Applied Mechanics and Materials Vol. 802

Abstract: Breakwaters made of sand container is one of the most economical options for wave protection at coastal areas. These breakwaters have been adopted with mixed success at several locations in Malaysia. Nevertheless, the performance of these structure has not been properly studied and documented to date. This study is undertaken to study the wave transmission ability of the submerged sand container breakwater with respect to its width and height as well as the water depth. A number of experiments have been conducted in a wave flume to quantify the wave transmission coefficient of the test models of different layouts when exposed to regular waves. The experimental result has shown that the breakwater is effective in arresting the shorter period waves, particularly in shallow water. The height of the breakwater has to be increased in order to arrest the longer period waves.

Abstract: This paper presents a case study of water flow over the chute spillway type for the Mengkuang Dam expansion project. It governs the surplus water from the dam to the downstream area. However, flows were driven by gravity along the curvature and vertical direction which cause unpredictable flow direction along the chute. Its cause’s thickening of turbulence, changing the velocity, pressure and depth of the water along the spillway. This study was simulated using a physical model with geometrical scale of 1:20. After some test conducted on the spillway, eleven locations on the spillway were selected for the test based on observation for the study. For each location, there were five points in a line with equal distance. Manometers were installed on six locations of the spillway. The water level, velocity and pressure were measured at every point for 100, 1000, 10000 years and PMF design discharge of the spillway. Several critical occurrences on the spillway such as turbulent and cross-wave were presented in this paper.

Abstract: Historical Churches in Armenia may have many experiences of earthquake ground motion. Thus, some of them have been damaged partially or severely. We had carried out the microtremor survey at a historical churches, which is Cathedral at Etchimiadzin around 5th century, to identify the dynamic characteristic. Four sensors are used simultaneously for the observations and modes of vibration are identified from some methods such as the Fourier spectrum and coherence function, and frequency domain decomposition (FDD) technique.

Abstract: This paper attempts to demonstrate the simulation of evacuation in the event of a tsunami disaster from the perspectives of microscopic dynamics of crowd behavior. In this contribution, microscopic modeling is performed by using DEM-based crowd behavior simulator, CBS-DE, in which each individual in a crowd is modeled distinctly. The simulator is capable to track the trajectory and rotation of each individual and therefore, suitable in reproducing the details of the evacuation process. In relation to the evacuation process, we have conducted a study at Langkawi International Airport, Malaysia (LIA). Current condition of evacuation process at LIA was reproduced microscopically under two conjectural scenarios. By using microscopic model, adverse scenarios at LIA were studied to highlight the evacuation behavior. The scenario where evacuees have to change their direction can be simulated significantly. In the present conducted simulations, a realistic scenario of an evacuation process evolving in the dynamics virtual 3D environment was produced. Time series of the accumulative number of persons completed the evacuation was presented graphically.

Abstract: Since global environmental issues are widely discussed nowadays, a number of studies are being carried out to resolve the challenges of reducing energy usage in buildings, especially related to energy use to sustain the indoor thermal comfort level. Among the methodologies used, Analytical Hierarchy Process (AHP) is commonly used to study the problems with multiple influencing factors which consist of different degree of implications. In this study, this model is used to investigate the effectiveness and consistency of respondents’ feedback onto the utility of passive design features in office buildings in order to sustain the indoor thermal comfort levels besides depending on artificial cooling equipment. A number of 122 academic staff from 5 units of primary schools within urban areas in Seremban District was involved in the study. All the schools were equipped with passive design elements, but different types of mechanical ventilation systems were installed in particular schools. Questionnaires with Likert scales were distributed to assist the respondents rank their subjective opinions with objective numerical values. The outputs of rankings generated through AHP by the respondents in different schools were studied, and their validities were further analyzed with ANOVA tests to justify the consistency of the findings. The results showed that there is not much significant difference among the evaluated batches, and thus, model is potential to be further developed into a more comprehensive evaluation tool to link with unidentified environmental and physical factors which generate important design data for future building designers.

