Tension structures

Little, B. Staehle, R. (2001). Fungal influenced corrosion in post-tension structures. The Electrochemical Society Interface, Winter 2001, 44-8. 

U. Ntirnberger, Special Problems in Post-tensioned Structures , COST 509 Workshop Corrosion and Protection of Metals in Concrete ,... 

When a high early strength is required, such as for post-tensioned structures or pre-tensioned precast elements, Portland cement with a strength class of 52.5 may be used. Blended cements are usually not suitable because of the slow rate of hydration, with the exception of Portland-silica fume cement and special (fast) slag cements. 

In the present discussion, reinforced concrete and prestressed concrete corrosion control methods are combined. Although prestressed concrete bridges have special concerns such as anchorage in both posttensioned and pretensioned structures and ducts for post-tensioned structures, the general corrosion control methods are applicable to both prestressed and conventional reinforced bridges. 

Particular problems arise when the corrosion problem is the black rust described in Chapter 2 and prestressed, post-tensioned structures where corrosion is difficult to detect as the tendons are enclosed in ducts. Tendon failure can be catastrophic as they are loaded to 50% or more of their ultimate tensile strength and modest section loss leads to failure under load. The particular problems of assessing prestressed concrete structures are addressed in Chapter 4. 

In the United States trials of impressed current cathodic protection have been conducted on pre-tensioned structures (Bennett and Schue, 1998). Many pre-tensioned bridge piles have been cathodically protected in Florida using galvanic anodes. This is unlikely to cause overprotection and hydrogen evolution. 

Nowadays, PVC-coated, high-quality, low-wick treated polyester fabrics with warranties of 10 years and a stmctural lifespan of more than 20 years are preferred for use as the membranes of tension structures. The PVC coatings mostly contain plasticizers, UV stabilizers, fire retardants, colouring and fungicidal additives. Topcoats of acrylic lacquers are mostly used... 

R. Blum Mechanics of fabrics in tension structures, in Mechanics of Flexible Fibre Assemblies, ed. J.W.S. Hearle, JJ. Thwaites and J. Amirbayat, Sijthoff Noordhoff, Alphen aan den Rijn, 1980... 

Terry WR (1994), Georgia Dome cable roof construction techniques , in Abel JF, Leonard JW and Penalba CU, Spatial Lattice and Tension Structures, New York, ASCE, 563-572... 

Due to the absence of a stabilising pressurisation in mechanically tensioned structures, another type of aerogel insulation is employed. This version is a fleece made of two-component fibres which is sprinkled with aerogel particles. This produces a flexible and pressure-resistant mat which has highly favourable insulating properties. This fleece can be used both in combination with transparent ETFE foils and with translucent membrane materials such as PTFE-coated, glass-fibre fabric - see Fig. 12.4. The... 

Leonard, J.W.1988. Tension structures. New York McGraw Hill. 

Classical Assumptions for Interfacial Tension Structure and for Partition Function... 

The phenomenological meaning of the given interfacial tension structure is in agreement with the free volume fluid model. Hence, a fluid is a system with ideal or ordered neighborhood elements distribution and with discontinuities of the package density (boundaries of the subsystems or microcollectives or clusters as some particular physical systems) [5,7]. 

The L S re.search will be watched with interest, It has already been noted that a post-tensioned bridge collapsed in Wales a few years ago. The bridge had no waterproofing on the deck, the ducts were poorly grouted and salt got into the joint.s between segments and corroded the steel. The UK DoT has no idea how many bridges are in a comparable condition in the UK, Further failures are therefore possible. As cathodic protection cannot protect the cables inside ducts on post-tensioned structures, it has limited applicability for protecting such structures,... 

The latest Concrete Society (1995) report on durable bonded post-tensioned concrete bridges will lead to improved design and construction of post-tensioned structures. However, improved repair and assessment methods for the existing structures are needed. 

Fig. 8-31. A 68,380-square-foot tension structure project is being built at La Verne College in...

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