Fastener Group Research Articles

Automated titanium fastener for surgical aortic valve replacement-preventive role for infective endocarditis?

Evidence on long-term clinical outcomes considering suture-securing techniques used for surgical aortic valve replacement is still uncertain. A total of 1405 patients who underwent surgical aortic valve replacement between January 2016 and December 2022 were included and grouped according to the suture-securing technique used (automated titanium fastener versus hand-tied knots). The occurrence of infective endocarditis during follow-up was set as the primary study end-point. As secondary study end-points, stroke, all-cause mortality, and a composite outcome of either infective endocarditis, stroke, or all-cause mortality were assessed. The automated titanium fastener was used in 829 (59%) patients, whereas the hand-knot tying technique was used in 576 (41%) patients. The multivariable proportional competing risk regression analysis showed a significantly lower risk of infective endocarditis during follow-up in the automated titanium fastener group (adjusted sub-hazard ratio 0.44, 95% confidence interval 0.20-0.94, p = 0.035). The automated titanium fastener group was not associated with an increased risk of mortality or attaining the composite outcome, respectively (adjusted hazard ratio 0.81, 95% confidence interval 0.60-1.09, p = 0.169), (adjusted hazard ratio 0.82, 95% confidence interval 0.63-1.07, p = 0.152). This group was not associated with an increased risk of stroke (adjusted sub-hazard ratio 0.82, 95% confidence interval 0.47-1.45, p = 0.504). Also, a significantly lower rate of early-onset infective endocarditis was observed in the automated titanium fastener group, (0.4% vs 1.4%, p = 0.032). Suture-securing with an automated titanium fastener device appears to be superior compared to the hand-knot tying technique in terms of lower risk of infective endocarditis.

Glulam frame corner joints built of birch plywood and mechanical fasteners: An experimental, analytical, and numerical study

This study investigates frame corner joints built of birch plywood plates and glulam elements connected via self-tapping screws. Analytical calculations based on the fastener group’s torsional moment resistance, the proposed fastener group’s elastic and post-elastic load-bearing criteria, and the design formulas in Eurocode 5 were performed to predict the connection capacity in both elastic and post-elastic stages. A combined action check formula was adopted to predict the capacity of birch plywood plates and glulam elements. Frame corner specimens constructed with three different plywood thicknesses were planned to study the influence on global behavior and rotational stiffness. The specimens were intentionally designed so that failure occurred either in plywood or in glulam, in order to examine the robustness and validity of analytical calculation models. Another supplementary test group with 21 mm plywood and fewer fasteners was also designed and tested, in which the plastic yield of fasteners was expected. The test results of this supplementary group served to calibrate the analytical model that predicts the elastic and post-elastic capacity of the connection group. As a result of the comparison, the analytical calculations gave reasonable predictions on the failure of plywood, glulam, and the capacity of the fastener group. Only when the exposed moment exceeded the post-elastic limit of the fastener group did the plastic yielding of fasteners become observable. Moreover, numerical finite element models adopting the foundation zone-modeling scheme were constructed, which were proven to capture all test configurations' linear loading stiffness satisfactorily.

Automated titanium fastener vs. hand-tied knots for prosthesis fixation in infective endocarditis.

To date, there is no evidence regarding the safety of automated titanium fastener compared with hand-tied knots for prosthesis fixation in infective endocarditis. Between January 2016 and December 2022, a total of 220 patients requiring surgery for infective endocarditis were included in this retrospective analysis. The primary study endpoint was re-endocarditis during follow-up. The secondary study endpoints included stroke onset, all-cause mortality, and a composite outcome of either re-endocarditis, stroke, or all-cause mortality during follow-up. Suture-securing with an automated titanium fastener was performed in 114 (51.8%) patients, whereas the conventional technique of hand knot-tying was used in 106 (48.2%) patients. The risk of re-endocarditis was significantly lower in the automated titanium fastener group, as shown in a multivariable proportional competing risk regression model (adjusted sub-hazard ratio 0.33, 95% confidence interval 0.11-0.99, p = 0.048). The multivariable Cox proportional hazards regression analysis showed that the automated titanium fastener group was not associated with an increased risk of stroke-onset or attaining the composite outcome, respectively, (adjusted hazard ratio 0.54, 95% confidence interval 0.27-1.08, p = 0.082), (adjusted hazard ratio 0.65, 95% confidence interval 0.42-1.02, p = 0.061). Also, this group was not associated with an increased risk of all-cause mortality, as demonstrated in the multivariable Poisson regression analysis (adjusted incidence-rate ratio 1.42, 95% confidence interval 0.83-2.42, p = 0.202). The use of automated titanium fastener device seems to be safe for infective endocarditis. Analyses of larger cohorts are required.

