UET Peshawar Publications Site (University of Engineering and Technology, Peshawar)
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STUDY OF MECHANICALLY PRESSED COMPOSITE EARTH BLOCKS
No full textThis paper presents the use of mechanically pressed composite earth blocks for low cost housing. In developing countries there is a considerable need to develop materials, which may replace or minimize the use of costlyconstruction materials. The soil when combined with a small percentage of fly ash, rice husk, surkhi, volcanic ash,lime, sand or cement, in the presence of moisture, and then mechanically pressed, gives more strength and satisfactory moisture resistance as compared to the ordinary burnt bricks. For this purpose, the research work was carried out to improve the engineering properties of soil for more strength and better moisture resistance. The paper outlines the research being carried out by the authors (for M.Sc structural engineering at N.W.F.P, U.E.T, Peshawar, Pakistan) on the compressive strength and erosion of mechanically pressed earth blocks. Pressed earth blocks were made of earth/clay with around 5-10% pozzolanic materials like fly ash, rice husk, volcanic ash, surkhi, and bentonite etc in a special steel mould. The soil was brought from different quarries, and about 200 pressed earth blockswere prepared from thirteen combinations of composite earth blocks. The composite pressed earth blocks were kept for 5 days natural drying before they were subjected to compression test. All the thirteen combinations were thensubjected to abrasion test, both with & without surface treatment. The performance of pressed soil blocks was not satisfactory without surface treatment against water. In order to improve their abrasion strength against water, ten surface treatment materials were prepared; three bricks from each combination were subjected to surface treatment for each material and the bricks were cured for 5 days. The bricks were subjected to 20 minutes heavy spray of water and the materials giving satisfactory surface treatment were lime + surkhi (1:4) and cement + sand (1:6) by weight. The masonry strength of the mechanically pressed earth blocks was then determined by preparing twoprisms of 9 x 9 x 24 inch, using mortars as binding materials, one with lime:surkhi (1:4) and other with cement:sand (1:6) by weight. The seven days compressive strengths of these prisms were 375 psi and 337 psi forcement: sand and lime: surkhi mortars respectively, which were quite satisfactory
EXPANSIVE SOILS IN PAKISTAN - CASE HISTORIES
No full textExpansive soils occur at some places of Pakistan. This paper describes the problems related to expansive soils discovered at Gomal University, Dera Ismail Khan and Shah Abdul Latif University, Khairpur. On the basis of field and laboratory tests for these two sites, certain corrective measures both for the design and construction of foundations/floors have been suggested
A NEW MANUFACTURING PROCESS OF IRON AND STEEL
No full textThe concept of producing a steel product direct from high purity sponge iron pellets necessarily implies that close attention must be paid to the purity of the concentrate and the siliceous binder (bentonite) conventionally used must be avoided. In this study therefore, efforts are being made to find a bitumen binder which gives the high crushing strength of magnetite pellets, without a pre-requirement offiring at high temperatures.The additional advantage of using bitumen is that it is an integral source of reducing potential which significantly contribute to the overall reduction of iron oxide in hydrogen at temperatures above 800 °C. At these temperatures, the residual sulfur and carbon contents are below 0.02% and 0.07% respectively in the reduced samples. New process given in this paper involves purification and reduction of iron on followed by direct rolling of the sponge iron pellets/blocks. Through both capital and production costs are significantly reduced, the finishedproduct (steel strip) has mechanical properties very similar to those of conventional low carbon steel. This process has particular significance to the demands of developing countries (such as Pakistan) to meet their requirements of socio-economic development by using local reserves of iron ore
SURFACE RUNOFF AS AFFECTED BY SURFACE GRADIENT AND GRASS COVER
No full textA field study was conducted to evaluate the effect of slope gradients and grass cover on surface runoff under medium rainfall zone of silt loam soils. Plots of 5 mx 2 m size with 1, 5 and 10 percent slope gradients were used under natural rainfall. The grass species consisted of Mott and Cenchrus. A statistically significant increase in surface runoff was observed with the increase in surface gradient. Mean values of runoff consisted of 11.2, 18.1 and 26.6 percent of incident rainfall under 1,5 and 10 percent slope gradients respectively. Surface runoff under Mott grass was low (16.3%) than Cenchrus grass (20.9%). The dry biomass of Mott was 3.5, 4.4 and 5.9 times greater than Cenchrus under 1,5 and 10 percent slope gradients respectively
BRIDGE LONGITUDINAL SPAN INFLUENCE ON WHEEL LOAD (LL) DISTRIBUTION IN AN I-BEAM BRIDGE
