BRIDGES by DETAIL

BRIDGES Potentialities and Perspectives

THORSTEN HELBIG Edition ∂

MICHAEL KLEISER

LUDOLF KRONTAL

Contents

Bridges – Potentialities and Perspectives – Preface

Bridge Construction Yesterday – Today – Tomorrow Designing Bridges – A prestigious discipline Bridges for Slow-Moving Traffic – Pedestrians and cyclists Road Bridges – Links for motorised traffic Bridges for Rail Traffic – Track-bound rolling and hovering Bridges and Traffic – Mobility in progress Preservation and Evaluation of Bridges – Refurbish or replace?

6 14 22 32 44 50

Requirements Impact – Internal and external loads Function – Routing and bridge equipment Economic Efficiency – Using financial resources responsibly Sustainability – Thinking about tomorrow today

58 66 74 78

Materials Materials – Properties, construction and gestalt

Designs Designs – Catalogue of options

Bridges in Detail Ten outstanding project examples

Appendix Picture credits, sources, authors

102

156

Imprint

Authors Thorsten Helbig, Michael Kleiser, Ludolf Krontal Co-authors Markus Friedrich, Martin Knight

The FSC-certified paper used for this book is manufactured from fibres proven to originate from environmentally and socially compatible sources.

Editing: Steffi Lenzen (Project management), Cosima Frohnmaier (Project examples), Jana Rackwitz (Copy-editing German edition and layout), Charlotte Petereit (Editorial assistance), Carola Jacob-Ritz (Proofreading German edition)

Translation into English Julian Jain, Berlin (DE)

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Designing Bridges A prestigious discipline

The bridge — cultural monument and contemporary witness Bridges overcome obstacles to allow people and goods to pass quickly and safely. Bridges are functional buildings of civilisation but also part of the history and cultural monuments of a society. In addition to the technological capabilities of a society, they reflect its values and the spirit of the times. From opulent stone arch bridges lined with religious sculptures, such as Charles Bridge in Prague from the 14th century (fig. 1), to Brooklyn Bridge in New York, completed in 1883, with its two large granite towers and first use of steel for the main support cable (fig. 3), to athletic-looking, shallow-span suspension bridges made of steel sheets and cables, such as the Millennium Bridge in London from 2000 (fig. 2), bridges are eminent historical markers of their time.

Sometimes they even lend a sense of identity to their respective place. Bridges clearly show the value that a society places on the civilised environment it has created and thus on itself. Bridges in public spaces are usually built for a long service life. With a current technically intended lifespan of no less than 100 years, bridges built today can still be used at least by the great-grandchildren of the generation that built them. However, bridges can also be used for a much longer period of time if they are structures that significantly shape their local landscape and have been planned with foresight. If the bridges are designed in an aesthetically pleasing manner, with a clear-cut and robust construction, they will also be maintained and preserved by society, and thus be usable for the general public for a long time. Bridges are difficult to convert. Once built, they can usually only be converted for higher loads, wider lanes or changed boundary conditions at disproportionately high expense. Their presence on site, shaped by form and materiality, is hardly modifiable, since it is, after all, the support structure that determines their shape. The old stone bridges of Rome or the Brooklyn Bridge in New York still function with their originally constructed supporting

1 Charles Bridge in Prague (CZ), 14th century

2 Millennium Bridge, London (GB) 2000 /2002, Norman Foster, Arup 3 Brooklyn Bridge, New York (US) 1883, John August Roebling 2

Designing Bridges

10 Stress ribbon bridge across the MainDanube Canal near Essing (DE), 1986, Richard Johann Dietrich, Heinz Brüninghoff 10

On foot and bicycles After bridges were initially built for communication and trade routes as well as for military purposes (pontes longi), pedestrian bridges were also used as deliberately designed elements in landscape gardening from the beginning of the 19th century. At that time, the middle classes, which was growing stronger with the Industrial Revolution, had bridges built “only” for strolling. For example, the Passerelle des Arts of 1804, one of the first cast-iron bridges in France, was designed exclusively for pedestrians (fig. 8, p. 10). From the end of the 19th century, bicycle traffic gained in importance. With the safety bicycle designed by John Kemp Starley in 1884, a further development of the pedalcrank penny farthing, and the invention of the air-filled tubed tyre by John Boyd Dunlop in 1888, cycling became safe and comfortable. The first cycle routes were laid out. One of these was the Great California Cycleway, opened in 1900, which was designed to connect Los Angeles and Pasadena (fig. 11). The cycleway ran at a height of up to 15 m as a bridge construction above the ground but was soon dismantled for various reasons. Today, a century later, approaches like the Cycleway are topical again.

From the second half of the 20th century onwards, the greater leeway in the design of footpath and cycleway bridges compared to the strict requirements of railway and road bridges was increasingly perceived as an opportunity for experimentation and (sometimes expressive) design (fig. 10). With their support structure and construction details up to the handrail material, pedestrian bridges are part of the everyday experience of the users’ environment in terms of the perceptibility of the scale and (also in the literal sense) “tangibility” of the components. Thus, pedestrian bridges are understood as “furniture of the city”, passed, inhabited and touched on a daily basis. Since the 2000s, there has been an increase in pedestrian bridges

11 California Cycleway in Los Angeles (US), 1900, partly completed, dismantled at the start of the 20th century

12 12 Charles Kuonen Suspension Bridge, Randa (CH), 2017, Swissrope 13 Pedestrian bridge made of glass over the Grand Canyon of Zhangjiajie, Zhangjiajie National Forest Park, Hunan Province (CN), 2016, Haim Dotan Ltd. Architects and Urban Designers

designed for special experiential effects in order to make certain places and regions more attractive for tourists. Suspension bridges with spans of up to 500 m and a walking surface made of transparent glass attract thousands of visitors every day. In China alone, nearly 2,300 glass-bottomed bridges and walkways were built by 2020 (fig. 13). The Charles Kuonen Bridge in Randa, Switzerland, is part of the Europe Trail and, at 494 m, the longest-span foot-

bridge in the world (fig. 12). With an emphatically sculptural design of expressively accentuated support structures, pedestrian bridges are used as attractions in urban spaces and often as catalysts for urban development. At the price of high costs for construction and maintenance, spectacular stand-alone objects are created that can – perhaps surprisingly for an infrastructural component – trigger a Bilbao effect (fig. 14).

14 Gateshead Millennium Bridge, Gateshead (GB), 2001, WilkinsonEyre, Gifford and Partners 14

Bridges for Slow-Moving Trafﬁc

Road Bridges Links for motorised traffic

Character Road bridges, in contrast to pedestrian bridges, are characterised by the higher loads from motorised traffic and the increased safety considerations against vehicle impact and crashes, and are therefore marked by more solid support structures. A crucial factor in Nordic and Alpine countries is the required winter maintenance, which generates chloride loads on roads and their bridges due to salt spreading. Unlike railway bridges, road bridges can follow complex routing specifications and can also reach great widths in the form of multi-lane motorways. Due to the fact that vehicles are not bound to a lane, a multitude of load positions and configurations have to be taken into account. A wide variety of traffic routing during construction within existing structures also poses major challenges. Despite these general parameters, the design of road bridges still allows a great deal of freedom compared to the tight deformation criteria and extreme load requirements of railway bridges. Considering the local conditions, the planned routing, the appropriate and economical use of materials and systems, as well as

the official requirements and stipulations, a concept to successfully embed a bridge in its surroundings also requires a certain sensitivity (fig. 1). Archetypes The development of bridges from simple stone slab, wooden or filigree constructions suitable for pedestrians and light, non-motorised traffic (see “Bridges for Slow-Moving Traffic”, p. 14ff.) to more solid support structures is due to the revolutionising of road traffic by the invention of the motor vehicle. The rapid expansion of functioning trade routes made it possible to transport ever greater loads over longer distances. Since the loads of carts and carriages increased constantly and arbitrarily, the Romans established a load regulation with a maximum load of initially 250 kg as early as 50 BC [1] in order to ensure the stability of road surfaces and thus also of bridge structures. The first bridges for higher loads were initially made with the proven building material of wood (see “Wooden bridges”, p. 14f.). However, not least for reasons of durability, other building materials such as stone and brick soon prevailed as the primary material of the solid bridge. After

