Pull-through Failure Research Articles

Experimental and numerical investigations on tensile failure mechanism and load-bearing capacity of expansion anchors under pull-through failure mode in HPSFRC

Pull-through(PT) is a unique failure mode of torque-controlled expansion(TCE) anchor after being pulled out from concrete. No universal design formula is available for predicting tensile bearing capacity of anchor of PT mode. In normal concrete(NC), PT failure usually occurs at large embedment depths(Hef), which is uncommon in the field and received less attention than the concrete breakout failure. However, due to the improved mechanical performance of the substrate, the PT mode dominates for anchors in high-performance steel fiber reinforced concrete(HPSFRC) substrate (even at small Hef). In this study, to study the PT mode in HPSFRC, the results of 34 PT failures from previous tests, including testing scenarios with different anchor diameters(D), Hef, and fiber contents(vf), are analyzed. The cracking morphology and load-bearing capacity distribution of PT mode are elaborated. Further, finite element models(FEM) of anchor pullout behavior in HPSFRC is established, which accurately identified different failure modes. The calculated Nu by FEM agree well with the tested Nu. The difference in damage domain between different failure modes is mainly reflected in the unloading stage. Parametric analyses were conducted on pre-tightening torque(Tini), Hef, D, sleeve length(Lsleeve), anchor cone width, anchor cone length(Lcone), and vf to study their influences on Nu of PT mode. Except for Lsleeve and Lcone, which do not affect Nu, changes in other factors can cause linear or nonlinear changes in Nu. The non-linear relationship between Nu and experimental parameters is formulated. Accordingly, a new prediction model that can accurately predict Nu of PT mode for anchors in HPSFRC is developed, of which calibration factors are derived using probability functions.

Progressive collapse behaviour of earthquake-damaged interior precast concrete joints with headed bars and plastic hinge relocation

This study investigated progressive collapse behaviour of earthquake-damaged interior precast concrete (PC) joints with headed bars. The main objective was to quantify the impact of slight and moderate earthquake damage on their residual collapse resistance. The research began with a numerical investigation to understand the interaction between a 2D frame’s global response to seismic loading and its local response during a threat-independent progressive collapse event. Additionally, a separate set of numerical studies examined interior PC joints under cyclic loading to determine maximum drift ratio demands, yielding 2.5% for slightly and 3.5% for moderately damaged joints. Subsequently, an experimental programme under quasi-static loading conditions was conducted on five interior PC joints under cyclic loading, followed by progressive collapse resistance tests. Test results indicated that damaged joints exhibited flexural and catenary action during progressive collapse, but compressive arch action could not be mobilised due to residual cracks from the initial cyclic loading phase. Comparing damaged joints to fully intact ones from a companion study revealed deterioration in stiffness and deformation capacity during a subsequent progressive collapse, with degree of severity proportional to the extent of damage sustained in the cyclic loading phase. Relative to the intact joints without being subjected to cyclic loading, moderately damaged specimens exhibited a degradation of 63% in stiffness and 38% in deformation capacity, compared to slightly damaged specimens, which showed reductions of 38% in stiffness and 28% in deformation capacity. In contrast, strain hardening of steel bars in both slightly and moderately damaged specimens led to slightly greater collapse resistance than the intact joints. Additionally, failure mode shifted from ductile fracture to premature pull-through failure of headed bars in moderately damaged specimens. In this regard, in post-earthquake progressive collapse assessment, it is recommended to use maximum crack width thresholds of 0.2 to 1.0 mm for slight damage and 1.0 to 2.0 mm for moderate damage.

Design of Cold-Formed Z-Shaped purlin-to-rafter connections subject to pull-through failure

The current study is focused on understanding the pull-through behaviour of Z-Shaped Cold-Formed Steel (CFS) purlin-to-rafter connection. A total of forty tests were conducted using small-scale testing methods to investigate the influence of parameters such as thickness, depth, and flange width of the purlin section along with the size of the screw head diameter. The results indicated that the test specimens exhibited two modes of pull-through failure (i) rupture-type failure and (ii) bearing-type failure. A transition from rupture-type to bearing-type was observed with an increase in thickness from 1 mm to 3 mm. Both the failure modes were accompanied by tilting of the screw due to eccentricity in the applied load for Z-Shaped purlins. A full-field measurement approach called Three-Dimensional Digital Image Correlation (3D-DIC) technique was employed to better understand the failure mechanism. The DIC strain contours adequately captured the tilting of the screw that can be attributed to the increased strain and out-of-plane deformation at the vicinity of the screw head. A comparison of the test with existing design standards indicates that the design guidelines are unconservative for Z-shaped purlin sections. A modified design equation is proposed to determine the pull-through capacity of Z-shaped purlin-to-rafter connection. Further, reliability study was carried out to determine the resistance and safety factors for the preliminary design equations proposed.

