Building types and design
A building is closely bound up with people，for it provides with the necessary space to work and live in .
As classified by their use ,buildings are mainly of two types :industrial buildings and civil buildings .industrial buildings are used by various factories or industrial production while civil buildings are those that are used by people for dwelling ,employment ,education and other social activities .
Industrial buildings are factory buildings that are available for processing and manufacturing of various kinds, in such fields as the mining industry, the metallurgical industry, machine building, the chemical industry and the textile industry. Factory buildings can be classified into two type’s single-story ones and multi-story ones .the construction of industrial buildings is the same as that of civil buildings .however, industrial and civil buildings differ in the materials used and in the way they are used.
Civil buildings are divided into two broad categories: residential buildings and public buildings .residential buildings should suit family life .each flat should consist of at least three necessary rooms : a living room ,a kitchen and a toilet .public buildings can be used in politics ,cultural activities ,administration work and other services ,such as schools, office buildings, parks ,hospitals ,shops ,stations ,theatres ,gymnasiums ,hotels ,exhibition halls ,bath pools ,and so on .all of them have different functions ,which in turn require different design types as well.
Housing is the living quarters for human beings .the basic function of housing is to provide shelter from the elements ,but people today require much more that of their housing .a family moving into a new neighborhood will to know if the available housing meets its standards of safety ,health ,and comfort .a family will also ask how near the housing is to grain shops ,food markets ,schools ,stores ,the library ,a movie theater ,and the community center .
In the mid-1960’s a most important value in housing was sufficient space both inside and out .a majority of families preferred single-family homes on about half an acre of land ,which would provide space for spare-time activities .in highly industrialized countries ,many families preferred to live as far out as possible from the center of a metropolitan area ,even if the wage earners had to travel some distance to their work .quite a large number of families preferred country housing to suburban housing because their chief aim was to get far away from noise ,crowding ,and confusion .the accessibility of public transportation had ceased to be a decisive factor in housing because most workers drove their cars to work .people we’re chiefly interested in the arrangement and size of rooms and the number of bedrooms .
Before any of the building can begin, plans have to be drawn to show what the building will be like, the exact place in which it is to go and how everything is to be done.
An important point in building design is the layout of rooms ,which should provide the greatest possible convenience in relation to the purposes for which they are intended .in a dwelling house ,the layout may be considered under three categories : “day”, “night” ,and “services” .attention must be paid to the provision of easy communication between these areas .the “day “rooms generally include a dining-room ,sitting-room and kitchen ,but other rooms ,such as a study ,may be added ,and there may be a hall .the living-room ,which is generally the largest ,often serves as a dining-room ,too ,or the kitchen may have a dining alcove .the “night “rooms consist of the bedrooms .the “services “comprise the kitchen ,bathrooms ,larder ,and water-closets .the kitchen and larder connect the services with the day rooms .
It is also essential to consider the question of outlook from the various rooms ,and those most in use should preferably face south as possible .it is ,however ,often very difficult to meet the optimum requirements ,both on account of the surroundings and the location of the roads .in resolving these complex problems ,it is also necessary to follow the local town-planning regulations which are concerned with public amenities ,density of population ,height of buildings ,proportion of green space to dwellings ,building lines ,the general appearance of new properties in relation to the neighborhood ,and so on .
There is little standardization in industrial buildings although such buildings still need to comply with local town-planning regulations .the modern trend is towards light ,airy factory buildings .generally of reinforced concrete or metal construction ,a factory can be given a “shed ”type ridge roof ,incorporating windows facing north so as to give evenly distributed natural lighting without sun-glare .Assessment of natural radioactivity levels and radiation hazards due to cement industry Abstract
The cement industry is considered as one of the basic industries that plays an important role in the national economy of developing countries. Activity concentrations of 226Ra, 232Th and 40K in Assist cement and other local cement types from different Egyptian factories has been measured by using γ-ray spectrometry. From the measured γ-ray spectra, specific activities were determined. The measured activity concentrations for these natural radionuclide were compared with the reported data for other countries. The average values obtained for 226Ra, 232Th and 40K activity concentration in different types of cement are lower than the corresponding global values reported in UNSCEAR publications. The manufacturing operation reduces the radiation hazard parameters. Cement does not pose a significant radiological hazard when used for construction of buildings.
