Cantilever Decks Research Articles

Investigations On the Effective Width of Wide Flange Steel Girders

AbstractEffective width, as presented in Eurocode 3 is analysed. Efforts have been made to distinguish between the behaviour of the various structural parts acting as wide flanges. Different mechanical models are adopted: for the bridge deck plate between girders, for the cantilever deck part, and for the bottom plate of box girders with the presumption to reflect more adequately their actual participation in the complex girder work at bending. Also, the interaction between girders in a superstructure at loading is simulated as far as possible in order to replace to some extent a sophisticated spatial analysis. The Eurocode 3 way of presenting the matter is preserved. The results obtained are compared with the corresponding Eurocode parts and an assessment on the reported differences is given. The goal is to supply the designers with extended understanding the effects arising from the shear lag phenomenon.

Design and Full-Scale Testing of New MASH Test Level 4 (TL-4) Alaska 2-Tube Bridge Rail

The purpose of this project was to design and test a new Alaska multi-state 2-tube bridge rail meeting the safety-performance evaluation guidelines included in the American Association of State Highway and Transportation Officials (AASHTO) Manual for Assessing Safety Hardware (MASH), Second Edition 2016. The new 2-tube bridge rail designed and tested for this project was crash tested in accordance with MASH Test Level 4 (TL-4). Three crash tests were performed. The new bridge rail is 38 in. tall from the top of asphalt overlay and anchors to a 10 in. high by 18 in. wide curb. The curb was cast on top of a 35 ¾ in. wide deck cantilever that varied in thickness from 6 in. at the extreme field side edge to 12 in. at the exterior girder element. The posts were spaced on 10 ft centers. The posts were anchored to the concrete curb and deck using four 7/8 in. diameter A449 anchor bolts. The two-tube rail elements consisted of two HSS7 × 5 × 3/8 tubular elements. The calculated strength of the design was 77 kip at a height of 30 in. The bridge rail was considered acceptable for strength as per the AASHTO Load and Resistance Factor Design (LRFD) Section 13 Bridge Design Specifications. A test specimen of the bridge rail was constructed and crash tested per MASH TL-4. The new two-tube bridge rail met all the performance requirements of MASH TL-4. Details of the design and testing of the new bridge rail are provided in this paper.

Comparison of Form-finding Methods to Shape Concrete Shells for Curved Footbridges

Shells are attractive and efficient structures that play a special role for engineers and architects. However, only few bridges supported by concrete shells have been designed and built after the Musmeci’s bridge in Potenza (Italy). Several numerical form-finding methods have been implemented in the last decades to optimize the shape of shells. In the present paper, a comparison of the Thrust Network Analysis (TNA) and Particle-Spring System (PS) is made by searching the optimal shape of a concrete shell supporting the curved cantilevered deck of a pedestrian bridge under the same boundary conditions. Finite Element Analysis was performed to compare the structural behaviour of the footbridges optimized by the two different form-finding techniques. The effectiveness of both form-finding methods in minimizing unfavourable tensile stresses in concrete shells, thus taking advantage of mechanical properties of concrete, is investigated. Furthermore, transverse deflections of the curved cantilevered deck were reduced introducing an external prestressing system applied to the upper flange of the ring box girder. Finally, the obtained results can help architecture and engineering practitioners to develop innovative bridge conceptual design.

Vertical Dynamic Responses of the Cantilever Deck of a Long-Span Continuous Bridge and the Coupled Moving Trains

It may be necessary to arrange railway traffic on the outer edge of the cantilever deck of a box girder bridge for the sake of transportation planning. A continuous box girder bridge was designed in China to carry a single-track urban rail transit traffic on the cantilever deck of the bridge and three-lane highway traffic on the other part of the deck. In order to investigate the possible resonant responses of the coupled train–bridge system, the resonance condition of the cantilever deck under moving train loads is discussed analytically, and then numerical analyses of the vertical train–bridge dynamic interaction considering local vibration of the cantilever decks are carried out. The degrees of freedom of the bridge modeled by shell elements are so large that mode superposition method is used to reduce the computation efforts. It is found that the resonance speed of the cantilever deck predicted by the analytical method is 305 km/h, which agrees well with the numerical result. The numerically computed results also indicate that the serviceability of the bridge deck and the ride quality of the railway vehicles in the vertical direction are in good condition below the critical speed of 200 km/h.

