THE ROLE OF MINERAL NUTRITION ON YIELDS AND FRUIT QUALITY IN GRAPEVINE, PEAR AND APPLE

ABSTRACT Fertilization of temperate fruit trees, such as grapevine ( Vitis spp.), apple ( Malus domestica), and pear ( Pyrus communis) is an important tool to achive maximum yield and fruit quality. Fertilizers are provided when soil fertility does not allow trees to express their genetic potential, and time and rate of application should be scheduled to promote fruit quality. Grapevine berries, must and wine quality are affected principally by N, that regulate the synthesis of some important compounds, such as anthocyanins, which are responsible for coloring of the must and the wine. Fermenation of the must may stop in grapes with low concentration of N because N is requested in high amount by yeasts. An N excess may increase the pulp to peel ratio, diluting the concentration of anthocyanins and promoting the migration of anthocyanins from berries to the growing plant organs; a decrease of grape juice soluble solid concentration is also expected because of an increase in vegetative growth. Potassium is also important for wine quality contributing to adequate berry maturation, concentration of sugars, synthesis of phenols and the regulation of pH and acidity. In apple and pear, Ca and K are important for fruit quality and storage. Potassium is the most important component of fruit, however, any excess should be avoided and an adequate K:Ca balance should be achieved. Adequate concentration of Ca in the fruit prevents pre- and post-harvest fruit disorders and, at the same time, increases tolerance to pathogens. Although N promotes adequate growth soil N availability should be monitored to avoid excessive N uptake that may decrease fruit skin color and storability

Role of Fire Resistance Issues in the Collapse of the

The twin towers of the World Trade Centre suffered significant damage from the impact of the planes, however, they withstood the impact. The severe fires that followed the impact brought down the twin towers, WTC 2 and WTC 1, at different intervals - 59 and 89 minutes respectively following the impact. Thus, fire issues played a major part in the collapse of the twin towers and the role of the various fire resistance issues is examined in this paper

Performance of high strength concrete-filled steel columns exposed to fire

Results from an experimental program on the behaviour of high strength concrete-filled steel hollowstructural section (HSS) columns will be presented for three types of concrete filling. A comparison will be made of the fire-resistance performance of HSS columns filled with normal strength concrete, high strength concrete, and steelfibre-reinforced high strength concrete. The various factors that influence the structural behaviour of high strength concrete-filled HSS columns under fire conditions are discussed. It is demonstrated that, in many cases, addition of steel fibres into high strength concrete improves the fire resistance and offers an economical solution for fire-safe construction.Les r\ue9sultats d'un programme exp\ue9rimental sur le comportement de colonnes en acier (HSS) dont la sectionvide est remplie de b\ue9ton \ue0 haute r\ue9sistance, sont pr\ue9sent\ue9s et ce, pour trois types de b\ue9ton de remplissage. Une comparaison de la r\ue9sistance au feu est faite pour des colonnes remplies avec du b\ue9ton \ue0 r\ue9sistance normale, du b\ue9ton \ue0 haute r\ue9sistance ou du b\ue9ton \ue0 haute r\ue9sistance renforc\ue9 de fibre. Les diff\ue9rents facteurs qui influencent le comportement structural des colonnes HSS remplies de b\ue9ton \ue0 haute r\ue9sistance sous des conditions d'incendie sont discut\ue9s. Il est d\ue9montr\ue9 que, dans de nombreux cas, l'ajout de fibres au b\ue9ton \ue0 haute r\ue9sistance am\ue9liore la r\ue9sistance au feu et offre une solution \ue9conomique pour obtenir une construction s\ue9curitaire en cas d'incendie.Peer reviewed: YesNRC publication: Ye

Factors governing redistribution of moment in continuous prestressed concrete beams

The failure load of a continuous prestressed concrete beam depends partially on the amount of redistribution of moment that occurs prior to failure. Results from a parametric study, carried out using a nonlinear finite element computer program, are presented to demonstrate the influences of various factors on redistribution of moment in two-span, continuous bonded prestressed concrete beams. Trends in the data from the numerical studies are compared with those from a theoretical expression for percentage of redistribution, and it is shown that the redistribution of moment occurring in a continuous prestressed concrete beam is a function of number of parameters.La charge extr\ueame d?une poutre de b\ue9ton pr\ue9contraint continue d\ue9pend en partie du degr\ue9 de redistribution des moments qui se produit pr\ue9alablement \ue0 la d\ue9faillance. Les r\ue9sultats d?une \ue9tude param\ue9trique, r\ue9alis\ue9e au moyen d?un programme de mod\ue9lisation par \ue9l\ue9ments finis du type non lin\ue9aire, sont ici pr\ue9sent\ue9s afin de d\ue9montrer les incidences de divers facteurs sur la redistribution des moments dans les poutres en b\ue9ton pr\ue9contraint continues \ue0 deux trav\ue9es. Les tendances des donn\ue9es issues des \ue9tudes num\ue9riques sont compar\ue9es \ue0 celles d?une expression th\ue9orique relativement au pourcentage de la redistribution des moments, et il est d\ue9montr\ue9 que celle-ci, dans une poutre en b\ue9ton pr\ue9contraint continue, est fonction d?un certain nombre de param\ue8tres.Peer reviewed: YesNRC publication: Ye

