Experimental Evaluation of P-Y Curves Considering Liquefaction Development
Author: Chang, Barbara University of California, San Diego Hutchinson, Tara C University of California, San Diego | Size: 10.08 MB | Format:PDF | Quality:Unspecified | Publisher: University of California, San Diego | Year: 2010 | pages: 98
This report presents details and findings of a test series conducted on a single pile embedded in homogeneous saturated Nevada sand, which was subjected to sequential dynamic shaking and lateral (inertial-equivalent) loading. This report documents the model test design and construction, details regarding the loading protocol, test observations and post test results. A key goal in the test program was to develop a data set capable of rendering insight into the characteristics of ’p-y’ resistance under developing liquefied soil conditions. While evidence in the literature indicates that this resistance is reduced as excess pore pressure increases, the shape and amplitude of how the reduced p-y curve develops during pore pressure build-up are needed for reliable design of pile foundations in areas prone to earthquake-induced soil liquefaction. Analyses of the experimental data show that mobilization of the partially liquefied soil was achieved during lateral loading. Additional data were evaluated including wave test measurements (hammer strikes to model), settlement, and acceleration measurements. Results presented focus importantly on the static p-y curves backcalculated from the bending moment distributions at the achieved excess pore pressures. A rich set of test data was produced from this testing series, which will be useful for model validation and subsequent design efforts.
Code:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
A special class of seismically isolated bridges shares a common feature in that both ends of the superstructure are restrained and isolators over the columns of bridge uncouple the superstructure from the ground motions. They are defined as partial isolation bridges. From measured acceleration responses, the effectiveness of full seismic isolation had been confirmed widely. However, the seismic isolation behavior in the partial isolation has not been widely observed. The effectiveness of partial isolation is evaluated in this study. The static design procedures for linear and nonlinear partially isolated bridges are developed. Results from the static analysis of linear and nonlinear partially isolated bridges, compared with conventional and fully isolated bridges, demonstrate that the effectiveness of nonlinear partial isolation is close to full isolation for reducing the yield force and displacement of the columns in some parameter ranges. However, increased displacement demands at the abutments are observed. Nonlinear time history analyses of the different bridge models under earthquake excitations are carried out to investigate the accuracy of the design procedure for nonlinear partial isolation. In addition, an example shows the application of nonlinear partial isolation to a practical bridge.
Code:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
Geophysical Testing of Rock and Its Relationships to Physical Properties
Author: Tran, Khiem T | Size: 6.27 MB | Format:PDF | Quality:Unspecified | Publisher: University of Florida, Gainesville | Year: 2011 | pages: 190
Testing techniques were designed to characterize spatial variability in geotechnical engineering physical parameters of rock formations. Standard methods using seismic waves, which are routinely used for shallow subsurface investigation, have limitations in characterizing challenging profiles at depth that include low-velocity layers and embedded cavities. This research focuses on overcoming these limitations by developing two new methods using both sensitive data and a global inversion scheme. The first method inverts combined surface and borehole travel times for a wave velocity profile. The technique is based on an extremely fast method to compute first-arrival times through the velocity models. The capability of this inversion technique is tested with both synthetic and real experimental data sets. The inversion results show that this technique successfully maps 2-D velocity profiles with high variation. The inverted wave velocities from real data appear to be consistent with cone penetration test (CPR), geotechnical borings, and standard penetration test (SPT) results. The second method inverts full waveforms for a wave velocity profile. The strength of this approach is the ability to generate all possible wave types and, thus, to simulate and accurately model complex seismic wave fields that are then compared with observed data to deduce complex subsurface properties. The capability of this inversion technique is also tested with both synthetic and real experimental data sets. The inversion results from synthetic data show the ability of detecting reverse models that are hardly detected by traditional inversion methods that use only the dispersion property of Rayleigh waves. The inversion results from the real data are generally consistent with crosshole, SPT N-value, and material log results. Employed for site characterization of deep foundation design, the techniques can provide credible information for material at the socket and partially detect anomalies near the socket. Lastly, based upon a laboratory testing program conducted on rock cores, it does appear that relationships between geophysical measurements and geotechnical engineering design parameters are credible, though significant scatter does exist in the data. It could be postulated that geophysical measurements should be capable of identifying large zones of poor quality rock, and the results can provide characterization of spatial variability in geotechnical engineering physical parameters useful in the design of deep foundations.