1 1 Bridges as links in the landscape and in the road network. Storseisundet Bridge, Atlantic Road (NO), 1989 2 Two Roman bridges in Mérida (ES) a across the Albarregas River b across the Guadiana River

possible to achieve spans of 35 – 38 m [2]. The Roman stone arch bridge, as the first true archetype of a solid bridge, is convincing because of its comprehensibility of the individual functional elements. Clearly visible from the outside is the separation of the radial stone arrangement’s load-bearing function in the stone arch from the ballast function of the horizontal stone layering in the spandrel areas, which was necessary due to the statically non-optimal shape of the circular arch. The offset cornice or a parapet on the bridge also visually illustrate its function as a lateral path delimitation independent of the structure (fig. 2). In the spandrel areas of low load concentration, openings were usually provided for flood drainage or there was room for ornamental stone masonry. Whereas, in structural elements with large internal forces – similar to ancient temple construction – it is evident that these are self-sufficient and do not tolerate any additional ornamentation [3].

the first solid constructions across canals and smaller streams made of corbelled arches with a span of 3 to 4 m starting from the 4th century BC in Greece, the Romans refined the engineering technology to a standard unique for the time, with an enormous number and variety of bridge structures. The vaulting technique already developed under the Etruscans and perfected by the Romans made it

Road Bridges

A slender stretch girder, a construction that became possible only with knowledge and mastery of the aerodynamic effects from wind excitation, possesses an extraordinary design quality. As the bridge over the Great Belt in Denmark shows (fig. 15), the sweep of the supporting cable and the slightly upwardly curved, extremely slender stretch girder also creates a special dynamic in terms of perception psychology, through the play of the oppositely directed curvatures [9]. Motorway bridges The development of the automobile at the beginning of the 20th century and the need for ever faster traffic connections led to the separation of roadways and the development of grade-separated traffic junctions. The first motorway-like road was constructed near New York in 1908 in the form of the Long Island Motor Parkway. In Europe, the Berlin Automobil-Verkehrsund Übungsstraße, or AVUS, and the Italian Autostrada Milano-Laghi project led the way [10]. However with the rapid expansion of motorway networks, especially in the second half of the 20th century, bridges became interchangeable and bland. The aim was to churn out roads and bridges with little funding in order to meet the economic boom of the post-war period, the new mass suitability of the motor vehicle and the expanded demands for mobility. In contrast to bridges with large spans or high local impact, which attract attention due to their size or publicity alone, today the priority for many bridges in motorway construction is functionality, practicality and rapid implementation. The flyover bridge is representative of many “forgotten” bridges with small and medium spans, which will be discussed below in order to explore expressive potential and avoid “soulless” bridges.

Over-bridging A characteristic feature of the motorway is the overbridge, which is even depicted in the corresponding traffic sign, not least for this reason. At regular intervals, overbridges enter the motorist’s field of vision from a distance and remain there for a long time. As recurring signatures, they are the calling card of a motorway and should therefore be given great care in the design – even overriding the route-bound support structures. The design of overbridges is primarily determined by the route characteristics, landscape integration and the perceptual experience from the driver’s perspective and less by the immediate location of the structure and its residents. Experts such as the early motorway architects Paul Bonatz and Wilhelm Tiedje prefer open-view type bridges instead of barrier-generating ones [11]. Column-free overbridges also highlight forward movement from a perceptualpsychological point of view [12]. From this, a wealth of variants can be derived, from the clearance-enclosing classic doublespan bridge to the support-free lightweight construction (fig. 17), which, depending on the design intention, contains different opportunities for expression from stringent to expressive forms [13].

15 Storebæltsbroen, Bridge across the Great Belt, Nyborg / Korsør (DK), 1998, COWI, Dissing+Weitling

Interlinking – Interweaving Bridges as nameless mass-built structures appear above all in the increasingly interwoven motorway junctions. In order to speed up the flow of traffic, interweaving areas of lanes are avoided and thus separate ramp structures are erected for each relation. The bridges pile up into multistorey structures and are absorbed in complex support and structural systems (fig. 16). Renovations of these nodes as well as reconstructions for capacity increases will certainly become one of the challenges of the future.

Outlook In parallel with societal developments towards accelerated, flexible and largely independent – and therefore unpredictable – mobility behaviour, corresponding trends are emerging today for road bridges. Resisting The current high expenditures for maintenance promote a trend towards the use of high-performance materials that have a low material degradation and thus lower life cycle costs. This particularly affects road bridges that are either exposed to frequent freeze-thaw cycles in alpine regions and high chloride exposure due to the use of de-icing salt, or are subject to highly aggressive environmental conditions in coastal or industrial areas. There are currently a number of research projects and pilot applications of tension elements made of non-corrosive and chemically resistant materials that are waiting for regular implementation. For example, prestressing members and construction methods with carbon fibres are being developed under the catchword of “carbon concrete” in combination with higher-strength fine-grained concretes. The Wild Bridge in Carinthia, made of ultra high performance concrete (UHPC) with steel fibre reinforcement, shows that fine-grained, resource-saving construction is possible if the surface’s pore density promises high robustness and resistance (fig. 18).

Openness and Dynamics

16 Traffic junction in Los Angeles (US) 17 Overbridge variants

Road Bridges

Beeline speed [km/h]

These requirements lead to a conflict of objectives. For example, the benefit of an additional diagonal traffic route might be at stake (fig. 5). In order to minimise construction and maintenance costs, but also land consumption, it is desirable to concentrate traffic flows on a few efficient roads. However, this leads to the fact that journeys between two locations cannot be undertaken directly. The mileage and thus the energy consumption increase. In many cases, higher mileage will also lead to more accidents. At the same time, diversions increase the time spent by motor vehicle drivers. This trade-off between concentrating traffic demand on a few traffic routes and appropriate diversion is a fundamental task of transport network planning. The conflict is solved in the network design guidelines [6] by setting specifications for two central parameters that can be used to quantify the quality of a transport service between two locations, the beeline speed and the degree of diversion: the beeline speed is defined as the ratio of travel time and beeline distance. The beeline distance thus describes the

4 Evaluation of the service quality of a route with the help of the parameters beeline speed (a) and diversion factor (b) in relation to the beeline distance. The service quality is described by six quality levels A (very good quality) to F (insufficient quality).

A B C

80 70

30 20 10 0 0

100

150

200

250

300

350 400 450 500 Beeline distance [km]

100

150

200

250

300

350 400 450 500 Beeline distance [km] 4

a 2.50 F

2.25 2.00

1.75

1.50

C B

1.25

A 1.00 0 b

100 90

Diversion factor

design transport routes in such a way that the requirements of network operators, network users and the environment are met as well as possible: • Requirements of the network operator - minimum construction costs - minimum maintenance costs • Requirements of the network user (car driver, public transport passenger) - minimum time expenditure - minimum operating costs or fares - high accident safety - high reliability • Environmental requirements - minimum land consumption - minimum fuel consumption - minimum fragmentation of space into sub-areas - bypassing of sensitive areas (e.g. landscape conservation areas)

time required for a change of location. The beeline speed is to increase with increasing beeline distance. The degree of diversion is given as the ratio of the travel distance and the beeline distance (diversion factor). The degree of diversion describes the spatial effort of a change of location. It should decrease with increasing beeline distance. Fig. 4 shows a diagram each for the beeline speed and the degree of diversion, which can be used to evaluate the quality of service of a relation. Depending on the beeline distance, different requirements arise in each case, which are evaluated as quality levels A (very good quality) to F (insufficient quality). The network depicted in fig. 5 shows that the decision to build an additional diagonal traffic route should depend on the length l

5 Transport network design: to build or not to build? Z Z

Central place

Existing trafﬁc route (with bridge)

Possible new trafﬁc route (with bridge) Z l Objective

Build a traffic route?

