scholarly journals QUANTIFYING THE EFFECTS OF EPOXY REPAIR OF REINFORCED CONCRETE PLASTIC HINGES

2020 ◽  
Vol 53 (1) ◽  
pp. 37-51
Author(s):  
Kai J. Marder ◽  
Kenneth J Elwood ◽  
Christopher J. Motter ◽  
G. Charles Clifton
Keyword(s):  
Reinforced Concrete ◽  
Large Scale ◽  
Plastic Hinge ◽  
Deformation Capacity ◽  
Structural Behaviour ◽  
Plastic Hinges ◽  
Strong Earthquakes ◽  
Beam Elements ◽  
Cover Concrete ◽  
Residual Deformations

Modern reinforced concrete structures are typically designed to form plastic hinges during strong earthquakes. In post-earthquake situations, repair of moderate plastic hinging damage can be undertaken by filling the crack system with epoxy resin and reconstituting spalled cover concrete. This study uses available experimental test data, including three large-scale ductile beams tested by the authors, to investigate the effects of epoxy repair on the structural behaviour of plastic hinges, with a focus on beam elements. Factors that have been neglected in past studies, including the effects of residual deformations at the time of repair, are given special attention. It is found that epoxy-repaired plastic hinges can exhibit different behaviour from identical undamaged components in terms of stiffness, strength, deformation capacity, and axial elongation. Potential explanations for the observed differences in behaviour are given, and recommendations are made for how these differences can be quantified in order to relate the expected response of an epoxy-repaired plastic hinge to the response that would be calculated for an identical undamaged component.

The Plastic Hinge

2015 ◽  
pp. 172-230
Keyword(s):  
Reinforced Concrete ◽  
Structural Analysis ◽  
Plastic Hinge ◽  
Steel Frames ◽  
Concrete Structures ◽  
Reinforced Concrete Structures ◽  
Plastic Hinges

The plastic hinge is a key concept of the theory of frames that differentiates this theory from the remaining models for structural analysis. This chapter is exclusively dedicated to define this concept and describe the different models of plastic hinges. It also discusses the differences of implementation between plastic hinges in steel frames (Sections 6.1-6.4) and those in reinforced concrete structures (Sections 6.5-6.6). This chapter is based on the ideas presented in Chapter 5 and it allows formulating the models for elasto-plastic frames that are introduced in the next chapter.

DYNAMIC ANALYSIS OF BRIDGES WITH PLASTIC HINGES UNDER EXTREME EARTHQUAKES

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
T. Y. Lee ◽  
K. J. Chung
Keyword(s):  
Plastic Hinge ◽  
Concrete Columns ◽  
Computational Method ◽  
Past Study ◽  
Plastic Hinges ◽  
Concrete Core ◽  
Cover Concrete ◽  
Deformable Bodies ◽  
Fiber Element ◽  
Isolated Bridge

This study is aimed to develop the model of fiber element in the Vector Form Intrinsic Finite Element (VFIFE) to analyze the plastic hinges of reinforced-concrete columns for bridges subjected to extreme earthquakes. The VFIFE, a new computational method, is adopted in this study because of the superior in managing the engineering problems with material nonlinearity, discontinuity, large deformation and arbitrary rigid body motions of deformable bodies. In the past study, a plastic hinge is idealized as a bilinear elastoplastic model with a fracture moment. In order to analyze the realistic behavior of the plastic hinge, especially in ultimate state, the fiber element is developed to simulate the plastic hinge by using stress-strain relations in cover concrete, core concrete and steel fibers. The developed fiber element is verified to be feasible and accurate through numerical simulation. A three-span-continuous isolated bridge is analyzed to investigate the function of the columns and unseating prevention devices and to predict the collapse situation of the whole bridge. In addition, the analysis results are compared between the fiber element and bilinear elastoplastic element.

scholarly journals Elongation and load deflection characteristics of reinforced concrete members containing plastic hinges

1993 ◽  
Vol 26 (1) ◽  
pp. 28-41 ◽  
Author(s):  
R. C. Fenwick ◽  
L. M. Megget
Keyword(s):  
Reinforced Concrete ◽  
Plastic Hinge ◽  
Major Influence ◽  
Test Results ◽  
Design Practice ◽  
Plastic Hinges ◽  
Concrete Members ◽  
Different Types ◽  
Current Design ◽  
Hinge Zone

