Truss Plate Research Articles

Joint Details in Post and Beam Framing

Although most wood design is now undertaken by firms specializing in this work, nonspecialists have occasion to design in wood from time to time. As with other structural materials, even a simple understanding of the characteristics of the material will enable designers to avoid many subsequent problems. The intent here is to present several relatively simple examples. Although nails may be the most commonly used connectors, bolts and lag screws tend to be used when member thickness increases from 38 to 89 mm ~1 1 2 to 3 1 2 in.!. With wood, the ideal connector when members overlap would be a device that develops shear over the entire contact face. Although this is a characteristic of adhesives, their use on-site is problematic. The development of the lightweight galvanized truss plate has revolutionized fabrication of house roof trusses by eliminating the lap joint, yet providing distributed shear connections. Similarly, the glulam rivet or nail with appropriate nail plates 4.8 to 6.4 mm ~3/16 to 1 4 in.! in thickness, has provided distributed shear connections for larger members. Concurrently with the development of the truss plate and glulam rivet, the Swiss are believed to have developed the equivalent of a two-sided truss plate that could be inserted between the contact faces of lap joints. As with truss plates, presses were needed

Sandwich Plates Actuated by a Kagome Planar Truss

Kagome truss plates have properties that suggest they should be uniquely effective as an actuation plane for sandwich plates: a Kagome truss plate has in-plane isotropy, optimal stiffness and strength, and its truss members can be actuated with minimal internal resistance. In this paper, sandwich plates are studied that are comprised of one solid face sheet and one actuated Kagome face sheet joined by a pyramidal truss core. Various aspects of the actuation behavior of these plates are investigated, including internal resistance and strains resulting from actuation and efficiency of actuation. Single and double curvature actuation modes are investigated. Contact is made with analytic results for actuation modes with long wavelength.

Nonlinear analysis of plate–truss composite steel girders

An efficient approach to the nonlinear analysis of plate–truss composite steel girders is presented in this paper. Using finite strip elements in transverse direction, a spatial displacement field in consideration of local buckling of a plate–truss composite structure is constructed. The updated Lagrangian formulation of the finite strip element is introduced based on the incremental virtual work principle of the three-dimensional continuum, and the effect of large deformation is taken into account with the Euler coordinate transformation. The effect of material nonlinear behavior is considered with inner-force plastic coefficients of cross section. As an illustrating example of the application of the presented approach, the nonlinear behavior of a plate–truss composite steel bridge model is studied, and the computational results are verified with test data.

Truss plate reinforced bolted connections in parallel strand lumber

This paper summarizes the results of an investigation into the behaviour of truss plate reinforced single and multiple bolted connections in parallel strand lumber (PSL) under static tension loading. Sixty single-bolt connections were tested with bolt and PSL size combinations of 12.7 mm bolts in 38×140 mm specimens, 15.9 mm bolts in 89×140 mm specimens, and 22.2 mm bolts in 133×191 mm specimens. Another sixty multiple-bolt specimens were tested, using the above-mentioned PSL size and bolt combinations. The multiple-bolt connections consisted of two rows of five bolts in the 38×140 mm and 89×140 mm specimens and two rows of two bolts in the 133×191 mm specimens. Each connection was configured according to the Canadian Standard for Engineering Design in Wood (CAN/CSA 086.1-94) in terms of bolt spacing, edge distances, and end distances. All reinforced single-bolt connections had average ultimate strength increases, compared to unreinforced connections, of 3% for the 133×191 mm, 12% for the 89×140 mm, and 37% for the 38×140 mm specimens. Reinforcement had little effect on the strength of multiple-bolt connections in both the 38×140 mm specimens and the 89×140 mm specimens. The reinforced four-bolt connections in the 133×191 mm specimens had a 7% increase in average ultimate strength. Reinforcement significantly improved the ductility in all the connections tested. Key words: timber connections, parallel strand lumber, multiple bolts, reinforcement, truss plates, ductility, composite wood products, testing, experimental, composite structural lumber.

Truss plate reinforced bolted connections in parallel strand lumber

This paper summarizes the results of an investigation into the behaviour of truss plate reinforced single and multiple bolted connections in parallel strand lumber (PSL) under static tension loadin...

