Flexural behaviour of structural fibre composite sandwich beams in flatwise and edgewise positions

The flexural behaviour of a new generation composite sandwich beams made up of glass fibre-reinforced polymer skins and modified phenolic core material was investigated. The composite sandwich beams were subjected to 4-point static bending test to determine their strength and failure mechanisms in the flatwise and the edgewise positions. The results of the experimental investigation showed that the composite sandwich beams tested in the edgewise position failed at a higher load with less deflection compared to specimens tested in the flatwise position. Under flexural loading, the composite sandwich beams in the edgewise position failed due to progressive failure of the skin while failure in the flatwise position is in a brittle manner due to either shear failure of the core or compressive failure of the skin followed by debonding between the skin and the core. The results of the analytical predictions and numerical simulations are in good agreement with the experimental results

Comparative tests of bamboo with other woods for structural purposes

Citation: Manalo, Vicente G. and Moffatt, George A. Comparative tests of bamboo with other woods for structural purposes. Senior thesis, Kansas State Agricultural College, 1908.Introduction: The apparatus used during the test was a “Riecle” Testing Machine of 100,000 lbs. capacity and located at the Engineering Laboratory, Kansas State Agricultural College. In general the machine is classified into the following parts. 1. The Straining Mechanism. 2. The Weighing Apparatus. 3. The Screw and Vernier Beams. 4. The Driving Mechanism

Experimental investigation on the flexural behaviour of pultruded GFRP beams filled with different concrete strengths

Glass fibre reinforced polymer (GFRP) pultruded profiles are being increasingly used in the construction industry due to their numerous advantageous over the conventional materials. However, most pultruded GFRP sections fail prematurely without utilising their high tensile strength due to their thin-walled sections. As a result, several hybrid systems made out of GFRP profiles and concrete as a filler material have been proposed in order to enhance their structural performance. Most of these studies utilised high strength concrete wherein the additional cost does not justify the enhancement in the stiffness and strength of the infilled GFRP profiles. This paper presents an experimental investigation on the effect of the compressive strength of concrete infill on the flexural behaviour of beams with a view to determine a lower cost infill for GFRP profiles. Pultruded GFRP square beams (125 mm x125 mm x 6.5mm) were filled with concrete having 10, 37 and 43.5 MPa compressive strength and tested under static four-point bending. The results showed that the capacity of the filled beam sections increased by 100 to 141% than the hollow sections. However, the compressive strength of the concrete infill has no significant effect on the flexural behaviour of the beams. The increase in concrete compressive strength from 10 to 43.5 MPa increased the ultimate moment by only 19% but exhibited an almost same flexural stiffness indicating that a low strength concrete is a practical solution to fill the GFRP profile

The Contribution of Non-Tropical Cyclone Vortices to the Rainfall of the Philippines

Weaker disturbances than tropical cyclones (TCs) such as tropical depressions and cold surges can significantly induce heavy rainfall and flooding events over the Philippines. However, the analysis of these disturbances including their rainfall contributions are often neglected in previous studies. As the first attempt to address this research gap, this study investigates the rainfall contribution of non-TC vortices over the Philippines from 1979 to 2020. Only those rainfall-producing non-TC vortices that formed and appeared within a 500-km radius from the Philippine coastline were examined in this study. A total of 7,686 non-TC vortex days (50% of the total days during the analysis period) were identified. The mean rainfall contribution of these non-TC vortices was found to be highest over the northeastern Mindanao Island (80–90% of the mean daily rainfall) and lowest over the central and western regions of Luzon Island (50–60%). Seasonal analysis of the occurrence frequency of these vortices shows that they are most frequent during the December–February (DJF) season. In this season, the rainfall contribution may increase to 50–80% of the mean daily rainfall over the whole country, while in the other seasons, the rainfall contribution may only increase to as much as 60%. Higher frequency of extreme rainfall days associated with these non-TC vortices were also found during the DJF season. The frequency of occurrence and percentage rainfall contribution of these non-TC vortices in relation to the different phases of the Boreal Summer Intraseasonal Oscillation (BSISO) during boreal summer (June–October) and the Madden–Julian Oscillation (MJO) during boreal winter (December–April) were also examined. Higher frequency and percentage rainfall contribution over the country were found during Phases 4–6 of both the BSISO and MJO, during which their respective active convections transition from the Maritime Continent to the western North Pacific

Influence of Boreal Summer Intraseasonal Oscillation on Rainfall Extremes in the Philippines

This study investigates the impact of the northward/northwestward propagating 30–60-day mode of the boreal summer intraseasonal oscillation (BSISO) on the extreme rainfall events in the Philippines during the June–September (JJAS) season from 1979 to 2018. The Philippines domain is divided into the three latitudinal regions: Luzon region (13°–22°N), Visayas region (10°–13°N), and Mindanao region (5°–10°N) to account for the regional differences in the timing of extreme rainfall events. The probability density functions of JJAS rainfall are skewed towards higher values relative to the non-BSISO days in BSISO Phases 6–8, Phases 5–7, and Phases 4–6 over the Luzon, Visayas, and Mindanao regions, respectively, during which the probability of extreme rainfall events at the 95th percentile increases by as much as 80% in some stations in these regions. Further analyses of the large-scale circulation features show that the increase (decrease) in the probability of extreme rainfall events is associated with enhanced moisture convergence (divergence) induced by the cyclonic (anticyclonic) circulation anomalies of the BSISO and appearance of multiple tropical cyclones. About 36% of the total extreme rainfall events over the Luzon region are associated with TCs during Phases 7–8. On the other hand, TCs contribute by no more than 24% in all phases over the Visayas and Mindanao regions, indicating less TC influence in these regions. This study is the first attempt to clarify the impact of the BSISO on the extreme rainfall events in the Philippines

