Proposal of concept for structural modelling of hybrid beams

Abstract

Investigation on the behaviour of a hybrid beam is presented. Hybrid beam stands for an element with hybrid cross sections. This means sections that consist of steel and concrete parts, connected together with composite dowels, and both are considered for shear flow analysis. In practice, a more general solution may be used for bridges in the form of a beam in which the span sections are hybrid and the support sections are concrete. Recently such a solution has been introduced for bridge engineering in Poland and a new problem with performing a global analysis of hybrid beams was identified. The solution is new itself and requires also a new approach for internal forces determination. Discussion of this problem is made in the paper. Influences of (1) concrete cracking, (2) rheology of concrete and (3) methods of modelling on the redistribution of internal forces are highlighted. On an example of one of the real bridge girder (being currently under design) analysis is made to show how the abovementioned factors are affecting obtained results. Results are analysed and conclusions are presented. As a final step, a new concept of hybrid beam design is proposed. The proposed solution enables a quick and easy engineering approach to perform a static calculation of the considered structure.

The new railway hybrid bridge in Dąbrowa Górnicza: innovative concept using new design method and results of load tests

“…This will be the subject of further analyses, but the present results indicate that fatigue of composite dowels could be analyzed in an "almost" uncracked state for this kind of hybrid girders. It is to be compared to other types of hybrid railway bridges like "Simmerbach" bridge [12], "Wierna Rzeka" bridge, and "Tczew" bridge [6,9]; cracked conditions in hybrid beams are being currently widely investigated by Kożuch [47,54] and this bridge is to be one of the reference points in studies of this topic. The simulations carried out by the authors [55] have shown that in the case of using the available HL sections, the solution is rational for simply supported spans with a span of 20-30 m and for continuous spans up to about 40 m (the analysis was performed with a fixed construction height of 1.8 m, and the load capacity in the elastic area and the limit deflections were considered conservatively, as in the case of the bridge).…”

Proposal of concept for global analysis of hybrid beams – numerical investigation

“…Publication [2] highlights the problems related to global analysis, which have been discussed all the time and so far no consensus has been reached on how global analysis of such objects should be carried out. At this point, it is noted that solutions such as those presented in [3] are still perceived as innovative and designed by a small group of engineers with appropriate knowledgethey are niche solutions. Development of a new form of composite dowel shear connection in 2019, the so-called SRCD [4] enabled a significant reduction in the thickness of the concrete web (Fig.…”

“…1: beam on the right side) and was a step towards construction of hybrid beams for road bridges with characteristics that would allow them to compete on the market with prestressed concrete precast elements. It is the concept of developing the entire system of typical road bridges with hybrid beams used in continuous systems that has resulted in comprehensively addressing the issue of how to perform the global analysis, and in particular the new problem of redistribution of bending moments in hybrid beams [3]. Bridges created in the new system are currently being built in Poland (Fig.…”

“…This is related to the experience they have gained modeling many new type (hybrid) structures and encountering problems that need to be solved. In a paper [3] a brief overview of composite dowels development [9][10][11] and existing and recently designed hybrid-beam type constructions was presented, and some motivators -mostly economical -for their development were described. Hybrid beams, comparing to standard steel-concrete composite structures, offer significantly less structural steel consumption [1,6,[12][13][14][15], and (depending on the market trends) this is usually the most decisive aspect of economical success of a design.…”

“…Two key aspects were distinguished as crucial for structural analysis. The first one is the issue of shear force flow (discussed in [16][17][18][19]), the second one is the issue of the redistribution of bending moments due to concrete cracking and its rheology, and how to handle it during design without utilization of advanced methods, difficult to apply during everyday design, mentioned in [3,20]. The issue of shear force transfer in such a cross section has already been described, and the dimensioning procedure is known at the level of cross section (hybrid cross section concept) [16][17][18][19]21].…”