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When the high-density polyethylene sheath of bridge cables is not cracked, the galvanized high-strength steel wires are not corroded and only subjected to the fatigue loads of vehicles (called prefatigue). Some studies have confirmed that the corrosion rate and fatigue life of certain alloy materials can be affected by the prefatigue, which is not clear for the corroded steel wires in bridge cables. In this paper, the mechanical properties of high-strength steel wires considering the prefatigue effect under fatigue-corrosion alternating loading were studied, and the residual fatigue life was predicted. First, the corrosion characteristics of high-strength steel wires with different degrees of prefatigue and corrosion were explored through an optical microscope and a surface roughness measuring instrument. Then, the static mechanical properties and fatigue life of corroded steel wires were obtained. The results show that when the prefatigue effect is greater than the corrosion effect, the surface roughness of the corroded steel wires decreases significantly, leading to a smoother surface and a weaker stress concentration. Compared with the results in the "corrosion + fatigue" case, the fatigue life of the steel wires in the "fatigue (prefatigue) + corrosion + fatigue" case may increase. The prefatigue effect has no significant effect on the static performance of the corroded steel wires. Finally, a fatigue life prediction model of corroded steel wires considering the effect of prefatigue was established based on the aforementioned experimental data. [ABSTRACT FROM AUTHOR]

As a crucial measure to promote the coordinated development of urban and rural areas in developing countries (such as China), how to provide and manage rural infrastructure investment is a major challenge. In line with the implementation of a coordinated urban–rural development strategy, inclusive growth provides direction for rural infrastructure investment. Taking Chongqing, China, as an example, informed by the goals of inclusive growth, this study develops a system dynamics model to investigate the interaction between interdependent infrastructure systems and socioeconomic systems and to explore priorities for rural infrastructure investment. The results indicate the following: (1) more rural infrastructure investment is still needed in Chongqing by 2030; and (2) based on the importance of all types of rural infrastructures for the impact of inclusive growth goals, the ratio of budget shares invested in each dimension is, in descending order, environment infrastructure, energy infrastructure, communication infrastructure, transportation infrastructure, education infrastructure, and medical infrastructure. The approach and results of this study allow governments to assess the contribution of infrastructure provision to the goals of inclusive growth and to make better-informed infrastructure investment options. [ABSTRACT FROM AUTHOR]

Large numbers of bridges have already suffered various types of damage but still operate all year round without proper treatment. Conducted primarily manually, the routine bridge inspections are ineffective in detecting potential damage in time due to a lack of relevant instruments and equipment, particularly modern measures. In this study, a rapid and intelligent bridge inspection system that integrates multiple modules and deep learning algorithms was established. First, the robot inspection equipment is established. Then, the You Only Look Once version 3 (YOLOv3) object detection algorithm is employed to classify four types of defects from the acquired data. Finally, an image segmentation algorithm is used to identify crack defects at a pixel level. Experimental results reveal that the proposed system can be effectively applied to accurately locate defects (e.g., cracks, spalls, exposed tendons, and free lime) and identify cracks at a pixel level on various types of bridges without affecting traffic. [ABSTRACT FROM AUTHOR]

The synergistic development of metropolitan areas led by megacities is considered a driving force in achieving regional coordination and the high-quality development of urban agglomerations. Extant studies have often neglected the spatial structure of metropolitan areas under the guidance of megacities. This study sought to explore the radiation effect of central cities, the development capacity of metropolitan subcentral cities, and the intermediary role of metropolitan hub cities in the metropolitan area. Based on the modified gravitational model and social network analysis, we constructed a spatial connection network of the Shanghai metropolitan area with districts and counties as the basic research units and analyzed the characteristics from two perspectives: network hierarchy and network structure. Our results indicated the following: (1) The connection strength of the metropolitan area decreased from the center of the network to the periphery. (2) The polycentric pattern was gradually forming, but a significant gap remained between the radiation range and capacity of central and subcentral cities. (3) The clustering phenomenon in the metropolitan area was significant, and the degrees of internal connection and external radiation ability of each subgroup differed. (4) The core–edge structure as obvious, but its intermediary role in the network was relatively weak. Our findings revealed the spatial relationship pattern of metropolitan areas led by megacities and have implications for formulating scientific policies to promote the coordinated spatial development of metropolitan areas and the high-quality development of urban agglomerations. A high-quality urban agglomeration is highly significant, and coordination and balanced development among cities has become a pressing need. In recent years, many scholars have researched how to improve the quality of urban agglomeration development. The construction of metropolitan areas—the basic unit of urban agglomeration—plays a strategic role in urban agglomeration. Accordingly, analyzing the spatial connection networks in metropolitan areas led by megacities is necessary. In response, this study explored the network hierarchy and structure of a notable metropolitan area led by megacities, the Shanghai metropolitan area, to uncover valuable findings about the radiation effect of central cities, the development capacity of metropolitan subcentral cities, and the intermediary role of metropolitan hub cities in promoting the coordinated development of metropolitan areas. These findings offer useful insights for policymakers seeking to promote the coordinated spatial development of metropolitan areas, optimize their spatial structure, and promote high-quality urban agglomeration. [ABSTRACT FROM AUTHOR]

