• Earthquakes and Structures
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• v.19 no.6
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• pp.411-425
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• 2020

Unreinforced masonry (URM) walls present low shear strength and are prone to brittle failure when subjected to inplane seismic overloads. This paper discusses the shear strengthening of URM walls with Textile Reinforced Mortar (TRM) jackets. The available literature is thoroughly reviewed and an extended database is developed including available brick, concrete and stone URM walls retrofitted and subjected to shear tests to assess their strength. Further, the experimental results of the database are compared against the available shear strength design models from ACI 549.4R-13, CNR DT 215 2018, CNR DT 200 R1/2013, Eurocode 6 and Eurocode 8 guidelines as well as Triantafillou and Antonopoulos 2000, Triantafillou 1998, Triantafillou 2016. The performance of the available models is investigated and the prediction average absolute error (AAE) is as high as 40%. A new model is proposed that takes into account the additional contribution of the reinforcing mortar layer of the TRM jacket that is usually neglected. Further, the approach identifies the plethora of different block materials, joint mortars and TRM mortars and grids and introduces rational calibration of their variable contributions on the shear strength. The proposed model provides more accurate shear strength predictions than the existing models for all different types of the URM substrates, with a low AAE equal to 22.95%.

• Korean Journal of Artificial Intelligence
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• v.11 no.4
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• pp.15-20
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• 2023

Machine learning is comprised of supervised learning, unsupervised learning and reinforcement learning as the type of data and processing mechanism. In this paper, as input and output are unclear and it is difficult to apply the concrete modeling mathematically, reinforcement learning method are applied for crawling robot in this paper. Especially, Q-Learning is the most effective learning technique in model free reinforcement learning. This paper presents a method to implement a crawling robot that is operated by finding the most optimal crawling method through trial and error in a dynamic environment using a Q-learning algorithm. The goal is to perform reinforcement learning to find the optimal two motor angle for the best performance, and finally to maintain the most mature and stable motion about EV3 Crawling robot. In this paper, for the production of the crawling robot, it was produced using Lego Mindstorms with two motors, an ultrasonic sensor, a brick and switches, and EV3 Classroom SW are used for this implementation. By repeating 3 times learning, total 60 data are acquired, and two motor angles vs. crawling distance graph are plotted for the more understanding. Applying the Q-learning reinforcement learning algorithm, it was confirmed that the crawling robot found the optimal motor angle and operated with trained learning, and learn to know the direction for the future research.

• KIEAE Journal
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• v.8 no.3
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• pp.77-83
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• 2008

The effective mixture of structural laminated timber and other materials is expected to extend the potentials of building structures because of the potentials to realize high performance in structural safety. The classical joint types using drift pin and bolts are occurred local failures due to the small bearing area. In result, new joints using H shaped steel were suggested in this research. The objective of this study is to evaluate elasto-plastic behaviors by strengthening types of wood frames with new joints connecting structural laminated timber with H shaped steel. A total of five specimens of about one-second scale were tested. Specimens had columns with 1,050 height and $84mm{\times}100mm$ section, and a beams with 1,950mm length and $130mm{\times}100mm$ section. Also, the specimens were stiffened by brace, hwang-toh brick, and autoclaved lightweight concrete. The results of the test showed that the specimen stiffened with autoclaved lightweight concrete was characterized by fairly good strength and stiffness than those of the other specimens. Initial stiffness of H-2.0D-NS specimen with 2 times inserting length of beam height showed 1.33 times than that of H-1.5D-NS specimen. However, the strength of H-2.0D-NS specimen has not improved too much than H-1.5D-NS specimen.

