Lightning protection of tanks is important problem as accidents can cause catastrophic consequences for people, infrastructure and environment. In the article analysis of typical defects of steel lightning rod towers' flange connections is carried out. 16 towers built in 2000 in Novorossiysk as a part of oil tank farm were studied. Each 55-meter tall tower consists of 3 girths and 3 sections with bolted flange connections. During the analysis of technical documentation the following common defects were observed: cracks and deformations of girths near welding joints that connect them with reinforcing ribs; gaps between flanges and their radial displacement; weld leg lengths longer than allowed; presence of water, biological damage and corrosion. Reasons of said defects are analyzed. They consist of non-compliance with regulatory requirements during welding as well as insufficient attention to the thermotechnical issues. Recommendations for the repair and safe exploitation of lightning rod towers are given. The results can be used during the technical inspection of steel lattice towers with flange connections.

Keywords: bolt, bolted flange joint, defect, flange, inspection, joint, lattice tower, lightning rod, steel, steel tower

Research of modeling methods of steel structures's joints with the use of computer-aided engineering (CAE) systems is important, because scheme that most accurately reflects an actual state of the elements makes it possible to select their rational design. The aim of the article is to analyze an influence of modeling variations of truss joints on the stress state of a transverse frame. The object of the research is the plane frame of a two-story building with the truss made of hot-rolled steel equal leg angles. The subject of the study is the stressed state of the structure. In the article the following problems are solved: two models of the frame (with flexible and rigid truss joints) were created with the use of LIRA-SAPR CAE program, loads were calculated, results were obtained, the values ​​of bending moments and shear forces in the elements were analyzed. Conclusions were drawn about the influence of variant modeling of truss joints on the stress state of construction.

Keywords: CAE, flexible joint, joint, plane frame, rigid knot, static scheme, steel, steel angle, stress-strain state, truss

High-rise buildings with CLT (cross-laminated timber) load bearing structures are being more actively developed in many countries. CLT-panels are lightweight, ecological and easy to assemble. In the article types of strengthening of three-layers and five-layers CLT-panels with carbon, basalt and flax fiber reinforced polymers (FRP) are considered. They can be used for panels under exploitation to reduce influence of defects and increase load bearing capacity and stiffness or in the production stage to reduce thickness and weigth of constructions. Known works of international authors are analyzed. Bending behaviour of externally reinforced CLT-panels is described. Areas that deserve further investigation are determined. They include investigation of different composite materials and wood types used for CLT-panels' production.

Keywords: CLT, composite, cross-laminated timber, external strengthening, FRP, high-rise building, lamella, reinforcement, timber structure, wood

Building information modeling (BIM) creates new opportunities not only in design and construction life cycle's phases, but also in operation of buildings. One of the most promising fields is historical building information modeling (HBIM). In the article areas of BIM's application during inspection and monitoring of timber strutures of historical buildings are outlined. Creation of 3D model of objects with complex geometry and structures with variable cross-sections is described. Questions of early warning system's creation during structural health monitoring (SHM) of buildings are considered. Works of domestic and international authors are analyzed. Areas that deserve further investigation are determined. They include integration of BIM with geographic information systems (GIS) and non-destructive testing (NDT) methods, creation of database of defects of buildings and structures.

Keywords: architectural monument, BIM, defect, early warning, HBIM, inspection of buildings, NDT, SHM, technical condition, timber structure

The use of composite materials based on epoxy matrix and carbon or glass fibers for strengthening of existing timber structures of buildings is analyzed. Main benefits and limitations of composite materials are discussed. High tensile strength and stiffness, light weight, corrosion and chemical resistance and relative ease of application without changing the static scheme of structures or stopping exploitation makes fiber reinforced polymers (FRP) suitable for strengthening of timber structures, including those in cultural heritage buildings. Application of FRP in the tension zone of elements under bending helps to arrest crack opening caused by defects and to better exploit the plastic compressive behavior of wood. The use of FRP is limited by their cost, low thermal resistance and limited research and normative documents base. Concluded that further study of materials properties, behaviour of strengthened elements under different types of loading, strength and durability of a bonded joint under different temperature and moisture conditions is required.

Keywords: external strengthening, timber structure, wood, composite, lamella, reconstruction, fiberglass, carbon fiber, reinforcement, epoxy resin

Analysis and comparison of Russian and European standards for mechanical strength of windows, such as resistance to racking and static torsion, are provided. Classification of mechanical properties of windows according to EN 13115:2020, normative characteristics of resistance to static loads according to GOST 23166-99 and recommendations of Quality Assurance Association for Windows and Doors (Germany) are compared. Russian requirements for resistance to racking are higher than 4th class, but for resistance to static torsion are lower than 2nd class of EN 13115, while 3rd class is recommended as minimum by German RAL-Association. Analysis of methodology for mechanical tests in accordance with GOST 24033-2018 and GOST 24033-80 is done. Concluded that refinement of methodology and criteria for determining test results with taking into account the provisions of European standards is necessary, as well as conduction of further research in the field of influence of mechanical strength of windows on other qualities, such as air permeability.

Keywords: window, translucent structure, enclosing structure, standardization, standard, mechanical strength, racking, static torsion