This thesis presents study of punching shear capacity of flat slab-column junctions. A three dimensional nonlinear finite element program based on 8 node solid elements was used to carry out the nonlinear analysis of flat-slab models with and without gabion-mesh. The effect of gabion arrangements for punching and the ultimate load prediction for each was presented in this thesis. The results obtained from abaqus were compared to code prediction results, and the failure mode also compared to experimental and code predicted failure modes. The predicted mode of failure and other responses are in a good correlation to euro code predicted values. In addition to punching gabion has greater resistance to flexure by increasing the stiffness of the slab. Finally it is concluded that using hexagonal gabion mesh at tension part is easy, effective and can solve construction difficulty of drop panels and one layer gabion can reduce 10mm of slab thickness. Punching strength is a critical point in the design of flat slabs and due to the lack of a theoretical method capable of explaining this phenomenon, empirical formulations presented by codes of practice are still the most used method to check the punching resistance of slab-column connections.
Flat slab is a reinforced concrete slab supported directly by concrete columns without the use of beams. This type of slab is appropriate for most floor situations and also for irregular column layouts. Because of its aesthetic view, simplicity for construction, reduction of foundation cost, this becomes very common and competitive structural system for cast-in-place slabs in buildings. Flat plates allow easy and flexible partitioning of space and reduce the overall height of tall buildings. But since the load is directly transferred from slab to column due to high localized force at the column punching effect or punching shear failure is critical. This type of failure is catastrophic because no visible signs are shown prior to failure.
To increase the punching resistance of the flat slab several methods have been used, such as drop panel, column capital, column head and shear reinforcements such as shear stud and stirrups. In our country Ethiopia the first three mechanisms are used to increase the resistance of punching shear in flat slabs but shear reinforcements are being used in other countries such as America and British.
Table of Contents
Chapter-1:-Introduction
1.1. The background
1.2. Statement of the problem
1.3. Objective of the study
1.4. Scope of the study
Chapter-2:-LITERATURE REVIEW
2.1. Introduction
2.2. Behavior of slabs falling by punching
2.3. Enhancing the punching shear strength of flat slabs
Chapter-3:- FINITE ELEMENT MODELING AND METHODS
3.1. Overview of abaqus
3.2. Material modeling
3.3. Selected geometry and modeling of flat slab
3.4. Material properties
3.5. Interaction
3.6. Element type selection
3.7. Loading and boundary condition
3.8. Mesh convergence
Chapter -4:- RESULTS AND DISCUSSIONS
4.1. Introduction
4.2. Ultimate load capacity
4.3. Effect of gabion arrangements and their ultimate load prediction
4.4. Load-deflection relationships
4.5. Failure mode and failure location
4.6 Effect of gabion for flexural resistance
4.7 Effect of column size on percentage enhancement of gabion for punching
4.8 Effect of thickness of slab on punching resistance
4.9 Effect of drop panel for punching resistance
4.10 Comparison of Numerical Results with euro Code Provision
Chapter:-5-Conclusion and recommendation
5.1. Conclusion
5.2. Recommendations
Research Objectives and Themes
This thesis investigates the punching shear capacity of flat slab-column junctions using nonlinear finite element analysis in Abaqus. The primary research goal is to evaluate the effectiveness of incorporating gabion mesh as an alternative reinforcement method to enhance the structural performance, load capacity, and stiffness of flat slabs.
- Nonlinear finite element modeling of slab-column connections.
- Enhancement of punching shear resistance using gabion mesh.
- Comparative analysis of gabion mesh against traditional reinforcement and drop panels.
- Evaluation of gabion influence on load-deflection relationships and failure mechanisms.
- Validation of numerical results against Eurocode design provisions.
Excerpt from the Book
3.2.1. Concrete
Concrete has low tensile strength, which results in cracking at very low tensile stress levels. These cracks reduce the stiffness of the concrete, which is the major contributor to the nonlinear behavior of reinforced concrete structures.
