Designing Timber Bridge Superstructures: A Comparison of US and Canadian Bridge Codes (original) (raw)
Related papers
Comparative Analysis of Design Codes for Timber Bridges in Canada, the United States, and Europe
Transportation Research Record: Journal of the Transportation Research Board, 2010
The United States recently completed its transition from the allowable stress design code to the load and resistance factor design (LRFD) reliability-based code for the design of most highway bridges. For an international perspective on the LRFD-based bridge codes, a comparative analysis is presented: a study addressed national codes of the United States, Canada, and Europe. The study focused on codes related to timber bridges and involved the following parameters: organization format, superstructure types, loads, materials, design for bending, design for shear, deflection criteria, and durability requirements. The investigation found many similarities and some distinctive differences between the three bridge codes. Although the United States and Canada have different design load configurations, these result in similar bending moments and shear effects over a typical span range. However, the design load configuration in the European code produces bending moment and shear effects tha...
Designing Timber Highway Bridge Superstructures Using AASHTO-LRFD Specifications
New Horizons and Better Practices, 2007
The allowable-stress design methodology that has been used for decades to design timber bridge superstructures is being replaced in the near future. Beginning in October 2007, bridge designers will be required by the Federal Highway Administration (FHWA) to utilize the Load and Resistance Factor Design (LRFD) design specifications published by the American Association of State Transportation and Highway Officials (AASHTO). Until recently, significant discrepancies existed between the two design methodologies as they pertain to the design of timber bridges. However, several modifications and improvements to the LRFD bridge design specifications were recently incorporated into the latest edition of the LRFD bridge design standards in an effort to mimic allowable-stress design techniques using current timber design standards. Timber bridge supstructures designed using the latest LRFD design requirements will still not be identical to those designed with allowable-stress design procedures, primarily due to new requirements for higher design vehicle live-loads and modified live-load distribution equations within AASHTO-LRFD design specifications. In addition, timber bridges designed using allowable-stress design methods prior to 2007 will be not be required to use AASHTO-LRFD methods for load rating purposes.
New Canadian Highway,Bridge Design Code design provisions for fibre-reinforced structures1
2000
This paper presents a synthesis of the design provisions of the second edition of the Canadian Highway Bridge Design Code (CHBDC) for fibre-reinforced structures. New design provisions for applications not covered by the first edition of the CHBDC and the rationale for those that remain unchanged from the first edition are given. Among the new design provisions are those for
New Canadian Highway Bridge Design Code design provisions for fibre-reinforced structures
Canadian Journal of Civil Engineering, 2007
This paper presents a synthesis of the design provisions of the second edition of the Canadian Highway Bridge Design Code (CHBDC) for fibre-reinforced structures. New design provisions for applications not covered by the first edition of the CHBDC and the rationale for those that remain unchanged from the first edition are given. Among the new design provisions are those for glass-fibre-reinforced polymer as both primary reinforcement and tendons in concrete; and for the rehabilitation of concrete and timber structures with externally bonded fibre-reinforcedpolymer (FRP) systems or near-surface-mounted reinforcement. The provisions for fibre-reinforced concrete deck slabs in the first edition have been reorganized in the second edition to explicitly include deck slabs of both cast-in-place and precast construction and are now referred to as externally restrained deck slabs, whereas deck slabs containing internal FRP reinforcement are referred to as internally restrained deck slabs. Resistance factors in the second edition have been recast from those in the first edition and depend on the condition of use, with a further distinction made between factory-and field-produced FRP. In the second edition, the deformability requirements for FRP-reinforced and FRP-prestressed concrete beams and slabs of the first edition have been split into three subclauses covering the design for deformability, minimum flexural resistance, and crack-control reinforcement. The effect of sustained loads on the strength of FRPs is accounted for in the second edition by limits on stresses in FRP at the serviceability limit state.
Ultimate Strength of Timber-Deck Bridges
Transportation Research Record, 1986
Contained in this paper is a discussion on the procedures for evaluating the ultimate strength of timber deck bridges. Three structural systems are considered: sawed timber stringers, nailed laminated decks, and prestressed laminated decks. The load and resistance are treated as random variables. Their parameters are determined on the basis of material tests, load surveys, and analysis. The bridge performance is measured in terms of the reliability index. Various safety analysis methods are discussed. The procedures used in calculations were selected on the basis of accuracy, requirements for input data, and simplicity of use. System reliability models were used to include load sharing between deck components. Reliability indices were calculated for three structures. It has been observed that the degree of load sharing determines the safety level. Reliability is highest for the prestressed laminates. Sawed stringers can be considered as a series system in the system-reliability sens...
Reliability-based geotechnical design in 2014 Canadian Highway Bridge Design Code
Canadian Geotechnical Journal, 2016
Canada has two national civil codes of practice that include geotechnical design provisions: the National Building Code of Canada and the Canadian Highway Bridge Design Code. For structural designs, both of these codes have been employing a load and resistance factor format embedded within a limit states design framework since the mid-1970s. Unfortunately, limit states design in geotechnical engineering has been lagging well behind that in structural engineering for the simple fact that the ground is by far the most variable (and hence uncertain) of engineering materials. Although the first implementation of a geotechnical limit states design code appeared in Denmark in 1956, it was not until 1979 that the concept began to appear in Canadian design codes, i.e., in the Ontario Highway Bridge Design Code, which later became the Canadian Highway Bridge Design Code (CHBDC). The geotechnical design provisions in the CHBDC have evolved significantly since their inception in 1979. This pap...
Canadian Journal of Civil Engineering, 2014
Recent research efforts have focused on the development of performance based seismic design methodologies for structures. However, the seismic design rules prescribed in the current Canadian Highway Bridge Design Code (CHBDC) is based largely on force based design principles. Although a set of performance requirements (performance objectives) for different return period earthquake events have been specified, there is no explicit requirement in the CHBDC to check the attainment of such performance objectives for the designed bridges. Also, no engineering parameters have been assigned to the specified performance objectives. This paper correlates seismic performance objectives (both qualitative and quantitative) with engineering parameters, based on the data collected from published experimental investigations and field investigation reports of recent earthquakes. A simple method has been developed and validated with experimental results for assessing the performance of bridges designed according to CHBDC. It has been found that the design rules prescribed in CHBDC do not guarantee that specified multiple seismic performance objectives can be achieved. An implicit seismic design rule in the form of performance response modification factor has been outlined for the performance based seismic design of bridges.