Plans for Progressive Collapse Demonstration
Abstract
A freestanding structure 410" in height (just over 34 feet, and just over 10 meters) and approximately 52" square, and weighing approximately 11,000 pounds will be constructed indoors atop a 33" high foundation platform. The main materials will be standard wood framing lumber and normal-density concrete. The structure will support 10 "floors" of sixteen square feet each, made of wooden trays filled with concrete, comprising most of its mass. The floors will be supported by columns in such a manner that the structure's weight puts tension on steel connectors whose tensile strength will be calibrated to withstand the static load but break under significant dynamic overloads. The structure will be subject to a horizontal impact of an inert 100-pound mass at a velocity of 12 meters per second striking a support column between the eighth and ninth floors, without the structure collapsing. The top floor, comprising less than 10% of the total mass of the structure, will be disconnected and raised an additional 77 inches (totaling 118 inches, or 300 cm, of clearance from the 9th floor) and dropped. The subsequent behavior will be observed and recorded. The test will be successful if it demonstrates complete progressive collapse of the test structure (not including the foundation). All appropriate safety precautions will be taken throughout.
Introduction
The process of progressive collapse of a structure is intimately related to the scale of the construction. This is because all other factors being equal, the total gravitational potential energy of a structure increases as the fourth power of the linear scale, while the strength needed to make the structure safe under the normal range of expected uses and conditions (which is the strength with which a structure will "resist" progressive collapse once initiated) increases as only the third power.
Generally speaking, structures or models made of common materials at small scales (less than a few meters) cannot progressively collapse. They simply don't contain enough gravitational potential energy in proportion to their mass or strength. It is probably possible to make a small model progressively collapse, but doing so would require such unconventional building methods (such as, perhaps, very thin glass rods as columns supporting very heavy floor plates) that it would be nearly useless as a demonstration of the actual possibility of progressive collapse in real structures.
Large-scale structures can and do progressively collapse once collapse is initiated, but a physical model of the same order of magnitude scale as a World Trade Center tower is not practical.
So, the proposition discussed here is a demonstration using an intermediate-scale model, approximately 10 meters tall. That scale is too small for any conventionally built useful structure (such as three-story wood frame house) to progressively collapse, but an appropriately designed model at that scale should be able to, while still being somewhat realistic.
Design of the Test Structure
Ten identical trays will be prefabricated off-site. Each tray will be 49 inches square and 7-1/4 inches high. A tray will consist of a square frame made of four pieces of 2x8 lumber (flooring joists) and a 47-1/4" square base of 3/4" plywood, mounted in a 13/16" deep 11/16" wide groove set 1" from the bottom edge of the frame. Each corner of the frame will be fastened with three #12 x 2-1/2 wood screws. Each corner will also be reinforced by right angle steel brackets at the top and bottom edge of the frame (bracket and fastener specifications TK) to resist any unbalanced torque applied to the tray frames by the loads on the steel connectors (see below). The capacity of a tray will be 46" by 46" by 5-1/2", or 6.73 cubic feet. The tray interior will be seamlessly lined with 4 mil plastic sheeting to prevent the moisture of the uncured concrete from affecting the wood framing.
The vertical columns of the test structure will be knot-free lengths of standard wood framing stud (2x4's) 55 inches in length, oriented so that their broader sides are flat against the sides of the trays. Each column will connect a pair of trays, overlapping the side of each tray by about 7 inches, leaving 41 inches clearance between trays. At each tray, the columns connecting upward will be laterally offset from the columns connecting downward. The columns will not butt end to end.
At the bottom of each column (excepting the ones below the first tray and the ones supporting the top tray), the column will be hung from the adjacent tray by an S-shaped steel connector, such that the attachment between tray and connector is above the attachment between connector and column, so that all of the load on the column is transmitted as tension in the fastener. At the top of each column, the upper tray is similarly hung from the column by a similar metal connector. The figure below shows the proposed connector design, as used at a column top. If fabricating that design proves infeasible, an off-the-shelf part like: hurricane anchors or joist hangers will be adapted for the purpose by machining. If necessary, the column orientation will be changed so that the longer edge of the columns are perpendicular to the tray sides. In all cases, the connectors will be fastened to the columns and tray frames with at least eight .148 x 1-1/2" nails (joist hanger nails).
The connectors are designed to fail in tension when overloaded by dynamic loads during the demonstration. This design was chosen over an earlier designs relying on column buckling or nails failing in shear, as having more consistent and more controllable failure loadings. (Nail failure in shear, though predictable enough for such purposes as breakaway walls designed to fail under flood conditions, appears to be affected by the properties of the wood and other factors that are difficult to control with sufficient precision for this test. This is because the actual failure often occurs through distortion of the nailed materials causing the nails to pull out, rather than shearing of the nails.)
Note that at each tray, the loads on the steel connectors for the upward columns, and the loads on the connectors for the downward columns, torque the tray frame segments in opposite directions, by amounts differing only by the contribution of the tray itself to the total load. So, the trays should be sufficiently strong without requiring any strength contribution from the concrete.
The number of columns at each level (which will, almost certainly, vary from level to level) and the dimensions to which the narrow point of the connectors are adjusted for each level, will be determined in the preliminary testing stage of the project. The dimensions of the connectors will be adjusted so that the breaking force of each connector in each column is 1.3 times the static load the column will bear in the completed fully loaded test structure.
The columns between the ninth and tenth (second highest and highest) trays will be attached differently. They will fit into sockets mounted to the tray sides, held in place by the weight of the top tray. They will not be nailed. This is to permit them to be removed, from a safe distance, by means of attached cords, when the top tray is lifted for the progressive collapse demonstration.
