Static Monitoring Research Articles

Analysis of Ultrasonic Guided Waves Propagation in Complex Composite Structures

The object of the investigation is a honeycomb structure of composite sandwich made of glass-epoxy laminating layers and a honeycomb core of epoxy impregnated paper. Large composite tanks possessing cylindrical shape are produced using the winding process. Therefore, the final products have uneven thickness and fibre orientation lamina layers, and also an unevenly impregnated honeycomb layer. The aim of this research is to develop an economically attractive embedded ultrasonic measurement technique for on-field diagnostics of complex composite structures used for production of large liquid storage tanks. Development of the relatively cheap and easy to operate embedded diagnostic/monitoring technique is important aiming to assure safety of liquid storage tanks (monitoring structural integrity against overpressure, etc.) and detection of accidental defects that may appear during transportation, installation and exploitation of those structures. Typical defects that are aimed to be detected are relatively large delaminations/disbonds (area having diameter of 150–200 mm) of skin layers caused by low energy impacts that cannot be detected visually and show severe influence on the structural strength and safety of liquid tanks. This work presents results of numerical modeling and experimental research in low frequency (50 kHz) ultrasonic guided waves (UGW) propagation in large honeycomb composite structures. Finite element (FE) simulation of UGW propagation has been made aiming to reduce quantity of ultrasonic transducers and optimize their placement on composite structure. The possibilities to place ultrasonic transducers and receivers on both sides (internal or external) of composite structures and to use such a proposed technique for detection of delamination/debonding areas caused by low energy impacts or alternating semi static loads (e.g. filling and draining of liquid from storage tank) and monitoring of partial self-healing of relatively rigid composite structures were proved by experimental testing.

Detection rates of wild harbour porpoises and bottlenose dolphins using static acoustic click loggers vary with depth

Acoustic echolocation click loggers are widely used to study the presence and behaviour of coastal cetaceans. Various studies have examined their performance and how animal behaviour may affect click detection. This study examined the effect of logger depth in the water column on click detection rates for harbour porpoises (Phocoena phocoena) and bottlenose dolphins (Tursiops truncatus) at a coastal nearshore site. There were significantly more harbour porpoise clicks logged at the click loggers moored in the water column, closer to the surface, compared with those near the seabed. No such difference was recorded for bottlenose dolphins. The results were consistent throughout the study period and across sites, apart from a site closest to a possible feeding site, indicating that cetacean behaviour is among the possible factors explaining these findings. The study emphasizes the need for prior understanding of the target species and its habitat use, and stresses the importance of pilot studies to achieve reliable and meaningful data from static acoustic monitoring programs.

C++ Builder and Inter Base Based Design and Realization of Intelligent Monitoring Control System of HV Static Reactive Compensator

SVC is a dynamic reactive compensator based on switching type HV electrical and electronic devices, well recognized as an effective means of resolving power quality problems. SVC is complex in structure, consisting of TCR valve sets, FC filter channel, etc. In particular, TCR valve set adopts thyristor serial connecting technology, and over 100 thyristors are adopted, which requires real-time status of devices in SVC to be monitored and uploaded, and even failures to be recorded. Therefore, the monitoring software becomes an important part in ensuring SVC safe operation. Combined with actual cases, this paper introduces a technology of using C++ Builder and Inter Base to design the static reactive compensator monitoring software. The user interface is elegant, with short development period, highly transplantable, and easily modified.

Solutions for Increasing the Bearing Capacity of Thrust Bearings

Design faults, imperfect manufacturing processes, change of technological operating modes of the turbocompressors in gas, petroleum, chemical and petrochemical industry cause axial rotor shifts. Therefore, the task of manufacturing the high-efficient and reliable thrust bearings is important nowadays along with effective rotor balancing, methods of axial forces calculation considering possible operating modes, improvement of static electricity elimination system, protective and monitoring systems of the axial shift. Effective methods for increasing the bearing capacity of thrust bearings, applied by TRIZ Ltd, have been studied in the report. The accepted and realized on the operating equipment solutions have enabled to increase the bearing capacity of thrust bearings significantly and to reduce oil consumption ratio, keeping down location dimensions to the equipment.

