Cyclic Response of Concrete Beams Reinforced by Plain Bars

There are many reinforced concrete structures throughout the world that have been built in the past decades that lack appropriate seismic details and reinforced by plain bars. To study the behavior of such buildings, seven beams have been tested under cyclic and monotonic load. The specimens include substandard specimens, with deficient seismic details and reinforced by plain bars, specimens designed in accordance with ACI-318-99 but reinforced by plain bars, and standard specimens reinforced by deformed bars. The tests indicate that the substandard specimens sustain relatively large slip of longitudinal bars, separation of specimen relative to foundation and sliding at large deformation phase, low initial stiffness ratio, limited lateral displacement capacity, and loss of nominal yield strength. The specimens reinforced by plain bars in accordance with ACI-318-99 perform almost similar to standard specimens with deformed bars, in terms of elastic stiffness and lateral displacement ductility; but, they sustain larger slip, and smaller yield strength. Failure of all specimens reinforced by plain bars is characterized by flexural cracks without visible shear failure. Residual shear strength of substandard specimens is modeled by dowel action of longitudinal bars to predict a lower limit for lateral strength of the specimens.     

Analytical Seismic Assessment of a Tall Long-Span Curved Reinforced-Concrete Bridge. Part II: Structural Response

The seismic assessment of special bridges, even under the hypothesis of full knowledge of site conditions, structural characteristics, and seismic activity at their location, is not an easy and straightforward task due to the complexities and uncertainties related to the finite-element modeling approaches, structural loading scenarios, and seismic analysis methodologies. In this article, a series of nonlinear static and dynamic finite-element analyses on the Mogollon Rim Viaduct are performed with consideration of both uniform and conditionally simulated non-uniform seismic motions. The failure modes of the bridge using different numerical modeling approaches are discussed, and the degree of sensitivity of its response to the different seismic assessment strategies is evaluated. The effect of the multi-component, multi-support and multi-directional excitations of ground motions on the design and response are studied, and the pros and cons of the commonly used structural analysis methodologies of bridges are also addressed. The numerical results of the present study provide a deeper insight into the nonlinear behavior of curved reinforced-concrete bridges, and suggest practice-oriented approaches for their seismic assessment.     

An XFEM Model for Seismic Activity in Indian Plate

Empirical approaches based on the available earthquake catalog are popular among engineers to estimate seismic hazard. The seismic activity on individual faults inferred from these approaches is associated with a large number of uncertainties, especially due to lack of data. This article proposes a mechanistic approach to quantify seismic and fault activity, thereby overcoming the difficulties in the existing empirical procedure. A finite element (FE) model for Indian Plate, with the geological ‘cratons’ is developed and subject to plate driving forces namely, the ridge push and the slab pull forces. The material properties and the thickness of both plate and cratons are obtained through inversion using the recently available Global Positioning System (GPS) data. The tectonic faults are modeled using the well-known ‘extended FE method (XFEM)’. The simulated strains at fault level are compared with the computed strain rates from the earthquake catalog. Further, the procedure to quantify fault activity is demonstrated for Gujarat, India.     

Analytical Seismic Assessment of a Tall Long-Span Curved Reinforced-Concrete Bridge. Part I: Numerical Modeling and Input Excitation

The seismic response of bridges is affected by a number of modeling considerations, such as pier embedment, buried pile caps, seat-type abutments, pounding, bond slip and architecturally flared part of piers, and loading considerations, such as non-uniform ground excitations and orientation of ground motion components, which are not readily addressed by design codes. This article addresses a methodology for the nonlinear static and dynamic analysis of a tall, long-span, curved, reinforced-concrete bridge, the Mogollon Rim Viaduct. Various modeling scenarios are considered for the bridge components, soil-structure interaction system, and materials, i.e., concrete and reinforcing steel, covering all its geotechnical and structural aspects based on recent advances in bridge engineering. Various analysis methodologies (nonlinear static pushover, time history response to uniform and spatially variable seismic excitations, and incremental dynamic analyses) are performed. For the dynamic analyses, a suite of nine earthquake accelerograms are selected and their characteristics are investigated using seismic intensity parameters. A recently developed approach for the generation of non-uniform seismic excitations, i.e., spatially variable simulations conditioned on the recorded time series, is used. Methods for the evaluation of structural performance are discussed and their limitations addressed. The numerical results of the seismic assessment of the Mogollon Rim Viaduct are presented in the companion article (Part II). The sensitivity of the bridge response to the adopted modeling, loading and analyzing strategies, as well as the correlation between structural damage and seismic intensity parameters are examined in detail.     

