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International Concrete Abstracts Portal

Showing 1-5 of 268 Abstracts search results

Document: 

SP-341-03

Date: 

June 30, 2020

Author(s):

Hyun-Oh Shin, Hassan Aoude and Denis Mitchell

Publication:

Symposium Papers

Volume:

341

Abstract:

Ultra-high-performance concrete (UHPC) is an innovative material that exhibits high compressive and tensile strength as well as excellent durability. The provision of fibers in UHPC results in improved ductility and increased toughness when compared to conventional high-strength concrete. These properties make UHPC well-adapted for use in the columns of high-rise buildings and heavily-loaded bridges. This paper summarizes the results from a database of tests examining the effects of various design parameters on the axial load performance of UHPC columns. Experimental results illustrating the effects of concrete type (UHPC vs. high-strength and ultra-high-strength concrete), UHPC compressive strength and transverse reinforcement detailing are presented. The results show that the use of UHPC in columns resulted in increased load carrying capacity and post peak ductility when compared to conventional high-strength or ultra-high-strength concrete due to the ability of steel fibers to delay cover spalling. However, greater amounts of confinement reinforcement were required to achieve the same level of axial load performance as the UHPC compressive strength was increased from 150 to 180 MPa. The results also showed that the amount, spacing, and configuration of transverse reinforcement, as well as their interaction significantly affected the axial load response of UHPC columns. However, increasing the amount of transverse reinforcement had the most pronounced effect on post-peak behavior. The effect of the confinement provisions in current codes (CSA A23.3-14 and ACI-318-14) on the ductility of the UHPC columns was also investigated. Based on the results, an alternative confinement expression for achieving ductile behavior in UHPC columns was proposed.


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-339_07

Date: 

March 1, 2020

Author(s):

Tom C. Xia and Doug Lindquist

Publication:

Symposium Papers

Volume:

339

Abstract:

Performance based seismic design (PBSD) has been widely used for tall buildings as a code alternative design method for concrete shear wall structures. However, most PBSD studies are done for buildings taller than 240’ (73 m). Very few studies have been done for buildings shorter than 240’ (73 m) because PBSD is not required for buildings under 240’ (73 m). It is unclear if and how the shear demand increases observed in typical PBSD analysis should be applied to buildings shorter than 240’ (73 m). This study includes two buildings in the Seattle area that are designed per current codes. The study compares the shear demands predicted by the elastic analysis method with the demands predicated by the nonlinear time history analysis used in PBSD method. The intent of this study is to examine the merits of the new Seattle requirement using a factor to amplify the shear demand for buildings designed at code level and for the building height in the range of 160’ (48.8 m) to 240’ (73 m). It also explores the proper factor to be used in ACI 318 to determine the shear wall capacity.


Document: 

SP-339_05

Date: 

March 1, 2020

Author(s):

Sugeng Wijanto, Nelson M. Angel, José I. Restrepo, and Joel P. Conte

Publication:

Symposium Papers

Volume:

339

Abstract:

The rapid development of tall building construction has taken place in Indonesia over the last decade, especially in its capital, Jakarta. Reinforced concrete has been the preferred material of choice used for these buildings because it is economical and is easily handled by local contractors. Along with this rapid development, the Indonesian codes for structural design practices have experienced major changes, following the latest development of USA building design codes and performance-based design guidelines, especially those related to seismic design. This paper describes the latest seismic code in Indonesia and presents the state-of-the-practice for the design of tall buildings there. It also discusses the use of performance-based seismic design as an alternative method of design, considering the risk-targeted maximum and service earthquakes, in the structural design of a tall residential tower in Jakarta.


Document: 

SP-333_07

Date: 

October 1, 2019

Author(s):

Martin Herbrand, Viviane Adam, Josef Hegger

Publication:

Symposium Papers

Volume:

333

Abstract:

Due to increased traffic loads and changes in the code provisions many highway bridges in Germany exhibit deficits in shear capacity according to current codes. The majority of these bridges’ structures comprises continuous concrete beams whose calculatory shear capacity is often exceeded by now. However, the actual shear capacity of prestressed concrete continuous beams is usually underestimated since the design procedures have been derived on the basis of single-span beam tests and neglect significant shear transfer mechanisms. In order to extend the service life of existing bridges, the reserves in the design procedures can be partially taken advantage of by the application of refined design approaches. For this reason, five shear tests on prestressed concrete continuous beams have been performed at the Institute of Structural Concrete of RWTH Aachen University in Germany. Within these tests, the influence of cross-section type (rectangular and I-shaped cross-section), load distribution (concentrated and distributed loads) and the shear reinforcement ratio are investigated. In this paper, the test results of three beams under concentrated loads will be presented.


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