Experimental Determination of the Residual Compressive Strength of Concrete Columns Subjected to Different Fire Durations and Load Ratios PDF Download
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Author: Anjaly Nair
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The superior thermal property of concrete associated to its great capability of thermally insulating the embedded reinforcing steel rebar is the main reason for the good behavior of reinforced concrete structural elements in fire condition, compared to other construction materials. However, at elevated temperatures, concrete still undergoes changes in its mechanical and thermal properties, which mainly cause degradation of strength and may lead to the failure of the structure. Retrofitting is a desirable alternative to rehabilitate post-fire concrete structures. However, in order to ensure safe reuse of fire-exposed buildings and to adopt proper retrofitting methods, it is essential to evaluate the residual strength capacity of fire-damaged reinforced concrete structural elements. The focus of this experimental research study is to investigate the fire performance of reinforced concrete columns exposed to elevated temperatures that followed CAN/ULC-S101 standard fire, and then evaluate their residual compressive strengths after fire exposure. In order to effectively study the fire performance of such columns, eight identical 200 x 200 x 1500mm high reinforced-concrete column test specimens were subjected to two different durations of standard fire exposure (1 hour and 2 hours) while being loaded with two different axial load ratios (20% and 40% of the column ultimate design axial compressive load capacity). In a subsequent stage and after complete cooling down, residual compressive strength capacity tests were performed on the fire-exposed columns. Experimental results showed that the residual compressive strength capacity dropped to almost 50% and 30% of its ambient temperature capacity for the columns exposed to 1- and 2-hour fire durations, respectively. It was also noticed that the applied load ratio has less effect on the column's residual compressive strength compared to that of the fire duration.
Author: Anjaly Nair
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The superior thermal property of concrete associated to its great capability of thermally insulating the embedded reinforcing steel rebar is the main reason for the good behavior of reinforced concrete structural elements in fire condition, compared to other construction materials. However, at elevated temperatures, concrete still undergoes changes in its mechanical and thermal properties, which mainly cause degradation of strength and may lead to the failure of the structure. Retrofitting is a desirable alternative to rehabilitate post-fire concrete structures. However, in order to ensure safe reuse of fire-exposed buildings and to adopt proper retrofitting methods, it is essential to evaluate the residual strength capacity of fire-damaged reinforced concrete structural elements. The focus of this experimental research study is to investigate the fire performance of reinforced concrete columns exposed to elevated temperatures that followed CAN/ULC-S101 standard fire, and then evaluate their residual compressive strengths after fire exposure. In order to effectively study the fire performance of such columns, eight identical 200 x 200 x 1500mm high reinforced-concrete column test specimens were subjected to two different durations of standard fire exposure (1 hour and 2 hours) while being loaded with two different axial load ratios (20% and 40% of the column ultimate design axial compressive load capacity). In a subsequent stage and after complete cooling down, residual compressive strength capacity tests were performed on the fire-exposed columns. Experimental results showed that the residual compressive strength capacity dropped to almost 50% and 30% of its ambient temperature capacity for the columns exposed to 1- and 2-hour fire durations, respectively. It was also noticed that the applied load ratio has less effect on the column's residual compressive strength compared to that of the fire duration.
Author: Guoqing Geng
Publisher: Springer Nature
ISBN: 9811973318
Category : Technology & Engineering
Languages : en
Pages : 1545
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Book Description
This book presents articles from The 17th East Asian-Pacific Conference on Structural Engineering and Construction, 2022, organized by National University of Singapore. These peer-reviewed articles, authored by professional engineers, academics and researchers, highlight the recent research and developments in structural engineering and construction, embracing the theme- “Towards a Resilient and Sustainable City”. The papers presented in this proceeding provide in-depth discussions with key insights into the future research, development and engineering translation in structural engineering and construction.
Author: Venkatesh Kodur
Publisher: McGraw Hill Professional
ISBN: 1260128598
Category : Technology & Engineering
Languages : en
Pages : 481
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Book Description
Actionable strategies for the design and construction of fire-resistant structures This hands-on guide clearly explains the complex building codes and standards that relate to fire design and presents hands-on techniques engineers can apply to prevent or mitigate the effects of fire in structures. Dedicated chapters discuss specific procedures for steel, concrete, and timber buildings. You will get step-by-step guidance on how to evaluate fire resistance using both testing and calculation methods. Structural Fire Engineering begins with an introduction to the behavioral aspects of fire and explains how structural materials react when exposed to elevated temperatures. From there, the book discusses the fire design aspects of key codes and standards, such as the International Building Code, the International Fire Code, and the NFPA Fire Code. Advanced topics are covered in complete detail, including residual capacity evaluation of fire damaged structures and fire design for bridges and tunnels. Explains the fire design requirements of the IBC, IFC, the NFPA Fire Code, and National Building Code of Canada Presents design strategies for steel, concrete, and timber structures as well as for bridges and tunnels Contains downloadable spreadsheets and problems along with solutions for instructors
Author: Derek R. Hibner
Publisher:
ISBN: 9780355236002
Category : Electronic dissertations
Languages : en
Pages : 134
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Book Description
Author:
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 462
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Book Description
Author: Reza Imani
Publisher:
ISBN:
Category :
Languages : en
Pages : 277
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Book Description
