Simulated Earthquake Loading Research Articles

Shaking Table Tests of a Novel Flat Slab-Flanged Wall (FSFW) Coupled System with Embedded Concrete-Filled-Steel-Tubes in Wall Piers

The flat slab-flanged wall (FSFW) coupled system has gained popularity in recent years; however, its seismic performance remains an issue, as beams and columns in it are commonly eliminated. To tackle this problem, embedding concrete-filled steel tubes (CFSTs) in wall piers has been proposed to strengthen the system; the viability of this approach has been verified at the member level. Along this line, this study embarks on a shaking table testing of a 1/8-scale five-story FSFW structure equipped with CFSTs in walls, with an aim to understand the overall seismic behavior of such an enhanced system. As with the practice in many countries, the plan layout of the test structure consisted of four rows of wall piers, thus presenting a ‘fish-bone’ floor configuration that relied only upon the walls to resist gravity and lateral loads. The structure was subjected to a suite of input ground motions along with white-noise excitations. By so doing, its damage progression, pattern and dynamic characteristics were clearly identified. Furthermore, a non-linear time history analysis was conducted using PERFORM-3D, and the goodness-of-fit of the computed responses to the experimental records was examined. Findings indicated that the application of CFSTs was instrumental in resisting the simulated earthquake loads acting on the FSFW system, hence the global response limits required by codes of practice were met, even in the case of extremely strong earthquakes. Nevertheless, the junction between the shear walls and floor slabs was found to be the weakest links in the whole system. Designers are thus cautioned to implement proper detailing in those regions to prevent local distress, though it did not appear to acutely impair the system’s collapse-resisting capacity.

Effect of simulated earthquake loading on radon exhalation from uranium tailings dam.

Uranium tailings sand will continuously release radon-222. When the external condition changes, the exhalation of radon will also change. Thus, radon is being recommended as a tracer for dam damage assessment. When an earthquake is simulated on the uranium tailings dam with a shaking table test and the change in radon concentration is measured, it is observed that the earthquake causes micro-fissures in the uranium tailings dam, which aggregate to form fractures. During the process, the radon concentration will climb dramatically, as will the radon exhalation rate. To verify that the radon monitoring date is accurate, the acceleration response, surface displacement, and interior displacement are all monitored. The results show that radon can be utilized as a tracer to evaluate uranium tailings dam damage.

Developing FEM Procedures for Four-Sided Structural Sealant Glazing Curtain Wall Systems with Reentrant Corners

In the cyclic racking evaluation of curtain wall systems, physical testing with instrumentation is the standard method for collecting performance data by most design professionals. The resulting testing of full-scale mockups can provide many types of data, including load and displacement values at different stages of loading through failure. While this type of data is valuable for product/system development/fabrication and design, such data can also provide a means for simulation validation of the curtain wall cyclic performance under simulated earthquake loading. Once the simulation study is validated using the test results, then parametric studies by designers can be conducted with greater ease, ideally with commercial software packages, without the need for testing. For the results of this research study, a practical industry formulated finite element modeling (FEM) approach was used to predict the performance of the curtain wall mockups. Here, unitized four-sided structural sealant glazing (4SSG) curtain wall system mockups that incorporate a re-entrant corner were subjected to cyclic racking displacements per the American Architectural Manufacturers Association (AAMA) 501.6 Structural Sealant protocol. System performances, including displacements, were obtained from the FEM study and used to calculate the effective shear strain of the structural silicone and the drift capacity of the system. This paper describes the details of the techniques developed for FEM, the analysis results, and shows an example application of the numerical modeling approach for mockups with racking test results available. The goal of this modeling approach was to create and test methods that practicing consulting engineers can quickly conduct in their offices on common commercially available software often available to them.

Lateral Resistance Reduction to Cold-Formed Steel-Framed Shear Walls under Various Fire Scenarios

This paper examines the structural response of cold-formed steel-framed building lateral force-resisting systems under combinations of simulated earthquake and fire loading. Full-scale experiments with gypsum-sheet steel composite panel sheathed walls, oriented strand board sheathed walls, and steel strap braced walls are presented. Twenty-two test specimens are subjected sequentially to combinations of cyclic shear deformation and fires of varying intensity; some approximate temperatures in standard furnace tests, and most have characteristics of actual building fires. In select tests, the walls are predamaged to simulate fire following an earthquake. The results show a progressive decrease of postfire lateral load capacity with increasing fire intensity for all walls; however, each wall type exhibits varied sensitivity to the fire intensity as well as to predamage. By understanding the response of these structural systems in real fires, designers can better plan for situations in which multiple hazards, including fire, exist.

