In the current resurgence of interest in the biological basis of animal behavior and social organization, the ideas and questions pursued by Charles Darwin remain fresh and insightful. This is ...especially true ofThe Descent of Man and Selection in Relation to Sex, Darwin's second most important work. This edition is a facsimile reprint of the first printing of the first edition (1871), not previously available in paperback.
The work is divided into two parts. Part One marshals behavioral and morphological evidence to argue that humans evolved from other animals. Darwin shoes that human mental and emotional capacities, far from making human beings unique, are evidence of an animal origin and evolutionary development. Part Two is an extended discussion of the differences between the sexes of many species and how they arose as a result of selection. Here Darwin lays the foundation for much contemporary research by arguing that many characteristics of animals have evolved not in response to the selective pressures exerted by their physical and biological environment, but rather to confer an advantage in sexual competition. These two themes are drawn together in two final chapters on the role of sexual selection in humans.
In their Introduction, Professors Bonner and May discuss the place ofThe Descentin its own time and relation to current work in biology and other disciplines.
The seismic behavior of the concrete slab in concrete-faced rockfill dams (CFRD) is investigated, considering concrete slab-cushion layer interface effect. The interface is simulated by an advanced ...constitutive model capable of simulating the complex behavior of soil-structure interfaces such as particle breakage, stress-dilatancy, stress-hardening, cyclic accumulative contraction, and stress degradation. Stage construction and reservoir impoundment of the dam are simulated and the dam is subjected to two earthquake records. The concrete slab responses under static and dynamic conditions are examined, and the effects of reservoir water level, interface roughness, and the interface modeling approach on the concrete slab response are investigated.
In this study, the effect of concrete face slab – cushion layer interface behavior on the performance of face slabs in concrete-faced rockfill dams (CFRDs) is investigated using the finite element ...method. The body of the CFRD is simulated by the cap elastoplasticity model while the interface zone between the concrete face slab and the gravelly cushion layer is simulated explicitly by an advanced interface constitutive model, developed in the framework of critical state soil mechanics and state parameters, and capable of simulating volumetric behavior and stress path dependency. The effect of elastic and elastoplastic material behavior and water level on the stress and displacement responses of the concrete face slab is examined, and the influence of the roughness at the interface area between the concrete face slab at the contact face and the cushion layer on the performance of the concrete face slab is investigated. Comparison of the results with and without the explicit consideration of the interface behavior shows the importance of incorporating advanced constitutive interface modeling in the design and analysis of CFRDs.
Many soil-structure interaction systems experience a three-dimensional loading condition (i.e. shear coupling) at their interfaces. In this study, an elasto-plastic constitutive formulation for ...interfaces in soil-structure interaction problems is proposed considering the effects of 3D shear coupling loading conditions. The proposed model is capable of simulating granular soil-structure interfaces for both monotonic and cyclic loading over a wide range of normal stress and normal stiffness using a single set of eleven calibration parameters. The model is capable of simulating a number of complex interface behaviour, including hardening and softening, compaction, dilation and phase transformation, stress path dependency, accumulative contraction and stabilization, stress degradation and particle breakage under monotonic and cyclic loading. The constitutive model performance is examined using available experimental data for gravelly and sandy soil-structure interfaces subjected to monotonic and cyclic loads involving shear coupling.
•An advanced 3-D elasto-plastic constitutive model for soil-structure interfaces under cyclic loading is proposed.•Capability of simulating cyclic behavior of granular soil-structure interfaces with a single set of 11 calibration parameters without recalibration.•Capability of simulating complex interface behavior, including shear and tangential coupling and stress path dependency.
In this paper, an implementation of an advanced two-surface plasticity interface constitutive model in a general-purpose finite element code ABAQUS for application in soil-structure interaction ...problems under static and dynamic loading conditions is presented. A recently developed constitutive model by the authors for gravelly soil-structure interface was improved to simulate the behavior of both gravelly and sandy soil-structure interfaces. A new failure surface was introduced into the model in order to simulate the softening behavior of interfaces under monotonic and cyclic loading. The constitutive model was then implemented in ABAQUS as a thin-layer interface element to demonstrate its capabilities in representing the complex behavior under different stress paths and normal stresses, including debonding and rebonding mechanisms at interface zones. The accuracy and robustness of the numerical implementation algorithm was examined by considering the effect of time step size, and by simulating different boundary value problems. The numerical predictions under different loading and boundary conditions were compared with experimental observations.
