The designs for live loads of bridges are specified by the codes. The codes are based upon data collected from traffic loads, after some adjustments, using a survey on truck weights in a weighing station. In recent decades, the characteristics of trucks can be found either by pavement weigh-in-motion or bridge weigh-in-motion (BWIM) systems. There are several algorithms used to perform BWIM; one of them is the area method (Helmi et al. in J Civ Struct Health Monit 4(3):195–208, 2014). The area method was developed based on the assumption that trucks move on the instrumented span with constant velocity. This paper includes a review of the theoretical derivation of the area method with constant velocity. Theoretical derivation for the case of variable velocity is derived and presented in this paper.

Composite action between steel girders and concrete slab is an important mechanical feature that needs to be maintained so that bridges can carry the applied load safely. This mechanical feature is maintained through the shear studs installed at the top flange of the steel girders. These shear studs keep the steel girders and the concrete slab working as one unit, resulting in a stronger section than if each element works separately. The composite action can be investigated using several methods of which one is the study of the position of the neutral axis (NA). The variation of the position of the NA over time gives an indication about the structural performance of the composite section. In this study, the variation of the position of the NA over time is investigated. Two bridges located in Manitoba were investigated in this study. The variation of the NA is observed as a result of variation of ambient temperature (temperature). Regression models are suggested to relate variation of the NA to the temperature that was measured beside the web of one of the bridge girders. Repeatability analysis over 4 years was conducted, confirming that the NA varies cyclically over years. It is suggested that this variation indicates that there is a change in the degree of composite action assuming that cold temperatures will induce more connection between the steel girders and the concrete slab as a result of thermal contraction of the shear studs. In addition, the stiffness of the material could be affected due to change of temperature. The other possibility is that an axial force develops in the beam as a result of the bearing restraint during the passing of vehicles on the bridge. The results found in this study will eventually lead to enhancements of the design procedures that currently assume a fixed position of the NA over time of composite sections of bridges, similar to the bridges presented in this study.

Three highway bridges in the Canadian province of Manitoba are being monitored continuously not only for their long-term performance but also for bridge weighing-in-motion (BWIM). Data collected for the BWIM study has led to some observations that have far-reaching consequences about the design and evaluation loads for highway bridges. This paper presents the well-known concept of equivalent base length, Bm, as a useful tool for comparing trucks with different axle weight and spacing configurations as they influence load effects in all bridges. It is discussed that the statistics of gross vehicle weights (GVWs), W, collected over a one-month period is not significantly different from that for the GVW data collected over a longer period. A rational method concludes that the value of W for the CL-W Truck, the design live load specified by the Canadian Highway Bridge Design Code, is 555 kN for Manitoba. The observed truck data in Manitoba presented on the W–Bm space is found to be similar to that collected in the Canadian province of Ontario more than four decades ago. It was also found that the multi-presence factors, accounting for the presence of side-by-side trucks in two-lane bridges, specified in North American bridge design and evaluation codes are somewhat conservative.

Manitoba has many ageing steel bridge structures on its highway network that are facing increased axle loads, speed, and traffic intensity, all of which accelerate their deterioration due to fatigue. An immediate replacement or rehabilitation is not feasible for the existing structures that have already approached their expected service life. The residual life of these types of structures, or their component, is estimated by conducting a fatigue evaluation and damage assessment. Field measurements are very accurate in estimating fatigue loading. This paper discusses a case study of the fatigue assessment on an ageing steel bridge in Winnipeg, Manitoba, which integrates a bridge-weighing-in-motion (BWIM) system. The South Perimeter Bridge is instrumented with a structural health monitoring system which is used to perform BWIM and fatigue analysis of the steel girder bridge. The identified sources of error in the fatigue evaluation using the BWIM system, if addressed properly, are expected to increase the accuracy of fatigue analysis.

Bridges in regions where temperature range between seasons is large are affected significantly by the temperature range. The temperature affects bridges in different forms, one of which is the reactions that they develop in the bottom flanges of girders against the horizontal movement. Bearing restraint due to temperature change was studied in two bridges in the province of Manitoba, Canada. The study results presented in this paper show that the bearing restraint forces are not negligible.

Engineers have proposed the idea that there may be some arching action present in bridge deck cantilever overhangs stiffened along their longitudinal free edge through a traffic barrier, subjected to a wheel load. This paper includes the details of a full-scale corrosion-free bridge deck with cantilever overhangs stiffened along their longitudinal free edge by a traffic barrier wall that has been constructed and tested under static and fatigue wheel loads at the University of Manitoba. It also reviews experimental test results and postulates various discussions that suggest the presence of arching action in cantilever slab overhangs. The test results indicated static ultimate load capacities significantly greater than the ultimate capacity if the mode of failure and behavior of the cantilever overhang was completely flexural. These early results confirm and indicate the presence of arching action resulting in a significant breakthrough in cantilever behavior when subjected to a wheel load. The theory to account for this arching action is not yet developed, and further research should be conducted. (C) 2013 American Society of Civil Engineers.