In regions, described as plastic hinge zones, in beams and columns, tensile yielding of the reinforcement through flexural action can occur in severe earthquakes. Where the beams and columns are lightly loaded, axially, member elongation can occur. Test results show that axial extensions of the order of several percent of the member depth may be expected. This deformation, which is ignored in current design practice, can have a major influence on the distribution of forces in a structure and its ability to survive without collapse. This paper describes the way in which elongation develops in plastic hinge zones together with the form of load deflection characteristics associated with the development of different types of plastic hinge zone.

scholarly journals Evaluation of elastic stiffness factor of 2D reinforced concrete frame system with different parameters

2021 ◽  
Vol 2 (2) ◽  
pp. 26-31
Author(s):  
Omar Ahmad
Keyword(s):  
Reinforced Concrete ◽  
Lateral Displacement ◽  
Plastic Hinge ◽  
Pushover Analysis ◽  
Shear Walls ◽  
Elastic Stiffness ◽  
Span Length ◽  
Base Shear ◽  
Reinforced Concrete Frame ◽  
Plastic Hinges

In general, the buildings are designed based on the applied loads on them, and these buildings generally have elastic structural behaviour. However, these structures may be subjected to unexpectedly strong seismic forces that exceed their elastic limits. In order to find the rigidity and load-bearing trend of the building without the formation of plastic hinges and failure, pushover analysis should be performed. Pushover analysis is a non-linear static analysis in which the structure is subjected to lateral loads, so some parameters are recorded, such as failure, formation of plastic hinges, and yield. The elastic stiffness factor is the ability of a building to bear the loads on it before the failure and existent of the plastic hinges. In this study, pushover analysis had been done on 12 two-dimensional reinforced concrete frames with a different number of stories, different span lengths and with or without shear walls to find the effect of the span length, shear wall and the number of stories on the elastic stiffness factor. After performing the pushover analysis, the elastic stiffness factor had been evaluated from the pushover curve by dividing the base shear over the lateral displacement at the first point of the occurrence of the plastic hinge. The results obtained from the study showed that the elastic stiffness factor increases with the increase of the span length, while it decreases with the increase of the number of stories. As well, the frames with shear walls are stiffer than the frames without shear walls.

Preliminary observations from biaxial testing of a two-storey, two-by-one bay, reinforced concrete slotted beam superassembly

2012 ◽  
Vol 45 (3) ◽  
pp. 97-104 ◽  
Author(s):  
C.A. Muir ◽  
D.K. Bull ◽  
S. Pampanin
Keyword(s):  
Reinforced Concrete ◽  
Large Scale ◽  
Plastic Hinge ◽  
Historical Earthquakes ◽  
Structural Performance ◽  
Moment Frames ◽  
Biaxial Testing ◽  
Subtle Change ◽  
Static Testing ◽  
Area Of Concern

Displacement incompatibility between reinforced concrete moment frames and precast flooring systems has been shown experimentally, and in historical earthquakes, to be an area of concern. Plastic hinge formation necessitates beam damage and the resulting elongation of the beam reduces the seating length of the floor, exacerbates the floor damage and induces unanticipated force distributions in the system. In severe cases this can lead to collapse. The slotted beam is a detail that protects the integrity of the floor diaphragm, respects the hierarchy of strengths intended by the designer and sustains less damage. The detail provides the same ductility and moment resistance as traditional details, whilst exhibiting improved structural performance. This is achieved with only a subtle change in the detailing and no increase in build cost. This paper briefly presents the development of the slotted beam in reinforced concrete. The design and construction of a large scale reinforced concrete slotted beam superassembly is described. The experimental method used to undertake biaxial quasi-static testing is introduced. Preliminary observations from the experiment are presented. It is shown that the reinforced concrete slotted beam is a viable replacement for the traditional monolithic detail. Extremely promising structural performance and significantly reduced damage compared to monolithic reinforced concrete details is presented.

