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Most civil engineering structures are subjected to cyclic loading during their service life, such as retaining walls, wave loading on offshore structures, seismic loading and the traffic loading of pavements. In the case of an integral abutment bridge (IAB), as an example, the backfill granular material is subject to slow cyclic stress and strain changes under drained conditions. These bridges are constructed so that the top deck is longitudinally continuous. In other words, IABs are joint-less bridges where the superstructure is connected with the abutment. The rigid connection enables the abutment and superstructure to act as a single structural unit, i.e., the expansion joints which are widely used in traditional bridges are removed in IABs. This removal is mainly due to the high costs of maintenance. The behavior of IABs is dominated by the cyclical temperature changes in the bridge deck. This results in the imposition of cyclical horizontal displacements to the backfill soil of the abutments. The present research is an effort to investigate the induced passive pressure on the IABs, using a laboratory model and an analytical approach. The results indicate that the passive pressure distribution is non-linear and its maximum value along the wall is dependent on the magnitude of the wall rotation and number of cycles. It seems that there are two different mechanisms for this behavior. In the above part of the wall, sand behaves as a plastic material. A decline in the passive pressure in the bottom part, however, is the result of arching. Večina inženirskih konstrukcij je v času uporabe podvržena cikličnim obremenitvam, kot npr. podporni zidovi, morske konstrukcije (valovanju), cestiča (prometnim obremenitvam) ter seizmičnim obremenitvam. V primeru intergralnega mostu z oporniki (IMO) je zasipni granulatni material podvržen počasnim cikličnim spremembam napetosti in raztezka v dreniranih pogojih. Ti mostovi so zgrajeni tako, da je prekladna konstrukcija vzdolžno neprekinjena. Drugače povedano, IMO so brezstični mostovi, pri katerih je preklada povezana z opornikom. Togi stik omogoča, da opornik in preklada delujeta kot ena konstrukcijska enota, brez dilatacijskih stikov, ki so pogosti pri tradicionalnih mostovih. Vzrok za odsotnost dilatacij so večinoma visoki vzdrževalni stroški. Na obnašanje IMO vplivajo ciklične temperaturne spremembe cestišča. To privede do pojavljanja cikličnih horizontalnih premikov zasipnega materiala pri podporah. Pričujoča raziskava je poskus preučevanja nastalega pasivnega pritiska na gredni IMO z uporabo laboratorijskega modela in analitičnega pristopa. Rezultati kažejo, da je porazdelitev pasivnega pritiska nelinearna in da je njegova maksimalna vrednost vzdolž stene odvisna od veličine rotacije stene in števila ciklov. Izgleda, da za takšno obnašanje obstajata dva različna mehanizma. V zgornjem delu stene se pesek obnaša kot plastični material, upad pasivnega pritiska v spodnjem delu pa je posledica usločenja. |
