Wood Joist Research Articles

A dynamic stiffness method to estimate the sound insulation of an arbitrarily installed thick cross laminated timber (CLT) plate

There is no generally accepted standard methodology to determine the dynamic constants of whole cross laminated timber (CLT) plates. Combined with the observation that CLT walls or floors are installed in situ under very different conditions to laboratory measurement conditions a methodology is sought to determine the sound insulation of CLT plates installed under arbitrary conditions without accurate information concerning the dynamic constants (and boundary conditions). The methodology may have applications where a panel can be tested in situ e.g. in pre-completion testing. In the laboratory measurement a CLT plate was mounted on the laboratory floor on two wooden joists placed at arbitrary positions to support the weight of the plate to represent a possible installation in situ.

EFFECTS OF CIRCULAR HOLES DRILLED IN WOOD JOISTS

Holes are drilled in wood joists for routing pipes, wires or other components. This research investigated the effects of these holes on the shear and bending stresses in a wood joist. Strengths are calculated using the reduced section properties accounting for the holes. The question is whether the reduction in cross-section may account for any other stress concentration factors that may be present due to the discontinuity. It is also important to determine whether a stress concentration factor needs to be applied to wood joists with holes in them. A finite element model was created to determine the actual stresses in members with holes in their cross-sections. Holes of variable size and location were added to the members. Structural analyses were performed using standard procedures and found out that the stresses based on reduced cross-sectional properties were much less than that of the finite element model. Therefore, the calculation of stresses based on the reduced cross-sectional properties of a member does not adequately account for stress risers at the discontinuity. It was also found from the finite element model that the reduction in cross-section generates an increase in stress that is a fraction of the actual stress increase. It was suggested from this research to limit the location of a hole within a member’s cross-section to the middle third and to apply some stress concentration factors to account for the holes for both shear and bending stresses.

Application of multiple dynamic vibration absorbers in reducing low-frequency vibration of a floor-like lightweight joist structure: Comparison of experimental and computational results

Typical solutions to reduce excessive floor vibration and radiated sound to the room below include increasing floor mass, stiffening floor structure, and adding a floating floor in the source room. However, these methods may not be effective for lightweight floors at low frequencies. The use of dynamic vibration absorbers (DVAs) to reduce low-frequency structural vibration has attracted the attention of researchers in recent years. In this paper, an analytical model is proposed to study the effect of DVAs on the vibration of a lightweight joist structure by combining the bending modes of the plate with the bending and torsional modes of the beams. The analytical model is compared with the results from finite element models and measurements on a scaled wooden joist floor structure with fabricated spring-mass-type DVAs. A good consistency between the analytical results with results from the latter two are found in terms of the structural vibration and the DVAs’ effects.

E90 round-robin—Status and path forward

A good understanding of the uncertainty of a test method is necessary to interpret the results of said test. The ASTM E90 test has many potential sources of variation that can lead to significant uncertainty in the test results, but this uncertainty is not well documented in the precision and bias statement within ASTM E90. The current precision and bias statement provides some limited repeatability data for a wood joist floor and a concrete slab and only provides reproducibility data for the ASTM E1289 reference specimen. The E1289 reference specimens are simple steel plates in single and double-layer configurations that yield STC ratings far below those of the wall and floor/ceiling assemblies that are commonly tested. The authors are in charge of a new round-robin that aims to provide more detailed repeatability and reproducibility data using common wall designs with STC ratings in the range more commonly seen in building code requirements and design guidelines. In this presentation, the authors will cover their proposed plan for the round-robin and will give an update on its status.

Comparison of the direct sound insulation for wooden joist, CLT and timber hollow box floors

Timber buildings are now present worldwide, and their market is growing rapidly, pushed by sustainability and environmental arguments. Several technological options for engineered wood systems are available and well developed, the most common being wooden joist, CLT and timber hollow box. In this paper, we present a comparative study of the airborne and impact sound insulation of the three options. The analysis is based on data collected from laboratory measurements. The results include the comparison of the bare floor construction and examples of assemblies with additional floating floor, suspended ceiling or a combination of the two. We identify the characteristic trends and highlight the effect of selected parameters as for instance mass per unit area, assembly thickness and properties of the resilient layers. The comparison attempts to show the constructive consequences of the different options on the sound insulation properties. It could help selecting the most suitable floor system in future projects and contribute making timber construction more efficient and affordable.

