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.

R. U. Halwatura

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

Opinion and choice strongly influence sustainability concepts. The building construction industry, in particular property developers, has been charged with promoting excess environmental impacts ranging from overuse of resources to pollution generation. This paper presents an application of sustainability concepts to building projects, as well as to the development of practices, methodology, and tools for evaluating existing buildings. This study will detail how current systems to evaluate building performance operate and how to improve them. This approach utilizes the analytic hierarchy process (AHP). AHP is a multicriteria method that evaluates the relative importance of criteria, subcriteria, and families of indicators, used in the proposed system of technical characteristics applied to the local culture. At the same time, AHP makes visible the critical factors involved in evaluation of sustainability of these buildings. A result of the application of this type of modeling is a system for sustainability assessment and evaluation of environmental aspects and socioeconomic perspectives of existing buildings in the state of Rio de Janeiro, Brazil.

L&#xfa;cio VillarinhoRosa

Assed Naked Haddad

Building Sustainability Assessment throughout Multicriteria Decision Making

This paper deals with the possibility of using fresh concrete waste as recycled aggregates in concrete. An experimental program based on two variables (proportion of fine aggregates replacement and proportion of coarse aggregates replacement) was implemented. The proportions of replacement were 0&#x25;, 50&#x25;, and 100&#x25; by mass of aggregates. Several mechanical properties were tested as compressive and tensile strengths. The results show a good correlation between aggregates replacement percentage and concrete properties. Concerning mechanical properties, a gradual decrease in compressive, splitting, and flexural strengthn with the increase in recycled aggregate percentage is shown.

Mamery S&#xe9;rifou

Z. M. Sbarta&#xef;

S. Yotte

M. O. Boffou&#xe9;

E. Emeruwa

F. Bos

A Study of Concrete Made with Fine and Coarse Aggregates Recycled from Fresh Concrete Waste

The inability of subcontractors/specialist contractors to contribute meaningfully to the construction process under the traditional construction procurement hampers the possibilities of improving value on projects and their integration with the rest of the supply chain. In particular, the main contractors and subcontractors in traditional construction procurement projects pursue their self-interests to such an extent that collaborative working has been impossible to achieve. In this research, qualitative and quantitative approaches were used to collect data to explore the problems at the root of the main contractor-subcontractor relationship. Intending to derive innovative ideas to reinvent the delivery process of traditional construction procurement, the principles of integrated project delivery (IPD) and the last planner system (LPS) were studied to seek useful ideas that can be employed to improve collaboration between main contractors and subcontractors. A high point of contention is the debate on the managerial competence of subcontractors; nevertheless, hope is expressed at the possibility of improving collaboration between the main contractor and subcontractor within traditional construction procurement work environment.

Obafemi A. Akintan

Roy Morledge

Improving the Collaboration between Main Contractors and Subcontractors within Traditional Construction Procurement

The present study investigates the improvement in the bearing capacity of silty clay soil with thin sand layer on top and placing geogrids at different depths. Model tests were performed for a rectangular footing resting on top of the soil to establish the load versus settlement curves of unreinforced and reinforced soil system. The test results focus on the improvement in bearing capacity of silty clay and sand on unreinforced and reinforced soil system in non-dimensional form, that is, BCR. The results show that bearing capacity increases significantly with the increased number of geogrid layers. The bearing capacity for the soil increases with an average of 16.67&#x25; using one geogrid layer at interface of soils with <svg     style="vertical-align:-2.22495pt;width:26.762501px;" id="M1" height="14.85" version="1.1" viewBox="0 0 26.762501 14.85" width="26.762501"  xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg">
	
