Behaviour of Shear Critical RC Beams with Corroded Longitudinal Steel Reinforcement

This thesis discusses the results of an experimental program designed to investigate the effect of corrosion on the behaviour of shear critical reinforced concrete (RC) beams. The results of twenty RC beams (ten deep beams and ten slender beams) are described and discussed. The test variables included: corrosion level (2.5%, 5% and 7.5%) and existence of stirrups (beams without stirrups and beams with stirrups). The feasibility of repairing the corroded shear critical RC beams with CFRP laminates was also investigated. Sixteen specimens were corroded using an accelerated corrosion technique whereas four specimens acted as control un-corroded. Following the corrosion phase, all specimens were tested to failure under three point bending. Test results revealed that the corrosion does not adversely affect the behaviour of shear critical RC beams rather it improves their behaviour. It was found that corrosion changed the failure mode of the corroded beams. The control un-corroded deep beams (beams with and without stirrups) failed in shear-compression failure whereas corroded deep beams (beams with and without stirrups) failed by splitting of the compression strut. The control un-corroded slender beams (beams with and without stirrups) failed in diagonal tension failure whereas the corroded slender beams failed in anchorage failure (beams without stirrups) and flexural failure (beams with stirrups). The analysis of the results showed that corrosion changed the load transfer mechanism and the change of failure mode was associated with the mechanism. The load transfer mechanism changed from a combination of beam and arch action in the control un-corroded deep beams to pure arch action in the corroded deep beams. The load transfer mechanism changed from pure beam action in the control un-corroded slender beams to pure arch action in the corroded slender beams. Two strut and tie models are proposed: one for corroded deep beams and one for corroded slender beams. The ultimate loads of the corroded beams were predicted using these struts and tie models and compared with the experimental results. A very good correlation was found between predicted and experimental results

Behaviour of Shear-Critical Reinforced Concrete Beams Strengthened with Fiber Reinforced Cementitious Mortar

Extensive research has been conducted on strengthening of shear-critical reinforced concrete (RC) beams, particularly using fiber reinforced polymer (FRP) strengthening systems. This previous research has helped to better understand the behaviour of shear strengthening systems and has improved the performance of existing shear strengthening systems. However, there is still a potential to further improve upon the performance of existing shear strengthening systems. A cement-based composite system is an innovative strengthening system that has similar benefits (such as light weight, ease of installation and non-corroding) to FRP systems, but overcomes some of the draw backs (such as poor compatibility with concrete substrate, lack of vapour permeability and fire resistance) of using epoxy as bonding agent in FRP systems. A cement-based composite replaces the epoxy with cementitious mortar and the fiber sheets with fabric or grids. The current study presents the results of an experimental study conducted to investigate the effectiveness of cement-based composite systems in comparison to an existing epoxy-based system (carbon fiber reinforced polymer, CFRP) to strengthen shear-critical RC beams. Two types of cement-based systems were investigated in this study: carbon fiber reinforced polymer (CFRP) grid embedded in mortar (CGM) and carbon fabric reinforced cementitious mortar (CFRCM). The experimental study consisted of two phases. Phase I focused on flexural testing of seven medium-scale shear-critical reinforced concrete (RC) beams. The objective of this phase was to evaluate the potential of FRCM shear strengthening. The test variables included the type of FRCM (carbon FRCM or CFRCM and glass FRCM or GFRCM) and the strengthening scheme (side bonded vs. U-wrapped). Phase II was designed based on results of Phase I study, and it consisted of flexural testing of twenty (20) large-scale shear-critical RC beams strengthened with cement-based systems. The objective of this phase was to evaluate the effectiveness of the two types of cement-based strengthening systems in comparison to the existing epoxy-based FRP system. The test variables included: the shear span to depth ratio (slender and deep beams), amount of internal transverse steel reinforcement and type of strengthening system (CFRCM, CGM and CFRP). The results showed that the cement-based systems (CFRP grid in mortar and CFRCM) performed better compared to the epoxy-based system (CFRP sheet) in terms of the increase in shear capacity relative to the ultimate strength of the strengthening systems. The results also showed that the bond of cement–based system with the concrete substrate was sufficient that u-wrapping may not be required; the studied side-bonded systems did not exhibit signs of premature debonding. This is in contrast to most FRP fabric strengthening systems were u-wrapping is required for adequate bond. In addition, cement-based systems exhibited a better ability to control diagonal (shear) crack widths compared to the epoxy-based system tested, providing a greater reduction in diagonal crack width despite the relative lower ultimate strength and stiffness of the cement-based systems. Shear strengthening resulted in reduced shear strength contribution from stirrups. The strengthened beams with stirrups exhibited steeper shear cracks compared to control unstrengthened beams with stirrups. Similarly, the presence of stirrups reduces the shear strength contribution from strengthening. Again, the addition of stirrups results in steeper shear cracks which intersect fewer fibers tows in the strengthening system which results in a reduced shear strength contribution from strengthening layer. Lastly, the existing models to predict the ultimate load of strengthened shear-critical RC beams were evaluated and modifications to these methods were proposed