OCSO: Off-the-cloud service optimization for green efficient service resource utilization

Many efforts have been made in optimizing cloud service resource management for efficient service provision and delivery, yet little research addresses how to consume the provisioned service resources efficiently. Meanwhile, typical existing resource scaling management approaches often rest on single monitor category statistics and are driven by certain threshold algorithms, they usually fail to function effectively in case of dealing with complicated and unpredictable workload patterns. Fundamentally, this is due to the inflexibility of using static monitor, threshold and scaling parameters. This paper presents Off-the-Cloud Service Optimization (OCSO), a novel user-side optimization solution which specifically deals with service resource consumption efficiency from the service consumer perspective. OCSO rests on an intelligent resource scaling algorithm which relies on multiple service monitor metrics plus dynamic threshold and scaling parameters. It can achieve proactive and continuous service optimizations for both real-world IaaS and PaaS services, through OCSO cloud service API. From the two series of experiments conducted over Amazon EC2 and ElasticBeanstalk using OCSO prototype, it is demonstrated that the proposed approach can make significant improvement over Amazon native automated service provision and scaling options, regardless of scaling up/down or in/out.

Static Monitoring and Non-Destructive Test of a Historic Damaged Palace

The City Hall of Mirandola was stricken and damaged by Emilia-Romagna earthquake sequence of May 2012. This paper presents the procedure for the structural monitoring control of a masonry historic building that presents a serious damage pattern. Structural monitoring was carried out with transducers installed to control the serious cracks that regards the main volumes of the building. The global structural health monitoring was useful to define the actual condition of the dynamic behavior of the damaged construction that are subjected to different mechanism. Ground penetrating radar allows to detect the depth of the cracks and the condition of the masonry. These researches are useful also for the structural future rehabilitation and to define the possible changes in the structural behavior.

Autonomous network repairing of a home security system using modular self-reconfigurable robots

Traditional wheeled robots cannot easily adapt to complex home environments with stairs and doorsills. This paper presents the design and implementation of a novel wireless sensor network based home security system with a modular self-reconfigurable robot (Transmote) as the mobile node. The security system is composed of some static monitoring nodes, a Transmote, and a home server. Static nodes with pyroelectric infrared (PIR) sensor and digital camera are mounted on doorframes and windows to detect intruders and send intrusion alarm messages to the home server. Transmote with PIR sensor and camera can patrol in the house for security surveillance. Transmote also can provide network repairing service when some static router nodes fail. Transmote modules and static monitoring nodes are controlled by two different wireless sensor networks. The remote house owner can get the alarm messages through Internet. Transmote can transform into I-shaped or O-shaped configuration according to different locomotion requirements. A prototype system has been implemented and some performance tests have been done. Experimental results show that the I-shaped Transmote can pass through an 8.8 cm high and 10 cm wide channel. The velocity of the I-shaped Transmote is up to 3 m/min and the maximum velocity of O-shaped Transmote is 9.3 m/min. A 12 kB captured photo can be transmitted to the gateway through 15 hops without any packet loss.

Distributed system contract monitoring

Runtime verification of distributed systems poses various challenges. A pivotal challenge is the choice of howto distribute the monitors themselves across the system.On one hand, centralised monitoringmay result in increased communication overhead and information exposure across locations, while, on the other hand, systems with dynamic topologies and properties are difficult to address using static monitor choreographies. In this paper we present mDPi, a location-aware π-calculus extension for reasoning about the distributed monitoring scenario.We also define numerousmonitoring strategies for a regular expression-based logic, including a novel approach in which monitors migrate to ensure local monitoring. Finally, we present a number of results which emerge from this formalism, justifying our approach.

