Assessment of precast stringer highway bridges using mean load method

2006 ◽  
Vol 33 (11) ◽  
pp. 1359-1367 ◽  
Author(s):  
Daman K Panesar ◽  
F Michael Bartlett
Keyword(s):  
Bending Moment ◽  
Highway Bridges ◽  
Design Code ◽  
Reliability Indices ◽  
Dynamic Load Allowance ◽  
Bridge Approach ◽  
Specific Factors ◽  
The Mean ◽  
Axle Loads ◽  
Critical Sections

The mean load method of the Canadian Highway Bridge Design Code is used to evaluate the shear and bending moment reliability of existing precast "type G" stringer bridges in Alberta that date from the late 1950s. The overall stringer population is categorized into distinct subpopulations using bridge-specific factors, including the degree of deterioration and approach span condition, which are readily identified during a brief field visit or from inspection reports. Critical sections to be investigated for reliability resisting shear forces or bending moments are determined. The reliability indices decrease if the reinforcement is corroded or the bridge approach is not smooth, and the reduction of the maximum axle loads permitted by legislation due to these factors is quantified. For bridge subpopulations where the actual reliability index is less than the target value for current legal axle loads, the critical axle load for moment is less than that for shear. Therefore, if flexural distress is not noted during inspection of such structures, they are likely adequate for the actual loading they are subjected to.Key words: corrosion, deterioration, dynamic load allowance, mean load method, reliability, visual inspection.

Calibration of design code for buried structures

2001 ◽  
Vol 28 (4) ◽  
pp. 574-582 ◽  
Author(s):  
Andrzej S Nowak ◽  
Chan-Hee Park ◽  
Peter Ojala
Keyword(s):  
Reinforced Concrete ◽  
Reliability Index ◽  
Water Pressure ◽  
Earth Pressure ◽  
Highway Bridges ◽  
Design Code ◽  
Buried Structures ◽  
Reliability Indices ◽  
Resistance Factors ◽  
Load And Resistance Factors

The reliability-based calibration procedures were applied to develop load and resistance factors for the Ontario Highway Bridge Design Code (1979, 1983, and 1991) and recently the Canadian Highway Bridges Design Code (2000). However, the load components for buried structures were not considered. The development of a statistical model for earth pressure requires a special approach. Therefore, this paper deals with the reliability-based calibration of the design code for buried (cut-and-cover) structures. A typical running structure consists of reinforced concrete walls forming a rectangular box section, while an underground station may have a one- to six-cell box. The major load components include earth pressure, water pressure and weight of the concrete. Other load components such as live load are relatively small. Statistical parameters are derived for representative structures and structural systems. The correlation between load components is estimated based on the available field data. Structural performance is measured in terms of the reliability index. Reliability indices are calculated for a representative spectrum of running structures and stations. In general, the reliability indices for existing buried structures are higher than those for bridges or buildings. The target reliability index has been selected on the basis of calculated reliability indices, comparison with other structures, and cost analysis (consequences of failure). The optimum load and resistance factors are calculated and recommended for the design code to achieve a uniform safety level.Key words: buried structure, code calibration, load models, reinforced concrete, reliability analysis, resistance models.

Load and resistance data for precast stringer highway bridges

2006 ◽  
Vol 33 (11) ◽  
pp. 1368-1378 ◽  
Author(s):  
Daman K Panesar ◽  
F Michael Bartlett
Keyword(s):  
Dynamic Load ◽  
Bending Moment ◽  
Highway Bridges ◽  
Normal Weight ◽  
Unit Weight ◽  
Statistical Parameters ◽  
Concrete Core ◽  
Load Effect ◽  
Reliability Indices ◽  
Resistance Data

Statistical parameters for the load effects and resistances of precast "type G" stringer bridges erected in Alberta since the late 1950s are presented to assist practicing engineers assessing similar bridges using the mean load method. The load effect data include unit weight data for normal weight and two lightweight concretes; traffic volumes, gross vehicle weights, and single, tandem, and tridem axle weights observed on primary, secondary, and local roads; and dynamic load allowances for shear and bending moment on short span bridges. Extreme annual traffic loads are derived. The resistance data include compressive and tensile strengths of normal weight and two lightweight concretes and yield strengths for corroded and uncorroded reinforcing steel. Additional statistical parameters are presented to account for other readily discerned bridge-specific idealization factors that affect the reliability indices. Professional factors for flexural and shear resistance are derived using experimental data reported from past investigations of type G stringers by others.Key words: concrete, core tests, corrosion, dynamic load allowance, material properties, single axles, tandem axles, tridem axles, reliability.

