Damage evolution in reinforced concrete columns subjected to biaxial loading   总被引：1，自引：0，他引：1  

Hugo Rodrigues  António Arêde  Humberto Varum  Aníbal Costa 《Bulletin of Earthquake Engineering》2013,11(5):1517-1540

An analysis of the damage observed in 24 reinforced concrete (RC) columns tested under uniaxial and biaxial horizontal loading is presented. The test results show that for biaxial loading conditions specific damage occurs for lower drift demands when compared with the corresponding uniaxial demand (a reduction of 50–75 % was found). The damage distribution observed in each column is also analysed. No significant differences are found in the plastic hinge length for uniaxial and biaxial loading. The drift demands associated with each damage state are compared with reference values proposed in international guidelines. Finally, and based on the philosophy of the Park and Ang uniaxial damage index, two new expressions are proposed for the evaluation of damage in RC elements under biaxial loading. The results of the application of these expressions to the experimental results are discussed.  相似文献   

8- to 13-μm spectrophotometry of Comet IRAS-Araki-Alcock     

Michael A. Feierberg  Fred C. Witteborn  James R. Johnson  Humberto Campins 《Icarus》1984,60(3):449-454

We present spectrophotometry between 8.0 and 13.0 microns at 2% spectral resolution for areas in and near the nuclear condensation of Comet IRAS-Araki-Alcock (1983d) on May 11 and 12, 1983. All the spectra can be fit very well by blackbody curves, and no 10 micron silicate emissions are seen. The temperature structure of the coma suggests the presence of small (radii <5 microns) dust particles within 150 km of the nucleus and larger ones further out. The change in the spatial distribution of the infrared flux between the two nights suggests that an outburst may have occurred sometime on May 11.  相似文献   

Expected characteristics of cometary meteorites     

Humberto CAMPINS  Timothy D. SWINDLE 《Meteoritics & planetary science》1998,33(6):1201-1211

Abstract— Recent developments in our understanding of comets provide insights into the topic of cometary meteorites. These developments include the identification of comet-asteroid transition objects (such as 4015 Wilson-Harrington and 3200 Phaethon), information on the composition of cometary solids, and new ideas on the collisional history of Jupiter-family comets. In this work, we revisit this question, and we conclude that comets do indeed yield macroscopic meteorites, which either have not been found or have not been recognized. We also consider the expected characteristics of cometary meteorites, with an emphasis on those that may help identify and differentiate them from other types of meteorites. If cometary meteorites have preserved the main characteristics of cometary dust, the mineralogy would be dominated by highly unequilibrated anhydrous silicates, and the chemistry would be nearly chondritic but with a high abundance of C and N. On the other hand, if an unknown process produced extensive aqueous alteration in the material that formed cometary meteorites, they would resemble (or could even be) CI carbonaceous chondrites. We do not expect cometary meteorites to have chondrules. So far, no single meteorite looks unequivocally cometary. However, we have identified xenoliths in ordinary chondrite regolith breccias that meet most of our criteria for a cometary origin and deserve further study.  相似文献   

Cyclic behaviour of interior beam–column joints reinforced with plain bars          下载免费PDF全文

José Melo  Humberto Varum  Tiziana Rossetto 《地震工程与结构动力学》2015,44(9):1351-1371

The seismic damages commonly observed on beam–column joints of old reinforced concrete structures, built with plain bars and without proper detailing, justifies the need to further study the behaviour of this type of structures. The response of these structures when loaded cyclically, as occurs during the earthquakes, is partially controlled by the bond properties between the reinforcing bars and the surrounding concrete. This paper presents the results of an experimental campaign of unidirectional cyclic tests carried out on six full‐scale beam–column joints built with plain bars. These joint specimens are representative of existing reinforced concrete structures, that is, built without adequate reinforcement detailing for seismic demands. For comparison, an additional specimen is built with deformed bars and tested. The seven specimens are designed and detailed to allow the investigation of the influence of bond properties, lapping of the longitudinal bars in columns and beams, bent‐up bars in the beams, slab contribution and concrete strength. The lateral force–drift relationships, global dissipated energy evolution, contribution of the joint, beams and columns to the global dissipated energy, ductility, equivalent damping, final damage observed, homogenized reinforced concrete damage index, displacement components, curvature evolutions and Eurocode requirements are presented and discussed. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Earthquake loss estimation for the Kathmandu Valley     

Hemchandra Chaulagain  Hugo Rodrigues  Vitor Silva  Enrico Spacone  Humberto Varum 《Bulletin of Earthquake Engineering》2016,14(1):59-88

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Seismic safety assessment of existing masonry infill structures in Nepal     

