Integration of PV system with SMES based on model predictive control for utility grid reliability improvement.

This paper describes the integration of a photovoltaic (PV) renewable energy source with a superconducting magnetic energy storage (SMES) system. The integrated system can improve the voltage stability of the utility grid and achieve power leveling. The control schemes employ model predictive control (MPC), which has gained significant attention in recent years because of its advantages such as fast response and simple implementation. The PV system provides maximum power at various irradiation levels using the incremental conductance technique (INC). The interfaced grid side converter of the SMES can control the grid voltage by regulating its injected reactive power to the grid, while the charge and discharge operation of the SMES coil can be managed by the system operator to inject/absorb active power to/from the grid to achieve the power leveling strategy. Simulation results based on MATLAB/Simulink® software prove the fast response of the system control objectives in tracking the setpoints at different loading scenarios and PV irradiance levels, while the SMES injects/absorbs active and reactive power to/from the grid during various events to improve the voltage response and achieve power leveling strategy.     

Performance of Pile-Supported Bridge Approach Slabs

A large number of pile-supported bridge approach slabs in southeastern Louisiana were examined to identify the factors that affect their long-term performance. Design drawings and subsoil conditions at these sites as well as their traffic and maintenance records were compiled, and seven representative test sites were selected for thorough field investigation that included inspection of the approach slabs, bridge decks, bridge abutments, and roadway pavement. Field evaluation included walking profiler, falling-weight deflectometer (FWD), laser profiler, geodetic survey, soil borings, cone penetrometer, and nondestructive testing. Measurements made with the walking profiler agreed well with the geodetic survey. The FWD and nondestructive testing were effectively used to detect voids under the approach slab. Results of the study indicated that the current empirical methodology used by the Louisiana Department of Transportation and Development for design of pile-supported approach slabs yields inconsistent field performance. It was concluded that this inconsistent performance is primarily due to the differences in roadway embankment design and construction and in subsoil conditions, which in turn affect the negative skin friction (downdrag) loads imparted on the piles. Impact of other variables such as ramp type, speed limit, traffic volume, and so on was found to be insignificant. Results of the field study were used to develop a new rating system for approach slabs (IRIS) based on International Roughness Index (IRI) measurements obtained with the laser profiler.     

Quantification of annular flow in lined pipelines

This paper attempts to quantify the amount of flow within the annular space that could exist between a polymeric liner and a deteriorated host pipe. Inadequate fit of the liner within sewer line segments is likely to cause annular flow that will result in a higher flow rate within the wastewater collection system. The results of full-scale field tests performed by the authors on 12 pipelines lined with four different deformed/reformed or fold-and-form (DR/FF) and cured-in-place-pipe (CIPP) liner products indicated that gaps of different sizes existed in all of the tested pipelines. These gaps have resulted in variable annular flow in the tested pipelines. Based on the results of the full-scale tests, a mathematical relationship was established between the annular flow in a lined pipeline and the annular space. The relationship between the annular flow rate and the average annular gap size depends on the difference in head between the entry and exit points along the pipeline. In turn, the average annular gap size depends on many factors including tolerances and imperfections in the host pipe and liner, conditions of the host pipe and the quality of liner installation. A third-order polynomial equation was found to best describe the relationship between the annular flow and average gap size under high differential heads (up to 3.0 m or 10 ft); whereas, a logarithmic relationship fits best under low differential heads for wider range of annular gap sizes (up to 17.8 mm or 0.70 in.). Based on the results of the full-scale tests, this is believed to be more representative of typical liner installations.     

Determination of Stoichiometry and Superconducting Properties of Tl-1234 and (Cu0.25Tl0.75)-1234 Phases Substituted by Erbium

Superconducting samples of type TlBa₂Ca_3?y Er _y Cu₄O_11?δ and Cu_0.25Tl_0.75Ba₂Ca_3?y Er _y Cu₄O_12?δ ,y ranging from 0.0 to 0.1, have been prepared by a single step of solid-state reaction technique at normal pressure using high-purity oxide elements. The lattice parameters, for prepared samples, have been estimated from X-ray powder diffraction (XRD). The elemental stoichiometry of the prepared samples has been determined using Particle Induced X-ray Emission (PIXE), whereas the oxygen-content has been determined using elastic backscattering spectroscopy at 3 MeV proton beam. The superconducting transition temperature T _c has been determined from the electrical resistivity measurements. The data of T _c , for TlBa₂Ca_3?y Er _y Cu₄O_11?δ , show enhancement in its value from 124.5 to 128.45 K as y (Er-content) increases from 0.0 to 0.05, whereas it began to suppress with further increase in y. T _c gradually suppresses with increase of yfor Cu_0.25Tl_0.75Ba₂Ca_3?y Er _y Cu₄O_12?δ . Finally, the applied magnetic field B=0.44 T shows enlargement in the transition width. The effect of magnetic field on Tl-1234 phase is a little higher than that on (Cu_0.25Tl_0.75)-1234, indicating that the anisotropy parameter Γ for Tl-1234 is slightly higher than that for (Cu_0.25Tl_0.75)-1234.     

