Hot-dip galvanizing is one of the most efficient ways of providing durable corrosion protection for prefabricated steel components. It contributes greatly to the sustainability of steel structures.
Technical rules for the design of steel components for zinc coating and for the execution of the hot-dip galvanizing process have been developed over a period of 100 years. The state of the art has been implemented in the standards EN ISO 1461 [1] and EN ISO 14713 [2] and in recommendations of the galvanizers. It was understood that the technology applied would cover the specific requirements that result from the steel used, the usual way of structural detailing, the fabrication up to the point of galvanizing the steel component and the pretreatment and hot-dip galvanizing process in the galvanizing plant so that any relevant cracking that might impair the structural safety should not normally occur.
Over the years 2000-2006, however, the use of newly developed zinc alloys for the zinc baths [3] - which were introduced at the same time as the use of steel components with larger dimensions and material thicknesses and also with steels of higher strength and with new production techniques, - resulted in significant damages in the shape of the formation of cracks that were filled with zinc and the alloying elements of the zinc melt. The cracks had formed in the zinc bath because zinc melt alloying elements could always be found between the grain boundaries of the steel. Hydrogen embrittlement, which up until then had often been considered as a prevailing hazard, could be excluded; “liquid metal assisted cracking” (LMAC) or “liquid metal embrittlement” (LME), which up to then had been not considered in the design and execution of hot-dip galvanized steel components and was even not properly mentioned in EN ISO 1461 and EN ISO 14713, could be identified as the relevant cause.
A survey of the relevant literature revealed that LMAC in hot-dip galvanizing had been investigated in studies and tests since 1930 [7]-[23], but only in particular non-coordinated projects with different approaches depending on the individual problem. These studies provided the first qualitative information, but due to shortcomings in the documentation were not applicable for concluding a general concept. Therefore, new research projects had to be carried out to analyse the LMAC phenomenon systematically, aiming to establish a method that allows quantification of the influences of structural detailing, steel type and semi-finished products, fabrication of steel components in the workshop and pretreatment and hot-dip galvanizing in the galvanizing plant in such a way that they can be implemented in a “limit state concept” for LMAC. That would enable clear rules to be derived for all parties involved in the supply of hot-dip galvanized structural steel components.
This work is interdisciplinary because metallurgy, materials mechanics, structural engineering approaches with respect to structural safety, galvanizing technology and simulation techniques for time-step analysis of fabrication and galvanizing processes have to be applied in order to arrive at quantifiable data for “actions” on the one side and “resistances” on the other side of the limit state equation. This “limit state” approach in particular requires quantifiable data regarding the steel resistance to LMAC cracking in the hot zinc bath, for which a particular small-scale test had to be developed that is able to quantify the reduction in plastic strain capacity (i.e. the strain withstood up to the time of relevant crack formation) under ambient liquid zinc alloy. This test supplies the relevant data (ultimate equivalent plastic strain capacity) needed for the limit state equation.
This article provides a brief survey of the research results that allow the identification of the causes of the cracks observed. It also outlines conclusions for the design of prefabricated steel components for hot-dip galvanizing and rules for the galvanizing process that have been implemented in the German guideline DASt-Richtlinie 022 [4]. These conclusions and rules could also be used as a basis for supplementing the rules in EN ISO 1461 [1] and EN ISO 14713 [2] as well as EN 1993 - Eurocode 3 [5] and EN 1090 [6].

The most economic form of stiffening is required for a steel sectorial plate. Stiffeners made from halved rolled I-sections are welded to the base plate with double fillet welds. The plate is subjected to a uniformly distributed normal load. Three stiffening types are designed as follows: (a) non-equidistant tangential stiffening with constant base plate thickness, (b) equidistant tangential stiffening with base plate thickness varying stepwise, and (c) equidistant tangential stiffening with constant base plate thickness combined with radial stiffeners.
Each form of stiffening is designed so that the maximum stress due to bending from the factored normal load in the base plate parts should not exceed the yield stress. The positions of the non-equidistant tangential stiffeners are calculated by a special mathematical algorithm. The costs of materials, assembly, welding and painting are calculated for each stiffening version and the costs are compared with each other.
The cost comparison shows that - for a given numerical problem - stiffening type (b) is the cheapest and type (a) the lightest. Type (c) needs too much welding and is also the most expensive.

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Steel trusses and other structures with angle section members are usually designed by elastic methods. This may lead to uneconomical designs when these sections are subjected - besides the axial force - to biaxial bending arising not only from eccentric connections, but also from direct transverse loading. This paper provides a simple inelastic interaction formula, Eq. (14), as well as an enhanced inelastic formula, Eq. (27), for the combination of axial force and bending moments about the principal axes which may be used for angle cross-sections of classes 1 or 2. The formulae do not always exhaust the full plastic cross-sectional resistance but do lead to a more economical design of the section, especially when bending is dominant. The formulae cover only the design of the cross-section and do not address stability considerations.

