Sensitivity Of Response Of Skewed Bridges To Their Span Length Number Of Bents And Abutment Modeling
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| Author | : Shayan Sheikhakbari |
| Publisher | : |
| Total Pages | : 86 |
| Release | : 2016 |
| Genre | : |
| ISBN | : 9781369688207 |
Sensitivity of the seismic performance of two typical bridges to the modeling variation of their abutment parameters is investigated and compared through a comparison parameter proposed in this study. One of the bridges is a two-span two-column-bent bridge with seat-type skew abutment and the other is a three-span three-column-bent bridge with seat-type skew abutment. A set of 40 pulse-like ground motions is applied to the bridges for nonlinear time-history analysis.In the transverse direction, two force-deformation models, which are based on strut-and-tie and sliding shear friction mechanisms, are used. The analytical models are based on the extensive experimental research previously conducted.A hyperbolic force-deformation model (General Hyperbolic Force Deformation) is used to represent the passive lateral resistance of the abutment backfill. For considering the possible variation in the backfill geotechnical property, three typical abutment backfill is chosen from the exciting data that was collected from multiple highway bridges in California. Two alternative methods are used to account for the effect of the abutment skew angle on the backfill reaction. The methods include an empirical relationship derived from experimental data, and an analytical method developed based on assumed log-spiral soil failure mechanism.A comparison parameter is proposed in this study, which is a representative of ductility demand of a skewed bridge to the same non-skewed bridge. For each case, the parameter is computed using the data derived from the nonlinear time-history analysis to investigate the seismic performance of bridges and compare the ductility demand of the specimen bridges.The outcome of this research reveals the significance of shear keys and abutment backfill on the global response of bridges. The sensitivity of the comparison parameter to the specimen bridges' geometry is also discussed in detail in this study.
| Author | : Peyman Kavianijopari |
| Publisher | : |
| Total Pages | : 279 |
| Release | : 2011 |
| Genre | : |
| ISBN | : 9781124881034 |
This study focuses on identifying, both qualitatively and quantitatively, the seismic behavior of reinforced concrete bridges with seat-type abutments under earthquake loading, especially with respect to abutment skew angle. To that end, the study proposes novel methodologies for modeling skew-angled seat-type abutments and for seismic response assessment of structures whose response is characterized as "multi-phased." The proposed methodologies are applied to a comprehensive database of bridges with combinations of a variety of bridge geometric properties, including: (1) number of spans; (2) number of columns per bent; (3) column-bent height; (4) span arrangement; and (5) abutment skew angle. An extensive nonlinear response history analysis was conducted using three sets of ground motions representing records for rock sites and soil sites, as well as others that contained pronounced velocity pulses, denoted as "pulse-like." We demonstrate that demand parameters for skew-abutment bridges, such as deck rotation, abutment unseating, and column drift ratio, are higher than those for straight bridges. By investigating the sensitivity of various response parameters to variations in bridge geometry and ground motion characteristics, we show that bridges with larger abutment skew angles bear a higher probability of collapse due to excessive rotation, and that shear keys can play a major role in reducing deck rotations and thus the probability of collapse. We further show that resultant peak ground velocity (PGVres) is the most efficient ground motion intensity measure (IM) compared to many other IMs. In view of the skewed bridges' explicit changes in demand parameter behavior due to shear key failure, we propose a probabilistic-based approach for multi-phase structural response assessment. This method, denoted as "Multi-Phase Probabilistic Assessment of Structural Response to Seismic Excitations," or M-PARS, provides a probabilistic framework for computing the complementary probability distribution function of an engineering demand parameter given the ground motion intensity measure, G(EDP\IM).