Hemchandra Chaulagain  Hugo Rodrigues  Enrico Spacone  Humberto Varum 《地震工程与工程振动(英文版)》2016,15(2):251-268

Reinforced concrete (RC) buildings in Nepal are constructed with RC frames and masonry infill panels. These structures exhibit a highly non-linear inelastic behavior resulting from the interaction between the panels and frames. This paper presents an extensive case study of existing RC buildings in Nepal. Non-linear analyses were performed on structural models of the buildings considered as a bare frame and with masonry infill, in order to evaluate the influence of infill walls on the failure mechanisms. Five three-storey buildings with different structural configurations and detailing were selected. The effect of masonry infill panels on structural response was delineated by comparing the bare-framed response with the infill response. Seismic performance is evaluated with regard to global strength, stiffness, energy dissipation, inter-storey drift, and total deflection of the structure. A parametric analysis of structures with masonry infill is also performed. For this, the influence of different material properties is studied, namely diagonal compressive stress, modulus of elasticity and tensile stress of masonry infill panels. Study results show that masonry infill increases the global strength and stiffness of the structures; it decreases the inter-storey drift and hence the total displacement of the structure. The results quantify the influence of the infill panels on structural response and, in particular, the effect of the diagonal compressive strength of the masonry wall.  相似文献   

A multiresolution ensemble Kalman filter using the wavelet decomposition     

Kyle S. Hickmann  Humberto C. Godinez 《Computational Geosciences》2017,21(3):441-458

We present a method of using classical wavelet-based multiresolution analysis to separate scales in model and observations during data assimilation with the ensemble Kalman filter. In many applications, the underlying physics of a phenomena involve the interaction of features at multiple scales. Blending of observational and model error across scales can result in large forecast inaccuracies since large errors at one scale are interpreted as inexact data at all scales due to the misrepresentation of observational error. Our method uses a partitioning of the range of the observation operator into separate observation scales. This naturally induces a transformation of the observation covariance and we put forward several algorithms to efficiently compute the transformed covariance. Another advantage of our multiresolution ensemble Kalman filter is that scales can be weighted independently to adjust each scale’s affect on the forecast. To demonstrate feasibility, we present applications to a one-dimensional Kuramoto-Sivashinsky (K–S) model with scale-dependent observation noise and an application involving the forecasting of solar photospheric flux. The solar flux application uses the Air Force Data Assimilative Photospheric Transport (ADAPT) model which has model and observation error exhibiting strong scale dependence. Results using our multiresolution ensemble Kalman filter show significant improvement in solar forecast error compared to traditional ensemble Kalman filtering.  相似文献   

Whole Ecosystem Evidence of Eutrophication Enhancement by Wetland Dredging in a Shallow Tropical Lake     

Humberto Marotta  Luiz Bento  Francisco de A. Esteves  Alex Enrich-Prast 《Estuaries and Coasts》2009,32(4):654-660

The purpose of this research was to assess the effects of dredging performed in a marginal wetland colonized by aquatic macrophytes on eutrophication of the adjacent shallow tropical lake (Imboassica Lake, Brazil). The river mouth of the Imboassica River that drains into Imboassica Lake had been densely colonized by aquatic vegetation dominated by Typha domingensis (Pers.) when it was dredged. Total and dissolved nitrogen and phosphorus concentrations were measured monthly over 13 years at four stations in the Imboassica river-lake system. Dredging activities reduced phosphorus and nitrogen retention at the river mouth and subsequently increased these nutrient stocks in the lake waters. Nutrient retention by non-dredged wetland was estimated to be ca. 1,200 kg year⁻¹ (87.3 g m⁻² year⁻¹) for nitrogen and 60 kg year⁻¹ (4.5 g m⁻² year⁻¹) for phosphorus. Our whole-lake approach suggested that dredging might intensify rather than mitigate eutrophication in shallow tropical lakes when the removal of aquatic macrophytes is coupled to the persistence of anthropogenic nutrient inputs from the watershed.  相似文献   

Erratum to: Downward longwave radiation estimates for clear and all-sky conditions in the Sertãozinho region of São Paulo, Brazil     

Nadiane Smaha Kruk  Íria Fernandes Vendrame  Humberto Ribeiro da Rocha  Sin Chan Chou  Osvaldo Cabral 《Theoretical and Applied Climatology》2010,102(3-4):483-483

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Seismic vulnerability and loss assessment of the Nepalese Pagoda temples     

Manjip Shakya  Humberto Varum  Romeu Vicente  Aníbal Costa 《Bulletin of Earthquake Engineering》2015,13(7):2197-2223

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