Generalized dynamic analysis of structural single rocking walls (SRWs)     

Dimitrios Kalliontzis  Arturo E. Schultz  Sri Sritharan 《地震工程与结构动力学》2020,49(7):633-656

The investigation of structural single rocking walls (SRWs) continues to gain interest as they produce self-centering lateral load responses with reduced structural damage. The simple rocking model with modifications has been shown to capture these responses accurately if the SRW and its underlying base are infinitely rigid. This paper advances previous rocking models by accounting for (1) the inelastic actions at or near the base of the SRW and (2) the flexural responses within the wall. Included in the proposed advancements are hysteretic and inherent viscous damping associated with these two deformation components so that the total dynamic responses of SRWs can be captured with good accuracy. A system of nonlinear equations of motion is developed, in which the rocking base is discretized into fibers using a zero-length element to locate the associated compressive deformations and damage. The flexural deformations of the rocking body are captured using an elastic term, while the impact events are modeled using impulse-momentum equations. Comparisons with experiments of structural precast concrete and masonry SRWs show that the proposed approach accurately estimates the dynamic responses of different SRWs with and without unbonded posttensioning, for various dynamic excitations and degrees of hysteretic action. Using the proposed approach, a numerical investigation employs different configurations of structural SRWs to quantify the various sources of energy loss, including hysteretic action and impact damping, during various horizontal ground motions.  相似文献   

Stability of rotating spherical stellar systems     

Jean-Michel Alimi  Jérôme Perez  Arturo Serna 《Monthly notices of the Royal Astronomical Society》1999,305(4):859-865

  相似文献   

DNAPL Characterization Methods and Approaches, Part 1: Performance Comparisons   总被引：4，自引：0，他引：4  

Mark L. Kram  Arturo A. Keller  Joseph Rossabi  Lorne G. Everett 《Ground Water Monitoring & Remediation》2001,21(4):109-123

Contamination from the use of chlorinated solvents, often classified as dense nonaqueous phase liquids (DNAPLs) when in an undissolved state, represents an environmental challenge with global implications. Mass-transfer limitations due to rate-limited dissolution can lead to long-term aquifer persistence for even small volumetric fractions. The identification of DNAPL source zones located beneath the water table is critical to ultimately achieve site remediation and aquifer restoration. This paper provides a comparison of the advantages and disadvantages of many of the methods being used for detecting and delineating DNAPL contaminant source zones. The objective is to determine which options are best to pursue based on site characteristics, method performance, and method costs. DNAPL characterization methods are grouped into approaches, which include site preparation, characterization, and data-processing activities necessary to design an effective remediation system. We compare the different approaches based on the level of chemical and hydrogeologic resolution, and the need for additional data requirements. Our findings can be used to assist with selection of appropriate site remediation management options.  相似文献   

Evolution of disturbed oak woodlands: the case of Mexico City's western forest reserve   总被引：1，自引：0，他引：1  

Arturo García-Romero 《The Geographical journal》2001,167(1):72-82

Mexico City is the largest city in population and area in the world. In the last 30 years it has expanded its area westwards to include the mountains of the Sierra de las Cruces. These mountains contain the nearest forest reserve for the citizens of Mexico City. Deforestation and severe ecological degradation resulting from the destruction of the natural environment; air, water and soil pollution; and hydrological and geomorphological imbalances, limit the capacity of these areas to support forest regeneration. This study focuses on the geo-ecology of the climax oak woodlands found in the Sierra de las Cruces. Based on morpho-structural evidence, bioclimatic type, degree of human intervention and general geo-ecological considerations, three territorial systems have been differentiated in which the oak woodlands exist in different climax facies: a) oak woodlands developed in very humid and cool environments located on low mountain slopes; b) disturbed oak woodlands developed in humid and cool environments located on high piedmonts; and c) highly disturbed oak woodlands developed in subhumid and temperate environments, located on low piedmonts. A comparative study of the content, structure and functional relationships of the secondary facies associated with these climax communities, allowed conclusions to be drawn on the way oak woodlands respond to human intervention, and the risky situations to which these communities are subjected, particularly the most sensitive facies that deserve immediate protection.  相似文献   

The CO2 fertilization factor and the ‘missing’ carbon sink     

Arturo A. Keller 《Climatic change》1996,33(1):63-68

  相似文献   

Spatial and temporal variation of heavy metals in a tropical estuary   总被引：6，自引：0，他引：6  

