physical test data for the appraisal of the design procedures for bolted - mttram & turvey.pdf
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Physical test data for the appraisalof design procedures for bolted
joints in pultruded FRP structuralshapes and systemsJ T Mottram1 and G J Turvey2
1 University of Warwick, UK2 University of Lancaster, UK
SummaryA review is presented of the tests undertaken tocharacterize bolted joints (no adhesive bonding)
for pultruded fibre-reinforced plastic (PFRP)
structural shapes and systems. The review is
written with regard to the appraisal of existing
connection design procedures for plate-to-plate
bolted joints. It is shown that 15 uncoordinated
series of tests on single-bolt and multi-bolt double
lap joints provide 800 ultimate strength results.
Each of the series of tests had different objectives
and so different joint variables were studied. This
reflects the current state of guidance on joint
design and installation in pultruders design
manuals and elsewhere, which is shown to be
limited and inconsistent.
By rationalizing the number of variables the
authors have tested a further 900 joints in order
to generate a larger database of strengths and
modes of failure, which may be used to appraise
connection design procedures, such as the Hart-
Smith and EUROCOMP Design Code and
Handbook simplified and rigorous methods.
Observations are made on the findings from 16
series of tests with respect to the current state of
design of PFRP plate-to-plate bolted joints.
Key words: pultruded FRP structurals; bolted joints; test data
Prog. Struct. Engng Mater. 2003; 5:195222 (DOI: 10.1002/pse.154)
Introduction
Pultruded FRP (PFRP) structural shapes and systemsconsist of thin-walled composite profiles havingoverall dimensions up to 1000 mm (typically 300 mm
or less) and wall thicknesses up to 25 mm (typicallyup to 13 mm). They have prismatic section andfirst-generation structural shapes are I, angle, channeland box[13]. Reinforcement is E-glass fibre in twoforms, namely unidirectional rovings and continuousfilament (or strand) mats. The matrix is a thermosetresin such as polyester or vinylester, which oftencontains filler and other additives. PFRP members areused in primary load-bearing structures[4]withmechanical fastening (fabricators often choosestainless steel bolts) being the preferred method ofconnection[5]. Primary joints are expected to provide
strength and stiffness to the PFRP structurethroughout its life[6]. Failure of such joints wouldconstitute major structural damage and be hazardousto life. The safe and reliable design of bolted joints istherefore clearly a priority.
The EUROCOMP Design Code and Handbook[6]isan independent source of guidance for the design ofload-bearing structures of Glass Reinforced Plastic(GRP) materials. The writers intended itsrecommendations to be suitable to PFRP shapes and
systems. Section 5 in the Code and Handbook provideguidance for connection design by bonding andmechanical fastening. Section 5.2 covers mechanicallyfastened joints with the principal methods ofconnection by bolts and rivets. Clause 5.2.2.2 statesthat the performance requirements of bolted andriveted joints in shear can be satisfied either by testingor by calculation. The following serviceability limitstate (SLS) and ultimate limit state (ULS) criteria givenin[6], are performance requirements that shall besatisfied:
a) SLS criteria:
* deflection due to excessive deformation offastener holes;
* onset of nonlinear loaddeflection behaviour ofjoint under constant load;
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* separation (at edges) of components or spliceplates fastened together;
* weather tightness (and/or water tightness) ofjoint;
* fibre debonding or matrix cracking under loador due to assembly techniques;
* durability of unsealed edges,* fatigue endurance of GRP and fasteners.
b) ULS criteria:
* ultimate load capacity of complete joint;* static failure of joined parts;* progressive failure of hole edge leading to
permanent hole elongation greater than 4% ofthe hole diameter;
* fatigue endurance of laminate and fasteners.
Turvey[4]has provided a brief overview of some ofthe more noteworthy PFRP structures. In his paper he
emphazises the extensive use of bolting as the mainmethod of connection for structural shapes. Hisoverview focuses on moment connections, which arerequired, for example, to join beam and columnmembers. Attention is also given to plate-to-plateconnections where the loading is in the plane ofsymmetry and load transfer can be assumed to be inbearing. Such a connection could be used, forexample, in splice and gusset plate joints in trusses [4].At the time of writing Turvey observed that thequality of the plate-to-plate joint test data was veryvariable and that the series of tests were limited to a
small numbers of joint tests. The lack of coordinationand cross-correlation was felt to have reduced theirvalue somewhat.
Since Turveys overview paper[4]appeared theauthors have completed a project on the structuralintegrity (SI) of bolted joints in PFRP structures. Itconcerns PFRP plate-to-plate joints with single-boltand multi-bolt configurations. Fig. 1 shows a 2 2multi-bolt joint with the various geometric ratiosdefined. Staggering the bolt columns is an option indesign. If a joint has a single bolt, the plates widthW2S. In this paper the completed project will be
known as the SI project. Its objectives were to:
* test virgin/degraded double lap bolted joints withpractical details; loading was concentric and themain forms of material degradation were roomtemperature/wet and hot/wet conditioning;
* start to understand the physical response anddamage mechanisms in joints under normal/adverse conditions;
* relate measured strengths and damage progressionto predictions by advanced finite element analysis;
* transform damage tolerant design procedures[6,7],used with composite materials in the aerospacesector, into joint design guidance for use inconstruction.
In this paper consideration is given to joint test datafor the design of plate-to-plate bolted connections[6].
In-plane loading can be concentric or eccentric innature. The material orientation of the joined PFRPplates is important since their mechanical propertieschange significantly with orientation[13]. In thepultrusion process the direction of pull is thelongitudinal direction, while the direction normal tothis is the transverse direction. The unidirectionalroving reinforcement is aligned with the longitudinaldirection and so mechanical properties are higher inthis direction. The lower strength and stiffnessproperties in the transverse direction are due to the
much lower volume fraction of glass fibres aligned inthis direction. In this paper the 08 orientation refers tothe longitudinal direction, while the transversedirection is the 908 orientation. Off-axis anglestherefore range between these limits.
By co-ordinating the work at the two Universitycentres of Lancaster (LU) and Warwick (WU), andincluding previous results from LU, there are nowsome 1100 double lap-joint test results in the largerdatabase, many with geometric ratios andenvironmental conditioning not previously tested.Not only are ultimate strengths/loads and modes of
failures available from these tests, but also initialfailure strengths/loads. This provides a wide-rangingand consistent body of data for the community toappraise the available design procedures, examinetest variability and analyse for cross-correlation. The
Column
of bolts
E/D
P/DP/D S/DS/D
D
First bolt row
Second bolt row
Concentric tension
Fig. 1 Plate-to-plate joint geometry definitions, D is boltdiameter,E is end distance, S is side distance, and Pis pitchdistance
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results of the SI project will make an invaluablecontribution to the characterization of PFRP boltedjoints. It is not only relevant to bolted joints for thecurrent range of pultruded profiles, but also providesunderpinning knowledge for similar mechanicallyfastened joints using second-generation profiles,
which are now reaching the market place as thepultrusion industry diversifies.The papers contents are presented in three parts. In
the first part current practice in Europe and Americafor PFRP bolted connections is reviewed inconjunction with practice in structural steelwork. Thesecond part presents basic details of the previous15 series of tests carried out to determine modes offailure, strengths, and occasionally stiffnesses ofbolted plate-to-plate joints. Part three presents therationale behind the 900 joints tests of the SI project.Where relevant, links are made between the test data
and the current rudimentary design specification, andwith the need to appraise and further developconnection design procedures, such as the Hart-Smith[7]and EUROCOMP Design Code andHandbook simplified and rigorous methods[6].
