Heung Youl Kim

An Experimental Study on Fire Resistance of Slim Floor Beam

Composite beam using asymmetric H-shaped steel is one of the constructional structures developed in the advanced countries in Europe since early 1990s. The purpose of this study on composite beams where H-shaped steel is partially laid in concrete slabs was to find how to design fire protection and improve fire-resistance to make deep deck plates provide the beams with advantages upon a fire and to improve stiffness in structural aspect. Only lower flange which is directly exposed to a fire was included in fire-resistance design in order to decide optimal fire- protection design condition and test was conducted for spray-coating and paint-coating. In the fire resistance test, web thickness and lower flange thickness were varied to derive the optimum condition for improving fire-resistance performance. It was observed from the test that 90-minute-protection employed to lower flange provided fire resistance for 3 hours. It was also observed that the basic shape resisted fire for 89 minutes, while web reinforcement and lower flange reinforcement provided fire-resistance for 112 and 157 minutes, respectively. The result showed that lower flange reinforcement is the most effective way to improve fire-resistance.

An Experimental Study on the Fire Behavior of Concrete Segments in Tunnel Linings

As soon as the plan to build deep and long tunnels in Korea was announced, guaranteeing fire-resistance of R/C tunnel linings became an important issue. As a matter of fact, the R/C segments used in bored tunnels are structural members which are requested to resist both the transverse pressure of the soil and the longitudinal thrust of the TBM. Because of the temperature sensitivity of the high-performance concrete (compressive strength>40 MPa) that will be used, proper measures should be taken against possible fire-induced damage, like surface spalling and deterioration of the reinforcement. In the past, concrete linings were built in Korea with scanty attention to their fire safety, as demonstrated by the lack of studies on fire resistance of both materials and structures. Therefore, in this study the objective is how to improve the safety of R/C tunnel linings in case of fire, by comparing the damage observed in some full-scale tests recently performance in Korea with the damage observed in the tests performed by EFNARC (European Federation of Producer and Applicators of Specialist Products for Structures) and by investigating the fire behavior of a concrete lining as a whole.

Fire Resistance Performance of High-Strength Concrete Columns Reinforced with Pre-Stressed Wire Ropes

In this study, the fire resistance performance of high-strength concrete columns was evaluated to see the influence of lateral confinement reinforcement with wire ropes for improving ductility, fire resistance reinforcement with fiber cocktail and load ratio. For this, loaded fire test was conducted under ISO834 standard fire condition. The axial ductility of the 60MPa high-strength concrete column reinforced with pre-stressed wire ropes was improved and its fire resistance performance was also improved by 23% compared with its counterpart without wire ropes. The appropriate load for the 60MPa concrete column reinforced with wire ropes was found to be 70% of design load. The fire resistance performance of the 100MPa high-strength concrete column reinforced with pre-stressed wire ropes and fiber-cocktail was improved as much as 4 times compared with that reinforced with tie bars only. The appropriate load for the 100MPa columns was found to be less than 70% of design load in order for the columns to secure required fire resistance performance.

An Experimental Study on Fire Resistance Performance and Evaluation of Asymmetric Slim Floor Beam

Composite beam using asymmetric H-shaped steel is one of the constructional structures developed in the advanced countries in Europe since early 1990s. The purpose of this study on composite beams where H-shaped steel is partially laid in concrete slabs was to find how to design fire protection and improve fire-resistance to make deep deck plates provide the beams with advantages upon a fire and to improve stiffness in structural aspect. Only lower flange which is directly exposed to a fire was included in fire-resistance design in order to decide optimal fire- protection design condition and test was conducted for spray-coating and paint-coating. In the fire resistance test, web thickness and lower flange thickness were varied to derive the optimum condition for improving fire-resistance performance. It was observed from the test that 90-minute-protection employed to lower flange provided fire resistance for 3 hours. It was also observed that the basic shape resisted fire for 89 minutes, while web reinforcement and lower flange reinforcement provided fire-resistance for 112 and 157 minutes, respectively. The result showed that lower flange reinforcement is the most effective way to improve fire-resistance.