The forced sound transmission of finite periodic plates using a variational approach

Many engineering structures consist of plates being periodically stiffened or loaded. Examples can be wooden joist floors, dry walls with wooden or metal beams, or metamaterials for increased sound insulation. Even though some of these structures are well known and thoroughly studied in the past, there lack prediction models that can handle both the finiteness and periodicity in a simple and accurate manner. In two previous attempts, the periodicity of the structure have been tried to be incorporated in a variational technique based on integral-differential equations of the fluid loaded plate, based on [J. Brunskog, JASA 132, 1482-1493, 2012]. These attempts have not worked well: they show a poor fit with measured data. In this paper, this issue is investigated again, and a different tactics is used to incorporate the periodicity, using space harmonics. In this way, the paper try to explain the previous misfit and improve the model.

A recent feedback of wooden multi-storey buildings in France

Wooden structures are becoming quite common in the French architectural landscape, and ACOUSTB has made it a specialty regarding acoustics. Its experience ranges from office buildings to residential buildings, and from small to high-rise constructions. Airborne and impact noise insulation are of first importance. Structural aspects, construction methods and architecture are also discussed. Constructive solutions concern both CLT and traditional wood joists flooring systems, alternatives to floating screeds in office buildings and visible wooden structures in dwellings. Buildings are described, then selected constructive solutions are presented and debated with respect to targeted acoustic performance. Finally, in-situ measurement results are compared with the theory that underlays them, as well with the targeted performance.

An Investigation into the Strength Properties of Three Reclaimed Structural Timber Joist Within the University of Ibadan Community

Background and Objective: The investigation presents the results of selected test assessment on physico-mechanical properties of three selected wood residues within the University of Ibadan Campus, Oyo State, Nigeria. Often, reclaimed planks were considered as useful material for heating and energy production, hence, potential re-usability of these residues for plate rack production were determined. Materials and Methods: Four planks of the selected three wood samples each were collected from the University of Ibadan community. The 12 pieces wood samples were cleaned, plained, and converted into required dimension; samples were dried to about 12%moisture content before tests. Selected physico-mechanical properties test (moisture content, volumetric shrinkage, modulus of elasticity, and modulus of rupture were carried out according to ASTM standards. The data obtained were subjected to analysis of variance (ANOVA). Results: The results of mean density show that <i>Gliricidia sepium, Milicia excelsa </i>and <i>Funtumia elastica </i>had 1032±0.97kg/m³, 548±0.57kg/m³ and 613±0.33kg/m³, respectively. The mean value for moisture content of <i>G. sepium, M. excelsa and F. elastica</i> ranges from 12.47±1.21, 20.84±1.21 and 18.13±1.21, respectively. While, volumetric shrinkage of <i>G. sepium, M. excelsa and F. elastica </i>ranged from 20.55±2.79, 7.48±2.79 and 11.43±2.79. The <i>G. sepium, M. excelsa and F. elastica </i>had MOE values of 8793.13±643.43 N/mm², 8083.64±643.43 N/mm² and 4299.54±643.43N/mm². The mean values for MOR of <i>G. sepium, M. excelsa and F. elastica </i>ranges 404.69±12.362 N/mm², 434.27±12.36N/mm² and 388.34±12.36N/mm². Conclusion: <i>Gliricidia sepium </i>wood had the highest mean density, low shrinkage value and modulus of elasticity. Therefore, it was found most suitable wood slab for plate rack production from reclaimed wood joist.

3D joist perception, detection, and climbing for hexapod robot

Avoiding obstacles is challenging for autonomous robotic systems. In this work, we examine obstacle avoidance for legged hexapods, as it relates to climbing over randomly placed wooden joists. We formulate the task as a 3D joist detection problem and propose a detect-plan-act pipeline using a SLAM algorithm to generate a pointcloud and a grid map to expose high obstacles such as joists. A line detector is applied on the grid map to extract parametric information of the joist, such as height, width, orientation, and distance; based on this information the hexapod plans a sequence of leg movements to either climb over the joist or move sideways. We show that our perception and path planning module work well on the real-world joists with different heights and orientations.