Post-depositional surface whitening of ceramic artifacts: alteration mechanisms and consequences

Surfaces on ceramic artifacts that are paler than the main sherd body are commonly interpreted as slips that were intentionally applied by the potter during the manufacturing process. However, due to post-depositional alteration, sherds that were not originally coated with a slip may macroscopically appear with deceptively similar pale surfaces. This paper presents a comparison of two sherds, both with pale to white surfaces, one of which is a real slip and the other a surficial corrosion that occurred during the burial stage. Observations using optical and scanning electron microscopy, as well as electron-probe image- and microanalysis, clearly illustrate the features of the two surfaces, as well as demonstrating their causes and effects. The superimposed slip is clearly delimited from the sherd body by a denser and much finer-grained fabric, in which clay minerals predominate and porosity is reduced by about 20% compared to the body. In the other sample, surface corrosion, due to invading fluids, has led to leaching of calcareous constituents and results in a remarkable increase in porosity close to the rim (ca. 25%). Sometimes called the “espresso crema effect” (Tschegg et al., 2009b), the surface becomes considerably brighter than the core and can easily be confused with intentional slips. This, as a consequence can lead to significant misinterpretations, to erroneous sherd characterizations and classifications, as well as to incorrect assignments to specific ware groups.     

《上海博物馆藏战国楚竹书（一）缁衣·性情论》释文补正

上博购藏的战国楚竹书《缁衣》、《性情论》释大部分可信。但仍存在误释、缺释之处,本对其释作了补正,指出其误释之处,对部分缺释之字提出了自己的看法。     

Art in time. Diachronic rates of change in the decoration of bone artefacts from the Beagle Channel region (Tierra del Fuego, Southern South America)

This paper explores the differential rates of diachronic change developed by diverse features of portable art in southern Tierra del Fuego. It is argued that decorative designs and techniques, which simultaneously constitute each decorated artefact, had asynchronic rates of change throughout the archaeological sequence. Results indicate that: (I) decorated harpoon points (1) had a broader and more complex design repertoire which entailed a higher labour investment and showed a faster rate of change than beads, due to a greater individual input in their decoration, (2) were richly decorated in spite of their high risk of loss/fracture, yet their decoration was concentrated in the early period of the archaeological sequence and then decreased in time due: a) to such loss/fracture risk, which jeopardised the labour invested in their decoration, (b) to a relative decrease in pinniped hunting which might have reduced the socio-economic and symbolic value of harpoons; (II) decorated beads (1) had a simpler and more standardised design repetoire which entailed a lower labour investment and showed a slower rate of change than harpoons, due to a stricter process of teaching/learning or imitation during their production and a collective way of ornamentation during their display, (2) increased with time and have been decorated during the three periods of the archaeological sequence due to: (a) their lower risk of loss/fracture, which did not endanger the labour invested in their decoration, (b) their social function as a shared form of ornamentation; (III) decorative techniques had a slower rate of change than decorative designs throughout the archaeological sequence due to their differential instrinsic variability potentials.     

Rates for the job. Measures of disease frequency in palaeopathology

Measures of disease frequency are discussed and their use in palaeopathology illustrated with examples, both hypothetical and real. It is shown that prevalence rates are the appropriate rates to use when calculating the frequency of diseases in skeletal populations. The extent to which prevalence rates accurately reflect those in the living population from which the skeletons were derived is also considered and it is suggested that they are a reasonable approximation for diseases that do not shorten life span, but not for those that do. Finally, suggestions are made for dealing with missing data.     

《战国楚竹书·孔子诗论·邦风》释文订补

《战国楚竹书·孔子诗论》内容十分重要,其中《邦风》部分的竹简编次和注释都有不当之处。本文是在订补的基础上对孔子论诗的体例及部分内容作了新的诠释。