Wood Members Research Articles

Charring rates and temperature profiles of wood sections

AbstractA research project was carried out at the Swiss Federal Institute of Technology (ETH) to study the fire behaviour of hollow core timber slabs and timber‐concrete composite slabs. This paper describes the main results of the basic fire behaviour of timber measured in the study. The first part of the analysis looks at the charring rate of timber. In the second part a new calculation model for the temperature development in wood members exposed to the standard ISO‐fire is presented and compared with the fire test results. Copyright © 2003 John Wiley & Sons, Ltd.

DiscussionDesign method for bolted connections loaded perpendicular-to-grain: Discussion

This paper and recent papers by the same authors (Quenneville and Mohammad 2000; Mohammad and Quenneville 2001) present a tremendous amount of valuable laboratory data on the subject of bolted connection behaviour in timber. The observations of behaviour and failure mechanisms are particularly relevant. The authors present new design equations, based on failure mechanisms, to predict connection strength — an improvement on the current code requirements found in O86.1 (CSA 1994). These new equations were shown to produce improved results in the paper’s figures; however, the equations lack a detailed analytical basis. All bolted connections, regardless of the material, will develop a three-dimensional stress field — the magnitudes of the stresses depend on the connection geometry and material properties. The ductility in the steel connector also plays a role. In the wood member, the stress distribution is complicated by material orthotropy and nonlinear behaviour of wood in compression. The connection behaviour is further complicated by brittle failure of wood in tension and in shear. The authors provide between three and six equations to predict the connection strength for different connection con figurations loaded perpendicular-to-grain, when strength is governed by bearing. They provide only one additional equation to predict connection strength when splitting governs. The authors later conclude that, based on their tests, tension perpendicular-to-grain splitting was found to govern connection strength in most cases. From their conclusion, one would expect that their proposed equation for the prediction of brittle failures would have been developed using a rigorous analysis of the stresses in a bolted connection, rather than curve-fitting to an expression originally devel oped to predict the strength of timber rivets. Foschi and Longworth (1975) used a combination of material nonlinearity and the weakest link theory to predict the strength of timber rivets undergoing brittle failure. This work forms the basis of the current O86.1 rivet design procedure. Their one-dimensional finite element model predicted stresses around each rivet over a series of load steps. At each step, the stresses were analyzed to determine if the tension or shear stresses exceeded the allowable stresses according to the Weibull weakest link theory (Weibull 1939). The model also pinpointed the governing mode of failure (i.e., tension perpendicular-to-grain or shear). This model was specifically developed for timber rivets — the boundary conditions for the governing displacement field equations were chosen specifically for the rivet connection analyzed at that time. Quenneville and Mohammad modified Foschi’s (1973) governing equation but gave no direct indication that the original field equations can be applied to the design of multiple-bolt connections. There are a number of reasons to believe that recalibrating

Load duration effects in wood members and connections: order statistics and critical loads

Load duration behavior, arising from creep-rupture, is one of the most significant effects distinguishing wood materials from other structural materials. The phenomenon of creep-rupture has been widely studied over the past two decades. Recent experimental programs have focused on duration-of-load (DOL) effects in full-size lumber and a number of different cumulative damage models have been proposed. These models have been used in reliability analyses that take into account the stochastic nature of the loading process to evaluate appropriate load duration adjustment factors for use in design. More recently, the stochastic damage accumulation process itself has been investigated. This has resulted in proposals for simplified cumulative damage analyses and the re-emergence of the ‘killer pulse’ concept for load duration effects in wood. Other recent studies have focused on evaluating analogous load–time effects in mechanical connections in wood. While the mechanisms in connections are recognized as different from those in wood members, the treatment of time effects in design are (at least at the present time) similar. With the tendency toward engineered design of wood structures subject to natural hazards loadings, such as wind and seismic loads, load duration effects in both the primary framing members and the structural connections may be of particular importance. The evolution of the new LRFD standard for wood provides a good opportunity to re-visit this important issue. This paper will briefly review DOL research, with particular emphasis on the work used as the basis for the time effects factors in the LRFD standard, and describe some recent work in (a) a simplified approach to cumulative damage analysis using order statistics, and (b) load–time effects in simple wood connections. It is shown that reliability analyses including DOL behavior can be performed more simply (efficiently) using an order statistics approach or even a simple FORM analysis. Thus, it may be possible to evaluate load duration factors for design without having to perform complex stochastic cumulative damage analyses.

