Seismic performance of tuned mass damper on Shazand Railway Bridge induced by train

Shazand Railway Bridge is located in Markazi province, Iran in north to south-west railway. The bridge consists of ten spans. In 1984, during Iran-Iraq war, that’s main span, which has a length of 72 m, was attacked and severely damaged. Eight month later, damaged span replaced with a steel deck. The deck is straight in plan, but the railway is curved and this causes eccentricity. Excessive vibration was observed during the train passage. Although the bridge was retrofitted in two stages, the problem has not been solved yet, and the trains’ speed should be reduced to around 10 km/h in order to avoid excessive vibration. The present study addressed the effectiveness of tuned mass damper (TMD) in reducing train-induced vibrations of Shazand Railway Bridge. A three dimensional finite-element model of the bridge is developed and dynamic time history analyses under train passage in both as-built and passively controlled with TMD are conducted. Sensitivity analyses are performed to demonstrate the effects of the damper parameters on structural response. The results show that considerable reduction in acceleration response of the bridge can be achieved by employing proper TMD

Cementitious composites reinforced with polypropylene, nylon and polyacrylonitile fibres

This paper compares the adhesion strength between three polymeric fibres (polypropylene (PP), nylon66 (N66) and polyacrylonitrile (PAN)) embedded in a cement paste. The specimens were prepared at a water to cement ratio (w/c) of 0.5, and tested after 7, 14 and 28 curing days. It was found that although the adhesion between the polymeric fibres to the cement matrix is an important factor, the energy absorption capacity or energy dissipation ability of the fibres plays a more important role in the improvement of the cementitious composites fracture toughness. Scanning electron micrographs was used to characterize the fibres surface before and after the Pullout tests

Evaluation of adhesion in polymeric fibre reinforced cementitious composites

In this study adhesion of some polymeric fibres to a cement matrix was evaluated both by a theoretical and by an experimental approach. In common methods adhesion of the fibres to the cementitious materials is determined by pull-out test. This test evaluates the energy failure during the fibre drawing out. This paper analyzes the adhesion theory for fibre reinforced cementitious composites to separate the share of the chemical and mechanical adhesion expressing new parameters, which are effective in the adhesion behaviour. Explanations about how the different fibres, matrix properties, test factors and environmental conditions can affect the adhesion results are given. It was found that for fibre/cement composites the fracture energy due to the interfacial interactions is for several orders of magnitude smaller that the polymeric fibre losses function. By employing adhesion theory, fibre/cement interac- tions are better described by a simple relationship of their surface free energy. Determination of the loss function (energy dissipation) leads us to predict the fibre behaviour in the cement matrix and the selection of the appropriate reinforcement

Simultaneous lidar and airglow temperature measurements in the mesopause region

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94970/1/grl5512.pd

Investigating the influence of surrounding soil properties on leakage discharge from cracks in polyethylene pipes

This is the final version. Available on open access from Elsevier via the DOI in this recordData availability: Data will be made available on request.Numerous factors affect the amount of leakage from pipes, e.g. inside pressure, type of pipe failure, soil around the pipe, etc. Few researches have been done on the effect of environment around the pipe on the leakage discharge. In the present study, the leakage from pipes in presence of different soils is experimentally investigated. Leakage from a cracked polyethylene pipe was simulated in the presence of various soils with different properties in a laboratory setup. Leakage- pressure relationships were obtained according to fixed and variable area discharge theory. By quantifying the soil characteristics, the relationship between leakage- pressure coefficients (m and Cd) and soil parameters was obtained. It was concluded that the soil environment affects the amount of leakage discharge. Results show that the particle diameter at 50% passing (D50), dry unit weight ( ) and hydraulic permeability coefficient (k) are more appropriate to represent the characteristics of soils. It was also concluded that there are no strong correlation between leakage and some soil parameters. The obtained relationships between different soil parameters and leakage discharge coefficients are also presented

Evaluating energy harvesting from water distribution networks using combined stakeholder and social network analysis

This is the final version. Available from Elsevier via the DOI in this record. Data availability: Data will be made available on request.The chance of success in implementing a new project in a water distribution network (WDN) significantly depends on the behaviour of the involved stakeholders. In this paper, the feasibility of installing the micro-turbines in WDNs for generating hydro-power energy is studied from the stakeholders’ perspective. Stakeholders’ analysis (SA) and social network analysis (SNA) are performed to methodically recognise the environment and the relationships among stakeholders. 18 stakeholders at the local, regional, and national levels were identified and their representatives were interviewed. In SA, the power, interest, access to information, and satisfaction from the current condition of the system were evaluated for each stakeholder. The Water and Wastewater Company and Ministry of Energy were found as the stakeholders with the highest power and interest. Unexpectedly, the Regional Electricity Company was discovered with medium power and low access to information. In SNA, cooperative and non-cooperative relationships between stakeholders were analysed and an assessment was made for the role of each stakeholder in their social network, through four centrality metrics. The correlation between SA and SNA results suggests that SA factors could be estimated using the SNA metrics.Iran National Science Foundation (INSF

Efficacy of Tree-Based Models for Pipe Failure Prediction and Condition Assessment: A Comprehensive Review

This is the final version. Available on open access from ASCE via the DOI in this recordData Availability Statement: All data, models, and code generated or used during the study appear in the published article.This paper provides a comprehensive review of tree-based models and their application in condition assessment and prediction of water, wastewater, and sewer pipe failures. Tree-based models have gained significant attention in recent years due to their effectiveness in capturing complex relationships between parameters of systems and their ability in handling large data sets. This study explores a range of tree-based models, including decision trees and ensemble trees utilizing bagging, boosting, and stacking strategies. The paper thoroughly examines the strengths and limitations of these models, specifically in the context of assessing the pipes’ condition and predicting their failures. In most cases, tree-based algorithms outperformed other prevalent models. Random forest was found to be the most frequently used approach in this field. Moreover, the models successfully predicted the failures when augmented with a richer failure data set. Finally, it was identified that existing evaluation metrics might not be necessarily suitable for assessing the prediction models in the water and sewer networks.Datatecnics Corporation LimitedUKR

Observables and a Hilbert Space for Bianchi IX

We consider a quantization of the Bianchi IX cosmological model based on taking the constraint to be a self-adjoint operator in an auxiliary Hilbert space. Using a WKB-style self-consistent approximation, the constraint chosen is shown to have only continuous spectrum at zero. Nevertheless, the auxiliary space induces an inner product on the zero-eigenvalue generalized eigenstates such that the resulting physical Hilbert space has countably infinite dimension. In addition, a complete set of gauge-invariant operators on the physical space is constructed by integrating differential forms over the spacetime. The behavior of these operators indicates that this quantization preserves Wald's classical result that the Bianchi IX spacetimes expand to a maximum volume and then recollapse.Comment: 23 pages, ReVTeX, CGPG-94/6-3, UCSBTH-94-3