Testing and analysis of screw-connected moment joints consisting of glued-laminated timbers and birch plywood plates

This study presents the feasibility of constructing moment joints using birch plywood plates and glulam beams. Beam-beam joints consisting of birch plywood gussets and glulam beams connected by self-tapping screws were built and tested in the four-point bending regime. Analytical calculations based on the fastener group’s torsional moment resistance, the proposed elastic and post-elastic fastener group’s load-bearing criteria, and the design formulas given in Eurocode 5, are performed to predict the connection capacity in both elastic and post-elastic stages. Under the four-point bending, all specimens with birch plywood plates with the face-grain orientation of either 0° or 22.5° to the beam length direction, showed brittle failure either in the glulam beam or birch plywood plate. Numerical models are constructed to capture the global load–deflection behavior of all beam specimens. The foundation zone modeling scheme is adopted to consider the influence of the fasteners’ embedment on the macroscopic load–deflection curves. As a result of comparison, the analytical calculations give reasonable predictions on both the elastic and post-elastic ultimate beam capacity, and the numerical models give satisfactory predictions on the bending stiffness for all tested beam specimens.

Local-distortional interaction behaviour and design of cold-formed steel built-up columns

This research highlights the possibility of LD interaction in the built-up columns and provides a detailed design procedure to account for the strength erosion due to LD interaction. For this, a comprehensive numerical study using finite element (FE) method is performed where the FE models are validated using the test results in the literature. In this study, three types of built-up sections, i) back-to-back I section made of two lipped channels, ii) nested section made of two lipped channels, and iii) nested section made of one lipped and one unlipped channel, are selected. The effects of LD interaction, fastener spacing, and end fastener group (EFG) on the ultimate strength of built-up columns are investigated. The study reveals that the LD interaction behaviour of the built-up back-to-back I section in terms of failure mode and normalized ultimate strength result (Pu/Py) is similar to that of a lipped channel. For the built-up nested section, improved strength is observed when the lipped channel fails in distortional buckling. No improvement is observed in the LD strength of built-up sections with reduced fastener spacing or by using EFG. The study shows that the traditional direct strength method (DSM) based design procedure for LD interaction is conservative for built-up sections. Hence, a reliable design procedure is proposed based on the modified DSM equations obtained from the literature. The strength and failure mode predictions of the proposed method match well with those of experimental studies in the literature and the numerical study of this paper.

Design of sheathed built-up nested CFS channel studs in load-bearing LSF walls

Cold-formed steel built-up nested channel (NC) sections have been increasingly used to replace the commonly used lipped channel sections as the load-bearing studs of light gauge steel framed (LSF) walls with higher compression capacity. However, the related knowledge is limited and no research study has investigated such NC stud walls yet. In this study, an investigation was undertaken on the compression behaviour and capacity of LSF walls made of slender NC studs sheathed with gypsum plasterboards on both sides. Compression tests of sheathed NC studs were conducted first, which were then used in developing and validating suitable finite element models. The results obtained from tests and finite element models showed that plasterboards and stud-to-board screw connections had significant influence on the failure mode and compression capacity of sheathed NC studs, while the end fastener groups recommended in the current cold-formed steel design standards and the stud-to-stud screw connections had only marginal effects. Finally, a simple and conservative design method was proposed based on the Direct Strength Method equations in the current design standards. This paper presents the details of this research study, including the results, discussions and main findings.

Design of Built‐up Nested Cold‐formed Steel Channel Compression Members

AbstractRecently, the use of built‐up cold‐formed steel (CFS) members in the form of nested channel (NC) compression members is becoming more popular in CFS construction. For NC compression members, the current CFS design standards have been shown to be inadequate, provide over‐conservative predictions, and include some cumbersome design rules relating to maximum allowable screw spacing and end fastener groups. New design guidelines have been proposed by some recent research studies, however, they are based on different assumptions and provide varying capacity predictions.This study has investigated (1) the design guidelines in the current design standards and past research studies, and (2) the effects of screw spacing as well as end fastener groups on the compression behaviour and capacity of NC members. It included a series of compression tests on short, intermediate and slender single channel and NC members, followed by developing validated finite element models and undertaking parametric studies. The results show that: (1) the compression capacity of NC members can be greater than twice that of their individual members, (2) the design rules on the maximum allowable screw spacing and end fastener groups are over‐conservative, and are mostly unnecessary, (3) the design rules in the current standards and past research studies are not suitable for predicting the compression capacities of the investigated NC members, and (4) proposed design guidelines based on the Direct Strength Method in the current CFS design standards can provide reliable predictions for the compression capacities of NC members.