System and method of assessing the structural properties of wooden members using ultrasound

A system and method of detecting anomalies and/or grain variations in a wooden member. At least one ultrasonic transmitter (401) applies an ultrasound waveform into a surface of a wooden member (100) so as to generate a multiplicity of ultrasonic waves including, e.g., longitudinal and shear waves. These ultrasonic waves are measured after propagation through the wooden member by at least one ultrasonic receiver (402) disposed on the same surface of the wooden member. At least one ultrasonic receiver (501) may also be placed opposite the ultrasonic transmitter (401) so as to detect radial transmission of the longitudinal ultrasonic wave at a point across the wooden member. The received ultrasonic waves are processed to determine anomalies and/or grain variations in the wooden member at positions of the wooden member between the ultrasonic transmitter and the ultrasonic receiver(s). The ultrasonic transmitters and receivers the ultrasound may be placed in rollers to facilitate high-speed, in-line processing of wooden members.

The base of the Portsdown Chalk Formation (Chalk Group, White Chalk Subgroup) in the BGS Big Almer Wood Borehole, Dorset, southern England

The mapped boundary between the Spetisbury Chalk Member of the Culver Chalk Formation and the overlying Portsdown Chalk Formation of the White Chalk Subgroup is taken in central Dorset at a pronounced negative feature break. In the absence of any section across the junction, the feature was thought to mark the upward change from marl-free chalk into chalk with numerous marl seams, as in the Isle of Wight. However, in the BGS Big Aimer Wood Borehole, drilled to investigate this boundary, marl seams are largely absent in the lower part of the Portsdown Chalk, and it is the upward change from flinty to flint-free chalk which marks the Spetisbury/Portsdown Chalk boundary. The basal beds are rich in comminuted inoceramid debris. A new member, the Big Aimer Wood Member, is introduced for this basal marl- and flint-free, ‘gritty’ chalk. This paper includes a revised foraminiferal zonal scheme for that part of the Lower Campanian corresponding to the G quadrata macrofossil Zone. In this scheme, the Big Aimer Wood Member is more-or-less co-extensive with the BGS20iv Subzone. New foraminiferal evidence shows that the basal Portsdown Chalk boundary in this part of Dorset lies at about the level of the Scratchell's Marls, i.e. a short distance above the basal boundary marl seam (Portsdown Marl) of the Portsdown Chalk of the Isle of Wight standard successions; i.e. the base of the Portsdown Chalk is slightly diachronous.

Design method for bolted connections loaded perpendicular-to-grain

A new design approach to evaluate the resistance of bolted timber connections loaded perpendicular-to-grain is presented in this paper. The design method consists of calculating the resistances of the ductile failure modes, based on the original European yield model, and that of the splitting mode, and of using the smallest of the two. The splitting calculations are adapted from the wood resistance calculation for timber rivet connections. The new design method is based on the assumption that the bolted connection is forming a cluster considered to be equivalent in dimension to a cluster of timber rivets. The rivet design equations were modified to reflect the fact that bolts extend to the full thickness of the wood members, whereas rivets do not. In this paper, the research program is described, results are presented and the alternative design approach is proposed to predict the failure modes and the ultimate strengths of steel–wood–steel, wood–wood–wood, and wood–steel–wood bolted connections.Key words: connections, strength, design, bolt, connection, prediction, failure, perpendicular-to-grain.