Low time expenditure

Yes

Low degree of diversion

Yes

Low fuel consumption

Yes

High network robustness

Yes

Low land consumption

Low fragmentation

Low construction and maintenance costs

of the network mesh. In the case of a small length, as is common in urban networks, a diversion is reasonable because the additional time required is hardly significant in relation to the total travel time. In networks for long-distance traffic, the traffic routes are designed in such a way that higher speeds are possible. Therefore, detours are also justifiable here. Provided there are no special requirements from traffic demand, network densification in long-distance traffic – e.g. through a diagonal line – is considered from a length of about 100 km. Bridges have a special significance as an element of transport network design for several reasons: • Traffic routes have to overcome natural obstacles such as rivers and valleys, but also other transport routes. Bridges are necessary for this. • Traffic routes should be routed as directly as possible, minimise gradients and be passable at a given design speed. A route that meets these requirements needs bridges and tunnels. • Bridges are particularly expensive traffic routes. Therefore, it is particularly important to bundle the traffic demand of several routes. The structure is more economical if it is used by as many road users as possible. • The bundling of many routes into one bridge structure means that bridges are particularly vulnerable structures. The failure of an object can considerably impair the connecting function of the transport network. The importance of a bridge structure in a transport network can be determined with traffic demand models. For this purpose, a demand matrix that contains the traffic demand between the sources and destinations of a study area is assigned to the transport network. This traffic assignment maps the route choice behaviour of users

Bridges and Trafﬁc

structure reactions. With these experimentally determined values, the theoretical models or calculation assumptions can be improved and the structural safety can be assessed more reliably. The improved findings can often open up load-bearing reserves that can be used to avoid costly reinforcements or even a replacement construction [12]. For existing bridges, there are different tasks for load tests (fig. 8): • Level 3 of the recalculation guideline as system measurement and for model calibration • Determination of static or dynamic properties of the structure • Brake load tests on long railway bridges • Dynamic load tests with different exciters (ambient action, falling weight, vibration exciter, train crossing) • Verification of sufficient structural safety against defined actions

Load tests When assessing existing structures, however, ignorance of the inner workings of the structures can lead to conservative models and assumptions; a recalculation is then often not very meaningful. For this reason, experimentally supported verification has become established in some European countries for the evaluation of existing structures (level 3 of the recalculation guideline), which is carried out by means of selectively applied actions directly on the structure as well as by the metrological ascertainment and evaluation of the

Monitoring – predictive maintenance – digital twin Monitoring is the systematic and continuous supervision of influencing variables or of building reactions by means of electronic measuring systems. Like in medical monitoring, buildings can also be monitored 24 hours a day, 7 days a week; in the event of malfunctions, appropriate notifications are sent according to defined process chains (fig. 10). For this purpose, critical conditions (warning and threshold values) are defined in advance. Depending on the task, there are very different requirements for the technology, the time period and the evaluation [13]. In recent years, structural monitoring has developed into a reliable and recognised method for measuring structural behaviour and its changes. Due to new sensor and evaluation technology as well as digitalisation, the importance of bridge monitoring and the potential for bridge evaluation has increased considerably in recent years. Typical applications for bridge monitoring are:

8 Different load tests a Load test with hydraulic presses to determine the substructure stiffnesses at the Itztal Bridge on the new ICE line Ebensfeld-Erfurt (DE) from 2004 b Load test with heavy truck-mounted concrete pumps to measure the suspension forces and stresses in the support structure, Köhlbrand Bridge, Hamburg (DE), from 1974 c Brake test on the Stöbnitztal railway bridge, new ICE line Erfurt-Leipzig / Halle (DE) from 2013.

Notes: [1] BASt Booklet B 68 [2] 2020 ARTBA Bridge Report (USA) [3] 2020 Working guide, p. 14 [4] Marx 2020 [5] ÖNORM B 40082:2019-11-15 [6] ibid. [7] Fingerloos / Marx / Schnell 2015 [8] as note 5 [9] ibid. [10] Federal Ministry of Transport, Building and Urban Development, Department of Road Construction 05/2011 [11] DB Netz AG, Guideline Ril 805, 2012 [12] DAfStb Guideline for load tests 2020 [13] DBV leaflet 08/2018

Actual building

Digital twin

Geometry + data

BIM

Condition

Monitoring + structural inspection

9 9 From the existing structure to the digital twin for the visualisation of actual structural condition data of the Köhlbrand Bridge in Hamburg (DE) from 1974

10 Applying sound emission monitoring at the Stennert Bridge in Hagen (DE) from 1959, which is at risk of stress corrosion cracking, it is proven that no prestressing steel fractures occur under continuous load and that further use is possible even without announcement behaviour.

• Increasing safety during construction work next to bridges in use • Confirmation of structure behaviour when new types of structures or components are introduced • Extension of the planned service life of a bridge • Increase of utilisation requirements (traffic load increases, speed increases on railway lines) • Measurement-based verification when calculated limit values are exceeded

structure and evaluated using artificial intelligence (AI) and condition indicators (fig. 9). The aim is to use pattern recognition to detect changes in the structure before damage is visible. The development, test phase and introduction of predictive maintenance in conjunction with machine learning will become a new future field of bridge maintenance.

Predictive, i. e. anticipatory, long-term monitoring, as already established in many other industrial sectors, enables a reduction in maintenance and repair costs and leads to an increase in operational safety and reliability. Research is currently being conducted on the development of a digital, predictive maintenance concept for bridges that provides a direct overview of the condition of the structure in different depths of data detail on the basis of Structural Health Monitoring (SHM) and the entire data integration in a digital building model according to the BIM method. The central data collection and evaluation via the sensors in the structure is expanded to include the processing of data from the vehicle sensors, the traffic recording, the climate data, etc. The consolidation of all data takes place in a digital building model according to the BIM method. All data is merged in a digital twin of the bridge 10

Preservation and Evaluation of Bridges

Impact Internal and external loads

Load ratio [gK /(gA+p)]

Structure’s impact on itself A structure impacts itself due to the dead weight of the construction, essentially due 100

Railway bridges Road bridges Pedestrian bridges

to the raw densities of the building materials used (e.g. steel, concrete, timber) and the material-specific properties occurring in the case of deformation restraints as well as due to the prestressing in prestressed concrete cross-sections. Dead weight and support loads Bridges are significantly loaded by their own weight. The longer the span of the support structure, the greater the ratio of dead weight to all other acting loads and the smaller the slenderness (fig. 1). The dead weight is determined by the gross weights of the materials and their volumes in the structure. Also Slenderness [λ = L/d]

In order to determine the structural dimensions of a bridge, all foreseeable actions on the structure must be reliably estimated. These factors, which depend on the specific use, geographical location and environmental conditions, are determined individually on the basis of the regulations applicable in the respective countries. The loads to be applied are to be subjected to appropriate safety factors for the staticconstructive dimensioning of the bridge structure.

35 30

Railway bridges Road bridges Pedestrian bridges

25 20 15

10 20 5 0

0 0 10 20 30 40 a

50 60 70 80 90 100 Span [m] b

0 10 20 30 40 50 60 70 80 90 100 Span [m] 1

1 Comparison of a singlespan rectangular concrete beam carrying pedestrian, road and railway traffic. a Ratio of construction loads (gK) and the sum of support loads (gA) and live loads (p) as a function of the span L of bridges. Here, the required girder height d is approximately calculated assuming a reinforcement content of 0.8 % in the ultimate limit state (state II). b Slendernesses O = L /d as a function of the span. For short spans (approx. up to 15 m), the influence of the individual loads to be applied to road bridges on the girder design is clearly evident.

the loads of the extensions necessary for the specific function of the bridge have to be taken into account. Constraint Depending on the material, forces occur from internal constraint due to creep, shrinkage, swelling or hydration processes of the building material over the service life of the structure. However, these constraining stresses can be relieved by cracking – especially when reinforced concrete is used – and therefore usually play a subordinate role for the ultimate limit state of the loadbearing capacity. Prestressing Prestressing can positively influence the stress state in a structural system by introducing tensile or compressive forces. A possible crack formation as in reinforced concrete is thus prevented and the durability is increased. A stiffening of the system also occurs, which in turn can be used, for example, in cable structures to avoid slack tension members. The prestressing remains inherent to the system and therefore also represents a self-impact inherent to the object. Loads from traffic The traffic loads, i.e. the loads to be transferred by the bridge user, are also of great importance for the calculation and design of the bridge. Due to the load movement inherent in the traffic over the bridge, dynamic effects, braking and starting forces as well as centrifugal forces also occur.