Review of current practice
STRUCTURAL STEELWORKPrior to summarizing the various recommendations
for current practice with PFRP bolted joints, it isappropriate to summarize what is current practicewith joints in structural steelwork. Specifications forbolted connections in steelwork as practised inEuropean countries are available[8]. Black ISO metricbolts are the most commonly used. With regard to thejoint detailing shown in Fig. 1, the geometric ratiosE/D and S/D should not be less than 1.2 and P/Dshould not be less than 2.2. The full bearing value of abolt through a connected plate cannot be developed ifthe end distance is less than 2D. For end distanceslying between the minimum of 1.2D and 2.2Dthe
bearing value is reduced proportionally. In generalsituations a clearance hole is present, often equal tobolt diameter plus 2 mm. For bolt diameters 424mmthe hole size is equal to bolt diameter plus 3 mm. Boltsfor bearing-type connections can be used with orwithout pre-load. There are also high-strength frictiongrip bolts where slip in the connection is notpermitted at the SLS or ULS, and for these joints theload is carried entirely by static frictional force (thereis no bolt bearing). The minimum end distance E forthe full resistance is now 3D. Fitted bolts can be usedwith the corresponding holes in steel members in
agreement with ISO fit b 11/H 11[8]. Only pre-loaded(torqued) bolts can be used when the joint is to besubjected to fatigue loading.
American practice is similar to that found inEurope. For joints that are not slip-critical no pre-load
is required. Installation of high-strength bolts toASTM A325 (types 13) required a high level ofpre-load prior to 1985, regardless of whether or not itwas necessary. Nowadays, when these bolts are usedin bearing-type joints they need only be tightened tothe snug-tight condition. This condition is defined as
the tightness that exists when all parts in a joint are infirm, but not necessarily continuous contact. Togenerate a pre-load of 70% of the specified minimumtensile strength of the bolt, the current specificationrequires half-a-turn of the nut from the snug-tightposition (the actual degree of the turn is dependent onthe bolt length/D ratio and the disposition of outerface of the bolted parts). This specification replacesthe need to apply a specified torque since it gives toomuch variability in bolt tension. The clearance holesize is constant at 1.6 mm (1/16 in). Hardenedwashers to ASTM F436 with an outer diameter twice
the bolt diameter (same as in Europe) are not requiredwhen A325 bolts are installed by the turn-of-nutmethod; they are if these bolts are tightened by thecalibrated wrench method.
STRUCTURAL PFRPFor PFRP shapes and systems several pultruders havewritten and maintained their own design manuals[13],based on in-house testing and a national level ofknowledge and understanding. Each manual
provides specific recommendations for boltedweb-cleat beam-to-column joints and other simpleframe joints[5]. Joint details[13]often mimic equivalentsimple joints in structural steelwork[4]. The resistanceof web-cleat joints is, however, not governed by therecommended joint geometric ratios in Table 1. Thetable presents suggested minimum geometric ratiosfor design of the strongest plate-to-plate boltedjoints; the material orientation is not specified. Thegeometric ratios are defined in Fig. 1. In what followsit is assumed that the P/D ratios are the same for thebolt rows and columns. The geometric ratios in Table
1 are known to be valid for room temperature (RT)conditions; RT is taken to be 20258C.
The design manuals of the US companiesStrongwell[1]and Creative Pultrusions Inc.[3]use theminimum geometric ratios given in the AmericanSociety of Civil Engineers Manual 63[9]. It is believedthat the writers of Manual 63 based these on thosegiven in the 1960 marine design manual for GRPs byGibbs & Cox Inc.[10]. These recommended minimumratios are for hand lay-up GRP materials (isotropic inthe plane) of unknown thicknesses and unknown boltand joint details. Therefore, the actual minimum
ratios might be expected to change when the joints areof PFRP, as many variables will now be different.Ratios from Fiberline Composites A/S[2], given inTable 1, are identical with those given in the DanishStandard DS456. Company and external laboratory
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tests have confirmed these ratios; none of the test datahas been made public.
The objective of specifying the minimum geometricratios given in Table 1, when there is a single-bolt, is tohave the strongest joint failing in the bearing mode(this failure mode is often considered benign, becauseit is characterized by progressive damage growth[5,6]).
Fig. 2 shows the fracture patterns (dashed lines) ofsingle-bolt joints failing in bearing and the otherdistinct modes known as cleavage, shear-out and net-tension. These four modes are for concentric tensionloading and a PFRP orientation of either 08 or 908.Bearing is characterized by the PFRP materialcrushing and delaminating in front of where the boltbears into the plate. Depending on the joints detailsits integrity may remain while this damage regiongrows, and the joint is still able to carry a substantialload. As shown in Fig. 2 the fracture patterns of theother three modes are characterized by significant
material rupturing, which is likely to occur over ashort period of time, and results in a joint that cancarry, post-failure, little or no load. Except for bearing,the modes are deemed unacceptable in connectiondesign because of the brittle nature of failure[6]. Bolt
shear or pull-out failures[6]do not need to beconsidered when steel bolts are used, because the boltdiameter is normally large enough to prevent suchfailures.
It is instructive to summarize and comment onother differences in the limited practical guidancegiven in the pultruders design manuals. Strongwell[1]
include tables of allowable loads for bolt bearing andshear failures. The allowable loads for their own FRPFIBREBOLT1 assume a factor of safety of four. Thetorque applied to these FRP bolts is not proportionalto the unthreaded cross-sectional area, and maximumtorques of 10.9, 21.7 and 32.5 N m are recommendedfor bolt diameters of 12.7 mm (1/2 in), 16.3 mm(5/8 in) and 19.05 mm (3/4 in). The shear loads givenin[1], for structural (unless the first S is for stainless)steel threaded bolts are of unknown origin. Holeclearance is given as 1.6 mm (1/16 in) in the notesaccompanying the engineering drawings of details of
web-cleat frame connections. The type, size or use ofwashers is not given.
