@article{ryu_matzen_2016, title={The nonlinear behavior of threaded piping connections: Application using a modified Ramberg-Osgood model}, volume={127}, ISSN={["0029-8018"]}, DOI={10.1016/j.oceaneng.2016.09.030}, abstractNote={Damage to nonstructural components such as piping systems and mechanical and electrical equipment can result in major economic loss, injuries, and loss of life in critical facilities like offshore structures, nuclear power plants, and hospitals. Failures in piping systems especially due to water leakage can lead to shut-down of a facility, and connections in the pipelines are particularly important since failures often occur at these locations. This paper presents a technique for modeling threaded connections as rotational springs, either linear or nonlinear. Laboratory tests were conducted on 1 and 2-in. diameter specimens of black iron Schedule 40 pipe in a cantilever configuration where the support is a threaded piping flange. The specimens were loaded monotonically into the inelastic region. The piping system was modeled as a straight pipe using Euler-Bernoulli beam theory with a support modeled as the proposed rotational spring. The correlation between test results and analytical predictions was quite good. A modified Ramberg-Osgood equation (1943) was used to model the nonlinear moment-rotational behavior of the support spring, and the criterion specified by ASME Boiler & Pressure Vessel Code (ASME, 2007) was used to determine the rotational limit for the threaded piping connection.}, journal={OCEAN ENGINEERING}, author={Ryu, Yonghee and Matzen, Vernon C.}, year={2016}, month={Nov}, pages={1–6} }
 @inproceedings{ryu_behrouzi_melesse_matzen_2012, title={Inelastic behavior of threaded piping connections: Reconciliation of experimental and analytic results}, DOI={10.1115/pvp2011-57949}, abstractNote={Modeling the behavior of piping systems with threaded joints is difficult because the joints do not act as rigid connections. At one level of approximation the connection can be modeled as a semi-rigid connection using a rotational spring. This study modeled a straight pipe using either Euler-Bernoulli beam elements [4] or Finite Element Analysis (FEA) shell elements and a support condition using the rotational spring. Laboratory tests were conducted on 1 in. diameter specimens of black iron Schedule 40 pipe in a cantilever configuration. The specimen was loaded monotonically into the inelastic region. A Ramberg-Osgood model [5] was used to represent the rotational spring and the correlation between test results and analytical predictions was quite good.Copyright © 2011 by ASME}, booktitle={Proceedings of the ASME Pressure Vessels and Piping Conference, PVP 2011, vol 8}, author={Ryu, Y. and Behrouzi, A. and Melesse, T. and Matzen, V. C.}, year={2012}, pages={357–362} }
 @article{matzen_hassan_2011, title={Special section: The international conferences on structural mechanics in reactor technology (SMiRT) preface}, volume={241}, number={3}, journal={Nuclear Engineering and Design}, author={Matzen, V. C. and Hassan, Y. A.}, year={2011}, pages={547–547} }
 @article{kripakaran_gupta_matzen_2008, title={Computational framework for remotely operable laboratories}, volume={24}, ISSN={["0177-0667"]}, DOI={10.1007/s00366-008-0089-y}, abstractNote={Decision-makers envision a significant role for remotely operable laboratories in advancing research in structural engineering, as seen from the tremendous support for the network for earthquake engineering simulation (NEES) framework. This paper proposes a computational framework that uses LabVIEW and web technologies to enable observation and control of laboratory experiments via the internet. The framework, which is illustrated for a shaketable experiment, consists of two key hardware components: (1) a local network that has an NI-PXI with hardware for measurement acquisition and shaketable control along with a Windows-based PC that acquires images from a high-speed camera for video, and (2) a proxy server that controls access to the local network. The software for shaketable control and data/video acquisition are developed in the form of virtual instruments (VI) using LabVIEW development system. The proxy server employs a user-based authentication protocol to provide security to the experiment. The user can run perl-based CGI scripts on the proxy server for scheduling to control or observe the experiment in a future timeslot as well as gain access to control or observe the experiment during that timeslot. The proxy server implements single-controller multiple-observer architecture so that many users can simultaneously observe and download measurements as a single controller decides the waveform input into the shaketable. A provision is also created for users to simultaneously view the real-time video of the experiment. Two different methods to communicate the video are studied. It is concluded that a JPEG compression of the images acquired from the camera offers the best performance over a wide range of networks. The framework is accessible by a remote user with a computer that has access to a high-speed internet connection and has the LabVIEW runtime engine that is available at no cost to the user. Care is taken to ensure that the implementation of the LabVIEW applications and the perl scripts have little dependency for ease of portability to other experiments.}, number={4}, journal={ENGINEERING WITH COMPUTERS}, author={Kripakaran, Prakash and Gupta, Abhinav and Matzen, Vernon C.}, year={2008}, month={Oct}, pages={405–415} }