WESTMINSTER HALL’S LOST STUART DOOR PASSAGE REDISCOVERED

In 2018 unpublished archaeological evidence was discovered recording a doorway and passageway concealed inside the Romanesque wall of Westminster Hall, near the south-east corner. Although commemorated by a bronze plaque in situ, their existence had largely been forgotten. Further investigations revealed an access panel in the 1951 cloakroom fittings in adjoining St Stephen’s cloister: this was located, and the space accessed, seemingly for the first time since c 1952. The many features of interest found within included the doorcase and soffits of a great doorway and iron pintles for the doors; Purbeck flagstones on the floor; complex masonry and plaster from several different eras; graffiti by masons from the nineteenth and twentieth centuries; a still-functional Osram lightbulb dating from the early 1950s; and wooden joists supporting the masonry of the ceiling. Isotope dating of the timbers produced a date of 1659, and works accounts showed that the doorway and passageway were created in 1660–1, to form a ceremonial route for the coronation of Charles ii. Further archaeological and historical investigations have enabled the authors to establish a full chronology for the changing fabric and uses of the doorway and passageway from the seventeenth to the twenty-first century, and to trace the masons who walled in the space in 1851. They have also established why the brass plaque in Westminster Hall marking the space erroneously ascribes it with Tudor origins: that ‘fake history’ was created by an over-enthusiastic late-nineteenth century Clerk of the House of Commons.

FLEXURAL STRENGTHENING OF DIMENSIONAL WOOD JOISTS WITH STEEL REINFORCEMENT

ABSTRACT Traditional approaches to the strengthening of dimensional wood roof joist systems are often intrusive and require a substantial amount of additional labour to remove ceilings or roof sections. In an effort to design a less intrusive system for reinforcing over-stressed dimensional wood joists, a roof joist strengthening system was designed consisting of a tension steel plate installed along the bottom of the existing joists with bolted side plate connections. An experimental program was conducted at the University of Manitoba to assess the viability of the reinforcement design. A total of 15 joists were tested to failure under four-point bending conditions, consisting of 5 unreinforced control joists, 5 joists with steel reinforcement, and another 5 reinforced joists with an artificial defect introduced at mid-span along the tension side. The purpose of introducing an artificial defect at mid-span was to simulate the failure modes observed at R.W. Bobby Bend School in Stonewall, Manitoba, where certain roof joists contained knots, splits or cracks along the bottom of the joist within the mid-span region. Service loads based on the applied snow and dead loads applied to these joists were calculated using the National Building Code of Canada [1] and were approximated in the experiment as 8.5 kN. The results indicated that the steel reinforcement produced a 46.8% increase in average load-carrying capacity compared to control joists, and a 33.1% increase in capacity for reinforced joists with artificial defects. The average deflection at service loads was 19.5% lesser than the deflection of the control joists, and the apparent stiffness was determined to increase by 50.0%. The results from this research support the conclusion that the steel reinforcement system for dimensional wood joists is a viable alternative to traditional systems that effectively increases the load-carrying capacity, stiffness, and ductility of the structure.

FLEXURAL STRENGTHENING OF DIMENSIONAL WOOD JOISTS WITH STEEL REINFORCEMENT

ABSTRACT Traditional approaches to the strengthening of dimensional wood roof joist systems are often intrusive and require a substantial amount of additional labour to remove ceilings or roof sections. In an effort to design a less intrusive system for reinforcing over-stressed dimensional wood joists, a roof joist strengthening system was designed consisting of a tension steel plate installed along the bottom of the existing joists with bolted side plate connections. An experimental program was conducted at the University of Manitoba to assess the viability of the reinforcement design. A total of 15 joists were tested to failure under four-point bending conditions, consisting of 5 unreinforced control joists, 5 joists with steel reinforcement, and another 5 reinforced joists with an artificial defect introduced at mid-span along the tension side. The purpose of introducing an artificial defect at mid-span was to simulate the failure modes observed at R.W. Bobby Bend School in Stonewall, Manitoba, where certain roof joists contained knots, splits or cracks along the bottom of the joist within the mid-span region. Service loads based on the applied snow and dead loads applied to these joists were calculated using the National Building Code of Canada [1] and were approximated in the experiment as 8.5 kN. The results indicated that the steel reinforcement produced a 46.8% increase in average load-carrying capacity compared to control joists, and a 33.1% increase in capacity for reinforced joists with artificial defects. The average deflection at service loads was 19.5% lesser than the deflection of the control joists, and the apparent stiffness was determined to increase by 50.0%. The results from this research support the conclusion that the steel reinforcement system for dimensional wood joists is a viable alternative to traditional systems that effectively increases the load-carrying capacity, stiffness, and ductility of the structure.

