A seismic retrofitting method that uses a newly expanded frame has recently gained popularity. For the joints of structures used in seismic retrofitting, post-installed adhesive anchors are generally used. For rigidly connecting such a newly expanded frame to an existing frame, a design of the joint is very crucial because the joints are subjected to shear and tensile forces during an earthquake. However, the behavior of the anchors under combined forces remains unclear. To address this issue, herein, we conducted cyclic shear loading tests on 13 anchor bolt specimens under constant tensile force.
In Chapter 2, the details of the test plan are explained. The test parameters considered were as follows: the anchor bolt diameter φ of 13 - 19 mm as well as tensile force T and concrete compressive strength σB of 10 - 30 N/mm2. We used the tensile force ratio rN (σN/σy) as an index of the tensile force, and it ranged from 0 to 0.66. σN and σy are the tensile stress and the yield strength of the anchor bolts.
In Chapter 3, the test results are described. First, we observed the relations of shear force Q and joint opening δN with slip δS. The results indicated that the shear force reduces and the joint opening increases as the tensile force increases.
Second, we investigated the allowable tensile and shear forces under the combined force using Equation (S1) which is used for a structural design6).
(T/Ta)α + (Q/Qa)α = 1 (S1)
Where, T is the allowable tensile force, Q is the allowable shear force, Ta is the allowable tensile force when Q = 0 kN, Qa is the allowable shear force when T = 0 kN and α is a coefficient, usually ranging 1 - 2. According to the test results, the range of α was 0.75 - 1.5.
In Chapter 4, we use the test results to investigate the work of post-installed anchors. We found that the total work was almost constant even at varying tensile force. In addition, we proposed an estimation formula of the total work, given by the equation (S2).
W = ∫QdδS + ∫TdδN = (5.1φ - 40)√( δ2S + δ2N ) (S2)
In Chapter 5, the conclusions were described. Findings obtained in this study were as follows:
1) The shear force was decreased and the joint opening increased as the tensile force increased.
2) For the relation between T/Ta and Q/Qa, the test results were reasonably estimated by choosing a in the range 0.75 to 1.5.
3) WS was dominant in the case of rN=0.33, but WN was higher than WS in the case of rN=0.56 - 0.66.
4) The total work was proportional to the absolute value of the displacement vector and was not significantly influenced by the concrete compressive strength in this tests.
5) A formula for estimating the energy absorption of post-installed anchors under a combined force was proposed.
Improvements to the proposed model in future studies will focus on considering bond stress–slip behavior of adhesives.
