Skew Reduction Factors for Moment in NEXT Beam Bridges with Integral Abutments

2018 ◽  
Vol 878 ◽  
pp. 49-53
Author(s):  
Jian Wei Huang ◽  
Jonathan Davis
Keyword(s):  
Accelerated Bridge Construction ◽  
Live Load ◽  
Skew Angle ◽  
Integral Abutments ◽  
Research Findings ◽  
Beam Section ◽  
Live Load Distribution ◽  
Aashto Lrfd ◽  
Beam Bridge ◽  
Reduction Factors

Northeast Extreme Tee (NEXT) beams have been recently developed for the accelerated bridge construction. The skew effect on live load distribution in a NEXT beam bridge, especially with integral abutments, is not clear and shall be assessed. In this paper, various skew NEXT beam bridges are evaluated through validated finite element (FE) analyses with solid brick elements. Parameters as studied include beam section, span length, and skew angle. Per AASHTO LRFD specifications, one- and two-lane loaded cases are examined to obtain the maximum tensile strains in beam stems under the design live loading (HL-93). Unskewed bridges are used as control specimens to compute skew reduction factors (SRF) for moment from the obtained FE strains. The FE- and LRFD-SRFs for moment are compared in terms of figures, which indicate the LRFD-SRFs have good agreements with the FE-SRFs at large. For the majority of the bridges, LRFD-SFRs govern the FE-SRFs. The research findings from this paper are useful for practicing engineers to safely design a skew NEXT beam bridge with integral abutments.

scholarly journals Structural Design Issues For Integral Abutment Bridges

2021 ◽  
Author(s):  
Navid Nikravan
Keyword(s):  
Finite Element ◽  
Load Distribution ◽  
Finite Element Models ◽  
Live Load ◽  
Skew Angle ◽  
Temperature Variations ◽  
Integral Bridges ◽  
Live Load Distribution Factors ◽  
Live Load Distribution ◽  
Load Distribution Factors

In recent years, integral abutment bridges have been increasingly used in Canada due to their low maintenance costs. Whereas a rational guideline to determine the maximum length and skew angle limits for integral bridges due to temperature variations do not exist in bridge codes. As such, structural behavior of integral bridges subjected to temperature variation was investigated through a numerical modeling. First, detailed 3D finite-element models were developed. The accuracy of finite-element models was validated against data collected from filed testing available in the literature on integral bridges subjected to the seasonal temperature variations and truck loading. Then, a parametric study was carried out to study the effects of key parameters on the performance of integral bridges when subjected to temperature variations. The numerical results indicated that number of design lanes, bridge length, abutment height, abutment-pile connection, pile size and skew angle had a significant impact on the behavior of integral bridges. Based on the data generated from the parametric study, new limits for the maximum length and skew angle of integral bridges based on displacement-ductility limit state of piles were established. Literature review revealed that live load distribution among girders in integral bridges due to truck loading conditions is as yet unavailable. This study is extended to develop new equations to estimate girder live load distribution factors for integral bridges. First, 2D and 3D finite-element models (FEMs) of integral bridges were developed. Then, a parametric study was performed to study the effects of parameters such as abutment height, abutment thickness, wingwall length, wingwall orientation, number of design lanes, span length, girder spacing and number of intermediate diaphragms. The results indicated that the live load distribution factors obtained from the FEMs were lower than those obtained from current CHBDC equations. Consequently, sets of empirical expressions were developed in the form of reduction factors that can be applied to CHBDC live load distribution factors to accurately calculate the girder distribution factors. Also, other set of equations for the live load distribution factors were developed in a similar form as that specified in CHBDC for possible inclusion in the bridge code.

Analysis on Live Load Distribution Factors of Widened Hollow Core Slab Bridges

2019 ◽  
Vol 953 ◽  
pp. 215-222
Author(s):  
Li Fang Zhang ◽  
Ying Wang ◽  
Ying Ge Lei ◽  
Yun Chang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Load Distribution ◽  
Live Load ◽  
Span Length ◽  
Hollow Core ◽  
Skew Angle ◽  
Hollow Core Slab ◽  
Live Load Distribution ◽  
Load Distribution Factors

There are some studies on live load distribution factors(LLDF) of hollow core slab bridges which mainly consider the influence of connecting method and rigidity, while the effects of span length and skew angle have not been fully involved. Influenced by the trend of road and river, the hollow core slab bridges are often skewed with rivers. So it is essential to study the span length and skew angle effects in bridge widening. Based on a highway widening project, some representative hollow core slab bridges are selected for widening analysis. Theoretical method and finite element method are used to analysis the LLDF of slab bridges before and after widening. Finite element method(FEM) can give high precision in LLDF calculating. The influences of span length, connecting stiffness and skew angle are studied. The result indicates that no matter before or after widening the LLDF become smaller with the increase of span length. After widening, the LLDF of the half slabs near to the widening seam reduce obviously and with the span length increases the variation becomes more obviously. The connecting stiffness brings small influence to the LLDF in hollow core slab bridges. And with the increase of skew angle, the LLDF of the new side slab changes obviously, but the variation of LLDF of original slabs is not obviously according to skew angle.

Shear live load analysis of NEXT beam bridges for accelerated bridge construction

2021 ◽  
Vol 17 (3-4) ◽  
pp. 111-119
Author(s):  
Jianwei Huang
Keyword(s):  
Prestressed Concrete ◽  
Precast Concrete ◽  
Structural Safety ◽  
Accelerated Bridge Construction ◽  
Live Load ◽  
Distribution Factor ◽  
Bridge Construction ◽  
Shear Design ◽  
Bridge Structures ◽  
Live Load Distribution

Using precast concrete elements in bridge structures has emerged as an economic and durable solution to enhance the sustainability of bridges. The northeast extreme tee (NEXT) beams were recently developed for accelerated bridge construction by the Precast/Prestressed Concrete Institute (PCI). To date, several studies on the live load distribution factor (LLDF) for moment in NEXT F beam bridges have been reported. However, the LLDFs for shear in NEXT F beam bridges are still unclear. In this paper, the lateral distributions of live load shear in NEXT F beam bridges were examined through a comprehensive parametric study. The parameters covered in this study included bridge section, span length, beam section, number of beams, and number of lanes loaded. A validated finite element (FE) modeling technique was employed to analyze the shear behavior of NEXT F beam bridges under the AASHTO HL-93 loading and to determine the LLDFs for shear in NEXT beam bridges. A method for computing the FE-LLDF for shear was proposed for NEXT beam bridges. Results from this study showed that the FE-LLDFs have a similar trend as the AASHTO LFRD-LLDFs. However, it was observed that some LRFD-LLDFs are lower than the FE-LLDFs by up to 14.1%, which implied using the LRFD-LLDFs for shear could result in an unsafe shear design for NEXT beam bridges. It is recommended that a factor of 1.2 be applied to the LRFD-LLDF for shear in NEXT F beam bridges for structural safety and design simplicity.

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