scholarly journals Nonlinear numerical simulation of punching shear behaviour of reinforced concrete flat slabs with shear-heads

2019 ◽  
Author(s):  
D.V. Bompa ◽  
A.Y. Elghazouli
Keyword(s):  
Reinforced Concrete ◽  
Failure Modes ◽  
Numerical Models ◽  
Three Dimensional ◽  
Structural Response ◽  
Analytical Models ◽  
Shear Behaviour ◽  
Flat Slabs ◽  
Modes Of Failure ◽  
Concrete Damage

This paper examines the structural response of reinforced concrete flat slabs, provided with fully-embedded shear-heads, through detailed three-dimensional nonlinear numerical simulations and parametric assessments using concrete damage plasticity models. Validations of the adopted nonlinear finite element procedures are carried out against experimental results from three test series. After gaining confidence in the ability of the numerical models to predict closely the full inelastic response and failure modes, numerical investigations are carried out in order to examine the influence of key material and geometric parameters. The results of these numerical assessments enable the identification of three modes of failure as a function of the interaction between the shear-head and surrounding concrete. Based on the findings, coupled with results from previous studies, analytical models are proposed for predicting the rotational response as well as the ultimate strength of such slab systems. Practical recommendations are also provided for the design of shear-heads in RC slabs, including the embedment length and section size. The analytical expressions proposed in this paper, based on a wide-ranging parametric assessment, are shown to offer a more reliable design approach in comparison with existing methods for all types of shear-heads, and are suitable for direct practical application.

Analytical and Experimental Simulation of Fan Blade Behavior and Damage Under Bird Impact

1991 ◽  
Vol 113 (4) ◽  
pp. 582-594 ◽  
Author(s):  
H. C. Teichman ◽  
R. N. Tadros
Keyword(s):  
Impact Analysis ◽  
Failure Modes ◽  
Three Dimensional ◽  
Structural Response ◽  
Analytical Models ◽  
Experimental Simulation ◽  
Experimental Program ◽  
Contact Algorithm ◽  
Bird Impact ◽  
Fan Blade

An extensive analytical and experimental program has been undertaken to investigate the Foreign Object Damage resistance capabilities of external components for small gas turbofan engines. A transient nonlinear impact analysis has been used to predict the structural response of fan blades under bird ingestion conditions. This analysis is based on finite elements, a three-dimensional bird load model, and an interactive structure-to-bird contact algorithm. Experiments were designed and carried out to record large blade deformations during bird impact, and were used to validate and calibrate the analytical models. The analytical models and testing program are described, and dominant fan blade response and failure modes are presented. Predicted results demonstrate good correlation with tests. Analysis application to fan blade design and other engine components is recommended.

3D Finite Element Modeling of GFRP-Reinforced Concrete Deep Beams without Shear Reinforcement

2017 ◽  
Vol 15 (02) ◽  
pp. 1850001 ◽  
Author(s):  
George Markou ◽  
Mohammad AlHamaydeh
Keyword(s):  
Reinforced Concrete ◽  
Mechanical Behavior ◽  
Numerical Investigation ◽  
Numerical Models ◽  
Design Guidelines ◽  
Design Parameters ◽  
Shear Reinforcement ◽  
Deep Beams ◽  
Modes Of Failure ◽  
Hexahedral Elements

This paper presents the numerical investigation of nine Glass Fiber-Reinforced Polymer (GFRP) concrete deep beams through the use of numerically-efficient 20-noded hexahedral elements. Cracking is taken into account by means of the smeared crack approach and the bars are simulated as embedded rod elements. The developed numerical models are validated against published experimental results. The validation beams spanned a practical range of varying design parameters; namely, shear span-to-depth ratio, concrete specified compressive strength and flexural reinforcement ratio. The motivation for this research is to accurately yet efficiently capture the mechanical behavior of the GFRP-reinforced concrete deep beams. The presented numerical investigation demonstrated close correlations of the force–deformation relationships that are numerically predicted and their experimental counterparts. Moreover, the numerically predicted modes of failure are also found to be conformal to those observed experimentally. The proposed modeling approach that overcame previous computational limitations has further demonstrated its capability to accurately model larger and deeper beams in a computationally efficient manner. The validated modeling technique can then be efficiently used to perform extensive parametric investigations related to behavior of this type of structural members. The modeling method presented in this work paves the way for further parametric investigations of the mechanical behavior of GFRP-reinforced deep beams without shear reinforcement that will serve as the base for proposing new design guidelines. As a deeper understanding of the behavior and the effect of the design parameters is attained, more economical and safer designs will emerge.

