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Many countries have started to use post-tensioned (PT) concrete because of its sustainability and low cost. However, it is not quite popular in Sri Lanka as the required knowhow and technology are not available within the country. By introducing PT concrete to the country, unwanted costs and time overruns could be eliminated from the construction projects. This paper, therefore, aims to identify the suitability and acceptability of PT concreting for/in Sri Lanka.

An extensive literature review was first carried out to gather knowledge on PT concreting. The four case studies that followed it included eight semi-structured interviews and a document review. Ten expert interviews were conducted finally to strengthen the findings of the literature review and case studies. Cross-case analysis and NVivo 11 content analysis software were used to analyze the data gathered.

Findings reveal that PT concreting saves cost and time of construction and that it can have a control over the resources required for construction, which makes it environment-friendly. PT concreting allows thinner concrete sections, extended spans, stiffer walls that resist lateral loads and stiffer foundations that resist the effects of shrinking and swelling soils.

It is found that PT concreting is more suitable for the construction industry in Sri Lanka than traditional concreting.

This paper aims to understand the structural fire performance of two-way post-tensioned flat slabs, particularly their deformations and load-carrying mechanisms in fire, and to explore the behaviour of post-tensioned high-strength self-compacting concrete flat slabs with unbonded tendons in fire.

Four tests of post-tensioned high-strength self-compacting concrete flat slabs were conducted under fire conditions. Numerical modelling using the commercial package ABAQUS was conducted to help interpret the test results.

Two of the specimens with lower moisture contents demonstrated excellent fire resistance performance, while the others with slightly higher moisture contents experienced severe concrete spalling.

The test results were discussed in respect of thermal profiles, deflections, crack patterns and concrete spalling. The performance of post-tensioned high-strength self-compacting concrete flat slabs with unbonded tendons under fire conditions was better understood.

This study aims to investigate the influence of tendon layout, pre-stressing force, bond condition and concrete spalling on the structural behaviour of two-way post-tensioned flat slabs at elevated temperatures.

Fire tests of four scale specimens of two-way post-tensioned concrete flat slabs were performed and analysed. Three of them were provided with bonded tendons, while the other was unbonded for comparison. The fabrication of specimens, phenomena observed during testing, temperature distributions, deflections and occurrence of concrete spalling were examined.

Different degrees of concrete spalling observed at the soffit had significant effects on the temperature distribution and stress redistribution. This was the major reason for the progressive concrete spalling observed, resulting in loss of structural integrity and stiffness.

The structural behaviour of two-way post-tensioned concrete flat slabs at elevated temperatures is less understood compared to their one-way counterparts. Therefore, the present study has focused on the structural behaviour of two-way post-tensioned concrete flat slabs with bonded tendons in fire, a field in which relatively little information on experimental work can be found.

The prevention through design (PtD) concept has been widely recognized as one of the most effective approaches to eliminate or reduce construction site hazards. It encourages engineers and architects to consider occupational safety and health during the planning and design phases. Nevertheless, the implementation of PtD is often inhibited because designers lack adequate knowledge about construction safety and the construction process, and limited design-for-safety tools and procedures are available for designers to use. The purpose of this paper is to provide designers a tool for assessing construction risks during early phases of multistory building projects at an activity level and on a daily basis in a 4D environment. By using the tool, proactive measures could be taken in the design and planning phase to reduce site hazards.

The proposed method consists of four steps including risk quantification at a design element level, 4D model integration with risk values, risk assessment, and design alternative selection and model acceptance. A case study was carried out to test and verify the proposed method.

The proposed tool has the capability to assess the safety risk for an entire multistory project and visualize safety risk in a particular time period, work space and task prior to construction. It benefits designers in conducting risk assessments and selecting design alternatives concerning safety. Contractors could also utilize the visualization and simulation results of the 4D model for site safety planning so that a range of risk mitigation strategies could be implemented during construction.

The study provides an innovative PtD tool targeting designers as primary end-users. The proposed tool helps designers assess construction risks and has potential to incorporate the top levels of the hierarchy of risk controls.

The fire-safe structural design and construction of unbonded post-tensioned (UPT) flat plate concrete structures has recently come under debate in the UK, and questions are being raised regarding the response to fire of post-tensioned concrete slabs. Related to these concerns is the real world response of continuous UPT tendons inside such structures both during and after a fire, which is largely unknown and depends on many potentially important factors which are not currently accounted for in standard fire tests. Several credible concerns exist for UPT concrete structures in fire, most notably the potential for premature tendon rupture due to localized heating which may result from a number of possible causes (discussed herein). The research presented in this paper deals specifically with the time-temperature-stress-strength interdependencies of stressed UPT tendons under localized transient heating, as may be experienced by tendons in a real UPT building in a real fire. Nineteen high temperature stress relaxation tests on UPT tendons of realistic length and parabolic longitudinal profile are reported. It is shown that localized heating of UPT tendons is likely to induce premature tendon rupture during fire, even in structures which meet the prescriptive concrete cover requirements imposed by available design codes.

