Lanterna Rally

Author: Jenifer Ann Albright

Publisher:

Published: 2022

Total Pages: 0

ISBN-13:

Reinforced concrete (RC) moment resisting frames (MRF) have traditionally been one of the most common structural systems used to resist lateral loads induced by seismic activities. Earthquake ground-shaking seismic loads cause displacement of the building, also known as “sway” or “drift”, over multiple displacement cycles. The RC MRF, which consists of beams, columns, and beam-column joints, is designed to achieve a ductile response through optimized detailing and proportioning to resist flexural, axial, and shear forces transferred into the structure during building sway. The current accepted design procedure for seismically active locations is to provide capacity protected members. This theory states that the columns of the beam-column system should be stronger than the beams, such that during ultimate design loads the beams will fail prior to the columns, which is a ductile failure mechanism.There is an abundant desire to improve reliability, safety, economic costs, efficiency, and performance of MRFs. To that end, many innovative MRF solutions have been proposed over the years, including precast or partially precast systems, steel braced RC joints, and concrete-steel composite systems. Among the many novel suggestions, the NPS system represents a recent and promising solution which aims to be unique, advanced, and technologically efficient to attain ductile MRFs capable of high seismic performance. The NPS system is a steel concrete composite system, consisting of a steel HSS square, circular, or rectangular cross sectional column with self-supporting beams made of a flexural steel plate bottom chord with a welded truss (to act as the beam shear reinforcement) and undeformed top rebar steel. The system is completed with concrete cast in-situ. Use of partially prefabricated elements as well as in-place elements represents a delicate challenge of providing adequate moment continuity of the beam-column joint while ensuring the integrity of the joint region. To attempt to solve this challenge and achieve moment continuity, integrative steel elements are inserted through the joint after the beam trusses have been set in position but before the concrete is cast. Prior to this project, no experimental evidence was available to support the dependability of this moment continuity configuration. This thesis presents and discusses the results of an experimental program of nine (five interior and four exterior) full-scale 2D concrete-steel composite NPS beam column joints, and two traditionally Eurocode compliant reinforced concrete beam-column joints (one interior and one exterior). This program was developed to investigate and ultimately assess the seismic performance of the NPS system with specific consideration to the integrative steel elements providing moment continuity. The different moment continuity solutions adopted included the use of integrated truss elements (i.e., continuity trusses) and straight or hooked deformed bars (i.e., continuity bars). Additional variables considered included the level of shear protection of the joint “panel” region and the presence/absence of additional shear reinforcement in the beam end-regions (i.e., the “critical” or “plastic hinge” length). This thesis provides a detailed discussion of the experimental outcomes and a careful analysis of the observed response mechanisms and any subsequent design implications. The results of the experimental investigation were extrapolated to assess the performance of the specimen in terms of shear stress and shear strain in the joint, sub-component contribution to the total drift, energy dissipation, peak and residual strength, initial and residual stiffness, and ductility. The response of the NPS specimens was compared against a tangible target performance from the traditionally Eurocode compliant RC specimens. The experimental results demonstrated that, in at least one configuration, the NPS system can effectively achieve modern proficient seismic performance objectives. This can be seen through equivalent or superior performance criteria comparison to their traditional RC counterparts.