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Between October 2003 and July 2004, Arup, in a joint venture with the Dutch airport planners NACO and the architects Foster & Partners, designed the Terminal and Ground Transportation Centre needed for the 2008 Olympic games at Beijing Airport. Work commenced on site in March 2004 and ended almost four years later with the opening ceremony in February 2008. This was the team's third airport together, the forerunners being Stansted Airport, London, in the late 1980s and Chek Lap Kok Airport, Hong Kong, in the late 1990s. For each terminal the basic engineering diagram is similar.
The design of airport terminals is predominantly influenced by functionality. Externally, they are constrained by the movements of land transportation systems on one side and aircraft on the other. Internally, large numbers of people and baggage must flow from entrances to departure gates or arrivals gates to exits. Both the non-public areas, like the baggage-handling facilities, and the public areas need column-free spaces to provide maximum flexibility and unimpeded passenger flow.
Forces in roofs and floors increase with the square of the span and result in large member sizes, but these must be limited because the overall height of airport facilities is restricted. Furthermore, a deep roof structure will impair the ability for natural light to pass through the roof into the building's interior. Both requirements can only be achieved with a carefully integrated design.
Airport terminals are characterized by the fact that the climatic and other physical conditions for which they must be designed vary across the world. For example, whereas Chek Lap Kok had to withstand typhoon wind loads and is located in a subtropical climate, Beijing is in an active seismic zone and experiences large seasonal temperature fluctuations. However, they must be able to accommodate the same aeroplanes worldwide while exhibiting their own form with respect to geometry, modularity, repetition and the use of information technology in the design, analysis, specification and fabrication.
Today, fabrication technology is changing rapidly thanks to the application of computerized analysis and fabrication methods in engineering. This in turn influences the structural concept and design. A manifestation of this is illustrated below.

This paper reports on the design and construction of the new bridge over the River Rhine being built near the cities of Wesel and Büderich, Germany, the “Niederrheinbrücke”.
The paper outlines the design and bidding process as well as the construction of the new bridge, which will be the longest cable-stayed bridge in Germany.
The new Rhine crossing is only the second cable-stayed bridge in Germany to use parallel strands (Suspa DSI) rather than steel wire ropes (locked coil ropes) and contributes to a new generation of cable-stayed bridges in Germany.

The motorway viaduct over the Nalón River is 1100 m long and 27 m wide. The longitudinal structural system consists of a single strict composite box that takes advantage of the different properties of structural steel and concrete, going beyond the double composite action systems already in use for a long time. The box girder is enlarged by means of composite trusses connected to the upper slab at both sides of the deck. Longitudinally, the structure can be divided into two sections:
- a 660 m long curving approach section over the river plain
- a 440 m long straight section crossing the riverbed. The central part of this section is a 124 m span rigid frame composed of a box girder with varying depth and two elegant piers, one on each side of the river.
The bridge was constructed by launching from both abutments. The launching of the main section, due to the varying depth of the box girder in the main span, required longitudinal auxiliary elements in order to launch it in the same way as the spans of constant depth. A temporary pier was built in the middle of the river in order to reduce the cantilever in the main span to a moderate length. The viaduct construction was completed in May 2007.

This article outlines the development of pier protection against ship collision over the last 25 years. The calculation of impact forces is developed from general formulas for equivalent loads, based on collision tests, to numerical FEM simulations. Comparisons between the results are given. Examples of the structural protection of 18 bridges are described.

The Centner Footbridge at Verviers, Belgium, is a successful design and artifact that links structural optimization and digital steel plate cutting techniques. This steel structure is designed as a statically determinate beam and has a U-profile in cross-section. The webs serving as the safety barriers are assembled from 10 different steel plates that exhibit a laser-cut aperture pattern. The aperture pattern and the steel plate thicknesses have been structurally optimized to deal with the maximum shear forces that occur. For construction purposes, the numerical FE analysis model was translated into a graphic digital model that serves as input data for the steel laser cutter. Once the laser has cut the aperture pattern, the plates are welded together and finished in the fabricator's workshop. The bridge was transported in one piece and installed overnight on site. Recently, the concept of the aperture patterned steel plates has also been successfully applied to other winning design projects. These designs demonstrate that the innovative link between structural optimization and digital steel cutting techniques offers a new and elegant solution for structural systems with a large variety of spans and shapes.

Wissekerke castle park in Belgium contains mainland Europe's oldest remaining iron suspension bridge (1824). In 1989, after years of neglect, the Kruibeke town council bought the castle, park and finally, in 2006, the bridge. The Architectural Engineering Lab of the Vrije Universiteit Brussel (æ-lab) was consulted to put the refurbishment on the right lines and to check whether this bridge can stand the shift in function from private to public.
This paper places the pedestrian bridge within the framework of 19th century bridge construction, determines its historical value, characterizes the used materials by metallographic methods combined with tensile and hardness tests, re-analyses the structure, proposes strengthening strategies and concludes with a renovation proposal that preserves all of the authentic elements, causes the least visual impact, is durable and guarantees continued public use.

This paper presents an improved analytical calculation model for unstiffened elements with nonlinear stress-strain relationships (e.g. aluminium and stainless steel) subjected to uniform in-plane compression. The model takes material nonlinearity into account by means of the Ramberg-Osgood constitutive law. It is based on the results of a numerical parametric study of the load-carrying behaviour of unstiffened elements. A comparative study shows good agreement between test results and analytically determined strengths according to the new calculation model.

Consecrated in the year 2000, the Herz-Jesu Church in Munich features a glass façade with advanced, bonded loadbearing structures, Ref. [1]. The exterior of the church was built almost completely in glass, creating the timeless shape of a parallelepiped as shown in Figure 1. The structural framework to the glass façade consists of loadbearing glass beam elements with lengths of up to 6.72m bonded to stainless steel channels by silicone adhesives. This design - leading to a U-type bonding geometry by joining the glass beams to the steel stringers of parallel-flange channel-type cross-sections, see Figure 2 - required comprehensive experimental and theoretical investigations. Existing regulations such as the European guideline ETAG 002, Ref. [2], were not applicable due to their limited scope. Whereas ETAG 002 covers only simple two-sided bonding geometries (explicitly excluding three-sided bonding designs), the bonding used here is more complex geometrically, leading to significantly different mechanical characteristics.

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