Nonlinear Analysis of 2D and Shell Reinforced Concrete Structures Including Creep and Shrinkage

The work deals with the static analysis of plane stress, plane strain, axisymmetric and shell reinforced concrete structures subject to short and long term loading conditions. Nonlinear short term material properties and structural nonlinear geometric behavior is considered. The effect of time factors is adopted in a linear form because of the lack of well established nonlinear models for creep and shrinkage of concrete. The Total and Updated Lagrangian formulation of the problem is used to derive structural governing equations via the principle of virtual displacements. The adopted formulation is suitable for structures with large deflections, large rotations but small strains. Constitutive smeared-type equations for both 2D and 3D analysis of reinforced concrete are also considered. For the 2D analysis isoparametric elements with variable number of nodes (four to nine) with Lagrangian approximation of geometry and displacements are employed using a simple linear material model accounting for cracking, crushing as well as for smooth tension stiffening of concrete. The reinforcement is modeled by piece-wise linear elastic isotropic constitutive equations. For shell analysis, the degenerated Ahmad's shell element using Serendipity, Lagrange and Heterosis geometry and displacement interpolating hierarchical approach is adopted. Special attention is focused on the problem of shear locking and thus full, selective and reduced integration rules are dealt with. Constitutive equations are assumed which are elastic-plastic for both concrete and steel materials. Also tension stiffening and compression hardening and softening of concrete is included. Nonlinear solution techniques are comprehensively reviewed and consequently some of them are significantly improved. A new algorithm for the solution of nonlinear equations, which is based on Newton-Raphson, Arc-length and Line search methods, has been developed. Analysis considering shrinkage and creep has also been developed. The Step-by-step analysis using the Dirichlet series ap- proximation to the creep function was adopted and its problem of numerical instability has been overcome. The derived theory has been extensively tested for both short and long term loading conditions. Short term analyses focus especially on the accuracy of the material models being used and on shell behavior near the loss of stability. This type of analysis has been feasible only with the implementation of a very robust nonlinear equation solver, which is capable of dealing with structural snap through and snap back phenomena. The long term analyses concentrate on the accuracy of various simplified solution techniques, comparing these results with the Step-by-step method. The collective results show that full time analysis is necessary to assess serviceability structural conditions, whilst the time factor is negligible for the total structural strength with a failure mechanism being controlled mainly by time-independent reinforcement. The above conclusions are applicable for the structures investigated herein, (i. e. relatively thin and well reinforced), and should not be generalized for any arbitrary structure. All developments in the work have been programmed into the nonlinear program NONSAP (University of Berkeley, USA) and CONCRETE (University of Swansea, U. K.). In addition other software has been created, such as material preprocessing program, library with graphics accessible from the FORTRAN environment etc

Vývoj webového rozhraní pro vizualizaci predikce protein-ligand interakčních míst a jejich konzervovanosti

Bílkoviny jsou základními stavebními kameny všech živých organismů. Fun- gují na základě interakcí s jinými molekulami. Tato práce se zabývá vazebnými místy mezi proteiny a malými molekulami, zejména protože většina současných léků jsou právě malé molekuly. Zatímco nástrojů na predikci těchto vazebných míst je mnoho, počet nástrojů na jejich vizualizaci je téměř nulový. Spojením několika projektů zabývajících se zobrazením proteinů jsme vytvořili nový vizua- lizační web. Jelikož evoluční konzervovanost koreluje s výskytem vazebných míst, umožňujeme její zobrazení společně s detekovanými vazebnými místy. Vyvinuli jsme několik metod pro výpočet konzervovanosti a použili je v experimentech pro zlepšení detekce vazebných míst. Zde představujeme PrankWeb, moderní webo- vou aplikaci pro vizualizaci struktury a sekvence proteinů, jejich vazebných míst a konzervovanosti. Doufáme, že PrankWeb bude vědcům poskytovat rychlý a po- hodlný prostředek pro analýzu bílkovin. 1Proteins are fundamental building blocks of all living organisms. They perform their function by binding to other molecules. This thesis deals with interactions between proteins and small molecules (so called ligands) because most of the currently used drugs are small molecules. While there are several tools that can predict these interactions, they are almost none for their visualization. Thus, we built a new visualization website by combining several protein visualizers toge- ther. Since evolutionary homology correlates with binding sites, our web interface also displays homology for comparison. We developed several ways how to calcu- late homology, and used it to improve detection of protein-ligand binding sites in our experiments. Here we present PrankWeb, a modern web application for structure and sequence visualization of a protein and its protein-ligand binding sites as well as evolutionary homology. We hope that it will provide a quick and convenient way for scientists to analyze proteins. 1Department of Software EngineeringKatedra softwarového inženýrstvíMatematicko-fyzikální fakultaFaculty of Mathematics and Physic

The public sphere and representations of the self: radio talk shows in post-apartheid South Africa