The current paper introduces a method that incorporates Bridge Weigh-in-Motion (WIM) technology into Structural Health Monitoring (SHM) data analysis. The method is intended to provide an understanding of the performance of bridges in light of establishing the fatigue life of girders and decks. As described herein, the technique chooses several corresponding strain peaks to calculate vehicle parameters, such as truck speed, axle spacing, axle weights, and gross weight. The system was tested on field data from the North Perimeter Highway Red River Bridge in Winnipeg and is in good agreement with actual vehicle characteristics. Work is currently underway to incorporate the parameters in a semi-continuum method of analysis for bridges (SECAN) to study bridge performance and estimate fatigue life.

About 30 years ago, the arching action in concrete bridge deck slabs of girder bridges was initially utilized in Ontario, Canada, by reducing significantly the amount of reinforcement in these slabs. The design method for such utilization of the arching action was adopted in the American AASHTO design specifications in 1996, and in the rest of Canada in 2000 through the Canadian Highway Bridge Design Code (CHBDC). Further utilization of the arching action led to steel-free, or corrosion-free deck slabs, which contain no tensile reinforcement, and are restrained transversely by means of steel straps connected to the top flanges of the supporting girders. The concrete of the steel-free deck slabs contained synthetic fibres of short lengths. While these fibers controlled cracks due to volumetric changes in concrete, they were not effective in arresting fatigue-induced cracks, with the result that all early steel-free deck slabs developed fairly wide longitudinal cracks roughly midway between the supporting girders. Fatigue tests on full-scale models have confirmed that the safety of the deck slabs is not compromised by the wide cracks. However, these cracks appear unsightly. The 2 nd edition of the CHBDC (2006) requires that all these slabs, which are now called externally restrained deck slabs, be provided with orthogonal meshes of bars of glass fibre reinforced polymer (GFRP) for controlling fatigue-induced cracks. The earlier externally restrained deck slabs with crack-control reinforcement are now referred to as those of the 1 st generation, and deck slabs with the crack control reinforcement as those of the 2 nd generation. The paper provides a brief history of the utilization of the arching action in bridge deck slabs, and provides details of the 2 nd generation of externally restrained deck slabs.

Reply to the discussion by A.K. El-Sayed on "New Canadian Highway Bridge Design Code design provisions for fibre-reinforced structures"

Erratum : New Canadian Highway Bridge Design Code design provisions for fibre-reinforced structures (Canadian Journal of Civil Engineering (2007) vol.34 (3) (267-283))

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-reinforced-polymer (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.Key words: beams, bridges, concrete, decks, fibre-reinforced-polymer reinforcement, fibre-reinforced-polymer sheets, prestressing, repair, strengthening, wood.

Many forestry bridges in Canada are typically single-lane, single span structures with two steel plate girders and a deck comprising of precast reinforced concrete panels. The concept of arching in deck slabs was utilized in the steel-free precast panels used in the Lindquist Bridge in British Columbia, Canada. The panels were completely devoid of tensile reinforcement and transverse confinement to the panels was provided by external steel straps. After the bridge was constructed in 1998, electrical strain gauges were installed on the girders and straps. Static and dynamic load tests were performed. The cracks on the top and bottom of the deck were mapped in 1999 and 2003. In 2006, a load test and crack mapping were performed on the bridge. The strain readings in the straps were compared with the data obtained 8 years prior. After analysis of the strain gauge readings, conclusions were drawn on the performance of the bridge. The cracks were formed to accommodate arching action and it was concluded that the bridge is still performing as it was designed.

The Canadian Highway Bridge Design Code (CHBDC) does not permit the use of glass-fibre-reinforced polymer (GFRP) for primary reinforcement or prestressing tendons in concrete components. The restriction on the use of GFRP in concrete was based on published laboratory studies indicating that GFRP is not stable in the alkaline environment of concrete. In 2004, ISIS Canada sponsored an extensive study of the durability of GFRP in concrete by removing cores from GFRP-reinforced concrete components of five 5- to 8-year-old structures from across Canada. Three teams working independently at several Canadian universities used a variety of analytical methods to (i) investigate whether the GFRP in concrete field structures had been attacked by alkalis and (ii) compare the composition of GFRP removed from in-service structures with the composition of control specimens that were saved from the projects and not exposed to the concrete environment. The analytical results have confirmed that the GFRP in concrete did not suffer any damage during the 5–8 years of exposure. As a result of this study, the CHBDC in its forthcoming (second) edition has permitted the use of GFRP for both primary reinforcement and prestressing tendons in concrete components, provided the maximum stress level in GFRP at the serviceability limit state is kept at or below 25% of its ultimate strength. It was also found that, contrary to some claims, concrete over GFRP bars does not crack even if the depth of cover is as thin as 28 mm.Key words: alkali attack, barrier wall, crack, deck slab, depth of cover, fibre-reinforced polymer (FRP), glass-fibre-reinforced polymer (GFRP).

