Post-tensioned (PT) components are frequently utilized in bridge construction, facilitating the economical creation of long spans. However, aging infrastructure faces numerous safety issues, including increased traffic loads, extended service lives, material degradation, and inadequate maintenance. A significant concern is the corrosion of steel tendons in post-tensioning systems, leading to reduced tensile strength and compromised load-bearing capacity. Grouting serves as a protective layer against corrosion for these tendons, but its efficacy is diminished if voids form in the grout, exposing the steel strands to environmental damage. The inspection of post tensioning system involves locating voids through non-destructive testing. This should be followed by measuring the volume of these voids before starting the re-grouting process. The traditional technique used to measure void volume, commonly referred to in the literature as vacuumetric method, was thoroughly examined, revealing various sources of error and limitations. This research also investigated a novel technique which was developed to address leakage effects by using pressure cycles to balance losses. Though this approach was a step in the right direction, it introduced further complexity. To overcome these challenges, an innovative and simplified third approach was devised. This new method aims to solve the problems associated with traditional techniques while maintaining ease of use. The primary motivation was to create a method suitable for use during the inspection stage, providing a quick and reliable estimate of void volume before commencing the reparation process. The basic principle of this method involves using a hand-operated pump to apply pressure change to the duct system. The pressure change is measured concurrently with the volume change of the system. By applying fundamental thermodynamic principles, the volume of the voids can be accurately determined. To validate the theoretical framework of this method, an initial prototype was developed in the laboratory. This prototype consisted of a dual-action pump, a pressure gauge, and a string potentiometer. Various tests were conducted using different empty containers designed to simulate voids within the duct system. The tests demonstrated the method's accuracy and effectiveness in real-world scenarios, showing its potential as a reliable tool for inspecting post-tensioned systems. In conclusion, this research highlights the development of a novel, practical method for void volume measurement in PT systems, addressing the limitations of existing techniques and contributing to the enhancement of bridge maintenance practices.
Gli elementi post-tesi in calcestruzzo (PT) sono spesso utilizzati nella costruzione di ponti, facilitando la creazione di lunghe campate. Tuttavia, le infrastrutture realizzate diversi decenni fa si trovano ad affrontare numerosi problemi di sicurezza, tra cui l’aumento dei carichi dovuti al traffico, l’estensione della durata in esercizio, il degrado dei materiali, spesso causato da una manutenzione inadeguata. Un importante motivo di preoccupazione è la corrosione dei cavi in acciaio armonico nei sistemi di posttensione, che comporta una minor resistenza a trazione e una capacità di carico ridotta. La malta di iniezione che dovrebbe riempire la guaina funge da strato protettivo contro la corrosione del cavo, ma la sua efficacia diminuisce se rimangono dei vuoti, esponendo i trefoli di acciaio all’ossidazione. L'ispezione del sistema di post tensionamento prevede l'individuazione dei vuoti attraverso controlli non distruttivi. Successivamente si dovrebbe misurare il volume di questi vuoti prima di iniziare i lavori di ripristino. La tecnica tradizionale utilizzata per misurare il volume vuoto, comunemente denominata metodo vacuometrico, è stata esaminata approfonditamente, rivelando varie fonti di errore e limitazioni. Questa ricerca ha inoltre studiato una nuova tecnica sviluppata per affrontare gli effetti delle perdite utilizzando cicli di pressione. Sebbene questo approccio rappresentasse un passo nella giusta direzione, introduceva ulteriore complessità sul piano operativo. Per superare queste limitazioni è stato ideato un terzo approccio innovativo e semplificato. Questo nuovo metodo mira a risolvere i problemi legati alle tecniche tradizionali mantenendo la semplicità di utilizzo. La motivazione principale era quella di creare un metodo adatto all'uso durante la fase di ispezione, fornendo una stima rapida e affidabile del volume vuoto prima di iniziare il processo di riparazione. Il principio di base di questo metodo prevede l'utilizzo di una pompa manuale per applicare la variazione di pressione al sistema di condotti. La variazione di pressione viene misurata contemporaneamente alla variazione di volume del sistema. Applicando i principi termodinamici fondamentali, il volume dei vuoti può essere determinato con precisione. Per convalidare il quadro teorico di questo metodo, è stato sviluppato un prototipo in laboratorio. Questo prototipo consiste in una pompa a doppia azione, un manometro e un potenziometro a filo. Sono state condotte numerose prove utilizzando diversi contenitori vuoti progettati per simulare i vuoti all'interno del sistema di condotti. I test hanno dimostrato l'accuratezza e l'efficacia del metodo negli scenari del mondo reale, dimostrandone il potenziale come strumento affidabile per l'ispezione dei sistemi post-tesi. In conclusione, questa ricerca ha prodotto lo sviluppo di un nuovo metodo pratico per la misurazione del volume dei vuoti nei sistemi di post tensione, affrontando i limiti delle tecniche esistenti e contribuendo al miglioramento delle pratiche di manutenzione dei ponti.
Innovative approach to void volume measurement in post-tensioning ducts
AL KADRI, RAOUF
2023/2024
Abstract
Post-tensioned (PT) components are frequently utilized in bridge construction, facilitating the economical creation of long spans. However, aging infrastructure faces numerous safety issues, including increased traffic loads, extended service lives, material degradation, and inadequate maintenance. A significant concern is the corrosion of steel tendons in post-tensioning systems, leading to reduced tensile strength and compromised load-bearing capacity. Grouting serves as a protective layer against corrosion for these tendons, but its efficacy is diminished if voids form in the grout, exposing the steel strands to environmental damage. The inspection of post tensioning system involves locating voids through non-destructive testing. This should be followed by measuring the volume of these voids before starting the re-grouting process. The traditional technique used to measure void volume, commonly referred to in the literature as vacuumetric method, was thoroughly examined, revealing various sources of error and limitations. This research also investigated a novel technique which was developed to address leakage effects by using pressure cycles to balance losses. Though this approach was a step in the right direction, it introduced further complexity. To overcome these challenges, an innovative and simplified third approach was devised. This new method aims to solve the problems associated with traditional techniques while maintaining ease of use. The primary motivation was to create a method suitable for use during the inspection stage, providing a quick and reliable estimate of void volume before commencing the reparation process. The basic principle of this method involves using a hand-operated pump to apply pressure change to the duct system. The pressure change is measured concurrently with the volume change of the system. By applying fundamental thermodynamic principles, the volume of the voids can be accurately determined. To validate the theoretical framework of this method, an initial prototype was developed in the laboratory. This prototype consisted of a dual-action pump, a pressure gauge, and a string potentiometer. Various tests were conducted using different empty containers designed to simulate voids within the duct system. The tests demonstrated the method's accuracy and effectiveness in real-world scenarios, showing its potential as a reliable tool for inspecting post-tensioned systems. In conclusion, this research highlights the development of a novel, practical method for void volume measurement in PT systems, addressing the limitations of existing techniques and contributing to the enhancement of bridge maintenance practices.File | Dimensione | Formato | |
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https://hdl.handle.net/10589/223601