APA Engineered Wodd Handbooks Episode 9 potx

7.1 CHAPTER 7 DESIGNING FOR LATERAL LOADS Thomas D. Skaggs, Ph.D., P.E. Senior Engineer Zeno A. Martin, P.E. Associate Engineer 7.1 INTRODUCTION This chapter addresses the design of wood-framed structural-use panel-sheathed diaphragms and shear walls, which also may be referred to as vertical diaphragms. The supplement does not cover the method in which lateral loads are determined, nor cover prescriptive requirements for nonengineered wall and roof construction, as these topics are addressed in complete detail by the applicable model building codes. 7.2 TERMINOLOGY Average story drift: is the average of the deformations of all lines of shear walls oriented parallel to the applied load. The deformation shall be calculated as a portion in each line of shear walls at the top of the shear wall (see Eq. [7.1]). Base shear: the total reaction at the base of a wall parallel to the axis of the wall or structure due to an applied lateral load; a ‘‘sliding’’ force. Blocked diaphragm: a diaphragm in which all panel edges occur over and are fastened to common framing; the additional fastening provides a load path to transfer shear at all panel edges, thus increasing the overall shear capacity and rigidity (stiffness) of the diaphragm. Boundary element: diaphragm and shear wall boundary members to which sheathing transfers forces. Boundary elements include chords and drag struts at diaphragm and shear wall perimeters, interior openings, discontinuities, and re- entrant corners. 7.2 CHAPTER SEVEN Box-type structure: when diaphragms and shear walls are used as the lateral force resisting system of a building, the structural system is called a box system. Chord: the edge members of a diaphragm or a shear wall, typically the joists, ledgers, truss elements, double top plates, end posts, etc., that resist axial forces. Chords are oriented perpendicular to the applied lateral load. Collector: a structural building component that distributes the diaphragm shear from one building element to another; typically served by the double top plate. Collectors are oriented parallel to the applied lateral load. Also called drag struts. Diaphragm: a flat, or nearly flat, structural unit acting like a deep, thin beam. The term is usually applied to roofs and floors designed to withstand lateral loads. Diaphragms are commonly created by installing structural-use panels over roof or floor supports. Diaphragm, blocked: a diaphragm in which adjacent sheathing edges are fas- tened to a common member for transferring shear. Examples to achieve blocked status are panels being fastened to common framing members, sheet metal fas- tened to adjacent panels typically with staples, or staples driven through the tongue-and-groove for 1 1 ⁄ 8 in. wood structural panels. Diaphragm, flexible: a diaphragm is flexible for the purpose of distribution of story shear when the lateral deformation of the diaphragm under the applied lateral load (see Eq. [7.2]) is greater than or equal to two times the average story drift. For analysis purposes, it can be assumed that a flexible diaphragm distrib- utes story shear by tributary area into lines of shear walls oriented parallel to the applied lateral load. Traditionally, wood diaphragms are considered flexible. Diaphragm, unblocked: a diaphragm in which only panel edges in one direction (i.e., the 4 ft wide panel ends) occur over and are fastened to common framing; the typical diaphragm for standard residential construction. Drag strut: see collector. Lateral load: horizontal forces that result from wind or seismic forces. Wind forces act on the side of the building and on sloped roofs. Seismic forces result from ground accelerations causing inertial forces to act on the structural mass. Lateral stiffness: the slope of the load-displacement for a lateral force-resisting system. Load path: the path taken by forces acting on a building. Loads are transferred by the elements in the building and by the connections between those elements into the foundation. Overturning: occurs when a lateral force acts on a wall or structure and the wall is restrained from sliding; a ‘‘tip-over’’ or overturning force results. Shear wall: a vertical, cantilevered diaphragm that is constructed to resist lateral shear loads by fastening structural-use panels over wood wall framing. This structural system transfers lateral forces from the top of the wall to