Effect Of Gap Size On Performance Of Metal-plated Joints In Compression

Metal-plate splice joints with gaps between butting pieces of 2 x 4 lumber were tested in compression to evaluate the effect of gap size on joint serviceability performance. The current design methodology for compression splice joints was also evaluated. Specimens representing floor and roof truss compression joints, with 16- and 20-gauge plates of staggered and aligned tooth configurations, were tested for each of two gap sizes.Generally, 20-gauge and 16-gauge plates on joints with 1/8 in. nominal maximum gaps buckled under compression loads while 16-gauge plates on joints with nominal 1/16 in. maximum gaps did not buckle before the gap closed. Gap closure with the latter joints was due principally to slip between the teeth nearest the splice and the wood. Joints with 16-gauge plates generally outperformed those with 20-gauge plates, based on the serviceability performance indicators of the test compression splice joints. Furthermore, gap size had less of an influence on joints with 16-gauge plates than on joints with 20-gauge plates.The current practice of sizing plates for compression splices to withstand one-half of the calculated chord force could not be physically confirmed using joint serviceability criteria. The test results indicated that basing allowable plate ratings on a surface-area basis derived from tension tests is misleading

Replicate Fire Endurance Tests of an Unprotected Wood Joist Floor Assembly

To encourage new developments in building technology, a solid basis for building code requirements is needed. Fire endurance is a code requirement, yet no objective procedure exists for computing a structure's chances of failing (degree of risk) in a fire. However, a model for predicting the fire endurance of part of a structure, a conventional unprotected wood joist floor, is available. The aim of this study was to determine the fire endurance performance of an unprotected wood joist floor for use in the model.Eleven ASTM Standard E 119 floor tests were conducted. All the floors were 2 by 10 Douglas-fir wood joists, sixteen inches on center with 23/32-inch-thick plywood as the floor sheathing. In addition to one trial test, five tests were conducted using a live load of 11.35 lb/ft2. For the other five tests, the live load was 79.2 lb/ft2. Twenty joists were tested for modulus of elasticity and modulus of rupture.The joist population had a mean modulus of rupture of 5.280 lb/in.2 and a mean modulus of elasticity of 1,530,000 lb/in.2. For the five floors loaded to 11.35 lb/ft2, the mean time for initial joist failure was 17.9 min with a coefficient of variation (COV) of 3.7%. For the five floors loaded to 79.2 lb/ft2, the mean time was 6.5 min with a COV of 11.6%. Based on linear interpolation of these results, first joist failure would have occurred in 13.1 min if a 40 lb/ft2 live load had been used, which is the typical live loading specified in the building codes for residential one- and two-family dwellings.As a result of this study, fire-resistance performance of a wood floor is known for a specific population of wood joists with known structural properties. These results can be used to verify and revise the model for predicting fire endurance

Roof Loads for Reliability Analysis of Lumber Properties Data

With load information reported in previous studies, distributions of maximum lifetime roof loads are developed in a form suitable for use in reliability analyses of lumber properties data. A lognormal distribution is chosen as best representing normalized maximum lifetime roof snow load.Examples are given in which contrasting lumber data sets are compared using the calculated load distributions and assuming that each set must provide equal reliability (equal safety) in the final design. A factor, k, resulting from this reliability analysis is shown to be a logical adjustment parameter for use in engineering design codes

Allowable Bending Strength Enhancement of 2 By 4 Lumber By Tension and Compression Proofloading

Simple 5th percentile and reliability analysis methods were used to evaluate increases in allowable bending strength from proofloading in tension and compression. The analysis included the use of realistic load data for residential roof and floor trusses, and combined stress present in truss chords was given consideration as part of the reliability analysis. Proofloading in tension or in compression both produced significant increases in allowable bending strength for 2 by 4 1650f-1.5E hem-fir. Proofloading in tension to a target 15% breakage level, or 2,838 psi, yielded for the survivors an increase of 72% in allowable bending strength. The allowable bending strength increased 60% because of compressive proofloading to a target 15% breakage level. Since relatively small sample sizes were used, the results are not definitive but provide justification for a comprehensive study

