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Modification Factors (modification + factor)
Selected AbstractsA simple procedure to approximate slip displacement of freestanding rigid body subjected to earthquake motionsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 4 2007Tomoyo Taniguchi Abstract A simple calculation procedure for estimating absolute maximum slip displacement of a freestanding rigid body placed on the ground or floor of linear/nonlinear multi-storey building during an earthquake is developed. The proposed procedure uses the displacement induced by the horizontal sinusoidal acceleration to approximate the absolute maximum slip displacement, i.e. the basic slip displacement. The amplitude of this horizontal sinusoidal acceleration is identical to either the peak horizontal ground acceleration or peak horizontal floor response acceleration. Its period meets the predominant period of the horizontal acceleration employed. The effects of vertical acceleration are considered to reduce the friction force monotonously. The root mean square value of the vertical acceleration at the peak horizontal acceleration is used. A mathematical solution of the basic slip displacement is presented. Employing over one hundred accelerograms, the absolute maximum slip displacements are computed and compared with the corresponding basic slip displacements. Their discrepancies are modelled by the logarithmic normal distribution regardless of the analytical conditions. The modification factor to the basic slip displacement is quantified based on the probability of the non-exceedence of a certain threshold. Therefore, the product of the modification factor and the basic slip displacement gives the design slip displacement of the body as the maximum expected value. Since the place of the body and linear/nonlinear state of building make the modification factor slightly vary, ensuring it to suit the problem is essential to secure prediction accuracy. Copyright © 2006 John Wiley & Sons, Ltd. [source] Estimation of strength reduction factors via normalized pseudo-acceleration response spectrumEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 6 2007Debasis Karmakar Abstract Estimation of design forces in ductility-based earthquake-resistant design continues to be carried out with the application of response modification factors on elastic design spectra, and it remains interesting to explore how best to estimate strength reduction factors (SRFs) for a design situation. This paper considers the relatively less explored alternative of modelling SRF spectrum via a given response spectrum. A new model is proposed to estimate the SRF spectrum in terms of a pseudo-spectral acceleration (PSA) spectrum and ductility demand ratio with the help of two coefficients. The proposed model is illustrated for an elasto-plastic oscillator, in case of 10 recorded accelerograms and three ductility ratios. The proposed model is convenient and is able to predict SRF spectrum reasonably well, particularly at periods up to 1.0 s. Coefficients of the proposed model may also be determined in case of a given design spectrum when there is uncertainty in SRF spectrum due to uncertainty in temporal characteristics of the ground motion. This is illustrated with the help of 474 accelerograms recorded in western U.S.A. and different scaled PSA spectra. It is shown that probabilistic estimates may be obtained in this situation for SRF spectrum by assuming the error residuals to be log normally distributed with period-dependent parameters. Copyright © 2006 John Wiley & Sons, Ltd. [source] Structural fire design according to Eurocode 5,design rules and their backgroundFIRE AND MATERIALS, Issue 3 2005Jürgen KönigArticle first published online: 18 NOV 200 Abstract This paper gives a review of the design rules of EN 1995-1-2, the future common code of practice for the fire design of timber structures in the Member States of the EU and EFTA, and makes reference to relevant research background. Compared with the European pre-standard ENV 1995-1-2, the new EN 1995-1-2 has undergone considerable changes. Charring is dealt with in a more systematic way and different stages of protection and charring rates are applied. For the determination of cross-sectional strength and stiffness properties, two alternative rules are given, either by implicitly taking into account their reduction due to elevated temperature by reducing the residual cross-section by a zero-strength zone, or by calculating modification factors for strength and stiffness parameters. Design rules for charring and modification factors are also given for timber frame members of wall and floor assemblies with cavities filled with insulation. A modified components additive method has been included for the verification of the separating function. The design rules for connections have been systemized by introducing simple relationships between the load-bearing capacity (mechanical resistance) and time. The code provides for advanced calculation methods for thermal and structural analysis by giving thermal and thermo-mechanical properties for FE analyses. The code also gives some limited design rules for natural fire scenarios using parametric fire curves. Copyright © 2004 John Wiley & Sons, Ltd. [source] Empirical models of UV total radiation and cloud effect studyINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 9 2010David Mateos Villán Abstract Several empirical models of hourly ultraviolet total radiation (UVT) have been proposed in this study. Measurements of UVT radiation, 290,385 nm, have been recorded at ground level from February 2001 to June 2008 in Valladolid, Spain (latitude 41°40,N, longitude 4°50,W and 840 m a.s.l.). The empirical models have emerged due to the lack of some radiometric variables in measuring stations. Hence, good forecasts of them can be obtained from usual measures in these stations. Therefore, some advantages of the empirical models are that they allow the estimation of past missing data in the database and the forecast of future ultraviolet solar availability. In this study, reported models in the bibliography have been assessed and recalibrated. New expressions have been proposed that allow obtaining hourly values of ultraviolet radiation from global radiation measures and parameters as clearness index and relative optical air mass. The accuracy of these models has been assessed through the following statistical indices: mean bias, mean-absolute bias and root-mean-square errors whose values are close to zero, below 7% and below 10%, respectively. Two new clear sky models have been used to evaluate two new parameters: ultraviolet and global cloud modification factors, which can help to understand the role of the clouds on solar radiation. The ultraviolet cloud modification factor depends on cloudiness in such a way that its value under overcast skies is half of the cloudless skies one. Exponential and potential fits are the best relationships between both cloud factors. Finally, these parameters have been used to build new UV empirical models which show low values of the statistical indices mentioned above. Copyright © 2009 Royal Meteorological Society [source] Molecular orientation, crystallinity, and flexural modulus correlations in injection molded polypropylene/talc compositesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 5 2010Marcia Cristina Branciforti Abstract In order to promote better understanding of the structure-mechanical properties relationships of filled thermoplastic compounds, the molecular orientation and the degree of crystallinity of injection molded talc-filled isotactic polypropylene (PP) composites were investigated by X-ray pole figures and wide-angle X-ray diffraction (WAXD). The usual orientation of the filler particles, where the plate planes of talc particles are oriented parallel to the surface of injection molding and influence the orientation of the , -PP crystallites was observed. The PP crystallites show bimodal orientation in which the c - and a*-axes are mixed oriented to the longitudinal direction (LD) and the b -axis is oriented to the normal direction (ND). It was found that the preferential b -axis orientation of PP crystallites increases significantly in the presence of talc particles up to 20,wt% in the composites and then levels-off at higher filler content. WAXD measurements of the degree of crystallinity through the thickness of injection molded PP/talc composites indicated an increasing gradient of PP matrix crystallinity content from the core to the skin layers of the molded plaques. Also, the bulk PP crystallinity content of the composites, as determined by DSC measurements, increased with talc filler concentration. The bulk crystallinity content of PP matrix and the orientation behavior of the matrix PP crystallites and that of the talc particles in composites are influenced by the presence of the filler content and these three composite's microstructure modification factors influence significantly the flexural moduli and the mechanical stiffness anisotropy data (ELD/ETD) of the analyzed PP/talc composites. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||