Michael D. Symans

Buried high-density polyethylene pipelines subjected to normal and strike-slip faulting — a centrifuge investigation

Permanent ground deformation is arguably the most severe hazard for continuous buried pipelines. This paper presents results from two pairs of centrifuge tests designed to investigate the differences in behavior of buried high-density polyethylene pipelines subjected to normal and strike-slip faulting. The tests results show that, as expected, the pipeline behavior is asymmetric under normal faulting and symmetric under strike-slip faulting. In the case of strike-slip faulting, the soil–pipe interaction pressure distribution is symmetric with respect to the fault. However, in the case of normal faulting, there is a pressure concentration close to the fault trace on the up-thrown side, with much lower soil–pipe interaction pressures at other locations on the pipe. The soil–pipe interaction force versus deformation relationship (i.e., the p–y relationship) was obtained based on the experimental data. The p–y relationships for both the strike-slip and normal faulting cases were also compared with the relatio...

Numerical Modeling of Buried HDPE Pipelines Subjected to Normal Faulting: A Case Study

A systematic study is presented herein on the seismic response of buried pipelines subjected to ground fault rupture in the form of normal faulting. In this study, advanced computational simulations are conducted in parallel with physical testing using a geotechnical centrifuge. For the numerical simulations, the pipeline was modeled using isotropic 3-D shell elements and the soil was modeled using either 1-D spring elements or 3-D solid (continuum) elements. The results from continuum finite-element analyses are compared with those from a Winkler-type model (in which the pipe is supported by a series of discrete springs) and with results from centrifuge tests. In addition, via appropriate modeling of the soil-pipe interaction, the q-z relation of the soil medium is elucidated for normal faulting events. The numerical analysis results demonstrate the potential for continuum modeling of events that induce pipe-soil interaction and results in improved understanding of pipe-soil interaction under normal faulting.

Analytical and Numerical Study of a Smart Sliding Base Isolation System for Seismic Protection of Buildings

The seismic response of a single-story steel building frame with a smart base isolation system is evaluated. The isolation system consists of sliding bearings combined with an adaptive fluid damper. The damping capacity of the fluid damper can be modulated in real time based on feedback from the earthquake ground motion and superstructure response. The adaptive capabilities of the fluid damper enable the isolation system displacement to be controlled while simultaneously limiting the inter-story drift response of the superstructure. This paper concentrates on the development of analytical models of the smart isolation system and control algorithms for operation of the system. In general, the results front numerical simulations demonstrate that, for disparate earthquake ground motions, the smart isolation system is capable of simultaneously limiting both the response of the isolation system and the superstructure.

Base Isolation and Supplemental Damping Systems for Seismic Protection of Wood Structures: Literature Review

This paper provides a literature review on the application of base isolation and supplemental damping systems for seismic protection of wood structures. The review reveals that both elastomeric bearings and sliding bearings have been considered for implementation within base isolation systems of wood-framed buildings. In addition, friction dampers, viscoelastic dampers, hysteretic dampers, and fluid viscous dampers have been considered for implementation within the framing of wood buildings. Although there are a number of impediments to the widespread implementation of such advanced seismic protection systems, the reviewed literature clearly demonstrates that advanced seismic protection systems offer promise for enabling light-framed wood structures to resist major earthquakes with minimal damage.

Earthquake Faulting Effects on Buried Pipelines – Case History and Centrifuge Study

Permanent ground deformation (PGD) is one of the most damaging hazards for continuous buried lifelines. This hazard is especially severe when the PGD results in net compression in the pipe. In that case, buckling of pipe material can occur. If buckling is moderate, deformation of the pipe cross-section can lead to flow restriction and high friction losses, and eventually require line replacement. If buckling is severe, high localized strains can lead to pipe rupture, loss of contents, and possible pollution of surrounding soil. In this article, centrifuge tests of buried pipelines subject to abrupt ground failure in the form of surface faulting are presented. The fault movement results in mostly compression in the pipe. The test results are compared with a case history of pipe failure in the 1999 Izmit, Turkey earthquake and also with the results from the centrifuge tests which result in net tension in the pipe. The experimental setup, procedures, and instrumentation are described in detail. Suggestions for design practice are offered based on the analysis of results from both the 1999 Izmit case history and the centrifuge modeling.

