R.U. Halwatura

Strategies for improved micro-climates in high-density residential developments in tropical climates

High-density residential developments on outskirts of cities with a large number of detached multistorey houses on small blocks of land are actively promoted as a solution to urban migration in many countries. Such a concentration of houses can have adverse effects on the micro-climate due to the presence of a large number of roofs which have a tendency to warm the surrounding air, leading to heat island effects. The use of insulated roof slabs provides an alternative that may enable the creation of green cover at roof level. In this research, the performance of different insulation thicknesses has been evaluated, indicating that a minimum thickness of 25 mm would be desirable in tropical climatic conditions. The effect of creating green cover was determined with actual models. It is proved with comparative studies that shading screens can be used to simulate the presence of green cover with computer simulations. This is important in predicting the performance of insulated roof slabs for buildings of different layouts.

Causes of variation orders in road construction projects in Sri Lanka

One of the most important problems in the construction industry is variations. They occur in every construction project and the magnitude of these variations varies considerably from project to project. Hence, the variations orders bear great importance right from the inception to completion in the construction industry. Most of the road construction projects in Sri Lanka have experienced a large number of variation orders. The client had to spend more than what was initially estimated in most cases. Sometimes, disputes and unnecessary delays occur due to variations. This study attempted to reveal the possible causes of variation orders in the road construction projects in Sri Lanka. The data were collected through a literature review, a case study analysis focused on 11 road construction projects, and a questionnaire administered to professionals in the road construction industry in Sri Lanka. The study found out that the causes in the local context differ from those in the international context. According to the questionnaire survey, poor estimation was the most significant cause of variation orders. Unforeseen site conditions, political pressure during construction stage, poor investigation, and client-initiated variations occupy the 2nd to 5th places, respectively, in the ranking. This ranking was further proven through the case study analysis.

Thermal performance and structural cooling analysis of brick, cement block, and mud concrete block

ABSTRACT This investigation is apropos the thermal analysis and structural cooling of brick, cement block and mud concrete block walling materials to compare the thermal comfort of different walling materials. Structural cooling is a method of cooling hot temperature by using the structure. Void spaces in a building block can be studied as porosity. It can be measured by assessing solid to void spaces. The thermal performance can be measured by calculating the time lag and the decrement factor. The initial testing was done in order to understand the thermal conductivity and heat capacity in both wet and dry conditions. The real-world analysis and simulation analysis were used to validate the argument. For the case studies, real-world buildings with an identical plan form but constructed with three different walling materials were used and their thermal performances were measured. And then one building was simulated in order to create an identical scenario. With the real-world observation, it was found that brick walling materials have better time lag and decrement factor with the thickness of 225 mm. An overall analysis shows that mud concrete block has better structural cooling ability and the thermal performance than other wall materials.

Effect of Turf Roof Slabs on Indoor Thermal Performance in Tropical Climates: A Life Cycle Cost Approach

Urbanization related to population growth is one of the burning issues that the world is facing today. Parallel to this, there is visible evidence of a possible energy crisis in the near future. Thus, scientists have paid attention to sustainable development methods, and in the field of building construction also, several innovations have been proposed. For example, green roof concept is one of such which is considered a viable method mainly to reduce urban heat island effect, to regain lost land spaces in cities, and to increase aesthetics in cities. The present study was aimed at investigating the impact of green roofs on indoor temperature of buildings, the effect of different types of roofs on the air conditioning loads, and the life cycle cost of buildings with different types of roofing. The study was conducted in several phases: initial small-scale models to determine the heat flow characteristics of roof top soil layers with different thicknesses, a large-scale model applying the findings of the small-scale models to determine temperature fluctuations within a building with other common roofing systems, a computer simulation to investigate air conditioning loads in a typical building with cement fiber sheets and green roof slabs, a comparative analysis of the effect of traditional type roofs and green roofs on the air conditioning loads, and finally an analysis to predict the influence of traditional type roofs and green roofs on life cycle cost of the buildings. The main findings of the study were that green roofs are able to reduce the indoor temperature of buildings and are able to achieve better heat transfer through the roof, and, thus a lower cooling load is necessary for air conditioning and has the possibility of reducing life cycle cost of a building.

Design of a durable roof slab insulation system for tropical climatic conditions

Flat roof slabs become popular day-by-day due to the advantages like cyclonic resistance, the possibility of future vertical extension, and the possibility of utilizing as an additional working space. However, a serious matter of concern is its thermal discomfort, for which air conditioning is used as the most common remedy. This has led to extensive use of energy, increasing the operational cost of the buildings, and contributing to global warming. Hence, the current trend is to go for passive techniques. Insulating roof slabs is identified as a better passive way to make buildings thermally comfortable. In this study, several existing roof slab insulation systems and their performances were investigated, and the most effective system for tropical climates was identified. Since that system had an issue in durability, a new system was developed with a discontinued-stripped supporting arrangement, which withstood a 4MT-point load. Further, it was proven by comparing literature that the newly designed system has a heat gain reduction of more than 75%.

Effectiveness of moodle application on technical tertiary education in Sri Lanka

Line up with the technology that many universities have reported an increase in the use of online educational tools worldwide. Therefore, the use of e-Learning systems is a success factor of any institution, and the main point is whether e-Learning is effective or not. By filling the gap of limited research, this study will help to identify whether existing online education system effectively helps to enhance the quality of the technical graduates with compare to traditional teaching environment in Sri Lanka by fulfilling the objectives of “Do students prefer their e-learning culture than the traditional teaching culture?” “How Moodle facilitate the students to enhance their learning skills?”. Participants in the study consisted of undergraduate students who are in their induction program to final year and who has different learning experience about Moodle in the Faculty of Engineering at University of Moratuwa, Sri Lanka. Findings show that students are preferred for e leaning culture than their traditional learning culture which helps to improve their learning ability through various teaching modes, enhance flexibility and usability of time & finally overall quality of the learning process.