Experimental Study and Direct Strength Method for Cold-Formed Steel Built-Up I-Sectional Columns under Axial Compression

The objective of this paper is to investigate the buckling behavior and design method of the ultimate strength for the cold-formed steel (CFS) built-up I-sectional columns under axial compression which failed in distortional buckling and interactive buckling. A total of 56 CFS built-up I-sectional columns subjected to axial compression were tested, and the different buckling modes and ultimate strengths were analyzed in detail by varying the thickness, the length, the spacing of screws, the end fastener group, and the cross-sectional dimensions of CFS built-up I-sectional columns. It was shown in the test that noticeable interaction of local and distortional buckling or interaction of local, distortional, and global buckling was observed for the built-up I-sectional columns with different lengths and cross-sectional dimensions. A finite element model (FEM) was developed and validated with experimental results. A further parametric study has been conducted including different cross sections and slenderness ratios for the built-up I-sectional columns. The load-carrying capacities obtained from the experimental and numerical study were used to investigate the feasibility of the current direct strength method (DSM) when DSM was applied to CFS built-up I-sectional columns. The comparison results showed that the current DSM is not safe for CFS built-up columns failed in distortional buckling and interactive buckling. Therefore, the improved design formulas were proposed, and their accuracy was verified by using finite element analysis (FEA) and experimental results of CFS built-up I-sectional columns subjected to axial compression.

Tests and design of built-up section columns

Built-up sections are increasingly used as structural elements in the cold-formed steel (CFS) industry. They are composed of two or more component sections connected by discrete fasteners, typically spaced evenly along the length and potentially with fastener groups at the ends. Conventionally, two singly symmetric C-sections are connected to form a doubly symmetric cross-section, and current design guidelines are limited to this particular application. As a means towards broadening the application of built-up CFS sections, the cross-sections in this study were composed of three or four lipped channel sections. The paper presents an experimental investigation of the strength and behaviour of built-up section columns of various lengths and cross-sectional shapes. As observed in the tests, singly-symmetric columns composed of three channel sections (3C) experienced either local, distortional and/or flexural-torsional buckling failure modes, while doubly-symmetric columns formed by four sections (4C) failed in local, distortional and/or flexural buckling modes. The current AISI Specification specifies the use of a modified slenderness ratio only for built-up sections composed of two sections connected back-to-back, whereas the design proposal in this paper recommends the use of an effective rigidity approach coupled with the Direct Strength Method for predicting the strengths of the test 3C and 4C built-up sections. This proposal also suggests a design procedure for the built-up sections experiencing flexural-torsional buckling, which is neither explicitly stipulated in current design standards nor in previous studies.

The mechanics of built-up cold-formed steel members

Abstract The paper presents methods of analysis of built-up sections in which the discrete locations of fasteners is accounted for explicitly, rather than by smearing their effect using continuous shear flexibility as in current approaches. By considering fasteners at discrete points, it is possible to analyse the effects of placing additional fasteners at the ends (end fastener groups), to account directly for actual support conditions and to determine the optimum locations of fasteners. The paper first outlines the linear analysis of beams in flexure and introduces the notion of the effective flexural rigidity to account for partial composite actions. Closed form solutions are provided for five load and end support cases to demonstrate the application of the analysis. Next, the paper describes the linear analysis of built-up sections in torsion, considering first uniform torsion followed by non-uniform torsion. Closed form solutions are obtained for the effective torsion rigidity (GJeff) of built-up sections featuring closed loops. A framework is also presented for determining the effective torsion rigidity (EIw,eff) of open built-up sections in non-uniform torsion. The paper concludes with the analysis of built-up sections subject to flexural buckling. A general variational buckling equation is derived followed by an energy-type method for calculating buckling loads for common end support conditions, including columns supported on flexible end tracks. Closed form solutions are presented for up to seven rows of fasteners longitudinally. While by nature approximate, the solutions are shown to be highly accurate. Comparisons are made between the presented closed form solutions and buckling load predictions obtained using current design provisions.

