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Photoreactive pressure-sensitive adhesives (PSAs) were prepared by grafting mono- or difunctional photoreactive monomers onto acrylic PSA, and their adhesion properties were evaluated before and after UV curing for application as dicing tape.

The simultaneous integration of diverse performance attributes, such as self-adhesive capability, stretchability, mechanical stability, and high ionic conductivity, is one of the key issues in the research of wearable electronic devices. Moreover, a facile preparation method, as well as time efficiency and no heating requirement, is desirable for the use of hydrogels in widespread applications. In this study, a multi-functional hydrogel P(AMPSs-co-AAm)/SC was prepared by the rapid photo-polymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt (AMPSs) and acrylamide (AAm) in the presence of sodium caseinate (SC). P(AMPSs-co-AAm)/SC exhibited tight contact and reversible adhesion on various substrates, including glass, steel, plastic, and even human skin. According to the dynamic interaction system of P(AMPSs-co-AAm) and SC, the hydrogel exhibited outstanding stretchability (reaching a fracture strain of 2929% and a stress of 128 kPa), as well as excellent fatigue resistance and network toughening even after multiple stretching/recovery cycles. In addition, a polymeric ionic charge carrier, such as AMPSs, not only endowed a high ionic conductivity (up to 1.2 S m−1) to the hydrogel, but also structural stability, leading to the excellent electric stability of the hydrogel throughout repeated mechanical strain cycles. Our developed approach demonstrates the potential for application as long-life wearable strain sensors for detecting human body motion.

Correction for ‘Preparation of UV-curable PSAs by grafting isocyanate-terminated photoreactive monomers and the effect of the functionality of grafted monomers on the debonding properties on Si wafers’ by Hee-Woong Park et al., RSC Adv., 2023, 13, 11874–11882, https://doi.org/10.1039/D3RA00398A.

In this study, ionic conductive hydrogels were prepared with 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS). Acrylic acid (AA), acrylamide (AAm), and 2-hydroxyethyl acrylate (HEA) were used as comonomers to complement the adhesion properties and ion conductivity of AMPS hydrogels. Hydrogels were prepared by irradiating a 20 kGy dose of E-beam to the aqueous monomer solution. With the E-beam irradiation, the polymer chain growth and network formation simultaneously proceeded to form a three-dimensional network. The preferred reaction was determined by the type of comonomer, and the structure of the hydrogel was changed accordingly. When AA or AAm was used as a comonomer, polymer growth and crosslinking proceeded together, so a hydrogel with increased peel strength and tensile strength could be prepared. In particular, in the case of AA, it was possible to prepare a hydrogel with improved adhesion without sacrificing ionic conductivity. When the molar ratio of AA to AMPS was 3.18, the 90° peel strength of AMPS hydrogel increased from 171 to 428 gf/25 mm, and ionic conductivity slightly decreased, from 0.93 to 0.84 S/m. By copolymerisation with HEA, polymer growth was preferred compared with chain crosslinking, and a hydrogel with lower peel strength, swelling ratio, and ionic conductivity than the pristine AMPS hydrogel was obtained.

To improve the heat resistance of acrylic-based pressure-sensitive adhesive (PSA), silicone-block-containing acrylic PSAs (SPSAs) were synthesized using a polydimethylsiloxane (PDMS)-based macro-azo-initiator (MAI). To evaluate the heat resistance of the PSA films, the probe tack and 90&deg, peel strength were measured at different temperatures. The acrylic PSA showed that its tack curves changed from balanced debonding at 25 &deg, C to cohesive debonding at 50 &deg, C and exhibited a sharp decrease. However, in the case of SPSA containing 20 wt% MAI (MAI20), the balanced debonding was maintained at 75 &deg, C, and its tack value hardly changed with temperature. As the MAI content increased, the peel strength at 25 &deg, C decreased due to the microphase separation between PDMS- and acryl-blocks in SPSA, but the shear adhesion failure temperature (SAFT) increased almost linearly from 41.3 to 122.8 &deg, C. Unlike stainless steel substrate, SPSA showed improved peel strength on a polypropylene substrate due to its low surface energy caused by PDMS block. Owing to the addition of 20 wt% silicone-urethane dimethacrylate oligomer and 200 mJ/cm2 UV irradiation dose, MAI20 showed significantly increased 90&deg, peel strength at 25 &deg, C (548.3 vs. 322.4 gf/25 mm for pristine MAI20). Its heat resistance under shear stress assessed by shear adhesion failure test (SAFT) exhibited raising in failure temperature to 177.3 &deg, C when compared to non-irradiated sample.

