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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.

DOI:

10.14359/51727058


Document: 

SP-341-05

Date: 

June 30, 2020

Author(s):

Yu-Chen Ou, Samuel Y.L.Yin, Yi-Qing Liu, and Jui-Chen Wang

Publication:

Symposium Papers

Volume:

341

Abstract:

The use of unstressed Grade 1860 (MPa) seven-wire steel strands as longitudinal reinforcement in columns has the advantage of reducing the cost of steel as compared with conventional Grade 420 (MPa) deformed steel bars. A preliminary experimental study was conducted to investigate the performance of a column with unstressed seven-wire strands as longitudinal reinforcement. Large-scale column specimens were designed and tested using double-curvature lateral cyclic loading under a constant axial load. Test results showed that the column with strands as longitudinal reinforcement (RH1) showed less and wider cracks and less energy dissipation than the column with deformed bars as longitudinal reinforcement (ORH1). Despite this, RH1 showed a slightly higher drift capacity than ORH1 even when the strands used in RH1 had a much lower ultimate strain than the deformed bars used in ORH1.

DOI:

10.14359/51727026


Document: 

SP-341-02

Date: 

June 30, 2020

Author(s):

Sarah De Carufel and Hassan Aoude

Publication:

Symposium Papers

Volume:

341

Abstract:

This paper presents the results from tests examining the blast performance of columns constructed with ultra-high-performance concrete (UHPC) and high-performance reinforcement (high-strength steel or stainless steel). As part of the study six columns with square cross-sections were tested under simulated blast loads using a shock-tube at the University of Ottawa. Parameters investigated include the effects of concrete type, longitudinal reinforcement type and longitudinal reinforcement ratio. The results demonstrate that the use of UHPC increases the blast performance of reinforced concrete columns by increasing blast capacity and improving control of maximum and residual mid-span displacements by an average of 30% and 40%. Substitution of normal-strength bars with high-strength or stainless steel bars in the UHPC columns resulted in further reductions in displacements, which ranged between 18-43% for maximum deformations and 38-66% for residual deformations. The failure mode of all columns with low steel ratio of 1.24% (4 – No.3 bars) was tension bar rupture, regardless of steel type. Increasing the steel ratio from 1.24% to 1.84% (6 –No.3 bars) increased blast capacity and delayed failure. The use of increased amount of stainless steel bars was particularly effective, and transformed the failure mode from bar rupture to fiber pullout. The analytical study confirms that dynamic inelastic SDOF analysis can be used to reasonably predict the blast response of UHPC columns reinforced with varying steel types.

DOI:

10.14359/51727023


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.

DOI:

10.14359/51727020


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.

DOI:

10.14359/51727027


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