A long-term static monitoring experiment on R.C. beams: damage identification under environmental effect

The authors have been conducting a static continuous monitoring experiment to assess the validity of some damage detection algorithms, consisting in non-model-based statistical data processing, previously validated, even for small levels of damage, on numerically simulated 2D finite element models of simply supported and continuous beams. Tests have been conducted in Italy on two specimens of pre-stressed R.C. beams equipped with fibre optic strain sensors and temperature sensors and placed outdoor. During the tests, several events have been artificially produced: a ballast load has been positioned on the beams and various known levels of damage have been introduced. One of the two beams was kept intact for reference. Preliminary data processing has disclosed substantial differences between the numerical simulations and the measurements obtained on the field for the case of simply supported beams. This paper shows that environmental variations have a great effect on measurements and should be correctly removed from the strain time histories before a reliable damage detection procedure can be successfully applied.

Development of a thick film PZT foil sensor for use in structural health monitoring applications

Acoustic emission (AE) monitoring is a technique of growing interest in the field of nondestructive testing (NDT). The use of AE devices to monitor the health of structural components is currently limited by the cost of AE equipment, which prohibits the permanent placement of AE devices on structures for the purposes of continuous monitoring and the monitoring of areas with limited access. Micro electromechanical systems (MEMS) can provide solutions to these problems. We present the manufacture of a 4.4-μm-thick lead zirconate titanate (PZT) film on a 110-μm-thick titanium foil substrate for use as an AE sensor. The thick-film sensor is benchmarked against commercially available AE sensors in static and dynamic monitoring applications. The thick-film AE device is found to perform well in the detection of AE in static applications. A low signal-to-noise ratio is found to prohibit the detection of AE in a dynamic application.

Goal-directed therapy in intraoperative fluid and hemodynamic management

Intraoperative fluid management is pivotal to the outcome and success of surgery, especially in high-risk procedures. Empirical formula and invasive static monitoring have been traditionally used to guide intraoperative fluid management and assess volume status. With the awareness of the potential complications of invasive procedures and the poor reliability of these methods as indicators of volume status, we present a case scenario of a patient who underwent major abdominal surgery as an example to discuss how the use of minimally invasive dynamic monitoring may guide intraoperative fluid therapy.

The diagnostic potential of static body-sway recording in orthodontics: a systematic review

Conflicting data have been reported in dentistry regarding the diagnostic potential of monitoring body sway while in a static standing bipedalic position. This systematic review reappraises previously reported effects of mandibular position, asymmetric occlusion, and temporomandibular disorders (TMDs) on body sway to determine whether there is sufficient evidence for such correlations and to define the potential diagnostic applications in orthodontics. A literature survey was performed using the Medline, LILACS, and SciELO databases, and the Cochrane Library, covering the period from January 1980 to December 2011. Twelve articles qualified for the final analysis. All of these studies investigated the effects of mandibular position, two focussed also on asymmetrical occlusion, and three on TMDs. Only two studies were judged to be of medium or medium/high quality, with all of the rest classified as low-quality design; no study included follow-up. According to the conclusions of these reports, four studies saw significant correlations between body sway and mandibular position or TMDs. After a reappraisal of the full data set, generally no clinically relevant correlations were uncovered in the comparisons. While more investigations with improved levels of scientific evidence are needed, according to current evidence, the static monitoring of body sway as a diagnostic aid in orthodontics may not be indicated.

