Insight - Civil Engineering

Research on bridge safety early warning method based on strain energy theory and health monitoring data

2024-10-23T08:39:07+00:00

Bridges are technology-intensive and heavily invested permanent infrastructure. After completion and opening to traffic, bridge structures are easy to be affected by factors such as traffic load and atmospheric environment. Therefore, it is necessary to do safety warning and evaluation of bridges, especially the abnormal behavior in the early stages of bridge operation. In this research paper, a large-span continuous rigid frame bridge installed with the health monitoring system (HMS), of which a large amount of health monitoring data are collected by the HMS, is used as an example, and then a bridge safety early warning method is proposed when the bridge is during early operating period. First of all, the research finding that the internal stress of the prototype bridge obeys normal distribution through statistical analysis is used; next, we deduce that the strain energy inside the prototype bridge is subject to the Non-central Chi-square distribution combined with the strain energy and statistical theories; in the end, the key probability density distribution function of strain energy and its parameters are derived by using the key stress distribution function of the high performance concrete C50 strength grade used in the prototype bridge. The method recommended in this paper is conducive to the formulation of bridge preventive maintenance strategies.

Important properties of central island and median island at roundabouts

2024-10-23T08:44:17+00:00

The central island and median island are very important elements of a roundabout, which strongly influence the impact on traffic and safety of road users. The central island should be designed in such a way that it is perceived as an obstacle in the approach. At roundabouts with an outside diameter of more than 35.0 m, the central island should prevent the view from the approach road straight ahead to the opposite exit. This can be achieved with various design options such as trees in the central island. The layout of the central island should be customized to suit the particular local conditions. When designing the central island, it is important to factor in the requirements of buses, along with municipal and emergency vehicles. While aesthetics is a consideration, the geometric design of the intersection is a critical aspect in roundabout planning. If sufficient space is available after considering the turning radii of key vehicles, curbs can be used to define boundaries. Alternatively, paved island sections that allow partial or full traversal can be a viable option.

Interaction between roadway and sewer/water pipes

2024-10-25T03:09:56+00:00

Sewage pipes and drinking water pipes as well as all other pipes such as gas, district heating, electricity, internet, telephone, cable TV, etc. in densely populated areas are located in the road space. Over time, the traffic loads as well as the road structure can change. In addition, the materials of the pipelines are subject to ageing processes. The consequences of leaking drinking water and wastewater pipes that lie in the body of the road can have extremely negative effects. Firstly, the wastewater contains harmful substances that must not be allowed to enter the groundwater under any circumstances. Secondly, the leaking drinking water pipes, especially a water pipe burst, cause the soil mechanical changes in the subsoil and the traffic surface pavements and can cause immense damage in the road surface or in the road body itself.

Plastic waste in dense asphalt mixes for road pavements

2024-11-01T02:28:38+00:00

Recycling plastic waste in asphalt pavements records increasing statistic figures of application during the last decade worldwide. Due to environmental constraints, but also, to some beneficial properties of plastic waste, recycling in asphalt tends to become current practice, in several countries. In the Aristotle University of Thessaloniki (AUTH), the first attempt to produce asphalt mix using plastic waste consisted of mixing recycled plastic flakes with non-modified binder. Following an asphalt mix design in the laboratory, the whole mass of conventional aggregates was replaced by PET flakes. Recycled PET flakes were chosen to be introduced in the asphalt mix since they are hard, resilient and water repellent. Bitumen emulsion was first preferred as a binder to produce a cold asphalt mix. At a second stage of experimental research, plastic flakes replaced a part of the limestone sand while conventional asphalt 50/70 was used as a binder. At this stage, the experimental research provided more encouraging outcomes. Stability of asphalt mixes decreases as the plastics content in the mix increases, but all recorded values were still within limits of acceptance. At a third stage of research, LDPE recycled material of fine gradation was used to replace a part of the asphalt binder in dense mixes. The objective was to produce a modified binder and a more durable asphalt structure. Test results showed a significant improvement of the performance of asphalt mixes, in terms of strength and deformability of the asphalt mix structure. The research is completed by comparing the conventional techniques with the outcomes of the recycling process and by delineating potential fields of application of the recycled plastics in asphalt pavements.

