Pull-through Failures Research Articles

Numerical studies of pull-through failures in cold-formed steel battens at sub-zero temperatures

Cold-formed steel (CFS) roof and wall cladding systems comprising thin, high strength steel battens and claddings are popularly used in the building industry worldwide. These cladding systems have been observed to encounter failures under combined snow and strong wind actions during blizzards. Significant damage is caused by the disengagement of the entire roof/wall cladding when localised pull-through failures occur in thin-walled steel battens at the batten to truss/rafter screw connections due to a splitting mechanism around the screw head. This study uses detailed finite element analyses of the pull-through failures of a range of batten configurations under combined wind and sub-zero temperature conditions. Suitable finite element models capable of simulating the pull-through failures of battens were developed and validated using experimental results, followed by detailed numerical parametric studies. The main outcomes of this study are accurate design equations and capacity reduction factors essential for predicting the pull-through capacities of CFS battens at sub-zero temperatures.

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.

Numerical investigation and design of crest-fixed corrugated steel claddings under static wind uplift loading

When crest-fixed corrugated steel roof claddings are subjected to wind uplift loading, local dimpling failures occur prematurely at their screwed connections because of the large stress concentrations around the fastener holes. Once the screwed crests are locally dimpled, high wind events such as storms and cyclones can cause severe fatigue cracking and pull-through failures, leading to the loss of entire corrugated roof cladding. Therefore, the pull-through capacity is an important parameter governing the wind uplift strength of corrugated roof claddings. This paper presents the details of a numerical investigation of the local dimpling behaviour of corrugated claddings under static wind uplift loading. It includes the details of the developed finite element model and validation, an extensive parametric study, and the results including a design equation to determine the pull-through capacity of crest-fixed corrugated cladding.

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.

Behaviour of stud-to-sheathing fastener connections in LSF walls at elevated temperatures

Light-gauge steel framed (LSF) walls used in low- and mid-rise buildings are usually sheathed with gypsum plasterboard to protect the thin-walled steel studs in fire. The structural failures of these walls in fire are mostly associated with local in-plane shear or pull-through failures at their stud-to-gypsum plasterboard sheathing screw fastener connections. The reductions in the mechanical properties of gypsum plasterboard and cold-formed steel studs at elevated temperatures significantly reduce the strength and stiffness provided by the stud-to-sheathing screw connections, which may lead to premature structural failure of LSF wall studs. Many detailed studies are available on the ambient temperature local in-plane response of stud-to-sheathing connections, however, the studies of both local in-plane and out-of-plane responses of stud-to-sheathing connections at elevated temperatures are limited. Therefore in this study local in-plane shear tests at elevated temperatures and pull-through tests at both ambient and elevated temperatures were conducted to determine the load–displacement behaviour, and capacity and stiffness reduction factors of stud-to-gypsum plasterboard sheathing screw connections. Suitable models of characteristic curves are also proposed to predict the in-plane and pull-through load–displacement responses of these connections at elevated temperatures. The results from this study can be used in advanced numerical analyses to optimize the design of load-bearing LSF walls under fire conditions.

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.

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.

Pull-through capacities of cold-formed steel roof battens considering loading rate sensitivity

Static and fatigue pull-through failures of thin steel roof battens in the vicinity of batten to rafter screw connections are part of the major premature connection failures which lead to severe roof failures during high wind events. As wind speed and thereby wind uplift loading rate on a building roof varies over a wide range, the loading rate which should be used to conduct prototype roof tests is a moot point. Current wind loading standards and guidelines recommend a wider range of loading rates/frequencies in simulating static and cyclic wind loads. This could adversely affect the test results of loading/strain rate sensitive materials. Since cold-formed steels appear to be sensitive to loading rate, it is necessary to investigate the effect of loading rate on both static and fatigue pull-through capacities of cold-formed steel roof battens. Therefore, a series of static and cyclic pull-through tests was conducted at various loading rates on roof battens made of two grades (G300 and G550) and two thicknesses (0.75/0.80 and 0.95/1.00 mm). Test results showed that both static and fatigue pull-through capacities increase with increasing loading rate. To understand the loading rate sensitivity of roof battens, the effect of loading rate on the ultimate tensile strength of cold-formed steels was also investigated through a series of tensile coupon tests. Based on both pull-through and tensile coupon test results, suitable modifications and recommendations have been made to the current pull-through capacity equations and the current Low-High-Low (LHL) cyclic test loading frequency. A suitable material model is also proposed to determine the dynamic mechanical properties of cold-formed steels.