Effect of Polar Anisotropy of Wood Loaded Perpendicular to Grain

This paper reports on an analysis and experimental verification of the effect of cylindrical an- isotropy of softwood loaded in the radial r and tangential t growth plane, i.e., perpendicular to grain. This off- axis loading mode is especially design-relevant for curved and tapered glulam beams. The very low shear stiffness in the r,t on-axis growth plane, together with a complex shear coupling effect in polar coordinates, contributes essentially to extremely variable off-axis strain and stress fields. Thus far, no explicit empiric proof exists for these effects with considerable consequences on damage-relevant stresses. The exemplary off-axis investigations were performed with a cross-sectional slab of a spruce board loaded in tension parallel to the longer edges. True on-axis stiffnesses were determined for the simulations from two on-axis specimens cut from the test volume. Throughout a good agreement between the finite-element predictions and the measured results was obtained. The experiments, for example, proved that off-axis strains parallel and normal to load axes may vary along specimen length by factors of about 4.5 and 9, respectively. The natural fiber-composite material, wood, globally shows a cylindrical anisotropy of stiffness and strength properties. The three principal axes of the cylindrical material anisotropy are (1) the stem (rotation) axis, termed pith, being parallel to the fiber direction; (2) the radial; and (3) tangential directions in the cross section normal to pith. In the radial-tangential plane the constitutive law thus is polar anisotropic. The as- sumption of a cylindrical material anisotropy represents, strictly speaking, an approximation of the actual conical an- isotropy bound to the conical shape of a stem. Growth bound, a periodically layered built-up material, exists in the radial direction with discontinuous stiffness changes at the interfaces of late and early wood of adjacent annual rings. When the regarded size scale covers several annual rings the material may however be approximated as smeared homogeneous in the radial and in the other principal directions. Consequently this homogenization excludes local effects of defects such as knots and resin pockets. The stiffness properties in the three principal material di- rections differ considerably. For most softwoods the stiffness in the fiber direction is about 10-15 times higher compared to radial stiffness, the latter being about 1.5-2 times higher than tangential stiffness. Due to the thin wall thickness of early wood cells within the aforementioned periodical buildup in the radial direction the shear stiffness in the radial-tangential plane is very low for most softwood species; the shear modulus is in the range of about 1/20 of the radial stiffness. Boards and dimension lumber are sawn parallel to the stem axis whereby the rectangular cross section breaks the cylin- drical symmetry according to respective cross-sectional size and position in the stem. Generally, a continuum analysis of bar or plate-shaped in-plane loaded wooden members is per- formed by plane 2D computations based on a rhombic or polar orthotropic material law for straight resp. curved beams. Hereby one of both principal material axes is the fiber direc-

Load Sharing Effects in Light-Frame Wood-Truss Assemblies

Load sharing among repetitive wood members interconnected by structural sheathing strengthens light-frame assemblies beyond that assumed in designing a single member. A repetitive member factor of 1.15 applied to bending resistance has been traditionally included in wood design standards to account for this effect. The focus of this study was to quantify load-sharing effects on members in metal-plate-connected wood trusses. This was accomplished using a detailed structural analysis model and statistical characterizations of lumber stiffness and strength properties. Monte Carlo simulations were conducted on six common truss configurations and one dimension lumber joist floor where wood member properties were randomly selected from distributions representing properties of the lumber grade. The assemblies were analyzed with and without attached sheathing to directly quantify the load-sharing effects in the system. The computed mean load-sharing factors ranged from 1.06 to 1.24 in the truss assemblies and fro...