| Author | : Robert J. Frosch |
| Publisher | : Joint Transportation Research Program |
| Total Pages | : 149 |
| Release | : 2011-08-15 |
| Genre | : |
| ISBN | : 9781622600120 |
Integral abutment (IA) construction has become the preferred method over conventional construction for use with typical highway bridges. However, the use of these structures is limited due to state mandated length and skew limitations. To expand their applicability, studies were implemented to define limitations supported by rational analysis rather than simply engineering judgment. Previous research investigations have resulted in larger length limits and an overall better understanding of these structures. However, questions still remain regarding IA behavior; specifically questions regarding long-term behavior and effects of skew. To better define the behavior of these structures, a study was implemented to specifically investigate the long term behavior of IA bridges. First, a field monitoring program was implemented to observe and understand the in-service behavior of three integral abutment bridges. The results of the field investigation were used to develop and calibrate analytical models that adequately capture the long-term behavior. Second, a single-span, quarter-scale integral abutment bridge was constructed and tested to provide insight on the behavior of highly skewed structures. From the acquired knowledge from both the field and laboratory investigations, a parametric analysis was conducted to characterize the effects of a broad range of parameters on the behavior of integral abutment bridges. This study develops an improved understanding of the overall behavior of IA bridges. Based on the results of this study, modified length and skew limitations for integral abutment bridge are proposed. In addition, modeling recommendations and guidelines have been developed to aid designers and facilitate the increased use of integral abutment bridges.
| Author | : Fikret Necati Catbas |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 831 |
| Release | : 2014-04-15 |
| Genre | : Technology & Engineering |
| ISBN | : 3319045466 |
This fourth volume of eight from the IMAC - XXXII Conference, brings together contributions to this important area of research and engineering. The collection presents early findings and case studies on fundamental and applied aspects of Structural Dynamics, including papers on: Linear Systems Substructure Modelling Adaptive Structures Experimental Techniques Analytical Methods Damage Detection Damping of Materials & Members Modal Parameter Identification Modal Testing Methods System Identification Active Control Modal Parameter Estimation Processing Modal Data
| Author | : Suiwen Wu |
| Publisher | : |
| Total Pages | : 790 |
| Release | : 2016 |
| Genre | : Electronic books |
| ISBN | : |
It is well known that skewed bridges with seat-type abutments are more vulnerable to unseating during strong earthquakes than straight bridges of the same length, due to excessive in-plane rotation. This rotation is believed to be due to the eccentricity between centers of mass and stiffness, and abutment pounding. Despite the common occurrence of this type of damage, little experimental research on the interaction between a bridge deck and abutment has been conducted to confirm this behavior, quantify its effect, and validate numerical models. As a consequence, many design codes specify the minimum support length for skewed bridges based on engineering judgment and not on rigorous analysis. In this study, an unseating mechanism is proposed after examining the behavior of skew bridges in recent earthquakes. It is hypothesized that the obtuse corner of superstructure engages the adjacent back wall during lateral loading and the superstructure then rotates about this corner, causing large displacement at the acute corner at the other end of the span. These displacements can be large enough to unseat the deck, especially in bridges with small seats.
| Author | : Andres F. Rodriguez |
| Publisher | : |
| Total Pages | : 112 |
| Release | : 2020 |
| Genre | : |
| ISBN | : |
The bias analysis of the nonlinear model concluded that both software agreed after improving the hinge length and the inclusion of gaps in the abutments. The same SAP2000 models were used to analyze the sensitivity of the most representative nonlinear parameters in the columns, superstructure, and abutments, as well as sensitivity to the hysteresis behavior of the concrete and the reinforcement steel. The prediction of the sensitivity was obtained applying the finite difference method, perturbing each parameter forward and backward by a coefficient of variation. The results obtained indicate that the selected bridges have a strong sensitivity in the longitudinal direction to the hysteretic assumptions and to small variations in parameters such as steel yield strength, superstructure Young’s modulus, and abutment strength, while the displacement response in the transversal direction seems to be insensitive.