Effect of Openings on the Seismic Response of AAC Infilled Frames and an Innovative Method to Improve Performance

Autoclaved aerated concrete (AAC) is an attractive building material with lightweight, good insulation, fireproofing, and durability characteristics. The seismic response of AAC requires an in-depth understanding as its use as infill walls is gaining popularity in seismically active regions of many countries in Europe, Middle East, and Asia. Recent studies on the seismic response of AAC infill walls were mostly conducted on solid AAC walls without considering openings and simulated earthquake loading was applied in the plane of the frame. In this study, recent tests on the out-of-plane and in-plane seismic response of AAC infill walls with openings were investigated experimentally. The door opening was considered for the purposes of the study. The limited deformation capacity of the AAC infill walls was observed. An innovative system to improve the performance of AAC infill walls was briefly discussed.

Effect of openings on the seismic response of AAC infilled frames and an innovative method to improve performance

Autoclaved aerated concrete (AAC) is an attractive building material with lightweight, good insulation, fireproofing, and durability characteristics. The seismic response of AAC requires an in-depth understanding as its use as infill walls is gaining popularity in seismically active regions of many countries in Europe, Middle East, and Asia. Recent studies on the seismic response of AAC infill walls were mostly conducted on solid AAC walls without considering openings and simulated earthquake loading was applied in the plane of the frame. In this study, recent tests on the out-of-plane and in-plane seismic response of AAC infill walls with openings were investigated experimentally. The door opening was considered for the purposes of the study. The limited deformation capacity of the AAC infill walls was observed. An innovative system to improve the performance of AAC infill walls was briefly discussed.

Seismic behaviour of steel-reinforced ultra-high-strength concrete composite frame: Experimental study

This article provides the results of an experimental study on the seismic behaviour of the steel-reinforced ultra-high-strength concrete frame. A two-bay and three-story one-fourth scale steel-reinforced ultra-high-strength concrete frame specimen was tested under simulated earthquake loading conditions. The seismic behaviours of the specimen, including the failure mode, concrete element cracks development, hysteresis loops, lateral load-carrying capacity, ductility, energy dissipation, strength and stiffness degradation, were investigated under low reversed cyclic lateral loading. The test results showed that the beam hinge failure mechanism of the steel-reinforced ultra-high-strength concrete frame was achieved. The steel-reinforced ultra-high-strength concrete frame would have rich and stable hysteretic loops when subjected to large axial load with an axial load ratio of 0.38. The roof and interstory ductility coefficients of the steel-reinforced ultra-high-strength concrete frame ranged from 5.06 to 6.78. The strength and stiffness degenerated gradually, indicating an excellent seismic behaviour of the steel-reinforced ultra-high-strength concrete frame with sufficient ductility and high energy dissipation capacity. The test and analysis results can be served as a design reference for practical engineering applications.

Seismic behavior of shear-critical circular TSRC columns with a shear span-to-depth ratio of 1.3

Beam-column connections of steel reinforced concrete (SRC) structures are complicated and difficult to be constructed due to the densely arranged longitudinal reinforcements and stirrups. One good alternative is to use the composite construction where the reinforcing cage in the SRC column is replaced by an outer thin-walled steel tube, known as tubed steel reinforced concrete (TSRC). This paper presents and discusses the results of an experimental study on the seismic behavior of short circular TSRC columns with a shear span-to-depth ratio of 1.3. A total of 6 specimens using the high strength concrete with fcu,150 = 86.6 MPa were tested under simulated earthquake loading conditions, considering the two main parameters of axial load ratio and the number of shear studs on the steel shape. The short TSRC columns that failed in shear failure mode still showed good ductile behavior due to the effective confinement from the steel tube. Increasing the axial load ratio resulted in an increase of the lateral load resistance and energy dissipation capacity but decreased the ductility and deformation ability of the specimens. The shear studs welded on the steel shape had little effect on improving the seismic behavior of shear-critical circular TSRC columns. A modified ACI design method is proposed to predict the nominal shear strength of circular TSRC columns.

