Vadims Goremikins

Decreasing displacements of prestressed suspension bridge

Abstract A suspension bridge is the most suitable type for a long-span bridge due to rational use of structural materials. Increased deformability, which is conditioned by the appearance of the elastic and kinematic displacements, is the major disadvantage of suspension bridges. The problem of increased kinematic displacements under the action of symmetrical and non-symmetrical load can be solved by the prestressing. A prestressed suspension bridge with span of 200 m was considered as an object of investigations. The cable truss with the cross web was considered as the main load carrying structure of prestressed suspension bridges and was compared with the single cable. The considered prestressed suspension bridge was investigated by the FEM program ANSYS 12 and by the small scale physical model. Rational, from the point of view of minimal vertical kinematic displacements, main load-carrying structure of prestressed suspension bridge was developed. The obtained results shows, that usage of cable truss wit...

EXPERIMENTAL METHOD ON INVESTIGATION OF FIBRE REINFORCED CONCRETE AT ELEVATED TEMPERATURES

Generally speaking, adding a certain amount of steel fibres to a concrete mixture improves its mechanical properties. Currently, a lack of information considering tensile and post cracking behaviour of FRC at elevated temperatures is an issue to be faced. An experimental study of steel fibre reinforced concrete, also containing polymer fibres (FRC), subjected to high temperature is presented herein. Compressive strength, split tensile strength and ultimate bending strength were evaluated. Specimens were heated by the use of ceramic heaters and repacked for testing consequently. A finite-element based model was developed to predict the temperature distribution inside a specimen during both the heating and the cooling process.

Fire design of arch-type timber roof

N.I. Vatin, Peter the Great St. Petersburg Polytechnic University, St. Petersburg, Russia Студент Т. Сакните, д-р техн. наук, профессор Д.О. Сердюк, д-р техн. наук, ведущий научный сотрудник В.В. Горемыкин, д-р техн. наук, руководитель кафедры Л. Пакрастиньш, Рижский технический университет, Рига, Латвия д-р техн. наук, директор Инженерностроительного института Н.И. Ватин, Санкт-Петербургский политехнический университет Петра Великого, СанктПетербург, Россия

Prestressed Cladding Elements for Tensioned Structures

Two types of prestressed cladding elements for the long span cable roofs were investigated. The first considered type of prestressed cladding element was pneumatic and formed by the generally woven by the basket weave fabric from the Vectra (LCP) yarns, which is covered by the PoliTetraFluoroEthylene (PTFE) copolymer foil, and compliant contour, consisting from the several glued together layers of the mentioned covered fabric. The second considered type of prestressed cladding element was formed by the steel cables steel pipes and the same type of covered fabric as the first type. Rational from the point of view of materials consumption heights and levels of prestressing for two considered types of cladding elements were evaluated.

Experimental Determination of Natural Frequencies of Prestressed Suspension Bridge Model

Abstract A suspension bridge is the most suitable type for a long-span bridge. Increased kinematic displacements are the major disadvantages of suspension bridges. This problem can be solved by application of prestressed cable truss. Dynamic approach is one of regulated bridge design parts. Determination of natural frequencies of a physical model of a prestressed suspension bridge is presented in this paper. Natural frequencies, as mode shapes, of the model depending on a prestressing level were determined. It was shown that a mode shape with one half wave did not appear. Experiments showed that dynamic characteristics of prestressed suspension bridge could be regulated by changing a prestressing level, which excludeda possibility of resonance appearance.

Analytical model of composite floors with steel fibre reinforced concrete slab subjected to fire

AbstractUnder fire, membrane action plays an important role in the performance of slabs subjected to large deflections. In this paper, a new model is proposed based on a proper approximation of horizontal displacements for a simply supported composite slab. The novelty of the proposed approach consists in a special treatment of the system of shape functions for the “in-plane” displacements. Moreover, a load applied to the slab is divided into two components, so that one component is balanced by the membrane forces, while the second one is transmitted by the bending forces (including transfer of shear and moment). The deflection due to thermal elongations is replaced by the identical deflection caused by a fictitious load. Unknown parameters are calculated using the principle of virtual displacements. The effectiveness of the model is validated by the results obtained from experiments.

