Precast structures are spread worldwide. Dry assembled joints are increasingly employed for faster and higher quality construction. As a matter of fact, the metallic mechanical devices needed to connect the different elements often become a strong discontinuity for the current cross-section due to their size and to the presence of cavities needed to assemble the joint. These devices are usually conceived to ensure correct flexural behavior of the connected elements, being the axial strength often not relevant for typical columns of industrial frame buildings. Recently, mechanical couplers have been proposed to be used in a dry-assembled precast wall system where the vertical wall joints are located in discrete positions. In these positions, especially for medium rise buildings, the axial compressive strength of the joints can be crucial. However, there is no information in the technical literature about the influence of the bulk mechanical connection devices employed in these joints over the joint axial strength. Within the framework of a wider research project carried out jointly between Politecnico di Milano and DLC Consulting Srl of Milan on this innovative wall system, axial tests on a reference monolithic benchmark and three single joint specimens have been carried out, showing an unexpected relevant axial strength loss of the mechanically jointed elements. This thesis is aimed at shedding light over this issue, by performing a numerical investigation through nonlinear static analyses performed with the software Abaqus. A parametric study is performed to investigate the effects of the replacement of a concrete area with steel elements or cavities, considered separately. A model of the reference benchmark tested within the above-mentioned program is validated against the experimental results. Then, the three complex joints provided with mechanical connections differing from specific reinforcement or filling details have been modeled and subjected to static nonlinear analyses. The difference found between experimental and numerical results has been then explained by further models including flaws of test setup and specimen assemblage procedure which have been identified following a critical review of the previous experimental activity.
Le strutture prefabbricate sono diffuse in tutto il mondo. I giunti assemblati a secco sono sempre più impiegati per una costruzione più veloce e di qualità superiore. I dispositivi meccanici metallici impiegati per collegare i diversi elementi spesso consistono in una forte discontinuità per la sezione trasversale corrente a causa delle loro dimensioni e della presenza di cavità necessarie per assemblare il giunto. Questi dispositivi sono generalmente concepiti per garantire il corretto comportamento alla flessione degli elementi collegati, essendo la resistenza assiale spesso non rilevante per i tipici pilastri di edifici a telaio prefabbricati. Recentemente, gli accoppiamenti meccanici sono stati proposti per essere utilizzati in un sistema di pareti prefabbricate assemblate a secco in cui i giunti verticali delle pareti sono posizionati in posizioni discrete. In queste posizioni, soprattutto per edifici di media altezza, la resistenza a compressione assiale dei giunti può essere cruciale. Tuttavia, non vi sono informazioni nella letteratura tecnica sull'influenza dei dispositivi di connessione meccanica sulla resistenza assiale del giunto. Nell'ambito di un più ampio progetto di ricerca realizzato congiuntamente tra Politecnico di Milano e DLC Consulting Srl di Milano su questo innovativo sistema a parete, sono stati effettuati test assiali su un campione monolitico di riferimento e tre campioni di giunto meccanico con differenti dettagli, evidenziando un’inattesa diminuzione significativa della resistenza assiale dei giunti. Questa tesi ha lo scopo di far luce su questo problema, eseguendo una ricerca numerica attraverso analisi statiche non lineari eseguite con il software Abaqus. Viene condotto uno studio parametrico per studiare gli effetti della sostituzione di un'area in calcestruzzo con inserti in acciaio o cavità, considerati separatamente. Un modello del giunto monolitico di riferimento testato nell'ambito del suddetto programma è validato rispetto ai risultati sperimentali. Quindi, i tre giunti con connessioni meccaniche sono stati modellati e sottoposti ad analisi statiche non lineari. La differenza riscontrata tra risultati sperimentali e numerici è stata poi avvalorata da ulteriori modelli che hanno incluso difetti di configurazione del test e di assemblaggio dei campioni che sono stati identificati in seguito a una revisione critica della precedente attività sperimentale.
Numerical analysis on the influence of bulk mechanical connections on the compressive behavior of precast concrete elements
SARACOGLU, CEM
2017/2018
Abstract
Precast structures are spread worldwide. Dry assembled joints are increasingly employed for faster and higher quality construction. As a matter of fact, the metallic mechanical devices needed to connect the different elements often become a strong discontinuity for the current cross-section due to their size and to the presence of cavities needed to assemble the joint. These devices are usually conceived to ensure correct flexural behavior of the connected elements, being the axial strength often not relevant for typical columns of industrial frame buildings. Recently, mechanical couplers have been proposed to be used in a dry-assembled precast wall system where the vertical wall joints are located in discrete positions. In these positions, especially for medium rise buildings, the axial compressive strength of the joints can be crucial. However, there is no information in the technical literature about the influence of the bulk mechanical connection devices employed in these joints over the joint axial strength. Within the framework of a wider research project carried out jointly between Politecnico di Milano and DLC Consulting Srl of Milan on this innovative wall system, axial tests on a reference monolithic benchmark and three single joint specimens have been carried out, showing an unexpected relevant axial strength loss of the mechanically jointed elements. This thesis is aimed at shedding light over this issue, by performing a numerical investigation through nonlinear static analyses performed with the software Abaqus. A parametric study is performed to investigate the effects of the replacement of a concrete area with steel elements or cavities, considered separately. A model of the reference benchmark tested within the above-mentioned program is validated against the experimental results. Then, the three complex joints provided with mechanical connections differing from specific reinforcement or filling details have been modeled and subjected to static nonlinear analyses. The difference found between experimental and numerical results has been then explained by further models including flaws of test setup and specimen assemblage procedure which have been identified following a critical review of the previous experimental activity.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/146439