On the failure modes and strength of steel-wood-steel bolted timber connections loaded parallel-to-grain

The current Canadian code provisions for the design of timber bolted connections were essentially developed based on connections showing a ductile behavior and then further modified to account for situations where connections fail in a brittle way. An experimental study was undertaken to evaluate the strength of bolted connections specifically experiencing a brittle mode of failure. Specimens consisting of steel-wood-steel connections with either 19.1 mm or 12.7 mm bolts were tested in tension. Test variables included end distance, bolt spacing, row spacing, number of bolts per row, number of rows, thickness and species of wood member, glulam or sawn lumber members. Connections were tested to the ultimate to observe possible modes of failure as variables were changed. Results show that the current Canadian standard approach to evaluate the resistance of timber bolted connections is not optimal although conservative. Brittle modes of failure such as row shear-out, group tear-out, and splitting were observed. The resistances calculated using the O86.1 design provisions are as little as a third as compared to tested results. Also, the design equations do not allow the designer to take advantage of the increases in strength as a result of increases in row spacing, as observed in tests. Analysis of the results show that the longitudinal shear stress at failure is related to a parameter which is a function of the smaller distance (end distance or bolt spacing) and the specimen thickness. This relation was used to formulate design equations to predict the row shear-out and group tear-out strengths of glulam specimens using the specified strength values listed in O86.1. As well, it was found that Mode I of the European yield model is the only ductile ultimate failure mode and that other equations for bearing failure can be neglected. In this paper, the research program is described, results are presented, and an alternate design approach is proposed to predict the failure mode and the ultimate strength of steel-wood-steel bolted connection groups.Key words: bolt, connection, strength, failure, design, code, ductile, brittle.

Failure modeling of sawn lumber with a fastener hole

There is a consistent reduction in member strength associated with long-term use of structural wood members. It is hypothesized that this reduction in strength is due to “use and aging” effects such as cracks, splits and checks developed from drying stresses, moisture cycling, and fastener holes originating from initial construction techniques. The focus of this research effort was to develop an accurate model of the behavior and performance of the recycled timbers containing fastener holes. The flexural capacity of structural wood joists and planks containing fastener holes was modeled utilizing finite element analysis (FEA) coupled with the tensor polynomial (Tsai–Wu) strength theory. Each model presented herein represents a connection detail that is commonly used in construction. To validate the analytical approach, virgin timbers with drilled holes were conditioned to simulate in situ conditions and tested to failure. Comparing the results of the analytical model to experimental behavior, the FEA results were slightly conservative with predicted strength values falling within one standard deviation from the mean value of the experimental data and thus, producing accurate results. A critical hole location exists where the hole produces the largest reduction in strength. Based on the results, it is recommended that the edge of the hole not be located within 6 mm from the extreme fiber in both the compression and tension regions. If this does occur, then possibly some post processing needs to be performed such as planing the member down such that the hole is located on the edge, or the hole is completely eliminated from the section.

Comparison of ASD and LRFD Codes for Wood Members. I: Axial Loading

A comparison of the economies of the structural design of wood members subjected to axial loads using the allowable stress design (ASD) and reliability-based [load and resistance factor design (LRFD) format] codes is presented. Analyses considered the combinations of dead load only and dead plus live loads due to floor occupancy, snow, wind, and seismic activity. Ratios of live-to-dead loads ranged from zero to 10. The relative economies of the ASD and LRFD codes show the combined influences of the time-related factors assigned to the various load types, load and resistance factor values, and live-to-dead load ratios. The behavioral equations in both codes are now virtually the same. Since the allowable material stresses of the LRFD code are equal to the ASD value multiplied by a constant, the resulting economies are not species- or grade-dependent. For tension and zero-length compression loading, the LRFD format provided the more optimal design for all loading combinations except snow and seismic loadings when the live loads exceed three and four times the dead load, respectively. For columns with the potential for buckling, the LRFD format yielded larger buckling adjustment factors for wind and seismic loadings than did the ASD code. For all other loading arrangements, the ASD format produced larger factors. For floor loading, a 20% advantage over the LRFD code was observed for very slender columns.

