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Column jacketing techniques have been widely used to improve the seismic performance of existing reinforced concrete buildings and to mitigate additional damage induced by subsequent earthquakes to earthquake-damaged structures. To numerically assess damage mitigation of structures due to column jacketing under successive earthquakes, this study proposes a numerical modeling technique for shear-critical reinforced concrete columns retrofitted and repaired using fiber-reinforced polymer wraps and validates the simulated results with existing experimental data. A non-ductile reinforced concrete frame with the potential of column shear failure is then selected and modeled using the proposed modeling technique to evaluate the effect of FRP retrofit and repair upon mainshock and aftershock responses. In addition, two rehabilitation parameters such as story-related rehabilitation and number of FRP wraps are selected, and used to create rehabilitated frame models to maximize the effectiveness of FRP installations for the as-built frame under successive earthquakes. This effectiveness is examined in terms of the damage level of maximum and residual deformation. [ABSTRACT FROM AUTHOR]

Many existing reinforced concrete buildings designed in accordance with pre-1971 codes are generally dominated by weak column-strong beam behavior under seismic loading due to inadequate reinforcement detailing. This behavior can lead to premature failure under seismic loads from damage concentrated in the first story of the structure. This paper presents the results of an experimental investigation into the seismic response of a full-scale, two-story non-ductile reinforced concrete frame. The frame was retrofitted with a fiber-reinforced polymer jacketing system on the first story columns to mitigate seismic vulnerability. Shake weight testing was performed to investigate the dynamic performance of the retrofitted building structure in terms of the modal response, inter-story drift, and effectiveness of the fiber-reinforced polymer jacketing system. The results demonstrate that the retrofit scheme helped develop a more uniform story drift distribution, working to counter the soft-story mechanism commonly found in reinforced concrete frames designed during this period. [ABSTRACT FROM AUTHOR]

• Effect of FRP jacketing system on seismic damage mitigation of non-ductile RC frames. • Investigation of seismic performance against various seismic loading hazard levels. • Identification of critical retrofit parameters influencing on the seismic performance. • Establishment of retrofit schemes for confinement and stiffness-related parameters. Many existing reinforced concrete building structures designed for gravity loads have seismic vulnerabilities owing to their deficiency in column detailing. A column jacketing system with prefabricated fiber-reinforced polymer materials provides additional confinement and stiffness to existing columns and mitigates their seismic vulnerabilities. This paper presents a seismic retrofit strategy for a low-rise gravity-designed reinforced concrete building frame for maximizing the retrofit effect against low, moderate, and high seismic hazard levels. The retrofit parametric models were created by varying the confinement and stiffness-related parameters and then simulated under various seismic loading scenarios. To establish the seismic strengthening strategy, the effectiveness of the retrofit system was examined in terms of its confinement and stiffness-related parameters. This retrofit effect was computed by comparing energy-based seismic demands between retrofitted and non-retrofitted models. Based on the parametric analysis, the critical parameters of the retrofit system were determined depending on the seismic hazard levels. Thus, the certain threshold values of the retrofit parameters for the seismic hazard levels to maximize the effectiveness of the retrofit system were proposed as the retrofit design scheme. [ABSTRACT FROM AUTHOR]

Piloti-type reinforced concrete building structures have vertically irregular configurations composing a moment frame for parking spaces in the lower story and heavy-weight shear wall system for residential spaces in the upper stories. Due to these vertically irregular configurations, such building structures are governed by a soft-story mechanism, damage concentration on the first story. Since the 2017 Pohang earthquake led to severe damage to the piloti-type building structures on a regional level, a decision-making tool mitigating the seismic damage for future events is needed. This paper aimed to propose a rapid decision-making tool promptly estimating seismic damage with simple information and determining a retrofit scheme using a pre-developed extensive database, i.e., multi-dimensional structural parameter surfaces. The multi-dimensional surfaces were created using a simplified modeling approach with five structural parameters: period, strength ratio, and ductility controlling failure modes as the input, and peak inter-story drift ratio and demand-to-capacity ratio as the output. The proposed methodology was validated using a finite element model for the piloti-type building structure with a soft-story mechanism. The seismic responses detected from the multi-dimensional surfaces have a slight difference from those of the numerical model. Nevertheless, the rapid tool predicted a reasonable agreement with performance evaluation from the finite element simulation. In addition, the rapid tool provided feasible retrofit options to meet target performance using brief structural information. Due to its simplified process, the proposed tool can be implemented to the regional seismic assessment for the residential areas where the piloti-type building structures were highly concentrated. • Seismic vulnerabilities to piloti-type buildings highly concentrated in urban areas due to their vertical irregularities. • Extensive database from simplified numerical models reproducing the seismic vulnerabilities of the piloti-type structures. • Development of a database-based tool for regional seismic damage assessment of the piloti-type buildings. • Validation of the proposed tool with finite element simulation of a vertically-irregular building structure. • Establishment of retrofit schemes for piloti-type building structures with brief structural information. [ABSTRACT FROM AUTHOR]

• A new rapid tool to determine multi-hazard performance and retrofit scheme. • Artificial neural network models developed for rapid performance evaluation. • A framework for combining seismic and blast performance limits using the ANN models. • Demonstration of the rapid tool to select an effective retrofit scheme under multi-hazards. Non-ductile reinforced concrete building frames have seismic and blast vulnerabilities due to inadequate reinforcement detailing resulting in premature failure. One option to mitigate these vulnerabilities is the installation of a retrofit system on susceptible structures. However, differences in code-defined performance limits depending on loading type may result in a non-conservative retrofit design under multi-hazard loads. This paper presents a rapid tool for multi-hazard assessment and mitigation for the seismically-vulnerable building frames using artificial neural network models, which can rapidly generate large datasets. Using the models, energy-based performance limits for multi-hazard loading are derived, and a rapid decision-making approach for the retrofit design is developed under seismic and blast loads. [ABSTRACT FROM AUTHOR]

Non-ductile reinforced concrete building structures built before the 1970s have been significantly damaged and collapsed under man-made disasters (e.g., blast loads) due to their inadequate column details. The structural deficiencies can be mitigated by a fiber-reinforced polymer jacketing system. This research investigated the blast performance of a low-rise non-ductile building frame strengthened with the jacketing system. Based on the investigation, a retrofit scheme was established to mitigate the blast-induced damage and maximize the effectiveness of the retrofit system. The retrofitted models varied with the main parameters of the retrofit system associated with the confinement effect and flexural stiffness, and blast simulation was performed under various loading scenarios. The retrofit effect was examined in terms of confinement and stiffness ratios. Since the effects of the retrofit parameters on the blast performance depend on the blast loads, the retrofit scheme needs to be established in terms of expected blast loading scenarios. [ABSTRACT FROM AUTHOR]