http://ir.bdu.edu.et/handle/123456789/10234 2001-01-13T06:39:03Z http://ir.bdu.edu.et/handle/123456789/16675 COMBINED EFFECT OF BLAST AND IMPACT LOAD ON EXTERNAL RC BEAM-COLUMN JOINT AND STRENGTHENING WITH CFRP Agdew, Amsalu Many Reinforced Concrete (RC) buildings are damaged by Terrorist attacks all over the world. It results in damages to assets, loss of life, and social panic. In principle, structural designs ensure the protection and safety of occupants and the integrity of the structure itself. However, in reality, this is not upheld when a structure is struck by extreme blast loading. There are limited previous studies that conducted the combined effect of blast and impact load on RC beam-column joints and the application of Carbon Fiber Reinforced Polymer (CFRP) strengthening mechanisms to increase the reduced load resistance capacity. The main aim of this study is to investigate the combined effect of blast and impact load on RC beam-column joints and the use of CFRP strengthening mechanisms. The explicit dynamic analysis software LS-DYNA 2022 is used to establish numerical investigations. The experimental results from the literature were used to validate the finite element analysis LS-DYNA explicit dynamic analysis software. The parametric studies were conducted with a variation of blast load stand-off distance, blast weight, blast load incident angle, weight of impact, impact load stand-off distances, and CFRP strengthening methods. The finite element investigation result shows that The blast load stand-off distance and blast weight variation have a considerable effect on displacement responses of RC beam-column joints under the combined effect of blast and impact loads. The maximum deflection is observed at 90⸰ blast load incident angle for both 5 kg and 50 kg blast weight at 2m SD of blast load. The 1 layer at 90 CFRP orientation is the best strengthening layout of RC Beam-column joint under the combined effect of blast and impact loads without debonding failure. Keywords: RC Beam-column joint, Impact–blast combined load, LS-DYNA, CFRP. 2024-10-01T00:00:00Z http://ir.bdu.edu.et/handle/123456789/16652 Comparative Analysis of Machine Learning Techniques for Predicting Flexural Behavior in RC Beams Yonas, Alemu Intelligent prediction of the flexural strength of reinforced concrete beams remains a challenging task due to variation in accuracy and precision of machine learning algorithms. It also becomes harder for users to assess and select best model, since several machine learning models has their own limitation and advantages with different circumstances. To overcome this problem this study aims to evaluate and compare the performance of various machine learning algorithms in terms of their accuracy and efficiency. Linear Regression, Decision Tree, Support Vector Machine, K-Nearest Neighbors, Random Forest, Adaptive Boosting, Gradient Boosting, and Extreme Gradient Boosting models were evaluated. Hyperparameters of each model were optimized using Grid Search cross validation with Mean Squared Error used as the Performance Index. The predictive efficiency of each model was rigorously evaluated through four distinct statistical performance measures. The results of the analysis revealed that the Linear Regression model encountered issues of underfitting, while the Decision Tree model demonstrated signs of overfitting and constrained generalization capabilities. Additionally, the Adaptive Boosting model exhibited a minor overfitting concern. Moreover, the Support Vector Machine, Random Forest, and Adaptive Boosting models yielded comparable levels of accuracy. In contrast, the proposed Extreme Gradient Boosting model achieved superior performance characterized by exceptional generalization capabilities, as evidenced by its minimal mean absolute error of 2.08 kN-m, a root mean squared error of 3.09 kN-m, and the highest coefficient of determination of 98.50% on the test data. Key Words: Machine Learning, Artificial Intelligence, Reinforced Concrete Beam 2024-10-01T00:00:00Z http://ir.bdu.edu.et/handle/123456789/16651 Numerical Investigation of Circular Hollow Reinforced Concrete Columns Confined with Carbon Fiber Reinforced Polymer (CFRP) Tewodros, Ebabye Concrete columns encased in carbon fiber reinforced polymer (CFRP) have been explored for usage in civil engineering constructions in recent years. This paper presents the results of a study to have better understanding of structural behavior of CHRCC wrapped by carbon fiber reinforced polymer (CFRP) sheets. The existing researches on CFRP confinement of reinforced concrete (RC) columns predominantly focuses on solid rectangular or square cross-sections, leaving a significant gap in understanding the behavior and performance of hollow circular RC columns under similar confinement. In the study, three dimensional finite element models have been presented to analyze reinforced concrete columns strengthened with CFRP composites, to evaluate the gain in performance (strength and ductility) due to strengthening, and to study the effect of the most important parameters considered. To achieve the desired objective, wrapping length of CFRP, diameter to thickness (D/t) ratio, lateral reinforcement ratio and concrete grade are considered as study parameters. A finite element model has been developed to investigate the behavior of RC circular hollow column strengthened with CFRP sheets by modeling twenty-two specimens, modeled under concentric loading. The numerical results using the (ANSYS APDL v.2024R1) were calibrated and validated with published experimental test results in the literature. The findings of the FE model and the experimental data were good similar. As a consequence, the model was found to be valid. The results of the study show that, external bonded CFRP sheets are very effective in enhancing the axial strength and ductility of the circular hollow reinforced concrete columns. Although CHRCC confined with 25% of its length by CFRP shows no significant difference in load carrying capacity, it is observed a 6.41% and 27% increment in load carrying capacity for 50 % and 100% CFRP confinement respectively. It was further observed that CFRP confinement has promising effect in strength enhancement for different variations in geometry and material. Keywords: Nonlinear Finite Element Analysis (NLFEA), Hollow Circular Column, CFRP Confinement 2024-09-01T00:00:00Z http://ir.bdu.edu.et/handle/123456789/16650 EFFECTS OF SEISMIC LOAD ON VARIOUS TYPES OF REINFORCED CONCRETE PIERS WITH INTEGRAL ABUTMENTS FOR CONTINUOUS TGIRDER REINFORCED CONCRETE BRIDGE KIBUR, ALEMAYEHU YAYEW The structural analysis for earthquake load is important to get structural behaviors for different types of bridge piers to get seismic demand resistance. The seismic performance evaluation of three types of reinforced concrete hammerhead piers, bent piers, and pier walls that have a similar superstructure to seismic zone 3 of the country is conducted. The seismic evaluations is performed by modal response spectrum dynamic analysis using CSi-Bridge v21 finite element analysis software. The deflected mode shape, the fundamental time period, the moment, the base shear force, and the pier displacements are the core findings. There is a larger pier top deflection and fundamental period for flexible pier configurations. The results show that the bent-type pier has better deflection resistance and a smaller fundamental time period than other pier types. The fundamental period of vibration and the deflection at the top of the pier in a longitudinal direction are larger for the pier wall among the three types of piers. For conventional foundation modeling without considering soil-structure interaction, the deflections occurred only at the top of the piers. Considering soil-structure interaction, the hammerhead pier has a larger foundation displacement demand in the longitudinal direction, and the pier wall has a greater transverse displacement demand. The hammerhead pier has a greater longitudinal shear demand than the other piers, but the transverse shear demand is high for the pier wall relative to the other two pier types. The longitudinal moment demand for the pier-wall and transverse moment demand for the hammerhead pier are large. Kay words: Bridge piers, Dynamic load, Response spectrum, Force, Displacement 2024-07-01T00:00:00Z