Recently, steel-framed houses began to be built even in Japan because of rise in timber price. A technology for building them has been mainly developed in warm regions, such as California and Florida. So the technology has to be verified and to be improved according to climate and custom of Japan if necessary. The paper discusses thermal insulation, moistureproofing and air-tightness of the steel-framed houses on basis of field data, which were measured in steel-framed houses existing in Japan.

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Steel-framed housings have a slip type force-displacement relation with low energy consumption in the slip area. The aim of this paper is to survey energy responses on Steel-Framed housing which have this type of hysteresis model under strong seismic motions. Simulated and recorded seismic waves are both used to define the influence made by their instantaneous energy input value. Seismic analyses are made by using a Steel-framed shear wall hysteresis model and by converting the building into a single as well as a multi-degree-of-freedom system. This multi-degree-of-freedom system will show the energetic properties of the building caused by the damage concentration that appears in particular story.

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Seismic performances of steel-framed housings are secured by bearing-wall panels composed of wooden panels or gypsum board with light steel members of 1.0mm thick, fabricated by screw bolts. Their hysteretic characteristics have been tested and modeled for time-history analyses, however, their damping values with finishing against large deformation zones are yet clarified. In this paper, real-size dynamic test of bearing walls are carried out, and their damping performances with finishing and visco-elastic dampers are verified. Their performances are discussed on 3 or 4 story steel-framed housing structures, followed by proposing easy damage evaluation method.

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This paper reports on the experimental studies on the durability of galvanized light-gauge steel shapes with thickness up to 1.6 mm, inclusive of the screw connections. The durability of the shapes and screw connections were examined by combined cyclic accelerated corrosion tests and shear tests on corroded connections. The test results show that aluminum zinc-alloy-coated shapes are superior in durability to conventional galvanized shapes, that the shear strength of screw connections is not reduced after the shapes reached to full red rust conditions. Thus, according to these test results, the durability of galvanized light-gauge steel shapes was clarified.

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 The number of cold-formed steel framed houses is increasing and they tend to be built as apartment houses rather than detached houses. Along with this trend, heavy-floor impact sound insulation performance of the houses is expected to be improved. In order to meet this expectation, experimental test and numerical analysis are carried out, using the really-constructed houses as specimens. The results indicate, 1) in order to improve the heavy-floor impact sound insulation performance of cold-formed steel framed houses, sound pressure in a frequency band of 63 Hz has to be reduced, 2) floors of cold-formed steel houses tend to vibrate in a perpendicular direction to floor joists axis in the low-ranged frequency band, which is caused by the anisotropy of floor bending stiffness, 3) considering the vibrating mode shape, to improve sound insulation performance, it seems one of the solutions to increase the floor bending stiffness of weak axis, and 4) the possibility of the suggested solution is confirmed through the on-site test.

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The purpose of the present study is to develop the elastic-plastic analytical model of screw which demonstrates slipping behavior in steel framed houses. This model consists of multiple yield surfaces and slip slot. The analytical results represent the characteristic behaviors of test which restoring force declines because screws becomes plastic by the influence of load behavior and increases little by little throughout slipping period. As a analytical result, it turned out that the behavior of wall was dependent on screws.

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 The bearing walls of steel-framed houses are composed of thin-thick steel frames, sheets such as plywood and drilling screws for fasteners. The sheet to frame joints fastened by drilling screws bring up the complicated behavior of bearing walls, Therefore, structural properties of the bearing walls have to be estimated by full-scale experiments to design steel-framed houses. In order to estimate those properties without experiments, it is needed to make clear sufficiently about the bearing mechanism of walls.
 In this paper, on the basis of studies on full-scale experiments by authors, it will be discussed the simple method which can be easily estimated the characteristics of load-deflection relationship on steel-framed bearing walls. Furthermore, the effectiveness of the proposed method is discussed by comparisons of experiments.
 On the bearing walls subjected to horizontal load H, the displacement u is given by the sum of three components (Fig. 2). These are displacement u_b caused by bending, displacement u_s by the shearing of sheet and displacement u_n caused by slip-displacement of sheet to frame joints. The experimental study¹⁴⁾ showed that the displacement u_n govern the elasto-plastic behavior of whole bearing walls. Then, it becomes important to estimate the displacement u_n for the bearing walls subjected to horizontal load H.
 The curve of H-u_n relationship can be calculated by Eq.(3)-Eq.(6) using numerical calculation of Fig. 6. Eq.(3) is derived geometrical relations with the sheet and framing members in Fig. 4. Eq.(6) are derived from the equations of equilibrium for the fastener forces acting at each framing members (Fig. 5). The example of the numerical calculation (Fig. 7) is indicated that the figure of H-u_n curve is similar to that of f-δ curve of drilling screw joints, which is idealized to multi-linear type.
 The repeated calculations are not practical for design of the steel-framed bearing walls. To achieve the simple method, f-δ curves and the H-u_n curves are modeled into multi-linear type in Fig. 8. For the tangent stiffness K_n,i and the load H_pi at tangent stiffness changing point of H-u_n curve idealized to multi-linear type, the simple estimation equations are discussed, and Eq.(13) and Eq.(21) are proposed. Just for information, H-u relationship is the sum amount of H-u_b relationship, H-u_s relationship estimated by elastic theory and H-u_n relationship by proposed method.
 The calculation results by the proposed methods are compared with the experiments on steel-framed bearing walls¹⁴⁾ in Fig. 14 and Fig. 15. The parameters of specimens are shown Table 1. The results by the proposed methods are agree with that of experiments except Specimen A-100, B-100 and C-100 of which maximum strength are given by buckling of plywood. And also, for the initial stiffness, yielding load and maximum load, the calculation values are good agreement to the results of experiments.

