Radim Čajka

Using DOProC Method in Structural Reliability Assessment

Reliability of load-carrying structures has been assessed by various calculation procedures based on probability theory and mathematic statistics, which have been becoming more and more popular. The calculation procedures are well-suited for the design of elements in load-carrying structures with the required level of reliability if at least some input parameters are random and contribute to a qualitatively higher level of the reliability assessment and, in turn, higher safety of those who use the buildings and facilities. This paper discusses application of the original and new probabilistic methods – the Direct Optimized Probabilistic Calculation (“DOProC”), which uses a purely numerical approach without any simulation techniques. This provides more accurate solutions to probabilistic tasks, and, in some cases, to considerably faster completion of computations.

Foundation Slab in Interaction with Subsoil

In the paper the experiment results of deformation in foundation slab segment in interaction with subsoil are presented. Pilot measurement is carried out on original subsoil with characteristics which were tested in cooperation with geotechnics specialists. Concrete precast slab with square dimensions 500 mm and with thickness 48 mm made of plain concrete is exposed to vertical load. The tests results are compared with bending moments and deformations analysed according to subsoil models given in Eurocodes using FEM analysis.

Fibre Concrete Foundation Slab Experiment and FEM Analysis

In November 2013 an experiment was carried out using the testing equipment called stand. During the experiment was loaded steel-fiber reinforced concrete foundation slab model. The stand measures deformation and monitors interaction between stress and deformation. The purpose of this paper is comparison of values measured during the experiment and results of numerical calculations based on FEM. The stress strain analysis of elastic halfspace by means of Gauss numerical integration and Jacobean of transformation is presented here. The objective of this paper is also improving and developing the soil-structure interaction analysis based on the experimental results and FEM.

Experimental Soil - Concrete Plate Interaction Test and Numerical Models

State of stress in foundation structure is structure is significantly influenced by the contact stress course in the subsoil. At the Faculty of Civil Engineering VSB TU Ostrava testing device was constructed so that the phenomena could be experimentally investigated and compared with numerical models. The objective of this paper is also improving and developing the soil-structure interaction analysis based on the experimental results and finite element method (FEM).

Validating a Computational Model of a Rooflight Steel Structure by Means of a Load Test

During erection of a rooflight steel structure excessive deformation started appearing in the steel structure designed for a rooflight. After repairing the load-carrying system it was necessary to check whether the structure was free of permanent deformations. The situation was consulted with the investor and it was proposed to carry out a load test which should prove that the real structure was in accordance with the computational model.

Bitumen Sliding Joints for Friction Elimination in Footing Bottom

Use of a sliding joint is an effective method to decrease the stress in foundation structure where there is a horizontal deformation of subsoil (areas afflicted with underground mining) or horizontal deformation of a foundation structure (pre-stressed foundations, creep, shrinkage, temperature deformation). A convenient material for a sliding joint is a bitumen asphalt belt. Experiments for different types of bitumen belts were undertaken at the Faculty of Civil Engineering - VSB Technical University of Ostrava in 2008. Since 2011 an extension of the 2008 experiments has been in progress and the shear resistance of a slide joint is being tested as a function of temperature in a temperature controlled room. In this paper experimental results of temperature dependant shear resistance are presented. The result of the experiments should be the sliding joint shear resistance as a function of deformation velocity and temperature. This relationship is used for numerical analysis of stress/strain relation between foundation structure and subsoil.

Measured Data Processing in Civil Structure Using the DOProC Method

This paper describes the use of measured values in the probabilistic tasks by means of the new method which is under development now - Direct Optimized Probabilistic Calculation (DOProC). This method has been used to solve a number of probabilistic tasks. DOProC has been applied in ProbCalc a part of this software is a module for entering and assessing the measured data. The software can read values saved in a text file and can create histograms with non-parametric (empirical) distribution of the probabilities. In case of the parametric distribution, it is possible to make selection from among 24 defined types and specify the best choice, using the coefficient of determination. This approach has been used, for instance, for modelling and experimental validation of reliability of an additionally prestressed masonry construction.

Accuracy of Stress Analysis Using Numerical Integration of Elastic Half-Space

In case of constructions placed on subsoil, it is necessary to create a rigidity matrix for the element subsoil. That rigidity matrix should be then added up in respective positions with the rigidity matrix of an element. To clarify the proposed model of the subsoil, a method is derived for determination of vertical subsoil stress analysis under any shape of a slab construction by means of numerical integration and theory of isoparametric elements using the Jacobian transformation. This approach is rather original and represents the key contribution of this work in interaction solutions. Using the proposed approach, the method can be employed for any shape of a finite element.

Numerical solution of soil - foundation interaction and comparison of results with experimetal measurements

Several experimental measurements of reinforced concrete slab - subsoil interaction are compared with numerical analysis of shallow foundation by means of FEM. At the Faculty of Civil Engineering VSB - Technical University of Ostrava testing device was constructed so that the phenomena of soil - foundation interaction could be experimentally investigated and compared with numerical models. Results of experimental loading test are compared with soil - foundation interaction analysis based on finite element method (FEM). The purpose of this paper is to compare resulting deformation of the slab, subsidence of the subsoil, bending moments and contact stress calculated by different software based on FEM. Currently there are several software that, can deal with the interaction of foundations and subsoil.

Analysis of Stress in Half-Space Using Jacobian of Transformation and Gauss Numerical Integration

Stress strain analysis of elastic halfspace by means of Gauss numerical integration and Jacobean of transformation is presented. The arbitrary shape and general course of the loaded area in nodal points is allowed by use of 4-and 8-node isoparametric elements, numerical integration and Jacobean transformation. Results of numerical examples are compared with other solutions.