Pseudodynamic Test Method Research Articles

Cross‐laminated timber for seismic retrofitting of RC buildings: Substructured pseudodynamic tests on a full‐scale prototype

AbstractThis paper presents an experimental study on an innovative timber‐based retrofit solution for reinforced concrete (RC) framed buildings, with or without masonry infills. The intervention aims to enhance seismic resistance through a light, cost‐effective, sustainable, and reversible approach integrating energy efficiency upgrades. The method employs cross‐laminated timber (CLT) panels as infills or external retrofitting elements, mechanically connected to the RC frame through steel fasteners. The system is combined with thermal insulation for improved energy efficiency. The seismic performance of the proposed retrofit technique was assessed experimentally on a full‐scale building model at the European Laboratory for Structural Assessment (ELSA). The experiments included tests on two five‐story building configurations: a masonry‐infilled RC building as a reference and the same structure strengthened with CLT panels. Each building was subjected to unidirectional earthquake simulations of increasing intensity using the pseudodynamic (PsD) testing method with substructuring. The physical substructure of the hybrid model consisted of the first story of a two‐story mockup built and retrofitted in the laboratory, while stories two to five were simulated numerically. The paper discusses major observations from the tests, comparing the damage evolution and hysteretic responses of the two configurations. The experiments yielded promising results, showing that the suggested retrofit solution significantly increased displacement and energy dissipation capacity. The retrofitted building survived earthquake intensities up to 50% higher than the non‐retrofitted counterpart, exhibiting only slight structural damage. These pioneering experiments provide compelling data on the high effectiveness of the proposed CLT‐based retrofit system in enhancing the seismic performance of full‐scale RC buildings.

Seismic performance of a full‐scale five‐story masonry‐infilled RC building subjected to substructured pseudodynamic tests

AbstractThis paper discusses the results of a series of hybrid earthquake tests on a full‐scale reinforced concrete (RC) building with masonry infills. The prototype was a five‐story structure representing the vulnerable part of a typical RC building in Southern Europe, with beams stronger than the columns and masonry infill walls weaker than the surrounding frame elements. The specimen was subjected to a sequence of unidirectional earthquake simulations of increasing intensity up to conditions of significant damage to the infills, using the pseudodynamic (PsD) testing method with substructuring. The input ground motion was a real earthquake recording, slightly modified in amplitude and frequency to match the elastic design code spectrum. The physical substructure of the hybrid model consisted of the first story of a two‐story mock‐up structure built in the European Laboratory for Structural Assessment (ELSA); the second story ensured realistic boundary conditions at the top of the first one. The characteristics of stories two to five were simulated by a numerical finite‐element model developed in OpenSEES and updated throughout the test sequence using data obtained from preceding tests. The experiments were terminated with the onset of a soft‐story mechanism at the first story of the physical substructure for an earthquake with a peak ground acceleration of 0.3 g. The paper summarizes the key characteristics of the specimen and the major observations from the hybrid tests, illustrating the evolution of structural/nonstructural damage and the cyclic hysteretic building response. The attainment of significant damage limit states is correlated with experimentally defined engineering demand parameters and ground‐motion intensity measures for the performance‐based seismic assessment of buildings. Data and observations from these experiments add substantially to our understanding of the effects of masonry infills on the seismic behavior of RC‐framed structures.

Substructure Pseudo-Dynamic Test Study for a Structure Including Soil–Pile–Structure Dynamic Interaction

An improved Penzien model is proposed in this paper as a simplified model of soil–pile–structure interaction. The dynamic nonlinearity of soil under earthquake excitation is simulated by ANSYS in a free-field model and added to the original Penzien model. The improved Penzien model uses the finite element software ANSYS 2021 to simulate the dynamic nonlinearity of soil. The improved Penzien model is then used as a simplified calculation model of the numerical substructure. A substructure pseudo-dynamic test based on the improved Penzien model is carried out. The realization of the substructure pseudo-dynamic test verifies the feasibility and effectiveness of this method, which provides a convenient test method for the study of soil–pile–structure interaction in general laboratories. Soil and structure interaction reduces the acceleration of the structure, and the response exhibited a hysteresis phenomenon because of the nonlinear characteristics of the soil. The influences of soil–pile–structure interaction on velocity and displacement are very complex. The conclusions are reasonable, which proves that the substructure pseudo-dynamic test method of soil–pile–structure dynamic interaction using the improved Penzien model is feasible.

