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Hanging sleepers, which result from the differential settlement of the ballast layer, are a prevalent issue that leads to the rapid degradation of track components that include the ballast, sleeper, fastener, and rail. A novel type of sleeper, the wedge-shaped self-leveling sleeper (WSS), was proposed as a solution to the hanging sleeper problem. The WSS leverages the train's dynamic loading and the gravity of the ballast to naturally allow the ballast particles to fill the gap between the ballast and the sleeper. This paper focuses on the dynamic performance of the WSS from different aspects, which include wedge angles (30°, 45°, and 60°), sleeper materials (concrete and plastic), and the number of WSS to replace regular sleepers in the transition zone. A series of numerical modeling [which coupled multibody simulation (MBS) and discrete-element methods (DEM)] were conducted to design, optimize, and test the WSS. The results reveal that a concrete WSS is well-suited to address the problem of hanging sleepers in transition zones. The WSS with a 45° angle demonstrated superior performance compared with other types of WSS. Importantly, the WSS could reduce vibrations in the vehicle and track, even when dealing with hanging sleepers. Due to the self-leveling function, the WSS shows significant promise for applications in transition zones, which could reduce the frequent need for track geometry maintenance. [ABSTRACT FROM AUTHOR]

This paper investigated the potential applicability of the specification equation for the shear pull-out strength of a power-actuated fastener (PAF) connection to nail connections between steel sheets thinner than 2.9 mm. The tested G300, G450, and G550 specimens had thicknesses ranging from 0.6 to 2.4 mm, connected with 2.5- or 3.6-mm helically knurled nails. The pull-out strength is a function not only of the thickness of the member not in contact with the fastener head, but also of the other member's thickness. The member thicknesses have greater influence than the nail diameter on the pull-out strength, contrary to the design equation. Based on the test results of 93 shear nailed connections failing in pull-out, the paper proposes a design equation that is applicable to connections using helically knurled nails of steel sheets thinner than 2.9 mm. A group effect factor of 0.75 is suggested for serial nail connections based on the test results of 19 multiple nail connections. A resistance factor of 0.55 is recommended for use with the proposed equation for determining the pull-out strength of shear nailed connections in thin steel sheets. An additional finding is that the current design equation for the bearing and tilting strength of a PAF connection is applicable to connections in which the member not in contact with the fastener head is much thinner than the specification minimum of 3.2 mm, and in which the fastener diameter is smaller than the specification minimum of 3.7 mm. [ABSTRACT FROM AUTHOR]

Light gauge metal decking is commonly used in the building and bridge industries for concrete formwork. In addition to supporting the wet concrete, the metal forms also improve the lateral-torsional buckling capacity of the beams or girders they are fastened to since they behave as a shear diaphragm and restrain the warping deformation of the top flange. The design requirements for shear diaphragm bracing are not well established. This is the second part of a two-part paper. The first part of the paper focused on the general stability bracing behavior for shear diaphragms connected to the top flanges of adjacent beams or girders. This part of the paper outlines the design requirements for shear diaphragm bracing and focuses on both the stiffness and strength requirements for beam stability. Design expressions are presented for the stiffness and strength requirements as well as a model that can be used to estimate the forces in the fasteners that connect the diaphragms to the top flanges of the beams. An example is presented at the end of the paper demonstrating the use of the design expressions. [ABSTRACT FROM AUTHOR]

Fastening systems play a significant role in railroad track dynamics. In this paper, three approaches are investigated for rail fastenings modeling using FEM: (1) spring–damper pairs covering the areas representing the fastening connections; (2) a solid-load approach that explicitly models the solid baseplates and includes toe loads by applying external loads; and (3) a solid-spring approach that takes into account the coupling of rail with the ties by using prestressed springs. Experimental tests were carried out to evaluate the performance of the FEM models. The mode shapes obtained from the FEM models and the experiments were used for the evaluation. A measurement quantifying the similarity of the mode shapes was proposed, which considers both shape similarity and distance similarity. The results showed that the rail foot's mode shapes obtained from the model using the spring–damper approach demonstrated the most similarity with the ones obtained from the experiments. [ABSTRACT FROM AUTHOR]

This paper reports on the behavior of simply supported (I-shaped cross section) steel beams prestressed by tendons. It is well known that this typology of beams has successfully been used mainly in the past. Prestressed steel beams are lighter than traditional ones that have the same length and vertical load capacity; this aspect could make them economically advantageous and a viable solution in many practical situations. This paper analyzes prestressed steel beams having a medium span ranging from 35 to 45 m and which are to be used as roof structural elements. This study focuses on two parameters that are considered two of the fundamental items for the design: the number of deviators and the value of the prestressing force. This study has been carried out with nonlinear finite-element analyses that take into account both mechanical and geometrical nonlinearities. In particular, the behavior of these beams has been investigated up to failure during tensioning and during loading (after tensioning). The effect on the structural response of bracing, which can be only at the top flange of the beams or at the top and bottom flanges of the beams, also has been considered. [ABSTRACT FROM AUTHOR]

Wind dynamics on a mechanically attached single-ply roofing assembly can lift the membrane and cause fluttering, introducing stresses at the attachment locations. To identify a component in a system that has the weakest resistance against wind uplift forces, a dynamic evaluation method is beneficial. Over the past 10 years, a number of mechanically attached systems were constructed and exposed to simulated dynamic wind uplift forces using the Dynamic Roofing Facility at the National Research Council of Canada. This paper presents data from this ongoing investigation that will help system designers to maximize wind uplift ratings by choosing the appropriate roof components at the early design stage or by replacing/adding components during reroofing to improve uplift resistance. By diagnosing roof system failures, one can identify the weakest link and select design alternatives that can improve the wind resistance. Through a case study, this paper concludes with a procedure for system optimization. [ABSTRACT FROM AUTHOR]