Simulation of screw connected built-up cold-formed steel back-to-back lipped channels under axial compression

The objective of this paper is to validate finite element (FE) modeling protocol for screw connected, back-to-back built-up cold-formed steel (CFS) columns. The protocol is developed and validated using results from previously conducted experiments. The effort is motivated by two applications: (1) to augment experimental findings on built-up CFS columns, particularly for fastener demands and (2) to provide a simulation path for modeling the built-up CFS columns that are used as shear wall chord studs. Shell FE-based models were created in ABAQUS and include monotonic loading, nonlinear geometric and material behavior, geometric imperfections based on laser scanned measurements of tested specimens and a contact model that includes friction. Additionally, the screw fasteners were integrated into the modeling protocol using user-defined element subroutines capable of reproducing strength and stiffness deterioration under monotonic load as well as the pinching that occurs when screw fasteners are subjected to cyclic loads. Monotonic, concentric compression tests on 17 back-to-back CFS columns using two cross-section sizes and varying fastener layouts with sheathing conditions were simulated. Deformations, strength, and collapse mechanisms obtained by the models were in close agreement with the experimental results. An assessment of the loading demand on screw fasteners reveals the conservatism in built-up column fastener layout and design as required by the North American Specification for the Design of Cold-Formed Steel Structural Members (AISI S100-16 Section I1.2). Also, under the tested semi-rigid column end conditions, there is a little boost in axial capacity with the addition of member end fastener groups (EFGs) at the top and bottom of the columns. Numerical models are also used to assess the cyclic performance of axially-loaded columns so that chord stud buckling limit states could be captured in seismic simulations of CFS-framed shear walls in future work.

The effect of adhesive tape versus endotracheal tube fastener in critically ill adults: the endotracheal tube securement (ETTS) randomized controlled trial

BackgroundThe optimal securement method of endotracheal tubes is unknown but should prevent dislodgement while minimizing complications. The use of an endotracheal tube fastener might reduce complications among critically ill adults undergoing endotracheal intubation.MethodsIn this pragmatic, single-center, randomized trial, critically ill adults admitted to the medical intensive care unit (MICU) and expected to require invasive mechanical ventilation for greater than 24 h were randomized to adhesive tape or endotracheal tube fastener at the time of intubation. The primary endpoint was a composite of any of the following: presence of lip ulcer, endotracheal tube dislodgement (defined as moving at least 2 cm), ventilator-associated pneumonia, or facial skin tears anytime between randomization and the earlier of death or 48 h after extubation. Secondary endpoints included duration of mechanical ventilation and ICU and in-hospital mortality.ResultsOf 500 patients randomized over a 12-month period, 162 had a duration of mechanical ventilation less than 24 h and 40 had missing outcome data, leaving 153 evaluable patients randomized to tube fastener and 145 evaluable patients randomized to adhesive tape. Baseline characteristics were similar between the groups. The primary endpoint occurred 13 times in 12 (7.8%) patients in the tube fastener group and 30 times in 25 (17.2%) patients in the adhesive tape group (p = 0.014) for an overall incidence of 22.0 versus 52.6 per 1000 ventilator days, respectively (p = 0.020). Lip ulcers occurred in 4 (2.6%) versus 11 (7.3%) patients, or an incidence rate of 6.5 versus 19.5 per 1000 patient ventilator days (p = 0.053) in the fastener and tape groups, respectively. The endotracheal tube was dislodged 7 times in 6 (3.9%) patients in the tube fastener group and 16 times in 15 (10.3%) patients in the tape group (p = 0.03), reflecting incidences of 11.9 and 28.1 per 1000 ventilator days, respectively. Facial skin tears were similar between the groups. Mechanical ventilation duration and ICU and hospital mortality did not differ.ConclusionThe use of the endotracheal tube fastener to secure the endotracheal tubes reduces the rate of a composite outcome that included lip ulcers, facial skin tears, or endotracheal tube dislodgement compared to adhesive tape.Trial registrationClinicalTrials.gov NCT03760510. Retrospectively registered on November 30, 2018

Titanium Fastener Utilization During HeartMate 3 Left Ventricular Assist Device Implantation.

