Timber and Concrete Frames in Construction - Assignment Example

CONSTRUCTION MATERIALS By Student’s name Course code and name Professor’s name University name City, State Date of submission Question 1 A Comparison between Timber and Concrete Frames in Construction The timber frame concept of construction originates back to the Greek temples and cathedrals that were built during the medieval period. This methodology of construction is simple in that the timber frame members are joined to each other through use of an appropriate method such as bolting and nailing to constitute a desirable framework. In most cases, timber frame buildings are intricate structures that are prefabricated prior to assembly. During the prefabrication process, the carpenters are engaged in coming up with sections such as roof trusses, floor frames and cross-wall frames as the major segments that form the skeleton of a building (Harris, 2006). Concrete frame construction on the other side involves building through use of bonded concrete and steel to form a single unit. These materials take a combined load that is due to compression in order to provide for the highly required stability attributed by tension resistance steel. In early ages, concrete frame construction was mainly applicable in areas where fire was deemed inevitable. Today, this process has revolutionized from bridge construction to buildings construction thereby becoming a highly preferred method all through the world due to strength and mouldability characteristics (Nawy, 2008). From the above section it can be noted that the two methods differ in terms of materials applied and the mode of coming up with the buildings. Despite the material differences it may become difficult to differentiate between two buildings completed using the above methods since the exterior materials used can be the same unless timber cladding is used. It has been noted that bricks and stones are increasingly becoming external walling material for both concrete and timber frames. Concrete frame construction engages both masonry and carpenter tradesmen in order to come up with a building and is therefore labour intensive as compared to its timber frame counterpart. The load bearing sections are built of concrete blocks which are supplemented with timber walling in the internals in order to come up with a complete structure. In contrast, timber frame buildings are built from fixed panels which are hoisted and positioned properly prior to assembly as noted in the introductory segment above (Tyrone Timber Frames, 2013). Offsite prefabrication of timber frame segments serves as an efficient building methodology thus saves on time and labour. This also saves the schedule in that it reduces the vulnerability that is seen in concrete frame building due to fluctuations in weather. The other parts such as windows and doors are pre-hung in order to reduce the errors that are due to miscalculations. Once erection of timber frame is completed, it is made watertight unlike the concrete frame in order to allow for the other trades such as plumbing, masonry and electricity to commence on the remaining scope. The waterproof envelope is meant to clad the external walls from the block work during construction (Tyrone Timber Frames, 2013). The advantages and disadvantages of concrete frame vary from one use to the other. One important advantage is that the weight or permitted load on concrete frames is extremely high as compared to timber frame counterpart. This method drastically reduces the weight of steel that is usually attributed to the formation process in order to amass enough strength. This reduction is approximated at 20 – 30% of the intended steel requirement for a frame. The results are a better economy especially in high rise buildings that require strong materials to be used. A lower floor to floor depth is also realized through the use of concrete framing thus saves the contractors money that would be used on such areas as wall masonry, electrical and plumbing works. The stiffness that is achieved from the concrete framing on the floor is greater compared to materials such as timber since the neutral axis is shifted upwards hence reducing deflection (Nawy, 2008). The cost of placing connectors to avoid shear force in concrete wall is actually perturbing since mobilization of other trades comes at an advanced stage thereby affecting the work schedule. Another disadvantage is that the small beam sizes that are emphasized by this methodology are composite oriented thus they are not practical. Utilizing of projecting shear connectors is risky to the safety of the workmen at site and may also result in delayed deck forms and metal decking. This methodology is also affected diversely by the weather during the construction process with a slow rate of drying out and on settling it might even result to settlement cracks. Thermal insulation of this method is also poor as compared to timber frame (Tyrone Timber Frames, 2013). The advantages of timber frame include the convenience of building due to speed. Due to the fact that the main segments are assembled offsite, it is relatively easy to transport them to the site and assemble them into a complete building. The convenience arises from the fact that the weather tight nature of building can be realized from this methodology. This type of building standardizes most of the accompanying parts thus making it easier to source them. The