This paper presents results from experimental studies on the seismic performance of RC-frame structures strengthened with glass-fiber-reinforced polymer (GFRP) infill panels. Three RC specimens were fabricated and then tested to evaluate the efficiency of the GFRP infill panels. The performance of GFRP infill panels installed in RC-frame structures was evaluated based on the results from measures of strength, failure mode, initial lateral displacement, displacement ductility and hysteretic dissipated energy. Both the strength and the initial lateral stiffness of the RC-frame structures strengthened with GFRP infill panels was greater than that of the un-strengthened specimen; however, the displacement ductility and energy-dissipation capacity of specimens strengthened only with GFRP infill panels decreased. This decreased-ductility issue was resolved by adding GFRP column reinforcement at the tops and bottoms of the columns. The strength, initial lateral stiffness, displacement ductility and energy dissipation capacity of the specimens strengthened with both GFRP infill panels and GFRP column reinforcement increased over the un-strengthened specimen. Finally, it is important that GFRP infill panels, if used together with GFRP column reinforcements, be considered in seismic-strengthening design in order to increase the seismic performance of existing RC-frame structures.

A mechanically post-installed anchor, which is one of the most widely used post-installed anchors in South Korea, was selected to evaluate long-term usage through a pullout test. Two types of specimens were constructed: the original specimens and freeze and thaw specimens. Mechanically post-installed anchors were installed in both of them. A freeze and thaw test method was utilized to consider the long-term usage. The compressive strength of concrete during the freeze and thaw test method is reduced by about 20% compared to that of the original concrete. From the pullout test results, the pullout strength of the freeze and thaw specimen was smaller by about 50% than that of the original specimens. Furthermore, the failure mode of the freeze and thaw specimens was changed. Cone shape destruction of anchors and anchor pullout destruction occurred in the original specimens; concrete pullout destruction occurred dominantly in the freeze and thaw specimens. Based on the comparison results, the reduction factor ( λ) for long-term usage of the mechanically post-installed anchor was derived using a probability function and was proposed to modify the concrete capacity design equation.

A seismic strengthening method using Velcro is proposed to improve the seismic performance of columns in RC frame structures. The proposed method was evaluated experimentally using three fabricated RC specimens. Velcro was wrapped around the columns of the RC-frame specimen to prevent concrete spall falling. The reinforcing performance of the Velcro was determined from comparison of results on seismic performance (i.e., strength, displacement, failure mode, displacement ductility capacity and amount of dissipated energy). As the displacement of the reinforced specimens was increased, the amount of dissipated energy increased drastically, and the displacement-ductility-capacity of the reinforced specimens also increased. The final failure mode of RC frame structure was changed. As a result, it was concluded that the proposed seismic strengthening method using Velcro could be used to increase the displacement ductility of RC columns, and could be used to change the final failure mode of RC-frame structures.

It has been many efforts for reinforcement of existing structure since the number of earthquake has been increased world widely. Especially the occurrence of earthquake surrounding area of Korean peninsular is dramatically increased. Since the buildings in Korea have not been designed to carry the lateral and shear force caused by earthquake, the building will experience massive damages even under moderate earthquake. For this reason, the viscoelastic damper is proposed in this paper to enhance the earthquake resistance of a steel frame buildings. The viscoelastic dampers have been able to increase the overall damping of the structure significantly, hence improving the overall performance of dynamically sensitive structures. In this paper, Viscoelastic dampers designed are consists of FRP panel and viscoelastic material. In this paper, evaluate the performance of the viscoelastic damper through the experiment.

