Experimental and numerical study about seismic retrofitting of corrosion-damaged reinforced concrete columns of bridge using combination of FRP wrapping and steel profiles

Hassan Afshin,Mohammad R. Nouri Shirazi,Karim Abedi 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.30 No.3

In the present study, a numerical and experimental investigation has been carried out on the seismic behavior of RC columns of a bridge which damaged under corrosive environments and retrofitted by various techniques including combined application of CFRP sheets and steel profiles. A novel hybrid retrofitting procedure, including the application of inner steel profiles and outer peripheral CFRP sheets, has been proposed for strengthening purpose. Seven large-scale RC columns of a Girder Bridge have been tested in the laboratory under the influence of simultaneous application of constant axial load and the lateral cyclic displacements. Having verified the finite element modeling, using ABAQUS software, the effects of important parameters such as the corrosion percentage of steel rebars and the number of CFRP layers have been evaluated. Based on the results, retrofitting of RC columns of the bridge with the proposed technique was effective in improving some measures of structural performance such as lateral strength degradation and higher energy absorption capability. However, the displacement ductility was not considerably improved whereas the elastic stiffness of the specimens has been increased.

Evaluation of sHLA-G levels in serum of patients with prostate cancer identify as a potential of tumor marker

Mohammad Hassan Heidari,Abolfazl Movafagh,Mohammad Amin Abdollahifar,Shabnam Abdi,Mohamadreza Mashhoudi Barez,Hadi Azimi,Afshin Moradi,Amin Bagheri,Matineh Heidari,Jafar Hessam Mohseni,Maryam Tadayon 대한해부학회 2017 Anatomy & Cell Biology Vol.50 No.1

Prostate cancer is the most common cancer type in men and is the second cause of death, due to cancer, in patients over 50, after lung cancer. Prostate specific antigen (PSA) is a widely used tumor marker for prostate cancer. Recently, PSA is discovered in non-prostatic cancer tissues in men and women raising doubts about its specificity for prostatic tissues. PSA exists in low serum level in healthy men and in higher levels in many prostate disorders, including prostatitis and prostate cancer. Thus, a supplementary tumor marker is needed to accurately diagnose the cancer and to observe the patient after treatment. Recently, soluble human leukocyte antigen-G (sHLA-G) has been introduced as a new tumor marker for different cancer types, including colorectal, breast, lung, and ovary. The present descriptive-experimental study was carried out including patients with malignant prostate tumor, patients with benign prostate tumor, and a group of health men as the control group, as judged by an oncologist as well as a pathologist. After sterile blood sampling, sHLA-G was measured by enzyme-linked immunosorbent assay in each group. The data was then analyzed using one-way ANOVA. P≤0.05 was considered as statistically significant. The results showed that the mean of sHLA-G level was high in patients. Also, it was found that there was a significant difference in sHLA serum level between the three groups. The data revealed that sHLA-G can be a novel upplementary tumor marker in addition to PSA to diagnose prostate cancer.

Experimental Evaluation of Relationship between Shear Deformation and Pinching in Lightweight-aggregate Reinforced Concrete Beams

Farrokh Aghamohammadzadeh,Hassan Afshin,Masoud Nekooei 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.1

An experimental program was arranged to investigate the relationship between shear deformation and pinching in lightweightaggregate reinforced concrete beams under cyclic loading. Lightweight-aggregate reinforced concrete beams and their connection to column were selected for the purpose of this study and their flexural and shear behaviors experimentally were investigated. Damaged part of the beams was determined after the test. Using the results, values of beam tip displacement, curvature, and shear distortion in the plastic hinge region of beam were measured and components of shear and flexural deformation of the beam were calculated. Investigations were also performed on the effect of damage extension at the beam-column connection joint as well as effect of shear deformation on pinching increase. It was concluded that, in the lightweight-aggregate reinforced concrete beams in which the damaged part was extended to the beam-column joint, pinching was higher and also shear deformation has a larger contribution of the total beam deformation.

High Deformable Concrete (HDC) element: An experimental and numerical study

Kesejini, Yasser Alilou,Bahramifar, Amir,Afshin, Hassan,Tabrizi, Mehrdad Emami Techno-Press 2021 Advances in concrete construction Vol.11 No.5

High deformable concrete (HDC) elements have compressive strength rates equal to conventional concrete and have got a high compressive strain at about 20% to 50%. These types of concrete elements as prefabricated parts have an abundance of applications in the construction industry which is the most used in the construction of tunnels in squeezing grounds, tunnel passwords from fault zones or swelling soils as soft supports. HDC elements after reaching to compressive yield stress, in nonlinear behavior have hardening combined with increasing strain and compressive strength. The main aim of this laboratory and numerical research is to construct concrete elements with the above properties so the compressive stress-strain behavior of different concrete elements with four categories of mix designs have been discussed and finally one of them has been defined as HDC element mix design. Furthermore, two columns with and without implementing of HDC elements have been made and stress-strain curves of them have been investigated experimentally. An analysis model is presented for columns using finite element method adopted by ABAQUS. The results obtained from the ABAQUS finite element method are compared with experimental data. The main comparison is made for stress-strain curve. The stress-strain curves from the finite element method agree well with experimental results. The results show that the dimension of the HDC samples is significant in the stress-strain behavior. The use of the element greatly increases energy absorption and ductility.