Finite element modeling of the influence of FRP techniques on the seismic behavior of an arch stone bridge of historical interest

2024-11-25T06:59:05+00:00

In this paper, a masonry bridge is simulated in order to assess both its structural and seismic vulnerability. Therefore, the present study aimed to approximately analyze the real behavior of Mikron Bridge structure. The modeling was conducted by combining the finite element method (FEM) and discrete element method (DEM) using the ABAQUS® software. By comparing the results of numerical and experimental modal analyses, the accuracy of simulation was verified. To simulate the seismic behavior of the Mikron Bridge, the component of Erzincan earthquake occurred in 1992 was used. The results extracted from the seismic analysis show that some parts of the bridge structure are damaged but not destroyed.

The use of machine learning for various predictive models of the occurrence of pipe defects

2024-12-03T07:01:12+00:00

The paper analyses and compares possible predictive models for predicting pipeline defects using machine learning. As an example of the models, the data from in-tube diagnostics for stress corrosion cracking are selected. Special attention was paid to the description of the learning process of models based on machine learning algorithms based on retrospective data. Extended metrics are presented for the prepared parameters of the defects themselves and related data from the survey reports. The performance metrics of the algorithms are given in comparison to the probabilities of a correct prognosis. Conclusions have been drawn on the correlation of defects of this type with data on the soil composition of the soil of the segment of the analysed pipe. The analysis of statistical data on the defects by the pipe orientation was carried out. An approach has been proposed and tested to improve the accuracy characteristics of the model based on the Random Forest algorithm using preliminary data selection, which made it possible to achieve a heuristic probability of more than 80%.

Stability evaluation of draft tube tunnels of Palamuru Ranga Reddy lift irrigation scheme lift-Ⅲ, Telangana state, India

2024-12-09T01:46:22+00:00

Geological and geotechnical evaluation for the 7–9 m diameter and 100 m length, 10 numbers of parallel draft tube tunnels were carried out. The draft tubes are constructed to connect the underground pump house and surge pool for lifting the water. Due to adverse geological conditions and the complex geometry of the structure, a sequential excavation method and controlled blasting were adopted, which minimized the risk of instability during the excavation of the draft tubes. To classify the rock masses and recommendation of support, detailed engineering geological investigations were done. The rocks encountered during the excavation of these tunnels are granites/granitic gneiss which are traversed by mafic dykes of Dharwar Craton. Prominent three to four joint sets were recorded during geological mapping and rock mass shows W-I to W-II weathering grade. For the determination of principal stresses, an in-situ hydrofracturing test was conducted in the borehole. Q-values were determined based on the rock joints and their characteristics, 3D mapping of geological units and stress measurement conducted inside the borehole. The Q-system provides a quantitative assessment of rock mass stability in jointed rock for underground tunnel design and construction. Good stability is indicated by high Q-values, while poor stability is shown by low values. Based on the “Q” system, the entire lengths of the tunnels were characterised as poor to fair rock mass categories. Wedge analysis was conducted along the tunnel alignments using RocScience Unwedge software and accordingly, stability was checked. Engineering geological investigations identified potential geotechnical issues, and corresponding engineering solutions were recommended. A support system was designed based on the Q-system and site-specific geological conditions.

Assessing and monitoring with ultrasonic pulse velocity testing the critical effects of hygrothermal actions on the infill masonry walls of the envelope of buildings with reinforced concrete structure

2024-12-16T08:14:47+00:00

The external envelope of buildings with reinforced concrete structures (RCS buildings) is usually subjected to various external environmental actions. Among these external environmental actions, hygrothermal actions are particularly relevant, mainly related to external temperature and humidity variations. These variations could negatively influence the hygrothermal behavior of that envelope and lead to problems related to an increased risk of material degradation of the external face of unreinforced masonry (URM) infill walls of the building envelope URM infill. In the survey of the degradation of these URM infill walls and of concrete elements, nondestructive evaluation (NDE), such as ultrasonic pulse velocity testing (UPV testing), had been used before. The main objective of the study is to assess the potential use of UPV testing in the evaluation of the influence of moisture content in the behavior of URM infill walls, and the methodology of the study consists, firstly, concerning the hygrothermal actions, which RCS buildings are subjected, which are here described summarily. An assessment is made of the most usual types of degradation of URM infill walls of the envelope of RCS buildings, mainly due to moisture and thermal effects in URM infill walls. UPV testing in the survey of the degradation of the external face of URM infill walls of the building envelope, essentially due to hygrothermal actions, is analyzed, based on an example of the use of UPV testing in a building façade. Subsequently, the potential use of UPV testing in evaluating the influence of moisture content in the behavior of URM infill wall is made, particularly with the use of UPV testing in a compression test of a masonry specimen with variable moisture content during the test. Their results are presented, followed by a discussion of these results, and finally by the conclusions of the study.