• Wind and Structures
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• v.10 no.3
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• pp.233-247
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• 2007

The insertion of steel braces has become a common technique to limit the deformability of steel framed buildings subjected to wind loads. However, when this technique is inadequate to keep floor accelerations within acceptable levels of human comfort, dampers placed in series with the steel braces can be adopted. To check the effectiveness of braces equipped with viscoelastic (VEDs) or friction dampers (FRDs), a numerical investigation is carried out focusing attention on a three-bay fifteen-storey steel framed building with K-braces. More precisely, three alternative structural solutions are examined for the purpose of controlling wind-induced vibrations: the insertion of additional diagonal braces; the insertion of additional diagonal braces equipped with dampers; the insertion of both additional diagonal braces and dampers supported by the existing K-braces. Additional braces and dampers are designed according to a simplified procedure based on a proportional stiffness criterion. A dynamic analysis is carried out in the time domain using a step-by-step initial-stress-like iterative procedure. Along-wind loads are considered at each storey assuming the time histories of the wind velocity, for a return period $T_r=5$ years, according to an equivalent wind spectrum technique. The behaviour of the structural members, except dampers, is assumed linear elastic. A VED and an FRD are idealized by a six-element generalized model and a bilinear (rigid-plastic) model, respectively. The results show that the structure with damped additional braces can be considered, among those examined, the most effective to control vibrations due to wind, particularly the floor accelerations. Moreover, once the stiffness of the additional braces is selected, the VEDs are slightly more efficient than the FRDs, because they, unlike the FRDs, dissipate energy also for small amplitude vibrations.

• Earthquakes and Structures
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• v.19 no.3
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• pp.189-196
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• 2020

The near-collapse performance limit is defined as the deformation at the 20% drop of maximum base shear in the decreasing region of the pushover curve for ductile framed buildings. Although monotonic pushover analysis is preferred due to the simple application procedure, this analysis gives rise to overestimated results by neglecting the cumulative damage effects. In the present study, the acceptabilities of monotonic and cyclic pushover analysis results for the near-collapse performance limit state are determined by comparing with Incremental Dynamic Analysis (IDA) results for a 5-story Reinforced Concrete framed building. IDA is performed to obtain the collapse point, and the near-collapse drift ratios for monotonic and cyclic pushover analysis methods are obtained separately. These two alternative drift ratios are compared with the collapse drift ratio. The correlations of the maximum tensile and compression strain at the base columns and beam plastic rotations with interstory drift ratios are acquired using the nonlinear time history analysis results by the simple linear regression analyses. It is seen that these parameters are highly correlated with the interstory drift ratios, and the results reveal that the near-collapse point acquired by monotonic pushover analysis causes unacceptably high tensile and compression strains at the base columns, as well as large plastic rotations at the beams. However, it is shown that the results of cyclic pushover analysis are acceptable for the near-collapse performance limit state.

• Earthquakes and Structures
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• v.6 no.5
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• pp.515-537
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• 2014

Current seismic codes (e.g. the NTC08 Italian code and the EC8 European code) adopt a performance-based approach for both the design of new buildings and the assessment of existing ones. Different limit states are considered by verifying structural members as well as non structural elements and facilities which have generally been neglected in practice. The key role of non structural elements on building performance has been shown by recent earthquakes (e.g. L'Aquila 2009) where, due to the extensive damage suffered by infills, partitions and ceilings, a lot of private and public buildings became unusable with consequent significant socio-economic effects. Furthermore, the collapse of infill panels, particularly in the case of out-of-plane failure, represented a serious source of risk to life safety. This paper puts forward an infill model capable of accounting for the effects arising from prior in-plane damage on the out-of-plane capacity of infill panels. It permits an assessment of the seismic performance of existing RC buildings with reference to both structural and non structural elements, as well as of their mutual interaction. The model is applied to a building type with RC framed structure designed only to vertical loads and representative of typical Italian buildings. The influence of infill on building performance and the role of the out-of-plane response on structural response are also discussed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.118-119
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• 2014

A fire in a steel framed building can decrease a structural stability and cause deformation. And the fire continues the building can be demolished. Therefore, every country requires fire resistance performance of structural elements. In case of column, fire protective thickness derived from a specific fire test using an horizontal furnace is allowed to apply any kinds of sections and lengths of column. However, the lengths and sections of the column in steel framed buildings are various. In this paper, to know the differences of fire performance of steel column according to variance of lengths, a maximum allowable stress, steel surface temperature history, deflection are calculated and the thickness of fire protective material for longer column(4700 mm) need to enforce about 10% more than shorter column (3500 mm).

