Paddy Engineering Consultant

The choice of whether a structure should be built of concrete, steel, masonry, or timber depends on the availability of materials and on a number of value decisions. 1. ECONOMY Frequently, the foremost consideration is the overall cost of the structure. This is, of course, a function of the costs of the materials and the labour and the time necessary to erect them. Concrete floor systems tend to be thinner than structural steel systems because the girders and beams or joists all fit within the same depth, or the floors are flat plates. This produces an overall reduction in the height of a building compared to a steel building, which leads to a; a. Lower wind loads because there is less area exposed to wind b. And savings in cladding and mechanical and electrical risers Frequently, however, the overall cost is affected as much or more by the overall construction time since the contractor and the owner must allocate money to carry out the construction and will not receive a retu...

SUITABILITY OF WATER FOR CONCRETE MIXING OBJECTIVE To assess suitability of water for use in concrete mix. EQUIPMENT Measuring cylinder Cube moulds Trowel Tamping rod Vibrating table Testing machine PROCEDURE Analyse water for its chemical compositions as per  IS 3025-1964  and compare these with permissible limits given in  IS: 456-2000 .In case water does not satisfy the permissible limits or it is not possible to obtain chemical analysis data readily, the suitability of water is tested by making concrete cubes. Concrete of desired grade is prepared with available water with designed proportions and cubes casted for testing. Prepare the same concrete mix with distilled water and cast the cubes in exactly the similar manner as with water of unknown nature. Cure both the sample in respective water under exactly the same conditions. Test both the cube specimens after 7 and 28 days in exactly the same manner. Compare the test results of strength and cond...

DURABILITY OF CONCRETE PILES Properly mixed concrete compacted to a dense impermeable mass is one of the most permanent of all constructional material and give little cause of concern about its long-term durability in a non aggressive environment. However, concrete can be  attacked by sulphate and sulfuric acid  occurring naturally in soils, by corrosive chemicals which may be present in industrial waste in fill materials and by organic acids and carbon dioxide present in ground water as a result of decaying vegetable matters. Attack by sulphates is a disruptive process whereas the action of organic acids or dissolved carbon dioxide is one of leaching. Attack by sulphuric acid combines features of both processes. The severity of attack by soluble sulphates must be assessed by determining the soluble sulphate content and the proportions of the various cat ions present in an aqueous extract of the soil. These determinations must be made in all cases where the concentration of s...

DURABILITY OF BUILDING FOUNDATION A foundation is that part of the structure which is in direct contact with ground. Therefore foundations are subjected to attack by chemicals present in soil, water and by mechanical abrasion and erosion. The extent of deterioration depends on the concentration of chemicals, the level of and fluctuations in the ground water table or the variation in tidal and river level or on climatic conditions. The only way to increase the durability of foundation is to protect the foundation material from the above mentioned attacks. There are 4 types of material commonly used as foundation material, such as Timber foundation Metal foundation Concrete foundation Brick work foundation Let us discuss methods of protecting different foundation material from deterioration. 1. PROTECTION OF TIMBER FOUNDATION Timber piles are liable to fungal attack and termites, if kept in moist conditions. The protection of timber is best achieved by pressure treatment w...

FAILURE OF SHALLOW FOUNDATION & PREVENTIVE MEASURES The major causes of foundation failures are as follow Unequal settlement of sub soil Unequal settlement of masonry Presence of expansive soil below foundation Presence of mature trees Seasonal changes 1. UNEQUAL SETTLEMENT OF SUB SOIL This is one of the most important reasons for foundation failure. Unequal settlement causes cracks in the foundation and ultimately leads to failure of the whole structure. Unequal settlement of the foundation generally occurs for the following reasons The sub soil may not be uniform throughout the site. This means if some part of the site consist of compressible soil (such as clay) and some part consist of hard stratum (such as rock). The load coming from the structure may not be uniform. It may occur also on building constructed on sloping ground. REMEDIES The foundation should be designed in such a way that the pressure on soil on different portions of the structure and correspondi...

TYPES OF LOADS External loads on a structure may be classified in several different ways. In one classification, they may be considered as static or dynamic. 1. Static loads  are forces that are applied slowly and then remain nearly constant. One example is the weight, or dead load, of a floor or roof system. 2. Dynamic loads  vary with time. They include repeated and impact loads. 3. Repeated loads  are forces that are applied a number of times, causing a variation in the magnitude, and sometimes also in the sense, of the internal forces. A good example is an off-balance motor. 4. Impact loads  are forces that require a structure or its components to absorb energy in a short interval of time. An example is the dropping of a heavy weight on a floor slab, or the shock wave from an explosion striking the walls and roof of a building. External forces may also be classified as distributed and concentrated. 5. Uniformly distributed loads  are forces that are, o...

GRADING In case of sands, it has been found that materials having a large deficiency or excess of any size fraction adversely affect the workability of concrete. The most important size fraction in a concrete sand are those passing the 0.30, 0.15 and 0.075 mm sieves. If these fractions are too low the concrete tends to be prone to segregation. A rule of thumb guideline for optimum percentage is 30%, 15% and 7.5% respectively passing the 0.30 mm, 0.15 mm and 0.075 mm sieves. The percentage passing the 0.075 mm sieve may be used as a first estimate of the concrete’s tendency to bleed -the greater this fraction the lower the bleeding. BULK DENSITY Bulk density is a measure of aggregate packing capacity and therefore influences water requirement and mix proportioning. It does not have a direct influence on workability, provided the mix is correctly proportioned. PARTICLE SPECIFIC GRAVITY Because bleeding and settlement are driven by the force of gravity, the higher the specific g...