During seismic events, inefficient steel moment frame building systems may exhibit soft-story failures. This thesis focuses on development and validation of a seismic retrofit strategy for avoiding soft-story failures in low-rise and mid-rise steel moment frame buildings. The considered retrofit strategy consists of a sufficiently stiff Rocking Core (RC) pinned to the foundation and pin connected to the existing frame. For demonstration purposes, two representative benchmark steel moment frames, which are modified from the three- and nine-story pre-Northridge steel moment frames designed for Los Angeles in the SAC Steel Project, are considered. Finite Element (FE) models of the benchmark buildings are developed with consideration of member yielding, connection rupture, and P-Delta effect, and validated using published results. Eigenvalue analyses are conducted to investigate the effect of the RC on system modal properties. It is found that in general the added RC with practical stiffness value does not significantly change the fundamental period and therefore does not attract excessive earthquake force to the system. In addition, nonlinear static pushover analyses are performed to address the beneficial contribution of the RC to the system under the performance objectives including immediate occupancy, life safety, and collapse prevention. The Monte-Carlo simulation technique is used to generate the random lateral force distribution required in the nonlinear static pushover analysis. It is found that RC works as expected in all considered scenarios and creates more uniform inter-story distribution along the vertical direction when it is sufficiently stiff. Furthermore, nonlinear dynamic analyses are conducted using three different ground motion suites (including two suites with ground motions having probabilities of exceedance of 2% and 10% in 50 years, and one suite with near-fault ground motions). It is shown that the systems with properly selected RC can achieve the Best Safety Objective defined in FEMA 356 and exhibit collapse prevention performance under near-fault earthquakes.

La Norma E.030 y gran parte de los códigos de diseño sismorresistente consideran el análisis unidireccional para cada uno de los ejes principales de manera independiente. A comparación de ello, en realidad los eventos sísmicos tienen un comportamiento bastante aleatorio. Además, imponen solicitaciones bidireccionales en diferentes orientaciones a las edificaciones. Se realizó el estudio de la respuesta en edificaciones sujetas a solicitaciones de carga sísmica con irregularidades de esquina entrante y de piso blando. Para ello, se ha realizado el análisis tiempo historia lineal (ATHL) de éstas imponiendo solicitaciones sísmicas en dos direcciones ortogonales simultáneas. Así, se obtiene la respuesta estructural con variaciones de ángulos de incidencia de 10° y se compara con la respuesta derivada del análisis unidireccional. Los resultados obtenidos muestran que el análisis tradicional subestima las respuestas de las estructuras. Se obtuvieron variaciones de hasta 50% en el modelo de esquina entrante y hasta 72% en el modelo de piso blando. En las edificaciones con irregularidad de piso blando extremo existen variaciones de hasta el 90%. Estos resultados confirman la necesidad de considerar la bidireccionalidad sísmica en el análisis y diseño sismorresistente. / Standard E.030 and most of the seismic-resistant design codes consider the unidirectional analysis for each of the main axes independently. By comparison, seismic events actually behave quite randomly. In addition, they impose bidirectional solicitations in different orientations to the buildings. The study of the response in structures subjects to earthquake loads with irregularity of l-shaped plan and soft story is carried out. For this, the linear time-story analysis (LTHA) of these has been carried out imposing seismic solicitations in two perpendicular directions at the same time. Thus, the structural response with incidence angle variations of 10° is obtained and compared with the response derived from the unidirectional analysis. Variations of up to 50 were obtained in the l-shaped plan model and up to 72% in the soft story model. In structures with extreme soft story variations of up to 90%. These results confirm the need to consider seismic bidirectionality in earthquake analysis and design. / Tesis

La tabiquería a pesar de estar aislada aporta cierta rigidez lateral a los pórticos como se demostró en el estudio de (Zhou, Kou, Peng, & Cui, 2018), por lo cual, se debe realizar en algunos casos un análisis considerando la interacción tabique pórtico En la primera parte de la tesis se evaluó que características de un pórtico son las más influyentes en el ancho efectivo (Wb) del puntal equivalente a partir de un análisis con el método de elementos finitos, donde se encontró que la longitud diagonal del pórtico es la variable más influyente. Luego en la segunda parte se realizó un análisis sísmico de 2 edificaciones que fueron predimensionadas con la deriva máxima y 50% de la deriva máxima de la norma E0.30. Estos 4 modelos se analizaron con tabiquería y sin tabiquería, con el método modal espectral y tiempo historia. Las principales conclusiones fueron que realizar un análisis considerando la ITP puede cambiar el comportamiento modal de la edificación, la cortante basal aumentó hasta en un 19.5% en la estructura rígida y 17% en la flexible, los desplazamientos laterales se redujeron en máximo el 53% en la estructura flexible y 16% en la rígida, y que el periodo disminuyó hasta un 25%. Se concluyó que una edificación más flexible amplifica las diferencias entre el modelo con ITP y sin ITP. Por último, se confirmó que el análisis considerando la ITP saca a la luz irregularidades por torsión y/o piso blando que no se encuentra en un análisis convencional. / The masonry wall, despite being isolated, provides a certain lateral stiffness to the frames, as demonstrated in the study by (Zhou, Kou, Peng, & Cui, 2018), therefore, in some cases an analysis must be carried out considering the masonry walls. In the first part of the thesis, it was evaluated which characteristics of a frame are the most influential in the effective width (Wb) of the equivalent prop from an analysis with the finite element method, where it was found that the diagonal length of the frame is the most influential variable. Then, in the second part, a seismic analysis of 2 buildings was performed that were pre-dimensioned with the maximum drift and 50% of the maximum drift of the E0.30 standard. These 4 models were analyzed with masonry and without masonry, with the spectral modal method and time history. The main conclusions were that carrying out an analysis considering the ITP can change the modal behavior of the building, the basal shear increased by up to 19.5% in the rigid structure and 17% in the flexible one, lateral displacements were reduced by a maximum of 53% in the flexible structure and 16% in the rigid structure, and that the period decreased to 25%. It was concluded that a more flexible building amplifies the differences between the model with ITP and without ITP. Finally, it was confirmed that in the analysis considering the ITP there are irregularities due to torsion and / or soft story. / Tesis

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