抄録
In this study, creep tests for cast-in-place anchor, inorganic-type post-installed bonded anchor and organic-type post-installed bonded anchor were conducted using deformed bar D13.
The inorganic-type anchor contained ultra-rapid hardening cement, sand, and other materials in a cartridge. As for the construction procedure, water was poured into the top of the cartridge. After that the materials were mixed using a special mixer in the cartridge. They were then injected into a drilled hole with a caulk gun.
The main component of the organic-type anchor is an epoxy acrylate resin. The organic-type anchor is formed by mixing a base agent and a hardening agent in a mixing nozzle, the resin filled in the drilled holes.
The concrete was placed in steel pipes to prevent splitting failure. The steel pipe had an outer diameter of 216 mm and a thickness of 4.5 mm. D13 was used for the anchors. The embedment length was seven times the nominal diameter of the deformed bar. The bond strength tests were performed in more than one month after the anchor was fixed.
In the creep test, a specimen was placed in the upper part of the apparatus, and a sustained load was applied with a coil spring. The bolt in the lower part of the apparatus was tightened after the spring was compressed with the hydraulic jack. The specimen was then subjected to sustained loading when the load applied by the hydraulic jack was removed. The tests were conducted at 20 °C and 60% relative humidity. The displacements were measured every 5 kN to reach the sustained load. The steel plate was positioned similar to the bond strength test. One-third of the ultimate load was first applied and removed. The procedure was repeated thrice after that. The sustained load was applied at the target load level. The sustained loads, which were 0.26-0.95 times of the ultimate load, were applied in over three months to evaluate the influence of the sustained load.
For the inorganic-type anchor, creep characteristics were evaluated in accordance with EOTA ETAG 001 Part5. The evaluation results from the free end are different from them from the loading end. If the displacement at ultimate load is small, the variations in specimens and the error of estimation formula are considered to affect to the estimated time to creep failure.
Creep deformation amount of long-term from the creep curve has been estimated by the exponential and logarithmic functions. In loading period 50 years, the value estimated by an exponential function is 1.5 times larger than the value estimated by the logarithmic function.
The slope of the estimated equation from the creep failure and the creep curve has become equal by applying a logarithmic function to the inorganic anchors.
Creep exponent of post-installed anchors from Norton law is approximately 3 at 20 °C.