A progressive damage model for carbon fiber-reinforced polymer laminates subjected to fastener pull-through failure

Most studies on composite joints focus on in-plane bearing mode, while little attention to fastener pull-through failure mode from out-of-plane loads. This paper presents a 3D continuum damage mechanics (CDM) model to investigate and assess the mechanical behaviors of carbon fiber-reinforced polymer (CFRP) laminates subjected to pull-through failure. The proposed model based on the use of intralaminar and interlaminar damage models is established and implemented by means of a user-defined subroutine VUMAT for Abaqus/Explicit. The novelty lies in the material model integrating the thresholds preset by the semianalytical approximation approach, which largely eliminates unnecessary fracture angle enumerations in Puck’s IFF theory, coupled with the simple parabolic interpolation search (SPIS) technique for optimal fracture angle search, considerably reducing the computational burden. Moreover, the numerical results compare well with experiments, effectively replicating the load–displacement response, damage modes, failure behaviors and damaged areas. This study provides an accurate and efficient computational methodology to analyze pull-through failures, enhancing the damage modeling and predictive capabilities for composite joints under out-of-plane loads.

Localised pull-through failures of cold-formed steel batten screw connections under combined wind and sub-zero temperature conditions

The utilisation of thin cold-formed steel (CFS) elements is widespread in contemporary lightweight building construction. Roof and wall cladding systems are predominantly made of thin, high-strength steel claddings and battens. Blizzards are predominantly observed in North American countries, resulting in significant roof damage. A localized pull-through failure mechanism, occurring at the batten to rafter/truss screw connections, has been extensively investigated at ambient temperature to comprehend the critical factors that influence the pull-through failure capacities of CFS battens. Nonetheless, the pull-through capacity of CFS battens at sub-zero temperatures has not been examined, and as a result, the performance of the steel cladding systems during blizzards under the combined action of strong winds and sub-zero temperatures remains unknown. To investigate the pull-through failure behaviour and capacities of batten screw connections, an experimental study comprising 96 tests was conducted involving two steel grades and three thicknesses of steel battens and two screw fasteners at sub-zero temperatures. The study was conducted at both ambient and sub-zero temperatures to understand the pull-through failure behaviour and capacities of batten screw connections. Appropriate pull-through capacity equations and associated increment factors were developed to predict the pull-through capacities of batten screw connections that are subjected to the combined effects of high wind uplift loads and sub-zero temperatures.

Experimental investigation and design consideration on pull-through capacity of a C-shaped purlin section

A small-scale experimental study was carried out to investigate the pull-through failure of the C-shaped Cold-Formed Steel (CFS) roof purlin sections subjected to wind uplift force. The parameters investigated to comprehend the pull-through behavior of roof purlin are thickness, web depth, flange width of the CFS purlin section, and size of the screw head diameter. The test specimens experienced two different modes of pull-through failure (rupture and bearing) along with the prying effect. It was observed that the pull-through failure mode transitions from rupture of the purlin section around the screw fastener in 1 mm thickness to bearing type in 2 mm and 3 mm thicknesses. The test results were compared with existing design limits and previous studies from the literature which concluded that the existing elastic design approach for the service limit state is unconservative. Hence, a suitable design limit to predict the critical pull-through capacity of C-shaped roof purlins under high wind load is proposed. Additionally, reliability studies were carried out to determine the resistance and safety factors for the proposed design equations. The suggested design specifications are applicable and conservative for the material strength in the range of 350 MPa.

