Prestressed Concrete Wire and Strand (PC) strands are the most used materials to introduce prestress in a Pre-Stressed Concrete (PSC) structure. However, it is difficult to evaluate the final prestress force of the PC strand after prestressing or its residual prestress force after completion of the structure on site. This impossibility to assess eventual loss of prestress of the PC strand has resulted in a number of serious accidents and even in the collapse of several structures. This situation stresses the necessity to maintain the prestress force residual or after prestressing for the evaluation of the health of the concrete structure throughout its lifespan. Recently, several researchers have studied methods enabling one to verify the prestress force by inserting an optical fiber sensor inside the strand but failed to provide simple techniques for the fabrication of these devices to fulfill measurement performance from the design prestress to failure. Moreover, these methods require the additional installation of electrical resistance strain gages, displacement sensors and load cells on the outer surface of the structure for long-term precise measurement. This paper proposes a method enabling one to evaluate precisely and effectively the prestress force of the PC strand and intends to verify the applicability of the proposed method on actual concrete structures. To that end, an innovative PC strand is developed by embedding a Fiber Bragg Grating (FBG) sensor in the core wire of the PC strand so as to enable short term as well as long term monitoring. The measurement performance of the developed strand is then evaluated experimentally and the reliability of the monitoring data is assessed.

Strong composition between FRP and concrete is an indispensable prerequisite to achieve the structural integrity of FRP-concrete composite deck. Accordingly, this study evaluates experimentally the behavioral characteristics of such shear connection systems realized by coarse sand coating and concrete wedge. The results show that coarse sand coating develops composite performance close to perfect composition in the shear direction but exhibits weakness against normal split. On the other hand, concrete wedge appears to be an efficient solution to resolve such problem. Therefore, a new shear connection system combining coarse sand coating and concrete wedge has been conceived and test revealed that the new shear connection system provides equivalent static performance together with significantly improved fatigue performance compared to the coarse sand coating composition. Following, the shear connection system combining both coarse sand coating and concrete wedge constitutes an efficient solution satisfying the strong composition requirement for the structural system.

No abstract

This paper revisits the creation and cancellation of the dynamic resonance phenomenon that occurs in bridge structures on high-speed lines when crossed by wheel loads. The resonance and its cancellation are mathematically formulated for a Bernoulli-type beam with general boundary conditions and subjected to loads moving at a regular spacing. The resonance of the bridge caused by the travelling loads occurs, regardless of the mode shape, when the natural frequency of the structure coincides with the loading frequency produced by the loads moving at a constant speed. In this study, the dependency of the cancellation phenomenon on the mode shape is determined based on the boundary conditions of the structure. In addition, the optimal span length that suppresses the response at resonance is proposed using the cancellation phenomenon for a simple beam with pinned-pinned, clamped-clamped and clamped-pinned boundary conditions; and a simply supported continuous beam.

Prestressed concrete (PSC) is one of the most reliable, durable and widely used construction materials, which overcomes the weakness of concrete in tension by the introduction of a prestress force. Smart strands enabling measurement of the prestress force have recently been developed to maintain PSC structures throughout their lifetime. However, the smart strand cannot give a representative indication of the whole prestress force when used in multi-strand systems since each strand sustains a different prestress force. In this paper, the actual distribution of the prestress force in a multi-strand system is examined using elastomagnetic (EM) sensors to develop a method for tracking representative indicators of the prestress force using smart strands.