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Evaluating Load-Carrying Capacity of Short Composite Beam Using Strain-Hardening HPFRC
Duy-Liem Nguyen,Vu-Tu Tran,Ngoc-Thanh Tran,Tri-Thuong Ngo,Manh-Tuan Nguyen 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.4
The main goal of this study was to develop the short composite beams using strain-hardening fiber-reinforced concrete (S_HPFRC) and conventional concrete (CC) together. Firstly, the sensitivity of the hybrid fiber system to the enhancement of mechanical properties of plain high performance concrete (P_mortar) was experimentally studied. The ranking of the mechanical properties in terms of sensitive coefficient was observed as follows: direct tensile > splitting tensile > compressive. Next, the responses of short composite beams with various thicknesses of S_HPFRC were investigated under a three-point bending test (3PBT). Six beams with no reinforcement (type A) and six beams with reinforcement were tested (type B) with their identical dimensions of 150 × 150 × 300 mm (depth × width × span length). The compressive strength of S_HPFRC and CC were about 80.65 MPa and 21.12 MPa, respectively. Most of the composite beams were observed to fail in shear mode. And, there was a favorable effect on enhancing the load-carrying capacity of a beam as S_HPFRC was placed at a critical tensile zone. Finally, based on the test data, the analytical equations were proposed for the purpose of predicting shear resistance of the S_HPFRC - CC beam.
Some Results of Recent Investigation and Application of Rubber Blends in Vietnam
Bui Chuong,Nguyen Thanh Liem,Dang Viet Hung,Nguyen Huy Tung,Nguyen Pham Duy Linh,Nguyen Thanh Nhan,Pham Ngoc Linh,Le Anh Kien,Chu Chien Huu 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.1
We have investigated the change of tensile strength (TS) of Natural rubber/chloroprene rubber (NR/CR) blends during combination ageing, including heating and dynamic mechanical loading. Using model of statistical experiment, we built the equation describing the dependence of TS on four factors: temperature T, number of cyclic loadings N, contents of NR (C<sub>NR</sub>) and chloroprene (CCR). This equation allows predict the TS change of NR/CR blends after combination ageing with accepted inaccuracy – less than 10%. We also investigated the effect of nanofillers, such as nanoclay, SiO2, Fe<sub>3</sub>O4, on adhesion of some rubber blends to polyester and steel cords. It was found, in the case of EPDM/CIIR rubber blends, both nanoclay and SiO2 have no effect on adhesion to steel cords, while nano SiO2 may enhance adhesion to polyester cords. On other side, Fe<sub>3</sub>O4 may remarkably enhance adhesion of NR/CR blends to steel. Mentioned results are successfully applied in some practical rubber products working under fatigue conditions, such as rubber/steel antivibration pad for locomotive, heat resistant conveyor, water dam, underwater lift bag.
Numerical investigation on local damage of proposed RC panels under impact loading
Thai, Duc-Kien,Nguyen, Duy-Liem,Kim, Seung-Eock Elsevier 2019 Nuclear engineering and design Vol.341 No.-
<P><B>Abstract</B></P> <P>The effects of transverse reinforcing rebar on the penetration resistant capacity of the reinforced concrete (RC) panel still remains a challenging problem in the field of civil and structural engineering. In the present paper, we numerically analyze the penetration resistant capacity of three proposed panels with different transverse reinforcing rebar arrangements. The obtained results are then compared with reference solutions derived from the conventional RC panel using T-bars. The components of the RC panel, missile, and support system are fully developed. Material nonlinearity, which considers erosion damage, is employed in this simulation. The IRIS Punching tests are used for validating the numerical modeling of the RC panel subjected to impact loading. Parametric studies with varying transverse reinforcing rebar arrangements and ratios are performed to investigate the penetration response of RC panels. The present numerical result shows that the proposed panels offer a better penetration resistant capacity than that of conventional panels using T-bars. We thus recommend an efficient design of RC panels with a proposed transverse reinforcing rebar arrangement.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Analysis of RC panels with different transverse reinforcement are presented. </LI> <LI> The conventional RC panel with T-bar is used for the purpose of comparison. </LI> <LI> Effects of transverse reinforcement arrangement and its ratio are presented. </LI> <LI> Efficient design of RC panel is recommended. </LI> </UL> </P>
Safety assessment of an underground tunnel subjected to missile impact using numerical simulations
Duc-Kien Thai,Duy-Liem Nguyen,Thanh-Tung Pham,Thai-Hoan Pham 사단법인 한국계산역학회 2021 Computers and Concrete, An International Journal Vol.27 No.1
This work presents a safety assessment of an underground tunnel subjected to a ballistic missile attack employing the numerical approach. For the impact simulation, a box shaped reinforced concrete (RC) structure with a cross section dimension of 8.0×10.0 m under a soil layer that was attacked by a SCUD missile was modeled using finite element (FE) software LS-DYNA. SCUD missile is one of a series of tactical ballistic missiles developed by Soviet Union during the Cold War, which is adopted for a short-range ballistic missile. The developed FE simulation for the penetration depth of the missile impacting into the soil structure was verified from the well-known formula of the penetration prediction. The soil-structure interaction, the soil type, and the impact missile velocity effects on the penetration depth of the missile into the different soil types were investigated. The safety assessment of the underground tunnel was performed with regard to the different depths of the underground tunnel. For each missile velocity and soil type, a specific depth called the unsafe depth was obtained from the analysis results. The structure beneath the soil beyond this depth remains safe. The unsafe depth was found to be increased with the increasing missile velocity.
Dung Tien Lai,Khuc Ha Duy,Nguyen Liem Van,홍기정,Nguyen Hai Nam 한국응용곤충학회 2022 Journal of Asia-Pacific Entomology Vol.25 No.3
This study investigated the influence of an nC24 mineral oil (MO) on some biological characteristics of a mos quito bug, Helopeltis theivora, reared on cashew under laboratory and greenhouse conditions. Aqueous emulsions of the oil were applied as sprays to eggs at four daily intervals after oviposition to assess impacts on egg hatch, and to cashew seedlings to assess adult longevity and female fecundity reared on the plants. Field applications were also carried out to assess the impacts of sprays on populations of the bug in a cashew orchard. The results of the laboratory study indicated that 1% (v/v) of the MO application reduced egg hatch when applied to eggs on cashew seedlings, in separate treatments, 1, 2, 3, and 4 days after oviposition (DAO). Egg mortality showed a negative linear correlation with egg maturity (DAO). The pre-oviposition period of adult females placed on sprayed cashew seedling, after deposits of 1% (v/v) sprays dried, was significantly prolonged. The longevity of males and females on dry oil-spray deposits was lower than on seedlings sprayed with water. The fecundity of females was also lower. Field sprays significantly reduced populations of the bug on mature cashew trees. Mixtures of MO and abamectin were more effective than oil alone. The results of the study indicate that mineral oils can be used to suppress populations of H. theivora in cashew plantations.