The usage of High-Performance Concrete (HPC) is gradually increasing in many structures exposed to extreme environmental conditions. One specific case is high temperature. Previous studies have made important achievements about the mechanical behavior of High-Performance Concrete (HPC) under high temperature on the basis of experiments. But so far little effort has been made on numerical simulation. Two topics will be discussed in the present work: the concrete cracking behavior in hot conditions and the evaluation of material stiffness decay. To study the former topic, the commercial software ABAQUS is also used. The present work not only studies the aspects concerning cracking behavior by using commercial software (Abaqus), but also develops algorithms implemented in Matlab. With known experimental data and elastic modulus decay (EC2), the software evaluates concrete behavior under high temperature. The software results have good agreement with ABAQUS but consumes much less time. Then a discussion about fracture energy cracking criterion will be carried out to study the implementation of constitutive law of concrete after cracking occurs. Finally, for the latter topic, how to monitor or estimate the concrete stiffness decay during high temperature is addressed. The present work addresses the development of another software to evaluate the concrete stiffness decay with temperature. It is an inverse analysis starting from experimental data, expressed in terms of thermal profile and tested member flexural behavior during heating. In this way, consideration on concrete stiffness decay will be carried out. Several experimental data from different tests (content different concrete mixes) will be estimated by the software. Comparisons will be made among the different specimens to verify the reliability of the software.
L'utilizzo di Calcestruzzo ad Alte Prestazioni (High-Performance Concrete - HPC) sta gradualmente aumentando in molte strutture esposte a condizioni ambientali estreme. Un caso specifico è l’alta temperatura. Studi precedenti hanno importanti risultati sul comportamento meccanico dell’HPC ad alta temperatura sulla base di prove sperimentali. Ma finora poco sforzo è stato fatto sulla simulazione numerica. Due temi saranno discussi nel presente lavoro: il comportamento a fessurazione del calcestruzzo a caldo e la valutazione del decadimento della rigidezza del materiale. Per studiare il primo aspetto, viene utilizzato anche il software commerciale ABAQUS. Il presente lavoro non solo studia gli aspetti relativi alla fessurazione utilizzando un software commerciale (Abaqus), ma riporta lo sviluppo di un algoritmo implementato in Matlab. Con dati sperimentali noti e il decadimento del modulo elastico (EC2), il software valuta il comportamento del calcestruzzo a temperatura elevata. I risultati del software hanno buon accordo con ABAQUS ma ad un costo compuazionale nettamente piu’ basso. Una discussione sull’energia di frattura sarà effettuata per studiare l’implementazione della legge costitutiva del calcestruzzo dopo il verificarsi di fessurazione. Infine, per il secondo argomento, viene trattato il monitoraggio del decamdimento del modulo elastico del calcestruzzo ad alta temperatura. Il presente lavoro riguarda lo sviluppo di un altro software per valutare il decadimento di rigidezza del calcestruzzo con la temperatura. Si tratta di un'analisi inversa partendo da dati sperimentali, espressa in termini di profili termici e comportamento flessionale durante il riscaldamento. Diversi dati sperimentali provenienti da diversi test (differenti miscele di calcestruzzo) saranno stimati dal software. I confronti saranno effettuati tra i diversi campioni per verificare l'affidabilità del software.
Concrete modeling in hot conditions : cracking behavior and material stiffness decay
WANG, XUEJING
2015/2016
Abstract
The usage of High-Performance Concrete (HPC) is gradually increasing in many structures exposed to extreme environmental conditions. One specific case is high temperature. Previous studies have made important achievements about the mechanical behavior of High-Performance Concrete (HPC) under high temperature on the basis of experiments. But so far little effort has been made on numerical simulation. Two topics will be discussed in the present work: the concrete cracking behavior in hot conditions and the evaluation of material stiffness decay. To study the former topic, the commercial software ABAQUS is also used. The present work not only studies the aspects concerning cracking behavior by using commercial software (Abaqus), but also develops algorithms implemented in Matlab. With known experimental data and elastic modulus decay (EC2), the software evaluates concrete behavior under high temperature. The software results have good agreement with ABAQUS but consumes much less time. Then a discussion about fracture energy cracking criterion will be carried out to study the implementation of constitutive law of concrete after cracking occurs. Finally, for the latter topic, how to monitor or estimate the concrete stiffness decay during high temperature is addressed. The present work addresses the development of another software to evaluate the concrete stiffness decay with temperature. It is an inverse analysis starting from experimental data, expressed in terms of thermal profile and tested member flexural behavior during heating. In this way, consideration on concrete stiffness decay will be carried out. Several experimental data from different tests (content different concrete mixes) will be estimated by the software. Comparisons will be made among the different specimens to verify the reliability of the software.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/123762