Search

The progressive failure analysis of wood-frame structures under wind loads requires the resistances of each of the components (such as roof, walls, and connections) as input. The resistance...

Structural insulated panel (SIP) wall systems have been used in residential and light commercial buildings for the past 60 years. Lack of sufficient published research results on racking load performance and understanding of the influence of fastener types on seismic response has been a deterrent in the widespread use of the wall system in seismically active areas. This paper summarizes the results of a full-scale racking load testing study in which a total of 17 2.4×2.4-m (8×8-ft) SIP wall panels were tested under monotonic and cyclic loading. Four 114-mm (4.5-in.) thick SIP specimens were tested under monotonic loading, while 13 114-mm (4.5-in.) thick SIP specimens were tested under the Consortium of Universities for Research in Earthquake Engineering loading protocol. Parameters such as fastener type, spline design, hold-down anchor location, and sheathing bearing were adjusted throughout the testing to determine their effects on the SIP’s performance. Performance parameters such as peak load a...

This paper presents an experimental investigation of the racking performance of light-frame wood shear walls to evaluate the effect of Type X gypsum wall board (GWB). Twelve shear walls she...

Drive-in storage racks, made of cold-formed steel, are the main racking system used in industry for storing goods. The storage space utilization of drive-in racks is high at the price of the weak downaisle stability. This paper presents a general analysis of the lateral stiffness of drive-in racks in the downaisle direction. A total of 24 static tests of drive-in rack systems have been conducted under single-point horizontal force. The effects of some constructional details, such as bracing configuration, cargo pallets, and the number of bays, are considered. The experimental results indicate that either top plan bracing or back-spine bracing can change the load transfer through rack structures and increase the lateral stiffness of racks. By acting as the horizontal bracings of adjacent columns and reinforcing the rotational stiffness of column bases, the stored pallets are also the beneficial factor for improving the lateral stiffness of racks. According to the special structural characteristic o...

The performance of portal frame walls was studied using a finite-element model verified with results from tests of full-size portal frame walls. Parameters such as wall height, metal strap type and location, doubling of the bottom plate, sheathing placement, and nailing pattern were investigated. Results indicate that in all cases, lateral load capacity and stiffness are greatly reduced with the increase of wall height. Considering the effect of different metal strap types and locations, the tensile strength of metal straps has the greatest impact on the lateral load capacity and stiffness. Walls with metal straps placed directly on the framing members outperform walls with metal straps placed over the sheathing. For walls with a double bottom plate and two rows of nails fastening the bottom plate, the stiffness and lateral load capacity are slightly increased compared with walls with a single bottom plate. For walls with unblocked sheathing at midheight, the lateral load capacity is the same as i...

A research project was undertaken at Pennsylvania (Penn) State University to study the simulated seismic performance of Structural Sealant Glazing (SSG) used to adhere glass panels to common curtain wall framing systems. In the most common type of SSG curtain wall construction, referred to as two-sided SSG, two glass panel edges (typically opposing vertical edges) are adhered to the support framing using structural sealant, while the other glass panel edges are mechanically fastened to the support framing. In this study, full-scale two-sided SSG curtain wall mock-ups consisting of three, side-by-side glass panels were subjected to cyclic racking displacements to characterize their performance and to identify sealant and glass component failure modes under serviceability and ultimate racking displacement conditions. In addition to testing, kinematic-based models were developed to predict failure states (e.g., structural sealant failure) of the SSG curtain walls. This paper discusses the details of the pred...

Steel storage racks, made of cold-formed steel, are used extensively in industry for storing goods. Two main racking systems prevail, referred to as selective racks and drive-in racks. International racking design codes deal mainly with selective racks, but limited design guidelines are available for drive-in racks. Drive-in racks require minimum floor space by storing pallets one after the other with no space between them. The forklift truck drives into the rack to store the pallets on the first-in, last-out principle. To allow forklift passage, drive-in racks can be braced only at the back (spine bracing) and at the top (plan bracing) in the down-aisle direction, resulting in a complex slender structure with poorly understood three-dimensional (3D) behavior and increased risk of collapse. Tests on drive-in rack systems to accurately capture their 3D behavior have not previously been available in the literature. This paper presents experimental results from full-scale tests conducted on a complete drive-...

