Capacity models for shear strength of exterior joints in RC frames: state-of-the-art and synoptic examination     

Carmine Lima  Enzo Martinelli  Ciro Faella 《Bulletin of Earthquake Engineering》2012,10(3):967-983

Damage observed in existing structures after recent earthquake events pointed out the key importance of beam-to-column joints in influencing the global response of reinforced concrete structures. In the last two decades several theoretical and empirical models have been proposed for evaluating shear strength of beam-to-column joints. The present paper reports an overview of the models currently available in the scientific literature for evaluating shear capacity of exterior beam-to-column joints. The present study is the first step of a wide analysis aimed at assessing such models and improving them. Moreover, the uncertainties deriving by applying the mentioned models will be also quantified therein, by means of well-established procedures for probabilistic seismic analysis of structures. The final results of that study are reported within a companion paper.  相似文献   

Capacity models for shear strength of exterior joints in RC frames: experimental assessment and recalibration     

Carmine Lima  Enzo Martinelli  Ciro Faella 《Bulletin of Earthquake Engineering》2012,10(3):985-1007

Several theoretical models are currently available in the scientific literature for evaluating the shear capacity of both exterior and interior beam-to-column joints in reinforced concrete (RC) frames. A reasonably wide set of those models, based on either analytical or empirical formulations, has been summarised within a companion work. The present paper firstly presents a wide database which collects results obtained in about two-hundred experimental tests carried out on RC joints. Those results are employed for assessing the above mentioned capacity models by considering a set of experimental data much wider than those usually utilised in the original formulation of such models. Accuracy and reliability of the various models are measured by quantifying some statistical parameters actually describing the relationship between the experimental evidence and the prediction of the various capacity models under consideration. Three relevant classes of joints (namely unreinforced, under reinforced and code-compliant) are considered with the aim of emphasising that the various models perform in a rather different way when applied to those different classes. Finally, a possible recalibration of the various models is proposed with the objective of enhancing their predictive capacity with respect to both the database as a whole and the three classes of RC joints mentioned above.  相似文献   

The relation between Lyman α absorbers and gas-rich galaxies in the local Universe     

Marco Pierleoni  Enzo Branchini  Matteo Viel 《Monthly notices of the Royal Astronomical Society》2008,388(1):282-292

We use high-resolution hydrodynamical simulations to investigate the spatial correlation between weak  ( N _{H  i} < 10¹⁵ cm⁻²)  Lyα absorbers and gas-rich galaxies in the local Universe. We confirm that Lyα absorbers are preferentially expected near gas-rich galaxies and that the degree of correlation increases with the column density of the absorber. The real-space galaxy auto-correlation is stronger than the cross-correlation (correlation lengths   r _0,gg= 3.1 ± 0.1 Mpc  h ⁻¹  and   r _0,ag= 1.4 ± 0.1 Mpc  h ⁻¹  , respectively), in contrast with the recent results of Ryan-Weber, and the auto-correlation of absorbers is very weak. These results are robust to the presence of strong galactic winds in the hydrodynamical simulations. In redshift space, a further mismatch arises since at small separations the distortion pattern of the simulated galaxy–absorber cross-correlation function is different from the one measured by Ryan-Weber. However, when sampling the intergalactic medium along a limited number of lines-of-sight, as in the real data, uncertainties in the cross-correlation estimates are large enough to account for these discrepancies. Our analysis suggests that the statistical significance of difference between the cross-correlation and auto-correlation signal in current data sets is ∼1σ only.  相似文献   

Modelling the cosmological co-evolution of supermassive black holes and galaxies – II. The clustering of quasars and their dark environment     

Silvia Bonoli  Federico Marulli  Volker Springel  Simon D. M. White  Enzo Branchini  Lauro Moscardini 《Monthly notices of the Royal Astronomical Society》2009,396(1):423-438

