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.

Simulation of Reinforced Concrete Frames with Nonductile Beam-Column Joints

2013 ◽  
Vol 29 (1) ◽  
pp. 233-257 ◽  
Author(s):  
Sangjoon Park ◽  
Khalid M. Mosalam
Keyword(s):  
Reinforced Concrete ◽  
Rc Buildings ◽  
Concrete Frames ◽  
Backbone Curve ◽  
Building Frames ◽  
Column Joint ◽  
Backbone Curves ◽  
The Moment ◽  
Nonlinear Dynamic Analyses ◽  
Relationship Of

The accurate prediction of shear strength and flexibility of beam-column joints without transverse reinforcement is essential to assess the seismic performance of nonductile reinforced concrete (RC) buildings characterized by having such unreinforced beam-column joints. In this study, a multilinear backbone curve to represent the moment-rotation relationship of an unreinforced corner beam-column joint is proposed. The modeling parameters of the backbone curve are estimated based on experimental results of four corner joint specimens recently tested by the authors. Furthermore, the proposed backbone curve is modified to be applicable to interior and roof beam-column joints. These backbone curves are validated by accurate reproduction of the force-drift responses of the four corner joint specimens and eight other exterior and interior joint specimens from literature. Using these backbone curves, nonlinear dynamic analyses are performed on three hypothetical building frames. The analytical results demonstrate the importance of joint flexibility for seismic assessment of nonductile RC buildings.

Experimental Study on the Effect of Moisture Content on Hysteretic Behavior of Reinforced Concrete Columns

2018 ◽  
Vol 12 (1) ◽  
pp. 47-61
Author(s):  
Wenjuan Lv ◽  
Baodong Liu ◽  
Ming Li ◽  
Lin Li ◽  
Pengyuan Zhang
Keyword(s):  
Reinforced Concrete ◽  
Energy Dissipation ◽  
Moisture Content ◽  
Early Stage ◽  
Damping Ratio ◽  
Concrete Columns ◽  
Hysteretic Behavior ◽  
Cyclic Test ◽  
Experimental Result ◽  
Reinforced Concrete Columns

Background: For reinforced concrete structures under different humid conditions, the mechanical properties of concrete are significantly affected by the moisture content, which may result in a great change of the functional performance and bearing capacity. Objective: This paper presents an experiment to investigate the influence of the moisture content on the dynamic characteristics and hysteretic behavior of reinforced concrete column. Results: The results show that the natural frequency of reinforced concrete columns increases quickly at an early stage of immersion, but there is little change when the columns are close to saturation; the difference between the natural frequencies before and after cyclic test grows as the moisture content rises. The damping ratio slightly decreases first and then increases with the increase of moisture content; the damping ratio after the cyclic test is larger than before the test due to the development of the micro-cracks. Conclusion: The trend of energy dissipation is on the rise with increasing moisture content, although at an early stage, it decreases slightly. According to the experimental result, a formula for the moisture content on the average energy dissipation of reinforced concrete columns is proposed.

Measures of the Seismic Vulnerability of Reinforced Concrete Buildings in Haiti

2011 ◽  
Vol 27 (1_suppl1) ◽  
pp. 373-386 ◽  
Author(s):  
Patrick O'Brien ◽  
Marc Eberhard ◽  
Olafur Haraldsson ◽  
Ayhan Irfanoglu ◽  
David Lattanzi ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Seismic Vulnerability ◽  
The United States ◽  
Faculty Members ◽  
Rc Buildings ◽  
Screening Process ◽  
Cross Sectional ◽  
Screening Criteria ◽  
Survey Results ◽  
Similar Survey

Following the 12 January 2010 Haiti earthquake, teams of students and faculty members from the United States and Haiti surveyed 170 reinforced concrete (RC) buildings in Port-au-Prince and Léogâne. This paper summarizes the survey results and compares them with results from a similar survey done after the 1999 earthquakes near Düzce, Turkey. The survey results demonstrate that the frequency of damage in RC buildings was higher in Haiti than in Turkey. This increased level of damage is consistent with practical screening criteria based on cross-sectional areas of building columns and walls. Based on these criteria, 90% of the structures surveyed in Haiti would have been classified as seismically vulnerable before the earthquake. Damage was more frequent in structures with captive columns. A two-tiered screening process is suggested to rapidly assess the vulnerability of scores of poorly built low-rise RC buildings in future earthquakes.