Heavy ring bolts (fastener dimensions TBD) will be attached to each corner of each tray. At trays 3, 5, 7, and 9, each corner ring bolt will be attached to 3/4" diameter nylon rope with relatively high elasticity and a breaking strength exceeding 10,000 pounds. These sixteen ropes will run diagonally from the ring bolts at the corners of the test structure to strong anchor points at or near floor level at a horizontal distance of at least 40 feet from the test structure. Each rope will have approximately 2 feet of slack. The ropes are not expected to become tensioned (except by their own weight) at any time during the demonstration, but they are a necessary safety precaution. Also, for reasons related to scaling of angular momentum explained in one of my previous challenge thread posts, should any of the ropes become tensioned during any part of the demonstration, this will not be considered a failure condition.
The ring bolts will also be used to lift trays as needed. Only the top tray is expected to be lifted this way, but all trays will be equipped with them for contingencies. A set of cables attached to the top tray will run to a lifting rig that includes a remotely operable quick-release mechanism. The lifting rig will remain attached to the top tray during and after the pouring of the concrete. The lifting cable will be slackened during the side impact test, then used to lift and drop the top tray for the progressive collapse demonstration. All rigging necessary for carrying out these actions from a safe distance will be in place before the concrete is poured.
The base of the test structure will be a 49-inch square frame of 2x6 timber similar to the frame of a tray, resting on a 52-inch square frame of two sistered 2x8 timbers. Both types of members will be lag bolted to vertical 6x6 posts at each corner. (Fastener dimensions TBD). Each post will be set in its own 24" high x 24" dia. concrete pier, which will rest on plywood pads placed directly on the floor of the facility. The posts will extend upward to just above the upper frame of the base. The columns connecting the base with the lower tray will rest upon the lower base frame and will each be fastened to the upper base frame with four 16d framing nails.
The lower 9 trays and the base will also be interconnected by diagonal braces running from tray to tray on all four sides, to limit swaying. Materials and fasteners TBD. The material may be rigid or may be tensile only, such as thin steel cable or perforated thin gauge steel strapping.
Design Discussion
Note that the way the test structure supports its own weight does not resemble the way the World Trade Center towers did. In the towers, the vertical forces on the columns did not bear on the floors below, as they do in the above test structure design. Instead, each floor was hung from the columns and had to bear only its own weight while bracing the columns horizontally.
A test model constructed similarly, with each tray (floor) hung from columns using fasteners of calibrated strength, would very easily demonstrate pancake collapse of the floors. It would also be much easier to design and safer to construct, because the fastener strength would only have to be calibrated for the load of a single tray. The problem is that full-height wood or steel columns sufficient to safely support the total load would tend to be too strong (at this scale; it's always about scale) to be completely broken up by the collapse forces or collapse under their self-weight, unlike the wtc columns that were about 60 times taller and less flexible.
Just seeing the floors progressively sheared away isn't good enough. (If it was, then all we'd need to demonstrate the principle of progressive collapse would be some dominoes and a smooth floor. Truthers might have a hard time believing that the energy of one toppling domino could possibly be enough to knock over 1,000 or 1,000,000 other dominoes, but we can prove it!) No, we have to see the columns falling down as well.
In principle, column segments of calibrated strength in compression or column joints of calibrated strength in shear or tension could be used instead of floor attachments of calibrated strength in tension. But my assessment so far is that the design above, using column segments of excessive strength but dependent (literally) on the metal connectors, is overall easier to calibrate, and safer.
Test Site Requirements
The test site must be a building interior, zoned for industrial use, with controllable access, electrical service, water supply, adequate ventilation, and full protection from the elements. Heating, air conditioning, or full-service plumbing are not required, unless the demonstration is to take place in a time of year when heating is necessary for sufficient curing of the concrete. A slab floor bearing directly on the ground is preferred, and in any case the floor must be sufficiently strong for the test, taking the planned test bed into account (see Site Preparation below).
There must be truck access to the interior space or to just outside an entrance.
The minimum floor extent is 60 by 80 feet, to allow for positioning of cameras on all sides at sufficient distance for good views of the test, and for an escape zone beginning at least 40 feet from the base of the structure.
A means to anchor the guy ropes approximately 40 feet or more diagonally from each corner of the structure, at or near floor level, must exist.
The test chamber must have a minimum of 42 feet of overhead clearance. The means to attach a pulley rated for a 5,000 pound load must exist over the center of the test structure, which must be 30 feet or more from any wall on any side.
Test Site Preparation
The following must be installed or determined to already exist:
1. The winch and overhead pulley portions of the lifting rig for the top tray.
2. Overhead rigging for the personal safety harness.
3. Sufficient lighting for high-speed video photography.
4. Anchor points for the guy ropes.
5. Door security and interior security systems (door lock, interior motion sensor, audible alarms)
Unless the facility has an earth floor, or is scheduled for floor demolition, it will be necessary to protect the floor from damage from the impact of heavy trays and other debris. A protective floor pad will be constructed, 24 feet square and centered on the test structure base. The exact design is TBD, but most likely will incorporate a layer of dense wooden cribbing and a deep gravel bed.
The rigging for the side impact test must also be prepared. The design of this is TK and will probably require some preliminary development and testing. The simplest possibility is to allow the weight to swing into the test structure from an attachment point directly above the planned impact point. However, to get sufficient velocity this way, the weight would have to begin its descent from over 7 meters above the impact point, requiring an additional two stories of total ceiling clearance, which is unlikely to be available.
A lesser weight at a faster velocity would better resemble the 9/11 plane crashes in terms of momentum transfer, but approaches using ballista, air cannons, and comparable methods present problems related to safety, accuracy, and sufficient control over the impact velocity. One workable approach might be battering ram running along a track (which might be mounted to scaffolding), powered by a speed-controlled motor connected via a windlass.