This paper explains an experimental study on a full-scale L-shape single story light frame wood house under the uniform lateral load simulated using a gasbag. The study verifies that shear walls are staggered to each other and the 1.0-m offset between them behave as a continuous shear wall, floor diaphragm with a reentrant corner up to 1.0 m that does not need a continuous end chord. Degradation in racking stiffness of light frame wood construction after continuously repeated cyclic lateral loads is not observable, while intermittent and larger amplitude cycling can cause observable settling of residual deformation and degradation in racking stiffness. The rigidity performance and high racking resistance of the floor diaphragm enables the light frame wood building to remain intact under ultimate lateral load, and recommends interstory percent drift restrictions for the lateral wind load design of the structures and the way to properly calculate racking capacity of gypsum sheathings. The conclusion of this paper can benefit the engineering practice of the light frame wood structures in hazard lateral load regions.

The tests were performed on 2.44 m by 2.44 m light-frame wall segments, having oriented strand-board sheathing nailed to sawn lumber framing, to determine their structural response to in-plane and out-of-plane forces applied separately or in combination. There was no evidence that simultaneous application of in-plane and out-of-plane forces negatively affects the strength of walls. However, it was found that interaction of different in-plane force components can substantially reduce strength capabilities of walls relative to when only one in-plane force component exists. Applying both in-plane tension and racking force in the ratio of 1:1 reduced the capacities of walls by 25 to 40%, with how lumber studs are connected to lumber base plates strongly influencing the absolute capacity of any wall.

Low-rise buildings are typically designed with shear walls and horizontal diaphragms to resist lateral load during windstorms and earthquakes. Although seismic performance and lateral load resistance behavior are generally well-understood for light-frame wood construction, this is not true for log construction. Research is needed to characterize log shear wall behavior subject to racking loads, and to develop recommendations for designing log walls to resist lateral loads from seismic or wind events. Monotonic and reverse-cyclic tests were conducted on log shear walls with 1:1, 2:1, and 4:1 aspect ratios. These walls showed higher resistance than conventional light-frame shear walls and similar hysteretic behavior to concrete and masonry shear walls. Log walls withstood large in-plane displacements without significant load reduction using lateral bracing typical of that used for light-frame wall testing; however, the test procedure would be improved by providing full-wall support to resist out-of-plane displacements of log shear walls. Design recommendations were developed based on the experiments reported herein.

This paper summarizes the findings of an experimental study to characterize the cyclic racking and monotonic loading performance of wood-stud and steel-stud wall specimens, which were sheathed on both faces with gypsum wall board (GWB). Some specimens were finished with joint compound at the GWB joints and over screw heads. The study provided data on monotonic and cyclic hysteresis load-displacement relationships. Based on the visual inspection of the specimens during the tests, several aspects of the failure modes were noted. Shear-load capacity and drift capacities were determined based on the envelope curves of the hysteresis cycles. A comparison of the envelope curves for steel-stud and wood-stud specimens provided insight as to the relative behaviors of the two wall system types, including capacity, measures of ductility, and energy dissipation. Finally, the study provided better understanding of the effects of finishing GWB joints on the shear capacity of the wall systems.

