The application of fiber reinforced plastics (FRP) to the civil engineering and building fields remained limited only due to restrictions on material cost and material properties. Recently, application to a largesized and large-loaded member is proceeding with a hybrid structure and a carbon fiber reinforced plastics plastic (CFRP) based on an optimum arrangement of multimaterials. Furthermore, thermoplastic FRP with short production cycle and excellent processability can be reprocessed by heat forming, and by supplying general-purpose structural members by continuous molding technology capable of high speed molding, It is a reality that bending and fusion welding are easy. As a result, it can be expected to greatly improve the cost of construction by applying the new processing method at the on site.
In study, shear properties and evaluation method of pultruded GFRP made of unidirectional materials (C75) were investigated. The several shear tests were conducted using the coupon and the beam specimen for shear properties. In 45-degree directional tensile test, it was found that the shear strength was lower, compared with that of the short beam test. In the V-notched beam method, it was found that the shear properties were equivalent of the result of the beam test. Therefore, the V-notched beam method was proper method for evaluation of shear properties of pultruded unidirectional GFRP members
In this study, the repair method of existing steel members has been developed using Vacuum assisted Resin Transfer Molding (VaRTM) technology. As a damaged member by corrosion, webs and vertical stiffeners in girder ends were selected. In order to study repair effect experimentally, the small-sized column models were fabricated and were repaired by externally bonded CF sheets and 3D CFRP stiffeners using VaRTM. The compressive tests were conducted for 4 kinds of specimen including the specimen with/without section loss. As a result, it was found that the load carrying capacity of the repaired specimens by the proposed method was improved and equivalent to the girder without damage.
This paper presents outdoor exposure and immersion tests on the alkali resistance of pultruded GFRP with in-filled mortar. An outdoor exposure test at Tsukuba exposure site shows that outdoor exposure from 6 to 11 months reduced the tensile strength of GFRP to about 70% of the initial tensile strength. An alkali immersion test shows that the tensile strength of GFRP decreased as alkali immersion time increased. A prediction model for alkali action is used to discuss the relationship between the outdoor exposure and immersion tests, and calculated tensile strength by the model agrees well with the result of outdoor exposure test, which depends on the alkali concentration.
Decreasing of plate thickness due to corrosion at part near ground of steel columnar structures like lighting pole causes lack of their strength and/or fatigue resistance. To reduce risks of their breaking, a repair and strengthening technique operated and expected a reliable strengthening effects in a short period of time can be keys. Then the authors are newly developing thermosetting epoxy resin prepreg sheet of carbon fiber for the repair and strengthening of steel structures. The thermosetting epoxy resin prepreg CF sheet will provide a shorter period to obtain an expected strengthening effect, different from ultravioletcuring type adhesive conventionally used. This report presents concepts of the repair and strengthening technique using the newly developed thermosetting prepreg CF sheet, results of static loading test on strengthening effects and a field test of the technique to a real lighting pole at the site. And fundamental strengthening effects on the ultimate strength and rapid practice of the repair technique were confirmed.
This study is aimed at rapid seismic retrofitting using externally bonded carbon fiber sheets for the buckled circular steel bridge pier by earthquake. 3 test specimens were fabricated as follows: 1) the reference specimen, 2) the specimen reinforced by 7 layers of carbon fiber sheets, 3) the buckled specimen repaired by 7 layers of carbon fiber sheets. Test specimens were designed considering JSHB. The reversed cyclic horizontal load under the constant vertical load was applied. The horizontal strength and energy absorption rate were investigated experimentally. As a result, it was found that in the reinforced specimen, the increase in the horizontal strength was small, and the energy absorption rate increased about 20% for the reference specimen. In the repaired specimen, the horizontal strength and energy absorption rate were equivalent for the reference specimen.
FRP is an attractive material for civil engineering structures because FRP has high strength-to-weight ratio, high stiffness-to-weight ratio, and high corrosion resistance. However, mechanical behavior and capacity of bolted connections of FRP members are not thoroughly understood yet. This study is focused on bearing-type bolted connections of GFRP members with different conditions such as geometrical parameters, bolt axial force, materials of cover plate. Strength tests of single-bolted connections were conducted to examine their strengths and failure modes. Results show that failure mode and strength of a connection depend on its geometric parameters, and bolt axial force increases bearing strength and shear strength.
The purpose of this study is to evaluate bearing characteristics of a bolted joint of hybrid FRP members. Therefore, in this study, the bearing test suggested by Mottram et al. and the pin joint bearing test were performed on five different hybrid FRP laminates consisting of both carbon fiber and glass fiber, CFRP laminate and GFRP laminate, and test results were compared. Then, the influence of different FRP types or stacking sequences on bearing strength was examined. Results showed that bearing strength could be about fifty percent of compressive strength depending on the type or the laminated structure of the reinforcing fibers. The bearing strength from the Mottram method was found to be smaller by about 20 percent than that from the pin joint method. Finally, the effect of bolt axial force on bearing strength was examined, and the significant increase of bearing strength due to the bolt axial force was confirmed.
JSCE Journal of Hybrid Structures, Vol.4 (Technical Report)
In the field that performs maintenance of infrastructures, there are a great topic about measure to make the life of a structure as long as possible, currently. Most of measures to lengthen the life of the structure are repair and retrofitting to perform after some damages occurred. Although a certain prolongation of the life span of the structures is possible with these repair and the retrofitting, large-scale renewal and reconstruction including the dismantling is finally necessary after all. On the other hand, there is already the history about renewal and improvement of the infrastructures in Japan, in order to improve the function that is installed in a structure, depending on the change of the condition around the structure including increase of the traffic and river repair. However, these techniques that have been already developed are hard to say that it is systematized. The subcommittee on renewal and improvement of structures in committee on hybrid structures, JSCE, carried out research activities for systematization of the renewal and improvement itself as well as technology of renewal and improvement, for two years, through the questionary survey to each management group, and the collection of construction examples about renewal and improvement technologies. In this report, the main points of contents provided in this committee are described.