• Advances in concrete construction
• /
• v.16 no.4
• /
• pp.217-230
• /
• 2023

Methods for designing the post-tensioned anchorage zones at ultimate limit state has been specified in current design codes based on strut-and-tie models (STM). However, it is still not clear how to estimate the serviceability behavior of the anchorage zones. The serviceability is just indirectly taken into account by means of the reasonable reinforcement detailing. To address this issue, this paper is devoted to developing a modified strut-and-tie model (MSTM) to predict the behavior of concentric anchorage zones throughout the loading process. The principle of stationary complementary energy is introduced into STM at each load step to satisfy the compatibility condition and generate the unique MSTM. The structural behavior of anchorage zones can be achieved based on MSTM from loading to failure. Simplified formulas have been proposed to estimate the first cracking load, bearing capacity and maximum crack width with the consideration of the details of reinforcement bursting bars. The proposed model provides a definite method to control the bursting crack width in concentric anchorage zones. Four specimens with different bearing plate ratios have been designed and tested to validate the proposed method.

• Journal of Wind Energy
• /
• v.15 no.2
• /
• pp.23-36
• /
• 2024

In this study, a health monitoring system was developed for the two most vulnerable parts of a wind tower support structure: the connection between steel towers (L-Flange) and the concrete foundation-steel tower connection. To select assessment parameters for health monitoring, detailed FEM analysis was conducted using the ABAQUS program. Additionally, a testbed was established near the Jeju Woljeongri wind turbine farm to evaluate the applicability of measurement data by installing sensors. Through computational analysis and relevant criteria review, we defined limits for measurement parameters by vulnerable section. We categorized the structural safety evaluation into four stages: normal, caution, warning, and danger, and selected management criteria for each stage. From this, an algorithm to evaluate safety was developed, and a visualized monitoring platform based on the established critical parts monitoring system was developed.

• Earthquakes and Structures
• /
• v.27 no.1
• /
• pp.69-82
• /
• 2024

In the conventional seismic design approach for a bridge pier, the function of the stopper, and shear key are to serve as mechanisms for unseating prevention devices that retain and transmit the lateral load to the pier under strong earthquakes. This frequently inflicts immense shear forces and bending moments concentrated at the plastic hinge zone. In this study, a shear panel damper plus gap (SPDG) is proposed as a low-cost alternative with high energy dissipation capacity to improve the seismic performance of the pier. Therefore, this study aimed to investigate the seismic performance of the pre-stressed concrete I girder (PCI-girder) bridge equipped with SPDG. The bridge structure was analyzed using nonlinear time history analysis with seven-scaled ground motion records using the guidelines of ASCE 7-10 standard. Consequently, the implementation of SPDG technology on the bridge system yielded a notable decrease in maximum displacement by 41.49% and a reduction in earthquake input energy by 51.05% in comparison to the traditional system. This indicates that the presence of SPDG was able to enhance the seismic performance of the existing conventional bridge structure, enabling an improvement from a collapse prevention (CP) level to an immediate occupancy (IO).

• Computers and Concrete
• /
• v.34 no.2
• /
• pp.195-212
• /
• 2024

The use of basalt fibers in various types of fiber-reinforced mortars has been increasing. One of the factors that expands the use of basalt fibers is that it is a natural fiber and therefore the production costs are lower than fibers such as PVA fiber. Basalt fibers have some drawbacks such as reducing the workability of mortars in which basalt fibers are added due to their structure, and negatively affecting the mechanical properties when used above a certain proportional amount depending on the type of mixture. For this purpose, in this study, as a different application, the surface of basalt fibers with different lengths (6 and 12 mm) was treated with Triton X-100 surfactant, and these disadvantages were tried to be reduced. In the study, a two-step method was followed. In the first one, the effectiveness of adding untreated and treated basalt fiber at 1, 1.25, 1.5, 1.75 and 2% by weight to the mortar mixtures was determined by conducting flow spread and flow rate as fresh mortar characteristics. In the second one, microstructural characterization and mechanical tests were performed as hardened mortar properties. The results showed that the flow characteristics of basalt fiber reinforced mortars treated with surfactant improved compared to untreated basalt fiber reinforced mortars. In terms of mechanical properties, the addition of 2% treated basalt fiber by weight to the mixtures allowed to obtain %18, %12, and%48 higher values of compressive, flexural, and tensile strength values, respectively, compared to the same amount of untreated basalt fiber mixtures.

• Dementia and Neurocognitive Disorders
• /
• v.21 no.1
• /
• pp.17-29
• /
• 2022

Background and Purpose: Verbal and nonverbal fluency tests are the conventional methods for examining executive function in the elderly population. However, differences in impairments result in fluency tests in patients with mild cognitive impairments (MCIs) and Alzheimer's disease (AD) and in neural correlates underlying the tests still necessitate concrete evidence. Methods: We compared the test performances in 27 normal controls, 28 patients with MCI, and 20 with AD, and investigated morphological changes in association with the test performances using structural magnetic imaging. Results: Patients with AD performed poorly across all the fluency tests, and a receiver operating characteristics curve analysis revealed that only category fluency test discriminated all the 3 groups. Association, category, and design fluency tests involved temporal and frontal regions, while letter fluency involved the cerebellum and caudate. Conclusions: Category fluency is a reliable measure for screening patients with AD and MCI, and this efficacy might be related to morphological correlates that underlie semantic and executive processing.