scholarly journals Thermomechanical analysis of reinforced concrete columns exposed to fire

2020 ◽  
Vol 13 (4) ◽  
Author(s):  
Matheus Wanglon Ferreira ◽  
Luiz Carlos Pinto da Silva Filho ◽  
Mauro de Vasconcellos Real
Keyword(s):  
Experimental Data ◽  
Reinforced Concrete ◽  
Three Dimensional ◽  
Concrete Columns ◽  
Thermomechanical Analysis ◽  
Structural Behavior ◽  
Mechanical Resistance ◽  
Reinforced Concrete Columns ◽  
Proposed Model ◽  
Main Factors

ABSTRACT: A three-dimensional (3D) transient numerical model for thermomechanical analysis developed with Finite Element Method (FEM) using the software ANSYS 19.1 is exposed in this paper. The proposed model aims to predict the structural behavior of reinforced concrete columns in a fire situation since it is known that high temperatures significantly reduce their mechanical resistance. For this, the main factors that govern their structural behavior should be considered. Analyses obtained by the proposed model were validated with results from experimental data, evidencing a good correlation between numerical and experimental fields.

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.

Seismic Vulnerability Assessment of Low-Rise Reinforced Concrete Buildings Affected by the 2015 Gorkha, Nepal, Earthquake

2017 ◽  
Vol 33 (1_suppl) ◽  
pp. 275-298 ◽  
Author(s):  
Svetlana Brzev ◽  
Bishnu Pandey ◽  
Dev Kumar Maharjan ◽  
Carlos Ventura
Keyword(s):  
Reinforced Concrete ◽  
Seismic Vulnerability ◽  
Rc Buildings ◽  
Seismic Vulnerability Assessment ◽  
Wall Area ◽  
Rc Frames ◽  
Wall Structures ◽  
2015 Gorkha Earthquake ◽  
Observed Damage ◽  
Masonry Shear Wall

Low-rise reinforced concrete (RC) frames with brick masonry infill walls up to five stories high have been used for housing construction in Nepal since the late 1980s. Many buildings of this type were damaged and/or collapsed in the 25 April 2015 Gorkha earthquake (M 7.8), even in areas characterized with moderate shaking intensity such as Kathmandu Valley. Due to inadequate design and/or construction of RC frame components, these buildings essentially behave like masonry shear wall structures with a shear-dominant failure mechanism. The paper presents the findings of a field survey of 98 RC buildings affected by the 2015 earthquake. The main objective of the study was to correlate the observed damage in the buildings using the modified European macroseismic scale (EMS)-98 and the wall index (defined as the wall area in the direction of shaking divided by the total building plan area above the level of interest). The results can be used to help establish recommendations regarding the required wall index for low-rise RC buildings in Nepal.

Axial Compression Capacity of Shear-Damaged Reinforced Concrete Columns and Lashing Belt Prestressing

2016 ◽  
Vol 711 ◽  
pp. 1012-1018
Author(s):  
Kozo Nakada ◽  
Kochi Masaaki ◽  
Yu Yun Dong ◽  
Long Yu
Keyword(s):  
Reinforced Concrete ◽  
Axial Compression ◽  
Concrete Columns ◽  
Hysteretic Behavior ◽  
Load Carrying Capacity ◽  
Vertical Load ◽  
Shear Strengthening ◽  
Rc Columns ◽  
Load Carrying ◽  
Strength And Ductility

The compressive strength and ductility of concrete can be considerably improved by lateral confinement. In this study, an emergency seismic retrofit technique using lashing belt prestressing is used as to manually retrofit damaged reinforced concrete (RC) columns. The initial prestressing is an important aspect of this technique and is introduced by the ratchet buckle. Thus, this technique offers active and passive confinement as well as shear strengthening. Furthermore, diagonal cracks in the damaged RC columns can be closed by using the active confinement of lashing belts, and the lateral and vertical load-carrying capacity and ductility of the damaged RC columns are recovered. In this study, the recovered axial compression capacity of the retrofitted RC columns and repaired RC columns using epoxy resin was investigated. Finally, the hysteretic behavior of the shear-damaged RC columns after the proposed emergency retrofit was investigated.

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