Seismic Design of Light Gauge Steel Structures: a Discussion

In a highly competitive and aggressive construction market, designers are always looking for new, proven ways to design safe, economical building structures. This is even more relevant in tract residential construction where a few dollars saved on one detail can affect who is awarded a project. In residential construction, a complete load bearing light gauge steel (LGS) system is now somewhat commonplace in the United States. Architects and engineers who once designed almost exclusively with other conventional materials are now consider LGS as an alternative. Although, it is feasible to make a direct substitution of LGS for conventional wood framing, the response of the system (and its components) may not be similar. Thus, designers who are not familiar with LGS should make every attempt possible to become aware of the statistical variability of computed values determined from design guidelines. In this paper, a few of the important design criteria related to lateral load design are discussed. Conventional light frame construction using LGS is similar to wood and in some cases one can make a direct stick-for-stick replacement of one material for the next. Where light gauge steel differs from wood framing is in the response of members to induced forces, and in some cases, flexibility and details of physical application/ construction. One area worthy of consideration (post 1994 Northridge earthquake) is the lateral load response of LGS construction in high seismic zones, particularly the vertical lateral support system. For wood framed construction, vertical lateral resistance is typically provided by wood structural panels attached to the frame. In light gauge steel construction, the designer has at least four options for providing lateral resistance: wood structural panels, flatstrap X-bracing, metal sheathing, or a braced system. These systems can be generic or one of the many proprietary systems available in the residential market today

Local and Distortional Buckling of Thin-walled Beams

Recent research has characterized the behavior of panel beams with laterally unsupported compression flanges as either a complex local buckling mode or an overall buckling mode. Tests have shown that the behavior of the unsupported flange and web is similar to that of lateral buckling, except, rotation is enforced along the axis of the web and the tension flange--a behavior which may be described as distortional buckling. In the work described here, an analytical expression is presented for computing the elastic distortional buckling stress based on a model which treats the web and compression flange as an elastically restrained beam. The formulation is similar to those for lateral and torsional buckling. The effect of web local buckling on the rotational restraint of the outstanding leg is modeled explicitly using the effective width equations described in the AISI Cold-Formed Steel Design Manual. The analytical results from the distortional buckling expression are shown to agree reasonably well with numerical results generated from an elastic fInite strip buckling program (BFINST6). A design approach is suggested for estimating the ultimate moment capacity of a section subjected to the interaction between local and distortional buckling

Flexural Capacity of Continuous Span Standing Seam Panels: Gravity Load

The standing seam panel is one of the most practical and economical roofing systems developed in recent years. Construction of the roof system requires that the panel legs be overlapped and crimped. Under gravity load, the crimped outstanding leg of the connected panels may be subject to distortional buckling. A design method was previously suggested for estimating the distortional buckling strength of the outstanding leg of a single simply supported standing seam panel. In this paper, an approximate method is present for estimating the capacity of a system of interconnected continuous span standing seam panels. Experimental results for three full-scale continuous span tests and one full-scale simple span test sbow that the approximate method provides a relatively accurate estimate the maximum capacity for a system subject to gravity load

Performance of Self-tapping Screws in Lap-shear Metal-to-metal Connections

The basic design requirement for screws in light gauge steel construction is the strength of the screw in a given application (metal-to-metal, wood-to-metal, or metal-to-wood) based on the body diameter of the screw. This statement is clearly obvious from the current AISI screw specifications for lap shear metal-to-metal connections. Recent research has shown that the performance of a screw fastener may also depend on other features of the screw including the head and thread style, and the method of installation (stripped versus unstripped screws). The data presented in this paper address these issues for lap shear connections designed with No. 12 self-tapping screw fasteners. The tests included connections in which the fasteners were properly installed and connections where the fasteners were stripped. The results show that the head style and thread form may have a significant effect on the capacity of the screw fastened lap shear, even where the screws are stripped. For a given type of screw, the results seem to indicate that any beneficial effect of a particular screw design may be diminished in connections where many fasteners are used