the bottom of the wall, and eventually transfers the lateral loads to the foundation. Shear wall segment: a portion of the shear wall that runs from the diaphragm above to the diaphragm/foundation below; also known as full-height segment. Shear wall segments occur between building wall discontinuities such as doors, windows or corners in the shear wall. Structural-use panel: a structural panel product composed primarily of wood and meeting the requirements of USDOC PS-1, USDOC PS-2, or equivalent DESIGNING FOR LATERAL LOADS 7.3 T C L b w w h Wind load, F (lb per sq ft) Side wall carries load to roof diaphragm at top, and to foundation at bottom Roof (horizontal diaphragm) carries load to end walls End wall (vertical diaphragm or shear wall) carries load to foundation v (lb per lin ft of diaphragm width) = w (lb per lin ft of wall) = F T ( lb ) = C = vh v v v h 2 wL 2b FIGURE 7.1 Distribution of lateral loads on buildings. proprietary standard recognized by the code authority. Structural-use panels in- clude all-veneer plywood, composite panels containing a combination of veneer and wood-based material, and matformed panels such as oriented strand board and waferboard. Subdiaphragm: a portion of a larger wood diaphragm designed to transfer local forces to primary diaphragm collectors. Tie-down (hold-down): a device used to resist uplift of the chords of shear walls. Wall bracing: a building element that resists lateral loads under low load situ- ations; the configuration and connections are prescribed by the building codes for light-framed wood structures. 7.3 SHEAR WALLS Shear walls and diaphragms are designed to transfer in-plane forces. When these two assemblies are used to resist lateral design forces of buildings, the structural system is sometimes referred to as a box system. The shear walls provide reactions for the roof and floor diaphragms, and transmit the forces into the foundation (see Fig. 7.1). The structural design of buildings using diaphragms is a relatively simple, straightforward process if the designer keeps in mind the overall concept of struc- tural diaphragm behavior. Actually, with ordinary good construction practice, any sheathed element in a building adds considerable strength to the structure. Thus, if the walls and roofs are sheathed with panels and are adequately tied together and tied to the foundation, many of the requirements of a diaphragm structure are met. This fact explains the good performance of structural-use panel sheathed buildings 7.4 CHAPTER SEVEN in hurricane and earthquake events even when they have not been engineered as diaphragms or shear walls per se. Various textbooks and other resources provide in-depth coverage of this topic (see the References). For the purposes of this chapter, the following assumptions are made: • These assemblies act as deep beams. • In-plane shear resistance is provided by the structural-use panel-to-framing con- nections. • Axial tension and compression resistance is provided by the chord members (anal- ogous to an I-beam flange). • Nailed assemblies, as shown in Tables 7.1, 7.2, and 7.7, exhibit ductile, energy- absorbing behavior. While shear resistance of these assemblies can be computed by principles of engineering mechanics 1 it is recommended that designers use Tables 7.1, 7.2, and 7.7 for typical design purposes. In addition to eliminating labor-intensive calcula- tions, these tables limit configurations to those that have proven to exhibit the aforementioned ductile behavior by demonstration via structural testing and years of successful in-use performance. 7.3.1 Shear-Wall Testing Buildings are subjected to a variety of loads during their lifetime. All loads resisted by the structure must be transferred into the foundation. Gravitational loads (roof live load, snow load, dead load) react vertically on the structure and are typically transferred to the foundation through load-bearing walls. Wind and earthquakes apply lateral load to a structure. Lateral loads are transferred to the foundation through lateral force-resisting systems. For light-frame construction, the gravita- tional forces are typically resisted by nominal dimension lumber in the form of wall studs, and the lateral loads are commonly resisted by wood structural panel sheathed shear walls. APA—The Engineered Wood Association has conducted research on the behav- ior of shear walls for almost 50 years. The first technical report