8,585 research outputs found
Behavior of RC beams patch repaired and strengthened with FRP composites : a numerical study
No full textIncludes bibliographical references.Reinforced concrete (RC) beams get deteriorated and become deficient mainly due to corrosion of steel reinforcements, poor maintenance and design, earthquakes and aging. Patch repair and structural strengthening using fiber reinforced polymers (FRP) have been increasingly adopted all over the world as an economical solution to upgrade the load carrying capacity of such beams. However, the failure modes of such repaired and strengthened RC beams are governed by brittle and sudden premature debonding which involves separation of external reinforcement; i.e. FRP and RC beam. Different researchers have used different approaches including experimental, analytical and numerical to investigate the behavior of patch repaired and FRP strengthened RC beams. It is noteworthy that there are no such numerical studies that investigated the effect of patch repair. In this study, a numerical investigation was carried out using the commercial finite elements analysis software ABAQUS with the aim of investigating the overall behavior of RC beams patch repaired and strengthened with FRP plates including the failure mechanisms
Modelling delay and noise in arbitrarily coupled RC trees.
No full textClosed-form equations for second-order transfer functions of general arbitrarily coupled resistance-capacitance (RC) trees with multiple drivers are reported. The models allow precise delay and noise calculations for systems of coupled interconnects with guaranteed stability and represent the minimum complexity associated with this class of circuits. Their accuracy is extensively compared against other relevant models and is found to be better or comparable to more expensive models. All results are derived from a theoretical approach, and their physical basis is examined. The simplicity, accuracy, and generality of the models make them suitable for use in early signal integrity analyses of complex systems and incremental physical optimization
Measurable parameters for performance of correded and repaired RC beams under load
No full textIncludes abstract.Includes bibliographical references.Structural engineers and asset managers rely on measurable parameters developed by researchers to predict residual load-bearing capacities of corroding in-service RC structures and to assess repair-effectiveness. Laboratory research that was used to develop these measurable parameters varied between researchers and in most cases, did not represent in-service conditions. As a result, they found different relations between measurable and non-measurable parameters which are unsafe and/or engineers find difficult to apply to in-service structures. A holistic research that emulates in-service conditions was therefore developed. Parameters that were looked at were corrosion crack widths and longitudinal strains together with their derivatives
A Compact 10-MHz RC Frequency Reference With a Versatile Temperature Compensation Scheme
No full textThis article presents the design and implementation of a compact CMOS RC frequency reference. It consists of a frequency-locked loop (FLL) that locks the period of a voltage-controlled oscillator (VCO) to the time an RC network takes to charge to a reference voltage. Conventionally, an RC time constant with a near-zero temperature coefficient (TC) is realized by using a trimmed network of resistors with different TCs. In this work, such a network is used to realize a temperature-dependent reference voltage whose TC cancels that of a single-resistor RC time constant. Compared with the conventional approach, which requires resistors with TCs of opposite polarity, the proposed approach can be implemented with resistors with TCs of similar polarity, and so it can be implemented in most CMOS processes. To compensate for RC spread, a trimmed capacitor is used to adjust the nominal frequency. Two prototype chips were made, one based on p- /n-polysilicon resistors and other based on silicided/p-diffusion resistors. Fabricated in a standard 180-nm CMOS technology, the polysilicon-based prototype has an active area of 0.01 mm2 and an absolute inaccuracy of ±2800 ppm from -45 °C to 125 °C with a fixed TC-trim and a one-point frequency trim. After one week of accelerated aging at 150 °C, however, significant drift (5000 ppm) was observed. The diffusion-based prototype exhibits greater inaccuracy (±14 400 ppm) but much less drift (600 ppm).Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic InstrumentationMicroelectronic
A CMOS Dual-RC frequency reference with ±250ppm inaccuracy from -45°C to 85°C
No full textTo comply with wired communication standards such as USB, SATA and PCI/PCI-E, systems-on-chip require frequency references with better than 300ppm accuracy. LC-based references achieve 100ppm accuracy [1], but suffer from high power consumption (∼20mW). Thermal diffusivity (TD) references require less power (∼2mW), at the expense of less accuracy (1000ppm) [2]. RC-based references offer the lowest power consumption, but their accuracy is typically limited to ∼0.1% [3]. In RC relaxation oscillators, comparator offset and delay are the major sources of inaccuracy [4,5]. References based on frequency-locked loops (FLLs) circumvent these by locking an oscillator's frequency to the time-constant of an RC filter, but their accuracy is then limited by the nonlinear temperature dependency of on-chip resistors [3,6].Session 3.3 Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic Instrumentation(OLD)Applied Quantum ArchitecturesMicroelectronic