 @article{wirgau_gupta_matzen_2006, title={Internet-enabled remote observation and control of a shake table experiment}, volume={20}, DOI={10.1061/(ASCE)0887-3801(2006)20:4(271)}, abstractNote={This paper describes a computational framework and the corresponding interfaces required to convert a shake table experiment for remote access including control, observation, and protection from misuse. The laboratory environment is expanded by this research to include remote controlling of the experiment, multiuser viewing, data storage, and download capabilities. The software technology selected for programming this application is LabVIEW and its real-time counterpart, LabVIEW RT. Practical and intuitive control panels coupled with easy to follow data flow block diagrams are made possible by using LabVIEW, which is also capable of handling the data acquisition. The setup in this laboratory environment connects an administrator-controlled host computer to a real-time board that controls the DAQ through a TCP/IP connection. The information sent and received through the DAQ card is processed by LabVIEW RT code embedded upon the real-time board. The information is then sent back to the host computer for saving, visualization, and distribution to remote clients. Data visualization is implemented through a graphical user interface that is intended to serve the functions of an oscilloscope for displaying the accelerations from both the table and the structure in real time. Physical visualization is made possible by way of a real-time video stream. Protection of the experimental system from unintended or accidental damage required sufficient safety protocols.}, number={4}, journal={Journal of Computing in Civil Engineering}, author={Wirgau, S. and Gupta, A. and Matzen, V.}, year={2006}, pages={271–280} }
 @inproceedings{gupta_gabr_matzen_2004, title={Alternatives in the implementation of internet-enabled laboratory experiments in undergraduate civil engineering courses}, booktitle={ASEE 2004 annual conference & exposition$h[electronic resource] :June 20-23, 2004, Salt Lake City, Utah : Engineering education reaches new heights : conference proceedings}, publisher={Washington, D.C.: American Soceity for Engineering Education}, author={Gupta, A. and Gabr, M. A. and Matzen, V. C.}, year={2004} }
 @article{matzen_2004, title={SMiRT 16 - Selected and updated papers from the 16th International Conference on Structural Mechanics in Reactor Technology - Washington, DC - Preface}, volume={228}, ISSN={["0029-5493"]}, DOI={10.1016/j.nucengdes.2003.09.004}, number={1-3}, journal={NUCLEAR ENGINEERING AND DESIGN}, author={Matzen, VC}, year={2004}, month={Mar}, pages={1–1} }
 @article{tan_matzen_2002, title={Correlation of in-plane bending test and FEA results for thin-walled elbows}, volume={217}, ISSN={["1872-759X"]}, DOI={10.1016/S0029-5493(02)00137-1}, abstractNote={The objective of this study is to validate a finite element analysis (FEA) simulation methodology to predict the global behavior of thin-walled elbows subjected to in-plane bending. Two in-plane closing mode bending tests and one in-plane opening mode bending test were conducted on 2″ schedule 10 elbows, and a nonlinear FEA procedure was used to simulate the tests. A detailed FEA study was carried out to determine the relative importance of weld size and location, measured wall thicknesses, and original cross-section dimensions on the reconciliation results. When the weld bead was included in the analysis, the reconciliation results for load–displacement behavior and some of the strain measurements were excellent. For those cases in which the strain measurements reconciliations were not so good, a possible explanation is provided.}, number={1-2}, journal={NUCLEAR ENGINEERING AND DESIGN}, author={Tan, Y and Matzen, V}, year={2002}, month={Aug}, pages={21–39} }
 @article{tan_wilkins_matzen_2002, title={Correlation of test and FEA results for elbows subjected to out-of-plane loading}, volume={217}, ISSN={["0029-5493"]}, DOI={10.1016/S0029-5493(02)00132-2}, abstractNote={The objective of this study is to validate a finite element analysis (FEA) simulation methodology to predict the out-of-plane behavior of piping elbows. Two out-of-plane elbow experiments and the corresponding FEA shell and elbow element models are presented. For load–displacements results, all the FEA predictions showed excellent agreement with measured experimental results, and for load–strain behavior, the shell FEA model results correlated quite well with the experimental results.}, number={3}, journal={NUCLEAR ENGINEERING AND DESIGN}, author={Tan, Y and Wilkins, K and Matzen, V}, year={2002}, month={Sep}, pages={213–224} }
