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Showing 1-5 of 23 Abstracts search results

Document: 

SP120-22

Date: 

June 1, 1990

Author(s):

A. S. Nowak, A. E. Naaman, and S. C.Ting

Publication:

Symposium Papers

Volume:

120

Abstract:

Evaluation of existing bridges is an important part of the strategy of dealing with the deteriorating infrastructure. Load and resistance parameters are random variables because of uncertainties in load components, material properties, and dimensions. Therefore, the reliability of a structure is a convenient measure of its performance. The load and resistance models are first summarized. The major load components in bridges are dead load and live load. The live load model is based on the weigh-in-motion studies. Girder distribution factors are derived using special computer procedures for bridge analysis. Behavior of composite girders is considered using a nonlinear model. The basic characteristic of the section is the moment-curvature relationship. The reliability is measured in terms of the reliability index. The approach is demonstrated on evaluation of a prestressed concrete girder bridge. Three cases are considered: original design condition, damaged with corroded strands, and repaired by external prestressing. The load components and load-carrying capacities are evaluated and then the reliability indexes are calculated for the three cases.

DOI:

10.14359/2868


Document: 

SP120-06

Date: 

June 1, 1990

Author(s):

Pham Xuan Thao

Publication:

Symposium Papers

Volume:

120

Abstract:

The use of tendons placed outside the concrete for the longitudinal prestressing of bridge decks is particularly well suited to the triangulated trusses that have now proven effective. Experience acquired first on the Tehran Stadium roofing (internal tendons) and then on the externally prestressed Bubiyan Bridge in Kuwait has highlighted the numerous advantages to be derived from the latter system. The technology has, therefore, been used again, with external tendons, in the construction of the Sylans and Glacieres viaducts located along the Macon-Geneva-Mont Blanc highway in France, on behalf of the Societe des Autoroutes Paris Rhin-Rhone. The two viaducts have a total length of 1500 m. Each consists of two parallel decks, 10.75 m wide. Typical spans are 60 m long. The deck is precast in forms as a series of 4.66 m long elements and erected by sequential cantilevering using a launching girder.

DOI:

10.14359/3424


Document: 

SP120-21

Date: 

June 1, 1990

Author(s):

Eilhard WoelfelI

Publication:

Symposium Papers

Volume:

120

Abstract:

In the near future, prestressed concrete structures will be designed in Europe according to Eurocode 2 (EC 2). The EC 2 principles governing the design of structures with bonded tendons and with external tendons are given in this paper, and a comparison is made between the structural behavior of the two different types of structures. It is shown that the reliability of both is comparable if the characteristic strain due to prestressing is introduced in the calculations.

DOI:

10.14359/2865


Document: 

SP120-07

Date: 

June 1, 1990

Author(s):

Alan Matejowsky

Publication:

Symposium Papers

Volume:

120

Abstract:

The state of Texas is involved in two projects that use precast concrete segmental erection methods with external post-tensioning tendons. Design and construction features of these projects, along with construction problems related to external tendons, are described. The future of segmental construction and use of external tendons in Texas are discussed.

DOI:

10.14359/3428


Document: 

SP120-05

Date: 

June 1, 1990

Author(s):

Holger S. Svensson

Publication:

Symposium Papers

Volume:

120

Abstract:

The main advantage of external prestressing is that it facilitates the placement and vibration of the web concrete and thus permits thinner webs. The main disadvantages of unbonded external prestressing are its reduced ultimate capacity and lack of contribution to crack control. The cost of bridges built with unbonded external tendons in Germany is currently higher than for those with bonded internal tendons, mainly because of code requirements for minimum web thickness and crack control, and higher costs for the external unbonded tendons. External prestressing has only limited application in Germany. For new concrete bridges, it has been used a few times since the 1950s for tendons bonded to the webs. The first experimental new bridge with unbonded external tendons in Germany is currently under construction. Special applications of external tendons are for incrementally launched bridges, the rehabilitation of bridges, and as longitudinal force couplers. In the future, unbonded external tendons will probably be used mainly for the rehabilitation of existing bridges in Germany.

DOI:

10.14359/3239


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