The acrylic pressure-sensitive adhesive (acrylic PSA) shows satisfactory adhesion to high-surface-energy substrates, such as glass, metal, and SUS, but it shows very low adhesion to low-surface-energy substrates, such as polyethylene, polypropylene, and polydimethylsiloxane (PDMS). To increase the adhesion strength of PSA to the low-surface-energy substrates, silicone dimethacrylate (SiDMA) was added to decrease the surface energy of the PSA, but it induced degraded peel strength due to plasticization and miscibility problems. In this study, various types of silicone urethane dimethacrylates (SiUDMAs) were synthesized by controlling the ratio of diisocyanate to PDMS to overcome the miscibility problem. As the ratio increased, their molecular weight and viscosity decreased, but their surface energy increased due to the reduced PDMS content. With the addition of SiUDMA2.0, which has a similar molecular weight to SiDMA, PSA showed 4- and 6-times higher loop tack and peel strength, respectively, on the PDMS substrate without UV curing. All types of SiUDMAs lowered the surface energy of the PSA and significantly increased the loop tack and peel strength on the PE, PP, and PDMS substrates. On the PDMS substrate, PSA that was modified with 20 wt% of SiUDMA2.0 and cured at 200 mJ/cm2 showed a peel strength of 520 gf/25 mm, which was more than 3 times higher than that of the control PSA (138 gf/25 mm). The shear adhesion failure test showed that SiUDMA2.0-modified PSA endured a temperature of 70 °C, which is higher than the 46.5 °C of the control PSA.

Modern structures is the tendency of being increasingly taller and larger. The concrete with large weight has the disadvantage of increasing the weight on the structure. therefore, the method of carrying out the weight saving of the concrete is required. one of such method is to use a lightweight aggregate. However, studies on structural lightweight concrete, lacking for the recognition of the lightweight concrete, so also is lacking. therefore it is necessary to study on the physical characteristic value of the lightweight concrete. In this study, in order to investigate the tensile properties of lightweight concrete, Crack mouth opening displacement (CMOD) experiments were carried out. the fracture energy of the lightweight concrete subjected to inverse analysis were derived from the CMOD experimental results.

The torsional performance of reinforced concrete (RC) beam members covered with high-performance fiber-reinforced cementitious (HPFRC) composite mortar was evaluated through pure torsion tests. The HPFRC composite mortar has higher compressive strength and higher split tensile strength than plain concrete. Four beam specimens were constructed for the pure torsion test. Two types of section, and different materials, were used to produce the RC beam specimens. Various types of torsional performance (i.e., first-cracking torque, ultimate torque, and twist angles) were compared experimentally to evaluate the performance of the RC beam specimens. The torque and twist angle at first visible cracking, of the HPFRC composite mortar specimens were greater than those of the others. Therefore, the use of HPFRC composite mortar appears a useful method to enhance the torsional performance of RC-beam members. Moreover, a simple design equation to determine ultimate torque was proposed and tested, for predicting the torsional strength of RC beams with covers of HPFRC composite mortar. The proposed equation performed well.

An advanced GFRP-composite was proposed for use in a seismic-strengthening strategy for steel-frame structures with welded joints. A GIP wall system was proposed to strengthen existing steel frames and to enhance emergency recovery of damaged steel frames under cyclic loads. The GIPs were designed in separate pieces to facilitate easier transportation and construction. The primary objective of this study was to improve the seismic performance of steel frames. The proposed GIP consisted of GFRP plates in a box-like form. Experiments were conducted to evaluate the performance of the proposed strengthening technique under quasi-static load. Three steel-frame specimens were constructed: one to evaluate the performance of an un-strengthened steel frame (OSF), and the others (RSF-1 and RSF-2) to evaluate the performance of steel frames strengthened by the GIP wall system. The experimental results showed greater stiffness and strength in RSF-1 and RSF-2 than in OSF. Based on these results, it can be concluded that the proposed GIP wall system is useful for strengthening steel frames.

