33 research outputs found
Calculation of a Multi-storey Monolithic Concrete Building on the Earthquake in Nonlinear Dynamic Formulation
AbstractThe article deals with a multi-storey monolithic concrete building calculation on the earthquake. The problem is solved in the time domain by a direct dynamic method. Direct integration of motion equations is carried out on an explicit scheme. This technique allows us to solve the problem in a nonlinear dynamic formulation considering geometric and physical nonlinearities. The paper presents and analyzes the main results of the calculation
Ensuring Seismic Resistance of Reinforced Concrete Buildings
There are a large number of works on a comprehensive assessment of the seismic resistance of buildings and structures. However, these studies, as a rule, do not take into account the random nature of the seismic impact, which is a pronounced non-stationary random process. An adequate assessment of the seismic resistance of buildings and structures is possible only on the basis of methods that allow taking into account the large variability of seismic impact parameters. The article presents a probabilistic method for calculating multi-storey reinforced concrete buildings designed in seismic regions, taking into account the interaction of a building with a non-linearly deformable foundation. The developed technique makes it possible to provide the required level of seismic resistance for the designed buildings based on the non-collapse criterion. As an ex-ample, the calculation of a multi-storey reinforced concrete building is considered. External seismic action is represented as a non-stationary random process. The external seismic action is considered as a non-stationary random process, which is obtained by multiplying the stationary random process by a deterministic envelope function. The parameters necessary for constructing the envelope and the stationary random process were obtained from the results of processing the available database of intense earthquakes. The stationary random process was generated by the shaping filter method. The impact parameters are based on the results of processing the available database of intense earthquakes. When modeling reinforced concrete structures, a concrete model is used with the function of damage accumulation under cyclic loads, as well as taking into ac-count the degradation of the strength and stiffness of the material during an intense earthquake. Accounting for the interaction of the building with the soil base is implemented using the SSI interface (Soil Structure Interaction). To prevent the influence of waves reflected from the boundaries of a limited ground massif, a PML layer (Perfectly Matched Layer) is used. The calculation was carried out using explicit methods for integrating the equations of motion on a computing cluster using parallel computing technology. The presented technique makes it possible to investigate the nature of the destruction of reinforced concrete structures during intense earthquakes and to identify zones with a deficiency in bearing capacity. The proposed probabilistic approach to modeling seismic impact as an implementation of a non-stationary random process with given parameters, together with taking into account the nonlinear deformation of the reinforced concrete structures of the building and foundation, allows you to control the level of reliability and design buildings with a given seismic resistance
VERIFICATION OF ELASTOMERIC BEARINGS FINITE-ELEMENT MODELS IN CALCULATING SOFTWARE PACKAGES
Introduction. While designing buildings and constructions with an elastomeric bearing with a lead core as a seismic isolation system, it is necessary to make calculations concerning effectiveness and reasonability of its usage. These demands lead to necessity to construct bearings in a common finite-element model, in order to consider how a bearing and a construction work together. Though a calculator has a lot of different variants of elastomeric bearing’s construction, which are connected to their implemented work model. To prove that obtained calculation results are sufficient and accurate, selection criteria of elastomeric bearings implemented work models are necessary.
Materials and methods. To get accurate results we will compare elastomeric bearing’s work diagrams and free periods of motion when there are different variants of their numerical modelling with the help of software packages with factory tests results.
Results. The researches have shown that lateral force’s and shear’s limit values are the same for all of the observed cases, although free periods of motion and work diagrams differ. Usage of more accurate bearing work model in software package Ansys/LS-Dyna can explain these differences, it can be seen if compare their work’s diagrams.
Conclusions. Analysis of constructions with elastomeric bearings’ work, which function according to the idealized linear model, can be possible only for II level constructions. Idealized nonlinear models should be used for I level constructions
NEXP-completeness and Universal Hardness Results for Justification Logic
We provide a lower complexity bound for the satisfiability problem of a
multi-agent justification logic, establishing that the general NEXP upper bound
from our previous work is tight. We then use a simple modification of the
corresponding reduction to prove that satisfiability for all multi-agent
justification logics from there is hard for the Sigma 2 p class of the second
level of the polynomial hierarchy - given certain reasonable conditions. Our
methods improve on these required conditions for the same lower bound for the
single-agent justification logics, proven by Buss and Kuznets in 2009, thus
answering one of their open questions.Comment: Shorter version has been accepted for publication by CSR 201
Explicit Evidence Systems with Common Knowledge
Justification logics are epistemic logics that explicitly include
justifications for the agents' knowledge. We develop a multi-agent
justification logic with evidence terms for individual agents as well as for
common knowledge. We define a Kripke-style semantics that is similar to
Fitting's semantics for the Logic of Proofs LP. We show the soundness,
completeness, and finite model property of our multi-agent justification logic
with respect to this Kripke-style semantics. We demonstrate that our logic is a
conservative extension of Yavorskaya's minimal bimodal explicit evidence logic,
which is a two-agent version of LP. We discuss the relationship of our logic to
the multi-agent modal logic S4 with common knowledge. Finally, we give a brief
analysis of the coordinated attack problem in the newly developed language of
our logic
TR-2014003: On the Complexity of Two-Agent Justification Logic
We investigate the complexity of derivability for two-agent Justification Logic. For this purpose we revisit Yavorskaya’s two-agent LP with interactions (2008), we simplify the syntax and provide natural extensions. We consider two-agent versions of other justification logics as well as ways to combine two justification logics. For most of these cases we prove that the upper complexity bound established for the single-agent cases are maintained: these logics ’ derivability problem is in the second step of the polynomial hierarchy. For certain logics, though, we discover a complex-ity jump to PSPACE-completeness, which is a new phenomenon for Justification Logic
Consolidation of Belief in Two Logics of Evidence
Recently, several logics have emerged with the goal of modelling evidence in a more relaxed sense than that of justifications. Here, we explore two of these logics, one based on neighborhood models and the other being a four-valued modal logic. We establish grounds for comparing these logics, finding, for any model, a counterpart in the other logic which represents roughly the same evidential situation. Then we propose operations for consolidation, answering our central question: What should the doxastic state of a rational agent be in a given evidential situation? These operations map evidence models to Kripke models. We then compare the consolidations in the two logics, finding conditions under which they are isomorphic. By taking this dynamic perspective on belief formation we pave the way for, among other things, a study of the complexity, and an AGM-style analysis of rationality of these belief-forming processes