Instrumentation
Apart from the instruments for safety monitoring, there is little need for instruments other than cameras for documenting the event. To put it bluntly, this demonstration has little value as scientific research. It is based upon, and it will illustrate, basic principles of Newtonian mechanics that have been thoroughly understood for centuries. [Note to self: delete previous two sentences if using this text for a grant application.]
However, if anyone wants to make a case for additional instrumentation such as accelerometers, strain gauges, load cells, microphones, seismograph, etc., I might be able to add them to the project. An example might be measurements that would help calibrate a computer model. (Strain gauges on the steel connectors might be needed for safety, which would add considerable cost and complication.)
For the photography, video recorded from multiple angles including top-down, with at least two of the cameras being high-speed, seems appropriate for such an elaborate and "one-take" demonstration. An additional video recording using an infrared camera will be included, to prove that no thermite is being used.
Site Safety Policies
1. Anyone entering the site for any reason at any time from the start of construction to the completion of the post-test clean-up must wear OSHA-approved hardhats, work gloves, boots, and safety goggles at all times. After the demonstration, dust filtering masks must also be worn until the completion of the clean-up phase.
2. No spectators will be permitted inside the test area at any time, except for one representative of the challenge sponsor, who must sign a personal injury liability waiver and must agree to obey all safety directives issued by the challenge claimant.
3. From the time concrete is poured in any of the trays, to the completion of the first stage of clean-up, the site will be attended from outside by a security guard at all times to prevent unauthorized entry. Hazard warning signs will be prominently posted in case unauthorized entry occurs despite these measures.
4. Personnel constructing the test structure may sit or stand on the test structure, during its initial assembly. Once any of the trays have been filled, this is no longer permitted. No ladders or other tools or equipment (other than equipment needed to be in place for the test itself, such as measuring devices) may be placed on or leaned against the test structure at any subsequent time. Freestanding scaffolding, a boom lift, or other similar means will be used to access the upper parts of the test structure during the filling of the trays and at any time thereafter.
5. The individual working the pouring nozzle for the pumping of the concrete will wear a safety harness, suspended from above and monitored and belayed from the escape zone in such a way that he or she can rapidly swing away from the test structure toward the escape zone should the structure begin to collapse. Escape drills will be conducted in advance.
6. Prior to pouring any concrete, and continuously thereafter, devices (such as accelerometers and optical sensors) will be in place to monitor the position of the test structure and detect any displacement. An audible alarm will sound if displacement occurs above a threshold pre-determined by the project engineer. (A certain amount of compression during the pouring of the concrete should be expected, but tilting or excessive compression must not occur.) Should the alarm sound, all personnel will immediately evacuate the test area until the cause can be assessed.
Procedure Summary
Preliminary Steps
- Formal agreement with the challenge sponsor for the full terms of both challenges (demonstrating 1/10th crushing 9/10's, and disproving the so-called "Heiwa axiom") completed
- Verification of $100,000 of the prize money placed in escrow under control of the designated challenge referee, and verification of the existence of the remaining $900,000 in available assets liquefiable within the agreed-upon time period
- Construction of several prototype trays for preliminary testing and connector calibration
- Arrangement for fabrication of the connectors; or testing to verify the suitability of an off the shelf substitute
- Full-scale testing of the trays and connectors, to determine the precision achievable in controlling the failure load. The project may proceed when 90% of tests exhibit connector failure within +/- 10% of their predicted failure loads, and 97% within +/- 20%. If these standards cannot be met with the methods planned and within a designated deadline, the remainder of the demonstration will be cancelled and the escrowed prize funds released to the challenge sponsor.
Off-Site Preparation
- Determination of a suitable site and closing of a contract for its use
- Purchase a suitable liability insurance policy (probably a pre-condition for the previous step, and probably the most difficult step in the entire project)
- Purchase of materials, including contracts for on-site concrete delivery and pumping, and on-site timber and gravel delivery
- Contracts for the rental, delivery, and removal of scaffolding, boom lift, safety harness gear, high-speed cameras, lighting equipment (if needed), portable lavatory (if needed), lifting rig, security system
- Contracts for contingency demolition, post-test waste removal, and removal for recycling of timber cribbing and gravel
- Design and assembly of electronic control systems, e.g. to trigger cameras if the displacement alarms go off
- Pre-fabrication of test structure components: construction of the remaining trays, pre-cutting the framing timbers, fabrication and labeling of the steel connectors
- Full-weight test of the quick release mechanism for the lifting rig
On-Site, Day 1
- Site inspection
- Installation and testing of the lifting rig. (Requires tall ladders or a boom lift to place the overhead pulley.) Since the lift cable must be perfectly centered over the test structure, this step precedes base construction
- Construction of the test structure base, including pouring the concrete for the piers
- Install site security devices (entry barriers, alarm, security cam, motion sensors)
On-Site, Day 2
- Begin construction of the test bed
- Install safety harness gear
- Prepare guy rope anchor points
On-Site, Day 3
- Complete construction of the test bed
- Set up initial scaffolding or boom lift
On-Site, Day 4
- Assemble the test structure
- Install displacement sensors and alarm
- Install hazard warning signs
- Install some of the cameras, those that go in positions that will not obstruct work, including automatic triggering devices tied to displacement alarm
On-Site, Day 5
- Install remaining instrumentation on or near the test structure, including side impact test gear
- Attach lifting rig at top of test structure
- Clean up site
- Re-inspect all construction
- Establish safety perimeter
- Run escape drills for the concrete nozzle operator
- Pump concrete
- 24 hour security guard outside the facility required from this point
On-Site, Day 6
- Install remaining instrumentation outside the safety perimeter
- Monitor condition of test structure
On-Site, Day 7
- Video recording on
- Lift cable slackened
- All personnel leave test area. All personnel must have dust-filtering respirators.
