Algirdas Juozapaitis

Displacement analysis of asymmetrically loaded cable

Abstract A deformed state of parabolic shape suspension cable subjected to asymmetric loading is under consideration. The cable kinematic nature of vertical and horizontal displacements, resulted from complementary asymmetrically distributed load are investigated, the expressions for their maximum values are derived. The deformability of suspension cable versus its curvature increment is investigated. The possibilities to stabilise the primary parabolic shape of suspension cable subjected to an asymmetric load are examined. Numerical simulation results are presented.

Student progress assessment with the help of an intelligent pupil analysis system

Students and lecturers would like to know how well students have learned the study materials being taught. A formal test or exam would cause needless stress for students. To resolve this problem, the authors of this article have developed an Intelligent Pupil Analysis (IPA) System. A sufficient amount of studies worldwide prove an interrelation between pupil size and a persons cognitive load. The obtained research results are comparable with the results from other similar studies. The original contribution of this article, compared to the research results published earlier, is as follows: the IPA System developed by the authors is superior to the traditional pupil analysis research due to the integration of pupil analysis with subsystems of decision support, recommender and intelligent tutoring systems and innovative Models of the Model-base, which permit a more detailed analysis of the knowledge attained by a student. This article ends with a case study to demonstrate the practical operation of the IPA System.

Unconventional double-level structural system for under-deck cable-stayed bridges

This paper presents a new morphology of a cable-staying system for an under-deck cable-stayed bridge. The computational method proposed in the paper has been derived for a one-strut conventional cable staying system and applied for an unconventional double-level cable-staying system. The paper describes an algorithm for the correct implementation of the interaction between the cable-staying system and the deck. The numerical examples demonstrate that the proposed computational method based on a non-linear analysis of a simply supported and additionally restrained beam-column can be used for obtaining deformation response to the considered structure. An analysis of the same problem using finite element (FE) software ANSYS was carried out to present the accuracy of the proposed method. The paper also demonstrates comparison analysis between the conventional and unconventional structural schemes for the under-deck cable-stayed bridge under symmetric and asymmetric loading.

Mast behaviour analysis and peculiarities of numerical modelling

Abstract Paper is assigned to numerical analysis peculiarities of masts applying specialised computer‐aided design packages. Masts deformable behaviour is described as non‐linear one. The test problem of mast is solved by two widely applied in Lithuania computational packages STAADpro and Robot Millennium and the specialised programme for mast design SUDM. A corrected analytical method for mast guy analysis, taking into account a force component, acting along the guy supports. A performed numerical experiment is aimed to clarify the possibilities of the above‐mentioned numerical analysis instruments for geometrical non‐linear modelling of structure. The accuracy errors when determining the mast stress and strain fields by numerical analysis packages comparing with the ones obtained by a corrected analytical method are indicated. Possibilities of employing the considered computer‐aided design programming packages for practical design of masts are discussed.

Static behaviour analysis of masts with combined guys

Abstract The purpose of this study was to develop a new type of guyed mast that incorporates a complex guy cable system with a particular focus on the effect of static loading on the response mast behaviour. The intension of such solution is to increase a number of elastic supports for the mast shaft that will impact on its stability under loading. The static analysis of a one‐level guyed mast has been undertaken. The effects of geometrical and physical design parameters on the displacements of the mast were determined. The analysis is illustrated with two‐guyed masts: the bending moments and lateral displacements were determined for a typical guyed mast and guyed mast with combined guys.

Technical and economical effectiveness of the combined guys mast

Santrauka Straipsnyje aptariama nauja plieninio stiebo konstrukcija, kurioje taikomos kombinuotosios atotampos. Analizuojamas sios naujos konstrukcijos techninis ekonominis veiksmingumas pagal medžiagu sanaudu kriteriju. Pateikiamos analizines israiskos racionaliems stiebo kamieno lenkiamiesiems momentams apskaiciuoti ir rekomendacijos atotampu tvirtinimo koordinatems nustatyti. Atliktu skaitiniu eksperimentu parodyta, kad nauju kombinuotuju atotampu taikymas leidžia sumažinti bendrasias stiebo medžiagu (plieno) sanaudas.

Innovative structural system of steel roofs

Abstract A novel lightweight roof structural system consisting of strut-framed beams and flexible decking is discussed. Two types of upper chord of the strut-framed beam, continuous beam or pinned beam have been studied. The peculiarities of behaviour of these structures under load and the possibilities of optimal adjustment of stresses have been investigated. Comparative analysis of the two types of upper chord at a different number of intermediate supports and slenderness of the chords is presented. Evaluation of technical and economical efficiency of the strut-framed beams and flexible decking is presented.

Efficient technique for constitutive analysis of reinforced concrete flexural members

Abstract One of the most difficult issues in the theory of reinforced concrete (RC) is an adequate modelling of deformation behaviour, cracking and, particularly, post-cracking behaviour, as one of the major sources of non-linearity. Applying the concept of average cracking and average strains, deformation behaviour of RC can be modelled by stress–strain tension–stiffening relationships. The authors proposed an innovative inverse technique for constitutive modelling of flexural RC elements. The technique is based on the smeared crack approach and layer model of RC section. The inverse technique aims at deriving tension–stiffening constitutive models from experimental moment–curvature diagrams. The present analysis takes into account the shrinkage effect that is often neglected in other studies. Based on the inverse technique, free-of-shrinkage tension–stiffening relationships are derived using test data of shrunk RC beams. Examples of the application for the analysis of the experimental data obtained by the authors are presented to illustrate the calculation efficiency of the proposed technique.

Stochastic Tension-Stiffening Approach for the Solution of Serviceability Problems in Reinforced Concrete: Exploration of Predictive Capacity

Dealing with short-term deformations and the tension-stiffening effect in reinforced concrete (RC), the current study consists of two parts as presented in two separate manuscripts. Based on the test data of more than 300 RC ties, alternative tension-stiffening relationships of different complexity were proposed in the first article (Part I). In the companion manuscript (Part II), a stochastic modeling technique for assessing the deformation response of RC elements, subjected to different combinations of tension and flexure, is proposed. Based on stochastic principles, this technique allows not only to predict the average deformation response, but also to establish bounds of these predictions that are of vital importance for practical problems. The proposed technique is verified with the help of independent test data in order to validate the accuracy of the predictions of deformation, using the tension-stiffening models proposed in Part I of the article. Test specimens with different arrangements of steel or GFRP bars in the tensile zone were considered. The analysis has revealed that the influence of the degree of sophistication of the tension-stiffening models on the analysis results is smaller than the one of an adequate assessment of the shrinkage effect. The prediction accuracy is also related to the specific arrangement of reinforcement.

Biometric and Intelligent Student Progress Assessment System

A number of methodologies (Big Five Factors and Five Factor Model, intelligence quotient tests, self-assessment) and strategies for web-based formative assessment are used in an effort to predict a student’s academic motivation, achievements and performance. These methodologies, biometric voice analysis technologies and 13 years of authors’ experience in distance learning were used in development of the Biometric and Intelligent Student Progress Assessment System for psychological assessment of student progress. Also the BISPA system was developed in consideration of worldwide research results involving the interrelation between a person’s knowledge, self-assessment and voice stress along with instances of available decision support, recommender and intelligent tutoring systems.