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In this thesis, we present our work in pursuit of a novel method for computing core-excited states of molecules: non-orthogonal configuration interaction singles, or NOCIS. NOCIS is a black-box variant of NOCI which, when applied to K-shell excitations, uses A different core-ionized determinants for a molecule with A atoms of a given element to form single substitutions. NOCIS is a variational, spin-pure, size-consistent ab initio method that dramatically improves on standard CIS for core excitations by capturing essential orbital relaxation effects associated with the core hole, in addition to essential configuration interaction. We also describe a more computationally efficient modification of NOCIS called one-center NOCIS (1C-NOCIS) for open-shell molecules which is intermediate between NOCIS and the computationally less demanding static exchange approximation (STEX). These methods are efficiently implemented and applied in the context of various core-excited state types, namely molecules initially in singlet, doublet, and triplet states represented by a single determinant wavefunction. Finally, this thesis also presents an overview of collaborative excited-state work in various settings, including a foray into valence excited states.

In high seismic areas of the world, dissipation of energy created by earthquakes is vital to keep structures intact and more importantly the conservation of life. Steel structures use braced and moment frames to dissipate this energy through various mechanisms. This paper’s focus is on moment frames, and more specifically on Bolted Flange Plate connections with non-orthogonal geometry. With the complexity of designs increasing due to advancements in research and the want for large open spaces in many structures, moment frames are a popular option because no diagonal bracing members are required. Yet, in AISC 358-10 (AISC, 2010b), only orthogonal moment frame connections are discussed without any mention of how to design for a non-orthogonal connection. Using the finite element software ABAQUS, the effects of non-orthogonal geometry on Bolted Flange Plate connections, both skewed and sloped, were analyzed. Unlike welded moment connections, this connection requires bolts, and therefore two different bolt configurations were also studied, one having the bolt rows staying parallel to the column face and the other having the bolt rows perpendicular to the beam axis. The performance of these finite element models were compared to previous experimental results, based on the orthogonal connection, conducted at the University of California – San Diego. Using the moment-rotation capacity of the connection, distribution of stresses, and location of the plastic hinge, recommendations for the design of non-orthogonal Bolted Flange Plate connections were determined.

Modern architectural designs for buildings often require innovative and unconventional structural solutions such as the use of non-orthogonally framed connections. Moment frames are seismic force resisting systems that provide architectural liberty when these unconventional designs are encountered. While a braced frame or a structural wall can be more cost efficient, a moment frame allows for the building space to be more efficiently utilized. Additionally, the moment frame allows for architectural liberty.When the seismic demand requires the use of an intermediate or special moment frame per the ASCE/SEI 7 specification, the document requires that the designing engineer implement a prequalified connection from the ANSI/AISC 358 document. However, the connections presented within this document do not account for non-orthogonally framed connections. Therefore, the designing engineer must either perform cyclic qualification of the proposed connection, or make a potentially ambiguous decision for the use of the connection based on their engineering judgment alone.The research investigates the effects of non-orthogonal connection framing of two connections presented in the ANSI/AISC 358 document with solid element finite element analyses. The responses of the connections are compared with traditional orthogonally framed connections validated from experimental testing. The results of the analyses provide insights on the expected behaviors as well as design recommendations that should be considered for practicing engineers.