Bayesian Parameter Identification and Model Selection for Normalized Modulus Reduction Curves of Soils

This work develops a procedure that involves the use of Bayesian approach to quantify data scatterness, estimates the optimal values of model parameters, and selects the most appropriate model for the construction of normalized modulus reduction curves of soils. The proposed procedure is then demonstrated using real observation data based on a set of comprehensive resonant column tests on coarse-grained soils conducted in the study.     

Seismic Behaviors of RC Frame Beam-Column Joints under Acid Rain Circle: A Pilot Experimental Study

This research was carried out to investigate the seismic performance of RC beam-column joints under acid rain circle via comparison of energy dissipation behavior and failure mechanism of joints with different corrosion levels and axial compression ratio. At the initial corrosion level, the strength, ductility, and energy consumption of RC beam-column joints improved slightly; at a later stage, the bearing and deformation capacity decreased as the corrosion rate of steel rebars increased. The test shows that with the increasing of the axial compression ratio, the initial stiffness and ultimate bearing capacity of the joints will increasing if the corrosion levels are the same, but the ductility of that will decrease.     

Evaluation of Strength Hierarchy of Beam-Column Joints of Existing RC Structures under Seismic Type Loading

To evaluate the strength hierarchy, three different types of exterior beam-column joint, i.e., gravity load designed, non ductile and ductile, following two different codes are considered. Strength of different components of beam-column joint, i.e., column, beam, and joint core, is individually calculated from different failure criteria. Shear strength of the joint is evaluated from softened strut and tie model. Strength hierarchy, ultimate strength, and critical failure modes of the specimens are analytically estimated and found to be well corroborated with the experimental results. The study will help in designing the earthquake resistant RC structures in a more rational way.     

Liquefaction Resistance of Silty Sands and Dynamic Properties of Cohesive Soils from Düzce,Turkey

This article presents results from a laboratory investigation into the cyclic and dynamic properties of soils from Düzce, Turkey, conducted after the destructive November 12, 1999 earthquake. The investigation was mainly conducted by means of monotonic and cyclic triaxial, as well as resonant-column tests. The triaxial tests allowed the determination of the liquefaction resistance of silty sands, as well as their critical state behavior, whereas the resonant-column tests allowed the determination of shear modulus and damping ratio of cohesive soils. The results are presented and then discussed together with their pertinence to soil behavior when subjected to earthquake loading.     

Revisiting the Great Compression: Wage inequality in the United States, 1940–1960

Seminal work by Goldin and Margo (1992 Goldin, C. D. and R. A. Margo.1992. The great compression: The wage structure in the United States at mid-century. Quarterly Journal of Economics 107 (1):1–34. https://doi.org/10.2307/2118322.[Crossref], [Web of Science ®] , [Google Scholar]) used the first available microdata samples of the United States decennial census to document the narrowing of the wage structure between 1940 and 1960, a pattern they refer to as the “Great Compression.” We revisit their findings using newly available, substantially enlarged samples of the decennial censuses covering this period. Our findings largely replicate the patterns initially reported by Goldin and Margo. However, differences emerge when estimating rates of return to education and experience for specific groups and in a decomposition exercise. A second goal is to indicate directions for future research that might benefit from the use of the complete count census data.     

Archaeological Quantification of Pottery: The Rims Count Adjusted using the Modulus of Rupture (MR)

Archaeological quantification is a recurrent issue in research about pottery, its typologies and its distribution. We accept the validity of other methods of quantification—sherd count, minimum number of individuals (MNI) or sherd weight—but the methodology that we have proposed for quantification of assemblages of archaeological contexts is the rims count, which has to be transformed into coefficients of reference through a correction using the modulus of rupture (MR). Such correctors are obtained through measuring the percentage of preserved rim of a significant number of sherds of each type and establishing the average of that percentage. This quantification method is easily applicable to all pottery types and it is also statistically reliable. Besides, it can be used in any study in which the gross number of rims is published. Finally, in the case of ceramic transport containers, a second correction can be applied by multiplying the corrected coefficient (number of rims × MR) by its average capacity (AC), another corrector that will allow us to gather statistics according to the litres of transported product. We believe that the rims count (the easiest part to classify) is a fast, relatively easy and very reliable method that needs to be corrected using the MR.     