was published in 1953. Two years later the Uniform Building Code (UBC) recognized shear-wall design values based on the APA tests. This recognition allowed shear walls to be used as lateral force-resisting systems in buildings designed per the UBC. The intent of the following sections are to review the methods in which current shear-wall values are derived, discuss some of the questions raised about shear-wall performance based on monotonic and reversed cyclic load testing, and briefly dis- cuss research efforts that are currently being conducted by APA. Static Test Methods ASTM E72. The current version of ASTM E72 2 covers standard tests of wall, floor and roof elements. Although ASTM E72 is often thought of as a racking test, the actual standard test method is much more broad-based. The racking test portion of ASTM E72 has the longest history of any of the standard test methods discussed in this chapter. Much of the data that have traditionally been used to support shear- wall design values have been developed from tests following ASTM E72. This DESIGNING FOR LATERAL LOADS 7.5 Load Stop Hold down rod 8 ft. (2.4 m) 8 ft. (2.4 m) FIGURE 7.2 Schematic diagram of shear-wall test following the methods out- lined by ASTM E72. 2 particular test method is based on one-directional (also referred to as monotonic) load tests on 8 ϫ 8 ft (2.4 ϫ 2.4 m) shear walls. Figure 7.2 is a schematic diagram of a typical shear wall with studs spaced 24 in. (610 mm) o.c., based on ASTM E72 test methodology. The ASTM E72 test method has several notable attributes. Since the standard test method does not specify any dead load on the top of the wall, some type of overturning restraint is required. The overturning forces in the wall are resisted by steel hold-down rods. Although it can be argued that the steel rods do not model the real world, the rods are designed not to represent real-world hold-down mech- anisms but to model the effects of dead load incurred in an actual structure. Another notable feature of an ASTM E72 test wall is the stop at the end of the wall. This stop is intended to prevent lateral slippage of the wall assembly on the base of the test frame. Typically, several incremental monotonic (unidirectional) loads are applied and removed before the wall is taken to failure. These loads allow the measurement of permanent wall set to be recorded at different load levels. The magnitude of the load cycles specified by this test standard is not related to the sheathing being tested. For example, low-strength and high-strength shear walls follow the same load cycle. The test method is partially intended to eliminate confounding factors of the test that may affect the overall results. The test method is intended primarily to evaluate panel shear resistance, including the sheathing attachments to framing, not the be- havior of the structural assembly or system. 7.6 CHAPTER SEVEN 8 ft. (2.4 m) 8 ft. (2.4 m) Hold-down connector FIGURE 7.3 Schematic diagram of shear-wall tests following the methods outlined by ASTM E564. 5 The following observations can be made. The vast majority of shear wall tests conducted over the past 50 years follow ASTM E72. One of the problems with following this test method is that it specifies load increments, regardless of the wall sheathing material. ASTM E72 was originally intended for evaluating nominal wall bracing for residential applications that exhibited relatively low shear capacities. The load increments for shear walls that are designed for high loads may represent only a fraction of the design load. Although ASTM E72 allows other loading patterns to be used, no suggestion is given on how the loads should be chosen. APA test methodology, covered in PRP- 108, 3 deviates from ASTM E72 on this point, in that the loads are determined as a function of the design load. This ensures that the wall will be loaded to design load at least three times. The results from ASTM E72 tests are often used to verify the allowable design values published in the U.S. model building codes or the 2000 International Building Code (IBC). 4 A load factor (strength limit state/design shear load) for a test series typically averages about 3.0. ASTM E564. Some designers and agencies have been critical of the ASTM E72 test method due to the use of the artificial hold-down mechanism (steel hold- down rods); therefore, an alternative ASTM standard was developed, ASTM E564. 