• Earthquakes and Structures
• /
• v.9 no.2
• /
• pp.281-303
• /
• 2015

The effects of infill panels on the response of r.c. frames subjected to seismic action are widely recognized. Numerous experimental investigations were effected and several analytical models were developed on this subject. This work, which is part of a larger project dealing with specific materials and structures commonly used in Italy, discusses experimental tests on masonry and samples of bare and infilled portals. The experimental activity includes tests on elemental materials, and 12 wall samples. Finally, three one-bay one-story reinforced concrete frames, designed according to the outdated Italian technical code D.M. 1996 without seismic details, were tested (bare and infilled) under constant vertical and cyclic lateral load. The first cracks observed on the framed walls occurred at a drift of about 0.3%, reaching its maximum capacity at a drift of 0.5% while retaining its capacity up to a drift of 0.6%. Infill contributed to both the stiffness and strength of the bare reinforced concrete frame at small drifts thus improving overall system behavior. In addition to the experimental activities, previously mentioned, the recalibration of a model proposed by Comberscue (1996) was evaluated. The accuracy of an OpenSees non linear fiber based model of the prototype tested, including a strut element was verified through a comparison with the final experimental results. This work has been partially supported by research grant DPC-ReLUIS 2014.

• Earthquakes and Structures
• /
• v.26 no.5
• /
• pp.327-336
• /
• 2024

Evaluation of tunnel performance in seismic-prone areas demands efficient means of estimating performance at different hazard levels. The present study introduces an innovative push-over analysis approach which employs the standard earthquake spectrum to simulate the performance of a tunnel. The numerical simulation has taken into account the lining and surrounding rock to calculate the rock-tunnel interaction subjected to a static push-over displacement regime. Elastic perfectly plastic models for the lining and hardening strain rock medium were used to portray the development of plastic hinges, nonlinear deformation, and performance of the tunnel structure. Separately using a computational algorithm, the non-linear response spectrum was approximated from the average shear strain of the rock model. A NATM tunnel in Turkey was chosen for parametric study. A seismic performance curve and two performance thresholds are introduced that are based on the proposed nonlinear seismic static loading approach and the formation of plastic hinges. The tunnel model was also subjected to a harmonic excitation with a smooth response spectrum and different amplitudes in the fully-dynamic phase to assess the accuracy of the approach. The parametric study investigated the effects of the lining stiffness and capacity and soil stiffness on the seismic performance of the tunnel.

• Structural Engineering and Mechanics
• /
• v.77 no.5
• /
• pp.673-689
• /
• 2021

This paper addresses the efficiency of thermal insulation layers applied to protect structural elements strengthened by fiber-reinforced polymers (FRP) in the case of fire event. The paper presents numerical modeling and nonlinear analysis of reinforced concrete (RC) columns externally strengthened by FRP and protected by thermal insulation layers when subjected to elevated temperature specified by standard fire tests, in order to predict their residual capacity and fire endurance. The adopted numerical approach uses commercial software includes heat transfer, variation of thermal and mechanical properties of concrete, steel reinforcement, FRP and insulation material with elevated temperature. The numerical results show good agreement with published results of full-scale fire tests. A parametric study was conducted to investigate the influence of several variables on the structural response and residual capacity of insulated FRP-confined columns loaded by service loads when exposed to fire. The residual capacity of FRP-confined RC column was affected by concrete grade and insulation material and was shown to improve substantially by increasing the concrete cover and insulation layer thickness. By increasing the VG insulation layer thickness 15, 32, 44, 57 mm, the loss in column capacity after 5 hours of fire was 30%, 13%, 7% and 5%, respectively. The obtained results demonstrate the validity of the presented approach for estimation of fire endurance and residual strength, as an alternative for fire testing, and for design of fire protection layers for FRP-confined RC columns.

• Structural Engineering and Mechanics
• /
• v.91 no.5
• /
• pp.427-441
• /
• 2024

Large-scale cantilever reinforced concrete (RC) columns with footing/stub were examined to determine their seismic response under a quasi-static increasing-magnitude cyclic lateral loading. Three-dimensional (3D) numerical models of RC columns with ductile and non-ductile reinforcement arrangements were developed in a Finite Element (FE) software, i.e., ABAQUS, to corroborate them with the experimental study conducted by the author. Both simulated models were validated with the experimental results in all respects, and the theoretical axial capacity of columns under concentric axial load (P₀) was calculated. Subsequently, a detailed parametric study was conducted by adopting the force and reinforcement variables. These variables include axial compression ratios (ACR) varying from 0.35P₀ to 0.7P₀ and the amount of lateral reinforcements taken as 0.33% and 1.31% representing the non-ductile and ductile columns, respectively. This research outcome conclusively quantifies the combined effect of ACR levels and lateral reinforcement spacing on the flexural response and ductility characteristics of RC columns. The comparative analysis reveals that increased ACR levels resulted in a severe reduction in strength, deformability and ductility characteristics of both ductile and non-ductile columns. Structural response of ductile columns at higher ACR levels was comparable to the non-ductile columns, nullifying the beneficial effects of ductile design provisions. Higher ACR levels caused decline in pre-peak and post-peak response trajectories, leading to an earlier attainment of peak response at lower drift levels.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.22 no.3
• /
• pp.185-191
• /
• 2018

Post-earthquake risk assessment technique in Korea is developed in 2013 by National Disaster Management Research Institute, at the same time, related manual and standard regulation is distributed to every local government by National Emergency Management Agency. The objectives of this research are to investigate and evaluate the post-earthquake risk assessment of 9.12 Earthquake (M5.8, Gyeongju City, 2016) and 11.15 Earthquake (M5.4, Pohang City, 2017). To suggest and improve the assessment process of post-earthquake risk, first post-earthquake risk assessment method of advanced foreign countries including US, New Zealand and Japan are compared, and post-earthquake evaluation activities in 9.12 Earthquake and 11.15 Earthquake are analyzed. From the results, it is needed to expand the adapted building and structure types and strengthen the earthquake disaster response capacity of local government.

