Pseudo-dynamic Tests Research Articles

Pseudo-dynamic testing of a fabricated composite frame with steel plate shear walls

A pseudo-dynamic testing program was generated on a fabricated composite frame with steel plate shear walls (SPSWs) to study its seismic performance. The specimen was a three-storey single-bay frame, which was composed of H-section steel columns and composite beams, and was assembled by bolted height-adjustable steel beam-to-column connections (BHA connections). Beam-only-connected SPSWs were selected as lateral load resisting members. The specimen was subjected to four ground motions of progressively increasing intensity. The results showed that: (1) beam-only-connected SPSWs provided sufficient lateral load resistance, lateral stiffness, and energy dissipation capacity to the fabricated frame via the tension field action developed in their infill panels; (2) the fabricated frame, assembled by BHA connections, exhibited substantial redundancy and good ductility; (3) an undesirable failure mode of the fabricated frame, in huge earthquakes, included severe cracking in composite beams and block shear failure in SPSWs’ connections; (4) the inter-storey shear force distribution determined by ASCE/SEI 7-10 was verified with experimental data.

Demountable Frame Structure with an Elastically Embedded Diaphragm

Precast reinforced concrete demountable column system with elastically mounted diaphragms inserted into frame sections developed within the TACR grant project [1] was verified by a pseudo-dynamic tests in the UTAM AV CR experimental facility. The experimental verification and theoretical analysis was aimed at identifying the stiffness characteristics and dynamic response of the “frame” section, including the evaluation of the effect of demountable joints while mounting the diaphragm on beams using elastic (rubber) bearings. The experimental verification was performed for three different diaphragm to beam connections made by a rigid screw connection and by a connection with elastic bearings with two different stiffness values. During the first phase of the experimental verification the structure was exposed to pseudo-dynamic loading by a hydraulic jack controlled by deformation or by amplitude and corresponding frequency of the jack. The absolute deformations of the structure as well as relative deformations between individual structural elements were monitored by means of linear deformation sensors. The force necessary for reaching these deformations was also monitored. In the second phase of the experimental campaign the natural frequencies and dampening characteristics were identified. Based on the obtained values, the stiffness and dynamic characteristics of the frame structure with three different types of the stiffening diaphragm connections were identified and were compared with numerical model. Theoretical analysis and results of experimental research proved the satisfactory resistance of the proposed multi storey building system.

Research on the Image Orientation Bridge Structural Stability Testing Platform Based on Feature Point Recognition and Genetic Algorithm

In this paper, we conduct research on image orientation bridge structural stability testing platform based on feature point recognition and the genetic algorithm. The pseudo-dynamic test in structural seismic test requires a step-by-step solution to the differential equation of motion of the whole structure. In each solution step, the calculated displacement is applied to the specimen, and then the measured feedback force is put into the differential equation. One-step displacement, and so on. As the number and capacity of a single laboratory equipment and test site is limited, often only one substructure tests. To deal with this challenge, this paper proposes the feature point recognition and the genetic algorithm based methodology to construct the image orientation bridge structural stability testing platform. The theoretical basis and numerical performance are proved.