5 The ASTM E564 test method is designed to evaluate the performance of shear wall assemblies instead of focusing only on the behavior of the sheathing. Figure 7.3 illustrates a schematic diagram of an ASTM E564 assembly test. For ASTM E564, hold-down connectors are required to resist overturning forces instead of hold-down rods as used in ASTM E72. Unlike ASTM E72, ASTM E564 provides an option to apply vertical loads to simulate gravitational forces. Another DESIGNING FOR LATERAL LOADS 7.7 difference in the two test methods is that ASTM E564 does not utilize a stop at the sole plate; lateral slippage is prevented only by the sole plate bolts. ASTM E564 test procedures also subject the shear walls to several monotonic load and unload cycles. In contrast to ASTM E72, the magnitude of the loads is based on the expected maximum shear capacity (strength limit state) of the walls. Although, some may view the ASTM E72 and E564 load tests as being cyclic, since the walls are loaded and unloaded several times, the methods do not model true behavior of earthquakes because: (1) the loads are only applied for a small number of cycles, (2) the load is not fully reversing (it only loads the wall mono- tonically in one direction) and (3) the monotonic tests are typically performed slowly, thus modeling static behavior. Such loading is considered applicable to wind loading conditions. Conversely, earthquake loads are typically fully reversing cyclic loads that continue for numerous cycles and cause dynamic loads on the structures. Quasi-static Cyclic Test Methods Structural Engineers Association of Southern California (SEAOSC) Test Method. Code officials, engineers, and researchers have questioned how well mon- otonic laboratory tests of shear walls relate to the behavior of full-size shear walls subjected to reversed cyclic loads. After the Northridge, California, earthquake (Jan- uary 17, 1994), the City of Los Angeles adopted several building code changes that effectively reduced (by 25%) the allowable design loads for shear walls based on monotonic tests, until cyclic (reversed) load shear wall tests were conducted to confirm or modify previously recognized values. Since very few data were available from matched monotonically and cyclically tested shear walls, the reductions were based on experience of structural engineers in Southern California and were some- what arbitrary. The intention of the interim reductions was to provide conservative design values until more informed design recommendations could be formed. One of the hurdles of cyclic testing was that there was no universally recognized protocol for cyclic load testing of shear walls. In 1994, the Structural Engineers Association of Southern California (SEAOSC) took on the task of developing a test standard for cyclic (reversed) loading of shear walls. The proposed standard was finalized in 1996, 6 with minor revisions in 1997. The shear-wall test specimen used in the SEAOSC test method is similar to the wall used for ASTM E564 monotonic tests (Fig. 7.3). The overturning forces that are generated in the wall are resisted by the use of hold-down connectors. Load applied to the top of the wall is a fully reversing, sinusoidal load with decay cycles, as illustrated by Fig. 7.4. The magnitude of the load cycles is based on the first major event (FME). By definition, the FME is the ‘‘first significant limit state to occur.’’ In lay terms, FME represents the point in which permanent damage to the wall begins to occur. This point can also be thought of as the proportional limit or yield limit state of the wall. The load cycle that is used by the SEAOSC test method is based on a proposed sequential phased displacement (SPD) procedure. 7 The proposed procedure was developed by a joint U.S. and Japan Technical Coordinating Committee on Masonry Research and is commonly referred to as either the SPD or the TCCMAR proce- dure. The SPD procedure is designed to provide fully reversing displacements with progressively increasing displacements. After FME occurs (after nine cycles in Fig. 7.4), a degradation cycle is included in the test cycle. This degradation cycle represents 100%, 75%, 50%, and finally 25% of the maximum displacement increment. The degradation cycle is included to analyze the effect of systems that develop slack. The area of the hysteresis loops 7.8 CHAPTER SEVEN -400 -300 -200 -100 0 100 200 300 400 010203040506070 Cycle Number Specimen Displacement (% of FME) FIGURE 7.4 Load cycle following the SPD procedure. 