• Geomechanics and Engineering
• /
• v.32 no.4
• /
• pp.453-462
• /
• 2023

Designing pile foundations subjected to the uplift forces such as buildings, oil platforms, and anchors is becoming increasingly concerned. In this paper, the conceptual design of a new type of driven piles called expanding pile is presented and assessed. Some grooves have been created in the shaft of the novel pile, and some moveable arms have been designed at the pile tip. At first, static analyses using the finite element method were performed to evaluate the effectiveness of the innovative pile on the axial bearing capacity. Then its effect on seismic behavior of moment frame is considered. Results show that the expanding arms were provided an ideal anchorage system because of the soil's noticeable locking-up effect increasing uplift bearing capacity. For example at the end of the static tensile loading procedure, displacement decrement up to 55 percent is observed. In addition, comparing the uplift bearing capacity of the usual and new pile with different lengths in sand and clay layers shows noticeable effect and sharp increase up to about two times especially in longer piles. Besides, a sensible reduction in the seismic response and the stresses in the beam-column connection between 23-36 percent are achieved that ensures better seismic behavior of the structures.

• Journal of the Korean Society of Safety
• /
• v.26 no.2
• /
• pp.62-69
• /
• 2011

This paper presents a new simple two-dimensional frame finite element able to accurately estimate the load-carrying capacity of reinforced concrete beams flexurally strengthened externally bonded fiber reinforced polymer (FRP) strips and plates. The proposed analysis model considers distributed plasticity with layer-discretization of the cross-sections and the bond-slip behavior of epoxy layer. The proposed model is used to predict the load-carrying capacity and the applied load-midspan deflection response of RC beams subjected to bending loading. Numerical simulations and experimental measurements are compared based on numerous tests available in the literature and published by different authors. The numerically simulated response agree remarkably well with the corresponding experimental results. Thus, the proposed model is suitable for efficient and accurate modeling and analysis of flexural strengthening of RC beams with externally bonded FRP sheets/plates and for practical use in design-oriented parametric studies.

• Journal of Animal Science and Technology
• /
• v.63 no.5
• /
• pp.984-997
• /
• 2021

This study sought to evaluate DNA damage and repair in porcine postovulatory aged oocytes. The DNA damage response, which was assessed by H2A.X expression, increased in porcine aged oocytes over time. However, the aged oocytes exhibited a significant decrease in the expression of RAD51, which reflects the DNA damage repair capacity. Further experiments suggested that the DNA repair ability was suppressed by the downregulation of genes involved in the homologous recombination (HR) and nonhomologous end-joining (NHEJ) pathways. The expression levels of the cell cycle checkpoint genes, CHEK1 and CHEK2, were upregulated in porcine aged oocytes in response to induced DNA damage. Immunofluorescence results revealed that the expression level of H3K79me2 was significantly lower in porcine aged oocytes than in control oocytes. In addition, embryo quality was significantly reduced in aged oocytes, as assessed by measuring the cell proliferation capacity. Our results provide evidence that DNA damage is increased and the DNA repair ability is suppressed in porcine aged oocytes. These findings increase our understanding of the events that occur during postovulatory oocyte aging.

• Biomolecules & Therapeutics
• /
• v.32 no.2
• /
• pp.183-191
• /
• 2024

The Unfolded Protein Response (UPR) serves as a critical cellular mechanism dedicated to maintaining protein homeostasis, primarily within the endoplasmic reticulum (ER). This pathway diligently responds to a variety of intracellular indicators of ER stress with the objective of reinstating balance by diminishing the accumulation of unfolded proteins, amplifying the ER's folding capacity, and eliminating slow-folding proteins. Prolonged ER stress and UPR irregularities have been linked to a range of neuropsychiatric disorders, including major depressive disorder, bipolar disorder, and schizophrenia. This review offers a comprehensive overview of the UPR pathway, delineating its activation mechanisms and its role in the pathophysiology of neuropsychiatric disorders. It highlights the intricate interplay within the UPR and its profound influence on brain function, synaptic perturbations, and neural developmental processes. Additionally, it explores evolving therapeutic strategies targeting the UPR within the context of these disorders, underscoring the necessity for precision and further research to effective treatments. The research findings presented in this work underscore the promising potential of UPR-focused therapeutic approaches to address the complex landscape of neuropsychiatric disorders, giving rise to optimism for improving outcomes for individuals facing these complex conditions.

• Earthquakes and Structures
• /
• v.7 no.5
• /
• pp.779-796
• /
• 2014

This experimental investigation was conducted to examine the behavior and response of high-strength material (HSM) reinforced concrete (RC) columns under combined high-axial and cyclic-increasing lateral loads. All the columns use high-strength concrete ($f_c{^{\prime}}$=100MPa) and high-yield strength steel ($f_y$=685MPa and $f_y$=785MPa) for both longitudinal and transverse reinforcements. A total of four full-scale HSM columns with amount of transverse reinforcement equal to 100% more than that required by earthquake resistant design provisions of ACI-318 were tested. The key differences among those four columns are the spacing and configuration of transverse reinforcements. Two different constant axial loads, i.e. 60% and 30% of column axial load capacity, were combined with cyclically-increasing lateral loads to impose reversed curvatures in the columns. Test results show that columns under 30% of axial load capacity behaved much more ductile and had higher lateral deformational capacity compared to columns under the 60% of axial load capacity. The columns using closer transverse reinforcement spacing have slightly higher ductility than columns with larger spacing.