Comparison of ASD and LRFD Codes for Wood Members. II: Flexural Loading

Comparison of ASD and LRFD Codes for Wood Members. II: Flexural Loading

Comparison of ASD and LRFD Codes for Wood Members. III: Connections

A study was conducted to evaluate the two design codes currently in use for the design of mechanical connections subjected to both lateral and withdrawal loading in wood structures. The allowable stress design (ASD) code and the new reliability-based code using the load and resistance factor design (LRFD) format were evaluated to see which offers the greatest efficiency (i.e., economy) with respect to the design of mechanical fasteners. When the allowable dead load plus live load (due to floor occupancy, snow, wind, and seismic activity) combinations were calculated in each format, comparisons revealed that the LRFD code proved to be more economical over a wider range of the two relevant input variables [dead-to-live load ratio (N) and effect of time under load]. When snow or floor live load governed the design, the LRFD format was always optimal. The amount of increase in load-carrying capacity exceeded 40% for floor live load with very small values of N. In the more commonly seen range of load ratios, t...

Fiber-Reinforced Composite and Wood Bonded Interfaces: Part 1. Durability and Shear Strength

Fiber-reinforced plastic (FRP) composites have shown the potential for reinforcement of wood structures (e.g., bonding of FRP strips or fabrics to wood members). Although significant increases in stiffness and strength are achieved by this reinforcing technique, there is a concern about the reliable performance of the FRP-wood adhesive bond, which is susceptible to delamination. The overall objective of this two-part paper is to develop a qualification program to evaluate the service performance and fracture of composite/wood bonded interfaces. Two types of FRP-wood interfaces are studied: phenolic FRP-wood and epoxy FRP-wood bonds. In the present paper, Part 1, the durability and shear strength of FRP-wood bonds are evaluated by modified ASTM tests. First, the service performance and durability of FRP-wood interface bond is evaluated using a modified ASTM delamination test. Then, the apparent shear strengths of bonded interfaces under both dry and wet conditions are obtained from modified ASTM block-shear tests. It is shown that the modified ASTM D 2559 standard test can be successfully used to study the effect of several parameters (e.g., bonding pressure, assembling time, and coupling agents) on bondline performance under wet-dry exposure cycles. Then for the best combination of parameters, the average interface shear strengths can be obtained from block-shear tests of ASTM D 905, modified for hybrid laminates. Mode I fracture of FRP-wood bonded interfaces and guidelines for FRP-wood bond performance evaluation are presented in the companion Part 2 paper.

Influence of semi-rigidity of joints on the behaviour of timber structures

The review starts by identifying the conditions for taking account of the semi-rigid behaviour of joints with dowel-type fasteners, i.e. well-defined load–displacement behaviour, no initial slip and reliable ductility. It is described how reinforcing a wood member perpendicular to the grain with fibre fabrics, plywood or densified veneer wood ensures that joints have reliable ductile behaviour. New types of fastener with desirable properties are described; with the expanded tube fastener being especially interesting. Modelling the load–displacement curves for single fasteners and joints with multiple fasteners is discussed. The so-called Plane Group of Mechanical Fasteners Model is most appropriate. The Spring Model is less suited to timber than steel. Some examples show how the semi-rigidity in the joints influences the behaviour of structural systems. The conclusions are that taking semi-rigidity of joints into account can lead to more efficient and economical structures.

