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Full-Text Articles in Engineering
Seismic Response Of Asymmetric Systems: Energy-Based Approach, Rakesh K. Goel
Seismic Response Of Asymmetric Systems: Energy-Based Approach, Rakesh K. Goel
Civil and Environmental Engineering
An energy-based approach has been used to investigate the seismic behavior of code-designed asymmetric-plan systems. The systems considered in this investigation had large eccentricities in both directions, were designed for bidirectional earthquake loading, and their responses were computed with both components of ground motion acting simultaneously. The presented results demonstrate that the total input energy is about the same whether the system plan is symmetric or asymmetric. Furthermore, flexible-side elements in asymmetric- plan systems may be more vulnerable to earthquakes than the same elements in symmetric-plan systems if they are not designed to accommodate the higher hysteretic-energy demands. This observation …
Period Formulas For Moment-Resisting Frame Buildings, Rakesh K. Goel, Anil K. Chopra
Period Formulas For Moment-Resisting Frame Buildings, Rakesh K. Goel, Anil K. Chopra
Civil and Environmental Engineering
Most seismic codes specify empirical formulas to estimate the fundamental vibration period of buildings. Evaluated first in this paper are the formulas specified in present U.S. codes using the available data on the fundamental period of buildings "measured" from their motions recorded during eight California earthquakes, starting with the 1971 San Fernando earthquake and ending with the 1994 Northridge earthquake. It is shown that, although the code formulas provide periods that are generally shorter than measured periods, these formulas can be improved to provide better correlation with the measured data. Subsequently, improved formulas for estimating the fundamental periods of reinforced …
Earthquake Characteristics Of Bridges With Integral Abutments, Rakesh K. Goel
Earthquake Characteristics Of Bridges With Integral Abutments, Rakesh K. Goel
Civil and Environmental Engineering
Earthquake analysis of bridges requires that the period and damping ratio be determined for each significant mode of vibration. Data on these vibration properties, identified from motions of bridges recorded during actual earthquake events, provide the most direct means of verifying and improving the current guidelines. Thus, the aim of this investigation was to measure the vibration properties of a two-span concrete bridge from its motions recorded during actual earthquake events. These data were then used to investigate how abutment participation affected the vibration properties of bridges with integral abutments. It is shown that the vibration period elongated and the …
Field Evaluation Of Ultrasonic Method For Assessing Well Seals, Nazli Yesiller, Craig H. Benson, Tuncer B. Edil
Field Evaluation Of Ultrasonic Method For Assessing Well Seals, Nazli Yesiller, Craig H. Benson, Tuncer B. Edil
Civil and Environmental Engineering
Field tests were conducted in three boreholes using an ultrasonic testing method to evaluate its ability to assess contact between the seal and riser (casing). The ultrasonic method is used inside the riser without disturbing the riser, seal, or formation soil. The risers were 50-mm-diameter (2-inch) Schedule 40 steel pipes that are used for ground water monitoring wells. Different types of seals were placed around the risers and defects were purposely introduced in the seals to test the ultrasonic method. The ultrasonic response changed as the neat-cement seals cured or hydration of the bentonite seals changed. When adequate moisture was …
Studying Initiation And Growth Of Shear Cracks In Reinforced Concrete Beams Using Full-Field Digital Imaging, Daniel C. Jansen, Sokhwan Choi, Surendra P. Shah
Studying Initiation And Growth Of Shear Cracks In Reinforced Concrete Beams Using Full-Field Digital Imaging, Daniel C. Jansen, Sokhwan Choi, Surendra P. Shah
Civil and Environmental Engineering
The mechanisms which lead to shear failure of longitudinally reinforced concrete beams are complex and often misunderstood. In this paper, a combination of a special closed loop test technique and machine vision are applied to tests on two reinforced concrete beams failing in shear: one made of normal strength concrete and the second of high strength concrete. To control the progression of the shear crack, a closed-loop test technique was devised and employed such that the crack propagation was stable even during the post peak. To locate the crack and to measure the crack displacements, machine vision, a nondestructive measuring …
Environmental Engineering Design, Harold M. Cota, Samuel A. Vigil
Environmental Engineering Design, Harold M. Cota, Samuel A. Vigil
Civil and Environmental Engineering
This paper outlines the capstone environmental engineering design course that has been used effectively at California Polytechnic State University. Senior level students work in teams on a multi-media industrial problem. The experience involves literature review, problem formulation, proposal writing, time management, technical and economic analysis and an oral and written presentation of the results. Feedback from alumni and employers has been positive.
Energy Based Approach To Earthquake Response Of Asymmetric Systems, Rakesh K. Goel
Energy Based Approach To Earthquake Response Of Asymmetric Systems, Rakesh K. Goel
Civil and Environmental Engineering
No abstract provided.