2 Load densities for different traffic loads caused by cyclists and pedestrians on a bridge (representation without scale and not referring to 1 m2)

Cyclist 1 kN/m2

Pedestrian 1 kN/m2

Vertical and horizontal live loads In addition to the dead load, the vertical load components from traffic are decisive for the dimensioning of the structure. The applied loads should take into account future developments with sufficient certainty, but also allow for an economic design. While in the case of footbridges and cycle bridges the increasing tendency to decouple pedestrian and cycle traffic could enable a specifically graded load assumption and thus also a partial reduction of the traffic loads in the future, a further increase in the load to be taken into account is to be expected for the other forms of traffic. In addition to the expected increase in real road traffic (see “Requirements for future bridge structures”, p. 48f.), train lengths that exceed the train length limit of 740 m currently valid in Europe are being considered for rail-bound traffic. For example, Europe-wide organisations are already discussing train lengths of up to 1,500 m with loads of up to 5,000 t and 25 t axle load, while in the Gulf region rail networks are being considered for goods trains up to 2,000 m long as container-carrying wagons with double-deck loading and up to 32.4 t axle load. Foot and cycle path traffic For pedestrian and cycle bridges (fig. 2), surface loads of approx. 3.5 to 5 kN/m2 are to be applied in accordance with the respective national standards, which in some countries can be reduced as the

Pedestrian 1.5 kN/m2

Pedestrian 2 kN/m2 2

Impact

Economic Efficiency Using financial resources responsibly

The question of costs has always been of importance when selecting a bridge type, since in modern times, as a structure of public interest, it is usually financed by public money. It is an unwritten law throughout history that the financial resources for infrastructure measures have always been limited, regardless of the form of government and therefore had to be used sparingly and appropriately. Even the Roman architect and engineer Vitruvius, in addition to his main requirements for architecture, namely firmitas, utilitas and venustas (see “Technical and design challenges”, p. 12), demanded that the architect should precisely allot and estimate the costs [1]. In

the 19th century, the German civil engineer, urban planner and university lecturer Reinhard Baumeister described the “money men” as important decision makers who influenced bridge building alongside the “utilitarians” as representatives of the exclusively utilitarian and the “art aristocrats” as guardians of the beautiful [2]. Not least because of their responsibility towards the public, many engineers such as Fritz Leonhardt, Pier Luigi Nervi or Eduardo Torroja, like Vitruvius and Reinhard Baumeister, combined attractive and functional construction with economic requirements [3]. Particularly in bridge construction and civil engineering, there is no way around

1 Simple elegance as an expression of efficiency and economy. One of the motorway bridges of the A11-Via Brugge infrastructure project, Bruges (BE), 2017, schlaich bergermann partner 1

Production costs [per m2]

Tensile construction

Haunched cantilever construction Beam bridge

100

2 Construction costs as a function of span according to Alfred Pauser

200

300

400

500 Span [m] 2

a comprehensible calculation of economic efficiency today, which certifies a moderate use of financial resources not only in the construction phase but also beyond. Considerations of economic efficiency must not be confused with cheap construction as a short-term effect, which characterised the so-called construction industry functionalism [4] of the post-war era with the aim of quick and cheap construction according to the formula “length times width times height times money” [5] and promoted faceless bridge construction (see “Motorway bridges”, p. 28). Bridges need quality according to Vitruvius’ requirements and quality demands its real price, especially if a positive image and sustainable use are to be taken into account. The question now arises as to how much the good design of a bridge should be worth to society? With the primary goal of connecting places (see “Designing Bridges”, p. 6ff.), a basic level of aesthetic quality is sufficient, which, if the formal logic is based on a unity of structure and design, entails no or only minor additional costs compared to the usual standard values. This applies

in particular to road and railway bridges, whose purpose-determined connecting character is in the foreground (fig. 1). Christian Menn recommends an additional cost for the fine-tuning of the design of approx. 5 % for large bridges [6] and for smaller bridges even more; i.e. percentages that are in any case within the range of bid fluctuations when awarding the construction work. Especially in the case of railway bridges, additional costs for structural stages and auxiliary facilities to maintain railway traffic are possible, which often increase the construction costs by a factor of three to ten. Additional costs for a minimum design requirement are practically irrelevant here. In contrast to the additional operational costs, which are unquestionably accepted (by the company) for the shortterm nature of the construction work under railway operation, the added design value remains visible over the entire service life of the bridge as a tangible structure or architectural cultural asset. Guidelines For the construction phase, the costs per bridge area unit (bridge benchmark) are the most important economic benchmark. In the case of road and railway bridges, there is always a dependency on the span width if standard designs and construction methods are assumed. The bridge builder Alfred Pauser has attempted to illustrate the qualitative dependencies of the construction costs on the span width according to the type of construction in a graph (fig. 2). The larger the span, the higher the costs per m2 of bridge surface, and the more economical are haunched or dissolved constructions. This shows that the choice of an incorrect load-bearing system can lead to a failure to achieve the economic goal even in the design phase. However, fig. 2 shows, as do cost analyses of 2,000 road bridges and 150 railway

Economic Efﬁciency

superstructure and reinforced concrete substructure are monolithically coupled. New types of material-hybrid construction methods (e.g. reinforced concrete-wood composite) lend themselves for use in road bridges, for example.

Construction and design Wooden bridges have to be constructed in a way that is appropriate for the material and maintenance. The trend towards robust, mass-intensive timber bridge structures that has been observed in recent years not only leads to greater durability but also points to a changed new view of the ancient building material. Unlike with all other materials, a more solid timber design is also more sustainable, since the higher CO2 storage in the large volume of timber and the lower technological processing depth lead to a comparatively low global warming potential, which is often negative when considering the superstructure alone. Compact, easy-to-manufacture block girder crosssections can be designed with few or even no exposed connecting elements. A design aligned with the flow of forces can be achieved by differentiated shaping of the horizontally or vertically arranged, blockbonded, glue-laminated timber layers. Stone Extracted from the Earth’s crust, stone, due to is worldwide occurrence, mechanical properties, and great durability, has for many cultures always been an important bridge-building material (see “Stone bridges”, p. 16, and “Arch bridges”, p. 37). Natural stone bridges were built all over the world until the 20th century, and many historical structures testify to how durable they can be. The mighty piers of the Brooklyn Bridge were made of granite blocks, as the high-strength, very homogeneous and fine-pored deep rock is able to safely and permanently dissipate the high bearing forces of the main supporting cables.

