Various methods for retrofitting prestressed concrete members: A critical review

Structures of a building can get exposed to adverse conditions resulting from overloading situations, which would eventually contribute to massive building degradation. The choice to repair the building structures seems to be very costly. The possible step that could be taken is by implementing a method of reinforcing and strengthening the building structures. For the past years, strengthening methods by implementing various innovative technologies has been seen to become a modern scientific topic in the fields of environmental and civil engineering study. Previous related studies on the reinforcement of pre-stressed concrete beams (PSC) by adding different elements have been observed by past researchers. The tests were carried out to evaluate the shear and flexural capacities of the building structures after the mechanisms were installed. A large number of scholars have conducted such studies with different types of interacting factors. In this study, a review will be presented by analyzing various techniques that have been implemented by multiple researchers for strengthening pre-stressed concrete beams, as well as their shear and flexure performances of the beams

Flexural strengthening of the continuous unbonded post -tensioned HSC beams by precast SIFCON laminates

Slurry Infiltrated Fiber Concrete (SIFCON) is a cementitious composite with outstanding durability and mechanical characteristics. Accordingly, the current research studies the behavior of continuous unbonded post-tensioned HSC beams that were flexural strengthened with precast SIFCON laminates. Four prestressed concrete beams with dimensions (200x300) mm and 4300 mm length were fabricated have been strengthened with 30 mm thick precast SIFCON laminates gluing with epoxy and were tested to understand the influence of their strengthening with using the various length of the laminates. The results showed that the use of precast SIFCON laminates is an effective method in enhancing the capacity of load-carrying and stiffness of continuous unbonded post-tensioned HSC beams. Used various lengths of precast SIFCON laminates in hogging and sagging regions led to positively affected by delaying the first crack appearance time of the tested beams between (56.1%-60%), Increased the ultimate flexural capacity of the test beams (36.9%-43.6%), and improving in stiffness about (153.7%-243.6%). When comparing specimens unstrengthened and strengthened, the strengthening generally leads to a reduction in the crack width in central support and mid-span regions. In other words, the crack behavior was enhanced

