ct the of hear all (196)concluded that overdriven box nails may W12x65 is used as the buttress column and two use n的5。 The loading unit consists of two sidesway cal supp for the force-applying system ded of shear walls with overdriven nails. the force-app to eacl Construction Method and Materials cure according to common construction practice Larch (Dt by ed at 40 net,surface No.2 Douglas 出路 studs was mes The force ing system was fabricated with two TS4X2 X3nhcanT72i5tm 3.3-mm-diam driven each end.The tubes straddle the stem of the ST section,which is s an to he dual end studs through the stem of the ST.which has a vertical slotted holea 10d framing nails that location snge-pin slotted c motion by the center stud (APA 1980).The par nels v 对 AM™q57595 The flanges of the channe of the top channel provides the flat surface needed for specimer es at 203 mm on cente temghanddiphcementepaci,i00%ofihehehmgaS down attachment. n and have been the overdriven nails measurements taken after final nail place structura ment found the nails to be within 0.4 mm of the desired depth. The loading sequence of a wall specimen is s:the actuator applie Test Setup The test fra installed is sche napplied t in Fig.3.The testing frame was designed with two main pur of friction between the stee and the wood.The wall specimen is 900/JOURNAL OF STRUCTURAL ENGINEERING/JULY 2002 dod 05 Jan 2009 to 222.66.175.206.Rodistribu to ASCE l .org/copyright will not significantly affect the strength of a shear wall until at least 20–25% of the nails are overdriven; and Ficcadenti et al. ~1996! concluded that overdriven box nails may even increase the strength and displacement capacity of shear walls. Clearly, due to the many variables affecting the behavior of shear walls with overdriven nails, the investigations conducted so far are not suf- ficient. Furthermore, testing has not been performed with a level of accuracy that allows bounds to be set on the strength and displacement capacity of a shear wall with overdriven nails. To determine strength and displacement-capacity bounds, it is neces￾sary to test variations of overdriven depth. A series of tests with 100% of the nails overdriven to certain depths have been con￾ducted in this research, resulting in a ‘‘worst-case’’ condition for analysis. Objectives of the testing are to characterize the behavior and to determine limits on the strength and displacement capacity of shear walls with overdriven nails. Construction Method and Materials Eight 2.432.4 m shear wall specimens, schematically shown in Fig. 2, were built according to common construction practice. Studs were 38 by 89 mm net, surfaced dry No. 2 Douglas fir￾Larch ~DFL! spaced at 406 mm on center. Moisture content of the studs was measured immediately after each shear wall test. Those measurements indicated a moisture content varying from 9.7 to 11. Studs were attached to the top and bottom plates using two 3.3-mm-diameter by 78-mm-long ~10d framing! nails driven through the plates into the end grain of the stud. End studs were doubled to allow the required uplift force to be transferred through the studs into a bolted hold down. The dual end studs were fastened together along their length with 10d framing nails at 102 mm on center. The specimens were sheathed with two 11 mm rated sheating OSB structural panels. The panels were installed with the 2.4 m dimension parallel to the studs and were spaced 3.2 mm along the vertical joint at the center stud ~APA 1980!. The panels were attached to the framing members with pneumatically driven, 2.9- mm-diameter 3 60-mm-long ~8d cooler! nails at 76 mm on center along the edges and 305 mm on center along intermediate sup￾ports. Bending yield strength of the 8d cooler nails was obtained by conducting several tests according to ASTM F 1575-95 ~ASTM 1997!. The average bending yield strength of the 8d cooler nails was 704,400 kPa. A nailing edge distance of 9.5 mm was maintained for all specimens. Two specimens were con￾structed for each of the following overdriven nail depths: flush driven, 1.6, 3.2, and 4.8 mm. To determine a lower bound on strength and displacement capacity, 100% of the sheathing nails in a given specimen were driven to the specified depth. The nail gun was set using an adjustable nose piece to underdrive the nails approximately 3.2 mm from their final desired depth. The slightly underdriven nails were then driven to their final depth using a hammer for the flush nails