Developments and new trends in composite truss bridges are reviewed, and recent designs are presented for road and railway bridges. The structural scheme may range from a continuous truss girder to a cable-stayed bridge with a double deck for both road and rail traffic.
Composite decks with 3D tubular triangular trusses for road bridges are discussed; design issues are outlined and some results for the elastoplastic redistribution of internal forces at ULS, based on recent numerical and experimental research studies, are presented.
Recent designs of skew semi-through composite trusses, for High Speed Railway, are reported in what concerns the dynamic behaviour under traffic loading and the stability of the compressed chord. The Base Case Design of a cable-stayed bridge, 540 m long main span, with a double composite truss deck, for the new railroad crossing of the Tagus River in Lisbon, is discussed.

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The occurrence of fires breaking out during a seismic event, or even delayed after an earthquake represents a common circumstance in earthquake prone Countries, which must be adequately taken into account as a possible design scenario. In fact the behaviour in fire of structures that have been damaged by earthquakes changes as respect to the undamaged ones, since the earthquake-induced damage makes the structure more vulnerable to fire effects. In view of the current seismic design approach, where a certain extent of damage in case of severe earthquake is acceptable, the analysis of the behaviour of structures under the effect of fires in combination or following an earthquake is a significant research field, which is not yet fully explored. The robustness assessment under fire of structures already damaged to different extent by the seism, through a performance - based approach, is required. The procedure should be valuable as a design tool, as well as a vulnerability evaluation of the built heritage against FFE. In this paper the proposed general methodology is exemplified with regards to steel structures.

From the beginning of structural steel construction until the 1950s, steel bridges were riveted structures. Rivets have not only been used for joining members as bolts are today used for but also for forming cross sections by joining the section elements e.g. web and flanges.
From this kind of bridges thousands - among many famous bridges - still fulfil the function that they have been erected for.
Rivets are often particular locations of accelerated corrosion in riveted bridges. In particular the heads of the rivets are subject of rust and corrosion. Therefore the question is whether and how much the pre-stressing effect of the rivet will be affected by the material degradation of the rivet’s head, such that the load deformation and the fatigue behaviour will be reduced. The pre-stress of a rivet reduces the stress-peak that is caused by the hole in the connection and is thus of big importance for the fatigue resistance.
The following paper presents latest investigations on the effect of rivet head corrosion on the pre-stressing of the rivet by means of milling the rivet’s head and numerical simulations. Fatigue tests are presented that give first results for the assessment of the residual lifetime of riveted connection with reduced rivet stress.
The paper also shows how the results of the investigations have been considered in an existing riveted bridge from 1920 of 2,3 km length.

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Following a period in which the governing factor was mainly functionality, bridges now seem to be returning to their role of shaping the urban landscape. In line with the change in traffic requirements and possibilities, we are experiencing a revival of the human-scale pedestrian/cyclist bridge as well. In a project supported by the European Union, the longest footbridge in Hungary - in Szolnok - was opened to traffic in January 2011. The total length of the crossing is 450 m, including a 120 m span steel arch over the River Tisza. Besides the description of the structure and its erection, this paper deals in detail with the examination of the pedestrian- and wind-induced excitations - the key issue in the design of lightweight, slender bridge structures.

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Four skyscrapers named regional “Best Tall Buildings” for 2011
IABSE Awards 2011 announced

Patterns and Structure - Selected Writings. Von Nordenson, G.
Steel Structures. Design using FEM. Von Kindmann, R., Kraus, M.

35th International Symposium on Bridge and Structural Engineering
ECCS Congress - Annual Meeting
Brazil Welding Show 2011
IABMAS 2012 - 6th International Conference on Bridge Maintenance, Safety and Management

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The use of double split tee (DST) connections in seismic zones may represent an interesting solution from the technological point of view because of easy substitution of damaged components after destructive seismic events. But despite this significant advantage, partial-strength DST connections have found limited application so far because their use requires that tee elements are characterized by high plastic deformation capacity to assure adequate energy dissipation. Therefore, in order to overcome the limitations to the energy dissipation capacity of traditional DST connections due to significant pinching of hysteresis loops and aiming at the development of a structural solution able to withstand severe seismic events without damage to members and connecting elements, this paper proposes two different innovative dissipative solutions for DST connections and investigates their performance by means of an experimental programme whose results are presented and discussed.