scholarly journals Failure Modes and Resistance of Perforated Steel Rib Shear Connectors under Uplift Forces

2019 ◽  
Vol 2019 ◽  
pp. 1-16 ◽  
Author(s):  
Xiaoqing Xu ◽  
Yuqing Liu
Keyword(s):  
Composite Structures ◽  
Failure Modes ◽  
Analytical Models ◽  
Shear Connectors ◽  
Steel Bar ◽  
Concrete Damage ◽  
Uplift Resistance ◽  
Transverse Steel ◽  
Uplift Forces

In recent years, there is a rapid increase in the application of perforated steel rib shear connectors in steel and concrete composite structures. The connectors must not only ensure shear transfer but also sufficient uplift resistance. The shear behavior of connectors has been extensively investigated. However, studies on uplift resistance are lacking so far. Therefore, three push-out test specimens were tested to investigate the shear and tension behavior of perforated L-shaped and plain steel rib shear connectors. The failure modes of connectors were analyzed, and analytical models for the determination of uplift resistance were derived based on test results. The results showed that the ductility of perforated steel rib shear connectors under uplift force was smaller than that under shear force, and more severe concrete damage surrounding the rib and larger bending deformation of transverse steel bar was observed. The rib flange of L-shaped perforated rib has a significant contribution to the uplift resistance. It was suggested to increase the rib height of L-shaped rib to avoid the horizontal crack at the height of the rib flange. The validity of the proposed analytical models was confirmed by comparing the failure modes and capacities of specimens.

scholarly journals Rapid Retrofit of Reinforced Concrete Frames after Progressive Collapse to Increase Sustainability

2019 ◽  
Vol 11 (15) ◽  
pp. 4195 ◽  
Author(s):  
Li ◽  
Shan ◽  
Zhang ◽  
Li
Keyword(s):  
Reinforced Concrete ◽  
Failure Modes ◽  
Design Method ◽  
Numerical Models ◽  
Progressive Collapse ◽  
Frame Structure ◽  
Rc Frame ◽  
Concrete Frames ◽  
Before And After ◽  
Test Frame

A structural progressive collapse is usually a local failure, in which the damage is concentrated at beams that bridge the removal column and the column itself. In many cases, retrofitting the damaged structure is more economical and more sustainable than reconstructing the entire structure. A progressive collapse test of a 1/3 scale, four-bay by two-story reinforced concrete (RC) frame was conducted, after which the structure was retrofitted with carbon fiber reinforced polymer (CFRP) wraps and retested. The center column in the first story was removed and the frame was pushed down quasistatically under displacement control to investigate the progressive collapse performances of the retrofitted RC frame. The test results were represented systematically at different areas in terms of the resistance forces, crack developments, and local and global failure modes. Numerical models were built to verify the test frame before and after the retrofitting. A design method was proposed to retrofit an RC frame using CFRP wraps after a progressive collapse. The test frame was redesigned to improve the retrofitting and used as an example to demonstrate the rationality of the proposed retrofit design method. The results indicated that the proposed retrofitting technology rapidly restored the frame structure to its original capacity before the progressive collapse occurred, whilst consistently satisfying the priorities of being economical and sustainable.

scholarly journals The Fluid-Solid Interaction Dynamics between Underwater Explosion Bubble and Corrugated Sandwich Plate

2016 ◽  
Vol 2016 ◽  
pp. 1-21
Author(s):  
Hao Wang ◽  
Yuan Sheng Cheng ◽  
Jun Liu ◽  
Lin Gan
Keyword(s):  
Shock Wave ◽  
Failure Modes ◽  
Sandwich Structures ◽  
Numerical Models ◽  
Near Field ◽  
Three Dimensional ◽  
Underwater Explosion ◽  
Bubble Collapse ◽  
Fe Model ◽  
Wave Load

Lightweight sandwich structures with highly porous 2D cores or 3D (three-dimensional) periodic cores can effectively withstand underwater explosion load. In most of the previous studies of sandwich structure antiblast dynamics, the underwater explosion (UNDEX) bubble phase was neglected. As the UNDEX bubble load is one of the severest damage sources that may lead to structure large plastic deformation and crevasses failure, the failure mechanisms of sandwich structures might not be accurate if only shock wave is considered. In this paper, detailed 3D finite element (FE) numerical models of UNDEX bubble-LCSP (lightweight corrugated sandwich plates) interaction are developed by using MSC.Dytran. Upon the validated FE model, the bubble shape, impact pressure, and fluid field velocities for different stand-off distances are studied. Based on numerical results, the failure modes of LCSP and the whole damage process are obtained. It is demonstrated that the UNDEX bubble collapse jet local load plays a more significant role than the UNDEX shock wave load especially in near-field underwater explosion.

