Finite element analysis of R.C. Arches with openings strengthened by CFRP laminates

The main objective of this research is to present an analytical study to investigate the behavior and performance of reinforced concrete arches with and without openings , un-strengthened and strengthened (externally by CFRP laminates or internally by steel reinforcement)and comparison with experimental results. Twelve tested reinforced concrete semi-circular arches with and without web openings were analyzed with cross-section of (150*250mm) and inner diameter (1500mm) and outer diameter (2000mm).The variables considered in this research included: curvature forces , location of opening through profile of arch, and type of strengthening.ANSYS computer program (version 11, 2007) was performed throughout this study. Full bond was assumed between the CFRP and concrete and between steel reinforcement and concrete. Brick elements SOLID 65 and SOLID 45 was used to represent concrete element and steel plate, respectively. While LINK8 and SHELL 41 were used to represent steel reinforcement and CFRP laminates, respectively. In general, a good agreement between the finite element and experimental results has been obtained concerning load –deflection response and mode of failure , where cracking and ultimate loads with average difference about 5.83% and 3.92%,respectively

Finite element analysis of R.C. Arches with openings strengthened by CFRP laminates

The main objective of this research is to present an analytical study to investigate the behavior and performance of reinforced concrete arches with and without openings , un-strengthened and strengthened (externally by CFRP laminates or internally by steel reinforcement)and comparison with experimental results. Twelve tested reinforced concrete semi-circular arches with and without web openings were analyzed with cross-section of (150*250mm) and inner diameter (1500mm) and outer diameter (2000mm).The variables considered in this research included: curvature forces , location of opening through profile of arch, and type of strengthening.ANSYS computer program (version 11, 2007) was performed throughout this study. Full bond was assumed between the CFRP and concrete and between steel reinforcement and concrete. Brick elements SOLID 65 and SOLID 45 was used to represent concrete element and steel plate, respectively. While LINK8 and SHELL 41 were used to represent steel reinforcement and CFRP laminates, respectively. In general, a good agreement between the finite element and experimental results has been obtained concerning load –deflection response and mode of failure , where cracking and ultimate loads with average difference about 5.83% and 3.92%,respectively

Effect of (B/D) ratio on ultimate load capacity for horizontally curved box steel beam under out of plane concentrated load

The intended of this research is to prepare an analytical study to investigate the best width to depth section ratio (b/d) of horizontally curved steel box beam with constant cross-sectional area (without stiffeners) under single concentrated load at mid-span of the beam. The research adopts three – dimensional nonlinear finite element analysis of steel box -section horizontally curved beams exposed to static load. The isoparametric brick element of twenty-node has been used to represent the steel element; also, the yield criterion used to compute the stress level of plastic deformation is Von-Mises. The simulation model of the behavior of steel under tension and compression stresses is elastic-perfect plastic. A semi-circular two-span continuous horizontally curved steel box beam was fabricated and tested under two point loads at midspan of the beam, the results was compared with the results of the computer program (NFHCBSL) used in this study. In general, it is found that the adopted finite element model to predict the structural response of horizontally curved steel box beam has a good agreement with the test results concerning estimate load-deflection response.The effect of b/d ratio is considered by taken different values (20–100) % with the identical area of cross-section. Also, the effect of curvature was studied by considering different values from beam with half circle to straight beam. The results appear that the best (b/d) ratio is in between (0.3 and 0.4) at curvature between (0° and 90°) and the best (b/d) ratio is in between (0.4 and 0.5) at curvature between (90° and 180°). Also, the result showed that the decrease in carrying load capacity as the beam curvature increased is independent on the value of b/d ratio

Structural behavior of reinforced concrete slabs containing fine waste aggregates of polyvinyl chloride

