Seismic Performance of Bridge Column-pile-shaft Pin Connections for Application in Accelerated Bridge Construction

Seismic Performance of Bridge Column-pile-shaft Pin Connections for Application in Accelerated Bridge Construction
Author: Mehrdad Mehraein
Publisher:
Total Pages: 1468
Release: 2016
Genre: Electronic books
ISBN:

Bridges with integral superstructures are common in high-seismic regions. The superstructure and substructure are connected using rigid connections in these bridges. However, hinge or “pin” connections may be used to connect columns to pile-shafts to reduce the overall force demand in the integral bridges, leading to smaller and more economical foundations. Additionally, prefabrication of structural elements facilitates accelerated bridge construction (ABC), which could improve the quality and economy of project compared to cast-in-place (CIP). The primary objectives of this research were to investigate the seismic performance of three types of bridge bent connections: (1) pipe-pin connections at column-pile shaft joints for CIP and precast constructions (2) rebar-pin connections at column-pile shaft joint for CIP and precast constructions, and (3) pocket connections to develop rigid joints between precast columns and precast pier caps. This research was comprised of experimental and analytical studies. The experimental portion of the study was conducted on a shake table at the Earthquake Engineering Laboratory at the University of Nevada, Reno including two 1/3.75 scale, two-column bents subjected to seismic loadings. The cap beam in each bent was precast and connected to the columns using pocket details. The pin connections were used to connect the columns to pedestals, which simulated the pile-shafts. The column-pedestal joints were formed using pipe-pins in one bent and rebar-pin in the other bent. The available details of pin connections were modified for utilizing in the bents because the tensile force transfer mechanism and pile-shaft failure modes had not been accounted for in the current practices. A proposed ABC method for pin connections was investigated by constructing one column in each bent as a precast shell filled with self-consolidating concrete (SCC), whereas the other column was CIP. Furthermore, engineered cementitious composite (ECC) was incorporated in one column plastic hinge region of each bent to explore the effects of ECC on the seismic performance of the columns. The shake table experiments confirmed that the proposed design methods meet the safety and performance requirements of the codes under seismic loadings. The analytical studies consisted of: (1) simple stick models for the pin connections that were developed for the bents as design tools, (2) nonlinear finite element (FE) models for the pin connections in OpenSEES that can be utilized for global analysis of bridges with pin connections, and (3) elaborate nonlinear FE models of the bent with pipe-pins using ABAQUS to investigate the microscopic performance and interactions of the components. The analytical models were evaluated based on their correlation with experimental data and were subsequently used in focused parametric studies to address the gaps in the experimental results and provide more insight into the pin behavior under various conditions. Lastly, design procedures and detailing recommendations for column-pile-shaft connections using pipe-pins and rebar-pins were developed and proposed based on the results of the experimental and analytical parametric studies.

Application of Accelerated Bridge Construction Connections in Moderate-to-High Seismic Regions

Application of Accelerated Bridge Construction Connections in Moderate-to-High Seismic Regions
Author:
Publisher: Transportation Research Board
Total Pages: 65
Release: 2011
Genre: Technology & Engineering
ISBN: 0309213436

TRB’s National Cooperative Highway Research Program (NCHRP) Report 698: Application of Accelerated Bridge Construction Connections in Moderate-to-High Seismic Regions evaluates the performance of connection details for bridge members in accelerated bridge construction in medium-to-high seismic regions and offers suggestions for further research.

Drilled Shaft Socket Connections for Precast Columns in Seismic Regions

Drilled Shaft Socket Connections for Precast Columns in Seismic Regions
Author: Hung Viet Tran
Publisher:
Total Pages: 167
Release: 2015
Genre:
ISBN:

A new type of connection between a precast concrete column and a drilled shaft has been developed for Accelerated Bridge Construction (ABC) in regions of moderate or high seismicity. This connection can be built quickly and allows generous placement tolerances. Three quasi-static tests of connections between a precast bridge column and a drilled shaft were performed (1) to investigate the seismic performance of this connection, and (2) to calibrate a new design methodology. The test specimens represented the most critical geometry in which the difference between the diameters of the shaft and column was minimized. Large-scale, lateral-load tests to a drift ratio of 10% showed that, if adequate confining steel is included in the splice zone, the plastic hinging mechanism forms in the column, without inducing damage in the splice or shaft. If the confinement is insufficient, the strength of the splice zone deteriorates rapidly with cyclic loading. A new design methodology, based on a strut-and-tie model of the transition region, allows the designer to proportion the connection to limit the strains in the connection transverse reinforcement.