Geometric and static analysis of the historical truss of the medieval truss Church of St. Martin in Dolní Újezd

The late-Romanesque St. Martin´s Church in Dolní Újezd was probably built in the mid-13th century. The nave has a wooden joist ceiling whose beams serve as tie beams too. The Gothic vaults above the presbytery date from ´30s of the 15th century. The truss of the church is dendro-dated to 1420 - 1421. Some members of a truss structure are dendro-dated to 1823 - 1824, when the repair was undertaken. The examined truss is a rafter-collar tie structure with collar beams and pedestal struts. It has a characteristic shape and may be typologically classified as a structure of the earlier period. This type of a truss structure was typically built in this region and represents one of the features occurring in the particular social and culture circles at the time. Consequently, a numerical model of the roof structure was created in order to perform a static analysis of the roof structure in accordance with present standards. With regard to the structural analysis results, it can be said that the original design of the structure based on geometrical and proportional principles satisfy the reliability conditions defined by current European standards for structural design.

An overview of new testing results on common wood joist and truss assemblies

This presentation is an overview of new testing results for common 18 in. open-web truss, TJI, and 2 × 10 joist assemblies with gypsum concrete poured directly to the plywood subfloor. The presentation will discuss the effect of underlayment thickness, underlayment attachment (glued versus loose), and floor finish. It will also cover the difference in IIC and HIIC ratings for all tested iterations of the assembly, showing how the HIIC rating gives greater differentiation between flooring and underlayment combinations.

ARCHITECTURAL AND DESIGN FEATURES OF RESIDENTIAL BUILDINGS IN SAINT-PETERSBURG IN THE SECOND HALF OF THE XVIII CENTURY

The paper presents a review of architectural and design techniques which were characteristic for residential development in the second half of the XVIII century in St. Petersburg. During that period, there was formed the urban planning, volumetric spatial and constructional structure of residential buildings, which later, in the XIX - early XX century, became a typical solution for residential development in St. Petersburg. The fi rewalled residential house was usually built along the perimeter of the possessory plot of land with an inner courtyard formed inside. The residential house consisted of a two-span front building and one-span side buildings located along the perimeter of the site. The constructional system of a residential building in the second half of the XVIII century was a vaulted-beam scheme along the longitudinal walls. The main construction structures are described, such as brick walls with subsequent fi nishing, strip stone footings based on wooden joists, roofs built on wooden batt er rafters in a cold att ic with no heating.

Mechanical Behavior of a Composite Lightweight Slab, Consisting of a Laminated Wooden Joist and Ecological Mortar.

The investigation reported in this paper is an evaluation of the mechanical behavior of full-scale ecological mortar slabs manufactured with a mixture of expanded clay and recycled concrete aggregates. The composite mortars form a compressive layer over laminated wooden joists to form a single construction unit. To do so, full-scale flexural tests are conducted of the composite laminated wood-ecological mortar slabs with different types of mortar designs: reference mortar (MR), lightweight mortar dosed with recycled concrete aggregates (MLC), and lightweight mortar dosed with recycled mixed aggregates (MLM). The test results showed that the mortar forming the compression layer and the laminated wooden joists worked in unison and withstood a higher maximum failure load under flexion than the failure load of the wooden joists in isolation. Moreover, the laboratory test results were compared with the simulated values of the theoretical model, generated in accordance with the technical specifications for structural calculations contained in the Spanish building code, and with the results calculated by a computer software package. From the analysis of the results of the calculation methods and the full-scale laboratory test results, it was concluded that the safety margin yielded by the calculations validated the use of those methods on this type of composite slab. In this way, a strong mixed wood–mortar slab was designed, contributing little dead-load to the building structure and its manufacture with recycled aggregate, also contributes to the circular economy of construction materials.

