In this study, several simplified constitutive models and a damage plasticity model for ultra-high performance fiber reinforced concrete(UHPFRC)material with micro and hooked ends steel fibers, Bekaert Dramix 5D steel fiber, and Forta-Ferro synthetic fiber had been developed. Later, these constitutive and damage plasticity models were applied as analytical model to numerically simulate the concrete members with different fibers, and to evaluate the behavior of the concrete sections. The constitutive models for UHPFRC of three mix designs were obtained experimentally by conducting uniaxial compression and tensile tests on both cylinder and dog-bone specimens. Next, a comparison was made among the three mix designs based on the outcomes retrieved from uniaxial compression and tensile stress–strain. These results were validated by numerically analyzing three hollow circular columns via finite element method. The numerical results revealed that the proposed material model possessed appropriate tensile strain-hardening behavior and uniaxial compression strengths of UHPFRC with different types of fiber. The lateral resistance responses of the tested hollow sections, which were obtained by using developed constitutive and damage plasticity models, displayed exceptional agreement with the experimental outcomes.
This study investigates the effect of certain parameters on the magnitude of plastic hinge length of RC shear walls and proposes an analytical expression for estimating the plastic hinge length. A finite element model was analyzed and validated with experimental test results for an existing study and a parametric study was performed for it. The established results were according to several parameters such as axial load ratio, slenderness ratio and wall length. The numerical results showed a different impact of these parameters on the formation of the plastic hinge length. In this study, a new simple expression was derived based on those parameters using statistical package software. Proposed plastic hinge expression was compared with the results of the plastic hinge length obtained from FE analysis. Finally, the accuracy of the proposed equation was validated by using the shear wall results from the literature researches.
The study aimed to explore the possibility of strengthening RC corbels with many strengthening techniques. The research analyzed the RC corbels behavior under a wide range of variables. The theoretical study consisted of twelve models reinforced with GFRP bars with strengthening by steel plate. Finite element analysis with ANSYS APDL was used to verify five specimens. This research deals with a static nonlinear FE simulation to investigate the behavior of RC Corbels reinforced internally and externally. The verification with experimental work demonstrated a satisfactory agreement in the load-displacement relationship, ultimate load and displacement, and failure mode. The parametric study was implemented which included strengthening the four concrete corbels externally and four corbels internally by a steel plate in many configurations while the remaining three were modeled with varied compressive strength (30, 40, and 50) MPa. The external strengthening included the placing of steel plate externally around the corbel in a U-shaped form and partial strengthening by strips and bottom plate. The models with internal strengthening involved placing the steel plate internally instead of stirrups. The results discovered that the strengthening provided enrichments in the stiffness, ductility, and energy absorption by 37 %, 4 %, and 26 %. In addition, in the case of full external strengthening more than internal retrofitting, there is a maximum improvement in the cracking and ultimate load carrying capacity. The external strengthening was better than internal one due to the confinement effect of the concrete. The stress distribution and crack pattern were affected by the strengthening techniques and more cracks appeared in the corbels with external steel plates.
This study herein presents investigations about behavior of circular flange bolted connection (CFBC) in ultra high performance fiber reinforced concrete (UHPFRC) hollow segmented communication tower subjected to lateral dynamic load. The CFBC consists of two flanged concrete, cast together with the structural segment tubes and then connected using steel bolts. The paper is illustrated with CFBC joint of 500mm flange thicknesses, and 8M25 high strength steel bolts coming from a typical real design tower. For this purpose, the full scale CFBC joints for communication tower are made from Ultra High Performance Fiber Reinforced Concrete (UHPFRC). The connection was cast and experimentally tested by applying cyclic lateral load using dynamic actuator. The lateral strength and stiffness resistance of the UHPFRC CFB connections were evaluated in this study. Besides, a rigorous FEM analysis was executed in order to evaluate the performance of CFBC in the communication tower by investigating the mechanism of force transfer, load bearing capacity as well as failure behavior of the circular flange bolted connection (CFBC) under lateral cycling loading. The experimental and numerical analysis results showed the ability of UHPFRC circular bolted connection to resist the applied lateral loads. In addition, the considered model revealed that for joints under tension, bolts were seriously not subjected to bending moments which is due to the prying effect. This was made possible by the provision of adequate flange thickness and strength of the UHPFRC material.
In this investigation, a kenaf/PLA composite specimen was subjected to the fatigue load, and the results were analyzed numerically. Some of the most significant fatigue tool aspects that were looked into were life expectancy, damage, alternative stress, and biaxiality indication. The static structural tool was utilized in order to predict the numerical analysis, and the calculations were performed with the GoodMan theory of fatigue. The loading was completely reversed so that it was equal to 30 kN. When it was discovered that the system could continue to function even after 1e6 cycles had been completed. After applying the alternative load of 30 kN, the biaxiality indication was found to be 0.425, with a minimum value of 0.9. It has been determined how much damage has occurred. The minimum amount of cycles necessary to reach the maximum damage potential is 1000, while the maximum amount of cycles necessary to reach the maximum damage potential is 1.7662·106. It has been established that there is another stress that is comparable to this one. Based on the findings of the investigation, it was determined that the fillet regions of the specimen were subjected to a maximum alternative stress of 716.4 MPa. The alternative stress cannot drop below 31.276 MPa under any circumstances. It has been determined that 106cycles have been spent living in total by the calculation. It has been found out that there is not going to be any damage regardless of the number of cycles that pass due to the fact that that number is 1. It was found that the alternative stress could reach a maximum value of 716.4 MPa, so that was the value that was used for the alternative stress
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