• Structural Engineering and Mechanics
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• 제18권6호
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• pp.769-790
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• 2004

The compressive behavior up to failure of short concrete members reinforced with fiber reinforced plastic (FRP) is investigated. Rectangular cross-sections are analysed by means of a simplified elastic model, able also to explain stress-concentration. The model allows one to evaluate the equivalent uniform confining pressure in ultimate conditions referred to the effective confined cross-section and to the effective stresses in FRP along the sides of section; consequently, it makes it possible to determine ultimate strain and the related bearing capacity of the confined member corresponding to FRP failure. The effect of local reinforcements constitute by single strips applied at corners before the continuous wrapping and the effect of round corners are also considered. Analytical results are compared to experimental values available in the literature.

• Computers and Concrete
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• 제19권5호
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• pp.589-597
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• 2017

Strut-and-tie modeling method, which evolved on truss-model approach, has generally been preferred for the design of complex reinforced concrete structures and structural elements that have critical shear behavior. Some structural members having disturbed regions require exceptional detailing for all support and loading conditions, such as the beam-column connections, deep beams, short columns or corbels. Considering the general expectation of exhibiting brittle behavior, corbels are somewhat dissimilar to other shear critical structures. In this study, reinforcement layout of a corbel model was determined by the participation of structural optimization and strut-and-tie modeling methods, and an experimental comparison was performed against a conventionally designed model.

• 한국정밀공학회지
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• 제28권3호
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• pp.308-314
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• 2011

In micro electrochemical machining (micro ECM), machining conditions have been determined to maintain a small side gap and to machine a workpiece stably However, machining speed is slow. To improve machining speed while maintaining the form accuracy, the paper investigates machining parameters such as pulse amplitude, duty ratio, pulse on-time, and the electrolyte's temperature and concentration. The experiment in this study shows that the electrolyte's concentration is the key factor that can reduce machining time while maintaining the form accuracy Micro square columns were fabricated to confirm the machining parameters' effects.

• Earthquakes and Structures
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• 제11권6호
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• pp.1061-1076
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• 2016

Prefabricated Modular Buildings are increasingly becoming popular in the construction industry as a method to achieve financially economical buildings in a very short construction time. This increasing demand for modular construction has expanded into multi-storey applications where the effect of lateral loads such as seismic loads becomes critical. However, there is a lack of detailed scientific research that has explored the behaviour of modular buildings and their connection systems against seismic loads. This paper will therefore present the nonlinear time history analysis of a multi-storey modular building against several ground motion records. The critical elements that need special attention in designing a modular building in similar seismic conditions is discussed with a deeper explanation of the behaviour of the overall system.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1998년도 가을 학술발표회 논문집
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• pp.423-430
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• 1998

Elastomeric bearings are frequently used as a means to isolate structural systems from earthquake loadings. The combination of rubber layers and reinforcing steel shims makes the bearings stiff axially but soft laterally The shear flexibility of these short columns can lead to relatively low buckling loads which may be further reduced when high shear strains are simultaneously imposed. The area reduction formula has been proposed to account for the reduction in buckling load due to shear. The result obtained from the formula is presumed to be conservative but the degree of conservatism is unknown. This paper describes a numerical study which aims at determining the effect of high shear strain on the critical load of rubber bearings. The results from the finite element analysis which accounts for both the material and geometric non-linearities are compared against the theoretical results in order to examine the validity of the theoretical formulas.

• Structural Engineering and Mechanics
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• 제52권5호
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• pp.857-873
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• 2014

Structural behaviors of a sustainable hybrid column with the ultra high performance cementitious composites (UHPCC) permanent form under compression and flexure were studied. Critical state and failure stage characters are analyzed for large and small eccentricity cases. A simplified theoretical model is proposed for engineering designs and unified formulas for loading capacity of the hybrid column under compression and flexure loads are derived, including axial force and moment. Non-linear numerical analysis is carried out to verify the theoretical predictions. The theoretical predictions agree well with the numerical results which are verified by the short hybrid column tests recursively. Compared with the traditional reinforced concrete (RC) column, the loading capacity of the sustainable hybrid column is improved significantly due to UHPCC confinements.