Abstract: Strong wind is an annual natural hazard in Malaysia due to the geographical location. The northeast monsoon season usually commences in early November and ends in March. During this season, steady easterly or northeasterly winds of 10 to 20 knots prevail. The strong wind events such as hurricane and storms often caused severe damage to the large number of low rise building especially at the roofing system. At end of year 2014, the series of thunderstorm hit the Northern area of Peninsular Malaysia and caused million ringgit losses. This paper is focused on the roofing system failure of the low rise houses at the rural area that constitute the great majority of the infrastructure in less affluent communities. These non-engineered structures are typically built with very little, or no technical engineering input, and are often the product of varied building traditions and cultures.

Abstract: The number of existing structures under repair and rehabilitation has extensively increased over the past two decades; these structures typically require performance enhancements including durable and safe repair and strengthening. The experimental program aimed to investigate the bond strength at the joint surfaces between conventional concrete substrate as existing concrete and reactive powder concrete RPC as new overlay concrete. Pull off test was used to quantify the direct tension of the bond strength. Different surfaces roughness were used for existing concrete. The obtained results, clearly showed that, RPC could be linked excellent to the existing concrete at early age; as a result, all failures occurred through the existing concrete, regardless of the surface roughness of existing concrete. RPC could be used as an excellent overlay concrete for increasing the durability at joint surfaces of the strengthened structural system.

Abstract: Inspired by the shape and helical pattern of perforations on Cholla skeleton, structural responses of cylindrical sections with multiple perforations have been studied. The common approach to define a helix however, has not been adopted to define the helix lines on the cylindrical sections. This paper proposed a systematic approach to be followed by researchers, for the generation of perforations in multiple helices pattern on surface of cylindrical section. Independent parameters were identified to offer the designers’ ability in taking control when making decision on the desired pattern of perforation along the generated helices covering the surface of the cylindrical section. Rules were imposed to standardize the process and to avoid duplications of similar models under different parameter combinations. Models with perforations along a single helix line were recommended to be generated for consideration prior to those with multiple helices. In this way, understanding the effect of factors found in single helix model can be obtained prior to the examination of the effects of much more complex factors in multiple helices.

Abstract: Heat treatment is one of the environmental friendly ways to treat timber that will lead to the improvement of timber natural quality and equip the timber with new properties. It is an eco friendly and alternative treatment method that will modify the properties of timber by using high temperature instead of using chemical preservatives as common practice. This paper presents the effect of heat treatment on physical properties which is density for two types of Malaysia hardwood namely kapur and keruing. Specially design electronic furnace was used as an oven for the heat treatment process. The result shows a reduction in density after heat treatment, however the difference is not merely significant. Lower in density indicates a weight loss which theoretically caused by moisture content loss thus leading to the increment of movement stability.

Abstract: The potential properties of carbon nanotube-cement based materials strongly depend on the dispersion of carbon nanotubes (CNTs) within the cement matrix and the bonding between CNTs and the hydrated cement. The homogeneous dispersion of CNTs in the cement matrix yet is one of the main challenges due to strong van der Waals forces between nanotubes. In this study, a polycarboxylic ether based superplasticizer and ultra-sonication technique was used for dispersion of multi-walled carbon nanotubes (MWCNTs). Portland cement concrete specimens with different concentrations of MWCNTs (0.04 and 0.1 % by the weight of cement), with and without the presence of superplasticizer were investigated. Compressive strength test results revealed a significant improvement in mechanical properties of sample containing 0.1 % MWCNTs and 0.2 % superplasticizer. Moreover, field emission scanning electron microscopy (FESEM) images of fractured surfaces of hardened specimens showed a good dispersion of MWCNTs within the cement matrix. This method was developed to facilitate the uniform dispersion of MWCNTs in the cementitious concrete for better reinforcement in nanoscale and mechanical properties enhancement by transfer of load between the nanotubes and matrix.