Truss plate reinforced bolted connections in parallel strand lumber

This paper summarizes the results of an investigation into the behaviour of truss plate reinforced single and multiple bolted connections in parallel strand lumber (PSL) under static tension loading. Sixty single-bolt connections were tested with bolt and PSL size combinations of 12.7 mm bolts in 38×140 mm specimens, 15.9 mm bolts in 89×140 mm specimens, and 22.2 mm bolts in 133×191 mm specimens. Another sixty multiple-bolt specimens were tested, using the above-mentioned PSL size and bolt combinations. The multiple-bolt connections consisted of two rows of five bolts in the 38×140 mm and 89×140 mm specimens and two rows of two bolts in the 133×191 mm specimens. Each connection was configured according to the Canadian Standard for Engineering Design in Wood (CAN/CSA 086.1-94) in terms of bolt spacing, edge distances, and end distances. All reinforced single-bolt connections had average ultimate strength increases, compared to unreinforced connections, of 3% for the 133×191 mm, 12% for the 89×140 mm, and 37% for the 38×140 mm specimens. Reinforcement had little effect on the strength of multiple-bolt connections in both the 38×140 mm specimens and the 89×140 mm specimens. The reinforced four-bolt connections in the 133×191 mm specimens had a 7% increase in average ultimate strength. Reinforcement significantly improved the ductility in all the connections tested. Key words: timber connections, parallel strand lumber, multiple bolts, reinforcement, truss plates, ductility, composite wood products, testing, experimental, composite structural lumber.

Steel Properties Used to Manufacture Wood Truss Metal Connector Plates

A study was conducted by surveying members of the Truss Plate Institute (TPI) on properties of steel used in the production of metal connector plates. Three out of eight truss plate manufactures (TPMs) responded with summary statistics, and one of the three provided raw data for both ASTM grade B (1993a) and grade 60 (1993b) steel coils. Statistical distributions were fit to the data and several conclusions were drawn. Ultimate strength of steel is an important attribute for modeling failure of a metal-plate-connected truss joints. A truss plate manufacturer could feasibly sample a coil of steel, and find that the ultimate and yield strengths are slightly below minimum specified standards. A truss simulation aimed at establishing minimum performance in a load test should include steel that is close to minimum specified ultimate strength. If average performance of populations of trusses is of interest, the steel properties should be modeled as random variables.

Strength and stiffness of glulam trusses with punched metal plated joints

Several Canadian wood truss manufacturers expressed a need to develop technical information to initiate the fabrication and acceptance of wood trusses made with glued-laminated timber (glulam) members and connected by punched metal plates. In collaboration with industrial participants, Forintek Canada Corp. developed a program for testing and analysis of metal plated glulam trusses. Twelve 3/12 pitched chord trusses and three parallel chord trusses, all 13.7 m long, were designed by three different plate manufacturers. All truss fabrication took place at a single truss manufacturing plant. Trusses composed of 79 mm wide and 152-229 mm deep glulam members connected by 16-gauge punched metal plates were tested to failure. The ratio of ultimate to design load averaged 3.5, and varied between 2.7 and 4.4. Both wood and plate failure modes were observed. The results suggest that the sizes of glulam members used in this study are structurally suitable for use with 16-gauge metal connector plates. Key words: wood, trusses, glued-laminated timber, truss plates, strength, stiffness.

Nonlinear Modeling of Truss‐Plate Joints

A theoretical model is developed for predicting mechanisms of load transfer between a wood member and a metal die‐punched truss plate. The model, which treats a truss‐plate tooth as a beam on an inelastic foundation of wood and applies Runge‐Kutta numerical analysis to solve the governing differential equations, predicts the load‐displacement trace and ultimate load of truss‐plate joints. The model is verified with eight truss‐plate joint types, three of which varied the number of teeth and five the plate and grain angle. Theoretical and experimental load‐displacement traces show good agreement. Experimental traces show no significant difference between multiple teeth in rows and columns, indicating little stress interaction among teeth. The theoretical model accurately predicts the ultimate load and failure modes for complete joint test types, which vary with plate and grain geometry; teeth face bearing on end grain failed by tooth withdrawal or plate tensile failure, teeth edge bearing on end grain failed by plate peelback, and teeth bearing on side grain failed in wood perpendicular to grain.

