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Earthquake damage to freestanding nonstructural components has occurred in past earthquakes. Ceramic vase is one of the most vulnerable freestanding nonstructural components in museums, residential, and historical buildings. To investigate the seismic performance of a freestanding vase, shaking table tests were conducted, where four motions, consisting of two historic and two artificial ones, were selected and generated. The kinetic friction coefficient was acquired with a slow-pull test, which was used to define the possible response modes. The rocking and sliding responses of the vase were observed by accelerometers and high-speed camera. Results showed that the response mode of the vase was highly dependent on the input peak acceleration, i.e., the higher the peak acceleration, the larger the peak and residual displacements and rocking angles. In addition, the dynamic response varies with the excitation of different input motions, indicating that the frequency contents of the input motion also affect the rocking intensity. Generally, the experimental kinetic friction coefficient from the shaking table test matched the one from the slow-pull test closely, demonstrating that the two approaches were reasonable and accurate enoughand can be accepted. Using the philosophy of the second generation of performance-based earthquake engineering, damage modes, performance levels, and fragility curves were defined and generated on account of crack intensity, repair actions, and rocking angles, respectively. These efforts are also beneficial for the seismic evaluation of the freestanding objects in building structures. [ABSTRACT FROM AUTHOR]

Shaking table tests are conducted to investigate the seismic performance of new steel dowel-pinned granite claddings with two support systems. Standard and modified body anchors are used for installing the granite cladding system on opposite sides of a strong reinforced concrete tube fixed to the shaking table. One recorded ground motion (El Centro) and two artificial motions are applied as the input motions. The whole cladding system remained intact and almost no visible damage was observed for El Centro. However, the seismic responses of the cladding system under the effect of the artificial motions were larger. The dynamic response of the standard body anchors was larger than that of the modified ones. The maximum component amplification factors are larger than those specified in current code provisions. It is noted that the load bearing capacity of the body anchors determines the seismic performance of the global granite cladding system. Therefore, additional measures should be taken to guarantee the required seismic capacity of the stone cladding system by using the proposed steel dowel pin connections. [ABSTRACT FROM AUTHOR]

Freestanding objects have endured seismic damage during major historical earthquakes, but their seismic performance is not fully understood yet. A steel frame was constructed with steel rods and moveable plates to investigate the effect of the center of gravity (CG) on the seismic response of nonstructural freestanding objects. The location of the CG can be tuned to change the CG in the frame. Two groups of shaking table tests were carried out using instrumented floor motion. To verify the shaking table test results, an analytical model was defined based on Housner's rocking model. The experimental response modes were predicted correctly. The experimental kinetic coefficient of friction obtained in the slow-pull tests agreed with the peak acceleration of the steel frame in the shaking table tests. The displacement amplitude generally decreased with increasing height of CG (h cg); however, this trend was not observed when the CG was fixed. Identical properties were observed for the rotational response of the frame. The experimental and analytical rocking responses were in agreement in terms of amplitude, but not in terms of time history and trajectories. The overturing criteria of overturing velocity, spectral velocity, and vulnerability, were evaluated using the experimental results. The overturning spectral acceleration was not accurately predicted using Housner's equation. The overturning probability and ratio were correctly predicted, and they increased with the increase in h cg. The findings of this work enable seismic risk mitigation of nonstructural freestanding objects. • A steel frame is fabricated which allows to tune the location of CG. • Shaking table tests are carried out using an instrumented floor motion. • The displacement amplitude generally decreases with increasing location of CG, h cg. • The experimental and analytical rocking amplitudes are in agreement. • The overturning probability and ratio increase with the increasing h cg. [ABSTRACT FROM AUTHOR]

