Dynamic Characteristics Of Building Research Articles

Computational Models of Dynamic Load Sources for Modeling of Construction Structures Operation Used in Monitoring of Technical Condition of Buildings and Structures

This research aims to develop principles for assessing the impact of mega-cyclic vibrodynamic loads on the reliability of construction structures. The relevance of the reasons for the development and improvement of algorithms for numerical modeling of multicycle dynamic loads on building structures is due to the steadily increasing intensity of such loads on buildings and structures in megacities, as well as the acute practical problem of significant differences in the dynamic characteristics of buildings and structures obtained as a result of mathematical modeling and determined by experimental methods. The article presents research materials on computational equivalent models of dynamic load sources for numerical modeling of the behavior of construction structures under their influence, using the method of vibroacoustic analogies. The article examines models of sources of dynamic impact on construction sites. Algorithms and final formulas for computational modeling of the simplest sources of dynamic load are developed using the method of vibroacoustic analogies. The dynamic properties of the simplest dynamic load sources were analyzed. A significant difference between the computational models of real and ideal dynamic load sources. The article presents research and development results intended for calculating the distribution of dynamic loads on elements of construction structures in industrial and civil engineering projects located in areas with high levels of transport vibrodynamic impacts. An important property of the proposed computational equivalent models of sources of dynamic impact on building structures is the possibility of computational verification of critical elements, points, or nodes of load-bearing structures of buildings and structures under dynamic overloads. The position of these critical elements, points, and nodes of load-bearing structures under dynamic loads can differ significantly from their position determined using static and quasistatic computational modeling methods.

Исследования математических моделей процессов деформаций зданий и сооружений

Purpose. The article is aimed at analyzing changes in the dynamic characteristics of a building and establishing the dependence of shear deformation accelerations on the building's storey to predict the effect of seismic vibrations on the technical condition of the building, taking into account the engineering and geological properties of the foundation. Methodology. A number of instrumental observations using geodetic devices, automated monitoring systems and engineering seismic stations were made to study the issues of assessing changes in the dynamic characteristics of high-rise buildings and structures. To create mathematical models of deformation processes of buildings and structures, the study of interaction of structural elements of the building with the engineering-geological structure of the ground in the upper and lower parts of the megapolis was proposed. Findings. The results on ground shaking intensity acceleration, effective duration, spectral coefficients and periods of spectrum maximum are obtained. The results of measurements of vibrations on different floors of a high-rise building based on instrumental records of seismic station of local and distant earthquake have been obtained. Dependences of accelerations of shear deformations on the floor of the building with regard to engineering-geological properties of the base have been established. Predictive models of deformation processes of the building taking into account dynamic characteristics of ground vibrations and energy class of earth crust movements have been proposed. Originality. The analytical technique of correlation analysis of random variables is proposed, by means of which normally distributed linear and nonlinear processes are studied to create a mathematical model of deformation processes of buildings of different storeys. Practical value. The obtained results of the study of deformation processes of buildings and their structural elements allow to predict the dynamic model of the process of displacements of points of the structure taking into account the dynamic characteristics of ground vibrations and energy class movements of the Earth's crust

Rational modeling of a wind unit tower taken into account of the features of its dynamic characteristics

Nowadays the level of development of finite element (FE) calculation systems allows us to count on the maximum level of design solutions quality, provided that is created an adequate and at the same time simple design model, which directly determines the level of accuracy of the results obtained when determining the parameters of the stress-strain state, as well as dynamic characteristics of buildings and structures. It is fundamentally necessary for the designer to know the degree of influence of various factors to the creation of a finite element design model on the dynamic response of the design object. There is no doubt the relevance of the problem of identifying the features of modeling tower-type structures, which will simplify the work of an engineer and at the same time reach a qualitatively new level in making design decisions. The purpose of this work is a comprehensive assessment of the influence of the features of creating a design model to the resulting parameter - the frequency behavior of a tubular tower for wind turbines which is the most popular at wind parks in Russia over the past two decades. For numerical research was used the domestic design complex SCAD Office. To create calculation models and perform a comparative analysis of the resulting parameters of tubular towers were used FE types 41, 42, 44, and 50. When determining the influence of the finite element type calculations were made for a cylindrical tower with fixed parameters, taking into account changes in the type and size of the FE. In the calculations the evaluating factors were: changing in the main and equivalent stresses, as well as the change in the frequency of the first form of own oscillations. When comparing the values of the main and equivalent stresses, the plate of the third row from the base was taken as the calculated one.