A design procedure of GFRP-infill panels (GIPs) was proposed for use in steel-frame structures. The design goal for these panels was to increase the strength of the steel-frame structures. The GIP was composed of a GFRP plate and a stiffener, in which the cross-sectional shape was assumed to be a box. Each GIP was intended to strengthen the existing steel frame and to provide emergency support for damaged steel frames under seismic loads. To achieve these goals, separate types of GIPs were made, that also provided easy transportation and construction. In this study, GIPs were designed and fabricated using the proposed design procedure. The maximum strength obtained in the experiments corresponded to the expected design strength. It was demonstrated that the proposed design procedure for GIPs could be used to improve the performance of infill-frame structures.

In the study, tensile, compression and in-plane tests about longitudinal direction of glass fiber were performed. Also, to obtain the material properties of GFRP fabric composite, tensile test was performed. All test were performed by the test method of ASTM. Maximum compressive strength was smaller than the maximum tensile strength at the longitudinal direction test results. Elastic modulus of the tensile and compressive was almost similar at the compression test results in the longitudinal direction. Based on the GFRP fabric composite test results, GF91 was showed good performance at maximum compressive, maximum strain and elastic modulus.

In this study, flexural strength properties of SC shear walls were investigated through static pushover test. Failure modes and stiffness characteristics of SC shear walls under lateral loads were inspected by analyzing the experimental results. Main failures of unstiffened SC shear walls were found to be the type of bending shear failure due to the unbonding of the steel plate at the concrete interface. The ductility capacity of SC structures was also confirmed to be improved, which is considered to be a confining effect on steel plates in the longitudinal behavior of SC shear walls. Key Words: Steel plate concrete, Pushover test, Failure mode 1. 서 론 에너지 가격의 급등과 지구온난화의 주범인 이산화탄소 배출량 저감을 위하여 원자력 발전은 주목받고 있다. 이러한 가운데 세계적으로 더 안전하고 경제적인 원자력발전을 위한 다양한 신기술 개발이 우리나라를 비롯한 미국, 일본 등 원전 선진국들에 의해 지속적으로 추진되고 있다. 강판콘크리트(Steel Plate Concrete, 이하 SC)구조는 기존 원자력발전소의 주요구조인 RC구조를 대체하여 모듈화 시공이 가능하도록 고안된 구조체로 향후 원자력발전소, 일반 플랜트, 군용 시설 및 건축물에 적용될 경우 공기단축 및 구조 성능 향상 등 많은 장점을 가지고 있다.SC구조는 콘크리트가 철근을 감싸는 형태가 아닌 강판이 콘크리트를 감싸고 있는 형태로, 양면 강판 내에 콘크리트를 채워 넣은 합성구조체이다. 강판 내에 부착된 전단 스터드(Shear Stud) 및 타이바(Tie-bar)를 통한 강판과 콘크리트의 합성 작용으로 구조적 기능을 수행한다. SC 구조의 구조특성으로 인해 시공시 콘크리트 타설을 위한 거푸집이 필요하지 않을 뿐만 아니라 철근콘크리트부재에 비하여 우수한 구조성능을 갖는다. 또한, 구조부재를 공장에서 제작하므로 시공품질을 향상시킬 수 있고, 제작한 부재를 현장에서 각 모듈을 연결·조립하여 설치함으로써 병행시공이 가능하여 건설공기를 단축시킬 수 있는 장점이 있다. 이러한 SC구조는 새롭게 시도하는 구조형식으로 국가별로 연구가 진행되고 있다.다른 국가에 비해 일본이 선도적으로 SC구조를 개발해 왔고 다른 나라에서는 강판 전단벽체의 강성특성(Li et al., 2011)과 지진거동(Berman, 2011), SC모멘트 프레임의 내진성능(Braconi et al., 2011) 등의 연구가 수행되었지만, SC전단벽 구조의 내진성능에 대한 실험적 연구사례는 부족하다. 국내에서는 SC구조의 거동특성에 관한 기초 연구(Moon et al., 2006)를 시작으로 최근에 SC 구조의 역학특성((Lee et al., 2009)

Social interest in the seismic retrofit of the structure is growing massive earthquake that occurred recently. The brittle fracture of Non-seismically designed Columns lead to full collapse of the building. In the past, cross-sectional expansion method, a steel plate reinforcing method is applied mainly in recent years, fiber-reinforced method utilizing the advantages of the composite material are preferred. However, the reinforcement methods such as this, there is a drawback to induce physical damage to structures, and time consuming work space is large. IIn this study, FRP seismic reinforcement was developed using the Aluminum connector and the composite material (Glass Fiber Reinforced Polymer). Then, the optimum quantities of FRP seismic reinforcement was determined using a nonlinear finite element analysis program. Finally, the quantity decision process through the design and analysis of FRP reinforcement was suggested.