Seismic Performance of Square Concrete Columns Confined with Glass Fiber–Reinforced Polymer Ties

AbstractThis paper assesses the seismic response of square concrete columns internally confined with glass fiber–reinforced polymers (GFRP). Tests were conducted under simulated earthquake loads on...

In-situ seismic verification of non-structural components of unreinforced masonry buildings

An experimental campaign was developed to evaluate the response of non-structural elements of unreinforced masonry buildings for simulated earthquake loads. Eleven walls within 4 URM properties were subjected, in situ, to uniformly distribute static loads applied using a system of airbags. The buildings were located in Darlington, a suburb of Adelaide, South Australia. Three of them were built in the 1960s and the fourth was built in the 1980s. Accompanying material tests were done in situ and in the laboratory, enabling a comparison to be made between the old buildings material strength and the default material strengths recommended in the Australian Masonry Standards, AS3700. Tests were also conducted on 3 URM chimneys to establish their failure mechanism and strength. A highlight of this research is the findings that existing masonry chimneys are vulnerable to a ‘design earthquake’ in Australia. The results also suggest that despite masonry material strength being significantly lower than the code default values, the walls satisfied expected seismic force demands. The reasons include the beneficial effects of in situ wall boundary conditions on out-of-plane wall strength.

Dynamic liquefaction of shear zones in intact loess during simulated earthquake loading

The 2010–2011 Canterbury earthquake sequence in New Zealand exposed loess-mantled slopes in the area to very high levels of seismic excitation (locally measured as >2 g). Few loess slopes showed permanent local downslope deformation, and most of these showed only limited accumulated displacement. A series of innovative dynamic back-pressured shear box tests were undertaken on intact and remoulded loess samples collected from one of the recently active slopes replicating field conditions under different simplified horizontal seismic excitations. During each test, the strength reduction and excess pore water pressures generated were measured as the sample failed. Test results suggest that although dynamic liquefaction could have occurred, a key factor was likely to have been that the loess was largely unsaturated at the times of the large earthquake events. The failure of intact loess samples in the tests was complex and variable due to the highly variable geotechnical characteristics of the material. Some loess samples failed rapidly as a result of dynamic liquefaction as seismic excitation generated an increase in pore water pressure, triggering rapid loss of strength and, thus, of shear resistance. Following initial failure, pore pressure dissipated with continued seismic excitation and the sample consolidated, resulting in partial shear strength recovery. Once excess pore water pressures had dissipated, deformation continued in a critical effective stress state with no further change in volume. Remoulded and weaker samples, however, did not liquefy and instead immediately reduced in volume with an accompanying slower and more sustained increase in pore pressure as the sample consolidated. Thereafter, excess pressures dissipated and deformation continued at a critical state. The complex behaviour explained why, despite exceptionally strong ground shaking, there was only limited displacement and lack of run-out: dynamic liquefaction was unlikely to occur in the freely draining slopes. Dynamic liquefaction, however, remained a plausible mechanism to explain loess failure in some of the low-angle toe slopes, where a permanent water table was present in the loess.

Experimental study on steel reinforced high-strength concrete columns under cyclic lateral force and constant axial load

This paper presents the results of an experimental study on the seismic behavior of steel reinforced high-strength concrete (SRHC) columns. A total of 21 SRHC columns were tested under simulated earthquake loading conditions, and the major experimental parameters were the axial load level, stirrup arrangement, structural steel details and studs. The effects of these parameters on the behavior of the SRHC columns were analyzed in detail. The test results showed that SRHC columns with multiple stirrups and commonly used structural steel ratios demonstrated excellent seismic behavior and were suitable for use in high-rise buildings in seismic regions. The axial load had a negative effect on the energy dissipation and deformation capacity. Stirrups exhibited little effect on the initial stiffness and lateral force at cover spalling, but had a positive effect on the energy dissipation and deformation capacity. The benefit of structural steel was more obvious when the effective confinement index was larger or the SRHC columns were subjected to a greater axial load. Structural steel also improved the positive effect of the stirrups. It is suggested that multiple stirrups should be adopted in SRHC columns to provide full play to structural steel; in addition, more structural steel should be adopted when significant axial loads are applied to SRHC columns. Studs did not significantly affect the performance of SRHC columns during the early loading stage. However, columns with studs exhibited better energy dissipation and deformation capacity along with slower stiffness degradation.