Simulation-Based Model-Updating Method for Linear Dynamic Structural Systems

The dynamic characteristics of buildings and their behavior under various dynamic loads play a crucial role in civil engineering applications, particularly for earthquake-resistant structural design. Employing a precise mathematical model of the structural system makes it possible to accurately predict the actual structural performance under dynamic loads, such as winds and earthquakes. Given this perspective, finite element model-updating approaches in structural systems have gained significant attention in recent decades. This paper proposes a simulation-based model-updating technique that utilizes measured free vibration responses to the correct structural parameters of multi-degree-of-freedom systems. A five-degree-of-freedom building model is subjected to shaking table tests to demonstrate the effectiveness of the proposed method. The experimental data for this method consists of the dynamic behavior of the system under the seismic excitation of the El Centro 1940 earthquake and the results of the free vibration tests. The MATLAB/Simulink parameter estimation tool is employed to establish a correlation between the analytical model and the measured dynamic response from the building model. Compared to the measured structural responses, the updated analytical model, which incorporates the proposed simulation-based model-updating technique, demonstrates high accuracy in predicting the responses through effective corrections of stiffness and damping coefficients.

Modelling of infill walls in reinforced concrete buildings under low-amplitude vibrations

A study was undertaken to analyse the capability of conventional finite-element (FE) models to represent the actual dynamic behaviour of masonry infill walls in reinforced concrete (RC) buildings under ambient conditions. Two commonly used modelling techniques were examined – shell elements and diagonal compression struts. An existing non-symmetrical, six-storey RC building was used as a reference structure. The dynamic characteristics of the real building were determined by an ambient vibration survey. Two FE models of the building were then constructed and the dynamic characteristics of the building were determined numerically. Comparisons of the experimentally obtained dynamic properties and those obtained using each numerical model revealed the most appropriate method for visualising the dynamic behaviour of RC buildings under low levels of vibration. The dynamic behaviour of RC buildings under earthquakes and the use of code-based period estimation formulas were then analysed. The results showed that each modelling technique affected the predicted dynamic frequencies substantially; choosing the most suitable model depends on the level of vibration.

Joint deconvolution of building and downhole seismic recordings: an application to three test cases

In this study, the joint deconvolution is applied to recordings of three test cases located in the cities of Bishkek, Kyrgyzstan, Istanbul, Turkey, and Mexico City, Mexico. Each test case consists of a building equipped with sensors and a nearby borehole installation in order to investigate different cases of coupling (impedance contrasts) between the building and the soil by analyzing the wave propagation through the building-soil-layers, and hence resolving the soil–structure-interactions. The three installations considering different dynamic characteristics of buildings and soil, and thus, different building-soil couplings, are investigated. The seismic input (i.e., the part of the wave field containing only the up-going waves after removing all down-going waves) and the part of the wave field that is associated with the waves radiated back from the building are separated by using the constrained deconvolution. The energy being radiated back from the building to the soil has been estimated for the three test cases. The values obtained show that even at great depths (and therefore distances), the amount of wave field radiated back by the building to the soil is significant (e.g., for the Bishkek case, at 145 m depth, 10% of the estimated real input energy is expected to be emitted back from the building; for Istanbul at 50 m depth, the value is also 10–15% of the estimated real input energy while for Mexico City at 45 m depth, it is 25–65% of the estimated real input energy). Such results confirm the active role of buildings in shaping the wave field.