•Implementation of an advanced interface constitutive model in a general purpose finite element code is presented.•Advanced interface constitutive model simulates both monotonic and cyclic behavior of granular soil-structure interfaces.•Performance of proposed model validated using single element, slide block test, shaft pullout test and CFRD numerical examples.•The numerical predictions under different loading and boundary conditions were compared with experimental observations.
An elasto-plastic model is proposed for modeling the constitutive behavior of the interface between gravelly soils and structural materials. This model is based on the two-surface plasticity ...formulation and it is compatible with the concept of critical state soil mechanics. The model requires the same set of eight calibration parameters for predicting the monotonic and cyclic responses of both loose and dense interfaces. The model simulates cyclic densification, shear degradation and the effects of normal pressure, soil density, and stress path. The performance of the proposed constitutive model is validated by tests data under different normal stresses and boundary conditions.
A plasticity constitutive model is proposed to simulate the monotonic and cyclic behavior of granular soil–structure interfaces. The model is built on two-surface plasticity models previously ...developed for interfaces between gravelly soils and structural materials (Saberi et al., 2016, 2017), which simulate strain hardening, stress degradation and phase transformation behavior. The proposed model in this study incorporates the softening behavior likely to occur in dense sandy soil–structure interfaces under monotonic and cyclic loading, and it provides a unified formulation for simulating the behavior of both sandy and gravelly soil–structure interfaces. The model accounts for the stress path dependency behavior of interfaces, and it requires a single set of nine calibration parameters, which can readily be obtained from standard interface shear tests. The interface model’s performance is evaluated for Constant Normal Load, Constant Normal Stiffness, and Constant Normal Height stress path conditions by comparing its predictions with experimental data.
The low-cycle characteristics of structural subassemblies under large cyclic strains play an important role in contemporary seismic design. Obtaining these characteristics can lead to an ...understanding of a structure's degradation and nonlinear response behaviour, and can serve as a basis for developing efficient numerical models to predict seismic collapse mechanisms. The austenitic stainless tubular grade of steel has shown promise in terms of strain hardening character, structural overstrength and ductility, but existing test data is limited or constrained to small plastic strains, which is hardly useful in earthquake engineering applications. This article presents an experimental study designed to characterize the hysteresis of stainless steel plates under large inelastic cyclic strains and to assess their potential use in buckling-restrained brace components for seismic applications. Axial coupons machined from austenitic Grade 304L stainless steel and from regular carbon steel Grade 350WT were tested under uniaxial tensile loading, as well as constant and variable strain amplitude cyclic loadings. Results of the uniaxial tests confirmed higher ductility and strain hardening capacity for the stainless steel plates compared to those of carbon steels. These results were subsequently used to validate a novel technique based on image analysis to derive the true stress-strain characteristics. The stainless steel Grade 304L plates showed higher cyclic hardening but shorter low-cycle fatigue life compared to the carbon steel. Parameters for representing the low-cycle fatigue behavior of these materials, useful for developing a cyclic plasticity hardening numerical model, were derived from the test data.
•Fully-reversed large strain-controlled cyclic tests of austenitic stainless steel designed.•A novel methodology based on image analysis implemented to determine the true stress-strain relationship.•Parameters representing low-cycle fatigue behavior and cyclic strain hardening models derived.
The behavior of interfaces between granular soils and structural construction materials has an important impact on the monotonic and cyclic response of many soil-structure interaction (SSI) systems. ...Understanding the mechanics and modeling of these interfaces is an important step towards a safe and effective design and analysis of SSI problems. An extensive literature search for a ‘one-stop shop’ providing a comprehensive exposition on the mechanical characteristics and numerical modeling approaches of granular soil-structure interfaces yielded less than encouraging results. This paper seeks to bridge this knowledge gap in as concise manner as possible. To this end, the effects of the essential elements of the SSI problem, including soil and structural features as well as loading conditions, on the deformation and stress transformation mechanism of the interface are critically examined. Simple and advanced interface constitutive modeling methods are discussed, and implementation techniques of interface elements in finite element codes are explained. Additionally, a method to incorporate the effect of particle breakage to improve the capabilities of an elasto-plastic constitutive simulation of the cyclic accumulative contraction in granular interface modeling is introduced.