During the period of rapid urban growth worldwide, China's urbanization process has soared. Based on China's National New-Type Urbanization Plan (NNUP), this paper takes 11 national-level urban agglomerations (UAs) as the research area, aiming to conduct a dynamic quantitative analysis of the sustainable development (SD) level of UAs and reveal inherent laws and effective strategies about spatial planning of UAs. Different from the existing literature, this paper analyzes the SD level of China's 11 major UAs during the urbanization process from a multidimensional perspective, including the comprehensive dynamic evolution of UAs, coupling coordinated development between the three subsystems, and internally coordinated distributions of UAs, which provides a crucial guarantee that the UAs' SD will be analyzed comprehensively. First, the evaluation index system of a new-type urbanization SD is constructed. Then, two principal component analyses and time-series global factor analyses are performed to evaluate the SD of new-type urbanization in China's 11 major UAs from the perspectives of the economy, society, and resources and environment. The characteristics of the SD levels of different UAs, the constraint factors of the SD levels, coupling coordinated development between the three subsystems, internally coordinated distribution characteristics of UAs, the relevant policy recommendations, and the reason why the Pearl River Delta UA has started to lag behind the Yangtze River Delta UA since 2010 are presented. Finally, we propose a plausible relation between the coupling coordinated degree (CCD) of UA subsystems and the internally coordinated development of UAs. Additionally, this paper provides a reference for policymakers to develop urban spatial planning policies to facilitate the SD level of relevant UAs by identifying the constraint factors of SD. [ABSTRACT FROM AUTHOR]

Public–private partnership (PPP) toll road projects are widespread around the world. However, it is difficult to predict traffic demand and cost accurately, which may lead to high profit risks for the private sector or increase the fiscal burden for the government. This paper proposes an effective methodological framework for the probabilistic evaluation of the excess profit allocation between the government and the private investor, as well as the corresponding subsidy mechanism. First, an annual profit function is introduced, taking particular care to include factors associated with uncertainties. Then, by applying Monte Carlo simulation to a proposed dynamic quantitative model, the excess profit allocation ratio and subsidy ratio are determined. The model was verified using SH 130, a PPP toll road in Texas, for which a sensitivity analysis was conducted to illustrate the impact of different risk factors. This paper provides a knowledge base so that decision makers can recognize the importance of accurately forecasting profit risks in order to provide a reasonable and fair profit redistribution mechanism to facilitate PPP contract design. [ABSTRACT FROM AUTHOR]

With the wide implementation of public–private partnerships (PPPs) in infrastructure projects and public services, numerous studies related to PPPs have emerged in the past two decades. Although several literature reviews of PPP research have been conducted, there still appears to be a lack of quantitative and visualized investigation and multidisciplinary scrutiny of the structure and evolution of this field. This paper applied a scientometric approach to map a visual document cocitation network and conducted cluster analysis to identify the intellectual structure and knowledge domains of PPP research. Next, the development path of each cluster, the pivotal points, and the citation history of the representative documents were identified by timeline visualization of the cocitation network. Finally, through burst analysis, some emerging trends, such as risk allocation, real option-based evaluation, contract design, and government guarantees, were summarized, which offered insights into future PPP research. [ABSTRACT FROM AUTHOR]

The public-private partnership (PPP) mode is increasingly being applied to implement infrastructure projects worldwide to alleviate the shortage of government funds and experience. However, many PPP projects encounter crises and are even terminated before the expiration of the PPP contract due to a variety of factors that differ from general risks. Based on 23 selected PPP projects in China, this paper uses a multicase study to identify and analyze factors that influence early termination. Eleven influencing factors are identified as the main causes of the early termination of PPP projects in China. Among them, government decision error and government payment default are the most common factors. Counterstrategies are proposed to mitigate the impact of these factors. The results are expected to serve as a reference and provide inspiration for the host governments and private sectors of PPP projects. [ABSTRACT FROM AUTHOR]