Displacement-based fragility analysis of typical multi-span RC bridges
No full textReliable risk assessment models for an infrastructure system require the detailed definition of bridge inventory characteristics, in order to evaluate the seismic vulnerability of the exposed structures. In this work, a detailed statistical analysis was carried out on the reference bridge stock, represented by the bridges of the Veneto Region (N-E of Italy) road network, consisting of 496 bridges belonging to the provincial and regional infrastructure systems, mostly located in medium-high seismicity areas. The extensive statistical analysis presented supplies a sound background to the analytical vulnerability assessment of existing multi span rc bridges. Using DBA procedures that assume strain and displacement measures as structural damage indexes and seismic performance control parameters, fragility curves have been developed for all rc bridges and a proposal for an average fragility curve, valid for a whole class of bridge structures is presented. © 2014 Taylor & Francis Group
A response to Taylor
No full textGiven the focus of this research, my ontological positioning is central to my response as I am a researcher from a mixed race (Black Caribbean and White British) background. My view of racism has been shaped by personal, professional and academic experiences. Within this article the author, Bunce addresses the position of race in the university experiences of Black students undertaking studies in health and social care related subjects. She charts her brief and seemingly recent journey into developing her understanding of the concept of racism and the ‘unfairness’ of inequality. Through research with her students the author describes their experiences with racism as ‘shocking and deeply saddening’ and provides a narrative of her reflections and actions in response to her new found knowledge and understanding. This article seeks to ‘inform and inspire educational change that promotes racial equality of outcomes both within and beyond [our] classrooms.
Investigation of impact behavior of shear deficient RC beams using nonlinear FEA
No full textIn the scope of this study, the impact behavior of shear deficient RC beam was investigated by performing numerical analysis based on the finite element method and comparing it with the experimental results. The explicit dynamic analysis of 27 shear-deficient RC beams of which experiments were previously carried out by one of the authors has been conducted by utilizing ABAQUS software, and also it is aimed to establish the reasonable finite element model that is accordant with the experimental results. The variables of the experimental study were the ratio of longitudinal reinforcement on the tension side of the member, the shear-span ratio, and impact velocities. The time histories of impact load, reaction forces on supports, and the displacements measured from the mid-span of the beams were recorded during the experiments, and the energy absorption capacities of RC beams were evaluated based on an area enclosed by the impact load vs. displacement loops. It is investigated and interpreted to what extent the proposed nonlinear finite element method could be successful for analyzing the values of impact load and mid-span displacements and to what extent the explicit dynamic solution technique could be successful for simulating experiments. It is found that the maximum differences between the results obtained by numerical analysis using ABAQUS and the experimental results are 7% and 14% for impact loads and mid-span displacements, respectively. © 2022 Taylor & Francis Group, LLC
Analytical behaviour of FRP strengthened reinforced concrete beams under low velocity impact load incorporating rate dependant material constitutive models
No full textIncludes bibliographical references.Since the 1980s, the use of fibre reinforced polymer (FRP) composites in strengthening and rehabilitation of existing reinforced and pre-stressed structures has gained popularity. Versatility, high strength to weight ratio, corrosion resistance, excellent creep and fatigue behaviour, and ease of installation are amongst some of the advantages offered by externally bonded FRP systems over traditional strengthening methods. In addition to strengthening for static loading, there are many scenarios where strengthening is required to elements subjected to dynamic loads. The static behaviour of FRP strengthened RC beams has been the subject of extensive research. However, the dynamic behaviour of FRP strengthened RC beam elements remains unclear. Limited experimental studies are available that are focused on the response of FRP strengthened RC beams subjected to low velocity impact events. Furthermore, many of the Finite Element (FE) analysis models developed in these studies yielded results that were inconsistent with the test data. Key shortcomings of these models relate to a lack of definition of the FRP-concrete bond interface and considering rate dependent material behaviour
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