scholarly journals Numerical analysis of waffle slabs in flexure considering the effects of concrete cracking

2015 ◽  
Vol 8 (2) ◽  
pp. 225-247
Author(s):  
B. R. B. Recalde ◽  
F. P. S. L. Gastal ◽  
V. R. D'A Bessa ◽  
P. F. Schwetz
Keyword(s):  
Reinforced Concrete ◽  
Numerical Model ◽  
Numerical Models ◽  
Heterogeneous Material ◽  
Physical Nonlinearity ◽  
Material Behavior ◽  
Crack Model ◽  
Finite Element Program ◽  
Area Element ◽  
Element Discretization

Waffle slab structures simulated by computational model are generally analyzed by simplified methods, for both the section geometry (converting into solid slabs or grids) and for the material mechanical properties (linear elastic regime). Results obtained by those studies show large differences when compared with test results, even at low loading levels. This is mainly due to lack of consideration of the eccentricity between the axis of the ribs and the cover, as well as the simplification of the mechanical behavior of concrete tensile strength. The so called more realistic numerical models do consider the effect of the eccentricity between the axis of the cover and ribs. One may also introduce physical nonlinearity of reinforced concrete in these models, obtaining results closer to tests. The objective of this work is to establish a numerical model for the typical section of waffle slabs given the recommendationslisted above. Such model considers the eccentricity between the axis of the ribs and the cover, the physical nonlinearity of concrete in compression and the concrete contribution between cracks (tension stiffening) through a smeared crack model. The finite element program SAP2000 version 16 is used for the non-linear analysis. The area element discretization uses the Shell Layered element along the thickness of layers, allowing for the heterogeneous material behavior of the reinforced concrete. The numerical model was validated comparing results with tests in slabs and, eventually, used to evaluate some waffle slabs subjected to excessive loading.

An experimental and numerical investigation on active compliant joint made by shape memory alloy actuator

2019 ◽  
Vol 234 (2) ◽  
pp. 156-164 ◽  
Author(s):  
Babak Katanchi ◽  
Alireza Fathi ◽  
Mostafa Baghani ◽  
Hamed Afrasyab
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Shape Memory ◽  
Numerical Models ◽  
Niti Alloy ◽  
Experimental Tests ◽  
Finite Element Program ◽  
Heating Source ◽  
Compliant Joint ◽  
Actuator Performance

In this paper, a novel active compliant joint for robotic and microdisplacement applications is investigated numerically and experimentally. The proposed actuator structure is simple and possesses a higher energy density compared to the available actuators. Experimental tests are performed employing the shape memory behavior of NiTi alloy by the electric current as a heating source. To verify the actuator performance, numerical models are simulated in a nonlinear finite element program through employing a user subroutine according to experimental tests. Finite element implementation of the proposed actuator is performed based on the constitutive equations developed in Boyd–Lagoudas phenomenological model. Comparing the test and numerical results revealed that the numerical model is successful in predicting the actuator response. Finally, based on the verified numerical model, the effects of different parameters, e.g. the compression spring stiffness on the actuator performance are studied, and an optimal design for the actuator structure is proposed.

scholarly journals Improving Blast Performance of Reinforced Concrete Panels Using Sacrificial Cladding with Hybrid-Multi Cell Tubes

Modelling ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 149-165
Author(s):  
Mahmoud Abada ◽  
Ahmed Ibrahim ◽  
S.J. Jung
Keyword(s):  
Reinforced Concrete ◽  
Numerical Models ◽  
Plate Thickness ◽  
Core Layer ◽  
Engineering Structures ◽  
Finite Element Program ◽  
Explicit Finite Element ◽  
Element Program ◽  
Thin Walled ◽  
The Impact

The utilization of sacrificial layers to strengthen civilian structures against terrorist attacks is of great interest to engineering experts in structural retrofitting. The sacrificial cladding structures are designed to be attached to the façade of structures to absorb the impact of the explosion through the facing plate and the core layer progressive plastic deformation. Therefore, blast load striking the non-sacrificial structure could be attenuated. The idea of this study is to construct a sacrificial cladding structure from multicellular hybrid tubes to protect the prominent bearing members of civil engineering structures from blast hazard. The hybrid multi-cell tubes utilized in this study were out of staking composite layers (CFRP) around thin-walled tubes; single, double, and quadruple (AL) thin-walled tubes formed a hybrid single cell tube (H-SCT), a hybrid double cell tube (H-DCT), and a hybrid quadruple cell tube (H-QCT). An unprotected reinforced concrete (RC) panel under the impact of close-range free air blast detonation was selected to highlight the effectiveness of fortifying structural elements with sacrificial cladding layers. To investigate the proposed problem, Eulerian–Lagrangian coupled analyses were conducted using the explicit finite element program (Autodyn/ANSYS). The numerical models’ accuracy was validated with available blast testing data reported in the literature. Numerical simulations showed a decent agreement with the field blast test. The proposed cladding structures with different core topologies were applied to the unprotected RC slabs as an effective technique for blast loading mitigation. Mid-span deflection and damage patterns of the RC panels were used to evaluate the blast behavior of the structures. Cladding structure achieved a desired protection for the RC panel as the mid-span deflection decreased by 62%, 78%, and 87% for H-SCT, H-DCT, and H-QCT cores, respectively, compared to the unprotected panels. Additionally, the influence of the skin plate thickness on the behavior of the cladding structure was investigated.

