Abstract:The experimental methods for determination of concrete resistance to chlorides – both the chloride permeability test methods (NT Build 492 NordTest – Non-S teady State Migration Test, AAS HTO T 277-AS TM C 1202 Test) and the methods for testing concrete resistance to surface scaling due to cyclic freezing and thawing in the presence of NaCl solution (deicing salts, saline sea water, etc.) (e.g. Slab Test according to CEN /TS 12390-9, based on the Borås method according to Swedish Standard SS 13 72 44) are presented in the paper. The R apid Chloride Test – the method used “in situ” to determine the chloride ion content in concrete is also described.
Abstract:This study presents the example of using extruded polystyrene for thermal insulation under the foundation slab of a building. Under the foundation slab of the thickness of 500 mm of a fivestorey reinforced concrete building there was applied a layer of XPS of the thickness of 150 mm. The authors monitored the deformation of insulation under the load of the building from the moment of concreting the foundation slab until the completion of its development. Additionally, there were conducted laboratory tests of the σ−ε dependence and of material creeping. On the basis of the results of material properties, for the purpose of conducting the analysis of XPS deformations and effort, there was constructed a numerical model in the FEM system. This work includes the results of the conducted measurements and analyses with proper comments. They became the basis for drawing the conclusions which will be of use for future work.
Abstract:Practical aspects of testing confined spaces, especially for the purpose of acoustic adaptations, are presented. The tests were carried out with use of prediction models, showing the possibilities of models that are used at present. Sound auralization, which is a reliable method for the assessment of sound signal quality and the acoustic conditions of tested rooms, is described. The basic criteria for the assessment of acoustic conditions in confined spaces are briefly discussed.
Abstract:This paper presents the results of a parametric study undertaken to analyse the influence that changes in the material model and contact zone parameters may have on residual stress levels. A simplified shakedown based mechanical model is used to estimate the residual stress distributions due to simulated contact loads. An information on final shakedown state of the rail subjected to given loading program is obtained at a substantially reduced computational cost compared to the standard incremental analysis. A 50% increase in peak contact pressure may increase the longitudinal residual stress level by over 700%. The dependence of peak residual stresses on changes in the hardening ratio is almost linear, while the dependence of peak residual stresses on changes in the yield limit indicates a quadratic relationship. The research indicates that in future applications, a simplified treatment of the rail/wheel interface is justified, as long as the peak pressure in the contact zone is estimated correctly. The residual stresses in rails induced by service conditions may reach very high values, on a par with the material yield limit. This effect is aggravated by the operating procedure of increasing wheel axle loads.
Abstract:An alternative design approach, helpful in the critical temperature evaluation for a gable steel frame exposed to fire, is proposed and discussed in this article. This approach is based on the specification of a system of equilibrium formulae, generalized to the case of fire. All these equations result from the graphical identification of the redundant bending moment distribution in the frame members relating to the particular collapse mechanisms being kinematically admissible. Only such a mechanism which corresponds to the activation of a suitable sequence of the appropriate number of plastic hinges while maintaining the requirements of the classical bending moment redistribution is recognized as conclusive for the considered frame structure.
Abstract:The paper is focused on the problem of durability of RC structure exposed to typical ambient conditions for bridges. The causes and degradation processes of the structures, mechanisms of concrete carbonation and chloride penetration are described. The theoretical model which allows for the prognosis of all changes affecting construction safety in time is presented. The findings of the theoretical analysis are compared with the results of the experimental research of a viaduct in a state of an advanced degradation as well as the material samples taken from it.
Abstract:This paper summarizes results of wind tunnel tests of a non-standard stadium roof. Aerodynamic laboratory studies were accomplished in a boundary layer wind tunnel. The main objective of the research was to determine the distribution of the mean wind net pressure coefficient over the stadium roof surfaces as affected by the aerodynamic interference between the stadium structure and a large oval sports event hall, located nearby. Interference coefficients of wind pressure and global wind forces acting upon the surfaces of the stadium roof were calculated. The aerodynamic studies showed a significant influence of the oval Atlas Arena sports-event hall on the wind load subjected to the stadium structure.
Abstract:This article presents and describes some qualitative changes that have occurred in the engineering design of building structures over the last forty years. With widespread access to computers and the development of software tools, optimization problems, which in the nineteenseventies were solved analytically or, when justifiable, using mathematical machinery (e.g. first Polish minicomputers type Odra 1,300) are now often settled through the use of specialized add-ins to spreadsheets. This state of affairs has created a basis for significant changes in the quality of educational opportunities in the context of construction faculties within technical universities. These changes are illustrated with a simple example of the optimization (determination of the dimensions of the beam subjected to bending).
Abstract:Structures located in areas affected by mining operation are subjected to movements and tilting. Continuous monitoring of the structure’s response to these forces allows for the control of their impact on the technical condition of the structure. In the case of railway structures, the measurements may allow further determination of the impact of modifications to the geometry of the structure on the track. This paper presents the results of observing indications of Structural Health Monitoring installed on an actual bridge construction under which mining operations were being conducted.
Abstract:The increasing interest in monitoring systems for soil displacements, prompted the authors to search for calculation methods which would allow the construction of monitoring devices without the need to place sensors in inclinometric tubes. The application of the spline interpolation method and the local approximation method by means of weighted moving squares allowed for the creation of curves which describe the soil deformation with the required accuracy. The basic equations of this calculation method and numerical examples are presented in the paper.