Testing of 17 Identical Ductile Reinforced Concrete Beams with Various Loading Protocols and Boundary Conditions

2018 ◽  
Vol 34 (3) ◽  
pp. 1025-1049 ◽  
Author(s):  
Kai Marder ◽  
Christopher Motter ◽  
Kenneth J. Elwood ◽  
G. Charles Clifton
Keyword(s):  
Reinforced Concrete ◽  
Large Scale ◽  
Loading Rate ◽  
Plastic Hinge ◽  
Reinforced Concrete Beams ◽  
Test Program ◽  
Residual Capacity ◽  
Cyclic Degradation ◽  
Axial Interaction ◽  
Repair Techniques

A set of tests on 17 large-scale, nominally identical, beam specimens with variations in loading protocol, loading rate, and restraint to axial elongation are described. Three specimens were also repaired by epoxy injection following an initial damaging earthquake loading. This paper provides a detailed description of the test program, and the corresponding data are made available at Design-Safe (DOI: 10.17603/DS2SQ2K). While the primary goal of the test program was to improve the state of knowledge regarding the post-earthquake residual capacity of reinforced concrete plastic hinges in beams, the data are useful for modeling approaches that consider loading rate, plastic hinge elongation, cyclic degradation, and flexure–shear–axial interaction, in addition to investigating the effectiveness of post-earthquake repair techniques by epoxy injection of cracks.

Post-earthquake assessment of moderately damaged reinforced concrete plastic hinges

2020 ◽  
Vol 36 (1) ◽  
pp. 299-321
Author(s):  
Kai Marder ◽  
Kenneth J. Elwood ◽  
Christopher J. Motter ◽  
G. Charles Clifton
Keyword(s):  
Reinforced Concrete ◽  
Reinforced Concrete Beams ◽  
Experimental Program ◽  
Plastic Hinges ◽  
Strong Earthquakes ◽  
Proposed Model ◽  
Residual Capacity ◽  
The Relationship ◽  
Crack Widths ◽  
Earthquake Assessment

Modern reinforced concrete buildings are often designed to dissipate energy during strong earthquakes by permitting the controlled formation of plastic hinges. Plastic hinges require assessment of residual capacity in post-earthquake situations. However, few past studies have investigated this topic, and results from experiments focused on undamaged structures are not always transferable to post-earthquake situations. Data from an experimental program, in which both cyclic and earthquake-type loadings were applied to nominally identical reinforced concrete beams, are used to investigate the relationship between residual crack widths and rotation demands. Assessment of the peak deformation demands incurred during a damaging earthquake is critical for post-earthquake assessments, but residual crack widths are shown to be dependent on several factors in addition to the peak rotation demand. Non-dimensional metrics capturing the distribution of cracking are proposed as a more informative alternative. The reduction in stiffness that occurs as a result of earthquake-induced plastic hinging damage was also investigated. A proposed model is shown to give a lower-bound estimate of the residual stiffness following arbitrary earthquake-type loadings.

scholarly journals Numerical Modelling of Reinforced Concrete Slender Walls Subjected to Coupled Axial Tension–Flexure

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Xiaowei Cheng ◽  
Haoyou Zhang
Keyword(s):  
Reinforced Concrete ◽  
Plastic Hinge ◽  
Element Model ◽  
Lateral Loading ◽  
Design Parameters ◽  
Seismic Behaviour ◽  
High Rise ◽  
Ultimate Deformation ◽  
Axial Tension ◽  
Plastic Hinge Length

AbstractUnder strong earthquakes, reinforced concrete (RC) walls in high-rise buildings, particularly in wall piers that form part of a coupled or core wall system, may experience coupled axial tension–flexure loading. In this study, a detailed finite element model was developed in VecTor2 to provide an effective tool for the further investigation of the seismic behaviour of RC walls subjected to axial tension and cyclic lateral loading. The model was verified using experimental data from recent RC wall tests under axial tension and cyclic lateral loading, and results showed that the model can accurately capture the overall response of RC walls. Additional analyses were conducted using the developed model to investigate the effect of key design parameters on the peak strength, ultimate deformation capacity and plastic hinge length of RC walls under axial tension and cyclic lateral loading. On the basis of the analysis results, useful information were provided when designing or assessing the seismic behaviour of RC slender walls under coupled axial tension–flexure loading.

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