The Ontario bridge code—Development and implementation

1984 ◽  
Vol 11 (4) ◽  
pp. 824-832
Author(s):  
R. A. Dorton
Keyword(s):  
Highway Bridges ◽  
Safety Index ◽  
Design Code ◽  
Limit States ◽  
Safety Level ◽  
New Development ◽  
Live Loads ◽  
Index Value ◽  
Correct Understanding ◽  
Short Time

The Ontario Highway Bridge Design Code was first issued in 1979 and has since been used for the design and evaluation of most bridges in Ontario. The code is in metric SI units, written in a limit states format, and calibrated to a target safety index value of 3.5. It has produced bridges with a more consistent safety level and capable of carrying design live loads twice those previously prescribed. Feedback from users was obtained and their concerns considered in formulating the provisions of the seeond edition in 1983. New bridge codes can be written in a short time and implemented most readily within a relatively small jurisdiction having control of all highways, bridges, and vehicles. Communications between the writers and potential users are important throughout the preparation and implementation phases. It is essential that a commentary volume be issued with a code to ensure correct understanding and interpretation of new provisions. Computer programs should be available, incorporating the code technology before the use of a new code becomes mandatory. Future code needs and likely areas of new development are outlined in the paper. Key words: calibration, codes, computer systems, highway bridges, loadings, safety, structures.

Seismic Isolation Design Code for Highway Bridges

2002 ◽  
Author(s):  
Kazuhiko Kawashima ◽  
Shigeki Unjoh
Keyword(s):  
Ground Motion ◽  
Seismic Design ◽  
Seismic Isolation ◽  
Highway Bridges ◽  
Design Code ◽  
Basic Principles ◽  
Design Specifications

This paper presents the seismic isolation design code for highway bridges. This is based on the 1996 Design Specifications for Highway Bridges, Part. V: Seismic Design, issued by the Japan Road Association in December 1996. This paper focuses on the outlines of the seismic isolation design code including the seismic design basic principles, design ground motion, and seismic isolation design.

Use of Fatigue Fuses for Prediction of Fatigue Life of Steel Bridges

1996 ◽  
Vol 1544 (1) ◽  
pp. 71-78
Author(s):  
Everett McEwen ◽  
George Tsiatas
Keyword(s):  
Fatigue Life ◽  
Highway Bridges ◽  
Fatigue Loading ◽  
Highway Bridge ◽  
Constant Amplitude ◽  
Bridge Inspection ◽  
Structural Details ◽  
Critical Issues ◽  
The Mean ◽  
Cycles To Failure

The fatigue fuse is a device for predicting the fatigue life of steel highway bridge members when the bridge is subject to variable loads. The fuse is calibrated so that the cracking of each of its four legs can be related to damage in the structure. In a preliminary laboratory study, fatigue fuses are attached to eight steel girders, selected to represent three types of structural details found in existing highway bridges. The fuses are cemented to the girders and the girders subjected to a constant-amplitude fatigue loading. Cracking of the fatigue fuses is monitored by checking electrical continuity across each fuse leg. Tests are continued until girder failure or until all fuse legs are broken and the mean fatigue life of the girder as predicted by AASHTO is reached. The breaking of the fuse legs is used to predict the fatigue life of each girder, which is then compared with the actual cycles to failure of the girder and the AASHTO mean life. The prediction gives satisfactory agreement with the AASHTO mean life in four of the tests. In two tests, the predictions vary significantly from the AASHTO mean life. Although several critical issues remain (such as adapting the fatigue fuse to the environment of a real bridge and conducting tests on a statistically valid sample), the results of this feasibility study indicate that the fuse could be a valuable tool for highway bridge inspection.

Methodology for the Determination of a Set of Safety Factors That are Consistent for Design Code and Fitness-for-Service Code: Framework

2009 ◽  
Author(s):  
Tai Asayama
Keyword(s):  
Reliability Evaluation ◽  
Light Water Reactors ◽  
Next Generation ◽  
Safety Factors ◽  
Design Code ◽  
Reliability Indices ◽  
Allowable Stresses ◽  
Complete Set ◽  
Water Reactors

This paper introduces a methodology for the determination of a complete set of safety factors that maintains consistency between design code and fitness-for-service code of nuclear components. The purpose of the work is to materialize the System Based Code concept, which is indispensable for the development of next generation nuclear reactors. The methodology consists of three principles proposed by the author which should be the basis of code development for new next generation reactors. The principles are; 1) Design to target reliability, 2) Continuous reliability evaluation from design to fitness-for-service, 3) Update of reliability evaluation based on information obtained during construction and operation. Effectiveness of the methodology is demonstrated using a simple example problem. The problem deals with pipe subjected to internal pressure under conditions which is typical in light water reactors. Following the reliability evaluation of current situation which meets the provisions of design code and fitness-for-serve code published from Japan Society of Mechanical Engineers, the three principles are applied step-by-step and safety factors and reliability indices are newly derived. It is shown that a complete application of the three principles could lead to a set of safety factors that assures consistency in terms of reliability in design and fitness-for-service, and improves allowable stresses as well. Technologies to be developed and issues to be discussed for application of the methodology to more complicated and practical situations are described as well.

