Civil and Environmental Engineering Faculty Research and PublicationsCopyright (c) 2016 Marquette University All rights reserved.
http://epublications.marquette.edu/civengin_fac
Recent documents in Civil and Environmental Engineering Faculty Research and Publicationsen-usThu, 31 Mar 2016 08:11:54 PDT3600A Multi-Modal Continuous-Systems Model of a Novel High-Q Disk Resonator in a Viscous Liquid
http://epublications.marquette.edu/civengin_fac/114
http://epublications.marquette.edu/civengin_fac/114Tue, 29 Mar 2016 11:41:00 PDTMohamad S. Sotoudegan et al.Finite Element Analysis of FRP Debonding Failure at the Tip of Flexural/Shear Crack in Concrete Beam
http://epublications.marquette.edu/civengin_fac/113
http://epublications.marquette.edu/civengin_fac/113Tue, 29 Mar 2016 11:15:35 PDT
One of the most common failure modes of strengthened RC beams with externally bonded FRP is intermediate crack (IC) debonding of FRP initiated at the tip of flexural/shear cracks. This study presents a method, using extended finite element method (XFEM), to model IC debonding in an FRP-strengthened concrete beam. In XFEM, as soon as a damage initiation criterion is reached in an element, additional degrees of element freedom are added to model crack initiation. Crack propagation is then modeled using fracture energy criterion. This method can be used to simulate debonding failure along an arbitrary, solution-dependent path without the requirement of remeshing. The numerical results are validated against experimental data and good agreement is found. A sensitivity analysis is conducted to study the effects of damage band properties and geometry on FRP debonding failure. This verifies that shear strength and critical mode II fracture energy are the parameters most affecting the FRP debonding model when the crack tip is subjected to mode II loading.
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Tayyebeh Mohammadi et al.Validation of Earthquake Simulations and Their Effects on Tall Buildings Considering Spectral Shape and Duration
http://epublications.marquette.edu/civengin_fac/112
http://epublications.marquette.edu/civengin_fac/112Fri, 18 Mar 2016 13:09:59 PDTTing Lin et al.Seismic Response of a Tall Building to Recorded and Simulated Ground Motions
http://epublications.marquette.edu/civengin_fac/111
http://epublications.marquette.edu/civengin_fac/111Fri, 18 Mar 2016 12:15:57 PDT
Seismological modeling technologies are advancing to the stage of enabling fundamental simulation of earthquake fault ruptures, which offer new opportunities to simulate extreme ground motions for collapse safety assessment and earthquake scenarios for community resilience studies. With the goal toward establishing the reliability of simulated ground motions for performance-based engineering, this paper examines the response of a 20-story concrete moment frame building analyzed by nonlinear dynamic analysis under corresponding sets of recorded and simulated ground motions. The simulated ground motions were obtained through a larger validation study via the Southern California Earthquake Center (SCEC) Broadband Platform (BBP) that simulates magnitude 5.9 to 7.3 earthquakes. Spectral shape and significant duration are considered when selecting ground motions in the development of comparable sets of simulated and recorded ground motions. Structural response is examined at different intensity levels up to collapse, to investigate whether a statistically significant difference exists between the responses to simulated and recorded ground motions. Results indicate that responses to simulated and recorded ground motions are generally similar at intensity levels prior to observation of collapses. Collapse capacities are also in good agreement for this structure. However, when the structure was made more sensitive to effects of ground motion duration, the differences between observed collapse responses increased. Research is ongoing to illuminate reasons for the difference and whether there is a systematic bias in the results that can be traced back to the ground motion simulation techniques.
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Nenad Bijelic et al.Advancement in Ion Exchange Processes for Municipal Wastewater Nutrient Recovery
http://epublications.marquette.edu/civengin_fac/110
http://epublications.marquette.edu/civengin_fac/110Tue, 01 Mar 2016 10:16:20 PST
Interest in the recovery of nitrogen and phosphorus from wastewater has increased as it provides a way of securing nutrient supply for crops, reducing energy costs in obtaining raw nutrients, and reducing eutrophication in waterways resulting from discharge of nutrients. For mainstream recovery, alternative nutrient removal technologies such as ion exchange (IX) must be considered to concentrate the nutrients in order for recovery to be economical. Nutrients are concentrated in the regenerant of IX. Batch and column tests were conducted to optimize desorption of NH_{4}^{+} and maintain IX capacity. During batch testing with clinoptilolite for NH_{4}^{+} exchange, regeneration with 8% NaCl or 7.5% NaCl at pH=12 maintained 84% of initial IX capacity after 7 IX cycles. When operating an NH_{4}^{+} IX column treating with secondary clarifier effluent dosed with nutrients, 120 bed volumes of sample was reduced from 32 mg/l to less than 1 mg/l NH_{4}^{-}N.