Faktori intenziteta napona višestrukih prslina na duraluminijumskim panelima

The aim of this thesis was to establish and demonstrate significant capacity and performances of extended finite element method (XFEM) to calculate stress intensity factors (SIFs) histories versus crack length for problems involving multiple, interacting cracks resulting from multiple site damage (MSD). The thesis includes two deferent types of a typical aero structural configuration were analyzed: the first was unstiffened flat panel made of aluminum Al 2024-T3, containing 11 holes, each of which is a site for crack growth. Analyzed model makes a unique 3D configuration with 22 cracks, propagating at the same time; the applied stresses were equal to 50,100 and 200 MPa. The computations were carried out in Morfeo/Crack for Abaqus software which relies on the implementation of XFEM. The accuracy of these computations was verified through FRANC2D/L software and superposition based approximate method. The conducted analysis showed that XFEM is efficient tool for the simulation of crack propagation even in the case of 3D configurations with MSD, and that the obtained solutions can be used for the prediction of SIFs in analyzed MSD configuration with acceptable accuracy. The second type of aero structural configuration which analyzed in this research using XFEM as following:- - The first model was unstiffened curved panel with 3 rivet holes containing 6 cracks propagating at the same time; the applied average pressure was (0.054 MPa). - The second model was unstiffened curved panel with 5 rivet holes containing 10 cracks propagating at the same time; the applied pressure was (0.054 MPa). - The third model was unstiffened curved panel with 7 rivet holes containing 14 cracks propagating at the same time; the applied average pressure was (0.054 MPa). - The forth model was unstiffened curved panel with 11 rivet holes containing 22 cracks propagating at the same time; the applied average pressure was (0.054 MPa). STRESS INTENSITY FACTORS EVALUTION AT TIPS OF MULTIPLE SITE CRACKS IN 2024-T3 ALUMINUM PANELS v - All curved panels simulations study includes the relationship between crack length and its corresponding SIFs values for every crack propagation step, Also, the study includes the effect of change fuselage diameters from 1.6m, 2.4 m, 3.2 m to 4 m on every crack of the whole models and its SIF values. - Also, the computations were carried out in Morfeo/Crack for Abaqus software which relies on the implementation of XFEM. The conducted analysis showed that XFEM is efficient tool for the simulation of crack propagation even in the case of 3D configurations with MSD, and that the obtained solutions can be used for the prediction of SIFs in analyzed MSD configuration with acceptable accuracy. - Additionally, the research includes study and comparisons of SIF values for two flat and curved panels which had the same dimensions and number of the cracks (22 cracks); and study the effect of truss by adding frames on the curved model with 22 cracks, the results showed a high decreasing in SIF values. - Finally, the research includes some SIFs calculations using standard model. The calculations are done using the empirical equations and NASGROW software. The comparisons showed excellent and accurate results using both methods.Osnovni cilj ove teze jeste demonstracija mogućnosti i značaja proširene metode konačnih elemenata (PMKE) u izračunavanju vrednosti faktora intenziteta napona (FIN) u slučajevima višestrukih međusobno uticajnih prslina nastalih kao posledica pojave višestrukih oštećenja na strukturi (VOS). Teza obuhvata analizu dve tipične aero-strukturne konfiguracije. Prva od njih je neojačana ravna ploča od duraluminijuma 2024-T3 sa 11 otvora za zakivke, od kojih svaki predstavlja mesto gde je rast prsline vrlo verovatan. Analizirani model čini jedinstvena 3D konfiguracija sa 22 prsline koje rastu istovremeno. Primenjeni naponi na krajevima ploče iznosili su 50, 100 i 200 MPa. Proračuni su sprovedeni u programu Morfeo/Crack for Abaqus koji se oslanja na implementaciju PMKE-a. Tačnost dobijenih rezultata verifikovana je pomoću softvera FRANC2D/L i približne metode zasnovane na principu superpozicije. Izvedena analiza pokazala je da je PMKE efikasan alat za simulaciju širenja prslina u slučaju ravnih 3D konfiguracija sa VOS i da se dobijena rešenja mogu koristiti za predviđanje FIN-a u analiziranoj VOS konfiguraciji sa prihvatljivom tačnošću. Druga aero-strukturna konfiguracija koja je analizirana korišćenjem PMKE u okviru ovog istraživanja sastojala se iz nekoliko modela VOS-a: - Prvi model bio je neojačani zakrivljeni panel sa 3 otvora za zakivke i ukupno 6 prslina koje se istovremeno šire iz otvora; primenjeni diferencijalni pritisak iznosio je 0,054 MPa. - Drugi model bio je neojačani zakrivljeni panel sa 5 otvora za zakivke i ukupno 10 prslina koje se istovremeno šire iz otvora; primenjeni diferencijalni pritisak iznosio je 0,054 Mpa. - Treći model bio je neojačani zakrivljeni panel sa 7 otvora za zakivke i ukupno 14 prslina koje se istovremeno šire iz otvora; primenjeni diferencijalni pritisak iznosio je 0,054 MPa. STRESS INTENSITY FACTORS EVALUTION AT TIPS OF MULTIPLE SITE CRACKS IN 2024-T3 ALUMINUM PANELS vii - Četvrti model bio je neojačani zakrivljeni panel sa 11 otvora za zakivke i ukupno 22 prsline koje se istovremeno šire iz otvora; primenjeni diferencijalni pritisak iznosio je 0,054 Mpa. Sve simulacija širenja višestrukih prslina na zakrivljenim pločama uključuju vezu između dužine prslina i odgovarajućih vrednosti FIN-a za svaki korak širenja prsline. Takođe, u istraživanju je u obzir uzet i efekat promene prečnika krivine panela, pa su vrednosti FIN-a računate za sva četiri modela u slučajevima zakrivljenosti od 1,6 m, 2,4 m, 3,2 m i 4 m. I u ovim slučajevima proračuni su vršeni u programu Morfeo/Crack for Abaqus zasnovan na PMKE. Analiza dobijenih rezultata pokazala je da je PMKE efikasan alat za simulaciju širenja prslina u slučaju 3D konfiguracija sa VOS i da se dobijena rešenja mogu koristiti za predviđanje zamornog veka sa prihvatljivom tačnošću. Pored toga, istraživanje predstavljeno u ovoj tezi uključilo je i proučavanje i upoređivanje vrednosti FIN-a u slučaju ravnog i zakrivljenog panela istih dimenzija i broja prslina (dvadeset i dve), kao i proučavanje efekta ojačanja panela dodavanjem okvira na zakrivljenom modelu sa 22 prsline. Rezultati su pokazali značajno smanjenje vrednosti FIN-a na ojačanom panelu. Najzad, istraživanje je obuhvatilo i određivanje FIN-a korišćenjem standardnih modela u svrhu evaluacije rezultata dobijenih pomoću PMKE. Proračuni su vršeni korišćenjem empirijskih jednačina i NASGRO softvera. Poređenje rezultata je pokazalo vrlo dobro poklapanje vrednosti dobijenih korišćenjem različitih metoda

Urban Characteristics of Qassim Region, An Applied Study with Rank-Size Rule According To 2010 Census

In the context of geographical quantitative revolution around the mid-20th century, George K Zipf’s model emerged, which was designed to measure sizes of cities by their population in what is known as the rank-size rule. It is important to apply that scientific base to measure sizes of cities at state level as well as level of administrative regions within the state. This is the scope of this study, which sought to apply the rule to the cities of Qassim region as a geographical unit within Kingdom of Saudi Arabia. The aim of the research is to study the urban system in Qassim and discover the urban hierarchy that runs the governorates within their administrative boundaries. The main question of the study was: What is the balanced geographical rank of the cities of Qassim region? The tools of the geographical statistical method were used to display and analyze data, where most important results were: The urban system in Qassim region is dominated by the city of Buraidah, which contains most of the geographical factors that formed the urban sites and their environmental conditions. The study concluded that the urban system in Qassim enjoys a natural formative background that depends on the fertile lands around its cities, whose characteristics are similar and their main features converge. In spite of this, the consequence of applying Zipf's rank-size rule was that: cities are far from the straight equilibrium line of the vertices of their sizes

