Collapse Simulation of CFRP Retrofitted Column using Hybrid Testing Technique

The performance of Reinforced Concrete (RC) structures and their collapse safety experiencing moderate to high-magnitude seismic excitations might not be fully understood. Factors related to the high levels of uncertainties in ground motion content, structural modelling and design uncertainties, or to the empirical nature of design codes and standards affect the collapse assessment of RC structures. Therefore, experimental test researches are very important in verifying and improving the accuracy of structural performance predictions and highlighting the actual behavior during seismic excitation. In this paper, the test results of a full-length damaged RC column retrofitted with Carbon Fiber Reinforced Polymer (CFRP) sheets and then retested using pseudo-dynamic experimental testing approach through the state-of-the-art hybrid simulation testing facility, referred to Multi-Axis Substructure Testing (MAST) system at Swinburne University of Technology are presented. A comparative collapse assessment of the initial and retrofitted column showed more ductile column response reaching higher drift ratios. In addition, the experimental test results displayed clearly the effectiveness of CFRP sheets under increasing intensity of earthquake demands in restoring the collapse resistance of the retrofitted RC column by altering concrete failure type.

Characterization of local and global capacity criteria for collapse assessment of code-conforming RC buildings

The paper investigates both local and global capacity criteria for collapse assessment of RC frame buildings. Both literature and regulations criteria are considered, also including the formulation recommended in the draft of the new Eurocode 8 (part 3) and other collapse criteria never investigated. The case studies consist of low-rise bare and infilled frame buildings, which are designed according to the Italian code provisions considering low-to-high seismicity sites in Italy. The seismic demand is estimated by performing multiple-stripe analysis based on inelastic modeling, also including the presence of the infills. The capacity assessment and the performance evaluation associated with the (building) collapse are carried out according to the latest approaches and methodologies of performance-based earthquake engineering. The investigated capacity criteria are characterized as a result of the collapse assessment in terms of (a) collapse demand to capacity ratios, (b) collapse fragility curves, (c) collapse margin ratios and probabilities, and (d) inter-capacity margin ratios. The findings provide novel information and technical insights into the influence of the collapse capacity criteria selection on the collapse features of the investigated buildings. In particular, the capacity criteria are quantitatively correlated to the building collapse performance, also outlining safety and economic considerations.

An Investigation of Vector Intensity Measures for Seismic Collapse Assessment Under Far-Field Aftershocks

Aftershock records have a considerable effect on the results of collapse assessments conducted on buildings. Thus, they should be selected cautiously. As the number of recorded aftershocks is not sufficient, mainshock records are often utilized instead. In order to increase the correlation between the aftershock time history and the seismic response of a structure, this research intends to investigate several Intensity Measures (IMs). For this study, three RC frames were considered. Forty-four far-field records from FEMAP-695 were selected as main and aftershock. Each building analysis was conducted under 44 mainshock–aftershock chains. According to the results, use of the summation of the first mode spectral acceleration value of aftershocks as the second part of a vector IM can lead to the sufficiency of the IM.