Improved definition of dynamic load allowance factor for highway bridges

Yongjun Zhou,Zhongguo John Ma,Yu Zhao,Xiongwei Shi,Shuanhai He 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.3

The main objective of this paper is to study the dynamic load allowance (DLA) calculationmethods for bridges according to the dynamic response curve. A simply-supported concrete bridge with asmooth road surface was taken as an example. A half-vehicle model was employed to calculate the dynamicresponse of deflection and bending moment in the mid-span section under different vehicle speeds using thevehicle-bridge coupling method. Firstly, DLAs from the conventional methods and code provisions wereanalyzed and critically evaluated. Then, two improved computing approaches for DLA were proposed. Inthe first approach, the maximum dynamic response and its corresponding static response or itscorresponding minimum response were selected to calculate DLA. The second approach utilized weightedaverage method to take account of multi-local DLAs. Finally, the DLAs from two approaches werecompared with those from other methods. The results show that DLAs obtained from the proposedapproaches are greater than those from the conventional methods, which indicate that the currentconventional methods underestimate the dynamic response of the structure. The authors recommend that theweighted average method based on experiments be used to compute DLAs because it can reflect thevehicle’s whole impact on the bridge.

Improved definition of dynamic load allowance factor for highway bridges

Zhou, Yongjun,Ma, Zhongguo John,Zhao, Yu,Shi, Xiongwei,He, Shuanhai Techno-Press 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.3

The main objective of this paper is to study the dynamic load allowance (DLA) calculation methods for bridges according to the dynamic response curve. A simply-supported concrete bridge with a smooth road surface was taken as an example. A half-vehicle model was employed to calculate the dynamic response of deflection and bending moment in the mid-span section under different vehicle speeds using the vehicle-bridge coupling method. Firstly, DLAs from the conventional methods and code provisions were analyzed and critically evaluated. Then, two improved computing approaches for DLA were proposed. In the first approach, the maximum dynamic response and its corresponding static response or its corresponding minimum response were selected to calculate DLA. The second approach utilized weighted average method to take account of multi-local DLAs. Finally, the DLAs from two approaches were compared with those from other methods. The results show that DLAs obtained from the proposed approaches are greater than those from the conventional methods, which indicate that the current conventional methods underestimate the dynamic response of the structure. The authors recommend that the weighted average method based on experiments be used to compute DLAs because it can reflect the vehicle's whole impact on the bridge.

Behavior of reinforced concrete beams filled with demolished concrete lumps

Bo Wu,Zhe Xu,Zhongguo John Ma,Qiongxiang Liu,Wei Liu 국제구조공학회 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.40 No.3

In the past decades, recycling use of demolished concrete was almost limited to the types of recycled coarse aggregate with a size of about 5-40 mm and recycled fine aggregate with a size of about 0-5 mm for concrete structures, and reuse of demolished concrete lumps (DCLs) with a size much larger than that of recycled aggregate, e.g., 50-300 mm, has been limited to roadbed, backfilling materials, or discarded to landfills. Treatment processes of DCLs are much simpler than those of recycled aggregate, leading to less cost and more energy-saving. In the future, the amount of demolished concrete is estimated to be much higher, so reuse of DCLs for concrete structures will become necessary. The objectives of this paper are to document the process of making reinforced concrete beams with DCLs, and to discuss the flexural and shear behaviors of those reinforced DCL beams through an experimental program, which includes three beams filled with DCLs and one conventional beam for investigating the flexural strengths and deformations, and 12 beams filled with DCLs and two conventional beams for investigating the shear strengths and deformations. The authors hope that the proposed concept offers another sustainable solution to the concrete industry.

Development of strut-and-tie model and design guidelines for improved joint in decked bulb-tee bridge

Lungui Li,Zhiqi He,Zhongguo John Ma,Lingkan Yao 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.2

This paper focuses on a development of strut-and-tie model (STM) to predict the capacity of an improved longitudinal joint for decked bulb-tee bridge systems. Nine reinforced concrete beam/slab specimens anchored by spliced headed bars with different details were tested. Test results were evaluated and compared with an anticipation of the validated STM. The proposed STM provides a lower bound of the ultimate capacity of the joint zone. It shows that the lap length of headed bars has a significant effect on structural behaviors of the improved joint. To develop a full strength joint, the range of the lap length can be determined by the strength and compatibility requirement. Design recommendations to spliced headed bars, concrete strength, as well as lacer bars in the joint zone are proposed for developing a full strength joint.