내진보강용 폴리우레아로 보강된 철근콘크리트 기둥의 내진성능 평가에 대한 유사동적실험 연구

국내외적으로 지진의 발생이 빈번함에 따라 인명 및 재산 피해가 발생하고 추가적인 경제적 손실을 초래한다. 국내의 비내진으로 설계된 구조물의 보수 보강이 시급할 뿐만 아니라 지진에 대한 관심이 고조됨에 따라 내진보강에 대한 연구가 활발히 진행되고 있다. 최근 고연성 보강재를 사용한 내진보강기법이 소개되면서 강성보강보다는 연성보강에 대한 신뢰도가 높아지고 있다. 따라서 본 연구에서는 연성보강 재료로써 최근 각광받고 있는 폴리우레아를 이용한 내진보강공법을 소개하기 위해서, 폴리우레아로 보강한 RC 시편에 대하여 일축압축시험과 유사동적실험을 수행하였다. 일축압축시험에서 폴리우레아 보강시 강도가 증진되었을 뿐 아니라 연성거동을 확인할 수 있었으며, 실제 지진파를 적용한 유사동적실험에서는 상대변위, 주철근의 변형률, 변위연성도, 소산에너지 모두 향상된 보강성능을 확인할 수 있었다. 연성보강의 목적으로 개발한 폴리우레아 보강방법은 기둥부재의 내진보강에 유용하게 사용될 것이라고 판단된다. As earthquakes have frequently happened all over the world, huge losses of human life and property have occurred. Therefore, retrofitting and strengthen technologies of non-seismically designed structures in Korea are urgent. Also, there has been a growing interest about seismic retrofitting, where researches on the topic have been actively pursued in Korea. The study results showed that ductility inducing retrofitting method is more superior stiffness inducing method. In Japan, Super Reinforcement with Flexibility (SRF) was introduced. Therefore, in this study, seismic performance evaluation was performed through pseudo dynamic test and uniaxial compression test for RC column retrofitted by PolyUrea for ductility inducing retrofitting material. Uniaxial compression test results showed that strength of all specimens retrofitted by PolyUrea was higher than that of RC specimens. Also, all specimens retrofitted by PolyUrea also showed ductile fracture behavior. In pseudo dynamic test, by appling real earthquake record, the seismic behavior of RC column reinforced by PolyUrea was evaluated through relative displacement, reinforcement strain, displacement ductility, and dissipation energy. The results showed that PolyUrea helped to enhance seismic performance of RC columns.

Numerical failure analysis of a continuous reinforced concrete bridge under strong earthquakes using multi-scale models

Previous failure analyses of bridges typically focus on substructure failure or superstructure failure separately. However, in an actual bridge, the seismic induced substructure failure and superstructure failure may influence each other. Moreover, previous studies typically use simplified models to analyze the bridge failure; however, there are inherent defects in the calculation accuracy compared with using a detailed three-dimensional (3D) finite element (FE) model. Conversely, a detailed 3D FE model requires more computational costs, and a proper erosion criterion of the 3D elements is necessary. In this paper, a multi-scale FE model, including a corresponding erosion criterion, is proposed and validated that can significantly reduce computational costs with high precision by modelling a pseudo-dynamic test of an reinforced concrete (RC) pier. Numerical simulations of the seismic failures of a continuous RC bridge based on the multi-scale FE modeling method using LS-DYNA are performed. The nonlinear properties of the bridge, various connection strengths and bidirectional excitations are considered. The numerical results demonstrate that the failure of the connections will induce large pounding responses of the girders. The nonlinear deformation of the piers will aggravate the pounding damages. Furthermore, bidirectional earthquakes will induce eccentric poundings to the girders and different failure modes to the adjacent piers.

Seismic safety evaluation of reinforced concrete masonry infilled frames using macro modelling approach

Many reinforced concrete buildings have been built with masonry infill walls for architectural needs without considering their mechanical contribution. However, ignoring the structural influence of infills may lead to significant inaccuracies in the prediction of the actual seismic capabilities of the structure. Aiming at providing numerical tools suitable for engineering practice, simplified methodologies for predicting the nonlinear seismic behaviour of infilled frame structures (IFS) have been proposed, mostly considering the contribution of the infill as an equivalent diagonal strut element. In this paper, an alternative plane macro-element approach for the seismic assessment of IFS is proposed, validated and applied to a benchmark prototype building. The model validation is focused on recent experimental and numerical results that investigate the influence of non-structural infills, also in the presence of different openings layouts. As a benchmark investigation, a multi-storey plane frame prototype, for which the results of pseudo-dynamic tests are available, is investigated and compared to the results obtained by using a commonly adopted single-strut model. The merits and drawbacks of the considered numerical approaches are highlighted.