Code:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
This report documents the findings and lessons learned from the February 27, 2010, M8.8 offshore Maule earthquake in Chile. Fewer than 0.15 percent of the bridges in Chile’s inventory, most built after 1995, collapsed or suffered damage that rendered them useless. Many spans of precast prestressed discontinuous girder bridges with continuous decks fell off their supports, probably due to significant in-plane rotation of the superstructure as a result of severe shaking. Lateral steel stoppers used to provide both vertical and lateral restraints on girders were largely unsuccessful due to their inadequate connection detail to cap beams and abutments. Reinforced concrete shear keys performed well as fuses limiting the transfer of excessive seismic loads from the superstructure to the foundation of bridges even though they could be optimized for maximum energy dissipation as part of the lateral restraint system at the bottom flange of girders. Vertical seismic bars were widely used to restrain the vertical motion of decks, and they also performed well. Bridge substructures (foundation, column, and cap beam) generally behaved satisfactorily except for two columns that suffered shear failure due to ground settlement and lateral spreading. All mechanically stabilized earth walls exceeded the expected performance.
Code:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
Effects of ground motion spatial variations and random site conditions on seismic responses of bridge structures
Author: Bi, K | Size: 1.92 MB | Format:PDF | Quality:Unspecified | Publisher: The University of Western Australia | Year: 2011 | pages: 204
The research carried out in this thesis concentrates on the modelling of spatial variation of seismic ground motions, and its effect on bridge structural responses. This effort brings together various aspects regarding the modelling of seismic ground motion spatial variations caused by incoherence effect, wave passage effect and local site effect, bridge structure modelling with soil-structure interaction (SSI) effect, and dynamic response modelling of pounding between different components of adjacent bridge structures. In the first part of this thesis (Chapters 2-4), a stochastic method is adopted and further developed to study the seismic responses of bridge structures located on a canyon site. In this approach, the spatially varying ground motions are modelled in two steps. Firstly, the base rock motions are assumed to have the same intensity and are modelled with a filtered Tajimi- Kanai power spectral density function and an empirical spatial ground motion coherency loss function. Then, power spectral density function of ground motion on surface of the canyon site is derived by considering the site amplification effect based on the one-dimensional seismic wave propagation theory. The influence of SSI is also examined (in Chapter 4) by modelling the soil surrounding the pile foundation as frequency-dependent springs and dashpots in the horizontal and rotational directions. A method is proposed to simulate the spatially varying earthquake ground motion time histories at a canyon site with different soil conditions. This method takes into consideration the local site effect on ground motion amplification and spatial variations.
Code:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
Seismic Behavior and Design of Segmental Precast Post-Tensioned Concrete Piers
Author: Dawood, Haitham ElGawady, Mohamed Washington State University, Pullman Cofer, William Washington State University, Pullman | Size: 7.37 MB | Format:PDF | Quality:Unspecified | Publisher: Transportation Northwest Regional Center | Year: 2011 | pages: 142
Segmental precast column construction is an economic environmental friendly solution to accelerate bridge construction in the United States. Also, concrete-filled fiber reinforced polymer tubes (CFFT) represents a potential economic solution for durability issues in the bridge industry. Combining the segmental precast and CFFT will result in a rapid durable construction system. The proposed research will build on recent work by the principal investigator (PI), where he experimentally investigated the seismic behavior of tens single-column and two-column bents constructed using precast post-tensioned CFFT. The columns were constructed by stacking precast CFFT segments one on top of the other and then post-tensioned using unbonded tendons. Two specimens had external energy dissipation devices and another two specimens had neoprene in the joints between the CFFT segments. The neoprene significantly reduced the seismic displacement demand. The columns re-centered upon the conclusion of the test resulting in minimal residual displacement, which represents, in the case of a real strong earthquake, a huge advantage since the post-earthquake repair measures will be minimal. 3-D finite element models were developed by the PI to predict the performance of the single-column under monotonic lateral loads. The main objective of this proposal is to improve and expand the capabilities of these finite element models to produce design recommendations. In particular, the models will be expanded to include dynamic loading, two-column bents, and the neoprene in the joints. Including dynamic loading in the model is essential to quantify the energy dissipation due to rocking of the columns segments. The output of this research will be recommendations on the optimum construction characteristics of the system including the segment height/column diameter ratio, neoprene thickness and hardness, external energy dissipater requirements, and post-tensioning force level. The proposed research will develop a durable environmental friendly rapid construction bridge system, which has low life-cycle costs, construction waste, noise, traffic disruption, and initial construction cost. In addition, the developed system will has high work zone safety, efficient use of construction material, a short construction time, and improved constructability. The proposed construction system will not have a leakage of wet concrete into waterways leading to pollution of water and harm migrating fish. Finally, when the proposed construction system is fully developed and implemented in construction, it will reduce the expense of bridge replacement, repair, and continuous operation interruption after earthquakes.
