Earticle

Recently, there have been many researches and developments on secondary mass dampers such as TMD (Tuned Mass Damper) and TLCD (Tuned Liquid Column Damper). LCVA (Liquid Column Vibration Absorber) is a special type of TLCD relying on the motion of a column of liquid in a U-shaped container to counteract the forces acting on the structure. Since it has different dimensions for vertical and horizontal portions of container, it has benefits of easy tuning and wide natural frequency range. In this paper, the control performance of LCVA against wind loading is evaluated using shaking table test. Total of three LCVAs with different mass are used in the test in order to assess the control performance In the test, the harmonic loads with varying frequencies were used. The peak and RMS accelerations subjected to resonant frequency input are compared for with and without LCVA. And the peak accelerations subjected to varying frequency inputs are also compared. As a result, it is found that the maximum acceleration and RMS acceleration of the structure decreases up to 49.1% and 54.1% respectively when LCVA is installed. Especially, as the mass of LCVA increases, i.e., the mass ratio of water mass to structure mass increases, the control performance of LCVA increases.

In this study, the seismic behavior of arch structure with lead rubber bearing(LRB) is analyzed. The arch structure is the simplest structure and has the basic dynamic characteristics among large spatial structures. Also, Large spatial structures have large vertical response by horizontal seismic vibration, unlike seismic behavior of normal rahmen structures. When horizontal seismic load is applied to the large spatial structure with isolation systems, the horizontal acceleration response of the large spatial structure is reduced and the vertical seismic response is remarkably reduced.

Various smart sensors have been used for the monitoring of damage predication of structures. In this study, piezoelectric (PZT) sensors were used for the damage prediction of steel member. An impact load was applied on a simply supported steel girder on which PATs were attached, and the dynamic responcd were measured. The voltage change of piezoelectric for the steel girder is used for damage prediction. Damage measuring of steel girder will use the change of voltage of the PZT sensor and it will be able to predict a damage. The measured natural frequency were compared with those of both theorerical analysis as well as those of numerical analysis results using finite element analysis program Midas The damage of steel girder was manipulated by the bolt loosening of ioint with bolt slice. The voltages from PZT sensor were converted to FFT data and the frequency change and magnitude were inspected to identify the damage. The basic data to identify the damage of steel girder were suggested based on the frequency change and magnitude ratio for the different modes.

The purpose of this study was to develop the systemic architectural walls for the middle-low rise steel structure. To analyze the construction method of the systemic architectural walls, we developed the new fundamental unit walls by strengthening steel plate to the basic unit using existing wire panel and manufactured full-scale walls. As a result, we found that the structural performance, especially bending capacity, was much more excellent compared to the existing walls. And we figured out the problems through manufacturing full-scale walls, and we want to derive an wall sub-system for the systemic architectural package.

This study summarizes basic results on the characteristics of the vertical mean wind pressure distribution, which is needed to estimate reasonable vertical wind load of buildings, through simultaneous multi-point wind pressure test. Side ratio of rectangular wind pressure models have been fixed to one and aspect ratios are changed into 4 types. Wind pressure tests are conducted on the Boundary Layer Wind Tunnel at Kumoh National Institute of Technology. The characteristics of vertical mean wind pressure distribution with respect to various heights of buildings are analyzed into windward direction and leeward. The result shows that wind pressure is decreased as the aspect ratio is decreased.

In these days RC(Reinforced Concrete) is widely used to build the structure because of good structural performance of RC. However, RC structure's durability is decreased by various factors. Therefore today the research about strengthening RC structures is actively going on. The purpose of this study is to present the basic data about the strenthening performance of FRP-Aluminum Composite Hollow Beam externally bonded. The results of test show that resisting force of strengthening beam(BT1) is increased upto 63% compared with unstrengthening beam(BC=control beam). Also deflection and crack of the central area of strenthening beam(BT1) is remarkably decreased. However, in case of strengthening beam(BT1) shear test is required because brittle failure and separation between FRP-Aluminum Composite Hollow Beam and RC structure appeared.

