Abstract:
Two energy dissipation devices, each comprising a first plate, a plurality of spaced tapered plates, a plurality of cylinders, a plurality of washers, and a base frame. The devices can absorb seismic energy through the yielding of the tapered plates and effectively reduce a building vibration response during an earthquake. The devices are particularly suitable for use in building structures that must be designed to dissipate a large amount of seismic energy to achieve economical earthquake-resistant construction.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a seismic energy dissipation device, and in particular to a seismic energy dissipation device having excellent energy dissipation capacity. 
     2. Description of Prior Art 
     During the past few years, it has been realized that earthquake-induced energy in building structures can be effectively dissipated by the use of certain structural devices. For example, one such device, known as bolted X-shaped steel plate added damping and stiffness (ADAS) devices, was disclosed by Whittaker et al. in &#34;Seismic Testing of Steel Plate Energy Dissipation Devices&#34;, Earthquake Spectral 7(4): at 563-604, EERI (Nov. 1991). Recent experimental results obtained by the National Taiwan University also indicate that properly welded steel triangular-plate added damping and stiffness (TADAS) devices can sustain a very large number of yielding reversals without any sign of stiffness or strength degradation. 
     FIG. 1 is a perspective exploded diagram of a typical welded TADAS device. The TADAS device comprises a plate 10, a plurality of triangular plates 20, a plurality of blocks 30, a base 40, and a plurality of pins 41. The narrower ends of the triangular plates 20 are respectively connected to the blocks 30, while the wider ends are connected to the plate 10. The blocks 30 are pivoted to the base 40 through the pins 41. FIG. 2 shows the assembly of the typical welded TADAS device. 
     The typical welded TADAS device has significant drawbacks. It has rigidly precise requirements for the distance between the blocks 30 to allow the pins 41 to be put into the holes 31, 42. However, such strict precision is difficult to attain because the plate 10, the triangular plates 20, and the blocks 30 are welded together (it is noted that casting them as a single piece can be done with greater precision but results in less ductility, an undesirable characteristic for an earthquake-resistance device). Therefore, assembling the welded TADAS is troublesome. 
     When a transverse force is applied, the triangular plates 20 can deform well into the inelastic range since the curvature distribution is uniform over the triangular plate height. However, the spacing between the triangular plates decreases as the device deformation increases. Thus, eventual collisions between the blocks may occur as shown in FIG. 3. This changes each end of the triangular plates from a roller to a more-fixed boundary condition, and results in sudden increases of the force response of the device after the collisions of the blocks. In other words, when the blocks 30 collide with each other the original design of the triangular-plate device fails to work creating a dangerous condition in the building structure. 
     SUMMARY OF THE INVENTION 
     A primary object of the present invention is to provide a seismic energy dissipation device that has excellent energy dissipation capacity. 
     A secondary object of the present invention is to provide a seismic energy dissipation device that is easily assembled. 
     Additional objects, advantages, and novel features of the invention will be set forth in the description that follows, and will become apparent to those skilled in the art upon reading this description or practicing the invention. 
     In accordance with the objects of the present invention, there is provided a seismic energy dissipation device. The seismic energy dissipation device comprises a first plate member; a plurality of cylinder members; a plurality of spaced tapered plate members, each tapered plate member having a first end connected to the first plate member and a second end connected to a respective one of the cylinder members, the second end being narrower than the first end; and a base frame member comprising a base plate and a pair of parallel wall members, each of the parallel wall members being secured to the base plate and provided with a plurality of notches for receiving the plurality of cylinder members, respectively. 
     Alternatively, the seismic energy dissipation device comprises a first plate member; a plurality of cylinder members; a plurality of spaced tapered plate members, each tapered plate member having a first end connected to the first plate member, and a second end connected to a respective one of the cylinder members, the second end being narrower than the first end; and a base frame member comprising a base plate, a pair of parallel wall members secured to the base plate, and a plurality of parallel partitions secured to the base plate between the parallel wall members to form a plurality of grooves for receiving the plurality of cylinder members, respectively. 