- Demonstration 1: with high-speed cameras running, side impact mechanism triggered
- Telephoto inspection of post-side-impact test structure condition from outside the test area (using viewports, remote cameras, or similar means)
- If allowable, further inspection from inside the test area, outside the safety perimeter; all personnel then exit again
- Demonstration 2: with high-speed cameras running, upper tray lifted, top columns removed, and upper tray dropped by means of the quick-release mechanism
- Remote inspection of outcome.
- When deemed safe, inspection of outcome from inside the test area.
- Initial clean-up procedures will depend on the structure's condition. If it has collapsed completely or near completely, the pieces will be collected and discarded. If instead, the top tray has bounced off the others leaving the lower levels intact, then it will be deemed safe to dismantle the structure from the top down using the lifting rig to remove each tray, after first inserting wood cribbing into any open gaps. If the top several levels have gotten tangled up in lower levels, leaving multiple trays in elevated positions, then a demolition company will be hired to safely take it down. (In that case, most likely the smartest thing to do is pull it.)
On-site, days 8-10
- Removal of all materials and dismantling and removal of all equipment
- Clean-up of the facility
Unresolved Issues:
The above still needs a lot of work. Some inconsistencies regarding safety measures (e.g. what is done inside vs. from outside the building) need to be cleared up. Flying splinters (or whole column segments) are a likely possibility, making it prudent for the demonstrations to be controllable from outside the facility, or from inside a shielded chamber (not included in the write-up above). But that's no help if an unexpected premature collapse occurs while preparations are being completed. Standard head, eye, and foot protection reduce the risk but it seems significant risk remains. (Hiring truthers who don't believe that a progressive collapse could occur, or that any debris could be ejected sideways if it did, is a tempting possibility. They should have no objection to working near the test structure. But in the end I don't want any of them harmed either. Especially because I perceive many of them as being perfectly capable of denying that X could possibly happen while simultaneously suing me for failing to prevent X from happening.)
I don't want any chance of fatigue developing in the connectors during the days of concrete curing e.g. due to temperature changes. This seems unlikely in such a short time period (about 48 hours) but if necessary, the requirement that the space be temperature controlled will be added.
Scaffolding would be useful especially if it could also support the side impact test device, but given the presence of the floor pad, would be difficult to remove prior to the final test and might get in the way and/or be damaged. A boom lift might be easier all around, but that leaves the problem of how to set up the side impact test unresolved.
The concrete of the foundation piers will only be cured to about 2/3 of its nominal strength by the test day. This may not be a problem since the main the purpose of the piers is to absorb and distribute shock to the floor transmitted by the base. But a schedule allowing earlier pouring of the piers might be preferable. (The concrete in the trays will be even less cured, but that doesn't matter because that concrete is only dead weight. It only has to be solidified, not fully cured.)
An unambiguous definition of "complete collapse" will be required for the formal agreement. I propose that the definition be along the lines of: complete collapse will have occurred if none of the trays is supported entirely by vertical columns. Note that at the outset, all of the trays are supported entirely by vertical columns. So for instance if after the demonstration, one tray is left propped on two column pieces and leaning against the ground pad, or against other rubble, or against part of the base structure, that is consistent with a complete collapse. But if, for instance, the top seven trays end up stacked on the third tray, and the first and second tray have collapsed to the foundation level, but the third tray is still supported above the second tray by columns, complete collapse will not have occurred. (This definition needs work; for instance the concrete could displace out of a tray, and the empty tray being relatively light could just happen to hang up on some remaining column pieces. That should still be consistent with complete collapse but by the definition above would not be. In fact the plastic lining in the trays might not be a good idea for that reason. Paint instead? Add some rebar running through holes in the tray sides?)
Elasticity of the 2x4's. Relative to scale, these are much more elastic than the steel columns of the World Trade Center towers. Might the falling mass "merely bounce" as a result? (Inertia of the trays would seem to make this unlikely, but I'm not certain.) It might help to add horizontal spandrel connections between the columns between trays, to limit outward bowing of the columns. But that would make the wood structure between trays disproportionately strong.
Load balancing between the columns, especially where there are more than four columns (which in the current design will definitely be necessary in the lower parts, due to the shear strength limitations of the nails used to attach the connectors to trays and columns). If some columns are loaded more than others, a different form of progressive collapse than the one intended to be demonstrated could occur. Even four corner columns could end up unbalanced. A triangular cross section with only corner columns would make balancing easier (automatic as long as the structure remains true), but would also make the whole thing even more slender. (Trays could be larger to compensate; costs of some materials goes up). Or the trays might have to be designed to be more flexible, allowing the load to self-distribute more readily. Or, construction to sufficiently precise dimensions might be enough. Using shims (as is common in wood frame construction) would be problematic because those would be very difficult to calibrate.
Initial Budget Estimates
TK (Will require extensive further consultation with multiple parties including insurance agent, real estate agent, materials suppliers, equipment rental companies, and contractors.)
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Discussion Guidelines
It goes without saying that the entire plan is ultimately contingent on the first two steps listed under "Preliminary Steps" above actually happening. There is no need for any further discussion of that aspect of the project in this thread. The challenge sponsor will either attempt to make suitable arrangements or not. If he does, the arrangements will either be successfully negotiated to the satisfaction of both sides so that the project can proceed, or not. I'll report on any progress should it occur.
What I would like to discuss is any questions, suggestions, objections, or predictions regarding this project. That includes (but of course is in no way limited to) any objections from the challenge sponsor regarding the validity of the test described for addressing each of his two challenges.
