A thorough investigation of the interdependent behavior of prestressed system

Due to the existing of many prestressed members in the structural system, the interdependent behavior of all prestressed members is the main concern in the analysis of the pretension process. A thorough investigation of this mutual effect is essential for an effective, reliable, and optimal analysis. Focus on this aspect, this paper presents an investigation of the interdependent behavior of all prestressed members in the whole structural system based on influence matrix (IFM). Four different types of IFM are introduced. Two different solving methods are brought forth to analyze the pretension process. The direct solving method solves for the accurate solution, whereas the iterative solving method repeatedly amends to achieve an approximate solution. A numerical example is then conducted. The result shows that various kinds of complicated batched and repeated tensioning schemes can be analyzed reliably, effectively, and completely based on IFM.

Finite element modelling of lamb wave propagation in prestress concrete and effect of the prestress force on the wave’s characteristic

In order to assess the structural reliability of bridges, an accurate and cost effective Non-Destructive Evaluation (NDE) technology is required to ensure their safe and reliable operation. Over 60% of the Australian National Highway System is prestressed concrete (PSC) bridges according to the Bureau of Transport and Communication Economics (1997). Most of the in-service bridges are more than 30 years old and may experience a heavier traffic load than their original intended level. Use of Ultrasonic waves is continuously increasing for (NDE) and Structural Health Monitoring (SHM) in civil, aerospace, electrical, mechanical applications. Ultrasonic Lamb waves are becoming more popular for NDE because it can propagate long distance and reach hidden regions with less energy loses. The purpose of this study is to numerically quantify prestress force (PSF) of (PSC) beam using the fundamental theory of acoustic-elasticity. A three-dimension finite element modelling approach is set up to perform parametric studies in order to better understand how the lamb wave propagation in PSC beam is affected by changing in the PSF level. Results from acoustic-elastic measurement on prestressed beam are presented, showing the feasibility of the lamb wave for PSF evaluation in PSC bridges.