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The nano-silica (NS) particles trigger hydration reactions reduce the less stable components (Calcium hydroxide), and produce better quality pozzolan gel products in concrete. This process gives the concrete have a dense structure, early strength growth, increase compressive strength, flexural strength, splitting strength, water anti-permeability, and corrosion resistance. This article aims to research the influence of NS on compressive strength and modulus of elasticity of high-performance concrete. Nano-silica particles are added into high-performance concrete mixture with the contents 0.5, 1, 1.5, 2, 2.5 and 3% by weight of the binder. The addition of NS resulted in enhancing compressive strength and modulus of elasticity up to 1.5% replacement level. When the NS content is 2–3%, the compressive strength and modulus of elasticity increases nonsignificantly and tends to decrease compared to NS’s rate using 1.5%. The experiment results will build a relationship function between the modulus of elasticity and nano-silica content.

Passive optical networks are the main technology behind the surge of Gigabit broadband services. As the bandwidth demand continues to increase, the wavelength dimension is added on top of the time dimension. Multiple wavelengths pose a challenge but also an opportunity to further optimize the network operation because the dynamic traffic pattern in which there is significant difference between peak and off-peak hours. Wavelength-agility enables dynamic sharing of both wavelengths and timeslots but requires tunable transceivers in ONUs with tuning times below 150 ms. It increases traffic handling capacity by 36.9% and saves 33% power as compared to wavelength-fixed because the traffic load can spread among wavelengths in peak time while some wavelengths can be shut down in off-peak time.

Nowadays, many methods have been employed to estimate the cable tension in a cable-stayed bridge. In these methods, the non-destructive test has a widespread application thanks to its feasibility and effectiveness. The vibration-based approach determines the cable tension based on natural frequency. In fact, there are many factors that can influence the tension values. Some of them are derived from objective factors, others from subjective factors. In this paper, a subjective issue, so-called measurement technique, is studied. A cable, without fillings between the HDPE duct and strands, is the main object of this study. In the first step, some scenarios related to the placement of sensors are conducted. The former considers the tension between different positions of sensors, directly and indirectly contact conditions with strands, under the ambient and pulling-rope excitation. The latter takes into account the directions, out-of-plane and in-plane, of sensor placement on the strands or HPDE duct. In the next step, the relationship between the force and frequency is utilized to identify the mean tension of the cable. In the finally step, results of cable tension estimation are compared with the real-time monitoring and finite element (FE) simulation. From the comparison, the effects of measuring technique in situ are discussed in the conclusion.

Nano silicate SiO2 (NS) in the high-performance concrete (HPC) mixture is becoming great interest because it improves the mechanical properties of concrete. As the ultra-fine SiO2 particles with a very high ratio of surface area to mass, NS can tightening the structure and produces better quality gel products and thus concrete strength increases. However, the optimal rate of NS in high-performance concrete has not been investigated. This study experimentally evaluates the influence of NS on compressive strength and flexure strength of HPC of which nominal strength is 70MPa. Seven mixtures of HPC at NS rate of 0%, 0.5%, 1%, 1.5%, 2%, 2.5% and 3% over the total weight of the adhesive were conducted. Each mixture provides six samples for compressive tests and six samples for flexure tests. Total samples are 336 samples for four ages of concrete. Reliability of test results was carried out and results shown that at the early stage of HPC, an NS ratio of 1.5% shows the optimal value to improve the performance of concrete. This result also helps to apply NS in HPC in quality control in site application.

The first two steps in Structural Health Monitoring (SHM) are to detect and localize damage in a structure. Transmissibility uses only output signals to extract the structural dynamic parameter and very sensitive to damage. In this paper, a simply supported beam is analyzed using a transmissibility-based damage detection methodology combined with Auto-Associative Neural Network (AANN). Firstly, the transmissibility is calculated between two points in the examined beam. Then a transmissibility indicator is taken as input for the neural network, which accounts only for the response data and is sensitive to damage. The target of AANN is the location and the severity of the damage. It is found that the network, after being trained, show good results and can be used to detect and localize damage.

Threaded pipe connections are commonly used to connect risers, tendons, drill pipes and wellcasing strings. In these applications fatigue resistance plays an important role. A large variety of patenteddesign features exist, all claiming to improve the connection’s fatigue life. However, patent documents onlycontain claims and numerical or experimental data about these connection’s performance is generally notpublished. This makes it hard to make a quantitative comparison between different designs. In this study anoverview is given of fatigue resistant threaded connections. Two major methods to improve the fatigue lifeof a connection were identified. First of all, local stress concentrations can be reduced by optimizing thegeometry of the threads. Second the global shape of the connection can be optimized to obtain a moreuniform load distribution.Using a parametric finite element model, different designs were compared. The connections were modelledby a 2D axisymmetric geometry with non-linear material properties and elaborate contact conditions.Selected designs have been subjected to experimental tests in a four-point bending fatigue setup. Theexperimental tests serve as a validation for the results of the numerical simulations. It was found that themultiaxial stress distribution at the thread roots is the defining factor for the fatigue life of the connection.Nevertheless, these stresses can be changed by the global geometry of the connection. It can beconcluded that the fatigue life of threaded connections is determined by a combination of global and localaspects which should both be analysed for fatigue life calculations.

Threaded pipe connections are used to connect well casing, well tubing, drill pipes and risers.For many of these applications fatigue resistance plays an important role. In this study the fatigueproperties of threaded connections are studied using a combination of finite element modelling andexperimental testing. Using 2D axisymmetric FE analysis several connections are compared. It is shownthat the load distribution over the engaged threads is an important feature. Experimental tests are carriedout on three setups. A small scale four-point bending setup is used to develop S-N curves. An S-N curve fora standard API Line Pipe connection is compared to an S-N curve for a connection that showed animproved load distribution over the engaged threads in the FE analysis. On a medium scale four-pointbending setup, strains together with crack opening are measured. The strain measurements are comparedwith the strains obtained by the numerical model. Finally a full scale resonant bending fatigue setup ispresented, which will be used in future testing of pipe connections ranging from 168 mm (6”) to 508 mm(20”) in diameter.