Creative Pultrusions Inc.[3]gives specific guidancefor web-cleat frame connections joining their standardshape structural members. Like Strongwell, this
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Table 1 Suggested and experimentally determined minimum joint geometric ratios for PFRP bolted joints (at room temperature and noenvironmental conditioning)
Reference Plate
thickness t
(mm)
Bolt
diameter/
plate
thickness
D/t
Edge
distance/
bolt
diameter
E/D
Side
distance/
bolt
diameter
S/D
Width
distance/
bolt
diameter
W/D
Pitch
distance/
bolt
diameter
P/D
Clearance
hole size
(mm)
Washer
diameter/
bolt
diameter
[1] 6.3519.05 1.03.0 2.04.5 (3.0)1 1.53.5 (2.0)1 4.05.0 (5)1 4.05.0 (5)1 1.6[2] 320 0.516.0 2.5, 3.5 2.0 44.0 44.0 1.0 2.0[3] 6.3512.7 Unspecified 2.04.5 (3.0)1 1.53.5 (2.0)1 4.05.0 (5.0)1 43.0 1.6 2.5
[6]2 Unspecified 1.01.5 43.0 4 0.5W/D 4 3.0 43 (4)1 50.05D 42.0
[13]3 6.35 1.6 3.0 Single-bolt 4.0 Close fit
(0.10.3)
[14]3 9.5319.05 0.51.0 5.04 Single-bolt 5.04 1.6
1Recommended minimum design value2General glass-fibre-reinforced plastics (including PFRPs)3From joint tests with tensile load in direction of pultrusion (PFRP material orientation is 08)4D is hole diameter (bolt diameter and hole clearance)
Bearing Shear-out Net-tensionCleavage
Concentric tension
Resultant boltforce
Fig. 2 Failure modes in single-bolt PFRP joints under concentric tension
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pultruder recommends clearance holes equal to thebolt diameter plus 1.6 mm. Based on steel constructionin the USA, the manual recommends high-strength(minimum 700 N/mm2) steel bolts to A325 with gradefive coarse threads. For a 12.7 mm bolt diameter, thespecified low torque is 39 N m (37.5% of bolt proof
load) and the high torque is 77 N m (75%). Thisincreases to 77 and 113 N m, respectively, for a16.3-mm-diameter bolt. This guidance, of unknownorigin, goes against the current USA specificationwhen using A325 bolts to join steel parts. There is areference[3]to single-bolt joint tests performed withsteel grade 8 oversized washers (2.5 times holediameter). Such tests were used to construct a tablewith bearing strengths defined by the 4% holeelongation (in accordance with ASTM D5691). Thesehole deformation strengths are typically 36% of thematerial nominal compressive strength (i.e. 210 MPa)
in the direction of pultrusion.Fiberline Composites A/S in Denmark givesguidance for general practice. For plate-to-plateconnection design the manual[2]covers flat plates(thicknesses 320 mm) fastened by A4 stainless steelbolts (M6 to M48) in a lap-joint configuration. Simpledesign equations, based on bearing, or net-tension orshear-out failure are given to determine joint strength.Two tables give bearing capacities at the ULS in the 08and 908 orientations, with a factor of safety of three.These tables enable many joint configurations to bedesigned from their structural shapes. Hole clearance
is 1 mm for M6 to M48 bolts and the steel washersunder nut and bolt head are twice the bolt diameter.No bolt torque is specified in the manual (on site atorque 4100 N m is applied to M16 bolts).
Although none of the three manuals[13]specifiesthat the shank in contact with the PFRP material mustbe plain, the authors understand that this is standardpractice when steel bolts are used. Such practice is notpossible with Strongwells FRP bolts (FIBREBOLT1)since they have a continuous moulded thread alongtheir whole length.
The EUROCOMP Design Code[6], in Clause 5.2.2.3,
provides general design requirements for glass-reinforced plastics, which have their roots in theaerospace industry. Prior to presenting therecommended GRP minimum geometric ratios (seeTable 1), it needs to be understood that Clause5.2.2.3(2) states that PFRPs do not always have a fibrereinforcement construction which is ideal. By idealthe code-writers are suggesting that single-bolt andmulti-bolt GRP joints, with suitableE/D, S/D and P/Dratios, will fail in bearing with a high bearing strength(i.e. a high joint load). The guidance is seen to be validfor other GRP materials and should therefore be used
with caution when the connected parts are of PFRP.Definition Clause 5.2.2.1, given in[6], introduce thesingle-bolt joint failures depicted in Fig. 2 (however itdoes not include cleavage) and says in 5.2.2.1(7)P thatShear-out failure also occurs in highly orthotropic
laminates, such as pultruded laminates,independently of the end distance. Clearly, if thisEUROCOMP definition is always true it precludesthe use PFRP bolted joints in all situations.
We turn now to the design requirements given inClause 5.2.2.3 and their implications for PFRP joint
details. Referring to Fig. 1 and Table 1 the minimumvalues ofE/D and P/D are 3, and S/D is1.5 (S/D 5 P/D). The joint should be designed,detailed and formed so that the fasteners (steel boltsthat should be self-locking or fitted with lock nuts,type(s) not specified) are tightened to a pre-set torque(not specified) to provide substantial clamping andlateral restraint around the bolt holes. However, thestrength should be assumed to be that correspondingto finger-tight conditions (not specified), in whichthere is little or no lateral restraint; this is to allow forthe effects of creep, cyclic loading, fatigue and
vibration or their combination. The hole diametershould not be less than the thickness of the thinnestpart being joined and be no more than one-and-a-halftimes the thickness (t) (1 4 D/t4 1.5). Any clearanceshould allow the bolt to be inserted easily, even whenall of the other bolts are in place and finger-tight, butshould not be more than 5% of the bolt diameter. Boltsshould be as tight as possible in the holes withoutcausing damage to the GRP parts. Great care isrequired, therefore, in forming the holes. Washersshall be fitted under the head and nut of the bolt andshall have an internal diameter equal to the least
diameter of the hole(s) through which the bolt passes.The least external diameter of the washer shall not beless than twice the larger or largest diameter of theholes. The thickness of the washer shall be sufficientto provide an even surface pressure over the outerGRP surfaces. Preferably, the thickness should be notless than 20% of the thickness of the outermost partthrough which the bolt passes.
There are further requirements given in 5.2.2.3 thatare adopted directly from practice in the aerospaceindustry. It is seen that this guidance iscomprehensive and in a number of respects
corresponds to what is used in structural steelwork.Not many of the detailed requirements are to befound in the pultruders design manuals[13], nor is itknown whether they are appropriate for the design ofPFRP bolted connections.
What is clear from the review of current PFRPpractice is that it is neither coherent nor recognized,and that it is loosely based on practice in steelworkconstruction. By way of very limited, andunpublished, in-house joint testing, two of thepultruders design manuals[1,3]do provide engineerswith tables giving allowable bearing strengths for
PFRP plate-to-plate joint design. Guidance in the threemanuals[13]and EUROCOMP Design Code andHandbook[6] is found to be different and not oftenbased on a sound scientific understanding gainedfrom physical testing and numerical modelling. The
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specific requirement, derived from the aerospaceindustry, to minimize (if not to eliminate) the holeclearance[6]is the most noteworthy difference fromwhat is recommended by pultruders[13]and what isgenerally practised in steelwork construction.The question as to whether or not bolts should be pre-
loaded on installation is another important issuewhich, as the summary shows, needs to be betterunderstood if we are to have reliable designprocedures for PFRP joints.
Single-bolt and multi-bolt joint tests:previous series
As mentioned in the Introduction and the Review ofCurrent Practice, relevant and reliable data (strengthsand modes of failure) from joint tests are required to:
* establish specified minimum joint configurationdetails, such as the geometric ratios given inTable 1;
* underpin the characterization of PFRP joints;* assess and refine connection design procedures, as
given in[6]and [7].
Each joints loaddisplacement response and itsmode(s) of failure will be dependent on its specificdetails and environmental conditioning. Fig. 3 showsthe two most common forms of loaddisplacement(stroke) curves from PFRP single-bolt and multi-bolt
joints, tested under stroke control. Some joints fail atthe ultimate load without any significant warning.This brittle loaddisplacement response is shown inFig. 3(a). Note that the ultimate load is attained whenthe initial failure load is reached and damage occurs.The ultimate failure load might occur at the same orlower load, and at a higher stroke; such a joint doesnot possess any damage tolerance[5, 6]. Other joints,however, do suffer initial damage at a load wellbelow that for ultimate failure. Their more benignloaddisplacement response is shown schematicallyin Fig. 3(b), whereby once damage (e.g. due to
bearing) occurs there is a reduction in joint stiffness
up to a higher ultimate load. Such joints do possessdamage tolerance and their design is more suited tothe structural integrity design procedures, such as thesimplified and rigorous methods described inEUROCOMP Design Code and Handbook[6].