The need for cement is so great. That it considered a basic industry. Workers exposed to cement or its raw materials for a long time especially in mines and at manufacturing sites as well as people, that spend about 80% of their time inside offices and homes (Mullah et al., 1986; Parades et al., 1987) result in exposure to cement or its raw materials being necessary reality so we should know the radioactivity for cement and its raw material. There are many types of cements according to the chemical composition and hydraulic properties for each one. Portland cement is the most prevalent one. The contents of 226Ra, 232Th and 40K in raw and processed materials can vary considerably depending on their geological source and geochemical characteristics. Thus, the knowledge of radioactivity in these materials is important to estimate the radiological hazards on human health.
The radiological impact from the natural radioactivity is due to radiation exposure of the body by gamma-rays and irradiation of lung tissues from inhalation of radon and its progeny (Papastefanou et al., 1988). From the natural risk point of view, it is necessary to know the dose limits of public exposure and to measure the natural environmental radiation level provided by ground, air, water, foods, building interiors, etc., to estimate human exposure to natural radiation sources (UNSCEAR, 1988). Low level gamma-ray spectrometry is suitable for both qualitative and quantitative determinations of gamma-ray-emitting nuclides in the environment (IAEA, 1989).
The concentration of radio-elements in building materials and its components are important in assessing population exposures, as most individuals spend 80% of their time indoors. The average indoor absorbed dose rate in air from terrestrial sources of radioactivity is estimated to be 70 nay h?. Indoors elevated external dose rates may arise from high activities of radionuclide in building materials (Zikovsky and Kennedy, 1992). Great attention has been paid to determining radionuclide concentrations in building materials in many countries (Armani and That. 2001; Rizzo et al., 2001; Kumar et al., 2003; Tortoise et al., 2003). But information about the radioactivity of these materials in Egypt is limited. Knowledge of the occurrence and concentration of natural radioactivity in such important materials is essential for checking its quality in general and knowing its effect on the environment surrounding the cement producing factories in particular.
Because of the global demand for cement as a building material, the present study aims to:
(1) Assess natural radioactivity (226Ra, 232Th and 40K) in raw and final products used in the Assist cement factory and other local factories in Egypt.
(2) Calculate the radiological parameters (radium equivalent activity Read, level index I γ r, external hazard index Hex and absorbed dose rate) which is related to the external γ-dose rate.
The results of concentration levels and radiation equivalent activities are compared with similar studies carried out in other countries.
2. Experimental technique
2.1. Sampling and sample preparation
Fifty seven samples of raw materials and final products used in the Assist cement factories were collected for investigation. Twenty five samples of raw materials were taken from (Limestone, Clay, Slag, Iron oxide, gypsum) which are all the raw material used in cement industry, 20 samples of final products were taken from Assist cement (Portland, El-Mohandas, White, and Soleplate resistant cement (S.R.C)). For comparison with products from other factories, 8 samples were taken from the ordinary Portland cement from (Helena, Quean, El-kalmia, and Torah) and 4 samples were taken of white cement (Sinai and Helena). Each sample, about 1-kg in weight was washed in distilled water and dried in an oven at about 110 °C to ensure that moisture is completely removed; the samples were crushed, homogenized, and sieved through a 200 mesh, which is the optimum size to be enriched in heavy minerals. Weighted samples were placed in a polyethylene beaker, of 350-cm3 volume. The beakers were completely sealed for 4 weeks to reach secular equilibrium where the rate of decay of the radon daughters becomes equal to that of the parent. This step is necessary to ensure that radon gas is confined within the volume and the daughters will also remain in the sample.
