Full-scale Dynamic Testing Research Articles

ДИНАМІЧНІ ВИПРОБУВАННЯ МОСТІВ ІМПУЛЬСНИМ НАВАНТАЖЕННЯМ

Introduction. This article deals with the practice of applying the method of dynamic testing of bridges, namely, modal control using impulse loading. The possibilities of this method for determining the technical condition of a bridge span structure by determining its natural characteristics: actual stiffness and parameters of natural vibration forms are shown. Problem Statement. The article is devoted to the problem of practical implementation of the latest theoretical developments in the field of diagnostics of the technical condition of road bridges by conducting full-scale dynamic tests. Purpose. The main purpose of the article is to demonstrate the effectiveness of dynamic impulse testing as a method for assessing the technical condition of bridges. The method involves the excitation of vibrations of bridge structures by means of pulse loads, recording the response of the structure and analyzing the data obtained. Materials and methods. The material for this article is the results of field tests of a curved overpass made of monolithic reinforced concrete located near Kyiv. The following research methods were used: information analysis, mathematical modeling, and general methods of theoretical research.

Application of computational fluid dynamics in design of viscous dampers - CFD modeling and full-scale dynamic testing

Application of computational fluid dynamics in design of viscous dampers - CFD modeling and full-scale dynamic testing

Quantification of the human–structure interaction effect through full-scale dynamic testing: The Folke Bernadotte Bridge

An analytical expression for the frequency response function of a coupled pedestrian-bridge system is presented and evaluated using an experimental measurement campaign performed on the Folke Bernadotte Bridge in Stockholm, Sweden. A finite element model and the modal models that consider the human–structure interaction effect are calibrated with respect to the measurements. The properties of the spring–mass–damper model representing the pedestrians were identified, considering the different structural modes of the system. Good agreement was obtained between the experimental and theoretical frequency response functions. A sensitivity analysis of the obtained solution was performed, validating the determined analytical expression for the frequency response function of the coupled pedestrian-bridge system that takes into account the human–structure interaction effect.

Effect of Friction Dependencies on the Bidirectional Earthquake Response of Double Concave Friction Pendulum Bearings

ABSTRACT The reliability of friction dependencies under real earthquakes has rarely been validated and the effect of the velocity and temperature increase caused by bidirectional excitation on the maximum displacement remains unclear. In this study, friction dependencies were validated using full-scale dynamic tests under earthquake response orbits, and their contribution to the maximum displacement was assessed under strong ground motions. In general, friction dependencies are still applicable to real earthquakes. Moreover, the effect of velocity increase can be ignored, but the effect of temperature increase on displacement is significant, particularly under ground motions with large magnitudes and small distances to faults.

Study of the dynamic performance of a gabion wall

Due to the wide increase in the usage of gabion-faced retaining walls in seismically active zones, like the Himalayas in India, it has become necessary to analyze the performances of gabion structures under dynamic conditions. In this study, in the absence of any full-scale dynamic test, shake table tests are conducted on a scaled-down (1:6.7) model gabion wall (without backfill) for different base accelerations (0.1 g, 0.2 g, 0.3 g, and 0.4 g) and frequencies (3 Hz, 5 Hz, 7 Hz, and 9 Hz). The performance of the gabion wall with and without bottom embedment is analyzed in terms of percentage displacements and acceleration amplification factors at different elevations. It is observed that the percentage displacements and acceleration amplification factors increase significantly with the increase in the frequency of the base motion. The bottom embedment has reduced the acceleration amplification factor at the top of the wall by a maximum of 8 %. The maximum lateral deformations are 0.9 % and 1 % of the height of the wall, with and without embedment, respectively. No damage to the gabion mesh, and no sliding at the base of the wall, is observed even at higher accelerations and frequencies. A finite element analysis, has been carried out to numerically simulate the observed behavior of the gabion wall in the shake table tests. The natural frequency and the damping of the gabion wall are calculated from the experimental free vibration responses and are utilized to derive Rayleigh damping coefficients. The inclusion of damping and the adoption of appropriate interaction properties between the gabion basket and the gravel fill/sand determined from the shake table tests have helped in achieving a good agreement between the numerical results and the experimental data. A large-scale shake table test on a gabion wall with backfill reported by Nakasawa et al. has been numerically simulated using the developed numerical model. A good match between the large scale experiment and the numerical results shows the validity and efficacy of the proposed model.