Effect of time step interval and time integration schemes in Pseudo-Dynamic analysis

Pseudo Dynamic Analysis technique is an alternative method for exploring structural performance by combining analytical and experimental investigation. Compared to shake table tests, it is a more economical method, and its reliability has been proven over many years of the studies. The damage occurrence and process can be monitored on the test sample due to experiments performed at low speeds. In this study, the behaviour of a single degree of freedom, cantilever column system, under the effect of the pulse load and earthquake record was investigated both numerically and experimentally using Pseudo Dynamic Analysis method. The effects of two different time integration schemes and various time step interval values on analyses were examined in the investigations and the results were compared. Numerical analyses were performed by α-operator splitting method and central differences method, and experimental studies were performed by α-operator splitting method. In experimental investigations, approximate results were obtained with numerical studies for certain values of the time step. At small time interval values, experimental results deteriorated. It is purposed to determine the optimum time step interval value that can be utilised in the Pseudo Dynamic Test method.

Seismic behaviour of steel Moment Resisting Frames with traditional and innovative connections

In the last decades, increasing efforts have been devoted to developing new types of beam-to-column connections able to accommodate the seismic local ductility demand and dissipate the seismic input energy. Among the proposed strategies, the so-called RBS (Reduced Beam Section) has been widely exploited in the construction market. Nevertheless, new proposals based on the partial-strength philosophy gained approval. Their main advantage is that, in the case of rare seismic events, similarly to RBSs, the connections exhibit wide and stable hysteretic cycles, yet concentrating damage in elements that undergo only minor yielding or are easy to replace. The FREE from DAMage (FREEDAM) and the double split (or X-shaped or hourglass) T-stub connections are promising solutions within this framework. The first strategy includes friction dampers in beam-to-column joints to dissipate the seismic input energy and fix the maximum bending moments transferred to the columns. The second solution differs from the traditional one because the flange of the T-element is appropriately cut according to an hourglass shape. This form replicates the bending moment in the plate part between the stem and the bolts, ensuring a uniform yielding of this part.Even though many research works have already been developed on such innovative connection typologies, experimental results on large-scale structures are still quite limited. Aiming to fill this knowledge gap, an experimental program is currently ongoing at the STRuctural ENGineering Test Hall Laboratory (STRENGTH) of the University of Salerno concerning the pseudo-dynamic testing of a large-scale two-storey steel building equipped with the connection typologies mentioned above. The mock-up has experienced the same sequence of five accelerograms in all the campaigns by the pseudo-dynamic test method. This paper discusses the comparison among the main results obtained so far in the experimental campaigns.

Pseudo-dynamic test and numerical analyses of staggered truss framing systems

To facilitate the popularization and application of high-rise staggered truss framing systems in high intensity area, the seismic performance of the staggered truss framing system was studied. A series of pseudo-dynamic tests were carried out on a 14-story staggered truss framing system model with a scale of 1/8. The time-history curves of displacement, acceleration and base shear under Taft earthquake record with different peak ground accelerations were obtained. Based on the test results, the stiffness degradation, equivalent viscous damping coefficient of the test model were analyzed. The proportion of plastic energy consumption of each component to the whole plastic energy consumption of the structure was obtained. Three different finite element models were established to study the effect of the Vierendeel panel length on the seismic performance. The test results show that the staggered truss framing system has a large lateral stiffness in the direction of the truss, but its seismic energy dissipation capacity is insufficient. Through the pseudo dynamic test method, it is found that the column base is the weak part of the staggered truss framing system. The research results can be used to guide the design of staggered truss framing systems.