The overall goal of this study is to gain an insight into the load sharing aspect between oriented strand board OSB and gypsum wall board GWB in shear wall assembly during racking load. Sixteen standard 2,4402,440 mm walls were tested monotoni- cally, in total, out of which 11 Type A were sheathed on both sides OSB on one side and GWB on the other, while five walls were tested without GWB Type B. Digital image correlation DIC was used for data acquisition and analysis which is a full-field, noncontact technique for measurement of displacements and strains. The system returns full-field three-dimensional displacement and strain data measured over the visible specimen surfaces. Overall, these tests suggest that initially during loading of a wall the load is shared between OSB and GWB. However, the proportion of load sharing is not known. As GWB fails first at about 60% of ultimate load capacity of the wall, the load shifts to the OSB panel which resists it until the failure of the wall. The tests also revealed that the load path in wall Types A and B is different and so is the failure pattern. Strains were locally concentrated around the fasteners, while the strains in the field of the panel were below the detection limit of DIC system.

A series of 11 tests of full-scale partition walls were conducted to determine the behavior of nonstructural gypsum wallboard partition walls during lateral deformation as might be expected during a major earthquake. The partition walls were constructed as double-sided, 1/2 in. (13 mm) gypsum wallboard partition walls with wood stud framing. The walls deformed laterally in one of two ways: either as a joint-failure mode with racking of the individual gypsum wallboard panels, or by a pier-rotation mode where all the gypsum wallboard panels in a pier rotated as a unit. In all of the tests, the fasteners failed by pulling through the back of the wallboard panel, cutting of the gypsum, or tearing out through the edge of a wallboard panel. In some tests, the strength of the tape and compound was seen to provide adequate support to cause the walls to roll as a single unit, especially when the spacing of fasteners was large. The maximum load resisted varied from 512 N/m (378 lb/ft) to 1,177 N/m (869 lb/ft) and occurred at drifts between 0.68 and 1.87%. The drift when specific damage thresholds occurred was monitored during testing. Damage initiated with slight cracking of the panels at the wall opening at drifts of 0.25%, followed by increasing damage up to drifts of 2%, and minimal additional damage at drifts above 2%. Damage thresholds for cyclic loading often occurred at lower drifts than comparable specimens under monotonic loading.

Formed from a thick layer of polystyrene foam sandwiched between two layers of oriented strand board, structural insulated panels (SIPs) are a viable alternative to traditional wood stud shear walls. Developed in North America, SIPs satisfy building performance criteria while being both sustainable and cost effective. This paper details a comprehensive experimental and parametric study at Napier University examining the structural performance of shear walls constructed of SIPs under the action of both racking loads and combined bending and axial compression. The effects of size and position of openings, for doors and windows, were examined and compared to designs carried out in accordance with BS 5268 and Eurocode 5. The study has demonstrated that SIPs perform as an effective composite material possessing the strength and stiffness necessary to sustain required design loads.

Laboratory experiments subjected full-scale autoclaved aerated concrete (AAC) cladding panel specimens to static monotonic loading and incrementally increased displacement amplitudes of cyclic racking movements. The objective of the study was to characterize the seismic performance of cladding panel walls made up of the newly introduced AAC in the U.S. market. The study found that conventional connectors used to attach AAC cladding panels to structural systems have not been designed for in-plane seismic resistance and would need to be redesigned in order to safely satisfy building code’s allowable drift.

This study addresses the development and structural testing of a hybrid sheathing panel designed to improve the lateral resistance of light wood-frame shear walls. The panel consists of thin outer sheets of oriented-strand board (OSB) bonded to strips of fiber-reinforced polymer (FRP) that are sandwiched between the OSB panels at the edges. The FRP-reinforced panel material selection and fabrication are summarized. Monotonic and cyclic tests were conducted to assess the performance of single-connector sheathing-to-framing connections using both OSB and FRP-reinforced OSB. Twenty-four full-scale shear walls were tested under monotonic and cyclic racking loads to determine the benefits of FRP-reinforced OSB to wall lateral load resistance. For a 102 mm perimeter nail spacing, FRP-reinforced OSB-sheathed walls exhibited increases in peak capacity and energy dissipation under cyclic loading of 27 and 73%, respectively, compared to walls sheathed with conventional OSB. Based on these experimental results, FRP-reinforced OSB panels appear to have significant potential for increasing the energy dissipation capacity and lateral load resistance of wood-frame structures subjected to extreme lateral loads. However, their full utilization will require higher strengths for critical shear wall components such as tension ties and framing interconnections, as well as improvements in sheathing-to-framing fastener performance.

