Reliability-based assessment of damaged concrete buildings

Sakka, Zafer I.,Assakkaf, Ibrahim A.,Qazweeni, Jamal S. Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.6

Damages in concrete structures due to aging and other factors could be a serious and immense matter. Making the best selection of the most viable and practical repairing and strengthening techniques are relatively difficult tasks using traditional methods of structural analyses. This is due to the fact that the traditional methods used for assessing aging structure are not fully capable when considering the randomness in strength, loads and cost. This paper presents a reliability-based methodology for assessing reinforced concrete members. The methodology of this study is based on probabilistic analysis, using statistics of the random variables in the performance function equations. Principles of reliability updating are used in the assessment process, as new information is taken into account and combined with prior probabilistic models. The methodology can result in a reliability index ${\beta}$ that can be used to assess the structural component by comparing its value with a standard value. In addition, these methods result in partial safety factor values that can be used for the purpose of strengthening the R/C elements of the existing structure. Calculations and computations of the reliability indices and the partial safety factors values are conducted using the First-order Reliability Method and Monte Carlo simulation.

Numerical investigation on the structural behavior of two-way slabs reinforced with low ductility steel

Sakka, Zafer,Gilbert, R. Ian Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.3

A numerical investigation of the impact of steel ductility on the strength and ductility of two-way corner and edge-supported concrete slabs containing low ductility welded wire fabric is presented. A finite element model was developed for the investigation and the results of a series of concurrent laboratory experiments were used to validate the numerical solution. A parametric investigation was conducted using the numerical model to investigate the various factors that influence the structural behavior at the strength limit state. Different values of steel uniform elongation and ultimate to yield strength ratios were considered. The results are presented and evaluated, with emphasis on the strength, ductility, and failure mode of the slabs. It was found that the ductility of the flexural reinforcement has a significant impact on the ultimate load behavior of two-way corner-supported slabs, particularly when the reinforcement was in the form of cold drawn welded wire fabric. However, the impact of the low ductility WWF has showed to be less prominent in structural slabs with higher levels of structural indeterminacy. The load-deflection curves of corner-supported slabs containing low ductility WWF are brittle, and the slabs have little ability to undergo plastic deformation at peak load.

Fabrication of Textured Nano-composite by Slip Casting in a High Magnetic Field and Reaction Sintering

Sakka Yoshio,Saito Sho,Honda Atsushi,Suzuki Tohru S.,Moriyoshi Yusuke 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1

We have demonstrated that textured nanocomposites can be fabricated by slip casting followed by partial oxidation. reaction sintering of mixed suspensions of and SiC powders in a high magnetic field. The sintered density was changed by the degree of oxidation at 1200C and 1300C. The degree of orientation of alumina in the nanocomposite was examined on the basis of the X-ray diffraction patterns and scanning electron micrographs. It is confirmed that aluminaoriented nanocomposites were fabricated. The three-point bending strength at room temperature was observed for the nanocomposites.

Antimicrobial Activity of Basil, Oregano, and Thyme Essential Oils

( Hercules Sakkas ),( Chrissanthy Papadopoulou ) 한국미생물 · 생명공학회 2017 Journal of microbiology and biotechnology Vol.27 No.3

For centuries, plants have been used for a wide variety of purposes, from treating infectious diseases to food preservation and perfume production. Presently, the increasing resistance of microorganisms to currently used antimicrobials in combination with the appearance of emerging diseases requires the urgent development of new, more effective drugs. Plants, due to the large biological and structural diversity of their components, constitute a unique and renewable source for the discovery of new antibacterial, antifungal, and antiparasitic compounds. In the present paper, the history, composition, and antimicrobial activities of the basil, oregano, and thyme essential oils are reviewed.

Numerical investigation on the structural behavior of two-way slabs reinforced with low ductility steel

Zafer Sakka,R. Ian Gilbert 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.3

A numerical investigation of the impact of steel ductility on the strength and ductility of two-way corner and edge-supported concrete slabs containing low ductility welded wire fabric is presented. A finite element model was developed for the investigation and the results of a series of concurrent laboratory experiments were used to validate the numerical solution. A parametric investigation was conducted using the numerical model to investigate the various factors that influence the structural behavior at the strength limit state. Different values of steel uniform elongation and ultimate to yield strength ratios were considered. The results are presented and evaluated, with emphasis on the strength, ductility, and failure mode of the slabs. It was found that the ductility of the flexural reinforcement has a significant impact on the ultimate load behavior of two-way corner-supported slabs, particularly when the reinforcement was in the form of cold drawn welded wire fabric. However, the impact of the low ductility WWF has showed to be less prominent in structural slabs with higher levels of structural indeterminacy. The load-deflection curves of corner-supported slabs containing low ductility WWF are brittle, and the slabs have little ability to undergo plastic deformation at peak load.

