scholarly journals Numerical Study on the Behavior and Bearing Mechanism of Flat Slabs in Column Loss Events

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Aidin Mohammadi ◽  
Alireza Pachenari ◽  
Behnam Sadeghi
Keyword(s):  
Numerical Study ◽  
Progressive Collapse ◽  
Great Tendency ◽  
Load Bearing ◽  
Collapse Potential ◽  
Flat Slabs ◽  
Collapse Mode ◽  
Damaged Zone ◽  
Initial Load ◽  
Cracking Pattern

This study investigates the behavior and the load-bearing mechanism of a typical flat slab with rectangular panels in several scenarios including the removal of a corner, penultimate, and internal columns. The scenarios are rather similar to those used in the conventional evaluation of the progressive collapse potential; however, application of the uniformly distributed loading over panels adjacent to the removed columns was not limited to twice the value of the initial load. Thus, load-deflection curves were drawn up to the point in which a great number of longitudinal slab bars ruptured. Introducing 5 stages on each curve, finite element outputs on concrete cracking pattern and rebar stress state were presented. A significant increase in the stresses along the diagonals of the slab panels accompanied by bar ruptures around columns adjacent to the removed column proved contribution of an important load-bearing mechanism in addition to the behavior called “quasiframe action.” Consecutive rupture of bars showed formation of a zipper-type collapse mode as well as a great tendency to transfer load share of missing column mainly along shorter direction of slab panels. Moreover, the findings indicated that the slab damaged zone could exceed the panels under uniform overloading.

scholarly journals Detection of Material Degradation of a Composite Cylinder Using Mode Shapes and Convolutional Neural Networks

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6686
Author(s):  
Bartosz Miller ◽  
Leonard Ziemiański
Keyword(s):  
Neural Networks ◽  
Convolutional Neural Networks ◽  
Composite Structures ◽  
Vibration Mode ◽  
Numerical Study ◽  
Mode Shapes ◽  
Zone Size ◽  
Composite Cylinder ◽  
Material Degradation ◽  
Damaged Zone

This paper presents a numerical study of the feasibility of using vibration mode shapes to identify material degradation in composite structures. The considered structure is a multilayer composite cylinder, while the material degradation zone is, for simplicity, considered a square section of the lateral surface of the cylinder. The material degradation zone size and location along the cylinder axis are identified using a deep learning approach (convolutional neural networks, CNNs, are applied) on the basis of previously identified vibration mode shapes. The different numbers and combinations of identified mode shapes used to assess the damaged zone size and location were analyzed in detail. The final selection of mode shapes considered in the identification procedure yielded high accuracy in the identification of the degradation zone.

Experimental Evaluation of the Ultimate Bending Moment of a Slender Thin-Walled Box Girder

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
José Manuel Gordo ◽  
C. Guedes Soares
Keyword(s):  
Residual Stresses ◽  
Progressive Collapse ◽  
Bending Moment ◽  
Bending Test ◽  
Postbuckling Behavior ◽  
Box Girder ◽  
Collapse Mode ◽  
Collapse Analysis ◽  
The Moment ◽  
Progressive Collapse Analysis

The results of a four points bending test on a box girder are presented. The experiment is part of series of tests with similar configuration but with different thickness and span between frames. The present work refers to the slenderest plate box girder with a plate's thickness of 2 mm but with a short span between frames. The experiment includes initial loading cycles allowing for partial relief of residual stresses. The moment curvature relationship is established for a large range of curvature. The ultimate bending moment (UM) of the box is evaluated and compared with the first yield moment and the plastic moment allowing the evaluation of the efficiency of the structure. The postbuckling behavior and collapse mode are characterized. Comparison of the experiment with a progressive collapse analysis method is made taking into consideration the effect of residual stresses on envelop of the moment curvature curve of the structure.

scholarly journals Response and Energy Absorption of Concrete Honeycombs Subjected to Dynamic In-Plane Compression: A Numerical Approach

Symmetry ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 175
Author(s):  
Wenjing Shen ◽  
Hongyuan Zhou ◽  
Xuejian Zhang ◽  
Xiaojuan Wang
Keyword(s):  
Energy Absorption ◽  
Progressive Collapse ◽  
Numerical Approach ◽  
Absorption Capacity ◽  
Foam Concrete ◽  
Stress Plateau ◽  
Collapse Mode ◽  
Particle Hydrodynamics ◽  
Plane Compression ◽  
Response Modes

Foam concrete exhibits long stress plateau with increasing strain subjected to compression and absorbs a considerable amount of energy, making them promising for building and structure protection. In the present study, hexagonal concrete honeycombs are employed to approximately represent foam concrete, whose response and energy absorption subjected to dynamic in-plane compression are investigated with smooth particle hydrodynamics method. The response modes under low to high velocity crushing are numerically investigated, with which the critical velocity separating quasi-static response and progressive collapse mode is determined. Furthermore, the dynamic energy absorption capacity is examined and discussed.