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Allen T. Williams et al.Toward Higher-Order Mass Detection: Influence of an Adsorbate’s Rotational Inertia and Eccentricity on the Resonant Response of a Bernoulli-Euler Cantilever Beam
http://epublications.marquette.edu/civengin_fac/109
http://epublications.marquette.edu/civengin_fac/109Mon, 29 Feb 2016 09:08:40 PST
In this paper a new theoretical model is derived, the results of which permit a detailed examination of how the resonant characteristics of a cantilever are influenced by a particle (adsorbate) attached at an arbitrary position along the beam’s length. Unlike most previous work, the particle need not be small in mass or dimension relative to the beam, and the adsorbate’s geometric characteristics are incorporated into the model via its rotational inertia and eccentricity relative to the beam axis. For the special case in which the adsorbate’s (translational) mass is indeed small, an analytical solution is obtained for the particle-induced resonant frequency shift of an arbitrary flexural mode, including the effects of rotational inertia and eccentricity. This solution is shown to possess the exact first-order behavior in the normalized particle mass and represents a generalization of analytical solutions derived by others in earlier studies. The results suggest the potential for “higher-order” nanobeam-based mass detection methods by which the multi-mode frequency response reflects not only the adsorbate’s mass but also important geometric data related to its size, shape, or orientation (i.e., the mass distribution), thus resulting in more highly discriminatory techniques for discrete-mass sensing.
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Stephen M. Heinrich et al.The Effects of an Antimicrobial on Anaerobic Digestion Microbial Communities
http://epublications.marquette.edu/civengin_fac/108
http://epublications.marquette.edu/civengin_fac/108Tue, 16 Feb 2016 07:53:20 PST
Over two hundred metric tons of micropollutants are discharged to the environment with biosolids each year in the U.S. Of particular concern is the antimicrobial agent triclosan, which accumulates under methanogenic conditions in wastewater treatment plants. Experiments were setup to test the impacts of triclosan on methanogenic community structure and function. Microbial communities that had not been exposed to triclosan were able to adapt to triclosan at environmentally relevant levels and maintain function. However, when communities with previous exposure to triclosan were amended with triclosan at approximately four-fold current environmental levels, their community structures shifted and methane production was cut in half.
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Patrick J. McNamara et al.Pyrolysis of Wastewater Biosolids: Lab-Scale Experiments and Modeling
http://epublications.marquette.edu/civengin_fac/107
http://epublications.marquette.edu/civengin_fac/107Tue, 16 Feb 2016 07:41:33 PST
Biosolids handling is an energy intensive and expensive process. Thus, the use of beneficial end-products is strongly desired to reduce costs. Pyrolysis, the thermal decomposition of organic matter under anaerobic conditions, has potential to be a beneficial biosolids handling process. Pyrolysis results in biochar that can be used as a fertilizer, pyrolysis oil (py-oil), and pyrolysis-gas (py-gas), which can be used to fuel the pyrolysis process. Two objectives of this work were to determine i) the impact of temperature on product yields and gas energy content and ii) the enthalpy of pyrolysis of biosolids from bench-scale experiments and modeling. Increased temperatures resulted in decreased char yields, but py-oil content did not increase after 500°C. The increase in temperature resulted in higher permanent gas yields, and higher energy content in the py-gas.
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Patrick J. McNamara et al.Addressing Uncertainty in Ensemble Sea-Level Rise Predictions
http://epublications.marquette.edu/civengin_fac/106
http://epublications.marquette.edu/civengin_fac/106Mon, 07 Dec 2015 08:17:10 PST
Sea-level rise represents a looming hazard to coastal communities which remains difficult to quantify. Ensemble climate change predictions incorporate epistemic uncertainty in the climate modeling process and climate forcing scenarios help portray a range of radiative forcing changes. This study proposes a method for incorporating both model and scenario uncertainty in ensemble projections of thermosteric sea-level rise. A Markov Chain Monte Carlo algorithm is utilized to weigh the contributions of eight process-based climate models as well as the four Representative Concentration Pathways based on convergence criteria and observational data. Hazard analysis and deaggregation combine these contributions over a range of sea-level rise thresholds and quantify the relative contributions of each pathway and prediction model. The hazard maps generated suggest improved accuracy in modeling regional trends over typical ensembles. Deaggregations effectively represent model and scenario differences and the impacts of the methods used.
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Matthew A. Thomas et al.Prediction of Solder Joint Geometry
http://epublications.marquette.edu/civengin_fac/105
http://epublications.marquette.edu/civengin_fac/105Tue, 03 Nov 2015 09:59:46 PSTStephen M. HeinrichCantilever-based Resonant Microsensors with Integrated Temperature Modulation for Transient Chemical Analysis
http://epublications.marquette.edu/civengin_fac/104
http://epublications.marquette.edu/civengin_fac/104Wed, 21 Oct 2015 11:30:56 PDT
This work introduces a resonant cantilever platform with integrated temperature modulation for real-time chemical sensing. Embedded heaters allow for rapid thermal cycling of individual sensors, thereby enabling real-time transient signal analysis without the need for a microfluidic setup to switch between analyte and reference gases. Compared to traditional mass-sensitive microsensors operating in steady state, the on-chip generation of signal transients provides additional information for analyte discrimination.
