scholarly journals Inspection and rehabilitation of old White Nile steel bridge substructure

2021 ◽  
Vol 9 (1) ◽  
pp. 57-64
Author(s):  
Eltayeb Elrayah Khalafalla ◽  
Ali Hussein Mohammed Ali
Keyword(s):  
Field Tests ◽  
Hardness Test ◽  
Life Time ◽  
Steel Plates ◽  
Bending Test ◽  
Steel Bridge ◽  
Concrete Core ◽  
Assessment Study ◽  
White Nile ◽  
Cathodic Protection System

The substructure of The Old White Nile Bridge consists of steel tubular piers (steel casings filled with concrete) supported by caissons drilled into the sandstone. This steel bridge which had been completed in 1928, was investigated and assessed for integrity and safety. The inspection and investigation of the piers covered visual inspection, field tests and laboratory tests. Steel plates tests included microstructure analysis for steel, tension test, bending test and hardness test to determine the chemical and mechanical properties, whereas concrete core tests were conducted for determining cubes crushing strength of concrete. The inspection tests and assessment study revealed that most of piers steel casing suffered from high corrosion problems. Thus, due to corrosion the thickness of the casing plate, which was originally 5 mm for fixed piers and 7mm for swing span pier, was reduced severely to about 1.5 mm or even in some cases to about only 0.4 mm (in the swing span piers). In some cases holes appeared in the casing plates indicating that the steel was corroded totally and all the thickness was lost. Then, the Foundation caissons which were permanently under water or fully buried in the ground were found sound and suffer no problem of corrosion. No sign of differential settlement was observed. The materil tests performed showed that the steel exceeded its expected life time and have lost their weld-ability. Moreover, cathodic protection system which had originally provided previously to protect against corrosion found damaged and not functioning. Therefore, this paper presents the results of inspection and rehabilitation of the bridge substructure.  

Weldability Studies on the Replacement Repair Welded Joints of a Damaged Steel Bridge

2008 ◽  
Vol 580-582 ◽  
pp. 655-658 ◽  
Author(s):  
Kyong Ho Chang ◽  
H.C. Park ◽  
Chin Hyung Lee ◽  
Gab Chul Jang ◽  
Sang Hyong Lee ◽  
...  
Keyword(s):  
Welded Joints ◽  
Welding Process ◽  
Hardness Test ◽  
Steel Plates ◽  
Composition Analysis ◽  
Steel Bridge ◽  
Repair Welding ◽  
Repair Method ◽  
Flux Cored Arc Welding ◽  
Safety And Reliability

In recent years, the replacement repair welding, through which damaged bridges are repaired by replacing of the damaged sections with new steel plates through cutting and welding under in-service conditions, has been highlighted for its brilliant features i.e. it can be achieved without incurring traffic dislocation. However, the validity of the repair method is not fully verified because of its lack of safety and reliability. Moreover, repair method by welding inevitably involves cutting and welding process, and the weldability of the replacement repair welded joints has not yet been clarified. In this paper, the weldability of the replacement-repair-welded joints was investigated in order to improve reliability in the repair welded joints of the aged steel bridge. A Steel plate was extracted from the steel bridge after the period of prolonged service, and was welded with a new plate, using replacement repair welding technique, in order to construct a specimen. Flux Cored Arc Welding (FCAW) process was used to fabricate the double "V" butt joints. Welded joints were characterized on the basis of chemical composition analysis, hardness test and micro-structural analysis.