Magneto-conductivity Analysis for GdBa2Cu3O7−δ Added with Nanosized Ferrite CoFe2O4

Superconducting samples of type (CoFe₂O₄) _x GdBa₂Cu₃O_7?δ , 0.0≤x≤0.1 wt.%, have been prepared by the conventional solid-state reaction technique and characterized using X-ray powder diffraction (XRD) and the scanning electron microscope (SEM). XRD analysis indicates that the orthorhombic structure of Gd-123 is not affected by the nanosized ferrite CoFe₂O₄ addition, whereas the volume fraction of Gd-123 increases with x up to 0.01 wt.%. Nanosized ferrite CoFe₂O₄ has been prepared by Co-precipitation method with grain size about 8 nm. The temperature dependence of electrical resistivity has been measured in zero and 0.44 T magnetic fields. Magneto-conductivity data has been analyzed in terms of Aslamazov–Larkin (AL) and Maki–Thompson (MT) models for layered superconductors, considering the orbital contribution. The superconducting parameters such as the coherence lengths along ab plane ξ _ab (0) and along c-direction ξ _c (0) at 0 K, anisotropic parameter Γ and phase breaking time τ _φ at 100 K have been determined as a function of nanosized ferrite CoFe₂O₄ contents. It is found that the low nanosized CoFe₂O₄ addition contents up to x=0.01 wt.% improves the physical properties of Gd-123, while for x>0.01 wt.% these properties are deteriorated.     

Seismic vulnerability of historical masonry buildings for different earthquake characteristics: Case study of the mosque of Takiyya al‐Sulaymaniyya

Different factors influence the collapse behaviour of masonry structures, and one of the major factors is the characteristics of the earthquake itself. This effect is going to be more complicated for historical constructions, which involve different structure members of different geometries. The present study focuses on the effect of earthquake characteristics on the collapse behaviour of historical masonry structures. The effect of earthquake direction and the frequency content of the earthquake are mainly considered. A brief background of the selected case study and modelling process are presented. The geometry of the whole structure is created using micro modelling strategy. The collapse analysis of the structure is performed under artificial model based on the earthquake characteristics. Unidirectional earthquake are applied to the structure from different angels in order to investigate the weakest situation. Finally, different earthquake models are generated with different frequency contents according the soil profiles and applied consequently on the structure to explore the worst situation. Seismische Gefährdung von historischen Mauerwerksbauten infolge Erdbebeneinwirkung — Fallstudie: Die Moschee von Takiyya al‐Sulaymaniyya. Verschiedene Faktoren beeinflussen das Versagen von Mauerwerksstrukturen. Ein wesentlicher ist die Erdbebeneinwirkung selbst. Deren Charakteristik und Auswirkung ist für historische Konstruktionen, welche aufgrund der verschiedenen verwendeten und zusammenwirkenden Tragelemente und der großen Bandbreite geometrischer Formen eine komplexe Versagensabhängigkeit aufweisen, noch schwieriger einzuschätzen. Die in diesem Beitrag beschriebene Fallstudie befasst sich mit dem Verhalten historischer Mauerwerkskonstruktionen beim Versagen infolge einer Erdbebenbelastung. Die Auswirkungen von Richtung und Frequenz eines Erdbebens sind die Hauptschwerpunkte der Studie. Ein kurz gefasster Hintergrund der gewählten Fallstudie und der Modellierungsprozess werden vorgestellt. Die Geometrie der gesamten Konstruktion wurde mittels Mikromodellierung erstellt. Die Versagensanalyse der Konstruktion ist mittels eines künstlich generierten Erdbebens durchgeführt worden. Das einachsige Erdbeben wurde mit variierenden Richtungswinkeln auf das Modell angesetzt, um die schwächste Achse zu ermitteln. Den Abschluss bildete die Erzeugung von verschiedenen Erdbebenverläufen in Abhängigkeit der Bodenprofile und Anwendung auf die Konstruktion, um wiederum den ungünstigsten Fall zu ermitteln.     