Design of thin steel battens subject to pull-through failures

Localized pull-through failures of cold-formed steel roof battens have often been observed at the roof batten to purlin/rafter/truss screw connections during storms and cyclones. Recent research studies have therefore proposed improved design capacity equations by undertaking both experimental studies and finite element analyses. However, they have not investigated the effects of very thin steel roof and ceiling battens (<0.50 mm), safety lip features and purlin flexibility on the localized pull-through failures. Hence this study was aimed at investigating the effects of all such practical design issues and to assess the suitability of current design equations. For this purpose, a series of static and fatigue pull-through failure tests of roof and ceiling battens was undertaken under simulated static and cyclic wind uplift loads. This paper presents the details and results obtained from this study including suitable design recommendations. It has shown that the recently developed pull-through capacity equations can be used for very thin steel battens. Higher capacity reduction factors are recommended for use with these design equations for battens made of Australian cold-formed steels used in this study. The use of safety lip features did not affect the static pull-through capacities, but it improved the fatigue performance of roof battens. Finally, the suitability of using low strength steel battens instead of high strength steel battens was evaluated.

Pull-through failure of crest-fixed steel claddings under combined wind and bushfire conditions

Cold-formed steel (CFS) roof and wall cladding systems are commonly used in Australia and around the world. The use of CFS claddings in bushfire prone areas is becoming more popular due to their non-combustibility and is recommended in the Australian standard AS3959 for construction in bushfire areas. However, severe fire events occur more frequently and in recent bushfire events, strong winds and fire–wind interactions have been observed. Thus, the behaviour of CFS claddings exposed to a combined action of fire and wind needs to be considered for the safe design of buildings in bushfire prone areas. In this study, a small-scale test set-up was developed and used to simulate the wind suction loading on crest-fixed CFS roof and wall claddings while also being exposed to elevated temperatures. Experiments were conducted on three commonly used 0.42 mm high strength (G550) CFS cladding profiles at ambient and elevated temperatures and their critical localised pull-through failures of the crests under the screw heads were investigated at increasing temperatures. The results showed that the failure mode of trapezoidal cladding profiles changed from a transverse splitting type to a localised dimpling type pull-through failure. They also showed different rates of reduction in the pull-through capacity with increasing temperatures and the type of cladding profile. This paper has proposed a suitable equation for the pull-through capacity reduction with increasing temperatures and made suitable recommendations in relation to the use of CFS cladding systems in bushfire prone areas.

Experimental study of sheathed cold-formed steel beam–columns

An experimental study of sheathed cold-formed steel C-lipped wall studs, with service holes, subjected to compression and major axis bending is presented in this paper. A total of 17 experiments were performed with both oriented strand board (OSB) and plasterboard used as sheathing and with varying connector spacing employed between the sheathing panels and the steel members. The tested specimens comprised a single 2.4 m long column sheathed on both sides and secured at the ends to top and bottom tracks. The member tests were complemented by material tests, stub column tests and initial geometric imperfection measurements. The specimens were tested in a dual-actuator rig where axial compression was applied by means of a vertical actuator through the top track, while bending was applied through the application of four lateral point loads. Eight pure compression tests with both plasterboard and OSB sheathing and with the spacing of the connectors varying between 75 mm and 600 mm were initially performed. Specimens with OSB sheathing were then tested under pure bending and combined loading. The full load–deformation responses and failure modes of the member test specimens are reported. The compressed studs connected to the plasterboard sheathing at wider spacings exhibited pull-through failure of the connectors, followed by flexural torsional buckling, while the specimens with denser connector spacings, failed by local buckling at the member ends. The OSB sheathed specimens under pure compression failed by local and distortional buckling, those under combined loading exhibited local failure at the service openings, while for those under pure bending, local buckling and stud-to-track connector failure occurred. Reducing the spacing of the connectors from 600 mm to 75 mm resulted in up to 20% and 30% increases in capacity for the studs sheathed with OSB and plasterboard respectively.

Performance evaluation of different shapes of headed barsin steel fiber reinforced concrete

The behavior of headed bars in concrete is investigated through 108 pullout tests having an embedment depth of eight times the bar diameter in the M20 concrete mix. Headed bars are designed based on ASTM A970-16 and ACI 318-19 recommendations. The primary parameters used in this study are the steel bar diameter, the steel fibers percentage, and the head shapes. Three failure modes namely, Steel, Concrete-Blowout & Pull-Through failure have been observed. Based on loaddeflection curves which are plotted to investigate the bond capacity of headed bars, it is observed that the circular-headed bars have displayed the highest peak load. The comparative analysis shows the smaller differences in the ultimate bond strength between MC2010 (0.89-2.26 MPa) and EN 1992-1-1 (2.32 MPa) as compared to ACI-318-19 (11-22 MPa) which is due to the absence of embedment depth and peak load factor in MC2010 and EN 1992-1-1 respectively.

