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Recent Advances in the Behavior of Reinforced Concrete Columns: A Session Honoring the Memory of Dr. Asad Esmaeily
Tuesday, October 19, 2021 4:00 PM - 6:00 PM
Dr. Asad Esmaeily was a Professor of Structural Engineering at Kansas State University between 2002 and 2018. He was an active member of Joint ACI-ASCE Committee 441, Reinforced Concrete Columns, for almost 18 years. He was a major contributor to the recently published document ACI 441.1R 18. His area of research was in reinforced concrete columns and health monitoring of structures. He passed away in June 2018 at the age of 59 after a short battle with cancer. His colleagues, students, and fellow committee members want to pay a small tribute to him by organizing this session in his memory. Joint ACI-ASCE Committee 441 is sponsoring the session. The session addresses recent advances in the behavior and modeling of reinforced concrete columns subjected to different loading conditions with the presence of innovative materials. The audience of this session are anticipated to be practitioners and researchers in the area of behavior, analysis, and design of reinforced concrete columns.
(1) Review nalysis methods for reinforced concrete columns;
(2) Discuss behavior of columns under biaxial flexure, axial compression and shear;
(3) Describe modeling of the effects of confinement;
(4) Identify seismic response of reinforced concrete columns.
This session has been approved by AIA and ICC for 2 PDHs (0.2 CEUs). Please note: You must attend the live session for the entire duration to receive credit. On-demand sessions do not qualify for PDH/CEU credit.
Combined Partial External FRP-Internal Steel Ties Confinement Modeling in Rectangular RC Columns
Presented By: Ahmed Al-Rahmani
Affiliation: SK&A Structural Engineers
Description: Fiber reinforced polymers (FRPs) have become a popular choice for design professionals in strengthening and retrofit applications for concrete structures. This can be attributed to their relative ease of installation and their superb properties such as high strength-to-weight ratio, high energy absorption and excellent corrosion resistance. Traditionally confinement in concrete columns is provided by steel ties. FRP wrapping of concrete columns contributes to the confinement effect and enhances its ultimate strength. The introduction of FRP complicates the nature of the confinement system, and necessities specialized nonlinear analysis to model and determine the upgraded ultimate capacity. This work proposes a combined confinement model that accounts for both steel and FRP systems in rectangular concrete columns. Effective lateral pressures are determined based on Mander model and Lam and Teng model for steel ties and FRP wraps, respectively. Load eccentricity is utilized as a parameter to model the compression zone, which represents the level of confinement in the section. Infinite eccentricity indicates unconfined behavior, while zero eccentricity indicates full confinement under compression. The model is then used to generate interaction curves for the full range of combined confinement levels.
Novel Element Capturing Axial-Shear-Moment Interactions in RC Columns Sustaining Seismic Degradation
Presented By: Rasool Ghorbani
Affiliation: University of Texas San Antonio
Dry Glass Fiber Wires Confinement for Concrete Columns
Presented By: Ahmed Abd El Fattah
Affiliation: King Fahd University of Petroleum and Minerals
Description: Dry glass fiber wires with 10, 20 and 30 bundles were wrapped around 75 x 150 mm concrete cylinders to act as active confinement for stub columns. Confinement level varied in the experimental program by changing the bundle thickness and the lateral spacing of the glass fiber rings. The specimens were tested in compression and axial force, and axial displacement along with lateral displacement were recorded. LVDTs captured the axial deformation and lateral strain gauges monitored the lateral deformation. It was recorded that there was an increase of strength about 100% on average compared to the control specimens. The strength increased proportionally to the confinement increase. The ductility also was increased with the increase of level of confinement. The maximum lateral strain recorded was for the moderate confinement level. A model was developed to predict the full stress-strain response of the concrete confined with active dry fibers. The proposed model was well correlated to experimental results.
Shear Capacity of Circular Columns Confined with FRP Wrapping
Presented By: Alaaeldin Abouelleil
Affiliation: AEDA LLC
Description: The importance of the analysis of circular reinforced concrete columns to accurately predict their confined load carrying capacity under full interaction domain (moment-shear force-axial force) is recognized in light of the extreme load event imposed by the current AASHTO LRFD based on the Simplified Modified Compression Field Theory (SMCFT). The confinement effect of steel as well as FRP is also discussed and evaluated for confined circular reinforced concrete columns. The confinement effect of FRP adds another layer of complexity to the shear transfer mechanism. However, there are many similarities between steel confinement and FRP confinement. Using these similarities, a simplified model for FRP confinement is presented. Then, the current procedure adopted by AASHTO LRFD 2014, based on the simplified modified compression field theory, is evaluated for non-prestressed circular concrete bridge piers confined with FRP. This evaluation is compared against experimental data available in the literature. Results are discussed and future improvements are proposed. The main parameters that control the cross-section shear strength are discussed based on the experimental results and comparisons.
A Comparative Study of Strength Assessment Methods for RC Columns
Presented By: Feraidon Ataie
Affiliation: California State University, Chico
Description: It has been shown by various experimental and analytical studies that the performance of a reinforced concrete section is affected by different factors such loading history and material behavior. A realistic performance assessment should consider not only proper models for the monotonic and cyclic response of the material, but also analytical methods and procedures that can capture the effects of loading pattern and provide realistic predictions of the section capacity.
Accuracy of the analytical methods in strength assessment of reinforced concrete sections was explored in a comparative study. These methods were compared and validated against the existing experimental data. The factors considered in these analytical procedures, included the effect of confinement, and the method employed in assessment of the axial-force-bending moment interaction response of a column section. The experimental data were collected from tests conducted on circular and rectangular columns under a constant axial load.
It has been shown that the axial force-bending moment interaction curve, constructed based on the moment-curvature response of a section using a more detailed analytical method such as fiber-model, considering the confining effect of the lateral reinforcement, represents the most realistic and optimal response of a cross section.
Short-and Long-Term Performance of Hollow-Core FRP-Concrete-Steel Columns
Presented By: Mohamed ElGawady
Affiliation: Missouri S&T
This presentation reports the short and long term performance of hollow-core fiber-reinforced polymer (FRP)-concrete-steel (HC-FCS) bridge columns. The typical HC-FCS column consists of a concrete shell sandwiched between an outer FRP tube and an inner steel tube. The HC-FCS column represents a compact engineering system; the steel and FRP tubes act together as stay-in-place formworks. The steel tube acts as a flexural and shear reinforcement. The presentation reports the static cyclic and dynamic response of twelve HC-FCS columns. Furthermore, the durability response of the columns after being subjected to different severe weather environment will be reported as well. The HC-FCS columns exhibited high lateral drift reaching
15.2% and fail gradually due to concrete crushing and local steel tube buckling, followed by FRP rupture. Analytical and numerical models predicted quite well the performance of the columns.