Respectfully,
Myriad
Abstract
A freestanding structure 410" in height (just over 34 feet, and just over 10 meters) and approximately 52" square, and weighing approximately 11,000 pounds will be constructed indoors atop a 33" high foundation platform. The main materials will be standard wood framing lumber and normal-density concrete. The structure will support 10 "floors" of sixteen square feet each, made of wooden trays filled with concrete, comprising most of its mass. The floors will be supported by columns in such a manner that the structure's weight puts tension on steel connectors whose tensile strength will be calibrated to withstand the static load but break under significant dynamic overloads. The structure will be subject to a horizontal impact of an inert 100-pound mass at a velocity of 12 meters per second striking a support column between the eighth and ninth floors, without the structure collapsing. The top floor, comprising less than 10% of the total mass of the structure, will be disconnected and raised an additional 77 inches (totaling 118 inches, or 300 cm, of clearance from the 9th floor) and dropped. The subsequent behavior will be observed and recorded. The test will be successful if it demonstrates complete progressive collapse of the test structure (not including the foundation). All appropriate safety precautions will be taken throughout.
Introduction
The process of progressive collapse of a structure is intimately related to the scale of the construction. This is because all other factors being equal, the total gravitational potential energy of a structure increases as the fourth power of the linear scale, while the strength needed to make the structure safe under the normal range of expected uses and conditions (which is the strength with which a structure will "resist" progressive collapse once initiated) increases as only the third power.
Generally speaking, structures or models made of common materials at small scales (less than a few meters) cannot progressively collapse. They simply don't contain enough gravitational potential energy in proportion to their mass or strength. It is probably possible to make a small model progressively collapse, but doing so would require such unconventional building methods (such as, perhaps, very thin glass rods as columns supporting very heavy floor plates) that it would be nearly useless as a demonstration of the actual possibility of progressive collapse in real structures.
Large-scale structures can and do progressively collapse once collapse is initiated, but a physical model of the same order of magnitude scale as a World Trade Center tower is not practical.
So, the proposition discussed here is a demonstration using an intermediate-scale model, approximately 10 meters tall. That scale is too small for any conventionally built useful structure (such as three-story wood frame house) to progressively collapse, but an appropriately designed model at that scale should be able to, while still being somewhat realistic.
Design of the Test Structure
Ten identical trays will be prefabricated off-site. Each tray will be 49 inches square and 7-1/4 inches high. A tray will consist of a square frame made of four pieces of 2x8 lumber (flooring joists) and a 47-1/4" square base of 3/4" plywood, mounted in a 13/16" deep 11/16" wide groove set 1" from the bottom edge of the frame. Each corner of the frame will be fastened with three #12 x 2-1/2 wood screws. Each corner will also be reinforced by right angle steel brackets at the top and bottom edge of the frame (bracket and fastener specifications TK) to resist any unbalanced torque applied to the tray frames by the loads on the steel connectors (see below). The capacity of a tray will be 46" by 46" by 5-1/2", or 6.73 cubic feet. The tray interior will be seamlessly lined with 4 mil plastic sheeting to prevent the moisture of the uncured concrete from affecting the wood framing.
The vertical columns of the test structure will be knot-free lengths of standard wood framing stud (2x4's) 55 inches in length, oriented so that their broader sides are flat against the sides of the trays. Each column will connect a pair of trays, overlapping the side of each tray by about 7 inches, leaving 41 inches clearance between trays. At each tray, the columns connecting upward will be laterally offset from the columns connecting downward. The columns will not butt end to end.
At the bottom of each column (excepting the ones below the first tray and the ones supporting the top tray), the column will be hung from the adjacent tray by an S-shaped steel connector, such that the attachment between tray and connector is above the attachment between connector and column, so that all of the load on the column is transmitted as tension in the fastener. At the top of each column, the upper tray is similarly hung from the column by a similar metal connector. The figure below shows the proposed connector design, as used at a column top. If fabricating that design proves infeasible, an off-the-shelf part like: hurricane anchors or joist hangers will be adapted for the purpose by machining. If necessary, the column orientation will be changed so that the longer edge of the columns are perpendicular to the tray sides. In all cases, the connectors will be fastened to the columns and tray frames with at least eight .148 x 1-1/2" nails (joist hanger nails).
The connectors are designed to fail in tension when overloaded by dynamic loads during the demonstration. This design was chosen over an earlier designs relying on column buckling or nails failing in shear, as having more consistent and more controllable failure loadings. (Nail failure in shear, though predictable enough for such purposes as breakaway walls designed to fail under flood conditions, appears to be affected by the properties of the wood and other factors that are difficult to control with sufficient precision for this test. This is because the actual failure often occurs through distortion of the nailed materials causing the nails to pull out, rather than shearing of the nails.)
Note that at each tray, the loads on the steel connectors for the upward columns, and the loads on the connectors for the downward columns, torque the tray frame segments in opposite directions, by amounts differing only by the contribution of the tray itself to the total load. So, the trays should be sufficiently strong without requiring any strength contribution from the concrete.
The number of columns at each level (which will, almost certainly, vary from level to level) and the dimensions to which the narrow point of the connectors are adjusted for each level, will be determined in the preliminary testing stage of the project. The dimensions of the connectors will be adjusted so that the breaking force of each connector in each column is 1.3 times the static load the column will bear in the completed fully loaded test structure.
The columns between the ninth and tenth (second highest and highest) trays will be attached differently. They will fit into sockets mounted to the tray sides, held in place by the weight of the top tray. They will not be nailed. This is to permit them to be removed, from a safe distance, by means of attached cords, when the top tray is lifted for the progressive collapse demonstration.