• Advances in concrete construction
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• v.2 no.4
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• pp.249-259
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• 2014

Mortar is a masonry product which is matrix of concrete. It consists of binder and fine aggregate and moreover, it is an essential associate in any reinforced structural construction. The strength of mortar is a special concern to the engineer because mortar is responsible to give protection in the outer part of the structure as well as at a brick joint in masonry wall system. The purpose of this research is to investigate the compressive strength and tensile strength of mortar, which are important mechanical properties, by replacing the cement and sand by stone dust. Moreover, to minimize the increasing demand of cement and sand, checking of appropriateness of stone dust as a construction material is necessary to ensure both solid waste minimization and recovery by exchanging stone dust with cement and sand. Stone dust passing by No. 200 sieve, is used as cement replacing material and retained by No. 100 sieve is used for sand replacement. Sand was replaced by stone dust of 15%, 20%, 25%, 30%, 35%, 40%, 45% and 50% by weight of sand while cement was replaced by stone dust of 3%, 5%, and 7% by weight of cement. Test result indicates that, compressive strength of specimen mix with 35% of sand replacing stone dust and 3% of cement replacing stone dust increases 21.33% and 22.76% respectively than the normal mortar specimen at 7 and 28 days while for tensile it increases up to 13.47%. At the end, optimum dose was selected and crack analysis as well as discussion also included.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.4
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• pp.20-27
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• 2021

The present study presents a nonlinear finite element analysis (FEA) approach using the general program of Abaqus to evaluate the seismic response of unreinforced masonry walls strengthened with the steel bar truss system developed in the previous investigation. For finite element models of masonry walls, the concrete damaged plasticity (CDP) and meso-scale methods were considered on the basis of the stress-strain relationships under compression and tension and shear friction-slip relationship of masonry prisms proposed by Yang et al. in order to formulate the interface characteristics between brick elements and mortars. The predictions obtained from the FEA approach were compared with test results under different design parameters; as a result, a good agreement could be observed with respect to the crack propagation, failure mode, rocking strength, peak strength, and lateral load-displacement relationship of masonry walls. Thus, it can be stated that the proposed FEA approach shows a good potential for designing the seismic strengthening of masonry walls.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.36 no.4
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• pp.153-161
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• 2020

This study investigates the recycling potential of demolition waste (DW) according to building structure, while considering economic aspects. For that, this study surveyed 1,034 residential buildings to collect reliable information on demolition waste generation rates (DWGRs). This study suggested a method for operational cost calculation for each stage and carried out an inventory analysis. The economic value of recycled DW materials was also calculated. And then, the recycling potential(RP) was calculated by building structures and waste types. RP by building structure was low (27-40%), and RP was found in the order of masonry-block, wooden, RC and concrete-brick. By type of DWs, the RP of aggregates was considerably lower than 7%, and DWs such as wood, plastics, and metals showed more than 100% RP. Considering the results of this study, In order to improve the RP of buildings and DWs, the diversification of products that recycled waste like aggregates (i.e., mortar, concrete, bricks, blocks, tiles) and the development of high value-added products are considered to be the most urgent problems. Based on the above RP results, this study proposed a more advanced method for life cycle assessment of buildings and demolition waste.

• Economic and Environmental Geology
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• v.55 no.4
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• pp.317-338
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• 2022

Physicochemical characteristics and evaluation were studied by subdividing the concretes, bricks and earth pipes on the site of the Japanese Ministry of General Affairs in Joseon Dynasty, known as modern architecture, into three periods. Concretes showed similar specific gravity and absorption ratio, and large amounts of aggregates, quartz, feldspar, calcite and portlandite were detected. Porosity of the 1907 bricks were higher than those of 1910 and 1950 bricks. All earthen pipe is similar, but the earlier one was found to be more dense. Bricks and earthen pipes are dark red to brown in color within many cracks and pores, but the matrix of the earthen pipe is relatively homogeneous. Quartz, feldspar and hematite are detected in bricks, and mullite is confirmed with quartz and feldspar in earthen pipes, so it is interpreted that the materials have a firing temperature about 1,000 to 1,100℃. Concretes showed similar CaO content, but brick and earthen pipe had low SiO₂ and high Al₂O₃ in the 1907 specimen. However, the materials have high genetic homogeneity based on similar geochemical behaviors. Ultrasonic velocity and rebound hardness of the concrete foundation differed due to the residual state, but indicated relatively weak physical properties. Converting the unconfined compressive strength, the 1st extended area had the highest mean values of 45.30 and 46.33 kgf/cm², and the 2nd extended area showed the lowest mean values (20.05 and 24.76 kgf/cm²). In particular, the low CaO content and absorption ratio, the higher ultrasonic velocity and rebound hardness. It seems that the concrete used in the constructions of the Japanese Ministry of General Affairs in Joseon Dynasty had similar mixing characteristics and relatively constant specifications for each year. It is interpreted that the bricks and earthen pipes were through a similar manufacturing process using almost the same raw materials.

