مقاله انگلیسی رایگان در مورد رفتارهای خمشی و برشی در تیرها بتونی – الزویر 2019

Detailed finite element (FE) models with 3-D solid elements are typically used to simulate impact behaviors of reinforced concrete (RC) beams and columns. However, the method usually requires a substantial amount of time and effort to model concrete and reinforcement and conduct nonlinear contact-impact analyses. Also, the accuracy of the method cannot be guaranteed due to the limitations in concrete material models implemented in general-purpose FE codes. In this paper, an efficient modeling method is proposed to capture both flexural and shear behaviors of RC beams and columns under low-velocity impact loading. A macroelement-based contact model was developed in the proposed method to capture interaction behaviors between impacting objects and RC members. In the contact model, a compression-only spring with an initial gap behavior was used to account for the stiffness and the kinematic response of an impacting object, and a combination of an elastic spring and a viscous damper in parallel was employed to simulate the contact stiffness and damping. By properly approximating the strain-rate effects, traditional fiber-section elements were demonstrated to be capable of predicting impact-induced flexural failures for RC members. On this basis, a general approach for both flexural- and shearcritical RC columns under impact loading was presented with the inclusion of additional shear springs in the fiber-section elements. Nearly fifty impact tests on RC beams and columns reported in the literature were employed to validate the proposed modeling method. Comparisons between the experimental and numerical results indicate that failure modes of the impacted members can be identified explicitly by the use of the proposed modeling method. Also, reasonable agreements were achieved for the impact forces and the impact-induced responses obtained from the impact tests and the analyses. The proposed method can be readily implemented without coding in any FE software as long as traditional fiber-section elements, and discrete macroelements are available. This feature would offer an advantage for the applications of the proposed method such as when assessing the structural response and vulnerability of a bridge structure subjected to vessel and vehicle collisions.

Introduction

Numerous catastrophic accidents such as vessel or vehicle collisions with reinforced concrete (RC) columns happened in recent years around the world [1–4]. In this context, many impact tests have been carried out to clarify the behaviors of RC beams and columns subjected to impact loading (e.g. [5–11]). However, it might be unrealistic always to perform physical experiments because of the massive investments in the economy and time. On the other hand, relatively small-scale RC specimens are usually used in these impact tests due to the limits in laboratory space and the capacity of impact testing facilities. Strictly speaking, these experimental results only partially addressed the impact behaviors of full-scale RC members. Hence, analysis methods should be well established based on these test data to efficiently and accurately assess the responses of RC members under impact loading. Currently, many studies have been carried out to develop detailed FE models with the use of general-purpose contact-impact nonlinear FE codes (e.g., LS-DYNA and ABAQUS) for RC members under impact loads [12–17]. Among these studies, 3-D solid elements were mostly used for concrete while beam/truss elements were employed to model reinforcing rebars.