• Structural Engineering and Mechanics
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• 제80권6호
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• pp.689-699
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• 2021

The present study aims to understand the behaviour of low-strength masonry prisms constructed with locally-produced low-strength hollow concrete blocks. Compression tests were conducted on masonry prisms constructed with three different mortar grades of cement-sand ratios of 1:3, 1:4.5 and 1:6 representing strong, moderately strong and weak mortar. Stress-strain curves were generated from the test results for the masonry prisms. The hollow concrete masonry units employed in this study are some of the weakest as compared to other masonry units employed by other researchers. The compressive strengths for masonry prisms with mortar grades 1:3, 1:4.5 and 1:6 are 2.21 MPa, 2.19 MPa and 2.25 MPa respectively. The results indicate that the masonry compressive strength of such low-strength hollow concrete block masonry prisms is not influenced by the mortar strength. Simple relationships to estimate the modulus of elasticity and compressive strength of masonry prisms is also proposed.

• Computers and Concrete
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• 제18권3호
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• pp.355-366
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• 2016

This paper reports the testing of concrete slabs reinforced with CFRP prestressed concrete prisms(PCP) on the flexural behavior. Four concrete slabs were tested, a reference slab reinforced with steel bars, and three slabs reinforced with CFRP prestressed concrete prisms (PCP). All slabs were made with dimensions of 600mm in width, 2200mm in length and 150 in depth. All concrete slabs reinforced with CFRP prestressed concrete prisms(PCP) exhibited CFRP bar rupture failure mode. It was shown that the application of the CFRP prestressed prisms can limit service load deflections and crack width, the increased level of prestress in the CFRP prestressed prism positively affected the maximum crack width. The deflection of concrete slabs reinforced with CFRP prestressed prisms decreased as prestress in the CFRP prestressed prism increased.

• Computers and Concrete
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• 제19권3호
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• pp.227-232
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• 2017

This paper describes an experimental study of the cyclic performance of concrete beams reinforced with CFRP prestressed concrete prisms (PCP). The failure modes, hysteretic loops, skeleton curve, ductility, energy dissipation capacity and stiffness degradation of concrete beams reinforced with CFRP prestressed concrete prisms were analyzed. The results show that The CFRP prestressed prisms reinforced concrete beams have good seismic performance. The level of effective prestress and cross section of CFRP prestressed prisms had a little influence on the bearing capacity, the ductility and energy dissipation capacity of CFRP prestressed prisms reinforced concrete beams.

• 한국안광학회지
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• 제13권3호
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• pp.51-55
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• 2008

목적: anamorphoser를 구성하는데 사용되는 anamorphic 프리즘을 계산, 평가할 수 있는 프로그램의 개발. 방법: anamorphic 프리즘 매질의 굴절률과 빔의 확대 비율에 의해 결정되는 프리즘의 정각과 프리즘의 볼륨을 확인해 줄 수 있는 프로그램이 있으면 anamorphic 프리즘 제작이 상당히 정확하게 진행될 수 있으며, anamorphic 프리즘이 사용되는 전체 광학계의 설계와 제작에 편리한 수단을 제공할 수가 있다. 이러한 프로그램을 개발하기 위해 우리는 먼저 프리즘 매질의 굴절률, 빔의 확대 비율이 주어졌을 때 anamorphic 프리즘의 정각 및 배치각을 결정할 수 있는 식을 유도하였고, 다음은 이것을 가시화하여 쉽게 확인 할 수 있도록 하기 위해 델파이 6.0 언어를 사용하여 프로그래밍하였다. 결과: anamorphoser를 구성하는데 사용될 수 있는 anamorphic 프리즘을 계산, 평가할 수 있는 프로그램을 개발하였다. 결론: 개발된 프로그램을 실제 업무에 적용하여 사용 해 본 결과로 볼 때, 이 프로그램은 생산자에게 많은 정확성과 신속성을 제공할 수 있기에 anamorphoser의 구성 부품으로 사용되는 anamorphic 프리즘의 계산과 생산에 유용한 것으로 판단된다.

• Structural Engineering and Mechanics
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• 제62권3호
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• pp.291-295
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• 2017

The behaviour of reinforced concrete beams strengthened with near surface mounted (NSM) CFRP prestressed prisms was experimentally investigated. Five RC beams were tested under four point bending. All beams were made with dimensions of 300 mm in width, 2000 mm in length and 150 in depth. The effects of presstress level of CFRP prestressed prisms and prism material type were studied. The failure mode, load capacity, deflection, CFRP strain, steel strain and ductility of the tested beams were all analyzed. The results showed that the behavior of the reinforced concrete beams strengthened with NSM CFRP prestressed prisms showed a significant increase in the load-carrying capacity and the deformation capacity. The NSM CFRP prestressed prisms strengthening technique could be considered as an effective method for repairing RC structures.

