•Dynamic tests of a typical façade fastening system in RC precast structures.•The failure criterion of the fastening system is identified.•New numerical models for connections are proposed and ...validated by dynamic tests.•The typical values of model parameters are proposed.
The paper presents experimental and analytical studies of the dynamic in-plane response of typical fastening systems for horizontal cladding panels in RC precast industrial buildings in Central Europe. The system consists of two main parts: a pair of top bolted connections, which provide the horizontal stability of the panel, and a pair of bottom cantilever connections, which support the weight of the panel. A typical response mechanism of the fastening system consists of three distinct stages: sliding with limited friction, contact with the panel causing an increase in the connection stiffness, and failure. It has been found that the capacity of the complete system is limited by the displacement capacity of the top connections, which are the most critical components. Therefore, it is better to express the capacity of the entire system in terms of displacements.
Appropriate numerical models for the complete fastening system have been proposed and validated by the results of the presented experiments. The top and bottom connections were analysed separately and showed physically different response behaviours. The typical Coulomb friction model was used to describe the friction in the top connection, whereas the viscous friction model better simulated variable friction in the bottom connection. The contacts that occur when the gap for sliding of panels closes were simulated by an abrupt increase of the stiffness of the connection.
The capabilities of certain standard macro numerical models were evaluated by simulating a shaking table experiment that was performed on a full-scale ten-storey fixed-base building with a frame and ...dual structural system in two perpendicular directions (denoted as the frame and wall directions) at the largest shaking table in the E-Defense centre in Japan. The lumped plasticity model for columns and beams, the multiple-vertical-line-element model for walls and the scissors model for beam-column joints were evaluated. The results indicated that the experiment was simulated reasonably well. The most significant discrepancy was observed between the maximum drifts along the wall direction in the strongest cycle of the strongest test (calculated drift of 1.9% versus measured drift of 1.5%). In other cycles and tests, these differences were smaller. The calculated and measured maximum accelerations along the wall direction in the strongest test were 13.8 m/s
2
and 13.5 m/s
2
, respectively. The discrepancy between the analysis and experiment results was smaller along the frame direction. The maximum calculated and measured drifts were 2.9% and 3.1%, respectively. The maximum calculated and measured accelerations were 15.8 m/s
2
and 19.0 m/s
2
, respectively. In general, the standard input parameters were used in the evaluated models. However, some parameters required modifications, particularly when modelling weakly reinforced beam-column joints with substandard reinforcement that were considerably damaged. Their yielding rotation and near-collapse strength were, on average, reduced to 55% and 30% of the standard value, respectively. One of the most important parameters influencing the response was the effective width of the slabs, which was increased to the total span length for the highly loaded beams. The ratios of the strength, stiffness and amount of dissipated energy in the joints, beams and columns also significantly influenced the response. The adequate ratio of the dissipated energy was obtained by reducing the standard unloading stiffness in the beams and columns. The initial stiffness considerably influenced the response, particularly under weaker excitations. This stiffness was reduced threefold to account for various factors that typically reduce its value, which, among others, includes the influence of preceding tests on the same building with sliding foundations, as well as the assembly, transportation and handling of the specimen.
Experimental tests on, and numerical simulations of, full-scale precast reinforced concrete structures with horizontal cladding panels are presented. First, the experimental tests are discussed. The ...tests were performed on a shaking table using the typical structural layout and cladding connections used in Europe. In particular, they were performed on symmetrical and asymmetrical panel configurations with peak ground acceleration (PGA) intensities of up to 0.4 g. Key observations concerning the seismic responses are presented. The most notable occurrences during the responses were panels sliding within connections and panels impacting columns. Second, the numerical model, which was developed in OpenSees, and simulation results are presented. The numerical model simulated all identified phenomena, including sliding within connections and panels impacting columns. The simulations aligned with the test results, validating the developed numerical model.
•Full scale shake table tests of a precast structure with non structural claddings.•Sliding of panels and impacts with columns.•New robust and accurate numerical model.
An extensive parametric study of the seismic response of one-storey precast buildings with horizontal cladding panels frequently used in Central Europe was conducted to analyse the panels’ influence ...on the overall response of buildings and to find out if the panels can be considered non-structural elements when they are attached to the main building with the connections typically used in practice in Central Europe. The studied structural system consisted of reinforced concrete columns and beams connected by dowels. Horizontal cladding panels were attached to columns using one of the most frequently used isostatic fastening systems. The top connections provided out-of-plane stability, and the bottom connections supported the panel in the vertical direction. The parametric study was preceded by extensive experimental research, including cyclic tests on connections and full-scale shaking table tests of whole buildings. The results of experiments were used to reveal the basic response mechanisms of panels and connections and to develop, validate and calibrate numerical models employed in the parametric study presented herein. Fifteen generalised structures with different masses and heights were subjected to 30 accelerograms with two peak ground acceleration (PGA) intensities of 0.3 g and 0.5 g, corresponding to significant damage and near-collapse limit states. The effects of the construction imperfections in connections, the silicon sealant panel-to-panel connections and different types of connections of the bottom panel to the foundation were analysed. The crucial parameter influencing the response was the displacement capacity of the connections, which was considerably affected by the construction imperfections and, consequently, difficult to estimate. It has been observed that in some buildings, particularly in shorter structures with smaller mass, cladding panels can have a somewhat more notable influence on the overall response. However, in general, when the considered types of connections are used, the panels can be considered as non-structural elements, which do not importantly influence the response of the main building. Owing to structural imperfections and relatively short available gaps, the failure of the considered top connections and falling of the panels is very likely in the high seismicity regions. In the most adverse cases, it can occur even in the moderate seismicity regions.
The cyclic behaviour of slender cantilever columns in full-scale models of precast industrial buildings, designed by Eurocode 8, was studied experimentally and analytically. The shear span ratio of ...the columns was 12.5, which is more than allowed by Eurocode 8 for columns in frame structures (10). High deformability and a large deformation capacity (8%~drift) of the columns was observed. A lumped plasticity model was used in the analysis. In the paper the observed behaviour of the models has been compared with the predicted behaviour obtained by several empirically based models and procedures. It was observed that these models, which were developed for much lower shear span ratios (2–6), were not applicable for the analyzed very slender columns without appropriate additional considerations and modifications. In the case of such columns the yield drift is dominated by the flexural mode (it is practically proportional to the height of the column) and the ultimate drift under cyclic loading conditions is only slightly dependent on the shear span (indicating that the ratio of the equivalent length of the plastic hinge to the height of the column decreases with the increasing shear span). An appropriately modified lumped plasticity model incorporating in-cycle and repeated-cycle strength deterioration was chosen for future use in performance-based design and seismic risk studies.
The stiffness of rubber bearings, which are widely used for the seismic isolation of different types of structures, changes under different seismic intensities. These bearings are typically designed ...considering only lateral displacements induced by design earthquakes. At lower displacements, induced by weaker earthquakes, the stiffness of rubber bearings is typically increased, and the efficiency of the seismic isolation is thus reduced. To improve the response of rubber isolators at lower seismic intensities, a new isolation device, which can adjust itself to the intensity of the load, has been developed. It is fabricated from a magnetically controlled elastomer (MCE), whose stiffness can be varied by applying a magnetic field. Variation of the device stiffness is regulated by a specifically designed control unit. The seismic response of this new device was tested experimentally and analytically. This study showed that the new device can substantially reduce the seismic demand, particularly in the case of fairly stiff structures, and the equipment installed in such structures. It was found that the group of equipment, which is critical in the case of weak earthquakes, can be substantially reduced or even completely eliminated when stiff structures are isolated using MCE devices.
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