Post-fire seismic performance of precast reinforced concrete columns

PCI Journal ◽  
2020 ◽  
Vol 65 (6) ◽  
pp. 62-80
Author(s):  
Ugur Demir ◽  
Mark F. Green ◽  
Alper Ilki
Keyword(s):  
Reinforced Concrete ◽  
Failure Modes ◽  
Precast Concrete ◽  
Concrete Columns ◽  
Fire Exposure ◽  
Residual Displacements ◽  
Lack Of Information ◽  
Seismic Tests ◽  
The Impact ◽  
The Given

Quantifying the seismic resistance of reinforced concrete buildings after fire is difficult because of the lack of information regarding their strength and ductility under earthquake loads. In this study, four full-scale flexure-controlled reinforced precast concrete columns were subjected to quasi-static reversed cyclic lateral loading under constant axial load to examine the seismic response of reinforced precast concrete columns damaged by 30, 60, and 90 minutes of fire. For the first time, the impact of fire damage on force-displacement behavior, moment-curvature relationship, stiffness, energy dissipation capacity, and residual displacements was investigated through postfire seismic tests. Test results clearly indicated that the fire exposure did not significantly affect the lateral-load-bearing capacity, failure modes, and ductility of the columns, with the exception of the specimen subjected to 90 minutes of fire exposure. The analytical study consisting of thermal and fiber-based structural analysis demonstrated that conventional principles of structural mechanics are valid for estimation of the postfire seismic behavior of reinforced precast concrete columns when the deteriorations in materials are realistically taken into account and the given algorithm is followed.

scholarly journals Predicting the behavior of reinforced concrete columns confined by fiber reinforced polymers using data mining techniques

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Sahar Y. Ghanem ◽  
Heba Elgazzar
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
Compressive Stress ◽  
Compressive Strain ◽  
Concrete Columns ◽  
Steel Reinforcement ◽  
Fiber Reinforced Polymers ◽  
Stress And Strain ◽  
Fiber Reinforced ◽  
The Impact

AbstractFiber Reinforced Polymer (FRP) usage to wrap reinforced concrete (RC) structures has become a popular technology. Most studies about RC columns wrapped with FRP in literature ignored the internal steel reinforcement. This paper aims to develop a model for the axial compressive strength and axial strain for FRP confined concrete columns with internal steel reinforcement. The impact of FRP, Transverse, and longitudinal reinforcement is studied. Two non-destructive analysis methods are explored: Artificial Neural Networks (ANNs) and Regression Analysis (RA). The database used in the analysis contains the experimental results of sixty-four concrete columns under the compressive concentric load available in the literature. The results show that both models can predict the column's compressive stress and strain reasonably with low error and high accuracy. FRP has the highest effect on the confined compressive stress and strain compared to other materials. While the longitudinal steel actively contributes to the compressive strength, and the transverse steel actively contributes to the compressive strain.

Seismic assessment of reinforced concrete columns with short lap splices

2021 ◽  
pp. 875529302199483
Author(s):  
Eyitayo A Opabola ◽  
Kenneth J Elwood
Keyword(s):  
Reinforced Concrete ◽  
Failure Mode ◽  
Failure Modes ◽  
Concrete Columns ◽  
Seismic Assessment ◽  
Rc Columns ◽  
Lap Splices ◽  
Displacement Response ◽  
Force Displacement ◽  
Probable Failure

Existing reinforced concrete (RC) columns with short splices in older-type frame structures are prone to either a shear or bond mechanism. Experimental results have shown that the force–displacement response of columns exhibiting these failure modes are different from flexure-critical columns and typically have lower deformation capacity. This article presents a failure mode-based approach for seismic assessment of RC columns with short splices. In this approach, first, the probable failure mode of the component is evaluated. Subsequently, based on the failure mode, the force–displacement response of the component can be predicted. In this article, recommendations are proposed for evaluating the probable failure mode, elastic rotation, drift at lateral failure, and drift at axial failure for columns with short splices experiencing shear, flexure, or bond failures.