6 represent the energy dissipated by the shear wall. Observing the load vs. displace- ment hysteresis loops enables a slack system to be identified by the load essentially approaching zero during the degradation cycles. A slack system will lose the ability to dissipate energy at lower displacements. Slack systems may occur for some bolted connections (localized wood crushing causing loose joints) or some types of brittle systems; however, wood structural panel shear walls with mechanical fasten- ers, such as nails, generally do not behave as a slack system. The next distinct portion of the load cycle is the stabilization load cycles. Each incremental displacement has three stabilization cycles. The intent of this cycle is for the strength and stiffness degradation to stabilize before the next incremental cycle. The stabilization cycle can be thought of as ‘‘at a given displacement, the wall incurs as much damage as it can’’; then the next load cycle increment is initiated. Although the original SPD proposed procedure was based on quasi-static load- ing, the SEAOSC procedure specifies that the tests will be conducted at a loading rate from 0.2–1.0 Hz. The specified load rate is at a lower (or at least on the low end) frequency than what is typically observed in an earthquake. There are several reasons to test at a lower frequency. First, it is believed that lower frequency tests will limit the inertial effects that might occur during the load tests. The second reason is that these types of tests are performed with the aid of an effective force- testing system. An effective force testing system simulates the dynamic loads of earthquakes by applying an effective force to the wall. This effective force is similar to forces generated by the mass of the structure and the ground acceleration. The effective force testing system is used in lieu of shake table testing. The lower frequencies are more attainable by typical effective force-testing systems. In 1997, the International Conference of Building Officials Evaluation Service, Inc. (ICBO ES) adopted the SEAOSC test protocol by means of an acceptance criteria 8 for evaluation of prefabricated sheathed shear-wall elements. Although the acceptance criteria do not currently apply to site-built wood structural panel DESIGNING FOR LATERAL LOADS 7.9 sheathed shear walls, it is believed that the recognition of the acceptance criteria sets a precedent for the evaluation for all light-frame lateral force resisting elements. Also in 1997, the SEAOSC test method was presented to ASTM Committee E06 for recognition as a consensus test method. The SEAOSC test method follows the guidelines of ASTM format to expedite approval. During the time this chapter was being written, the test method was balloted several times. It is expected that the standard will be balloted at the main committee level soon. In 1995, APA—The Engineered Wood Association installed a cyclic loading system that has the capability to test shear walls following the SEAOSC procedure. One of APA’s objectives is to gain knowledge about shear-wall performance in the cyclic domain. An extensive multiyear test program has been initiated to answer many questions that have not been addressed in the cyclic test domain. A few of the tests programs are: • Investigate the behavior of narrow shear walls subjected to cyclic loading and develop design recommendations for their design and construction. • Analyze the behavior of walls that contain two dissimilar sheathing materials: for example, wood structural panel on one side, gypsum wallboard on the other side. • Analyze the effect of sheathing orientation (vertical or horizontal). • Analyze the effect of blocked and unblocked sheathing. • Study alternative sheathing fastener systems. The test programs are designed to study factors that have raised questions about the behavior of cyclically loaded shear walls. Due to the importance of resolving several of the initial issues, APA funded a series of tests at the University of California-Irvine (UCI). This test program consisted of eight different shear walls tested with fully reversed cyclic tests in accordance with the SEAOSC procedure (note that the test method was not finalized when these test were conducted, but the tests were conducted following a draft of the test method). However, no match- ing monotonic