		
			<g transform="matrix(.017,-0,0,-.017,.062,12.012)"><path id="x1D462" d="M515 96q-37 -44 -84.5 -76t-71.5 -32q-12 0 -18 7t-6 34t10 75l19 89h-2q-87 -113 -181 -176q-43 -29 -83 -29q-46 0 -46 63q0 31 9 67l52 222q7 36 -1 36q-10 0 -76 -50l-13 24q47 45 92 71.5t67 26.5q18 0 21 -16.5t-8 -65.5l-56 -242q-16 -67 13 -67q41 0 114 74&#xA;t114 146l32 145l74 26h11q-52 -199 -80 -347q-8 -39 6 -39q7 0 32 17.5t47 39.5z" /></g><g transform="matrix(.017,-0,0,-.017,9.208,12.012)"><path id="x2F" d="M368 703l-264 -866h-60l265 866h59z" /></g><g transform="matrix(.017,-0,0,-.017,16.211,12.012)"><path id="x1D435" d="M594 511q0 -122 -171 -157l1 -2q158 -33 158 -159q0 -52 -34.5 -95t-90.5 -65q-76 -33 -217 -33h-223l8 28q63 5 79.5 19t26.5 72l83 426q9 48 -2.5 60t-77.5 17l6 28h259q195 0 195 -139zM499 509q0 59 -37 83t-91 24q-36 0 -51 -9q-17 -9 -22 -44l-35 -195h62&#xA;q82 0 128 37t46 104zM481 199q0 71 -48 102.5t-121 31.5h-56l-37 -201q-11 -58 7.5 -77t80.5 -19q76 0 125 44.5t49 118.5z" /></g>

		
	
</svg> equal to 0.667 and the bearing capacity increases with an average of 33.33&#x25; while using one geogrid in middle of sand layer with <svg     style="vertical-align:-2.22495pt;width:26.762501px;" id="M2" height="14.85" version="1.1" viewBox="0 0 26.762501 14.85" width="26.762501"  xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg">
	
		
			<g transform="matrix(.017,-0,0,-.017,.062,12.012)"><use xlink:href="#x1D462"/></g><g transform="matrix(.017,-0,0,-.017,9.208,12.012)"><use xlink:href="#x2F"/></g><g transform="matrix(.017,-0,0,-.017,16.211,12.012)"><use xlink:href="#x1D435"/></g>

		
	
</svg> equal to 0.33. The improvement in bearing capacity for sand underlain silty clay maintaining  <svg     style="vertical-align:-2.22495pt;width:26.762501px;" id="M3" height="14.85" version="1.1" viewBox="0 0 26.762501 14.85" width="26.762501"  xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg">
	
		
			<g transform="matrix(.017,-0,0,-.017,.062,12.012)"><use xlink:href="#x1D462"/></g><g transform="matrix(.017,-0,0,-.017,9.208,12.012)"><use xlink:href="#x2F"/></g><g transform="matrix(.017,-0,0,-.017,16.211,12.012)"><use xlink:href="#x1D435"/></g>

		
	
</svg> and <svg     style="vertical-align:-2.22495pt;width:26.387501px;" id="M4" height="15" version="1.1" viewBox="0 0 26.387501 15" width="26.387501"  xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg">
	
		
			<g transform="matrix(.017,-0,0,-.017,.062,12.162)"><path id="x210E" d="M499 88q-41 -46 -83.5 -73t-68.5 -27q-41 0 -19 98l52 225q10 43 8 59.5t-16 16.5q-37 0 -112 -65t-117 -135q-14 -42 -38 -179q-36 -7 -75 -20l-7 8l127 594q8 40 2.5 49t-35.5 9h-35l5 25q36 3 71.5 13t56.5 18t25 8q11 0 3 -38l-88 -417h2q77 102 195 167q44 24 79 24&#xA;q61 0 30 -130l-52 -220q-8 -33 4 -33q8 0 31 14.5t43 33.5z" /></g><g transform="matrix(.017,-0,0,-.017,8.834,12.162)"><use xlink:href="#x2F"/></g><g transform="matrix(.017,-0,0,-.017,15.837,12.162)"><use xlink:href="#x1D435"/></g>

		
	
</svg>  equal to 0.33; for two, three and four number geogrid layer were 44.44&#x25;, 61.11&#x25;, 72.22&#x25;, respectively. The finding of this research work may be useful to improve the bearing capacity of soil for shallow foundation and pavement design for similar type of soil available elsewhere.