Pseudodynamic tests with substructuring of a full‐scale precast box‐modularized structure made of reinforced concrete shear walls

SummaryA novel horizontal and vertical wall‐to‐wall and wall‐to‐floor connection methods for precast box‐modularized structure with reinforced concrete shear walls (PBSRCSWs) are proposed in this paper. The entailing behavior of the proposed connections and the seismic performance of one full‐scale six‐story PBSRCSWs were experimentally studied by means of pseudodynamic substructure tests. In order to improve the relevant experimental accuracy, we presented and validated one versatile testing platform Hytest, combined with external displacement feedback control (EDFC; Hytest with EDFC). In greater detail, it was shown from the pseudodynamic substructure test results that the proposed Hytest with EDFC can effectively impose the desired displacements on the specimens rather than on the actuators. Moreover, both the horizontal and vertical wall‐to‐wall connections proposed for the PBSRCSWs exhibited a favorable behavior whilst the PBSRCSWs subjected to earthquake records showed an excellent seismic performance.

Fragility Analysis of A Scaled Model of Reinforced Concrete Column in Accordance with Similitude Law

Many studies are conducted in several fields for fragility analysis of structures or elements which is a probabilistic seismic safety analysis in consideration with uncertainty of seismic loading. It is hard to directly conduct fragility analysis for an infrastructure with social importance due to its size. Therefore, a fragility analysis for an infrastructure mainly conducted in element level or conducted with scaled model built in accordance with similarity law. In this article, fragility analysis for prototype and scaled model of reinforced concrete column was conducted with numerical models which had been updated by the results of shaking table test and pseudo dynamic test. As a result, response stress from the numerical analysis result of prototype model was higher than that from scaled model due to different stiffness ratios between steel and concrete. However, the probability of failure for scaled model was higher than that for prototype model because failure criteria for scaled model was down due to similarity law. Also it was evaluated that probability of failure by using log normal standard deviation of response stresses by spectrum matched accelerograms was more reliable than probability of failure by using existing coefficient of variation normally used.

Experimental Investigation on Steel W-Shaped Folded Plate Dissipative Connectors for Horizontal Precast Concrete Cladding Panels

ABSTRACTA dissipative connector device, consisting of a steel plate folded at right angle along three lines to get a W-shaped profile, is proposed for the safe fastening of the horizontal cladding panels of new or existing precast structures under seismic action. Experimental tests are carried out to characterize the hysteretic behavior of the connector device. Different technological features, restraint conditions, and loading protocols are considered. Nonlinear hysteretic models are validated against the results of pseudo-dynamic tests on a full-scale prototype of precast building with cladding panels. Guidelines for the design of the dissipative connector device are provided.

Toward Robotic Pseudodynamic Testing for Hybrid Simulations of Air-to-Air Refueling

Hybrid simulation couples experimental tests of novel components to validated numerical models of the remainder of a system and provides high-confidence predictions of their coupled dynamic behavior. Air-to-air refueling (AAR) is an example of the type of system that can benefit from this development approach. The work in this paper concerns the on-ground validation and preflight verification of probe–drogue contact–impact scenarios in AAR maneuvers using off-the-shelf multiaxis industrial robots as part of a hybrid test to interface the refueling hardware with numerical models of the flight environment. While industrial manipulators present a cost-effective solution, bandwidth and power limitations inevitably cause practical problems for real-time hybrid testing. These deficiencies typically manifest themselves as significant tracking inaccuracies or instabilities when sharp nonlinearities or discontinuities are encountered as part of a contact phase. Here, the novel robotic pseudodynamic testing (RPsDT) method is employed to circumvent the contact-response speed limitations of industrial robots. This paper presents and discusses the application of RPsDT to contact–impact problems, outlines the challenges and limitations of the technique in an easily reproducible validation experiment, and details the first RPsDT hybrid simulation of an AAR maneuver using scaled refueling hardware. It is concluded that RPsDT provides a useful tool for the investigation of a particular subclass of multibody contact–impact problems including AAR, where the response of the contacting structures does not possess significant rate-of-loading effects. Future work will comprise tests with full-scale AAR hardware.