Guidelines for fire resistance design of high-strength concrete columns

An overview of the research program, aimed at developing fire resistance design guidelines for high strength concrete (HSC) columns, is outlined. A comparison is made of the fire resistance performance of HSC column with that of normal strength concrete column. The various factors that influence the structural behaviour of high strength concrete columns under fire conditions are discussed. Design guidelines are presented for mitigating spalling and enhancing fire endurance of HSC columns.On donne une vue d'ensemble du programme de recherche visant la cr\ue9ation de lignes directrices sur la conception en mati\ue8re de tenue au feu des colonnes en b\ue9ton \ue0 haute r\ue9sistance. Une comparaison est r\ue9alis\ue9e entre la tenue au feu d'une colonne en b\ue9ton \ue0 haute r\ue9sistance et celle d'une colonne faite de b\ue9ton \ue0 r\ue9sistance ordinaire. On y traite des divers facteurs qui influent sur le comportement structural des colonnes en b\ue9ton \ue0 haute r\ue9sistance en conditions d'incendie, et des directives de conception en vue de limiter l'effritement et d'am\ue9liorer la tenue au feu de ces colonnes sont \ue9galement pr\ue9sent\ue9es.Peer reviewed: YesNRC publication: Ye

Fire resistance requirements for FRP structural members

Peer reviewed: YesNRC publication: Ye

Performance-based fire resistance design of concrete- filled steel columns

Peer reviewed: YesNRC publication: Ye

Integrating fire resistance into infrastructure projects

Fire represents one of the most severe environmental conditions to which structures may be subjected and hence, the provision of appropriate fire safety measures for structural members is an important aspect of design. While the fire resistance provisions are one of the major requirements in buildings, the need for extending such provisions to infrastructure is being debated after some of the recent fire incidents in tunnels and bridges. Also, the wider use of high-performing materials (HPM), such as high-strength concrete (HSC) and fibre-reinforced polymers (FRP) in infrastructure applications, has brought fire issues t the forefront of this debate. In the paper, the different fire scenarios associated with infrastructure projects will be explained. The complexities associated with the fire resistance performance of HPM, mainly HSC and FRP, will be outlined. An approach will be suggested to integrate fire safety into overall structural design. Through case studies, it will be illustrated that cost-effective design can be achieved by integrating fire resistance into the overall design.Le feu constitue l?une des conditions environnementales les plus rigoureuses auxquelles des structures peuvent \ueatre expos\ue9es. Par cons\ue9quent, la prescription de mesures de s\ue9curit\ue9 incendie appropri\ue9es pour les \ue9l\ue9ments structuraux repr\ue9sente un aspect important de la conception. Bien que la prescription li\ue9e \ue0 la r\ue9sistance au feu demeure l?une des exigences majeures pour les b\ue2timents, on examine actuellement la n\ue9cessit\ue9 d?\ue9tendre de telles prescriptions \ue0 l?infrastructure, \ue0 la suite de certains incendies ayant r\ue9cemment \ue9clat\ue9 dans des tunnels et sur des ponts. En outre, l?utilisation \ue9largie aux applications d?infrastructure des mat\ue9riaux \ue0 haute performance (MHP), comme le b\ue9ton \ue0 haute r\ue9sistance (BHR) et les polym\ue8res renforc\ue9s de fibres (PRF), a rendu les questions li\ue9es \ue0 la r\ue9sistance au feu prioritaires dans ce d\ue9bat. Dans ce document, les diff\ue9rents sc\ue9narios d?incendie associ\ue9s aux projets d?infrastructure seront expliqu\ue9s, et l?on d\ue9crira les complexit\ue9s qui sont associ\ue9es \ue0 la performance en mati\ue8re de tenue au feu des MHP, essentiellement le BHR et les PRF. Une m\ue9thode sera sugg\ue9r\ue9e pour int\ue9grer la s\ue9curit\ue9 incendie \ue0 m\ueame la conception globale des structures. Il sera d\ue9montr\ue9 par des \ue9tudes de cas que l?on peut en arriver \ue0 une conception efficace en termes de co\ufbts en int\ue9grant la r\ue9sistance au feu dans la conception globale.Peer reviewed: YesNRC publication: Ye