One of the most critical connections in wood frame construction is that of the roof rafter and the top plate of the wall. This type of connection typically uses mechanical fasteners, such as metal straps or clips fastened with nails. Manufacturers base the allowable capacity of connections with one fastener on results of tests performed on such connections. However, it is assumed in current design practice that the capacity of a connection with two mechanical fasteners is twice the capacity of a connection with a single fastener. Implicit in this practice is the assumption that the connection's capacity is proportional to the number of fasteners per connection joint. This approach, based as it is on testing a single fastener per joint, disregards the fact that the failure modes of a connection joint may depend on the number of fasteners per joint. This paper presents results of tests that establish this fact. The results, based on testing with three types of wood (spruce pine fir, southern yellow pine, and douglas fir), are used to modify the current design approach and propose a realistic relationship between the capacity of the connection joint and the number of fasteners in the joint. The results show that current design practices may overestimate the capacity of these joints and can therefore be the cause of roof-to-wall connection failures in extreme wind events. The research reported herein is limited to the case of unidirectional loading. Future research is planned on the case of multidirectional loading. [ABSTRACT FROM AUTHOR]

This paper presents a review of the design provisions for screw-fastened cold-formed steel connections in the United States, including criteria for testing and evaluating the strength of screw fasteners. In addition, the paper examines the relationship between the connected elements/components computed connection strength and the strength of the connector (screws). Fastener strength test data from three independent manufacturers is presented and it is shown that as the thickness or yield strength of the connected elements/components is increased, the ratio of the fastener strength to the bearing/tilting strength decreases to values less than one-half in some cases. Analysis of the test data showed that even when the 2001 North American Specification (NASPEC) for the Design of Cold-Formed Steel Structural Members statistical requirements for distribution of the test data are met, the computed safety and resistance factors can exceed the recommended limits in Section E4 of the 2001 NASPEC. On this basis, it is recommended that the current language in the 2001 NASPEC be revised to specify, if necessary, limits on manufacturer computed safety and resistance factors. Finally, it is recommended that fastener tilt during screw shear strength tests be eliminated to facilitate an accurate evaluation of the shear strength of a fastener. [ABSTRACT FROM AUTHOR]

The article comments on the paper “Effective Flange Width Definition for Steel— Composite Bridge Girder” by Methee Chiewanichakorn and Amjad J. Aref, Stuart S. Chen and II-Sang Ahn. A prominent role is played by the degree of interaction between steel and concrete in the theoretical determination of effective widths. The authors express dissatisfaction with the computational results obtained for bridge girders.

Cross-laminated timber (CLT) panels, when used as shear walls or diaphragms, are commonly connected with multiple (n) doweltype fasteners in a row. For such connections, it is frequently observed that the load-carrying capacity of multiple fasteners is less than the sum of the individual fastener capacities, a phenomenon referred to as the group effect. The research presented in this paper investigated the group effect in self-tapping screw (STS) shear connections between CLT panels. Different joint types (surface splines with STS in shear, and half-lap and butt joints with STS in either shear or withdrawal) were evaluated in a total of 175 quasi-static monotonic and reversed cyclic tests, with the number of STS in one row varied between 2 and 32. The results showed that the group effect for the joint capacity (strength) can be expressed as neff = 0.9n for all joints under static loading, where neff is the effective number of fasteners. In case of cyclic loading, a more pronounced group effect was observed that can be expressed as neff = n0.9. These reductions are significantly less conservative than the current Canadian design provisions for lag screws. For the reduction in stiffness and ductility, neff = n0.8 and neff = n0.9 can be used for all joints under static and cyclic loading, respectively. Finally, the capacity, ductility, and stiffness for joints under cyclic loading where the STS acted in withdrawal were on average 10% lower compared with the static values. [ABSTRACT FROM AUTHOR]

Built-up beams and columns comprised of dimension lumber fastened with nails, bolts or lag screws, are common in construction. Current design practice for stability checks is to use the lower-tail modulus of elasticity (Emin) value tabulated for dimension lumber; however, this ignores the averaging effect on Emin that occurs when the mechanically fastened laminations are constrained to deflect in unison. In this paper, we propose a method for checking stability of these assemblies that is based on established statistical theory. A factor (Cs) is proposed to adjust Emin value used in column and beam stability calculations to account for the reduced variability of E when the laminations are constrained to deflect together. Using Cs to account for the reduction of Emin variability produces more efficient designs with respect to stability. Two examples are provided and each results in larger design capacities compared to current design methods for built-up beams and columns. [ABSTRACT FROM AUTHOR]

Screws are the only fasteners approved in the 2006 International Building Code for attaching wood structural sheathing to cold-formed steel framing for shear walls. Steel pins also provide an effective and efficient means of attaching wood structural sheathing. However, the proprietary nature of steel pins, coupled with the need to demonstrate equivalent performance to code-approved elements, necessarily requires manufacturers to consider some form of reversed cyclic testing to justify shear wall values for seismic design. This paper presents the results of an experimental program that evaluated the performance of wood panel sheathed cold-formed steel frame shear walls in which the wood panels were attached using one type of pneumatically driven steel pins. For the assemblies tested and the specific pin type used, several useful performance characteristics and characteristic values were identified to facilitate overall performance comparisons with other types of shear wall configurations. It is shown that the average ratio of the peak strength to the derived allowable strength exceeded 2.8, the average maximum usable displacement exceeded 3.5% of the wall height, the average ratio of the peak strength displacement to the allowable strength displacement exceeded 9.3, and the average maximum usable displacement was 35% greater than the peak strength displacement. [ABSTRACT FROM AUTHOR]