Numerical and experimental analysis of an innovative lightweight precast concrete wall

A series of non-linear structural analyses is presented in this paper, aimed at investigating the structural behaviour of an innovative light-weight precast concrete wall system made with discretely connected moduli. A model with 2D damage-sensitive elements has been used to investigate the axial and flexural behaviour of a case study wall element. The numerical analyses allow to estimate the crack pattern and to define monotonic capacity curves. The effect of different reinforcement schemes on the structural behaviour of the wall has been also investigated and an innovative solution has been also proposed on the basis of the results, to increase the ductility of a heavily shear-reinforced wall when subjected to seismic action. The numerical results obtained with the 2D damage model have been compared with those of a simplified non-linear beam model. Furthermore, the effectiveness of the simplified model in catching the dynamic non-linear behaviour of the element has been validated with respect to the results from pseudo-dynamic tests performed at the ELSA/JRC laboratory of Ispra (Italy) in the framework of the Safecast project on a full scale prototype of a multi-storey precast building braced by the walls under investigation.

Experimental investigation on the influence of silicone sealant on the seismic behaviour of precast façades

Silicone sealant is usually interposed between panels of precast facades. In ordinary cladding panel configurations, relative sliding between panels occurs under lateral actions. The shear drifts and consequent stresses arising in the silicone strips may lead to a significant increase of the load demand in the cladding panel connections and affect the seismic behaviour of the structural system. This paper presents the results of experimental tests and numerical analyses carried out to clarify the role of the silicone sealant on the seismic response of precast structures with cladding panels. An experimental campaign including monotonic and cyclic tests on both silicone strips applied to small concrete blocks and two panel sub-assembly sealed with silicone, has been developed at Politecnico di Milano. Furthermore, cyclic and seismic pseudo-dynamic tests on a full-scale prototype of precast building with cladding panels sealed with silicone, have been performed at the Joint Research Centre of the European Commission. The results of the experimental tests are presented and compared with the results of numerical simulations. Some recommendations for seismic design of precast frame structures with cladding panels, considering the effect of silicone sealant, are finally provided.

STRUCTURAL IDENTIFICATION OF DYNAMIC SYSTEMS USING PARAMETER UPDATING REANALYSIS METHOD: EXPERIMENTAL INVESTIGATION USING THE MEASURED DATA

In this study, the proposed parameter updating reanalysis method was directly used on the measured data of the structures. Structural reanalysis generates a correlated analytical model that defines the structure on applying the initially assumed baseline analytical model and is presented through the structure’s FRF (frequency response function). Two numerical tests were previously conducted in order to demonstrate the effectiveness of the suggested reanalysis method. The suggested method generates the correlated analytical model with higher precision, as compared to the existing method, despite the application of the noise factor to the observed data. The method initially proven by the numerical experiment of an actual structure was applied to a pseudo-dynamic test on the full-scale concrete pier. The results indicate that the proposed reanalysis is useful even for application to response data of the actual structure.

Seismic response of precast structures with vertical cladding panels: The SAFECLADDING experimental campaign

The SAFECLADDING Project was aimed at improving the connection systems between cladding panels and precast RC buildings in seismic-prone areas. Three design criteria have been assessed: isostatic, dissipative and integrated. They can be realised using different strategies, which are represented by several test setups within the experimental campaign.The paper describes the results obtained with vertical panels arrangement and the comparison with the bare frame, which is the reference for the current design practice that considers panels like non-structural elements. The mock-up and the test sequence were designed to assess all setups with a single frame structure. The mock-up was a one-storey building, made by two parallel frames with two bays and square columns, inserted into pocket plinths. The building was designed for earthquake actions according to the Eurocode 8. Each setup was assessed using increasing levels of action, either with cyclic or pseudo-dynamic tests. The latter were performed both for serviceability and ultimate limit states. The experimental programme for vertical-panels and the bare-frame arrangement involved ten different setups, resulting in a total of twenty-eight tests.As for the isostatic criterion, the results confirm that considering panels as simple masses without stiffness is far from the real system behaviour, even using apposite devices to uncouple panels and frame displacements. In fact, despite a previous and positive experimental qualification, several devices failed in operative conditions tests.Conversely, the integrated criterion requires to bear high loads, transferred by the frame through connections, which becomes the weak point for this configuration, as demonstrated by different failures of bolts and connections.The reliability of the dissipative criterion has been confirmed by twelve tests completed without any damage. This solution in fact combines lower relative displacements with limited loads within connections, avoiding both the compatibility problems and excessive forces.

