Different types of base plate connections are currently used to anchor steel columns to concrete foundations. This connection can be realized with the steel plate in direct contact with the concrete surface, known as flush mounted, or with the plate elevated, leaving an exposed length of the anchors, known as stand-off. The stand-off solution can offer constructional advantages; however, it alters the force transfer mechanism, introducing additional bending in the anchors and therefore requiring a more detailed analysis. This dissertation aims to describe the static and fatigue response of base plate connections, with a specific focus on comparing flush mounted and stand-off configurations. A case study was introduced to assess the static performance of these connections, considering a noise barrier in the two configurations. The structures were investigated to provide an comparison of stress and load distribution. Both solutions were then verified according to EN1992-4 and Hilti SOFA design checks and they resulted to be structurally safe, although the steel resistance is drastically reduced when the lever arm is introduced. A numerical model was developed by means of Finite Element method to further investigate the stress distribution. The results showed that, when the exposed length is present, stresses are distributed along it, while in the flush mounted case the maximum stress is consistently localized at a single point inside the concrete, at a depth of half the nominal diameter of the anchor. Static monotonic shear tests were also carried out, showing that the flush mounted configuration exhibits higher stiffness and strength compared to the stand-off. These findings provided the basis for experimental fatigue investigations on stand-off connections. The fatigue response of flush mounted connection is widely discussed and analyzed by means of recommendation guidelines, while for the stand-off case, no specific provisions currently exist. To address this gap, experimental tests were performed, providing a clearer understanding of the fatigue behavior of stand-off base plates.
Diverse tipologie di piastre di base sono attualmente utilizzate per ancorare colonne in acciaio a fondazioni in calcestruzzo. Tali connessioni possono essere realizzate con la piastra a contatto con la superficie del calcestruzzo (flush mounted), oppure con la piastra sollevata, lasciando una porzione di ancoraggi esposta (stand-off). Sebbene la configurazione stand-off presenti alcuni vantaggi costruttivi, essa modifica il meccanismo di trasmissione dei carichi, introducendo momenti flettenti negli ancoraggi e richiedendo pertanto analisi più approfondite. Questa tesi mira a descrivere il comportamento statico e a fatica delle connessioni con piastre di base, confrontando le configurazioni flush mounted e stand-off. Un caso studio su una barriera antirumore è stato introdotto per valutare la risposta statica delle due configurazioni. Le strutture sono state analizzate per fornire un confronto della distribuzione degli sforzi e dei carichi. Le connessioni sono state poi verificate secondo l'EN1992-4 e mediante il metodo Hilti SOFA. Entrambe sono risultate sicure dal punto di vista strutturale, nonostante la resistenza dell'acciaio si riduca sensibilmente con l'introduzione del braccio di leva. Un modello agli elementi finiti ha evidenziato che, nella configurazione stand-off, gli sforzi massimi si distribuiscono lungo la lunghezza esposta, mentre nel caso flush mounted il picco è localizzato in un unico punto posto a mezzo diametro nel calcestruzzo. Inoltre, sono state condotte prove sperimentali di taglio che hanno evidenziato una maggiore rigidezza e resistenza della configurazione flush mounted rispetto a quella stand-off. Tali risultati hanno costituito la base per indagini a fatica sulle connessioni stand-off. Difatti, se per le configurazioni flush mounted sono disponibili numerose linee guida per la resistenza a fatica, mancano invece riferimenti specifici per le connessioni stand-off. Per questo motivo, sono state condotte prove sperimentali che hanno permesso di ottenere una comprensione più chiara della risposta a fatica delle piastre di base in configurazione stand-off.
Analysis of base plate connections: static and fatigue shear response
LONGINOTTI, LETIZIA;Marinoni, Chiara
2024/2025
Abstract
Different types of base plate connections are currently used to anchor steel columns to concrete foundations. This connection can be realized with the steel plate in direct contact with the concrete surface, known as flush mounted, or with the plate elevated, leaving an exposed length of the anchors, known as stand-off. The stand-off solution can offer constructional advantages; however, it alters the force transfer mechanism, introducing additional bending in the anchors and therefore requiring a more detailed analysis. This dissertation aims to describe the static and fatigue response of base plate connections, with a specific focus on comparing flush mounted and stand-off configurations. A case study was introduced to assess the static performance of these connections, considering a noise barrier in the two configurations. The structures were investigated to provide an comparison of stress and load distribution. Both solutions were then verified according to EN1992-4 and Hilti SOFA design checks and they resulted to be structurally safe, although the steel resistance is drastically reduced when the lever arm is introduced. A numerical model was developed by means of Finite Element method to further investigate the stress distribution. The results showed that, when the exposed length is present, stresses are distributed along it, while in the flush mounted case the maximum stress is consistently localized at a single point inside the concrete, at a depth of half the nominal diameter of the anchor. Static monotonic shear tests were also carried out, showing that the flush mounted configuration exhibits higher stiffness and strength compared to the stand-off. These findings provided the basis for experimental fatigue investigations on stand-off connections. The fatigue response of flush mounted connection is widely discussed and analyzed by means of recommendation guidelines, while for the stand-off case, no specific provisions currently exist. To address this gap, experimental tests were performed, providing a clearer understanding of the fatigue behavior of stand-off base plates.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/243875