Properties and use In contrast to the upwardly striving wood, stone is earthy, like clay and bricks, and is connected to the earth. Historically, stone was used for short slab bridges or for arch bridges. The arch composed of natural stones or bricks visualises the flow of forces in the support structure and at the same time reveals the very high compressive strength (fig. 9). The stones are usually staggered in the mortar bed, the joints giving the structures a structural grid. The mortar, which is matched to the strength of the stones, compensates for the unevenness of the stones and ensures that the forces are transmitted over the entire cross-section. Due to the very low tensile strength of the material, stone arches were designed in such a way that no tensile forces would occur in the support structure. Additions of steel fixtures for tensile transmission were not common. This is a major reason why arch and vault bridges are indestructible: only the stone can corrode – and these processes are not comparable in time to steel corrosion. The appeal of natural stone bridges is in their

5 One of four pedestrian bridges with prestressed granite superstructure and a span of 10.30 m, Kurpark Bad Herrenalb (DE), 2016, Execution: Kusser Granitwerke, Design: bbzl – böhm benfer zahiri landschaften städtebau 6 Tension band bridge with 40-m opening. The granite walkway slabs are prestressed via steel bands below. Pùnt da Suransuns, Viamala (CH), 1999, Conzett Bronzini Partner

7 The inner-city pedestrian bridge hangs from 16 tension rods that transmit their loads to a tree-like mast made of individual natural stone blocks. Bad Homburg (DE), 2002, schlaich bergermann partner 8 Bahrebachmühlen Viaduct, Chemnitz (DE), 1872, restored in 2010, Marx Krontal Partner 9 Compressive strengths of different building materials relevant for solid bridge construction

geometric shape and in the detail of the stone workmanship. Since natural stone is not a homogeneous building material, its strength and durability properties vary greatly depending on the type of stone and its occurrence. Numerous types of stone such as granite, porphyry, diorite, sandstone, basalt, shell limestone, marble and travertine are used in bridge construction as load-bearing components or as facing. As a rule, natural stone is a very weatherresistant building material, has high abrasion resistance to water and sand erosion, and was often used for the facing of river piers due to its durability.

Material

Compressive strength [N/mm²]

Marble, granite

up to 300

Sandstone

up to 150

Limestone

up to 90

Today, the knowledge of engineers in solid construction is concentrated exclusively on industrially producible building materials, and experience in natural stone bridge construction is almost completely lost. In new construction, natural stone is currently used almost exclusively for veneering to enhance appearance and increase durability. This does not do justice to to it as a building material. The 3D-supported natural stone processing available today at many specialised companies is also economically feasible for modern bridge support structures with high sustainability and low CO2 emissions. In recent years, some pedestrian bridges have been built as

Solid clinker up to 80 Solid brick

up to 48

Concrete

> 20

Highstrength concrete

up to 150

Ultra high over 150 performance concrete

Natural stone in contemporary bridge construction

hybrid structures with natural stones and internal prestressing or external loadbearing elements with extremely high slenderness (fig. 5 and fig. 6). Today, however, the focus is rather on the preservation and rehabilitation of the many arch bridges from previous centuries, which are in great need of renovation due to weathering, traffic and alterations (fig. 8). Since these restorations require knowledge of old construction principles, materials and damage processes, planning and implementation represent a special engineering and construction task. Iron and steel Processed iron ore has been used as a raw material for tools, jewellery and in weaponry for more than 3,000 years. Later, the Romans, for example, used iron for fittings and clamps as connecting elements of stone blocks, also in bridge construction [1]. The breakthrough of iron for structural bridge building and civil engineering did not occur until the 18th century, due to the improved opportunities for the large-scale production of pig iron with the use of coke instead of charcoal and the further development of the blast furnace. The superiority of iron structures over stone in their ability to withstand large forces compared to the weight of the structure used meant that costs could be reduced and construction time significantly shortened. Starting from

Materials

1 2 3 4 5

Arch Elevations Abutment End wall Parapet

Stone arch bridge Anji Qiao, Zhao Xian (CN), 605 AD, Li Chun

Classical viaduct

Arches 22

Bar arch as continuous girder

Bar arch as support for the roadway

Arch with re-suspension of the tension force in the carriageway

Langer‘s girder

Network arch

The arch is the oldest load-bearing system after the beam. Early on, a benefit was recognised in stacking stone blocks radially and activating the arch thrust as a force transfer exclusively via compressive forces (fig. 20). Stone viaducts as railway bridges, which take up the design of the viaducts and aqueducts of the Roman Empire, are imposing contemporary witnesses of a robust but no longer modern bridge type (fig. 21). With uniform vertical loads, the arch unfolds its full effectiveness. Halfsided loads from traffic have to be transferred by bending moments or over-pressed by high dead weight. For this reason, the use of arched structures for larger spans only makes sense if the traffic loads are small in relation to the dead load and the building ground is very stiff (e.g. rock). Starting from the haunched beam (fig. 9, p. 95) via the resolved truss (fig. 17, p. 97), the haunch is further widened and articulated downwards in bar arch constructions so that the compressive force is not suspended high via filler bars but can be led directly to the support as a bar arch via arch action (fig. 22). The acting strut forces at the supports must either be directly introduced into the subsoil (fig. 23), suspended back into the bridge deck or shortcircuited there, as shown by the example of the bar arch in fig. 22. The bar arch in fig. 23 acts as a support structure for the bridge deck, which is offset from the arch and absorbs the bending moments from half-sided loads. The load-bearing behaviour can be clearly understood on the basis of the component dimensions. For carriageways with a low height above the ground, arch-supported structures are suitable, which are arranged above the carriageway and return the horizontal force into the carriageway (fig. 24). In the case of the so-called Langer’s

girder, the arch runs entirely above the carriageway and its abutment forces are connected by the stretch girder integrated into the carriageway as a tension band (fig. 25). Due to the vertical hangers, it is predominantly this stretch girder that has to absorb the half-sided loads via bending and is usually dimensioned larger than the arch cross-section. In contrast, the network arch functions similarly to a bending girder due to the diagonally and crosswise arranged tension elements (fig. 26). The support structure here represents a symbiosis between the arch and the truss and is extremely stiff in relation to the pure bar arch. Asymmetrical live loads are effectively distributed between the arch and the stiffening girder by the hanger arrangement, which reduces the bending stresses there and allows the structure to be very slender. By analogy with the truss frame (fig. 11 at the top, p. 95) and the bar arch (fig. 22), fig. 27 and fig. 28 show two variants in which the arch apex merges with the deck. In contrast to the continuous effect (fig. 27), the arch in fig. 28 introduces the forces into the rock flanks. In doing so, a clearer centre reference to the apex axis can be observed, which characterises the arch as a suitable, dynamically acting support structure over obstacles such as deep ravines. Fig. 29 shows the classic, true arch with elevated carriageway, which, in contrast to the bar arch in fig. 23, appears as the dominant structural element. It braces itself powerfully against the rock, takes on the bending moments from half-sided loads, and its dimensions stand out accordingly. As pedestrian bridges, arch bridges can also be designed in different variations, such as with an overlying tension band that short-circuits the arch horizontal force again (fig. 30).

Arch with continuous beam effect

Arch with pronounced centre reference

Classic (true) arch bridge

Arch with counterweight (e.g. Dyckerhoft Bridge, Wiesbaden, 1967)

Arch with overlying tension bands (e.g. overpass near Olomouc, 2007) 30

Arch variations for pedestrian and cycle path bridges

Designs

Bridges in Detail

Pedestrian and cycle path bridges “Stuttgart Wooden Bridge” in Weinstadt (DE) Knippers Helbig Advanced Engineering / Cheret Bozic Architects Chain Bridge in Weimar (DE) Marx Krontal Partner (renovation) Tintagel Castle Bridge (GB) Ney & Partners / William Matthews Associates

104 110 114

Road bridges Queensferry Crossing near Edinburgh (GB) Jacobs Arup Joint Venture / Leonhardt Andrä und Partner / Rambøll Group / Rambøll UK / Sweco UK Tamina Bridge in the Canton of St. Gallen (CH) Leonhardt Andrä und Partner / dsp Ingenieure + Planer / Smolczyk & Partner A5.Ü20 near Wilfersdorf (AT) Asfinag Bau Management / Öhlinger und Partner / Mayer Ingenieurleistungen Lower Hātea River Crossing in Whangarei, New Zealand (NZ) Knight Architects / Peters & Cheung (now Novare Design)

120 125 132 136

Railway bridges Scherkondetal Bridge near Krautheim (DE) DB ProjektBau / Steffen Marx, Ludolf Krontal Second Hinterrhein Bridge near Reichenau (CH) Dissing+Weitling, WaltGalmarini, Cowi UK Getwing Bridge in Zermatt (CH) schlaich bergermann partner / SRP Schneider & Partner Ingenieur-Consult / mls architekten