Capacity of Lightly Reinforced Bridge Deck Cantilever Overhang Subjected to Static Loading

Concrete bridge deck cantilever overhang supported by reinforced concrete T -beam is expected to have an enhanced carrying capacity resulting from the stiffness of T -beam elements. In this paper, full scale static load test on bridge deck cantilever overhang sample and its numerical modelling is presented. The deck slab was supported by two wide concrete T -beams and subjected to static simulated vehicular wheel load applied at the free end of the deck cantilever. The performance of the deck slab is considered to be enhanced by the supporting wide flange T -beams. The slab was therefore reinforced with only anti-cracks steel reinforcement mainly for thermal and shrinkage cracking. The ultimate load, deflection and strain results from both laboratory test and finite element model showed a satisfactory ultimate strength capacity of the system, in which an ultimate load far beyond codes specified vehicular wheel load was obtained, thus highlighting the contribution of the T -beam stiffness in the bearing capacity of the lightly reinforced cantilevered slab.

Experimental investigation on fatigue of concrete cantilever bridge deck slabs subjected to concentrated loads

Shear has been observed to be often the governing failure mode of RC cantilever deck slabs of bridges without shear reinforcement subjected to concentrated loads when tested under a quasi-static application of the load. However, concentrated loads of heavy vehicles have a repetitive nature, causing loss of stiffness and potential strength reductions due to fatigue phenomena.In this paper, the fatigue behavior of cantilever bridge deck slabs is investigated. A specific experimental programme consisting on eleven tests under concentrated fatigue loads and four static tests (reference specimens) is presented. The results show that cantilever bridge deck slabs are significantly less sensitive to shear-fatigue failures than beams without shear reinforcement. Some slabs failed due to rebar fractures. They presented significant remaining life after first rebar failure occurred and eventually failed due to shear. The test results are finally compared to the shear-fatigue provisions of the fib-Model Code 2010 and the Critical Shear Crack Theory to discuss their suitability.

Live-Load Response of a 65-Year-Old Pratt Truss Bridge

AbstractThe Kettle River Bridge is an arched, steel cantilevered deck, Pratt Truss bridge. To quantify the live-load performance of the bridge superstructure and provide a baseline for future comparisons, it was instrumented with 151 strain gauges on various beam, stringer, and truss members. In addition, 8 displacement gauges were attached along the truss. All gauges were simultaneously monitored while the bridge was subjected to a nondestructive, live-load test. The recorded bridge response was analyzed to quantify in situ behavior. The measured behavior was then used to validate a finite-element model using solid and frame elements, which was subsequently used to obtain an inventory- and operating-load rating of 2.03 and 2.64, respectively. Based on the results of the test, it was concluded that the large gusset plates added partial fixity to the truss members, as evident from the significant measured in-plane bending strains. However, the beam-and-stringer deck support system showed minimal rotational...

캔틸레버를 갖는 PCC-Deck의 구조보강

본 연구는 현재 내측 거더부에 적용하고 있는 LB-Deck를 캔틸레버부까지 확대 적용하기 위하여 Precast Concrete Cantilever Deck를 제안하고, 제안된 PCC-Deck의 구조적인 안전성과 처짐등 거동특성을 평가하였다. PCC-Deck의 구성은 일반부 LB-Deck와 캔틸레버부의 Deck를 주철근과 격자봉을 연장하여 제작하는 방식으로, 기존 LB-Deck을 사용할 경우 발생하는 전도에 대한 문제를 보완하였다. 수치해석 및 실험 결과 최적의 구조로 제안된 D-Type (상부근 16 mm, 격자봉 6 mm, 하부근 12 mm)의 경우 최대하중 28 kN, 최대처짐 27.49 mm로 나타났으며, 자중을 제외한 하중 10kN에서의 시공하중에 대한 내하하중 비율이 2.8로 가장 좋은 결과를 나타냈다. 이러한 결과는 다른 Type의 PCC-Deck 실험체 대비 77.5%의 개선효과가 있는 것으로 평가되었다. LB-Deck is one of the widely used member in interior part of girders as a permanent formwork in structures, but it is not easy to apply to the exterior part of girder due to the overturning and excessive deflection. Considering allowable deflection and safety of the exterior part, Precast Concrete Cantilever Deck (PCC-Deck) is proposed with normal LB-Deck in inner part and extended bars of LB-Deck in outer part. Both numerical analyses and experimental tests were compared to check the safety and allowable deflection for 6 types of PCC-Deck, and D-type (with 16 mm top bar, 6 mm lattice bar, 12 mm bottom bar) is suggested as an optimal structural reinforcement to the 28 kN of maximum load and 27.49 mm of final deflection. The load resisting ratio of D-type under working load of 10 kN was about 2.8 times and 77.5% of improvement was observed.

Examining the Presence of Arching Action in Edge-Stiffened Bridge Deck Cantilever Overhangs Subjected to a Wheel Load

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.

