Recent Adopted

Optimization of Filling Concrete Size in Composite Beam Box Based on IGRNN

wangyafeng , Liu Jian , KE Hongjun

Adopted date: March 20,2024

[Abstract](26) [HTML](0) [PDF 0.00 Byte](0)

Abstract:
The mechanical performance of the negative bending moment zone of steel-concrete composite continuous beams has always been a focus of attention in bridge engineering. Existing research mainly proposes improvement measures for the tension of concrete bridge decks, but rarely considers the common phenomenon of steel beams bearing pressure. The steel beams in the steel-concrete composite beam, especially the steel bottom plate in the negative bending moment area of the pier top, bear almost the maximum compressive stress of the entire bridge. Therefore, taking a steel-concrete composite beam bridge in Zhejiang as the engineering background, it is proposed to fill a part of the cast-in-place concrete inside the negative bending moment area of the pier top box girder during the construction phase to reduce the compressive stress borne by the steel bottom plate. Firstly, an Ansys finite element model of the composite beam bridge is established for stress analysis. Then, the length and vertical thickness of the filled concrete along the longitudinal direction of the bridge are used as variable parameters, and the minimum peak compressive stress of the steel beam bottom plate is taken as the optimization objective. IGRNN (Improved Generalized Regression Neural Network) is used to optimize its size. Finally, the predicted optimal size result is substituted into the finite element model to verify the accuracy of the prediction results. The research results indicate that pouring and filling a certain amount of concrete blocks into the negative bending moment area of the pier top inside the box beam can significantly reduce the compressive stress on the bottom plate of the steel beam; At the same time, IGRNN can greatly improve the efficiency of size optimization. For the case of composite beam bridges, the predicted optimal size and corresponding steel beam bottom plate compressive stress value are within 5% of the compressive stress value calculated by the finite element model, and the optimized steel beam bottom plate compressive stress is reduced by 74.9% compared to the original structure, with good results. This research achievement and method can provide reference for reducing the compressive stress of the steel beam bottom plate at the pier top and related issues for similar bridges.

Study on reasonable seismic system of long-span concrete beam bridge in strong earthquake area

yudeen , hanjianshan , sunpingkuan , chenchao

Adopted date: April 20,2022

[Abstract](250) [HTML](0) [PDF 0.00 Byte](0)

Abstract:
Based on the engineering background of Hainan Nandu River Bridge, the three-dimensional finite element dynamic model of the bridge is established. Firstly, the selection of ground motion input and the establishment of finite element model are introduced. Secondly, the influence of different design parameters (bearing radius) of friction pendulum vibration reduction and isolation bearing on the seismic response of the bridge is discussed, and the optimal bearing parameters suitable for the bridge are obtained; Finally, the seismic responses of the bridge under three different restraint structures, namely, conventional restraint system, friction pendulum bearing vibration reduction and isolation system and rigid frame bridge system, are compared and analyzed. The results show that the vibration reduction and isolation system with friction pendulum bearing can not only greatly reduce the seismic response of the whole bridge structure under transverse or longitudinal seismic input, At the same time, the displacement response can be controlled within a reasonable range, which proves that this seismic system is very effective for the bridge.

Study on performances of foamed lightweight road materials based on coal-burnig slag

jiangshanguo , hanjiaqi , chenzhongping , yukuangdi

Adopted date: December 28,2021

[Abstract](90) [HTML](0) [PDF 0.00 Byte](0)

Abstract:
The slag from the furnace bottom in Shandong province is mixed with Portland cement and limestone powder to prepare composite powder. Carbonate was used as the activator, and the coal-fired slag-based foam lightweight soil road materials are prepared by physical foaming method. The influence of wet volume-weight of slag base lightweight soil materials on mechanical properties, working performance, defoaming rate and porosity was studied. The results show that the unconfined compressive strength of slag-based lightweight soil decreases greatly with the decrease of wet unit weight, and the flowability decreases linearly with the increase of foam rate. The defoaming rate of lightweight soil has little change in the range of 650~750kg/m3 wet volume-weight. Considering various performance factors, lightweight soil with 650 kg/m3, Slag accounts for 50%, cement for 40%, limestone powder for 10%, and the activator admixture dosage for 4% can be prepared, which can better meet the workability of foamed lightweight soil, and the defoaming rate is low. 3d strength of sample can reach 0.79 MPa and 28d strength can reach 1.63 MPa.

