Abstract. Lattice timber structures, which are made of elements connected by punched steel plates, are widely used for residential and industrial buildings. The main types of the structures are trusses, frames, and arches, which enables covering spans up to 30 m and more. The behavior of structures on fire plays an important role in the design process of the structures. The cylindrical roof with a 30 m span and the main load-bearing structures of lattice arches with elements connected by punched metal plates was considered as an object of investigation. The rational geometrical parameters of a lattice timber arch with punched steel plated joints were evaluated. Fire resistance and a possibility to increase it for an arch-type timber roof was also considered. It was obtained that using a protective layer is a preferable method of a fire resistance increase for the lattice timber arch due to arch joints; the material consumption was also increased by 1.65 times. It was shown that the rational values of the height of the arch, depth of the arch cross-section, and distance between the nodes on the top chord are equal to 7.85, 1.10, and 0.95 m respectively.Аннотация. Решетчатые деревянные конструкции с узлами, выполненными с применением зубчатых стальных пластин, широко используются в промышленном и гражданском строительстве. Фермы, рамы и арки являются основными типами данных конструкций позволяющих перекрывать пролеты до 30 м и более. Оценка огнестойкости конструкций имеет большое значение при проектировании. Цилиндрическое покрытие пролетом 30 м с главными несущими элементами в виде решетчатых деревянных арок с узлами, выполненными с применением зубчатых стальных пластин, рассмотрено в качестве объекта исследования. Рациональные с точки зрения расхода конструктивных материалов геометрические параметры цилиндрического покрытия определены при помощи численного эксперимента. При этом произведена оценка огнестойкости основных конструктивных элементов, а так же возможности ее повышения. Показано, что наиболее эффективным способом повышения огнестойкости решетчатых деревянных арок является использование защитных покрытий. Расход конструктивных материалов при этом возрастает в 1.65 раз. Показано, что рациональные с точки зрения расхода материалов величины высоты арки, высоты сечения арки и длинны панели верхнего пояса равны 7.85, 1.10 и 0.95 м, соответственно.

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 with the cross web as the main load carrying structures of prestressed suspension bridge in comparison with the single cable, reduces vertical displacements upwards by 63.1%, downwards by 1.8% and total displacements by 29.6% under the action of worth situated load.

Cable truss usage allows developing bridges with reduced requirements for girder stiffness, where overall bridge rigidity is ensured by prestressing of the stabilization cable. The advantages of prestressed suspension trusses to provide required stiffness without massive stiffness girders and the ability of cross-laminated timber to behave in both directions are combined in the analysed structure. Prestressed cable truss with coincident (unclear meaning, difficult to translate) in the centre point of the span main and stabilization cables and vertical suspenders only was considered as the main load carrying system in the considered structure of suspension bridge. Two numerical models evaluated influence of cross-laminated timber deck on the behaviour of prestressed cable truss. Two physical models of the structure with the span equal to 2 m were developed for verification of the numerical models. The first physical model was developed for the case, when panels of the deck are placed without clearances and behaving in the longitudinal direction in compression so as in the transversal direction in bending. The second physical model was developed for the case when panels of the deck are placed with clearances and are behaving in the transverse direction in bending only. The dependences of maximum vertical displacements and horizontal support reaction of the cable truss on the intensity of vertical load in cases of symmetric and unsymmetrical loading were obtained for both physical models. Possibility to decrease the cable truss materials consumption by 17% by taking into accountcombined work of prestressed cable trusses and cross-laminated timber panels was stated.

No abstract

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.