Flexural Resistance of Steel-Coconut Shell Concrete-Steel Composite Beam with Normal and J-Hook Shear Studs

2020 ◽  
Vol 12 (9) ◽  
Author(s):  
Lakshmi Thangasamy ◽  
◽  
Gunasekaran Kandasamy ◽  
Keyword(s):  
Concrete Strength ◽  
Steel Plates ◽  
Coconut Shell ◽  
Core Material ◽  
River Sand ◽  
Concrete Core ◽  
Conventional Concrete ◽  
Moment Capacity ◽  
The Moment ◽  
Core Concrete

Many researches on double skin sandwich having top and bottom steel plates and in between concrete core called as steel-concrete-steel (SCS) were carried out by them on this SCS type using with different materials. Yet, use of coconut shell concrete (CSC) as a core material on this SCS form construction and their results are very limited. Study investigated to use j-hook shear studs under flexure in the concept of steel-concrete-steel (SCS) in which the core concrete was CSC. To compare the results of CSC, the conventional concrete (CC) was also considered. To study the effect of quarry dust (QD) in its place of river sand (RS) was also taken. Hence four different mixes two without QD and two with QD both in CC and CSC was considered. The problem statement is to examine about partial and fully composite, moment capacity, deflection and ductility properties of CSC used SCS form of construction. Core concrete strength and the j-hook shear studs used are influences the moment carrying capacity of the SCS beams. Use of QD in its place of RS enhances the strength of concrete produced. Deflections predicted theoretically were compared with experimental results. The SCS beams showed good ductility behavior.

scholarly journals Quality assessment of brands of erythromycin stearate tablets marketed in Abuja, Nigeria

2020 ◽  
Vol 17 (1) ◽  
pp. 29-33
Author(s):  
Kudirat B. Mustapha ◽  
Marlene D. Ekpo ◽  
Isa H. Galadima ◽  
Rukaiyatu A. Kirim ◽  
Olubukola A. Odeniran ◽  
...  
Keyword(s):  
Quality Assessment ◽  
Quality Evaluation ◽  
Hardness Test ◽  
Spectrophotometric Analysis ◽  
Assessment Study ◽  
Uniformity Test ◽  
Quality Assessment Study ◽  
Percentage Weight ◽  
Pharmaceutical Industries ◽  
Erythromycin Stearate

Erythromycin is one of the most frequently prescribed antibiotics. With the increasing number of pharmaceutical industries, the possibility of  purchasing a substandard product is on the high side. This makes it necessary to subject various commercially produced brands of erythromycin to quality evaluation in order to ascertain the quality. In this quality assessment study, six (6) brands of erythromycin tablets were subjected to physicochemical assay using standard physical methods and UV/VIS spectrophotometric analysis at 480 nm. The calibration curve for reference erythromycin was linear over a concentration range of 10-100 μg/ml with a correlation coefficient (R2) of 0.999. All the brands had standard deviation of weight greater than ±5 for the weight uniformity test. 66.67% of the brands passed the test for content of active ingredient. 83.33% of the brands examined passed the hardness test. All the brands failed the friability test because the percentage weight loss are greater than 1% as specified in the official book. Keywords: Erythromycin stearate; Tablets; Brands; Pharmaceutical Industries

scholarly journals Experimental Study on Laser-MIG Hybrid Welding of Thick High-Mn Steel Plate for Cryogenic Tank Production

2021 ◽  
Vol 9 (6) ◽  
pp. 604
Author(s):  
Du-Song Kim ◽  
Hee-Keun Lee ◽  
Woo-Jae Seong ◽  
Kwang-Hyeon Lee ◽  
Hee-Seon Bang
Keyword(s):  
Low Temperature ◽  
Yield Strength ◽  
Steel Plate ◽  
Weld Zone ◽  
Base Material ◽  
Hardness Test ◽  
Steel Plates ◽  
Hybrid Welding ◽  
Temperature Impact ◽  
Mn Steel

The International Maritime Organization has recently updated the ship emission standards to reduce atmospheric contamination. One technique for reducing emissions involves using liquefied natural gas (LNG). The tanks used for the transport and storage of LNG must have very low thermal expansion and high cryogenic toughness. For excellent cryogenic properties, high-Mn steel with a complete austenitic structure is used to design these tanks. We aim to determine the optimum welding conditions for performing Laser-MIG (Metal Inert Gas) hybrid welding through the MIG leading and laser following processes. A welding speed of 100 cm/min was used for welding a 15 mm thick high-Mn steel plate. The welding performance was evaluated through mechanical property tests (tensile and yield strength, low-temperature impact, hardness) of the welded joints after performing the experiment. As a result, it was confirmed that the tensile strength was slightly less than 818.4 MPa, and the yield strength was 30% higher than base material. The low-temperature impact values were equal to or greater than 58 J at all locations in the weld zone. The hardness test confirmed that the hardness did not exceed 292 HV. The results of this study indicate that it is possible to use laser-MIG hybrid welding on thick high-Mn steel plates.