• Structural Engineering and Mechanics
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• 제62권4호
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• pp.391-399
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• 2017

This study investigates the effects of soft story, short columns, heavy overhangs, pounding, and construction and workmanship quality parameters on seismic response of reinforced concrete buildings through nonlinear static and dynamic procedures. The accounted parameters are selected for their common use in rapid screening of RC buildings. The 4- and 7-story buildings designed according to pre-modern codes are used to reflect majority of the existing building stock. The relative penalty scores are employed in this study to evaluate relative importance of certain irregularities in the existing rapid seismic assessment procedures. Comparison of relative scores for the irregularities considered in this study show that the overall trend is similar. The relatively small differences may be accounted for regional construction practices. It is concluded that initial-phase seismic assessment procedures based on architectural features yield in somewhat similar results independent of their bases. However, the differences in the scores emphasize the proper selection of the method based on the regional structure characteristics.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1996년도 추계학술대회논문집; 한국과학기술회관, 8 Nov. 1996
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• pp.243-247
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• 1996

This paper presents a vibration control of a flexible structure using a controllable ER fluid damper. A clamped-clamped flexible structure system supported by two short columns mimicking a small-sized bridge system is considered. An ER fluid damper which is operated in shear mode is designed and attached to the middle of the flexible structure. The governing equation of motion and associated boundary conditions are derived from Hamilton's principle. A sliding mode control is formulated in order to actively suppress the vibration of the structure due to external excitations. Experimental control results are presented in the frequency domain.

• Computers and Concrete
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• 제24권3호
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• pp.271-282
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• 2019

Concrete undergoes a series of thermo-based physio-chemical changes once exposed to elevated temperatures. Such changes adversely alter the composition of concrete and oftentimes lead to fire-induced explosive spalling. Spalling is a multidimensional, complex and most of all sophisticated phenomenon with the potential to cause significant damage to fire-exposed concrete structures. Despite past and recent research efforts, we continue to be short of a systematic methodology that is able of accurately assessing the tendency of concrete to spall under fire conditions. In order to bridge this knowledge gap, this study explores integrating novel artificial intelligence (AI) techniques; namely, artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS) and genetic algorithm (GA), together with traditional statistical analysis (multilinear regression (MLR)), to arrive at state-of-the-art procedures to predict occurrence of fire-induced spalling. Through a comprehensive datadriven examination of actual fire tests, this study demonstrates that AI techniques provide attractive tools capable of predicting fire-induced spalling phenomenon with high precision.

• Structural Engineering and Mechanics
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• 제74권3호
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• pp.351-363
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• 2020

Based on the dynamic tests of recycled aggregate concrete (RAC) short columns confined by the hoop reinforcement, the dynamic failure mechanism and the mechanical parameters related to the constitutive relation of confined recycled aggregate concrete (CRAC) were investigated thoroughly. The fracturing sections were relatively flat and smooth at higher strain rates rather than those at a quasi-static strain rate. With the increasing stirrup volume ratio, the crack mode is transited from splitting crack to slipping crack constrained with large transverse confinement. The compressive peak stress, peak strain, and ultimate strain increase with the increase of stirrup volume ratio, as well as the increasing strain rate. The dynamic confining increase factors of the compressive peak stress, peak strain, and ultimate strain increase by about 33%, 39%, and 103% when the volume ratio of hoop reinforcement is increased from 0 to 2%, but decrease by about 3.7%, 4.2%, and 9.1% when the stirrup spacing is increased from 20mm to 60mm, respectively. This sentence is rephrased as follows: When the stirrup volume ratios are up to 0.675%, and 2%, the contributions of the hoop confinement effect to the dynamic confining increase factors of the compressive peak strain and the compressive peak stress are greater than those of the strain rate effect, respectively. The dynamic confining increase factor (DCIF) models of the compressive peak stress, peak strain, and ultimate strain of CRAC are proposed in the paper. Through the confinement of the hoop reinforcement, the ductility of RAC, which is generally slightly lower than that of NAC, is significantly improved.