Heavy ring bolts (fastener dimensions TBD) will be attached to each corner of each tray. At trays 3, 5, 7, and 9, each corner ring bolt will be attached to 3/4" diameter nylon rope with relatively high elasticity and a breaking strength exceeding 10,000 pounds. These sixteen ropes will run diagonally from the ring bolts at the corners of the test structure to strong anchor points at or near floor level at a horizontal distance of at least 40 feet from the test structure. Each rope will have approximately 2 feet of slack. The ropes are not expected to become tensioned (except by their own weight) at any time during the demonstration, but they are a necessary safety precaution. Also, for reasons related to scaling of angular momentum explained in one of my previous challenge thread posts, should any of the ropes become tensioned during any part of the demonstration, this will not be considered a failure condition.
The ring bolts will also be used to lift trays as needed. Only the top tray is expected to be lifted this way, but all trays will be equipped with them for contingencies. A set of cables attached to the top tray will run to a lifting rig that includes a remotely operable quick-release mechanism. The lifting rig will remain attached to the top tray during and after the pouring of the concrete. The lifting cable will be slackened during the side impact test, then used to lift and drop the top tray for the progressive collapse demonstration. All rigging necessary for carrying out these actions from a safe distance will be in place before the concrete is poured.
The base of the test structure will be a 49-inch square frame of 2x6 timber similar to the frame of a tray, resting on a 52-inch square frame of two sistered 2x8 timbers. Both types of members will be lag bolted to vertical 6x6 posts at each corner. (Fastener dimensions TBD). Each post will be set in its own 24" high x 24" dia. concrete pier, which will rest on plywood pads placed directly on the floor of the facility. The posts will extend upward to just above the upper frame of the base. The columns connecting the base with the lower tray will rest upon the lower base frame and will each be fastened to the upper base frame with four 16d framing nails.
The lower 9 trays and the base will also be interconnected by diagonal braces running from tray to tray on all four sides, to limit swaying. Materials and fasteners TBD. The material may be rigid or may be tensile only, such as thin steel cable or perforated thin gauge steel strapping.
Design Discussion
Note that the way the test structure supports its own weight does not resemble the way the World Trade Center towers did. In the towers, the vertical forces on the columns did not bear on the floors below, as they do in the above test structure design. Instead, each floor was hung from the columns and had to bear only its own weight while bracing the columns horizontally.
A test model constructed similarly, with each tray (floor) hung from columns using fasteners of calibrated strength, would very easily demonstrate pancake collapse of the floors. It would also be much easier to design and safer to construct, because the fastener strength would only have to be calibrated for the load of a single tray. The problem is that full-height wood or steel columns sufficient to safely support the total load would tend to be too strong (at this scale; it's always about scale) to be completely broken up by the collapse forces or collapse under their self-weight, unlike the wtc columns that were about 60 times taller and less flexible.
Just seeing the floors progressively sheared away isn't good enough. (If it was, then all we'd need to demonstrate the principle of progressive collapse would be some dominoes and a smooth floor. Truthers might have a hard time believing that the energy of one toppling domino could possibly be enough to knock over 1,000 or 1,000,000 other dominoes, but we can prove it!) No, we have to see the columns falling down as well.
In principle, column segments of calibrated strength in compression or column joints of calibrated strength in shear or tension could be used instead of floor attachments of calibrated strength in tension. But my assessment so far is that the design above, using column segments of excessive strength but dependent (literally) on the metal connectors, is overall easier to calibrate, and safer.
Test Site Requirements
The test site must be a building interior, zoned for industrial use, with controllable access, electrical service, water supply, adequate ventilation, and full protection from the elements. Heating, air conditioning, or full-service plumbing are not required, unless the demonstration is to take place in a time of year when heating is necessary for sufficient curing of the concrete. A slab floor bearing directly on the ground is preferred, and in any case the floor must be sufficiently strong for the test, taking the planned test bed into account (see Site Preparation below).
There must be truck access to the interior space or to just outside an entrance.
The minimum floor extent is 60 by 80 feet, to allow for positioning of cameras on all sides at sufficient distance for good views of the test, and for an escape zone beginning at least 40 feet from the base of the structure.
A means to anchor the guy ropes approximately 40 feet or more diagonally from each corner of the structure, at or near floor level, must exist.
The test chamber must have a minimum of 42 feet of overhead clearance. The means to attach a pulley rated for a 5,000 pound load must exist over the center of the test structure, which must be 30 feet or more from any wall on any side.
Test Site Preparation
The following must be installed or determined to already exist:
1. The winch and overhead pulley portions of the lifting rig for the top tray.
2. Overhead rigging for the personal safety harness.
3. Sufficient lighting for high-speed video photography.
4. Anchor points for the guy ropes.
5. Door security and interior security systems (door lock, interior motion sensor, audible alarms)
Unless the facility has an earth floor, or is scheduled for floor demolition, it will be necessary to protect the floor from damage from the impact of heavy trays and other debris. A protective floor pad will be constructed, 24 feet square and centered on the test structure base. The exact design is TBD, but most likely will incorporate a layer of dense wooden cribbing and a deep gravel bed.
The rigging for the side impact test must also be prepared. The design of this is TK and will probably require some preliminary development and testing. The simplest possibility is to allow the weight to swing into the test structure from an attachment point directly above the planned impact point. However, to get sufficient velocity this way, the weight would have to begin its descent from over 7 meters above the impact point, requiring an additional two stories of total ceiling clearance, which is unlikely to be available.
A lesser weight at a faster velocity would better resemble the 9/11 plane crashes in terms of momentum transfer, but approaches using ballista, air cannons, and comparable methods present problems related to safety, accuracy, and sufficient control over the impact velocity. One workable approach might be battering ram running along a track (which might be mounted to scaffolding), powered by a speed-controlled motor connected via a windlass.