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.458-461
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• 2008

The primary objective of this study is to provide simple analytical tools to estimate dynamic characteristics of steel framed floor system in hospital building for vibration serviceability due to human activities, bogie, medical equipment. and so on. In order to evaluate the dynamic characteristics and vibration levels according to steel framed floor system, we had executed impact test and measurement on steel structure floor system in various hospital buildings. But perhaps most importantly, how to make the most of deduced design factor for design of hospital building. therefore we presented the access method such as the three-dimensional F.E. numerical analysis on the basis of the design drawing, and the properties of all floors for estimation of vibration level in hospital building.

• International Journal of High-Rise Buildings
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• v.9 no.2
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• pp.113-125
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• 2020

Beginning in the late 19th century, construction of skyscrapers spread throughout Chicago, New York City, and then the world as demand of space in buildings and increase of cost of land. With this change curtain wall systems have evolved to be more visually complex; these unique profiles of the skyscraper became powerful images and symbols of our cities. A curtain wall is defined as usually aluminum-framed wall containing in-fills of glass and metal panels. The framing is attached to the building structure and does not carry the floor or roof loads of the building.

• International Journal of High-Rise Buildings
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• v.9 no.3
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• pp.255-260
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• 2020

This research and technology development project is based on the concept and plan of Sumitomo Forestry Co., Ltd., and designed by Nikken Sekkei Ltd., and is aiming to realize 350 m supertall timber-framed buildings in urban areas by 2041, the 350 year anniversary of Sumitomo Forestry's founding(Fig. 1). By constructing office-based multi-use buildings which have 70 stories above ground with GFA of 455,000 ㎡, using a huge amount of timber of 185,000 ㎥, this project envisions to connect forests and cities, and to solve the problems in both of forests and cities. At the present stage, the main objective is to identify the issues related to wood, such as building structural systems, construction methods, materials used, and resource development, and to create a roadmap for future technologies to be researched and developed.

• Steel and Composite Structures
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• v.36 no.4
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• pp.383-398
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• 2020

This paper investigates the progressive collapse behavior of 3D steel-framed gravity buildings under fires with a cooling phase. The effect of fire protections and bracing systems on whether, how, and when a gravity building collapses is studied. It is found that whether a building collapses or not depends on the duration of the heating phase, and it may withstand a "short-hot" fire, but collapses under a mild fire or a "long-cool" fire. The collapse time can be conservatively determined by the time when the temperature of steel columns reaches a critical temperature of 550 ℃. It is also found that the application of a higher level of fire protection may prevent the collapse of a building, but may also lead to its collapse in the cooling phase due to the delayed temperature increment in the heated members. The tensile membrane action in a heated slab can be resisted by a tensile ring around its perimeter or by tensile yielding lines extended to the edge of the frame. It is recommended for practical design that hat bracing systems should be arranged on the whole top floor, and a combination of perimeter and internal vertical bracing systems be used to mitigate the fire-induced collapse of gravity buildings. It is also suggested that beam-to-column connections should be designed to resist high tensile forces (up to yielding force) during the cooling phase of a fire.

• Journal of the Korean Wood Science and Technology
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• v.40 no.6
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• pp.431-444
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• 2012

Constituents of timber framed floor affect the insulation performance against impact sound significantly. Among them, installation of massive sound absorbing layer and reinforcement of stiffness of timber floor have been considered as major factors that improve the insulation performance against impact sound. Researches on evaluating the effect of floor constitutions have been carried out through the field measurements for timber framed buildings in Korea. It is concluded that the impact sound pressure level at the relatively lower frequency governs the overall insulation performance, and can be improved by the installation of sound absorbing layer and reinforcement of floor stiffness. Especially, the insulation performance against heavy impact sound was improved significantly when the massive cement mortar layer for floor heating system was installed and the stiffness was reinforced by shortening the joist span using additional beam at the mid-position of original span.

• Structural Engineering and Mechanics
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• v.40 no.1
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• pp.65-84
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• 2011

In this paper a simple mathematical model for approximate static analysis of combined system of framed tube, shear core and two outrigger-belt truss structures subjected to lateral loads is presented. In the proposed methodology, framed tube is modeled as a cantilevered beam with a box section and interaction between shear core and outrigger-belt truss system with framed tube is modeled using torsional springs placed at location of outrigger-belt truss; these torsional springs act in a direction opposite to rotation generated by lateral loads. The effect of shear lag on axial deformation in flange is quadratic and in web it is a cubic function of geometry. Here the total energy of the combined system is minimized with respect to lateral deflection and rotation in plane section. Solution of the resulting equilibrium equations yields the unknown coefficients of shear lag along with the stress and displacement distributions. The results of a numerical example, 50 storey building subjected to three different types of lateral loading obtained from SAP2000 are compared to those of the proposed method and the differences are found to be reasonable. The proposed method can be used during the preliminary design stages of a tall building and can provide a better understanding of the effects of various parameters on the overall structural behavior.