Laterally Driven Polysilicon Resonant Microstructures

Interdigitated finger (comb) structures are demonstrated to be effective for exciting electrostatically the resonance of polysilicon microstructures parallel to the plane of the substrate. Linear plates suspended by a folded-cantilever truss and torsional plates suspended by spiral and serpentine springs are fabricated from a 2 μm-thick phosphorus-doped low-pressure chemical-vapor-deposited (LPCVD) polysilicon film. Resonance is observed visually, with frequencies ranging from 18 kHz to 80 kHz and quality factors from 20 to 130. Simple beam theory is adequate for calculating the resonance frequencies, using a Young's modulus of 140 GPa and neglecting residual strain in the released structures.

A Comparison of Five Laminated Wall Column Designs

FOUR nail-laminated wall column designs previously reported in the literature are compared with new results from a fifth study. A wide range of strength values are achieved by the five wall column designs. This study uses 2X6 No. 1 Dense KD15 southern pine lumber and two splice-type truss plates applied to the outside wide faces of the three laminate assembly at the butt joints between the treated and untreated lumber. Twenty wall columns were tested to failure in bending under a two point loading arrangement. An allowable normal duration bending strength of 13.25 MPa (1,921 psi) was estimated from the load tests. The effective modulus of elasticity, MOE, of the 3.66 m (12 ft) jointed section was also measured. The mean MOE was 8,660 MPa (1.256 million psi) with a coefficient of variation of 8.1%

Factors affecting the behaviour and modelling of toothed metal-plate joints

An efficient approach to determine the behaviour of toothed metal-plate joints is to use analytical techniques to model the behaviour on the basis of known properties of plate and wood, and loading conditions, backed by an actual testing of the joints for verification or calibration of the models. Existing computer-based techniques such as the Structural analysis of trusses (SAT) and Purdue plane stress analyzer II (PPSA II) were developed for modelling wood trusses. The applicability and usefulness of these techniques can be expanded if better joint models can be incorporated into SAT, or if PPSA II can be advanced to describe the behaviour of joints. The present experiment included obtaining load–deformation data on specimens of two designs — one for the shear properties of plate and the other resembling the heel joint of a truss. These data were compared with predictions given by SAT. In addition, data from the heel joint specimens were used to calibrate the property requirements of fictitious members used in PPSA II to model semirigid joint behaviour. Predictions of joint stiffness by SAT were reasonably accurate, but the ultimate load was overestimated when the joint failed in plate buckling. The heel joint test method shows potential as a proper and efficient test method for assessing joint behaviour. However, as is normal with any joint testing, a significant frictional force can develop between joint members and contribute to the ultimate strength and stiffness of the joint. This frictional force should be accounted for in modelling. Key words: design, interface friction, modelling, shear strength, stiffness, structural analysis, truss plate, wood truss.

Behaviour of truss plate and metal web joints in machine-stress-rated lumber trusses

In project A, 1500 pieces of 38 × 89 mm spruce–pine–fir lumber from three mills, in two machine-stress-rated (MSR) grades, 1650f–1.5E and 2100f–1.8E, were proof-loaded to obtain the mean modulus of elasticity, the fifth percentile modulus of elasticity, and the fifth percentile modulus of rupture. Relative density was measured for each piece, and values of the 33.3 and 52.3 percentiles of the relative density ranges were determined for each species/grade category and related to the minimum values stipulated by the National Lumber Grades Authority (NLGA) Special Product Standard SPS-2-82 for machine-stress-rated lumber. The values of relative density at the 33.3 and 52.3 percentiles that will cause the NLGA mean modulus of elasticity MOE (mean), criterion to be just barely satisfied were estimated.In project B, the lateral resistances of 480 truss plate joints were determined. The variables were two common types of truss plates (thicknesses of 0.91 mm and 1.5 mm) in two grades of MSR lumber (1650f–1.5E and 2100f–1.8E) subdivided into two species groups (pine alone and spruce–fir combined), tested at four orientations of load to grain and load to plate axis. These tests showed that, in most cases, an increase in the design capacity of truss plates in MSR lumber over the values now used for spruce–pine–fir lumber is justified.In project C, 30 commercially designed metal web floor trusses of three span/depth combinations were tested to determine their stiffnesses and strengths. Trusses with 2100f grade lumber in the chords were stiffer than the trusses with 1650f chords. In both grades, larger trusses are relatively less stiff than smaller trusses. With respect to strength, the results indicate that higher design values may be used with higher grades of MSR lumber provided that design is governed by either tooth withdrawal at the joints or by chord strength. An improved analytical model, taking into account four distinct failure modes, is required for the behaviour of floor trusses. Key words: machine-stress-rated lumber, truss plates, trusses, metal webs, strength, density.