In the context of PFRP bolted joints, damage
tolerance means that there is progressive damagegrowth, often associated with bolt bearing when theload is higher than that which causes initial materialdamage.
What makes the scope of joint testing enormousand possibly impractical to cope with is the largenumber of joint variables that need to be studied tocover those found in practice. Inherent test variabilityis another important factor, not least because PFRPmaterials can have a fibre reinforcement constructionthat is nonuniform. The influence of this factor will beshown later. Ideally, there should be a consensus on
what is a preferred test methodology; to date there isno recognized test standard available to characterizePFRP bolted joints.
Initial variables to be studied ought to include: thetype of loading, the materials (bolts and PFRP); theplate thicknesses and orientations, the jointgeometries (see Fig. 1); the bolt arrangements and theinterface conditions (washer, torque, and clearancehole). To include data that characterizes the long-termdurability and structural integrity of PFRP joints newvariables to be added to any initial set are likely to bethe serviceability (SSL) loading (creep and cyclic) and
the working environment (e.g. hot/wet, etc.).Before we can embark on appraising, and furtherdeveloping design procedures it is necessary to knowthe quality and limitations of the test data, if suchwork is to succeed. In this paper nine tables arepresented that report, in a single source, the variablesstudied in 16 series of tests on double lap-joints usingPFRP flat sheet materials[1127]. Loading is concentricand, except as part of one series[15], always tensile. It isusually applied short-term, by way of a monotonicstroke rate. The number of joints tested are given inthe tables in parentheses and italic type, e.g. (25)
represents 25 tests. In the tables a question mark
Load
Load
Stroke Stroke
initial failure
ultimate failure
initial failure
ultimate failure
(a) (b)
Fig. 3 Typical loadstroke characteristics for single-bolt and multi-bolt PFRP joints under stroke controlled concentric tension:(a)brittle load-displacement characteristic, no damage tolerance; (b) benign loaddisplacement characteristic, damage tolerance
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identifies when that column entry has not beenreported in the source reference. The number ofquestion marks weakens the quality and increases thelimitations of the test results with respect to theobjectives listed above. Joint strengths (andsometimes stiffnesses) derived from the test
loaddisplacement responses are to be foundelsewhere[1125], and were used to constructTables 25. The results from many of the tests inTables 69 have not been reported at the time ofwriting this article.
PRE-SI PROJECT JOINT TESTSTables 2 and 3 present, respectively, a summary of theconcentric single-bolt and multi-bolt tests prior to thestart of the SI project. These 15 series of tests[1125]were unco-ordinated and it is therefore unsurprising
to find that their scope is very wide ranging. All of thejoints were tested, accept for those by Erki[15], in thedouble lap arrangement with either the central orthe outer two plates of PFRP, and, respectively, thetwo outer plates or the central plate of structuralgrade steel. It is noteworthy that the tests by Erki[15]had the only joints with all three plates of PFRP.
Table 2 gives information on the 10 series of single-bolt tests on 640 joints, while Table 3 gives the sameinformation on 5 series of multi-bolt tests on 160joints. Tables 49 present equivalent information onabout 270 single-bolt and about 640 multi-bolt joint
tests from the SI project. To date, therefore, this gives atotal of about 1710 strength (and mode of failure)data points, split 910: 800 between single-bolt andmulti-bolt configurations. Most of the 16 series of testshad a degree of replication of two or three joints perbatch.
Each table summarizing the joint tests isconstructed of 12 (single-bolt) or 13 (multi-bolt)columns. The columns are numbered in the first rowof a table. The reference number for the source ofinformation is given in column 12 or 13 (last), togetherwith the total number of joints tested. Columns 1 and
2 define the PFRP flat sheet material and the nominalor measured thickness(es) used. The PFRP materialswere from three pultruders, with by far the majorityof the tests using Strongwell EXTREN1 500 Series flatsheet with nominal thicknesses of 6.35, 9.53 and12.7 mm[1]. It is to be noted that the FibreforceComposites Ltd. materials labelled Grey 2, Yellowand Grey 1 are custom flat sheets[12, 21]. Columns 36present information on the bolts and their installation.Except for the tests by Erki[15] (fifth series in Table 2)the bolts were of structural steel grade. The range ofclearance hole sizes is large, varying from tight fitting
(say 0.10.3 mm clearance) to 6.35 mm[17]. Column 6gives the bolt torque, or torques when this was avariable to be studied. Irrespective of the boltdiameter the torque was often either zero(pin loaded), or finger-tight (believed to be
53 N m). The washer size is relevant only if the outerplates are of PFRP[14, 15], or if used to separate theinner PFRP plate from the outer plates[12]. Column 7shows that 15 series had the material orientation at 08to the direction of loading. Eight series had thematerial orientation at 908 and of these six also tested
with material at 458
and other material orientations. InTables 2 and 46, columns 8 and 9 give the geometricratios W/D and E/D (see Fig. 1). E/D values inparentheses and underlined are for the single W/Dvalue given in bold type. Column 10 in Tables 3 and79 gives theS/Dratios in the multi-bolt tests (Fig. 1).Column 10 (single-bolt) and 11 (multi-bolt) give, whenavailable, the stroke or load rate, and information onthe environmental conditioning. Prior to the start ofthe SI project, only 30 of the 800 joint tests reported inTables 2 and 3 had been subjected to wet ageing [19]before the loading was applied at RT. None of the
series listed in Tables 2 and 3[1125]include tests onjoints whose temperature is above RT. For multi-boltjoints, column 12 also presents the constant P/Dratioin Table 3 and the variable P/D ratios in Tables 79.Finally, column 11 (single-bolt) and 12 (multi-bolt)give information on the joint configurations and inTables 2 and 3 a breakdown of the number of jointsper group of variables.
SINGLE-BOLT TESTS
Regarding the relevance of the test data in[1120]to ourprogress in appraising and developing designprocedures, a number of points can be made from thebasic details given in Tables 2 and 3. Returning toTable 1 the minimum geometric ratios proposed byRosner & Rizkalla[14]and Cooper & Turvey[13] weresupported by their single-bolt tests, in which the jointvariables E/D and W/D were varied from 1.33 and13.33 (third and fourth row entries in Table 2). Bothseries of tests used EXTREN1 500 Series flat sheetwith a polyester matrix. To explain why the two seriesrecommend different minima (and different from
those given in the Strongwell design manual[1]), weneed look no further than the differences in the testset-up. Rosner & Rizkalla used PFRP of thicknesses9.53 mm (3/8 in), 12.7 mm (1/2 in) and 19.05 mm(3/4 in), with a bolt hole 1.6 mm (1/16 in,[1]) largerthan the 19.05 mm diameter of the high-strength plainshank steel bolt. The double lap tests had two outerPFRP plates and an inner steel plate and standardsteel washers of outer diameter 2D were used. Tocomply with Strongwells design manual[1]specification for their proprietary FIBREBOLT1 studsand nuts, a constant torque equal to 32.5 N m (24 ftlb)
was applied to the 19.05 mm diameter steel bolts. Norecommendation for bolt torque is given byStrongwell[1]for steel bolts. They tested at a strokerate of 2 mm/min, loading at 08, 458 and 908 to thedirection of pultrusion.
