Lan Chung

Lattice Shear Reinforcement for Slab-Column Connections

This study develops a new type of shear reinforcement using lattice bars to increase the punching shear strength and ductility of slab-column connections. To study the structural performance of the lattice shear reinforcement, direct punching shear tests for four specimens with the lattice shear reinforcement and four specimens without the lattice shear reinforcement were performed. The test results showed that the punching shear strength and deformation capacity of the specimens with the lattice shear reinforcement were improved up to 1.4 and 9.2 times those of the specimens without the lattice shear reinforcement, respectively. A method for estimating the shear strengths of slab-column connections with the lattice shear reinforcement was developed using these test results. Although more research is needed, the lattice shear reinforcement is expected to be suitable for the earthquake design of flat plate structure.

Investigations on Flexural Strength and Stiffness of Hollow Slabs

A new type of hollow slab making use of plastic air balls has been developed, which can effectively reduce the amount of concrete and self weight of concrete structures. In this study, flexural and free vibration tests were carried out to investigate flexural behaviour, including the flexural stiffness, cracking, strength, and ductility. Six test specimens were examined: two conventional RC slabs; two hollow slabs; and two partially precast concrete slabs. The test parameters also included two different types of plastic balls. The test results showed that the hollow slabs yield a satisfactory flexural behaviour (i.e., crack pattern, and flexural strength) which is similar to that of conventional concrete solid slabs up to the ultimate state. It was also found that the current design provisions for concrete solid slabs are applicable to hollow slabs, without significant modification, for the evaluation of flexural strength and initial stiffness essential to the serviceability check.

Design of Frequency-Dependent Weighting Functions for H2 Control of Seismic-Excited Structures

In this paper we investigate a systematic procedure for determining frequency-dependent weighting functions for an H2 controller in the frequency domain. Based on experimental results from the system identification of a model structure with an active mass driver, we choose frequency-dependent weighting functions, including filters on an earthquake input model, sensor noise, control output, and control force. These are incorporated into the plant to produce an optimal controller. Combining the weighting functions and filters and comparing the trade-off problem between response reduction and control force, an optimal combination of weighting functions and filters is determined. The performance of the designed H2 controller is evaluated by shaking-table tests of a three-story scaled model with an active mass driver.

Seismic Performance Preliminary Evaluation Method of Reinforced Concrete Apartments with Bearing Wall system

In Korea, the seismic design regulations was established since 1988 about regularity scale of structures. However, It was not established about seismic performance and evaluation method as the most existing buildings was constructed before Earthquake-Resistant Design(1988). In this study, for model structures which are 4 units of non-seismic designed apartment and 3 units of seismic designed in Korea performed seismic performance evaluation by suggested KISTC (2004). And the result compare to evaluate Capacity Spectrum Method by using MIDAS Gen and SDS. As a result, we observed that suggested KISTCs method have overestimated for shear stress and drift index. The purpose of this study provides most conformity seismic performance evaluation process and the appropriate method of calculating the seismic performance index in Korea.

Evaluation of Natural Frequency Through Measurement of Ambient Vibration for Wall-type RC Structures

Abstract Presently, apartment structure plans tend to depart from the standard pattern based on owners′ requests and frame structures are becoming popular instead of wall-type structures and typical structure systems. Moreover, traditional concepts concerning effective land use in addition to importance of view lead to building high-rise buildings with heights of more than 100 m. According to UBC97, the seismic design of such buildings is gaining more attention, specifically, calculations of exact period are very important for equivalent static analysis. The purpose of this study was to consider the safety factors for the natural period of wall-type and high-rise apartments by comparing the natural period obtained by ambient vibration tests and period simplified formulae recommended by UBC97. Target structures followed by a building′s height, structural system and plan type were selected. The reinforced concrete structure apartment′s natural periods were measured using the ambient vibration method. An approximately 30% error between the eigenvalue analysis and test data obtained by the ambient vibration method has been reported.

