PowerPoint Presentation

Seminar on STRESS RIBBON BRIDGEGuided by, Mr.V.Harish(Asst .Prof-Dept of CE)By Sreeraj.S

CONTENTS

IntroductionFeaturesStructureFabricationMulti spanned bridgesConcluding notesRecent advancementsSome important bridges

INTRODUCTION

Uses theory of catenary transmission of loads Stress ribbon bridge: Modern analogy of rope bridge

Concept introduced by Ulrich Finsterwalder

Suspended concave span and supported convex span

FEATURES:

Mostly used as Pedestrian bridgesMedium span bridges longest span ever constructed is 330 ft (about 100m)Highly stressed freely suspended pre-stressed tendons Precast or cast in situ deck slab No false work needed Catenary shape or funicular shape

Stress Ribbon Bridge

STRUCTURE

Supports:

Stress Ribbon Bridge

Deck:

Might be pre-fabricated or cast in-situ

Supported by bearing tendons during construction

Prestressing tendons are tensioned to form final geometric form

Stressed only by normal forces hence might be reduced by waffles

Stress Ribbon Bridge

Deck:

Stress Ribbon Bridge

Lake Hodges Bridge, USA

Sub structure:

Cables are pre-tensioned by anchoring into support structure, hence this region is highly stressed.

Abutments transfer horizontal forces from duck cables into ground via ground anchors.

Stress Ribbon Bridge

Stress Ribbon BridgeIdeal ground condition is a rock base

If soil condition is so poor piles can be used

Combination of anchors and drilled shafts can also be used

Battered micro piling is another alternative

GOUND CONDITIONS

FABRICATION

Stress Ribbon Bridge

Leviation Stage: Cables are hung from supports Pre cast segments are slided over the bearing tendons to desired position Segments are joint by cast in-situ composite slabs

Stress Ribbon BridgeLeviation Stage:

Typical precast segment on bearing cables

Stress Ribbon BridgeLeviation Stage:Shifting of precast segment on bearing cables

Stress Ribbon BridgeBasic Stage:

After sufficient hardening of joints, post tensioning is done by pre-stressing tendons.

Shape at this stage determines the final sag in the bridge.

Stress Ribbon BridgeService /Ultimate Stage:Analysis of structure for all service loads is done

Multi-spanned Bridges

Stress Ribbon BridgeThese can be of following types: (1)

Concrete or steel columns as intermediate supports

Stress Ribbon Bridge (2)Concrete arch as intermediate supports

MODIFIED STRESS RIBBON BRIDGESTRESS RIBBON BRIDGES STIFFENED ARCHES

STRESS RIBBON BRIDGES STIFFENED BY CABLES

Horizontal force in stress ribbon (HSR) and arch (HA) are equal and oppositeMoment by horizontal forces HSR . h resisted by V.Lp

STRESS RIBBON BRIDGES STIFFENED BY ARCHES

STRESS RIBBON BRIDGES STIFFENNED BY CABLES

Fig(a) Arch fixed at anchor blocks of slender prestressed concrete deckFig(b&c) stress-ribbon and arch footing connected by strut

Concluding notesAesthetic impression PT concrete minimise cracking and increase durabilityBearing and expansion joints rarely required so maintenance and inspections are minimisedLabour saving erection and short time deliveryNo false work and preservation of environment24

Advantages:

Can be erected without falsework or shoringMinimal environmental and visual impact Minimal long-term maintenance is requiredQuick and covenient construction.Minimum number of piers and shorter piers compared to suspension bridge

Stress Ribbon Bridge

Disadvantages:

Large horizontal forces at the end and intermediate supports which determines economy of bridge.

Remedy- i) construction of flexible member close to supports ii) widening of deck at the ends iii) By modifying support with arches or cables

Danger of overturning and oscillations due to high span to width ratio.

Remedy- i) increasing sag ii) proper dynamic analysis

Stress Ribbon Bridge

Recent advances:

Innovative design uses unidirectional solid carbon fibre cables (TSC).

Unsupported spans were significantly increased

Supporting structure was reduced

Installation time and cost were reduced by over 80%

Stress Ribbon Bridge

Some important bridges in this category:

Stress Ribbon BridgeNameCountryMainSpanRio Colorado BridgeCosta Rica146 mLake Hodges BridgeUSA100.9 mEast Golf Cart BridgeUSA86.9 mYumetsuri Bashi BridgeJapan147.6mAaresteg MlimattSwitzerland78 mGlacis BridgeGermany76 mAaresteg RupperswilSwitzerland74.05 mPhyllis J. Tilley Memorial BridgeUSA49.5 mKent Messenger Millennium BridgeUnited Kingdom48 mPnt da SuransunsSwitzerland40 m1)2)3)4)5)6)7)8)9)10)

Stress Ribbon BridgeReferences:1) Strasky,J.- Stress-ribbon pedestrian bridges supported or suspended on arches. Brijuni Islands, 10-14 July 2008.

2) Strasky,J.: Precast stress ribbon pedestrian bridges in Czechoslovakia. PCI JOURNAL, May-June 1987.

3) Strasky,J.: Stress-ribbon pedestrian bridges. International Bridge Conference. Pittsburgh 1999.

4) Nakazawa, Tsutsumi, Yokota- Experimental study on dynamic characteristics of Stress-Ribbon bridge. Ninth world Conference on Earthquake Engineering, JAPAN, Aug 2-9, 1988.

5) Strasky,J.: Stress ribbon and cable supported Pedestrian bridges

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