The objective of this study was to investigate the feasibility of using titanium fasteners for securement of the inflow sewing ring during HeartMate 3 implantation. The secondary objective was to compare cardiopulmonary bypass and total operative times between the titanium fastener and hand-tied knot groups. Clearance between the sewing ring and the HeartMate 3 device was assessed in vitro. Thirty-one patients undergoing HeartMate 3 implantation via median sternotomy at a single center from April 2017 to February 2018 were reviewed. The sewing ring was secured with hand-tied knots (n = 18) or titanium fasteners (n = 13). Cannulation strategy and implantation technique were otherwise identical between groups. Central arterial and venous cannulation was performed for cardiopulmonary bypass. The left ventricular apex was cored, and the sewing ring was attached with hand-tied knots or titanium fasteners. There was adequate clearance for the titanium fastener to secure the inflow sewing ring and then connect to the HeartMate 3 in vitro. The inflow sewing ring was successfully secured during HeartMate 3 implantation in the titanium fastener group. Cardiopulmonary bypass time was 75 and 92 minutes for the titanium fastener and hand-tied groups, respectively (P < 0.03). Total operative time was 177 and 193 minutes for the titanium fastener and hand-tied groups, respectively (P = 0.513). The inflow sewing ring of the HeartMate 3 was efficiently secured using titanium fasteners. Titanium fasteners resulted in shorter cardiopulmonary bypass times compared with the hand-tied group. There was no difference in total operative time.

07.07: Numerical study of screw fasteners in built‐up CFS chord studs

ABSTRACTThis paper presents the development of finite element (FE) models for advanced analyses of screw connected and axially‐loaded back‐to‐back, built‐up cold‐formed steel (CFS) chord studs. Results are validated using column test data from displacement‐controlled experiments conducted at Johns Hopkins University. Shell finite element‐based models have been assembled in ABAQUS and include non‐linear geometric, material, and contact behavior. A unique feature of the developed models is the simulation of screw‐fastener connections using a user‐defined element (UEL), which can reproduce strength and stiffness deterioration under a monotonic load as well as the pinched response that occurs in the shear behavior of these connections when subjected to cyclic loading. Connection stiffness and strength data from pure shear tests of steel‐to‐steel and steel‐to‐oriented strand board (OSB) connections are used in the formulation of the subroutine and is discussed herein. Seventeen monotonic and concentric compression tests on two different built‐up CFS cross‐section sizes with varying fastener layouts and sheathing conditions were simulated. The buckling, peak, and post‐peak behavior of the built‐up columns is examined. Good agreement was reached among experimental and numerical results in terms of load‐deformation histories, as well as buckling and failure modes. Results indicate that under the tested end boundary conditions there is no significant boost in axial capacity with the addition of member end fastener groups at the top and bottom of the built‐up columns in common sheathed configurations; further, the response of screw fasteners remains elastic up until the post‐peak regime, revealing conservatism in the built‐up column fastener layout currently required by AISI S100‐16 section I1.2. The goal of this study is to improve existing design guidelines in which all relevant failure modes are considered in the design of built‐up CFS columns. In addition, the characterization of monotonic and cyclic behavior of columns is sought so that chord stud buckling limit states are captured in simulations of shear walls.

Analysis of Influence Factors of Switching Force and Inadequate Displacement of Switch Rail of NO.9 Turnout

Switching force and inadequate displacement are two key issues in the conversion of switch rail, which determined some important parameters such as the traction position of switch machine, the displacement of traction point and the length of switch rail. This paper taking the NO.9 turnout of 60kg/m rail in a line of Wuhan rail transit as the research object, using the open architecture of ANSYS software and its secondary development, establishing the calculation procedure of switching force, calculating and studying the influence of switch force and inadequate displacement of switch rail by the stiffness, the number of fastener groups and the friction coefficient of sliding bed on the heel of switch rail.

Plug shear failure in nailed timber connections

Brittle failures in mechanical timber joints should be avoided, because this often results in low capacity and brittle failure of the structure. Nailed joints experience three ultimate failure modes: embedding, splitting or plug stear failure. To avoid plug shear failure, short and wide joints are preferred, limiting the number of fasteners in line with the load and grain direction. Plug shear failure was examined in short-term experiments on nailed steel-to-timber joints in glulam loaded in tension parallel to the grain with five different joint geometries. The aim of the study was to examine if the fastener group layout can be adjusted to avoid plug shear failure and to gain an insight into the causes of failure initiation. Using spring models, it is shown that the load distribution creates pronounced stresses at the last nail in the joint, which probably initiates the plug shear failure. Test results are compared with prediction models found in the literature. It was found that fasteners placed in groups can be a successful way of reducing the risk of plug shear failure. The failure is probably initiated at the nail farthest from the free end, where tensile stresses perpendicular to grain occur.

