PSI - Issue 64

Visal Thay et al. / Procedia Structural Integrity 64 (2024) 925–931 Visal Thay/ Structural Integrity Procedia 00 (2019) 000–000

926

2

1. Introduction Recently, externally bonded patch plates, steel plates and Carbon Fiber Reinforced Plastics (CFRP) laminates for instance, have proven to be effective for repair or strengthening steel structures (JSCE (2012), JSCE (2013), Zhao (2013)). However, there are problems remain for the design method of repair and strengthening for steel structures. Amongst, adhesively debonding from the end of patch plates prior to the yielding of steel members is one of the major concerns in application due to sudden change of cross section at the end of adhered patch plate which leads to the occurrence of high shear stress  e and normal stress  ye (Nakamura et al. (2005), Lin et al. (2011)). Although there have been experimental studies to date that have focused on the static strength of adhesive joints, there have been few cases in which static tests have been carried out that take the patch plate end design (geometrical treatment at the end of adhered patch plate) into account (Deng and Lee (2007)). Patch plate end design has been proposed as a way to improve the debonding load of adhesive joints, and examples include adding adhesive to the end of the patch plate to create a triangular or circular shape (fillet), or using a taper or inverse taper on the end of the patch plate (JSCE (2013)). In this study, the patch plate end design method and dimensions of the patch plate were determined by FEM analysis, and a test specimen was fabricated based on that method. Afterwards, a bending loading test was conducted to clarify the improvement rate of the static strength of the adhesive joint due to patch plate end design. 2. Specimen and Principal Stress Fig. 1 shows the geometries and dimensions of the specimen. The specimen is the adhesively bonded joints of the single patch plate (75×19×250 mm) adhered to the base plate (75×25×800 mm). The epoxy resin Konishi E258R is used as the adhesive. The material properties of the steel plates and epoxy resin are given in Table 1.

800

240

250

10

125

20

250

270

240

40

SideB

75

SideA

25 19

ひずみゲージ Strain gauge

固定部 Fixed part

ひずみゲージ Strain gauge

5 Fixed part 固定部

(a) Plane view

(b) Side view

Fig. 1. Specimen geometries and dimensions.

Table 1. Material properties. Material Base plate (Steel SS400) Patch plate (Steel SS400)

Elastic modulus (GPa)

Poisson’s ratio

Yield strength (MPa)

Tensile strength (MPa)

205 205

0.30 0.30 0.34

277 283

436 444

Adhesive (Konishi E258R)

3.6

-

33

In this study, the principal stress  pe of the adhesive is calculated using the following equation (Eq. (1)). Here,  ye is normal stress and  e is shear stress occur in the adhesive layer, which is calculated using the convergence equations (JSCE (2018)).

2





   

  

2

ye  

ye

(1)



e 

pe

2

2