We use semi-analytic modelling on top of the Millennium simulation to study the joint formation of galaxies and their embedded supermassive black holes. Our goal is to test scenarios in which black hole accretion and quasar activity are triggered by galaxy mergers, and to constrain different models for the light curves associated with individual quasar events. In the present work, we focus on studying the spatial distribution of simulated quasars. At all luminosities, we find that the simulated quasar two-point correlation function is fit well by a single power law in the range  0.5 ≲ r ≲ 20  h ⁻¹ Mpc  , but its normalization is a strong function of redshift. When we select only quasars with luminosities within the range typically accessible by today's quasar surveys, their clustering strength depends only weakly on luminosity, in agreement with observations. This holds independently of the assumed light-curve model, since bright quasars are black holes accreting close to the Eddington limit, and are hosted by dark matter haloes with a narrow mass range of a few  10¹²  h ⁻¹ M_⊙  . Therefore, the clustering of bright quasars cannot be used to disentangle light-curve models, but such a discrimination would become possible if the observational samples can be pushed to significantly fainter limits. Overall, our clustering results for the simulated quasar population agree rather well with observations, lending support to the conjecture that galaxy mergers could be the main physical process responsible for triggering black hole accretion and quasar activity.  相似文献   

Peculiar velocity reconstruction with the fast action method: tests on mock redshift surveys     

Enzo Branchini  Amiram Eldar  Adi Nusser 《Monthly notices of the Royal Astronomical Society》2002,335(1):53-72

We present extensive tests of the fast action method (FAM) for recovering the past orbits of mass tracers in an expanding universe from their redshift-space coordinates at the present epoch. The tests focus on the reconstruction of present-day peculiar velocities using mock catalogues extracted from high-resolution N -body simulations. The method allows for a self-consistent treatment of redshift-space distortions by direct minimization of a modified action for a cosmological gravitating system. When applied to ideal, volume-limited catalogues, FAM recovers unbiased peculiar velocities with a one-dimensional, 1σ error of ∼220 km  s⁻¹  , if velocities are smoothed on a scale of  5 h ⁻¹  Mpc. Alternatively, when no smoothing is applied, FAM predicts nearly unbiased velocities for objects residing outside the highest density regions. In this second case the 1σ error decreases to a level of ∼150 km  s⁻¹  . The correlation properties of the peculiar velocity fields are also correctly recovered on scales larger than  5 h ⁻¹  Mpc. Similar results are obtained when FAM is applied to flux-limited catalogues mimicking the IRAS PSC z survey. In this case FAM reconstructs peculiar velocities with similar intrinsic random errors, while velocity–velocity correlation properties are well reproduced beyond scales of  ∼8 h ⁻¹  Mpc. We also show that FAM provides better velocity predictions than other, competing methods based on linear theory or the Zel'dovich approximation. These results indicate that FAM can be successfully applied to presently available galaxy redshift surveys such as IRAS PSC z .  相似文献   

The generalization of the Mie—Grüneisen equation of state     

F. Mulargia  E. Boschi 《Geophysical Journal International》1978,55(1):263-267

Summary. A generalized Mie—Grüneisen equation of state is found without thermodynamical limits of validity. The range of applicability of the classical Mie—Grüneisen equation is discussed and results are presented of a particular case of the present equation. The various definitions of the Grüneisen's parameter are analysed in comparison with their generalized theoretical expression, given here.  相似文献   

A Representation Theorem in the Dynamic Theory of Porous Media     

E. Boschi  F. Mainardi 《Geophysical Journal International》1973,34(3):313-320

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Generation of complete theoretical seismograms for SH-III     

Enzo Mantovani 《Geophysical Journal International》1978,53(1):55-60

Summary. Earlier efforts to generate the entire theoretical seismograms, including both body and surface waves for realistic sources buried in a radially heterogeneous anelastic, spherical earth, are extended to include the summation of 16 modes. The comparison between a real seismogram and theoretical time series, relative to different attenuation models in the upper mantle, yields information concerning the anelasticity under the Pacific Ocean.  相似文献   

Equations of state of close-packed phases of iron and their implications for the Earth's core     

F. Mulargia  E. Boschi 《Physics of the Earth and Planetary Interiors》1979,18(1):13-19

Theoretical equations of state for Fe at high pressures and temperatures are derived from the expression of the free energy written as a sum of the static energy, the harmonic, the anharmonic and the electronic contributions. All the calculations have been performed for the various crystal structures of Fe using different intermolecular potentials, and namely: Lennard-Jones, Morse and Rydberg functions. The available experimental data do not allow a definite choice between them thus leaving open the problem of the composition of the earth's core.  相似文献   

Body force,body couple and heat source equivalents for seismic dislocations     

Enzo Boschi 《Pure and Applied Geophysics》1973,111(1):2147-2157

Summary An explicit expression is derived for the body force, body couple and heat source to be applied in the absence of a seismic dislocation, which produces a thermodynamical behaviour equivalent to that produced by the dislocation.  相似文献