• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.85-88
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• 2006

This paper deals with shaking table tests on RC piers to evaluate the seismic performance under near fault motion. Small scale models were fabricated and axial force was applied by introducing prestress at the centroid of the column section. Mass effect of the superstructures was simulated by mass frame which was linked with a pier model by steel bars because of the limited payload of shaking table. Friction of the mass frame when it moves was minimized by special details and it was proved before tests. Scale factor of the RC piers was 4.25. Main parameters of the test were details of reinforcements. After verifying the results of shaking table tests, seismic performance was evaluated by increasing the acceleration of the near fault motion.

• Coupled systems mechanics
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• v.2 no.4
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• pp.329-348
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• 2013

This study aims at observing the coupling behaviours between suspended ceilings and partition walls in terms of their global seismic performance using full-scale shake table tests. The suspended ceilings with planar dimensions of $6.0m{\times}3.6m$ were tested with two types of panels: acoustic lay-in and metal clip-on panels. They were further categorized as seismic-braced, seismic-unbraced, and non-seismic installations. Also, two configurations of 2.7 m high partition wall specimens, with C-shape and I-shape in the plane layouts, were tested. In total, seven ceiling-partition-coupling (CPC) specimens were tested utilizing a unidirectional seismic simulator. The test results indicate that the damage patterns of the tested CPC systems included failure of the ceiling grids, shearing-off of the wall top railing, and, most destructively, numerous partial detachments and falling of the ceiling panels. The loss of panels was mostly concentrated near the center of the tested partition wall. The testing results also confirmed that the failure mode of the non-seismic CPC systems was brittle: The whole system would collapse suddenly all at once when the magnitude of the inputs hit the capacity threshold, rather than displaying progressive damage. Overall, the seismic capacity of the unbraced and braced CPC systems could be up to 1.23 g and 2.67 g, respectively; these accelerations were both achieved at the base of the partition wall. Nonetheless, for practical applications, it is noteworthy that the three-dimensional nature of seismic excitations and the size effect of the ceiling area are parameters that exacerbate the CPC's seismic response so that their actual capacity may be dramatically decreased, leading to important losses even in moderate seismic events.

• Smart Structures and Systems
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• v.8 no.4
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• pp.385-398
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• 2011

This paper discusses the applicability of Acoustic Emission (AE) to assess the damage in reinforced concrete (RC) structures subjected to complex dynamic loadings such as those induced by earthquakes. The AE signals recorded during this type of event can be complicated due to the arbitrary and random nature of seismicity and the fact that the signals are highly contaminated by many spurious sources of noise. This paper demonstrates that by properly filtering the AE signals, a very good correlation can be found between AE and damage on the RC structure. The basic experimental data used for this research are the results of fourteen seismic simulations conducted with a shake table on an RC slab supported on four steel columns. The AE signals were recorded by several low-frequency piezoelectric sensors located on the bottom surface of the slab. The evolution of damage under increasing values of peak acceleration applied to the shake table was monitored in terms of AE and dissipated plastic strain energy. A strong correlation was found between the energy dissipated by the concrete through plastic deformations and the AE energy calculated after properly filtering the signals. For this reason, a procedure is proposed to analyze the AE measured in a RC structure during a seismic event so that it can be used for damage assessment.

• Structural Engineering and Mechanics
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• v.59 no.2
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• pp.291-312
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• 2016

Seismic performance evaluation of shear wall is essential as it is the major lateral load resisting member of a structure. The ultimate load and ultimate drift of the shear wall are the two most important parameters which need to be assessed experimentally and verified analytically. This paper comprises the results of monotonic tests, quasi-static cyclic tests and shake-table tests carried out on a midrise shear wall. The shear wall considered for the study is 1:5 scaled model of the shear wall of the internal structure of a reactor building. The analytical simulation of these tests is carried out using micro and macro modeling of the shear wall. This paper mainly consists of modification in the hysteretic macro model, developed for RC structural walls by Lestuzzi and Badoux in 2003. This modification is made by considering the stiffness degradation effect observed from the tests carried out and this modified model is then used for nonlinear dynamic analysis of the shear wall. The outcome of the paper gives the variation of the capacity, the failure patterns and the performance levels of the shear walls in all three types of tests. The change in the stiffness and the damping of the wall due to increased damage and cracking when subjected to seismic excitation is also highlighted in the paper.