Dynamic Performance of Light Gauge Steel Framed Shear Walls

The results of a series of reversed cyclic 4 ft. x 8 ft. (length x height) 15/32-in. plywood and 7/16-in. oriented strand board (OSB) shear wall tests are presented in this paper. The walls were framed with C-shaped 3-1/2 in. 20 gauge (0.036 in.) studs at 24 in. on center. Each wall was subjected to a sequential phase displacement time history at a frequency of 0.67 Hz. Performance of the wall was shown to depend on the type of sheathing material, the strength of the chord studs, and the screw fastener schedule. Although the hysteretic loops were significantly pinched (a characteristic of the light framed shear wall), the wall was shown to be capable of dissipating significant energy before failure. Based on these limited test data, recommendations for interpretation of these data for design are presented

Shear Wall Values for Light Weight Steel Framing

The purpose of this experimental research program was to investigate the behavior of light gauge steel framed shear walls sheathed with plywood, oriented strand board (OSB), and gypsum wallboard (GWB). To accomplish this a total of 48 tests were completed, 42 of which are reported here. Toe overall scope of the program is described in the following section

Le lit de Napoléon et de Louis XVIII à Saint-Cloud retrouvé

L’identification récente dans les réserves du Centre des monuments nationaux d’un lit en bois doré d’époque Consulat a fourni l’occasion de retracer son histoire. Ce lit a probablement été réalisé par les frères Jacob vers 1799 pour les Directeurs au Luxembourg, avec un jumeau aujourd’hui conservé dans la chambre des petits appartements de l’Empereur à Fontainebleau. Le lit fut remployé en 1802 dans la chambre du Consul puis de l’Empereur Napoléon Ier au château de Saint-Cloud, dans son appartement ouvrant sur l’Orangerie. Renvoyé au Garde-Meuble vers 1815, le lit fut à nouveau réutilisé en 1820 à Saint-Cloud pour composer une chambre provisoire destinée au comte d’Artois, pièce qui devint l’année suivante la chambre de représentation de Louis XVIII. Cette chambre, dont l’existence était jusqu’à présent inédite, est une tentative insoupçonnée de la Restauration de rétablir l’usage des chambres de parade de l’Ancien Régime. Son usage désuet dans la France du xixe siècle n’eut pas de suite, et la pièce redevint un salon de réception dès 1825. Renvoyé au Garde-Meuble, le lit fut probablement vendu dans la seconde moitié du xixe siècle, avant d’être racheté en 1983 par le Centre des monuments nationaux.The recent identification in the reserve collections of the national monuments centre (Centre des monuments nationaux) of a gilded wooden bed of the Consulate period has offered the opportunity to look more closely at its history. The bed was probably made by the Jacob brothers in about 1799 for the Directors at the Luxembourg palace, with an identical bed which is held today in the bed chamber of the Emperor’s small apartments at the palace of Fontainebleau. The bed was installed, in 1802, in the Consul’s bed chamber at the palace of Saint-Cloud and remained in the apartments that open onto the Orangery when the Consul became the Emperor Napoleon 1. The bed was sent back to the state’s furniture repository, the Garde-Meuble, in 1815 but was brought out again in 1820, at Saint-Cloud, in order to compose a provisional bed chamber for the Comte d’Artois. The following year, this room became King Louis XVIII’s state reception bed chamber. This type of royal bedroom, not seen since the Revolution, was an unsuspected attempt by the restored Bourbon monarchy to re-establish the practice of state bedrooms of the Ancien Régime. But the function was too outdated at the beginning of the nineteenth century and the bedroom was transformed into a reception room from 1825. The bed was sent back to the Garde-Meuble and was then sold, probably during the second half of the nineteenth century. It was purchased by the Centre des Monuments nationaux in 1983

Reference Section Method for Local Web Buckling

The present AISI effective width approach for determining flexural section capacities of sections with slender webs requires an iterative approach. A simplified method, called the Reference Section Method or RSM, which eliminates the need for iteration is presented and discussed. The reference section is defined as one that is similar to the actual section except for the web height. This simplified method is based on the premise that the flexural capacity of a section with slender webs is proportional to that of a reference section with compact web. The ratio of the web height of the actual section to that of the reference section defines the constant of proportionality. To demonstrate the applicability of the RSM, parametric study is performed on channel joist/rafters (MSMA sections). The capacities of the sections predicted using the RSM are compared to the AISI predicted capacities. Although the results using RSM compares well with that using the AISI specification, refinement is still possible through experimental research