Cantilever Construction and Control of Long-span Steel-Concrete Hybrid Continuous Box Girder Bridge with Variable Sections

lvhaijun , tangliang , zhouye , qile

Adopted date: September 29,2024

[Abstract](2) [HTML](0) [PDF 0.00 Byte](0)

Abstract:
In order to solve the overall lifting difficulty of mid-span steel beam in the steel-concrete hybrid continuous box girder bridge with variable sections under special environmental conditions, and to provide guidance for the construction and design of such bridges. This study analyzed the external measures adopted by different construction methods and their impacts on the bridge-building state of the structure. It also studied key factors and control points for sub-segment cantilever assembly method in both theoretical research and real bridge calculations. The results indicate that the effect of the temporary load and the temporary external prestressing will not be offset by the demolition after the system transformation, and will affect the structure in the bridge-building state. Additionally, it is found that the sub-segment cantilever assembly method can achieve the bridge bending moment corresponding to the overall lifting method by construction measures, and the external prestressing at the lower part can significantly improve closing state adjustment efficiency compared to using it at the upper part, leading to a substantial reduction in axial force on the steel beam. Furthermore, crane weight has a greater impact on internal forces in sub-segment cantilever assembly method than in whole lifting method. This study provides valuable insights for process design guidance in constructing this type of bridge, including proposing a temporary articulation device at closing ports to mitigate adverse influences from bridge floor cranes on bending moments at the steel beam root.

Letters Lessons learned from 60 years of pavement trials in continental climate regions of Canada

Di Wang , Jingxiao Li , Xueyuan Ren , Dongdong Yuan

Adopted date: September 29,2024

[Abstract](1) [HTML](0) [PDF 0.00 Byte](0)

Abstract:
In order to study the influence of the dry and wet method on the road performance of……In the early 1960s, increasing traffic demanded that transportation agencies use progressively harder asphalt binders to prevent premature wheel path rutting. Using stiffer binders increased stress from cold temperature shrinkage, typically manifesting, for the first time, as rather regularly spaced transverse cracks. Trials to investigate this phenomenon confirmed the importance of binder consistency, temperature sensitivity, phase homogeneity and durability. Studies in the 1990s focused on evaluating the new Superpave? specification, developed in the United States, to address the increasing use of modified binders in preceding decades. Air-blown materials were found to perform poorly and polymer modifiers only provided benefits in softer grades. Current trials, commissioned by the Ontario government in the 2000s, were designed to refine binder specification tests, by accounting for well-documented phase separation and transformation, associated thermoreversible changes in rheology (gel formation), and to investigate high polymer and fiber modification. Benefit/cost ratios vary by 2–3 fold for test sections of equal Superpave design but different rheological type (sol, sol/gel or gel). Long-life pavements can be designed through a judicious and balanced choice of binder properties. Albertan binders of high phase angle (sol-type), which are low in wax and modified with small amounts of polymer or fiber, outperform less stable materials, such as those with too much polymer, oxidized residue, or wax (gel-type). Improved binder specification will provide substantial savings and prepare the world’s 25 million kilometers of asphalt pavements for climate change.

Research on The Evaluation Index of Low-temperature Semicircle Bending Test of Asphalt Mixture

LYU Song-tao , CHEN Qi , LU Wei-wei , ZHAO Pei , WANG Jinping

Adopted date: September 29,2024

[Abstract](2) [HTML](0) [PDF 0.00 Byte](0)

Abstract:
This article aims to investigate the low-temperature crack resistance performance of asphalt mixtures under different aging and loading rates, and select appropriate indicators to accurately characterize and quantify their performance. The study, based on the semi-circular bending test, investigated the influence of different aging degrees (unaged, short-term aged, long-term aged for three days, long-term aged for five days) and different loading rates (50 mm/min, 5 mm/min, 0.5 mm/min, 0.1 mm/min) on the low-temperature performance of asphalt mixtures. The evaluation effect and applicable range of 5 crack resistance performance indicators, including fracture energy (Gf), stress intensity factor (KIC), flexibility index (FI), crack resistance index (CRI), and balanced cracking index (BCI), were studied through variance analysis and variability analysis. The results indicate that aging decreases the low-temperature performance of asphalt mixtures. After short-term aging, the Gf decreased by approximately 23%. As the degree of aging deepens, it decreases by about 6% and 3%, respectively. As the loading rate increases, the evaluation effect of FI and BCI deteriorates. Conducting a semi-circular bending test at a loading rate of 0.1 mm/min can provide a more comprehensive evaluation of the low-temperature performance of asphalt mixtures. The results of variance analysis and variability analysis indicate that Gf and CRI can significantly characterize the influence of aging and loading rate on the low-temperature performance of asphalt mixtures. The variability of the FI and BCI is significantly higher than the other three indicators. Hence, the article recommends selecting Gf and CRI from the semi-circular bending test as more reasonable indicators for evaluating the low-temperature performance of asphalt mixtures.

