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Confinement of reinforced concrete members has repeatedly proven crucial when structures are exposed to strong ground motions. Yet, unconfined concrete is still widely used in developing countries with significant seismic hazard. To quantify the effect of lack of confinement on collapse probability of reinforced concrete frames, incremental dynamic analyses were conducted on two 4-story reinforced concrete moment resisting frame buildings using 5 ground motions. The structures are identical and comply to Eurocode demands except for the fact that one is completely unconfined whereas the other is confined according to the code. The analyses were conducted in OpenSEES using Mander’s material model for confined and unconfined concrete. Based on the results of the analyses, collapse fragility curves were created for each structure. The results show statistically significant effect of confinement on the collapse probability of the reinforced concrete frame. The prabability of collapse is 1.2 and 12 %, respectively, for the code complying and the unconfined structure exposed to a design level earthquake. [ABSTRACT FROM AUTHOR]

In this study, the multihazard response of code-designed conventional and base-isolated steel frame buildings is evaluated using nonlinear response history analysis. The results of hazard and structural response analysis for 3-story moment-resisting frame buildings are presented in this paper. Three-dimensional models for both buildings are created, and seismic response is assessed for three scenario earthquakes. The response history analysis results indicate that the performance of the isolated building is superior to the conventional building in the design event. However, for the Maximum Considered Earthquake, the presence of outliers in the response data reduces confidence that the isolated building provides superior performance to its conventional counterpart. The potential causes of the outliers have been carefully evaluated. [ABSTRACT FROM AUTHOR]

A detailed seismic performance assessment procedure has been developed for reinforced concrete (RC) frame buildings with masonry infill walls. The procedure is based on member damage functions, in terms of interstory drift ratios. These functions are developed for the primary components, namely, columns, beams, and infill walls. For developing these functions, analytical investigations to determine the influence of several parameters on the damageability of components were combined with experimental data. A new approach has been developed to synthesize component damage states to determine the story and eventually the building level performance states. The procedure has been calibrated and compared with other procedures by predicting the observed performance of three buildings exposed to recent earthquakes in Turkey. It is concluded that the developed procedure can satisfactorily predict the damage experienced by most of the components of the studied buildings. Moreover, the procedure reasonably captured the observed building damage states. Accordingly, the developed procedure can be used for a reliable performance assessment as well as performance-based design of RC frame structures. [ABSTRACT FROM AUTHOR]

Reliable estimation of energy demands imposed on a structure by a design ground motion is a key component of energy-based design. Although several studies have been conducted to quantify the energy demands in single-degree-of-freedoms systems, few have focused on multi-degree-of-freedom systems. This study aims to build on the knowledge from previous studies on multi-degree-of-freedom systems with special focus on the distribution of hysteretic energy demands among the components of the structure. Nonlinear response history analyses conducted under ground motion sets representing three different hazard levels show that the total input and hysteretic energy demands of multi-degree-of-freedom systems can be accurately estimated from equivalent single-degree-of-freedom systems for low- and medium-rise buildings. The distribution of hysteretic energy demands over the height of the multistory structures has been shown to vary significantly from ground motion to ground motion. Analyses results also show that the relative strength of adjoining beams and columns has a significant influence on the hysteretic energy demand distribution. On the other hand, the energy distribution is relatively insensitive to the damping model used in the analysis of the multi-degree-of-freedom system. [ABSTRACT FROM AUTHOR]