• Structural Engineering and Mechanics
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• v.83 no.6
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• pp.745-756
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• 2022

This study aims to determine the cause of the load resistance loss in storage racks that can be attributed to external forces such as earthquakes and to improve safety by developing reinforcement systems that can prevent load resistance loss. To this end, a static cyclic loading test was performed on pallet racks commonly used in logistics warehouses. The test results indicated that a pallet rack exposed to an external force loses more than 50% of its load resistance owing to the damage caused to column-beam joints. Three reinforcement systems were developed for preventing load resistance loss in storage racks exposed to an external force and for performing differentiated target functions: column reinforcement device, seismic damper, and viscoelastic damper. Shake table testing was performed to evaluate the earthquake response and verify the performance of these reinforcement systems. The results confirmed that, the maximum displacement, which causes the loss of load resistance and the permanent deformation of racks under external force, is reduced using the developed reinforcement devices. Thus, the appropriate selection of the developed reinforcement devices by users can help secure the safety of the storage racks.

• Journal of the Earthquake Engineering Society of Korea
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• v.25 no.3
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• pp.93-102
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• 2021

The dynamic characterization of a three-story auxiliary building in a nuclear power plant (NPP) constructed with a monolithic reinforced concrete shear wall is investigated in this study. The shear wall is subjected to a joint-research, round-robin analysis organized by the Korea Atomic Energy Research Institute, South Korea, to predict seismic responses of that auxiliary building in NPP through a shake table test. Five different intensity measures of the base excitation are applied to the shaking table test to get the acceleration responses from the different building locations for one horizontal direction (front-back). Simultaneously to understand the global damage scenario of the structure, a frequency search test is conducted after each excitation. The primary motivation of this study is to develop a nonlinear numerical model considering the multi-layered shell element and compare it with the test result to validate through the modal parameter identification and floor responses. In addition, the acceleration amplification factor is evaluated to judge the dynamic behavior of the shear wall with the existing standard, thus providing theoretical support for engineering practice.

• Earthquakes and Structures
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• v.20 no.2
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• pp.149-160
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• 2021

Buildings made using the locally available clay materials are amongst the least expensive forms of construction in many developing countries, and therefore, widely popular in remote areas. It is despite the fact that these low-strength masonry structures are vulnerable to seismic forces. Since transporting imported materials like cement and steel in areas inaccessible by motorable roads is challenging and financially unviable. This paper presents, and experimentally investigates, adobe masonry structures that utilize the abundantly available local clay materials with moderate use of imported materials like cement, aggregates, and steel. Shake-table tests were performed on two 1:3 reduce-scaled adobe masonry models for experimental seismic testing and verification. The model AM1 was confined with vertical lightly reinforced concrete columns provided at all corners and reinforced concrete horizontal bands (i.e., tie beams) provided at sill, lintel, and eave levels. The model AM2 was confined only with the horizontal bands provided at sill, lintel, and eave levels. The models were subjected to sinusoidal base motions for studying the damage evolution and response of the model under dynamic lateral loading. The lateral forcedeformation capacity curves for both models were developed and bi-linearized to compute the seismic response parameters: stiffness, strength, ductility, and response modification factor R. Seismic performance levels, story-drift, base shear coefficient, and the expected structural damages, were defined for both the models. Seismic performance assessment of the selected models was carried out using the lateral seismic force procedure to evaluate their safety in different seismic zones. The use of vertical columns in AM1 has shown a considerable increase in the lateral strength of the model in comparison to AM2. Although an R factor equal to 2.0 is recommended for both the models, AM1 has exhibited better seismic performance in all seismic zones due to its relatively high lateral strength in comparison to AM2.

