Experimental Study on the System Performance of Adjacent Precast Concrete Box Beam Bridges (original) (raw)
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Structural Redundancy Assessment of Adjacent Precast Concrete Box-Beam Bridges in Service
Advances in Materials Science and Engineering
Present approaches for assessing bridge redundancy are mainly based on nonlinear finite element (FE) analysis. Unfortunately, the real behavior of bridges in the nonlinear range is difficult to evaluate and a sound basis for the nonlinear FE analysis is not available. In addition, a nonlinear FE analysis is not feasible for practitioners to use. To tackle this problem, a new simplified approach based on linear FE analysis and field load testing is introduced in this paper to address the particular structural feature and topology of adjacent precast concrete box-beam bridges for the assessment of structural redundancy. The approach was first experimentally analyzed on a model bridge and then validated by a case study. The approach agrees well with the existing recognized method while reducing the computation complexity and improving the reliability. The analysis reveals that the level of redundancy of the bridge in the case study does not meet the recommended standard, indicating tha...
System Reliability Models for Bridge Structures
Lecture Notes in Engineering, 1987
There is a growing need for a more accurate assessment of the load carrying capacity of highway bridges. The traditional approach is based on consideration of individual components rather than structures. Consequently, the acceptance criteria are formulated in terms of the allowable stress, or ultimate moment, in a component. However, it has been observed that the load carrying capacity of the whole structure (system) is often much larger than what is determined by the design of components. The difference can be attributed to the system behaviour. Quantification of this difference is the subject of the system reliability. There is a need to take advantage of the available system reliability methods and advanced structural analysis methods and apply them in the design of bridges and evaluation of existing structures. The current advanced analytical procedures allow for a numerically accurate but deterministic analysis of strain/stress in a bridge. Mathematical procedures exist for the calculation of reliability for various idealized systems: parallel, series, and combinations. There are also new developments in materials, technology, and field testing which can be used to improve bridge design and evaluation. This paper deals with calculation of the reliability of the whole bridge structure, taking into account realistic boundary conditions, and site-specific load and resistance parameters.
Revista IBRACON de Estruturas e Materiais
Nowadays it is known that it is important to study the safety of structures to avoid tragic accidents or economic losses. The most widely used method in the world to evaluate the safety of structures is structural reliability. The reliability index of prestressed precast beams of bridges designed using Brazilian standards (NBR6118 and NBR7188) is not known. This work evaluates the annual reliability indexes of a prestressed precast beam bridge at the serviceability limit state (SLS) projected using the Brazilian standard and compares it with results from the literature. The studied bridge has 33.5 meters of span, is simply supported, constituted by five precast concrete beams with U section. The reliability analysis was carried out using two methods for the four limit state equations: First Order Mean Value (FOMV) and First Order Reliability Method (FORM). Sensitivity analyzes were performed to consider both the relative contribution of these variables and the effect of their distri...
Structural Safety of Prestressed Concrete and Composite Steel Highway Bridges
1995
Traditionally, the safety evaluation of existing bridges and code calibration of newly developed structural design specifications for the ultimate limit states are usually based on the maximum factored design loads. The advantage of this approach is that it does not require detailed design computations. Past experience with prestressed concrete girder bridges indicates that the design of such bridges is governed by the allowable stresses requirement at release or under service load effects. Similarly, the design of composite steel beam bridges is generally controlled by overloading for compact sections and by the maximum stress criterion for noncompact sections. The reliability of bridges designed according to AASHTO's Load Factor Design code is evaluated on the basis of actual designs. Reliability is measured in terms of the reliability index for the ultimate flexural capacity limit state. The statistical data on strength are generated starting from statistics on material properties and using simulation methods. Statistical data on load components are compiled from the available hterature. The scope of the study covers a wide range of precast sections and rolled beams, span lengths, and beam spacings.
