Requirements for Stairway Landings According to IBC 2009

There shall be a floor or landing at the top and bottom of each stairway. The width of landings shall not be less than the width of stairways they serve. Every landing shall have a minimum dimension measured in the direction of travel equal to the width of the stairway. Such dimension need not exceed 48 inches (1219 mm) where the stairway has a straight run. Doors opening onto a landing shall not reduce the landing to less than one-half the required width. When fully open, the door shall not project more than 7 inches (178 mm) into a landing. When wheelchair spaces are required on the stairway landing in accordance with Section 1007.6.1, the wheelchair space shall not be located in the required width of the landing and doors shall not swing over the wheelchair spaces. 

 

1007.6.1Size. Each area of refuge shall be sized to accommodate one wheelchair space of 30 inches by 48 inches (762 mm by1219 mm) for each 200 occupants or portion thereof, based on the occupant load of the area of refuge and areas served by the area of refuge. Such wheelchair spaces shall not reduce the required means of egress width. Access to any of the required wheelchair spaces in an area of refuge shall not be obstructed by by more than one adjoining wheelchair space.

Bangladesh Building Construction Rules 2008

These rules superseded the previous Building Construction (BC) rules of 1984. These rules seek to control development plot‐by‐plot and case‐by‐case. It controls development by imposing conditions on set backs, site coverage, construction of garages, access to plot, provision of lift, land use of that particular plot and height of building. Restricting the height of a building in BC Rules 1996 helps to control the density of an area and manage the growth of the city in some way.

The Dhaka Metropolitan Building Construction Rules 200810 superseded the earlier set of rules issued in 1996 for the Dhaka Metropolitan Area and provided more authority to RAJUK in the following way;

1. Clear‐cut responsibility to monitor the development of the city,

2. Spread out the responsibilities to various actors,

 

3. Spelled out responsibilities of building designers, structural engineers, site supervisors and their penalties etc.

One of the most significant improvements is the introduction of Floor Area Ratio (FAR). To manage the growth of the city it provides rules of building coverage area, allowable floor space and relation among building height ‐ road width and plot size.

Effectiveness of the new BCR rules will depend on how successfully implementation of these rules can be effected by RAJUK in a transparent way and keeping themselves away from corruption.

Structural System can be Handled with STAAD.Pro.

A STRUCTURE can be defined as an assemblage of elements. STAAD is capable of analyzing and designing structures consisting of both frame, plate/shell and solid elements. Almost any type of structure can be analyzed by STAAD.

A SPACE structure, which is a three dimensional framed structure with loads applied in any plane, is the most general.

A PLANE structure is bound by a global X-Y coordinate system with loads in the same plane.

A TRUSS structure consists of truss members which can have only axial member forces and no bending in the members.

A FLOOR structure is a two or three dimensional structure having no horizontal (global X or Z) movement of the structure [FX, FZ & MY are restrained at every joint]. The floor framing (in global X-Z plane) of a building is an ideal example of a FLOOR structure. Columns can also be modeled with the floor in a FLOOR structure as long as the structure has no horizontal loading. If there is any horizontal load, it must be analyzed as a SPACE structure.

Specification of the correct structure type reduces the number of equations to be solved during the analysis. This results in a faster and more economic solution for the user. The degrees of freedom associated with frame elements of different types of structures is illustrated in Figure 1

Different Types of Earth Pressure Cells, Their Applications and Construction of Isobar Diagram Using Them-25

The above formulas apply to pressures acting on a free surface. However, in the confined case, Y, at the edge of the cell, can be assumed to be nearly zero and so Y, at the center, is assumed to be:

i.e. the same difference as before.

