Engineering Commons^™

Statistics Of Sdf-System Estimate Of Roof Displacement For Pushover Analysis Of Buildings, Anil K. Chopra, Rakesh K. Goel, Chatpan Chintanapakdee

Civil and Environmental Engineering

Investigated in this report is the basic premise that the roof displacement of a multistory building can be determined from the deformation of an SDF system. For this purpose, the response of both systems is determined rigorously by nonlinear response history analysis, without introducing any of the approximations underlying the simplified methods for estimating the deformation of an SDF system (see, e.g., FEMA-273 or ATC-40 guidelines). The statistics of the SDF-system estimate of roof displacement are presented for a variety of building frames and six SAC buildings subjected to ground motion ensembles.

Two sets of structural systems and ground motions …

Determination Of Thickness Of Smooth Geomembranes, Nazli Yesiller, Arif Cekic

Civil and Environmental Engineering

Tests were conducted to determine thickness of smooth, nonreinforced geomembranes using three methods: mechanical (according to ASTM and European standards), ultrasonic, and magnetic methods. The mechanical method is the standard procedure used for determining thickness of geomembranes. The ultrasonic and magnetic methods are not commonly used for geomembranes; however, they are used for testing other materials such as metals. Tests were conducted on 15 geomembranes representing five types of polymers (HDPE, LLDPE, PVC, PP, and EPDM). The results of the testing program indicated that the level of pressures applied affected the thickness measurements in mechanical tests. While the low pressures …

Ultrasonic Pulse Velocity In Concrete Using Direct And Indirect Transmission, Ismail Ozgur Yaman, Gokhan Inci, Nazli Yesiller, Haluk M. Aktan

Civil and Environmental Engineering

The relationship between velocities of ultrasonic stress waves transmitted along direct and indirect paths was investigated. Tests were conducted on plain concrete slabs of dimensions 1000 x 1500 mm, with a thickness of 250 mm. Direct ultrasonic wave transmission tests were conducted between top and bottom surfaces of the slabs and indirect tests were conducted along the slab surface. A test procedure, described in BS 1881 to determine indirect wave velocities, was refined by defining the number and spacing of transducers. Comparisons were made between direct and indirect wave velocity measurements using statistical analysis. The statistical analysis revealed that direct …

Compressive Behavior Of Concrete With Vitrified Soil Aggregate, Shane M. Palmquist, Daniel C. Jansen, Christopher W. Swan

Civil and Environmental Engineering

The compressive behavior of portland cement concrete with vitrified soil coarse aggregate is the focus of this paper. A total of 10 batches of concrete were examined at four different coarse aggregate volume fractions with three different combinations of vitrified and natural coarse aggregates. For comparison purposes, the ratios of cement, water, and fine aggregates were held constant. The stress-strain curves, modulus of elasticity, compressive strength, and Poisson's ratio are examined as a function of coarse aggregate content. Results show a decrease in compressive strength as the volume fraction of vitrified soil aggregate increased. Moduli of elasticity for concrete with …

Evaluation Of Geomembranes Using An Ultrasonic Method, Nazli Yesiller, Sevil Sungur

Civil and Environmental Engineering

An ultrasonic testing procedure was developed to evaluate geomembranes. The pulse-echo inspection technique was used on the surface of geomembranes without disturbing the material. The equipment required consists of a P-wave transducer, a pulser-receiver, and a signal acquisition system. Travel time of ultrasonic waves and waveform energy are measured to evaluate the condition of geomembranes. Laboratory tests were conducted to assess the effectiveness of the method. Defects that simulate installation damage and various in-service degradation conditions were induced on samples. The defects were identified with the ultrasonic method at a success rate higher than 98%. Changes in the thickness or …

Watershed Management Technique To Control Sediment Yield In Agriculturally Dominated Areas, John W. Nicklow, Misgana K. Muleta

Civil and Environmental Engineering

Non-point source pollution is recognized internationally as a critical environmental problem. In Illinois, soil erosion from agricultural lands is the major source of such pollution. The erosion process, which has been accelerated by human activity, tends to reduce crop productivity and leads to subsequent problems from deposition on farmlands and in water bodies. Comprehensive watershed management, however, can be used to protect these natural resources. In this study, a discrete time optimal control methodology and computational model are developed for determining land use and management alternatives that minimize sediment yield from agriculturally-dominated watersheds. The solution methodology is based on an …

Simplified Analysis Of Asymmetric Structures With Supplemental Damping, Rakesh K. Goel

Civil and Environmental Engineering

This study investigated the effects of neglecting off‐diagonal terms of the transformed damping matrix on the seismic response of non‐proportionally damped asymmetric‐plan systems with the specific aim of identifying the range of system parameters for which this simplification can be used without introducing significant errors in the response. For this purpose, a procedure is presented in which modal damping ratios computed by neglecting off‐diagonal terms of the transformed damping matrix are used in the traditional modal analysis. The effects of the simplification are evaluated first by comparing the aforementioned modal damping ratios with the apparent damping ratios obtained from the …

Removing Barriers To High-Strength Concrete In Boston, Daniel C. Jansen, Herman Protze

Civil and Environmental Engineering

No abstract provided.

The Role Of The Journal In Mentoring Students, Harold M. Cota

Civil and Environmental Engineering

No abstract provided.

