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Impact Behavior of Textile Reinforced Concrete Slabs
(01. Izmir Institute of Technology, 2021) Batarlar, Baturay; Saatçi, Selçuk
Reinforced concrete (RC) technology is still the most preferable and common method to build civil engineering structures. In accordance with design purposes and needs, these structures are built to resist various loading scenarios. Throughout the lifespan of RC structures, they may be subjected to high rate loading scenarios due to either expected or unexpected reasons such as impacts caused by vehicular collisions, debris generated by typhoons, tsunami or floods, rock or object falls to protective shelters. Therefore, understanding of impact behavior of RC members plays a vital role not only for design stages but also retrofitting and strengthening purposes thereafter. For this purpose, an experimental program was carried out to reveal the impact behavior of RC slabs strengthened with carbon textile reinforcements. In this program, four slabs specimens, two unstrengthened and two strengthened with two different carbon textile reinforcements, having dimensions of 1.5 m × 1.5 m × 0.2 m were tested by using an advanced impact testing facility at Otto-Mohr Laboratiorum of Technische Universität Dresden. In these tests, all slabs were tested under repeated impact loads by using the same steel striker with a 200 mm - diameter flat contact surface in the velocity range of 25.2 to 30.2 m/s. The results obtained from these tests are presented in terms of midpoint-displacement histories, reaction force histories, slab accelerations, and strain histories of steel reinforcements for each impact. As a result of the test program, it is shown that carbon textile reinforcements have significant effects on enhancing impact capacity as well as limiting maximum and residual midpoint displacements. By using the data obtained from tests, a finite element (FE) modeling study was performed by using the LS-DYNA software tool. In this study, two FE models with different mesh sizes were created and compared with each other to obtain efficient modeling conditions. In the light of the tests and validated models, a parametric study was performed to figure out efficient impact conditions and parameters for carbon textile reinforcements. It is shown that carbon textile reinforcements are more effective for limiting damage levels under low-velocity impacts.
Finite Element Simulations of Impact Test for Light Alloy Wheels
(Izmir Institute of Technology, 2016) Pehlivanoğlu, Uğur; Yardımoğlu, Bülent
Static and dynamic finite element models for the simulation of the wheel impact test defined in ISO7141 were developed for the AlSi7Mg and AlSi11Mg alloy wheels. The dynamic model consists of the striker, the wheel with radial pneumatic tire, and the hub adapter structure. Two types of tire models, composite and simplified, are formed in this study. The finite element model in the dynamic model, referred to as composite tire, involves bead, bead core, casing and crown plies, tread, and side walls. A simplified tire model that does not include bead cores, casing and crown plies is also generated. Although these items are not used in the second model directly, they are considered using their equivalent effects. It is shown that a simplified tire model can be used instead of the composite tire model. The dynamic model is validated by experimental studies. Such studies are related to the plastic deformations at the impact point of the wheel. It is shown that simulation of the failure of the wheel during impact tests can be determined using von Mises and effective plastic strain occurs in the wheel. In total, forty-one experiments are done to see the wheel behaviors and whether it performes according to the standard. The experimental results and the corresponding simulations focusing on von Mises stresses along with effective strains are shown in box plots. Thus, critical values for design are found. The static model consists of the wheel with simplified tire and the lumped model of the hub adapter structure. The stiffness characteristic of the impact point of the wheel is determined by using the static model. It is shown that the maximum von Mises stress that occurs in the wheel due to impact load is found using energy conversions. Significant time can be saved by this manner.

Phd Degree / Doktora

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