscientific
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Standard Number BS EN 480-11:2005
Title Admixtures for concrete, mortar and grout. Test methodsDetermination of air void characteristics in hardened concrete
Status Current
Publication Date 14 December 2005
Vulnerable buildings and their rehabilitation are important problems for earthquake regions. In recent decades the goal of building rehabilitation and strengthening has gained research attention and numerous techniques have been developed to achieve this. However, most of these strengthening techniques disturb the occupants, who must vacate the building during renovation. In this study, a new strengthening alternative for RC structures, namely exterior shear walls, has been experimentally investigated under reversed cyclic loading. Using the proposed technique, it is possible to strengthen structures without disturbing their users or vacating the building during renovation. In this technique, shear walls are installed in parallel to the building’s exterior sides. It has been observed that the usage of exterior shear walls considerably improve the capacity and sway stiffness of RC structures. The experimental results have also been compared and found to be in agreement with the numerical solutions. Post attached exterior shear walls behaved as a monolithic member of the structure.
Design considerations for the exterior shear wall-strengthened buildings have also been discussed in the paper.
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This paper provides a brief review of recent work on the development of solutions for the seismic design and retrofit of steel structures by va rious members of the U.S. research community, including solutions being developed at the Univers ity at Buffalo for the seismic retrofit of bridges and buildings.
Author: Michel Bruneau | Size: 3.8 MB | Format:PDF | Quality:Unspecified | Publisher: Center for Earthquake Engineering Research, and Professor, Department of Civil, Structural, and Environmental Engineering, 105 Red Jacket Quadrangle, University at Buffalo, Buffalo, NY, 14261, USA. | pages: 16
This paper provides a brief review of recent work on the development of solutions for the seismic
design and retrofit of steel structures by various members of the U.S. research community,
including solutions being developed at the University at Buffalo for the seismic retrofit of bridges
and buildings.
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HOW HAVE CHANGES IN BUILDING CODE PROVISIONS FOR REINFORCED CONCRETE FRAME STRUCTURES IMPROVED SEISMIC SAFETY?
Author: . B. Liel , C. B. Haselton , and G. G. Deierlein | Size: 0.3 MB | Format:PDF | Quality:Unspecified | Publisher: Dept. of Civil Engineering, Stanford University, Stanford | pages: 10
This study provides an analytical comparison of seismic performance of a typical California office building designed according to the 1967 Uniform Building Code and the 2003 International Building Code. The seismic performance predictions are based on a performance assessment method developed by the Pacific Earthquake Engineering Research (PEER) Center, which employs incremental nonlinear dynamic time-history analyses. Comparisons are made for a four-story reinforced concrete (RC) moment frame building designed to be representative of a) pre-1970 non-ductile reinforced concrete construction and b) modern (2003) ductile reinforced concrete construction. The plan and elevation of the building are identical for both structures; differences are evident in the magnitude of design loading, the relative strength of structural elements, and detailing of beams, columns, and beam column joints. For each building, a nonlinear dynamic analysis model captures the behavior of the important failure modes up to the onset of collapse, accounting for uncertainties in structural behavior, modeling, and ground motions. The performance quantity of interest in this study is the collapse risk, particularly mean annual frequency of collapse. By comparing the computed
collapse risk for the two structures, performance improvements in RC frame buildings over the three decades since the San Fernando earthquake can be
quantified.
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Finite-element analyses are performed for the response to lateral monotonic, slow-cyclic, and seismic loading of rigid footings carrying tall slender structures and supported on stiff clay. The response involves mainly footing rotation under the action of overturning moments from the horizontal external force on—or the developing inertia at—the mass of the structure, as well as from the aggravating contribution of its weight (P-delta effect). Emphasis is given to the conditions for collapse of the soil-foundation-structure system. Two interconnected mechanisms of nonlinearity are considered: detachment from the soil with subsequent uplifting of the foundation (geometric nonlinearity) and formation of bearingcapacity failure surfaces (material inelasticity). The relation between monotonic behavior (static “pushover”), slow-cyclic behavior, and seismic response is explored parametrically. We show that with “light” structures uplifting is the dominant mechanism that may lead to collapse by dynamic instability (overturning), whereas “very heavy” structures mobilize soil failure mechanisms, leading to accumulation of settlement, residual rotation, and ultimately collapse.
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FURTHER PROBING OF THE SUITABILITY OF PUSH- OVER ANALYSIS FOR THE SEISMIC ASSESSMENT OF BRIDGE STRUCTURES
Author: ALESSIO LUPOI University of Rome “Sapienza”, Dpt. of Structural and Geotechnical Engineering, PAOLO FRANCHIN University of Rome “Sapienza”, Dpt. of Structural and Geotechnical Engineering, .PAOLO E. PINTO University of Rome “Sapienza”, Dpt. of Structural and Geotechnical Engineering, | Size: 0.67 MB | Format:PDF | Quality:Unspecified | pages: 16
The applicability of non-linear static analyses for the assessment of less-thanregular bridges has been subject of recent research by a number of authors ([11,13,14]), with mixed results. The study presented in the paper intends to provide a further example of application of the approach to a bridge whose characteristics are such as to test it in a rather extreme case. This is an existing important highway viaduct built in the sixties, of total length equal to 420m, with 11 spans of 33m each and a continuous RC deck pinned over the piers. These latter, whose height varies irregularly between 14m and 41m, consist of slender single-bay frames with intermediate transverse beams. Among the numerous proposals available, the multi-modal nonadaptive approach as proposed by Chopra et al. [4] has been chosen as the preferred compromise between accuracy and complexity. The selected structure is characterised by at least two modes providing comparable contributions to the transversal response. In view of the final comparison of the results with those from non-linear dynamic analyses, the critical question of the choice of the reference response dof to be monitored has been investigated as well as the approximation of the method as a function of the intensity of the seismic action (inducing a variable degree of inelasticity in the structure).
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