In this study, full-scale tests were conducted on unblocked shear walls with various sheathing details and reference blocked shear walls. A total of eight 4.88 m×4.88 m shear walls were tested. Monotonic and reversed cyclic displacement schedules were used as loading protocols. Load–displacement response of each test specimen was recorded, from which the initial stiffness, yield point, ultimate load and displacement, and energy dissipation were calculated. The test results were analyzed to study the influence of different configurations on unblocked shear wall strengths. Relative load-carrying capacities between unblocked and blocked shear walls were determined. The results show that the provisions currently in CSA O86-01 for 2.44 m tall shear walls may be conservatively applied to the four wall configurations tested in this study. Data from this study are suitable for verifying structural analysis models that may be used to further refine the adjustment factors.

In routine design of steel storage rack frames, it is far more common to perform two dimensional (2D) rather than three dimensional (3D) linear buckling analyses. In this paper, it is demonstrated that the global buckling behavior of high-rise steel storage rack frames may not be revealed by 2D buckling analyses as 3D interaction modes are involved. It is shown that the monosymmetric upright columns of a high-rise rack frame fail in a flexural.torsional mode due to the shear-center eccentricity of the sections, and that the 3D frame buckling analysis is more reliable in determining the critical members of a rack frame. Current steel storage rack design standards combine independent 2D flexural buckling analyses and simplified flexural.torsional buckling analysis of individual columns to account for 3D behavior. Comparisons between the buckling stresses of the rack columns determined from 3D buckling analyses and the buckling stresses determined in accordance with the steel storage racking standards are presented. It is concluded that the use of 2D analysis based procedures can lead to poorly proportioned pallet rack structures in terms of safety or economy. By comparing the buckling analysis results using 3D beam elements of varying degrees of refinement to each other, it is also demonstrated that the beam elements available in most commercial frame analysis programs are not sufficiently refined for accurate 3D buckling analyses of high-rise rack frames composed of monosymmetric thin-walled open sections.

Results are presented of a pilot study conducted recently at the Pennsylvania State University Building Envelope Research Laboratory (BERL) to investigate the response of curtain wall mock-ups glazed with 6 mm (1/4 in.) annealed monolithic architectural glass panels fitted with anchored applied film under simulated earthquake conditions. Three common film-to-frame anchoring methods were evaluated: (1) structural silicone adhesive [13 mm (1/2 in.) triangular cross section] application along the entire glass panel perimeter; (2) an aluminum bar extrusion to anchor the film to the frame horizontal along only the top of the glass panel; and (3) two aluminum bar extrusions to anchor the film to the frame verticals along the two vertical edges of the glass panel. Serviceability (glass cracking) and ultimate (glass fallout) limit-state data were collected during in-plane dynamic racking tests. Other performance characteristics, such as cohesive failure of the structural silicone adhesive, loss of film-to-glass adhesion, film tearing, damage to aluminum anchor bars, pullout of the filmed glass unit from the frame glazing pockets, and eventual entire unit fallout, were also recorded. These preliminary tests indicated that anchorage type can demonstrably influence both the serviceability (initial glass cracking) and ultimate (glass fragment fallout and entire unit fallout) limit states of “unweathered” filmed glass panels. In this study, the structural silicone anchor provided the best serviceability limit-state performance of the three anchor methods tested, and the top anchor provided the best entire-unit glass fallout resistance.