Structural health monitoring of the Tamar suspension bridge

This paper presents experiences and lessons from the structural health monitoring practice on the Tamar Bridge in Plymouth, UK, a 335-m span suspension bridge opened in 1961. After 40 years of operations, the bridge was strengthened and widened in 2001 to meet a European Union Directive to carry heavy goods vehicles up to 40 tonnes by a process in which additional stay cables and cantilever decks were added and the composite deck was replaced with a lightweight orthotropic steel deck. At that time, a structural monitoring system comprising wind, temperature, cable tension and deck level sensors was installed to monitor the bridge behaviour during and after the upgrading. In 2006 and 2009, respectively, a dynamic response monitoring system with real-time modal parameter identification and a robotic total station were added to provide a more complete picture of the bridge behaviour, and in 2006 a one-day ambient vibration survey of the bridge was carried out to characterize low-frequency vibration modes of the suspended structure. Practical aspects of the instrumentation, data processing and data management are discussed, and some key response observations are presented. The bridge is a surprisingly complex structure with a number of inter-linked load–response mechanisms evident, all of which have to be characterized as part of a long-term structural health monitoring exercise. Structural temperature leading to thermal expansion of the deck, main cables and additional stays is a major factor on global deformation, whereas vehicle loading and wind are usually secondary factors. Dynamic response levels and modal parameters show apparently complex relationships among themselves and with the quasi-static load and response. As well as the challenges of fusing and managing data from three distinct but parallel monitoring systems, there is a significant challenge in interpreting the load and response data firstly to diagnose the normal service behaviour and secondly to identify performance anomalies. Copyright © 2012 John Wiley & Sons, Ltd.

Study on Short Span Deck Bridges with Encased Steel Beams

A study focusing on optimization and efficiency of relatively common solution for small span railway bridges is presented. The superstructure of the bridges is created by reinforced concrete deck with encased steel beams. Especially, flexural behaviour was analysed in the study. Actual bridge cross-sections as well as spans were taken into account. Actions according to new European codes were implemented. Usually, simplified uniform transverse redistribution of load for every one of encased steel girders across bridge cross-sections is practised in global analysis. As concrete slab and steel beams are composed together through encasement into steel concrete composite deck, its real behaviour is strongly influenced by the plate effects. Simplified procedures were compared to the models developed by finite analyses. Different types of steel cross sections have been analysed. Particularly, hot-rolled and built-up steel beams are compared. Moreover, unsymmetrical I-shaped and upside-down T-shaped welded steel sections were investigated. In addition, optimisation aspects based on material consumption as criterion would be presented. Finally, the influence of deck cantilever and cornice on flexural behaviour would be studied.

Assessment of traffic-induced low frequency sound radiated from a viaduct by field experiment

This study is intended to assess low frequency sound radiated from a viaduct under normal traffic. The bridge comprises steel box girders and wide cantilever decks on which vehicles pass. The low frequency sound and the acceleration response of the bridge under normal traffic are measured to investigate how bridge vibrations affect the low frequency sound observed near the bridge. Observations demonstrate that strong relationships exist between frequency characteristic of bridge's acceleration response and the sound pressure level of low frequency sound. A noteworthy point is that the dynamic feature of the sound pressure level is mostly affected by dynamic feature of the span locating near the observation point.

Behaviour of bridge deck cantilever overhangs subjected to a static and fatigue concentrated load

Innovative steel-free deck slabs and deck slabs reinforced with fibre reinforced polymers (FRPs) are a solution to the problem of corrosion of internal steel reinforcement. Engineers have proposed the idea that there may be some arching-action present in bridge deck cantilever overhangs subjected to a concentrated load. An experimental research program was undertaken at the University of Manitoba to investigate this hypothesis. This paper includes the details of the experimental program required to test a full-scale innovative bridge deck with cantilevers reinforced with different top transverse reinforcing bars. The experimental results include specific information related to the static and fatigue deflection related results, strain related results, crack related results, and modes of failure. The experimental test results indicated that the static and fatigue behaviour of an unstiffened bridge deck cantilever overhang may not be completely flexural. The experimental static and fatigue destructive testing of bridge deck cantilever overhangs subjected to a concentrated load suggests that there may be the presence of arching-action. Further experimental research is required to confirm the behaviour of bridge deck cantilevers with a barrier wall subjected to a concentrated load.