Design Criteria for Bolted Connection Elements in Aluminum Alloy 6061

Plates frequently find use as connecting elements in structures built from aluminum alloys. Many structural elements employ mechanical fasteners. Design of connections necessitates that due consideration be given to: (a) bolt or rivet failure, (b) progressive bearing distress of material adjacent to the fastener(s), (c) net-section tensile failure, and (d) tear out of the fastener group(s). Current design provisions for block shear failures of bolted and riveted joints in aluminum-based alloys make use of models initially developed for structural steels or, alternatively, fail to address an estimation of joint capacity. Shear failure of aluminum connecting elements is the focus of this paper. An experimental and analytical program was undertaken with the objective of studying block shear failure of aluminum connecting elements. Twenty aluminum alloy 6061-T6 gusset plates, representing four different bolt patterns, were mechanically deformed. Models to estimate the capacity of the joints are examined and compared with experimental results. Strain distribution around the periphery of the connections were measured and compared to finite element predictions. The correlations between the design models and experimental observations are highlighted.

Mechanical Response and Failure of Bolted Connection Elements in Aluminum Alloy 5083

In a spectrum of structures made from pure aluminum and aluminum-base alloys, plates are used frequently as the choice candidate for connecting elements. Design of safe, efficient, and reliable connections necessitates that adequate consideration be given to failure of the fastener element, distress of material in the immediate vicinity of the fastener(s), tensile failure of the net section, and even tear out of the fastener group(s). The mechanical response and failure characteristics of aluminum connecting elements are presented and discussed in this paper. An experimental and analytical program was conducted to rationalize failure of connecting elements made from an aluminum-magnesium alloy. Gusset plates representing different bolt patterns were mechanically deformed. Models to estimate the capacity of the joints were examined and compared with experimentally determined results.

Simple Formula for Eccentric Bolted Connection Design

This paper develops a simple formula to calculate the strength capacity of an eccentrically loaded bolted connection. The formula is based solely on connection geometry, can include mixed connector sizes, and is shown to be suitable for skewed load cases. The formula includes computations for both high and low eccentricity connections including lap splices. The results compare favorably with experimental data and the ultimate strength method described in the American Institute of Steel Construction (AISC) manual. Because the formula is based only on connection geometry and connector sizes, strength properties can be determined for each connection. These strength properties, once calculated, allow for rapid determination of connection capacity for any eccentricity. One advantage is that connection capacity coefficients can be calculated without using the iterative approach of the ultimate strength method. Because mixed connector sizes and skewed loadings are considered, the formula provides a wider range of connection capacities than the eccentric loads on fastener groups tables in the AISC Manual of Steel Construction .

Analysis of fastened structural connections

An approach for modeling the transfer of forces in fastener groups is described which takes nonlinearities into account. The method is used for analyzing two problems which involve design of repairs and damaged structures. The model predictions are found to be in a good agreement with available experimental results. The study demonstrates the importance of fastener stiffness and initial clearance on load distribution. R ELIABLE structural analysis of mechanically fastened connections is of major importance in modern design of aircraft structures where requirements for optimal design must be met. In current practice, extensive full-scale testing is used mainly because the reliability of mathematical models has not been established to the satisfaction of engineers who have to make or approve design decisions. Improved reliability of mathematical models will make it possible to reduce the scope of experimental programs and the time required for developing information on which design decisions can be based with confidence. Also, extensive testing programs can improve the safety of design (at a substantial cost) but cannot be used for optimizing design with respect to weight and durability. Only reliable mathematical models can do that. In this paper, the problem of simulating the elastostatic response of fastened structural connections, with guarantee of reliability, is discussed. Some aspects of this problem were presented in Ref. 1 where the interaction between the fasteners and the plates was simulated by distributed springs. Friction was treated by the addition of external tractions in an iterative process. Each fastener was represented by a nonlinear relation between the transferred force and the relative displacements. The accuracy of the method was verified through tight quality control of the numerical approximation errors and comparisons with experimental results. This paper is concerned with the accuracy and reliability of the mathematical model. Two kinds of error have to be considered2: 1) The differences between the exact solution of the mathematical problem formulated to represent a physical system and the actual response or behavior of the physical system are called errors of idealization. 2) The differences between the exact solution of the mathematical problem formulated to represent a physical system or process and its numerical approximation are called errors of discretization. In some cases the two errors, the errors of idealization, and discretization may partially cancel one another. Therefore it is important to verify by means other than the experiment itself that the numerical solution is close to the exact solution of the model. Only then is it possible to investigate whether the errors of idealization are large or small by making comparisons with experimental observations. The load distribution in bolted or riveted joints had been investigated both experimentally and theoretically, (e.g., Refs. 3-25). In these studies, a number of assumptions had been