Search results for "LIMIT"
showing 10 items of 2826 documents
Strengthening of steel-reinforced concrete structural elements by externally bonded FRP sheets and evaluation of their load carrying capacity
2014
Abstract The paper proposes a preliminary design tool for reinforced concrete (RC) elements strengthened by fiber-reinforced-polymer (FRP) sheets to be used in civil engineering applications and in particular in medical buildings. The design strategy is based on limit analysis theory and utilizes a numerical procedure which provides a direct method to determine peak load, failure mode and critical zones of the structural elements of interest.
Fatigue methodology for life predictions for the wheel-rail contact area in large offshore turret bearings
2016
The present report presents a fatigue life prediction method for large roller bearings applied in the turret turn table for large loading buoy units. The contact points between wheel and rail in these bearings are subjected to a multi-axial fluctuating stress situation and both surface wear and fatigue cracking may occur. A methodology based on the Dang Van fatigue criterion is adopted. The criterion is based on an equivalent stress defined as a combination of the fluctuation of the shear stress from its mean value at a critical plane and the associated hydrostatic stress at the given time. The present work is supporting the theoretical model by extensive laboratory testing. Both full scale…
Serviceability of segmental concrete arch-frame bridges built by cantilevering
2013
The evaluation of the safety degree in service life for a segmental prestressed concrete bridge built by the cantilever method presents different aspects related to strength, deformability, durability and to effects of time-dependent phenomena as creep and shrinkage. The case-study of a prestressed concrete frame bridge with inclined piers is presented, built by cantilevering, with precast segments. By considering the fundamental items of design and construction stages, the implications due to the arch effect in this static scheme are investigated, with respect to an equivalent bridge with a final scheme of continuous girder on vertical piers. The birth of a significant value of axial force…
Modeling Round Robin Test: An Uncoupled Approach
2014
Abstract The solution of the modeling test presented in the paper is based on an uncoupled hydro-mechanical approach. Firstly, the controlled infiltration process is modeled by a finite element transient groundwater seepage software. Afterwards, calculated pore water pressures at successive instants are used for the slope stability analysis. Time evolution of the slope stability is analysed by using the infinite slope model, according to the classical limit equilibrium method.
A criterion for the assessment of the reliability of ASHRAE conduction transfer function coefficients
2010
This paper presents a new mathematical approach, which, when applied to conduction transfer functions (CTFs) of a multi-layered wall, is able to predict the reliability of building simulations. This new procedure can be used to identify the best set of CTF coefficients, which are a critical point at the core of the ASHRAE calculation methodology founded on the transfer function method. To evaluate the performance of different CTF coefficient sets, the authors performed a large number of thermal simulations on the multi-layered walls included in the ASHRAE Handbook, volume fundamentals, and on other walls typical of Mediterranean building heritage. Those data were employed to test an algorit…
Modeling the Sequential Switching Shunt Series Regulator
2005
This letter characterizes, in terms of the bandwidth and limit cycle frequency of its constituent subsystems, the sequential switching shunt series regulator -S/sup 4/R, a high-efficiency, low-mass and volume power cell devised to power the next generation of regulated power buses in telecommunication spacecrafts. Transconductance power source modeling is used to obtain linear and nonlinear models. These are used to establish a design control strategy which involves the dynamic response in large load requirements or at the end of the satellite life. Simulations and experimental results are also given to demonstrate the validity of the model.
Soft switched interleaved boost converters used as high-power battery discharge regulator for space power systems
2004
In the following years the telecommunication satellites will have a much greater power demand than nowadays. One reason for this is that the geostationary orbit required by this kind of satellites is becoming too crowded. Probably power levels of l0 kW to l00 kW will be the standard and with life duration of 25 years. It is not possible to keep 0.5 kW modules with more than 100 in parallel and therefore higher power modules (5 kW) must be used. A higher bus voltage seems also necessary and keeping a safety limit of 150 V, any voltage below it and above 100 V could meet the needs. In this paper we will propose a topology that fits the application: two soft switched interleaved boost converte…
Multipactor prediction with multi-carrier signals: Experimental results and discussions on the 20-gap-crossing rule
2014
This work analyzes the 20-gap crossing rule from a theoretical point of view. It has been found that, depending on some signal parameters, the 20-gap-crossing rule yields predictions laying between two limit cases: It may be either excessively conservative or closer to breakdown value with little (or nonexistent) margin. Such limit cases have been experimentally assessed with two test campaigns in C and Ku-bands. © 2014 European Association on Antennas and Propagation.
Mechanical behaviour of Palermo and Marsala calcarenites (Sicily), Italy
2016
Abstract This paper aims at finding a framework for the Sicilian Calcarenites relating the strength and the deformability of these materials to their geological and structural features: fabric, bonding, initial and actual specific volume. In particular, this study sets out to separate the effects of fabric and of bonding on the mechanical response. The investigated lithotypes, Calcarenites from Palermo and Marsala, outcropping in many areas of southwestern Sicily, are characterized by sudden changes in their deformability, strength and permeability characteristics. The geotechnical identification, by means of computerized axial tomography and thin section petrographic analysis suggested a s…
Arc Fault Detection Method Based on CZT Low-Frequency Harmonic Current Analysis
2017
This paper presents a method for the detection of series arc faults in electrical circuits, which has been developed starting from an experimental characterization of the arc fault phenomenon and an arcing current study in several test conditions. Starting from this, the authors have found that is it possible to suitably detect arc faults by means of a high-resolution low-frequency harmonic analysis of current signal, based on chirp zeta transform, and a proper set of indicators. The proposed method effectiveness is shown by means of experimental tests, which were carried in both arcing and nonarcing conditions and in the presence of different loads, chosen according to the UL 1699 standard…