Experimental and Analytical Seismic Studies of Bridge Piers with Innovative Pipe Pin Column-footing Connections and Precast Cap Beams

Experimental and Analytical Seismic Studies of Bridge Piers with Innovative Pipe Pin Column-footing Connections and Precast Cap Beams
Author: Ali Mehrsoroush
Publisher:
Total Pages: 1518
Release: 2014
Genre: Electronic books
ISBN:

The use of prefabricated structural elements is an integral part of many accelerated bridge construction (ABC) efforts. Connections of these prefabricated elements to the rest of the structural system is critical to the performance of the structure under service loads and extreme events such as earthquakes. Two types of novel joints were developed in this study: 1) base pipe pin connections to substantially reduce the moment transfer between the column and footing, and 2) pocket connections to provide structural continuity at column-cap beam joints. The pipe pin consists of two steel pipes to transfer shear and a tension member to transfer uplift forces. Pocket connection is formed by extending the column into a pre-fabricated pocket in a precast cap beam and grouting the space between the column segment and the pocket. The primary objective of this research was to investigate the seismic performance, response, and behavior of base pipe pins for both cast-in-place (CIP) and precast construction, to study the performance of column-cap beam pocket connections to be utilized in ABC, and to develop a reliable design guideline for base pipe pins. This research was comprised of comprehensive experimental and analytical studies. The experimental portion of the study was conducted at the University of Nevada, Reno Large Scale Structural Laboratory including three sets of tests: 1) cyclic loading test of a large-scale two-column bent model, and 2) two direct pull tests of CIP and precast pipe pin connections. The bent model was composed of a precast engineered cementitious composite (ECC)-concrete column, a conventional CIP reinforced concrete column, a precast cap beam, and two single footings. The columns were connected to the footing and cap beam utilizing pipe pin and pocket connections, respectively. Direct pull tests were carried out to investigate the failure mode of the pipe pins under direct tension and determine the ultimate tensile capacity of the pins. The proposed pipe pin connections were found to be successful even under high drift ratios. Test results revealed that pipe pins needs to be designed for shear forces that exceed the column design shear due to reversed friction under large base rotations. Direct pull tests of the pipe pins showed that the dominant failure mode of the connection under pure tension was rupture of the tension member and all the other connection elements remained damage free. The pocket connection using corrugated steel pipes with a column embedment length of 1.2 times the column diameter performed well in forming the plastic hinge when conventional concrete was used in the embedded region. However, longitudinal bars in the precast column with embedded ECC debonded at 4% drift ratio. The analytical study consisted of 1) elaborate finite element (FE) modeling of the pipe pin connections and footings under direct tension, 2) FE study of the two-column bent, and 3) analytical modeling of pipe embedded in the footing (pipe shear key). ABAQUS and OpenSees were used in the analyses. The analytical models were evaluated based on correlation with experimental data, and were then used to investigate the effects of different parameters on the seismic performance of pipe pins. Results of the parametric studies along with the experimental observations led to an iterative procedure to determine seismic demands and methods for designing pipe pins. This was followed by development of design and detailing methods and illustrative examples.

Next Generation of Bridge Columns for Accelerated Bridge Construction in High Seismic Zones

Next Generation of Bridge Columns for Accelerated Bridge Construction in High Seismic Zones
Author: Mostafa Tazarv
Publisher:
Total Pages: 406
Release: 2014
Genre: Columns, Concrete
ISBN:

Longitudinal bar debonding allowed spread of yielding and prevented premature failure of reinforcements in UHPC-filled duct connections and grouted coupler column pedestal. The SMA-reinforced ECC column showed superior seismic performance compared to a conventional column in which the plastic hinge damage was limited to only ECC cover spalling even under 12% drift ratio cycles. The column residual displacements were 79% lower than CIP residual displacements on average due to the superelastic NiTi SMA longitudinal reinforcement, and higher base shear capacity and higher displacement capacity were observed. The analytical modeling methods were simple and sufficiently accurate for general design and analyses of precast components proposed in the present study. The proposed symmetrical material model for reinforcing NiTi superelastic SMA was found to be a viable alternative to the more complex asymmetrical model.

