Zhoudao Lu

Efficiency of Externally Bonded L-Shaped FRP Laminates in Strengthening Reinforced-Concrete Interior Beam-Column Joints

AbstractThis study investigated the efficiency of externally bonded L-shaped fiber-reinforced polymer (FRP) laminates in strengthening seismically damaged reinforced concrete (RC) interior joints. Ten ½-scale interior beam-column joints, including two reference specimens, were constructed and then damaged under simulated cyclic lateral loads. In addition to repairing visual cracks with epoxy injections, four of eight specimens were strengthened with externally bonded L-shaped carbon fiber–reinforced polymer (CFRP) laminates and the rest were strengthened with basalt fiber–reinforced polymer (BFRP) laminates. Retesting after retrofitting showed that the average peak strength of the CFRP-strengthened and BFRP-strengthened specimens increased by approximately 20 and 10%, respectively. The two strengthening systems also clearly enhanced the deformability of the specimens. Further analysis indicated strength increase was controlled by the end debonding of FRP laminates near critical sections of the specimens, ...

Mechanical Characteristics of Ultra High Performance Strain Hardening Cementitious Composites

Ultra high performance engineered cementitious composites (UHP-ECC) combines the strain-hardening and multiple crack characteristics and the high strength of mortar matrix. The tensile strength and elongation of the UHP-ECC was around 20 MPa and 8.7%, respectively. The ultra-high-molecular-weight polyethylene fibers were utilized to reinforce the ultra high strength mortar. The tensile stress-strain curves, the compressive strength and elastic modulus, and the flexural behavior of UHP-ECC were investigated to understand its mechanical performance.

Average Fracture Energy for Crack Propagation in Postfire Concrete

Wedge-splitting tests of postfire concrete specimens were carried out in the present research to obtain the load-displacement curves. Ten temperatures varying from room temperature to 600°C were employed. In order to calculate the accurate fracture energy, the tails of load-displacement curves were best fitted using exponential and power functions. Three fracture energy quantities (fracture energy , stable fracture energy , and unstable fracture energy ) with their variation tendency and their mutual relationship were determined to predict energy consumption for the complete fracture propagation. Additionally, the stable fracture work was also calculated. All these fracture parameters sustain an increase-decrease tendency which means that the fracture property of postfire concrete shares the same tendency.