 @article{tan_matzen_yu_2002, title={Correlation of test and FEA results for the nonlinear behavior of straight pipes and elbows}, volume={124}, ISSN={["1528-8978"]}, DOI={10.1115/1.1493806}, abstractNote={This paper summarizes the literature on reconciliation of finite element analyses with in-plane bending experiments on piping elbows. It then describes in detail two four-point-bending tests on straight pipes and two in-plane bending tests on elbows and the corresponding nonlinear finite element analyses. Using a new procedure for obtaining a stress-strain curve for stainless steel using only values for E,Sy, and Su and a representative stress-strain curve from a test on a similar material specimen, the nonlinear responses of the piping components tested are shown to be simulated more accurately than previously published results.}, number={4}, journal={JOURNAL OF PRESSURE VESSEL TECHNOLOGY-TRANSACTIONS OF THE ASME}, author={Tan, Y and Matzen, VC and Yu, LX}, year={2002}, month={Nov}, pages={465–475} }
 @article{matzen_tan_2002, title={The history of the B-2 stress index}, volume={124}, ISSN={["0094-9930"]}, DOI={10.1115/1.1464564}, abstractNote={The history of the primary stress design equations for Class 1 and 2 elbows in the ASME Boiler and Pressure Vessel Code (Section III, Division 1, Subsections NB and NC) is reviewed. The review includes the early analytical solutions for elbow bending, Markl’s stress-intensification factor, the development of Code equation (9), the relationship between SIFs and the C2 and B2 stress indices, development of B2 equations that are functions of internal pressure and bend angle, and a suggested definition of the B2 index which is based on nonlinear finite element analysis.}, number={2}, journal={JOURNAL OF PRESSURE VESSEL TECHNOLOGY-TRANSACTIONS OF THE ASME}, author={Matzen, VC and Tan, Y}, year={2002}, month={May}, pages={168–176} }
 @article{yu_matzen_1999, title={B-2 stress index for elbow analysis}, volume={192}, ISSN={["0029-5493"]}, DOI={10.1016/S0029-5493(99)00112-0}, abstractNote={The purpose of this study is to evaluate the effect of end constraint, geometric dimension and internal pressure on the B2 stress indices, and thus to determine the conservativeness of the code equation for B2 stress indices. For a series of stainless steel elbow-straight pipe connections of different sizes and schedules, with flanges attached at different locations and with different levels of applied internal pressure, nonlinear finite element analyses were performed considering both material and geometrical nonlinearities. Load-deflection curves were obtained, and from these curves, collapse limit loads were determined. B2 stress indices were computed using the equation B2=Sy/(Mcl/Z). The B2 stress indices of elbows with flanges attached at different locations were compared. Also compared were B2 stress indices of elbows with different levels of internal pressure. Finally the B2 stress indices from the finite element analysis are compared with the B2 stress indices computed from code equation. Regression analysis is used to determine revised numerical values for the code equation for B2. A new, less conservative equation is proposed to be used to compute B2 stress indices for elbow component.}, number={2-3}, journal={NUCLEAR ENGINEERING AND DESIGN}, author={Yu, LX and Matzen, VC}, year={1999}, month={Sep}, pages={261–270} }
 @article{matzen_yu_1998, title={Elbow stress indices using finite element analysis}, volume={181}, ISSN={["0029-5493"]}, DOI={10.1016/S0029-5493(97)00352-X}, abstractNote={Existing ASME Code provisions allow for an experimentally determined collapse load. This collapse (limit) load can then be used in the Code equation defining stress indices to obtain a stress index experimentally. This paper describes a research project to investigate the use of inelastic finite element analysis, rather than experiments, to obtain the collapse load. An example is given for a 2-in., schedule 40, long radius, 90°, stainless steel elbow with 10-in.-long straight pipes on each end. A B2 index is found using this approach which is nearly 50% lower than the one obtained using the Code equation for B2.}, number={1-3}, journal={NUCLEAR ENGINEERING AND DESIGN}, author={Matzen, VC and Yu, LX}, year={1998}, month={May}, pages={257–265} }
 @article{hassan_zhu_matzen_1998, title={Improved ratcheting analysis of piping components}, volume={75}, ISSN={["0308-0161"]}, DOI={10.1016/S0308-0161(98)00070-2}, abstractNote={It is well known that ratcheting (defined as the accumulation of deformation with cycles) can reduce fatigue life or cause failure of piping components or systems subjected to seismic or other cyclic loads. This phenomenon is sometime referred to as fatigue-ratcheting, which is yet to be understood clearly. Commercial finite element codes cannot accurately simulate the ratcheting responses recorded in tests on piping components or systems. One of the reasons for this deficiency has been traced to inadequate constitutive models in the existing analysis codes. To overcome this deficiency, an improved cyclic plasticity model, composed of the Armstrong–Frederick kinematic hardening rule and the Drucker–Palgen plastic modulus equation, is incorporated into an ANSYS material model subroutine. The modified ANSYS program is verified against three sets of experimental results. The simulations from this modified ANSYS show a significant improvement over the unmodified ANSYS and the ABAQUS codes.}, number={8}, journal={INTERNATIONAL JOURNAL OF PRESSURE VESSELS AND PIPING}, author={Hassan, T and Zhu, Y and Matzen, VC}, year={1998}, month={Jul}, pages={643–652} }