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C. Carron et al.Fundamental Theory of Resonant MEMS Devices
http://epublications.marquette.edu/civengin_fac/103
http://epublications.marquette.edu/civengin_fac/103Wed, 21 Oct 2015 09:21:26 PDTStephen M. Heinrich et al.[Review of] Variational Methods in Mechanics
http://epublications.marquette.edu/civengin_fac/102
http://epublications.marquette.edu/civengin_fac/102Tue, 20 Oct 2015 10:24:50 PDTStephen M. HeinrichForeword to Special Issue on Solder Geometry
http://epublications.marquette.edu/civengin_fac/101
http://epublications.marquette.edu/civengin_fac/101Tue, 20 Oct 2015 10:20:07 PDTStephen M. HeinrichStress Interference in a Transversely Isotropic Body under Axisymmetric Loading
http://epublications.marquette.edu/civengin_fac/100
http://epublications.marquette.edu/civengin_fac/100Mon, 19 Oct 2015 10:05:20 PDT
An unbounded homogeneous transversely isotropic body of revolution containing two twin spheroidal cavities is subjected to an axisymmetric loading. The axis of loading symmetry coincides with the axis of elastic symmetry of the material and the axis of revolution of the body. The elasticity solution is obtained in series form utilizing the displacement potential representation for the equilibrium of transversely isotropic solids, and numerical results are presented for the cases of two spherical cavities perturbing uniaxial and hydrostatic tension fields in certain hexagonal crystals and in isotropic materials. Of primary interest is the influence of cavity spacing and material type on the degree of stress interference between the two perturbations.
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Stephen M. Heinrich et al.Analysis of Constrained Filament Deformation and Stiffness Properties of Brushes
http://epublications.marquette.edu/civengin_fac/99
http://epublications.marquette.edu/civengin_fac/99Mon, 19 Oct 2015 09:58:42 PDT
In this paper, an analytical procedure is developed for evaluating the filament loading, constrained elastic deformation, and overall stiffness of a circular brush, Filament deformation is computed on the basis of a large displacement mechanics analysis in conjunction with kinematic constraints for a flat, rigid workpart with smooth surface finish. Numerical results are reported which examine the relationship between workpart penetration, brush stiffness, and force distribution characteristics of the workpart contact zone.
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R. J. Stango et al.Solder Joint Formation in Surface Mount Technology—Part I: Analysis
http://epublications.marquette.edu/civengin_fac/98
http://epublications.marquette.edu/civengin_fac/98Mon, 19 Oct 2015 09:46:23 PDT
An analytical model of solder joint formation during a surface mount reflow process is developed in the present paper, and the solution is obtained in an explicit integral form. For two limiting cases—infinitesimal and infinite solder areas—the solution is expressed in closed form. Numerical results illustrate the influence of the process parameters (surface tension, density, and cross-sectional area of the molten solder, and the contact angles between the solder andpretinning) on joint shape and overall fillet dimensions. Comparisons between theoretical predictions and laboratory data show excellent agreement.
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Stephen M. Heinrich et al.Solder Joint Formation in Surface Mount Technology—Part II: Design
http://epublications.marquette.edu/civengin_fac/97
http://epublications.marquette.edu/civengin_fac/97Mon, 19 Oct 2015 09:31:59 PDT
In this paper dimensionless design curves relating fillet height and length to joint cross-sectional area are presented for surface-mount solder joints. Based on an analytical surface tension model, the advantage of these dimensionless curves is that they may be used for arbitrary values of solder density and surface tension. The range of applicability of previously developed approximate formulae for predicting joint dimensions is also investigated. A simple example problem is included to illustrate the use of both the design curves and the approximate formulae.
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Stephen M. Heinrich et al.Effect of Workpart Curvature on the Stiffness Properties of Circular Filamentary Brushes
http://epublications.marquette.edu/civengin_fac/96
http://epublications.marquette.edu/civengin_fac/96Mon, 19 Oct 2015 09:19:21 PDT
In this paper the role which workpart geometry plays in the stiffness properties and contact zone characteristics of circular filamentary brushes is investigated. The problem is examined by employing a recently developed mechanics-based procedure for evaluating large filament deformation, in conjunction with appropriate kinematic constraints for filament tip contact with a smooth, rigid workpart of prescribed constant curvature. Numerical examples for a circular filamentary brush system are presented and discussed for the purpose of illustrating the basic nature of brush stiffness response characteristics for a range of prescribed constant-curvature workpart surfaces
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Stephen M. Heinrich et al.Torsional Stress Interference in Transverse Isotropy
http://epublications.marquette.edu/civengin_fac/95
http://epublications.marquette.edu/civengin_fac/95Mon, 19 Oct 2015 09:11:21 PDT
An unbounded homogeneous transversely isotropic body of revolution containing two twin spheroidal cavities is subjected to a torsional loading at infinity. The axis of twist coincides with the axis of elastic symmetry of the material and the axis of revolution of the body. The linear elasticity solution is obtained in series form by employing the Lekhnitskii stress function approach, and numerical results are presented for the case of two spherical cavities perturbing the Saint‐Venant torsion field for a circular cylinder. Of particular interest is the influence of cavity spacing and material constants on the degree of stress interference between the two perturbations.
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Stephen M. Heinrich