A Practical Finite Element Modeling Strategy to Capture Cracking and Crushing Behavior of Reinforced Concrete Structures

Nonlinear finite element (FE) analysis of reinforced concrete (RC) structures is characterized by numerous modeling options and input parameters. To accurately model the nonlinear RC behavior involving concrete cracking in tension and crushing in compression, practitioners make different choices regarding the critical modeling issues, e.g., defining the concrete constitutive relations, assigning the bond between the concrete and the steel reinforcement, and solving problems related to convergence difficulties and mesh sensitivities. Thus, it is imperative to review the common modeling choices critically and develop a robust modeling strategy with consistency, reliability, and comparability. This paper proposes a modeling strategy and practical recommendations for the nonlinear FE analysis of RC structures based on parametric studies of critical modeling choices. The proposed modeling strategy aims at providing reliable predictions of flexural responses of RC members with a focus on concrete cracking behavior and crushing failure, which serve as the foundation for more complex modeling cases, e.g., RC beams bonded with fiber reinforced polymer (FRP) laminates. Additionally, herein, the implementation procedure for the proposed modeling strategy is comprehensively described with a focus on the critical modeling issues for RC structures. The proposed strategy is demonstrated through FE analyses of RC beams tested in four-point bending—one RC beam as reference and one beam externally bonded with a carbon-FRP (CFRP) laminate in its soffit. The simulated results agree well with experimental measurements regarding load-deformation relationship, cracking, flexural failure due to concrete crushing, and CFRP debonding initiated by intermediate cracks. The modeling strategy and recommendations presented herein are applicable to the nonlinear FE analysis of RC structures in general.

Structural Redundancy Assessment of Adjacent Precast Concrete Box-Beam Bridges in Service

Present approaches for assessing bridge redundancy are mainly based on nonlinear finite element (FE) analysis. Unfortunately, the real behavior of bridges in the nonlinear range is difficult to evaluate and a sound basis for the nonlinear FE analysis is not available. In addition, a nonlinear FE analysis is not feasible for practitioners to use. To tackle this problem, a new simplified approach based on linear FE analysis and field load testing is introduced in this paper to address the particular structural feature and topology of adjacent precast concrete box-beam bridges for the assessment of structural redundancy. The approach was first experimentally analyzed on a model bridge and then validated by a case study. The approach agrees well with the existing recognized method while reducing the computation complexity and improving the reliability. The analysis reveals that the level of redundancy of the bridge in the case study does not meet the recommended standard, indicating that the system factor recommended by the current bridge evaluation code for this bridge is inappropriate if considering the field condition. Further research on the redundancy level of this type of bridges is consequently recommended.

The Mechanics and Snap in Force Estimation of Cantilever Snap Fit Joint of Lock Plate by FEA

Snap fit joints are widely used in industry for assembling different parts. Nowadays snap fits are found in wide range of application ranging from household appliances, toys, telephones to automobiles. This study is carried out to find the most accurate snap in force of cantilever snap fit by using finite element analysis. Snap in force is the most important term in design of cantilever snap fit because while in manual assembly process it is very much important to perceive the snap fit engagement. This study focuses on the nonlinear FE analysis method to calculate insertion force of the plastic snap fit part. Behavior of plastic material is nonlinear so it difficult and time consuming to calculate the snap in force by mathematical formulae only so nonlinear FE analysis will be best method to get the realistic snap in force value. This research work also included the mathematical model and linear FE analysis calculations for the estimation of snap in force. In nonlinear analysis contact, geometric and material nonlinearity is defined in the FE model. For the verification of the results the physical testing is also carried out with the help of force gauge tool. The analytical calculations and linear FE analysis estimates higher snap in force than the actual, while nonlinear FE analysis estimates more accurate snap in force value.