Thesis for the scientific degree of Doctor of Technical Sciences in specialty 05.23.01 «Building constructions, buildings and structures» (19 – Architecture and Civil Engineering). – State higher educational establishment «Prydniprovska State Academy of Civil Engineering and Architecture» of the Ministry of Education and Science of Ukraine, Dnipro, 2020.
The thesis is devoted to the solution of the actual scientific and practical problem of calculation and design of hybrid timber-reinforced concrete multi - storey buildings taking into account the deformation diagrams, creep of the materials and the parameters of the ecological impact on the environment during the life cycle as well as the demands of reliability, load bearing capacity and serviceability.
The analysis of researches and projects in the field of multi-storey construction using timber structures showed that the use of wood is a promising direction in the context of sustainable development and circular economy. Today there is a limited number of theoretical and experimental studies of joint work of timber and reinforced concrete load-bearing structures in the spatial system of multi-storey buildings, their calculation and design as well as a lack of integrated standards for the assessment of harmful emissions of the building.
The classification of structural systems of hybrid timber-reinforced concrete multi-storey buildings on the basis of the nature and method of distribution of load-bearing functions between elements and the material of the vertical load-bearing structures, as well as structural solutions of prefabricated monolithic and prefabricated timber-reinforced concrete floors, typical joints of load-bearing structures.
The stress-strain parameters of hybrid timber-reinforced concrete multi-storey buildings depending on the type of structural system are established. Using the prototype building, the choice of structural scheme and method of ensuring the spatial rigidity of hybrid reinforced concrete multi-storey buildings up to 20 floors are substantiated. The following systems were considered: frame, combined frame with stiffness diaphragms and rigidity core, combined frame with rigidity core and outriggers at different levels. The method of providing spatial rigidity taking into account the dependences of "stress-strain" and creep properties of materials was proposed.
A significant difference in the deformation characteristics and creep causes the appearance of nonuniform vertical displacements, which causes the skew of the floor cells and the appearance of the additional tensile longitudinal forces in the floor beams. A method for compensating for nonuniform vertical displacements of load-bearing structures of hybrid timber-reinforced concrete multi-storey buildings was proposed, which consists in correcting the cross-sectional dimensions of vertical elements.
Based on the results obtained, the recommendations for the calculation of hybrid timber-reinforced concrete multi-storey buildings are formulated, which include the requirements for the physical model of the building, assignment of material characteristics, methods for determining of the stress-strain state parameters, joints modeling and necessary checks according to the calculation results.
The complex of experimental studies of materials and products for use in multi-storey buildings of the hybrid system is carried out. The data on physical and mechanical characteristics of glued timber, load-bearing capacity and deformability of real-scale beams, dowelled joints and joints on metal toothed plates were obtained.
Experimental studies of full-scale bolted joints on metal plates on tension parallel to the grain, as well as of connections of timber elements on metal toothed plates for tensile and bending were performed. An empirical model is proposed to describe the "load-displacement" diagram of the connection on metal toothed plates (MTP) depending on the direction of the fibers to take into account the nonlinear behaviour of the connection on mechanical connections when calculating hybrid structures.
The results of the conducted research are the development of a general methodological approach, basic principles and methods of calculation and design of hybrid timber-reinforced concrete multi-storey buildings, considering the deformation diagrams, creep of the materials and substantiation of their application in terms of life cycle sustainability and circular resource efficient economy criteria as well as in accordance with the demands on reliability, load-bearing capacity and serviceability.
Keywords: hybrid timber-reinforced concrete multi-storey building, structural system, connection, stress-strain state, displacement, timber-reinforced concrete floor, carbon footprint.