In-plane dynamic racking crescendo tests were performed on full-scale curtain wall mock-ups dry glazed with six different insulating glass unit (IGU) configurations and one laminated glass unit configuration. The tests were conducted to determine the serviceability and ultimate limit state behaviors of these configurations tested under simulated earthquake-induced lateral drifts. All IGU configurations tested were manufactured with an annealed monolithic pane and a laminated pane with an argon fill and an anodized aluminum spacer between the panes. Several parameters were varied in the laminated pane of each configuration including glass lite thickness and glass type in the laminated pane (annealed, heat strengthened, and fully tempered), and PVB interlayer thickness for the laminated pane. Properties of the annealed inside pane were not varied. For each configuration, average drift values for the occurrence of glass cracking in each IGU pane, glass fallout from the monolithic pane, and pullout and fallout of the entire glass unit are reported. Relevant damage to the aluminum framing is also reported. Results of these tests can be used to assess the seismic resistance of similarly glazed architectural glass panels in practice and to improve the design of asymmetric IGU configurations for use in seismic regions.

The point fixed glass facade system (PFGFS), also known as a spider glass system, is popular because it is the most transparent facade system available for buildings. The glass facade system is fixed to the support structure at minimal points using bolts and spider arms. Generally, the racking performance of these systems is not considered at the design stage. The facade system will be vulnerable to racking actions mainly during severe earthquakes and wind actions if the system does not have sufficient in-plane drift capacity. A unique real-scale in-plane racking laboratory test on a typical PFGFS was conducted to assess the in-plane racking performance. A maximum drift of 2.1% was measured, which was much larger than initially anticipated because of the rigid-body articulation of the system and higher than typical maximum allowable interstory drift for buildings in regions of lower seismicity. A sophisticated nonlinear finite-element (FE) model was developed and conservatively benchmarked against...

This paper presents a detailed investigation into the contribution of plasterboard to the lateral resistance of cold-formed steel-framed residential structures. It details the development of a finite-element model for laterally loaded plasterboard-lined cold-formed steel wall frames for residential construction. The model utilizes nonlinear element properties and three-dimensional geometrical configurations and is capable of simulating the influence of boundary conditions such as corner return walls and ceiling cornices. The analytical results from the finite-element model were successfully verified against experimental racking test results. A sensitivity analysis was conducted using the model to study the influence of return walls, ceiling cornices, and wall length on the lateral capacity of the wall system. It is concluded that a wall with corner return walls, ceilings cornices, and skirting boards has more than three times the lateral capacity of an identical isolated wall panel. The relationship between the wall length and the ultimate lateral load-carrying capacity of the wall system is dependent on the presence of these boundary conditions.

This paper describes an innovative wall system for use in residential and commercial construction projects that is reusable, uses less dimensional lumber, and is faster to assemble and install compared to traditional stud wall systems. The wall system is an engineered wall design composed of components fabricated from 5.08 × 5.08 cm (2 in.) (nominal dimensions) nailing strips and oriented strand board fins located in the midsection of the nailing strip. Components can be connected to one another by hinges allowing the system to be collapsible. Laboratory testing has shown that this wall system has significantly improved racking capabilities compared to the traditional stud wall system both with and without sheathing. Additional research is required, however, to enhance this wall system's structural characteristics in bending and axial loads. An economic analysis showed that material costs are cheaper for this wall and assembly, and installation times are less compared to traditional stud wall construction...

Recent results from full-scale static racking tests and small-scale lateral shear tests on plywood, oriented strand board (OSB), gypsum wallboard (GWB), and FiberBond wallboard (FB) attached to light gauge steel studs are presented and discussed in this paper. The objectives of the tests were to investigate the performance of sheathed light gauge steel framed shear walls and determine whether simple static lateral shear values for the panel connection can provide a useful correlation with full-scale test values. The full-scale tests were conducted in accordance with the basic test criteria defined in ASTM E 72-80. A procedure similar to that described in ASTM D 1761-88 was used for the small-scale tests. Panels used in the tests included 11.9 mm APA rated four-ply plywood sheathing, 11.1 mm APA rated OSB sheathing, 12.7 mm gypsum wallboard (ASTM C 36), and 12.7 mm FiberBond wallboard. Results obtained from tests showed that failure of the walls resulted from rotation (tilting) of the fasteners about the p...

