Fiber self-compacting concrete (FSCC), is a concrete that has been combined with fiber in its mix design. Extensive benefits of self-compacting concrete (SCC) in full fill the mold and achieving full compaction without vibration, with good behavior after concrete cracking, raise the idea of self-compacting concrete production. The fundamental challenge in this area is the unsatisfactory performance of concrete with fibers; In other words, using fibers in concrete will reduce concrete fluidity. Therefore, determining the appropriate percentage of fibers in SCC can be a precursor to extending the use of FSCC. In this study, polypropylene fibers with 0.5, 1, 0.1, and 2% of concrete mix design have been added to the self-compacting concrete mix design. Its impact on the performance of concrete has been evaluated using time and diameter of slump-flow, L-Box, J-ring, and V-funnel flow time tests. Based on the criteria defined by EFNARC standard, it was indicated that the FSCC containing 0.5% polypropylene fibers has an acceptable performance. Additionally, the effect of polypropylene fiber on the mechanical properties of hardened concrete has been studied using compressive strength and tensile tests and shown that changes in FSCC compressive strength and tensile with 0.5% polypropylene fiber are negligible.
In the use of non-linear structural performance models, including models that consider the critical over-performance at the failure stage, is very important when performing seismic calculations of reinforced concrete buildings and structures.The use of such models is especially important if the structures have primary damage caused by fire or corrosion, as well as mechanical damage caused by force factors. The purpose of this study is to develop an analytical model of the deformation of eccentrically compressed reinforced concrete columns by considering the failure stage, which includes processes such as peeling of the protective layer, reduction of the stability of the compressed reinforcement and softening of the encased concrete after reaching the design strength. , the existing models that describe the residual behavior of reinforced concrete structures under low cycle loading have been investigated. The models are analyzed considering monotonic curves, which are cyclic deformation boundaries. The model proposed in the research is constructed by analyzing the stages of the stress-strain state of a reinforced concrete column. At each stage, formulas are found for determining moment and curvature by solving equations of equilibrium of internal forces. Calculations based on the obtained model for a particular reinforced concrete column are carried out, monotonous diagrams are obtained, and a conclusion about the significant influence of the level of axial load on the character of deformation is made. On the basis of the obtained model, the construction of hysteresis diagrams under low-cycle loading is expected in the future.
Flood drainage ditches serve as critical infrastructure, directing and managing floodwaters to prevent indiscriminate flow, reduce flooding risks, and curb erosion. Vegetation plays a crucial role in enhancing the effectiveness of these ditches. It acts as a natural barrier, mitigating floodwater speed and impact while stabilizing soil and preventing erosion. Furthermore, vegetation aids in water quality improvement by filtering pollutants and nutrients, making it safer for humans, animals, and plants. It also reduces peak flows and attenuates floodwaters, thereby minimizing urban flooding risks. Additionally, the presence of vegetation in floodplains provides extra storage capacity for excess water, supporting floodplain management and biodiversity conservation. The study emphasizes the importance of carefully considering vegetation type, characteristics, and management practices to optimize flood drainage ditch performance. Selection of suitable plant species and morphological optimization significantly enhances drainage capacity and infiltration rates. Proper maintenance and management practices are vital to ensure unimpeded water flow and prevent obstruction.
Fiber Reinforced Polymer (FRP) composites have been broadly applied in substitution of steel members at rehabilitation interventions thanks to their lightweight, high strength, and high corrosion resistance. Producing novel FRP-concrete hybrid structures is the next step researchers are dealing with. In this context, the present study focuses on the numerical and analytical modeling of the experimentally obtained response of hybrid FRP-concrete slabs subjected to three points bending tests. The analyzed hybrid elements consisted of an omega shape Carbon Reinforced Polymer (CFRP) sheet on which a concrete layer was cast forming a unidirectional slab member. A Glass Fiber Reinforced Polymer (GFRP) fabric was bonded to the CFRP sheet and embedded into the concrete block to provide a connection between CFRP and concrete in one of the specimens. Simulation results showed agreement with the experimental response in terms of load-displacement curve, concrete plastic strain and failure mode. After validating the model, alternative designs (width, height, and thickness of CFRP sheet and concrete block on it) were numerically tested to study the influence of the geometry of the structural system on the load-bearing capacity. Lastly, analytical formulation assuming total compatibility and based on Euler-Bernoulli theory were implemented and contrasted with the experimental response. Overall results pointed out that the optimum design would be the one with increased height of both concrete and CFRP. For this improved configuration, the load-bearing capacity was increased by up to 44%.
Seismic Strengthening offers a cost-effective and sustainable solution for constructing bridges in seismic zones. In these rehabilitation interventions, Fiber Reinforced Polymer (FRP) composites are often used instead of steel members due to their lightweight nature, high strength, and excellent corrosion resistance. Researchers are now focusing on creating innovative FRP-concrete hybrid structures. This study specifically investigates the numerical modeling of the response of a hybrid FRP-concrete jacket bridge pier subjected to quasi-static tests. The Finite Element Method (FEM) results demonstrated a significant correlation with the experimental response, particularly in terms of the load-displacement curve failure mode. Once the model was validated, various alternative designs were numerically tested to evaluate the impact of each model on the load-bearing capacity. These designs included altering the height of the CFRP sheet, adjusting the height and congestion of the CFRP bar, and comparing the performance of the concrete jacket with and without the CFRP sheet. After reinforcing the CFRP sheets and incorporating Near-Surface-Mounted (NSM)-CFRP bars, the reinforcement system, along with the new concrete jacket, effectively transferred the integrity of the broken pier area and maintained a constant load-bearing capacity for the bridge pier. However, when the CFRP sheet was added to the aforementioned system, the load capacity of the bridge pier increased by more than 60%. Therefore, it can be concluded that seismic enhancement techniques utilizing CFRP sheets and mounted NSM-CFRP bars are successful in enhancing the strength and resilience of the concrete bridge pier.
Nanotechnology is poised to offer a viable solution for achieving high performance in future construction projects. Among the innovative technologies being explored, smart concrete has garnered significant attention and undergone extensive research in reputable scientific centers worldwide in recent years. A notable advancement within this field is the development of self-healing concrete. Concrete structures are undeniably susceptible to cracking, primarily due to natural processes. These cracks serve as pathways for harmful substances to infiltrate and corrode the reinforcement bars, ultimately leading to the degradation of the concrete. Traditional approaches to address this issue involve the use of repair materials, particularly various polymers. However, these materials not only complicate the repair process but also have adverse environmental consequences. In light of these challenges, scientists have discovered an alternative method that involves incorporating bacteria into concrete production to create self-healing properties. This method not only reduces maintenance and repair costs but also minimizes environmental impact, thereby enhancing the durability and performance of the concrete while extending its service life. By harnessing the power of bacteria, self-healing concrete represents a significant breakthrough in sustainable construction practices.