Stress-Temperature Effects On Peat Compression, James L. Hanson, Tuncer B. Edil, Patrick J. Fox

Civil and Environmental Engineering

Laboratory and field tests have shown that accelerated compression of peat soils occurs in response to moderate heating and an effective overconsolidation is produced on subsequent cooling. This phenomenon has been termed thermal precompression. In this study, long-term laboratory and field tests were conducted to investigate secondary compression behavior of peat as a function of stress and temperature. Stepstress and step-temperature compression tests were conducted on two peat soils. Dramatic effects were observed upon heating and cooling. A field test site in Middleton, Wisconsin, USA was constructed to test the thermal precompression concept for in situ peats. The site contained …

Ultrasonic Assessment Of Stabilized Soils, Nazli Yesiller, James L. Hanson, Mumtaz A. Usmen

Civil and Environmental Engineering

The feasibility of using ultrasonic testing, in particular P-wave velocities, to evaluate stabilized soils was investigated. A high-plasticity clay soil that was stabilized with lime, cement, and lime - fly ash mixtures was used in the study. The testing program consisted of determination of P-wave velocities and compression characteristics of the stabilized soils immediately after compaction and subsequent to 7 days and 28 days of curing. Variation of velocity with stabilizing agent, curing time, and also with the compression characteristics of the soils was investigated. It was observed that P-wave velocities were higher for samples stabilized with cement compared with …

Improved Direct Displacement-Based Design Procedure For Performance-Based Seismic Design Of Structures, Rakesh K. Goel, Anil K. Chopra

Civil and Environmental Engineering

Direct displacement-based design requires a simplified procedure to estimate the seismic deformation of an inelastic SDF system, representing the first (elastic) mode of vibration of the structure. This step is usually accomplished by analysis of an “equivalent” linear system using elastic design spectra. In this paper, an equally simple procedure is developed that is based on the well-known concepts of inelastic design spectra. This procedure provides: (1) accurate values of displacement and ductility demands, and (2) a structural design that satisfies the design criteria for allowable plastic rotation. In contrast, the existing procedure using elastic design spectra for equivalent linear …

Using Genetic Algorithms And Swat To Minimize Sediment Yield From An Agriculturally Dominated Watershed, Misgana K. Muleta, John W. Nicklow

Civil and Environmental Engineering

Non-point source pollution is well recognized as one of the most critical environmental hazards of modern times. In Illinois, non-point source pollution is the major cause of water quality problems, and soil erosion from agricultural lands is the major source of such pollution. Accelerated by anthropogenic activities, soil erosion reduces crop productivity and leads to subsequent problems from deposition on farmlands and in water bodies. Watershed management, however, promotes protection and restoration of these natural resources while allowing for sustainable economic growth and development. In this study a discrete time optimal control methodology and computational model are developed for determining …

Effects Of Supplemental Viscous Damping On Inelastic Seismic Response Of Asymmetric Systems, Rakesh K. Goel

Civil and Environmental Engineering

This paper investigates the effects of supplemental viscous damping on the seismic response of one‐storey, asymmetric‐plan systems responding in the inelastic range of behaviour. It was found that addition of the supplemental damping reduces not only deformation demand but also ductility and hysteretic energy dissipation demands on lateral load resisting elements during earthquake loading. However, the level of reduction strongly depends on the plan‐wise distribution of supplemental damping. Nearly optimal reduction in demands on the outermost flexible‐side element, an element generally considered to be the most critical element, was realized when damping was distributed unevenly in the system plan such …

Direct Displacement‐Based Design: Use Of Inelastic Vs. Elastic Design Spectra, Anil K. Chopra, Rakesh K. Goel

Civil and Environmental Engineering

Direct displacement‐based design requires a simplified procedure to estimate the seismic deformation of an inelastic SDF system, representing the first (elastic) mode of vibration of the structure. This step is usually accomplished by analysis of an “equivalent” linear system using elastic design spectra. In this paper, an equally simple procedure is developed that is based on the well‐known concepts of inelastic design spectra. We demonstrate that the procedure provides the following: (1) accurate values of displacement and ductility demands, and (2) a structural design that satisfies the design criteria for allowable plastic rotation. In contrast, the existing procedure using elastic …

A Modal Pushover Analysis Procedure To Estimate Seismic Demands For Buildings: Theory And Preliminary Evaluation, Anil K. Chopra, Rakesh K. Goel

Civil and Environmental Engineering

The principal objective of this investigation is to develop a pushover analysis procedure based on structural dynamics theory, which retains the conceptual simplicity and computational attractiveness of current procedures with invariant force distribution, but provides superior accuracy in estimating seismic demands on buildings.

The standard response spectrum analysis (RSA) for elastic buildings is reformulated as a Modal Pushover Analysis (MPA). The peak response of the elastic structure due to its nth vibration mode can be exactly determined by pushover analysis of the structure subjected to lateral forces distributed over the height of the building according to s^*_n = …

Enhanced Biodegradation Of Hydrocarbon Contaminants Using Photocatalytic Pretreatment, Chad E. Green, Anita Stansberry, Jeff Sczechowski, Yarrow Nelson

Civil and Environmental Engineering

Photocatalysis was investigated as a pretreatment for hydrocarbon groundwater contamination at an abandoned oil field in Guadalupe, CA. A laboratory photoreactor, with a UV fluorescent lamp submerged in a suspension of TiO₂ catalyst particles, was used to determine oxidation rates and the increase in biodegradability of the hydrocarbon mixture. Chemical oxidation demand (COD) and 5-day biological oxygen demand (BOD₅) were measured as a function of exposure time using standard methods. During eight-hour photoreactor runs in a nitrogen atmosphere, the COD of diluent solutions in de-ionized water and diluent solutions in simulated groundwater both decreased by approximately 50%, …