Theoretical and experimental analysis of load-carrying capacity of steel-concrete composite beams with glass-fibre-concrete slab
The paper deals with the problems of the theoretical and experimental investigation of load-carrying capacity of steel-concrete composite beams with glass-fibre-concrete (GFC) slab. The paper presents some selected results of the more extensive research realized on the authors workplace and oriented to the utilization of high-strength steels and high-performance concretes in steel-concrete composite structural members. This paper is directed towards one part of this research only, which represents theoretical analysis of the bending moment capacity and experimental verification of the actual bending moment capacity of steel-concrete composite beams with glass-fibre-concrete (GFC) slab in connection with their actual behaviour and corresponding relevant failure mechanism. Within the framework of the bending moment capacity analysis four basic types of beams have been (or will be, respectively) investigated, all of them composed of 3 different steel IPE cross-sections (IPE180, IPE200, IPE220) and concrete slab: (i) beams with GFC slab without usual steel reinforcement subjected to sagging bending moment, to investigate the contribution of GFC only to the sagging moment capacity; (ii) beams with GFC slab with steel reinforcement (reduced amount) subjected to sagging bending moment, to investigate the contribution of GFC slab and steel reinforcement together to the sagging moment capacity and to compare it with the first case; (iii) beams with plain concrete (PC) slab subjected to the sagging bending moment, to compare the results with the first case only; (iv) beams with GFC slab without steel reinforcement subjected to hogging bending moment, to verify the contribution of GFC to the hogging moment capacity. During the experimental parts of this research in common 27 loading tests of steel-concrete composite beams have been realized so far (but no all results are evaluated in detail so far) and other 9 specimens will be tested immediately. The attention was paid mainly to the following significant problems: the efficiency of the utilization of fibre-concrete slab in steel-concrete composite beams subjected to sagging or hogging bending moments, too; the effectiveness of the contribution of glass-fibre-concrete to the moment capacity of steel-concrete composite beams in comparison with reinforced concrete and plain concrete. Key-Words: Composite member, steel-concrete beam, glass-fibre-concrete, load-carrying capacity, resistance, sagging bending moment, experimental verification, theoretical analysis.
Design assisted by testing applied to the determination of the design resistance of steel-concrete composite columns
The paper is focused on the problems of the philosophy, methodology and application of the design assisted by testing. In this paper the examples of the application of the methods for the design resistance determination based on this approach are shown, mainly. The examples presented here are especially oriented to the determination of the design resistance of steel and steel-concrete composite columns composed of high-strength materials and the comparison of these two cases from the viewpoint of the material properties of steel and concrete and their statistic parameters, which can significantly influence the resulting design resistances. The rules for the design resistance of steel-concrete composite columns given in EUROCODE 4 are generally valid for the steel grade up to S420 and concrete class up to C50/60 only. Because high-strength steels and concretes are utilized more widely even for compression structural members, it is needed to verify the usability of the normative rules also for these ones. One of the possible ways can be the experimental verification of the failure mechanisms and load-carrying capacities, which gives information and knowledge on the real behaviour of these structural members in the loading process, and subsequent elaboration and correct statistic, respectively probabilistic evaluation of the test results. For the design resistance determination the methods of the design assisted by testing are suitable, namely because they are usable for the evaluation of small or even too small number of the tests.
An operational method for estimating signal to noise ratios from data acquired with imaging spectrometers
A method, using the concept of local means and local standard deviations of small imaging blocks and using a box counting procedure, has been developed for unsupervised estimation of the average signal to noise ratios of images in which the noise is additive. The method has been applied to simulated images with Gaussian noise, to images acquired with the Airborne Visible Infrared Imaging Spectrometer and with the Geophysical and Environmental Research Imaging Spectrometer. The method is compared with other techniques for estimating signal to noise ratios from imaging data. It is believed that the method is generally applicable to images having many small homogeneous blocks. Because the method does not take into account interband effects, it is not appropriate to use the method to estimate signal to noise ratios from images having nonnegligible interband radiometric calibration errors at spatial scales less than or equal to the size of the small imaging blocks used in the noise estimation.