Influence of soil–structure interaction (structure-to-soil relative stiffness and mass ratio) on the fundamental period of buildings: experimental observation and analytical verification

In order to investigate the influence of soil–structure interaction (SSI) on the dynamic characteristics of buildings, a series of free-vibration experiments were performed on a 1/4-scale steel-frame structure. The structural fixed-base fundamental period was for the first time determined by experiments as to avoid evaluation errors in the conventional SSI analyses, and its numerical counterpart obtained by using SAP2000® was also given for comparison. A total of 34 scenarios, which varied with regard to overall stiffness and mass of the structure, were examined in the experiments and the numerical simulations. In each experimental scenario, the fundamental period of the structure was determined under fixed-base and flexible-base conditions. A newly proposed method by Luco using Dunkerley’s formula to evaluate the lower bounds for structural natural frequencies considering SSI was validated by both experimental and numerical results. This method was found to exhibit excellent accuracy in predicting the fundamental period of the structure with SSI. This experimentally verified formula, having a broader application potential than the Jennings and Bielak and Veletsos and Meek expressions, could apply to a variety of researching areas in earthquake engineering and would be a useful reference for future seismic code revisions in assessing the basic period of the structure with SSI.

Effect of staircase on seismic performance of RC frame building

Staircase is a vertical transportation element commonly used in every multistoried structure. Inclined flights of staircase are usually casted monolithically with RC frame. The structural configuration of stairs generally introduces discontinuities into the typical regular reinforced concrete frame composed of beams and columns. Inclined position of flight transfers both vertical as well as horizontal forces in the frame. Under lateral loading, staircase in a multistory RC frame building develops truss action creating a local stiffening effect. In case of seismic event the stiff area around staircase attracts larger force. Therefore, special attention is required while modeling and analyzing the building with staircase. However, in general design practice, designers usually ignore the staircase while modeling either due to ignorance or to avoid complexity. A numerical study has been conducted to examine the effect of ignoring staircase in modeling and design of RC frame buildings while they are really present in structure, may be at different locations. Linear dynamic analysis is performed on nine separate building models to evaluate influence of staircase on dynamic characteristics of building, followed by nonlinear static analysis on the same models to access their seismic performance. It is observed that effect of ignoring staircase in modeling is severe and leads to unsafe structure. Effect of location and orientation of staircase is also important in determining seismic performance of RC frame buildings.

Stochastic structural control under earthquake excitations

SUMMARY Structural control is an alternative tool, which can be used for the reduction of the response caused by earthquake excitations. Research and implementation in practice have shown that seismic control of structures has not only a lot of potential but also many limitations. Many control strategies are based on the dynamic characteristics of buildings. During the life of the structures, these dynamic characteristics change. So there is a need of modifying the control algorithm. The question that arises is what would happen to the response of controlled structure if the parameters that influence the dynamic characteristics such as mass and stiffness would change while the control algorithm would remain the same. In this paper, this practical issue is discussed, using a stochastic control approach. The influence of the random character of the loads and the stiffness to the response of structures controlled by a modified pole placement algorithm are investigated. Loads and stiffness are considered as random variables, and the response of a structure subjected to dynamic loads is calculated using Monte Carlo methods (i) without control and (ii) controlled by the mentioned algorithm. The methodology is implemented for three characteristic buildings. The cumulative distribution function of acceleration, velocity, and displacement is obtained using the controlled and the uncontrolled analysis for the examined buildings. Deterministic results of the response are also calculated and compared with the random characteristics of the stochastic analyses. Conclusions regarding the influence of the variance of loads and stiffness to the response of structures are presented. Copyright © 2013 John Wiley & Sons, Ltd.

Site amplification investigation in Dhaka, Bangladesh, using H/V ratio of microtremor

The degree of damage during earthquakes strongly depends on dynamic characteristics of buildings as well as amplification of seismic waves in soils. Among the other approaches, microtremor is, perhaps, the easiest and cheapest way to understand the dynamic characteristics of soil. Non-reference microtremor measurements have been carried out in 45 locations in and around the capital Dhaka city of Bangladesh. Subsoil investigations (Standard Penetration Test and Shear Wave Velocity) have also been executed in those locations. Soil model has been developed for those locations for site response analysis by means of the program SHAKE. Among those 45 locations, predominant frequency of microtremor observation varies from 0.48 to 3.65 Hz. Out of those 45, for 35 locations Transfer function obtained from the program SHAKE have higher frequency compared to microtremor H/V ratio and for one location it has lower predominant frequency. For six locations, frequencies obtained from two methods are identical. For three other locations, there are no similarities between predominant frequency obtained from microtremor and transfer function. The seismic Vulnerability Index (Kg) for 45 sites varies between 0.45 and 31.85. Ten sites have been identified as having moderate vulnerability of soil layers to deform.

