Strength service factor

The allowable stress for occasional loads of short duration, such as surge, extreme wind, or earthquake, may be taken as the strength reduction factor times 90% of the yield strength at temperature times Mj for materials with ductile behavior. This yield strength shall be as listed in ASME BPV Code Section II, Part D, Table Y-l (ensure materials are suitable for hydrogen service see API 941), or determined in accordance with para. 

The proper approach is to consider the application in which a material is used such as in panels with identical dimensions with the service requirements of stiffiiess and strength in flexure. Their flexural stiffnesses and strengths depend directly on the respective material s modulus and strength. Other factors are similar such as no significandy different Poisson ratios. The different panel properties relative to stiffness and strength are shown in Figure 8.21. The metal panels are stiffer and stronger than the plastic ones because the panels with equal dimensions that use equal volumes of materials. 

Normally a cast-in-place solid slab qualifies as a diaphragm, if it is monolithically coimected to the elements of the lateral-force-resisting system and has thickness and two-way reinforcement which meet the requirements of design codes concerning the flexural strength under factored gravity loads, the limits on deflection and crack width under service loads, and the minimum slab reinforcement. 

Figure 6a shows the plan view of the prototype building used for this study. The study focuses on the interior steel MRF shown in Fig. 6b. The yield stress of structural steel is equal to 300 MPa. The design seismic action, referred to herein as DBF, has a return period equal to 475 years and is expressed by the elastic design spectrum of Eurocode 8 (2004) with peak ground acceleration equal to 0.3 g and soil B. The interior MRF is first designed as a conventional MRF according to EC3 (2003) and EC8. The behavior (or strength reduction) factor q is equal to 6.5. Eurocode 8 imposes a serviceability limit on the peak story drift, 0max, under the frequent earthquake (FOE) with a return period equal to 95 years. The FOE has intensity equal to 40 % the intensity of the DBE, and the limit on is 0.5 % and...

As a result of uncertainties in both measured mechanical properties and in-service applied stresses, design or safe stresses are normally utilized for design purposes. For ductile materials, safe (or working) stress is dependent on yield strength and factor of safety as described in Equation 6.24. 

Another problem occurs when some fire retardant formulations ate exposed to elevated temperatures (eg, when used as roof tmsses or as roof sheathing) thermal-induced strength reductions can occur in-service. The thermo-chemical factors were discussed by LeVan and Winandy (26), and a kinetic degrade model was developed (27). The treater should be consulted to obtain appropriate in-service modifications for specific fire retardant treatments. 

Metals Successful applications of metals in high-temperature process service depend on an appreciation of certain engineering factors. The important alloys for service up to I,I00°C (2,000°F) are shown in Table 28-35. Among the most important properties are creep, rupture, and short-time strengths (see Figs. 28-23 and 28-24). Creep relates initially applied stress to rate of plastic flow. Stress... 

If, in service, a material is required to have a certain strength in order to perform its function satisfactorily then a useful way to compare the structural efficiency of a range of materials is to calculate their strengdi desirability factor. 

If in the service of a component it is the deflection, or stiffness, which is the limiting factor rather than strength, then it is necessary to look for a different desirability factor in the candidate materials. Consider the beam sim-ation described above. This time, irrespective of the loading, the deflection, S,... 

Maximum Load Rating Bases. The maximum load rating will be based on the design safety factor and the yield strength of the material. Crown block beams are an exception and shall be rated and tested in accordance with API Spec 4E Specification for Drilling and Well Servicing Structures. ... 

One of the most effective methods of preventing corrosion is the selection of the proper metal or alloy for a particular corrosive service. Once the conditions of service and environment have been determined that the equipment must withstand, there are several materials available commercially that can be selected to perform an effective service in a compatible environment. Some of the major problems arise from popular misconceptions for example, the use of stainless steel. Stainless steel is not stainless and is not the most corrosion-resistant material. Compatibility of material with service environment is therefore essential. For example, in a hydrogen sulfide environment, high-strength alloys (i.e., yield strength above 90,000 psi or Rc 20 to 22) should be avoided. In material selection some factors that are important to consider are material s physical and chemical properties, economics and availability. 

Important properties of zeolite adsorbents for a fixed-bed application are adsorptive capacity and selectivity, adsorption-desorption rate, physical strength and attrition resistance, low catalytic activity, thermal-hydrothermal stability, chemical stability, and particle size and shape. Apparent bulk density of zeolite adsorbents is important because it is related to the adsorptive capacity per unit volume and also somewhat to rate of adsorption and desorption. However, more important properties related to the rates and therefore to the actual useful capacity would be the zeolite crystal size and the macropore size distribution. Although the ultimate basis in selecting a zeolite adsorbent for a specific application would be the performance, the price, and the projected service life of a product, these factors depend largely upon the above properties. 

---