In several areas worldwide, the high cost and shortage of natural resources have encouraged researchers and engineers to explore the serviceability and feasibility of using recycled aggregates in concrete mixtures, substituting a normal aggregate percentage. This technique has advantages for the environment by reducing the accumulation of waste materials, while it impacts the fresh and hardened concrete performances, reducing workability, flexural strength, compressive strength, and tensile strength. However, most studies have investigated the influence of replacing normal aggregates with waste aggregates on the concrete mechanical properties without examining the impact of using waste materials on concrete structural performance. The aim of this research is to investigate the effect of replacing 75% of sand volume with polyvinyl chloride (PVC) fine waste aggregates on the performance of reinforced concrete slabs. Different thicknesses of the concrete layer (0%, 25%, 50%, and 100% of slab thickness) containing PVC fine waste aggregates are investigated. Based on the reductions in the toughness and flexural strength capacity due to incorporating 75% PVC fine aggregate dosage, two approaches are used to strengthen the slabs with 75% PVC fine aggregates. The first approach is adding polyvinyl alcohol (PVA) to the PVC fine aggregate concrete mix to improve the mechanical properties of the concrete. The PVA increases the water viscosity in the concrete, which reduces the dry out phenomenon. With that said, the PVA modified fresh concrete does enable the use of the limits of the PVC fine aggregate dosage for high dosage plastic aggregate concrete. The second approach uses two fiber wire mesh layers as an additional reinforcement in the tested slab. Results show that the PVC-30 slab exhibits an 8% decrease in total area toughness compared to the control (Con) slab, while for PVC-60 slab toughness, the total area shows 26% less. Additionally, the inclusion of PVA in the concrete with 75% PVC plastic waste fine aggregate replacement greatly influences the pre-and post-cracking ductile performance among other slabs, representing that using PVA with higher contents might increase the flexural performance. Therefore, due to the substantial effect of PVA material on the concrete flexural performance, it is proposed to utilize PVA with an optimum PCV fine aggregate dosage in the concrete mix

Seepage Velocity : Large Scale Mapping and the Evaluation of Two Different Aquifer Conditions (Silty Clayey and Sandy)

Seepage velocity is a very important criterion in infrastructure construction. The planning of numerous large infrastructure projects requires the mapping of seepage velocity at a large scale. To date, however, no reliable approach exists to determine seepage velocity at such a scale. This paper presents a tool within ArcMap/Geographic Information System (GIS) software that can be used to map the seepage velocity at a large scale. The resultant maps include both direction and magnitude mapping of the seepage velocity. To verify the GIS tool, this study considered two types of aquifer conditions in two regions in Iraq: silty clayey (Babylon province) and sandy (Dibdibba in Karbala province). The results indicate that, for Babylon province, the groundwater flows from the northwest to southeast with a seepage velocity no more than 0.19 m/d; for the Dibdibba region, the groundwater flows from the west to the east with a seepage velocity not exceeding 0.27 m/d. The effectiveness of the presented tool in depicting the seepage velocity was thus demonstrated. The accuracy of the resultant maps depends on the resolution of the four essential maps (groundwater elevation head, effective porosity, saturated thickness, and transmissivity) and locations of wells that are used to collect the data.Validerad;2020;Nivå 2;2020-08-25 (alebob)</p

SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study

Background: Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling. Methods: The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18-49, 50-69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty. Results: NNVs were more favourable in surgical patients than the general population. The most favourable NNVs were in patients aged 70 years or more needing cancer surgery (351; best case 196, worst case 816) or non-cancer surgery (733; best case 407, worst case 1664). Both exceeded the NNV in the general population (1840; best case 1196, worst case 3066). NNVs for surgical patients remained favourable at a range of SARS-CoV-2 incidence rates in sensitivity analysis modelling. Globally, prioritizing preoperative vaccination of patients needing elective surgery ahead of the general population could prevent an additional 58 687 (best case 115 007, worst case 20 177) COVID-19-related deaths in 1 year. Conclusion: As global roll out of SARS-CoV-2 vaccination proceeds, patients needing elective surgery should be prioritized ahead of the general population