If the average Y, across the cell is assumed to be half this value and if the deformation of the medium on either side of the cell is assumed to be the same then the average total expansion of the cell is given by:

Y = 0.73 PR (1-ν²) x 0.5 x 2/E = 0.73 PR (1-ν²)/E...........(3.8)

Equating 3.8 & 3.9 gives:

P (D/G + 0.73 R (1- ν²)/E) = KD ...........(3.9)

If one side of the cell lies in contact with a rigid structure, e.g. a concrete retaining wall or a concrete bridge footing, then

Y = 0.73 PR (1-ν²) x 0.5/E = 0.36 PR (1-ν² )/E ...........(3.10)

P (D/G + 0.73 R (1- ν²)/E) = KD  ...........(3.11)

Where E pertains to the soil material. Since these expressions are only approximate they can be simplified even further: for all E < 10 x 106 psi the term D/G is negligible so long as the cell is designed and constructed properly, i.e., G is large, (no air trapped inside the

^{cell), and D is small. Also, the term} (1-ν²) can be replaced by 0.91 since v usually lies between 0.25 and 0.35. Hence, for total embedment: 

P = 1.5 EKD/R  psi / ^oC

And, for contact pressure cells:

P = 3 EKD/R  psi / ^oC

Some typical values of the various parameters are:

Liquid	K x 10-6 / ºC	G x 106 psi
Oil	700	0.3
Mercury	180	3.6
Water	170	0.3
Glycol	650
50/50 Glycol/Water	400

Embedment Material	E x 106 psi	ν
Plastic Clay	0.003
Soil	0.001 to 0.02 [Ref 2]	0.25 to 0.45
Sand	0.02 to 0.06 [Ref 3]	0.28 to 0.35
Compacted Ottawa Sand	0.2
Weathered Rock	0.04 to 0.11 [Ref 4]
Concrete	5.0	0.25

Examples.

For an oil-filled cell, 9 inches diameter and D = 0.060 inches, totally embedded in:

SI No	Soil Type	E(PSI)	ν	P(psi /oC)
1	Plastic Clay	3000	0.3	0.042
2	Soil, medium stiffness	10000	0.3	0.138
3	Coarse Sand	50000	0.3	0.69

(For contact pressure cells, multiply the above values for P by 2.)

For a concrete stress cell, 9 inch diameter and D = 0.020 inches:

4. Concrete, E = 5 x 106 psi, ν = 0.25 ……….P = 22.7 psi /^oC

Same cell, embedded in concrete, filled with mercury instead of oil, P = 5.8 psi / ^oC

For an oil-filled cell embedded in a completely rigid medium ……… P = 210 psi / ^oC

For a mercury-filled cell embedded in a completely rigid medium …P = 650 psi / ^oC

References:
[1] Roark, R.J. and Young, W.C. “ Formulas for Stress and Strain,” McGraw Hill, fifth edition, 1982, p 519.
[2] Weiler, W.A. and Kulhawy, F.H. “ Factors Affecting Stress Cell Measurement in Soil” J. Geotech. Eng. Div. ASCE . Vol. 108, No. GT12.
[3] Lazebnik, G.E., “Monitoring of Soil-Structure Interaction.” Chapman & Hall.
[4] Fujiyasu, Y. and Orihara, K. “Elastic Modulus of Weathered Rock.” Proc. of the 5th Intl. Symp. on Field Measurements in Geomechanics - Singapore 1999. p 183
[5] Arora, K. R., “Soil Mechanics & Foundation Engineering.”- p 218

Different Types of Earth Pressure Cells, Their Applications and Construction of Isobar Diagram Using Them-24

3.6. Temperature Effect on Earth Pressure and Concrete Stress Cells

Some Theoretical Considerations

The following theoretical treatment is by no means rigorous - there are some questionable assumptions and approximations – but it should give some idea of the magnitude of the thermal effect to be expected on hydraulic earth pressure cells, buried in soil, or installed at the contact between soil and structure, and on concrete stress cells embedded in concrete. Consider a circular cell of radius R containing a liquid film of thickness D, coefficient of thermal expansion Kppm/°C, and bulk modulus G.

For a temperature rise of 1° C the expansion, YT of the liquid film is given by the equation:

Y_T = KD ……………………………(3.5)

Expansion of the liquid is resisted by the confinement of the surrounding medium (soil or concrete) and this causes a pressure rise, P, in the liquid and a compression of the liquid, Y_c, given by the equation:

Yc = PD/G……………………………(3.6)

So that the net expansion, Y, of the cell is equal to:

Y = D (K- P/G)…………………………..(3.7)

Liquid pressure inside the cell causes deformation of the surrounding medium. The amount of deformation can be quantified by modification of formulas found in [1], where the deformation, Y, produced by a uniform pressure, P, acting on a circular area, R radius, on the surface of a material with modulus of elasticity, E, and Poissons ratio, ν, is given by:

SI NO	CONDITION	Y=	DIFFERENCE
1	AT THE CENTER
2	AT THE EDGE

Different Types of Earth Pressure Cells, Their Applications and Construction of Isobar Diagram Using Them-23

3.5. THERMISTOR TEMPERATURE DERIVATION

Resistance to Temperature Equation:

Equation to Convert Thermistor Resistance to Temperature

The explanation for symbols are; 

T = Temperature in °C. 