J. Bahena-Manjarrez  L. Rosales-Hoz  A. Carranza-Edwards 《Environmental Geology》2002,42(6):575-582

The lower part of the Coatzacoalcos River has great industrial development in which high pollution has been reported. Surface sediments of this area were studied over a year to observe spatial and seasonal sedimentological and chemical variations. Higher metal concentrations were found during the dry season, Pajaritos Dock and Teapa sampling points showing the highest values. Ni (182 ppm) and Co (37 ppm) concentrations are elevated relative to other estuarine areas. Metal normalization against Al₂O₃ content shows contaminant input in areas where urban and industrial discharges exist. A cluster analysis of the data separates sediment samples from the different sampling trips, suggesting the dynamic nature of the sediments. Through the statistical t-test, metal enrichment of Cd, Cu, Cr, Ni, Pb, and Zn was evaluated and compared with metal concentration in sediments of the river higher parts. The percentage of bioavailable metals is a function of the physicochemical characteristics of the system.  相似文献   

Vorläufige Mitteilung über einen Meteoritenregen an der Quillagua-Oase,Provinz Antofagasta,Chile     

Dipl.-Geol. Arturo Thomas N. 《International Journal of Earth Sciences》1968,58(2):903-908

Zusammenfassung Im Rahmen einer weiträumigen geologischen Kartierung für das Instituto de Investigaciones Geológicas wurde 1956 direkt östlich der Oase Quillagua in Nordchile eine sehr auffallende Kratergruppe entdeckt und photogeologisch ausg  相似文献   

Ductility reduction factors for steel buildings considering different structural representations     

Alfredo Reyes-Salazar  Edén Bojórquez  Juan I. Velazquez-Dimas  Arturo López-Barraza  J. Luz Rivera-Salas 《Bulletin of Earthquake Engineering》2015,13(6):1749-1771

  相似文献   

Design and implementation of an image stabilization device at the THEMIS solar telescope     

Bernard Gelly  Claude Le Men  Arturo López Ariste  Cyril Delaigue  Ruyman Gónzalez Perez 《Experimental Astronomy》2008,22(1-2):67-85

An image stabilizer has been inserted into the optical path of the THEMIS solar telescope. THEMIS is a Ritchey–Chretien reflector telescope using an altazimuthal mount and closely tied to its spectrograph. The optical and mechanical design, implementation and system tests are described, and emphasis is put on the complexity of situations that this stabilizer must accept, including the scanning of the solar surface while stabilizing. The current closed-loop crossover frequency of the device is 65 Hz at ??3 dB on all typical solar scenes.  相似文献   

Force reduction factors for steel buildings with welded and post-tensioned connections     

Alfredo Reyes-Salazar  Mario D. Llanes-Tizoc  Juan Bojorquez  Edén Bojórquez  Arturo López-Barraza  Achintya Haldar 《Bulletin of Earthquake Engineering》2016,14(10):2827-2858

The seismic responses of steel buildings with perimeter moment resisting frames (MRF) with welded connections (WC) are estimated and compared to those of similar buildings with semi-rigid post-tensioned connections (PC). The responses are estimated in terms of ductility reduction factors (R _µ,), ductility demands (µ _G ) and force reduction factors (R). Two steel model buildings, which were modeled as complex-3D-MDOF systems, were used in the study. Results indicate that the reduction magnitude of global response parameters is larger than that of local response parameters, contradicting the same reduction implicitly assumed in the static equivalent lateral force procedure, implying that non-conservative design may result. The value of 8 for R, suggested in many codes for ductile steel MRF, and the value of 1 suggested in the well known Newmark and Hall procedure for the ratio of R to µ _G , cannot be justified. The reason for this is that SDOF systems were used to model actual structures, where higher mode effects, energy dissipation and structural overstrength weren’t explicitly considered. The codes should be more transparent regarding the magnitude and the components involved in the force reduction factors. The seismic performance of steel buildings with PC may be superior to that of the buildings with WC, since their force reduction factors are larger and their ductility demands smaller, implying that PC buildings could be designed for smaller lateral seismic forces. The conclusions of this paper are for the particular structural systems and models considered. Much more research is needed to reach more general conclusions.  相似文献