Load Combinations for the Evaluation of Redundancy in Steel Bridges

2022 ◽  
pp. 036119812110621
Author(s):  
Francisco Javier Bonachera Martin ◽  
Robert J. Connor
Keyword(s):  
Bridge Engineering ◽  
Live Load ◽  
Steel Bridge ◽  
Bridge Design ◽  
Load Model ◽  
Load Models ◽  
Evaluation Procedures ◽  
Tension Member ◽  
Service Period ◽  
Aashto Lrfd

Over the past decade, there has been considerable interest in the development of quantitative analytical procedures to determine if a primary steel tension member (PSTM) is a fracture critical member (FCM). Traditionally, this designation has most often been arbitrarily determined based simply on the bridge geometry, for example, the number of girders in the cross section, rather than an evaluation of the bridge in the faulted state. Clearly, such a redundancy evaluation must address the loading scenarios concurrent with failure of the PSTM, the likelihood of the member failure, the acceptable probability of load exceeding resistance in the faulted state, and the application of vehicular live load models. This research was conducted to develop a load model and load combinations that are specific to evaluating the performance of a bridge in the event a steel member was to fracture. Specifically, two load combinations were developed to evaluate the strength of a steel bridge, one for the event in which the failure of a PSTM occurs, and another for a post-failure service period. The development adhered to the reliability-based principles and procedures applied in the calculation of load combinations currently used in bridge engineering to facilitate direct implementation and to ensure consistency with current steel bridge design and evaluation procedures contained in the AASHTO LRFD Bridge Design Specifications.

Live-Load Response of Alabama’s High-Performance Concrete Bridge

2003 ◽  
Vol 1845 (1) ◽  
pp. 115-124 ◽  
Author(s):  
Robert W. Barnes ◽  
J. Michael Stallings ◽  
Paul W. Porter
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Highway Bridges ◽  
Live Load ◽  
Bottom Flange ◽  
Actual Behavior ◽  
Bridge Design ◽  
Design Specifications ◽  
Special Procedure ◽  
Aashto Lrfd

Results are reported from live-load tests performed on Alabama’s high-performance concrete (HPC) showcase bridge. Load distribution factors, deflections, and stresses measured during the tests are compared with values calculated using the provisions of the AASHTO LRFD Bridge Design Specifications and AASHTO Standard Specifications for Highway Bridges. Measured dynamic amplification of load effects was approximately equal to or less than predicted by both specifications. Distribution factors from both specifications were found to be conservative. Deflections computed according to AASHTO LRFD Bridge Design Specifications suggestions matched best with the measured deflections — overestimating the maximum deflections by 20% or less. Bottom flange stresses computed with AASHTO distribution factors were significantly larger than measured values. AASHTO LRFD Bridge Design Specifications provisions suggest a special procedure for computing exterior girder distribution factors in bridges with diaphragms. When two or more lanes were loaded, this special procedure did not reflect the actual behavior of the bridge and resulted in very conservative distribution factors for exterior girders. Further research is recommended to correct this deficiency.

Evolution of Bridge Live Load Models and Truck Weight Limits:The Case of Manitoba, Canada

2021 ◽  
Author(s):  
Amanda Pushka ◽  
Jonathan D Regehr ◽  
Aftab Mufti ◽  
Basheer Hasan Algohi ◽  
Graziano Fiorillo
Keyword(s):  
Operational Performance ◽  
Potential Range ◽  
Live Load ◽  
Design Codes ◽  
Bridge Design ◽  
Evaluation Codes ◽  
Load Models ◽  
Truck Size And Weight ◽  
Truck Weight ◽  
Regulation Changes

Truck size and weight regulations have been a key instrument used to improve trucking productivity, safety, and operational performance in Canada. In response to these changes, bridge design codes undergo modifications to envelop the potential range of trucks in operation. A five-decade timeline is presented: (1) to document how bridge codes and their live load models have evolved, with a focus on the Manitoba-specific HSS-25 truck, and (2) to discuss how responsive bridge design codes have historically been to changes in truck size and weight regulations. While at times bridge codes are released in conjunction with expected regulation changes, there is often delay in the issuance of revised bridge design and evaluation codes. Assessments of the current truck fleet, which now includes long combination vehicles (LCVs), may be a consideration for future bridge design live load models.

