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Showing 2 results for Seismic Design
The effect of abutment modeling on the seismic response of bridge Under the earthquake records
Behzad Haseli,
Volume 1, Issue 2 (12-2017)
Abstract
One of the influential factors in the response of the collapse of the bridge and the collage is its modeling. Seismic behavior analysis and bridging modeling are usually performed using simplifying assumptions. This simplification may lead to major changes in the prediction of bridle shaking behavior. In this research, the collapses in three general modes of modeling under the influence of earthquake records in the near field (due to the occurrence of the critical behavior of the bridge under the influence of near-field records in comparison with the far-field domains) were analyzed by nonlinear time-based analysis method in SAP 2000 software and the results in scenarios Different collage modeling is compared. Of noteworthy points in this study is the modeling of the shells as a wall base and the equivalent hardness calculation using static pressure and dynamic pressure of the back of the collar. The results of the analysis show that the modeling of the end nests in addition to the bridge displacement on other seismic parameters including axial force distribution, bending anchor, anchor response, and base cutting effect, in such a way that the results represent the maximum difference of 78% in the longitudinal displacement of the end nests , The 90% difference in the central axis force and the 82% difference in the bending relationship between the middle base based on the collage modeling is simplified, compared to the modeling of the collage as a roller. On the other hand, the results of studies in this study show that with the height of the back of the knoll in the range of 4 to 9 meters in height, with acceptable accuracy (the difference of responses is 29% to 13%), the collateral modeling can be replaced in the base form of Diviara Designed for modeling the shell according to the Caltrance directive (2013).

Investigation of pre-stressed skewed box-girder bridges subjected to seismic loads
Tina Jalalzadeh, Majid Barghian,
Volume 2, Issue 2 (9-2018)
Abstract
Earthquakes are the major cause of bridges destruction. It is obvious that the seismic ability of bridges and in general all transportation systems are very important in management of crises. For this reason, the seismic performance and behavior of particular types of bridges have been researched in this study. Skewed bridges are most popular and applicable in the design of highways and inter-city roads. Wherever roads cannot be continued straightly, bridges and in some cases skewed geometry of the bridges are practiced. The design of this kinds of bridges has become a normal practice within engineering communities in recent decades with emphasis on the construction of pre-stressed skewed box-girder bridges due to their characteristics and behavior. In this study three-span pre-stressed box-girder bridges with different skew angles were modeled using CSiBridge software. Seismic analysis was performed on the above-mentioned bridge with different skew angles and demand to capacity ratios for columns and internal forces of deck and columns were extracted from program to find out the general behavior of structure. Results indicate that increasing the skew angle of the bridge decreases the capacity ratio of the columns. An increasing trend is observed for the axial force of columns when increasing the skew angle in first bent columns while the converse is true for the second bent. Shear force in longitudinal direction of the bridge for columns tend to decrease while an increase is noticeable in the transversal direction in first column. Torsional moment in first bent rises in contrast to that of the second bent which declines. Bending moment about transversal axis decreases. For internal forces of deck with increase of skew angle the axial force increases, vertical shear force at beginning of bridge (obtuse corner) increase and at the end (acute angle) decrease. This force reduces on bents and increases in the middle of the bridge. The torsional moment of deck at beginning of bridge increases and at the end of bridge decrease, and at the middle increases. Transversal bending moment of beginning and the end of the bridge decrease and it is increased on bents and in the middle of bridge. Longitudinal bending moment at beginning, end and on bents of bridge decrease and on the middle of bridge increases.
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