Behavior of reinforced concrete beams filled with demolished concrete lumps

Wu, Bo,Xu, Zhe,Ma, Zhongguo John,Liu, Qiongxiang,Liu, Wei Techno-Press 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.40 No.3

In the past decades, recycling use of demolished concrete was almost limited to the types of recycled coarse aggregate with a size of about 5-40 mm and recycled fine aggregate with a size of about 0-5 mm for concrete structures, and reuse of demolished concrete lumps (DCLs) with a size much larger than that of recycled aggregate, e.g., 50-300 mm, has been limited to roadbed, backfilling materials, or discarded to landfills. Treatment processes of DCLs are much simpler than those of recycled aggregate, leading to less cost and more energy-saving. In the future, the amount of demolished concrete is estimated to be much higher, so reuse of DCLs for concrete structures will become necessary. The objectives of this paper are to document the process of making reinforced concrete beams with DCLs, and to discuss the flexural and shear behaviors of those reinforced DCL beams through an experimental program, which includes three beams filled with DCLs and one conventional beam for investigating the flexural strengths and deformations, and 12 beams filled with DCLs and two conventional beams for investigating the shear strengths and deformations. The authors hope that the proposed concept offers another sustainable solution to the concrete industry.

Comparison of long-term behavior between prestressed concrete and corrugated steel web bridges

Yulin Zhan,Fang Liu,Zhongguo John Ma,Zhiqiang Zhang,Zengqiang Duan,Ruinian Song 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.30 No.6

Prestressed concrete (PC) bridges using corrugated steel webbing have emerged as one of the most promising forms of steel-concrete composite bridge. However, their long-term behavior is not well understood, especially in the case of largespan bridges. In order to study the time-dependent performance, a large three-span PC bridge with corrugated steel webbing was compared to a similar conventional PC bridge to examine their respective time-dependent characteristics. In addition, a threedimensional finite element method with step-by-step time integration that takes into account cantilever construction procedures was used to predict long-term behaviors such as deflection, stress distribution and prestressing loss. These predictions were based upon four well-established empirical creep prediction models. PC bridges with a corrugated steel web were observed to have a better long-term performance relative to conventional PC bridges. In particular, it is noted that the pre-cambering for PC bridges with a corrugated steel web could be smaller than that of conventional PC bridges. The ratio of side-to-mid span has great influence on the long-term deformation of PC bridges with a corrugated steel web, and it is suggested that the design value should be between 0.4 and 0.6. However, the different creep prediction models still showed a weak homogeneity, thus, the further experimental research and the development of health monitoring systems are required to further progress our understanding of the long-term behavior of PC bridges with corrugated steel webbing.

Development of strut-and-tie model and design guidelines for improved joint in decked bulb-tee bridge

Li, Lungui,He, Zhiqi,Ma, Zhongguo John,Yao, Lingkan Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.2

This paper focuses on a development of strut-and-tie model (STM) to predict the capacity of an improved longitudinal joint for decked bulb-tee bridge systems. Nine reinforced concrete beam/slab specimens anchored by spliced headed bars with different details were tested. Test results were evaluated and compared with an anticipation of the validated STM. The proposed STM provides a lower bound of the ultimate capacity of the joint zone. It shows that the lap length of headed bars has a significant effect on structural behaviors of the improved joint. To develop a full strength joint, the range of the lap length can be determined by the strength and compatibility requirement. Design recommendations to spliced headed bars, concrete strength, as well as lacer bars in the joint zone are proposed for developing a full strength joint.

Evaluation of Time-dependent Strain Loss in CFRP Eccentrically Reinforced Shrinkage Compensating Concrete (SHCC) Flexural Members

Qi Cao,Jianpu Zhou,Xiaofeng Wang,Jizhong Wang,Zhongguo John Ma 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.1

Eccentrically CFRP enclosed Shrinkage Compensating Concrete (SHCC) flexural members show benefits of easy prestressing, better durability and self-made camber compared with traditional prestressed concrete. This paper presents the experimental and analytical work to evaluate the expansion strain losses in the proposed flexural members. A proposed analytical model to calculate the time-dependent strain losses is established including variables of shrinkage and creep of SHCC concrete based on GL2000 model. The relationship between maximum expansion strain and axial stiffness of FRP (EA) is also constructed. The same procedure was also conducted for Portland Cement Concrete (PCC) for the CFRP-PCC beam specimens. It is indicated that the proposed analytical model produces an accurate prediction in strain losses over time.

Experiment on the Behavior of a Self-Anchored Suspension and Cable-Stayed Hybrid Bridge during Structural Transformation

Yu Zhao,Yongjun Zhou,Lingling Wu,Changchang Li,Zhongguo John Ma 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.6

The Longgang Bridge in Shaanxi, China, is a complex continuous hybrid structure composed of two cable-stayed self-anchored suspension parts and one single-pylon cable-stayed part. A 1:20-scaled model was established due to the effect of multiple structural transformation, frequent internal force changes during the construction process, and differences between actual material parameters and theoretical calculation parameters. In this paper, the design, materials, counterweight, experimental instrumentation, and construction stages of the scaled model are introduced. Based on the experimental data, the nonlinear behavior of the self-anchored suspension and cable-stayed hybrid bridge during the structural transformation of the construction process is systematically and comprehensively studied. The evolutions of the hanger force and stayed cable force, the variation in the subcable and back-cable forces, the displacement characteristics of the suspension cable and the deflection of the stiffened girder are analyzed, and the relationships among these variables in different states of the structural system are discussed. This paper will serve as a technical reference for the construction of similar bridges in the future.