Effect of heat treatment on siliceous rocks used in prehistoric lithic technology

Stone tool manufacture by many prehistoric and recent societies was characterized by deliberate heating of fine grained siliceous rocks to improve their flaking properties. Extensive mechanical testing of heated and unheated cryptocrystalline and macrocrystalline quartz lithologies has shown that thermal treatment causes a consistent marked reduction in fracture toughness. This mechanical property can be used as an objective measurement of the flaking qualities of stone materials, and a reliable criterion for the recognition of intentionally heated artefacts in the archaeological record. X-ray diffraction studies and scanning electron microscopy have demonstrated that the change in fracture toughness with heating is the result of recrystallization. The poorly ordered, strongly interlocking cryptocrystalline fabric of the unheated samples becomes more equigranular and better crystallized with thermal treatment. As a consequence, fractures propagate more readily in heated samples, accounting for their better flaking properties.     

Optimal Control of Structures under Earthquakes Including Soil-Structure Interaction

It is well known that the soil-structure interaction (SSI) changes the dynamic response of a structure supported on flexible soil. The analysis of optimally controlled SSI systems has certain difficulties due to the nature of the SSI and the optimal control problem. In this paper, a two-step iteration-based numerical algorithm is proposed to handle optimally controlled SSI systems under earthquakes. First, the optimal control forces are obtained by using a fixed-base system. Then, the optimal control forces are converted to the frequency domain by the Fourier transform technique to be used in the equations of the SSI system. The lateral displacement and the rocking of the foundation are obtained from the equations of the SSI system containing the optimal control forces in the frequency domain. The lateral displacement and rocking of the foundation are then converted to the time domain by the inverse Fourier transform technique, and the lateral accelerations and the rocking accelerations of the foundation are obtained by the forward finite difference method. During the second step, the optimal control forces are calculated again by using the lateral acceleration and the rocking acceleration of the foundation along with the earthquake ground motion. Using the method explained above, the optimal control forces obtained in the time domain are used in the equations of the soil-structure system from which the behavior of foundation and structure is obtained. In the final section of the paper, a numerical study is conducted for a controlled structure supported on flexible soil.     

Development and Performance Evaluation of Disk-Type Piezoelectric Transducer for Measurement of Shear and Compression Wave Velocities in Soil

A piezoelectric transducer capable of measuring both shear and compression wave velocities in soil simultaneously in triaxial testing conditions is presented. Performance evaluation of disk transducer system showed that the use of low-noise coaxial cables, proper grounding, and high resolution wave recorder can significantly enhance signal quality and eliminates crosstalk deterioration. Distortions due to near-field effects were found to diminish by increasing input frequency and by using sinusoidal input waveform, compared to square input. Disk-type piezoelectric transducers show significant future potential for laboratory determination of shear, and compression modulus of soil because of their robustness and noninvasive nature.     

Shear Modulus and Damping Ratio of Cohesive Soils

This article presents results from a laboratory investigation into the dynamic characteristics of reconstituted and undisturbed cohesive soils by means of resonant-column tests. In particular, results showing the influence of various soil parameters, such as confining stress, overconsolidation ratio, void ratio, plasticity index, calcium carbonate content, and time of confinement on shear modulus and damping ratio at small and high shear strains are presented and then discussed. Relationships for the small-strain shear modulus, the degradation of shear modulus at high strains, and the increase of damping ratio at high strains over its small-strain value are proposed. Finally, the practical implications of the results in the context of seismic site response analysis are discussed.