Repair and Service Safety Evaluation of a Fire Damaged Concrete Bridge

The Yao Zhou downlink Viaduct damaged in a fire accident was repaired using steel plate and concrete composite strengthening (SPCCS) technique. After strengthening and servicing normally for 1.5 years, two loading tests, meanwhile, a three-day traffic information observation and dynamic strain monitoring were carried out. The static loading test and monitoring results all showed that the Yao Zhou downlink Viaduct had good service condition since reinforcement, which satisfying the safety requirement. In order to evaluate the effectiveness of the SPCCS technique in-depth, structural behaviour under the ultimate limit state (ULS) and the serviceability limit state (SLS) were analyzed. The SLS and ULC of the key sections before and after reinforcement were calculated using the simplified formula and the finite element models calibrated by filed test results. The post-evaluation results showed that the behaviour of the spans damaged in fire accident could be improved obviously under the SLS using SPCCS technique, as well as the bridge stiffness enlarged than the original bridge structure. The ultimate bearing capacity (UBC) of the key sections was improved about 75% using SPCCS technique, which was two times as the most disadvantageous load effect combinations. Whats more, the fatigue life of fire damaged box girders strengthened using SPCCS technique was evaluated based on monitoring strain data, and the further bridge maintenance suggestions were proposed based on the assessment results.

Static and dynamic measurement of low-level strains with carbon fibers

A signal processing method used to treat the structural strain responses of long-gage carbon fiber (CF) sensors for static and dynamic strain measurements is developed in this paper. This method includes a high-confidence denoising method for continuous static monitoring and a wavelet transform (WT)-based signal processing method for dynamic strain measurements. The static denoising method is based on the measuring error range of CF sensors which defined by a long-term continuous loading and unloading experiments. For the experiment involving 1-measure-time at each strained point, the influence of noise on CF sensors follows a normal distribution with a standard deviation of 50 microstrain. For the experiment involving 25-measure-time at each strained point, the signals are concentrated in a smaller range, and the probability density clearly increases. For a high-confidence signal selection based on multiple-measure-time, the range of error measurement of CF sensors is concentrated from 50 microstrain to 10 microstrain. Furthermore, a study on the signal processing of the dynamic strain signal of CF sensors through WT-based signal processing method is presented. Due to the influence of the dynamic measurement of small strains, the baseline of the dynamic signal of CF sensors drifts. With the WT denoising method, the discrete degree of the dynamic signals was reduced. It is beneficial to find the peak position of each wave in the vibration response of CF sensors. With the peak positions, the baseline drift can be removed by a mathematical regression. Finally, the experimental results are presented to show the effectiveness of the processed signal of the CF sensors studied herein.

A New Type of Automatic Monitoring System of Static and Dynamic Displacement on Dam and Slope

It is imperative to explore a type of automatic long-term fixed-point displacement monitoring technology with low cost and high precision in the current monitoring system of dam and slope. The new system obtains information of slope stability through mutual transformation of photoelectric signals which are magnified by a telescope, and it is of strengths of accuracy, timeliness and low cost compared to conventional monitoring instruments, through remote wireless monitoring. In addition, it can also be used to measure the vibration parameters of slope during the blasting. According to the testing and field observations, it has been verified that the system monitored well, without site operations. Therefore, the system may be applied to automatic static and dynamic displacement monitoring for both long-term and short-term without wiring and operations.

Technical Research on Monitor of SLMSS Grider Fabrication for the Passengers Dedicated Line

The yanmiao bridges are used in the 32m prestressed concrete simply-supported box girders on the wuhan-guangzhou passengers dedicated line,they are constucted in the mobile form.To ensure the constuction safety and the accurated line,static load test and monitor for the mobile form were did.The result of test and monitor showed that in the state of work the different parts’force of the mobile form is in the elastic range. The entire beam deflection curve linear is reasonable, they provided the test reference for the the setting of the pre-camber and the control of the box girder’s height.

Presence of harbor porpoises near a pile driving site and modeling of cumulative acoustic effects.

The construction of the a small wind farm in the southern North Sea has just been completed. Possible effects on harbor porpoise (Phocoena phocoena) distribution and habitat use caused by the pile driving impulses emitted during the installation of the foundations for 12 offshore wind turbines (OWTs) were assessed by ship surveys, aerial surveys, and static acoustic monitoring (SAM). SAM data and sighting data revealed that during the pile driving activities for the construction of the transformer platform as well as for the first OWTs the presence of harbor porpoises decreased significantly. However, the number of porpoise detections by the SAM units increased during the pile driving activities toward the end of the construction period. Habituation, ecological parameters, and external effects are considered as potential reasons for this increased presence of harbor porpoises in the vicinity of the construction site. The cumulative acoustic energy received by the animals exposed to repeated pile driving i...