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This paper addresses several salient issues associated with the design of typical configurations of concentrically braced (CB) frames, with particular emphasis on European seismic provisions. A brief assessment of the underlying design philosophy and strength demand considerations for capacity design checks incorporated within Eurocode 8 is presented first. It is shown that brace overstrength in conventional CB frames is largely dependent on the idealizations related to the treatment of brace buckling in compression, and that the level of such overstrength decreases as brace slenderness increases when tension-only design approaches are adopted, as is the case with Eurocode 8. Results from extensive non-linear response-history analyses on a set of CB frames are presented, and are used to illustrate the main behavioural aspects related to ductility demands on CB buildings for moderately stiff, stiff and soft soil conditions. These results are also used to examine the applicability of the ‘equal displacement’ rule typically adopted in Eurocode 8 for steel structures. The findings indicate that this rule offers reasonable upper-bound estimates of deformations in CB structures, but only for those with initial periods > 0.5 s built on moderately stiff to stiff soils and for moderate to relatively low slenderness values. The influence of column stiffness continuity and brace capacity-to-demand ratio on the distribution of plasticity in CB buildings is also demonstrated, and its implications on the interpretation of code provisions are highlighted. Finally, based on a parametric investigation of simplified frame models, the study shows that properly designed secondary systems such as gravity frames can play a significant role in mitigating the probabilities of dynamic instability in CB buildings.

Capacity design principles used in modern seismic design codes are deemed to confine plastic deformations to dissipative elements only. In conventional structures, this can be undesirable as the plastic deformations mean damage to structural elements, interruption to building operations and substantial repair works. If these elements are removable and can be replaced, the structure has the ability to return to the initial undeformed shape after an earthquake, provided restoring forces are supplied by part of the structure still within the elastic range. The objective of the present work, which continues the previous research of the authors, is to present a general methodology for designing structures with removable dissipative elements and re-centring capability. Two applications are also presented.

Buckling-restrained braces (BRBs) are a relatively recent development in the field of seismic-resistant steel structures. Their distinctive feature is the non-buckling behaviour typically achieved by encasing a steel core in a concrete-filled tube, but alternatives have been proposed. Restraining the brace from buckling enhances ductility significantly and allows a symmetric response under tension or compression forces. The design of BRB frames must consider a number of specific issues that are currently not covered by European standards and regulations. This paper presents a brief summary of the most recent research results and attempts to summarize the basic design issues as they emerge from both research and the codification rules of non-European Countries. Conclusions are drawn regarding future research required to address the development of design rules in Europe, too.

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This report deals with the results of an international research project ”Plastotough”, the aim of which is to discover the toughness requirements for structural steel to make it suitable for plastic design for ”static loads” and for loads that vary over time, as from seismic events. These toughness requirements should be specified as the Charpy energy value KVUS in the upper shelf domain of the toughness-temperature diagram and as the extension of KVUS to the minimum temperature TUS for which it is still valid. This report, after recalling empirical rules for toughness requirements, first gives the methodological tools from fracture mechanics and damage mechanics to tackle the task. The use of these tools is connected with experimental tests on specimens that are detailed such that they are representative of local (from notch effects) and global (from plastic hinges with plastic rotations) ductility demands. The steels for the test specimens were taken from regular ”European production”; rolled sections in particular exhibit a quality level that far exceeds the minimum requirements of EN 10025. For the steels considered, it was proved that they follow the EricksonKirk correlation between the T27J values and TUS so that they can be classified in a group of steels together with pressure vessel steels and naval steels. All strain requirements from local strain raisers and from global plastic rotations could be met on the safe side using the fracture mechanics and damage mechanics resistances determined for these steels. For seismic design in particular it could be shown that the cracking associated with ultra-low-cycle fatigue is not relevant for buildings if the behaviour factor q is determined using reasonable limits for inter-storey drift. Therefore, the key conclusion is that for the safe use of plastic design in ”static” and ”seismic” situations, the elevated level of toughness quality of steels usually available from European producers must be used. To this end it is recommended to specify these steels either in the context of brandnames or by additional options in EN 10025.

A simple method for designing floor structures against humaninduced vibrations is presented in a joint JRC-ECCS publication, which was developed from two major European research projects supported by the Research Fund for Coal and Steel (RFCS). The simple method is appropriate for floors where the response is dominated by the first eigenmode being excited by walking. This paper presents a general design method that was also developed within the scope of these RFCS projects and is based on a modal superposition approach. The method has a wider range of application as it may be applied to any floor type and, in addition to walking, other human activities can be readily included. The general design methodology has been successfully used in the UK since 2004 on a variety of steel-framed floors, which have included office, hospital, residential and dance floors.

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The Modern Teahouse is a small nomadic building formTL designed together with Kengo Kuma. It is used for Japanese tea ceremonies in the garden of the ”Museum für Angewandte Kunst” in Frankfurt am Main. The mattress-like structure can be erected and taken down by just four people. The internal air pressure of this single-chamber air house is 1500 Pa  -  only 1 % that of a high-pressure beam but five times higher than a normal pneumatic structure. The Modern Teahouse ”wanders” between the entrance hall of the museum and a little hill in the museum garden. When it is not in use, it is packed away on a trolley.

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