In this study, multiple regression analysis (MRA) and polynomial regression analysis (PRA), which are traditional statistical methods, were applied to analyze factors affecting the tensile strength of basalt and glass fiber-reinforced polymers (FRPs) exposed to alkaline environments and predict the tensile strength degradation. The MRA and PRA are methods of estimating functions using statistical techniques, but there are disadvantages in the scalability of the model because they are limited by experimental results. Therefore, recently, highly scalable artificial neural networks (ANN) have been studied to analyze complex relationships. In this study, the prediction performance was evaluated in comparison to the MRA, PRA, and ANN. Tensile strength tests were conducted after exposure for 50, 100, and 200 days in alkaline environments at 20, 40, and 60 °C. The tensile strength was set as the dependent variable, with the temperature (TP), the exposure day (ED), and the diameter (D) as independent variables. The MRA and PRA results showed that the TP was the most influential factor in the tensile strength degradation of FRPs, followed by the exposure time (ED) and diameter (D). The ANN method provided the best correlation between predictions and experimental values, with the lowest error and error rate. The PRA method applied to the response surface method outperformed the MRA method, which is most commonly used. These results demonstrate that ANN can be the most efficient model for predicting the durability of FRPs.

Estimating the compressive strength of high strength concrete (HSC) is an essential investigation for the maintenance of nuclear power plant (NPP) structures. This study intends to evaluate the compressive strength of HSC using two approaches: non-destructive tests and concrete core strength. For non-destructive tests, samples of HSC were mixed to a specified design strength of 40, 60 and 100 MPa. Based on a dual regression relation between ultrasonic pulse velocity (UPV) and rebound hammer (RH) measurements, an estimation expression is developed. In comparison to previously published estimation equations, the equation proposed in this study shows the highest accuracy and the lowest root mean square error (RMSE). For the estimation of compressive strength using concrete core specimens, three different concrete core diameters were examined: 30, 50, and 100 mm. Based on 61 measured compressive strengths of core specimens, a simple strength correction factor is investigated. The compressive strength of a concrete core specimen decreases as the core diameter reduces. Such a relation is associated with the internal damage of concrete cores and the degree of coarse aggregate within the core diameter from the extracting process of the cores. The strength estimation expressions was formulated using the non-destructive technique and the core strength estimation can be updated with further test results and utilized for the maintenance of NPP.

Corrugated steel plate culvert bridge has been more commonly used as soil steel bridges because it is the cost-effective alternative for railway-highway crossings. The corrugated steel plate culvert bridge is considered the most suitable for quick rebuilding of bridges compared with the conventional bridges. This study intends to experimentally investigate the static and fatigue performance of the bolted connection of deep corrugated steel plate. Test variables are the thickness of deep corrugated steel plate and the types of bolted connection such as bolted-only, gasket, slot hole, and washer. For static test, the failure is mainly caused by a local buckling of deep corrugated steel plate member and bearing failure of bolts. Type of gasket and slot hole showed the largest stiffness so that they may be recommended for structural safety and redundancy under a static flexural behavior. For fatigue test, the bolted-only specimen exhibited no increase in the strain until failure and the highest fatigue life among the test variables. For structural safety under cyclic loading, bolted-only connection is recommended. According to AASHTO LRFD Bridge Design Specification, fatigue life category can be determined as category D level and the fatigue limit was estimated to be 48.3 MPa. The deep corrugated steel plate members tested in this study can provide a sufficient fatigue performance in compliance with the design specification.

In this study, porosity assessment of cement mortars containing Precious Slag (PS) Ball – an industrial waste produced by rapid cooling of slag generated from steel making process by Slag Atomizing Technology – is done by Back-Scattered Electron (BSE) image analysis. PS incorporated mortars were fabricated and subsequently evaluated for compressive strength. BSE images were analyzed by pore segmentation method. Binarization on the images using Otsu’s thresholding method was done followed by the porosity determination. As the interfacial attributes were the primary concern, the porosity was determined from the aggregate surface to the 100 μm width. A total of 24 sections were analyzed and the mean values were plotted. Although the PS Ball incorporated mortar exhibited 10% lower strength at 28-day age, it showed stronger and less porous aggregate- matrix interface between (from particle surface up to 35 μm width) as compared to that of normal mortar containing sand, which is justifiable by the chemical composition of PS Ball attributed to the potential chemical binding. Further, the porosity decreased as the distance from aggregate surface increased. While the use of PS Ball is environmentally friendly, its enhanced interfacial properties with some strength loss of resulting cement mortars encourages its use in sustainable construction materials.

FRP (fiber-reinforced polymer)-reinforced concrete members have larger deflection than reinforced concrete members because of the low modulus of elasticity of the FRP bar. In this paper, we proposed a new effective moment of inertia equation to predict the deflection of FRP-reinforced concrete members based on the harmony search algorithm. The harmony search algorithm is used to optimize a function that minimizes the error between the deflection value of the experimental result and the deflection value expected from the specimen’s specifications. In the experimental part, four GFRP (Glass Fiber-Reinforced Polymer)- and BFRP (Basalt Fiber-Reinforced Polymer)-reinforced concrete slab specimens were manufactured and tested. FRP-reinforced concrete slabs were reinforced with GFRP and BFRP rebars on spiral rib surfaces. The effects of the FRP reinforcement ratio and balanced reinforcement ratio (${\rho }_f$/${\rho }_{fb}$), the moment of inertia of the transformed cracked section and the gross moment of inertia ($I_{cr}$/$I_g$), and the cracking moment and the maximum service load moment ($M_{cr}$/$M_a$) on the effective moment of inertia have been considered. The experimental results and predicted results of the flexural testing of concrete slabs reinforced with FRP rebars were compared, and the experimental results were in good agreement with the calculated values using the proposed effective moment of inertia equation.

This study intends to investigate the flexural bond performance of glass fiber-reinforced polymer (GFRP) reinforcing bar under repeated loading. The flexural bond tests reinforced with GFRP reinforcing bars were carried out according to the BS EN 12269-1 (2000) specification. The bond test consisted of three loading schemes: static, monotonic, and variable-amplitude loading to simulate ambient loading conditions. The empirical bond length based on the static test was 225 mm, whereas it was 317 mm according to ACI 440 1R-03. Each bond stress on the rib is released and bonding force is enhanced as the bond length is increased. Appropriate level of bond length may be recommended with this energy-based analysis. For the monotonic loading test, the bond strengths at pullout failure after 2,000,000 cycles were 10.4 MPa and 6.5 MPa, respectively: 63–70% of the values from the static loading test. The variable loading test indicated that the linear cumulative damage theory on GFRP bonding may not be appropriate for estimating the fatigue limit when subjected to variable-amplitude loading.