Calculation methods of bending moments on supports in precast prestressed hollow-core slabs with platform joints

Experimental results of intermediate floors strength with precast prestressed hollow-core slabs with platform joints are presented. Precast prestressed hollow-core slabs with ?5mm reinforcement of high-strength wire are produced by a continuous formless molding method, which imposes particular features on its reinforcement such as absence of transverse reinforcement near joints and danger of its destruction from shear on supports

Simulation of bending reinforced concrete elements with cracks

Лазовский Д. Н., Глухов Д. О., Лазовский Е. Д. Моделирование работы железобетона с трещинами при изгибеOn the basis of deformational design analytical model of the cross section and block model of reinforced concrete element, a new analytical model is proposed by the authors. This model takes into account the work of tensioned concrete between cracks by applying additional stress in the reinforcement (steel bars) due to the difference in relative deformations between the tension reinforcement and concrete during the formation of a crack. The developed model of analysis of reinforced concrete with cracks makes it possible to obtain the parameters of stress-strain state af the element in any cross-section along the length under the action of a bending moment and a longitudinal force

Access and Usage Control in Grid

Grid is a computational environment where heterogeneous resources are virtualized and outsourced to multiple users across the Internet. The increasing popularity of the resources visualization is explained by the emerging suitability of such technology for automated execution of heavy parts of business and research processes. Efficient and flexible framework for the access and usage control over Grid resources is a prominent challenge. The primary objective of this thesis is to design the novel access and usage control model providing the fine-grained and continuous control over computational Grid resources. The approach takes into account peculiarities of Grid: service-oriented architecture, long-lived interactions, heterogeneity and distribution of resources, openness and high dynamics. We tackle the access and usage control problem in Grid by Usage CONtrol (UCON) model, which presents the continuity of control and mutability of authorization information used to make access decisions. Authorization information is formed by attributes of the resource requestor, the resource provider and the environment where the system operates. Our access and usage control model is considered on three levels of abstraction: policy, enforcement and implementation. The policy level introduces security policies designed to specify the desired granularity of control: coarse-grained policies that manages access and usage of Grid services, and fine-grained policies that monitor the usage of underlying resources allocated for a particular Grid service instance. We introduce U-XACML and exploit POLPA policy languages to specify and formalize security policies. Next, the policy level presents attribute management models. Trust negotiations are applied to collect a set of attributes needed to produce access decisions. In case of mutable attributes, a risk-aware access and usage control model is given to approximate the continuous control and timely acquisition of fresh attribute values. The enforcement level presents the architecture of the state-full reference monitor designed to enforce security policies on coarse- and fine-grained levels of control. The implementation level presents a proof-of-concept realization of our access and usage control model in Globus Toolkit, the most widely used middleware to setup computational Grids

Modeling the behaviour of statically indeterminate reinforced concrete structures under load

Лазовский Д. Н., Глухов Д. О., Лазовский Е.Д. Моделирование работы статически неопределимых железобетонных конструкций под нагрузкойOne of the main differences of reinforced concrete is the possibility of cracking in concrete, which leads to a significant change in stiffness along the length of the element with cracks. The current state of the issue of the analysis of reinforced concrete elements is characterized by the widespread use of complex mathematical models and computational tools based largely on empirical and semi-empirical approaches to the analysis of the operation of reinforced concrete with cracks (deformation design model of the cross section based on concrete and reinforcement deformation diagrams, block model based on the dependences of the adhesion of reinforcement to concrete and the finite element method for calculating internal forces). So, the deformation design model of a flat section is used to calculate the moment of cracking and the strength of the element; block model of reinforced concrete between cracks – to calculate the opening width and crack pitch; structural mechanics methods (including the finite element method) for calculating internal forces and deflections. Using these approaches in the calculations of the stress-strain state of reinforced concrete elements (successively, moving from one method to another), the accumulation of calculation errors invariably occurs, since the parameters of the reinforced concrete structure calculated using different approaches have a mutual influence on each other. The purpose of this work is to attempt to combine these approaches for calculating the stress-strain state of reinforced concrete elements at all stages of work within the framework of a single calculation model, avoiding, if possible, the use of empirical relationships between them. On the example of a continuous two-span reinforced concrete beam, the authors analyzed the proposed calculation model and obtained satisfactory results of convergence with experimental dat

An Implementation of Role-Base Trust Management Extended with Weights on Mobile Devices

AbstractThis paper describes the implementation of a library for the management and evaluation of Role-based Trust Management (RT) credentials and policies written in RTML, also extended with weights, in mobile devices. In particular, it describes the implementation of the library in J2ME. It is worth noticing, that RTML credentials are XML-like documents and thus the capability of porting these features on mobile devices makes the overall framework very interoperable with other RT frameworks (as for GRID systems). As policy language, we use actually a variant of RTML, whose policies are added with weights and are able to express quantitative experience-based notions of trust. It allow also to encode certain reputation and recommendation models. The obtained results show how the implementation on mobile devices is feasible and the running time acceptable for several applications

Calculation methods of bending moments on supports in precast prestressed hollow-core slabs with platform joints

Experimental results of intermediate floors strength with precast prestressed hollow-core slabs with platform joints are presented. Precast prestressed hollow-core slabs with ?5mm reinforcement of high-strength wire are produced by a continuous formless molding method, which imposes particular features on its reinforcement such as absence of transverse reinforcement near joints and danger of its destruction from shear on supports

Vertical pressure of platform joint of precast prestressed hollow core slabs

The analysis of calculation methods of tangent bond stresses of concrete with high-strength wire taking into account stresses from vertical pressure, comparison of theoretical calculation results and experimental data is provided

Strength of reinforced concrete beams, strengthened with additional prestressed transverse reinforcement

In this article the author gives the results of the experimental and theoretical studies of the strength of the reinforced concrete beams, strengthened with additional pre-stressed transverse reinforcement