Daniel Pak

Design of composite dowels as shear connectors according to the German technical approval

Composite dowels are known as powerful shear connectors in steel-concrete-composite girders. More and more they are used in practice especially for prefabricated composite bridges. Advantages over headed studs are in particular the increased strength, the sufficient deformation capacity even in high strength concrete and the simple application in steel sections without upper flange. However, missing provisions in standards for composite dowels with the economic clothoid and puzzle strip have led to retentions of clients and delays in the approval process. Hence, the aim of the recently finished German research project P804 [15] founded by FOSTA- Research Association for Steel Application was to solve open questions concerning these innovative shear connectors and to prepare a general technical approval available for any design office and construction company. In this paper design concepts for ultimate limit state and fatigue limit state, structural design principles and instructions for production and construction are presented and background information are given.

Wind turbine tower design, erection and maintenance

: Higher towers for wind turbines are the main trend to achieve better effectiveness in the conversion of wind energy to electrical energy. This leads to an increasing contribution of the tower costs to the total investment costs. Optimization of the structural design by improving the design of connections in the tower is an important issue for the competitiveness of the wind energy sector. The basis of the design model of the flange connection and the possibilities of retrofitting are shown. A short overview of the main structural solutions for towers and the most common criteria for the design are provided in the text.

Field measurements at a composite bridge with composite dowels as shear connectors

Within the demonstration project ECOBRIDGE, funded by the Research Fund for Coal and Steel (RFCS), a monitoring program has been developed and applied to survey a composite railway bridge. The stress distribution between concrete and specially designed composite dowels, which have a better fatigue resistance compared to conventional headed studs, has been investigated as well as the forces in several rail support points. The German railway operator DB Netz AG requested the survey to prove the applicability of state of the art calculation methods, which were not part of compulsory codes.

High-strength tower in steel for wind turbines (Histwin) : Final report

Innovative solutions for assembling joints of a tubular tower for wind turbines were studied and the project provides a background for design. This solution is simpler to produce and 80 % less expe ...

Influence of execution tolerances for friction connections in circular and polygonal towers for wind converters

Friction connections with long open slotted holes have been proven to be a competitive alternative to the conventional flange connections in steel tubular towers for wind energy converters. As full-scale tests are not available, results of Finite Element Analysis (FEA) of the real-scale tower geometry are used in this paper to investigate the influence of tower cross section shape, execution tolerance (gap between the shells) and length of the connection on the bending resistance. Buckling behaviour of the shell in the vicinity of the friction connection in circular and polygonal towers is compared. The friction connection is thoroughly examined and recommendations for execution tolerances are given. The influence of two types of the execution tolerances on the connection strength is considered: inward bended “fingers”, leading to inclined gaps, and a parallel gap created by different tower diameters.

Design Temperature Load Spectrum for the Fatigue Verification of Composite Bridges with Integral Abutments

For (low cycle) fatigue design of steel foundation piles of composite bridges with integral abutments, not only traffic loads but also temperature loads as well have to be considered. Regarding this temperature fatigue load case, no specific rules and recommendations are given in EN 1991-2 (Eurocode 1: Actions on structures—Part 2: Traffic loads on bridges). The current paper proposes a simplified temperature load spectrum, to be used for (low cycle) fatigue design of constructional steel members of composite bridges with integral abutments. Therefore, effective bridge temperature hydrographs (100 year period) are derived by means of FE-calculations for various locations based on actual weather data. They are converted into pile strain hydrographs, taking into consideration residual strains and plastic deformations. The calculations are verified by laboratory low cycle fatigue tests and monitoring results. Finally, a design temperature load spectrum is proposed, based on classified temperature variations.

Economic Design of Composite Bridges with integral Abutments

In this paper, a method for the pre-design of integral abutment bridges is presented. It is based on the use of common design tools developed for conventional bridges with bearings and joints. The soil-pile-abutment system is hereby replaced by a single rotational spring. Therefore the determination of the spring properties is described in detail. Furthermore the calculation procedure for the moment induced by uniform temperature and for the normal force in the superstructure induced by the restraint moment is presented. As these calculations are not integrated in conventional design tools, simple hand calculation formulas have been developed. Their application is shown via a design example in this paper.