•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.
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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