Neue Wege zur seismischen Ertüchtigung von Weltkulturerbe im Lehmbau: Das Beispiel der Zitadelle von Bam,Iran

Im Dezember 2003 zerstörte ein schweres Erdbeben die Stadt Bam in Südostiran. Opfer der verheerenden Zerstörung wurde nicht nur die bewohnte Neustadt, sondern auch die historische Zitadellenanlage aus Lehm. Sie ist eines der größten Komplexe, die komplett aus Lehmwerkstoffen errichtet worden sind. Die sofort im Anschluss ergriffenen Restaurierungs‐ und Rekonstruktionsbemühungen sind auf Grund des extremen Ausmaßes der Zerstörungen stark durch den Wunsch geprägt sowohl die geretteten Reste, als auch rekonstruierte Bauteile gegen seismische Einwirkungen zu ertüchtigen. In diesem Zusammenhang sind auch die Arbeiten des Lehrstuhls für Tragwerksplanung der TU Dresden (Inhaber Prof. W. Jäger) in Bam zu betrachten. Um dieser Aufgabenstellung in einer Weltkulturerbestätte gerecht zu werden, mussten neue Technologien entwickelt und in die Praxis umgesetzt werden. Diesen neuen Technologien widmet sich dieser Beitrag. New approaches for seismic retrofitting of world heritage: The Citadel of Bam, Iran. In December 2003 a heavy earthquake destroyed the city of Bam in southeast Iran. The destructions affected not only the new town of Bam but also the historical Citadel constructed entirely with earthen materials. The rehabilitation measures commenced immediately and are characterized by the desire of defining methods that strengthen the preserved rests against future seismic activity. The projects of the Dresden University of Technology, department of structural design (Head: Prof. Dr.‐Ing. W. Jaeger) presented here, are to be seen as a part of these efforts. In order to meet the demands of heritage conservation within a world heritage site (listed in 2004), new methods and technologies had to be developed and applied. The presented article intends to give a figure of these works.     

Determination of a model partial safety factor for unreinforced masonry walls under buckling

The design/verification method in the Eurocodes is based on the partial safety concept. Eurocode 6 suggests a constant partial safety factor for the material γ_M for all design/verification problems, without consideration of model uncertainty in the design/verification formula. In the following, a model partial safety factor is determined for the problem of unreinforced masonry walls mainly subjected to vertical loading. For that purpose, the newly proposed formula for EC 6, annex G will be considered [1–3]. In order to cover all aspects in tests and to use the results for design purposes, several methods have been included in EN 1990 Annex D for design based on test data. In this study, the recommended methods in Annex D of EN 1990 for resistance of the material are used to extract the partial safety factors. A database including more than 119 experimental tests on unreinforced masonry shear walls is used to compare the model prediction and the test results and to determine the model partial safety factor.     

Effect of close-fit sliplining on the hydraulic capacity of a pressurized pipeline

A full-scale laboratory testing setup was used to examine the flow conditions through a new steel pipe with relatively smooth interior (no tubercles, encrustations, holes, scales, etc.) before and after sliplining with a high density polyethylene (HDPE) liner. Results of the tests indicate that the relative roughness of the lined pipe section was generally lower than that of the new steel pipe at Reynolds Numbers of 200,000 to 500,000. The average friction factor (Swamee–Jain) for the lined pipe was 0.0180 compared to 0.0185 for the original steel pipe. The minimum and maximum friction coefficients were 0.0146 and 0.0208 for the lined pipe and 0.0148 and 0.0241 for the new steel pipe, respectively. This indicates that a deteriorated pipe with significant roughness could be restored back to its original condition using close-fit sliplining. Meanwhile, installation of the 6.35 mm (1/4 in.) thick liner in the 152.4 mm (6 in.) pipe reduced its cross-sectional flow area by about 16% and, accordingly, would decrease the flow by about 20% under the same head loss. To further explore this condition, two design parameters, the liner thickness and its buckling resistance, were examined analytically using a practical application of 152.4 mm (6 in.) pipeline with an internal negative pressure due to a water hammer. Results of the analysis indicate that a 3.4 mm (1/8 in.) thick HDPE liner with average quality installation would provide about 100 kPa ( 10 m or 33 ft water column) of buckling resistance, but would also reduce the flow capacity by about 12.7%. While the laboratory tests were only performed on one type of liner material (i.e., HDPE), the general concepts and findings of this study would apply to other types of polymeric liners.