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International Concrete Abstracts Portal

Showing 1-5 of 889 Abstracts search results

Document: 

SP-341-10

Date: 

June 30, 2020

Author(s):

Royce Liu and Alessandro Palermo

Publication:

Symposium Papers

Volume:

341

Abstract:

Structural redundancy and robustness are necessary to protect against beyond design seismic loads. In this paper, the idea of improving these properties is applied to single column bridge piers using the hybrid PRESSS/Dissipative Controlled Rocking (DCR) system through a novel technique called hierarchical activation. This technique involves the inclusion of more “hinges” (rocking interfaces) and or sets of dissipative devices in such a way that they are activated in a hierarchy with respect to the displacement of the structure. A 2/3 scale cantilever column designed to use this technique was tested. The specimen was capable of multiple configurations, two of which are focused on in this paper: conventional DCR; and segmented DCR (segDCR), which used hierarchical activation. Hierarchical activation was successfully achieved in the experiment; and despite the global response being similar, segDCR was found to be advantageous with respect to reducing the cyclic strain demand on the dissipaters.


Document: 

SP-341-11

Date: 

June 30, 2020

Author(s):

Ahmed Ibrahim, Sabreena Nasrin, and Riyadh Hindi

Publication:

Symposium Papers

Volume:

341

Abstract:

The spiral reinforcement is a special detailing technique used for reinforcing columns in regions of high seismic activities because of its ability in energy absorption and ductility. In this paper, the results of the experimental testing on cross spiral confinement in reinforced concrete columns are presented. The experimental results were verified by nonlinear finite element analysis as well as an analytical model. The developed analytical model was based on the octahedral stress criterion and compared with other models available in the literature. In the Finite element model, the concrete damage plasticity and steel yielding criterion were used in the constitutive equations. The finite element showed very good prediction of the ultimate load and failure strain for various spiral reinforcement ratios. Analytical stress-strain models have been developed and compared to the experiment results in the literature and found work well in predicting the columns behavior under monotonic axial loads. The authors see that the proposed technique is a very good potential of industry implementation and provides a more seismic resiliency to structures.

Such detailing technique could be used as a mitigation system for columns in high seismic zones.


Document: 

SP-341-04

Date: 

June 30, 2020

Author(s):

Mahmoud Aboukifa, Mohamed A. Moustafa and Ahmad Itani

Publication:

Symposium Papers

Volume:

341

Abstract:

Ultra-High Performance Concrete (UHPC) is a versatile building material as it is characterized by very high compressive strengths reaching 30 ksi [200 MPa], ductile tensile characteristics, and energy absorption. Currently, UHPC is commonly used in limited structural applications, such as joints and connections between precast structural elements. To extend the use of UHPC in full structural elements, a better understanding of the structural behavior and failure mechanism of such elements is needed. One potential application of UHPC for structural elements is columns, which is the focus of this study. This paper presents an experimental investigation of the behavior of UHPC column subjected to combined axial and lateral loading. A large-scale UHPC column is tested under axial and quasi-static cyclic lateral loading at the Earthquake Engineering Laboratory at the University of Nevada, Reno. To establish a comparison with conventional columns, a normal strength concrete (NSC) column with same dimensions and design as the tested UHPC column is analytically modeled and analyzed under similar loading protocol using OpenSEES. The experimental response of the UHPC column is evaluated and compared to the analytical response of the NSC column. Both global and local behavior are presented and discussed to include damage progression, failure type, peak moment strength, stiffness degradation, and displacement and curvature ductility.


Document: 

SP-341-06

Date: 

June 30, 2020

Author(s):

Mostafa Tazarv and M. Saiid Saiidi

Publication:

Symposium Papers

Volume:

341

Abstract:

Current seismic codes prevent bridge collapse under strong earthquakes. For conventional reinforced concrete (RC) bridges, this performance objective is usually achieved through confinement of ductile members such as columns. When an RC bridge column undergoes large displacements, its reinforcement yield and sometimes buckle, the cover concrete spalls, and the core concrete sometimes fail. Damage of reinforcement and core concrete is not easy to repair. Advanced materials and new technologies are emerging to enhance the seismic performance of RC bridge columns by reducing damage, increasing displacement capacities, and/or reducing permanent lateral displacements. Two types of advanced materials, shape memory alloy (SMA) bars and engineered cementitious composite (ECC), are the focus of the present study. SMA bars are viable reinforcement for concrete structures since they resist large stresses with minimal residual strains. Furthermore, ECC, which is a type of fiber-reinforced concrete, shows significant tensile strain capacities with minimal damage. SMA-reinforced ECC bridge columns are ductile with minimal damage and insignificant residual displacements under extreme events. A displacement-based design method for NiTi superelastic SMA-reinforced ECC bridge columns is proposed based on large-scale experimental and extensive analytical studies. A summary of the proposed guidelines, background information, and supporting studies are presented for this novel column type to facilitate field deployment. Finally, the details of the world first SMA-reinforced ECC bridge constructed in Seattle, USA, is discussed.


Document: 

SP-341-07

Date: 

June 30, 2020

Author(s):

Maher AL-Hawarneh, AHM Muntasir Billah, and M. Shahria Alam

Publication:

Symposium Papers

Volume:

341

Abstract:

In recent years, shape memory alloys (SMA) have drawn significant attention and interests among researchers and structural engineers for diverse civil engineering applications. Superelasticity, shape memory effect, and hysteretic damping are the three major characteristics of SMAs that make them appropriate for bridge engineering applications in high seismic zones. Recent earthquake events have shown the most devastating earthquake loading that structures could experience are the near-fault ground motions. On the other hand, the ground motion duration effect on structural response has attracted a lot of interest over the last decade. This study aims to evaluate the comparative seismic fragility of concrete bridge piers reinforced with SMA rebars and steel rebars in the plastic hinge region under long duration and near-fault earthquakes. The bridge pier is assumed to be part of a lifeline bridge located in Western Canada and has been designed following a performance-based design approach. Fragility analysis has been conducted considering uncertainty in the material properties and the seismic hazard of the site location. Fragility curves are developed using suits of long duration and near-fault motions where each suite contains 20 ground motions. The vulnerability of the SMA-RC bridge piers and steel-RC bridge piers has been evaluated in terms of maximum drift and residual drift as the demand parameters. The outcome of this study indicates how the performance of the SMA-RC bridge pier and steel-RC bridge pier are affected by the duration of ground motion and fault location.


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