A method of modifying the lateral load–lateral displacement relationship obtained by a simple monotonic racking test to represent the skeleton hysteresis curve of an arbitrary dynamic response of a reinforced-masonry wall is proposed. The results of tests of 32 equal reinforced-masonry walls, tested by imposing monotonically increasing displacements, cyclic lateral displacements of two different shapes, and simulated displacement seismic response, have been used as a basis for the development of the procedure of modification. The amount of input energy, defined as the actuator work done to deform the specimens during the test, has been taken into account as the decisive parameter for carrying out this modification. On the basis of experimental results, correlation factors between the monotonic and cyclic hysteresis envelope curves, as well as stiffness and strength degradation parameters, which define the hysteretic rules, have been evaluated. Good agreement between predicted and experimental cyclic behavior of the walls has been obtained.

The theory presented in this paper predicts racking deformations in wood‐stud shear walls. The energy method employed defines the wall performance in terms of the lateral nonlinear load‐slip behavior of the nails which fasten the sheathing to the frame. Using power curves to define the nail loadslip relationship, the theory predicts that wall deformation due to nail slip will also be defined by a power curve. The theory also includes linear deformation due to shear distortion of the sheathing material, and provides accurate estimation of wall performance up to moderate load levels. The method presented should be of interest to engineers who design light frame structures, to researchers, and to those who are concerned with building codes.

An approximate method for estimating the drift of multi-bent structures is presented. Structures that are singly or doubly symmetrical in plan and comprising any combination of shear walls, coupled walls, rigid frames and braced frames, can be considered. Results for structures that are uniform with height compare closely with results from stiffness matrix computer analyses. The method is developed from coupled-wall deflection theory which is expressed in terms of two non-dimensional structural parameters. The parameters involve three structural properties: the individual bending stiffness of the walls, the overall bending stiffness related to axial deformations of the walls and racking stiffness caused by reverse bending of the beams. Similar properties are calculated for rigid frames, braced frames and shear walls and then combined to determine values of the two parameters for the total structure. These values are then substituted into a generalized equation to obtain the deflection profile. This method accounts for axial deflection of the vertical components and is, therefore, more accurate for very tall structures. The method provides a rapid estimate of the drift in a high-rise structure as well as allowing an easy means of comparing the suitability of different structural solutions for a tall building. The method also illustrates the fundamental dependence of the behavior of continuous type cantilevers on two characteristic parameters.

Horizontal forces, such as wind, are resisted by the walls parallel to the wind direction. These forces, which lie in the plane of the wall, are known as the shear or racking loads, and are transmitted to the sheathing through the fastener system. Qualification of sheathing materials has generally been limited to performance testing of 8-ft by 8-ft (2.4-m by 2.4-m) stud wall assemblies. An analytical procedure has been developed that accurately predicts racking strength based upon the lateral resistance of the individual fasteners. The structural model is applicable to any sheathing size or geometry, so it is possible to determine the racking strength of light frame walls from simple lateral nail tests or small scale racking tests. The procedure offers a direct means for designers and code officials to predict racking strengths of panels incorporating various sheathing materials and fasteners.

The influence of adhesive rigidity on the stress distribution in a prefabricated plywood wall panel subject to a racking load has been investigated. A typical low-cost housing wall panel, joined by means of a thick-layer adhesive, was studied analytically and experimentally. The results of stress analyses of the panel were performed with two different adhesive rigidities—a rigid adhesive and a relatively flexible adhesive. For each analysis, the stresses in the plane of the sheathing were compared. The analytically predicted critcal rolling shear stress between framing and sheathing was found to be three times greater in the panel joined by the rigid adhesive than in the panel joined by a flexible adhesive. The flexible adhesive serves to reduce stress concentrations by distributing loads uniformly throughout the structural system. The results of a limited testing program partially substantiate the results of the analytical study. A wall panel was fabricated and constructed with a material similar to a flexible thick-layer adhesive. The agreement was good which in part substantiates the conclusions drawn from the finite element analysis.