PULTRUDEDFRP STRUCTURAL SHAPES AND SYSTEMS 201
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Tab
le2Summ
aryo
fpreviousconcentrical
lyloadedsingle-
boltdoub
lelap-jointtestswit
hPFRPflatsheetmateria
l
[1]
Plate
[2]
Thickness
(mm)
[3]
Bolt
diameter
D(mm)
[4]
Hole
cleara
nce
(mm)
[5]
Washer
size
(mm)
[6]
Bolt
Torque
(Nm)
[7]
Orienta-
tion(0ois
directionof
pultrusion)
[8]
W/D
[9]
E/D
[10]
Testrate
(tempera-
ture)
[11]
Joint
configura-
tions
(No.oftests)
[12]
Reference
Creative
Pultrusions
Inc.
12.7
A307mild+
high-s
trengt
h
12.7
(shank
incontact)
Interfe
rence
fit
2.7D
2o
ff
13.5
0,40
.8,
81.6,
112.4,
163.4
0 90
4 4
1,2,3,4,6
1,2,3
? stro
ke(RT)
Outer
(?thic
kness)a
nd
innerplatesin
ner
plate
PFRP
[11]
Noreplication
(20)
Total
No.
(20)
Non-stan
dard
Fibreforce
Composites
Ltd.
(not
given)
9.53
?
2.2D
Smal
l
finger-t
ight?
For
bearing
failure
Forbearing
failure
Threegroups(12)
Sizeof
clampingarea
[12]
Grey
2
6
0
7.34
4.19
0.5mm
/min
(RT)
1.Tig
ht-f
itting
was
her
(between
PFRPan
do
uter
plates
)
Yel
low
?
2.Stee
lplates
coveringal
l
potentia
ldamage
area
Grey
1
?
3.Smoot
h
composite
plates
(as2
.)
Y2.10
1.05,1.57
,
2.1,3
.15,
4.2
Outerplates
?
stee
l(?thickness)
innerplatePF
RP
Y3.15
1.05,2.1,
3.15,4.2,
6.3
Yan
dG2
Y4.0
1.05,2.1,
3.15,5.2,
6.3,7
.34
0
G23.15
4.2,5
.2,
6.3,
8.4,10.5
3per
batc
h
(95+3)
G24.72
5.2,6
.3,
7.3,9
.44,
13.6
G27.34
6.3,8
.4,
9.44,10
.5,
12.6,
14.7
Total
No.
(110)
Continued
NEW MATERIALS IN CONSTRUCTION202
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Strongwel
l
EXTREN1
500series
polyester
6.35
M10Gra
de
8.8
Tig
htfit
(0.10.3
)
None
0,3,30
(torque
wrenc
h)
0
2,3,4,5,7
4,4,4
,
(1.5,2
,
3,4,5
),4
Outerplates
?
stee
l(?thickn
ess)
innerplatePF
RP
[13]
Shan
kin
contact
2,4,6,8,10
5,5,5
,5,
(2,3,
4,5,6)
10kN/min
2,4,6,8,10
6.5,6
.5,
6.5,6
.5,
(2,3,
4,5,
6.5)
(RT)
3per
batc
h(8
1)
Total
No
.(81)
Strongwel
l
EXTREN1
500series
polyester
9.53
12.7
19.0
5
19.0
5
high-s
trengt
h
shan
kin
contact
1.6
(initial
slipof
1.1mm
)
? Photo
shows
was
her
impression
32.5
as
specified
for
FIBREBOLT1
boltan
d
nutof
3 4inf[1]
0 (22)
0,45
,90
(20
,20,20)
0 (20)
Complexmatrixo
fvalues
1.33
13.33
20specimens,
withsamegeometricratios
forthe
fivetestgroup
s
0.01mm
/s
(RT)
Outerplates
PFRP
andinnerplate
?
stee
l(?thickn
ess)
[14]
Noreplication
(102)
Tota
lNo.
(102)
?Strongwel
l
EXTREN1
500
seriespo
lyester
12.7
19.0
5
FIBREBOLT1
mildstee
l
threadedan
d
shan
k[1]
1.6
None
?
Finger-t
ight
ortig
htened
byhalfturn
ofnut
0,45
,90
Notspecified}
estimated
fromphotos
2.5mm
/min
(RT)
As
Rosner
andRiz
kalla[14
]
Inner
PFRP
plate
25.4
mm
thic
k
[15]
8(Tension
)
3(T)
Tension
(28)
Total
No
.(63)
8(Comp.
)
?(C)high
Compression
(35)
?
3
6stee
l?
Tight
fit
?
?
0,90
2to
7
2
1mm
/min
(RT)
Outerplates
?
stee
l(?thickn
ess)
innerplatePF
RP
2per
batc
h(2
0)
[16]
Total
No
.(20)
No
loadsreporte
d
EXTREN1
500series
polyester
9.53
12.7
shan
kin
contact
06.35
?
Finger-t
ight
0
8
8
?
Effectof
hole
clearance
(25)
[17]
Total
No
.(25)
Strongwel
l
EXTREN1
500series
polyester
6.35
M10
Gra
de8.8
Tig
htfit
(0.10.3
)
None
Finger-t
ight
(about
3)
30
4,6,8,10
6,6,6
,
(3,4.5
,6)
10kN/min
Outerplates
?
stee
l(?thickn
ess)
innerplatePF
RP
[18]
shan
kin
contact
45
4,6,8,10
6,6,6
,
(3,4.5
,6)
(RT)
Threeper
batch
(81)
Total
No
.(81)
90
4,6,8,10
6,6,6
,
(3,4.5
,6)
Continued
PULTRUDEDFRP STRUCTURAL SHAPES AND SYSTEMS 203
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? EXTREN1
625series
viny
lester
6.35
12.7
stee
l
ASTMA325
shan
kin
contact
1.6
Pin-
loaded
,
nowas
her
(spacers
?)
Pin-
loaded
0
5
3,4,5
0.64mm
/min
(RT
,dry
)
Outerplates
76.2
mmstee
l
(6.4
mmthickness
)
innerplatePF
RP(15)
[19]
30,4
5,90
6
5
(RT
,dry
)
(5,
4,5)
0,90
0
5 5
5 5
(22oCwet
)
(RT
,humid
)
Submerge
din
distilledwater
171days
(5,5
)
Moisture
ASTMD5229
,
138days
(0.57%)(5)
Glavanize
d
USS2.5mm
thic
k
35.6
mm
diameterplaced
oneithersi
de
ofPFRPplate
Finger-t
ight
0 30,4
5,60
,90
5 6
3,4,5
5
(RT
,dry
)
(15)
(4,
4,4,
5)
0,90
0
5 5
5 5
(22oCwet
)
(RT
,humid
)
Submerge
din
distilledwater
171days
(5,5
)
Moisture
AST
M
D5229
,138days
(0.5
7%)(5)
(61dry,
30
wet
)
Tota
lNo
.(91)
?
