End plate connection pdf

As such, it is recommended that Be, sustain moderate or severe earthquake loads, it may be pre- be selected such that it exceeds the flat width of the HSS ferable to design the connections to behave mainly elastically column. Connection loads due to beam bending. Arrangement of welds to end plate. As a result, an improved dynamic response can be the shear resistance of a weld must be evaluated on the basis expected by both minimizing the connection stiffness degra- of both the resistance of the weld itself and of the base metal For personal use only.

While this version of the code recog- tics of the plastic flexural hinges in beams. Accordingly, the mini- where wind loads govern the design, while Mdesignis sug- mum size for the beam flange fillet weld will be the greater gested to be equal to 1. It is assumed that the beam moment can be replaced by a couple whose forces act at the beam flange level, as shown in Fig. Hence, the design flange force Pdesign is given as where Xu is the ultimate tensile strength of the weld, Fy is where db and tbf are the beam depth and beam flange thick- the minimum yield strength of the base metal, L, is the ness, respectively.

For the earthquake-governing design case, Pdesign in the above equations is suggested to be based on the beam plastic Design of welds moment Mp rather than 1.

Welds that by the code. Normally, the size of the fillet weld w,, which connect the end plate to the beam are crucial, because weld is based on the weld metal, governs the weld design. This fractures may be brittle and sudden. In reasonably small value is nearly equal to that obtained from the American beam sections, flange fillet welds may be used rather than Institute of Steel Construction specification, although full-penetration welds, since the cost of edge preparation is it uses different factors.

The load and resistance factor design eliminated and the risks associated with lamellar tearing are LRFD standard uses a higher factor of 0. It resistance compared with 0. Such precautions reduce the be obtained by using [2] and [3] with the substitutions of Vb stress concentration in welds. The Canadian steel code and 2 db - 2tbf instead of Pdesign and L,respectively.

Mourad et al Fig. Bending and prying action of end plate. Table 1. In addition to the direct tension in the bolts, the vided by the manufacturer and given in Table 1, and 4 b b is effect of prying action must also be accounted for.

Due to the the resistance factor for HSBBs. Based on the results of 24 applied load, the end plate bends about the bolt line and the tensile tests conducted on 20 mm HSBB, the resistance factor prying force Q develops together with the bending moment was calculated to be equal to 0. For comparison, the in the plate, as illustrated in Fig. The bolt force Tb resistance factor for A high-strength bolts in tension as includes contributions from the applied load and prying given by Fisher et al.

Although the action. The prying force is a function of the end-plate thick- limit-states design code of steel buildings CANICSA- ness and the location of the bolt. Based on analytical and S Grundy et al. Moreover, equal to 0. Normally, the size of blind bolts several models have been developed to predict the magnitude can be selected so that of prying forces in bolted connections. These include the studies of Fisher and Struik , Agerskov , and Kennedy et al. The prying-force model described in Since shear forces acting on the connection will frequently the Handbook of Steel Construction CISC is used here be sufficiently small, these can generally be resisted entirely to account for prying forces in the HSBBs for end-plate con- by the bolts located on the compression side.

This assertion nections, and is based on tests carried out on tees bolted to should, however, be checked in clause It is assumed that prying action will The design of the end plate that has to resist the tensile force only increase the forces in the two exterior bolts. Therefore, Pdesigndepends upon whether the frame design is governed the maximum force Tb maxin each of the exterior bolts is by wind or earthquake loads.

In the former case, it is determined as follows: designed so that it fully yields under the beam moment Mf. In the latter instance, full yielding occurs at a hypothetical flange load of 1. End-plate yield line mechanism. End-plate yielding with bolt failure. Plastic hinges rn Can. For HSBBs a thicker end plate is preferable to reduce the bending of the bolts due to the end-plate deformation. Morris has been used with a slight modification to Design of HSS column flange design the end plate.

The tension side of the end plate is Two modes of HSS column flange failure were observed assumed to behave as a T-stub, and the yield lines assumed from testing extended end-plate connections using HSBBs For personal use only. One possible mode of failure is excessive as shown in Fig. Such a design has been proven to sustain out-of-plane yielding of the column flange on the tension side the beam plastic moment with limited plastic deformation of the connection. Another is pull-out failure through the Packer and Morris In the case of ordinary high- thickness due to the tensile force of the bolt.

In the latter strength bolts, it has been suggested that the work done in case, a relationship can be developed to link the minimum causing them to deform can compensate for the loss of plate column flange thickness of the hollow-section column with strength due to the holes. However, no attempt is made here the maximum strength of a single HSBB. The minimum to determine the bending stiffness of the HSBBs.

As such, a thickness of the column flange can be found by requiring the conservative estimate is to incorporate a reduction in end- material shear resistance around the primary sleeve of the plate strength resulting from the existence of the bolt holes.