tests (either ASTM E72 or ASTM E564) were conducted on these shear walls. The preliminary findings 9 of these load tests indicate that the maximum shear loads tended to be lower than monotonic tested walls following ASTM E72 test procedures. Although this finding could be significant, the comparison is not based on matched specimens. For example, fastener fatigue failure, as related to cyclic load protocol, has a significant effect on the final results but is not a failure mode for monotonic testing. Most of the UCI tests were conducted following the SPD test procedure. One test was conducted following a modified SPD procedure. This modified procedure eliminated the degradation cycles that occur after FME. Figure 7.5 is a represen- tation of the load cycle followed for one of the eight tests. Matched walls were tested following the SPD procedure (with degradation cycles and stabilization cycles) and the modified SPD procedure (stabilization cycles only). The two tests indicated that the degradation cycles did not significantly affect the results of wood structural panel shear-wall tests. The degradation cycles may not be necessary for future shear-wall tests, although other tests in progress with wood structural panels and other sheathing materials over steel framing indicate that deg- radation cycles may provide useful information. One of the significant observations of the APA tests conducted at UCI was that sheathing nails around the perimeters exhibited fatigue. The majority of the load cycles in the SPD procedure exceed the FME displacement (yield limit state). Since wall damage is dependent on total number of cycles and the number of cycles and 7.10 CHAPTER SEVEN -400 -300 -200 -100 0 100 200 300 400 0 5 10 15 20 25 30 35 40 Cycle Number Specimen Displacement (% of FME) FIGURE 7.5 Simplified SPD load cycle as reported by Rose. 9 the amount of displacements that exceed FME, it follows that the behavior of the wall will be dependent on the load history. Since nail fatigue was not reported in observations of damaged shear walls after the Northridge, California, earthquake or other recent seismic events, Ficcadenti et al. 10 conducted cyclically loaded shear-wall tests following a modification of the SEAOSC procedure. Steel hold-down rods, similar to ASTM E72, were utilized. The hold-down rods were required on both ends of the test wall to resist overturning loads in both directions. The SPD load cycle was also modified by removing the stabilization cycles, but included the degradation cycles of the SPD procedure. Figure 7.6 illustrates the modification of the load cycle. In these tests, failures due to nails pulling through the structural panel were observed. Smaller-sized nails and thinner panels were used in these tests. Some of the differences may be attributed to load history, and some may be attributed to the fastening conditions. These walls also achieved maximum shear loads in excess of 3.0 times design load. The maximum shear capacity of the walls was achieved about 2 in. (50 mm) displacement. Conversely, several of the APA tests reached the maximum shear loads at around the 1 in. (25 mm) displacement cycles. Figure 7.7 is a typical hysteresis loop observed in one of the eight APA wall tests conducted at UCI. Note that the cycled shear capacity occurred at about 1 in. of displacement. The maximum shear capacity of shear walls tested following the SEAOSC test procedure will clearly be affected by the fatigue failures of the nails. It appears unrealistic to assume that cyclically tested walls will achieve load factors that are as high as matching monotonically tested counterparts due to the difference in failure modes. CUREe Protocol and Others. As previously discussed, the SPD loading pro- tocol, in many researchers’ opinions, is a very severe test cycle that causes a failure mode (nail fatigue) that is not typical of seismically loaded shear walls. Researchers realize the need and importance of cycle testing and its importance in aiding ad- vanced shear wall modeling tools. However, it is also important to match real shear- [...]... 420 545 715 10d 390 600 770ƒ 1020 13⁄8 8d 505 645 855 555d 705d 94 0d 600 770 1020 480 715 93 0ƒ 1220 – – – – 270 490 630 250 380 490 630 280 420 545 715 8d 280 420 545 715 450d 575d 740d 335d 490 d 630d 820d 10d 365 530 685ƒ 895 895 – – – – – – – – – – ⁄32 365 530 685 ⁄32 435 645 840ƒ 1080 715 ƒ 1220 ⁄32 280 355d 15 APA Rated Sidingg and other APA grades except species group 5 2e d 15 19 3 310d ⁄16 or... 6d common nail 8d common nail 10d common nail 14-ga staple 14-ga staple 11⁄4 13⁄8 11⁄2 1 to 2 2 180 220 260 140 170 (Vn / 434)2.314 (Vn / 857)1.8 69 (Vn / 97 7)1. 