In-plane behaviour of lightweight façade systems installed in masonry and concrete under simulated seismic loading

The protection of ancillary elements is of paramount importance in earthquake engineering. During a seismic event, in fact, they may be subjected to severe loading conditions with high absolute accelerations and potential distortion due to building structure deformations. The loss of functionality and the collapse of some attached element, as lightweight façade systems, may even precede any damage to the structures. For such elements, a good design practice should always consider special detailing to accommodate imposed deformations with reliable connections to the structural parts. While for the former several ready-to-use technologies are available, fastening solutions still need additional research, particularly considering possible in-plane amplification due to the substructure layout. Within this context, an extensive experimental campaign was recently carried out to investigate the in-plane behaviour of lightweight façade systems under simulated seismic loading. The results of the experiments are presented in this paper, where full-scale mock-ups were installed in concrete, masonry, and a combination of the two, and then tested using a one-directional shaking table. The following variables are considered in the study: (i) the base-material, (ii) the angle bracket type, and (iii) the mass of the cladding panel. Results from full-scale dynamic tests are discussed focusing on the load redistribution at the fixing points and on the residual capacity of fastenings. Measured axial forces on the fasteners are compared with design methods demonstrating the need for a revision to cope with the effects of resonance. Finally, an analytical model for the in-plane behaviour of lightweight façades is presented and verified against the experimental results.

Energy response of a passive variable friction damper and numerical simulation on the control effects for high‐rise buildings

In this study, the behavior of a passive displacement-dependent variable friction damper (VFD) was evaluated. The energy response behavior of a VFD specimen was investigated by conducting full-scale dynamic loading tests. Full-scale tests demonstrated that the VFD specimen produced a lower sliding force when the device response exceeded a predetermined displacement, resulting in a decreased dissipated energy ratio as the displacement increased. The VFD specimen exhibited stable energy response behavior as well as a stable friction sliding force and friction coefficient under sinusoidal, seismic response, and 100-cycle loadings. The energy response of the VFD specimen was almost independent of the loading frequency. Moreover, a response simulation was conducted using a two-dimensional 30-story nonlinear mainframe model with brace-type VFDs under various input motions, including observation records and long-period, long-duration waves. From the numerical simulations, the peak story drift in the case with brace-type VFDs was not significantly greater than in the case with conventional friction dampers (FDs). The dissipated energy ratios of the mainframe and dampers in the case with the VFDs were approximately identical to those in the case with the FDs. In comparison with conventional FDs, VFDs can produce a lower peak story shear force and axial compressive force in the lowest-story columns at the device installation span.

Earthquake Response of Connected and Unconnected Back-to-Back Geosynthetic-Reinforced Soil Walls

A two-dimensional finite-element analysis based on PLAXIS 2D was used to study the behavior of connected and unconnected back-to-back mechanically stabilized earth walls under earthquake loading. The numerical model was first validated with the results from the full-scale dynamic centrifuge tests on reinforced soil-retaining walls. The behavior of connected and closely spaced unconnected back-to-back mechanically stabilized earth walls (BBMSE) was compared in terms of tensile forces mobilized in geogrids, and the lateral earth pressures and maximum displacements of the wall. The total seismic earth thrusts at the end of the reinforced zone and at the facing of BBMSE walls and their points of application were presented. These results were compared with the widely used Mononobe–Okabe method. The connected walls were found to significantly reduce the dynamic loads on the walls compared with those on unconnected walls.

Three-dimensional modelling of slab-track systems based on dynamic experimental tests

The accurate computational modelling of railway systems is crucial for analysis and design, which allows for excellent and enduring performance of such systems. It is capable of providing the industry with data for improving speed, comfort, load capacity and reliability. Further, as accurate solutions serve as an aid to improve railway systems, they contribute to quality services, social welfare, cost effectiveness and sustainability. An important component of a railway system is the track, which, in general, requires high investments for construction and maintenance. This work develops calibrated three-dimensional (3D) Finite Element (FE) models for slab track systems which can be employed for analysis and design with great level of reliability. These models are developed based on full-scale dynamic tests performed under the application of loads which simulate the passage of high-speed trains. The components considered are the rails, rail pads, slab track, grout, Hydraulicaly Bonded Layer (HBL), Frost Protection Layer (FPL) and subgrade. The FE models are built and calibrated in order to reproduce the measured displacement and acceleration test results. Due to the uncertainties in some material properties, a parametric analysis is also performed to establish to which material characteristics of the system the model is more sensitive to. It has been found that the Young’s moduli for the FPL layer and subgrade are the most important parameters. Further, the stiffness properties of rail pads play a paramount role in the accuracy of the model.