Strength and structural safety of long-span light wood roof trusses

Seventy-five light wood roof trusses were tested to failure in order to evaluate their safety and serviceability, and to examine the effects of size (members and spans) and load distribution (balanced and unbalanced) on truss performance. Two spans were tested: 21 m (45 trusses) and 12 m (30 trusses). It was found that the trusses were not consistent in their ratios of failure load to design load. Failures in the low-strength trusses included shear in the heel region of the top chord and tension in the scarf-cut bottom chord. It was subsequently demonstrated that these weaknesses could be removed through improved heel detailing. Key words: wood, trusses, strength, stiffness, safety, truss plates.

Strength of Nail Laminated Columns with Metal Plated Joints

ABSTRACT THE laminated columns tested in this study were manufactured with treated lumber spliced to untreated lumber with 16 gauge splice type truss plates and pneumatically driven nails having the approximate size and diameter of a 12 penny common wire nail. Two configurations and two lumber grades were studied. The lumber grades of the treated as well as untreated lumber were No. 2 KD Southern Pine and No. 2 KD Dense Southern Pine. The post configurations were a 2x4-2x6-2x4 combination intended to replace a solid-sawn 4x6 and a 2x6-2x8-2x6 combination intended to replace a solid-sawn 6x6. The nail laminated columns of this study rated well when compared to the allowable stress of a No.2 SR Southern Pine post which has an allowable bending stress value of 7584 kPa (1100 psi)

Strength interactions of finger joints and truss plate joints in light wood trusses

This study examined two questionable aspects of using truss plates together with finger-joined wood truss members, namely the possible strength reductions in either the truss plate joint or the member. The lumber was kiln-dried No. 2 grade spruce–pine–fir. The finger joints were "horizontal" and glued with a phenol resorcinol adhesive. Project A dealt with the strength of truss plate joints; in this project, truss plate joints were tested in tension on both faces of 38 × 64 mm lumber and on the 89 mm face of 38 × 89 mm lumber, and both parallel and perpendicular to grain loading. Project B examined the effect of truss plates on the tensile and flexural strengths of finger-joined lumber. Specimens waisted to 38 × 38 mm containing truss plates pressed into both faces of the finger joints were tested in tension parallel to grain, whereas specimens of 38 × 89 mm also containing plates in both faces were tested in bending about both weak and strong axes.The statistical analysis indicated no reduction in strength for the ten-replication tests in both projects A and B. However, the test results suggest that there is a possible inherent weakness associated with the plug-shear failures in project A and the failures at the last row of the plate teeth in project B. The implications of these results on the design of truss plate joints have been adopted by the CSA Technical Committee on Engineering Design in Wood.

Nail Laminated Posts with Metal Plated Joints

ABSTRACT THE post-frame construction industry is presently seeking an alternative to the use of solid-sawn, penta-treated posts for post frame buildings. A nail-laminated post made with either three nominal 2 x 6's or three 2 X 8's has been proposed to replace the solid 6x6 and 6x8 post, respectively. The use of penta-treated lumber spliced to untreated lumber with metal truss plates elimi-nates the need for a post having treated lumber above ground level. Tests conducted on sixteen 6x6 posts of treated and untreated No. 2 KD Southern Pine and seventeen 6x8 posts of treated and untreated No. 2 KD Southern Pine involved loading the posts to failure in bending. The allowable stress of each size post was determined on the basis of its equivalent nominal size post, that is 140 mm X 140 mm (5.5 in. x 5.5 in.) for the 6 x 6 post and 140 mm X 184 mm (5.5 in. x 7.50 in.) for the 6 x 8 post. An allowable stress in bending of 6895 kPa (1000 psi) was obtained for both post sizes.

Punched-Metal Truss Plates Used in Timber Joints

Punched-Metal Truss Plates Used in Timber Joints