• Journal of the Korea Institute of Building Construction
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• v.16 no.6
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• pp.571-578
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• 2016

Recently, review on viability of various industrial by product and natural materials as raw material for concrete has been actively done in aspect of environment-friendly issue and depletion of natural resource. This study conducted fundamental study on the possibility of utilizing mud flat as admixture and filling material for concrete. First, chemical analysis on the viability of mud flat as admixture was done and the researchers compared it with the substance of fly ash and blast furnace slag. According to the result, substance content was proven to be inadequate. In addition, as the replacement rate of mud flat increased, compressive strength and tensile strength decreased. According to the estimated result of chemical substance analysis, possibility of utilizing mud flat as admixture was low. According to the result of experiment done as filling material, 10% ~ 30% replacement rate of mud flat manifested more than 8 Mpa of compressive strength of block which may be utilized for secondary product. However, additional experiment such as making block is required afterward. According to the result of flow experiment, as the replacement rate of mud flat increased, flow value decreased, and through chloride content analysis test, it was proven that mud flat is inappropriate to be applied as steel beam using structure since it has high content of sodium. It may be utilized as products that does not use steel beam such as internal brick.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2006.11a
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• pp.297-300
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• 2006

Various buildings constructed by environmentally friendly resources are being built in KOREA. Especially the building made by the wood, which has environmental characteristics that the reinforced concrete and brick doesn't have, are acknowledged with its superiority. Then, studies on indoor thermal control capability of the wooden building and influence of its indoor environment to sensory environment of occupants are not enough proceed. Thus, there were proceeded 24 hours measurements for indoor and outdoor thermal environmental elements of Log Cabins and the hourly subjective tests to evaluate indoor amenity of occupants in this study. The results of the study are following: 1) Upon evaluation on thermal environment elements, indoor and outdoor dry bulb temp were 22.0$^{\circ}C$ and -2.9$^{\circ}C$, and Indoor and outdoor average relative humidity were 25.8%and 52.7%. Differences of indoor and outdoor temperature and humidity were 24.9$^{\circ}C$ and 26.9%. 2) Upon contrastive analysis between the results of subjective tests, warm and cold sensation vote, and PMV (Predicted Mean Vote) and PPD (Predicted Percent Dissatisfaction), values of subjective tests W.9

• Explosives and Blasting
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• v.29 no.2
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• pp.67-80
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• 2011

Recently, the number of structure demolitions has increased in both civil and architecture fields due to various reasons such as redevelopment of a city, utilization of sites and restoration of deteriorated structures. In the past, domestic shell structures had been constructed with brick masonry and they were not high. Therefore, their demolition had been executed with ease. Recently, however, taller reinforced concrete shell structures have become a target for the destruction. Under these circumstances, how to efficiently demolish a structure and how to minimize effects of the destruction on environment including vibration and noise have become a main issue. One of the possible solutions is the explosive demolition. In this study, a case of explosives demolition of the stack, which is located in Jeju Thermal Power Plant in Republic of Korea and is 70 m tall, is addressed. In order to fall down the structure against the desired direction, 13.5 kg dynamite and 100 electric detonators were used.