Dynamic compaction of crushed concrete fill, full-scale test at Jätkäsaari, Helsinki

Concrete waste in the form of crushed concrete can be utilized in street and road structures. Today, a significant amount of concrete waste generated by various demolition and other activities is not fully utilized in infrastructure projects within Helsinki; as a result, a portion of concrete waste generated in the city is be transported to other sites outside the Helsinki metropolitan area. In Helsinki, large-scale land reclamation projects have been implemented, and this trend will continue in the near future. Utilization of concrete waste as fill material in land reclamation projects will reduce the need to transport concrete waste outside the Helsinki metropolitan area, with a concurrent reduction in need to transport blasted rock to the land reclamation sites. This will promote reuse and recycling of waste and will reduce heavy traffic and CO2 emissions. Crushed concrete has not been previously tested in Finland as a fill material in land reclamation projects subjected to deep compaction methods. In 2018-2019 suitability of crushed concrete for land reclamation purposes was tested in a full-scale dynamic compaction test. The objective of the test was to assess the degree of compaction produced by dynamic compaction, determine the compression rate of compacted layers under pre-loading embankment, and measure environmental impacts of the fill material. The pilot structure was implemented in Tritoninpuisto (Triton Park) located in the southern part of Jatkasaari. Crushed concrete with varying grain size was compacted using the dynamic compaction method. All materials compacted well. Results of the pilot study indicate that dynamic compaction can be applied to densify crushed concrete fill material for land reclamation. Settlement plates on the top and the bottom of the pilot structure were used to monitor short-term settlement during dynamic compaction and long-term settlement after completion of the work. Long-term settlement was minor after compaction and placement of a pre-loading embankment. Implemented study has indicated that compacted crushed concrete is a suitable material for land reclamation in street and park areas.

Approbation of an effective method for dynamic calculation of the steel and concrete bridge span

Problem statement. The article describes the method and results of determining the dynamic response of a continuous steel-reinforced concrete span of a road bridge to the passage of heavy vehicles, which is focused on the use of finite element computing systems. The data of dynamic calculations are compared with those obtained during full-scale dynamic tests of the operated structure. Results. Modern algorithms for dynamic calculation of continuous bridge structures on the action of sprung vehicles are analyzed, which allow taking into account the irregularities on the roadway, the influence of wheel bearing point movements on the vibrations of moving vehicles. It describes the sequence of performing dynamic calculations using modal analysis blocks and dynamic calculation of KE-complexes for a system of moving non-inert loads, followed by calculating the dynamic component of deflections and forces of elements of the bridge structure, taking into account the inertia of the vehicle and unevenness on the roadway. According modal analysis of steel-concrete span structures road bridge operated by means of spatial finite element calculation schemes are determined by their own shape supporting structure, which are then used for dynamic calculations in a moving inertial load. The results of dynamic calculations of the operated road bridge on the action of a three-axle truck moving at a constant speed are presented. Calculated deflections are compared with those obtained during full-scale static tests of the bridge. Numerical calculations estimate the effect of speed, roadway irregularities, and feedback between the vibrations of the bridge and the moving vehicle. Conclusion. The proposed method of dynamic calculation of bridge structures allows evaluating the dynamic quality of transport structures at the design stage and making optimal design decisions.

Full-scale dynamic testing of pendulum isolators (Curved surface sliders)

In the recent years, the experimental investigation on the frictional response of Curved Surface Sliders (CSS) - the European name for pendulum isolators - has been increased and improved, by performing full-scale dynamic testing, using facilities of large capabilities. Experimental data allows a better understanding on the dependence of the frictional properties of the sliding material under different loading conditions and velocities. This paper presents an investigation of the dependence of friction coefficient on these two parameters by analysing experimental results collected from a number of type tests performed at four dynamic testing facilities on full-scale Double Concave Curved Surface Sliders (DCCSS). All isolators are equipped with Ultra-High Molecular Weight Poly-Ethylene (UHMW-PE) sliding material, a material that in past studies was not frequently investigated. Most of said tests were according to the European Standard EN 15129. The tested isolators have different capacity in terms of vertical load (from 1670 kN to 17500 kN) and displacement. The test velocities range from 250 mm/s to 660 mm/s.