Critical issues in parameter calibration of cyclic models for steel members

Accurate response predictions of steel structures subjected to earthquake loading involve the use of models able to simulate properly the cyclic behaviour of the regions where nonlinear phenomena take place. In case of full-strength joints, they are represented by the members connected, which may present softening response due to local buckling. Even though a number of phenomenological models have been developed in the last decades, their calibration seems to have received less attention. Usually, calibration is based on matching the experimental and numerical cyclic responses under loading protocols proposed by standards. Since these were not developed to this aim, the predictive capability of so calibrated models deserves investigation. In this work, a calibration procedure based on the minimisation of response misfit is presented and critically discussed, with reference to an experimental programme carried out at the University of Salerno. Different assumptions about the function to minimise, the ultimate rotation and number of objectives are compared and analysed. The main outcome of this investigation is that a calibration based on cyclic response only is not robust, since its accuracy under different loading conditions may deteriorate. The introduction of the monotonic test in a multi-objective framework may be effective, and its accuracy is confirmed by the results of pseudo-dynamic tests.

Seismic performance assessment of blind bolted steel-concrete composite joints based on pseudo-dynamic testing

This paper aims to investigate seismic behavior and dynamic responses of semi-rigid composite joints composed of steel-concrete composite beams and concrete-filled thin-walled steel tubular (CFTST) columns. A range of pseudo-dynamic tests (PDTs) was performed on two full-scale blind bolted end-plate joint specimens, including one flush and one extended end-plate typed joint. The input ground motion adopted for the PDTs was Ispara seismic acceleration record and scaled to represent various seismic hazard levels. Using Ispara earthquake record with different peak ground accelerations (PGAs), a lot of useful data about hysteresis behavior, stiffness degradation and energy dissipation capacity was obtained. The data was also estimated in detail to characterize the seismic performance of this kind of composite joints. Dynamic responses of beam-to-column joint including displacement and acceleration responses, and dynamic magnification factor were discussed. The experimental results indicated that the structural responses of the test joints under seismic actions coincided with the desired performances analyzed for varying damage levels. The study affirms that the blind bolted end-plate composite joints to CFTST columns possess good energy dissipation seismic performance, so they can provide sufficient ductility and adequate strength to satisfy the seismic design requirement.

Experimental and numerical investigation of the seismic performance of an A-frame–truss–column hybrid supporting structure

A hybrid structural system designed for use in large thermal power plants in China to house air-cooled condenser systems is investigated. The hybrid structure consists of a series of metal A-frames resting on a steel space truss supported by an array of reinforced concrete columns. To gain a better understanding of this structural system, a one-eighth (1:8) scale test structure modeled after a prototype structure was constructed and tested. The test structure was subjected to both free vibration and forced excitation tests with the following objectives: (1) determining its modal properties and seismic response characteristics, (2) gaining insight into its response and most probable failure modes under dynamic excitations, (3) obtaining some useful experimental data for future research, and (4) providing important data to complement the Chinese seismic design code as well as to guide the design of this type of structure in practical engineering applications. The free vibration tests were carried out by inducing an initial displacement to the structure and measuring its natural frequencies and mode shapes. The forced excitation tests consist of a series of quasi-static and pseudo-dynamic tests. For the quasi-static tests, 10 reciprocating displacement excitations with peaks ranging from 6 to 100 mm were used, and for the pseudo-dynamic tests, six ground motions with scaled maximum accelerations ranging from 50 to 800 cm/s2 were employed. Based on the results of these tests, modal properties of the hybrid structure such as natural frequencies, mode shapes, and equivalent damping ratios, as well as some seismic response characteristics such as seismic shears, accelerations, deformations, interstory drifts, roof drifts, and hold-down forces were determined and presented. In addition, nonlinear analysis of the test and prototype structures was conducted using the finite element software ANSYS and compared with the test results. Detailed damage inspection was performed, and important findings were summarized.