scholarly journals Mechanical Characterization of Timber-to-Timber Composite (TTC) Joints with Self-Tapping Screws in a Standard Push-Out Setup

2020 ◽  
Vol 10 (18) ◽  
pp. 6534
Author(s):  
Chiara Bedon ◽  
Martina Sciomenta ◽  
Massimo Fragiacomo
Keyword(s):  
Mechanical Characterization ◽  
Numerical Models ◽  
Three Dimensional ◽  
Analytical Models ◽  
Small Scale ◽  
Load Bearing ◽  
Timber Constructions ◽  
Technical Interest ◽  
Push Out

Self-tapping screws (STSs) can be efficiently used in various fastening solutions for timber constructions and are notoriously able to offer high stiffness and load-carrying capacity, compared to other timber-to-timber composite (TTC) joint typologies. The geometrical and mechanical characterization of TTC joints, however, is often hard and uncertain, due to a combination of various influencing parameters and mechanical aspects. Among others, the effects of friction phenomena between the system components and their reciprocal interaction under the imposed design loads can remarkably influence the final estimates on structural capacity, in the same way of possible variations in the boundary conditions. The use of Finite Element (FE) numerical models is well-known to represent a robust tool and a valid alternative to costly and time consuming experiments and allows one to further explore the selected load-bearing components at a more refined level. Based on previous research efforts, this paper presents an extended FE investigation based on full three-dimensional (3D) brick models and surface-based cohesive zone modelling (CZM) techniques. The attention is focused on the mechanical characterization of small-scale TTC specimens with inclined STSs having variable configurations, under a standard push-out (PO) setup. Based on experimental data and analytical models of literature, an extended parametric investigation is presented and correlation formulae are proposed for the analysis of maximum resistance and stiffness variations. The attention is then focused on the load-bearing role of the steel screws, as an active component of TTC joints, based on the analysis of sustained resultant force contributions. The sensitivity of PO numerical estimates to few key input parameters of technical interest, including boundaries, friction and basic damage parameters, is thus discussed in the paper.

Flexible Pipe Modeling Using Finite Macro-Elements

2014 ◽  
Author(s):  
Rodrigo Provasi ◽  
Clóvis de Arruda Martins
Keyword(s):  
Numerical Models ◽  
Local Level ◽  
Three Dimensional ◽  
Analytical Models ◽  
Great Effort ◽  
Algebraic Equations ◽  
Flexible Pipe ◽  
Commercial Software ◽  
Macro Elements ◽  
Pipe Model

Modeling flexible pipes in the local level is not a trivial task and many authors have employed a great amount of time in such task. The non-triviality arises from the various layers and their interaction, which are pretty tough to correctly model. The possible approaches to solve the problem are divided in to major categories: analytical models and numerical models. The analytical ones rely on a great number of hypotheses and, after a great effort, result in a system of algebraic equations. The numerical ones can be further differentiated in the ones developed using commercial software and the other ones using proprietary models. The authors choose the second way to approach the problem and presented in previous works a group of elements called macro-elements, including a cylindrical element for orthotropic layers, a three dimensional curved beam for helical elements, a rigid connection and a contact element, both dealing with different node displacement natures. These elements take into account the physical and geometrical characteristics of the components. In this paper a pipe model, with a flexible internal core, two tensile armors and an external sheath, will be simulated and its the results will be checked against commercial software and commented.

Punching in two-way RC flat slabs with openings and L section columns

2019 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Valdemir Colares Pinto ◽  
Vitor Branco ◽  
Denio Ramam Oliveira
Keyword(s):  
Reinforced Concrete ◽  
Cross Section ◽  
Failure Modes ◽  
Computational Simulation ◽  
Experimental Results ◽  
Design Codes ◽  
Nonlinear Simulation ◽  
Content Type ◽  
Flat Slabs ◽  
Failure Loads

