Iztok Peruš

TORSIONAL EFFECTS IN THE PUSHOVER-BASED SEISMIC ANALYSIS OF BUILDINGS

The general trends of the inelastic behaviour of plan-asymmetric structures have been studied. Systems with structural elements in both orthogonal directions and bi-axial eccentricity were subjected to bi-directional excitation. Test examples include idealised single-storey and multi-storey models, and a three-storey building, for which test results are available. The response in terms of displacements was determined by nonlinear dynamic analyses. The main findings, limited to fairly regular and simple investigated buildings, are: (a) The amplification of displacements determined by elastic dynamic analysis can be used as a rough, and in the majority of cases conservative estimate in the inelastic range, (b) Any favourable torsional effect on the stiff side, which may arise from elastic analysis, may disappear in the inelastic range. These findings can be utilised in the approximate pushover-based seismic analysis of asymmetric buildings, e.g. in the N2 method. It is proposed that the results obtained by pushover analysis of a 3D structural model be combined with the results of a linear dynamic (spectral) analysis. The former results control the target displacements and the distribution of deformations along the height of the building, whereas the latter results define the torsional amplifications. The proposed approach is partly illustrated and evaluated by test examples.

A NON-PARAMETRIC APPROACH TO ATTENUATION RELATIONS

Abstract A non-parametric multidimensional regression method is proposed for the prediction of seismic ground motion parameters. The main features which distinguish the method from standard regression procedures are: (1) The relationship between the input and output variables is not selected a priori by a prediction law, (2) an arbitrary number of input variables Can be taken into account, provided that an appropriate data base exists, and (3) the computational procedure is very simple. The results can be easily updated when new information becomes available. The method has been applied for the derivation of attenuation relations by using a combination of databases compiled by other researchers. In the majority of the cases discussed in this paper, the method was used for the prediction of horizontal peak ground acceleration as a function of magnitude and distance. In some cases, ground conditions were also taken into account. Some results on the attenuation relations of peak ground velocity and displacem...

A non-parametric CAE approach to office rents: Identification of Helsinki metropolitan area submarkets

The study attempts to identify and estimate the office rents of submarkets in the Helsinki metropolitan area. We applied a non-parametric empirical approach called the CAE method to identify six parameters: highway APD (access point distance), car traffic density, light rail APD, main retail distance, office building density and effective age. Our results suggest that car traffic density is the single most influential parameter. Office rent decreases with effective age and increases with the density of office buildings. Longer distances to highway access points and to the main retail centres decrease office rents, while shorter distances to the light rail access points increase office rents in general and particularly for locations close to highway access points. We identified local peaks by inspecting multiple graphs. The local peaks were considered evidence for the existence of commercial office submarkets within the Helsinki metropolitan area. We identified seven submarkets at different rent levels. Interpreting submarkets from the CAE graphs allowed us to recognise particular business districts in the Helsinki metropolitan area. In addition, it is of great significance that the roles of the given and estimated variables can be exchanged. The method is directly applicable in real estate studies using adapted database and prescribed smoothing parameters.

Assessment of the seismic performance of low-rise RC structures by procedures with different levels of complexity

In the paper, five procedures for the assessment of the seismic performance of low-rise RC buildings at different levels of complexity are presented and discussed. They include simple procedures based on methods originally developed in Japan (levels 1 and 2), the N2 method with two variants of the mathematical model (levels 3 and 4), and non-linear dynamic analysis (level 5). The procedures have been applied to seismic assessments of three RC building structures. A small difference between the N2 and NDA results was observed, whereas the results of the procedures at the first two levels are much more conservative. On the other hand, the amount of input data and of computational work increases with the increasing complexity level. Research is still needed on the definitions of capacities, especially the shear capacity of the structural members, and on the capacity of the whole structure. The initial effective stiffness of the structure proved to be the most important quantity which determines the seismic demand.

Wear Progress of Nitrided Layer at Low, Medium and High Contact Pressures During a Laboratory Simulation of Aluminium Hot Extrusion

The progress of wear associated with the compound and diffusion layers of nitrided samples was studied by employing laboratory tests at low, medium and high contact pressures, simulating the conditions occurring during the hot extrusion of aluminium. It was found that with increasing of contact pressure also wear rates increase that indicates on predominately frictional removal of compound layer which was confirmed by scanning electron microscopy and back-scattered electron micrographs as well as energy-dispersive spectroscopy analysis of tested surfaces. Testing at medium contact pressures reveals some common features observed at testing at lower as well as at higher contact pressures. The essential difference between the testing at medium and low contact pressures is in the density of the obtained micro-craters and appearance of their extension in sliding direction at medium contact pressures. At higher contact pressure, removal of compound layer is already preferentially oriented in sliding direction in the first stage, while at medium contact pressure, this is observed only in later stages of degradation progress.