Substructure hybrid test examining the seismic response of point-supported glass façades attached to large-span spatial steel structures

Point-supported glass façade (PSGF) is one of the most widely used types of non-structural components. Its earthquake damage may not only cause economic loss, but also interruption of building use and even casualties. This paper aims at investigating the seismic response of the large-span spatial structure and PSGF coupling system through the substructure hybrid test. The substructure pseudo-dynamic (PSD) test method is used, that is, the loading rate of the test is slow as that of the quasi-static tests. The finding is that when the glass panel begins to fail, the cracks occur and instantly spread to the whole glass panel along the diagonal direction due to the stress concentration at a bolt hole of double-layer laminated glass, accompanied by looseness of several point-fixed fitting screws. The drift angle of one glass panel is about 50.0%–81.9% of that of glass façade δ in the critical and failure state, indicating that the supporting system can reduce the in-plane deformation of the glass panel. And the glass façade can reduce the acceleration responses of the mid-span upper chord nodes of the large-span spatial structure by 4.74%–13.98%. Finally, the seismic performance evaluation indexes of PSGF are determined based on the drift angle δ and percentage of damaged glass panels for the slight, moderate, and extensive limit states. It will provide an example and reference for the seismic performance evaluation of the PSGF.

Experimental response of a large-scale two-storey steel building equipped with low-yielding friction joints

The recent earthquakes have underlined the need for more advanced design philosophies able to avoid or reduce direct and indirect costs related to the occurrence of destructive seismic events. According to the traditional seismic design approach, under rare and very rare seismic events, the onset of damage to structural components is usually accepted. However, to address social expectations and the need for resilient buildings, recently, novel low-damage design philosophies have been proposed. These are based on the introduction of friction devices able to dissipate large amounts of energy with negligible damage. The cost of repair of these devices is typically only related to the re-tightening of bolts and, eventually, the substitution of friction shims. Noteworthy examples of this technology are the Sliding Hinge Joints (SHJs), developed at the University of Auckland, and the FREEDAM joints, developed at the University of Salerno within the framework of a homonym research project.In the last two decades, significant efforts have been devoted to understanding the seismic behaviour of such connections. The novelty of this work consists in investigating, for the first time, the seismic response of a large-scale building mock-up equipped with FREEDAM joints. The mock-up has been tested with a sequence of five accelerograms using the pseudo-dynamic testing method. The results have confirmed that FREEDAM connections provide large energy dissipation and rotation supply with almost no damage. The experimental results have been used to verify the accuracy of a numerical model developed with the software OpenSees, showing the capabilities of current simplified phenomenological modelling approaches in capturing the actual structural response.

Strengthening of reinforced concrete frames with engineered cementitious composite panels

Infill walls in reinforced concrete frames are susceptible to failure owing to their brittle nature. Their interaction with boundary columns during earthquakes may also cause shear damage in the columns. It is crucial to employ effective seismic strengthening strategies in order to mitigate the seismic risk induced by the infill walls. In this study, a new strengthening technique, conducted by bonding engineered cementitious composite (ECC) precast panels onto infill walls, was investigated. Three reinforced concrete frames, termed bare frame, infilled frame and strengthened frame, were tested by using the pseudo-dynamic testing method. The test specimens were three-storey, three-bay, half-scaled frames with the central bay having hollow clay brick infill walls. The specimens were subjected to three consecutive ground motions scaled to represent earthquakes with return periods of 144, 475 and 2475 years. The experimental results were compared to observe the influence of the infill walls on the reinforced concrete frames, and to demonstrate the performance of the proposed strengthening technique. It was found that application of ECC panels significantly increased the frame strength and stiffness while allowing the system to have a displacement ductility of about four.

