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.

This paper presents a short-term durability test program for E-glass/vinylester composite exposed to various environmental conditions. The main objective of this study is to investigate the degradation of GFRP composite and its influence on the tensi le strength. A total of 530 strand-type E-glass/vinylester specimens were fabricated and exposed to six different environmental conditions for up to 150 days. To examine the degradation of conditioned specimens, the weight gain was measured and scanning electronic microscope images were taken at fractured section. Also, the tensile strength of the specimens was tested. From the test results, it is clear that the tensile strength of the conditioned specimens was significantly reduced due to the degradation of GFRP under the environmental conditions considered.

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.

Steel bent reinforcing bars (rebars) are widely used to provide adequate anchorage. Bent fiber-reinforced polymer (FRP) rebars are rarely used because of the difficulty faced during the bending process of the FRP rebars at the construction site. Additionally, the bending process may cause a significant decrease in the structural performance of the FRP rebars. Therefore, to overcome these drawbacks, a headed glass fiber-reinforced polymer (GFRP) rebar was developed in this study. The pull-out tests of the headed GFRP rebars with diameters of 16 and 19 mm were conducted to evaluate their bond properties in various cementitious materials. Moreover, structural flexural tests were conducted on seven precast concrete decks connected with the headed GFRP rebars and various cementitious fillers to estimate the flexural behavior of the connected decks. The results demonstrate that the concrete decks connected with the headed GFRP rebar and ultra-high-performance concrete (UHPC) exhibited improved flexural performance.

This paper describes the feasibility of software-defined demodulator of DVB-T2 standard using the scalable DSP processor. This paper focuses mainly on the DVB-T2 receiver design and implementation of four major software blocks of the demodulator: FFTs, channel estimator, multi-level de-interleavers and rotated QAM soft-demapper. In particular, 2K-point FFT function is analyzed and mapped on the scalable architecture of coarse-grained reconfigurable array (CGRA) processors resulting 51dB signal to quantization noise ratio (SQNR) performance. The computational burden of frequency interpolator and frequency/cell deinterleavers are greatly reduced with specially designed intrinsics, 30% and 85%, respectively, from the original implementation. The softdemapper for rotated QAM constellation becomes feasible with the latest 1D-MMSE decorrelation method though it is still the most expensive function covering 40% of DTG106 mode. By implementing full chain demodulation software including abovementioned four major functions, it is demonstrated that the software-defined DVB-T2 demodulator is realizable with software on two scalable CGRA processors running at 300MHz.

This study aims to develop a prestressed concrete steel (PC) strand with an embedded optical Fiber Bragg Grating (FBG) sensor, which has been developed by the Korea Institute of Civil Engineering and Building Technology since 2013. This new strand is manufactured by replacing the steel core of the normal PC strand with a carbon-fiber-reinforced polymer (CFRP) rod with excellent tensile strength and durability. Because this new strand is manufactured using the pultrusion method, which is a composite material manufacturing process, with an optical fiber sensor embedded in the inner center of the CFRP Rod, it ensures full composite action as well as proper function of the sensor. In this study, a creep test for maintaining a constant load and a relaxation test for maintaining a constant displacement were performed on the proposed sensor-type PC strand. Each of the two tests was conducted for more than 1000 h, and the long-term performance verification of the sensor-type PC strand was only completed by comparing the performance with that of a normal PC strand. The test specimens were fabricated by applying an optical fiber sensor-embedded PC strand, which had undergone long-term performance verification tests, to a reinforced concrete beam. Depending on whether grout was injected in the duct, the specimens were classified into composite and non-composite specimens. A hydraulic jack was used to prestress the fabricated beam specimens, and the long-term change in the prestress force was observed for more than 1600 days using the embedded optical fiber sensor. The experimental results were compared with the analytical results to determine the long-term prestress loss obtained through finite-element analysis based on various international standards.