Capacities of wood connections with laterally loaded dowel fasteners by plastic analysis can be predicted using the European yield models (EYM) equation. The underlying concept is that failure occurs due to crushing of wood beneath fasteners and / or formation of plastic hinges in fasteners with a rigid-plastic representation of the materials involved. EYM prediction is now “the” way within design codes to calculate the maximum attainable capacity per fastener. Subsequent adjustments discount those predictions through factors which account for unequal sharing of force between fasteners and premature connection failure by fracturing. In North America the EYM is the basis for lateral load capacities of connections made with bolts, drift-pins, screws, nails, and timber rivets. This paper addresses the capability of the EYM for predicting load carrying capacities of solid wood (sawn softwood lumber) and laminated strand lumber (LSL) connections employing tight-fitting steel tube fasteners with external diameters up to 12.7 mm. EYM prediction is compared with experimental test results for arrangements with one or four fasteners loaded in double shear. Accuracy of predictions depends on factors such as connection geometry and the type of wood member involved. Prediction is always accurate if a connection has only one fastener, or if joined members are made from LSL. If members are made from sawn softwood lumber premature brittle splitting type failure modes occur for multiple fastener situations, with impairment of capacity inversely proportional to the fastener outside diameter. Suggestions are made here regarding the nature of codified design rules for steel tube fastener connections, with the intent that such provisions be enacted within North America. [ABSTRACT FROM AUTHOR]

This paper presents the results of two 610 mm×2,438 mm and six 1,219 mm×2,438 mm reverse cyclically tested cold-formed steel frame shear walls where the sheathing was attached with a structural adhesive and pneumatically driven steel pins. The sheathing materials included 0.69-mm sheet steel and 11.1-mm OSB rated sheathing. Limited in scope, the goal of the study was to explore potential structural and economical benefits that may be available when the primary mechanism of load transfer between the framing and the structural sheathing is a continuous adhesive bond. Mechanical fasteners (steel pins) are expected to provide a means of keeping the sheathing tight against the framing as the adhesive cures and a minimum level of postpeak load resistance. The results showed that the peak wall resistances significantly exceeded the nominal values in the current building codes and standards for similarly sheathed walls without adhesives. However, compared to shear walls without adhesives, the tested walls exhibited more linear responses with higher stiffness and generally larger degradation in strength after the peak resistance. Based on these limited test results and a relatively simple interpretation of the test data, the use of structural adhesives with mechanical fasteners may be beneficial in some applications and warrants a more comprehensive study. [ABSTRACT FROM AUTHOR]

Timber rivets are fasteners for glued-laminated timber construction that were first sanctioned for use in the United Stated by adoption in the 1997 National Design Specification for Wood Construction (NDS). Rivet connections can exhibit a brittle failure when a volume of wood bounded by the perimeter of the rivets pulls out from the timber, or a ductile failure due to a combination of fastener yielding and localized wood crushing. The NDS approach to the former failure mode is so complex that closed form solution is not possible and designers must refer to limited tabular data, and the NDS approach to the latter failure mode is inconsistent with the approach used for other dowel fasteners. This paper describes an improved analysis based on the capacity of wood failure planes and the well-established dowel fastener yield model. Results of tests of large rivet connections highlighting the crossover from ductile to brittle failure modes verify the analysis. In addition, these results provide the first data for timber rivets in Southern Pine glued-laminated timber. [ABSTRACT FROM AUTHOR]

Lateral reinforcements can enhance serviceability of wood-based floor systems. However, because of a lack of proper analysis models, the benefit from installing these components has not been fully recognized in floor design. In this paper, a finite-element model for predicting static and dynamic characteristics of wood-based floor structures with various types of lateral reinforcements is presented. In this model, shell elements were employed to represent floor decking and ceiling, and beam elements were utilized to model joists and structural members in the lateral reinforcements. Special connector elements were developed to model the fasteners connecting various structural components. Other structural features, such as gaps perpendicular to joists in the subfloor, additional objects on floor and flexible supports, were also considered. A computer model incorporating these new features has been developed. For verification and validation purposes, the predicted deflections and natural frequencies for a number of full-size floors were compared with experimental values. Good agreement has been observed. These numerical test results indicated that the present finite-element model is reliable and unique, particularly in modeling floors with lateral reinforcements. [ABSTRACT FROM AUTHOR]

An experimental program was undertaken to investigate the inelastic seismic response of metal deck roofing systems. The load carrying capacity of roof diaphragms for low-rise steel buildings, subjected to lateral loads from wind and/or earthquakes, is directly dependent on the performance of the connections. This paper provides information on the cyclic response, including load versus displacement hysteresis and energy absorption capacity of 45 screwed, button punched, and welded side lap connections, for different steel deck types. All of the connections were able to sustain some degree of inelastic response. Typically, welded side lap connections are able to carry the largest shear forces and absorb the greatest amount of energy. [ABSTRACT FROM AUTHOR]

An experimental program was undertaken to investigate the inelastic seismic response of metal deck roofing systems. The load carrying capacity of roof diaphragms for low-rise steel buildings, subjected to lateral loads from wind and/or earthquakes, is directly dependent on the performance of the connections. This paper provides information on the inelastic cyclic response, including load versus displacement hysteresis and energy absorption capacity of 144 deck-to-frame screwed, powder-actuated fastener, and welded connection tests for different steel deck and structure thickness. Powder-actuated fastener connections were able to provide the highest energy dissipation results, followed closely by screwed connections. In many cases, the welded connections exhibited significant ultimate capacities, but failed at small displacements, resulting in low energy dissipation values. However, when welds with washers were used, the ductility and energy absorption ability of the connection were substantially improved. [ABSTRACT FROM AUTHOR]

The research presented in this paper examines the shear resistance performance of self-tapping screws (STS) in three-ply crosslaminated timber (CLT) panels. Specifically, the feasibility of using innovative STS assemblies with double inclination of fasteners was investigated for the shear connection of CLT panels. The specimens (1.5 × 1.5 m) were subjected to quasi-static and reversed-cyclic loading. The tests were set up to approximate pure shear loading, with three-panel CLT assemblies connected with STS. The resulting loaddisplacement and hysteretic curves were used to determine an equivalent energy elastic-plastic curve to estimate assembly capacity, yield load, yield displacement, ductility ratio, stiffness, and damping. Excellent structural performance in terms of capacity and stiffness was obtained while still providing the required ductility for the system to be used in seismic applications. The average static and cyclic yield loads were 6.0 kN=screw and 5.9 kN=screw, respectively. Average static and cyclic and ductility ratios were 7.7 and 4.1, respectively, allowing the connection to be classified as highly ductile under quasi-static loading and moderately ductile under reversed cyclic loading. The data obtained allow engineers to specify an innovative connection assembly with double inclination of fasteners for lateral load-resisting systems of CLT structures. [ABSTRACT FROM AUTHOR]