The a' factor is a After designing the end-plate thickness, the maximum numerical modifier to convert Tminto an expected maximum force developed in the exterior bolts has to be checked when bolt strength. This is done to minimize the possibility of a prying forces are included, using [4] - [7]. Since the end bolt pull-out failure.

From the very limited number of tensile plate was designed to be fully yielded, it remains necessary tests mentioned earlier 20 mm HSBBs , a maximum tensile to ensure that such a mechanism will occur before the HSBBs strength based on two times the standard deviation above the themselves fail. This can be done by evaluating the beam mean value was found to be reasonable.

Hence, a' was found flange force P, ,, which would cause the mechanism shown to be equal to 1. Rearranging [lo], the minimum thick- in Fig. Yield lines are assumed to form along the beam ness of the column flange can be obtained as flange junctions at the same time as the bolts reach the ulti- mate state.

Should the column flange have a smaller thickness, a doubler If this resistance is less than the beam flange design force plate welded to the column flange can be selected so that the PdeSign, then larger bolts may have to be selected.

Yield line mechanisms for unstiffened HSS column flange. If equal to Ho to allow for proper flare bevel welding along the the required column flange thickness is greater than the avail- HSS corner edges. Tests on the end-plate To establish the appropriate yield-line model to be employed connection to HSS columns Ghobarah et al. Therefore, it is important to check for column the inner face of HSS column flange as well as on the doubler flange strength, especially in the tension region.

Based on the plate on the tension side of the connection. Such an observa- experimental observations and analytical results of Ghobarah tion is attributed to the presence of the bolts' clamping forces et al. Consequently, the yield-line Fig. The first is a rectilinear mechan- modified to take into account the variation in the yield ism, whereas the second involves yield line fans.

The strength in both the column flange and the doubler plate, as corresponding column flange thicknesses are given for well as to account for the reduction in strength due to the mechanism 1 as holes. The minimum required thickness for the doubler plate t d pcan be determined by equating the factored resistance of the stiffened column flange PrcCo to the beam flange design force Pdebign. The stiffened column flange factored resis- tance is derived from mechanism 3, shown in Fig. The code only shows how to deal with the tensile axial force in the end-plate connection [1], so we want to convert the moment into equivalent axial force which has a clear design procedure in the AISC hollow sections Design Guide 24 [2].

If there is a moment value equals to MT in the rounded hollow section HSS, that same moment will be transferred to the connection, and the bolts will resist this value. However, each bolt will be subjected to a different axial value based on its distance from the centerline of the hollow section see Figure 3.

Accordingly, the farthest couple of bolts Position-D will be carrying the largest portion of MT, and the one on the neutral axis of the hollow section will be carrying a zero moment value see Figure 4. Now after we find the values for dD, dC , equation 1 can be written as in equation The next step will be writing the forces with reference to FB as in Table 2, then equation can be written as in equation And from that value, we can find the value for FD, which is the highest value among the three positions as it is the farthest from the neutral axis of the hollow section, making it the controlling tensile force that will determine the bolt size of the connection: Assuming that all bolts are being subjected to the same force at this point, and that force will be the highest value FD, and if we multiply it with N, the number of bolts, it will be reasonable to consider the hollow section to be subjected to an axial force AT with a value of N x FD.

Equation 3 Discussion Sometimes the connections can have axial forces in addition to the moment, and to take the combined effect of the two different stresses; first, the moment should be converted to a tensile axial force using equation 3. And second, the newly converted tensile axial force is added to the original axial force in the member, taking into consideration the sign of the axial force; the tension takes a positive sign and the compression takes a negative one. Moreover, if there is a moment in the two axes, the moment value that should be used in equation 3 is the resultant value.

What makes this equation even more convenient is that we only need to use the dD, which is the easiest bolt distance to be measured, where dD is the largest distance between any two bolts in the End-plate connection see Figure 5. And even though the previous calculations were based on a bolts end-plate, but it works on any number of bolts as long as these bolts are symmetrically distributed around the center of the hollow section and around the center of the End-plate connection.

Some might argue that end-plates designed using equation 3 are overdesigned because we take the bolt that is subjected to the highest level of stress and we generalize that on the rest of the bolts.

And that can be very risky as there is no guarantee that the steel erection crew on the construction site will not confuse one bolt with another, jeopardizing the safety of the connection as well as the entire moment frame. Declaration of interests: This paper received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. The author also declares that he has no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Care should be taken before amending the standard details as the resulting connection may fall outside the provisions of the UK National Annex [2]. In particular:. The UK Building Regulations require that all buildings should be designed to avoid disproportionate collapse. Commonly, this is achieved by designing the joints in a steel frame the beam-to-column connections and the column splices for tying forces.

The requirements relate to the building Class , with a design value of horizontal tying force generally not less than 75 kN, and usually significantly higher. Full depth end plate details have been developed to provide an increased tying resistance compared to partial depth end plate details.