894 (Vn / 90 2)1.464 (Vn / 674)1.873 (Vn / 456)3.144 (Vn / 616)3.018 (Vn / 7 69) 3.276 (Vn / 596 )1 .99 9 (Vn / 461)2.776 Fabricated green / tested dry (seasoned); fabricated dry / tested dry Vn ϭ fastener load (lb / nail) Values based on Structural... 230 255 170 190 2 3 270 300 360 400 530 600 600 675 240 265 180 200 2 3 290 325 385 430 575 650 655 735 255 290 190 215 2 3 320 360 425 480 640 720 730 820 285 320 215 240 Minimum nominal panel thickness (in.) 11⁄4 5 8d 13⁄8 3 10dd APA Rated Sheathing, APA Rated Sturd-I-floor and other APA grades except species group 5 6de 11⁄2 15 6de 11⁄4 5 ⁄16 ⁄8 3 ⁄8 3 8d 13⁄8 7 15 ⁄32 10dd 11⁄2 15 ⁄32 19 ⁄32 6 4 21⁄2c... panel thickness (in.) 5 1 ⁄16 3 APA Structural I grades Minimum nail penetration in framing (in.) 1 ⁄4 Nail size (common or galvanized box) 6 6d 200 ⁄8 230 15 APA Rated Sheathing; APA Rated Sidingg and other APA grades except species group 5 ⁄8 3 ⁄16 300 390 510 10d 280 430 550ƒ 730 670d 430 550 730 510 665ƒ 870 – – – – 270 350 450 180 270 350 450 200 300 390 510 8d 200 300 390 510 220d 1 1 ⁄4 13⁄8 6d 320d... 1.00 1.00 1.00 0.67 0. 69 0.71 0.74 0.77 0.80 0.83 0.87 0 .91 0 .95 1.00 Percent full-height sheathingb 0% 10% 20% 30% 40% 50% 60% 70% 80% 90 % 100% Effective shear capacity ratio 0.50 0.53 0.56 0. 59 0.63 0.67 0.71 0.77 0.83 0 .91 1.00 0.40 0.43 0.45 0. 49 0.53 0.57 0.63 0. 69 0.77 0.87 1.00 0.33 0.36 0.38 0.42 0.45 0.50 0.56 0.63 0.71 0.83 1.00 a H ϭ the vertical dimension of the tallest opening in the shear... at supported panel edges will provide an adjusted allowable capacity, vallow of: vallow ϭ 490 (0 .92 )(1.0) ϭ 451 lb / ft (6582 N / m) Ն 392 lb / ft (5720 N / m) І OK 4 The hold-downs must be designed to resist the unadjusted allowable shear capacity ϭ 350 (note that the 40% increase in the wind resistance is reversed for this calculations, 490 / 1.4 ϭ 350): H ϭ vh ϭ 350(8) ϭ 2800 lb (12,500 N) Additionally,... 510 8d 200 300 390 510 220d 1 1 ⁄4 13⁄8 6d 320d 410d 530d 8d 240d 350d 450d 585d 10d 260 380 490 ƒ 640 640 – – – – – – – – – – ⁄32 260 380 490 ⁄32 310 560 600ƒ 770 510 ƒ 870 ⁄32 200 510 15 APA Rated Sidingg and other APA grades except species group 5 8d d 15 19 2e 505d 180 ⁄8 7 3 460 340 ⁄16 or ⁄ 3 510 d 4 395 d 10d 1 c 4 5 380 d 6 Nail spacing at panel edges (in.) 360 255d 280 ⁄32 2e 3 300 d 8d ⁄32 15... is adequate for E-W load (max ϭ 64 lb / ft (93 4 N / m)) 3 The maximum chord force, T or C, is obtained by resolving the maximum diaphragm moment into a couple (dividing the moment by the depth): TN-S ϭ CN-S ϭ wl 2 516( 192 )2 ϭ ϭ 19. 8 kips (88,100 N) 8B 8(120) TE-W ϭ CE-W ϭ wl 2 206(120)2 ϭ ϭ 1 .92 kips (85,400 N) 8B 8( 192 ) WN-S=516 lb/ft 120' WE-W=206 lb/ft 192 ' FIGURE 7.15 Building plan view for blocked... except species group 5 2e d 15 19 3 310d ⁄16 or ⁄ ⁄8 545 d 4 250 10d 1 c 4 3 420 6 8d 2e 3 390 11⁄2 ⁄32 8d ⁄32 15 4 Nail spacing at panel edges (in.) 320 13⁄8 ⁄16 15 Nail size (common or galvanized box) Nail spacing at panel edges (in.) d 3 APA Structural I grades APA Rated Sheathing; APA Rated Sidingg and other APA grades except species group 5 Minimum nail penetration in framing (in.) Panels applied... group 5 Minimum nail penetration in framing (in.) Panels applied over 1⁄2 in or 5⁄8 in gypsum sheathing Panels applied directly to framing 1 1 ⁄2 10d 475 93 0 Nail size (galvanized casing) Nail size (galvanized casing) ⁄16c 11⁄4 6d 195 295 385 505 8d 195 295 385 505 3 13⁄8 8d 225 335 435 575 10d 225 335 435ƒ 575 5 ⁄8 7.16 a For framing of other species: (1) find specific gravity for species of lumber in the . 1 3 ⁄ 8 220 (V n /857) 1.8 69 (V n /616) 3.018 10d common nail 1 1 ⁄ 2 260 (V n /97 7) 1. 894 (V n /7 69) 3.276 14-ga staple 1 to 2 140 (V n /90 2) 1.464 (V n / 596 ) 1 .99 9 14-ga staple 2 170 (V n /674) 1.873 (V n /461) 2.776 a Fabricated. 335 d 490 d 630 d 820 d 10d 365 530 685 ƒ 895 and other APA 15 ⁄ 32 365 530 685 895 grades except 15 ⁄ 32 435 645 840 ƒ 1080 – – – – – species group 5 19 ⁄ 32 1 1 ⁄ 2 10d 475 715 93 0 ƒ 1220 – – – – – APA Rated Nail size. level soon. In 199 5, APA The Engineered Wood Association installed a cyclic loading system that has the capability to test shear walls following the SEAOSC procedure. One of APA s objectives