Assessment of progressive collapse potential of special moment resisting RC frames – Experimental and FE study

2019 ◽  
Vol 105 ◽  
pp. 896-918 ◽  
Author(s):  
Hussein M. Elsanadedy ◽  
Yousef A. Al-Salloum ◽  
Tarek H. Almusallam ◽  
Tuan Ngo ◽  
Husain Abbas
Keyword(s):  
Progressive Collapse ◽  
Collapse Potential ◽  
Rc Frames ◽  
Moment Resisting

scholarly journals Experimental and Numerical Study on Hydromechanical Coupled Deformation Behavior of Beishan Granite considering Permeability Evolution

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Z. H. Wang ◽  
W. G. Ren ◽  
Y. L. Tan ◽  
Heinz Konietzky
Keyword(s):  
Pressure Difference ◽  
Numerical Study ◽  
Volumetric Strain ◽  
Initial Pressure ◽  
Numerical Code ◽  
Permeability Evolution ◽  
Beishan Granite ◽  
Pore Pressures ◽  
Damaged Zone ◽  
Hlw Repository

Beishan granite is a potential host rock for a high-level radioactive waste (HLW) repository in China. Understanding the hydromechanical (HM) behavior and permeability evolution of Beishan granite is important for the HLW repository safety. Therefore, the granite of Beishan in Gansu province was studied. HM coupled tests are carried out on Beishan granite under different pore pressures. The results show that the initial pressure difference has little influence on permeability measurement before dilatancy starts. However, after onset of dilatancy, the permeability increases with the increasing initial pressure difference. The initial permeability of Beishan granite is about 10−18 m2 under a confining pressure of 20 MPa. In the initial loading phase, the permeability shows a relatively large reduction. Then, the permeability almost keeps constant until dilatancy starts. From dilatancy point to peak stress, permeability increases linearly with volumetric strain. The proposed permeability evolution rule is implemented into a numerical code to perform HM coupled simulations. The simulation results show that the damaged zone first appears at the model boundary and then extends to the inside, forming high volumetric strain areas. And it provides seepage channels for fluid flow. The macroscopic fracture patterns indicate that pore pressure accelerates rock degradation during HM coupling. The obtained results help to understand the damage mechanisms of granite caused by pore pressures and are of great importance for the safety of a HLW repository.

scholarly journals Numerical and Experimental Study on Deficient Short Steel Tubes Strengthened with CFRP Under Compression

2019 ◽  
Author(s):  
Mohammad Reza Ghaemdoust ◽  
Omid Yousefi ◽  
Kambiz Narmashiri ◽  
Masoumeh Karimian
Keyword(s):  
Bearing Capacity ◽  
Numerical Study ◽  
Three Dimensional ◽  
Local Buckling ◽  
Steel Tubes ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Steel Columns ◽  
Repair Costs ◽  
The Impact

In view of development and repair costs, support of structures is imperative. Several factors, for example, design and calculation errors, absence of appropriate installation, change of structures application, exhaustion, seismic tremor, fire and natural conditions diminish their strength. In such cases, structures have need of rehabilitation and restoration to achieve their original performance. One of the most up to date materials for retrofitting is carbon fiber reinforced polymer (CFRP) that can provide an amount of restriction to postpone buckling of thin steel walls. This paper provides a numerical and experimental investigation on CFRP strengthened short steel tubes with initial horizontal and vertical deficiency under compression. Ten square and circular specimens were tested to study effects of the following parameters: (1) position of deficiency, horizontal or vertical; (2) tube shape, square or circular; (3) CFRP strengthening. In the experiments, axial static loading was gradually applied and for the numerical study three-dimensional (3D) static nonlinear analysis method using ABAQUS software was performed. The results show that deficiency reduces load-bearing capacity of steel columns and the impact of horizontal deficiency is higher than the impact of vertical deficiency, in both square and circular tubes. Use of CFRP materials for strengthening of short steel columns with initial deficiency indicates that fibers play a considerable role on increasing load bearing capacity, reducing stress at the damage location, preventing deformation caused by deficiency and delaying local buckling. Both numerical and experimental outcomes are in good agreement, which underlines the accuracy of the models adopted.

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