Pseudodynamic Test of a Deficient RC Frame Strengthened with Buckling Restrained Braces

Three story–three bay reinforced concrete (RC) frames with and without chevron braces were tested using the continuous pseudodynamic test method. New steel–concrete composite lateral load–carrying members called Buckling Restrained Braces (BRBs) were used as chevron brace members while retrofitting the RC frame. The BRBs were fitted to the interior span of the RC frame by using anchorage rods. The chevron braced frame was observed to be effective in controlling interstory drift. The test results indicated that retrofitting with BRBs was beneficial in resisting deformation without significant damage under simulated ground motions. Furthermore, significant yielding that occurred on the core plate of the BRBs enabled the braced frame to dissipate energy induced by dynamic loading. The test results were compared with the results of the nonlinear time-history analysis. The analysis results were capable of estimating the base shear capacity and displacement demands with reasonable accuracy.

Pseudo-Dynamic Test for Soil-Structure Interaction Analysis using Shake Tables

This paper presents an effective pseudo-dynamic (PSD) test method for analyzing the response of a multi degree of freedom structural system. In addition to the physical and numerical substructuring of the structure, the effect of the soil-structure interaction (SSI) is numerically modeled without a large soil box. The governing equation is separated into those for the superstructure and the base. These are coupled equations that can be solved recursively with the prediction of the superstructure acceleration, for which polynomial extrapolation is employed. The input for the structure is then obtained by solving the coupled equilibrium equations for experimental and analytically modeled systems. The restoring force applied underneath the superstructure is measured and used to update the superstructure acceleration. The stability condition for the proposed method is investigated, revealing a longer range of the convergence criterion than the Newmark explicit method. The implicit feature of the proposed method enables PSD tests irrespective of the modal properties, if the sampling frequency condition is satisfied. Additionally, the amplitude decay and period elongation are investigated for accuracy comparison in the structural responses. A series of PSD tests are performed using a two degree of freedom shear-building model to validate the proposed method. The experiment is performed on one part of the physical structure, while a numerical simulation is performed on the other part of the structure and on the SSI. The test results confirm that the proposed PSD algorithm is reliable for simulating the substructure and SSI effect.

Development and Application Based on MTS Hybrid Test System

It is meaningful to further explore the hardware and software functions of MTS loading system widely used in building structure test at home and abroad. This paper proposes a kind of seismic pseudo-dynamic test method based on internal command control of software. Three programs including monitor station, sincycle test and rampcontrol test were developed by VB, and the connection with NetSLab platform was completed via master-slaver network, then the test system was established. A single degree of freedom hybrid test of single span bridge was carried out, and a short column of CFRP reinforced was used to be an experimental element. Secondary load for the partial damaged model was implemented to research the mechanics performance of the specimen. The result confirms that the established system is capable of conducting the pseudo-dynamic hybrid test. The hybrid test demonstrates that the proposed internal command control method is feasible and effective, which can provide reference for the system development and seismic research.

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.

Seismic Hybrid Simulation of Stiff Structures: Overview and Current Advances

Advances in the area of structural testing have in recent years led to hybrid simulation, that is, the advanced structural experimental method that encompasses the traditional pseudodynamic testing method and relies on substructuring to offer the advantage of combining the actual experimental testing of selected parts of the structure to the numerical treatment of the rest. The experimental part usually involves simplified test setups and structural elements with few degrees of freedom. Thus, issues of cross-coupling present in testing MDOF structures have not been treated adequately so far. In addition, it has been realized that when it comes to testing very stiff structures, in which the above phenomena are accentuated, further problems arise in relation to the quality of actuator control (accuracy of imposed displacements and stability of the test process). Few studies have focused on these issues, thus necessitating more work in the future. The present study provides an overview of the approaches that have been adopted so far, reports on recent advancements, and raises the points in which more research is needed.