2.2. Instrumentation and calibration
Activity measurements were performed by gamma ray spectrometry, employing a 3″×3″scintillation detector. The hermetically sealed assembly with a Nay crystal is coupled to a PC-MCA (Canberra Accuses). Resolution 7.5% specified at the 662 kef peaks of 137Cs. To reduce gamma ray background a cylindrical lead shield (100 mm thick) with a fixed bottom and movable cover shielded the detector. The lead shield contained an inner concentric cylinder of copper (0.3 mm thick) to absorb lead X-rays. In order to determine the background distribution in the environment around the detector, an empty sealed beaker was counted in the same manner and in the same geometry as the samples. The measurement time of activity or background was 43 200 s. The background spectra were used to correct the net peak area of gamma rays of measured isotopes. A dedicated software program (Genie 2000 from Canberra) analyzed each measured γ-ray spectrum.
The natural radionuclide 226Ra, 232Th and 40K were measured for raw materials and final products used in the Assist cement factory in Upper Egypt and compared with the results in other countries. The activity concentration of 40K is lower than all corresponding values in other countries. The activity concentration of 226Ra and 232Th for all measured samples of Portland cement are comparable with the corresponding values of other countries. The obtained results show that the averages of radiation hazard parameters for Assist cement factory are lower than the acceptable level 370 By kg?1 for radium equivalent Rae, 1 for level index I γ r, the external hazard index Hex ≤1 and 59 (nay h?1) for absorbed dose rate. The manufacturing operation reduces the radiation hazard parameters. So cement products do not pose a significant radiological hazard when used for building construction. The radioactivity in raw materials and final products of cement varies from one country to another and also within the same type of material from different locations. The results may be important from the point of view of selecting suitable materials for use in cement manufacture. It is important to point out that these values are not the representative values for the countries mentioned but for the regions from where the samples were collected.
Concrete is strong in compression, but weak in tension its tensile strength varies from 8 to 14 percent of its compressive strength. Due to such a low tensile capacity, flexural cracks develop at early stages of loading. In order to reduce or prevent such cracks from developing, a concentric or eccentric force is imposed in the longitudinal direction of the structural element. This force prevents the cracks from developing by eliminating or considerably reducing the tensile stresses at the critical misspend and support sections at service load, thereby rising the bending, shear, and tensional capacities of the sections. The sections are then able to behave elastically, and almost the full capacity of the concrete in compression can be efficiently utilized across the entire depth of the concrete sections when all loads act on the structure.
Such an imposed longitudinal force is called a prestressing force, i.e., a compressive force that priestesses the sections along the span of the structural element prior to the application of the transverse gravity dead and live loads or transient horizontal live loads. The types of prestressing force involved, together with its magnitude, are determined mainly on the basis of the type of system to be constructed and the span length and slenderness desired. Since the prestressing force is applied longitudinally along or parallel to the axis of the member, the prestressing principle involved is commonly known as linear prestressing .
Tension caused by the load will first have to cancel the compression induced by the prestressing before it can crack the concrete. Figure 4.39a shows a reinforced concrete simple-span beam cracked under applied load. At a relative low load, the tensile stress in the concrete at the bottom of the beam will reach the tensile strength of the concrete, and cracks will form. Because no restraint is provided against upward extension of cracks, the beam will collapse.
Figure 4.39b shows the same unloaded beams with prestressing forces applied by stressing high strength tendons. The force, applied with eccentricity relative to the concrete centric, will produce a longitudinal compressive stress distribution varying linearly from zero at the top surface to a maximum of concrete stress, =, at the bottom, where is the distance from the concrete centric to the bottom beam, and is the moment of the inertia of the cross-section, is the depth of the beam. An upward camber is then created.
Figure 4.39c shows the priestesses beams after loads have been applied. The loads cause the beam to deflect down, creating tensile stresses in the bottom of the beam. The tension from the loading is compensated by compression induced by the prestressing. Tension is eliminated under the combination of the two and tension cracks are prevented. Also, construction materials (concrete and steel) are used more efficiently.