The effect of changing surface emissivity on the natural ventilation rate of a narrow air cavity integrated in a transparent insulation façade

A transparent insulation material (TIM) can be incorporated in a building element in order to improve its thermal performance, including solar heat gain. However, some overheating protection needs to be implemented. The provision of natural ventilation in a façade cavity to avoid overheating, along with other potential techniques, could require a completely different approach to TIM integration in solar façade concepts. This paper concerns an analysis of the effect of different absorber emissivity behind a transparent insulation system. The emissivity changes are primarily studied in order to determine their effects on the overall radiation - natural convection heat transfer through a narrow façade air cavity. A comparative investigation was conducted using experimental full-scale dynamic outdoor tests and the building energy simulation (BES) approach. The thermodynamic response affected by the radiation - natural convection transfer is identified, specifically during the summer peak period, that corresponds to overheating. Depending on the ventilation regime, a low emissivity solar absorber inside a narrow air façade cavity may increase the cooling energy load and temperature response of a façade by 25 and 36%, respectively, in comparison with a high emissivity absorber. When the emissivity of the zone inside the cavity was changed, significant limitations were identified in the BES calculation methods for both vented and unvented cases.

Dynamic Response of FRCM Reinforced Masonry Arches

The problem of the dynamic behavior of masonry arches and vaults has gained increasing interest in recent years, since the key role of these structural elements in the masonry constructions, especially of historic interest. Despite this, the literature still lacks a sufficiently large number of contributions on this important subject, and this deficiency is even more marked for the case of reinforced masonry. In this context, the present paper shows and discusses some preliminary experimental results on full-scale dynamic tests on unreinforced and GFRCM-reinforced Apulian tuff masonry arches. The experiments have been performed by using a test bench appositely designed and built; the dynamic excitation consisted of a harmonic base motion with fixed amplitude and increasing frequency. The acceleration in suitable points of the arches, the base shear and the base motion have been continuously monitored during the tests.

Seismic mobile shaker testing of full-scale RC building frames with high-strength NSM-FRP hybrid retrofit system

Past seismic events have led to the premature failure of many existing seismically-vulnerable reinforced concrete building frames due to their inadequate column details. To ensure the ductile behavior of the non-ductile building frames, a hybrid retrofit system combining high-strength near surface mounted bars (flexural retrofit) with carbon fiber reinforced polymer sheets (shear retrofit) can be installed to the seismically-vulnerable columns. This study presents the experimental dynamic assessment of the non-ductile building frames retrofitted with the hybrid system. To prevent the column shear failure due to the flexural strengthening, a two-stage design procedure for the hybrid retrofit system was proposed. The full-scale dynamic testing was performed on the retrofitted test frame to realistically measure dynamic responses and quantify the retrofit effects. The hybrid retrofit system reduced the peak inter-story drift of the first-story columns by about 25% and their hinge rotation by approximately 76%. Additionally, the retrofit system can uniformly distribute the damage or drift over the entire structure, i.e. mitigation of soft-story mechanism.

Vibrations of continuous slab reinforced concrete bridge when driving a three-axle car

Problem statement. The technique and its approbation on the reconstructed transport construction of full-scale dynamic tests of the continuous slab span of the road bridge using a refined algorithm of dynamic calculation of the mobile inert load are presented. Results. The modern methods and algorithms of calculation of transport facilities for mobile road load, which can be used in the design and full-scale dynamic tests of road bridges, are analyzed. Affected by many factors, including design features bearing system of the bridge and the moving crew, the presence of unevenness on the carriageway etc., which need to be considered in the evaluation of the dynamic characteristics of transport facilities. Describes the methodology and processing of data from the field dynamic testing of a road bridge, which studied dynamic response of a slab of reinforced concrete spans for the passage of a three-axle truck through the artificial a single bump. The spectral analysis of the registered vibration patterns is performed, the results of which are compared with the eigen frequency spectrum of the superstructure. The calculated analysis of the situation of the vehicle passage on the roadway of the bridge with the allocation of quasi-static and dynamic components of the oscillations is carried out. The latter is used for the lower self-forms a bridge, which defines the dynamic quality transport facilities. Conclusion. The performed approbation of the proposed technique can be effectively used both in the dynamic tests of constructed or operated bridges, and in the design of new transport facilities.