Instrumentation
Apart from the instruments for safety monitoring, there is little need for instruments other than cameras for documenting the event. To put it bluntly, this demonstration has little value as scientific research. It is based upon, and it will illustrate, basic principles of Newtonian mechanics that have been thoroughly understood for centuries. [Note to self: delete previous two sentences if using this text for a grant application.]
However, if anyone wants to make a case for additional instrumentation such as accelerometers, strain gauges, load cells, microphones, seismograph, etc., I might be able to add them to the project. An example might be measurements that would help calibrate a computer model. (Strain gauges on the steel connectors might be needed for safety, which would add considerable cost and complication.)
For the photography, video recorded from multiple angles including top-down, with at least two of the cameras being high-speed, seems appropriate for such an elaborate and "one-take" demonstration. An additional video recording using an infrared camera will be included, to prove that no thermite is being used.
Site Safety Policies
1. Anyone entering the site for any reason at any time from the start of construction to the completion of the post-test clean-up must wear OSHA-approved hardhats, work gloves, boots, and safety goggles at all times. After the demonstration, dust filtering masks must also be worn until the completion of the clean-up phase.
2. No spectators will be permitted inside the test area at any time, except for one representative of the challenge sponsor, who must sign a personal injury liability waiver and must agree to obey all safety directives issued by the challenge claimant.
3. From the time concrete is poured in any of the trays, to the completion of the first stage of clean-up, the site will be attended from outside by a security guard at all times to prevent unauthorized entry. Hazard warning signs will be prominently posted in case unauthorized entry occurs despite these measures.
4. Personnel constructing the test structure may sit or stand on the test structure, during its initial assembly. Once any of the trays have been filled, this is no longer permitted. No ladders or other tools or equipment (other than equipment needed to be in place for the test itself, such as measuring devices) may be placed on or leaned against the test structure at any subsequent time. Freestanding scaffolding, a boom lift, or other similar means will be used to access the upper parts of the test structure during the filling of the trays and at any time thereafter.
5. The individual working the pouring nozzle for the pumping of the concrete will wear a safety harness, suspended from above and monitored and belayed from the escape zone in such a way that he or she can rapidly swing away from the test structure toward the escape zone should the structure begin to collapse. Escape drills will be conducted in advance.
6. Prior to pouring any concrete, and continuously thereafter, devices (such as accelerometers and optical sensors) will be in place to monitor the position of the test structure and detect any displacement. An audible alarm will sound if displacement occurs above a threshold pre-determined by the project engineer. (A certain amount of compression during the pouring of the concrete should be expected, but tilting or excessive compression must not occur.) Should the alarm sound, all personnel will immediately evacuate the test area until the cause can be assessed.
Procedure Summary
Preliminary Steps
- Formal agreement with the challenge sponsor for the full terms of both challenges (demonstrating 1/10th crushing 9/10's, and disproving the so-called "Heiwa axiom") completed
- Verification of $100,000 of the prize money placed in escrow under control of the designated challenge referee, and verification of the existence of the remaining $900,000 in available assets liquefiable within the agreed-upon time period
- Construction of several prototype trays for preliminary testing and connector calibration
- Arrangement for fabrication of the connectors; or testing to verify the suitability of an off the shelf substitute
- Full-scale testing of the trays and connectors, to determine the precision achievable in controlling the failure load. The project may proceed when 90% of tests exhibit connector failure within +/- 10% of their predicted failure loads, and 97% within +/- 20%. If these standards cannot be met with the methods planned and within a designated deadline, the remainder of the demonstration will be cancelled and the escrowed prize funds released to the challenge sponsor.
Off-Site Preparation
- Determination of a suitable site and closing of a contract for its use
- Purchase a suitable liability insurance policy (probably a pre-condition for the previous step, and probably the most difficult step in the entire project)
- Purchase of materials, including contracts for on-site concrete delivery and pumping, and on-site timber and gravel delivery
- Contracts for the rental, delivery, and removal of scaffolding, boom lift, safety harness gear, high-speed cameras, lighting equipment (if needed), portable lavatory (if needed), lifting rig, security system
- Contracts for contingency demolition, post-test waste removal, and removal for recycling of timber cribbing and gravel
- Design and assembly of electronic control systems, e.g. to trigger cameras if the displacement alarms go off
- Pre-fabrication of test structure components: construction of the remaining trays, pre-cutting the framing timbers, fabrication and labeling of the steel connectors
- Full-weight test of the quick release mechanism for the lifting rig
On-Site, Day 1
- Site inspection
- Installation and testing of the lifting rig. (Requires tall ladders or a boom lift to place the overhead pulley.) Since the lift cable must be perfectly centered over the test structure, this step precedes base construction
- Construction of the test structure base, including pouring the concrete for the piers
- Install site security devices (entry barriers, alarm, security cam, motion sensors)
On-Site, Day 2
- Begin construction of the test bed
- Install safety harness gear
- Prepare guy rope anchor points
On-Site, Day 3
- Complete construction of the test bed
- Set up initial scaffolding or boom lift
On-Site, Day 4
- Assemble the test structure
- Install displacement sensors and alarm
- Install hazard warning signs
- Install some of the cameras, those that go in positions that will not obstruct work, including automatic triggering devices tied to displacement alarm
On-Site, Day 5
- Install remaining instrumentation on or near the test structure, including side impact test gear
- Attach lifting rig at top of test structure
- Clean up site
- Re-inspect all construction
- Establish safety perimeter
- Run escape drills for the concrete nozzle operator
- Pump concrete
- 24 hour security guard outside the facility required from this point
On-Site, Day 6
- Install remaining instrumentation outside the safety perimeter
- Monitor condition of test structure
On-Site, Day 7
- Video recording on
- Lift cable slackened
- All personnel leave test area. All personnel must have dust-filtering respirators.