Circular prestressing , used in liquid containment tanks , pipes , and pressure reactor vessels , essentially follows the same basic principles as does linear prestressing . The circumferential hoop . or “hugging” stress on the cylindrical or spherical structure , neutralizes the tensile stresses at the outer fibers of the curvilinear surface caused by the internal contained pressure .
From the preceding discussion, it is plain that permanent stresses in the priestesses structural member are created before the full dead and live loads are applied in order to eliminate or considerably reduce the net tensile stresses caused by these loads. With reinforced concrete, it is assumed that the tensile strength of the concrete is negligible and disregarded. This is because the tensile forces resulting from the bending moments are resisted by the bond created in the reinforcement process. Cracking and deflection are therefore essentially irrecoverable in reinforced concrete once the member has reached its limit state at service load.
The reinforcement in the reinforced concrete member does not exert any force of its own on the member, contrary to the action of prestressing steel. The steel required to produce the prestressing force in the priestesses member actively preloads the member, permitting a relatively high controlled recovery of cracking and deflection. Once the flexural tensile strength of the concrete is exceeded, the priestess’s member starts to act like a reinforced concrete element.
Priestess’s members are shallower in depth than their reinforced concrete counterparts for the same span and loading conditions. In general, the depth of a priestess’s concrete member is usually about 65 to 80 percent of the depth of the equivalent reinforced concrete member. Hence, the priestess’s member requires less concrete, and about 20 to 35 percent of the amount of reinforcement. Unfortunately, this saving in material weight is balanced by the higher cost of the higher quality materials needed in prestressing . Also, regardless of the system used , prestressing operations themselves result in an added cost : formwork is more complex ，since the geometry of priestesses sections is usually composed of flanged sections with thin webs .
In spite of these additional costs, if a large enough number of precast units are manufactured, the difference between at least the initial costs of priestesses and reinforced concrete systems is usually not very large. And the indirect long-term savings are quite substantial, because less maintenance is needed, a longer working life is possible due to better quality control of the concrete, and lighter foundations are achieved due to the smaller cumulative weight of the superstructure.
Once the bean span of reinforced concrete exceeds 70 to 90 feet (21.3 to 27.4 m), the dead weight of the beam becomes excessive, resulting in heavier members and, consequently, greater long-term deflection and cracking. Thus, for larger spaces, priestesses concrete becomes mandatory since arches are expensive to construct and do not perform as well due to the severe long-term shrinkage and creep they undergo. Very large spans such as segmental bridges or cable-stayed bridges can only be constructed through the use of prestressing .
Priestesses concrete is not a new concept, dating back to 1872,when P.H. Jackson ,an engineer from California, patented a prestressing system that used a tie rod to construct beams or arches from individual block. After a long lapse of time during which little progress was made because of the unavailability of high-strength steel to overcome priestess losses, R.E. Dill of Alexandria, Nebraska, recognized the effect of the shrinkage and creep (transverse material flow) of concrete on the loss of priestess. He subsequently developed the idea that successive post-tensioning of unbounded rods would compensate for the time-dependent loss of stress in the rods due to the decrease in the length of the member because of creep and shrinkage. In the early 1920s, W. H .Hewitt of Minneapolis developed the principles of circular prestressing His hoop-stressing horizontal reinforcement around walls of concrete tanks through the use of turnbuckles to prevent cracking due to internal liquid pressure, thereby achieving water tightness. thereafter , prestressing of tanks and pipes developed at an accelerated pace in the United States, with thousands of tanks for water,liquid,and gas storage built and much mileage of priestesses pressure pipe laid in the two to three decades that followed.
Linear prestressing continue to develop in Europe and in France, in particular through the ingenuity of Eugene Freyssinet .who proposed in 1923-28 methods to overcome priestess losses through the use of high-strength and high-ductility steels.In1940,he introduced the now well-known and well-accepted Freyssinet system.