Experimental determination of the residual compressive strength of concrete columns subjected to different fire durations and load ratios

2020 ◽  
Vol 11 (4) ◽  
pp. 529-543
Author(s):  
Anjaly Nair ◽  
Osama (Sam) Salem
Keyword(s):  
Experimental Study ◽  
Compressive Strength ◽  
Reinforced Concrete ◽  
Concrete Columns ◽  
Fire Exposure ◽  
Fire Performance ◽  
Content Type ◽  
Residual Compressive Strength ◽  
Standard Fire ◽  
Strength Capacity

Purpose At elevated temperatures, concrete undergoes changes in its mechanical and thermal properties, which mainly cause degradation of strength and eventually may lead to the failure of the structure. Retrofitting is a desirable option to rehabilitate fire damaged concrete structures. However, to ensure safe reuse of fire-exposed buildings and to adopt proper retrofitting methods, it is essential to evaluate the residual load-bearing capacity of such fire-damaged reinforced concrete structures. The focus of the experimental study presented in this paper aims to investigate the fire performance of concrete columns exposed to a standard fire, and then evaluate its residual compressive strengths after fire exposure of different durations. Design/methodology/approach To effectively study the fire performance of such columns, eight identical 200 × 200 × 1,500-mm high reinforced concrete columns test specimens were subjected to two different fire exposure (1- and 2-h) while being loaded with two different load ratios (20% and 40% of the column ultimate design axial compressive load). In a subsequent stage and after complete cooling down, residual compressive strength capacity tests were performed on each fire exposed column. Findings Experimental results revealed that the columns never regain its original capacity after being subjected to a standard fire and 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-h fire durations, respectively. It was also noticed that, for the tested columns, the applied load ratio has much less effect on the column’s residual compressive strength compared to that of the fire duration. Originality/value According to the unique outcomes of this experimental study and, as the fire-damaged concrete columns possessed considerable residual compressive strength, in particular those exposed to shorter fire duration, it is anticipated that with proper retrofitting techniques such as fiber-reinforced polymers (FRP) wrapping, the fire-damaged columns can be rehabilitated to regain at least portion of its lost load-bearing capacities. Accordingly, the residual compressive resistance data obtained from this study can be effectively used but not directly to adopt optimal retrofitting strategies for such fire-damaged concrete columns, as well as to be used in validating numerical models that can be usefully used to account for the thermally-induced degradation of the mechanical properties of concrete material and ultimately predict the residual compressive strengths and deformations of concrete columns subjected to different load intensity ratios for various fire durations.

An Experiment on Seismic Shear Capacity for HRB500 Grade R/C Frame Columns within Yield Hinge Regions

2011 ◽  
Vol 105-107 ◽  
pp. 948-952
Author(s):  
Pin Wu Guan ◽  
Meng Chen
Keyword(s):  
Experimental Study ◽  
Reinforced Concrete ◽  
Structural Design ◽  
Failure Modes ◽  
Seismic Loading ◽  
Concrete Columns ◽  
Shear Capacity ◽  
Reinforced Concrete Columns ◽  
Seismic Shear

An experiment on shear capacity for HRB500 grade R/C frame columns within yield hinge regions is studied. The different failure modes for specimens within yield hinge regions are classified, and the hysteretic curves are studied. The shear contributions of stirrups and concrete for columns are analyzed in detail. Based on the experimental study, formulas for the shear capacity of reinforced concrete columns are supposed under seismic loading, and the different formulas are adopted to estimate the shear capacity for columns at different seismic levels, Both security and economy of structural design are all considered.

scholarly journals Experimental Study on Seismic Behavior of Precast Frame Columns with Vertical Reinforcement Spliced with Grouted Sleeve Lapping Connectors

2021 ◽  
Vol 2021 ◽  
pp. 1-21
Author(s):  
Qiong Yu ◽  
Liang Zhang ◽  
Shaohua Bai ◽  
Baoxiu Fan ◽  
Zhenhai Chen ◽  
...  
Keyword(s):  
Seismic Performance ◽  
Failure Modes ◽  
Precast Concrete ◽  
Hysteresis Loops ◽  
Concrete Columns ◽  
Type I ◽  
Type Ii ◽  
Force Transfer ◽  
Steel Sleeve

Grouted splice connector is widely employed in precast concrete structures, but its utilization is still limited by shortcomings such as high construction cost, inconvenience in assemblage, and uncompacted grout caused by its small sleeve diameter. The grouted sleeve lapping connectors proposed by the authors can not only provide reasonable force transfer and convenient construction processing but also have the characteristics of low price and easy grouting. In this paper, the seismic performance of two full-scale precast concrete columns with two types of grouted sleeve lapping connectors was investigated, where type-I connector connected two lapped rebars and type-II connector connected four lapped rebars by a steel sleeve, respectively. A cast-in-situ column was also tested as a reference. All the specimens were tested under reversed cyclic horizontal load with a constant axial force. The distribution of cracks, failure modes, loading capacities, deformation abilities, stiffness, ductility, hysteresis loops, and energy dissipation of the specimens were studied. The type-I and type-II grouted sleeve lapping connectors satisfactorily transferred the stress of rebars when the columns reached their ultimate loads, and the seismic performance of the precast concrete columns was found to be comparable to that of the cast-in-situ column. Thus, the grouted sleeve lapping connector has a potential to replace the grouted splice connector in cast-in-situ connection.