Experimental investigation on the effects of overhang length variations of steel roof cladding under uplift pressure

In the rural areas of northern Peninsular Malaysia, the common profiled steel cladding systems in many low-rise buildings are classified as non-engineered structures. These structures are made of thin steel and are crest-fixed. However, these claddings often suffer from local pull-through failure at the screw connections during a windstorm. Due to the unavailability of standard information and design formulae in Malaysia, investigation in this area is much needed. Hence, this study aims to investigate the changes in the pull-through capacity of different overhang lengths (150 mm and 300 mm) for corrugated and trapezoid roof claddings. A new simple test method using single-span cladding was conducted under loading of static uplift pressure using a hydraulic testing machine. The results demonstrated that the pull-through capacity of corrugated roof cladding was higher than the capacity of the trapezoidal roof cladding. Moreover, as the overhang length was increased, the pull-through capacity of the steel cladding became smaller for both cladding profiles. Based on this observation, localised dimpling failure for corrugated cladding and cross-sectional distortion for trapezoidal roof cladding was observed. In conclusion, the pull-through capacity and applied load decreased with increased roof cladding length for both cladding profiles.

Recommendations for design of sheathing bracing systems for slender cold-formed steel structural members

The use of sheathing material as a structural component in the Cold-formed steel (CFS) construction holds great potential for stability of the structure and savings in the construction cost. However, there is no robust design method to account the structural contribution of sheathing boards. This paper presents the experimental results of 107 (including unsheathed and sheathed) CFS wall frame studs subjected to out-of-plane loading to study the feasibility of using gypsum board as a structural bracing sheathing material. The test parameters include various shapes and slendernesses of the CFS frame stud, thickness of the sheathing board and spacing between the sheathing bracing connections. The out-of-plane loading is applied as it causes lateral torsional buckling in the CFS structural members thereby creates pull-through failure at the sheathing bracing connections. Moreover, the suitability of the current AISI and Eurocode specification for the design of sheathing braced CFS structural member is studied. The experimental results indicate that the lateral buckling of the symmetric shaped (against the loading axis) CFS wall frame studs can be inhibited by gypsum sheathing. Whereas most of the singly symmetric and point symmetric CFS studs exhibit lateral torsional buckling and biaxial bending, respectively, due to the inadequate bracing effect of gypsum sheathing resulting in pull-through failure at the sheathing bracing connections. Therefore, a set of limitations for the use of gypsum sheathing as a structural bracing is suggested in the form of a generalized design parameter. Finally, the experimental results indicates that the design strength of the CFS wall frame stud can be increased in the range of 39% to 595% based on the shape and slenderness.

Stiffness and strength characteristics of cold-formed steel clip angles subjected to pull-through failures

Load bearing cold-formed steel clip angles are commonly used in various connections, subjected to different loading conditions. This numerical parametric study was performed in order to investigate the effect of various parameters on pull-through strength of fasteners on the anchored leg of cold-formed steel clip angles. In this regard, a finite element analysis is conducted, using ABAQUS program, to model the specimens subjected to tension forces. The finite element modeling is verified, using the existing tested clip angles and the ability of the validated finite element models in predicting the pull-through strength of other clip angle cases is evaluated, by comparing the obtained results with the experimental results. This parametric study provides a detailed information on the effect of any effective parameters, such as clip angle geometry, basic mechanical properties, and screw fastener head or washer sizes on the pull-through failures of bearing clip angles. According to the results, although the effects of parameters, such as screw fastener head or washer sizes and mechanical properties, on the pull-through strength are significant, the effect of clip angle geometry can be neglected. Finally, a suitable design equation is proposed to calculate the pull-through failure of load bearing clip angles. Moreover, a new equation is presented to calculate elastic stiffness of cold-formed steel clip angles, using a simple analytical model. The results obtained from this equation are in a proper agreement with the initial slope of force-displacement curves. • Pull-through strength of load bearing cold-formed steel clip angles are investigated. • Effect of various mechanical and geometrical parameters is considered. • New pull-through design equations are presented for clip angles with low and high strength steel. • New initial elastic stiffness equation is presented for cold-formed steel clip angles. • The new stiffness equation can be applied to component-based method of clip angles.