Precast Column-footing Connections for Accelerated Bridge Construction in Seismic Zones

Precast Column-footing Connections for Accelerated Bridge Construction in Seismic Zones
Author: Zachary Benjamin Haber
Publisher:
Total Pages: 1224
Release: 2013
Genre: Electronic books
ISBN:

Accelerated bridge construction (ABC) has become increasingly popular in the eyes of state and federal transportation agencies because of its numerous advantages. To effectively execute ABC projects, designers utilize prefabricated structural elements that can be quickly assembled to form functional structural systems. It is advantageous to the bridge designer if these systems emulate the design and behavior of conventional cast-in-place systems. If this can be achieved, typical analysis and design procedures can be used. The difficulty with developing emulative systems is usually encountered in the design and detailing of connections. Substructure connections are particularly critical in seismic zones because they must dissipate energy through significant cyclic nonlinear deformations while maintaining their capacity and the integrity of the structural system. The research presented in this dissertation focused on developing and evaluating earthquake resistant connections for use in accelerated bridge construction. The project was comprised of three main components; testing of five large-scale precast reinforced concrete column models, a series of individual component tests on mechanical reinforcing bar splices, and extensive analytical studies. Column studies included the design and construction of five half-scale bridge column models that were tested under reversed slow cyclic loading. Four new moment connections for precast column-footing joints were developed each utilizing mechanical reinforcing bar splices to create connectivity with reinforcing bars in a cast-in-place footing. Two different mechanical splices were studied: an upset headed coupler and grout-filled sleeve coupler. Along with the splice type, the location of splices within the plastic hinge zone was also a test variable. All column models were designed to emulate conventional cast-in-place construction thus were compared to a conventional cast-in-place test model. Results indicate that the new connections are promising and duplicate the behavior of conventional cast-in-place construction with respect to key response parameters. However, it was discovered that the plastic hinge mechanism can be significantly affected by the presence of splices and result in reduced displacement ductility capacity. In order to better understand the behavior of mechanical splices, a series of uniaxial tests were completed on mechanically-spliced reinforcing bars under different loading configurations: monotonic static tension, dynamic tension, and slow cyclic loading. Results from this portion of the project also aided the development of analytical models for the half- and prototype-scale column models. Results indicated that, regardless of loading configuration, specimens failed by bar rupture without damage to the splice itself. The analytical studies conducted using OpenSEES included development of microscope models for the two mechanical reinforcing bars splices and full analytical models of the five half-scale columns, which were both compared with respective experimental results to validate the modeling procedures and assumptions. Prototype-scale analytical models were also developed to conduct parametric studies investigating the sensitivity of the newly developed ABC connections to changes in design details. In general, the results of this study indicate that the newly develop ABC connections, which utilize mechanically-spliced connections, are suitable for moderate and high seismic regions. However, emulative design approaches are not suitable for all of the connections develop. A set of design recommendations are provided to guide bridge engineers in the analysis and design of these new connections.

Seismic Performance of Column-to-drilled-shaft Connections in Reinforced Concrete Bridges

Seismic Performance of Column-to-drilled-shaft Connections in Reinforced Concrete Bridges
Author: Michelle Teng Chang
Publisher:
Total Pages: 248
Release: 2021
Genre:
ISBN:

Drilled shaft foundations are often used to support reinforced concrete bridge columns founded in soft soils or in locations where a small footprint is desired. Increasingly, the shaft is being built with a diameter larger than that of the column, to allow tolerance in the column placement and to facilitate plastic hinge formation in the column rather than in the shaft. The column-shaft connection, which involves a noncontact splice between the column and shaft bars, is a key component in this structural system. However, there is limited research on the behavior of these connections under seismic loads. In order to understand the force-transfer mechanism of column-shaft connections under seismic loading, one quasi-static cyclic experimental test was conducted on a column-shaft subassembly. Measured results were compared with those from three previous experiments performed at the University of Washington. The study found that the amount of shaft transverse reinforcement in the connection region was critical in determining the failure mode of the connection. In specimens with relatively low amounts of transverse reinforcement, including the specimen tested during this study and a previous specimen tested at the University of Washington, the connection failed through a shaft prying failure mode; the specimens developed large vertical cracks between the confined column core and the annular shaft transition region, and the shaft transverse reinforcement eventually fractured at large drift ratios. Therefore, three methodologies for detailing the shaft transverse reinforcement were evaluated, and a new analysis procedure using a strut-and-tie model was proposed. It is consistent with the measured and observed performance of the tested connections, and is applicable to shafts supporting either precast or cast-in-place columns. The new procedure allows engineers to more accurately predict the behavior of a column-shaft connection and prevent an undesirable below-ground failure in the shaft transition region. Lastly, a set of design equations based on the strut-and-tie findings and existing design models is proposed for use in practice.