The roof-to-wall connection in a house is designed to transfer the uplift and lateral loads during strong winds by providing a continuous load path from the roof to the foundation. The uplift capacity and failure mode of the connection depends on the number and type of fasteners (nails), timber species, type of framing anchor, and constructions defects. This paper presents experimental results that were used to assess the uplift capacity variation of typical roof-to-wall connections. Based on tests with two types of connections (triple grip and truss grip) assembled with two types of timber (radiata pine and spruce pine), nails (hand and gun), and framing anchors (triple grip and universal triple grip), the results show that the variation in timber species, nail, and triple grip type changes the strength and the failure modes of the connection. The strength of the connection was reduced by about 24% when the timber species was changed from radiata pine to spruce pine and the hand nail to gun nail on the triple grip connection. This study also showed that construction defects in roof-to-wall connections influence the design uplift capacity. If there are two missing nails in the hand-nailed triple grip connection (i.e., one nail on the truss and another one on the top plate) the design uplift capacity reduces by about 40% of the ideal hand-nailed triple grip connection. This study identified the critical nails and their locations required to mitigate failure of the roof-to-wall triple grip connection subject to wind loading. [ABSTRACT FROM AUTHOR]

This paper assesses the performance of a newly developed blind bolt, intended for use in constructing bolted moment-resisting connections to concrete-filled tubular steel profiles. A total of ten connection tests are reported, with each configuration having been subjected to a predominantly tensile force in a representation of the tension region of a typical moment connection. The test variables included type of fastener, addition of concrete to the tube, strength of the concrete, spacing among bolts, and bolt class. On the basis of deformability response, the benefits of filling the tubular member with concrete are highlighted. The favorable performance that results from using a relatively, high-grade concrete infill is also highlighted. The addition of a concrete infill to the tube stiffens and strengthens the otherwise relatively flexible tube walls, enhancing overall connection behavior in terms of stiffness, strength, and ductility. The performance of connections to concrete-filled tubular steel profiles using blind bolts with headed anchors is shown to be suitable for moment-resisting construction. [ABSTRACT FROM AUTHOR]

Despite extensive research on externally bonded fiber-reinforced polymer (EB-FRP) for rehabilitation of concrete structures in the past two decades, the industry has been slow to embrace the technology owing to some difficult problems that are yet to be resolved fully. Among these, premature debonding is one of the critical problems. Since the tensile strength of concrete is inherently low and unreliable (in the long term), EB-FRP by surface adhesion might not be the final solution; augmentation of the interfacial bond by mechanical fastening may be unavoidable. To this end, the first author proposed a bond augmentation system, hybrid-bonded FRP (HB-FRP), where a special type of mechanical fasteners are used to enhance the interfacial bond. Although the HB-FRP system has been experimentally shown to increase bond strength several fold, effectively overcoming the debonding problem, there has been no systematic theoretical study of the system. In this paper, HB-FRP joints are characterized through experimental testing and analytical modeling, leading to a theory for design and construction of the HB-FRP system. [ABSTRACT FROM AUTHOR]

The effectiveness of using an externally bonded carbon-fiber-reinforced polymer (EB-CFRP) system with mechanical end anchorage to retrofit severely shear-damaged reinforced concrete (RC) beams is examined in this paper. A total of 14 tests were performed on eight RC beams with a -shaped section and low compressive strength. To represent a severe shear-damage condition, five beams were tested to failure, retrofitted, then retested to failure for a second time. Test parameters included the number of EB-CFRP layers and type of end anchorage system. The results demonstrated that retrofitting of severely shear-damaged RC -beams with EB-CFRP composites and proper mechanical end anchorage can fully restore the original shear capacity of the beams. The use of a sandwich composite panel in combination with a threaded anchor rod inserted through the entire web width (thru-bolt) as an end anchorage system was more effective than using the panel with side powder-actuated fasteners. Increasing the number of EB-CFRP layers did not result in additional gain in shear capacity. The accuracy and validity of four different international guidelines/standards were examined by comparing their predictions with the experimental results. [ABSTRACT FROM AUTHOR]

A roofing system consists of a waterproof membrane, attachments, cover board (if present), insulation, and vapor or air barrier [retarder (if present)]. A roof assembly is a roof system that includes the structural deck. Wind-uplift ratings are reported by subjecting roof assembly mockups to wind dynamics. Most of the time, technical reports clearly document the properties of membranes and attachment systems (fasteners, plates, and seams) and only briefly mention the strength of the fastener-deck interface. Research by a North American roofing consortium established at the National Research Council of Canada, the Special Interest Group for Dynamic Evaluation of Roofing Systems, has demonstrated the significant influence of fastener-deck parameters on the wind-uplift resistance of mechanically attached roofs. This paper presents data and information from this ongoing investigation. Seven different roofing assemblies using three widely used roofing membranes with different fastener-deck combinations were constructed and tested under dynamic wind conditions. Assembly responses were measured based on two design factors: pressure and force. The present study identified three parameters characterizing the fastener-deck interface strength: deck grade, deck gauge, and fastener type. The study found that assemblies tested with steel decks having thicker gauge or higher yield strength tend to have greater fastener-deck strength and therefore they sustain higher wind-uplift pressures compared to assemblies with thinner gauge or lower yield-strength decks. Similarly, assemblies where the membrane attachment is made with fasteners with larger shank diameters sustained higher wind-uplift pressures compared to assemblies installed with smaller shank diameter fasteners. This study also found that fastener pullout resistance could be used as a verification factor for estimating assembly wind resistance. [ABSTRACT FROM AUTHOR]