Evaluation Of Code Period Formula For Concrete Mrf Buildings, Rakesh K. Goel, Anil K. Chopra
Evaluation Of Code Period Formula For Concrete Mrf Buildings, Rakesh K. Goel, Anil K. Chopra
Civil and Environmental Engineering
The empirical formula specified in US building codes for fundamental vibration period of concrete moment resisting frame buildings is evaluated using periods of buildings measured from their strong motion records. The presented results show that the current code formula may lead to fundamental periods that are much shorter than the measured periods. In order to obtain better correlation between measured and computed periods, regression analysis technique has been used. The results indicate that the value of C, in the current code formula should be increased from its present value of 0.030 to 0.035.
Permeability Study Of Cracked Concrete, Kejin Wang, Daniel C. Jansen, Surendra P. Shah, Alan F. Karr
Permeability Study Of Cracked Concrete, Kejin Wang, Daniel C. Jansen, Surendra P. Shah, Alan F. Karr
Civil and Environmental Engineering
Cracks in concrete generally interconnect flow paths and increase concrete permeability. The increase in concrete permeability due to the progression of cracks allows more water or aggressive chemical ions to penetrate into the concrete, facilitating deterioration. The present work studies the relationship between crack characteristics and concrete permeability. In this study, feedback controlled splitting tests are introduced to generate crack width-controlled concrete specimens. Sequential crack patterns with different crack widths are viewed under a microscope. The permeability of cracked concrete is evaluated by water permeability tests. The preliminary results indicate that crack openings generally accelerate water flow rate in concrete. …
Ultrasonic Method For Evaluation Of Annular Seals For Wells And Instrument Holes, Nazli Yesiller, Tuncer B. Edil, Craig H. Benson
Ultrasonic Method For Evaluation Of Annular Seals For Wells And Instrument Holes, Nazli Yesiller, Tuncer B. Edil, Craig H. Benson
Civil and Environmental Engineering
An ultrasonic testing method employing the pulse-echo inspection technique was developed to assess the integrity of annular seals surrounding casings (i.e., instrument tubes or well casings). This nondestructive testing method permits testing a seal from inside a casing without disturbing the casing, seal, or formation. Seals constructed with cement-based and bentonite-based sealants surrounding various types and sizes of casings can be evaluated using the method. An evaluation is conducted by sending and receiving ultrasonic waves using a single piezoelectric transducer and commercially available hardware (a pulser receiver and a waveform analyzer). A probe was designed and constructed for downhole testing. …
Evaluation Of Bridge Abutment Capacity And Stiffness During Earthquakes, Rakesh K. Goel, Anil K. Chopra
Evaluation Of Bridge Abutment Capacity And Stiffness During Earthquakes, Rakesh K. Goel, Anil K. Chopra
Civil and Environmental Engineering
The “actual” capacity and stiffness values of the abutment‐soil systems at the US 101/Painter Street Overpass, determined from its earthquake motions, are used to investigate how abutment stiffness varies during earthquakes and to evaluate current modeling procedures. It is found that the “actual” abutment stiffness may be significantly different during different phases of the shaking and decreases significantly as the abutment deformation increases. The CALTRANS modeling procedure leads to a good estimate of the transverse abutment stiffness and capacity. However, this procedure may overestimate the normal abutment stiffness and capacity by a factor of over two, indicating that the assumed …
Effect Of Length On Compressive Strain Softening Of Concrete, Daniel C. Jansen, Surendra P. Shah
Effect Of Length On Compressive Strain Softening Of Concrete, Daniel C. Jansen, Surendra P. Shah
Civil and Environmental Engineering
The concept of localization during the postpeak of compressive strain softening is presented. To explore localization in compression, a feedback-control method using a linear combination of displacement and force that partially subtracts the elastic response of the specimen to give a stable feedback signal is used. Results are presented from two test series (45 and 90 MPa) that use this method to test cylinders with length-to-diameter ratios ranging from 2.0 to 5.5. It is shown that compression failure is in fact a localized phenomenon. The compressive fracture energy is divided into energy dissipated in the prepeak and the postpeak portions …
Assessment Of Cased-Borehole Seals Using An Ultrasonic Method, Nazli Yesiller, Craig H. Benson, Tuncer B. Edil, James Klima
Assessment Of Cased-Borehole Seals Using An Ultrasonic Method, Nazli Yesiller, Craig H. Benson, Tuncer B. Edil, James Klima
Civil and Environmental Engineering
Tests were conducted in Wisconsin from 1994 through 1996 in several boreholes using an ultrasonic method that was developed at the University of Wisconsin-Madison to assess the integrity of annular seals. Initially, three model boreholes simulating monitoring wells were installed to evaluate the effectiveness of the ultrasonic method. Different types of seals were placed around the casings and defects were purposely introduced in the seals to test the ultrasonic method. The ultrasonic method was effective for detecting the presence of different types of seals and defects and also the changes in the condition of seals with time. Then tests were …