The above figure shows two main options of reinforcement at the anchorage zone.

The first apply hoop reinforcement, and the next with helical reinforcement. In general,

the three types of reinforcement at the anchorage are:

›   Anchorage reinforcement

›   Main reinforcement

›   Splitting reinforcement

The anchorage reinforcement is to avoid local concrete crusting due to big concentrated

prestressed tendon force in the vicinity of the anchor (2720kN for a 13C15). It can be

designed as crossed hoops (equivalent stirrups) or helical  reinforcement, cf. Freyssinet

ETA-06/0226 or VSL ETA-06/0006.

The main reinforcement is normal reinforcement designed in deck before placing of the

anchorage reinforcement. These transversal reinforcement verified in ICDAS-LUSAS are

called YTop and YBot. In tables of Freyssinet the main reinforcement are called ‘Additional

reinforcement’ which means they help the anchorage reinforcement to avoid longitudinal

crack in concrete top and bottom surfaces at the vicinity of the anchor.

The splitting reinforcement are designed also to carry transverse tension in concrete due

to the big concentrated prestressed tendon in the cable direction. These reinforcement may be

distributed uniformly in the thickness direction of the deck in the vicinity of the anchor.

EN1992-1-1:2004 (9.14) may be refered.

Crossed hoops (equivalent stirrups)

The concentrated force in prestressed tendon direction transfer forces to the concrete surrounding

also in transversal and vertical direction in the vicinity of the anchor. These prestressed forces cause

big tensile stress in concrete and need therefore crossed hoops  and  respectively,

in transversal and vertical direction (also called bursting reinforcement).

Helical reinforcement

The anchorage zone for C-system as a starting point is quadratic and a spiral (helical) reinforcement for

anti-burst followed with a presstressing cable as an option vs. using crossed hoops.

 

Refer /7/ for the Table above at fcm,0=44MPa.

Refer /10/ p.14 for re-calculation the helical reinforcement option to crossed hoops option. 

7. Stress limitation

This section highlights stress limitation from Eurocodes for SLS and ULS combination of actions.

For concrete element

› Stress SX and SY reported in Max/Min values from Lusas envelope of smart combinations.

› The results are plotted along the deck and the pier elements, with values and contours.

For reinforcement and prestressed tendons

› Stress and force calculate in ICDAS Excel based on sectional forces from Lusas.

› Calculations are performed on cross section at a selected nodes, with the sectional forces are

  obtained from Lusas.

Further, Wood-Armer forces are used for concrete and reinforcement in ULS combinations of actions. The results

are plotted along the deck and the pier elements, with values and contours. Verification for these forces required

the maximum allowable values calculated from Eurocode. The utility ratios are plot in Lusas as ‘used defined

values’, along the deck and the pier elements.

Check of acceptable stresses in concrete and reinforcement are performed for the following load case and

combinations of actions:

SLS Prestressing

SLS Quasi-permanent loads combination

SLS Characteristic loads combination

SLS Frequent loads combination

ULS combinations of actions.

All criteria for check of limitations of stresses are found in ‘Concrete Bridge User’s Manual’ incl. links to Eurocodes,

National Annex and Danish Vejregler. The manual is installed in your PC/Laptop together with ICDAS COB subscription.

Reference

/1/ Prestressing Concrete Bridge using LUSAS 2017,  Truc Huynh, Technical University of Denmark, Ballerup Campus.

/2/ Eurocode 2 Design of concrete structures, Part 1-1 General rules, DSEN 1992-1-1+AC, 3.udg, 2008-10-28

/3/ Eurocode 2 Design of concrete structures – Concrete bridges - Design and detailing rules BS EN 1992-2:2005

     Incorporating corrigendum July 2008

/4/ Eurocode 2 DESIGNERS' GUIDE TO EUROCODE 2 EN1992-1-1 & 1992-1-2

/5/ ETA 06-0226 Freyssinet Post-tensioning Cables Skandinavisk Spændbeton comments, 08-12-2006.

     From 25.01.2007 To 24.01.2012

/6/ ETA 06-0226 Freyssinet Spændkabler. Optimering af Design, Skandinavisk Spændbeton 25.01.2007

/7/ ETA 06-0226 Freyssinet Prestressing, The System of the Inventor of Prestressing Concrete, Freyssinet  Sustainable

     Technology, C III 1, V13, 09.2014.pdf

/8/ ETA-06-0006 VSL Post-Tensioning System 26-05-2015; Annex 1 p. 13 Multistrand System; Annex 2 p. 82 Slab System

/9/ ETA-13-0978 VSLab-S-System From 28-06-2013 To 28-06-2018.

/10/ ETA-07-0035 Skandinavisk Spaendbeton Post-Tensioning tendons CCL. Post-Tensioning Kit for prestressing of structures

       with bonded/unbonded tendons of 3–55 strands. From 08-08-2012 To 08-08-2017.

/11/ VSL Post Tensioning Solutions 03-2013; en.vsl.cz.

/12/ VSL-Strand-post-tensioning-systems 01-2015

/13/ Vej- og Stibroer, Belastnings- og belastningsregler Med Bilag Applicationsdokument til Eurocode 1 Basis of Design and

       Action on Structures – Part 3 Traffic Loads on Bridges, Vejregelrådet November 2002

/14/ Håndbog Vejledning til Belastnings- og beregningsgrundlag for broer, Anlæg og Planlægning, med opdaterede udgaver af

       DK NA til DS/EN 1992-1-1, DS/EN 1993-1-1 og DS/EN 1997-1, Vejregler April 2015.

/15/ Spændbeton, Efterspændte konstruktioner. Hans Nyvold, Januar 1990