Structural Performance and Usability of Void Slab Established in T-deck Plate

In recent years, extension of life span of buildings is becoming an important issue in our society. To improve the life span of buildings, rhamen structure construction and long-spanned structures are advantageous. And in order to achieve this goal, structural elements of buildings must be light and slender. As an alternative method, general porous slabs are used frequently domestically and internationally. But the study on the porous slabs using T-deck plate and assembly of light weight precast construction is insufficient at present. In this study, flexural and fatigue tests were performed on six specimens to verify structural performance and serviceability. The main parameters of the specimens were light weight and T-deck plate construction possibility as well as slab thickness. The test results indicated that the strength of porous slabs using T-deck plate and assembly of light weight were much better than general RC slabs and porous slabs without T-deck plate. And stiffness was much better than that of other tested slabs.KwangJang Structural Co. Ltd., Seoul 137-875, KoreaABSTRACT In recent years, extension of life span of buildings is becoming an important issue in our society. To improve thelife span of buildings, rhamen structure construction and long-spanned structures are advantageous. And in order to achieve thisgoal, structural elements of buildings must be light and slender. As an alternative method, general porous slabs are used frequentlydomestically and internationally. But the study on the porous slabs using T-deck plate and assembly of light weight precast construc-tion is insufficient at present. In this study, flexural and fatigue tests were performed on six specimens to verify structural perform-ance and serviceability. The main parameters of the specimens were light weight and T-deck plate construction possibility as well asslab thickness. The test results indicated that the strength of porous slabs using T-deck plate and assembly of light weight were muchbetter than general RC slabs and porous slabs without T-deck plate. And stiffness was much better than that of other tested slabs.Keywords : void slab, T-deck plate, long span, bending performance, vibration performance

Evaluation of Dynamic Collapse Behavior of Steel Moment Frames Damaged by Blast

Blast effects on structures and blast mitigation strategies have been vigorously studied in the world. The alternate path method, or common progressive collapse analysis method, of structures assumes the threat-independent removal of vertical load-carrying elements. However, in reality, a blast-induced column-missing event will produce the damage on adjacent structural elements and the rapid dynamic response of the structures. In this study, the strain rate effects on the dynamic collapse behavior of steel moment frames are investigated by performing the blast-induced sequential progressive collapse analysis. Then, the improvement of the progressive collapse analysis method is discussed based on the numerical results.

Optimal Design of Tuned Mass Damper Considering the Friction between the Moving Mass and the Rail

In this study, based on the results from the sinusoidal base excitation analyses of a single degree of freedom system with a tuned mass damper (TMD), it is verified that optimal friction force can improve the performance of a TMD like a linear viscous damper which has been usually used in general TMD. The magnitude of the optimal friction increases with increasing mass ratio of the TMD and decreases with increasing structural damping. Particularly, it is observed that the optimized friction force gives better control performance than the optimized viscous damping of the TMD. However, because the performance of the TMD considerably deteriorates when the friction force increases over the optimal value, it is required to keep the friction force from exceeding the optimal value.

Shaking Table Test for Seismic Performance Evaluation of Non-Seismic Designed Wall-Type Apartment

Earthquakes are reported thai building structures have been colossal damaged, but before 1988 designed structures which were not applicate seismic design code have no seismic performance. Especially, for the apartment structures were indicated that it have no resist wall element of earthquake before 1988 designed structures. We have to evaluate for seismic performance this structures, therefore it will be retrofitted for seismic index sufficient structures. We performed seismic performance evaluation for model structures by MIDAS which is general structure analysis software. In this study, it was performed shaking table test to evaluate model structure which is reinforcement concrete and 5 floors for seismic performance index. We made specimens by similar`s law and tested shaking table test. In the shaking table test it is not performed prototype model test because of space and equipment condition. So we had made scale-down model for 1/5 by similar`s law. That`s why it needs for the evaluation of performance. However, it is not possible to do an experiment of prototype owing to the shortage of space and the limit of an experimental instrument in the shaking table test. Then, modeling and reducing the part of prototype do the experiment. In this experiment a shaking table test is done and seismic performance of model structures is evaluated by using similitude laws for scale down specimen. As a result it is proved that non-seismic design structures need to retrofit since seismic performance shows life safe grade in 0.12g of an earthquake.

Forced Vibration Test of a Real-Scale Structure and Design of HMD Controllers for Simulating Earthquake Response

Forced vibration testing is important for correlating the mathematical model of a structure with the real one and for evaluating the performance of the real structure. There exist various techniques available for evaluating the seismic performance using dynamic and static measurements. In this paper, full scale forced vibration tests simulating earthquake response are implemented by using a hybrid mass damper. The finite element (FE) model of the structure was analytically constructed using ANSYS and the model was updated using the results experimentally measured by the forced vibration test. Pseudo-earthquake excitation tests showed that HMD induced floor responses coincided with the earthquake induced ones which were numerically calculated based on the updated FE model.