Author: Gabriele Guerrini Publisher: ISBN: 9781321516630 Category : Languages : en Pages : 133
Book Description
This study presents an innovative bridge column technology for application in seismic regions. The proposed technology combines a precast post-tensioned composite steel-concrete hollow-core column with supplemental energy dissipation, in a way to reduce on-site construction burdens and minimize earthquake-induced residual deformations, damage, and associated repair costs. The column consists of two steel cylindrical shells, with high-performance concrete cast in between. Both shells act as permanent formwork; the outer shell substitutes the longitudinal and transverse reinforcement, as it works in composite action with the concrete, whereas the inner shell removes unnecessary concrete volume from the column, prevents concrete implosion, and prevents buckling of energy dissipating dowels when embedded in the concrete. Large inelastic rotations can be accommodated at the end joints with minimal structural damage, since gaps are allowed to open at these locations and to close upon load reversal. Longitudinal post-tensioned high-strength steel threaded bars, designed to respond elastically, in combination with gravity forces ensure self-centering behavior. Internal or external steel devices provide energy dissipation by axial yielding. This dissertation reviews the main principles and requirements for the design of these columns. The experimental findings from two quasi-static reversed cyclic tests are then presented, and numerical simulations of the experimental response are proposed.
Author: Mostafa Tazarv Publisher: ISBN: Category : Columns, Concrete Languages : en Pages : 406
Book Description
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.
Author: Yu-Chen Ou Publisher: ISBN: Category : Languages : en Pages : 255
Book Description
A simplified analytical model for static pushover analysis and a three-dimensional detailed finite element model for cyclic analysis of the proposed bridge columns are developed in this research. In addition, a stiffness degrading hysteretic model is proposed for response-history analysis. With the analytical models, a parametric study is conducted to examine the seismic performance of the proposed columns with different design parameters.
Author: Bryan Kennedy Publisher: ISBN: Category : Languages : en Pages : 300
Book Description
Traditional cast-in-place, concrete bridge construction is often a lengthy undertaking, which is burdensome to the motoring public because of the traffic delays that it causes. Precast construction can accelerate the process by moving fabrication offsite, and then rapidly erecting and connecting bridge components onsite. However, designing connections that are both easy to complete and are robust under seismic loading is challenging. This thesis describes a connection that is intended to meet those criteria, and builds on previous work to do so. Experimental, precast, pre-tensioned specimens developed by Davis et al. (2012) showed good seismic performance, but had significant damage at low drift levels. Adding experimental, ductile materials resulted in less structural damage (Finnsson, 2013), but required unconventional construction materials and awkward fabrication. A new precast, pre-tensioned, column-to-cap beam connection has been developed. The design utilizes (1) unbonded prestressing strands to help the column re-center, (2) bonded reinforcing bars to dissipate energy, (3) a baseplate to permit rigid-body, rocking behavior of the column, and (4) a steel tube to confine the column concrete at the rocking interface. The strands are pre-tensioned when the column is cast, so the connection can be completed without any onsite stressing operations. The connection's seismic performance was evaluated with pseudo-static, cyclic testing of one subassembly. The test results showed that the specimen was stiff at low loads, re-centered well, dissipated energy, and was ductile and durable. Damage to the concrete was negligible and the peak moment strength was measured at drifts exceeding 10%. The system offers a method for achieving accelerated bridge construction that also provides excellent seismic performance and uses only conventional construction materials.
Author: Zachary Benjamin Haber Publisher: ISBN: Category : Electronic books Languages : en Pages : 1224
Book Description
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.
Author: Gabriele Guerrini
Author: Catherine Tucker
Author: Mostafa Tazarv
Author: Yu-Chen Ou
Author: Sarira Motaref
Author: Joshua T. Hewes
Author: Grishma Shrestha
Author: Bryan Kennedy
Author: 
Author: Zachary Benjamin Haber