LnR = Natural Log of Thermistor Resistance

A = 1.4051 × 10^-3 (coefficients calculated over the −50 to +150° C. span)

B = 2.369 × 10^-4 , C = 1.019 × 10^-7

 

Table 3.3- Thermistor Resistance versus Temperature

Different Types of Earth Pressure Cells, Their Applications and Construction of Isobar Diagram Using Them-22

3.3 TROUBLESHOOTING

Maintenance and troubleshooting of Pressure Cells is confined to periodic checks of cable connections. Once installed, the cells are usually inaccessible and remedial action is limited.

Symptom: Pressure Cell Readings are Unstable

1. If the readout box is not positioned correctly to record readings and the swept frequency excitation settings are not correct then the cell should be set up on a different readout position. For instance, channel A of the GK-403 might be able to read the pressure cells. To convert the Channel A period display to digits Equation 1 can be used.

2. If there a source of electrical noise nearby and most probable sources of electrical noise are motors, generators, transformers, arc welders and antennas. It should be checked that the shield drain wire is connected to ground whether using a portable readout or data logger. In case of GK-403 the clip is connected with the blue boot to the shield drain wire.

3. If the readout does not work with another pressure cell then the readout may have a low battery or be malfunctioning.

Symptom: Pressure Cell Fails to Read

1. If the cable is cut or crushed can be checked with an ohmmeter. Nominal resistance between the two gage leads (usually red and black leads) is 180Ω, +/- 5%. The cable resistance is added when checking (22 AWG stranded copper leads are approximately 14.7Ω/1000' or 48.5Ω/km, multiply by 2 for both directions). If the resistance reads infinite or very high (megohms), a cut wire must be suspected. If the resistance reads very low (<100Ω) a short in the cable is likely.

2. If the readout does not work with another pressure cell then the readout may have a low battery or be malfunctioning.

Figure 3.1 - Calibration Sheet

Model:	4800 Earth Pressure Cell (rectangular)	4800 Earth Pressure Cell (circular)	4810 Contact Pressure Cell	4820 Jack-Out Pressure Cell
Ranges:	350 kPa (50 psi) 700 kPa (100 psi) 1.5 MPa (250 psi) 3.5 MPa (500 psi) 5 MPa (750 psi) 7 MPa (1000 psi) 20 MPa (3000 psi)	350 kPa (50 psi) 700 kPa (100 psi) 1.5 MPa (250 psi) 2.5 MPa (500 psi) 5 MPa (750 psi) 7 MPa (1000 psi) 20 MPa (3000 psi)	2 MPa (300 psi) 3.5 MPa (500 psi) 5 MPa (750 psi)	0.3 MPa (50 psi) 0.7 MPa (100 psi) 1.5 MPa (200 psi)
Sensitivity:	0.025% FSR
Accuracy:	0.5% FSR (0.1% FSR with a polynomial expression)
Linearity:	0.5% FSR (standard) 0.1% FSR (optional)
Overrange:	200% FSR
Operating Temperature:	-30 to +70° C
Frequency range	1400-3500Hz
Cell Dimensions: (active area)	100 × 200 mm 4 × 8"	230 mm OD 9" OD	230 mm OD 9" OD	125 mm OD 5" OD
Coil Resistance:	150 Ω
Cell Material:	304 Stainless Steel
Transducer Material:	303 & 304 Stainless Steel
Weight:	2.3 kg. 5 lbs.	2.3 kg. 5 lbs.	4.7 kg. 10.3 lbs.	2.7 kg. 6 lbs.
Electrical  Cable:	2 twisted pair (4 stranded conductor), 22 AWG Foil shield (with drain wire), PVC jacket, nominal OD=6.3 mm (0.250")

Table 3.2- Earth Pressure Cell Specifications