Multi-algorithm approach for identification of structural behavior of complex structures under cyclic environmental loading

In the past years, an increasing number of structures have been equipped with permanent monitoring systems, able to record the structural response in terms of displacements and strains over very long periods of time, and theoretically, for the entire life of the structure (Structural Health Monitoring). Despite the high number of applications, to date, very few studies have been presented aimed at interpreting the data, in particular, when the spatial and behavioral complexity of the structure under investigation requires a non-model-based approach. This article shows that the interpretation of data from a long-term static monitoring can be very helpful for the comprehension of the structural behavior under complex interaction structure–environment. The discussion aims at underlining that a scheduled and unique procedure is very hard to define depending on the great variety of structures and applications and on the right identification of the parameters able to explain structural degradation evolutions or sudden changes. In these cases, a multi-step algorithm with different signal processing techniques applied in cascade seems to be the only reliable approach. The proposed procedure will be carried out using available data from the long-term monitoring of a quay wall in the Port of Genoa, in Italy, but it can be generalized to several structures under cyclic environmental loading (tides, temperature, etc.). The characterization of the structural behavior under temperature variations will be used here to define the representative features of the quay. Once defined, these parameters will provide a means for detecting and localizing the insurgence of damage or material degradation from the measurements.

Application of advanced statistical methods for extracting long-term trends in static monitoring data from an arch dam

The objective of this article is to develop methods for extracting trends from long-term structural health monitoring data and try to set an early warning threshold level based on the results of analyses. The long-term monitoring data in this study is the continuous monitoring of the dam static deformation. Two different approaches were applied to extract features of the long-term structural health monitoring data of the static deformation of the Fei-Tsui Arch Dam (Taiwan). The methods include the singular spectrum analysis with auto regressive model (SSA-AR) and the nonlinear principal component analysis (NPCA) using auto-associative neural network method (AANN). The singular spectrum analysis is a novel nonparametric technique based on principles of multi-variance statistics. An AR model is optimized for each of the principal components obtained from SSA, and the multi step predicted values are recombined to make the time series. Different from SSA method the NPCA-AANN method is also used to extract the underlying features of static deformation of the dam. By using these two different methods, the residual deformation between the estimated and the recorded data was generated, through statistical analysis, the threshold level of the dam static deformation can be determined. Discussion on the two proposed methods to the static deformation monitoring data of Fei-Tsui Arch Dam (Taiwan) is discussed.

The S. Marco Church in L’Aquila: Provisional Interventions after the 2009 Abruzzo Earthquake

The 6th of April 2009 a strong earthquake (rated 5.8 on the Richter scale) struck the Abruzzo region in central Italy, causing hundreds of casualties and devastating the historical city of L’Aquila and several small towns in the area. The toll in terms of structural damage was enormous, also considered that a vast amount of buildings was made of poorly arranged masonry composed by round pebbles and mortar of scarce mechanical characteristics. In particular, the buildings belonging to cultural heritage (e.g. churches and monumental buildings) were between the structures that suffered more from seismic damage, considered their dimensions, mass and general lack of adequate connections. Few weeks after the seismic event, a church in the historical city centre of L’Aquila, the S. Marco church, was “adopted” by the Italian Veneto Region, which paid and provided the necessary technical support for the first necessary provisional structural interventions. The paper describes the steps undertaken in order to provide the building with the minimum safety conditions necessary to face the aftershocks, and to survive without further collapses to be subsequently retrofitted. A static and dynamic structural monitoring system was also installed in the church since the beginning of the works, in order to control the safety conditions of the area during the execution of the interventions and to assess the damage progression or stationariness.