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Steel framed houses consist of wall and floor panels made of structural boards and light-gauge cold-formed steel frames that are fastened with drilling screws. We had already made clear that the conventional shear walls show poor ductility and low damping ability and we developed a new type of shear wall with a few built-in friction-type dampers. Through the static loading tests results, we confirmed that this wall exhibits high energy absorbing capacity as well as high ductility. In this study, we first give general information on conventional and newly developed shear walls. Then, an analytical study to evaluate ductility reduction factor of the buildings designed using this wall will be conducted by Incremental Dynamic Analysis (IDA). Finally, we confirm that this wall has higher effects on suppressing seismic response compared with conventional shear walls.

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Cold-formed thin-walled steel members with thicknesses of around 1mm are relatively new structural members in Japan. It is because such a thin steel member had not been long allowed to use as a structural member under the Japanese Building Standard Law. This situation has been changed in recent years through the development of steel-framed houses. Although the use of such a thin steel member is currently possible, there are still some design issues to be clarified for realizing the broader applications, mainly related to its complex buckling behavior. The complex buckling is called distortional buckling and is often seen in the floor and roof panels in steel-framed houses. To study the behavior of distortional buckling in detail therefore, negative bending tests were conducted in this paper for panels consisting of two lipped-channels and structural plywood fastened together with screws. Twelve bending tests provided detailed behavioral information on distortional buckling and the possible strength evaluation methods for improving the design of thin-walled steel members.

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 A steel framed house consists of walls and floors made by panels that plywood boards and light-gauge cold-formed steel frames are fastened with drill screws. Seismic performance of steel framed houses mainly depends on force-deformation relation of shear walls. Most conventional plywood shear walls show poor ductility because they may suddenly lose strength triggered by the break of the screw or punching out of the board when deflection angle becomes around 1/30[rad]. Therefore the energy absorbing ability of this wall is very low because of its pinching property in load-deflection relations. Since Japan is an earthquake prone country, the use of steel framed houses has been limited to three story buildings until recent years. But the revision of the design code in 2012 made it possible to apply the structure to a medium-rise building up to four stories. However, when we want to build a four-story house using conventional plywood shear walls, the amount of walls often becomes too much, spoiling the flexibility of the construction. In addition, it is a big problem that response acceleration and stress acting on specific parts of a house will become excessive.
 In this paper, we first proposed a method of inserting plywood inside the peripheral frames consist of the light-gauge cold-formed steels and fastening it with drill screws. By using this method, it is possible to prevent the punching failure of drill screw joints and the dropout of the plywood. As a result, it was shown by static loading test that the ductility of this shear wall is improved.
 Then, we proposed a method to install friction devices that consist of lubricated coated galvanized steel tightened with high-strength bolts between the studs and the inserted panel. This method is intended to make use of energy absorption by frictional force caused by the relative deflection generated between the studs and inserted panel. We conducted a number of the static loading tests on this built-in friction mechanism shear wall and found that it has very high ductility and damping capacity compared with conventional plywood shear wall. As a result of the shaking table tests, it is also confirmed that the wall can hold a stable energy absorbing capacity even when subject to repetition of large amplitude ground motions.
 Finally, we investigated the seismic performance of 2-story house models designed with built-in friction mechanism shear walls by earthquake response analyses. In this analytical study, we used seismic waves recorded in Japan with the maximum speed over 50[cm/sec] as waves exceeding the level required by seismic design regulations. We investigated the quantity of walls that can secure safety against these seismic waves comparing with the models designed by using conventional plywood shear walls. As a result of a number of analytical studies, it was shown that the models using built-in friction mechanism shear walls can suppress the responses to severe earthquake ground motions significantly as well as reduce quantity of walls.

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The formulas, reflecting the characteristic of failure modes, about the ultimate strength of self drilling tapping screw connections fastening two thin steel plates, are presented in this paper. The theoretical investigation on the transfer mechanism of forces makes clear the characteristics of each failure mode. And also, it derives the relations between the ultimate strength and the factors by which it is governed. The value of unknown parameters for establishing the efficient formulas of each failure mode are decided from the data of experiments which examined 124 specimens. Moreover, the availability of these presented formulas is confirmed by the results of another experiments quoted from the reference.