No full textThe design method specified by the American Association of State Highway and Transportation Officials (AASHTO Standard) does not account for the effect of bridge span, skew and continuity. As such the simplified design procedure of AASHTO Standard for design of girders under live load is extremely deficient. Similarly the simplified design procedure suggested by AASHTO LRFD does involve the effect of bridge span, skew angle and girder spacing but does not cater for support continuity or negative moment section separately. This paper presents the result of finite element analysis done on number of 3-D bridge models of continuos composite nature. Essentially, fraction of total bridge live load (also, sometime referred in bridge engineering literature as wheel load fraction) decreases with bridge span for critical interior girder, and increases for critical exterior girder for any relative girder to deck stiffness, and loading condition. Variation in live load sharing among various bridge girder is more predominant in small span bridges (approx. 50 feet or below) and are to be treated more carefully
SAFETY TRENDS IN SMALL-SCALE COAL MINES IN DEVELOPING COUNTRIES WITH PARTICULAR REFERENCE TO CHINA, INDIA AND PAKISTAN
No full textSmall-scale mining for coal is practiced all over the world. But major proportions of these mines are located in developing countries in Asia. China, India and Pakistan are the main producers of coal from small-scale mines. Due to prevailing poor safety conditions in these mines, a large number of workers receive injuries ranging from minor to fatal. Gas explosions/outbursts, roof falls, material handling, etc. are the main causes of majority of accidents occurring in small-scale mines, in China, thousands of workers are killed due to gas explosions/outbursts every year. Lack of financial resources, inadequate education and training of workers, contractual labour systems and lack of commitment to improve safety and health are the reasons that mainly contribute to the poor safety performance in this sector of mining
FERROCEMENT UNDER UNIAXIAL TENSION AND COMPRESSION
No full textFerrocement is cement mortar heavily reinforced with thin section mild steel meshes in multiple layers. Ferrocement is usually used in thin sections. This material has come under widespread use during the last two decades. It has been used in the construction of boats, silos, bio-gas holders, houses, water tanks and other such, structures. For rational design in ferrocement, engineering design properties of ferrocement are necessary. This paper presents the results of tests on ferrocement under uniaxial tension and compression. This paper is based on author’s experimental work
THE ROLE OF ESCAPED SOIL AIR ON EROSION IN SAND
No full textTHE ROLE OF ESCAPED SOIL AIR ON EROSION IN SAN
INFLUENCE OF SKEW ANGLE ON LIVE LOAD DISTRIBUTION IN AN I-BEAM COMPOSITE BRIDGE
No full textBridges constructed on Skew alignment have the most complex behavior. In this study bridges with skew angles of 45 and 63.4 degrees were analyzed under the loading models of 1994 AASHTO code, keeping all other parameters same as those of corresponding right bridges. Whenever a skew is introduced, the bridge (specially bridge deck) behaves as a much stiffer unit relative to its right counterpart, bridge deck tries to bend perpendicular to the skew abutment in the short diagonal direction. Also, part of a loaded lane gets closer to the support, and these features of skew bridge reduces the composite moment of critical interior and exterior girders, i.e. Mcg-skew/Mcg-right . is less than one. Generally, the reduction in composite moment of all the girders in a skew bridge relative to a right bridge, is primarily, due to the fact that part of the loading model gets closer to the supports of a skew bridge. This forces the slab to transmit the loads directly to the abutments, rather than through supporting girders. This observation is substantiated by the fact, that sum of LLF of all the girders in skew bridge is less than one, whereas, this sum of LLF for all the girders in a corresponding right bridge is always equal to one, suggesting that all the LL on skew bridge is not transferred by girders. It should also be noted that, when skew is introduced to a bridge the volume of slab increases as the c/c of girder spacing, b, of a right bridge increases to b/Cos(α) in a skew bridge with an angle of skew equal to α. This increase in volume of a slab increases the stiffness of a bridge structure as a whole, which decreases the deflections and girders composite moments
SLAB ANALYSIS AND DESIGN SOFTWARE BASED ON ACI CODE
No full textThis paper describes, ESSAD (Edge Supported Slab Analysis and Design) Ver 1.0 software based on the ACI code. Commercially available packages for slab analysis and design based on finite element methods are generally demanding for structural engineers as they require extensive knowledge and background in Structural Analysis. However, ESSAD follows the ACI code which is much easier to understand and is widely used as an approximate but sufficiently reliable method for slab analysis and design problems. Therefore, while using ESSAD, an engineer knows precisely what the software is going to perform with the data it requires and what are its limitations and approximations for a specific case. This is extremely important as without knowing the mechanism and limitations of a slab analysis and design package, its use can pose problems