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The process of Structural Health Monitoring aims to detect changes in material and/or geometric properties, boundary conditions or member connectivity of a structural system in time. However, the transfer of research results into engineering practice poses several challenges, especially for stiff structures with very diverse geometry that could not be well dynamically exited like low and medium-rise structures under ambient vibration conditions. Noise in modal parameters from output-only modal analysis due to variable environmental and operational conditions is considered one of the most problematic aspects of detecting structural damage using a vibration-based method. This research proposes a new way to reduce environmental noise in vibration data and dynamic parameters by merging dynamic response data from two similar shear wall buildings. The object of the study is a three-story reinforced concrete building. First, the damage features as natural frequencies and zero-order temporal moment of the vibration response are studied. Further, those feature changes are explored by means of modelling wall removal/opening introduction into the finite element models. It is established that the variation in the base excitation spectrum has more impact on dynamic response than introduced structural changes. Therefore, a time-domain feature like a zero-order temporal moment of the vibration response is not applicable for the proposed method. The appropriate damage sensitive feature vector for this approach is the difference of natural frequencies from two monitored buildings. The proposed method for fusion of vibration information from several buildings that share the same environmental and operational conditions filter out environmental noise effectively and give a clear advantage in reducing false alarm possibility during continuous and automated structural health monitoring process.

High-performance fibre-reinforced concrete is gaining popularity due to fibres ability to improve the poor properties of high-performance concrete. High-performance materials make using of thin-wall structures possible. Square section with square hollow provides decreasing of non-renewable material consumption, column’s high stiffness in the both planes and possibility to integrate the engineering communication inside of columns. The current study focuses on the development of analytical simplified calculation method that approximate output results of finite elements calculations for columns under eccentric loading with complicate hollow square-section. Analytical simplified calculation method to determine column’s load-carrying capacity is developed as the second-degree polynomial equation which is based on response surface method. The variables of equation are column height and material consumptions of the high-performance fibre reinforced concrete and steel of the additional longitudinal reinforcement. Data set of 27 experiments calculations was used to get the coefficients of adequate equation. Based on the results, the obtained equation makes it possible to predict the load-carrying capacity of the column in selected the factors interval on which a function was defined with sufficient precision. The difference between load-carrying capacities determine by numerical model based on the finite element method and by obtained second-degree equation does not exceeds 3.3%.

Global vibration-based methods in the field of structural health monitoring are intended to capture structural stiffness changes of buildings or other civil engineering structures. Natural frequencies of buildings or bridges are commonly used parameters to monitor these stiffness changes. Therefore, it is essential to clarify the limit at which this method is no longer sensitive enough to be useful for structural health monitoring purposes. This paper numerically investigates the effect of structural damage and soil–structure interaction on cellular-type reinforced concrete buildings' natural frequencies. These buildings are a common housing stock of Eastern Europe but are rarely investigated in this context. Comparisons with a reinforced concrete frame and infill structure building are made. Finite element models representing three structural system types of nine-story reinforced concrete buildings were used for the numerical simulations. Furthermore, a five-story finite element model was used for a damage sensitivity comparison. It is established that, for cellular-type structure buildings to detect damage comparable to that investigated in the paper, structural health (fixed base model frequency) should be monitored directly. Then, a statistical significance level for frequency changes of no more than 0.1% should be adopted. Conversely, the rocking frequency is a very sensitive parameter to monitor building base condition changes. These changes are often a cause of the cracking of building elements. [ABSTRACT FROM AUTHOR]

Highlights • A numerical method for design of beams and frames with complex topology is proposed. • The method is based on extended multi-scale finite element method. • This finite element technology is validated and tested using beam and frame structures. • By reducing length of extra window, the displacement continuity increases and stress fields are more accurate. Abstract A numerical method for design of beams and frames with complex topology is proposed. The method is based on extended multi-scale finite element method where beam finite elements are used on coarse scale and continuum elements on fine scale. A procedure for calculation of multi-scale base functions, up-scaling and downscaling techniques is proposed by using a modified version of window method that is used in computational homogenization. Coarse scale finite element is embedded into a frame of a material that is representing surrounding structure in a sense of mechanical properties. Results show that this method can capture displacements, shear deformations and local stress-strain gradients with significantly reduced computational time and memory comparing to full scale continuum model. Moreover, this method includes a special hybrid finite elements for precise modelling of structural joints. Hence, the proposed method has a potential application in large scale 2D and 3D structural analysis of non-standard beams and frames where spatial interaction between structural elements is important. [ABSTRACT FROM AUTHOR]