A complete project, step by step

Transcript

A complete project, step by step, with ILX Connection.

The project and the plan

In this video we design the connections of a small job, the Riverside Medical Office Building, from start to finish. We will look at the options, change things by hand, make a few mistakes on purpose, and see what ILX Connection does in the background. B-1 is a single plate shear connection, a W18x35 beam into the web of a W24x68 girder. MC-1 is a fully restrained moment connection to a column flange. BP-1 is a column base plate that sits on a concrete pier.

Every connection follows the same steps. Create it, enter the members and the loads, set the details, fix what fails, then review the drawing and the report.

Start from the project

Everything lives in a project. The tree on the left lists its connections, each with its status and highest ratio. Project info holds the job name, number, client and people. It feeds the title block of every sheet and the header of every report, so fill it in first. Then open the project menu, and select New connection.

Pick the connection type

B-1 only carries a beam end reaction, so it is a simple shear connection. In the Simple shear group, select Plate, then Single plate. A single plate, or shear tab, is the usual choice for a gravity beam. It is shop welded to the support and bolted to the beam web, so it is cheap and quick to erect. For a much larger reaction, you might pick a double plate or a double angle.

Joint and configuration

Our beam frames into a girder web, so select Beam to girder web. Then the configuration. A shear tab follows the conventional procedure of the AISC Manual, with one row of bolts close to the support. An extended shear tab reaches farther out. An all-welded plate is welded on both sides. Cards that cannot be built on this joint are greyed out. So we select Shear tab.

Members

Give the connection its mark, B-1. Type the beam, a W18x35, and the girder, a W24x68, from the AISC shape database. Then select Next.

Loads, service or factored

Enter the service loads, not the factored ones: 8 kips dead and 22 kips live. ILX applies the load factors for you. If you already have a factored reaction, choose Required strength, and it is used as entered. Leave Auto-design clear for now, because we want to see every choice ourselves. Select Create.

The editor

This is the editor. The inputs are on the left. The status, the drawings and every check are on the right. Right away, the status is red: the connection is not feasible. That is not a strength failure. It means the connection cannot be built as drawn, so ILX does not report strength results yet.

The cope

Both tops of steel are at the same level, so the beam's top flange runs into the girder flange. ILX works out the cope you need, and offers it as a suggested fix: one and a quarter inches deep and three and three-quarter inches long. Select Apply all. The cope appears in the inputs and in the elevation, the status turns green, and ILX adds the coped beam checks.

LRFD or ASD

At the top of the inputs, choose the design method. With LRFD, factored loads are compared with the design strength. With ASD, service loads are compared with the allowable strength. Open the Required strength card to see the combination. With LRFD, 1.2 times the dead load plus 1.6 times the live load gives 44.8 kips. Switch to ASD, and dead plus live gives 30 kips. Use the method your project specifies. We go back to LRFD.

Load combinations

The Input list offers other ways to enter loads. With service components, you enter dead, live, roof live, snow, wind and seismic loads separately. ILX builds every ASCE 7 load combination, designs for each one, and keeps the envelope. The Load combinations table marks the one that governs, here 1.2 dead plus 1.6 live. You can also type your own factored load cases.

Members and materials

In Members, you can change the beam and the support at any time. Both are A992, the usual grade for wide flange shapes, and the plate is A36. The top of steel offset sets how much lower the beam sits. A lower beam may not need a cope at all.

Bolts

Next, the bolts. A good default is the A325 bolt, three-quarters of an inch in diameter. A490 bolts give more strength per bolt. Threads included is the safe assumption. The joint type is bearing, snug tight, for most shear connections. Choose slip critical only when slip matters, such as with oversized holes or load reversal. Watch what happens when we pick it: ILX adds the slip resistance check, and it fails. So we go back to bearing. The plate has short slotted holes, as the conventional shear tab expects. Last, four rows of bolts at three inches.

Plate, edge distances and set-back

In Plate and geometry, set the plate thickness and the edge distances. The vertical edge distance runs to the top and bottom of the plate. The horizontal ones run to the plate edge and to the beam end. The conventional procedure asks for at least twice the bolt diameter there, so the connection can rotate. The distance from the weld line to the bolts sets the eccentricity. The strip above the drawings sums it up, including the set-back of the beam end.

Welds

The Welds section sets the fillet weld to the support, on both sides of the plate, with E70 electrodes. For a shear tab, the weld must be at least five-eighths of the plate thickness, so the plate yields before the weld breaks. Remember that rule.

What ILX does in the background

Here is what happens behind every change. ILX builds the load combinations, and finds the one that governs each check. It follows the AISC Manual design procedure for this connection. For an eccentric bolt group or weld group, it uses the instantaneous center of rotation method. Then it checks each limit state in order: the bolts in shear, bearing and tearout, the welds and the support, plate yielding, rupture and block shear, plate flexure, and the coped beam web. Last, it checks the detailing: spacing, edge distances, weld sizes and the ductility rules. All of it runs again a second after you stop typing.

Reading the checks

Start with the status bar. Green means adequate. It names the governing check, the one closest to its limit: plate block shear, at 0.844. Strength OK and Code compliant sum up the two kinds of checks. Below, All checks lists every check in groups, each with its code reference, the governing combination, the required and the available strength, and the ratio.

A check, step by step

Select a check to see where the numbers come from. Here is the bolt group. The load acts one and a half inches from the bolts, and the instantaneous center method gives a coefficient of 3.556, a little less than our four bolts. Each bolt takes the least of its shear, bearing and tearout strengths. Scaled by the coefficient and the resistance factor, that gives a design strength of 60.4 kips, against 44.8 required. Every value has its equation and its clause, so you can check it by hand.