Civil Engineers should develop innovative structures using advanced nanotechnology-based materials such as FRPs that utilize nano-clays. For these new structures to be accepted by the engineering community, it is mandatory that they be monitored and that the results are reported to the engineering community as well as being incorporated into civil engineering codes. ISIS Canada has been developing such structures and monitoring them through an innovative concept, which involves the development of the new discipline of Civionics where Civil Engineering and Electrophotonics are being integrated. In this paper, some of the innovations that have been implemented will be described.

The reliability index is used in modem bridge design codes as a measure of the likelihood of the failure of its components; the target value of this index is obtained from the variability of the strengths of a given component, and the maximum load effects it is likely to be subjected to during its lifetime. The Canadian Highway Bridge Design Code permits smaller values of this index than that for new design, provided that reliable information is available about the strength of a component. Usually this information is obtained only from visual inspection. It is argued in the paper that structural health monitoring (SHM) of a component by means of sensors can provide more reliable information about the strength of the component than by visual inspection. Therefore, SHM can be used to lower the target value of the safety index, thereby increasing available live load capacity.

Synopsis: Synopsis: Synopsis: Synopsis: Synopsis: Recently, ISIS Canada studied the durability of GFRP in concrete in several field structures across Canada. The objective of the study was to provide the engineering community with the results of the performance of GFRP materials that have been exposed to the concrete environment in built structures. Cores of GFRP-reinforced concrete were removed from five field structures. Analytical methods, namely optical microscopy, scanning electron microscopy and energy dispersive x-ray, differential scanning calorimetry and infrared spectroscopy, were used to determine the composition of GFRP after being subjected to the alkaline environment of concrete for five to eight years. Three research teams from four Canadian universities performed microanalyses of the GFRP and surrounding concrete independently. Results indicate that no deterioration of GFRP took place in any of the field structures. No chemical degradation processes occurred within the GFRP due to the alkalinity of the concrete. The overall conclusion of the study is that GFRP is durable in concrete. Also, it was concluded that the CHBDC was conservative in its first edition by not permitting GFRP as primary reinforcement. As a result of the study, the second edition of the CHBDC, currently in the final stages of approval, permits the use of GFRP as primary reinforcement.

Fiber-reinforced concrete (FRC) deck slabs without internal tensile reinforcement are also known as steel-free and corrosion-free deck slabs. The cast-in-place version of these slabs has already been applied to five highway bridges in Canada. This paper describes the significant design details of a 150 mm-thick precast steel-free deck slab supported on girders at a spacing of 3.5 m. The results of tests on full-scale models of the precast slab are also reported. It was found that the precast panels, made composite with the supporting beams, were able to sustain concentrated loads that were several times larger than the factored design loads. The experimental investigation included the study of the panel's performance to sustain construction loads when it is not connected to the girders. This investigation led to an improved design of the panel, also reported in the paper When a precast panel without any reinforcement was incorporated in a forestry bridge several years ago, it developed several wide cracks. While these cracks have not impaired the load-carrying capacity of the deck, it is now believed that unsightly wide cracks should be avoided by providing in the panel a crack-control grid of nominal reinforcement, either made of steel or of glass fiber-reinforced polymer (GFRP).

The arching action in concrete deck slabs for girder bridges is utilized fully in steel-free deck slabs. These concrete slabs, requiring no tensile reinforcement, are confined longitudinally by making them composite with the girders, and transversely by external steel straps connecting the top flanges of external girders. Between 1995 and 1999, five steel-free deck slabs without any tensile reinforcement were cast on Canadian bridges. All these slabs developed fairly wide full-depth cracks roughly midway between the girders. While extensive fatigue testing done in the past three years has confirmed that the presence of even wide cracks does not pose any danger to the safety of the structures, wide cracks are generally not acceptable to bridge engineers. The developers of the steel-free deck slabs have now conceded that these slabs should be reinforced with a crack-control mesh of nominal glass fibre reinforced polymer (GFRP) bars. Steel-free deck slabs with crack-control meshes are being referred as the second generation slabs. With the help of testing on full-scale models, it has been found that deck slabs with GFRP bars have the best fatigue resistance and those with steel bars the worst.

The investigation focuses on the evaluation of a novel acoustic transmission technique (ATT) for tracking the fatigue-induced damage in a steel-free bridge deck slab under laboratory conditions. The technique comprises the identification of changes in acoustic waveform attenuation through concrete by comparing integrated waveform amplitudes recorded at two or more acoustic sensors. This methodology is based on the experimental observation that cracking in concrete leads to increases in attenuation of the acoustic signals. The mapping of cracks and other means of detecting damage induced by cracks were used to independently verify the conclusions from the ATT Each of the four deck slab panels was subjected to approximately 1700 cycles of a heavy wheel load; the damage induced by this loading was tracked reliably by the ATT. The procedure of evaluating dimensionless integrated amplitude ratios rather than absolute signal magnitudes proved to be a highly robust and stable means of measuring attenuation, hence damage in the slab.