Recent content by J1D

Thanks. I understand it is in a transitional period using limit states design in evaluating geotechnical capacities. But it should a smooth process to correlate to the traditional allowable capacities. What we encountered now, in many cases, is the real geotechnical design capacity is lower...

You can embed a spreadsheet in MathCad for the sectional properties.

In all the geotechnical reports (in Canada) now Factored ULS (Ultimate Limit State) Resistances are given instead of traditional Allowable Resistance. When using factored ULS you find the capacity is lower than before. For example, I have two geotech reports done by the same geotechnical...

We used pre-painted black even on the exterior grating for years, no issues. As per Fisher & Ludlow, the grating mats are supplied in 3'x24' standard size. The bearing bars are in the 24' direction. If we have a 3'x24' walkway Option A needs only one panel. The price is about $770/lot. To...

I realized recently this is specified differently among my colleagues. There is no standard for the spanning direction of grating mats on platforms, walkways, etc. But for an elevated walkway or catwalk it is preferred in some client specs to have the bearing bars perpendicular to the walking...

We encountered a situation where grout is required to fill into a tube formed by two I beams. The beam is about 39ft long and the tube is about 8"x10" section. Is the curing of the grout a concern in this case? I mean whether the grout can get strength inside a steel tube permernantly. The...

graybeach, the damage happened during transportation by the owner. bridgebuster, does the drill hurt the concrete? Or I need wire mesh in the patch? Thanks j1d

A precast girder is damaged at the end as shown. Would anybody suggest how to repair. It is 70MPa strength concrete with prestress strands. Thanks in advance j1d

I see your good points. There is a 12" thick voidfoam under the pilecap (i.e. foundation). The design soil heave under the pilecap is 4", this is also the compression amount of the voidfoam. My point (to support the adfreeze on pile still existing) is the soil is not restrained by the pilecap...

The piles are designed to be deep enough to resist all the upward heaving force. So the piles with foundation won't move. Regards, j1d

It seems clear to me that the upward heaving force develops in two ways: 1 frost heave pressure on underside surface of foundation, 2 upward adfreeze force on the side surfaces of foundation AND on the pile perimeter. But when some engineers suggested that the afreeze on pile can be ignored...

I have this book. But I only found the critical damping equation on page 513 (Eq. 7.50). But when I used it for rocking mode, the unit problem occurred as described about. The equation looks like being for translational modes only. Regards, j1d

Thanks Vulcanhammer, you provide pretty good info on the web. But still I don't know how to calculate the critical damping for rocking. In a specification it is required that the geometric damping ratio of pile group for rocking mode is less than 0.10. Regards, j1d

When calculating the damping ratio of rotational vibration of a concrete block foundation I realized that I am not sure the critical damping equation is correct. If I use the quation: Cc=2*sqrt(K*m) (where K is the stiffness, m is the mass, Cc is the critical damping constant) and compute the...

Thanks Structureguy, You're right F1554 Gr 105 is about same strength as A320 Gr L7. F1554 Gr 55 (with Fy=55ksi) looks better for me if it suits old temperature as well.