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

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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Live Load Distribution in Prestressed Concrete Girder Bridges with Curved Slab

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.284-287.1441 ◽

2013 ◽

Vol 284-287 ◽

pp. 1441-1445

Author(s):

Doo Yong Cho ◽

Sun Kyu Park ◽

Woo Seok Kim

Keyword(s):

Finite Element ◽

Prestressed Concrete ◽

Parametric Study ◽

Load Distribution ◽

Critical Parameters ◽

Live Load ◽

Finite Element Analyses ◽

Distribution Factor ◽

Girder Bridges ◽

Live Load Distribution

This paper presents the live load distribution in straight prestressed concrete (PSC) girder bridges with curved deck slab utilizing finite element analyses. Numerical modeling methodology was established and calibrated based on field testing results. A parametric study of 73 cases with varying 6 critical parameters was used to determine a trend over each parameter. Through live load girder distribution factor (GDF) comparisons between the AASHTO LRFD, AASHTO Standard factors and finite element analyses results, both AASHTO live load distribution predicted conservatively in most bridges considered in the parametric study. However, in the bridges with curved slab, GDF was underestimated due to curvature influences. This study proposes a new live load distribution formula to predict rational and conservative live load distribution in PSC girder bridges with curved slab for a preliminary design purpose. The proposed live load distribution provides better live load analysis for the PSC girder bridge with curved slab and ensures the GDF is not underestimated.

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Evaluation of existing prestressed concrete bridges considering the randomness of live load distribution factor due to random vehicle loading position

Advances in Structural Engineering ◽

10.1177/1369433216664350 ◽

2016 ◽

Vol 20 (5) ◽

pp. 737-746 ◽

Cited By ~ 8

Author(s):

Junyuan Yan ◽

Lu Deng ◽

Wei He

Keyword(s):

Prestressed Concrete ◽

Load Distribution ◽

Random Variable ◽

Live Load ◽

Distribution Factor ◽

Live Load Distribution ◽

Load Distribution Factors ◽

Bridge Assessment ◽

Load Distribution Factor ◽

Transverse Position

The live load distribution factor is a very important parameter in both the design of new bridges and the evaluation of in-service bridges. Studies have shown that there can be large discrepancy between the actual load distribution factors of field bridges and the load distribution factors predicted by bridge design codes. In addition, the load distribution factor is always treated as a constant in bridge assessment even though it is a random variable with certain statistical properties. In this study, the reliability indexes of 15 prestressed concrete girder bridges designed following the AASHTO LRFD code are calculated by considering the randomness of the load distribution factors induced by the random vehicle transverse position. It is found that there is a considerable increase in the calculated bridge reliability indexes, especially for short-span bridges, when the load distribution factor is modeled as a random variable with the statistical properties obtained from numerical simulations. This suggests that vehicle transverse position is one important factor that can be considered if a refined analysis is desirable when traditional evaluation methods predict unsatisfactory bridge assessment results. The findings in this article also highlight the importance of considering the actual vehicle transverse position in the evaluation of existing bridges.

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Single-Lane Live Load Distribution Factor for Decked Precast, Prestressed Concrete Girder Bridges

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198105192800116 ◽

2005 ◽

Vol 1928 (1) ◽

pp. 142-152 ◽

Cited By ~ 4

Author(s):

Jason L. Millam ◽

Zhongguo (John) Ma

Keyword(s):

Prestressed Concrete ◽

Load Distribution ◽

Live Load ◽

Distribution Factor ◽

Girder Bridges ◽

Girder Bridge ◽

Live Load Distribution ◽

Load Distribution Factor ◽

Precast Prestressed Concrete ◽

Bridge System

The live load distribution factor equations provided by AASHTO load and resistance factor design specifications for the decked precast, prestressed concrete (DPPC) girder bridge system do not differentiate between a single-lane or a multilane loaded condition. This practice results in a single-lane load rating penalty for DPPC girder bridges. This paper determines distribution factor equations that accurately predict the distribution factor of the DPPC girder bridge system when it is subjected only to single-lane loading. Eight DPPC girder bridges were instrumented. Each bridge was loaded with a single load vehicle to simulate the single-lane loaded condition. The experimental data were used to calibrate grillage models of the DPPC girder bridge system. The calibrated grillage models were used to conduct a parametric study of the DPPC girder bridge system subjected to a single-lane loaded condition. Four new equations that describe the single-lane loaded distribution factor for both shear and moment forces of these bridges are developed in this paper.

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