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International Concrete Abstracts Portal

Showing 1-5 of 12 Abstracts search results

Document: 

SP341

Date: 

July 17, 2020

Publication:

Symposium Papers

Volume:

341

Abstract:

ACI Committees 441 – Reinforced Concrete Columns and 341A – Earthquake-Resistant Concrete Bridge Columns, Mohamed A. ElGawady Columns are crucial structural elements in buildings and bridges. This Special Publication of the American Concrete Institute Committees 441 (Reinforced Concrete Columns) and 341A (Earthquake-Resistant Concrete Bridge Columns) presents the state-of-the-art on the structural performance of innovative bridge columns. The performance of columns incorporating high-performance materials such as ultra-high-performance concrete (UHPC), engineered cementitious composite (ECC), high-strength concrete, high-strength steel, and shape memory alloys is presented in this document. These materials are used in combination with conventional or advanced construction systems, such as using grouted rebar couplers, multi-hinge, and cross spirals. Such a combination improves the resiliency of reinforced concrete columns against natural and man-made disasters such as earthquakes and blast.


Document: 

SP-341-08

Date: 

June 30, 2020

Author(s):

Ruchin Khadka, Mustafa Mashal, and Jared Cantrell

Publication:

Symposium Papers

Volume:

341

Abstract:

Recently titanium alloy bars (TiABs) have been gaining popularity in civil engineering applications. They offer good deformation capacity, better fatigue performance, high-strength-to-weight ratio, lighter weight (60% that of steel), and excellent corrosion resistance. Recently, TiABs were used in the strengthening of two bridges in Oregon to increase the shear and flexural capacities of the concrete beams. The research in this paper quantifies some common mechanical properties of TiABs using experimental investigation. This is done to explore suitability of the material for wider applications in civil infrastructure. The four types of testing conducted in accordance with ASTM standards included tension, hardness, Charpy V-Notch, and galling tests. Samples of 150 ksi (1034 MPa) high strength steel were also tested for comparison. Test results showed good performance of TiABs. Analytical models are proposed for stress-strain and toughness-temperature relationships.


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-341-01

Date: 

June 30, 2020

Author(s):

Amer Hammoud and Hassan Aoude

Publication:

Symposium Papers

Volume:

341

Abstract:

This paper presents the results from tests examining the performance of high-strength concrete (HSC) and normal-strength concrete (NSC) columns subjected to blast loading. As part of the study six columns built with varying concrete strengths were tested under simulated blast loads using a shock-tube. In addition to the effect of concrete strength, the effects of longitudinal steel ratio and transverse steel detailing were also investigated. The experimental results demonstrate that the HSC and NSC columns showed similar blast performance in terms of overall displacement response, blast capacity, damage and failure mode. However, when considering the results at equivalent blasts, doubling the concrete strength from 40 MPa to 80 MPa (6 to 12 ksi) resulted in 10%-20% reductions in maximum displacements. On the other hand, increasing the longitudinal steel ratio from ρ = 1.7% to 3.4% was found to increase blast capacity, while also reducing maximum displacements by 40-50%. The results also show that decreasing the tie spacing (from d/2 to d/4, where d is the section depth) improved blast performance by reducing peak displacements by 20-40% at equivalent blasts. The use of seismic ties also prevented bar buckling and reduced the extent of damage at failure. As part of the analytical study the response of the HSC columns was predicted using single-degree-of-freedom (SDOF) analysis. The resistance functions were developed using dynamic material properties, sectional analysis and a lumped inelasticity approach. The SDOF procedure was able to predict the blast response of HSC columns with reasonable accuracy, with an average error of 14%. A numerical parametric study examining the effects of concrete strength, steel ratio and tie spacing in larger-scale columns with 350 mm x 350 mm (14 in. x 14 in.) section was also conducted. The results of the numerical study confirm the conclusions from the experiments but indicate the need for further blast research on the effect of transverse steel detailing in larger-scale HSC columns.


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