Design Methods for Load-bearing Elements from Crosslaminated Timber

Cross-laminated timber is an environmentally friendly material, which possesses a decreased level of anisotropy in comparison with the solid and glued timber. Cross-laminated timber could be used for load-bearing walls and slabs of multi-storey timber buildings as well as decking structures of pedestrian and road bridges. Design methods of cross-laminated timber elements subjected to bending and compression with bending were considered. The presented methods were experimentally validated and verified by FEM. Two cross-laminated timber slabs were tested at the action of static load. Pine wood was chosen as a boards material. Freely supported beam with the span equal to 1.9 m, which was loaded by the uniformly distributed load, was a design scheme of the considered plates. The width of the plates was equal to 1 m. The considered cross-laminated timber plates were analysed by FEM method. The comparison of stresses acting in the edge fibres of the plate and the maximum vertical displacements shows that both considered methods can be used for engineering calculations. The difference between the results obtained experimentally and analytically is within the limits from 2 to 31%. The difference in results obtained by effective strength and stiffness and transformed sections methods was not significant.

Experimental investigation on SFRC behaviour under elevated temperature

This work aims to present an experimental study of steel fibre-reinforced concrete (SFRC) subjected to high temperature, especially focusing on residual behaviour.,Compressive strength and split tensile strength of SFRC cubes and ultimate bending strength of prisms were evaluated under ambient and elevated temperatures. The specimens were heated by ceramic heaters and then repacked for testing.,The results showed that a compressive strength of SFRC is reduced by 38 and 66 per cent, tensile strength is reduced by 25 and 59 per cent and ultimate bending force is reduced by 33 and 56 per cent in case of 400°C and 600°C, respectively, comparing with ambient temperature.,The developed testing procedure could be used for determination of material properties of SFRC under elevated temperatures.

Behaviour of load-carrying members of velodromes’ long-span steel roof

Long-span roofs have been of an increased interest within the last sixty years. An archtype steel roof of velodrome with the maximum span, height, and length equal to 109.50, 23.07, and 126.00 m respectively, is considered as the object of the current investigation. The choice of the preferable structural solution and behaviour analysis of load-carrying members of the long-span arch-type steel roof of the velodrome is considered as the aim of the current study. The distribution of internal forces and stresses in the trihedral lattice steel arch with a triangular web such as displacements under the action of design loads were investigated for fixed, double-hinged, and three-hinged static schemes. It was stated that the preferable structural scheme is the fixed arch. Аннотация. Большепролетные крыши вызывают повышенный интерес в течение последних шестидесяти лет. Арковидная стальная крыша велодрома с максимальным пролетом, высотой и длиной, равными 109.5, 23.07 и 126 м соответственно, была выбрана как объект исследования. Выбор предпочтительного конструктивного решения и анализ поведения несущих элементов большепролетной арки велодрома является целью исследования. Распределение внутренних усилий и напряжений в элементах стальной арки с трехгранной решеткой, а также перемещения, под воздействием расчетной нагрузки были исследованы для защемленной, двухшарнирной и трехшарнирной статических схем. Было показано, что предпочтительной статической схемой для большепролетной арки является защемленная арка. Introduction Long-span roofs have been of an increased interest among civil engineers and architects within the last sixty years [1]. Structures with one span cause a special interest due to the possibility to use the rational internal space for several types of residential and industrial buildings [2]. Sporting halls, indoor swimming pools, velodromes, ice halls, exhibition and concert halls, market halls as well as roofs of railway stadiums, buss stadiums, and airports are examples of such residential buildings [3]. Buildings in the aircraft industry and plants for producing structures with overall dimensions such as storages of bulked materials are examples of such industrial buildings [4]. The length of the buildings spans changes within the limits from 30 to 70 m [5]. The buildings with especially long spans within the limits from 70 to 300 m are used quite rarely [6, 7]. The interior of the velodrome where spans of the roof׳s structures change within the limits from 50 to 80 m is shown in Figure 1.

CONSTITUTIVE MODEL OF STEEL FIBRE REINFORCED CONCRETE SUBJECTED TO HIGH TEMPERATURES

Research on structural load-bearing systems exposed to elevated temperatures is an active topic in civil engineering. Carrying out a full-size experiment of a specimen exposed to fire is a challenging task considering not only the preparation labour but also the necessary costs. Therefore, such experiments are simulated using various software and computational models in order to predict the structural behaviour as exactly as possible. In this paper such a procedure, focusing on software simulation, is described in detail. The proposed constitutive model is based on the stress-strain curve and allows predicting SFRC material behaviour in bending at ambient and elevated temperature. SFRC material is represented by the initial linear behaviour, an instantaneous drop of stress after the initial crack occurs and its consequent specific ductility, which influences the overall modelled specimen behaviour under subjected loading. The model is calibrated with ATENA FEM software using experimental results.