Clinical and Safety Outcomes of Endovascular Therapy 6 to 24 Hours After Large Vessel Occlusion Ischemic Stroke With Tandem Lesions

Galecio-Castillo Milagros,Farooqui Mudassir,Hassan Ameer E.,Jumaa Mouhammad A.,Divani Afshin A.,Ribo Marc,Abraham Michael,Petersen Nils H.,Fifi Johanna T.,Guerrero Waldo R.,Malik Amer M.,Siegler James 대한뇌졸중학회 2023 Journal of stroke Vol.25 No.3

Background and Purpose Effect of endovascular therapy (EVT) in acute large vessel occlusion (LVO) patients with tandem lesions (TLs) within 6–24 hours after last known well (LKW) remains unclear. We evaluated the clinical and safety outcomes among TL-LVO patients treated within 6–24 hours. Methods This multicenter cohort was divided into two groups, based on LKW to puncture time: early window (<6 hours), and late window (6–24 hours). Primary clinical and safety outcomes were 90-day functional independence measured by the modified Rankin Scale (mRS: 0–2) and symptomatic intracranial hemorrhage (sICH). Secondary outcomes were successful reperfusion (modified Thrombolysis in Cerebral Infarction score ≥2b), first-pass effect, early neurological improvement, ordinal mRS, and in-hospital and 90-day mortality. Results Of 579 patients (median age 68, 32.1% females), 268 (46.3%) were treated in the late window and 311 (53.7%) in the early window. Late window group had lower median National Institutes of Health Stroke Scale score at admission, Alberta Stroke Program Early Computed Tomography Score, rates of intravenous thrombolysis, and higher rates for perfusion imaging. After adjusting for confounders, the odds of 90-day mRS 0–2 (47.7% vs. 45.0%, adjusted odds ratio [aOR] 0.71, 95% confidence interval [CI] 0.49–1.02), favorable shift in mRS (aOR 0.88, 95% CI 0.44–1.76), and sICH (3.7% vs. 5.2%, aOR 0.56, 95% CI 0.20–1.56) were similar in both groups. There was no difference in secondary outcomes. Increased time from LKW to puncture did not predicted the probability of 90-day mRS 0–2 (aOR 0.99, 95% CI 0.96–1.01, for each hour delay) among patients presenting <24 hours. Conclusion EVT for acute TL-LVO treated within 6–24 hours after LKW was associated with similar rates of clinical and safety outcomes, compared to patients treated within 6 hours.

Flexural Strength of Light-Weight Steel Fiber Reinforced Concrete Containing Biodegradable LDHs Microparticles: Experimental Study and Multiscale Finite Element Model

Pari Ramazani,Taleb Moradi Shaghaghi,Masood Farzam,Hassan Afshin,Mohammad A. Behnajady 한국콘크리트학회 2024 International Journal of Concrete Structures and M Vol.18 No.4

This study investigates the influence of LDHs (Layered Double Hydroxides) microparticles and steel fibers on the mechanical properties of lightweight concrete. Through a combination of experimental analysis and finite element modeling, the effects of LDHs and steel fibers on flexural strength and crack resistance were evaluated. The experimental results demonstrate a significant increase in flexural strength and toughness with the incorporation of LDHs microparticles and steel fibers. The finite element model corroborates these findings, highlighting the synergistic enhancement of mechanical properties due to LDHs and steel fibers. Additionally, the study discusses the frontier applications of LDHs in improving fracture characteristics and highlights the potential of hybrid reinforcement strategies in lightweight concrete. The findings reveal that both the quantity of microparticles and steel fibers significantly impact the concrete's residual strength. In scenarios without steel fibers, an optimal weight fraction of approximately 1 wt.% LDHs demonstrate a 39% increase in bearing capacity. Notably, under comparable conditions, the influence of LDHs microparticles on enhancing concrete mechanical characteristics appears to surpass the effects induced by steel fibers. However, at 2 wt.% LDHs usage, a decrease in load capacity by 3.3% is observed compared to the 1 wt.% LDHs configuration. This research provides valuable insights into optimizing concrete properties through novel material combinations and paves the way for future advancements in structural engineering.

3D finite element modelling of composite connection of RCS frame subjected to cyclic loading

Mohammad Hossein Habashizadeh Asl,Mohammad Reza Chenaglou,Karim Abedi,Hassan Afshin 국제구조공학회 2013 Steel and Composite Structures, An International J Vol.15 No.3

Composite special moment frame is one of the systems that are utilized in areas with low to high seismicity to deal with earthquake forces. Composite moment frames are composed of reinforced concrete columns (RC) and steel beams (S); therefore, the connection region is a combination of steel and concrete materials. In current study, a three dimensional finite element model of composite connections is developed. These connections are used in special composite moment frame, between reinforced concrete columns and steel beams (RCS). Finite element model is discussed as a most reliable and low cost method versus experimental procedures. Based on a tested connection model by Cheng and Chen (2005), the finite element model has been developed under cyclic loading and is verified with experimental results. A good agreement between finite element model and experimental results was observed. The connection configuration contains Face Bearing Plates (FBPs), Steel Band Plates (SBPs) enveloping around the RC column just above and below the steel beam. Longitudinal column bars pass through the connection with square ties around them. The finite element model represented a stable response up to the first cycles equal to 4.0% drift, with moderately pinched hysteresis loops and then showed a significant buckling in upper flange of beam, as the in test model.