Development of Suitable Strengthening Methods for Thin Steel Roof Battens Subject to Pull-Through Failures

Failures of the connections of thin-walled steel roof battens to rafters or trusses were increasingly observed in the form of a localized pull-through failure in the batten bottom flanges during recent extreme wind events. Therefore, an extensive research study was conducted to investigate this local connection failure, and suitable test and design methods were developed to accurately determine the design pull-through capacities of roof battens. The study also showed that optimizing the batten geometry is unlikely to increase the pull-through capacity of batten connections to rafters or trusses because they essentially depend on the diameter of the screw fastener head, batten thickness, and steel ultimate tensile strength. Hence, the study was extended to develop suitable strengthening methods to delay or prevent this critical localized connection failure and thus enhance the pull-through capacity. This article first presents the investigations of some current roof construction practices recommended and used by roof batten manufacturers and builders, then proposes the details of suitable strengthening methods. Detailed experimental investigations were undertaken for this purpose, and their results and discussions are presented in this article. In addition, suitable capacity-improvement factors are proposed for the strengthening methods to accurately determine the design pull-through capacities of roof batten connections to rafters or trusses.

New test and design methods for steel roof battens subject to fatigue pull-through failures

Thin steel roof claddings and battens are widely used in low rise buildings all around the world. However, they are vulnerable to premature connection failures when subjected to severe wind uplift actions such as those induced by cyclones and storms. Current design methods exclusively depend on full scale prototype roof tests. This paper proposes an alternative design method using a simple equation for thin-walled steel roof battens subjected to fatigue pull-through failures, developed through a series of small scale cyclic wind load tests of roof battens. Since an acceptable small scale connection test method is not available for fatigue pull-through failures of roof battens, various types of small scale connection tests were initially examined to propose the most suitable test method. For this purpose, a series of constant amplitude cyclic tests was conducted using three different small scale test methods (short, cantilever and two-span battens), for a commonly used steel roof batten. Test results showed that the present state of knowledge based on static pull-through studies could lead to the use of a wrong test method in fatigue pull-through studies. This paper has used the cyclic test results from the selected small scale test method to propose a fatigue pull-through design equation. The use of the proposed design equation will lead to conservative outcomes for roof battens and will enable safe roof batten design without the need for full scale cyclic tests of prototype roof assemblies.

Numerical studies and design of thin steel roof battens subject to pull-through failures

High wind uplift loads acting on the light gauge steel roofing systems during tropical cyclones and storms frequently cause premature failures of roof connections, which lead to extensive damage to roofing systems. Such roofing system damage was observed in recent cyclones due to premature failures of steel roof batten to rafter/truss connections. They were mostly observed to be due to a localised pull-through failure in the bottom flanges of roof battens. Hence a series of small scale and full scale tests of roof battens was first conducted to study their pull-through failures. To further enhance the understanding gained from the experimental study and to predict the pull-through capacities of a wide range of roof battens, finite element models were developed and analysed using a suitable failure criterion. This paper first presents the applicability of the failure criterion for different roof batten geometries and screw fastener head sizes. Then it provides the details of a numerical parametric study conducted to study the pull-through failures of roof battens in relation to influential parameters such as batten geometry and screw fastener head sizes. Finally, this paper proposes suitable design equations and capacity reduction factors for the calculation of the design pull-through capacities of thin-walled steel roof battens.

Development of fragility curves for localised pull-through failures of thin steel roof battens

Recent extreme wind events such as tropical cyclones and severe storms have shown that thin steel roof battens fail prematurely at their screw connections to the rafters or trusses. The screw heads connecting the bottom flanges of thin steel roof battens to the rafters or trusses often pull through the roof batten bottom flanges. Since such localised pull-through failures occur in the lower level of roof connections, they often cause the loss of the entire roofing system during extreme wind events. Therefore detailed experimental and numerical studies were conducted at the Queensland University of Technology, and suitable test, design and strengthening methods were developed to accurately design the roof batten to rafter/truss connections and to enhance the roof batten performances under wind uplift loads. However, the levels of possible damages at community level due to the pull-through failures of roof battens are still unknown. Therefore fragility curves were developed in this study to determine the likely level of roof damage during extreme wind events, based on the governing pull-through failures of thin steel roof battens. Detailed probabilistic analyses and Monte Carlo simulations were conducted for this purpose. Fragility curves were also used to evaluate the effects of roof batten span and spacing and, levels of enhancement that could be achieved with the strengthening method proposed for roof battens. This paper presents the details of this study on the development of fragility curves and the results.