Re-using Engineering Tools: Engineering SaaS web application framework

While early days of structural analysis (and other engineering) software have been dominated by self-developed and self-maintained programs and applications, most of these tools have lately been abandoned in favor of out-of-the-box commercial software packages, usually due to the inability to cope with the advancements in the computer industry from both software and hardware perspective. Even though the computational engines of these software tools and applications are still sound, the pre- and post-processors are outdated and not suitable for the modern engineering use. On the other hand, the last decade offered simple, intuitive, effective and widely accessible services of the modern web resulting in the fusion of services blurring the boundaries between desktop computers, laptops and other consumer devices. Consequently, more and more applications are developed as web services, moving from desktop environment to the browser. This paper presents the architecture, development and deployment of the web application framework that can transform console standalone tools into fully functional web applications. The framework was developed following the principles of the service-oriented architecture using cloud computing guidelines and the software-as-a-service model of deployment. The use of modern web programming principles and techniques provides the ability to use the framework on a wide range of consumer devices while the underlying high performance/throughput computing system ensures scalability, flexibility and performance. Last but not least, two case applications utilizing the proposed framework are presented.

Determination of scrap/supply probability curves for the mechanical properties of aluminium alloys in hot extrusion using a neural network-like approach

In this paper a neural network-like approach that accounts for the different uncertainties in the hot extrusion of AA6082 alloys is given. The results, presented in the form of scrap/supply curves, suggest the use of a probabilistic approach in the process of hot extrusion. The proposed approach considers both the epistemic and aleatory uncertainties and takes into account all the available influential input variables. The use of the CAE neural network, which is a special type of probabilistic neural network, is proposed as a powerful tool in the design and partial optimization of the hot-extrusion processes in real, industrial aluminium production. It was found that mechanical properties and the yield can be additionally optimized by reducing the epistemic uncertainties, which consequently requires more accurate measurements and more reliable control of the production processes.

Seismic Assessment of RC Frame Buildings

In the chapter, the N2 method and the non-linear dynamic analysis (NDA) are applied for the assessment of seismic performance of two variants of a 4-storey reinforced concrete (RC) frame building. The first variant is represented by the bare frames, whereas in the second variant infill panels are included in the upper three storeys, thus creating a soft first storey structure. In one direction, the results clearly show the detrimental effect of infills which generate a storey mechanism instead of a global mechanism which occurs in the case of the bare frame structure. In the other direction, a story mechanism occurs also in the case of the bare frame structure. The infills shift the mechanism from the third to the first storey. There is good agreement of the results obtained by the N2 method and NDA. The results indicate that both variants of the building are able to survive the design ground motion.

A Toolbox and Web Application for the Seismic Performance Assessment of Buildings

A software tool, known as a PBEE toolbox, for the seismic performance assessment of buildings, which was developed in Matlab in conjunction with the software framework OpenSees, and a web application for the prediction of approximate IDA curves are presented in this chapter. Although, in its present version, the PBEE toolbox supports only simple nonlinear models, its capabilities exceed usual software tools for computational simulation, since it enables seismic performance assessment of buildings with various procedures and adopts an open-source philosophy so that it can be easily extended or modified to suit specific user requirements. The capabilities of the PBEE toolbox and the web application, which involves the response database of a single-degree-of-freedom system with a quadrilateral force-displacement relationship, are demonstrated by means of an assessment of the seismic response parameters of an eight-storey reinforced concrete frame, using incremental dynamic analysis, progressive incremental dynamic analysis, approximate incremental dynamic analysis, and the N2 method. It is shown that, for the case of the presented example, all the methods produce similar results, although each method has some advantages and some disadvantages.

Amelioration of surface cracking during hot rolling of AISI D2 tool steel

ABSTRACT Reported is a relationship between a profile edge cracking during hot rolling of AISI D2 tool steel and material and processing parameters. Several months of observation of industrial hot rolling was done for neural network analysis and complemented with equilibrium thermodynamics calculations and laboratory hot deformation tests. Industrial results, in general, show that for the same chemical composition, hot rolling yield decreases with an increased profile aspect ratio. Cr content is significant for the soaking and strongly correlated with a hot workability at upper and lower limits of the hot working temperature range. Laboratory hot compression tests were employed to determine the optimal soaking temperature and to study hot workability to expand safe hot working temperature window.