and a hammer and custom punch for the overdriven nails. Measurements taken after final nail place￾ment found the nails to be within 0.4 mm of the desired depth. Test Setup The test frame with a specimen installed is schematically shown in Fig. 3. The testing frame was designed with two main pur￾poses: to ensure that a ‘‘true’’ horizontal force ~or displacement! was applied to the specimen and to prevent out-of-plane motion of the specimen. The frame has a reaction unit and a loading unit. The reaction unit is assembled with wide-flange steel sections. A W12365 is used as the buttress column and two W8331 are used as braces. Steel plates are welded at each end of the braces and at the bottom of the buttress column. The braces are attached to the column with four 19 mm A325 steel bolts. The reaction unit is secured to the laboratory strong floor with three 35 mm dywidag bars. The loading unit consists of two sidesway braces, a force￾applying system, and a force-resisting system. Each sidesway frame was designed as an adjustable ‘‘H’’ frame. Two W8331 wide flange sections are used as uprights. Two structural tubings, TS 63333/8, connect the uprights and provide vertical support for the force-applying system. Two spacers are welded to the tubings, maintaining them parallel to each other and providing a sliding ‘‘window’’ for the force-applying system. Steel plates are welded at each end of the tubings and connected to each upright with four 19 mm A325 steel bolts. The double-tubing system can be attached to the uprights at different elevations according to the height of the specimen to be tested. Each upright is firmly secured to the structural floor with a 32 mm dywidag bar. The H frames are connected to each other with two L43431/4 steel angles. Two 16 mm A325 steel bolts are used to attach each end of the steel angle to the top of the uprights. The force-applying system was fabricated with two TS432 33/8 structural tubes and a ST9327.35 structural tee. The tubes are parallel to each other and are connected with a steel plate at each end. The tubes straddle the stem of the ST section, which is set inverted ~flange down!. The tubes and the ST are connected at midlength. A 25 mm hardened steel pin fits through the tubes and through the stem of the ST, which has a vertical slotted hole at that location. The single-pin slotted connection allows for wall rotation and uplift while maintaining the load in the horizontal direction. Force is always applied horizontally because the tubes are restrained from out-of-plane and vertical motion by the H braces. To provide a smooth riding for the tubes, the two sliding windows in the H braces are dressed with nylon pads to reduce the friction generated by the confinement. Two steel channels, C8318.75, serve as the force-resisting system, or foundation. The channels are stacked and welded to￾gether along their length. The flanges of the channels are perpen￾dicular to the structural floor, and the webs are parallel. The web of the top channel provides the flat surface needed for specimen connection. The channels are securely attached to the structural floor by two 38 mm dywidag bars at each end. The double￾channel unit has been drilled with holes at 203 mm on center along its length, and nuts are welded to the bottom channel at hole locations. Two additional holes are provided in the unit for hold down attachment. The hydraulic actuator is attached to the buttress column and to one of the ends of the force-applying system. All dywidag bars have been posttensioned to attach the testing frame firmly to the structural floor. The testing frame has been aligned horizontally and vertically to a tolerance of 3.2 mm. The loading sequence of a wall specimen is as follows: the actuator applies force ~or displacement! to the tubes of the force￾applying system. The tubes transfer the force through the 25 mm hardened steel pin to the inverted ST section, which is attached to the specimen with bolts. A nonslip 3M™ tape has been applied to the bottom of the inverted ST section to provide a high coefficient of friction between the steel and the wood. The wall specimen is attached to the double steel channel force-resisting system with steel bolts. The nonslip 3M™ tape has also been applied to the 900 / JOURNAL OF STRUCTURAL ENGINEERING / JULY 2002 Downloaded 05 Jan 2009 to 222.66.175.206. Redistribution subject to ASCE license or copyright; see http://pubs.asce.org/copyright