DEM Algorithm for Progressive Collapse Simulation of Single-Layer Reticulated Domes under Multi-Support Excitation

In this paper, the Member Discrete Element Method (MDEM) is modified and perfected for three aspects: the algorithm itself, loading and computational efficiency, and to accurately and quantitatively simulate the progressive collapse for large-span spatial steel structures. In addition, the corresponding computational programs are compiled. First, from the perspective of the method, a meshing principle for discrete element models is determined, a treatment for material nonlinearity and strain rate effect is proposed, and a damping model is established. Next, the Displacement Method is introduced to determine the multi-support excitation for the MDEM, and then motion equations of particles under multi-support excitation are derived. On this basis, the specific process of gravitational field loading is presented. Furthermore, parallel implementation strategies for the MDEM based on OpenMP are constructed. Finally, the collapse simulation of a 1/3.5-scaled single-layer reticulated dome shaking table test model under multi-support excitation is carried out. The comparison demonstrates that the ultimate load and failure mode as well as the complete collapse time of the numerical results are consistent with the experimentally measured responses, and the configuration variations from member buckling and local depression until collapse failure are fully captured. Moreover, the displacement time-history curves obtained using MDEM are almost identical to the experimental measurements, and there is a nuance only in the amplitude. It is verified that MDEM is capable of precisely addressing the collapse failure for large-span spatial steel structures. Additionally, the failure mechanism for structures of this type is naturally revealed.     

秦汉政治史观的演变历程

秦汉时期共有三种主要的政治史观：以五行相胜原则运转的五德终始说、以五行相生原则运转的汉为尧后说,以及董仲舒所创三统说。秦到汉武帝时,五行相胜的五德终始说占政治史观的主流,汉昭帝以后则被五行相生的政治史观代替,董仲舒创立的三统说在汉武帝时形成,此后便和五行相生政治史观平行发展。这三种政治史观都与阴阳五行有密切关联,并对秦汉乃至以后两千余年封建社会产生深远影响。     

A Damage Index for the Seismic Analysis of Reinforced Concrete Members

This article proposes a damage index for the seismic analysis of Reinforced Concrete members using the hysteretic energy dissipated by a structural member and a drift ratio related to failure in the structure. The index was calibrated against observed damage in laboratory tests of 76 RC column units under various protocols. Values obtained in this calibration had acceptable agreement with the levels of damage observed in the test specimens. An analysis of the parameters involved in the definition of the proposed damage index shows the importance of displacement history in the drift ratio capacity of structures.     

Trace Element Classification Diagrams of Pyroclastic Rocks from the Volcanic Districts of Central Italy: the Case Study of the Ancient Roman Ships of Pisa

Identification of the volcanic material (pozzolan) stored in a Roman ship of the fourth to third century bce , wrecked in the ancient harbour of Pisa (central Italy), was based on ratios of selected trace elements. The compositions of the major volcanic products erupted by the volcanoes of the Roman province, including the volcanic districts of Latium (Vulsini, Vico, Monti Sabatini and the Alban Hills) and Campania (Roccamonfina, the Phlegraean Fields, Ischia, Procida and Vesuvius) are compared with the pozzolan from the Pisa ship. Superposition of the Zr/Y, Nb/Y and Nb/Zr ratios of the pyroclastic material from the wrecked ship (computed from the published literature) allows correlation with the products of the Onano eruption from the Vulsini Volcanic District. The Vulsini rocks outcrop extensively in a sector drained by the hydrographic network of the Fiora River, which has been a well‐developed commercial water trade route since Etruscan times, with a river port and a sea port connected to the important town of Vulci, and, since 273 bce , part of the larger Roman harbour system of Cosa.     

胡家草场汉简与尹湾汉简数术文献中的“刑德行时”

荆州胡家草场12号汉墓出土竹简《五行日书》按端、令、罚、刑、德五时占测为事、初病、生子诸事项的吉凶。这篇文献与尹湾汉墓出土的《刑德行时》大体属于同一文献的不同版本,两相比照,有助于加深对其文本源流、内涵的理解和认识。     

五管瓶初论

五管瓶为古人沟通天地的媒介,发源于东汉,经历代发展至宋到达鼎盛,其作用也由随葬的明器发展为具有象征意义的陈设用器。其象征意义与阴阳五行等中国传统文化思想相关,蕴涵吉祥之意。     