From the Murat Family Album

One by one the four children, having climbed the wooden stair, appear in early light, clothed who knows how, on the deck of HMS Tremendous. One after the other, they yawn; then they stretch out their arms. Up and out go their arms, as if they were sending telegrams by semaphore. The amaranthine dawn of the Adriatic welcomes the children, their names are imprinted on the salt air: Achille, Letitia, Lucien, Louise. Their father is hiding in a cave behind Toulon; a farmer comes crunching up the mountain trail to the mouth of the cave: I have a place for you in my chicken house, nobody will find you there. The father follows the farmer and accomodates himself in the chicken house. Cluck. Having ferreted about in some straw, he can now eat a raw egg. At that moment his wife, the Queen of Naples, also appears on the deck of HMS Tremendous. Oh, good morning, children, she says. How high the sun is rising. Captain Robert Campbell, rather fat, who finds this Corsican woman, so self-possessed, quite admirable, calls from the galley: This capital cook is doing what he knows best; it's bacon again, grissini, and eggs Adriatica. Ha ha, how's that for Latin? Remark the space: the deck of a man-of-war. Here time is stored in tubs that are roped together beneath the booms. The ship creaks, all its wooden members call to the water, hush, call out, and strain again. There is time stored between the strakes and the shrouds which are bellying in the south wind now. Space too is stored with time in the oakwood deckboards. And on the deckboards skip the children's small bare feet and mother's in slippers. Mama, they shout, and they snuggle up to her huge underskirt. How close to the shore were they sailing? The Tremendous-- had it rounded the toe, sole, and heel of Italy, heading for Trieste, past Bari, all the way up the length of the Neapolitan kingdom? Meanwhile the children are using up the stored time, fooling, and prancing over ropes, and being interpreters, since the sailors can say no more than rumpy-pumpy, fooky-fooky, and shufty kush. The children speak Italian, French, elementary English, and a few phrases in German. Their mother, in her fingers a crisp rasher of bacon, says hardly anything. Joachim, she says to herself. Joachim: first Russia, now where can he be. Oh my, his thighs in those white trousers, when he rode his chestnut mare, his fancy waistcoat, velvet, green, gold frogging over his wounds, under his decorations. …

Rate-of-Load and Duration-of-Load Effects for Wood Fasteners

It has been suggested that duration-of-load (DOL) effects in connections differ substantially from those in wood members and that the factors developed using cumulative damage models based on tests of wood members in bending (i.e., creep rupture) are not appropriate for the design of connections. This paper presents the results from a test program that attempts to quantify rate-of-load and short-term DOL effects for wood fasteners (such as nails and screws) subject to withdrawal or lateral loads. The results from this preliminary study suggest that no obvious rate-of-loading effects exists for nailed connections subject to either lateral or withdrawal loading. This has particular significance, for example, in the design of roof sheathing systems and roof-to-wall connections to resist high-wind uplift loads. Although by no means a complete treatment of the topic of DOL (i.e., time) effects in fasteners, this study serves to highlight differences between connection and wood member time effects and both raises and answers some questions about the validity of adjustment factors for time effects for short-term loadings (i.e., wind and seismic) in wood connection design.

Prediction of the load carrying capacity of bolted timber joints

Failure of bolted timber joints is analyzed experimentally and numerically. In this study, the prediction of the load-carrying capacity of dowel-type joints with one dowel under static loading is based on the analysis of fracture in wood contrarily to most engineering methods that are based on the yield theory. Mechanical joints consist of glued laminated spruce members and steel dowels. In the different analyzed tests, the bolt loads the wood parallel or perpendicular to the grain. The wood member thickness is chosen sufficiently thin to avoid the fastener from presenting plastic hinges. The influences of different structural parameters such as the dowel diameter, the edge- and end-distances are investigated. The fracture propagation analysis is carried out with the Finite Element (FE) method in the framework of Linear Elastic Fracture Mechanics (LEFM). The only identified parameter is the critical energy release rate in mode I (GIc). The comparison between experimental and numerical results shows that the fracture must be considered for a correct prediction of the ultimate load and that LEFM can help to improve design codes.