The Current Status of Analysis and Design for Annoying Wooden Floor Vibrations

One result of improved material utilization in the design and construction of wooden buildings is a dramatic increase in undesirable, annoying floor vibrations. Whereas static criteria provide a sound method of ensuring a safe structure, these same criteria may not ensure that vibrational serviceability requirements are met. The major drawback of static criteria is that they do not address dynamic variables that become increasingly important as the span is lengthened, or the weight and/or the stiffness of the floor structure is reduced by either efficient design methods or the inclusion of engineered joist products. This paper discusses not only pertinent current research findings but suggests areas for future research to develop the dynamic criteria needed for the design of lightweight floor systems constructed with wood-based materials.The development of such criteria may have a positive economic impact on the forest products industry. Although vibrational problems also occur in steel and concrete structures due to the reduction in weight of the floor components (steel joists and concrete slabs), researchers (Allen and Rainer 1976, 1985; Murray 1991) have made great strides in the understanding and control of vibrations in steel and concrete structures. If serviceability criteria for wooden structures are developed that will ensure acceptable vibrational performance, then the forest products industry will have the potential to be competitive in the profitable light-commercial construction market

Floor Loads for Reliability Analysis of Lumber Properties Data

Utilizing load information reported in previous studies, we have developed distributions of maximum lifetime floor live loads in a form suitable for use in reliability analyses of lumber properties data. An extreme value type I distribution is chosen as best representing normalized maximum lifetime floor live loads.Examples are given in which contrasting lumber data sets are compared using the calculated load distributions and assuming that each set must provide equal reliability, or equal safety, in the final design. A factor, k, resulting from the reliability analysis is shown to be a logical adjustment parameter for use in engineering design codes.Combining these results with those of an earlier paper, the selection of load distributions for use in reliability analysis of lumber properties data is discussed

Pollen flow and paternity in an isolated and non-isolated black walnut (Juglans nigra L.) timber seed orchard.

Artificial pollination of black walnut (Juglans nigra L.) is not practical and timber breeders have historically utilized only open-pollinated half-sib families. An alternate approach called "breeding without breeding," consists of genotyping open-pollinated progeny using DNA markers to identify paternal parents and then constructing full-sib families. In 2014, we used 12 SSR markers to genotype 884 open-pollinated half-sib progeny harvested from two clonal orchards containing 206 trees, comprised of 52 elite timber selections. Seed was harvested in 2011 from each of two ramets of 23 clones, one upwind and one downwind, based on prevailing wind direction from the west-southwest. One orchard was isolated from wild black walnut and composed of forward selections while the other orchard was adjacent to a natural forest containing mature black walnut composed of backward selections. Isolation significantly increased within-orchard pollination (85%) of the progeny from the isolated orchard compared to 42% from the non-isolated orchard. Neither prevailing wind direction nor seed tree position in the orchard affected paternity patterns or wild pollen contamination. Genetic diversity indices revealed that progeny from both orchards were in Hardy-Weinberg equilibrium with very little inbreeding and no selfing. A significant level of inbreeding was present among the forward selected parents, but not the first generation (backward selected) parents. Some orchard clones failed to sire any progeny while other clones pollinated upwards of 20% of progeny

Bi-allelic Mutations in M1AP Are a Frequent Cause of Meiotic Arrest and Severely Impaired Spermatogenesis Leading to Male Infertility

Male infertility affects ∼7% of men, but its causes remain poorly understood. The most severe form is non-obstructive azoospermia (NOA), which is, in part, caused by an arrest at meiosis. So far, only a few validated disease-associated genes have been reported. To address this gap, we performed whole-exome sequencing in 58 men with unexplained meiotic arrest and identified the same homozygous frameshift variant c.676dup (p.Trp226LeufsTer4) in M1AP, encoding meiosis 1 associated protein, in three unrelated men. This variant most likely results in a truncated protein as shown in vitro by heterologous expression of mutant M1AP. Next, we screened four large cohorts of infertile men and identified three additional individuals carrying homozygous c.676dup and three carrying combinations of this and other likely causal variants in M1AP. Moreover, a homozygous missense variant, c.1166C>T (p.Pro389Leu), segregated with infertility in five men from a consanguineous Turkish family. The common phenotype between all affected men was NOA, but occasionally spermatids and rarely a few spermatozoa in the semen were observed. A similar phenotype has been described for mice with disruption of M1ap. Collectively, these findings demonstrate that mutations in M1AP are a relatively frequent cause of autosomal recessive severe spermatogenic failure and male infertility with strong clinical validity.This work was carried out within the frame of the German Research Foundation Clinical Research Unit ‘‘Male Germ Cells: from Genes to Function’’ (DFG CRU326). Funding for sequencing of the GEMINI cohort was provided by the National Institutes of Health, United States (R01HD078641). The analyses in the Turkish family were supported by a grant from the Bursa University of Uludag Project Unit [KUAP(T)-2014/36].info:eu-repo/semantics/publishedVersio