Published online in January 2017.
Osama Mohammed Elmardi
Abstract:Dynamic Relaxation (DR) method is presented for the geometrically nonlinear laterally loaded, rectangular laminated plates. The analysis uses the Mindlin plate theory which accounts for transverse shear deformation. A computer program has been compiled. The convergence and accuracy of the DR solutions for elastic large deflection response are established by comparison with various exact and approximate solutions. New numerical results are generated for uniformly loaded square laminated plates which serve to quantify the effects of shear deformation, length to thickness ratio, number of layers, material anisotropy and fiber orientation. It was found that linear analysis seriously over predicts deflection of plates. The shear deflection depends greatly on a number of factors such as length to thickness ratio, degree of anisotropy and number of layers. As the degree of anisotropy increases, the plate becomes stiffer and when it is greater than a critical value, the deflection becomes virtually independent on the degree of anisotropy. It was also found that deflection of plates depends on the angle of orientation of individual plies and the size of load applied.
International Journal of Bridge Engineering, Vol. 4, No. 3, 2016: pp. 1-19
Jennifer Kearney, Jeffrey A. Laman
Abstract:Pedestrian suspension footbridges have low stiffness, low mass, and low damping, making them prone to significant displacements, velocities, and accelerations under normal pedestrian loads. The present study analyzed two scaled, laboratory physical models and conducted simulations on forty numerical models to determine how particular design parameters affect modal frequencies and the dynamic response as compared to human comfort limits. The parametric study, validated through the physical model results, analyzed span length, cable sag, vertical stiffening, and lateral stiffening of the numerical models. The present study established an accurate modeling methodology based on calibration with the scaled laboratory physical models. The modeling methodology was employed to conduct an extensive simulation parametric study. The study results indicate that modal frequencies of common pedestrian suspension bridges fall outside recommended ranges – the vertical velocities, lateral accelerations, and vertical accelerations of the structure under a single pedestrian load exceed published human comfort limits. The present study observed that shorter span lengths respond with higher modal frequencies and dynamic responses, that lower cable sag results in higher vertical frequencies and lower vertical dynamic responses, and that the addition of stiffening elements increases modal frequencies and decreases dynamic response. It was also concluded that limited cable stiffening, while influencing the bridge response, was not entirely sufficient to meet human comfort limits.
International Journal of Bridge Engineering, Vol. 4, No. 3, 2016: pp. 21-35
George N. Stamatopoulos
Abstract:The Bailey bridge is a space truss structure composed entirely from prefabricated panels which are assembled in situ by placing pins through the holes of the lugs at the ends of the panels’ chords. The present paper deals with the fatigue assessment of these panel pins. The bridge is modelled as 3D space truss using beam elements and the Fatigue Load Model 3 (FLM 3) is chosen to verify the fatigue life of the pin detail. The model is analysed using both static and dynamic analyses and the range of the shear stresses on the pin are calculated. Finally, following the λ-method, recommended in EN 1993-2: 9.5.2, the fatigue strength of the pin is checked.
International Journal of Bridge Engineering, Vol. 4, No. 3, 2016: pp. 37-48
Muhammad Adeel Arshad
Abstract:This paper discusses different Live Load Models currently in practice for the design of highway bridges in Pakistan. These include the models from the Pakistan Code of Practice for Highway Bridges 1967 and American Association of State Highways and Transportation Officials Load Resistance Factored Design, Bridge Design Specifications. To study the effect of these Live Load Models, a typical simply supported RC-girder bridge having 12.8 meter span was selected as a case study. A weigh station was installed in field from which load data of various trucks were recorded. Then line analysis was performed by taking the Live Load Models currently in practice, the actual live loads traversing the bridge and the legal load limits specified by the National Highway Authority, Pakistan. The results show that the highway loading in Pakistan produces much greater load effects than anticipated from the 1967 bridge design code usually used for their design.
International Journal of Bridge Engineering, Vol. 4, No. 3, 2016: pp. 49-60
Sharanabasava G., Anilkumar S. Katageri
Abstract:A bridge is a structure built to span physical obstacles such as a body of water, valley or road for the passage. In India, RC road bridges are designed and constructed according to Indian Road Congress guidelines as per IRC: 21-2000 code in which working stress method is used. Recently Indian Road Congress has introduced another code IRC: 112-2011 for design of bridges. More research in bridge design using limit state method has to be carried to enlighten the recently introduced IRC-112 code. In regards to this, present study has been performed to know how design of IRC-112 differs from IRC-21 and attempt is made to study undefined parameters of IRC: 112-2011 such as span to effective depth (L/d) ratio. It is observed that L/d ratio for slab culvert is 20. Quantity of materials required in limit state method is compared with quantity of material required in working stress method. On comparison for slab culvert, steel can be saved up to 5 to 10% and quantity of concrete can be saved up to 33 to 44% using limit state method. It can be concluded that concrete and steel can be saved by adopting limit state method in design of bridge in comparison to working stress method.
International Journal of Bridge Engineering, Vol. 4, No. 3, 2016: pp. 61-72
Y. H. Chai, H. J. Hung
Abstract:California practice requires relatively long waiting period before closure pour can be made in bridge widening and staged construction, leading to unnecessary delay in project completion. The delayed casting of the closure slab is intended to avoid potential damage in the connected decks as a result of the differential displacement occurring between the new and previously constructed decks. The waiting period, which can take up to 60 days in California, does not take into account of the displacement capacity of the slab and the time-dependent deformation of the bridge. This paper proposes a more rational approach to the estimation of waiting period by limiting the displacement demand across the connected bridges to the displacement capacity of the closure slab. Numerical examples are provided in the paper to illustrate the procedure and preliminary results indicate that the current waiting period may be quite conservative, especially in staged construction.
International Journal of Bridge Engineering, Vol. 4, No. 3, 2016: pp. 73-91