Dynamic responses of reinforced ultra-high performance concrete members under low-velocity lateral impact

2021 ◽  
Vol 150 ◽  
pp. 103818
Author(s):  
P.C. Jia ◽  
H. Wu ◽  
R. Wang ◽  
Q. Fang
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Dynamic Responses ◽  
Lateral Impact ◽  
Ultra High Performance Concrete ◽  
Low Velocity ◽  
Concrete Members

Flexural design of precast, prestressed ultra-high-performance concrete members

PCI Journal ◽  
2020 ◽  
Vol 65 (6) ◽  
pp. 35-61
Author(s):  
Chungwook Sim ◽  
Maher Tadros ◽  
David Gee ◽  
Micheal Asaad
Keyword(s):  
Prestressed Concrete ◽  
High Performance ◽  
High Performance Concrete ◽  
Limit State ◽  
Design Guidelines ◽  
Design Tool ◽  
Supplementary Cementitious Materials ◽  
Ultra High Performance Concrete ◽  
Concrete Members ◽  
Cylinder Strength

Ultra-high-performance concrete (UHPC) is a special concrete mixture with outstanding mechanical and durability characteristics. It is a mixture of portland cement, supplementary cementitious materials, sand, and high-strength, high-aspect-ratio microfibers. In this paper, the authors propose flexural design guidelines for precast, prestressed concrete members made with concrete mixtures developed by precasters to meet minimum specific characteristics qualifying it to be called PCI-UHPC. Minimum specified cylinder strength is 10 ksi (69 MPa) at prestress release and 18 ksi (124 MPa) at the time the member is placed in service, typically 28 days. Minimum flexural cracking and tensile strengths of 1.5 and 2 ksi (10 and 14 MPa), respectively, according to ASTM C1609 testing specifications are required. In addition, strain-hardening and ductility requirements are specified. Tensile properties are shown to be more important for structural optimization than cylinder strength. Both building and bridge products are considered because the paper is focused on capacity rather than demand. Both service limit state and strength limit state are covered. When the contribution of fibers to capacity should be included and when they may be ignored is shown. It is further shown that the traditional equivalent rectangular stress block in compression can still be used to produce satisfactory results in prestressed concrete members. A spreadsheet workbook is offered online as a design tool. It is valid for multilayers of concrete of different strengths, rows of reinforcing bars of different grades, and prestressing strands. It produces moment-curvature diagrams and flexural capacity at ultimate strain. A fully worked-out example of a 250 ft (76.2 m) span decked I-beam of optimized shape is given.

Fire-Damage or Freeze-Thaw of Strengthening Concrete Using Ultra High Performance Concrete

2009 ◽  
Vol 79-82 ◽  
pp. 2047-2050 ◽  
Author(s):  
Min Gin Lee ◽  
Yi Shuo Huang
Keyword(s):  
High Temperature ◽  
High Performance ◽  
High Performance Concrete ◽  
Fire Damage ◽  
Ultra High Performance Concrete ◽  
Freeze Thaw ◽  
Concrete Members ◽  
Repair Materials ◽  
Environmental Durability ◽  
Temperature Exposure

There are some reinforced concrete structures exposed to severe environmental conditions might require maintenance or strengthening. Many of these severe circumstances are the result of extreme climate conditions such as low temperature, freeze–thaw action, fire attack, and exposure to deicing salts. Because of this, the environmental durability of both the repair materials and methods used in rehabilitation applications are of utmost importance. A small fire can reach 250°C, while a common blaze can easily produce temperatures of around 800°C. In major conflagrations the temperature can even reach 1100°C. At this level, the heat affects most materials, provoking the spontaneous combustion of some of them and affecting the resistance of others. However, very little research has been performed in evaluating the environmental durability of strengthening materials for concrete members. Very little work has been done on the effects of freeze–thaw cycling on bonding and repair materials. In this study, ultra high performance concrete (UHPC) was used to investigate the effect of strengthening concrete members by fire-damage test or freeze-thaw test. The results show that the mechanical properties of UHPC possess high strength, toughness, and freeze-thaw resistance. The CFRP (carbon fiber reinforced plates) wrapping specimens exposed at 300 °C showed totally failure with the deterioration of the adhesive. The UHPC with bonding 10 mm thickness specimens exposed at 400 °C and duration of 1 hour still in good shape. The UHPC with 1-cm or 2-cm thickness on strengthening concrete members could be obtained specific retrofit effects. The performance of UHPC specimens is better than those of CFRP wrapping specimens during high temperature exposure. The results of slant shear tests show that the bond strength of PC/PC, UHPC/PC and UHPC/UHPC decreased significantly after 600 freeze–thaw cycles or high temperature exposure.

Experimental and Numerical Investigation of the Polyurea-Coated Ultra-High-Performance Concrete (UHPC) Column under Lateral Impact Loading

2021 ◽  
Author(s):  
Bin Gao ◽  
Jun Wu ◽  
Pengcheng Jia ◽  
Shutao Li ◽  
Qiushi Yan ◽  
...  
Keyword(s):  
Axial Force ◽  
Impact Loading ◽  
High Performance ◽  
Shear Failure ◽  
High Performance Concrete ◽  
Impact Resistance ◽  
Fe Model ◽  
Strengthening Effect ◽  
Lateral Impact ◽  
Ultra High Performance Concrete

It was found that polyurea coating could improve the integrity and the corresponding durability of the structural components. However, the strengthening effect of polyurea coatings for structures built with emerging ultra-high-performance concrete (UHPC) is still unknown due to the lack of studies. Therefore, this paper investigated the effect of the polyurea coating on the lateral impact resistance of UHPC columns through a combined numerical and experimental study. A total of five specimens were fabricated, including two UHPC columns and three UHPC columns with polyurea coating. To better characterize the structural response under dynamic loading, impact cases with different drop weight impact heights and axial force ratios were employed. The results showed that the UHPC column with polyurea coating exhibited superior lateral impact resistance compared to the UHPC column. The presence of the axial force increased the lateral impact stiffness and further reduced the deflection of the specimen. In contrast, the polyurea coating improved the specimen’s ductility and mitigated the peak impact force, thereby maintaining the specimen’s integrity without sudden shear failure. A three-dimensional finite element (FE) model of polyurea-coated UHPC columns under impact loading was then established and confirmed the experimental results. With the validated FE model, an intensive parametric study was conducted to investigate the effects of polyurea thickness, axial force ratio and impact energy on the lateral impact resistance of the UHPC column. The presence of the polyurea coating could significantly improve the lateral impact resistance of the specimen, thereby preventing the shear failure of the UHPC column, and thus, the effective thickness of the polyurea layer for the UHPC column was determined to be 2–6[Formula: see text]mm. The outcome of this research demonstrates the great merits of polyurea coating in improving the ductility and integrity of the UHPC column under lateral impact loading.

Sign in / Sign up

Export Citation Format

Share Document