Sound Absorption Characteristics of Polyurethane and Polystyrene Foams as Inexpensive Acoustic Treatments

This work examines the absorption characteristics of two well-known porous materials—polyurethane foam (PUF) and polystyrene foam (PSF)—both of which are locally produced and readily available in Saudi Arabia. Nine samples were selected after a careful investigation of the local markets. The chosen samples were systematically tested in conformance with the ISO 354 and ISO 9613-1 standards in the reverberation chamber. The samples were subjected to three sets of measurements. The first set of measurements was obtained with the samples installed directly against the chamber wall (DOW, Type A mounting). For the second and third sets of measurements, the samples to be tested were installed with an air gap of 50 and 100 mm from the wall using wooden joists of 50 × 50 and 50 × 100 mm, respectively. Results showed that polyurethane foam is an efficient absorber, whereas polystyrene is not. It was also observed that sound absorption improves remarkably in the low-frequency range by increasing the air gap between the tested sample and the solid wall behind it, but this improvement becomes very limited in the mid- and high-frequency range. Adding a polystyrene and/or CF13 layer under the tested material generally improves the absorption characteristics when compared with the case where the material is installed directly against the wall or floor. Nevertheless, the best performance is achieved when the material is installed at least 50 mm from the wall or floor. Furthermore, results showed that the thickness of the material has a stronger effect on the absorption than the density in terms of the “correlation coefficient”. The other factors that affect the sound absorption include air flow resistivity, air permeability, and the microstructure of the tested samples.

Houses Based on Natural Stone; A Case Study—The Bay of Kotor (Montenegro)

The Bay of Kotor, in its exceptional natural conditions, thanks to its geographical location and influenced by historical events, saw the development of rural settlements that are historically, artistically and culturally worthy of recognition. These stone settlements were acquired completely spontaneously, keeping the same pace as the settling, and transformed to some degree due to contemporary social movement and migration. Up until the middle of the 20th century, structures on the coastline in general were built by applying the same verified methods, which remained unchanged for centuries. Unreinforced stone walls as load-bearing vertical elements, coupled with wooden floor joists attached in a traditional way are typically present in the stone architecture of the Adriatic region and karst areas in general. The construction characteristics of the stone houses built in such a way meet all needs in terms of strength, thermal insulation, and are suitable for the coastal climate of this region. The fast-paced development in the past 50 years, the inadequate legal protection of residential buildings in the Bay of Kotor, poverty, and the new rich have brought about the devastation of not only buildings built in traditional architecture styles themselves, but also the urban landscape of the bay. Throughout the Bay of Kotor, buildings built in traditional architecture styles are nowadays more and more rare to see in their original shape—houses outside of cities but which display all characteristics of civic coastal houses and buildings free of rigid style rules, even though closely in contact with them. Regardless of efforts to preserve the heritage inherited by our ancestors, cultural monuments and houses referenced here deteriorate on a daily basis due to troubles and neglect.

Biodegradation of Wood Treated with Copper Based Preservative by Two Dematiaceous Fungi: Alternaria Tenuissima and Ulocladium Consortiale

As cases of treated wood colonization by fungi still happen, the understanding of fungal survival abilities could contribute in the creation of new efficient preservatives. For that reason, two dematiaceous fungi Alternaria tenuissima and Ulocladium consortiale isolated from treated wooden joists with discolorations were tested for their wood decomposition ability and tolerance to a copper based preservative. Our results indicated that the copper based preservative failed to suppress completely cellulose and lignin biodegradation by discoloring fungi studied in wood. Moreover, cellulose degradation was higher in the treated sawdust for both fungi after 30 days than in the untreated. Comparing the results of two strains U. consortiale that is little studied as a wood decomposer, was stronger lignin degrader than A. tenuissima in treated and untreated sawdust. The copper sulphate tolerance test showed that both fungi were able to grow up to 7 mM concentration in a solid medium. DOI: http://dx.doi.org/10.5755/j01.ms.25.3.20563

Influence of between-joists bridging elements on static and dynamic response of wood joisted floors

Excessive vertical vibration of lightweight floors caused by walking or similar activities can be annoying to building occupants. Previous studies have shown that the vibrational performance of floors having wood joists is enhanced by installing one or more lines of bridging elements that form transverse spines in the across-span direction. This paper presents an experimental study that defined relationships between the effective flexural rigidity of such spines and response characteristics of wood joisted floors. Behaviors of spines having both normal and special types of bridging elements were investigated, with the special types of elements able to create a broad range of spine flexural rigidities. It was found that all types of transverse bridging spines have a small influence on fundamental natural frequency but can increase higher order modal frequencies considerably. Relatively stiff types of transverse bridging spines reduced static deflections caused by concentrated gravity forces considerably. An experimental method is presented for quantifying effective flexural rigidities of transverse bridging spines. Suggestions are made concerning application of the research findings in vibration serviceability design of lightweight wood joisted floors.