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Ductility reduction factor Ds used in second phase design is based on the energy constant rule proposed by Newmark. In addition, it is also important to set a story drift limit to the structure on seismic design. Accordingly, allowable story drift and Ds factor are required to consider in design; however, the building code does not specifically address the relationship between these two values. The duration of the ground motion has less effect on the structure that has spindle-shaped response. On the other hand, the structure having an origin progress slip response will cumulate the deformation during the seismic event; response deformation will increase lineally with the cycle of earthquake and f value. As a result, the relationship between allowable story drift and Ds factor for origin progress slip response structure should consider the characteristic of input ground motion.
In this paper, firstly, Ds factor for the structure shows origin progress slip responses are discussed based on energy method and a formula for Ds factor based on cumulative plastic deformation ratio is proposed. Secondly, the relationship between allowable story drift and Ds factor for origin progress slip and the hybrid of origin progress slip and spindle-shaped responses are discussed. The results obtained from this research will make it possible to apply through dynamic analysis to second phase design uniformly. Finally, controversial point of current Ds formula is clarified from the comparison study between proposed Ds formula.

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In this study, the cyclic hysteretic characteristics and collapse mode of hybrid structure, which is constructed of light gauge steel construction and steel moment frame, is cleared by static cyclic loading. These hybrid structures are composed of different restoring force characteristic components, steel moment frames and shear walls. Using this experimental results, structural characteristic factor (Ds) is evaluated by current methods, and it is shown that Ds factor by current methods are not agreeable to actual condition of hybrid structures. So, a new evaluation method for adapting to hysteretic characteristics of hybrid structure is presented.
Additionally, the seismic response analysis is done by using the hysteretic characteristics of steel moment frame and light gauge steel house shear wall which are obtained from experiments. The Ds factor corresponding to the allowable story drift angle is evaluated by cumulative plastic deformation magnification. This Ds factor is compared with the Ds factor getting by new evaluation method, in order to show that the new evaluation method is correct and available.

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This paper shows the outline of steel framed houses and the promotion activities by the Kozai Club. Steel framed houses, in which galvanized thin steel plate shapes were used in stead of lumber to the framing materials used in two by four lumber houses, were originally developed in the U.S.A. Recently, because of the increase in lumber cost and the quality of lumber needed, steel framed houses have caught much attention, and already have a sufficient share in the market in the U.S.A. In Japan, after the Great Hanshin earthquake, as steel framed houses were built for the temporary houses, construction of steel framed houses had already begun, and it is estimated that future development will continue because of the saving of forest resources. This paper shows the researches for steel framed houses by the Kozai Club, and the targets and problems in the promotion of steel framed houses.

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外装用塗装鋼板は，紫外線や熱などによる塗膜の変質と，水・塩分及び湿潤乾燥などによる鋼板の腐食が複合的に進行して劣化していく．それを再現するために紫外線照射，塩水噴霧，湿潤などを連続的に行える新規サイクル試験機を開発し，それを用いた複合サイクル試験を実施し，適切と考えられる試験条件と評価項目を選定した．そこで今回は，その試験条件と評価項目で，建築用途で使用されている，めっきの種類や塗料の種類の異なる5種類の外装用塗装鋼板について，複合サイクル試験を実施した．そして，その結果に基づいて，住宅の尾根板金類として15年間および30年間使用した場合の劣化状況を推定し，再塗装などの必要な措置を検討した．

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A system that controls the rocking behavior of multistory shear walls is proposed as an innovative damage-control system for cold-formed steel structures. In this system, we have developed a new hold-down equipped with a fuse function (HDF) that controls the rocking behavior, and is placed on the foundation of multistory shear walls. The HDF contributes to reducing damage to both structural and nonstructural members in cold-formed steel framed buildings, dissipating seismic input energy in the event of a large earthquake. The present paper describes the static tests performed using HDF specimens and folded-steel sheet walls specimens with the HDFs. It has been confirmed, from the test reuslts, that the shear walls systems using the HDFs have high energy-dissipating performance in comparison with the exiting shear wall systems.

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In general, shear walls with corrugated thin steel sheets in residential cold-formed steel framing have undesirable lateral deformation capacity as a result of the buckling of the corrugated sheets or pull-out of the screws used to connect the corrugated sheets to the cold-formed steel members. The purpose of the present study is to provide corrugated shear walls with a large deformation capacity by designing "bearing-failure critical" screw joints. The validity of this design was experimentally investigated using a series of in-plane cyclic racking shear tests of the corrugated sheet shear walls. The tests showed that the local bearingfailures provide a shear wall with a stable and ductile behavior.

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We have clarified the mechanisms used to prevent concealed condensation and heat bridging in the wall of a light-gauge steel framed residential house, built with an external thermal insulation structure, from the long-term field measurements of a residential house constructed in Hokkaido, Japan. The key points of our study are: 1). The light-gauge steel can prevent a fall in temperature inside the wall by transferring energy from space heating. 2). The light-gauge steel can raise the temperature of self-drilling screws to connect outside and inside wall materials. 3). Computer simulations were used to analyze these mechanisms of thermal heat transfer and distribution. The result of this study is that there is very little possibility of concealed condensation or heat bridging in the wall of the house. The evaluation shows that the energy consumption efficiency for space heating is therefore extremely high in this building.

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