• Geomechanics and Engineering
• /
• v.38 no.6
• /
• pp.571-581
• /
• 2024

Concrete linings in tunnels constructed by drilling and blasting such as NATM serve as a secondary support structure. However, these linings can face unexpected earth pressures if the primary support deteriorates or if ground conditions become unfavorable. It is crucial to determine the loosening earth pressure that allows the lining to maintain its structural integrity and prevent damage caused by this pressure. This study proposes a numerical model for simulating the trapdoor test and developing a method for calculating the loosening earth pressure. The discrete element method (DEM) was employed to describe the soil characteristics around the tunnel. Using this numerical model, a sequence of experimental trapdoor steps was simulated, and the loosening earth pressure was analyzed. Contact parameters were calibrated based on an analysis of a triaxial compression test. The reliability of the developed model was confirmed through a comparison between simulation results and laboratory test findings. The model was used to calculate the contact force applied to the trapdoor plate and to assess the settlement of soil particles. Furthermore, the model accounted for the soil-arching effect, which effectively redistributes the load to the surrounding areas. The proposed model can be applied to analyze the tunnel's cross-sectional dimensions and design stability under various ground conditions.

• Geomechanics and Engineering
• /
• v.38 no.4
• /
• pp.397-408
• /
• 2024

Buried box culverts are crucial elements of transportation infrastructure. However, their behavior under foundation loads is not well understood, indicating a significant gap in existing research. This study aims to bridge this gap by conducting a detailed numerical analysis using the Finite Element Method and Abaqus software. The research evaluates the behavior of buried box culverts by examining their interaction with surrounding soil and the pressures from surface foundation loads. Key variables such as embedment depth, culvert wall thickness, concrete material properties, foundation pressure, foundation width, soil elastic modulus, and friction angle are altered to understand their combined effects on structural response. The methodology employs a validated 2D numerical model under plane strain conditions. Parametric studies highlight the critical role of culvert depth (H) in influencing earth pressure and bending moments. Foundation pressure and width demonstrate complex interdependencies affecting culvert behavior. Variations in culvert materials' elastic modulus show minimal impact. It was found that the lower wall of the buried culvert experiences higher average pressure compared to the other two walls, due to the combined effects of the culvert's weight and down drag forces on the side walls. Furthermore, while the pressure distribution on the top and bottom walls is parabolic, the pressure on the side walls follows a different pattern, differing from that of the other two walls.

• Computers and Concrete
• /
• v.34 no.3
• /
• pp.355-365
• /
• 2024

TECSolverApp is an application that calculates the total equivalent seismic load (base shear) and shows the design spectra in accordance with the Turkish Earthquake Code (TEC). TECSolverApp software can present the spectral acceleration-period graph and the base shear (in terms of unit building weight) in MATLAB and .NET Core frameworks according to TEC 2007 and TEC 2018. In the software, three different building period evaluation options were provided, as entering the period directly, empirical calculation, and using the period calculation formula. In different period calculation scenarios, particular design input parameters such as site-specific spectral acceleration coefficients, local soil class, building importance coefficient, and structural system behavior coefficient are expected. TECSolverApp was produced in two different programming languages and published in MATLAB App Designer and ASP.NET Core MVC environments. To be shared in MATLAB App Designer, it was aimed at availability through the program and distributability as a desktop application. By deploying in ASP.NET Core MVC, open-source cross-platform coding and web-based accessibility were targeted. One of the strongest aspects of TECSolverApp is its developability thanks to software architecture. In this respect, it can be foreseen that other international seismic codes can be added to the calculations in the future.

• Advances in materials Research
• /
• v.13 no.5
• /
• pp.375-389
• /
• 2024

Installing wiring or plumbing fixtures necessitates creating chases within masonry walls, which, while serving practical purposes, raises a crucial concern regarding the potential compromise of the masonry's structural integrity. Given these concerns, it becomes essential to thoroughly understand the impact of incorporating chases on masonry strength. In this study, 37 AAC masonry prisms (200×330×100 mm³) were cast and tested for compression. The prisms were equipped with chases of various depths -10 mm, 20 mm and 30 mm; and orientations (horizontal, inclined, and vertical), which were then filled with mortar using 1:2, 1:4, and 1:6 cement-to-sand ratios. The primary objectives were to assess the strength decrease in the prisms with different chase characteristics compared to a control specimen and to determine the percentage strength increase due to filling materials compared to unfilled chases. Key findings indicate that as chase depth increases, there is a substantial reduction in prism strength. However, the orientation of the chase does not significantly affect strength reduction. Importantly, filling the chases with mortar leads to a significant increase in prism strength. This study not only unveils the complex impact of chase characteristics on masonry strength but also emphasizes the crucial role of filling materials in strengthening these prisms.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.17 no.3
• /
• pp.10-19
• /
• 2013

Recently, researches related to precast modular construction have been actively conducted for nuclear power plant, LNG gas tank, and small-medium PCCV as well as bridges and buildings. In this study, the precast panel cast with steel mesh reinforced mortar (SRM) which is similar reinforced ferrocement was developed for efficient precast construction, construction time reduction, and easy transportation. Mortar mixture with high strength and flowability was obtained from various case studies using silica fume and GGBS. Also, $1,200{\times}600{\times}150mm$ SRM and reinforced concrete (RC) panels were manufactured with reinforcing ratio of 2% and 4%. To verify structural performance of the SRM specimen, the basic material tests, free shrinkage test, and 3-point flexural test with a line loading were carried out. From the test results, it was determined that SRM specimens showed outstanding flexural capacity and ductility. However, the 4% reinforced SRM specimens must consider shear reinforcing to be used as a precast modular member.