In order to incorporate the nonlinear behavior of the concrete, the concrete damaged plasticity model in abaqus was used. The concrete damaged plasticity model considers both the tensile cracking and compressive crushing of concrete as possible failure modes. This provides a general capability for modeling concrete and other quasi-brittle materials in all types of structures (beams, trusses, shells, and solids). This model uses the concepts of isotropic damaged elasticity in combination with isotropic tensile and compressive plasticity to represent the inelastic behavior of concrete
Summary of Chapters
Chapter-1:-Introduction: This chapter provides the background on flat slab structural systems, highlighting the criticality of punching shear failure and outlining the research objectives for investigating gabion mesh as an enhancement method.
Chapter-2:-LITERATURE REVIEW: This section reviews existing experimental and numerical research regarding punching shear failure, current code provisions, and various established techniques for enhancing the resistance of flat slabs.
Chapter-3:- FINITE ELEMENT MODELING AND METHODS: This chapter details the setup of the numerical simulations, covering the use of the Abaqus software, material modeling, geometry, interaction settings, element selection, and mesh convergence analysis.
Chapter -4:- RESULTS AND DISCUSSIONS: This section presents the outcomes of the nonlinear finite element simulations, including ultimate load capacity, load-deflection responses, failure modes, and the comparative effects of varying gabion arrangements and slab parameters.
Chapter:-5-Conclusion and recommendation: This chapter synthesizes the research findings, confirming the effectiveness of gabion mesh in enhancing punching and flexural resistance, and suggests directions for future study.
Keywords
gabion mesh, flat slab, Concrete Damaged Plasticity model, Finite Element Analysis, Punching shear, slab-column connection, nonlinear analysis, structural reinforcement, ultimate load capacity, load-deflection, Eurocode, concrete cracking, flexural resistance, column size, mesh convergence
Frequently Asked Questions
What is the core focus of this thesis?
The research focuses on the analytical study of the punching shear capacity of flat slab-column junctions, specifically evaluating the use of gabion mesh as an economical and effective reinforcement technique.
What are the primary themes addressed in the work?
Key themes include finite element analysis of concrete, the behavior of punching shear failure, the impact of various gabion mesh arrangements on slab performance, and comparisons with standard design codes.
What is the main objective of this study?
The principal objective is to address a better analytical understanding of punching in flat slabs with gabion, specifically analyzing the increase in strength and deflection capacity by varying the layers and positions of the gabion mesh.
Which scientific method is employed?
The study utilizes three-dimensional nonlinear finite element analysis via the Abaqus software, employing 8-node solid elements to model the concrete and truss elements for the reinforcement and gabion mesh.
What is discussed in the main body of the research?
The main body covers the theoretical background, the detailed finite element modeling methodology, and a comprehensive analysis of the simulation results, including the effects of gabion layers, column sizes, and slab thicknesses on punching resistance.
Which keywords best characterize this work?
The work is characterized by terms such as gabion mesh, flat slab, finite element analysis, punching shear, and Concrete Damaged Plasticity.
How does the placement of gabion mesh affect punching resistance?
The study concludes that gabion mesh is most effective when placed in the tension zone of the slab, with effectiveness decreasing as the mesh is placed closer to the compression zone.
Can gabion mesh be a substitute for other methods?
Yes, the findings suggest that using one layer of gabion mesh can effectively replace 10mm of slab thickness and a 37.5mm depth drop panel, offering a solution to construction difficulties.
How do the numerical results compare to Eurocode?
The numerical results obtained from the Abaqus simulations show a good correlation with the predictions provided by the Eurocode, with gabion mesh providing additional strength beyond standard code predictions.
- Citation du texte
- Hailemelekot Haileslassie (Auteur), 2018, Enhancement of flat flabs' shear resistance using gabion mesh, Munich, GRIN Verlag, https://www.grin.com/document/937892