Manual modifications

The starting values are only a starting point, and you can override any of them. Let's make the plate thicker, three-eighths instead of one quarter. ILX checks everything again at once. Block shear drops well below its limit, and the bolt group now governs, at 0.704. But the status bar is red again.

Mistake: the weld no longer fits the plate

Select the Failed filter to list only what fails. It is the weld rule: a three-eighths inch plate needs at least a quarter inch weld, and we still have three sixteenths. This is the classic mistake of changing one part and forgetting the part that depends on it. The check ends with How to fix. Change the fillet to a quarter inch, and the connection is adequate again.

Mistake: too few bolts

Now a strength mistake: only two bolts. The bolt group is at 1.804, far over its strength, and plate rupture and block shear fail too. Failing parts are outlined in red in the drawing. How to fix says to add bolts, use a larger bolt, or a thicker ply. Two advisories appear as well, because the plate is now short for this beam. We go back to four bolts.

Mistake: a short edge distance

One more. Set the vertical edge distance to seven-eighths of an inch. The strength still passes, but the status turns red, because this is a detailing failure. A three-quarter inch bolt needs at least one inch to the edge. The field carries a red badge. Point at it to read the rule and How to fix. We set it back to one and a half inches.

Failures, warnings and Code compliance

So, strength failures mean the load is more than the available strength. Detailing failures mean a rule of the Specification or the Manual is broken. Both make the connection not adequate. Advisories and recommendations are warnings: they do not fail the connection, but read each one and decide. The Code compliance tab lists every detailing requirement by topic, with the value required and the value provided.

Auto-design

Now let ILX search for a design. To keep our manual version, duplicate B-1, and open the copy. Pin the fields you want to keep, such as the beam, and select Auto-design. ILX tries bolt counts, sizes and grades, plate thicknesses, welds and edge distances, and checks every candidate in full: 38 of them, in a fraction of a second. Choose the objective: lightest, fewest bolts, or lowest cost. Each row shows its ratio and exactly what changes. The lightest uses three A490 bolts and a five-sixteenths inch plate. Select Apply.

Compare the two designs

Select Compare in the header, and pick the two. Every strength ratio is lined up, with the lower one highlighted. Our manual design has more reserve. The automatic one is lighter, but needs A490 bolts and runs at 0.876. Neither is wrong: that choice is yours. We keep B-1.

The drawing

Now really look at the drawing. It is drawn to scale from the same inputs as the checks, so it is the quickest way to catch a wrong input. The elevation shows the coped beam, the plate and the bolts, with every dimension. The plan section shows the plate on the girder web and the set-back. Click any part, and the inputs jump to its section.

Bolt and weld callouts

The bolt callout gives the number, the diameter, the length, the grade and the hole type. The weld uses the AWS symbol. The arrow points to the joint. A triangle on each side of the line means a fillet weld on both sides of the plate. The number is the weld size, and the tail carries the electrode.

The drawing sheet

The output bar makes the documents. Drawing sheet makes a PDF, eleven by seventeen or letter size. The sheet has the views at scale, the general notes, the seal block, and a design summary with the governing check. The title block holds the project, the revisions, the engineer, the status line and the sheet number, all from your settings.

The DXF

Drawing DXF gives you the same sheet as a CAD file, for your drawing set.

The calculation report

Calc report makes the calculation report. It opens with the status and the governing check, the project information, the drawings and the inputs. Then the required strength, a summary of every check with its ratio, and the code compliance table. Then every check in full, with the equations, the values and the clauses, just as in the app. A reviewer reads this, so read it yourself first.

A moment connection

Next, MC-1. In the wizard, choose FR moment, then Bolted flange plates: shop welded to the column and field bolted to the beam, so there is no field welding. Enter the W18x50 beam and the W14x61 column, dead and live moments of 42 and 126 kip-feet, and shears of 7 and 21 kips.

How the moment connection is checked

It is adequate, and the flange plate welds govern, at 0.919. The factored moment is 252 kip-feet. Divided by the distance between the flange plates, it gives a flange force of 161 kips. ILX designs the flange plates, their bolts and welds, and the web plate. Then it checks the column: flange bending, web yielding, web crippling and panel zone shear. The bare column is not strong enough, so ILX adds three-eighths inch stiffeners and a five-sixteenths inch doubler, and checks them too.

A column base plate

BP-1 was created the same way, from the Column bases group: a W12x96 column with axial load, moment and shear, entered as service loads. Set the plate and the anchor rods, with their grade, diameter and embedment. The design follows AISC Design Guide 1, with the anchorage checks of ACI 318.

How the base plate is checked

ILX checks concrete bearing, plate bending, anchor rod tension and the shear transfer, in this case by friction. It also checks the welds, the rods during erection, and the detailing. The drawing shows the section through the pier and the plan.

Wrap up the project

Back to the project. The tree shows every status and ratio at a glance, and the Issues filter shows what needs attention. When everything is green, open the project menu. Calc package makes one PDF with a cover, a table of contents and every connection. All sheets makes the full sheet set, numbered in order.

Check your own work

Before you issue anything, check your own work. Read the governing checks, open the calculations, fix every failure, read every warning, and look at the drawing and the report. ILX Connection helps. The engineer of record is responsible.

Thanks for watching. Try it at ilxconnection.com, or write to us at support@ilxstudio.com. ILX Studio, LLC is not affiliated with AISC.