• Advances in materials Research
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• 제13권5호
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• pp.375-389
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• 2024

Installing wiring or plumbing fixtures necessitates creating chases within masonry walls, which, while serving practical purposes, raises a crucial concern regarding the potential compromise of the masonry's structural integrity. Given these concerns, it becomes essential to thoroughly understand the impact of incorporating chases on masonry strength. In this study, 37 AAC masonry prisms (200×330×100 mm³) were cast and tested for compression. The prisms were equipped with chases of various depths -10 mm, 20 mm and 30 mm; and orientations (horizontal, inclined, and vertical), which were then filled with mortar using 1:2, 1:4, and 1:6 cement-to-sand ratios. The primary objectives were to assess the strength decrease in the prisms with different chase characteristics compared to a control specimen and to determine the percentage strength increase due to filling materials compared to unfilled chases. Key findings indicate that as chase depth increases, there is a substantial reduction in prism strength. However, the orientation of the chase does not significantly affect strength reduction. Importantly, filling the chases with mortar leads to a significant increase in prism strength. This study not only unveils the complex impact of chase characteristics on masonry strength but also emphasizes the crucial role of filling materials in strengthening these prisms.

• Wind and Structures
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• 제9권1호
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• pp.1-22
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• 2006

The response characteristics and suppression of flow-induced vibrations of rectangular prisms with various width-to-depth ratios were experimentally investigated. The prisms were rigid and elastically mounted at both ends to enable constrained torsional vibrations only. The present study focused on torsional vibrations, one of the three types of flow-induced vibrations generated in a rectangular prism. First, the response characteristics of torsional vibrations generated in rectangular prisms were investigated by free-vibration tests. It was found that the response characteristics of torsional vibrations generated in rectangular prisms could be classified into six patterns depending on the width-to-depth ratio. Next, the response characteristics of torsional vibrations observed in the free-vibration tests were reproduced by forced-vibration tests, and the mechanisms by which the three types of flow-induced vibrations, low-speed torsional flutter, vortex excitation and high-speed torsional flutter, are generated in the rectangular prisms were elucidated on the basis of characteristics of fluid forces and visualized flow patterns. Experiments were also carried out to establish an effective method for suppressing flow-induced vibrations generated in the rectangular prisms, and it was found that low-speed torsional flutter and high-speed torsional flutter could be suppressed by placing a small normal plate upstream of the prism, which results in suppression of the alternating rolling-up of the shear layers separating from the leading edges of the prism. It was also found that vortex excitation could be suppressed by placing a splitter plate downstream of the prism, which results in suppression of the generation of wake vortices.

• Wind and Structures
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• 제21권2호
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• pp.183-202
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• 2015

Experiments on two-dimensional rectangular prisms with various side ratios (B/D=2, 3, and 4, where B is the along-wind dimension, and D is the across-wind dimension) and rounded corners (R/D=0%, 5%, 10%, and 15%, where R is the corner radius) are reported in this study. The tests were conducted in low-turbulence uniform flow to measure the wind pressures on the surfaces of 12 models for Reynolds numbers ranging from $1.1{\times}10^5$ to $6.8{\times}10^5$. The aerodynamic force coefficients were obtained by integrating the wind pressure coefficients around the model surface. Experimental results of wind pressure distributions, aerodynamic force coefficients, and Strouhal numbers are presented for the 12 models. The mechanisms of the Reynolds number effects are revealed by analyzing the variations of wind pressure distributions. The sensitivity of aerodynamic behavior to the Reynolds number increases with increasing side ratio or rounded corner ratio for rectangular prisms. In addition, the variations of the mean pressure distributions and the pressure correlations on the side surfaces of rectangular prisms with the rounded corner ratio are analyzed at $Re=3.4{\times}10^5$.

• Wind and Structures
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• 제22권5호
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• pp.573-594
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• 2016

Simultaneous pressure measurements on 2D square prisms with various corner modifications were performed in uniform flow with low turbulence level, and the testing Reynolds numbers varied from $1.0{\times}10^5$ to $4.8{\times}10^5$. Experimental models were a square prism, three chamfered-corner square prisms (B/D=5%, 10%, and 15%, where B is the chamfered corner dimension and D is the cross-sectional dimension), and six rounded-corner square prisms (R/D =5%, 10%, 15%, 20%, 30%, and 40%, where R is the corner radius). Experimental results of drag coefficients, wind pressure distributions, power spectra of aerodynamic force coefficients, and Strouhal numbers are presented. Ten models are divided into various categories according to the variations of mean drag coefficients with Reynolds number. The mean drag coefficients of models with $B/D{\leq}15%$ and $R/D{\leq}15%$ are unaffected by the Reynolds number. On the contrary, the mean drag coefficients of models with R/D=20%, 30%, and 40% are obviously dependent on Reynolds number. Wind pressure distributions around each model are analyzed according to the categorized results.The influence mechanisms of corner modifications on the aerodynamic characteristics of the square prism are revealed from the perspective of flow around the model, which can be obtained by analyzing the local pressures acting on the model surface.

• 한국지진공학회논문집
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• 제25권1호
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• pp.21-32
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• 2021

Concrete masonry prisms are strengthened with steel fiber-reinforced mortar (SFRM) overlay and tested for compressive and diagonal tension strength. Masonry prisms are produced in poor condition considering standard workmanship for masonry buildings in Korea. Amorphous steel fibers are adopted for SFRM, and appropriate mixing ratios of SFRM are derived considering constructability and strength. Masonry prisms are strengthened with different fiber volume ratios, while numerous strengthened faces and additional reinforcing meshes are produced for compression and diagonal tension tests. Compression and diagonal tension strength are increased by up to 122% and 856%, respectively, and the enhancement effect for diagonal tension strength was superior compared to compression strength. Finally, the test results and strength prediction equations based on existing literature and regression analysis are compared.