Ultrasonography of fetal kidney length as the approach for estimation of gestational age in Sudanese

A true estimation of gestational age (GA) plays an important role in quality maternity care and scheduling the labor date. This study was to evaluate the  application of kidney length (KL) measurement to the determine GA between the 14th and 40th weeks and to compare its accuracy with that of other  fetal biometric indices. This study has been designed as a prospective descriptive cross-sectional study in Khartoum and Gezira states - Sudan. 389  Sudanese healthy pregnant women, age between 15 – 45 years were examined by ultrasound with normal and wellbeing fetuses. Linear regression  models for estimation of GA were derived from the biometric indices and kidney length. Also, stepwise regression models were constructed to detect the  best model for determining GA between 14 and 40 weeks. Comparisons were then made between the accuracy of these models in the determination of  GA. The equations derived from linear regression analysis when the individual variables were considered separately. Among the variable parameters  considered in this study, the most accurate was the kidney length with a standard error (SE) of (0.04) day, after that the biparietal diameter with (SE=0.10  day) and femur length, (SE=0.13 day). While the least accurate one was the abdominal circumference with an SE of 1.35 days. A significant correlation was  found between GA and KL (r=0.72, P<0.002). The Kidney length is the easy to identify and measure. It is the most accurate parameter for estimating  GA than other biometric indices in late 2nd and 3rd trimesters.&nbsp

A survey of microbiological quality of fish sold in two local wet markets

Eight marine fish species were obtained from two nearby wet markets (Sungei Besi and Kajang). The fish were analysed for total viable counts, coliforms, Vibrio parahaemolyticus and histamine-producingbacteria. Total viable count was determined using Plate Count Agar; coliforms using McConkey Broth; Vibrio parahaemolyticus by TCBS a garand histamine-producing bacteria were determined using Niven's media. The total counts on all fish from both markets ranged from 1rf to 1rf per gram offish, coliforms ranged from 1rJ to 1rf pergram, and all thefish examined were positive for both Vibrio parahaemolyticus and histamine-producing bacteria

Dichloridobis(2-{1-[2-(1H-indol-3-yl)ethyl­iminio]eth­yl}phenolate-κO)zinc(II)–2-{1-[2-(1H-indol-3-yl)ethyl­iminio]eth­yl}phenolate (1/2)

In the mononuclear complex mol­ecule of the title compond, [ZnCl2(C18H18N2O)2]·2C18H18N2O, the Zn atom, which lies on a twofold rotation axis, is coordinated by phenolate O atoms in a tetra­hedral coordination geometry. The coordinated Schiff base uses its indole NH donor site to form a hydrogen bond to the negatively charged phenolate O atom of the uncoordinated zwitterionic Schiff base. There is an intra­molecular N—H⋯O hydrogen bond in the coordinated and uncoordinated Schiff bases. The indole NH site of the uncoordinated Schiff base does not engage in a hydrogen-bond inter­action. The CH2—CH2 group in the uncoordinated Schiff base is disordered equally over two positions

Bis{2-[2-(1H-indol-3-yl)ethyl­imino­meth­yl]phenolato-κ2 N,O}nickel(II) N,N-dimethyl­formamide disolvate

The Ni atom in the title compound, [Ni(C17H15N2O)2]·2C3H7NO, lies on a twofold rotation axis. It is N,O-chelated by the deprotonated Schiff base 2-[2-(1H-indol-3-yl)ethyl­imino­meth­yl]phenolate ligand in a square-planar coordination environment. The mol­ecule is linked to a solvent mol­ecule by an indole–dimethyl­formamide N—H⋯O hydrogen bond

Performance of Different Tomato Genotypes in the Arid Tropics of Sudan during the Summer Season. I. Vegetative Growth

Selected, eleven tomato genotypes of diverse origin were grown in a glasshouse of the Humboldt University of Berlin, Germany during 2002 and under field conditions in Shambat, University of Khartoum, Sudan for two successive seasons (2002/2003, 2003/2004). High temperatures under field conditions resulted in poor stand and stunted growth of tomato plants. Highly significant differences were encountered among the different genotypes for leaf area, leaf area ratio, leaf weight ratio, stem fresh and dry weight and leaf fresh and dry weight. Based on results obtained from this study, the genotype ‘Summerset’ proved to be more tolerant under high temperature conditions in comparison to other investigated genotypes and may be useful for exploitation under arid tropical region of Sudan