An study on a measurable turn-buckle started from an idea to measure tensile force of tension member in the suspension structure system. The straight tensile elements of conventional turn-buckle were pre-deformed to a diamond shape, and the lateral displacement of the curved elements is gotten when tensile force is applied to the measurable turn-buckle. The previous studies proposed an analytical model and boundary condition, and, then found the relationship of load(P ) and displacement(δ). And the final shape of measurable turn-buckle was determined by the theoretical analysis, the experiment, and FEM using ABAQUS. The deformation of the measurable turn-buckle combines the large bending deformation and small axial deformation. So the measurable turn-buckle grows big so as to resist more high tensile force. We start out a parallel connection of turn-buckle to solve this problem, and it may resist by two times of one. The final objective of this study is to convert displacement(δ) to load(P ) in field using vernier-calipers or micrometer. The measured values using vernier-calipers is in error by less than 5% as compared with the results of experiment in range of over 100kN.

Deteriorated four reinforced concrete beam using high ductile fiber-reinforced mortar composites were constructed and tested under monotonic loading. Experimental programs were carried out to evaluate the repair performance of such test specimens, such as the failure mode, the maximum strength, and crack control. All the specimens were modeled in one-fourth scale size. Test result shows that specimens(BSHT 1.5, BSHT 3.0, BSHT 5.0) designed by the improving of repair performance using the high ductile fiber composite mortar(PVA 1.5%) were attained significantly cracking control due to the fiber bridging and increased the load carrying capacity by 21% in comparison with the standard specimen(BSS).

In order to demonstrate possible higher resistances of composite behaviors between H-shaped steel and concrete, this study intends to investigate a three-dimensional finite element analysis and evaluation for the behavior of shear connectors of stud couplers between H-shaped steel and concrete. To achieve more advanced composite action between H-shaped steel and concrete, a newly developed shear connector type using added U-type reinforcements was compared with stud head connectors. The current three-dimensional finite element model was considered nonlinearity of steel and cracked concrete by damage plasticy model. Tthe bond characteristics between shear connectors and concrete was also considered using a surface-to-surface contact model. Experimental and finite element results are well matched each other in shear behaviors of specimens.

The evaluation of joint rotational stiffness of Mero system is studied and discussed in this paper. Four types of pipes, ∅ 60.5×3.2, ∅89.1×3.2, ∅114.3×4.5, and ∅139.8×4.5 were used in the bending test models. In the test results, the initial rotational stiffnesses of the Mero system were evaluated as about 3,800kN․cm/rad in BS605m20, 7,100kN․cm/rad in BS891m24, 12,300k N․cm/rad in BS1143m30, and 30,000kN․cm/rad in BS1398m36.

This study was conducted to develop self-repairing ability for concrete so that inspection could be available even in the event of minute cracks, for more economic concrete structure maintenance and longevity. This is a basic attempt to develop self-repairing concrete using the biochemical reaction of bacteria through an innovative method. In this study, the characteristics and problems posed by self-repairing concrete as proposed in international scientific journals were examined, and the potential of new concrete reformation and performance improvement using bio-mineralization was explored. Bio-mineralization, which is an action of creating bio-minerals using an organism, was proposed. A new concept of bacteria such as Sporosarcina pasteurii using bio-mineralization that precipitates calcium carbonate, as well as the possibility of mechanical performance and durability of concrete and repair of cracks, was introduced. Directions for further study through basic experiments and developmental feasibility of self-repairing concrete were also presented.

The purpose of this study is a seismic performance evaluation of middle-height apartment building which was strengthened by shear wall and steel hysteretic damper, respectively. Therefore, an apartment which has deficiency in seismic capacity was selected and analyzed by nonlinear dynamic analysis with three earthquake waves. The analysis results were evaluated by story displacement and acceleration, and story shear. The seismic performance of hysteretic damper strengthened case shows better responses than shear wall strengthened case. Therefore damper strengthening will make a good seismic performance and economical benefits.

Recently, using 600㎫ steel tube connection having the structural advantage over large scale structure and high-rise building has increased. However, research on 600㎫ steel tube connection is currently lacking. Therefore, stability of use of previous steel tube strength of connection formula(KBC 2008) was compared and examined when strength of 600㎫ steel tube connection was produced by using finite element analysis program in this research. As results of research, formulas of previous strength of connection were available when lateral load acted to gusset plate connected to length direction. However, formulas of previous strength of connection need examination for usability in case lateral load acts to right angle direction or moment and shear force act to length direction to gusset plate connected on steel tube. Thus, it is necessary that developed formulas of strength of connection are presented through tests and research on the strength of connection of 600㎫ steel tube.