Numerical Modeling of Buried HDPE Pipelines Subjected to Strike-Slip Faulting

A systematic study of buried pipeline response to strike-slip faulting was performed wherein advanced computational simulations were conducted in parallel with a series of physical tests employing split-boxes within the geotechnical centrifuge at Rensselaer Polytechnic Institute and the full-scale testing facility at Cornell University. This article describes the numerical modeling and simulations of the experimental tests. The buried pipeline and the surrounding soil are modeled using nonlinear beam (shell) elements and elasto-plastic springs distributed along the pipeline, respectively. Using the finite element method, reasonable predictions are obtained for the axial and bending strain distributions measured during the tests. It is also shown that finite element analysis using pipe beam elements and a modified soil spring model can accurately predict the pipeline seismic behavior due to strike-slip fault rupture, especially when the pipe is subjected to combined bending and tension. In addition, existing closed-form solutions are evaluated.

Seismic Behavior of Wood-framed Structures with Viscous Fluid Dampers

The suitability of viscous fluid dampers for seismic protection of light-framed wood buildings is investigated in this paper. Nonlinear finite-element models of wood building components (shear wall) and systems (three-dimensional buildings) are developed and numerical analyses are performed to evaluate their response to seismic loading. For both the single wall and the building system, seismic protection is provided by installing viscous fluid dampers within the wall cavities. The results of the numerical analyses demonstrate the ability of fluid dampers to dissipate a significant portion of seismic input energy, reducing the inelastic strain energy demand on the wood framing system. In addition, the study revealed some important practical issues associated with implementation of fluid dampers within light wood-framed buildings.

Performance Evaluation of Negative Stiffness Devices for Seismic Response Control of Bridge Structures via Experimental Shake Table Tests

A newly developed passive device that provides negative stiffness has been implemented within a quarter-scale highway bridge model and subjected to seismic loading via shake table testing. Details of the experimental results and their comparison with numerical simulations under a wide range of ground motions are presented. In addition, performance indices were developed to systematically evaluate the relative performance of different isolation system configurations that employ combinations of positive and negative stiffness as well as various levels of damping. Further, the influence of boundary conditions (rigid versus flexible bridge piers) on the effectiveness of employing negative stiffness devices has been evaluated.

Current Directions of Structural Health Monitoring and Control in USA

Structural Health Monitoring (SHM) is an important and growing field in civil engineering. The goal of SHM techniques is to identify, quantify and locate damage in structures. In light of the aging infrastructure and recent failures of important bridges, long-term monitoring techniques are being increasing investigated and adopted. In addition to SHM, structural control (SC) is increasingly adopted in modern structures around the world. In the past two decades a number of SC techniques, including, passive, semi-active, and active control methods have been developed and adopted in civil engineering–particularly, in infrastructure such as important tall buildings, critical facilities, and long span bridges. Both SHM and SC technology face significant challenges due to the size and scale of civil engineering structures. In response of these challenges researchers in the U.S.A and around the world have developed new and innovative techniques.This paper summarizes some of the ongoing research in the U.S.A. in the area of monitoring, damage detection and control in civil engineering structures.

Experimental Seismic Performance Evaluation of a Full-Scale Woodframe Building

This paper discusses the on-going shake table testing program on a full-scale two-story woodframe townhouse building conducted within the NSF/NEES-funded NEESWood Project. The test building represents the worlds largest woodframe structure tested on a shake table. The size and weight of the test structure required the simultaneous use of the two tri-axial shake tables in the Structural Engineering and Earthquake Simulation Laboratory at the University at Buffalo. The testing program is focusing on the various construction elements that may have significant influence on the seismic response of woodframe buildings and that should be considered in performance-based seismic design. This paper focuses on the effects of gypsum wallboard finishes. The results obtained so far indicate that the influence of gypsum wallboard finishes applied to the interior surfaces of structural (load bearing) walls substantially improved the seismic response of the test building. On the other hand, the same gypsum wallboard wall finishes applied to interior partition walls had no beneficial effect on the seismic response of the test building because of the lack of structural connections between those partition walls and adjacent floor and roof diaphragms.