Code:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
Evaluation of Nondestructive Methods for Determining Pavement Thickness
Author: Snyder, Rick Vander Werff, J R Thiemann, Zach Sritharan, Sri | Size: 4.36 MB | Format:PDF | Quality:Unspecified | Publisher: Edwards, Lulu | Year: 2011 | pages: 105
The U.S. Army Engineer Research and Development Center was tasked by the U.S. Air Force to evaluate emerging nondestructive thickness measuring devices to determine their ability to accurately estimate the pavement surface thickness without requiring large footprint equipment or repairs. Companies with products using nondestructive technology were down-selected to participate in a study requiring them to estimate the thickness of 40 asphalt and concrete locations with nondestructive devices. For each of the different pavement types, a single core was extracted to provide vendors with calibration points. Vendors provided initial thickness estimates, and upon receiving the calibration core thicknesses, vendors provided final thickness estimates. The results were compared to determine the accuracy and feasibility of the devices tested. Among the devices tested were ground penetrating radar sensors, sensors for wave propagation methods (sonic, seismic, and vibration), falling weight deflectometers, and borescopes.
Code:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
Seismic Performance of an I-Girder to Inverted-T Bent Cap Connection
Author: Snyder, Rick Vander Werff, J R Thiemann, Zach Sritharan, Sri | Size: 10.83 MB | Format:PDF | Quality:Unspecified | Publisher: Iowa State University, Ames | Year: 2011 | pages: 306
California Department of Transportation (Caltrans) current design practice assumes that connections between precast I-girders and inverted-T bent caps will degrade in a seismic event, making the precast girder option for seismic bridges inefficient. A prototype I-girder to inverted-T bent cap bridge and a 50% scale test unit was designed in order to investigate the behavior of the as-built girder-to-cap connection region. Analysis of test results shows that the current I-girder to inverted-T bent cap bridge connection is capable of acting as a fully continuous connection for both positive and negative moments during both gravity and seismic loading, contrary to the design assumptions stated in Caltrans’ Seismic Design Criteria. The improved connection detail demonstrated the ability to ensure a fully continuous moment connection between the I-girders and inverted-T bent cap. Both connection details also exhibited a significant moment resistance beyond what was expected during the vertical load test although the as-built connection eventually failed under positive moments at moderate to large displacements.
Code:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
Author: A Murali Krishna | Size: 5.93 MB | Format:PDF | Quality:Unspecified | Publisher: Indian Institute of Technology Guwahati | Year: 2012 | pages: 135
India has emerged as one of the fastest growing economies in the world. Various new infrastructure projects are under progress across the country especially in Northeast India. Geotechnical engineering is the first and most important aspect of any infrastructure project and urban development. Over the years many new trends were being developed and practiced in terms of analysis, design and construction of geotechnical structures and associated site investigations. These trends occurred in site investigation, laboratory testing and analysis, design methods and designs, ground improvement methods, geoenvironmental applications, utilisation of waste byproducts, predicting soil behaviour, dealing with underground structures and offshore geotechnical structures, earthquake related problems and designs, construction methods under challenging situations, etc. These workshop proceedings present some of the emerging trends in geotechnical engineering practice and research activities. The chapters of this book cover and present some of the ongoing trends in analyses of ground improvement methods, utilisation of waste products, ground stabilisations, ground response analyses of rock structures, foundation treatments, designs and analysis, and geoenvironmental challenges and applications, along with construction trends for roads under challenging conditions.