Ph.D. University of the Witwatersrand, Faculty of Humanities 2012A vibrant media environment is fast becoming a prerequisite for democratic culture. Recent studies in radio in Africa have also paid attention to how the deregulation of the media space in the continent can be a catalyst to the growth of democratic culture. Yet, in so doing, current research pays less attention to the crucial aspect of self-fashioning which reflects power relations as well the existing relationships among individuals and different groups in society. This thesis examines the representation of the self on two ‘popular’ radio talk shows in contemporary South Africa. Using ‘The After Eight Debate’ and ‘The Redi Direko Show’ the thesis looks into the dynamics of representational politics which characterise the post-apartheid public sphere in South Africa. It deals with the way ‘imagined communities’ emerge through different kinds of discursive practices on radio talk shows and how participants react to different kinds of situations when they feature on radio. The study reveals access inequalities, performance and performative practices which translate to the silencing of various aspects of the self on radio talk shows. It concludes that the democratic credentials of radio talk shows are dwarfed by these silences which have the potential of privileging power and the power elite in contemporary South Africa

The African intellectual and the making of selfhood in Wole Soyinka's You must set forth at dawn

ABSTRACT In recent times, the autobiography is fast becoming a form of literary expression through which writers address various issues concerning their identity as well as socio-political realities in society. For African intellectuals, the urgency of the post-independence realities confronting different countries on the continent makes it imperative for them to deploy their life narratives beyond the traditional ends which autobiographical works are generally expected to address. It is in light of this that this study probes into Wole Soyinka’s making of selfhood in his recent autobiographical work You Must Set Forth at Dawn (2006). While trying to investigate how the writer creates a new identity for himself through his life narrative, the study argues that the prevailing circumstances around the individual intellectual in the postcolonial environment should be seen as major determining factors in the representation of the life of the public intellectual in Africa. It identifies the pains of colonialism, the failure of post-independence leadership as well as the lack of promise in contemporary administrations in most African states as exemplified by Nigeria in Soyinka’s narrative as the key factors mediating the composition of life narratives by public intellectuals in Africa. In this research report, Soyinka’s approach to history, memory, exile and nationalism are closely examined towards a better appreciation of his personality as well as his stance on various issues which continue to crop up in view of the dislocations which have constituted hindrances to the progress of Nigeria. The thesis also examines how Soyinka produces individual and communal agency as an African intellectual whose activism often translates to commitment in his literary works. The work draws the conclusion that the composition of the lives of individuals, and by extension public intellectuals especially in Africa, is often a product of both internal and external factors which combine to determine the personality of the subjects of life narratives

Modelling the bond between concrete and reinforcing steel in a fire

This is the post-print version of the final paper published in Engineering Structures. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2010 Elsevier B.V.A non-linear procedure is presented for modelling the bond characteristic between concrete and reinforcing steel for reinforced concrete structures in a fire. The accuracy and reliability of the model are demonstrated by the analysis of one pull-out test and one beam test at ambient temperature and four full-scale beams tested under two fire conditions. The model is clearly capable of predicting the response of reinforced concrete members and structures in a fire with acceptable accuracy. The bond-link element has been found to have good computational stability and efficiency for 3D analysis of reinforced concrete structures in fires. It is shown that the bond condition between the concrete and reinforcing steel bar has an important influence on the fire resistance of reinforced concrete structures, especially when the temperature of the reinforcing steel bar is high (more than 500 °C). Hence, the current assumption of a perfect bond condition for analysis of reinforced concrete structures under fire conditions is unconservative

PrankWeb: a web server for ligand binding site prediction and visualization.

PrankWeb is an online resource providing an interface to P2Rank, a state-of-the-art method for ligand binding site prediction. P2Rank is a template-free machine learning method based on the prediction of local chemical neighborhood ligandability centered on points placed on a solvent-accessible protein surface. Points with a high ligandability score are then clustered to form the resulting ligand binding sites. In addition, PrankWeb provides a web interface enabling users to easily carry out the prediction and visually inspect the predicted binding sites via an integrated sequence-structure view. Moreover, PrankWeb can determine sequence conservation for the input molecule and use this in both the prediction and result visualization steps. Alongside its online visualization options, PrankWeb also offers the possibility of exporting the results as a PyMOL script for offline visualization. The web frontend communicates with the server side via a REST API. In high-throughput scenarios, therefore, users can utilize the server API directly, bypassing the need for a web-based frontend or installation of the P2Rank application. PrankWeb is available at http://prankweb.cz/, while the web application source code and the P2Rank method can be accessed at https://github.com/jendelel/PrankWebApp and https://github.com/rdk/p2rank, respectively

Numerical modeling of the tension stiffening in reinforced concrete members via discontinuum models

[prova tipográfica]This study presents a numerical investigation on the fracture mechanism of tension stiffening phenomenon in reinforced concrete members. A novel approach using the discrete element method (DEM) is proposed, where three-dimensional randomly generated distinct polyhedral blocks are used, representing concrete and one-dimensional truss elements are utilized, representing steel reinforcements. Thus, an explicit representation of reinforced concrete members is achieved, and the mechanical behavior of the system is solved by integrating the equations of motion for each block using the central difference algorithm. The inter-block interactions are taken into consideration at each contact point with springs and cohesive frictional elements. Once the applied modeling strategy is validated, based on previously published experimental findings, a sensitivity analysis is performed for bond stiffness, cohesion strength, and the number of truss elements. Hence, valuable inferences are made regarding discontinuum analysis of reinforced concrete members, including concrete-steel interaction and their macro behavior. The results demonstrate that the proposed phenomenological modeling strategy successfully captures the concrete-steel interaction and provides an accurate estimation of the macro behavior