scholarly journals Experimental Study and Numerical Simulation of Seismic Behavior for RC Columns Subjected to Freeze-Thaw Cycles

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Qing Qin ◽  
Shansuo Zheng ◽  
Lei Li ◽  
Liguo Dong ◽  
Yixin Zhang ◽  
...  
Keyword(s):  
Seismic Behavior ◽  
Constitutive Relations ◽  
Rc Buildings ◽  
Rc Columns ◽  
Premature Failure ◽  
Rc Structures ◽  
Freeze Thaw ◽  
Different Depths ◽  
Strength And Stiffness ◽  
Good Agreement

Freeze-thaw of concrete is significantly responsible for serious damage to RC buildings, which may result in premature failure with little warning. Therefore, it is necessary to consider the effects of freeze-thaw environment when assessing seismic performance for RC structures. In this study, pseudo-static experiments of four RC columns were conducted in terms of different number of freeze-thaw cycles (FTCs). The results showed that the FTCs had an influence on the bearing capacity, ductility, strength, and stiffness of RC columns. What is more, the simulation results were commonly smaller than the experimental ones when simply assuming that the degrees of freeze-thaw damage for RC components were uniform. Thus, a numerical model considering uneven distribution of freeze-thaw damage was proposed by utilizing the results of Petersen’s test for relative dynamic modulus of elasticity (RDME) for different depths of concrete sample and based on Berto’s method which was proved to be effective to convert the numbers of FTCs under different freeze-thaw conditions. On the basis of the existing constitutive relations for concrete, four RC columns subjected to different numbers of FTCs were simulated by OpenSees. As a result, the simulation hysteretic curves were in good agreement with the experimental ones.

Sensitivity Studies of the Resilience of RC Columns to Various Fire Scenarios

2019 ◽  
Author(s):  
Shuna Ni ◽  
Ruben Van Coile ◽  
Danny Hopkin ◽  
Negar Elhami Khorasani ◽  
Thomas Gernay
Keyword(s):  
Critical Parameters ◽  
Fire Performance ◽  
Rc Buildings ◽  
Fire Event ◽  
Rc Columns ◽  
Rc Structures ◽  
Frame Building ◽  
Fire Scenarios ◽  
Sensitivity Studies ◽  
Residual Deformations

<p>Reinforced concrete (RC) structures generally fare well under fire, but exhibit damage and residual deformations which require repairs. Besides the repair cost, the building downtime can also be expensive. However, current fire design approaches focus solely on life safety, and do not consider resilience. To improve post-fire performance of buildings, recover functionality, and facilitate fast reuse, an important step is to develop a predictive capability for the effect of a fire event on residual deformations and load-bearing capacity in structures. This research investigates the residual deformations in RC buildings after a fire, with a focus on the columns as one of the key structural members. The case study is a five-story RC frame building with a fire developing on the first story. Thermo-structural finite element analyses were used to analyze the columns performance under various fires. The sensitivity of the RC columns’ responses to main parameters related to fire characteristics, material properties and mechanical loading was analyzed. Based on the sensitivity studies, the most critical parameters were determined for the vulnerability of the RC columns to the different fire scenarios. These critical parameters will be used for the subsequent probabilistic damage evaluation of the RC columns and their design alternatives. The results will contribute to improved understanding of the effects of fire on the resilience of RC buildings and infrastructure, as well as the identification of designs which provide enhanced post-fire performance.</p>

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

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 506 ◽  
Author(s):  
Alexandre Mathern ◽  
Jincheng Yang
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Constitutive Relations ◽  
Fe Analysis ◽  
Rc Beams ◽  
Cracking Behavior ◽  
Concrete Cracking ◽  
Rc Structures ◽  
Nonlinear Fe Analysis ◽  
Modeling Strategy

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.

Influence of floor system on seismic behavior of RC buildings to forward directivity and fling-step in the near-fault region

Structures ◽  
2021 ◽  
Vol 30 ◽  
pp. 803-817
Author(s):  
Sayed Mahmoud ◽  
Ali Alqarni ◽  
Joseph Saliba ◽  
Amal H. Ibrahim ◽  
Magdy genidy ◽  
...  
Keyword(s):  
Seismic Behavior ◽  
Rc Buildings ◽  
Near Fault ◽  
Forward Directivity ◽  
Fling Step ◽  
Floor System ◽  
Fault Region

scholarly journals Modelling of Corrosion-Induced Concrete Cover Cracking Due to Chloride Attacking

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1440
Author(s):  
Pei-Yuan Lun ◽  
Xiao-Gang Zhang ◽  
Ce Jiang ◽  
Yi-Fei Ma ◽  
Lei Fu
Keyword(s):  
Service Life ◽  
Corrosion Current ◽  
Practical Experience ◽  
Concrete Cover ◽  
Premature Failure ◽  
Rc Structures ◽  
Structural Capacity ◽  
Cover Cracking ◽  
Deterioration Process ◽  
Cracking Process