Further details on structural robustness are presented in SCI P The selection of beam end connections can often be quite involved. The relative merits of the three connection types partial depth end plates , full depth end plates and fin plates are summarised in the table below. Selection of beams and connections is generally the responsibility of the steelwork contractor who will choose the connection type to suit the fabrication workload, economy and temporary stability during erection.

It is recognised that interaction with a composite floor will affect the behaviour of a simple connection. Common practice is to design such connections without utilising the benefits of the continuity of reinforcement through the concrete slab. However, SCI P enables reinforcement continuity to be allowed for in providing relatively simple full depth end plate connections with substantial moment resistance. In a braced frame, this resistance may be used to reduce the mid-span moment and deflection, facilitating the selection of a smaller beam.

Simple connections are invariably cheaper to fabricate than moment-resisting connections , because they involve much less fabrication effort, particularly in welding. Giving specific guidance on costs is difficult, as a Steelwork Contractor's workmanship rates can vary considerably and are dependant upon the level of investment in plant and machinery. However, the main objective is to minimise work content. The material cost for fittings and bolts is small compared with workmanship costs which are dominated by welding content.

Standardised connections are efficient in their production. Steelwork Contractors equip their workshops with specialist machinery that increases the speed of fabrication , allowing them to produce fittings and prepare the members much more quickly than they would if the connection configuration were different each time. The standardised details mean the steelwork is straightforward to erect , which provides a safer working environment for the steel erectors.

Due to the nature of most bolted joints, the connections are demountable at the end of the service life of the structure. The steelwork can be dismantled, reused or recycled , therefore reducing the environmental impact of the construction. Efficient connections will therefore have the lowest detailing, fabrication and erection labour content.

The design procedures given below are suitable for either hand calculation or for the preparation of computer software. Designing connections by hand can be a laborious process and so a full set of resistance tables has been included in the ' Green Book ' SCI P For normal design there are ten design procedure checks for all the parts of a beam to beam or beam to column joint for vertical shear.

A further six checks are necessary to verify the tying resistance of the joint. Beam to column connections must be able to resist lateral tying forces unless these forces are resisted by other means within the structure, such as the floor slabs. The table below summarises the design procedure checks required for partial depth end plates , full depth end plates and fin plates.

Notes: Checks on the bending, shear, local and lateral buckling resistance of a notched beam section are included in this table as it is usually at the detailing stage that the requirement for notches is established, following which, a check must be made on the reduced section. Typical flexible end plate connections are shown in the figure right.

The end plate, which may be partial depth or full depth, is welded to the supported beam in the workshop. The beam is then bolted to the supporting beam or column on site. This type of connection is relatively inexpensive but has the disadvantage that there is little opportunity for site adjustment.

Overall beam lengths need to be fabricated within tight limits, although packs can be used to compensate for fabrication tolerances and erection tolerances. End plates are probably the most popular of the simple beam connections currently in use in the UK.

They can be used with skewed beams and can tolerate moderate offsets in beam to column joints. Flowdrill, Hollo-Bolts, Blind bolts or other special assemblies are used for connections to hollow section columns. Detailing requirements and design checks for partial depth and full depth end plates connections, which are applicable to beam-to-beam connections as well as beam-to-column connections, are comprehensively covered in the ' Green Book ' SCI P These include procedures, worked examples, detailing and design resistance tables.

An End plate designer tool is also available. Standard flexible end plate details full depth and partial depth end plates are shown in the figure below, together with recommended dimensions and fittings. Fin plate connections are economical to fabricate and simple to erect.

These connections are popular, as they can be the quickest connections to erect and overcome the problem of shared bolts in two-sided connections.

A fin plate connection consists of a length of plate welded in the workshop to the supporting member, to which the supported beam web is bolted on site, as shown in the figure below.

There is a small clearance between the end of the supported beam and the supporting column. In the design of a fin plate connection it is important to identify the appropriate line of action for the shear.

There are two possibilities: either the shear acts at the face of the column or it acts along the centre of the bolt group connecting the fin plate to the beam web. For this reason both critical sections should be checked for a minimum moment taken as the product of the vertical shear and the distance between the face of the column or beam web and the centre of the bolt group. Both critical sections are then checked for the resulting moment combined with the vertical shear.

Due to the uncertainty of the moment applied to the fin plate, the fin plate welds are sized to be full strength. Fin plate connections derive their in-plane rotational capacity from the bolt deformation in shear, from the distortion of the bolt holes in bearing and from the out-of-plane bending of the fin plate. Note that fin plates with long projections have a tendency to twist and fail by lateral torsional buckling.

An additional check to consider this behaviour is included in the design procedures for fin plate connections. The ' Green Book ' SCI P covers detailing requirements, design checks and procedures applicable to fin plate design.

Worked examples and design resistance tables are also given in this publication. A Fin plate designer tool is also available. Increasing interest in the use of S for fin plates prompted questions about the stiffness of such connections — are they still nominally pinned?