Rehabilitation of existing structures with carbon fiber reinforced polymers (CFRP) has been growing in popularity because they offer resistance to corrosion and a high stiffness-to-weight ratio. This paper presents the flexural strengthening of seven reinforced concrete (RC) beams with two FRP systems. Two beams were maintained as unstrengthened control samples. Three of the RC beams were strengthened with CFRP fabrics, whereas the remaining two were strengthened using FRP precured laminates. Glass fiber anchor spikes were applied in one of the CFRP fabric strengthened beams. One of the FRP precured laminate strengthened beams was bonded with epoxy adhesive and the other one was attached by using mechanical fasteners. Five of the beams were tested under fatigue loading for two million cycles. All of the beams survived fatigue testing. The results showed that use of anchor spikes in fabric strengthening increase ultimate strength, and mechanical fasteners can be an alternative to epoxy bonded precured laminate systems. [ABSTRACT FROM AUTHOR]

In recent years important research activity has been undertaken in order to determine the earthquake performance of light gauge steel house structures. Usually, studies approach the problem of earthquake performance through experiments on wall panels conducted either under monotonic or cyclic loads. All studies underline the overwhelming importance that the behavior of the connections has in determining the overall performance of wall panels. However, although these studies focused on the global behavior of the panel, they did not try to characterize the behavior of and provide design criteria for connections, as components of the structural system, and to provide relevant design criteria. The present paper attempts to fill this gap. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate the behavior, and provide recommendations on, the design of open cross-section thin-walled cold-formed steel members that employ complex stiffeners. Complex stiffeners are formed when the free edge of an open section is folded multiple times, as opposed to simple stiffeners which employ a single fold (a lip). Simple stiffeners become ineffective when long lips are required to stabilize the flange, as the lip itself initiates the instability. In the elastic buckling regime, complex stiffeners are shown to hold a distinct advantage in local buckling over simple stiffeners. Closed-formed solutions for both local and distortional buckling of members with complex stiffeners can provide conservative and reliable solutions, but remain cumbersome and somewhat limited in applicability, therefore numerical solutions are preferred. Nonlinear finite element analysis is used to examine the post-buckling and ultimate strength regime. Complex stiffeners are shown to provide improved ultimate strength performance over simple stiffeners, but with a slight increase in imperfection sensitivity. Further, for an equivalent amount of material, complex stiffeners only provide advantages for specific stiffener lengths, though global optimal designs (maximum strength while minimizing material) still favor complex stiffeners over simple stiffeners in the investigated examples. The cold-formed steel design specification in current use is shown to be a poor predictor for the ultimate strength of bending members with complex stiffeners. However, the direct strength method, recently adopted as an alternative design method in the North American Specification for cold-formed steel members is shown to be a reliable predictor of ultimate strength. The direct strength method is recommended for design and optimization of members with complex stiffeners. [ABSTRACT FROM AUTHOR]

This paper experimentally investigates the cyclic inelastic performance of concentrically braced frames with and without cold formed steel stud (CFSS) infills designed to laterally restrain braces and delay their buckling. Specimens have either diagonal tube or solid bar braces with and without CFSS and U brackets providing out-of-plane and in-plane buckling restraint. Behavioral characteristics of the specimens are quantified with an emphasis on hysteretic energy dissipation. Experimental results show that, at the same ductility levels, the cumulative energy dissipation of braced frames can be significantly increased when CFSS members are used to laterally restrain the braces against buckling. However, when tubular cross sections are used for braces, local buckling led to a reduced fracture life compared to the case without CFSS members. CFSS members appear to be relatively more effective when solid bar braces having large slenderness (tension-only braces) are used, since the difference between dissipated energies obtained with and without studs is substantial. [ABSTRACT FROM AUTHOR]

The cold expansion technique is often used to introduce beneficial compressive stress at fastener holes, and can be used for remedial work where cracks already exist. In this paper, results are presented showing the effect of preexisting cracks on the residual stress field produced by cold expanding a fastener hole, and on subsequent fatigue crack growth. The effect on the residual stresses was experimentally evaluated in two ways: indirectly, in terms of retained expansion and directly, by measurement of the stresses using the X-ray and neutron diffraction techniques. The retained expansion ratio showed that cold expansion is more sensitive to the existence of precracks at lower levels of applied interference, and the inlet and outlet faces have different behavior. The stress measurements showed that preexisting cracks reduce the compressive residual stresses more on the mandrel inlet face than on the outlet face and in the middle of the specimen. The effect on fatigue crack growth rates was modeled using a linear-elastic fracture mechanics approach. It was found that cold expansion of a hole containing a preexisting crack longer than 1 mm introduces little benefit for subsequent fatigue crack growth behavior. [ABSTRACT FROM AUTHOR]

Vibration energy harvesters (VEHs) can utilize the vibration of the track to generate electricity and provide power for other devices within the harvester. To analyze whether energy harvesters arranged in an array harm track operation, we conducted a simulation analysis. Based on the vehicle–track coupling model, the influence of inductive electromotive force on track vibration was analyzed and compared with the simulation results obtained from the classical vehicle–track coupling model. The rail vibration displacement was reduced from 0.5 to 0.0692 mm, and the maximum vibration acceleration of the rail was reduced from 2.3759 to 0.4534 m/s2. The energy harvester can attenuate the vibration of the track significantly, and has a minor influence on the regular operation of the track. The vibration of a railway can be transformed to electric energy and used to power sensors at the railway side and train sides, such as velocity sensors, temperature sensors, accelerometers, wireless transmission modules, and other wireless sensor network (WSN) devices. It also can be used as backup power for the auxiliary load on the railway side, such as traffic lights and speed measuring radar. A vibration energy harvester installed at the fastener has a simple structure and can provide enough power for WSN sensors. It provides a good energy supply for line-side monitors and auxiliary devices. Because safety is the most critical issue for track devices, the effect of the installation of VEHs on the operation of the track should be analyzed. The vibration of a track with a fastener VEH is less than that without a VEH, which will reduce the impact of vibration on the environment and ensure the safe running of trains. This method also applies to the safety analysis of other track energy harvesting devices. [ABSTRACT FROM AUTHOR]

