Search results for "T method"
showing 10 items of 1254 documents
Structural Safety Assessment of Marine Operations From a Long-Term Perspective: A Case Study of Offshore Wind Turbine Blade Installation
2019
Abstract A marine operation is a complex non-routine activity of limited duration carried out in offshore environment. Due to safety reasons, these operations are normally performed within specific sea state limits, which are derived from numerical modelling and analysis of hazardous events. In view of the uncertainties in the assessment of structural responses under stochastic environmental conditions, these limiting curves correspond to a target structural failure probability recommended in offshore standards (for example, 10−4 per operation as specified by DNV-GL). However, one of the main limitations is that these curves do not reflect site-specific safety assessment. The current paper …
Transparent boundary condition for acoustic propagation in lined guide with mean flow
2008
A finite element analysis of acoustic radiation in an infinite lined guide with mean flow is studied. In order to bound the domain, transparent boundary conditions are introduced by means of a Dirichlet to Neumann (DtN) operator based on a modal decomposition. This decomposition is easy to carry out in a hard‐walled guide. With absorbant lining, many difficulties occur even without mean flow. Since the eigenvalue problem is no longer selfadjoint, acoustic modes are not orthogonal with respect to the L2‐scalar product. However, an orthogonality relation exists which permits writing the modal decomposition. For a lined guide with uniform mean flow, modes are no longer orthogonal but a new sca…
Design of an FBG based-on sensor device for large displacement deformation
2013
This article deals with the modeling of a strain-displacement transducer conceived for extending the FBG measurement range. The intrinsic fragility of the optical fiber limits their application to cases characterized by relatively small deformations. To extend the employ to the large displacement field (i.e. morphing applications), a dedicated device was conceived, constituted by a circular ring connected to the structure and laterally integrated with a FBG sensor. This device was mathematically modeled minimizing the potential energy this way arriving at a description of the displacement and deformation field along the curvilinear abscissa. The theoretical predictions were then validated t…
Earthquake Excited Base-Isolated Structures Protected by Tuned Liquid Column Dampers: Design Approach and Experimental Verification
2017
Abstract In this contribution a direct approach for optimal design of a Tuned Liquid Column Damper (TLCD) device attached to the base slab of a base-isolated structure is presented, aiming at reducing the seismic displacement demand of the base-isolation subsystem. Assuming white noise base excitation, for a wide parameter range a direct optimization procedure yields design charts for optimal TLCD quantities. The performance of the base-isolated structure equipped with optimally tuned TLCD device in comparison to the simple base-isolated one is evaluated both numerically and experimentally. In a numerical study the system is subjected to the 44 records of the FEMA P-695 far-field ground mot…
Optimal Design of New Steel Connections
2018
The Limited Resistance Rigid Perfectly Plastic Hinge (LRPH) are special steel connections mainly usable to join beam elements of plane or spatial steel frames. The fundamental characteristics of these devices are the mutual independence of their own resistance and stiffness features as well as the respect of assigned constraints related to the elastic and limit behaviour of the joined elements. Within the frame structural scheme, the device plays the role of a rigid perfectly plastic hinge, constituted by a suitably sized sandwich section. The efficient use of the LRPH in the relevant frame depends on the appropriate design of the device geometry. In the present paper, a new approach devote…
Shakedown optimum design of reinforced concrete framed structures
1994
Structures subjected to variable repeated loads can undergo the shakedown or adaptation phenomenon,-which prevents them from collapse but may cause lack of serviceability, for the plastic deformations developed, although finite, as shakedown occurrence postulates, may exceed some maximum values imposed by external ductility criteria. This paper is devoted to the optimal design of reinforced concrete structures, subjected to variable and repeated loads. For such structures the knowledge of the actual values taken by the plastic deformations, at shakedown occurrence, is a crucial issue. An approximate assessment of such plastic deformations is needed, which is herein provided in the shape of …
Process parameters calibration in 3D tube hydroforming processes
2007
In tube hydroforming the concurrent actions of pressurized fluid and mechanical feeding allow to obtain tube shapes characterized by complex geometries such as different diameters sections and/or bulged zones. What is crucial in such processes is the proper design of operative parameters aimed to avoid defects (for instance shape defects or ductile fractures). The main process parameters are material feeding history (i.e. the punches velocity history) and internal pressure path during the process. In more complex three dimensional processes, also the action of a counterpunch is generally useful to reduce thinning in particular in expansion zones of the tube (i.e. T or Y shaped tubes). The g…
Computational methods for optimal shakedown design of FE structures
1998
The paper concerns the optimal shakedown design of structures discretized by elastic perfectly plastic finite elements. The design problem is formulated in four alternative versions, i.e. as the search for the minimum volume design whose shakedown limit load multiplier is assigned or as the search for the maximum shakedown limit load multiplier design whose volume is assigned; both problems are approached on the grounds of the shakedown lower bound and upper bound theorems. Correspondingly four computational methods, one for each original problem, are presented. These methods consist in solving iteratively new problems which are simpler than the original ones, but expressed in such a way th…
Multiobjective optimization of an ultrasonic transducer using NIMBUS
2005
The optimal design of an ultrasonic transducer is a multiobjective optimization problem since the final outcome needs to satisfy several conflicting criteria. Simulation tools are often used to avoid expensive and time-consuming experiments, but even simulations may be inefficient and lead to inadequate results if they are based only on trial and error. In this work, the interactive multiobjective optimization method NIMBUS is applied in designing a high-power ultrasonic transducer. The performance of the transducer is simulated with a finite element model, and three design goals are formulated as objective functions to be minimized. To find an appropriate compromise solution, additional pr…
Determination of a pre-heating sequence for the DONES Target Assembly
2021
Abstract Within the activities promoted by the EUROfusion consortium in support of the design and construction of the DEMO Oriented NEutron Source (DONES), a mock-up of its Target Assembly (TA), based on the configuration with a “bayonet” Back-Plate (BP) and available at ENEA Brasimone labs, is being adopted for the execution of experimental activities aiming at the validation of specific aspects of the target design. Despite the “integral”-TA concept is the current reference, experimental tests concerning the TA pre-heating phase are not significantly affected by the TA concept and are still representative even though conducted on the bayonet-TA concept. Indeed, the main objective of the p…