Toxicity, analgesic and sedative potential of crude extract of soil-borne phytopathogenic fungi Aspergillus flavus

Background: Aspergillus flavus  is one of the most abundant mold present around the world. The present study was conducted to investigate the acute toxicity, analgesic and sedative effect of the crude extract obtained from soil borne fungi A. flavus.Methods: The fungi was isolated from soil samples and identified morphologically and microscopically. The growth condition i.e. media, temperature, pH, and incubation period were optimized. In these optimized growth condition, A. flavus was grown in batch culture in shaking incubator. Crude contents were extracted by using ethyl acetate solvent. Crude secondary metabolites were screened for acute toxicity, analgesic and sedative effect.Results: Upon completion of the experiment, blood was collected from the tail vein of albino mice, and different haematological tests were conducted. White blood cells counts displayed a slight increase (10.6× 109/L) above their normal range (0.8–6.8 × 109/L), which may be due to the increment in the number of lymphocytes or granulocytes. However, the percentage of lymphocytes was much lower (17.7%), while the percentage of the granulocytes was higher (61.4%) than its normal range (8.6–38.9%). A reduction  in  the  mean  number  of  writhing  in  the different  test  groups  was caused by the application of the crude ethyl acetate extract through the i.p. route at different doses (50, 100, and 150 mg/kg body weight). The results of our investigation showed the EtOAc extract of A. flavus can cause a significant sedative effect in open field.Conclusion: It was concluded from the present study that the A. flavus has the potential to produce bioactive metabolites which have analgesic and sedative effect

Chattering Free Sliding Mode Control and State Dependent Kalman Filter Design for Underground Gasification Energy Conversion Process

The fluctuations in the heating value of an underground coal gasification (UCG) process limit its application in electricity generation, where a desired composition of the combustible gases is required to operate gas turbines efficiently. This shortcoming can be addressed by designing a robust control scheme for the process. In the current research work, a model-based, chattering-free sliding mode control (CFSMC) algorithm is developed to maintain a desired heating value trajectory of the syngas mixture. Besides robustness, CFSMC yields reduced chattering due to continuous control law, and the tracking error also converges in finite time. To estimate the unmeasurable states required for the controller synthesis, a state-dependent Kalman filter (SDKF) based on the quasi-linear decomposition of the nonlinear model is employed. The simulation results demonstrate that despite the external disturbance and measurement noise, the control methodology yields good tracking performance. A comparative analysis is also made between CFSMC, a conventional SMC, and an already designed dynamic integral SMC (DISMC), which shows that CFSMC yields (Formula presented.) and (Formula presented.) improvement in the root mean squared tracking error with respect to SMC and DISMC, respectively. Moreover, CFSMC consumes (Formula presented.) and (Formula presented.) less control energy as compared to SMC and DISMC, respectively

IMPACT OF LAND USE CHANGE ON CLIMATE: A CASE STUDY OF GULBERG SCHEME, LAHORE, PAKISTAN

    With embryonic pressure of climate change vulnerability, climate change adaptation and mitigation has become a sizzling issue of 21st century. The whole globe is facing perilous impacts of abrupt climate changes. In Pakistan, the concept of climate change adaptation has been promoted during the last decade. Focussing on land surface temperature, this study determined the impact of commercialization on climate by considering the case of Gulberg Scheme, Lahore. The methodology included: literature review, data collection, procurement of satellite imageries and the use of state of the art sofwares to determine the land surface temperature of various land uses. The study found that change of land use was causing significant rise in temperature. There is need to give due consideration to climate change vulnerability while formulating land use reclassification schemes. Use of green infrastructure may prove to be effective in climate change adaptation. &nbsp

The Response of Pakistan to COVID-19 and Current Situation of Disease in the Country

Background: Coronavirus 2019 (COVID-19) was reported for the first time in China and then quickly spread to other countries. In Pakistan, the first case appeared in Sindh province on February 26, 2020, and within a few weeks, more than 100 cases were reported across the country. Currently, all provinces and territories of the country are affected and cases are growing faster every day. Pakistan is among those countries that have problems with health and diagnostic facilities due to poor economic conditions. Objectives: The present review aims to highlight the emergence, spread and control of the disease in Pakistan. Furthermore, it also highlights the response of Pakistan in the management of COVID-19 outbreak, and the country's contribution in the field of science and technology for the betterment of diagnostic and treatment capabilities against the disease. Methodology: Collection of data was done through national and international forums like Covid-WHO report and COVID-19 Health advisory platform by Ministry of National Health Services Regulation. Results: The important mean for prevention is the proper use of Standard Operating Procedure (SOPs). Quarantine and isolation centers help in limiting the spread of this deadly disease. Conclusion: It is concluded that no vaccine is available for the treatment of this emerging disease so far. The only prevention is to properly and strictly follow the SOPs guidelines