Damage tolerance of CFRP airframe bolted joints in bearing, following bolt pull-through failure

The experimental study presented herein, investigated the residual strength of bolted joints on Carbon Fiber Reinforced Polymer (CFRP) airframe structures within the context of structural damage tolerance and airworthiness regulations. The damage scenario assumed, subjected a series of bolted joint CFRP laminate specimens to quasi-static bearing loading, following bolt pull-through failure events of different magnitude. Representative CFRP laminate specimens manufactured from AS7/8552 carbon fiber/epoxy matrix system were artificially damaged under bolt pull-through loading, following the herein proposed modifications to the current pull-through ASTM testing procedure. The specimens were subsequently tested in static bearing loading for examining the specimen residual bearing strength. The residual joint bearing strength was related to the displacement travelled passed the initial failure stage in pull-through mode and was measured up to a maximum of a 13% decrease for the tested samples and the maximum damage imposed. The study explored the safe utilization of bolted joints at higher operating loading levels, within the context of the current airworthiness regulations. The inherent damage arrest features of the joints were highlighted. The study concluded with comments and suggestions on the expansion of the current utilization spectrum of damaged bolted joints from pull-through loading in airframe design, bound by the current airworthiness certification requirements.

Mechanical integrity of friction-riveted joints for aircraft applications

The predictability of damage evolution is a challenge for mechanical joints of composite structures due to the highly nonlinear material behavior. In this study, friction riveting was investigated as an alternative joining technology for composite laminates by analyzing experimentally the joint mechanical behavior under different loading scenarios. The failure and fracture micro-mechanisms of composite laminate single lap joints were studied under quasi-static and cyclic loading. The joints failed mainly by rivet detachment from the composite hole, followed by adhesive/cohesive failure of the squeezed material, and rivet pull-through failure. Despite lower quasi-static strength of friction-riveted joints (6.2 ± 0.3 kN) compared to reference bolted joints (8.7 ± 0.2 kN), their fatigue life was higher by 88%. The main improving contributions were: the squeezed material, working as an adhesive between the composite parts and an additional fracture micro-mechanism, and the absence of clearance at the rivet-composite interface, which promoted an improved load transfer between the joined parts.

Sheathing braced design of cold-formed steel structural members subjected to torsional buckling

The objective of this work is to examine the bracing effect of sheathing boards in inhibiting the instability failure modes of cold-formed steel (CFS) studs in the wall panel construction. A development of accurate and robust sheathing braced design concepts for CFS wall panels will eliminate the need for additional lateral steel bracing, thereby leading to efficient use of construction materials. The current design method by the American Iron and Steel Institute lacks in accurately predicting the design strength of the sheathed CFS stud. Therefore, the current investigation endeavors to fill the gap by carrying out experiments that simulate the behavior of the CFS studs subjected to out-of-plane loading. A total of sixty-seven experiments were carried out with seven different sheathing board types and ten different CFS studs to accomplish the objective. The experiments were carried out using a newly devised test set-up that simulates the worst case failure mode of the sheathing board. The experimental results indicate that the strength, stiffness and failure modes of the sheathing boards vary depending on the following; (i) fiber composition and material properties of the sheathing board; (ii) dimensions of the CFS stud. In addition, the test results also indicated that the stiffness of the sheathing board against the pull-through failure was not influenced by the thickness of the sheathing boards. Based on the inferences (trend of sheathing stiffness and failure modes) from the test results, a new expression is formulated to determine the stiffness of the sheathing board on a function of the tensile modulus of the sheathing board (Es) and dimensions of the CFS stud (d/2). The validation study indicates that the new expression is accurate in terms of both statistical and design application.