Probabilistic assessment of a design truck model and live load factor from weigh-in-motion data for Mexican Highway bridge design

2015 ◽  
Vol 42 (11) ◽  
pp. 970-974 ◽  
Author(s):  
A.D. García-Soto ◽  
A. Hernández-Martínez ◽  
J.G. Valdés-Vázquez
Keyword(s):  
Bridge Engineering ◽  
Load Factor ◽  
Engineering Practice ◽  
Live Load ◽  
Bridge Design ◽  
Statistical Characterization ◽  
Motion Data ◽  
Weigh In Motion ◽  
Load Factors ◽  
Truck Load

This study is focused on the statistical characterization of live load effects on bridges using weigh-in-motion data from a Mexican highway. A truck load model that is simpler than the design truck model implemented in the current Mexican requirements is suggested for design. The statistics are employed in target-reliability based calibration and verification of load factors in Mexican bridge design. Suggestions that could be useful for the Canadian bridge engineering practice are included.

Probabilistic assessment of live load effects on continuous span bridges with regular and irregular configurations and its design implications

2020 ◽  
Vol 47 (4) ◽  
pp. 405-417
Author(s):  
A.D. García-Soto ◽  
A. Hernández-Martínez ◽  
J.G. Valdés-Vázquez
Keyword(s):  
Probabilistic Assessment ◽  
Live Load ◽  
Load Model ◽  
Motion Data ◽  
Load Models ◽  
Weigh In Motion ◽  
Single Vehicle ◽  
Load Effects ◽  
Extreme Distribution ◽  
Live Load Model

Studies on live load effects reported in recent literature are based on simple span bridges or on a limited number of continuous span bridges and regular configurations. In this study, an extensive probabilistic assessment of live load effects on continuous bridges is carried out for regular and irregular span configurations using weigh-in-motion data. Single vehicle passage is considered, and live load effects are compared with those from a live load model developed for simple spans from the same database. Truck models from Canada are also used for comparison purposes. Discussion of the fitting of extreme distribution is included, and an optimization scheme for the fitting is proposed. The most important finding of the study is that the use of live load models developed from simple spans or a limited number of continuous spans may not be suitable for designing continuous bridges, especially those with irregular configurations and short spans.

Development of Live Load Model for Strength II Limit State in AASHTO LRFD Design Specifications

2018 ◽  
Vol 2672 (41) ◽  
pp. 11-23
Author(s):  
Peng Lou ◽  
Hani Nassif ◽  
Paul Truban
Keyword(s):  
New Jersey ◽  
Limit State ◽  
Extreme Value Distribution ◽  
Generalized Extreme Value Distribution ◽  
Load Factor ◽  
Live Load ◽  
Load Model ◽  
Design Specifications ◽  
Live Load Model ◽  
Aashto Lrfd

The AASHTO LRFD Bridge Design Specifications defines Strength II limit state for agencies to consider the load combination by owner-specified special design vehicles, evaluation permit vehicles, or both. The configuration and characteristics of permit vehicles vary from state to state. In addition, the code calibration process performed in 1994 for the development of the live load factors was applied only to the Strength I limit state. In New Jersey, the design permit vehicle was not developed based on actual permit records or weigh-in-motion (WIM) data. Recently, with the development of permit-issuing management and WIM technology, there is a need to evaluate the effectiveness of design permit vehicles. This study aims to develop a live load model for the assessment of Strength II limit state for New Jersey Department of Transportation (NJDOT). Five years of permit vehicle records are provided by NJDOT for the development of the live load model. The distribution of Gross Vehicle Weight is best described as the Generalized Extreme Value distribution. Load effects are simulated for different span lengths. The mean and standard deviation (SD) of the 75-year maximum loads are predicted using different extrapolation approaches. The results show that NJDOT Design Permit Vehicle provides stable mean and SD of bias ratios at 75-year level. In comparison with the current AASHTO live load factor of 1.35, the averages of the bias ratios at the 75-year level are found to be 1.31, 1.23, and 1.16 for the positive moment, shear, and negative moment, respectively.

Australia’s Bridge Design Load Model: Planning for an Efficient Road Transport Industry

2000 ◽  
Vol 1696 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Rob Heywood ◽  
Ross Gordon ◽  
Geoff Boully
Keyword(s):  
Moving Load ◽  
Road Transport ◽  
Bridge Engineering ◽  
Bridge Design ◽  
Transport Efficiency ◽  
Load Model ◽  
Design Load ◽  
Vehicle Loading ◽  
The Future ◽  
Transport Industry

A new Australian bridge design traffic loading standard for design and construction of Australian bridges was developed. The loading model is expected to set the bridge design standard for the next 25 years. This is an important visionary task, an investment for future improvements in transport efficiency, and an investment for our grandchildren, which was motivated by the increased transport efficiency that this generation has been able to achieve because of the investment of our grandparents. The challenge is to appropriately and effectively provide for the future in a manner that is consistent with the potential benefits and costs. The complexities of a range of traffic and vehicle loading scenarios, vehicle loading practices and enforcement, an infinite variety of bridge spans and forms of construction, and future unknown vehicle and bridge technologies are combined to develop, in collaboration with AUSTROADS and other interested bodies, a recommended bridge design load. The load model represents a substantial increase from the current design load to be one of the heaviest in the world. The load model’s features include a moving load model (M1600) that forms the basis for the application of dynamic load allowances, centrifugal and braking forces, and a stationary load model (S1600). The load model is designed to represent the traffic of the future and hence ensure the future productivity of Australia’s road transport industry. It is a bridge engineering contribution to Australia’s international competitiveness.