9.53
12.7
stainless
stee
lshan
k
incontact
Close
fit
5
0.8
?
0to
34J
(Nm
)(6
.8,
13.6,
20.3,
27.1,
33.9
J)
?orientation
0,15
,30
,45,
60,7
5,90
?
(RT)
Orientation
tests
(three
per
batc
hfrom
Fig.
4)(21)
[20]
EXTREN1
seealso[17]
?bolttorque
Toensure
bearing
failure
W/D
7an
dE/D
4.5
Bo
lttorquetests
(fourper
batc
h
from
Fig.
5)(2
4)
Tota
lNo
.(45)
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....
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Tab
le2Continued
[1]
Plate
[2]
Thickness
(mm)
[3]
Bolt
diameter
D(mm)
[4]
Hole
cleara
nce
(mm)
[5]
Washer
size
(mm)
[6]
Bolt
Torque
(Nm)
[7]
Orienta-
tion(0ois
directionof
pultrusion)
[8]
W/D
[9]
E/D
[10]
Testrate
(tempera-
ture)
[11]
Joint
configura-
tions
(No.oftests)
[12]
Reference
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Cooper & Turvey[13], in contrast, used a single PFRPthickness of 6.35 mm (1/4 in) with a bolt hole slightlylarger (0.10.3mm) than the plain shank M10 steelbolt (grade 8.8). Their double lap-joints had outer steelplates and the inner plate was PFRP, and no washerswere installed between the PFRP inner plate and steel
outer plates. Testing characterized the three differenttorque levels of 0 N m (pin-bearing), 3 N m (lightlyclamped) and 30 N m (fully clamped). Load wasapplied at a constant rate of 10 kN/min, and thematerial orientation was 08. The positive effect onlateral constraint of increasing the torque from 3 to30 N m increased the mean failure load (strength) by50%. Recommending assembly with fully clampedbolts, Cooper & Turveys parameters[13] in Table 1were based on the resistance data at the lower(finger-tight) torque of 3 N m. This is in accordancewith the EUROCOMP design code requirements from
Clause 5.2.2.3 given earlier. Both series support aminimumW/Dof 4 (higher than the value of 3 in theDesign Code and Handbook[6], and demonstrate thatthe design manuals minimumE/Dof 2 (Table 1) is toolow if failure is to be in bearing (Fig. 2).
All of the series in Tables 2 and 3 provide usefuldata for the future preparation of generalized designguidance (which might be based on severalconnection design procedures). It is observed that the15 series of tests each set out with their own specificobjectives. From the single-bolt series in Table 2 wesee that Abd-El-Naby & Hollaway[12]considered the
effect of friction (by changing the clamping area whenthe bolt torque was finger-tight), and changing theratios W/Dand E/D. Erkis tests[15]provide the onlycompression loaded strength results (520 in number).She compared the mean ultimate failure loads underdifferent torques when the bolts were FRP(FIBREBOLT1) and steel. This showed that the FRPbolt was the weak link and that the strength wasbetween 0.4 and 0.6 of its value when a steel boltwould ensure that the PFRP failed first. Yuan,Liu & Daley[17]investigated how strength changedwith clearance (06.35 mm, in increments of 1.6 mm).
They found that for a clearance above 1.6 mm therewas a decrease in joint strength with increasingclearance. For the American recommended clearanceof 1.6 mm, the tests by Yuan et al. showed no loadreduction compared to the no-clearance situation.Turvey[18]showed that if material orientation is not 08there is little evidence of any benign failure undertension loading. The failures for orientations of 308and 458 were interesting, because they also showedthat cracks propagated along the unidirectionalrovings. Fig. 4 shows schematically the fracturepatterns as observed on the surface of joints with 30
and 45 degrees orientations. Turvey[18] saw that thesecould be viewed either (negatively) as zones ofweakness, or alternatively (positively) as crack guidesand/or arresters. Steffen[19]was the first to show thatthere is a strength reduction on ageing stress-free
PFRP joints in water (even at RT) prior to testing.Finally, Yuan & Liu[20]looked at changing materialorientation and bolt torque for an unspecified jointgeometry that gave bearing failure for 08 orientation.They conducted their tests according to ASTM D953,Procedure A, Standard Test Method for Bearing
Strength of Plastics and found that the bearingstrength at 4% bolt hole deformation, as defined inD953, compared favourably with the incipient failureload (or initial failure load) in their test series. Thisfinding appears to contradict the findings of Yuan, Liu& Daley[17].
Fig. 2 shows the four most common ultimate modesof failure when the single bolts resistance does notcause joint failure. Of these four, those of bearing,shear-out and net-tension are considered as distinctmodes in various connection design procedures[2,57].The tests on 08 material[1120] confirm that all these
modes can occur by changing E/D and W/D. Noseries showed that the mode of failure changed onincreasing bolt torque (probably because the E/Dratios were not less than 4 in these tests).
The degree of clamping between the plates doesraise the load for initial damage and causes the jointspost-yield response to show less damage growth.Doyle[11]comments on the need to define a relativejoint displacement or some other predetermined valueto define the onset of (initial) bearing failure. Whenthe UD reinforcement is at 908 to the load the mostprobable failure mode is net-tension (or cleavage,
which might be due to a tension rupture on one sideof the hole first)[14,15,1820]. Off-axis joint tests[14,18,20]allshow (Fig. 4) that the resultant crack patterns do notcorrespond to one of the distinct modes shown inFig. 2. Several papers mention that failure couldappear to be a combination of the distinct modes inFig. 2[14,16,18,19]. These observations on failure willinfluence joint design.
Most sources for the 10 series of tests citedin Table 2 present a limited number of typicalloaddisplacement plots. Their characteristics can beseen to fit one of the two common joint responses
shown in Fig. 3. The beneficial restraint on initialfailure from a clamping pressure when the bolt ispre-loaded is seen to make the response inFig. 3(b) more likely. Vangrimde[28] has suggestedthat the usefulness of the joint displacement isdependent on what it measures. He states thatdesigners are not interested in hole elongation, butrather in the local bearing deformation. He advocatesthat the design property should be the bearingdisplacement and not the elongation of the hole asprescribed in ASTM D5961. In order to determine abearing displacement the second measurement point
must be at a sufficient distance from the hole such thatthe stress concentrations no longer have aninfluence[28].
Such a measurement methodology is notuniversally recognised and so Vangrimdes
PULTRUDEDFRP STRUCTURAL SHAPES AND SYSTEMS 205
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Tab
le3Summaryofpreviousconcentrical
lyloadedm
ulti-b
oltdoub
lelapjointtestswit
hPFRPflatsheetmateria
l
[1]
Plate
[2]
Thick-
ness(mm)
[3]
Bolt
diameter
(D)(mm)
[4]
Hole
cleara
nce
(mm)
[5]
Washer
size(mm)
[6]
Bolt
torque
(Nm)
[7]
Orientation
(0degrees
isdirection
ofpultru-
sion)
[8]
W/D
[9]
E/D
[10]
S/D
[11]
Test
rate
(temp)
[12]
Joint
configura
-
tionsNo.
oftests(
)
[13]
Reference
Non-s
tandard
Fibreforce
Composites
Ltd.
