Concrete Olympics: Design, Construction, Evaluation, and Repair of Concrete Bridges and Structures with Members of the ACI, KCI, TCI, and FIB, Part 3 of 4
Korea Concrete Institute
Taiwan Concrete Institute
International Federation for Structural Concrete
The special sessions present recent advances in the design, construction, evaluation, and repair of concrete structures and materials with an emphasis on international perspectives with members from four major concrete institutes around the globe: the American Concrete Institute (ACI), Korea Concrete Institute (KCI), Taiwan Concrete Institute (TCI), and International Federation for Structural Concrete (FIB). Presentations encompass a variety of technical aspects such as the refined analysis and assessment techniques of concrete members, damage detection and mitigation, seismic behavior, durability performance, and repair/strengthening of constructed structures. Both experimental and analytical investigations are of interest. The sessions bring to light state-of-the-art knowledge and provide an opportunity to discuss current challenges and technical demands. Critical information will be provided to those who lead tomorrow’s structural design, construction, evaluation, and repair, including practicing engineers, government officials, and academics.
(1) Define current trends in concrete research;
(2) Recognize the practical aspect of seismic resistance;
(3) Assess the need for developing specifications;
(4) Disseminate cutting-edge research and practice in the concrete engineering community.
This session has been AIA/ICC approved for 2 CEU/PDH credits.
Optimum Content of Polycarboxylate Ester for Dispersion of Multiwalled Carbon Nanotube and its Effect on Properties of Cement Paste
Presented By: Chul-Woo Chung
Affiliation: Pukyong National University
Description: Polycarboxylate ester (PCE) has been used as a dispersing agent of carbon nanotube (CNT) to enhance mechanical properties of cementitious composites. Most of literature reported the increase in mechanical properties by use of CNT, but there were other reports that showed negative impact on mechanical strength. The reason for reduction in mechanical strength was mostly attributed to poor dispersion of CNT within cementitious composites. However, according to the results from our previous works, air entrainment associated with overdose of PCE (for better dispersion of CNT) was found to be another key reason for reduction in mechanical properties of cementitious composites. This work discusses up-to-date progress on optimal content required for dispersion of MWCNT on properties of cement paste, depending on changes in dispersion procedure, method and surface functionalization of MWCNT.
Effect of Stiffness on Drift Response of Reinforced Concrete Structures Subjected to Seismic Demands
Presented By: Aishwarya Puranam
Affiliation: National Taiwan University
Description: A large volume of research has been conducted recently in Taiwan and the United States to expand the scope of use of high-strength steel reinforcement (HSSR) in reinforced concrete (RC) structures in seismic areas. In addition to making room for further design innovation, the use of HSSR would help reduce rebar congestion and as a result it would lead to reduction in longitudinal reinforcement ratios and therefore post-cracking stiffness. The implication of this reduced post-cracking stiffness needs to be considered with respect to the response of structures to earthquakes as past research has shown that controlling drift (or displacement) of a structure is key to controlling the damage it experiences. The objective of this research project is to investigate through large-scale experiments the drift response of RC moment frames with conventional- and high-strength steel reinforcement with a focus on the effect of post-cracking stiffness.
Two ‘full-scale’ two-story RC moment-frames (C1, H1) shall be subjected to a series of scaled ground motion records on the earthquake simulator at NCREE Tainan Laboratory in Taiwan. The specimens are two stories tall (each with a height of 3.15 m) and consist of one bay spanning 6 m in the direction of ground motion. The grade of longitudinal reinforcement in specimen C1 is SD 420 and it is SD 685 in specimens H1. The nominal cross-sectional dimensions of the beams (35 cm x 40 cm) and columns (50 cm x 50 cm) are the same in both specimens and the reinforcement is proportioned such that they have similar base shear strengths. The tests are being conducted on the earthquake simulator at NCREE Tainan and they are currently underway.
