Overall buckling analysis of frames- Approximate methods

method of overall buckling load are included because it indicates an upper bound for the critical gravity load and it allows an assessment of the relative vulnerability of the building to transverse buckling or torsional buckling and for structures which an approximate p-delta analysis to amplification factor for the displacements and moments.

Shear mode

this mode is when double bending of the columns and girders buckling occurs in resistant frames as a result of story sway.

shear buckling

Flexural mode

in this mode, the entire structure buckles as a flexural cantilever by axial deformations of the columns. the greater the slenderness of structure it becomes more vulnerable  to instability in the flexural mode as opposed to the shear mode.

flexural buckling in structure

Combined shear and flexural modes

this is a contribution of shear and flexural modes, in this case of the buckling of a vertical cantilever with a gravity load as its top, below solution exists

1/Pcr = 1/Pf + 1/Ps

Pcr, Pf and Ps = critical loads for the combined, flexural and shear modes of buckling respectively.

flexural-shear buckling in structure

Manpower mechanical wood robot

Common types of roof truss - wood or steel truss

what we call a truss is a structural composed of slender members joined at there end points making a frame sort a thing, in construction industry its widely used either with wood struts, metal bars, angles or channels. these thing are joined with bolts, nail, or welding depending on the material used.

Truss used to support roof depends on the span, slop, and the roof materials. below are the common types used:

1. scissors
2. Howe
3. Pratt
4. Fan
5. Fink
6. Cambered fink
7. warren
8. Sawtooth
9. Bowstring
10. Three-Hinged arch

1. Scissors

2. Howe

3. Pratt

4. Fan

5. Fink

6. Cambered fink

7. warren

warren truss used in bridges

8. Sawtooth

sawtooth is very famous used in factory roofs

9. Bowstring

bowstring roof

10. Three-Hinged arch

below is a list of truss used in construction industry depending on design and use.

permeability and seepage in soil - Darcy's Law

Darcy's Law

In 1984, Darcy publish a simple equation for the discharge velocity of water through saturated soil with a simple equation below;

v=Ki

v = discharge velocity (flow of water right angles to the of the cross section)
K = permeability coefficient or hydraulic conductivity

Dacy got this equation from experiments he did in clean sand which flows water, v is discharge of velocity of water based on gross cross section of soil, but in actual case void space velocity of water is high than v, relationship between the discharge velocity and the seepage velocity can be derived as

vs = v/n

vs= seepage velocity
n= porosity

How to field determination of saturation flow of Traffic

To know traffic flow,  two people are needed to carry out this study, one person needs to have a stop watch or a timer equipped device, and other to record a events with a appropriate software or a notebook computer. details such as area type, width, and grade of the lane being evaluated to be measured and recorded.

thak you need to have a good point for observation with a clear vision without any obstetrical and able to see traffic light, mark a specific point for traffic to enter, than follow below steps:
1. Timer starts the stop watch as green light and record the time
2. recorder immediately notes the last vehicle in the stopped queue and describes the timer and also notes vehicles details such as heavy and light and who turns right and left
3. timer than reads all the vehicles passing
4. timer records all the vehicles that passed and noted
5. width of the lane and slope of approach are then measured and recorded together with any unudal occurrence that might have effected the flow
6. just after the green phase is less than saturation flow, the time considered for calculating the saturation flow is theat between the time the rear axle of the car crosses the reference point t4 and the time the rear axle of the fourth car crosses the reference point tn. below equation can be used

Saturation flow = 3600/((t4-tn)/(n-4))

where n is the number of last vehicle surveyed.

field sheet for direct observation of prevailing saturation flow ratio