This study proposes an innovative type of simple connection utilizing power-actuated fasteners to join a cold-formed steel channel to a rectangular hollow section column via a web-side plate or a T-section. An experimental program composed of 26 specimens was carried out to investigate the behavior of the connections under the combination of shear and rotation. The experimental results are discussed in two limit states including bearing and pull-out by shear. An analytical model is proposed to predict the shear strength of the connections based on the provided information of vectorial force at a fastener, displacement, and rotation at the connections. The proposed model yields a conservative prediction for the tested connections with a mean test-to-prediction ratio of 1.05 and the coefficient of variation of 6% or 9%, depending on the limit state. A design example is provided to illustrate the implementation of the proposed model in practice. [ABSTRACT FROM AUTHOR]

Wood shear wall performance is affected by the materials used for construction including the sheathing fasteners. The model building codes permit different fasteners for sheathing attachment in terms of diameter and length. In general, the nail head geometry is designated in the fastener schedule footnotes by terminology, such as “common,” “sinker,” “casing,” or “finish.” Power-driven nails are collated and the heads are formed to facilitate collation, so the heads may be flat and round with full round geometries or the flat round head may be clipped or notched. The European Yield Limit equations of the National Design Specification assume a smooth round dowel with no head, which leaves the engineering community without a rational basis for specification of head geometry requirements for shear wall construction. To address this issue, three types of nails distinguished by different head geometries were used in shear wall tests to investigate the potential effects of sheathing nail head geometry on shear wall performance. The head geometries were full-round heads (FRH), clipped heads (CLP), and casing heads (CSE), but the nails were otherwise the same. The head-area ratios for these fasteners were 0.83, 0.74, and 0.55 for the FRH, CLP, and CSE nails, respectively. These were used to fabricate shear walls sheathed one side with plywood (height/length ratio=2.0) that were tested using the sequential phase displacement method of fully-reversed cyclic testing. Shear walls with the FRH nails and the CLP nails had the same nominal strength while the CSE nails had a nominal strength that was 78% of the nominal strength of the shear walls with FRH nails. The elastic stiffness’ of shear walls were not statistically different when the source of variation was sheathing-nail head geometry. The test performance was compared to nominal strength calculated from published design values. The walls with FRH and CLP exceeded the expected nominal shear while shear walls with CSE nails underperformed the design value. Nails with FRH and CLP heads cannot be distinguished in performance and are interchangeable for design and construction. Even though CSE nails produce shear walls with the same elastic stiffness, they cause shear capacity to be less than that of walls built with FRH and CLP nails and about 8% less than allowable shear design. [ABSTRACT FROM AUTHOR]

The goal of this research was to develop a rational method of designing dowel-type connections for hollow wood-plastic composite sections. Models consisting of six controlling yield modes were developed to predict the hollow section connection behavior. The models were validated with double-shear unconstrained bolted connection tests using two wood-plastic composite formulations, three wall thicknesses, and three dowel diameters. The hollow section yield model performed well with an average difference between the theoretical maximum load and tested maximum load of 5.7%. The maximum connection loads were compared to the theoretical load calculated by entering the dowel bearing strength based on maximum load and a bending yield strength based on the stress in the dowel at the displacement of maximum connection load. Proposed design equations for WPC hollow section connection maximum loads were based on maximum dowel bearing strength and the codified 5% diameter offset dowel bending yield strength. [ABSTRACT FROM AUTHOR]

Presents information on a study which focused on the results of a test program that attempts to quantify rate-of-load and short-term duration-of-load (DOL) effects for wood fasteners. Damage models; Other types of DOL models; Test programs for wood fasteners; Conclusions.

A total of 105 cross-tension tests were conducted to investigate the strength and behavior of power-actuated fastener (PAF) connections under quasi-static monotonic tensile loading. Three types of PAF were used to join sheets with thicknesses ranging from 0.75 to 4.00 mm to thicker plates with thicknesses ranging from 3.00 to 20.0 mm. All of the steel materials were high-strength cold-formed steel, except for the 20-mm-thick steel, which was hot-rolled steel. The studied parameters were the type and diameter of the fasteners and the thicknesses of the top and base steel materials. The majority of the specimens failed by pull-out failure, although some thinner sheets failed by transverse fracture of the top sheet. The test results reveal that PAF connections exhibit a high tensile capacity as long as a sufficient embedment length is provided. A model is proposed to evaluate the pull-out strength of PAF connections based on the base material strength and the average embedded diameter and embedment length of the fastener. The proposed model produces a mean of test-to-prediction ratio equal to 1.02 with a coefficient of variation ranging from 0.12 to 0.16. Reliability analyses were carried out and resulted in a resistance factor of 0.56–0.69 for Load and Resistance Factor Design. [ABSTRACT FROM AUTHOR]

The installation of guardrails around a roof perimeter is an efficient way to protect construction workers against falls from heights, provided the guardrails are strong enough to arrest a fall. A guardrail's strength relies heavily on its fastening to the roof parapets, and an improper fastening could lead to unsafe guardrails. This article investigates the in situ strength of temporary steel guardrails installed on the flat roof parapets of two existing buildings, respectively built in 2008 and 2013. Thirty-six strength tests were conducted on three different guardrails and four different parapets, considering different methods of fastening the vertical posts to the parapets and varying the fastening hardware. The results show that some guardrails are not easily installed on smaller roof parapets, which could lead to improper installation on some work sites. Fastening using only one plane of the parapet often resulted in guardrails failing before reaching the regulatory strength requirement. Fastening using two planes of the parapets gave satisfactory results in comparison, and that should be the preferred fastening method to guarantee workers' safety. [ABSTRACT FROM AUTHOR]

Embedment strength is an important parameter that governs the ductile load-carrying capacity of timber joints with dowel-type fasteners. This property is dependent upon several factors, especially on the surface conditions of fasteners. In current design standards, however, the embedment strength depends only on the timber density and the diameter of fastener, though the surface conditions of dowels and fully threaded bolts are different. In this study, embedment tests for dowels, fully threaded bolts and glued-in rods in the direction parallel to the grain were carried out. Comparisons with the existing design equations in Eurocode 5 Design of Timber Structures (EC5) and American National Design Specification (NDS) were performed. It is found that the embedment strength in timber for dowels can be accurately predicted by EC5 and NDS, while the embedment strength for fully threaded bolts is underestimated. In addition, the embedment strength for glued-in rods is not addressed in the current design standards. Based on the presented experimental results, new empirical expressions for the embedment strength parallel to the grain in timber for fully threaded bolts and glued-in rods were proposed. [ABSTRACT FROM AUTHOR]