An indirect method for determining the dynamic properties of soils at modeling the vibrating effects of technological equipment on the building structures

The results of experimental studies of the elastic characteristics of soil bases are presented in the simulation of dynamic loads from machinery and equipment to building structures. In the course of work on the inspection of the technical condition of building structures, the authors developed an experimental and theoretical method for determining the elastic characteristics of soil bases. The proposed method involves carrying out full-scale dynamic tests in the mode of natural and forced oscillations.

Evaluation of the Increased Dynamic Effects on the Highway Bridge Superstructure

Dynamic properties of the bridge superstructure vary depending on many characteristics of the bridge and the loading conditions. In this paper, maximum Dynamic Amplification Factor was calculated for six different types of typical pre-stressed concrete beam bridges. It showed that each type of bridge with similar loading has a different range of Dynamic Amplification Factor. At the same time, every recently built bridge has different geometry and design load. Hence, it is difficult to determine a characteristic value of Dynamic Amplification Factor for the similar type of structures. By using fullscale dynamic and static bridge tests, it is possible to determine the necessary characteristics which show possibly high Dynamic Amplification Factor. This factor indicates if it is necessary to make a full-scale bridge dynamic analysis. It was found that those characteristics are natural frequency (first mode), damping ratio, relative deflection, and span and depth ratio. Obtained results from tests show a range of values for each of the characteristic. These ranges were analysed for reinforced concrete slab and pre-stressed concrete slab, and girder bridges.

Constructing and evaluating generalized models for a base‐isolated structure

Full-scale dynamic testing and earthquake engineering experiments are often costly, yet they are vital for advancing the understanding of the complex interactions between seismic protective systems and structural responses. E-Defense (a part of the Japan's National Research Institute for Earth Science and Disaster Resilience) constructed and tested a four-story reinforced-concrete base-isolated building to study, among other things, how different anti-seismic devices in the isolation layer of a building improve its response. This structure was subjected in August 2013 to a series of tests, including random ground motions and simulated earthquakes. Analyzing the acceleration responses from these random excitations forms the first step in identifying the dynamic characteristics of this test structure. The advanced numerical algorithm for subspace state-space system identification (N4SID), from the family of subspace identification methods, is used to estimate the nominal modal parameters of this structure for both input–output and output-only models. These models are then evaluated for their generalizability by using them to predict the response of the structure to both random excitations and seismic inputs. Additional identification is performed using responses recorded during simulated earthquakes, and the recovered modal parameters are compared against the nominal parameters to analyze how the building's isolation system impacts its response. The results indicate that the interaction between seismic excitation and the base-isolation layer has both local and global structural effects. Locally, the modes most directly associated with isolation layer displacements experience, as expected, significant decreases in frequency and increases in damping; globally, the modes with more substantial displacements across the superstructure also experience decreases in frequency and increases in damping but at a greatly reduced scale. Further, even in the presence of seismic forces large enough to induce nonlinear restoring forces in the isolation layer, the relative changes in identified modal parameters for the superstructure associated modes remained modest.

Full-scale dynamic testing of raised floor structures

At the moment there is a rather small piece of the information about the behavior of the raised floor under the seismic impacts, and at the same time the spectrum of such structure application is continuously expanding, that leads to the necessity of the detailed assessment of their characteristics. The research purpose is to determine the resonant frequencies and transfer functions of the raised floor elements and the whole structure at all. The determination of the raised floor structure vibrostability in the frequency range 1 - 30 Hz is determined in the case of the sinusoidal oscillations influence of the basement, too. During the preparatory work the testing platform was constructed, it simulates the full-scale boundary conditions for a raised floor panel installed on the concrete basement in the enclosed room with a tight fit to vertical walls along the contour. Thus, the deformations of the raised floor fragments were neglected because of the racks compliance and joints. Also, the stepwise loading scheme was developed to determine the limiting states and possible destruction of the raised floor elements. As a result of the studies, the oscillation accelerograms of the raised floor fragments were obtained at the given level of seismic impacts; the dependence of the stresses in the raised floor elements on the time at the given level of seismic impact and fixing the defects of the raised floor elements during and after the test series are determined.