Optimization of mix proportion for New Jersey precast concrete guardrails and performance tests under overall vibration

CHEN Lin , FU Liyong , LI Beian , ZHAO Zixiang

Adopted date: September 14,2024

[Abstract](7) [HTML](0) [PDF 0.00 Byte](0)

Abstract:
New Jersey guardrails are the most commonly used form of guardrail in highway median strips due to their excellent safety protection. In response to the cost reduction and quality improvement, efficient and rapid preparation process, and quality issues of New Jersey precast guardrails, this article adopts the New Jersey precast guardrail automation production process to study the optimization of concrete mix ratio and its performance for precast guardrails. The experimental results show that in the designed C30 concrete, the compressive strength of the concrete mixed with 15% fly ash reaches 39.2MPa and the slump reaches 189mm, and the concrete performance meets the requirements of the fabric; Compared with the compressive strength of concrete formed by traditional vibrating rods and integral vibrating tables, the compressive strength of concrete formed by integral vibrating tables at all ages is higher than that formed by vibrating rods, and the coefficient of variation is smaller; The concrete formed by the overall vibration table has a smaller electrical flux at each age and better resistance to chloride ion penetration. Research has shown that adjusting fly ash to optimize the concrete mix proportion, combined with the application of overall vibration compaction technology, reduces concrete porosity and pore size, improves the compressive strength and durability of concrete, and can efficiently and economically obtain concrete that meets the high-performance requirements of guardrails, which has engineering application value.

Study on the Mechanical Characteristics of Hydraulic Climbing Structure of Variable Cross-section Hollow Thin-walled High Pier in Shallow Hilly Area

wangchengye , liuchuanqi , lilei , liangbin , liwenjie

Adopted date: September 14,2024

[Abstract](6) [HTML](0) [PDF 0.00 Byte](0)

Abstract:
In order to solve the problems such as more damage to pier concrete caused by the wall attachment of guide rail and low efficiency in traditional hydraulic climbing construction, a new type of hydraulic climbing structure suitable for hollow thin-wall high pier construction was designed based on Miaolu River Bridge project of Zhengzhou-Luoyang Expressway. To ensure the safety of the structure during construction, a finite element model of the climbing structure was established using Midas Civil to analyze the stress and deformation of components such as formwork, climbing formwork frame, construction operation platform, and support bracket, moreover, the stability of the structure was checked finally. The results show that the maximum combined stress of the formwork panel is 16.85MPa, the maximum combined stress of transverse and vertical ribs are 89.18MPa and 153.52MPa, and the maximum deformation of the formwork are 4.60mm and 3.68mm, both meeting the requirements. The maximum stresses of the climbing formwork frame and the construction operation platform are 162.16MPa and 122.97MPa respectively, which are both less than the yield strength of Q235 steel, and the maximum deformations are 7.63mm and 7.98mm, meeting the requirements. The support brackets are anchored to the pier body through bolts. The stability and safety factor are calculated according to the maximum reaction force when the climbing formwork structure is completed, and the results are within the specified range. During actual construction, the new hydraulic climbing structure relied on four vertical hydraulic devices setting on the support brackets to complete the climbing, making it simpler and easier to operate, and this improves construction efficiency.

Calculation and Reinforcement Recommendations for Cast-in-Place Cover Slabs in Slab Culverts

LI Yukun , WAN Kecheng , FU Fulin

Adopted date: September 14,2024

[Abstract](3) [HTML](0) [PDF 0.00 Byte](0)

Abstract:
To address the complexity and lack of practical methods for calculating bending moments of cast-in-place cover slabs in slab culverts, the slabs were simplified as one-way slabs with a pair of opposing edges simply supported and the other pair of edges free, and derived theoretical formulas for calculating the bending moments within the slabs under uniformly distributed loads using elastic theory. The accuracy of the theoretical formulas was validated through case studies using finite element software. Various combinations of length, width, and fill heights exist in highway projects, making the use of theoretical formulas for bending moment calculations cumbersome. Therefore, a simple and efficient method for calculating maximum bending moments in both primary and secondary directions is proposed, which can be used for reinforcement design. Three reinforcement recommendations are provided based on engineering practices.

Research on Identification of Underground Diseases on Urban Roads and Risk Assessment of Collapse

tiangang , zhanghaijun , wangchengliang , duyanqing , shihai

Adopted date: September 14,2024

[Abstract](8) [HTML](0) [PDF 0.00 Byte](0)

Abstract:
Based on Ground Penetrating Radar technology, the paper examines the characteristics, electrical property features and morphological variations of common underground diseases in urban roads. It provides a comprehensive analysis of the radar spectrogram characteristics of various subsurface road diseases, which not only helps in their accurate identification, but also provides a basis for subsequent evaluation of road collapse. In addition, the paper integrates various factors, including underground diseases, into the evaluation of road collapse risk and establishes a "5-level" evaluation model. This leads to a unified research mechanism for detecting underground road diseases and assessing collapse risks. Taking a specific road project in Beijing as a case study, the paper uses the trapezoidal membership function to assign values to various indices that affect road collapse. Through fuzzy calculation, the collapse risk levels for road disease bodies 1#, 2#, 3# and 4# are determined to be level II (low risk), level III (medium risk), level IV (medium-high risk) and level V (high risk), respectively. It is recommended that for low-risk disease body 1#, routine patrols should be intensified; for moderate-risk disease bodies 2# and 3#, periodic inspections should be intensified; and for high-risk disease body 4#, immediate grouting reinforcement or excavation and backfilling should be undertaken.