The Natural Bending Vibration of the Continuous Beam and the Impact Factor of Bridge

2011 ◽  
Vol 90-93 ◽  
pp. 1245-1249 ◽  
Author(s):  
Xiang Rong Yuan
Keyword(s):  
Impact Factor ◽  
Impact Force ◽  
Bending Moment ◽  
Highway Bridges ◽  
Mode Shapes ◽  
Impact Factors ◽  
Beam Model ◽  
Continuous Beam ◽  
The Impact ◽  
Selection Of

The natural frequencies and mode shapes of 2, 3 and 4 spans continuous beam with universal cross section are calculated, and these dynamic parameters of 2 spans continuous beam model are measured. From the analysis and the model test, the locations of the maximum curvatures of the mode shapes are determined, and comparing that with the maximum bending moment of the beam under the action of uniformly distributed load, the selection of the natural frequency of the beam is discussed with the General Code for Design of Highway Bridges and Culverts as the impact factors of the beam is calculated. It is shown from the results of the analysis and the test that, for the impact factor, when the effect of positive bending moment caused by impact force is calculated, the fundamental frequency must be used as shown in the General Code, and the 2nd or 3rd frequency must be used when the effect of negative bending moment caused by impact force is calculated. The selection of the frequency should be combined with the mode shape into account for the specific circumstances.

Preliminary design of standard CPCI prestressed bridge girders by linear programming

1985 ◽  
Vol 12 (1) ◽  
pp. 213-225 ◽  
Author(s):  
Sami M. Fereig
Keyword(s):  
Linear Programming ◽  
Prestressed Concrete ◽  
Programming Model ◽  
Concrete Strength ◽  
Bending Moment ◽  
Highway Bridges ◽  
Concrete Bridges ◽  
Preliminary Design ◽  
Concrete Girders ◽  
Prestressing Force

The design of prestressed concrete bridges using standard CPCI (Canadian Prestressed Concrete Institute) girders is generally done by trial and error, requiring extensive computation. This study will use a linear programming mathematical model to establish preliminary design charts for such cases and to obtain the required prestressing force after losses for a given CPCI bridge interior girder with different spans and spacings. The bridge is designed to carry the MS200-77 loading, and the design conforms with the Canadian Standards Association CAN3-S6-M79 for design of highway bridges. The bridge considered is single-span, with a cast in situ concrete deck acting compositely with the prestressed girders under live load. The linear programming model is also used to determine the design criteria that will control the design for the cases investigated, and to perform the parametric study to evaluate the effect of variations in deck thickness, girder concrete strength, and prestressing losses on the value of the required prestressing force. Key words: bending moment, concrete, girders, highway bridges, linear programming, load, prestressing, span.

Calibration of the Ontario Highway Bridge Design Code 1991 edition

1994 ◽  
Vol 21 (1) ◽  
pp. 25-35 ◽  
Author(s):  
Andrzej S. Nowak ◽  
Hid N. Grouni
Keyword(s):  
Reinforced Concrete ◽  
Reliability Analysis ◽  
Prestressed Concrete ◽  
Highway Bridge ◽  
Live Load ◽  
Design Code ◽  
Reliability Indices ◽  
Resistance Factors ◽  
Load And Resistance Factors ◽  
Selection Of

The paper describes the calculation of load and resistance factors for the Ontario Highway Bridge Design Code (OHBDC) 1991 edition. The work involved the development of load and resistance models, the selection of the reliability analysis method, and the calculation of the reliability indices. The statistical models for load and resistance are reviewed. The considered load components include dead load, live load, and dynamic load. Resistance models are developed for girder bridges (steel, reinforced concrete, and prestressed concrete). A reliability analysis is performed for selected representative structures. Reliability indices are calculated using an iterative procedure. The calculations are performed for bridge girders designed using OHBDC 1983 edition. The resulting reliability indices are between 3 and 4 for steel girders and reinforced concrete T-beams, and between 3.5 and 5 for prestressed concrete girders. Lower values are observed for shorter spans (up to 30–40 m). The acceptance criterion in the selection of load and resistance factors is closeness to the target reliability level. The analysis confirmed the need to increase the design live load for shorter spans. Partial resistance factors are considered for steel and concrete. The criteria for the evaluation of existing bridges are based on the reliability analysis and economic considerations. Key words: bridge code, calibration, load factor, resistance factor, reliability index.

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