insulation level of timber frame building is also high in comparison to the other methods. Self building is also enabled whenever a client is not able to get a professional to carry out the task (Fewins, 2013). Timber frame does not however lack its share of shortcomings given that the foundations have to observe extreme accuracy and the inability to have a first floor made of concrete. This material strength is considerably low and does not therefore support massive loads. The labour required for this job should be highly qualified in order to get the job done in a proper manner. At one point it is considered that timber is expensive due to the diminishing natural resources. Timber does not allow extensions of large spans since this may compromise its strength. As much as timber is considered cheap, it is inferior to concrete in terms of fire safety and durability (Tyrone Timber Frames, 2013). Question 2 a. Moisture content of timber after immersion. Weight of dry timber = 3.27kg Weight of timber after immersing in water = 3.87kg Moisture content after immersing in water = (3.87-3.27) kg = 0.60kg Converting the above value into percentage we have: 1 = 18.35% moisture. b. Hygroscopic Material Hygroscopic materials are materials that possess the ability to absorb or desorb and hold water molecules from the surrounding. This however comes with changes in material physical properties and subsequent deterioration with continued exposure to such environment. Hiziroglu (2009) points out that timber is a good example of hygroscopic materials which when exposed to humid environments rapidly absorb water. This distinct property causes dimensional fluctuations based on the moisture content in the surrounding environment at a given time. c. Specific moisture content requirements of timber for internal use Timber meant for internal usage has to be carefully selected in accordance to the specific moisture content. It is recommended that the moisture content be lower than that of timber used for external areas since the moisture content can be optimized by the warm atmosphere. Excessive drying of timber prior to usage can be catastrophic due to excessive shrinkage that may be caused by excessive drying if the specific moisture content is not checked as per the set conventions (Mitchell, 1999). d. Visual and olfactory signs of dry rot and means of prevention From the physical perspective dry rot in timber is characterised by shrinkage, splitting and crumbing. This can also be identified by being on the lookout for pancake like growth in the middle of the timber depending on accessibility. Mycelium which is seen as a cotton growth is also highly likely as one of the physically observable features of this effect. The major olfactory sign is a mushroom like smell that emanates from the affected areas (What Price?, 2011). In order to prevent this effect, the source of moisture such as plumbing leaks should be checked and completely eliminated. Affected timber should be replaced if the strength levels have been considerably lowered. Chemical treatment through application of borate fungicides should be carried out to prevent further damage on the remaining sections so as to inhibit fungus growth (What Price?, 2011). Question 3 a. Sample Size in consideration = 1400g SIEVE SIZE (MM) MASS (G) % ON SIEVE % PASSING 125 0 0 100 75 0 0 100 63 88 6.29 93.71 37.5 55 3.93 96.07 20 87 6.21 93.79 10 98 7.00 93.00 6.3 95 6.79 93.21 3.35 102 7.29 92.71 2 129 9.21 90.79 1.18 89 6.36 93.64 0.6 85 6.07 93.93 0.3 90 6.43 93.57 0.212 92 6.57 93.43 0.15 84 6.00 94.00 0.063 90 6.43 93.57 Table 1: Sieve analysis table. b. Particle size distribution graphs Graph 1: Particle size distribution for sample 1 Graph 2: Particle size distribution for sample 2. The graph 1 above depicts that the sample size that was being used for this experiment was basically chosen using the smallest sieve size. It is also evident that large particles that were included in the sample to a tune of approximately 90g thereby distorting the direction of this experimentation. This explanation leads to the conclusion that the aggregate size was not uniform and from the graph that the large particles were only meant to go through a 75mm sieve or above. The non-uniformity in graph 1 is as therefore as a result of the small sized aggregates being trapped among the larger particles. Sample 1 on the other side contained uniform grained aggregates that were suitable for the experiment. Therefore, this should have been the best sample aggregate since it contained uniform particles that could have depicted the true percentage that remains on the sieve. List of References Fewins, C. (2013) 'The Pros and Cons of Different Construction Systems', http://www.homebuilding.co.uk/, 1-11. Harris, R. (2006) Discovering Timber-framed Buildings, Buckinghamshire: Osprey Publishing. Hiziroglu, S. (2009) 'Dimensional Changes in Wood', Division of Agricultural Sciences and Natural Resources, pp. 1-4. Mitchell, G. (1999) Carpentry and Joinery, London: Cengage Learning EMEA. Nawy, E.G. (2008) Concrete Construction Engineering Handbook, 2nd edition, Florida: CRC Press. Tyrone Timber Frames (2013) Concrete vs. Timber Frame House, [Online], Available: http://tyronetimberframes.com/blog/concrete-vs-timber-frame-house/ [31 December 2013]. What Price? (2011) Dealing with Dry Rot, [Online], Available: http://www.whatprice.co.uk/building/dry-rot.html [30 December 2013]. Read More