Standard methods of testing the racking capacity of light‐frame walls are inefficient and may give erroneous estimates of shear wall performance. This study is concerned with improving the data base for racking resistance of light frame walls with plywood and gypsum sheathings. The shear resistance of small walls sheathed with gypsum was compared to that of full‐size walls. Results of both tests indicated that racking strength was linearly proportional to wall length. Contributions of sheathing layers and panel sections appear be additive, and length of wall sections containing door and window openings may be neglected in determining racking resistance of conventional walls. One notable difference in the performance of these racking tests involved the effect of panel length on racking stiffness. Stiffness of small walls increased linearly with length while the stiffness of full‐size walls increased nonlinearly. Knowledge that gypsum wallboard can contribute to shear wall performaoee and that it is additiv...

Wood-frame houses (light-frame timber construction) suffer widespread losses in high winds. Improvements in construction techniques and practices can greatly reduce wind damage to such buildings. The most serious problem contributing to wind damage in wood-frame houses is inadequate tie-down of roofs. Other serious problems include inadequate tie-down of wall frames to foundation, weak joints, lack of racking resistance, and sloppy construction practice. Simple and inexpensive means exist to correct most of these problems. Research needs include the development of better methodologies to analyze the response of wood-frame houses, especially the response of joints, full-scale testing of wood-frame houses, testing of dissected joints, improved understanding of wind loads, and post-disaster investigations focused on individual houses.

The results of a program of racking tests of wall panels can be incorporated into the analysis of high-rise structures influenced by nonstructural partitions. Stiffness and energy-absorbing characteristics were obtained from racking tests of wall panels simulating lateral interstory displacements in high-rise buildings. These characteristics were combined with structural frame periods and damping to estimate overall building periods and damping. Illustrative examples are presented. The research program was part of the structural response research program being conducted for the U.S. Energy Research and Development Administration, Nevada Operations Office by URS/John A. Blume & Associates, Engineers.

Three major field test programs conducted to determine response of structures and structure elements to sonic booms indicate that sonic booms with nominal peak overpressures of 2 psf to 3 psf should not produce damage in properly designed and constructed houses. However, damage has occurred in other structures from sonic booms. Response can be predicted adequately if the characteristics of the boom and structure elements are known, and a boom pressure wave model can be used to simplify prediction methods. Predicted plate and racking deformations of structure elements are compared to measured values. Experience to date indicates that a great percentage of damage incidents involves glass damage. Implications regarding possible future damage from supersonic flights are drawn from structural response data and damage investigation results.

From 1940 to 1965, use of softwood plywood increased from 1 billion to 13 billion sq ft, the increase being mostly in building construction. Major construction uses are sheathing and subflooring. Contributing factors were low in-place costs ($0.10 per sq ft for roof sheathing) through labor savings plus acceptance of plywood as an engineering material. An important engineering property of plywood is its ability to act as a shear diaphragm in bracing a building against lateral wind or seismic loads. This was first recognized through wall racking tests, and later extended to horizontal diaphragms by the development of tested design methods. These design methods are also used in analysis of folded plate construction. Interesting uses for plywood have been developed as gusset plates to splice lumber into moment-resisting joints. Applications include trussed rafters and rigid gable frames. The connections are commonly made with nails, or glue or both. More recent developments include the acceptance, based on extensive testing, of plywood for one-hour fire-rated floor and wall assemblies, for heavy-timber roof construction, and for fire-retardant treated roof assemblies.