6
9.5stee
l
Close-
fitting
0.1mm
Fromsing
le-
boltjoint
tests
[12]
was
her
hadouterf
2.2Dinner
Smal
ll
clamping
torque
(finger-tig
ht
condition
)
0
7.36
,15.7
6.32
?
AllP/D1
0
Alltwobo
lts,
one
column
Outerplatesstee
l,
inner
plate
PFRP
Changedsteel
platethickness
(?)to
determine
effectofsti
ffness
(12)?
[21]
Tota
lNo
.
(12)
Grey
2
Blue
1
4 4
f
1D
0 0
12.6
6
6.32
6
Blue
2
Nominal
Creative
Pultrusions
Inc.
Series
1500
12.7
15.9
highstrength
stee
l
0.127mm
0.005inch
tightfit
Stan
dard
was
hers
Finger-t
ight
? 0
4.8
2.4
Type
A
sing
lebolt
[22]
4.8
2.4
?
AllP/D
4.8
Type
B:tw
obolts
,
oneco
lum
n
4.8
2.4
1
(RT)
Type
C:tw
obolts
,
onerow
4.8
2.4
1
Type
D:fo
urbolts,
tworowsan
dtwo
columns
4.8
2.4
1
Type
E:four
bolts
,
tworowsan
d
twoco
lum
ns
(staggered
by2.4D)
Outerplat
es
stee
l(thick
ness
?),
innerplate
PFRP
(15)
Tota
lNo
.
(15) C
ontinued
NEW MATERIALS IN CONSTRUCTION206
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-
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13/28
Strongwel
l
EXTREN1
500series
polyester
12.7
19.0
5
high
strength
shan
kin
contact
1.6
(initial
slipof
1.1mm
)
Stan
dard
was
herswith
bolts
,see
Rosner
Riz
kalla
sing
le-b
olt
series[14]
32.5
asspecified
for
FIBREBOLT
boltan
dnut
of3 4inf[1]
0,90
45 0,90
45 0,90
0,90
0,90
4.9,7.4,
9.86
,12
.33
9.86
4.9,6.17
,
7.4
4.9
7.4,9.86
,
12.3
3,14
.8
4.11
,4.93
,
5.75
4.9,6.17
,
7.3
1.85
,3.08
,
4.93
1.85
,3.08
,
4.93
1.85
,3.08
,
4.93
1.85
,3.08
,
4.93
1.85
,3.08
,
4.93
1.85
,3.08
,
4.93
1.85
,3.08
,
4.93
0.73
,1.04
,
1.35
0.73
,1.04
,
1.35
N/A
0.54
,0.85
,
1.16
0.001mm
/s
RT
AllP/D
4
Type
A:tw
obolts
,
oneco
lumn
Type
B:tw
obolts,
onerow
Type
C:th
ree
bolts,one
column
Type
D:th
ree
bolts,one
row
Type
E:four
bolts
,
tworowsan
d
twoco
lum
ns(105)
[23]
Outerplates
PFRP,inner
platestee
l
(thickness
?)
Proce
dure
sameas
for
sing
le-b
olt
jointtests
byRosner
and
Riz
kalla[14]
Total
No
.
(105)
?
12.7
15.9
stee
l
tightfit
?
Stan
dard
was
hers
Finger-t
ight
27to
81
?0
4.8
4.8
4.8
4.8
N/A
N/A
?
Oneto
four
bolts,
oneco
lumns
(?)
[24]
0.254,
0.381,
0.584
0.813,
?
4.8
4.8
N/A
RT
2bolts
,on
e
column(?)
Outerplates
stee
l
(thickness
?),
innerplate
PFRP
2bolts
,on
e
columnthree
per
batch
Suggests
replication
(12)
Tota
lNo.
(12)
? Fibreforce
Composites
Ltd.
?
?
? (tig
htfit)
?
4 pinne
d
? 0 0
2,3.3,4.2,
5,6
16
? 3
N/A
3
? (RT)
Four
bolts
in
oneco
lumn
(10)
AllP/D
5?(6)
[25]
Nine
bolts
,
threerowsan
d
columns
Eight
bolts
,one
two
boltrow
,
twothree
bolt
rows
Twoper
batc
h
Continued
PULTRUDEDFRP STRUCTURAL SHAPES AND SYSTEMS 207
Copyright & 2003 John Wiley & Sons, Ltd. Prog. Struct. Engng Mater. 2003; 5:195222
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8/10/2019 Physical test data for the appraisal of the design procedures for bolted - MTTRAM & TURVEY.pdf
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.
Tab
le3Continued
[1]
Plate
[2]
Thick-
ness(mm)
[3]
Bolt
diameter
(D)(mm)
[4]
Hole
cleara
nce
(mm)
[5]
Washer
size(mm)
[6]
Bolt
torque
(Nm)
[7]
Orientation
(0degrees
isdirection
ofpultru-
sion)
[8]
W/D
[9]
E/D
[10]
S/D
[11]
Test
rate
(temp)
[12]
Joint
configura-
tionsNo.
oftests(
)
[13]
Reference
(nooftests)
.
.
.
.
.
.
.
.
.
.
.
.
....
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
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.
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.
.
.....
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.
.
.
.
.
.
.
.
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.
.
.
.
.
.
.
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.
.
.
.
....
.
.
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.
.
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.
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.
.
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.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.....
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
....
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
Six
bolts,one
,
twoan
dthree
boltsperr
ow
Eight
bolts
,two
three
boltrows,
andonetw
o
boltrow
Outer
plates
?
inner
plate
PFRP
Six
bolts,three
,
twoan
done
boltsperr
ow
Eight
bolts
,
two
,threean
d
two
bolts
perrow
?No
replication
Tota
lNo.
(16)
1Theor
derofthe
W/Dratiosinco
lumn
8is
direct
lylinkedtotheord
erofS/Dratiosinco
lumn
10[23]
NEW MATERIALS IN CONSTRUCTION208
Copyright & 2003 John Wiley & Sons, Ltd. Prog. Struct. Engng Mater. 2003; 5:195222
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.....
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....
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....
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....
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.....
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....
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....
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....
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Tab
le4Summ
aryo
fconcentrical
lyloadedsing
le-b
olt
doub
lelap-jointtests
from
SIprojectsub
jectedtoelevatedtemperaturesan
dno
wetageing
[1]
Plate
[2]
Thickness
(mm)
[3]
Bolt
diameter
(D)(mm)
[4]
Hole
cleara
nce
(mm)
[5]
Washer
size(mm)
[6]
Bolt
torque
(Nm)
[7]
O
rientation
(0oisdirec-
tionof
p
ultrusion)
[8]
E/D
[9]
W/D
[10]
Environmental
conditioning
[11]
Joint
configurations
[12]
Reference
(No.oftests)
Strongwel
l
EXTREN1
500series
polyester
6.40
M10
Gra
de8.8
9.8mm
0.2
(tig
htis
hfit)
None,outer
plateso
fstee
l
(8mmthic
k)
innerplate
PFRP
Finger-
tight
(53Nm
)0
5 2 2 7
7 5 103
RT
,40oC
,
60oC
,80oC
Bearing
design
Cleavage
design
Shear-out
design
Net-t
ension
design
[26]
Batchesof
3
45
5
7
RT
,40oC
,
Bearing
design
(to
bereported
2
5
60oC
,80oC
Cleavage
design
byTurveyan
d
2
10
Shear-out
design
Wang)
7
3
Net-t
ension
design
Batchesof
2
90
5
7
RT
,40oC
,
Bearing
design
2
5
60oC
,80oC
Cleavage
design
2
10
Shear-out
design
7
3
Net-t
ension
design
[27]
Batchesof
3
*Fourelevated
temperatures,
noageinginwater
.