PSEUDODYNAMIC TECHNIQUE TO OBTAIN RELIABLE SHOCK RESPONSE

The use of a pseudodynamic testing method to obtain a response from an impulsive loading may lead to an incorrect test result even though the test setup is properly adjusted and the time step is appropriately chosen based on general considerations. The cause to this problem is analytically explored and a pseudodynamic technique is proposed to overcome this difficulty. The technique is to perform a single small time step immediately upon termination of the applied impulse, while the other time steps can still be conducted by the time step determined from general considerations. The feasibility of this technique is analytically verified and confirmed by a series of pseudodynamic tests for both linear elastic systems and inelastic systems.

Remote Hybrid Testing of Asymmetric Structures under Earthquake Excitation

Based on the pseudo-dynamic testing method and substructure technique, a remote hybrid dynamic testing method for asymmetric-plan buildings considering torsional effects is described. Besides, this paper presents the method and control principle for testing substructures in a single-story frame system under loading due to eccentric lateral responses of superstructure to earthquake motion. Several validated simulation tests of an asymmetric bridge system have been conducted successfully based on the remote testing platform NetSLab and the crossed-response of torsional and translational vibration of bridge structures under three representative ground motions was studied.

Shear Failure Behavior of Y-Eccentrically Brace in RC Frame Structures under Earthquake Action

In order to study the mechanical characteristics and the shear failure behavior under earthquake action, a single-storey single-span RC frame structure strengthened with Y-eccentrically brace were designed and manufactured to be 1/3 scale. The pseudo-dynamic testing method was carried out under El-Centro earthquake action with different peak acceleration adjusted by Code for Seismic Design of Buildings in mainland China. The testing result indicates that RC frame structure strengthened with Y-eccentrically steel brace presents perfect seismic performance under strong earthquake action, at one time, the seismic performance maybe affected by the length of outsourcing steel at the joint between energy dissipation element of eccentric steel brace and RC frame beam. The joint should be considerably designed to make sure that shear failure can firstly occur in energy dissipation element.

Pseudo-Dynamic Test Analysis of Rigid Pile Composite Foundation

According to the similarity theory, this paper established a geometric similarity 1:10 and 3 × 3 rigid pile composite foundation pile group model. Pile strain , cushion deformation and flask displacement were obtained through pasting resistance strain gauges in pile, embedding strain gauge in cushion, connecting to displacement sensor at out of flask, etc., basing on pseudo-dynamic test method. These date were analyzed and studied, and then can conclude the response pattern under earthquake action on rigid pile composite foundation, which provide a basis for application of rigid pile composite foundation in practical engineering.

Pseudo dynamic test of a deficient reinforced concrete frame upgraded with internal steel frames

ABSTRACTTwo‐story, three‐bay reinforced concrete (RC) frames with and without internal steel frame (ISF) retrofits were tested using continuous pseudo dynamic test method. The ISFs were installed to the middle bay of the RC frame. Test results indicated that ISF retrofit was beneficial in resisting deformation demands without significant damage under simulated ground motions. The ISF shifted the failure mode of the system from a brittle to a ductile mode. The test results were compared with the results of the nonlinear time history analysis. The analysis results were capable of tracing the overall behavior of global response parameters; however, estimations of local demand parameters were less accurate. Copyright © 2012 John Wiley & Sons, Ltd.

Performance of Beam-to-Column Connection of a Well-Detailed RC Moment Frame Building under Pseudodynamic Loading

AbstractThe performance of RC frame members under earthquake loading may differ significantly from that of the frame. Even if the story drifts are not significant, a collapse mechanism may be observed because of extensive deformations in the beams, columns, or joints. Therefore, the seismic performance of each member should be investigated independently from that of the frame. In this experimental research, the seismic performance of one exterior and one interior beam-to-column connection region of a one-half–scale 3-story, three-bay RC frame is studied. The RC moment resisting frame building is designed following the code recommendations and earthquake excitations with different intensities applied sequentially to the frame by pseudodynamic testing method. At the end of the tests, under high seismic loads, the strength of members was exceeded, and a collapse mechanism formed. The joint shear distortions were significant for even the basic safety earthquake level, when soft soil conditions are present. In...