scholarly journals Effect of microwave disinfection on physical and mechanical properties of acrylic resins

2008 ◽  
Vol 19 (4) ◽  
pp. 348-353 ◽  
Author(s):  
Rafael Leonardo Xediek Consant ◽  
Erica Brenoe Vieira ◽  
Marcelo Ferraz Mesquita ◽  
Wilson Batista Mendes ◽  
João Neudenir Arioli-Filho
Keyword(s):  
Flexural Strength ◽  
Room Temperature ◽  
Physical And Mechanical Properties ◽  
Hardness Test ◽  
Knoop Hardness ◽  
Microwave Energy ◽  
Bending Test ◽  
Acrylic Resins ◽  
Strength Tests ◽  
The Impact

This study evaluated the effect of microwave energy on the hardness, impact strength and flexural strength of the Clássico, Onda-Cryl and QC-20 acrylic resins. Aluminum die were embedded in metallic or plastic flasks with type III dental stone, in accordance with the traditional packing technique. A mixing powder/liquid ratio was used according to the manufacturer's instructions. After polymerization in water batch at 74ºC for 9 h, boiling water for 20 min or microwave energy at 900 W for 10 min, the specimens were deflasked after flask cooling at room temperature, and submitted to finishing. Specimens non-disinfected and disinfected by microwave irradiation were submitted to hardness, impact and flexural strength tests. Each specimen was immersed in distilled water and disinfected in a microwave oven calibrated to 650 W for 3 min. Knoop hardness test was performed with 25 g load for 10 s, impact test was carried out using the Charpy system with 40 kpcm, and 3-point bending test with a crosshead speed of 0.5 mm/min until fracture. Data were submitted to statistical analysis by ANOVA and Tukey's test (?=0.05). Disinfection by microwave energy decreased the hardness of Clássico and Onda-Cryl acrylic resins, but no effect was observed on the impact and flexural strength of all tested resins.

Mechanical Properties and Microstructure of LR Grade a Thick Plate Welded by Double Side Gas Metal Arc Welding

2016 ◽  
Vol 851 ◽  
pp. 168-172
Author(s):  
Yustiasih Purwaningrum ◽  
Triyono ◽  
Tegar Rileh Argihono ◽  
Ryan Sutrisno
Keyword(s):  
Mechanical Properties ◽  
Gas Flow ◽  
Gas Metal Arc Welding ◽  
Charpy Impact ◽  
Hardness Test ◽  
Charpy Impact Test ◽  
Optical Microscope ◽  
Steel Plates ◽  
Weld Metals ◽  
Metal Arc Welding

Mechanical and microstructure of double side weld with various angle groove was studied in this research. LR Gr A steel plates (12 mm thickness) were welded using GMAW with corresponding 180 A, 23 V, and 20 l/min respectively with current, voltage, and gas flow. Shielding gas and filler metals used are argon and ER 70S-6. The angle groove that used were 20⁰, 40⁰ and 60⁰. The measured of mechanical properties with regard to hardness, toughness and strength using, Vickers hardness test, Charpy impact test and tensile test respectively The microstructure examined with optical microscope. The results show that the highest hardness values found in welds with groove angle 40ͦ. The transition temperatures of weld metals are at temperatures between -20°C to 0°C. Weld metals with all variations of the groove angle has a value of less than 0.1 mmpy. Microstructure of base metals and HAZ were ferrite and pearlite. While the microstructure of weld metals are accicular ferrite, grain boundary ferrite and Widmanstatten ferrite.