Experimental studies of thin-walled steel roof battens subject to pull-through failures

Despite the increasing usage of thin and high strength steel roof battens in the roof structures of low-rise buildings, recent cyclones and storms have shown that they prematurely fail at their screw fastener connections to the rafters or trusses due to the screw heads pulling through the batten bottom flanges. Such pull-through failures can lead to catastrophic failures of the entire roofing systems as observed during recent high wind events. Therefore a detailed experimental study consisting of both small scale and full scale tests was undertaken to investigate the pull-through failures of roof battens under wind uplift loading in relation to many critical parameters such as screw fastener tightening, roof batten geometry, batten thickness, steel grade, screw fastener head size and screw fastener location. Effects of underside surface and edge details of the screw fastener head, and screw fastener types were also considered. This paper presents the details of the tests conducted in this study and the pull-through failure load results obtained from them. Finally it presents the details of suitable design rules and capacity reduction factors developed in this study that can be used to accurately determine the design pull-through capacities of steel roof battens under wind uplift loads.

Development of Suitable Test Methods for the Screw Connections in Cold-Formed Steel Roof Battens

AbstractThe roofing systems of low-rise buildings are commonly made of thin, high-strength steel roof sheeting and battens. These light-gauge steel roofing systems are subjected to high-wind uplift loads during tropical cyclones and thunderstorms. In recent times, roof batten–to–rafter or truss connection failures have been identified as a major cause of severe roof failures during high-wind events. Most of these connection failures are in the form of localized pull-through failures of the bottom flanges of steel roof battens at their screw connections. The design practice at present is based on expensive and time-consuming full-scale tests or inappropriate small-scale tests. Hence, there is an urgent need to develop suitable test methods to determine the pull-through capacity of roof battens. This paper presents the details of an experimental study undertaken to investigate pull-through failures of light-gauge steel roof battens using both full-scale and small-scale tests. The investigation showed that t...

Wind uplift strength of trapezoidal steel cladding with closely spaced ribs

When crest-fixed thin trapezoidal steel cladding with closely spaced ribs is subjected to wind uplift/suction forces, local dimpling or pull-through failures occur prematurely at their screw connections because of the large stress concentrations in the cladding under the screw heads. Currently, the design of crest-fixed profiled steel cladding is mainly based on time consuming and expensive laboratory tests due to the lack of adequate design rules. In this research, a shell finite element model of crest-fixed trapezoidal steel cladding with closely spaced ribs was developed and validated using experimental results. The finite element model included a recently developed splitting criterion and other advanced features including geometric imperfections, buckling effects, contact modelling and hyperelastic behaviour of neoprene washers, and was used in a detailed parametric study to develop suitable design formulae for local failures. This paper presents the details of the finite element analyses, large scale experiments and their results including the new wind uplift design strength formulae for trapezoidal steel cladding with closely spaced ribs. The new design formulae can be used to achieve both safe and optimised solutions.

A strain criterion for pull-through failures in crest-fixed steel claddings

Crest-fixed steel claddings made of thin, high strength steel often suffer from local pull-through failures at their screw connections during high wind events such as storms and hurricanes. Adequate design provisions are not available for these cladding systems except for the expensive testing provisions. Since the local pull-through failures in the less ductile steel claddings are initiated by transverse splitting at the fastener holes, numerical studies have not been able to determine the pull-through failure loads. Numerical studies could be used if a reliable splitting criterion is available. Therefore, a series of two-span cladding and small scale tests was conducted on a range of crest-fixed steel cladding systems under simulated wind uplift loads. The strains in the sheeting around the critical central support screw fastener holes were measured until the pull-through failure occurred. This paper presents the details of the experimental investigation and the results including a strain criterion for the local pull-through failures in crest-fixed steel claddings.

Finite element analysis and design of crest-fixed trapezoidal steel claddings with wide pans subject to pull-through failures

Crest-fixed trapezoidal steel claddings made of thin, high strength steels often suffer from local pull-through failures at their screw connections during high wind events. Loss of claddings often leads to a progressive collapse of the entire building. At present the design of these cladding systems is mainly based on laboratory testing. Since the local pull-through failures in these less ductile high strength steel claddings are often initiated by transverse splitting at the fastener holes, analytical studies have not been able to determine the pull-through failure loads accurately. However, an appropriate splitting/fracture criterion has been developed recently using a series of large scale experiments of crest-fixed steel claddings. A finite element model has then been developed for trapezoidal steel cladding with wide pans that included the new splitting criterion and other advanced features including geometric imperfections, residual stresses, buckling effects, contact modelling and hyperelastic behaviour of neoprene washers. A series of parametric studies considering the effects of material properties and geometric parameters of trapezoidal claddings was undertaken using finite element analysis. Design formulae for the local failure loads were then derived for design and optimization purposes. This paper presents the details of the numerical study, the results and design recommendations.