The effect of assembling location on the performance of precast concrete beam under impact load

2017 ◽  
Vol 21 (8) ◽  
pp. 1211-1222 ◽  
Author(s):  
Qiushi Yan ◽  
Bowen Sun ◽  
Xuemei Liu ◽  
Jun Wu
Keyword(s):  
Reinforced Concrete ◽  
Impact Velocity ◽  
Concrete Beam ◽  
Concrete Beams ◽  
Impact Load ◽  
Precast Concrete ◽  
Reinforced Concrete Beams ◽  
Impact Location ◽  
Weight Impact ◽  
The Impact

With incorporation of assembling joints, precast concrete beams could behave very differently in resisting both static and dynamic loads in comparison to conventional reinforced concrete beams. With no research available on the dynamic behavior of precast concrete beams under impact load, a combined experimental and numerical study is conducted to investigate the dynamic response of precast concrete beams under impact load. The results were also compared with reinforced concrete beams. Four groups of concrete beams were tested with all beams designed with the same reinforcement, but different assembling locations were considered for precast concrete beams. The effects of the assembling location in resisting drop weight impact of precast concrete beams were analyzed. The influence of impact mass and impact velocity on the impact resistance of precast concrete beams were also investigated. The results revealed that the further the assembling location is away from the impact location, the closer the mechanical performance of the precast concrete beam is to that of the reinforced concrete beam. When the assembling location and the impact location coincided, the assembling region suffered from severe local damages. With increased impact velocity and impact energy, the damage mode of the precast concrete beams may change gradually from bending failure to bending–shear failure and eventually to local failure. In addition, the bonding around the assembling interface was found to be effective to resist drop weight impact load regardless of the magnitude of the impact velocity and energy.

scholarly journals THE STUDY OF IMPACT OF FACTORS ON PROFITABILITY INDEX OF RECONSTRUCTION OF THE DWELLINGS

2020 ◽  
Vol 1 (154) ◽  
pp. 178-184
Author(s):  
T. Dubelt
Keyword(s):  
Graphical Models ◽  
Mathematical Analysis ◽  
Efficient Solutions ◽  
Graphical Modeling ◽  
Mathematical Formula ◽  
Technological Factors ◽  
Simultaneous Impact ◽  
Lack Of Information ◽  
The Impact ◽  
The Given

The article deals with the study of impact of organizational and technological factors on the index of recon-struction profitability of dwellings of first mass series on condition of habitants’ eviction while doing operations. We find lack of information on the methodology of the study of such objects in informative sources . Factual dwellings’ reconstruction has an incidental character and does not allow to define the impact of factors on the indexes of reconstruction because it takes place by fixed values of factors and limited quantities of objects. And as a consequence we find investors’ unwillingness to put money into the reconstruction of the dwellings of typical series. The purpose of the study is to define the efficient solutions of reconstruction of the dwelling of typical series 1-4382.5-7. The given task is solved by making abstract models of the series imitating reconstruction’s operations by simultaneous impact of organizational and technological factors. While conducting the investigation we defined the factors and the levels of their variation that have impact on the dwellings’ reconstruction. The plan of multiple experiment was elaborated considering the simultaneous effect of the given factors on reconstruction indexes. On the basis of the given series of dwelling we made informative and graphical models, and we also got the indexes of reconstruction. Graphical modeling allowed to obtain numerical values of operations’ durability. Simultaneous impact of factors and the conditions of habitants’ eviction defined numerical value of operations’ cost. With the help of formula we obtained the value of profitability index. We defined the dependency of profitability index on varying factors using the methods of mathematical analysis. It is shown in the form of dependency charts and is described by mathematical formula. We substantiated the admissible numerical values of profitability index of reconstruction of the dwellings of first mass series. The conclusions about effective solutions on reconstruction of such dwellings are made by graphical image and the areas of effective solutions are defined Keywords: factors, reconstruction indexes, reconstruction models, mathematical analysis, charts of dependency.

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