Purpose This study aims to contribute to a better understanding of the influence of the position of openings around L cross-section columns in reinforced concrete flat slabs through a nonlinear computational analysis compared to experimental results. Design/methodology/approach Tests on four reinforced concrete flat slabs of 1800 x 1800 x 120 mm3 were carried out under symmetrical punching; one slab was referenced (without hole) and three had square holes of 100 x 100 mm2 close to columns and with centroid on the critical perimeter at 0.5 d and 2.0 d of the loaded area. A nonlinear analysis of the slabs was performed to aid the interpretation and preview of the experimental results, and to estimate the ultimate loads and failure modes. These estimates followed recommendations of ACI 318, Eurocode 2, NBR 6118, MC 2010 and critical shear crack theory. Findings The results showed that the presence of holes in the analyzed regions does not influence significantly the behavior of the slabs, leading to conservative structural design once the ultimate load estimates are low, while the computational results adequately estimated the slabs’ behavior. Research limitations/implications A few limitations were observed on how to implement the correct modeling system for computational nonlinear simulation. Practical implications All design codes underestimated failure loads and the theoretical method was not much better. The nonlinear computational simulations were satisfactory, presenting results close to experimental ones (97 per cent accuracy). Computational simulation also showed that the presence of holes does not significantly influence the load-vertical displacement behavior or failure loads. Social implications Structural and civil engineers and designers can observe with better details the punching phenomenon and make take secure decisions to building projects. They can preview accurate cases that are not cited in design codes and literature. Originality/value This is a very rare subject in literature that interests the entire scientific community and especially reinforced concrete designers. Presenting a new methodology to nonlinear flat slab with openings modeling to punching shear provoked by L cross section columns, case that is not cited in literature and design codes.

Size effect on the shear capacity of headed studs

2020 ◽  
pp. 136943322096903
Author(s):  
Ahmet Abdullah Dönmez
Keyword(s):  
Size Effect ◽  
Failure Modes ◽  
Three Dimensional ◽  
High Strength ◽  
Shear Capacity ◽  
Microplane Model ◽  
Effect Factor ◽  
Shear Connectors ◽  
Concrete Damage ◽  
Damage Constitutive Model

This study aimed to reveal the existence of size effect on the shear connectors used in the steel-concrete composite beams and slabs. The experimental study contains the monotonic tests of nine pushout specimens with the headed studs. Three-dimensional scaling was used for geometrically similar specimens of three sizes. High strength concrete slabs were used on both sides of the steel I-beam. The failure modes of the specimens include both concrete crushing and stud yielding. Finite element (FE) verification of the specimens was conducted using a realistic concrete damage constitutive model, Microplane Model M7. It is shown that there may be a non-negligible size effect based on the fracture patterns of the composite member. Bažant’s size effect law (SEL) can fit the size effect behavior of the shear connectors. The design equations which do not include a size effect term have high correction factors that overestimate the tested specimens. A new design equation can be drawn using the size effect factor for strength reduction of shear connectors.

scholarly journals Influence of Beam-to-Column Linear Stiffness Ratio on Failure Mechanism of Reinforced Concrete Moment-Resisting Frame Structures

2020 ◽  
Vol 2020 ◽  
pp. 1-24
Author(s):  
Jizhi Su ◽  
Boquan Liu ◽  
Guohua Xing ◽  
Yudong Ma ◽  
Jiao Huang
Keyword(s):  
Reinforced Concrete ◽  
Failure Modes ◽  
Numerical Models ◽  
Frame Structures ◽  
Material Strength ◽  
Stiffness Ratio ◽  
Limit Values ◽  
Failure Patterns ◽  
Moment Resisting Frame ◽  
Moment Resisting

The design philosophy of a strong-column weak-beam (SCWB), commonly used in seismic design codes for reinforced concrete (RC) moment-resisting frame structures, permits plastic deformation in beams while keeping columns elastic. SCWB frames are designed according to beam-to-column flexural capacity ratio requirements in order to ensure the beam-hinge mechanism during large earthquakes and without considering the influence of the beam-to-column stiffness ratio on the failure modes of global structures. The beam-to-column linear stiffness ratio is a comprehensive indicator of flexural stiffness, story height, and span. This study proposes limit values for different aseismic grades based on a governing equation deduced from the perspective of member ductility. The mathematical expression shows that the structural yielding mechanism strongly depends on parameters such as material strength, section size, reinforcement ratio, and axial compression ratio. The beam-hinge mechanism can be achieved if the actual beam-to-column linear stiffness ratio is smaller than the recommended limit values. Two 1/3-scale models of 3-bay, 3-story RC frames were constructed and tested under low reversed cyclic loading to verify the theoretical analysis and investigate the influence of the beam-to-column linear stiffness ratio on the structural failure patterns. A series of nonlinear dynamic analyses were conducted on the numerical models, both nonconforming and conforming to the beam-to-column linear stiffness ratio limit values. The test results indicated that seismic damage tends to occur at the columns in structures with larger beam-to-column linear stiffness ratios, which inhibits the energy dissipation. The dynamic analysis suggests that considering the beam-to-column linear stiffness ratio during the design of structures leads to a transition from a column-hinge mechanism to a beam-hinge mechanism.

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