Failure of a (probably the largest

in the world ) timber falsework

The Sand bridge

Common method for concrete

bridge construction

however

in order to create as little disturbance as possible to the ship traffic during construction, a new erection method was adopted

The falsework, a timber arch construction with span of 250m was constructed on the shore and then shipped to the building place

Proposed bridge construction method

The longest concrete arch bridge of the world, at the time of construction (1939). Span length: 247,5 m (during shipping, a tension tie was used to take the horizontal trust)

Detail of the abutment

(construction phase)

Background

The works started in April 1938

Collapse of the timber falsework in 31 August 1939

The timber falsework failed during concreting

18 fatalities

Background

The works started in April 1938

Collapse of the timber falsework in 31 August 1939

The timber falsework failed during concreting

18 fatalities

(On September 1 (the day after the collapse) Hitler declared

war on Poland. Therefore, the news about the collapse of the Sand Bridge did not reach the big headlines and it was soon forgotten by the general public).

Cross section of the falsework arch

Main reasons of the collapse

Most probable out-of-plane buckling of the arch falsework

Buckling caused by insufficient transversal stiffness of the arches

Misjudgment concerning the stiffness of nailed planks

The bridge was finally rebuilt in 1943, however, now using a timber falsework supported all along its length

The timber falsework used for the second attempt (and this time successful) to bridge the river ngermanlven at Sand

The Sand bridge

Importance of right form

Spaghetti structure competition: span:1 m

weight: < 1 kg failure load: ver 450 kg!

Royal Albert Bridge, Saltash, 1899

fish-belly beams

Axial force N and bending moment diagrams caused by uniformly distributed load (L= 75m, hmax=9m, load 2,5 kN/m

2)

M

N

N in the vertical struts is negligible (almost zero)

Traversina bridce, switzerland (span:56 m)

New traversina bridge

The suspension cable is tensioned

Timber walkway (upside down arch) Is loaded in compression

The stiffness of the system increases significantly

Nya traversina bridge

Structures that carry the load mainly

in tension

Stress-ribbon bridge: steel tension tie of steel

+ concrete deck

Stress ribbon timber bridge in Essing, Germany

Stress ribbon timber bridge in Erlebnis, Germany,

span: 225 m

Steel plate 40x200

A special suspension bridge

Feldbach / austria

built: 1998

A special suspension bridge

Truss without lower chord: simple

node connections

Diagonals are always subjected to tensile forces,

regardless the load position

Truss bridge in Austria

Arch bridges

Deck arch in Brans, Sweden

Brans 2007, Ltot 130m, B = 5,3m. Bgens spnnvid 50m

Through arch bridge in Kinna, Sweden

Kinna 2008, Ltot 40 m, B = 3m

Half- through arch bridge in Hgerns,

Sweden

Hgerns 2007, Ltot 42m, B = 3,5m. Bgens spnnvid 34m

Bridge Hgerns, elevation and plan

Cross section

Hinges

At the apex

At the springing

Details

Suspension of the deck

Connection arch-hanger

Static system

Buckling of arches

Out-of-plane buckling of slender arches

Out-of-plane buckling

Buckling length (out-of-plane)

Second order analysis

Isoleringsmatta

Fretheim Bridge

- a three-hinged arch with steel tension tie

38 m

Fretheim Bro

An interesting system which is extremly

efficient in reducing the bending moments in

the arch the network arch

The Brandanger steel network arch in western Norway. Span 220m. The worlds most slender arch bridge

Traditional vs. network

traditional through arch bridge

Network through arch bridge

Reduction of bending moments in the arch

Inclined hangers distribute patch load into a wider part of the arch

Influence line for bending moment at the

most stressed cross section

Truss and trussed arch bridges

Connection with slotted-in plates and

dowels

Olimpic games in Hamar, 1994

Span: 71 m

Design Load for the lower chord: 7000 kN!!

Skubbergsenga bridge a zero-hinged trussed arch

Total length 40 m

Arch span 32 m

Bridge width 4 m

Building year 1997

Tynset bridge

- a two-hinged trussed arch bridge (max span: 71m)

Tynset bru bygger 2001

Tynset bridge

preassembly of the

trussed arch in the

factory

Tynset bridge

To increase the out-of-

plane stability:

- K-shaped bracing

- Wider cross section at

the springings of the

arch

- Moment stiff

connection for out-of-

plane bending

Flisa Bridge

Total length 197 m

Bridge width 9,0 m

Span 70 m

Bulding year 2003

Flisa bridge

The same

statical

system

The low weight made it

possible to reuse the old

supports

Flisa bridge

Rena Bridge Designed for military load

Concrete deck, but not in composite action (the deck can freely slide on the top of the timber truss)

Max load: 110 ton!!

8mm plate, 10mm slots, 12mm dowel

The gap is filled up with a mortar (akrylat). The transmission of

compression occurs through contact. The dowels transmit only shear.

Concrete deck not in composite action. Longitudinal movements of : free. Lateral movement: restrained.

Rena Bridge

Max span: 45m

Three recent bridge projects

LVSBACKA BRIDGE

LVSBACKA BRIDGE

CHALLENGES OF THE SUPERSTRUCTURE LVSBACKA BRIDGE, Peter Jacobsson et al.

LVSBACKA BRIDGE

The Anaklia Pedestrian Bridge in Georgia

The Anaklia Pedestrian Bridge in Georgia

Timber-frame Construction: HESS TIMBER, Kleinheubach Load Assumptions, Structural Engineering Calculation, Design: Leonhardt, Andr & Partner , Stuttgart

The deck

The deck

Tretten bridge, Norway

A 148m long 2-lanes timber bridge

Tretten bridge, Norway

Tretten Bridge Timber and Steel in Harmony, John Are Hrstad-Evjen et al (2013)

Combination of timber and weathering steel

(COR-TEN)