Effect of Ductile Detailing on the Performance of a Reinforced Concrete Building Frame Subjected to Earthquake and Fire

AbstractA nonductile reinforced concrete (RC) frame was constructed and was subjected to a predefined level of damage by subjecting the frame to simulated earthquake loading. The damaged RC frame was then subjected to 1-h designed compartment fire. The RC frame was instrumented with a number of sensors that recorded strains, displacements, and temperatures during the test. The resulting data provided a distinctive record of earthquake-damaged RC structures in fire through a complete heating–cooling cycle. The experimental results were compared with the results from an earlier test done on the RC frame having ductile detailing. The results show a marked influence of reinforcement detailing on the postearthquake fire performance of the concrete structures. The simulated earthquake loading caused wider cracks and more severe concrete spalling in the frame without ductile detailing compared to the frame with ductile detailing. The fire damage was also more pronounced with extensive spalling due to the attainm...

Nondestructive monitoring of subsurface damage progression in concrete columns damaged by earthquake loading

The assessment of the structural integrity of infrastructure after extreme events is an important application of nondestructive technology. Advancements in elastic wave-based methods in recent years have allowed for productive and accurate quantitative analysis which was previously lacking. In this study, ultrasonic array measurements coupled with a modified signature analysis method were implemented for damage detection purposes. Full-scale testing of a reinforced concrete column subjected to simulated earthquake loading was tested using ultrasound nondestructive testing at various stages of loading. A signature analysis technique was adapted to create improved reconstructions and was coupled with a quantitative analysis incorporating Pearson’s correlation coefficient. The results demonstrated the ability to detect internal damages and defects prior to appearance on the surface using one-sided access, showing promise for health monitoring applications.

Micro- and macro-observations of liquefaction of saturated sand around buried structures in centrifuge shaking table tests

A novel experimental method was designed to study the micro-behavior of saturated sand around a buried structure in centrifuge shaking table tests under strong simulated earthquake loading, in addition to the traditional macro-measurements. One free field test was first carried out as a reference, followed by one test with a deep buried structure and one with a shallowly buried structure. During the tests with the buried structure, high quality pictures of moving sand around the structure were recorded by a newly developed image acquisition system. By analyzing the interesting pictures at reasonable intervals using an image analysis software, the evolutions of microstructural features were obtained such as the orientations of the long axes of particles, the orientations of contact normals between particles and the average contact number of the interesting group of particles. The results showed that the evolutions of the micro-features were consistent with those of the macro-measurements such as excess pore pressures and accelerations, which help illuminate the mechanism of sand liquefaction.

Full-scale fire test on an earthquake-damaged reinforced concrete frame

Fire, in the aftermath of an earthquake has evolved as a severely destructive force since the last century [1]. Codes and regulations exist in countries situated in seismically active regions of the world in order to ensure safety of buildings and their occupants in the event of an earthquake; it is however rare to find regulations that also require the consideration of fire following an earthquake, thereby leaving this possibility to be dealt with entirely by emergency responders on an ad-hoc basis with little preparedness. Fire following earthquake (FFE) events in the past, although rare, have sometimes been as destructive as the original earthquake. The aim of this study was to carry out a set of full-scale loading tests on an earthquake damaged, reinforced concrete frame subsequently exposed to fire. The sequential loading was devised in the form of a three phase testing procedure – simulated earthquake loading facilitated by cyclic quasi-static lateral loads; followed by a compartment fire; and finally by subjecting the earthquake and fire damaged frame to a monotonic pushover loading to assess its residual capacity. The reinforced concrete frame was well instrumented with numerous sensors, consisting of thermocouples, strain gauges, linear variable differential transducers (LVDTs) and pressure sensors. A large database of results consisting of temperature profiles, displacements and strains has been generated and salient observations have been made during each stage of loading. This paper describes the experimental investigation and serves as a vehicle for dissemination of the key findings and all the important test data to the engineering community which could be used for validating numerical simulations for further advancing the knowledge and understanding in this relatively poorly researched area.