IEC2018 Proceedings Book, 2018
Given the vital importance of bridges in life arteries, safety of these structures against destructive agents such as earthquake is of utmost importance. Using pre-stressed columns in bridges will improve their seismic response, because these columns have high displacement capacity during earthquake and a small permanent displacement after earthquake. Therefore, the need for further study on these structures is felt more than ever. In this paper, firstly, prestressed columns were analyzed under reciprocating static load using OpenSees software and results show that pre-stressing bridge columns will improve the quasi-static response of columns and column section bearing. Below, we examine the reliability analysis of pre-stressed bridge samples against force of the earthquake and the effect of different random variables on reliability of bridge. The results show that structural damping and earthquake magnitude have a significant effect on reliability of bridges. Changes in characteristic strength of concrete at ultimate limit and mean resistance of section, effect significantly on reliability of bridge structure.
A system reliability based design equation for steel girder highway bridges
2007
Although structures are commonly designed and assessed on an element basis, the true measure of structural safety is its systems reliability. To be accurate, structural systems reliability must consider multiple failure paths, load sharing and load redistribution after member failures, and cannot be captured by element reliability analysis. The incremental loading method (ILM) in which the magnitude of the vector of external load variables is slowly increased from zero up to a pre-determined cut-off condition (while keeping the direction of the vector constant) and in which the structural state is updated within the confines of static equilibrium at each successive component failure is a versatile method for identifying failure sequences. This paper presents an improved procedure to assess the system factor to be used in a component-based design equation that will help achieve a target structural system reliability. System failure is defined as the union of strength and local instability failures. Adaptive importance sampling is used for system reliability analyses. A simple span five-girder steel highway bridge is selected for illustration.
Structural reliability as applied to highway bridges
Progress in Structural Engineering and Materials, 2000
The paper presents the application of reliability methods in the development of a load and resistance factor design (LRFD) bridge codes. Structural performance is measured in terms of the reliability index. Load and resistance models are summarized. An important step is the selection of the target reliability index and calculation of load and resistance factors. Load and resistance factors are derived so that the reliability of bridges designed using the proposed provisions is at the predefined target level.
Reliability analysis of bridge structures for earthquake excitations
In this paper, a numerical approach to the reliability analysis of prestressed reinforced concrete long span bridges is presented. A bridge is modeled by nite element software and the analysis is performed in time domain by considering the bridge material nonlinearity. The considered random variables are: Speci c strength of concrete, yield stress of steel bars, yield stress of prestressed bars, all sectional dimensions, structural damping ratio, e ective depth of steel bars and the magnitude and PGA of earthquake. In this study, the reliability of a bridge structure is evaluated under earthquake excitations. For this purpose, the First-Order Second-Moment (FOSM) method is used. In this method, the mean value and standard deviation of the random variables are considered for evaluating structural reliability. The proposed procedure is applied to evaluate the reliability of an existing prestressed arch concrete bridge located in Bandar-e-Anzali in Iran. Bandar-e-Anzali is a very high-risk earthquake zone. The results of the study show that the structural damping ratio, magnitude and PGA of earthquakes have a signi cant e ect on the variation of reliability in the structure, while variations in the dimensions of the structure have little e ect on the reliability index. a nite element approach. Loads and mechanical and geometrical properties were selected as random variables. The results were presented as graphs that show di erent reliability for di erent limit states. Nowak et al.
Structural reliability of existing city bridges
IABSE Conference, Geneva 2015: Structural Engineering: Providing Solutions to Global Challenges, 2015
Full probabilistic reliability analysis may be valuable for assessing existing structures. Measures for increasing the safety level are quite costly for existing structures and may be unnecessary when such a decision is grounded on a conservative analysis for determining the structural reliability. This may be avoided by applying a more detailed analysis as well as considering local traffic loading conditions rather than general load models. In this paper we present the structural reliability analysis of a small span inner city concrete bridge beam using Monte Carlo simulation. The resistance is based on results from an optimal design according to a given code. The load is represented by the extreme value distribution of the load-effect, resulting from a probabilistic traffic load model based on Weigh-In-Motion (WIM) measurements. Using commercial software typically available to engineers, the reliability is calculated and compared to the required minimum reliability level.