An Experimental Study on the Fire Resistance Performance and Spalling of 100MPa HSC Column Mixed with Fiber-Cocktail

As the fire-resistance performance of high-strength concrete has emerged as a social issue and Korean Ministry of Land, Transport & Maritime Affairs has announced the standard for the fire-resistance performance of the concrete, studies to improve its fire-resistance have been conducted actively. In this paper, the study to develop high-strength concrete mixed with fiber-cocktail, a hybrid of polypropylene fiber and steel fiber was conducted. The fire-resistance test of 100MPa high-strength concrete and the analysis of steel bar temperatures for finding the optimal cross-sectional condition showed that the larger the section size is, the lower the temperature of steel bars is. It was also shown that the concrete columns with section sizes of 600mm x 600mm and 800mm x 800mm secure fire-resistance performance and the former is the optimal section size in terms of economic efficiency. The analysis of steel bar temperatures of the column having section size of 600mm x 600mm showed that the polypropylene fiber to steel fiber ratio of 1.5 to 40 (㎏/㎥) is the optimal for the fiber cocktail.

A Study on Empirical Model for Combustible Supplies in Intelligent Buildings

In this study, real fire tests have been performed for the fire behavior and temperature analysis of the compartment. The size of Mock-up experiments were 3 m length, 3.2 m wide, 2.5 m height m. The BFD curve method of C.R. Barnett is adopted to study a empirical model for fire compartment temperatures. The fire load was with office combustible supplies including access floors. The temperatures in the Mock-up compartment were measured using two different locations of thermocouple trees. These conclusions and experiment data obtained in this paper could be helpful in reference for the fire simulation, fire hazard assessment and fire protection design (including PBD). Based on experimental data, BFD curve and mathematical models need to be discussed to predict temperature curve in flashover and fire spread in the compartment. Also, this empirical model study needs more test to verify and optimize.

A Study on the Microstructure of Welded Structural Steel Members at High Temperature

This research is to show the microstructure of fracture parts of structural steels by welding at the high temperature. Discontinuity of mechanical and chemical property at HAZ of welding parts is the cause of decreasing structure safety. Therefore, this study was determined the effect of the welding of steels through a high temperature tensile tests and fracture portion of the microstructure. The results showed that does not cause destruction until temperature reached 600°C.

A Study on the Collapse Mechanism of High Strength Concrete Columns Apply to Fiber-Cocktail

More high-rise structures are currently being constructed and correspondingly, the compressive strength of concrete has been increased. However, compared to conventional strength concrete the high strength concrete (HSC) exhibits coarse inner pore structure which blocks escape routes of vapour generated in the event of fire. This results in spalling and subsequently, are responsible for fire vulnerability of the structure. In addition, spalling phenomena is also affected by the section dimensions of HSC which is also another crucial factor from socio-economic considerations. Thus, this study was carried out to evaluate the fire resistance performance of hybrid fiber (i.e. steel-polypropylene-fibre)-reinforced HSC columns with different cross-section dimensions. The result of the fire resistance performance testing using 100MPa concrete showed that delay to failure was observed by approximately 76 per cent.

Experimental Study on Horizontal Shear Crack Control of Prestressed Corrugated Composite Beams

In case the structure is exposed to the high temperature, the lateral shear crack is the major cause exposing the steel bar to the high temperature and also the major cause of the collapse of buildings. In the study, in order to control the lateral shear crack, the presterssing using strands in a reverse direction of the lateral shear crack has applied and the fire resistance test of the PS corrugated web composite beam has been carried out, produced in a corrugated type of the steel to increase the efficiency of the prestressing. As a result of the test, the lateral shear crack introducing the PS has been reduced but it has been concluded that in case the strands are failed, the brittle failure can be taking place.

Evaluation Study on Mechanical Properties of Submarine Structural Steel at High Temperatures

Steel framed structures have been increasingly built in Korea since the early 1970s and the use of submarine structural steel is being increased thanks to the easiness in welding and superior seismic performance. But, the risk of fire outbreak goes up because of the increase in fire load density. The evaluation of the structural stability of the structural frames at high temperatures can be done based on the mechanical properties of the applied steel at the high temperatures. In this paper, in order to get the fundamental data as to the structural stability of the steel frames built with submarine structural steel at high temperatures, coupon tests for SM 400, SM 490 and SM 520 at high temperatures were conducted and the results were compared with each other and with those of the euro-code for verification.