Das Erweiterte Druckbogenmodell für die Nachrechnung von Spannbetonbrücken – Theoretische Hintergründe/Application of the extended arch action model for the reassessment of prestressed concrete bridges

Abstract

Zusammenfassung Die Nachrechnungen bestehender, älterer deutscher Spannbetonbrücken auf Grundlage der aktuell gültigen Normen und Richtlinien zeigen im Allgemeinen erhebliche Defizite in Bezug auf die erforderliche Querkraftbewehrung. Im Zuge von Forschungstätigkeiten im Auftrag der Bundesanstalt für Straßenwesen (BASt) wurden an der TU Dortmund Großversuche durchgeführt, um das Querkrafttragverhalten durchlaufender Spannbetonbalken genauer zu untersuchen. Daraus wurde auf Basis des Druckbogenmodells (DBM) das Erweiterte Druckbogenmodell (EDBM) abgeleitet, welches ein mögliches analytisches Verfahren zur Bestimmung des Betontraganteils bei Querkraft ist. So lässt sich die Querkrafttragfähigkeit vorgespannter Balken realitätsnäher bestimmen, als nach dem Fachwerkmodell mit Rissreibung gemäß aktueller Normung. Der vorliegende Beitrag liefert Hinweise und Erläuterungen zum DBM und EDBM hinsichtlich der Anwendung auf reale Bauwerke mit zugehörigem Sicherheitskonzept für eine Stufe-4-Nachrechnung.

Experimental investigations on the shear strength of prestressed beam elements with a focus on the analysis of crack kinematics

“…For the evaluation of existing bridges and especially in the light of specific questions on prestressed concrete bridge construction, theoretical and experimental efforts for the assessment of the shear strength capacity have been intensified in the recent past, as in particular characteristic load-bearing mechanisms of prestressed continuous beams with a low amount of shear reinforcement are continuously under discussion. [1][2][3][4][5][6] A feature that is largely common to previous experimental investigations is found in the comparatively high degree of longitudinal reinforcement of the test specimens, which should avoid premature bending failure in favor of the desired shear failure. Individual test series on the influence of the degree of longitudinal reinforcement or the strain state of the longitudinal reinforcement in connection with the shear behavior of reinforced concrete beams suggest that an oversized longitudinal reinforcement implicitly influences the shear transfer actions and thus possibly falsifies the transferability of experimental evidence to economically designed bridge girders.…”

“…For the evaluation of existing bridges and especially in the light of specific questions on prestressed concrete bridge construction, theoretical and experimental efforts for the assessment of the shear strength capacity have been intensified in the recent past, as in particular characteristic load‐bearing mechanisms of prestressed continuous beams with a low amount of shear reinforcement are continuously under discussion 1–6 . A feature that is largely common to previous experimental investigations is found in the comparatively high degree of longitudinal reinforcement of the test specimens, which should avoid premature bending failure in favor of the desired shear failure.…”

“…However, the range of shear force tests carried out on prestressed beam elements demonstrates in a unified manner that further, far more dominant load‐bearing components are effective and thus an extension in the consideration of classical resisting mechanisms is required to capture those effects and make a more precise assessment of the shear strength to be expected. There are already various empirically or mechanically analytical approaches to this 2,5,6,12–14 . Accompanying thoughts on the description of an additional concrete transfer action component are tackled in this paper in such a way that basic mechanical thoughts on the phenomenological description of the shear cracking behavior are discussed on the basis of processed evaluations of the digital image correlation (DIC).…”

“…There are already various empirically or mechanically analytical approaches to this. 2,5,6,[12][13][14] Accompanying thoughts on the description of an additional concrete transfer action component are tackled in this paper in such a way that basic mechanical thoughts on the phenomenological description of the shear cracking behavior are discussed on the basis of processed evaluations of the digital image correlation (DIC). The DIC analysis allows continuous, full-surface evaluation of the crack formation progress and resulting kinematics.…”

Arch Action Model for the structural assessment of existing prestressed concrete bridges

“…Arch action in prestressed concrete beams was measured with adequate instrumentation and verified by means of numerical nonlinear FEM‐based comparative calculations. The Dortmund tests are comprehensively documented and evaluated especially in Gleich 15 …”