• Journal of the Korea Concrete Institute
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• v.20 no.4
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• pp.451-458
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• 2008

The near-fault ground motion (NFGM) is characterized by a single long period velocity pulse of large magnitude. NFGM's have been observed in recent strong earthquakes, Izmit Turkey (1999), Kobe Japan (1995), Northridge USA (1994), etc. These strong earthquakes have caused considerable damage to infrastructures because the epicenter was close to the urban area, called as NFGM. Extensive research for the near-fault ground motion (NFGM) have been carried out in strong seismic region, but limited research have been done for NFGM in low or moderate seismic regions because of very few records. The purpose of this study is to investigate and analyze the effect of near-fault ground motions on reinforced concrete (RC) bridge piers with lap-spliced longitudinal reinforcing steels. The seismic performance of four RC bridge piers under near-fault ground motions was investigated on the shake table. In addition, a RC bridge pier is subjected to pseudo-dynamic loadings. Test results showed that large residual displacements were observed in RC bridge piers under NFGM. RC specimens on the shake table failed at relatively low displacement ductility, compared with the displacement ductility of RC bridge pier subjected to pseudo-dynamic loadings.

• Computers and Concrete
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• v.2 no.6
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• pp.423-437
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• 2005

In this study two single-bay, three-storey space frames, one with brick masonry infill in the second and third floors representing a soft-storey frame and the other without infill were designed and their 1:3 scale models were constructed according to non-seismic detailing and the similitude law. The models were excited with an intensity of earthquake motion as specified in the form of response spectrum in Indian seismic code IS 1893-2002 using a shake table. The seismic responses of the soft-storey frame such as fundamental frequency, mode shape, base shear and stiffness were compared with that of the bare frame. It was observed that the presence of open ground floor in the soft-storey infilled frame reduced the natural frequency by 30%. The shear demand in the soft-storey frame was found to be more than two and a half times greater than that in the bare frame. From the mode shape it was found that, the bare frame vibrated in the flexure mode whereas the soft-storey frame vibrated in the shear mode. The frames were tested to failure and the damaged soft-storey frame was retrofitted with concrete jacketing and, subjected to same earthquake motions as the original frames. Pushover analysis was carried out using the software package SAP 2000 to validate the test results. The performance point was obtained for all the frames under study, therefore the frames were found to be adequate for gravity loads and moderate earthquakes. It was concluded that the global nonlinear seismic response of reinforced concrete frames with masonry infill can be adequately simulated using static nonlinear pushover analysis.

• Smart Structures and Systems
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• v.25 no.2
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• pp.155-167
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• 2020

This paper demonstrates a real-time hybrid substructuring (RTHS) shake table test to evaluate the seismic performance of a base isolated building. Since RTHS involves a feedback loop in the test implementation, the frequency dependent magnitude and inherent time delay of the actuator dynamics can introduce inaccuracy and instability. The paper presents a robust stability and performance analysis method for the RTHS test. The robust stability method involves casting the actuator dynamics as a multiplicative uncertainty and applying the small gain theorem to derive the sufficient conditions for robust stability and performance. The attractive feature of this robust stability and performance analysis method is that it accommodates linearized modeled or measured frequency response functions for both the physical substructure and actuator dynamics. Significant experimental research has been conducted on base isolators and dampers toward developing high fidelity numerical models. Shake table testing, where the building superstructure is tested while the isolation layer is numerically modeled, can allow for a range of isolation strategies to be examined for a single shake table experiment. Further, recent concerns in base isolation for long period, long duration earthquakes necessitate adding damping at the isolation layer, which can allow higher frequency energy to be transmitted into the superstructure and can result in damage to structural and nonstructural components that can be difficult to numerically model and accurately predict. As such, physical testing of the superstructure while numerically modeling the isolation layer may be desired. The RTHS approach has been previously proposed for base isolated buildings, however, to date it has not been conducted on a base isolated structure isolated at the ground level and where the isolation layer itself is numerically simulated. This configuration provides multiple challenges in the RTHS stability associated with higher physical substructure frequencies and a low numerical to physical mass ratio. This paper demonstrates a base isolated RTHS test and the robust stability and performance analysis necessary to ensure the stability and accuracy. The tests consist of a scaled idealized 4-story superstructure building model placed directly onto a shake table and the isolation layer simulated in MATLAB/Simulink using a dSpace real-time controller.