Mountain Pass Slope Failure Retrofitted with a Half Viaduct Bridge Structure, South Africa

The Garden Route, one of the main tourist attractions and also a major national road on the south coast of South Africa, experienced abnormally high rainfall in August 2006. A major slip failure occurred in one of the road cuttings, known as Kaaimans River Pass, which severely damaged the roadway. The owner (South African National Road Agency Ltd.), immediately took measures to restore this vital link in the national road network. Several preliminary concepts were developed by the project team which included bridge and geotechnical specialists from the owner and the project-consulting engineers. These included a tied pile anchor wall, a tied mechanically stabilized embankment and a half-width pre-cast beam bridge structure. The selection of the most suitable option relied heavily on the geotechnical conclusions by specialists from the project-consulting engineers, after an extensive drilling programme was undertaken to investigate the competency of the underlying rock substrata. A modified version of the first concept was finally decided upon, as this was considered to provide the optimum solution, considering interaction with the adjacent road formation as well as the bedrock profile.uThe new viaduct is supported on eight 1200 mm diameter reinforced concrete oscillator bored piles approximately 14 m long, spaced at 8 m centres and socketed 4 m into competent rock. The superstructure comprises a 7 m wide, 60 m long cantilevered deck that is counterbalanced by an integrated buried jockey slab and supported on the piled substructure. This configuration eliminated a problematic longitudinal joint. The structure is anchored with re-stressable rock anchors, ensuring the stability of the structure and rock formation. In order to minimize the movement between the roadway and structure, the jockey slab is also tied down with anchors. (A)

Application of a 3-D crack analysis model to RC cantilever decks of excessive cracking

The excessive cracking of RC cantilever decks, which often requires special attention for structural engineers, is studied using a three-dimensional crack analysis model. The model is based on a fracture energy approach for analyzing cracks in concrete, and the numerical analysis is carried out using a modified load control method. The problem of excessive cracking is then studied with four different span-ratios. Based on the numerical results, the crack behavior with respect to the patterns of crack propagation, dissipation of the fracture energy, and effects on the structural integrity are discussed. The mechanisms which cause the excessive cracking are also explained.

Three-dimensional finite element analysis on crack behaviors of RC cantilever decks

Crack behaviors of RC cantilever decks, which often require special attention for bridge engineers, are studied. Because of the three-dimensional characteristics of stress states in the cantilever decks, a three-dimensional numerical model for crack analysis is proposed. It is based on a fracture energy approach for analyzing cracks in concrete. The effectiveness of the model is examined by comparing with the results of fracture tests. On the basis of three-dimensional crack analyses of RC cantilever decks, the crack behaviors and their effects on the structures are discussed.

Living Lightly on the Earth: a Fieldweek at the Centre for Alternative Technology

AbstractHaving ascended the water-powered cliff railway that takes us from the carpark up to the main site we stand on the cantilevered deck of the upper station looking out across the hills and autumn colours of the wooded Dulas valley below us. The branches on the silver birches are whipped by a cold wind blowing in from the Dovey estuary as we turn to walk across the old slate workings that are now the site of one of the best known eco-centres in Europe. Later, having been given a guided tour of the site, we retire to our self-catering cabins where we split and stack the wood that will later keep us warm. The annual Gobal Futures fieldweek at the Centre for Alternative Technology has come round again.

Discussion of “ Analysis of Cantilever Decks of Thin‐Walled Box Girder Bridges ” by Shih Toh Chang and Jiang Zhi Gang (September, 1990, Vol. 116, No. 9)

Discussion of “ <i>Analysis of Cantilever Decks of Thin‐Walled Box Girder Bridges</i> ” by Shih Toh Chang and Jiang Zhi Gang (September, 1990, Vol. 116, No. 9)

Closure to “ Analysis of Cantilever Decks of Thin‐Walled Box Girder Bridges ” by Shih Toh Chang and Jiang Zhi Gang (September, 1990, Vol. 116, No. 9)

Closure to “ <i>Analysis of Cantilever Decks of Thin‐Walled Box Girder Bridges</i> ” by Shih Toh Chang and Jiang Zhi Gang (September, 1990, Vol. 116, No. 9)

Analysis of Cantilever Decks of Thin‐Walled Box Girder Bridges

A spline finite strip approach is presented to analyze the cantilever deck of single‐cell box girder bridges. The effects of distortion of a thin‐walled box section are taken into account by treating the cantilever deck as a cantilever slab with horizontally distributed spring support along the cantilever root. Perspex model tests have been conducted in the model structural laboratory at Tong Ji University. The results based on the spline finite strip method are compared with those of a perspex model test. Simplified solutions are also given for the distribution of transverse moment along the cantilever root, satisfying the following essential conditions: (1) For a given loading condition, the moment at root has a peak value; (2) the area under the transverse moment curve plotted for a given distance c is P ⋅ c; and (3) moment approaches zero as longitudinal ordinate y tends to infinity. Further, sagging moment is detected exactly in the region where the concentrated load is applied. This moment, particul...