An envelope-based pushover analysis procedure is presented that assumes that the seismic demand for each response parameter is controlled by a predominant system failure mode that may vary according to the ground motion. To be able to simulate the most important system failure modes, several pushover analysesneed to be performed, as in a modal pushover analysis procedure, whereas the total seismic demand is determined by enveloping the results associated with each pushover analysis. The demand for the most common system failure mode resulting from the "first-mode" pushover analysis is obtained by response history analysis for the equivalent "modal-based" SDOF model, whereasdemand for other failure modes is based on the "failure-based" SDOF models. This makes the envelope-based pushover analysis procedure equivalent to the N2 method provided that it involves only "first-mode" pushover analysisand response history analysis of the corresponding "modal-based" SDOF model. It is shown that the accuracy of the approximate 16th, 50th and 84th percentile response expressed in terms of IDA curves does not decrease with the height of the building or with the intensity of ground motion. This is because the estimates of the roof displacement and the maximum storey drift due to individual ground motions were predicted with a sufficient degree of accuracy for almost all the ground motions from the analysed sets.
COBISS.SI-ID: 6305121
Within the international scientific cooperation of the Faculty of Civil and Geodetic Engineering of University of Ljubljana, Slovenia, the Institute of Earthquake Engineering and Engineering Seismology - UKIM-IZIIS, Skopje, Republic of Macedonia and the Civil Engineering Faculty, University of Zagreb, Croatia, experimental testing of full scale composite timber-glass innovative panels was carried out on the seismic shaking table at IZIIS for the purpose of defining their behaviour and stability under real earthquake conditions. The seismic excitations selected for the shake-table testing of the model were four representative accelerograms recorded during the following earthquakes: El Centro, Petrovac, Kobe and Friuli. The idea was to investigate the seismic behavior of the model under several types of earthquakes, considering their different frequency content, peak acceleration and time duration. The performed tests showed clearly the behaviour of the composite panels and the failure mechanism under strong earthquake motion.
COBISS.SI-ID: 6329441
Assessment of multi-leaf stone masonry in earthquake-prone areas is mostly related to the evaluation of its texture, morphology, leaf detachment and structural cracking due to previous seismic activity, as well as disintegration due to material deterioration. For the plastered masonry with heritage or artistic value (paintings, frescoes etc.), both the type of structure and the extent of damage should be characterized with minimal interference to the structure, which could be overcome solely by non-destructive testing (NDT). However, due to the complexity of plastered multi-leaf masonry structure, the performance of well-known NDT methods could be significantly worsened. Therefore, as a prerequisite for applying NDT on multi-leaf stone masonry in practice, a validation process should be carried out. In this study, complementary ground penetrating radar (GPR) and infrared (IR) thermography measurements on plastered laboratory three-leaf stone masonry walls were performed. Apart from assessing the wall texture and morphology with the type of connection between the leaves, detection of gradual plaster delamination and crack propagation while subjecting the walls to an in-plane cyclic shear test was taken into account. The results showed that GPR could successfully visualize header stones passing through the whole depth of the specimen. The masonry texture behind the plaster could be well resolved by both methods, although GPR near-field effects worsened its localisation. For the detection of plaster delamination, IR thermography outperformed GPR by detecting delamination as small as 2 mm as well as structural crack patterns, whereas GPR only detected delamination larger than 8 mm. It was shown that the performance of both methods for defect detection could be further improved by image fusion based on unsupervised clustering methods.
COBISS.SI-ID: 16804697
The objective of the study presented in this paper is to investigate the effects of masonry infills on the shear demand and failure of columns for the case when reinforced concrete frames with such infills are modeled by means of simplified nonlinear models that are not capable of the direct simulation of these effects. It is shown that an approximate simulation of the shear failure of columns can be achieved through an iterative procedure that involves pushover analysis, post-processing of the analysis results using limit-state checks of the components, and model adaptation if shear failure of columns is detected. The fragility parameters and the mean annual frequency of limit-state exceedance are computed on the basis of nonlinear dynamic analysis by using an equivalent SDOF model. The proposed methodology is demonstrated by means of two examples. It was shown that the strength of the four-story and seven-story buildings and their deformation capacity are significantly overestimated if column shear failure due to the effects of masonry infills is neglected, whereas the mean annual frequency of limit-state exceedance for the analyzed limit states is significantly larger than that estimated for the case if the shear failure of columns is neglected.
COBISS.SI-ID: 6102113
The dowel type of the connection is the most common in Europe. However, the knowledge about its seismic behaviour was incomplete and poorly understood. To analyse the failure of dowel mechanism the numerical model in the FEA software ABAQUS was defined and calibrated using the results of the experimental investigations. Cyclic as well as monotonic response was analyzed. The most important observations are: (1) standard theory assuming that the failure mechanism is initiated by flexural yielding of the dowel and crushing of the surrounding concrete has been confirmed, (2) the strength of the connection considerably depends on the depth of the plastic hinge in the dowel, (3) in the case of the cyclic loading the strength is reduced due to the smaller depth of the plastic hinge, (4) neoprene bearing pad can considerably increase the strength of the connection, particularly when large relative displacements between the beam and the column are developed, and (5) in the case of large rotations between the beam and the column, cyclic resistance is reduced by 15–20%, because the dowel is loaded not only in flexure but also in tension.
COBISS.SI-ID: 6331233