142 146 152

103

A New Type of Bridge Made of Wood Pedestrian and cycle bridge at the Birkelspitze in Weinstadt, Germany

“Solid, integral, and durable – this type of wooden bridge could help revive the use of this renewable building material in bridge construction. In addition to innovative static-constructive aspects, an independent design language is introduced into timber bridge construction, which is oriented towards manufacturing principles and load-bearing behaviour. A well-proportioned, sculptural bridge that cuts a fine figure even from a worm’s-eye view.” Ludolf Krontal

On the occasion of the Remstal Garden Show 2019, the Rems Valley east of Stuttgart was transformed into a giant garden for 164 days. A total of 16 towns and municipalities along the Rems river organised this unique show and designed a landscape space with parks and green spaces as well as a new network of cycling and hiking paths over a length of 80 km. To connect the paths on both sides of the Rems, the municipalities of Weinstadt and Urbach were provided with three new pedestrian and cycle bridges based on the concept of the Stuttgart Wooden Bridge. Stuttgart Wooden Bridge The so-called Stuttgart Wooden Bridge is a new, durable type of bridge that requires as little maintenance as possible. This bridge

View Scale 1:250

104

type was developed by engineers, architects and timber construction experts in cooperation with the University of Stuttgart. As part of a research project launched in 2013, common causes of damage were first analysed on eleven existing wooden bridges from the 1980s and 1990s in the Stuttgart area that are still in use. The results of the investigation clearly show the reasons for the sometimes considerable damage. These include, among other things, accumulating moisture in the support area and waterproofing leaking underneath. Connecting structures that are exposed to weathering and do not dry sufficiently after moisture penetration shorten the service life of the bridges, in some cases considerably. The newly developed bridge type based on these findings is a covered bridge in which

Bending moment curve of a single-span girder clamped on both sides under equal load (top) Beam shape aligned with the bending moment curve (below)

the protruding walkway decking protects the girder made of block-glued gluelaminated timber from direct weathering. On the top side, the solid wood crosssection is also sealed with a breathable film. A distance of 15 cm to the walkway decking allows sufficient rear ventilation. Design and construction: Knippers Helbig Advanced Engineering, DE-Stuttgart, Thorsten Helbig (project management) Cheret Bozic Architects, DE-Stuttgart, Peter Cheret (project management)

The first integral bridge with a wooden superstructure In contrast to historical wooden bridges, the new development is an integral bridge, i.e. without bearings or joints: the girder and the abutment are monolithically connected to each other. Glued-in threaded rods, which are integrated into the reinforcement of the abutment with a corresponding over-

lap length, transmit the bending tensile and normal forces between the timber superstructure and the reinforced concrete substructure. However, the direct coupling between the solid, block-glued gluelaminated timber carcass and the reinforced concrete substructure carries the risk of cracking as swelling and shrinkage due to moisture-related changes in the wood are obstructed. To validate the connection concept, the planners developed a prototype on which measurements were taken and evaluated. Load tests on glulam and reinforced concrete test specimens, which were connected by reinforcing steel bars with a diameter of 16 mm and glued in with

“Stuttgart Wooden Bridge” in Weinstadt (DE)

105

Railway Bridge on a Slender Footing Scherkondetal Bridge near Krautheim, Germany

“A linear and compelling bridge with a consistent style, which meets the purpose of a high-performance line and bears the imprint of engineering excellence. With its joints and bearings reduced to an absolute minimum, low maintenance, and attention to detail from the overall composition to the drainage, the structure impresses with its compactness and the fine form accents of the haunches and piers.” Michael Kleiser

The Scherkondetal Bridge, commissioned in 2015, is located in the Weimarer Land district and is part of the Erfurt-Leipzig / Halle high-speed ICE line. North of Krautheim, it crosses the small river Scherkonde, which is dammed up to form a lake here. Design and load-bearing concept Compared to conventional road or railway bridges, high-speed railway bridges have to meet significantly higher requirements in terms of load-bearing capacity and serviceability. Ensuring dynamic stability and limiting structural deformations require extremely rigid structures, which is manifested by very massive component geometries. In contrast to the single-span girder chains commonly used in the past, the Scherkondetal Bridge breaks new ground with its semi-integral support structure: as is usual for semi-integral structures, the superstructure is monolithically connected

Design and construction: DB ProjektBau, DE-Leipzig, Steffen Marx, Ludolf Krontal Detailed design: Büchting + Streit,

142

DE-Munich Test engineer: Curbach Bösche Ingenieurpartner, DE-Dresden Client: DB Netz, DE-Leipzig

01a

Section Scale 1:2,000

Scherkondetal Bridge near Krautheim (DE)

143

to the piers and partly to the abutments. With this load-bearing concept, the bridge fulfils all static and dynamic requirements while being extremely slender and transparent. Longitudinal force transfer The dissipation of the large horizontal forces resulting from the combination of braking, approach and constraining forces posed a particular challenge in the design process. The planners examined numerous variants with regard to the choice of fixed points and came to the conclusion that the superstructure would have to be monolithically connected to the western abutment and to eleven piers (from 01a to 10). The high forces are transferred with little deformation into the ground at the western abutment via two almost rigid, bored pile walls arranged in the longitudinal direction of the structure. Since the distance between the fixed point and the last connected pier is very large at 452 m, very high constraining stresses from temperature, creep and shrinkage occur in the monolithically connected piers. To minimise these, the piers and their foundations are designed to be very flexible and slender in the longitudinal direction of the structure.

The piers rest on single-row, vertically very stiff pile foundations, which also absorb constraining loads. Through the specific selection of the concrete’s aggregates, the modulus of elasticity was controlled so that the piers have softer stiffnesses and the superstructure has high, more effective stiffnesses. The reduction of bearings and joints allows for improved durability and thus a significant reduction in maintenance costs. Construction process The construction of the superstructure was carried out in sections, with the help of a scaffold mounted on brackets from the eastern abutment, where the temporary longitudinal fixed point was located for the construction of the superstructure. By changing the fixed point to the western abutment during the construction process, the constraints during construction could be minimised considerably. Each superstructure section was concreted in one go, without a construction joint. Other Deutsche Bahn high-speed railway bridges have since been built according to this innovative, semi-integral construction principle.

92.44 13.90

36.36 44.00

144

Longitudinal section • Cross-sections superstructure Scale 1:250

View of movable scaffolding Scale 1:600 1 Scaffolding girder U 3000 2 Formwork girder HEB 550 3 Coupling joint 4 Suspension 5 Scaffolding on the pier

Scherkondetal Bridge near Krautheim (DE)

145

Picture credits The authors and the publisher would like to express their sincere thanks to all those who have contributed to the production of this book by providing their images, by granting permission for reproduction and by providing information. All drawings in this work have been specially produced. Despite intensive efforts, we were unable to identify some of the authors of the illustrations but their copyrights are protected. We kindly ask you to inform us accordingly. Drawing on the cover: Tamina Bridge in the canton of St. Gallen (CH) Leonhardt Andrä und Partner, dsp Ingenieure + Planer , Smolczyk & Partner Designing Bridges 1 By Estec GmbH, cheap hotel in Prague – Own work, CC BY 3.0, https://commons.wikimedia.org/w/index. php?curid=7053219 2 form PxHere 3 Ludolf Krontal 4 Ralph Feiner 5 By Ezzeldin.Elbaksawy – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index. php?curid=92099689 6 https://pixabay.com/de/photos/parisbr%C3%BCcke-pont-neuf-seine-368384/ 7 A. Liebhart/pixelio.de 8 By Dinkum – Own work, CC0, https://commons.wikimedia.org/w/index. php?curid=20742587 9 By Behrad09 - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index. php?curid=52072141 10 Jean-Luc Deru/ Photo-daylight.com 11 By Mike Lehmann, Mike Switzerland – Own work, CC BY-SA 2.5, https://de.wikipedia.org/w/index.php?curid=3891352 12 a ETH Library Zurich, Picture Archive 12 b ETH Library Zurich, Picture Archives / Photographer: Boissonnas, FrançoisFrédéric / Hs_1085-1935-36-1-24/Public Domain Mark Bridges for Slow-Moving Traffic 1 By Axel Hindemith, CC BY-SA 3.0, https://commons.wikimedia.org/w/index. php?curid=80287773 2 By Vinayak Hegde - Flickr: A double decker living bridge, CC BY 2.0, https://commons.wikimedia.org/w/index. php?curid=18808200 3 Lothar Henke / pixelio.de 4 wikipedia Ochsenklavier_Pfrimmpark_CC BY-SA 4.0_Goldener Käfer.jpg 5 By Davepark – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.

