Delay Factor Analysis for Indian HAM Highway Construction Projects

Government has approved the hybrid annuity model (HAM) for building National Highways (NH) to speed up the construction of roads in the country by renewing interest of private developers in highway projects. 40% the Project Cost is to be provided by the Government as Construction Support during the construction period and the balance 60% as annuity payments over the operations period along with interest thereon to the concessionaire. Execution of hybrid annuity model (HAM) projects, which is the preferred mode of awarding by the National Highways Authority of India (NHAI), is largely on schedule with about 60% of projects, covering 3,200 km of roads, completed on time. The rest of the projects, however, are delayed largely due to various reasons. In order to identify and analysis of delay causes in highway projects of HAM model, this study provides a questionnaire survey-based study. Land acquisition delay is found as the most severe delay cause of highway projects of HAM model. Waste of time in controlling the traffic is found as the least severe delay cause of highway projects of HAM model. The study is supposed as useful to HAM construction managers for delay analysis of highway projects. Keywords: Hybrid annuity model, Highway projects, Delay analysis, Questionnaire survey.

The precision analysis of the Chinese VLBI Network in probe delay measurement

We propose a VLBI precision evaluation method for probe delay measurement, so as to investigate the error contributions from different components in the Chinese VLBI Network (CVN). This method takes the idea of traditional closure delay analysis for distant radio sources. It focuses on the VLBI closure delay only and therefore excludes the influence of probe orbit determination, which makes it very suitable to evaluate the capability of VLBI probe delay measurement. In this paper, we first introduce the principles of closure delay analysis. Then the statistical results of typical CE5 (Chinese Chang'e 5 lunar exploration mission) and HX1 (Chinese Mars exploration mission) observations are presented, including the comparison of the closure delay precisions between CE5 and HX1 for four closed baseline triangles in CVN. According to the result, we realize that, the precision discrepancy between CE5 and HX1 in the closure delay analysis is less than that of residual delay after orbit determination, which reflects the precision level of the VLBI delay measurement.

IFC-Based 4D Construction Management Information Model of Prefabricated Buildings and Its Application in Graph Database

Effective data interoperability and schedule analysis play a significant role in improving the management of prefabricated buildings. However, there is a lack of efficient strategies and comprehensive approaches for data interoperability and data-based automated schedule analysis. This paper intends to promote prefabricated buildings’ management by solving these two problems via developing an IFC-based framework consisting of three parts. Firstly, this framework proposed a mechanism to establish an IFC-based 4D construction management information model of prefabricated buildings. Furthermore, a non-relational database—graph database—is introduced to twin this model into a task-centered network to realize the interoperation of construction information among different participants. Finally, graph database-based strategies to update data, automatically analyze construction schedules and visualize the 4D construction management information model are described. The proposed framework is validated in a prefabricated engineering case. In this case, an IFC-based and graph database-based 4D construction management information model is established through IFC standard’s extension. The graph database-based analysis of the model automatically recognizes the engineering case’s critical path information, delay analysis information, and schedule network analysis information. It is illustrated that this framework can successfully establish a unified IFC-based information model of prefabricated buildings’ construction management to prompt effective data interoperability. In addition, the application of this IFC-based information model in graph database can automatically analyze the construction schedules to prevent possible delays in advance. In short, the significance of this paper is to innovatively propose an IFC-based and graph data-based information model to solve the difficulties of ineffective data interoperation and unautomated schedule analysis in prefabricated buildings’ construction management. This study can be the digital foundation of further IFC-based digital twin.