Applied Research of Highly-Flowable Strain Hardening Fiber Reinforced Concrete on New RC Building System
Presented By: Wen-Cheng Liao
Affiliation: National Taiwan University
Description: The purpose of Taiwan New RC project is aimed to reduce the member section sizes and increase the available space of high-rise buildings by using high strength concrete (f’c > 70 MPa) and high strength reinforcement (fy > 685 MPa). Material consumptions can be further saved thanks to the upgrade of material strengths. However, the ductile nature under compression turns to brittle in high strength concrete. In term of additional transverse reinforcement to ensure the member ductile, an alternative is application of Highly flowable strain hardening fiber reinforced concrete (HF-SHFRC). HF-SFRC has excellent workability in the fresh state and exhibits the strain-hardening and multiple cracking characteristics of high-performance fiber reinforced cementitious composites (HPFRCCs) in its hardened state. This paper presents development and design recommendations of critical New RC members made of HF-SHFRC. Previous test results show that the HF-SHFRC perform as well as specimens with intensive transverse reinforcements regarding failure mode, ductility, energy dissipation and crack width control. HF-SHFRC offers opportunities to significantly simplify the design and assure construction qualities while ensuring adequate ductility and damage tolerance. The proposed design equations of flexural strength, shear strength, strut strength and confinement for base columns, beam-column joints and D-regions made of HF-SHFRC are also provided.
High-Frequency Diffuse Wave Techniques for Evaluation of Concrete Structures and Materials
Presented By: Myoungsu Shin
Description: To evaluate distributed micro-cracking damage in concrete, many researchers recently have focused on techniques based on high-frequency (200 kHz to 1 MHz) incoherent content of the signal that is set up by multiple scatter of the propagating ballistic wave in concrete rather than techniques based on conventional analysis of propagating ballistic wave pulses. Despite these research efforts, the viability of diffuse ultrasound techniques to characterize, in a reliable and practical fashion, the extent of micro-cracking damage in concrete has yet to be to established. Firstly, one barrier to progress in this regard is the ability to create concrete test samples with realistic, controlled and known volumes of distributed micro-cracking that would enable careful and quantifiable experiments to be carried out. Secondly, the effects of transducer spacing on diffuse wave measurements in concrete have not been examined in a quantitative manner. Thirdly, the effects of moisture content in concrete on diffuse wave parameter also have not been studied, yet. Fourth, some issues in the application on in-situ concrete members: long measurement time from multiple locations (owing to the need for spatial averaging) with detachment and reattachment of sensors should be improved. Therefore, overall studies on the aforementioned issues on diffuse-wave techniques for the evaluation of concrete structures and materials were presented.
Risk Management of State-Controlled Transportation Highway Concrete Assets
Presented By: Wael Zatar
Affiliation: Marshall University
Description: Federal and state transportation agencies face a multitude of challenges to effectively maintain cost-effective core maintenance programs for managing a safe, yet sustainable transportation assets’ program. The decision-making process involves several risk factors, and the prioritization of these factors could considerably affect both the level of utilization of these assets, as well as affect the short- and long-term management protocols and plans for these organizations. This study primarily focuses on demonstrating the relationship between environmentally influenced risk management and sustainable maintenance programs of state-controlled transportation highway concrete assets. Several key parameters including risk assessment, maintenance programs and protocol, innovative and sustainable materials, longevity, financial model cost-benefit, financial risk and organizational behavior will be addressed.
Defining Material Properties and Testing Requirements for FRP Strengthening of Bridges
Presented By: Scott Arnold
Affiliation: FYFE Co LLC
Description: The application of fiber reinforced polymer (FRP) composites to strengthen bridge components was initiated by Caltrans in the 1980s based on testing at the University of California at San Diego. The characterization of the material properties was initially conducted by the Aerospace Corporation as they worked with Caltrans on the prequalification of several FRP systems. As the industry has evolved there has been several different methods used to characterize the design properties of FRP materials. There are systems that report the “dry fiber” properties while others have reported the “net fiber area” properties. Today it is more common to see the “gross laminate” properties, but even this method has various approaches, and it has led to more confusion and inconsistencies in the industry. This presentation will review the various ASTM methods (i.e., D3039, D7565 & D7290) and compare how they are referenced by guidelines such as ACI 440.2R and AASHTO Guide Specifications. The presentation will provide suggested wording and details to attempt to “level the field” and give designers the confidence that they are using consistent and reliable properties.