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Blast loading and seismic excitations are widely recognized as the most detrimental occurrences that a building structure may encounter throughout its lifespan. Therefore, this study investigated the retrofitting capacity of external devices (ENTA damper systems) for reinforced concrete (RC) frames in term of enhancing their resistance under the combined effects of blast and seismic loads. This study presents the establishment of finite element (FE) models for retrofitted RC frames with ENTA damper systems through the utilization of the dynamic analysis software LS-DYNA. The investigation involved the validation for blast performance of RC column in order to identify the most effective method for modeling blasts. Additionally, the study aimed to validate the performance of RC frame models through effects of ENTA damper systems under seismic loading. Subsequently, a performance evaluation of RC frame structures was carried out to examine the impact of the ENTA damper systems when subjected to blast loading. The findings of the study indicate that the use of external ENTA damper systems effectively enhanced the rigidity and structural integrity of RC frames, while maintaining their ability to resist deformation. Finally, the damage assessment of blast and seismic performance is investigated based on various parameters such as ductility, drift and energy-based damage limits. • Finding the suitable model blasts based on the blast performance of RC column. • Validating performance of the RC frame models under seismic loading. • Investigating the blast performance of RC frame and retrofitted RC frame. • Considering the damage performance of RC frames under blast and seismic loadings. [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]

In building design codes, buildings having less than 3 stories and a floor area less than 1000 m 2 are generally defined as small-scale buildings, and these are generally exempted from seismic requirements. To prevent potential loss of life and economic damage in the event of an earthquake, such buildings should be retrofitted so as to conform to current seismic design codes. In this study, a seismic retrofit scheme using buckling-restrained knee brace (BRKBs) was developed for a 2-story non-seismic gravity-designed steel frame building using the fragility contour method. To develop an effective retrofit scheme using BRKB for this building, 75 types of BRKB analytical models were used to achieve the desired performance levels and analyzed. Then, the seismic performance of the building before and after the retrofit was evaluated using the fragility contour method, and the improvement in the performance level of the probability against the structural limit state, such as component failures and structural collapse, was investigated. Based on the analytical studies, the most effective BRKB model for the retrofit scheme was proposed based on various scenarios in terms of the weight of the developed BRKB models. This study shows that the fragility contour method can be used for rapid evaluations and should be an effective tool for structural engineers to perform the seismic retrofit of buildings. [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]