Edge-clamped two-way slabs containing low-ductility steel

Zafer Sakka,R. Ian Gilbert 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.78 No.6

This paper describes a series of full range load tests on two-way, edge-clamped reinforced concrete slab panels containing either Class L WWF or Class N deformed bars. Five rectangular slab panels were tested each with two adjacent fully restrained edges and two free edges. A point support was included under the corner of each panel at the intersection of the two free edges. Each slab specimen was loaded by four transverse loads applied symmetrically in the mid-panel region by a deformation-controlled actuator in a stiff testing frame. The continuous edge supports were provided by clamping two adjacent edges in a carefully designed and constructed testing frame. The slabs were instrumented with load cells to measure applied forces and reactions, strain gauges to measure strain in the steel reinforcement and on the concrete surfaces, linear variable displacement transducers and lasers to measure deflections at all stages of loading. The results of the tests are presented and evaluated, with particular emphasis on the strength, ductility and failure mode of the slabs.

Using Evolutionnary algorithms to Design Mobile Manipulators

S. Sakka,O. Chocron 제어로봇시스템학회 2001 제어로봇시스템학회 국제학술대회 논문집 Vol.2001 No.10

Condition assessment of aged underground water tanks-Case study

Zafer Sakka,Ali Saleh,Thamer Al-Yaqoub,Hasan Karam,Shaikha AlSanad,Jamal Al-Qazweeni,Mohammad Mosawi,Husain Al-Baghli 국제구조공학회 2024 Structural Engineering and Mechanics, An Int'l Jou Vol.90 No.5

This paper presents the methodology and results for the investigation of the structural safety of 40 aged underground water tanks to support the weight of photovoltaic (PV) systems that were supposed to be placed on their roof reinforced concrete (RC) slabs. The investigation procedure included (1) review of available documents; (2) visual inspection of the roof RC slabs; (3) carrying out a series of nondestructive (ND) tests; and (4) analysis of results. Out of the 40 tanks, eleven failed the visual inspection phase and were discarded from further investigation. The roof RC slabs of the tanks that passed the visual inspection were subjected to a series of ND tests that included infrared thermography, impact echo, ultrasonic pulse velocity (UPV), Schmidt hammer, concrete core compressive strength, and water-soluble chloride content. The NDT results proved that eight more tanks were not suitable to support the PV systems. Based on the results of the visual inspection and testing, a probabilistic decision-making criterion was established to reach a decision regarding the structural integrity of the roof slabs. The study concluded that the condition of the drainage filter was essential in protecting the tanks and its intact presence can be used as a strong indication of the structural integrity of the roof RC slabs.

Reliability-based assessment of damaged concrete buildings

Zafer I. Sakka,Ibrahim A. Assakkaf,Jamal S. Qazweeni 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.6

Damages in concrete structures due to aging and other factors could be a serious and immense matter. Making the best selection of the most viable and practical repairing and strengthening techniques are relatively difficult tasks using traditional methods of structural analyses. This is due to the fact that the traditional methods used for assessing aging structure are not fully capable when considering the randomness in strength, loads and cost. This paper presents a reliability-based methodology for assessing reinforced concrete members. The methodology of this study is based on probabilistic analysis, using statistics of the random variables in the performance function equations. Principles of reliability updating are used in the assessment process, as new information is taken into account and combined with prior probabilistic models. The methodology can result in a reliability index β that can be used to assess the structural component by comparing its value with a standard value. In addition, these methods result in partial safety factor values that can be used for the purpose of strengthening the R/C elements of the existing structure. Calculations and computations of the reliability indices and the partial safety factors values are conducted using the First-order Reliability Method and Monte Carlo simulation.

Dehydroepiandrosterone and Erectile Function: A Review

Ahmed I. El-Sakka 대한남성과학회 2018 The World Journal of Men's Health Vol.36 No.3

To review the contemporary knowledge regarding the dehydroepiandrosterone and erectile function. Medline was reviewed for English-language journal articles spanning the time between January 1990 and December 2017, using the terms ‘erectile function’, ‘dehydroepiandrosterone’. We used original articles and review articles that found to be relevant to the purpose of this review. Criteria included all pertinent review articles, randomized controlled trials with tight methodological design, cohort studies and retrospective analyses. We also manually revised references from selected articles. Several interesting studies have addressed the age-related decline in dehydroepiandrosterone levels with many age-related phenomena or deterioration in various physiological functions. Particularly, aging; neurological functions including decreased well-being, cognition, and memory; increased depression, decreased bone mineral density, obesity, diabetes, increased cardiovascular morbidity, erec-tile dysfunction (ED), and decreased libido. Supporting this result, some trials of dehydroepiandrosterone supplementation in healthy, middle-aged, and elderly subjects have reported improvements in different aspects of well-being. Several studies had demonstrated that dehydroepiandrosterone level is declined as a part of aging. Large-scale well-designed prospective studies are warranted to better define indications and therapeutic implications of dehydroepiandrosterone in men with ED.