To investigate the seismic performance of granite cladding with undercut bolt anchorage and aluminum connectors, shaking table testing of full-scale specimens was performed. The floor spectrum was constructed and its compatible floor motion time history was generated and used as the input motion. A stiff steel frame was designed to provide the floor earthquake excitation to the cladding specimens installing on its four sides. Experimental results show that the aluminum connectors are the most seismically vulnerable components of the cladding system. The excessive relative in-plane sliding of the two-parts of the aluminum connectors governs the seismic performance of the whole system. While the out-of-plane deformation of the connectors absorbs part of the dynamic energy passed from the steel frame, which reduces the potential damage to the granite panels. The largest component acceleration amplification factor was determined to be about 2.9, which is larger than the recommended values in the current code provisions. Moreover, the experimentally estimated peak bending stress exceeded the design value. Finally, the seismic performance levels of the cladding were quantified and the corresponding fragility curves were also developed. [ABSTRACT FROM AUTHOR]

Structural Behavior of reinforced concrete (RC) buildings under earthquake excitation are highly nonlinear, particular for cracked RC structures with stiffness changing across elastic, pinched and hybrid regimes. This study investigates a structural health monitoring (SHM) method for an experimental scaled 12-storey RC frame building with cracks visually observed in the beam-column joints prior to a sequence of 4 shaking table tests. Hysteresis loops for every two floors are reconstructed using corrected acceleration and displacement measurements based on a multi-rate Kalman filter. The changes of nonlinear stiffness over time are calculated for divided half cycles using a hysteresis loop analysis (HLA). The effective elastic pinching stiffness are then extracted from the identified nonlinear stiffness values to examine the evolution of structural degradation during these events. A critical validation analysis is whether the final identified stiffness values match the initial values in a subsequent event, to ensure the method is robust in finding an accurate and repeatable value. In addition, fundamental frequencies, often used for SHM, are assessed using the identified effective stiffness and compared to those from modal analysis before-after each event. Results show the effective pinching stiffnesses for each floor are identified consistently between larger and small events. Final stiffness values for one event are within 9.7% of initial values for the next. The fundamental frequency results compare well further validating the method, but also show little sensitivity to large changes in effective stiffness. The overall results indicate the capability of the HLA to accurately identify damage that may not be found by vibration-based methods for highly nonlinear RC structures. [ABSTRACT FROM AUTHOR]

Seismic demands of a curtain wall (CW) relate to the floor response of the main structure. These demands include both acceleration and deformation. Floor capacity spectrum combines these demands into one acceleration-displacement response spectrum (ADRS) representing the CW as a single degree of freedom system. The in-plane (IP) load-displacement relationship can be transformed to the acceleration-displacement format (capacity curve) of the ADRS. The intersection of the capacity curve and the ADRS is the performance point (PP) of the CW system. Another way to determine the PP is through the floor response analysis of the main structure where the pairs of acceleration and displacement demands form the demand PPs. In shaking table testing of the CW system, the two coordinates of the PP can be simulated by applying the IP deformation with a specially designed loading frame, then exciting the test specimen by the shaking table in the out-of-plane direction. PPs are accurately reproduced and the seismic performance of the CW system is evaluated. The applicability and reliability of this novel shaking table test method are discussed in this paper. [ABSTRACT FROM AUTHOR]

• Obtain 3D dynamic response of shaking table structures by high-speed videogrammetry. • Accuracy of better than 0.5 mm in the X, Y and Z directions is achieved. • High-speed videogrammetric results are consistent with those of traditional sensors. This paper proposes a practical videogrammetric technique to measure shaking table tests of multi-layer structure models using two CMOS cameras. Three major issues, including high-speed videogrammetric hardware system configuration and network configuration, image sequence processing, and deformation information retrieval, are studied. The implementation of the proposed method is illustrated with a shaking table experiment for a multi-layer reinforced concrete structure in Tongji University, Shanghai. Sub-millimeter-level accuracy for the deformation measurements was achieved with the image resolution of 1280 (H) by 1024 (V) pixels. The velocity and acceleration of the shaking table structure are obtained accordingly. The results from the videogrammetric technique are compared with those from the traditional gauging and accelerometer methods. The experimental results show that, when compared with the traditional methods, the proposed videogrammetric method measures the deformation with sub-millimeter accuracy and can obtain more detailed peak values at the critical points on the shaking table structure. [ABSTRACT FROM AUTHOR]