Hydrogen Induced Stress Cracking of Superduplex Steels: Effect of Operation Temperature

2018 ◽  
Author(s):  
Lars M. Haldorsen ◽  
Bård Nyhus ◽  
Gisle Rørvik
Keyword(s):  
Cathodic Protection ◽  
Life Time ◽  
Oil Companies ◽  
Stress Cracking ◽  
Operation Temperature ◽  
Induced Stress ◽  
Duplex Steel ◽  
Future Revision ◽  
Cathodic Protection System ◽  
Guidelines And Recommendations

Duplex stainless steel has been used on subsea facilities since the mid 80-ties. The experiences with these materials have been relative good and only a few failures have been reported. However, BP and Shell experience some serious cracking of duplex steel in the mid 90-ties and in beginning of the century. The root cause of these failures was identified to be Hydrogen Induced Stress Cracking, HISC, where the hydrogen source was the cathodic protection system of the subsea facility. These and other similar failures resulted establishment of Joint Industry Projects, JIPs with financial and technical contribution from leading oil companies, contractors, material suppliers and research institutions as TWI, SINTEF and DNVGL. The objective of the JIPs was to establish practical usage limits for duplex stainless steels. The JIPs resulted in a recommended practice “DNV-RP-F112 - Design of duplex stainless subsea equipment exposed to cathodic protection.” This document minimized the failure rate of duplex steel components used subsea. However, since duplex steels components have been used on subsea facilities long before the guidelines and recommendations were issued, there are lot of components presently in use that may be overloaded compared to guidelines and recommendations. As a part of life time extension of one of Statoil’s long time producing fields, a HISC re-calculation of spools connecting SPSs to infield pipelines showed that many of the spools were exposed to stresses above the recommended stresses given in DNV-RP-F112. Since these recommendations were primarily based on testing at ambient seabed temperature (4°C), Statoil, together with SINTEF, started in 2016 a project where the aim was to evaluate the resistance against HISC as an effect of the operation temperature. The results of this project show that the critical net section stress/AYS (HISC resistance) increases with increasing temperature. Based on this, the before mentioned spools can be considered safe even though the spools are exposed to stresses above the recommendations in DNV-RP-F112. Further, the investigations show that the guidelines and recommendations given in DNV-RP-F112 may be conservative for temperatures above 4°C. It is therefore recommended to perform more testing to confirm and incorporate the findings from the present investigation in future revision of DNV-RP-F112.

scholarly journals Utilization of rapid prototyping technology for the fabrication of an orthopedic shoe inserts for foot pain reprieve using thermo-softening viscoelastic polymers: A novel experimental approach

2020 ◽  
Vol 53 (3-4) ◽  
pp. 519-530
Author(s):  
Shubham Sharma ◽  
Jujhar Singh ◽  
Harish Kumar ◽  
Abhinav Sharma ◽  
Vivek Aggarwal ◽  
...  
Keyword(s):  
Rapid Prototyping ◽  
Thermoplastic Polyurethane ◽  
Research Work ◽  
Testing Machine ◽  
Three Dimensional ◽  
Hardness Test ◽  
Thermoplastic Elastomer ◽  
Bending Test ◽  
Foot Orthosis ◽  
Orthotic Insoles

This research work has been completed by concentrating on the structure of inserts for foot orthosis fabricated by utilizing rapid prototyping technology. Thermoplastic elastomer and thermoplastic polyurethane are the most commonly used materials that are being used in customized three-dimensional printed orthotic insoles, which are comfortable and prevent the user in many foot disorders. Thermo-softening viscoelastic polymers, explicitly Filaflex and Ninjaflex, have been printed by utilizing Flash Forge three-dimensional printers to evaluate the mechanical properties of specimens with alterations of the percentage rate fill-up design replicas. The results are compared on the basis of hardness test, flexural/bending test, and tensile test using Durometer and Universal Testing Machine (UTM). It has also been observed that the most significant effecting factor is infill density.