P. K. Kolay

S. Kumar

D. Tiwari

Improvement of Bearing Capacity of Shallow Foundation on Geogrid Reinforced Silty Clay and Sand

Due to the cement hydration heat, concrete deforms during curing. These deformations may lead to cracks in the concrete. Therefore, a method which estimates the strain during curing is very valuable. In this research, two methods of multivariable regression and neural network were studied with the aim of estimating strain changes in concrete. For this purpose, laboratory cylindrical specimens were prepared under controlled situation at first and then vibration wire strain gauges equipped with thermistors were placed inside each sample to measure the deformations. Two different groups of input data were used in which variables included time, environment temperature, concrete temperature, water-to-cement ratio, aggregate content, height, and specimen diameter. CEM I, 42.5&#x2009;R was utilized in set (I) and strain changes have been measured in six concrete specimens. In set (II) CEM II, 52.5&#x2009;R was employed and strain changes were measured in three different specimens in which the diameter was held constant. The best multivariate regression equations calculated the determined coefficients at 0.804 and 0.82 for sets (I) and (II), whereas the artificial neural networks predicted the strain with higher <svg     style="vertical-align:-2.3205pt;width:29.174999px;" id="M1" height="18.725" version="1.1" viewBox="0 0 29.174999 18.725" width="29.174999"  xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg">
	
		
			<g transform="matrix(.017,-0,0,-.017,.062,15.775)"><path id="x28" d="M300 -147l-18 -23q-106 71 -159 185.5t-53 254.5v1q0 139 53 252.5t159 186.5l18 -24q-74 -62 -115.5 -173.5t-41.5 -242.5q0 -130 41.5 -242.5t115.5 -174.5z" /></g><g transform="matrix(.017,-0,0,-.017,5.944,15.775)"><path id="x1D445" d="M627 18l-10 -26q-79 6 -116 27t-69 76q-41 71 -71 138q-13 29 -27.5 39t-42.5 10h-46l-27 -145q-13 -74 -2.5 -88.5t78.5 -20.5l-6 -28h-271l5 28q66 6 82.5 21.5t30.5 87.5l71 387q12 66 2 78.5t-77 19.5l8 28h233q102 0 147 -29q65 -43 65 -129q0 -69 -45.5 -117&#xA;t-115.5 -72q40 -86 66 -133q39 -68 65 -101q28 -37 73 -51zM491 483q0 67 -33.5 101t-91.5 34q-35 0 -51 -10q-13 -8 -20 -48l-45 -245h49q71 0 113 28q79 52 79 140z" /></g>

			<g transform="matrix(.012,-0,0,-.012,16.887,7.613)"><path id="x32" d="M412 140l28 -9q0 -2 -35 -131h-373v23q112 112 161 170q59 70 92 127t33 115q0 63 -31 98t-86 35q-75 0 -137 -93l-22 20l57 81q55 59 135 59q69 0 118.5 -46.5t49.5 -122.5q0 -62 -29.5 -114t-102.5 -130l-141 -149h186q42 0 58.5 10.5t38.5 56.5z" /></g>

			<g transform="matrix(.017,-0,0,-.017,23.225,15.775)"><path id="x29" d="M275 270q0 -296 -211 -440l-19 23q75 62 116.5 174t41.5 243t-42 243t-116 173l19 24q211 -144 211 -440z" /></g>

		
	
</svg> of 1 and 0.996. Results show that the neural network method can be utilized as an efficient tool for estimating concrete strain during curing.