Current design practice of electric transmission tower is based on allowable stress design. Design strength of compression member of the electric transmission tower is determined by buckling strength of member itself without considering the joint strength. There is a possibility of joint failure prior to buckling of member. Therefore, in this study, joint strength is calculated for various member force, and shape of joint and database of strength was established. These data was compared with the member strength obtained from previous research based on equivalent nonlinear analysis technique. Finally, practical evaluation and design method to distinguish failure mode in member of electric transmission tower is proposed.

The purpose of this experimental study is investigate the curling influence on structural behavior of single shear bolted connection of in thin-walled carbon steel fabricated by four bolts. The end distance parallel to the loading direction is considered as main variables. As the previous research regarding cold-formed stainless steel bolted connections, the curling also occurred in this carbon steel joints. It is concluded that the curling preceded the other fracture type such as tensile fracture, shear failure and led to the ultimate strength reduction of thin-walled carbon steel bolted connection with a long end distance.

Reinforced concrete structures have an excellent durability under a good construction and continuous maintenance. But reinforced concrete construction is influenced by atmospheric phenomena and it is creating a deterioration. One of the deterioration cause on concrete is a freezing and thawing action. Freezing and thawing leads to the reduction in concrete durability by the cracking or surface spalling. If we are carried out freezing and thawing, deterioration of reinforced concrete construction will be reduction. Therefore, this study was performed to investigate the flexural behavior of reinforced concrete beams exposed to freezing and thawing cycles. The presence of damage and cycles were considered as variables in this study.

In these days, carbon fiber-reinforced polymer (CFRP) has been widely used for retrofitting and/or strengthening structural elements in structure. However, there are not enough test data to predict the long-term performance of the retrofitted structures exposed to weathering. The purpose of this study is to evaluate the effect of freezing and thawing on the structural performance of reinforced concrete (RC) beams strengthened in shear with carbon fiber sheet and plate. Seven small-scale RC beams (100 ㎜ × 100 ㎜ × 400 ㎜) were strengthened with CFRP in shear, subjected to up to 400 cycles freezing and thawing from -18～4℃, and tested to failure in four-point bending. The test data also indicated that no significant damage to carbon fiber sheet and plate strengthened concrete beams had occurred because of 400 cycles freezing and thawing.

Generally, reinforced concrete structures exposed to the outside temperature are affected by freezing and thawing process during winter and early spring. These freezing and thawing process can lead to the reduction in durability of concrete as cracking or surface spalling. This paper is to study the hysteretic behavior of RC beams exposed to freezing and thawing under cyclic loadings. To compare the difference in hysteretic behavior of RC Beams, limited tests were conducted under different types of damage and freezing and thawing cycles. For this purpose, six specimens were tested. It is thought that experimental results will be used as basic data to evaluate hysteretic behavior of RC beams exposed to freezing and thawing.

The purpose of construction project management is to achieve planned quality by adequate cost and schedule of the project, thus the effective time management is a critical factor to actualize the object. But the traditional time management by using milestone has several limitations which are not sufficiently considered mutual relation and variated from the task. On this wise, applying the concept and principles of lean construction to the project will be the best way not only reduce waste and variation, but also improve the productivity and ability to overcome limitation as mentioned above. Thus the study, Last Planner System, specially focuses on constraint analysis which is used in lookahead planning system. The results of this research will provide the constraint analysis checklist that is able to improve work reliable and percent plan complete when time planning by controlling constraints of project.

This study conducted a test of pulverized air cooling slag, the previous state of which was air cooling slag powder which falls into disuse in the country, until it went through 2nd processing, following a mix properties by replacement rate & various admixtures, to get a basic data for practical use of air cooling slag powder using concrete in future, through a comparative analysis and examination of flow properties, intensity properties, to solve the insufficiency problem of 3 low-priced blast furnace slag powder. A comparative analysis on mechanical performance of the flow and strength properties, durabilities of concrete, the admixture of which is air cooling slag powder, has brought up a result as follows. 1. The more the replacement rate increased, the slump increased and the air content was decreased. 2. The early strength was higher than the standard of other admixture and the long term strength showed a similar level to 3 blast furnace slag powder 3. The tensile strength of strength appeared as 1/7～1/13