Large-Beam Tests on Mechanical Behavior of Dam Concrete under Dynamic Loading

AbstractThe objective of this study was to determine the tensile behavior for dam concrete under simulated earthquake loading conditions (loading frequency 5 Hz). Four-point loading tests were conducted on large beam specimens (1,700×450×450 mm). This paper describes the behavior of dam concrete subjected to dynamic elevated-amplitude cyclic loading with different initial static load levels. Stress-strain measurements were made on the concrete specimens. The test results show that dynamic increase factor of dam concrete increases with increasing initial static stress levels. The results of this study should be useful in determining the earthquake resistance of dam structures.

Damage Assessment of Connections Used in Cross-Laminated Timber Subject to Cyclic Loads

AbstractCross-laminated timber (CLT) products are gaining popularity in the North American market and are being used in midrise wood buildings, in particular, in shearwall applications. Shearwalls provide resistance to lateral loads such as wind and earthquake loads, and therefore it is important to gain a better understanding of the behavior of CLT shearwall systems during earthquake events. This paper is focused on the seismic performance of connections between CLT shearwall panels and the foundation. CLT panels are very stiff and energy dissipation is accomplished by the connections. A literature review on previous research work related to damage prediction and assessment for wood frame structures was performed. Furthermore, a test program was conducted to investigate the performance of CLT connections subjected to simulated earthquake loads. Two different brackets in combination with five types of fasteners were tested under monotonic and cyclic loading protocols. In total, 98 connection tests were co...

Time-Dependent Behavior of FRP Retrofitted RC Columns after Subjecting to Simulated Earthquake Loading

Seismic retrofit of reinforced concrete (RC) columns using fiber-reinforced plastic (FRP) jacketing has been widely investigated. However, the residual performance of FRP retrofitted columns after surviving earthquake attacks remains as an issue with little research. As a follow up of a previous experimental study, this paper reports the analysis of the axial loading creep behavior of FRP retrofitted RC columns with different degrees of simulated earthquake damage. The damage degree and residual strains in FRP after lateral loading are assessed based on previous maximum lateral displacement excursion. A creep model for damaged columns with FRP jacket is presented based on the age-adjusted effective modulus method for creep of concrete and the Findley’s power law function for creep of FRP jacket. The creep model considers the effects of previous damage, sealed concrete, multiaxial stress state of stresses and stress redistribution. The proposed model is validated against previous creep tests of fiber-wrapped concrete columns by other researchers and the long-term tests conducted by the authors. Finally, a detailed study is carried out to identify the practical design parameters affecting creep of hybrid columns. The analytical results show that the creep of the FRP confined column increases as the damage degree becomes larger and exhibits notable nonlinear feature. The creep life declines and may cause creep rupture of the FRP when retrofitted columns suffer serious earthquake damage or under high axial load.

Implementation of online model updating in hybrid simulation

SUMMARYHybrid simulation combines numerical and experimental methods for cost‐effective, large‐scale testing of structures under simulated earthquake loading. Structural system level response can be obtained by expressing the equation of motion for the combined experimental and numerical substructures, and solved using time‐stepping integration similar to pure numerical simulations. It is often assumed that a reliable model exists for the numerical substructures while the experimental substructures correspond to parts of the structure that are difficult to model. A wealth of data becomes available during the simulation from the measured experiment response that can be used to improve upon the numerical models, particularly if a component with similar structural configuration and material properties is being tested and subjected to a comparable load pattern. To take advantage of experimental measurements, a new hybrid test framework is proposed with an updating scheme to update the initial modeling parameters of the numerical model based on the instantaneously‐measured response of the experimental substructures as the test progresses. Numerical simulations are first conducted to evaluate key algorithms for the selection and calibration of modeling parameters that can be updated. The framework is then expanded to conduct actual hybrid simulations of a structural frame model including a physical substructure in the laboratory and a numerical substructure that is updated during the tests. The effectiveness of the proposed framework is demonstrated for a simple frame structure but is extendable to more complex structural behavior and models. Copyright © 2013 John Wiley & Sons, Ltd.