In this study, performance of fiber-reinforced polymer-modified mortar was studied for the development of eco-friendly materials for high performance repair and reinforcement. The general cement mortar and eco-friendly UM resin was mixed with a certain percentage for increased durability. To increase the strength of the polymer-modified mortar, PVA fiber, steel fiber and hybrid fiber were added at a constant rate. Hybrid fiber is contains the same percentage of PVA fiber and steel fiber . In order to determine the strength properties of fiber-reinforced polymer-modified mortar, the compressive strength test, the splitting tensile strength test and the flexural strength test were performed. And, in order to determine the durability properties of fiber-reinforced polymer-modified mortar, water absorption test and chemical resistance test were performed. From the experimental results, polymer-modified mortar using UM resin was improved durability. And the tensile strength and flexural strength increased, which were the vulnerability of fiber reinforced polymer-modified mort ar. From this study, fiber-reinforced polymer-modified mortar u sing eco-friendly UM resin can be used to repair and reinforcement for the external exposure of concrete structures to improve the durability.

The post-installed anchors were installed in non-cracked concrete. And then pullout and shear strength of the anchor were investigated. The test of pullout and shear was conducted torque, diameter and insertion depth of the anchor. If it subjected to pullout load, the performance of it was affected by torque, diameter and insertion of anchor. It it subjected to shear load, the performance of it was affected by diameter and insertion of anchor, but torque was less affected. In failure mode of pull-out test, steel failure of the anchor and concrete cone failure occur. And shear failure mode, most of the tests showed shear failure of the anchor. A commercially available finite element program, ABAQUS, is used in this study, and then the behavior of pull-out of anchor were analyzed. When the interpretation of the available anchor system are derived for finite element modeling of concrete structure, interpreted the resulted with the installation of a target anchor for a relatively accurate prediction was possible.

Because of earthquakes that have recently struck, seismic design criteria that considered performance of structure were included in the design concepts. Thus, a simple analysis tool is needed to predict the strength and ductility of RC structures. In this study, three-dimensional lattice model was developed to expand the two-dimensional lattice model. Torsional analysis of the structure was done to evaluate the developed three-dimensional lattice model. Lattice model was evaluated by comparing analytical results with experimental results. Lattice element size was evaluated using the results of analysis. Torsional analysis results, using three-dimensional lattice model, show that the results are relatively consistent with the experimental values.

Damage of reinforced-concrete (RC) structures commonly occurs during major earthquakes, and becomes worse because of aftershocks. For these reasons, repair technology for seismic damage is needed to prevent possible collapse of damaged RC structures before aftershocks. In this paper, a seismic retrofitting device is proposed to improve the seismic performance of damaged RC columns using glass fiber–reinforced polymer (GFRP), which can be easy to install and quick to repair. The proposed GFRP-strip device consists of a GFRP-composite strip and aluminum clip connectors, used to increase the shear strength of the damaged column. Three RC specimens were constructed with reference to existing RC structures. Two of the specimens were damaged before installing the GFRP-strip devices. After the pretest damage was done, the GFRP-strip devices were installed along the plastic-hinge regions on both ends of the test columns. A comparison of the experimental results indicates that the seismic performance of th...

This study is to develop nonlinear analysis algorithm for transfer matrix method, which can be applied to continuous beam analysis. Gauss-Lobatto integral rule is adopted and the transfer matrix is derived from stiffness matrix. In the transfer matrix method, the system equation has a constant number of unknowns regardless of number of D.O.F. Therefore, the transfer matrix method has computational efficiencies not only in linear elastic analysis but also in nonlinear analysis. To verify the developed method, the analysis results of several examples are compared with commercial code in moment-curvature, moment-displacement and load-displacement relation.