In existing wood strength prediction models for parallel to grain failure in timber connections using dowel-type fasteners, different methods consider the minimum, maximum, or summation of the tensile and shear capacities of the failed wood block planes. It is postulated that these methods are not appropriate since the stiffness of the adjacent wood loading the tensile and shear planes differs, and this leads to uneven load distribution among the resisting planes. A closed-form analytical method to determine the load-carrying capacity of wood under parallel-to-grain loading in small-dowel-type connections in timber products is thus proposed. For the wood strength, the stiffness of the adjacent loading volumes and strength of the failure planes subjected to nonuniform shear and tension stresses are considered. The effective wood thickness for the brittle failure mode is derived and related to the elastic deformation of the fastener. A mixed failure mode is also defined (a mixture of brittle and ductile) and depends on the governing ductile failure mode of the fastener. To help the designer, an algorithm is presented that allows the designer to calculate the resistances associated with predictions of the different possible brittle, ductile, and mixed failure modes. The proposed stiffness-based model has already been verified in brittle and mixed failure modes of timber rivet connections. In the research reported in this paper, an extended application is proposed for other small-dowel-type fasteners such as nails and screws. Results of nailed joint tests on laminated veneer lumber (LVL) and the test data available from the literature on glulam confirm the validity of this new method, and show that it can be used as a design provision for wood load-carrying capacity prediction of small-dowel-type timber connections. [ABSTRACT FROM AUTHOR]

The objective of this work is to investigate the shear capacity of small end distance lap joints in sheet steel fastened with a single bolt. For bolted connections in shear, the current American Iron and Steel Institute (AISI) specification does not differentiate between tilting limit states, in which the fastener rotates and thin sheet curls, and nontilting limit states, such as bearing and tearing. An experimental program consisting of 36 bolted specimens with a small end distance, 18 subject to tilting and 18 not subject to tilting, were conducted to explore this phenomenon. The conducted tests were compared to available predictions in the design specifications and the literature. The comparison indicates that tilting needs to be explicitly considered in the tested condition. Recommendations are provided for design. There is a need for future work to investigate multibolt configurations with small end distance and connections with members. [ABSTRACT FROM AUTHOR]

The existing models for the prediction of the splitting failure of dowel-type connections loaded perpendicular to grain are determined generally based on crack growth of the entire member cross-section. These models can be appropriate for stocky or rigid fasteners installed through the full thickness of the wood member. However, for slender dowel-type fasteners such as timber rivets, particularly when the penetration depth of the fastener does not cover the whole member thickness, the crack formation is different. Observations from current tests in thick members show that the crack growth across the grain occurs to a depth corresponding to the effective embedment depth of the fastener and propagates along the grain until it reaches its unstable condition. The design method presented in this paper to predict the connection splitting capacity takes into account the observed two possible failure modes of wood: either partial or full width splitting. In the proposed method, the effect of geometry parameters such as connection width and length, fastener penetration depth, loaded and unloaded edge distances, end distance, and member thickness as observed by others are considered. Results of the tests undertaken with laminated veneer lumber (LVL) and glulam manufactured from New Zealand Radiata Pine (RP) and data available from literature confirm the validity of this new method and show that the proposed design approach can be used advantageously in comparison to other existing models for timber rivet connections under transverse loading. [ABSTRACT FROM AUTHOR]

The article presents the response by Methee Chiewanichakorn, Amjad J. Aref, Stuart S. Chen and Il-Sang Ahn to the comment about their article “Effective Flange Width Definition for Steel—Concrete Composite Bridge Girder.” The authors discussed several important points made by the discusser that warrant further discussion. The writers agree with the discusser on the role of an increased effective flange width in increasing the effective section properties.

The simplicity of steel gravity framing systems in their load paths and construction has led to questions regarding their structural integrity or robustness. When considering structural integrity, the problem is often framed around the concept of column-removal scenarios, in which the structure must develop alternate load paths. The sometimes prohibitive space and resource requirements for experimental evaluation of steel gravity framing systems subjected to column-removal scenarios have resulted in the development of computational approaches to the problem. Recent computational research on this topic has highlighted the importance of considering the contribution of the composite slab to system robustness. A shell-based composite layup strip approach is the current state of the art for representing the composite slab in computational models. However, this approach has not been fully validated with experimental data and contains inherent assumptions, such as continuity of the metal deck between bays, that may not reflect construction realities. This study uses the results of experimental component level tests of the composite slab to evaluate those assumptions at the material, component, and system levels of modeling. [ABSTRACT FROM AUTHOR]

Currently, there is no formula for tie and direct fixation fastener (DFF) spacing. Because the rail does not bend between the tie/DFF, it is not possible to calculate spacing by the bending stress formula. Usually, rail-stress analysis confirms a trial spacing. Such analysis may support a longer spacing that might not address issues related to load distribution, pressure on formation, torsional rigidity, noise, and vibration. Thus, tie spacing is formulated from the perspective of wheel-load distribution and load dispersion by ballast, considering the fact that ties under the Benkel beam support the vertical load. The DFF/tie spacing is related to the characteristic length of the track, and this study shows that the desired DFF/tie spacing should be less than the characteristic length. Codes and practical examples validate spacing formulated for DFFs, concrete ties, and wood ties. [ABSTRACT FROM AUTHOR]

The article presents a three-dimensional nonlinear finite-element model that was developed for the study of a top and seat angle bolted steel connection with double web angles. Unilateral contact and friction laws were used to simulate the interaction among the connected parts. Large displacements as well as the von Mises failure criterion were also considered for the steel parts and bolts. Numerical results were compared with the experimental research conducted on the same steel joint. This study finds yielding of the top angle as well as shear failure of the bolts connecting the beam bottom flange with the seat angle to be very important for the overall response of the structure. For this reason, a parametric investigation of the influence of the top angle on the behavior of the structure and the study of the prying forces developed at the top angle were conducted. [ABSTRACT FROM AUTHOR]