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php?curid=17874542 wikipedia CC BY-SA 3.0_Davepark www.bernd-nebel.de Petra Egloffstein By MOSSOT – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index. php?curid=9403804 10 By Pufacz – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index. php?curid=21782053" 11 Junkyardsparkle Wikimedia Commons, Public Domain, https://upload.wikimedia. org/wikipedia/commons/ 8/8e/California_ Cycleway_1900.jpg 12 By Theo lauber – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/ index.php?curid=77913620 13 By Sunyiming – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index. php?curid=80878228 14 A.Windmüller / pixelio.de 15 Rasmus Hjortshøj – COAST 16 ipv Delft – Beeldtaal 17 Foster + Partners / Exterior Architecture 18 visualization Dissing+Weitling / POSCO, Engineering Division 6 7 8 9

Road Bridges 1 iStock photo, Photo: Lukas Bischoff 2 a from: Merckel, Curt: Die Ingenieurtechnik Im Alterthum. Berlin 1899, p. 301, fig. 108 2 b agefotostock /Alamy Stock photo, Photo: Tono Balaguer 3 https://structurae.net/de/fotos/76196seinebruecke-neuilly 4 Tak /Adobe Stock Photo 5 a Gesellschaft für Ingenieurbaukunst / Clementine Hegner-van Rooden 5 b Eugen Brühwiler 6 Michael Kleiser 7 from Pauser, Alfred: Entwicklungsgeschichte des Massivbrückenbaues. Österreichischer Betonverein, 1987, p. 89, fig. 96; Drawing: Michael Kleiser 8 ASFINAG / Drawing: Michael Kleiser 9 Data according to PIARC 2017 10 Ralph Feiner 11 By Michael from Germany – originally posted to Flickr as Skarnsundbrua, CC BY 2.0, https://commons.wikimedia.org/w/ index.php?curid=11460269 12 Photo by Maarten de Vries from FreeImages 13 By HK Arun - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index. php?curid=14202705 14 Michael Kleiser 15 By Storebæltsbroen.jpg: Alan Francisderivative work: pro2 - Storebæltsbroen. jpg, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=15320759

16 PantherMedia photo agency / iofoto 17 Michael Kleiser 18 Lutz Sparowitz 19 Walo 20 Michael Kleiser 21, 22 Sparowitz, Lutz; Freytag, Bernhard; Oppeneder, Johannes; Tue, Viet Nguyen: Quickway – smart mobility for the liveable city of the future. Proceedings, 25th Czech Concrete Days. 2018 Bridges for Rail Traffic 1 form PxHere, https://pxhere.com/de/ photo/663341 2 a, b www.letchworthparkhistory.com 2 c By Andre Carrotflower - Own work, CC BY-SA 4.0, https://commons.wikimedia. org/w/index.php?curid= 82896860 3 Nicolas Janberg 4 Vincent Le Quéré 5 a By Andreas Passwirth, Own work, CC BY-SA 3.0, https://de.wikipedia.org/wiki/ Langwieser_Viadukt#/media/Datei: Langwieser_Viaduct_Underneath.jpg 5 b By a, https://commons.wikimedia.org/w/ index.php?curid=22012846 6 Marx Krontal Partner 7 Steffen Marx 8 According to DB Netz AG database 9 HyperloopTT 10 Max Bögl Group 11 Knight Architects 12 Hanno Thurnher Photography 13 Nicolas Janberg 14 Ludolf Krontal 15 SSF Engineers 16 Marx Krontal Partners 17 Nicolas Janberg 18 Marx Krontal Partner 19 SSF Ingenieur AG: Brücken mit VerbundFertigteil-Trägern. VFT-Bauweise. Project brochure 20 Marx Krontal Partner Bridges and Traffic 1 Lindsay Corporation 2 Markus Friedrich 3 (p. 45) various sources: – Network length: according to BMVI: Verkehr in Zahlen. Berlin 2018 and estimates by the author – Number of bridges: long-distance public transport: DB Netze 2018; cars on federal trunk roads: BASt 2019; cars on state, district and other roads, walking and cycling: Arndt 2013 and Difu 2015 (see Note 4; Bridges and Traffic, p. 159). – Passenger kilometres: author’s calculations based on BMVI: Mobilität in Deutschland – MiD. Results Report. Bonn / Berlin 2019 and Bäumer, Marcus et al.: Fahr-

leistungserhebung 2014. Bundesanstalt für Straßenwesen. Bergisch Gladbach, 2017 4 FGSV No. 121 Forschungsgesellschaft für Straßen- und Verkehrswesen (ed.): Richtlinien für integrierte Netzgestaltung (RIN). Cologne, 2008 5, 6 Markus Friedrich 7 ASFINAG, Statistics Austria Preservation and Evaluation of Bridges 1 According to BASt vol. B 68: Auswirkungen des Schwerlastverkehrs auf die Brücken der Bundesfernstraßen. p. 36 2 Marx Krontal Partner 3 According to Mark, Peter: Erhalt unserer Bausubstanz. In: Betonkalender 2015. Vol. 1. Berlin 2014, p. 8 4 Evaluation of data from Deutsche Bahn AG, research project: Digitale Instandhaltung von Eisenbahnbrücken - DiMaRB, Leibniz University, Hanover, 2019. 5 a Ludolf Krontal 5 b ZKP 5 c Laumer Bau 6 – 8, 10 Marx Krontal Partner 9 wtm-engineers, Marx Krontal Partner Impact 1 Michael Kleiser 2 Thorsten Helbig 3 According to Eurocode 1 DIN EN 19912:2010-12 4 According to historical sources and current standards, e.g. DIN EN 1991-2:2010 5 According to Eurocode 1 DIN EN 19912:2010-12 6 According to Krontal, Ludolf: Zum Entwurf von Eisenbahnbrücken. In: structurae Projektbeispiele Eisenbahnbrücken. Berlin 2014, p. 3 7 Wacker-Ingenieure.de 8 Thorsten Helbig 9 Nahrath, Niklas: Modellierung Regen-Windinduzierter Schwingungen. Dissertation. TU Braunschweig, 2004, p. 34 10 According to Richtlinien für den Entwurf, die konstruktive Ausbildung und Ausstattung von Ingenieurbauten (RE-ING) 2017. 11 According to Wenk, Thomas: Erdbebensicherung bestehender Bauwerke. Lecture notes. Zurich, 2000 12 Thomas L. Rewerts, of Thos. Rewerts & Co, LLC 13 a From: Varela, Sebastian; Saiidi, Mehdi: Resilient deconstructible columns for accelerated bridge construction in seismically active areas. Journal of Intelligent Material Systems and Structures. 2017, vol. 28 (13), fig. 1 (C). Function 1 David Boureau 2 Marx Krontal Partner 3, 4 Essentially based on Eichwalder, Bernhard: Fugenlose Fahrbahnübergangskonstruktion für lange integrale Brücken. Dissertation. Institut für Tragkonstruktionen,