P.W. Abeles of England introduced and developed the concept of partial prestressing between the 1930s and 1960s . F. Leonard of Germany, V. Mikhail of Russia, and T.Y. Lin of the United States also contributed a great deal to the art and science of the design of priestess’s concrete .Lin's load-balancing method deserves particular mention in this regard, as it considerably simplified the design process, particularly in continuous structures. These twentieth-century developments have led to the extensive use of prestressing throughout the world, and in the United States in particular.
Ordinarily, concrete of substantially higher compressive strength is used for priestess’s structures than for those constructed of ordinary reinforced concrete. There are several reasons for this:
(1) High-strength concrete normally has a higher modulus of elasticity. This means a reduction in initial elastic strain under application of priestess force and a reduction in creep strain, which is approximately proportional to elastic strain. This results in a reduction in loss of priestess.
(2) In post-tensioned construction, high bearing stresses result at the end of beams where the prestressing force is transferred from the tendons to the anchorage fittings, which bear directly against concrete. This problem can be met by increasing the size of the anchorage fitting or by increase the bearing capacity of the concrete by increasing its compressive strength. The latter is usually more economical.
Today priestess’s concrete is used in building, underground structures, TV towers, floating storage and offshore structures, power stations, nuclear reactor vessels, and numerous types of bridge systems including segmental and cable-stayed bridges. They demonstrate the versatility of the prestressing concept and its all-encompassing application. The success in the development and construction of all these structures has been due in no small measures to the advances in the technology of materials, particularly prestressing steel, and the accumulated knowledge in estimating the short-and long-term losses in the prestressing forces.
建材及其组件的无线电元素浓度在人口风险评估是重要的，因为大多数人花费80％的时间是在室内。平均室内从地面的放射性源的空气中吸收剂量估计70 NGY H？1。室内升高，可能出现的外部剂量率从高建筑材料放射性核素（爱因斯坦和肯尼迪，1992年）的活动。已支付的高度重视，以确定在许多国家建筑材料放射性核素浓度（Armani和Tanta，2001;佐等，2001; Kumar等。，2003年。Tortoise等，2003）。但这些材料在埃及的放射性的信息是有限的。知识的发生与浓度等重要材料的天然放射性是一般检查其质量和对周围环境，特别是水泥生产工厂明知其效果的关键。
活度测量进行伽玛射线光谱仪，采用3“×3”闪烁探测器。密封装配用的N a I晶体耦合的PC-MCA（坎培拉）。分辨率7.5％，在662 k e V峰的137Cs指定。为了减少伽玛射线背景圆柱底部固定和移动盖屏蔽探测器。铅屏蔽含有铜的同心圆筒内部，X射线吸收铅。为了确定探测器周围环境中的背景分布，一个空的密封烧杯计算以同样的方式，在相同的几何形状的样品。活动或背景的测量时间为43 200秒。背景光谱被用来纠正的净峰面积测量同位素的γ射线。一个专用的软件程序（2000）从堪培拉精灵分析每个测量γ射线谱。
在上埃及的艾斯尤特水泥工厂使用，并与其他国家的结果相比，原材料和最终产品的天然放射性核素镭，钍和40K测定。 40K的活度浓度低于所有其他国家的相应值。硅酸盐水泥的所有测量样品中226Ra和232Th的活度浓度与其他国家的相应值相媲美。所获得的结果表明，辐射危险参数的平均值为艾斯尤特水泥厂的镭当量Read的，1的水平的指数I γ r，外部风险指数六角≤1和59（NGYĤ低于可接受水平的370贝克公斤1？ 1）吸收剂量率。生产操作减少辐射危害的参数。因此，水泥制品不构成重大建筑施工中使用时的辐射危害。在水泥的原料和最终产品的放射性变化，从一个国家到另一个内同一类型的材料，从不同的地点。从选择合适的材料在水泥生产中使用的角度来看，结果可能是重要的。重要的是要指出，这些值不为上述国家，但是从那里收集样品的地区的代表值。
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