Investigation on sheathing-fastener connection failures in cold-formed steel wall panels

Torsional buckling is a common mode of failure in highly slender Cold-formed Steel (CFS) stud wall frames. The torsional buckling mode will induce pull-through in sheathings attached on either side of wall panel leading to failure. This paper presents an experimental investigation to understand the performance of various sheathing boards against torsional buckling of CFS structural members. A total of forty-two specimens were tested including various parameters such as seven types of sheathing boards and six different types of CFS studs. In addition, the influence of different fasteners types that are used in the installation of sheathing boards on the CFS wall frames is also examined. The test results indicate that it is necessary to use the fastener with rubber washer (hex-washer head fasteners) to avoid pull-through failures in the sheathing. The load magnitudes at which the pull-through failure or the sheathing breakage occurs is reported for the different sheathing and CFS studs. In general, the sheathing board with the fiber composition performed well compared to the sheathing materials made of particle composition. In addition, the study also indicates that the performance of the sheathing board depends on the geometric dimensions of the CFS studs. The influence of CFS stud geometry in the sheathing-fastener connections is pictorially presented in the form of a plot. The force developed at each sheathing-fastener connection to achieve the target design moment in the CFS wall panels is calculated using a simple theoretical expression and compared against the experimental results obtained from this study. An appropriate sheathing board that offers resistance against torsional buckling of CFS stud is suggested based on the observed experimental failure modes.

Fatigue damage models for steel roof battens subject to variable amplitude cyclic wind suction loading

Pull-through failure of steel roof batten to rafter connections is one of the critical failures observed in cold-formed steel roofs during tropical cyclones. Although design equations are available for steel roof battens subject to static pull-through failures, no suitable design equations are available for fatigue pull-through failures. Currently, a Low-High-Low (LHL) cyclic test method based on expensive and time consuming large scale prototype tests is being used to design roof battens for fatigue pull-through failures. Therefore, this research study proposes suitable design equations based on both linear and nonlinear damage models to determine the fatigue life and capacity of steel roof battens by understanding the fatigue behaviour of steel roof battens subject to variable amplitude cyclic wind suction loading. This was achieved through a series of multi-level cyclic tests, including LHL cyclic tests, conducted on roof battens made of different steel grades and thicknesses and fastened with different screw fasteners. This paper presents the details of the experimental study and its results, and proposes suitable fatigue pull-through design equations based on linear and nonlinear fatigue damage models.

Sheathing Bracing Requirements for Cold-formed Steel Wall Panels: Experimental Investigation

This paper presents an experimental investigation to arrive at minimum sheathing requirements to inhibit the lateral torsional buckling (LTB) of the hat-shaped cold-formed steel (CFS) member subjected to out-of-plane loading. This study also describes the need for explicit minimum sheathing requirement provisions for different geometries of CFS structural members which are currently absent in the present design specifications. The design parameters for wall panels such as slenderness of the CFS member, the thickness of the sheathing board, the spacing between the fasteners that connect the sheathing and CFS member are considered in the experimental tests. A total of 30 full-scale tests (24 sheathed panels and 6 unsheathed tests) were carried out to study the behaviour of unsheathed CFS stud, sheathed panel and to determine their corresponding ultimate moment capacities. While all the unsheathed inverted hat-shaped CFS studs failed in LTB, the CFS stud with the gypsum sheathing effect did not undergo lateral torsional buckling and the sheathing effect led to reach its corresponding yield moment which is significantly higher than the lateral torsional buckling moment of the unsheathed CFS stud. It was also observed that until the failure of CFS stud, the gypsum sheathing did not experience damage (no bearing or pull-through failure). Based on the experimental investigation, it is shown that the gypsum sheathing board of thickness (tb) 12.5 mm with intermediate fastener spacing (df) 300 mm is sufficient to inhibit the LTB of the inverted hat shaped CFS studs. In addition, the analytical investigations were also performed to check the strength of the sheathing bracing. The analytical investigation results showed a good agreement with the experimental results in terms of sheathing failure mode and bracing requirement. Hence, the explicit minimum sheathing requirements to inhibit the LTB of the different geometry of CFS studs are suggested conservatively by considering the practicality of the wall construction.

Simulation of Fastener Pull-through Failure for Honeycomb Sandwich Structures with Inserts

Honeycomb sandwich structures are commonly assembled using a local reinforcement called “inserts” at the junction. In this paper, fastener pull-through tests are firstly conducted to investigate the strength properties and failure process of Nomex honeycomb sandwich structures with carbon fiber-reinforced composite skins and inserts. Loading capability and failure modes are analyzed and discussed. Based on these experiments, an analytical model simulating the failure process is then developed and implemented using the finite element code ANSYS, and a degradation model is proposed for the stress redistribution analysis. The database for determining the stiffness degradation factors Di of the honeycomb core is established by means of parametric fitting. The simulated results of the fastener pull-through failure process are will coincided with experimental results.