(132)
PULTRUDEDFRP STRUCTURAL SHAPES AND SYSTEMS 209
Copyright & 2003 John Wiley & Sons, Ltd. Prog. Struct. Engng Mater. 2003; 5:195222
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8/10/2019 Physical test data for the appraisal of the design procedures for bolted - MTTRAM & TURVEY.pdf
16/28
..
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.
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....
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.....
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.....
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.....
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.....
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.
.
Tab
le5Summ
aryo
fconcentrical
lyloadedsing
le-b
olt
doub
le-la
pjointtests
from
SIprojectsu
bjecte
dto
differentenvironmenta
lconditions
[1]
Plate
[2]
Thickness
(mm)
[3]
Bolt
diameter
[4]
Hole
cleara
nce
[5]
Washer
size(mm)
[6]
Bolt
torque
[7]
Orienta-
tion(0ois
[8]
E/D
[9]
W/D
[1
0]
Environmental
co
nditioning
[11]
Joint
configuratio
ns
[12]
Reference
(No.oftests)
D(mm)
(mm)
(Nm)
directionof
pultrusion)
Tempera-
tu
re
Water
immersion
(weeks)
Strongwel
l
6.40
M10
0.2
None
Finger-t
ight
0
5
7
RT
0
Bearing
design
(to
bereported
EXTREN1
500series
polyester
Gra
de8.8
9.8mm
1.2
(53Nm
)
0
5
7
60
oC
6.5
byTurveyan
d
2.2
0
5
7
80
oC
13
Wang)
2.2
45
5
7
60
oC
0
Batcheso
f3
0.2
45
5
7
80
oC
6.5
1.2
45
5
7
RT
13
1.2
90
5
7
80
oC
0
Outerplatesof
2.2
90
5
7
RT
6.5
stee
l(8mmthick
)
0.2
90
5
7
60
oC
13
innerplate
PFRP
0.2
0
2
5
RT
0
Cleavage
design
1.2
0
2
5
60
oC
6.5
2.2
0
2
5
80
oC
13
2.2
45
2
5
60
oC
0
0.2
45
2
5
80
oC
6.5
1.2
45
2
5
RT
13
1.2
90
2
5
80
oC
0
2.2
90
2
5
RT
6.5
0.2
90
2
5
60
oC
13
0.2
0
2
10
RT
0
Shear-out
1.2
0
2
10
60
oC
6.5
design
2.2
0
2
10
80
oC
13
2.2
45
2
10
60
oC
0
0.2
45
2
10
80
oC
6.5
1.2
45
2
10
RT
13
1.2
90
2
10
80
oC
0
2.2
90
2
10
RT
6.5
0.2
90
2
10
60
oC
13
Tota
lNo:(81)
Continued
NEW MATERIALS IN CONSTRUCTION210
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-
8/10/2019 Physical test data for the appraisal of the design procedures for bolted - MTTRAM & TURVEY.pdf
17/28
observation is a reason why the plots givenelsewhere[1120]cannot readily be compared. When themode of failure is bearing, the loaddisplacementcharacteristics for 08 single-bolt joints, withoutsignificant bolt torque, are seen to be similar to thoseshown in Fig. 3(a)[13,14]. The initial part showsvirtually linear elastic behaviour up to the ultimateload (a change in slope between 80 and 100% of theultimate load would indicate the presence of initialfailure). Following attainment of the ultimate load, theload reduces to between 70 and 80% of its ultimate,
and remains constant (or increases if the failingmaterial in front of the bolt(s) is laterally restrainedand has nowhere to go), as the displacement increasesup to several times the displacement at ultimate load.Under these conditions the loaddisplacementresponse (Fig. 3(a)) provides evidence ofpseudo-ductility[14,15,20].
It can be expected that joint collapse in realstructures will be dynamic in nature. Stresses causingsuch failure will be generated by a load situation thatwill, for a short period of time at least, remain thesame as it was for the joint state just prior to the
ultimate load situation. In stroke control joint tests,the load must follow the instantaneous stiffness of thespecimen. Here, when there is progressive damage,the continuous change in the joints stiffness governsthe load that can be transferred by the joint itself. Inthe real situation, an instantaneous change in loadwith instantaneous change in stiffness cannot occur,and so ultimate failure is more likely to occur withlittle additional joint displacement (unless theultimate load is higher than the initial damage load).We conclude from this observation that bearingfailure and its progressive damage growth (see
Fig. 3a) does not always guarantee a joints ductility.Ductility can be realized only if the jointdisplacement can be several times greater than at theinitial damage load and the higher ultimate load isreached only after this higher displacement has..
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Strongwel
l
EXTREN1
500series
polyester
6.40
M10
Gra
de8.8
9.8mm
0.2
1.2
2.2
2.2
0.2
1.2
1.2
2.2
0.2
None
Finger-t
ight
(53Nm
)
0 0 0 454545909090
7 7 7 7 7 7 7 7 7
3 3 3 3 3 3 3 3 3
RT
60
oC
80
oC
60
oC
80
oC
RT
80
oC
RT
60
oC
0 6.5
130 6.5
130 6.5
13
Net-t
ension
design
(tobereported
by
Turveyan
d
Wang)
Batcheso
f3
Outerplates
ofstee
l(8mm
thic
k)inner
plate
PFRP
[27]
Tota
lNo:(108)
30
45
(a) (b)
Concentric tension
Fig. 4 Failure modes in single-bolt joints under concentrictension and off-axis PFRP plate orientation (from[18]): (a) 308;(b) 458
PULTRUDEDFRP STRUCTURAL SHAPES AND SYSTEMS 211
Copyright & 2003 John Wiley & Sons, Ltd. Prog. Struct. Engng Mater. 2003; 5:195222
-
8/10/2019 Physical test data for the appraisal of the design procedures for bolted - MTTRAM & TURVEY.pdf
18/28
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Tab
le6Summ
aryo
fconcentrical
lysing
le-b
oltloaded
doub
le-la
pjointtests
from
SIprojectsu
bjecte
dto
differentenvironmenta
lconditions
[1]
Plate
[2]
Thickness
(mm)
[3]
Bolt
diameter
[4]Ho
le
clearance
[5]
Washer
size(mm)
[6]
Bolt
torque
[7]
Orientation
(0oisdirec-
[8]
E/D
[9]
W/D
[10]
Environmental
conditioning
[11]
Joint
configur
a-
[12]
Ref.
(No.
oftests)
D(mm)
(mm)
(Nm)
tionof
pultrusion)
Tem-
perature
Waterim-
mersion
(week)
tions
Strongwel
l
EXTREN1
500series
polyester
6.40
M10
Gra
de8.8
9.8mm
0.2
None
Finger-t
ight
(53Nm)
0
5
7
RT
60oC
80oC
RT
6.5
6.5
6.5
13
Bearing
design
(to
bereported
byTurveyan
d
Wang)
Batcheso
f2
60oC
13
80oC
13
Outerplatesof
stee