- Demonstration 1: with high-speed cameras running, side impact mechanism triggered
- Telephoto inspection of post-side-impact test structure condition from outside the test area (using viewports, remote cameras, or similar means)
- If allowable, further inspection from inside the test area, outside the safety perimeter; all personnel then exit again
- Demonstration 2: with high-speed cameras running, upper tray lifted, top columns removed, and upper tray dropped by means of the quick-release mechanism
- Remote inspection of outcome.
- When deemed safe, inspection of outcome from inside the test area.
- Initial clean-up procedures will depend on the structure's condition. If it has collapsed completely or near completely, the pieces will be collected and discarded. If instead, the top tray has bounced off the others leaving the lower levels intact, then it will be deemed safe to dismantle the structure from the top down using the lifting rig to remove each tray, after first inserting wood cribbing into any open gaps. If the top several levels have gotten tangled up in lower levels, leaving multiple trays in elevated positions, then a demolition company will be hired to safely take it down. (In that case, most likely the smartest thing to do is pull it.)
On-site, days 8-10
- Removal of all materials and dismantling and removal of all equipment
- Clean-up of the facility
Unresolved Issues:
The above still needs a lot of work. Some inconsistencies regarding safety measures (e.g. what is done inside vs. from outside the building) need to be cleared up. Flying splinters (or whole column segments) are a likely possibility, making it prudent for the demonstrations to be controllable from outside the facility, or from inside a shielded chamber (not included in the write-up above). But that's no help if an unexpected premature collapse occurs while preparations are being completed. Standard head, eye, and foot protection reduce the risk but it seems significant risk remains. (Hiring truthers who don't believe that a progressive collapse could occur, or that any debris could be ejected sideways if it did, is a tempting possibility. They should have no objection to working near the test structure. But in the end I don't want any of them harmed either. Especially because I perceive many of them as being perfectly capable of denying that X could possibly happen while simultaneously suing me for failing to prevent X from happening.)
I don't want any chance of fatigue developing in the connectors during the days of concrete curing e.g. due to temperature changes. This seems unlikely in such a short time period (about 48 hours) but if necessary, the requirement that the space be temperature controlled will be added.
Scaffolding would be useful especially if it could also support the side impact test device, but given the presence of the floor pad, would be difficult to remove prior to the final test and might get in the way and/or be damaged. A boom lift might be easier all around, but that leaves the problem of how to set up the side impact test unresolved.
The concrete of the foundation piers will only be cured to about 2/3 of its nominal strength by the test day. This may not be a problem since the main the purpose of the piers is to absorb and distribute shock to the floor transmitted by the base. But a schedule allowing earlier pouring of the piers might be preferable. (The concrete in the trays will be even less cured, but that doesn't matter because that concrete is only dead weight. It only has to be solidified, not fully cured.)
An unambiguous definition of "complete collapse" will be required for the formal agreement. I propose that the definition be along the lines of: complete collapse will have occurred if none of the trays is supported entirely by vertical columns. Note that at the outset, all of the trays are supported entirely by vertical columns. So for instance if after the demonstration, one tray is left propped on two column pieces and leaning against the ground pad, or against other rubble, or against part of the base structure, that is consistent with a complete collapse. But if, for instance, the top seven trays end up stacked on the third tray, and the first and second tray have collapsed to the foundation level, but the third tray is still supported above the second tray by columns, complete collapse will not have occurred. (This definition needs work; for instance the concrete could displace out of a tray, and the empty tray being relatively light could just happen to hang up on some remaining column pieces. That should still be consistent with complete collapse but by the definition above would not be. In fact the plastic lining in the trays might not be a good idea for that reason. Paint instead? Add some rebar running through holes in the tray sides?)
Elasticity of the 2x4's. Relative to scale, these are much more elastic than the steel columns of the World Trade Center towers. Might the falling mass "merely bounce" as a result? (Inertia of the trays would seem to make this unlikely, but I'm not certain.) It might help to add horizontal spandrel connections between the columns between trays, to limit outward bowing of the columns. But that would make the wood structure between trays disproportionately strong.
Load balancing between the columns, especially where there are more than four columns (which in the current design will definitely be necessary in the lower parts, due to the shear strength limitations of the nails used to attach the connectors to trays and columns). If some columns are loaded more than others, a different form of progressive collapse than the one intended to be demonstrated could occur. Even four corner columns could end up unbalanced. A triangular cross section with only corner columns would make balancing easier (automatic as long as the structure remains true), but would also make the whole thing even more slender. (Trays could be larger to compensate; costs of some materials goes up). Or the trays might have to be designed to be more flexible, allowing the load to self-distribute more readily. Or, construction to sufficiently precise dimensions might be enough. Using shims (as is common in wood frame construction) would be problematic because those would be very difficult to calibrate.
Initial Budget Estimates
TK (Will require extensive further consultation with multiple parties including insurance agent, real estate agent, materials suppliers, equipment rental companies, and contractors.)
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Discussion Guidelines
It goes without saying that the entire plan is ultimately contingent on the first two steps listed under "Preliminary Steps" above actually happening. There is no need for any further discussion of that aspect of the project in this thread. The challenge sponsor will either attempt to make suitable arrangements or not. If he does, the arrangements will either be successfully negotiated to the satisfaction of both sides so that the project can proceed, or not. I'll report on any progress should it occur.
What I would like to discuss is any questions, suggestions, objections, or predictions regarding this project. That includes (but of course is in no way limited to) any objections from the challenge sponsor regarding the validity of the test described for addressing each of his two challenges.
Respectfully,
Myriad