scholarly journals Towards actual brazilian traffic load models for short span highway bridges

2015 ◽  
Vol 8 (2) ◽  
pp. 124-139 ◽  
Author(s):  
C. E. Rossigali ◽  
M. S. Pfeil ◽  
R. C. Battista ◽  
L. V. Sagrilo
Keyword(s):  
Highway Bridges ◽  
Traffic Load ◽  
Live Load ◽  
Heavy Vehicles ◽  
Load Model ◽  
Load Models ◽  
Short Span ◽  
Live Load Model ◽  
Traffic Simulations ◽  
Gathering Data

New live load models for highway bridge design in Brazil are under development by assembling real traffic database, traffic simulations, analytical-numerical modeling of the dynamic interaction between vehicle and structure and statistical extrapolations. This paper presents and discusses the results obtained in the first stages of this work which includes the comparison between the static effects due to the actual traffic of heavy vehicles and those generated by the live load model given in the current national code NBR 7188. It is demonstrated that this live load model is not appropriate to represent the actual traffic effects and may be, in some cases, non-conservative. The present work deals with short span bridges for two lanes single carriageway under free flow traffic scenarios. The representative static effects in these bridges due to the actual traffic of heavy vehicles are obtained by extrapolating its probability density functions to a certain return period. To this purpose, a traffic database was constructed by gathering data from several weighing stations in Brazilian highways which was then applied to perform traffic simulations through a specially developed computational tool.

Reliability analysis of typical highway bridges in Manitoba designed to the Modified HSS-25 live load model

2021 ◽  
Author(s):  
Amanda Pushka ◽  
Jonathan D Regehr ◽  
Graziano Fiorillo ◽  
Aftab Mufti ◽  
Basheer Hasan Algohi
Keyword(s):  
Reliability Analysis ◽  
Prestressed Concrete ◽  
Highway Bridges ◽  
Live Load ◽  
Load Model ◽  
Reliability Indices ◽  
Structural Capacity ◽  
Live Load Model ◽  
Aashto Lrfd ◽  
Precast Prestressed Concrete

Several provinces in Canada have modified the live load model specified in national bridge design codes to account for locally permitted trucks. Manitoba similarly introduced a live load model for the design of provincial bridges in accordance with AASHTO LRFD, the Modified HSS-25. This article presents truck weight datasets and methods used to develop Manitoba-specific live load statistics to conduct a reliability analysis for three typical simply supported structure types: precast prestressed concrete box girder, precast prestressed concrete I-girder and steel girder. The average reliability indices ranged from 4.69 to 4.95 with respect to the AASHTO LRFD live load statistics used to calibrate the code and 4.65 to 5.04 with respect to the Manitoba statistics. The results demonstrate a level of safety that exceeds the code requirements, indicating that structures designed to the HSS-25 potentially possess the structural capacity to withstand increased vehicular load effects for the considered bridge types.

scholarly journals Standardised bridge weigh-in-motion data and its applications in bridge engineering

2021 ◽  
Author(s):  
Jami Qvisen ◽  
Weiwei Lin ◽  
Heikki Lilja ◽  
Timo Tirkkonen ◽  
Mikko Peltomaa ◽  
...  
Keyword(s):  
Bridge Engineering ◽  
Traffic Load ◽  
Bridge Design ◽  
Design Assessment ◽  
Motion Data ◽  
Load Models ◽  
Weigh In Motion ◽  
Bridge Weigh In Motion ◽  
Orthotropic Bridge Deck

<p>Applying actual traffic data in bridge analyses will provide more accurate results compared to the results obtained according to the Eurocode traffic load models. Bridge Weigh-in-Motion (B-WIM) measurements are an excellent tool to produce such data. Using B-WIM data as a part of the bridge design or assessment processes has a large potential, but the lack of widely adopted standardised data format hinders broader utilisation of it. This study proposes a new standardised format to present the measured B-WIM data so that in the future, developed software can directly utilise any available B-WIM data. This would make calculations with multiple different traffic compositions and types straightforward and enable the basis for further utilisation of B-WIM data in bridge design/assessment. To demonstrate the benefits, a fatigue case study of an orthotropic bridge deck was conducted, and the results were compared to ones obtained according to Eurocode FLM 4.</p>

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