Design of Shear

The theory and design requirements for shear have been covered in EC3 and the relevant design equations were derived based on the requirements of EC2 using the variable strut inclination method. 

The shear reinforcement will usually take the form of vertical links or a combination of links and bent-up bars. Shear reinforcement may not be required in very minor beams such as door or window lintels with short spans of less than say 1.5 m and light loads. 

The following notation is used in the equations for the shear design 

max — the maximum design value of the shear which can be resisted by the concrete strut 

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Nakamura, X, Tsuji, M. (1996). Inverse damping perturbation for stiffness design of shear buildings. Journal of Structural Engineering, 122(6), 617-625. doi 10.1061/(ASCE)0733-9445(1996)122 6(617)... 

Xsuji, M., Nakamura, X. (1996). Optimal viscous dampers for stififiiess design of shear buildings. Structural Design of Tall Buildings, 5, 217-234. doi 10.1002/(SICI)1099-1794( 199609)5 3<217 AID-XAL70>3.0. CO 2-R... 

Peachey J, van Alsten J and Granick S 1991 Design of an apparatus to measure the shear response of ultrathin liquid films Rev. Sci. Instrum. 62 463-73... 

Ultrasonic Welding. Ultrasonic welding has been appHed to Tefzel with weld strength up to 80% of the strength of the base resin. Typical conditions include a contact pressure of 172 kPa (25 psi) and 1—2 s cycle time. The two basic designs, the shear and butt joints, employ a small initial contact area to concentrate and direct the high frequency vibrational energy. 

Normal Stress (Weissenberg Effect). Many viscoelastic fluids flow in a direction normal (perpendicular) to the direction of shear stress in steady-state shear (21,90). Examples of the effect include flour dough climbing up a beater, polymer solutions climbing up the inner cylinder in a concentric cylinder viscometer, and paints forcing apart the cone and plate of a cone—plate viscometer. The normal stress effect has been put to practical use in certain screwless extmders designed in a cone—plate or plate—plate configuration, where the polymer enters at the periphery and exits at the axis. 

Brookfield has introduced a new digital cone—plate viscometer in two versions. The CAP 1000 is a single speed instmment (12,000 or 3, 000 with 60 Hz current) that upgrades the ICl cone—plate design (ASTM D4287). The CAP 2000 is a multispeed viscometer with a viscosity range of 1 15, 000 mPa-s. This instmment covers a wide range of shear rates (166-26, 600 ) and complements the low shear WeUs-Brookfield viscometer. 

A wide variety of nonnewtonian fluids are encountered industrially. They may exhibit Bingham-plastic, pseudoplastic, or dilatant behavior and may or may not be thixotropic. For design of equipment to handle or process nonnewtonian fluids, the properties must usually be measured experimentally, since no generahzed relationships exist to pi e-dicl the properties or behavior of the fluids. Details of handling nonnewtonian fluids are described completely by Skelland (Non-Newtonian Flow and Heat Transfer, Wiley, New York, 1967). The generalized shear-stress rate-of-strain relationship for nonnewtonian fluids is given as... 

The SE values in Table 10-49 are equal to the basic allowable stresses in tension S multiplied by a quality factor E (see subsection Pressure Design of Metallic Components Wall Tliick-ness"). The design stress values for bolting materials are equal to die basic allowable stresses S. The stress values in shear shall be 0.80 times the allowable stresses in tension derived from tabulated values in Table 10-49 adjusted when applicable in accordance widi Note 13. 8tress values in bearing shall be twice those in shear. 

Part AD This part contains requirements for the design of vessels. The rules of Division 2 are based on the maximum-shear theoiy of failure for stress failure and yielding. Higher stresses are permitted when wind or earthquake loads are considered. Any rules for determining the need for fatigue analysis are given here. 

When macro-scale variables are involved, every geometric design variable can affect the role of shear stresses. They can include such items as power, impeller speed, impeller diameter, impeller blade shape, impeller blade width or height, thickness of the material used to make the impeller, number of blades, impeller location, baffle location, and number of impellers. 

The strong dependence of apparent viscosity on shear rate. This necessitates particular care in the design of complex extrusion dies. 

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