Code:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
Seismic Design Considerations, Volume I: Technical Approaches and Results and Volume II: Appendices II - VIII
Author: Agrawal, Anil K City College of New York of the City University of New York Liu, Huabei Imbsen, Roy A Imbsen Consulting Zong, Xin | Size: 40.96 MB | Format:PDF | Quality:Unspecified | Publisher: New Jersey Department of Transportation | Year: 2012 | pages: 604
New Jersey Department of Transportation (NJDOT) has adopted “AASHTO Guide Specifications for LRFD Seismic Bridge Design” approved by the Highway Subcommittee on Bridges and Structures in 2007. The main objective of research presented in this report has been to resolve the following issues for an effective implementation of American Association of State Highway and Transportation Officials (AASHTO) Guide Specifications: (i) AASHTO Guide Specifications don’t provide any specific guidelines for classification and performance requirements for critical bridges. This issue is resolved by proposing performance requirements and classification criteria for critical bridges in New Jersey. (ii) Guide Specifications present displacement based approach, which is significantly different than the force-based approach in previous versions of seismic guidelines. Nine examples of reinforced concrete and steel bridges of different characteristics (spans, skew, etc.) illustrating the use of newly adopted seismic guide specifications have been developed for training of engineers in New Jersey. (iii) NJDOT maintains an extensive electronic database of soil boring logs for the State of New Jersey. A zip-code based soil site map for New Jersey has been developed by analyzing soil boring data and other available New Jersey soil information. This map can be used for a rapid seismic hazard evaluation for the entire state or for a network of bridges in the state. (iv) AASHTO Guide Specifications introduce seismic design categories based on local seismicity and soil properties. Using the seismic soil map and zip code based seismic spectra provided in the AAHSTO Guide Specifications, seismic design category maps for critical and standard bridges in New Jersey have been developed. A detailed analysis has also been carried out to develop liquefaction potential maps for the state of New Jersey. These maps can be used to determine the need for a detailed liquefaction analysis for a particular bridge site. A detailed guideline on developing site-specific spectra has also been developed, since AASHTO Guide Specifications recommend site-specific spectra for critical bridges. (v) Existing bridges in New Jersey are required to be retrofitted on the basis of the 2006 Edition of the “Seismic Retrofitting Manual for Highway Structures: Part 1 – Bridges”. Simplified guidelines for seismic retrofit of existing bridges, that are consistent with guidelines for the design of new bridges in AASHTO Guide Specifications, have been developed.
Code:
***************************************
Content of this section is hidden, You must be registered and activate your account to see this content. See this link to read how you can remove this limitation:
![[Image: 25754346092418962558.png]](https://pic.civilea.com/images/25754346092418962558.png)
![[Image: info.png]](http://postgen.civilea.com/icon/info.png){kind=icon}
![[Image: download.png]](http://postgen.civilea.com/icon/download.png){kind=icon}
![[Image: 41575673479658890313.png]](https://pic.civilea.com/images/41575673479658890313.png)
![[Image: 09783890736099764289.png]](https://pic.civilea.com/images/09783890736099764289.png)
![[Image: 24156947604699967370.png]](https://pic.civilea.com/images/24156947604699967370.png)
![[Image: 97955458175661126828.png]](https://pic.civilea.com/images/97955458175661126828.png)
![[Image: 27128989834939147981.png]](https://pic.civilea.com/images/27128989834939147981.png)
![[Image: 13838199451541364785.png]](https://pic.civilea.com/images/13838199451541364785.png)
![[Image: 50207771583635871482.png]](https://pic.civilea.com/images/50207771583635871482.png)
![[Image: 69139852632096345555.png]](https://pic.civilea.com/images/69139852632096345555.png)