Influence of different mechanical column-foundation connection devices on the seismic behaviour of precast structures

Dry-assembled precast concrete frame structures are typically made with dowel beam-to-column connections, which allow relative rotation along the beam direction. In the orthogonal direction the rotation of the beam is prevented but again the connections of the superimposed floor elements allow for relative rotation. All the ductility and energy dissipation demand in case of seismic action is therefore concentrated at the base of cantilever columns. Hence, the column-to-foundation connection plays a key role on the seismic performance of such structures. Mechanical connection devices, even if correctly designed for what concerns resistance, may affect the behaviour of the whole joint modifying the ductility capacity of the columns and their energy dissipation properties. An experimental campaign on different mechanical connection devices has been performed at Politecnico di Milano within the Safecast project (European programme FP7-SME-2007-2, Grant agreement No. 218417, 2009). The results of cyclic tests on full scale structural sub-assembly specimens are presented. Design rules are suggested for each of the tested connections on the basis of the experimental observations, and numerical analyses have been performed with hysteretic parameters calibrated on the experimental loops. The seismic performance of structures provided with those connections is investigated through a case study on a multi-storey precast building prototype, which has also been subject to full-scale pseudo-dynamic testing within the same research project at the European Laboratory of Structural Assessment of the Joint Research Centre of the European Commission. The comparison of the results from the structure provided with the different studied connections clearly highlights how some solutions may lead to both reduction of ductility capacity and dissipation of energy, increasing the expected structural damage and the seismic risk.

A pseudodynamic testing algorithm for obtaining seismic responses of structures

A new family method is proposed for pseudodynamic tests. This family method can integrate favourable numerical properties together, such as the unconditional stability, explicit formulation, second-order accuracy and favourable numerical dissipation. Since the proposed family method can generally have an explicit formulation of each time step its pseudodynamic implementation involves no iteration procedure. Hence, the pseudodynamic tests can be easily conducted when compared to an implicit pseudodynamic method, where an iteration procedure must be involved for each time step. On the other hand, the properties of unconditional stability, second order accuracy and numerical dissipation indicate that the proposed pseudodynamic algorithm is promising for solving inertial problems, where the total response is dominated by low frequency modes and the high frequency responses are of no interest. The unconditional stability implies that there is no limitation on step size for the high frequency modes. Besides, the dominated low frequency modes can be reliably integrated by choosing an appropriate time step since the proposed family method can have a second order accuracy. Finally, the spurious growth of high frequency responses can be suppressed or filtered out by the desired numerical dissipation. As a result, the proposed pseudodynamic algorithm is very promising for a general pseudodynamic test or a substructure pseudodynamic test.

Real-time hybrid simulation technique for performance evaluation of full-scale sloshing dampers in wind turbines

As a variation of the pseudodynamic testing technique, the real-time hybrid simulation (RTHS) technique is executed in real time, thus allowing investigation of structural systems with rate-dependent components. In this paper, the RTHS is employed for performance evaluation of full-scale liquid sloshing dampers in multi-megawatt wind turbines, where the tuned liquid damper (TLD) is manufactured and tested as the physical substructure while the wind turbine is treated as the numerical substructure and modelled in the computer using a 13-degree-of-freedom (13-DOF) aeroelastic model. Wind turbines with 2 MW and 3 MW capacities have been considered under various turbulent wind conditions. Extensive parametric studies have been performed on the TLD, e.g., various tuning ratios by changing the water level, TLD without and with damping screens (various mesh sizes of the screen considered), and TLD with flat and sloped bottoms. The present study provides useful guidelines for employing sloshing dampers in large wind turbines, and indicates huge potentials of applying RTHS technique in the area of wind energy.