Experimental and Numerical Evaluation of UHPFRC Slabs Subjected to Contact and Close-In Explosion

2020 ◽  
Vol 309 ◽  
pp. 180-185
Author(s):  
Ondřej Janota ◽  
Marek Foglar
Keyword(s):  
Numerical Simulation ◽  
Reinforced Concrete ◽  
Numerical Model ◽  
High Performance ◽  
Numerical Evaluation ◽  
Numerical Models ◽  
Blast Resistance ◽  
Near Field ◽  
Fibre Reinforced Concrete ◽  
High Performance Fibre

This paper presents achievements in the field of the numerical simulation of the fibrere reinforced concrete (FRC) and ultra-high performance fibre reinforced concrete (UHPFRC). The numerical simulations were performed to verify results of two experimental programmes focused on the blast resistance of FRC and UHPFRC. The response of the FRC and UHPFRC slabs to the contact and near-field blast was studied in these two experiments. As the detail behaviour of specimens could not be observed because of the blast load, the numerical models were prepared. The accuracy of the numerical models was evaluated based on the comparison of numerical and experimental results. Different approaches for blast simulation were tested and compared. The results indicate that the various phenomena (e.g. overpressure propagation, stress cumulation, crack propagation and damage extend) can be successfully simulated. However, the comparison of the soffit velocity, measured with the PDV unit and numerical model showed shortcomings of the numerical model. These numerical model inaccuracies are discussed and their reasons presented.

scholarly journals Common irregularities and its effects on reinforced concrete building response

2021 ◽  
Vol 17 (1) ◽  
pp. 63-73
Author(s):  
Krishna Ghimire ◽  
Hemchandra Chaulagain
Keyword(s):  
Reinforced Concrete ◽  
Seismic Vulnerability ◽  
Numerical Models ◽  
Time History ◽  
Functional Requirements ◽  
Finite Element Program ◽  
Reinforced Concrete Building ◽  
Concrete Building ◽  
Element Program ◽  
Dynamic Time

In most of the countries, the irregular building construction is popular for fulfilling both aesthetic and functional requirements. However, the evidence of past earthquakes in Nepal and the globe demonstrated the higher level of seismic vulnerability of the buildings due to irregularities. Considering this fact, the present study highlighted the common irregularities and its effect on reinforced concrete building response. The effect of structural irregularities was studied through numerical analysis. The geometrical, mass and stiffness irregularities were created by removing bays in different floor levels and removing the columns at different sections respectively. In this study, the numerical models were created in finite element program SAP2000. The structural performance was studied using both non-linear static pushover and dynamic time history analysis. The results indicate that the level of irregularities significantly influenced the behavior of structures.

scholarly journals DIC in Validation of Boundary Conditions of Numerical Model of Reinforced Concrete Beams Under Torsion

2018 ◽  
Vol 64 (4) ◽  
pp. 31-48 ◽  
Author(s):  
B. Turoń ◽  
D. Ziaja ◽  
L. Buda-Ożóg ◽  
B. Miller
Keyword(s):  
Reinforced Concrete ◽  
Numerical Model ◽  
Boundary Conditions ◽  
Numerical Simulations ◽  
Experimental Research ◽  
Concrete Beams ◽  
Numerical Models ◽  
Experimental Tests ◽  
Reinforced Concrete Beams ◽  
Image Correlation

AbstractThe paper presents the experimental research and numerical simulations of reinforced concrete beams under torsional load. In the experimental tests Digital Image Correlation System (DIC System) Q-450 were used. DIC is a non-contact full-field image analysis method, based on grey value digital images that can determine displacements and strains of an object under load. Numerical simulations of the investigated beams were performed by using the ATENA 3D – Studio program. Creation of numerical models of reinforced concrete elements under torsion was complicated due to difficulties in modelling of real boundary conditions of these elements. The experimental research using DIC can be extremely useful in creating correct numerical models of investigated elements. High accuracy and a wide spectrum of results obtained from experimental tests allow for the modification of the boundary conditions assumed in the numerical model, so that these conditions correspond to the real fixing of the element during the tests.

scholarly journals An Accurate Numerical Model Simulating Hysteretic Behavior of Reinforced Concrete Columns Irrespective of Types of Loading Protocols

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Chang Seok Lee ◽  
Sang Whan Han
Keyword(s):  
Reinforced Concrete ◽  
Numerical Model ◽  
Seismic Vulnerability ◽  
Numerical Models ◽  
Concrete Columns ◽  
Hysteretic Behavior ◽  
Rc Buildings ◽  
Backbone Curve ◽  
Proposed Model ◽  
Backbone Curves