Extending ground-motion prediction equations for spectral accelerations to higher response frequencies

Ground-motion prediction equations (GMPEs) for spectral accelerations have traditionally focused on the range of response periods most closely associated with the dynamic characteristics of buildings. Providing predictions only in this period range (from 0.1 to 2 or 3 s) has also accommodated the assumed limitations on the usable period range resulting from the processing of accelerograms. There are, however, engineering applications for which estimates of spectral ordinates are required at shorter response periods. Recent work has demonstrated that high-frequency spectral ordinates are relatively insensitive to record processing, contrary to previous assumptions. In the light of this finding, additional regressions are performed to extend a recent pan-European GMPE to higher response frequencies. This model and others that also include coefficients for spectral ordinates at several high response frequencies are used to explore options for interpolating coefficients for equations that do not provide good coverage in this range. The challenges and uncertainties associated with such interpolations are discussed. The paper concludes that a set of standard response frequencies could be usefully established for future GMPEs.

地盤・建物系の高密度強震観測の展開と建物動的挙動の検討

地盤・建物系の高密度強震観測の展開と建物動的挙動の検討

Effects of infill walls and floor diaphragms on the dynamic characteristics of a narrow-rectangle building

Most buildings in Singapore are lightly reinforced concrete structures, which are mainly designed for gravity loading only, because Singapore is an island country located in a low-to-moderate seismic region. The dynamic properties of a typical high-rise residential building with a long, narrow rectangular floor plan are studied using both experimental and numerical methods. The effects of the brick infill walls and the flexible diaphragms on the dynamic characteristics of the building are discussed in detail. The results from the ambient vibration tests are correlated with the numerical results of three different finite element models with different levels of sophistication. They include a bare frame model, a frame model with brick infill walls, and a frame model with both brick infill walls and flexible diaphragms. The dynamic properties of the third model match very well with the measured results in terms of both the natural frequencies and the mode shapes. The correlation results demonstrate the respective effects of the brick infill walls and the flexible diaphragms on the dynamic characteristics of the narrow-rectangle building structure. Copyright © 2006 John Wiley & Sons, Ltd.

Aspects of the dynamic wind-induced response of structures and codification

This paper describes the work of the International Association for Wind Engineering Working Group E -Dynamic Response, one of the International Codification Working Groups set up at the Tenth International Conference on Wind Engineering in Copenhagen. Comparisons of gust loading factors and wind-induced responses of major codes and standards are first reviewed, and recent new proposals on 3-D gust loading factor techniques are introduced. Then, the combined effects of along-wind, crosswind and torsional wind load components are discussed, as well as the dynamic characteristics of buildings. Finally, the mathematical forms of along-wind velocity spectra for along-wind response calculation and codification of acceleration criteria are discussed.

Dynamic identification of a masonry building using forced vibration tests

The aim of the paper is to check the capability of dynamic identification procedures, usually applied to reinforced concrete or steel buildings, in the estimation of the dynamic characteristics of masonry buildings. To this purpose, the dynamic behaviour at low vibration levels of an existing masonry building subjected to forced, sinusoidal or sweep, vibration test, was investigated. Possibly on account of weak nonlinearities of the building, the measurements obtained with sinusoidal tests seemed more suited than those obtained by sweep tests for the application of identification techniques. These concern both modal and physical models: the dynamical characteristics of the building, the frequencies and some eigenvector components obtained by modal identification, were assumed as experimental data to update suitably selected stiffness parameters of a finite element model of the structure. The updating was performed by means of a specially developed dynamic identification code based on an output error equation. Criteria for a rational choice of physical parameters and measurements were applied. A very good agreement between numerical and experimental frequency response functions was obtained with the modal identification, while the physical model showed some rigidity in fitting all the experimental data, albeit with an acceptable level of scatter. Taken as a whole, the results show that well-established identification techniques can furnish useful information concerning the dynamic properties of existing masonry structures.

Dynamic characteristics of buildings constructed on soils prone to slump-type settlement under conditions of complex relief

Dynamic characteristics of buildings constructed on soils prone to slump-type settlement under conditions of complex relief