     According to another aspect of the present invention, a device for dissipating seismic energy is provided, comprising a first member; a plurality of spaced tapered plate members each having a first end fixed to the first member and a second end, the second end being narrower than the first end; a plurality of cylindrical members each connected to a respective one of the second ends of the tapered plate members; and a base assembly having a plurality of spaced receiving means for receiving the cylindrical members, the receiving means being open on a side facing the first member to receive the cylindrical members. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and form a part of the specification, illustrate an embodiment of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings: 
     FIG. 1 is a perspective exploded diagram of a typical welded TADAS device; 
     FIG. 2 shows the assembly of the typical welded TADAS device; 
     FIG. 3 shows the collision of the blocks of the typical welded TADAS device; 
     FIG. 4 is a perspective exploded diagram of a seismic energy dissipation device according to a first embodiment of the invention; 
     FIG. 5 shows an example of mounting the seismic energy dissipation device according to the first embodiment to a steel frame; 
     FIG. 6 shows the assembly of the seismic energy dissipation device according to the first embodiment; 
     FIG. 7 shows the rotating situation of the cylinders of the seismic energy dissipation device according to the present invention upon a transverse force being applied thereto; 
     FIG. 8 is a perspective exploded diagram of a seismic energy dissipation device according to the first embodiment having a plurality of rectangular washers; 
     FIG. 9 is a perspective exploded diagrams of a seismic energy dissipation device according to the first embodiment having two plate washers; 
     FIG. 10 is a perspective exploded diagram of a seismic energy dissipation device according to a second embodiment of the invention; and 
     FIG. 11 shows the assembly of the seismic energy dissipation device according to the second embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 4 is a perspective exploded diagram of a seismic energy dissipation device according to the first embodiment of the invention. The seismic energy dissipation device comprises a first plate 5, a plurality of spaced tapered plates 6, a plurality of cylinders 7, a plurality of circular washers 8 (i.e.,spacers), and a base frame 9. The wider ends 61 of the tapered plates 6 are connected to the first plate 5, while the narrower ends 62 of the tapered plates 6 are connected to the cylinders 7 (e.g., by welding). The circular washers 8 are disposed on both sides of the tapered plates 6 on each one of the cylinders 7. The base frame 9 comprises a base plate 91 and a pair of parallel walls 92. The walls 92 are secured to the base plate 91 and are provided with a plurality of notches 921 (i.e., open grooves). Each of the notches 921 have an inner surface comprising a first surface 9211, a second surface 9212, and a third surface 9213. The third surface 9213 is arcuate and is formed between the first surface 9211 and the second surface 9212 so that the first surface 9211 is opposite to the second surface 9212. 
     An example of mounting the seismic energy dissipation device to a steel frame 1 is shown in FIG. 5. The steel frame 1 comprises a beam 11 and two columns 12. The first plate 5 is connected to the beam 11, and the base frame 9 is connected to the columns 12 through two inclined struts 3. 
     FIG. 6 shows the assembly of the seismic energy dissipation device according to FIG. 5. The cylinders 7 can be put directly into the notches 921 without touching the third surfaces 9213 thereof (i.e., there is a space between the third surface 9213 and the cylinder 7). In this manner, the assembly method of the present invention is easier than the assembly of the prior art TADAS device because it does not require such rigid precision in distances between the cylinders 7. The circular washers 8 fill the space between the walls 92 and the narrower ends 62 of the tapered plates 6 to prevent undesirable free play after assembly. 
     As shown in FIGS. 5 and 7, when lateral forces 21 are applied to the steel frame 1, the tapered plates 6 deform and no eventual collisions between the cylinders 7 occur. Each end of the tapered plates always remains a roller, thereby eliminating any unexpected destruction of the seismic energy dissipation device resulting from sudden increases of stiffness. In other words, the seismic energy dissipation device has improved energy dissipation capacity. 
     As described above, the cylinders 7 do not touch the third surfaces 9213 of the notches 921. Such as arrangement allows the cylinders 7 to move with respect to the base frame 9 in the vertical direction. Therefore the effects of gravity load in the steel frame 1 can be separated from the seismic energy dissipation device(i.e., no vertical forces resulting from gravity, such as the weight of the beam 11, are exerted on the tapered plates 6). This makes inelastic responses of the seismic energy dissipation device highly predictable. 
     It is not necessary for the washers 8 to be circular. A plurality of rectangular washers 8&#39; can be used instead, as shown in FIG. 8. Alternatively, two plate washers 8&#34;, as shown in FIG. 9, can be placed around the cylinders 7 on both sides of the tapered plates 6 to fill the space between the walls 92 and the plurality of tapered plates 6. Another example of the base frame 9 is shown in FIG. 9. It is noted that each third surface 9213&#39; formed between the first surface 9211 and the second surface 9212 is flat. 
     FIG. 10 is a perspective exploded diagram of a seismic energy dissipation device according to a second embodiment of this invention. The seismic energy dissipation device according to the second embodiment comprises a plate 5, a plurality of spaced tapered plates 6, a plurality of cylinders 7, and a base frame 9&#39;. Only the base frame 9&#39; is described here because the other elements are the same as those of the first embodiment. 
     The base frame 9&#39; comprises a base plate 91&#39;, a pair of parallel walls 92&#39;, and a plurality of parallel partitions 93. The walls 92&#39; and the partitions 93 are secured to the base plate 91&#39;. The partitions 93 are positioned between the two walls 92&#39; to form a plurality of grooves 94 for correspondingly receiving the cylinders 7. FIG. 11 shows the assembly of the seismic energy dissipation device according to the second embodiment. It should be noted that the cylinders 7 do not touch the base plate 91&#39; of the base frame 9&#39;. 
     FIG. 7 also shows the rotating situation for the cylinders of the seismic energy dissipation device according to the second embodiment, under a transverse force applied thereto. It is obvious that no eventual collisions between the cylinders occur. 
     Although this invention has been described in its preferred forms using various examples with a certain degree of particularity, it is understood that the present invention can vary in the details of construction according to the particular use contemplated. The scope of the invention should only be limited by the appended claims and not by the specific examples given.