Forschungsbereich für Stahlbeton- und Massivbau. TU Wien, 2017, p. 27, drawing Michael Kleiser. 5 mageba 6 a ASFINAG 6 b Michael Kleiser 7 According to Ril 804.5202 8, 9 Michael Kleiser according to RVS (AT), BASt Richtzeichnungen, Astra (CH), Deutsche Bahn, SSF, ÖBB, Kantbalk Typ 8 KTH, The Illinois State Toll Highway Authority 10 Michael Kleiser 11 schlaich bergermann partner / Michael Zimmermann 12 Marx Krontal Partner 13 Schréder Economic Efficiency 1 Kris Provoost 2 According to Pauser, Alfred: Eisenbeton in der ersten Jahrhunderthälfte. In: 100 Jahre Beton- und Bautechnik. Vom Beton-Eisen zum Spannbeton. Österreichische Vereinigung für Beton- und Bautechnik. Vienna, 2007, p. 127 3 According to Kessler, Anne; Marx, Steffen: Ingenieurwettbewerbe im Brückenbau. Eine Projektanalyse über Aufwand und Qualität. In: Deutsches Ingenieurblatt 10/2018, p. 36ff. 4 Alan Karchmer 5 According to FSV: RVS 13.05.11 – Lebenszykluskostenermittlung für Brücken. Directive. Österreichische Forschungsgesellschaft Straße – Schiene – Verkehr 2017 Sustainability 1 By AngMoKio – Own work, CC BY-SA 2.5, https://commons.wikimedia.org/w/index. php?curid=1253561 2 Data according to ÖKOBAUDAT 3 a Hansjörg Lipp, CC BY-SA 2.0, http://geo.hlipp.de/photo/87371 3 b wilfried-dechau.de 3 c Burkhard Walther 4 – 6 Data from Thorsten Helbig, Jana Nowak 7 From RVS 13.05.11: Lebenszykluskostenermittlung für Brücken 8 From Van Eygen, Emile; Fellner, Johann: Ökobilanzierung im Brückenbau. Eine vergleichende Lebenszyklusanalyse einer Spannbeton- und einer Verbundbrücke. Study. TU Wien, 2019 Materials 1 According to Neuhaus, Helmuth: Engineered timber construction. Wiesbaden, 2017 2 Ronald Knapp 3 Thorsten Helbig 4 Schaffitzel Holzindustrie GmbH + Co. KG 5 Kusser Granitwerke GmbH 6 Conzett Bronzini Partner AG 7 schlaich bergermann partner 8 Marx Krontal Partner 9 According to Natursteindatenbanken, DIN EN 771-1, DIN EN 1992-1-1:2011, and DIN EN 206 10 Compilation Michael Kleiser

11 From Marti, Peter; Monsch, Orlando; Schilling, Birgit: Ingenieur-Betonbau. Gesellschaft für Ingenieurbaukunst. Zurich, 2005, illustration p. 47 12, 13 Michael Kleiser 14 schlaich bergermann partner 15 BridgeDesign2 by Joris Laarman Lab 16 Marc Lins, M+G INGENIEURE 17 ETH-Bibliothek Zurich, Image archive / Photographer: Unknown /Hs_1085-1933-218/Public Domain Mark 18 Lisa Ricciotti 19 Tsinghua University (School of Architecture)-Zoina Land Joint Research Center for Digital Architecture (JCDA) 20 According to Bau-Überwachungsverein – BÜV e. V. (ed.): Tragende Kunststoffbauteile. Heidelberg / Berlin 2014 21, 23 www.solidian.com 22 wilfried-dechau.de Designs 1– 40 Michael Kleiser Bridges in Detail p. 102 Hufton+Crow p. 105, 106 Burkhard Walther p. 107 top MPA Stuttgart p. 107 centre, bottom Schaffitzel Holzindustrie p. 109 top Wilfried Dechau p. 109 bottom Burkhard Walther p. 111, 113 Alexander Burzik p. 112 Marx Krontal Partner p. 114 –115 Hufton+Crow p. 115 Ney & Partner, Laurent Ney p. 116, 118, 119 top Hufton+Crow p. 119 bottom Ney & Partner, Laurent Ney p. 120 –122 top Transport Scotland p. 122 bottom Bastian Kratzke / LAP Consult p. 123, 124 left PA Images p. 124 right, 125 Lukas Kohler / LAP Consult p. 126 Bastian Kratzke / LAP Consult p. 127, 128 top Tiefbauamt Canton of St. Gallen p. 128 top centre, bottom centre, bottom Leonhardt, Andrä und Partner p. 129, 130 Tiefbauamt Canton of St. Gallen p. 131 Leonhardt, Andrä und Partner p. 132 –135 Michael Kleiser, Mayer Ingenieurleistungen p. 136 –137 Patrick Reynolds p. 138 top, centre Knight Architects p. 138 bottom, 140 Patrick Reynolds p. 141 top Peters & Cheung Ltd. p. 141 bottom Knight Architects p. 142 –143 Alexander Burzik p. 144, 145 bottom Ludolf Krontal p. 145 top Alexander Burzik p. 146 Walt Galmarini p. 147 Stephane Braune p. 148 top, centre Roman Sidler p. 148 bottom Andreas Ludin p. 149, 151 Roman Sidler p. 150 Andreas Galmarini p. 152 David Hannes Bumann p. 154 –155 schlaich bergermann partner

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Authors Thorsten Helbig

Ludolf Krontal

Born 1967 in Nordhausen 1984 –1990 Bricklayer apprenticeship and assembly work in Erfurt 1990 –1994 Degree in Civil Engineering at FH Bielefeld / Minden campus 1994 –2001 Structural engineer at schlaich bergermann partner, Stuttgart since 2001 Founding partner of Knippers Helbig, with offices in Stuttgart, Berlin, and New York since 2018 Associate Professor at the Irwin S. Chanin School of Architecture, The Cooper Union, New York since 2020 American Society of Civil Engineers, Aesthetics in Design Committee

Born 1969 in Osterburg 1985 –1988 Apprenticeship as a carpenter and work at VEB Denkmalpflege Magdeburg 1991–1998 Studies in Civil Engineering at Bauhaus-Universität Weimar and the Universitat Politècnica de València 1999 –2002 Office manager, Engineering office for bridge construction in Dessau 2002 – 2011 DB ProjektBau Leipzig, Head of the Structural Engineering Department since 2011 Managing Director and Partner of Marx Krontal Partner, based in Hanover and Weimar

Michael Kleiser Born 1967 in Vienna 1994 Degree in Civil Engineering at TU Wien 1994 –1997 Research activities at TU Wien, TU Aalborg and the University of California, San Diego 1998 – 2011 Structural engineering at schlaich bergermann partner, Stuttgart, and Ingenieurbüro Pauser / PCD-ZT, Vienna since 2011 Bridge expert at ASFINAG Bau Management GmbH, Vienna since 2014 Lectureship at FH Campus Wien, Department of Construction and Design 2017 Dissertation at TU Wien: Formlogik und Formdynamik am Beispiel von integralen Überführungsbrücken (Form logic and form dynamics exemplified by integral overpass bridges) since 2017 Lectureship at TU Wien, Institute of Structural Engineering, with lecture on “Ingenieurformkunst” (“Structural Form Art”), among others.

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Markus Friedrich Born 1967 in Munich 1983 –1989 Studies in Civil Engineering at TU Munich 1994 Doctorate in Engineering Subject: Rechnergestütztes Entwurfsverfahren für den ÖPNV im ländlichen Raum (Computer-aided design procedure for local public transport in rural areas) 1989 –1995 Research assistant to the Chair of Transport and Urban Planning, TU Munich 1995 – 2003 Head of the Transport Planning Systems Division at Planung Transport Verkehr AG (PTV), Karlsruhe since 2003 Professor at the University of Stuttgart, Chair of Transport Planning and Traffic Control Engineering

Martin Knight Born 1967 since 2006 Director of Knight Architects, internationally renowned for bridge design Various teaching positions at schools and universities in the UK and Europe, including TU Delft 2017 Visiting professor at TU Graz Regularly holds lectures on bridge design