AbstractIn older reinforced concrete (RC) buildings, columns are fragile elements that can induce collapse of entire buildings during earthquakes. An accurate assessment of the seismic vulnerability of RC buildings using nonlinear response history analyses requires an accurate numerical model. The peak-oriented hysteretic rule is often used in existing numerical models to simulate the hysteretic behavior of RC members, with predefined backbone curves and cyclic deterioration. A monotonic backbone curve is commonly constructed from a cyclic envelope. Because cyclic envelope varies according to loading protocols, particularly in a softening branch, it is difficult to obtain a unique backbone curve irrespective of loading protocols. In addition, cyclic deterioration parameters irrespective of loading protocols cannot be found because these parameters are estimated with respect to the backbone curves. Modeling parameters of existing numerical models can also vary with respect to loading protocol. The objective of this study is to propose a loading protocol-independent numerical model that does not require estimates of modeling parameters specifically tuned for a certain loading protocol. The accuracy of the proposed model is verified by comparing the simulated and measured cyclic curves of different sets of identical RC column specimens under various loading protocols.

scholarly journals Numerical-computational analysis of reinforced concrete structures considering the damage, fracture and failure criterion

2013 ◽  
Vol 6 (1) ◽  
pp. 101-120 ◽  
Author(s):  
L. A. F. de Souza ◽  
R. D. Machado
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Numerical Models ◽  
Classical Model ◽  
Concrete Structures ◽  
Constitutive Models ◽  
Reinforced Concrete Structures ◽  
Element Discretization ◽  
Structural Parts ◽  
Elastoplastic Constitutive Model

The experimental results of testing structures or structural parts are limited and, sometimes, difficult to interpret. Thus, the development of mathematical-numerical models is needed to complement the experimental analysis and allow the generalization of results for different structures and types of loading. This article makes two computational studies of reinforced concrete structures problems found in the literature, using the Finite Element Method. In these analyses, the concrete is simulated with the damage classical model proposed by Mazars and the steel by a bilinear elastoplastic constitutive model. Numerical results show the validity of the application of constitutive models which consider the coupling of theories with the technique of finite element discretization in the simulation of linear and two-dimensional reinforced concrete structures.

The mathematical modelling of corrosion in hot dip galvanized steel reinforced concrete

2011 ◽  
Vol 2 (1) ◽  
pp. 1-12
Author(s):  
A. Hegyi ◽  
H. Vermeşan ◽  
V. Rus
Keyword(s):  
Mathematical Model ◽  
Reinforced Concrete ◽  
Numerical Model ◽  
Equation System ◽  
Galvanized Steel ◽  
Steel Reinforced Concrete ◽  
Numeric Model ◽  
Physical And Mathematical Models ◽  
Physical Phenomena ◽  
The Mathematical Model

Abstract In this paper we wish to present the numerical model elaborated in order to simulate some physical phenomena that influence the general deterioration of steel, whether hot dip galvanized or not, in reinforced concrete. We describe the physical and mathematical models, establishing the corresponding equation system, the initial and boundary conditions. We have also presented the numeric model associated to the mathematical model and the numeric methods of discretization and solution of the differential equations system that describes the mathematical model.

scholarly journals Preliminary Results on the Dynamics of a Pile-Moored Fish Cage with Elastic Net in Currents and Waves

2020 ◽  
Vol 9 (1) ◽  
pp. 14
Author(s):  
Gianluca Zitti ◽  
Nico Novelli ◽  
Maurizio Brocchini
Keyword(s):  
Numerical Model ◽  
Laboratory Experiments ◽  
Numerical Models ◽  
Offshore Structures ◽  
Fish Farm ◽  
Maximum Displacement ◽  
Drag Forces ◽  
Real Size ◽  
Lift And Drag ◽  
Mesh Grid

Over the last decades, the aquaculture sector increased significantly and constantly, moving fish-farm plants further from the coast, and exposing them to increasingly high forces due to currents and waves. The performances of cages in currents and waves have been widely studied in literature, by means of laboratory experiments and numerical models, but virtually all the research is focused on the global performances of the system, i.e., on the maximum displacement, the volume reduction or the mooring tension. In this work we propose a numerical model, derived from the net-truss model of Kristiansen and Faltinsen (2012), to study the dynamics of fish farm cages in current and waves. In this model the net is modeled with straight trusses connecting nodes, where the mass of the net is concentrated at the nodes. The deformation of the net is evaluated solving the equation of motion of the nodes, subjected to gravity, buoyancy, lift, and drag forces. With respect to the original model, the elasticity of the net is included. In this work the real size of the net is used for the computation mesh grid, this allowing the numerical model to reproduce the exact dynamics of the cage. The numerical model is used to simulate a cage with fixed rings, based on the concept of mooring the cage to the foundation of no longer functioning offshore structures. The deformations of the system subjected to currents and waves are studied.

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