scholarly journals Effect of Gamma Radiation and Endodontic Treatment on Mechanical Properties of Human and Bovine Root Dentin

2016 ◽  
Vol 27 (6) ◽  
pp. 670-674 ◽  
Author(s):  
Veridiana Resende Novais ◽  
Priscilla Barbosa Ferreira Soares ◽  
Carlla Martins Guimarães ◽  
Laís Rani Sales Oliveira Schliebe ◽  
Stella Sueli Lourenço Braga ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Flexural Strength ◽  
Gamma Radiation ◽  
Hardness Test ◽  
Knoop Hardness ◽  
Endodontic Treatment ◽  
Bending Test ◽  
Human Teeth ◽  
Significant Difference ◽  
Root Dentin

Abstract This study evaluated the effect of gamma radiation and endodontic treatment on the microhardness and flexural strength of human and bovine root dentin. Forty single-rooted human teeth and forty bovine incisor teeth were collected, cleaned and stored in distilled water at 4 °C. The human and bovine teeth were divided into 4 groups (n=10) resulting from the combination of two study factors: first, regarding the endodontic treatment in 2 levels: with or without endodontic treatment; and second, radiotherapy in two levels: with or without radiotherapy by 60 Gy of Co-60 gamma radiation fractioned into 2 Gy daily doses five days per week. Each tooth was longitudinally sectioned in two parts; one-half was used for the three-point bending test and the other for the Knoop hardness test (KHN). Data were analyzed by 3-way ANOVA and Tukey HSD test (α=0.05). No significant difference was found for flexural strength values. The human dentin had significantly higher KHN than the bovine. The endodontic treatment and radiotherapy resulted in significantly lower KHN irrespective of tooth origin. The results indicated that the radiotherapy had deleterious effects on the microhardness of human and bovine dentin and this effect is increased by the interaction with endodontic therapy. The endodontic treatment adds additional negative effect on the mechanical properties of radiated tooth dentin; the restorative protocols should be designed taking into account this effect.

scholarly journals Screw head plugs increase the fatigue strength of stainless steel, but not of titanium, locking plates

2018 ◽  
Vol 7 (12) ◽  
pp. 629-635 ◽  
Author(s):  
L-W. Hung ◽  
C-K. Chao ◽  
J-R. Huang ◽  
J. Lin
Keyword(s):  
Stainless Steel ◽  
Fatigue Strength ◽  
Steel Plates ◽  
Bending Test ◽  
Type I ◽  
Locking Plates ◽  
Type Ii ◽  
Screw Head ◽  
Type Iii ◽  
Four Point Bending

ObjectivesScrew plugs have been reported to increase the fatigue strength of stainless steel locking plates. The objective of this study was to examine and compare this effect between stainless steel and titanium locking plates.MethodsCustom-designed locking plates with identical structures were fabricated from stainless steel and a titanium alloy. Three types of plates were compared: type I unplugged plates; type II plugged plates with a 4 Nm torque; and type III plugged plates with a 12 Nm torque. The stiffness, yield strength, and fatigue strength of the plates were investigated through a four-point bending test. Failure analyses were performed subsequently.ResultsFor stainless steel, type II and type III plates had significantly higher fatigue strength than type I plates. For titanium, there were no significant differences between the fatigue strengths of the three types of plates. Failure analyses showed local plastic deformations at the threads of screw plugs in type II and type III stainless steel plates but not in titanium plates.ConclusionThe screw plugs could increase the fatigue strength of stainless steel plates but not of titanium plates. Therefore, leaving screw holes open around fracture sites is recommended in titanium plates. Cite this article: L-W. Hung, C-K. Chao, J-R. Huang, J. Lin. Screw head plugs increase the fatigue strength of stainless steel, but not of titanium, locking plates. Bone Joint Res 2018;7:629–635. DOI: 10.1302/2046-3758.712.BJR-2018-0083.R1.

Sign in / Sign up

Export Citation Format

Share Document