Antivortices due to competing orbital and paramagnetic pair-breaking effects

Thermodynamically stable vortex-antivortex structures in a quasi-two-dimensional superconductor in a tilted magnetic field are predicted. For this geometry, both orbital and spin pair-breaking effects exist, with their relative strength depending on the tilt angle \Theta. The spectrum of possible states contains as limits the ordinary vortex state (for large \Theta) and the Fulde-Ferrell-Larkin-Ovchinnikov state (for \Theta=0). The quasiclassical equations are solved near H_{c2} for arbitrary \Theta and it is shown that stable states with coexisting vortices and antivortices exist in a small interval close to \Theta=0. The results are compared with recent predictions of antivortices in mesoscopic samples.Comment: 11 pages, 3 figure

Satisfaction of Filipino Crop Farmers on Agricultural Credit

Agricultural credit is an important part of the broader Agribusiness, which is encompassing farming and farming-related commercial activities. Hence, the study determined the level of satisfaction of crop farmers on agricultural credit in two barangays San Juan and San Andres, Malvar, Batangas, with an end goal of enhancing agricultural credit management. Through descriptive method of research, the study revealed that majority of the farmers used to plant rice with a land area of 0.5 - 1.0 hectare that avail agricultural credit 2 to 3 times a year. Further, the level of satisfaction of crop farmers on agricultural credit along with documents/requirement, penalties and charges, interest rates, credit terms and conditions and repayment scheme are dissatisfied. This study offered recommendations, if properly implemented and actualized by concerned authorities, may ensure sustainable and accessible rural credit facilitation

Analysis of retrofitted corroded steel pipes using internally bonded FRP composite repair systems

Steel pipelines play an important role in the oil and gas industry. Hence corrosion of the steel pipe systems during its service life is a critical issue for the industry. Fibre reinforced composites offer solutions with broad applicability and efficiency for the internal repair of these corroded pipelines. Understanding the behaviour of internal composite repair systems against different internal pressure regimes is an important aspect in the development of a repair system. This study develops the analyses of internal composite bonded repair systems for long steel pipes with an axisymmetric defect, based on Lame’s equation. Various levels of bonding between the steel and composite are studied. Fully bonded optimum internal composite repair thicknesses are determined using biaxial carbon and glass fibre composites for different levels of corrosions, using the Von Mises yielding and Tsai-Hill failure criterion approaches. Two case studies are illustrated using the design nomographs. The analysis technique used was found to be accurate when compared with finite element modelling results

Compressive, tensile and thermal properties of epoxy grouts subjected to underwater conditioning at elevated temperature

Oil and gas pipes are susceptible to failure initiated by corrosion due to their operating pressure under adverse atmospheric conditions. Repairs, comprising a composite shell assembled around the pipe with a small gap, which is then infilled with grout, are considered a suitable option for corroded pipelines. This paper presents the investigation on the mechanical (compression, tension) properties and glass transition temperatures of two infill grouts, after 1000 hour of hot/wet conditioning. An extended investigation on the moisture absorption behaviour was also carried out, revealing the highest absorption to be about 6% after 2520 hours of immersion. The glass transition temperatures of the grouts are reduced by approximately 20ºC. The results suggest that the grouts underwent significant reduction of strength and stiffness due to hot/wet conditioning when tested at an elevated temperature, compared to room temperature. This reduced strength and stiffness is the result of the grouts being tested in close proximity to their glass transition temperatures

Effect of elevated in-service temperature on the mechanical properties and microstructure of particulate-filled epoxy polymers

In civil engineering applications, epoxy-based polymers are subject to different environmental conditions including in-service temperature, which might accelerate their degradation and limit their application ranges. Recently, different particulate fillers were introduced to enhance the mechanical properties and reduce the cost of epoxy-based polymers. This paper addresses the effect of in-service elevated temperature (from room temperature to 80o C) in particulate-filled epoxy based resin containing up to 60% by volume of fire retardant and fly ash fillers through a deep understanding of the microstructure and analysis of their mechanistic response. An improvement in the retention of mechanical properties at in-service elevated temperature was achieved by increasing the percentages of fillers. The retention of compressive and split tensile strength at 80o C for the mix containing 60% fillers was 72% and 52%, respectively, which was significantly higher than the neat epoxy. Thermo-dynamic analysis showed an increase in glass transition temperature with the inclusion of fillers, while these mixes also experienced less weight loss compared to neat epoxy, indicating better thermal stability. Scanning electron microscopy images showed the formation of dense microstructures for particulate-filled epoxy based resin at elevated temperatures. This indicates that the particulate filled epoxy resin exhibits better engineering properties at in-service elevated temperatures, increasing their durability and therefore their suitability for civil engineering applications. A simplified prediction equation based on power function was proposed and showed a strong correlation to the experimental compressive and splitting tensile strength at different levels of in-service elevated temperature