The premature failure of reinforced concrete (RC) structures is significantly affected by chloride-induced corrosion of reinforcing steel. Although researchers have achieved many outstanding results in the structural capacity of RC structures in the past few decades, the topic of service life has gradually attracted researchers’ attention. In this work, based on the stress intensity, two models are developed to predict the threshold expansive pressure, corrosion rate and cover cracking time of the corrosion-induced cracking process for RC structures. Specifically, in the proposed models, both the influence of initial defects and modified corrosion current density are taken into account. The results given by these models are in a good agreement with practical experience and laboratory studies, and the influence of each parameter on cover cracking is analyzed. In addition, considering the uncertainty existing in the deterioration process of RC structures, a methodology based on the third-moment method in regard to the stochastic process is proposed, which is able to evaluate the cracking risk of RC structures quantitatively and predict their service life. This method provides a good means to solve relevant problems and can prolong the service life of concrete infrastructures subjected to corrosion by applying timely inspection and repairs.

Morphing Continuum Theory: Incorporating the Physics of Microstructures to Capture the Transition to Turbulence Within a Boundary Layer

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Louis B. Wonnell ◽  
James Chen
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Ad Hoc ◽  
Constitutive Relations ◽  
Turbulence Models ◽  
Continuum Theory ◽  
Transition To Turbulence ◽  
Flow Turbulence ◽  
Good Agreement ◽  
Inherent Advantage

A boundary layer with Re = 106 is simulated numerically on a flat plate using morphing continuum theory. This theory introduces new terms related to microproperties of the fluid. These terms are added to a finite-volume fluid solver with appropriate boundary conditions. The success of capturing the initial disturbances leading to turbulence is shown to be a byproduct of the physical and mathematical rigor underlying the balance laws and constitutive relations introduced by morphing continuum theory (MCT). Dimensionless equations are introduced to produce the parameters driving the formation of disturbances leading to turbulence. Numerical results for the flat plate are compared with the experimental results determined by the European Research Community on Flow, Turbulence, and Combustion (ERCOFTAC) database. Experimental data show good agreement inside the boundary layer and in the bulk flow. Success in predicting conditions necessary for turbulent and transitional (T2) flows without ad hoc closure models demonstrates the theory's inherent advantage over traditional turbulence models.

scholarly journals Investigations on Efficiently Interfaced Steel Concrete Composite Deck Slabs

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
K. N. Lakshmikandhan ◽  
P. Sivakumar ◽  
R. Ravichandran ◽  
S. Arul Jayachandran
Keyword(s):  
Longitudinal Shear ◽  
Advanced Technology ◽  
Shear Connector ◽  
Premature Failure ◽  
Shear Connectors ◽  
Reinforced Concrete Slabs ◽  
Composite Slabs ◽  
Strength And Stiffness ◽  
The Cost ◽  
Deck Slab

The strength of the composite deck slab depends mainly on the longitudinal shear transfer mechanism at the interface between steel and concrete. The bond strength developed by the cement paste is weak and causes premature failure of composite deck slab. This deficiency is effectively overcame by a shear transferring mechanism in the form of mechanical interlock through indentations, embossments, or fastening studs. Development of embossment patterns requires an advanced technology which makes the deck profile expensive. Fastening studs by welding weakens the joint strength and also escalates the cost. The present investigation is attempted to arrive at a better, simple interface mechanism. Three types of mechanical connector schemes are identified and investigated experimentally. All of the three shear connector schemes exhibited full shear interaction with negligible slip. The strength and stiffness of the composite slabs with shear connectors are superior about one and half time compared to these of the conventional reinforced concrete slabs and about twice compared to these of composite slabs without mechanical shear connectors. The scheme2 and scheme3 shear connector mechanisms integrate deck webs and improve strength and stiffness of the deck, which can effectively reduce the cost of formworks and supports efficiently.

scholarly journals Practical method to predict the axial capacity of RC columns exposed to standard fire

2018 ◽  
Vol 9 (4) ◽  
pp. 266-286 ◽  
Author(s):  
Salah F. El-Fitiany ◽  
Maged A. Youssef
Keyword(s):  
Concrete Strength ◽  
Practical Method ◽  
Simple Method ◽  
Rc Columns ◽  
Content Type ◽  
Natural Fire ◽  
Rc Structures ◽  
Axial Capacity ◽  
Standard Fire ◽  
Structural Engineers

Purpose Existing analytical methods for the evaluation of fire safety of reinforced concrete (RC) structures require extensive knowledge of heat transfer calculations and the finite element method. This paper aims to propose a rational method to predict the axial capacity of RC columns exposed to standard fire. Design/methodology/approach The average temperature distribution along the section height is first predicted for a specific fire scenario. The corresponding distribution of the reduced concrete strength is then integrated to develop expressions to calculate the axial capacity of RC columns exposed to fire from four faces. Findings These expressions provide structural engineers with a rational tool to satisfy the objective-based design clauses specified in the National Code of Canada in lieu of the traditional prescriptive methods. Research limitations/implications The research is limited to standard fire curves and needs to be extended to cover natural fire curves. Originality/value This paper is the first to propose an accurate yet simple method to calculate the axial capacity of columns exposed to standard fire curves. The method can be applied using a simple Excel sheet. It can be further developed to apply to natural fire curves.

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