Testing of Superelastic Recentering Pre-Strained Braces for Seismic Resistant Design

Over the past decade, the use of shape memory alloys (SMAs) in passive control devices has been explored. Nevertheless, some aspects in regards to the cyclic behavior of SMAs and the effect of pre-straining need to be clarified. In this study, small-scale shake table tests have been performed to explore the effectiveness of SMA bracing systems as compared to steel bracing systems. The reduced-scale experimental results imply that SMAs used in braces are more effective in controlling the response of a steel frame compared with a traditional bracing system. A finite element model (FEM) of the frame is developed in order to compare the analytical results with the shake table tests. Further, the effect of pre-straining the SMA braces is evaluated through both experimental and analytical studies. The results show that pre-straining improves the performance of the frame compared to the nonpre-strained case. However, as the level of pre-straining increases above approximately 1.0% to 1.5%, the benefits of pre-straining decrease compared with low-to-moderate pre-strain levels.     

Relative Displacement Floor Spectra for Seismic Design of Non Structural Elements

Relative displacement floor spectra represent a powerful tool to evaluate the seismic displacement requirements of non-structural elements relative to their attachment points and can be used for displacement-based design of ductile components.

This article examines the displacement floor spectra on single-degree of freedom systems subject to accelerograms of varying intensity. A new method is proposed to predict floor spectra on single degree of freedom supporting structures. The results of nonlinear time-history analyses of a series of case-study structures indicate that the new methodology provides good results.

Future research will aim to validate this approach for multi-degrees of freedom supporting structures.     

Blue governmentality: Elemental activism with conservation technologies on plundered seas

For the Sea Shepherd Conservation Society, the atmosphere and ocean are channels for movement that are to be used and overcome in direct actions to protect marine environments. To accomplish these missions, they deploy a fleet of ships, helicopters, and drones that intervene to stop violations of conservation laws. In this way, oceanic elements—waves, winds, icebergs, and storms—mediate conservation and conservation technologies. The elements and the technologies that Sea Shepherd exploit both inhibit and make conservation possible.This paper argues that the drone is an exteriorization of the human body whose liberatory potentials are mediated by the atmosphere and ocean. Through ethnographic, textual, and videographic analysis, this article explores blue governmentality—how the azure sky and cyan ocean and the technologies that flow through these elements at once afford and constrain the control of biopower. Understanding blue governmentality means appreciating how the elements mediate movement, communication, and life itself. It requires comprehending how technologies emerge from the body, extend political intentionality, work across the elements, and network with other technologies. This article challenges conservation geography to see governmentality not as a totalizing force but one that is tempered by elemental mediations, technological affordances, and human fallibility.     

Biological mineral content in Iberian skeletal cremains for control of diagenetic factors employing multivariate statistics

The aim of this study was to define a strategy for a correct selection of bone samples by employing inductively coupled plasma optical emission spectroscopy (ICP-OES) for reconstructing the biological mineral content in bones through the determination of major elements, trace elements and Rare Earth Elements (REE, lanthanides) in skeletal cremains of ancient Iberians (III–II B.C), discovered in the Necropolis of Corral de Saus (Moixent, Valencia) between 1972 and 1979. The biological mineral content was determined taking into account diagenetic factors. A control method for a better reading of results was applied. To explore large geochemical datasets and to reduce the number of variables, Principal Component Analysis (PCA) was used, thus, providing a deeper insight into the structure of the variance of the dataset. PCA shows that the elemental profiles of bone and soil samples are clearly different. Bone samples obtained from the outer bone layer were shown to have a different elemental composition; more similar to soil samples than samples of the inner bone layer. PCA scores and loadings plots were preferred to dendrograms obtained using Cluster Analysis, due to the limits of the latter one to appreciate the spatial ordering of samples. Partial least squares discriminant analysis (PLS-DA), a frequently used supervised classification method, was applied to differentiate between degradation states of bone samples. PLS-DA results obtained in this study confirmed that changes derived from different burning conditions were associated with transformations in the mineral part of the bones. Accordingly, carbonized bones can be differentiated from cremated bones. Class assignment of bone samples with uncertain thermal conditions in dependence on their elemental composition has shown to be feasible. Consequently, for biochemical-archaeological studies the analysis and statistical classification of carbonized and cremated archaeological bones, as well as those exposed to unknown thermal conditions together with experiments in modern bones, are recommended.