Fire following an earthquake has been a major cause of damage in a number of historic seismic events. Considering the amount of damage and statistics showing a high probability for the occurrence of post-earthquake ignitions, there is a need to study the effects of seismic damage on the fire resistance of structures. Concrete Filled Double-Skin Tube (CFDST) columns, a special composite structure which has been shown to have satisfactory performance under separate seismic loading and fire conditions, were studied in this research when subjected to post-earthquake fire scenarios. Experimental studies were conducted to examine the behavior of concrete filled double-skin tube (CFDST) columns exposed to fire after being subjected to simulated seismic loads. The experiments were conducted in two separate phases, consisting of the quasi-static cyclic tests followed by fire tests. Three nominally identical column specimens were constructed for these studies. One of the specimens was directly tested under fire to quantify its resistance in an undamaged condition. The other two specimens were first subjected to quasi-static cyclic lateral loads, imposing varying degrees of lateral drift to simulate two different seismic events with moderate and high damage levels before being exposed to fire. Both of the specimens were pushed to the maximum drift of 6-6. 5% with different residual drifts of 1. 4% and 3. 9% for moderate and high damage levels, respectively. The undamaged and damaged columns were then subjected to the same fire tests following the standard ASTM E119 (ASTM 2012) temperature-time curve while sustaining an axial load until the column failed due to global buckling. Local buckling of the tubes was also observed in the specimens due to the thermal expansion and separation from the concrete. Overall, the results showed marginal differences in the fire resistance of the three specimens, providing evidence for the resilient performance of these columns under post-earthquake fire scenarios. An additional quasi-static cyclic loading test was conducted on the specimen that had been exposed to fire without any prior damage, to investigate the behavior of the column subjected to seismic loads after the fire test. Again, differences in behavior were modest, except for a 5. 7% drop in strength attributed to permanent degradation in material properties due to the fire test. In addition to the experimental studies, detailed finite element analyses were conducted using ABAQUS and LS-DYNA to simulate the behavior of CFDST columns subjected to post-earthquake fires. The models were shown to be capable of replicating the experimental results with sufficient accuracy. A simplified step by step analytical procedure was proposed for calculation of the axial load capacity of CFDST columns subjected to fire. The procedure was defined based on an analytical solution to the heat transfer problem and calculation of axial load capacity using the fire-modified material properties. A number of design recommendations, based on the knowledge gained from the experimental and analytical studies, were proposed for CFDST columns subjected to fire.
Author: Bengt Baltzar Broms
Publisher:
ISBN:
Category : Columns, Concrete
Languages : en
Pages : 86
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Book Description
Author: Stanley S. Low
Publisher:
ISBN:
Category : Axial loads
Languages : en
Pages : 144
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Book Description
Author: H. Bizri
Publisher:
ISBN:
Category : Columns, Concrete
Languages : en
Pages : 518
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Book Description
Author: Saleh Mohammad Alogla
Publisher:
ISBN: 9781392074220
Category : Electronic dissertations
Languages : en
Pages : 256
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Book Description
Structural members experience significant creep deformations in later stages of fire exposure and are susceptible to failure due to temperature induced creep strains. Fire in a concrete structure can burn for several hours, and temperatures in concrete and reinforcing steel can exceed 500 °C. At such temperatures, high levels of creep strains can develop in concrete and steel, especially in reinforced concrete columns. However, temperature induced creep strains are not fully accounted for in evaluating fire resistance of concrete members even through advanced analysis, and there is a lack of data on high-temperature creep strains for specific types of concrete. To overcome current limitations, comprehensive experiments on evolution of transient creep strain are undertaken under various heating and loading regimes. Transient creep tests are conducted in the temperature range of 20 °C to 750 °C on four types of concrete; normal strength concrete, steel fiber reinforced concrete, high strength concrete, and high strength concrete with polypropylene fibers. The test variables include temperature, load level, rate of heating, strength of concrete and presence of fibers. Data from these tests indicate that transient creep strain constitutes a significant portion of the total strain developed during high-temperature exposure. Data also affirm that temperature range and stress level have significant influence on transient creep strain. However, rate of heating and presence of fibers have only a moderate influence on the extent of transient creep in concrete. Presence of steel fibers in normal strength concrete slightly reduce transient creep strain, while the presence of polypropylene fibers in high strength concrete leads to higher transient creep strain. Generated data from experiments is then utilized to propose temperature and stress dependent creep strain relations for concrete. These transient creep strain relations can be implemented in fire resistance evaluation of concrete members. To account for transient creep in undertaking fire resistance analysis of reinforced concrete (RC) columns, a three-dimensional finite element based numerical model is developed in ABAQUS. Temperature-induced creep strains in concrete and reinforcing steel are explicitly accounted for in this advanced analysis. The model also accounts for temperature induced degradation in concrete and reinforcing steel, and material and geometrical nonlinearities. The validity of the model is established by comparing fire response predictions generated from the model with measured response parameters in fire tests on RC columns. Results from the analysis clearly indicate that transient creep strain significantly influences the extent of deformations when the temperatures in concrete exceed 500 °C for stress level of 40% or more, and this in turn influences fire resistance of RC columns. The validated model is applied to assess the influence of transient creep on fire response of RC columns under different conditions, including different fire scenarios, load level, and number of exposed sides in a column. Results from the numerical studies clearly indicate that severe fire exposure induces higher creep strains in RC columns in much shorter duration than exposure to a standard building fire. Moreover, asymmetric thermal gradients resulting from two or three side fire exposure on a column, can increase transient creep effects and, thus, affect fire resistance. The extent of the developed transient creep in concrete columns under various scenarios of fire exposure is highly dependent on the type of concrete. Overall, results from the analysis infer that neglecting transient creep can lead to a lower prediction of deformations and, thus, overestimation of fire resistance in RC columns, particularly when subjected to severe fire exposure scenarios, with higher thermal gradients.