| Author | : Chern Kun |
| Publisher | : |
| Total Pages | : 316 |
| Release | : 2018 |
| Genre | : Arch bridges |
| ISBN | : |
Observations from major earthquakes in the past have revealed that skewed bridges are more vulnerable to damage than straight bridges. Due to the irregular geometry, they are prone to in-plane rotations of the girder that are not induced by the girders of straight bridges. Previous studies have found that these rotations could be aggravated by the presence of pounding between the bridge segment and abutments. The interaction between the underlying soil support and the bridge footing could also significantly affect the response of the bridge. However, most of the studies on skewed bridges have been conducted either numerically or analytically. Experimental work on the topic had been scarce. Hence, the early parts of this doctoral research aim to provide better understanding on the behaviour of skewed bridges under the influence of bridge-abutment pounding and soil support separately and simultaneously, through experimental studies. The skew angles considered were 0°, 30°, and 45°. The bridge-abutment model was subjected to spatially uniform ground motions. Although the vulnerability of skewed bridges had been known as early as the 1970s, due to simplicity, many design specifications still do not sufficiently consider the effects of the skew angle, pounding, or supporting soil. Pounding is usually ignored, and an idealised fixed base condition is often assumed. For example, the New Zealand Transport Agency Bridge Manual recommends that the seat lengths of skewed bridges in the longitudinal and transverse directions are simply 25% larger than that calculated for a straight bridge. Hence, the later part of this doctoral research aims to address this issue by proposing a simple approach using empirical formulae to provide better prediction of the responses of skewed bridges. For more conservative results, it was suggested that the proposed formulae be incorporated in addition to the current NZTA recommendations, i.e. have a 25% factor of safety.
| Author | : Daniel N. Farhey |
| Publisher | : |
| Total Pages | : |
| Release | : 2002 |
| Genre | : Concrete bridges |
| ISBN | : |
An analytical study was carried out for the structural performance assessment of precast-concrete, short-span, skewed bridges with integral abutment walls. Typically, these structures are designed as simplified two-dimensional rigid portal frames, neglecting the degrading effects of the skew angle and laterally unsymmetrical vertical loading. This design practice produces under-designed bridges for certain aspect ratios, causing cracking and local deterioration symptoms, observed in some instances out in the field. To evaluate the limitations of this practice, three-dimensional finite-element models were developed and analyzed. Accordingly, these finite-element models simulate various geometric configuration parameters, as well as, laterally symmetrical and unsymmetrical vertical load conditions, capturing the amplification of the structural response. Field-testing was also performed on a bridge to substantiate and calibrate the finite-element results. The results of the simplified plane frame analyses and three-dimensional finite-element analyses were presented in correlation diagrams, enabling simple comparison and quantification. The correlation diagrams provide correction factors to amend the simple frame design. The response observations offer a qualitative insight into the actual behavior of the structure, allowing the performance assessment of existing bridges of the same type and a more reliable design in the future.
| Author | : Stein Sture |
| Publisher | : |
| Total Pages | : 754 |
| Release | : 1995 |
| Genre | : Mechanics, Applied |
| ISBN | : |
| Author | : Shree Krishna Tripathi |
| Publisher | : |
| Total Pages | : 188 |
| Release | : 2020 |
| Genre | : Box girder bridges |
| ISBN | : |
Many highway bridges are skewed to maintain the profile of natural obstacles to road like rivers, and depressions. Generally, we analyze straight bridge girders making it a line element which makes our hand calculations simpler. However, if we follow the same procedure for skewed bridges like straight ones, we cannot fully visualize and determine their behavior properly which may lead to over estimation or underestimation on different structural forces like bending moment, shear force and most importantly deflection. It is because when we look on skewed bridges in three dimension, the ends of the bridges are skewed to the centerline of the bridges and we can clearly realize that the concrete materials in the acute side is less than that in the obtuse side. If the skew angle is relatively large, it might be the case that there is unbalancing forces along the cross section of the skewed bridge which might lead to the camber at the center of the bridge to be inclined to the vertical which might tend to rotate the entire bridge about the vertical plane. This implies that highly skewed bridges tend to attract more torsion making the design more complicated. If these aspects are not taken into consideration, the skewed bridges might not be good fit while taking the limit state of serviceability. This thesis paper investigates into the three-dimensional analysis of a skewed bridge. Finite element modeling is utilized to analyze the skewed bridges and we can know how it behaves. After the modeling and analysis of a simple span cast in place post tensioned skewed bridge, it is seen that the deflection and bending moment at the mid-span of a skewed bridge is less compared to the non-skewed bridge. Moreover, a skew effect factor is also found which is very useful while designing skewed bridges.
