• 대한토목학회논문집
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• 제28권4D호
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• pp.485-492
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• 2008

본 논문에서는 차량의 주행속도가 아스팔트 포장의 변형률 거동에 미치는 영향을 알아보기 위하여 현장시험을 실시하고 그 결과를 3차원 유한요소해석과 비교, 분석하였다. 한국도로공사 시험도로에서 기층의 두께가 다른 세 단면(A2, A5, A8)을 선정하고, 각 단면별로 세 가지의 주행속도(25, 50, 80km/hr)에 대한 종, 횡방향 변형률을 측정하였다. ABAQUS를 이용한 수치해석에서는 시험차량인 덤프트럭(단축-탠덤축)의 축하중을 단계하중(step loading)으로 모사하였으며, 시험도로 아스팔트 혼합물에 대한 선형 점탄성 물성 계수(E(t))를 적용하여 보다 현실적인 거동해석을 실시하였다. 주어진 시험 조건에서 아스팔트 층 하부에서 측정한 종, 횡방향 변형률의 차이(이방성)는 모든 단면에서 목격되었고, 수치해석결과 차량의 주행속도가 증가함에 따라 임계 지점에서 발생하는 최대 변형률의 크기는 감소하는 것으로 예측되었다. 또한, 최대변형률의 크기도 횡방향 변형률이 종방향 변형률에 비하여 약 27% 정도 작았으며, 차량의 속도가 증가함에 따라 최대 변형률의 감소폭도 횡방향이 약간 큰 것으로 나타났다.

• Journal of the Korean Wood Science and Technology
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• 제15권3호
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• pp.44-55
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• 1987

In order to study the effect of sawdustboard combined with plastic chips, 0.5mm($T_1$), 1mm($T_2$), 1.4mm($T_3$) thick nylon fiber. polypropylene rope fiber(RP), and 0.23mm thick moth-proof polypropylene net fiber(NP) were cut into 0.5, 1, 2cm long plastic chips. Thereafter, sawdustboard combined with plastic chips prepared as the above and plastic non-combined sawdustboard(control) were manufactured into 3 types of one-, two-, and three layer with 5 or 10% combination level. By the discussions and results at this study, the significant conclusions of mechanical and physical properties were summarized as follows: 1. The MORs were shown in the order of 3 layer> 2 layer> 1 layer among plastic non-combined boards, and $T_3$ < $T_2$ < $T_1$ < RP (NP(5%) < NP(l0%) among plastic combined boards. In 2cm long plastic chip in 1 layer board, the highest strength through all the composition was recognized. 1 layer board showing the lower strength with 0.5cm plastic chip rendered to the bending strength improvement by 2 or 3 layer board composition. On the other hand, 2 or 3 layer combined with 1, 2cm long polypropylene net fiber chips incurred MOR's conspicuous decrease requiring optimum plastic chip combined level and consideration to combined type. 2. MOE in plastic non-combined 3 layer board exhibited sandwich construction effect by higher resin content application to surface layer in the order of 3layer>1layer>2layer with the highest stiffness of the board combined with polypropylene chip, while nylon chip-combined board had little difference from plastic non-combined board. In relevant to length and layer effect, 3 layer board combined with the 0.5cm long polypropylene net fiber chip in 5% and 10% combined level presented 34-43% and 44-76% stiffness increase against plastic non-combined board(control), respectively. Moreover, in 1 layer board, 30% stiffness increase with 10% against 5% combined level in the 1 and 2cm long polypropylene net fiber chip was obtained. 3. Stress at proportional limit(Spl) showing the fiber relationship (r: 0.81-0.97) between MOR presented in the order of 1 layer<2 layer<3 layer in plastic non-combined board. Correspondingly, combined effect by layer and plastic chip length was similar to MOR's. 4. Differently from previous properties(MOR, MOE, Spl). work to maximum load(Wml) of 2 layer board approached to that of 3 layer board. Conforming the above phenomenon. 2 layer combined with 0.5cm long polypropylene net fiber chip kept the greater work than 1 layer. The polypropylene combined board superior to nylon -and plastic non - combined board seemed to have greater anti - failing capacity. 5. Internal bond strength(IB), in contrast to MOR's tendency. showed in the order of T1