Exterior decks must be designed to resist all applicable load cases. Vertical (gravity) loads are well defined, but less is known about designing decks for lateral loading. The focus of this study was to better understand the ultimate strength and load paths of two common deck constructions subjected to monotonic lateral loading. A portion of a conventional light-frame wood-floor diaphragm was built, to which the decks were attached. One deck was constructed with a lateral hold-down tension connector and the other deck had no hold-down tension connector. The lateral resistance and load path of each deck were investigated by applying a monotonic force through the centroid of the deck surface. The ledger board was connected to the house rim board with lag screws. Forces in each lag screw and hold-down connecting the deck to the diaphragm were recorded. Preliminary tests revealed a weakness in the deck joist-to-deck ledger connection; this was resolved by using joist hangers that featured a perpendicular fastener attachment and manufacturer-approved screws. With this weak link reinforced, the connection between the deck ledger and the house rim board was investigated and it was found that it remained structurally intact with no observed damage up to a maximum load of approximately 31 kN for both deck constructions (with and without the tension hold-down connector). The main failure mechanism was splitting of the top edges of the joists (tension perpendicular to grain) caused by a resisting force couple created by pairs of deck board screws fastening the deck boards to the joists. In both cases and as expected, the lags screws near the end of the ledger experienced the greatest tensile forces. [ABSTRACT FROM AUTHOR]

An experimental study was carried out to investigate the shear behavior of corrugated metal ties anchoring brick veneer walls to light wood frame backing. Connection subassemblies were tested under monotonic and cyclic shear, simulating in-plane loading of veneer wall systems, and statistical analyses were conducted to identify and quantify the parameters influencing their behavior. Force-displacement curves obtained under monotonic loading can be considered an upper bound for the hysteresis loop envelopes. Fastener slippage during cyclic loading enabled by the localized damage of the surrounding wood fibers diminished the energy dissipation capacity of the connection and caused pronounced pinching in the hystereses. When corrugated ties with minimum thickness permitted by the Masonry Standards Joint Committee (MSJC) Code were considered under in-plane loading, tie design and bend eccentricity were found to be the most important factors, while tie location in the bed joint, fastener type, and fastener quantity were influential to a lesser degree. [ABSTRACT FROM AUTHOR]

In the past, gravimetric corrosion data for fasteners exposed to treated wood has been reported as a percent weight loss. Although percent weight loss is a valid measure of corrosion for comparing identical fasteners, it can distort the corrosion performance of fasteners with different geometries and densities. This report reevaluates a key report on the corrosiveness of wood treated with chromated copper arsenate (CCA) and ammoniacal copper arsenate (ACA) and converts the previous data into corrosion rates. In addition, similar experiments were run in wood treated with alkaline copper quaternary (ACQ). Comparison of the corrosion rates reveals ACQ treated wood is more corrosive than CCA treated wood for every metal. The corrosion rate of aluminum was found to be lower than both hot-dip galvanized steel and electroplated galvanized steel in ACQ, ACA, and CCA treated wood. In ACA and ACQ treated wood, the electroplated galvanized fastener had a lower corrosion rate than the hot-dip galvanized fastener. [ABSTRACT FROM AUTHOR]

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 2,440×2,440 mm walls were tested monotonically, 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. [ABSTRACT FROM AUTHOR]

Where faulting takes place due to the absence of dowel bars and inadequate subbase support in jointed concrete pavement (JCP), dowel bar retrofit (DBR) is used to improve load transfer efficiency (LTE) and to prevent further faulting of slabs at transverse joints. Even though DBR generally improves LTEs and overall performance of JCPs, not all DBR projects have been successful. Faulting reoccurred within 2 years after DBR treatment on US59 in Texas. An investigation from the cores taken in the project revealed excessive voids under a dowel bar due to poor consolidation of the grouting material. A laboratory investigation was performed to determine the most critical factors for adequate consolidation of grouting materials in DBR. Typical rapid-setting grout materials widely used in DBR were selected and full-scale specimens were made for evaluations. Four testing variables for consolidation performance were investigated: time of placement after mixing, vibration time, slot width, and maximum aggregate size. Maximum aggregate size and slot width were not critical factors for consolidation performance of grout. The most significant factor was vibration time. Twenty s of vibration is recommended. Placement time was also an important factor, with grout materials placed after initial set performing poorly. Delayed placement of grout materials without vibration led to the most voids under the dowel bars. [ABSTRACT FROM AUTHOR]

In Texas, many miles of plain jointed concrete pavement (JCP) were constructed without proper load transfer devices such as dowels. After a number of years of service, some JCP sections without dowels showed distresses in the form of faulting at transverse joints. Some of the sections were designed in accordance with the AASHTO 1986 Guide, which required 50–75 mm thicker slabs in exchange for not using dowels. This pavement design did not work, with faulting at transverse joints that cause poor ride. Dowel bar retrofit (DBR) was performed on four projects to restore the pavement condition. Overall, DBR restored load transfer efficiency and resulted in improvement of ride quality. Even where the subbase stiffness is 5–10 times less than the minimum value required for proper performance of JCPs, properly installed DBR effectively restored pavement condition with minimum faulting after decades of service. Therefore, it indicated that DBR is able to minimize the faulting even where there is poor base/subgrade support. This is significant in that there are no effective and practical methods to improve subbase conditions in existing concrete pavement, whereas DBR can restore pavement conditions at a reasonable cost. However, not all DBR projects were successful. In one DBR project, faulting in the range of 6.4–9.5 mm occurred after less than 2 years of treatment. Forensic investigation revealed voids under the dowel bars, which indicates poor consolidation of the grout material. Efforts are currently underway in TxDOT to improve specifications for grout materials and DBR construction. [ABSTRACT FROM AUTHOR]