Determination of bending modulus of elasticity of Pterygota macrocarpa K. Schum (Kyere) and Piptadeniastrum africanum (Dahoma) using two International testing norms

Two different international testing norms, DIN52186 (1978) and ISO8375 (1985) were used to determine the bending modulus of elasticity (MOE) of Pterygota macrocarpa K. Schum (Kyere) and Piptadeniastrum africanum (Dahoma). The results from the two testing norms for each timber species were highly correlated, with correlation co-efficients of 0.92 and 0.96 obtained for Kyere and Dahoma respectively. The MOE determined using ISO 8375 (1985), employing deflections within loading points (i.e. within the shear free zone) was, however, significantly higher than that determined using DIN 52186 (1978), employing deflections along the whole specimen length, for both species at 5% probability level. The difference in MOE's may be attributed to the influence of shear stresses in bending, in the case of specimens tested using DIN 52186 (1978). The results indicate that, test standards which recommend computation of MOE using total deflection along the whole length of the test specimen may under-estimate the actual rigidity of a wooden member. JOURNAL OF THE GHANA SCIENCE ASSOCIATION Volume 1 Number 3, July (1999) pp. 126-132

Prevention of Colony Foundation by Cryptotermes brevis and Remedial Control of Drywood Termites (Isoptera: Kalotermitidae) with Selected Chemical Treatments

A wooden trap-block bioassay, tested over 2 flight seasons, was found to be a suitable colonization platform for Cryptotermes brevis (Walker) dealates. A crevice designed into trap blocks Was the preferred locus for nuptial chamber construction by dealates. Lone heterosexual pairs were found in 52%of chambers containing live termites. Of colonies containing brood, 80%were headed by lone heterosexual pairs. The broods in 4- or 6-mo-old C. brevis colonies were small, with ≤3 eggs, larvae, or a combination. In 1995, a choice test of disodium octaborate tetrahydrate (DOT) solution, chromium copper arsenate (CCA), and water-treated (control) trap blocks was exposed to swarming C. brevis . Four months after swarming ceased, live dealates and brood were recovered from nuptial chambers in control blocks, but not from DOT or CCA-treated blocks. These results indicated that DOT and CCA-treated wood surfaces were unpreferred substrates for colony foundation by C. brevis , but that these deposits were not toxic to dealates as demonstrated by their survival in neighboring control blocks. In 1996, no-choice tests were conducted using trap blocks partially treated with DOT solution or water (control). Live dealates, heterosexual dealate pairs, and brood were detected in all control treatments at 6 mo. The mean number of nuptial chambers and live termites was not significantly different among the control treatments. The number of nuptial chambers in all DOT treatments, however, was significantly lower compared with control blocks and no live termites were found in any DOT-treated blocks. These results demonstrate that partial DOT deposits deterred C. brevis dealates from colonizing blocks. Choice tests also were conducted in 1996. A silica gel-pyrethrin dust, spinosad suspension concentrate (SC), and DOT dust were applied to trap block tops and tested against control blocks. Significantly fewer nuptial chambers and live termites were found in silica gel-treated blocks compared with neighboring controls. Although the number of nuptial chambers was reduced significantly in spinosad-treated blocks compared with control blocks, there was no significant difference in the number of live termites. No live termites were detected in either DOT-dusted trap blocks or in adjacent control blocks, implying that dealates searching for colonization sites were intoxicated by DOT dust and unable to colonize neighboring control blocks. In remedial control tests, mature colonies of C.brevis and Incisitermes snyderi (Light) in naturally infested wood were exposed to single-point gallery injections of spinosad SC or surface applications of aqueous DOT. Infested wood members were bisected, and the resultant halves differentially treated with chemical or water. Member halves were destructively censused at 28-33 d and 97-109 d after treatment with spinosad and DOT, respectively. Spinosad-treated halves yielded 92-100% mortality in 8 of 9 wood members containing either I. snyderi or C. brevis infestations. Surface applications of DOT caused partial and sporadic mortality. Mortality ranged from 1 to 88% for I.snyderi and was significantly greater overall compared with water-injected halves, whereas mortality in C. brevis infestations treated with DOT ranged from 0 to 35%.Mortality in water-treated half members ranged from 0 to 9%.Results of remedial control tests demonstrate the advantages of intragallery applications over surface-only treatments for drywood termite infestations.