Kaveh Ahangari

Zahra Najafi

Seyed Jamal Sheikh Zakariaee

Alireza Arab

Estimating Strain Changes in Concrete during Curing Using Regression and Artificial Neural Network

This paper investigates the use of three-dimensional (3D) <svg     style="vertical-align:-3.56265pt;width:36.412498px;" id="M1" height="16.3125" version="1.1" viewBox="0 0 36.412498 16.3125" width="36.412498"  xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg">
	
		
			<g transform="matrix(.017,-0,0,-.017,.062,11.813)"><path id="x1D719" d="M542 242q0 -106 -80 -176.5t-192 -72.5l-55 -251l-6 -3q-18 7 -28 38t1 91l23 124q-85 16 -133.5 72.5t-48.5 137.5q0 95 62.5 159.5t166.5 97.5l14 -31q-77 -32 -115 -82.5t-38 -128.5q0 -63 31.5 -107t74.5 -59l125 597l56 43l16 -10l-40 -168q-9 -40 3 -45&#xA;q77 -33 120 -85.5t43 -140.5zM469 232q0 67 -37 115t-77 62l-76 -370q89 -4 139.5 52.5t50.5 140.5z" /></g><g transform="matrix(.017,-0,0,-.017,13.441,11.813)"><path id="x2212" d="M535 230h-483v50h483v-50z" /></g><g transform="matrix(.017,-0,0,-.017,27.193,11.813)"><path id="x1D462" d="M515 96q-37 -44 -84.5 -76t-71.5 -32q-12 0 -18 7t-6 34t10 75l19 89h-2q-87 -113 -181 -176q-43 -29 -83 -29q-46 0 -46 63q0 31 9 67l52 222q7 36 -1 36q-10 0 -76 -50l-13 24q47 45 92 71.5t67 26.5q18 0 21 -16.5t-8 -65.5l-56 -242q-16 -67 13 -67q41 0 114 74&#xA;t114 146l32 145l74 26h11q-52 -199 -80 -347q-8 -39 6 -39q7 0 32 17.5t47 39.5z" /></g>

		
	
</svg> potential-based fluid elements for seismic analyses of deep water pile foundation. The mathematical derivations of the potential-based formulations are presented for reference. The potential-based modeling technique is studied and validated through experimental data and analytical solutions. Earthquake time history analyses for a 9-pile foundation in dry and different water environments are conducted, respectively. The seismic responses are discussed to investigate the complex effect of earthquake-induced fluid-structure interaction. Through the analyses, the potential-based fluid and interface elements are shown to perform adequately for the seismic analyses of pile foundation-water systems, and some interesting conclusions and recommendations are drawn.

Kai Wei

Wancheng Yuan

Seismic Analysis of Deep Water Pile Foundation Based on Three-Dimensional Potential-Based Fluid Elements

The deterioration of concrete structures in the last few decades calls for effective methods for condition evaluation and maintenance. This resulted in development of several nondestructive testing (NDT) techniques for monitoring civil infrastructures. NDT methods have been used for more than three decades for monitoring concrete structures; now it has been recognized that NDT plays an important role in the condition monitoring of existing RC structures. NDT methods are known to be better to assess and evaluate the condition of RC structures practically. This paper reviewed several available NDT methods developed and used in the last few decades.

Sanjeev Kumar Verma

Sudhir Singh Bhadauria

Saleem Akhtar

Review of Nondestructive Testing Methods for Condition Monitoring of Concrete Structures

The main goal of this paper is to present results on an experimental field about the green roofs thermal behavior, compared to other traditional roof covering systems. On the one hand, it intends to describe shortly the constructive system of a green roof with a lightweight building system, which has a sustainable building materials character and, on the other, it worries with the water reuse and with the run-off delay. The main methodological procedure adopted to study the thermal behavior of green roof was installing thermocouples to collect surface temperatures and indoor air, later comparing them with existing prototypes in an experimental plot. The thermal behavior analysis of cover systems was assessed by a representative episode of the climate fact, based on the dynamic climate approach. The experimental results from internal air temperature measurements show that the green roofs applied to warm and dry climates also provide an interesting time lag with surface and internal air temperature reduction.

Grace Tib&#xe9;rio Cardoso

Francisco Vecchia

Thermal Behavior of Green Roofs Applied to Tropical Climate

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Journal of Construction Engineering