This is Part II of a two part paper dealing with the current state of knowledge of the fire-safe structural design and construction of unbonded post-tensioned (UPT) flat plate concrete structures. Part I provided detailed results of nineteen transient high temperature stress relaxation tests on restrained UPT tendons of realistic length and parabolic longitudinal profiles. Experimentation identified several credible concerns for UPT concrete structures in fire, most notably the potential for premature tendon rupture due to localized heating, which may result from a number of possible causes in a real structure. The real world response of continuous UPT tendons both during and after heating is largely unknown, and is dependent on factors which are not currently accounted for either in standard fire tests or by available prescriptive design guidance. This second part of the paper presents and applies a numerical model to predict the time-temperaturestress-strength interdependencies of stressed UPT tendons under localized transient heating, as may be experienced by tendons in a real concrete building in a real fire. The model is used, along with previously developed and validated computational models for heat transfer and prestress relaxation in UPT tendons, to assess existing prescriptive concrete cover requirements for UPT slabs. It is shown that localized heating of UPT tendons is likely to induce premature tendon rupture during fire, and that current prescriptive code procedures based on concrete cover alone are, in general, insufficient to prevent this. Based on the data presented it appears that minimum code prescribed concrete covers for UPT structures require revision if premature tendon rupture during fire is to be avoided.

The application of an artificial neural network (ANN) to forecast the construction duration of buildings at the predesign stage is described in this paper. A three‐layered back‐propagation (BP) network consisting of 11 input nodes has been constructed. Ten binary input nodes represent basic information on building features (i.e. building function, structural system, foundation, height, exterior finishing, quality of interior decorating, and accessibility to the site), and one real‐value input represents functional area. The input nodes are fully connected to one output node through hidden nodes. The network was implemented on a Pentium‐150 based microcomputer using a neurocomputer program written in C+ +. The Generalized Delta Rule (GDR) was used as learning algorithm. One hundred and thirty‐six buildings built during the period 1987–95 in the Greater Bangkok area were used for training and testing the network. The determination of the optimum number of hidden nodes, learning rate, and momentum were based on trial‐and‐error. The best network was found to consist of six hidden nodes, with a learning rate of 0.6, and null momentum. It was trained for 44700 epochs within 943 s such that the mean squared error (judgement) of training and test samples were reduced to 1.17 × 10−7 and 3.10 × 10−6, respectively. The network can forecast construction du‐ration at the predesign stage with an average error of 13.6%.

The purpose of this paper is to examine the relationship between building floor and labor productivity of the structural work including formwork installation and rebar fabrication/installation.

The case study methodology and learning curve theory are adopted for the paper. Records from the structural work of a 20-storey apartment building were analyzed to calculate floor-based labor productivities.

Labor productivity of the formwork activity increased more than twice in the first five floors. If the first cycle (floor 2) is omitted, the straight-line learning curve model shows a learning rate of 83.5 percent. Labor productivity of the rebar activity tended to increase in the first 15 floors. If the first two cycles are omitted, the straight-line learning curve model indicates a learning rate of 83.6 percent.

Future research is needed to examine and quantify factors that affect the level of learning in high-rise building construction. The relationship between building floor and labor productivity should be further investigated for other construction activities.

Practitioners should consider the relationship between building floor and labor productivity and learning effects when planning manpower and construction duration for individual activities and for a building.

The paper substantiates the hypothesis that labor productivity does not reach 100 percent of the normal level at the very first floors while they do not support the hypothesis that labor productivity does not reach 100 percent at the top floors.

This paper aims to investigate the operational mechanism, project performance, motives behind, benefits, difficulties and success factors of adopting the guaranteed maximum price (GMP) scheme based on a real‐life case study of Chater House, an international Grade A private office project in Hong Kong.

The case project was analysed by means of the related project documentation and a series of face‐to‐face interviews with the relevant senior project representatives.

All the interviewed key project stakeholders perceived that the GMP contract helped achieve competitive price, value for money and superior quality of products as well as provided stronger incentives to innovation and cost saving. The case study revealed that the overall success of this GMP project was underpinned by several key attributes.

The paper provides solid groundwork for client bodies and contracting organisations to develop a best practice framework for implementing successful GMP schemes in future construction.

Hybrid concrete construction is a technologically advanced approach to frame construction. It utilizes an optimal mix of structural materials;eg, in situ concrete with precast concrete and steelwork. The process of selecting an hybrid‐optimized solution, however, often requires several factors to be considered, eg, “hard”criteria such as time and cost, and “soft” criteria such as safety and aesthetics (to be considered simultaneously) – the complexities of which can often be a core barrier to implementation. This paper introduces the concept of hybrid concrete construction and presents a virtual prototyping tool to assist the decision‐making process. This model is able to import computer aided design information into a central database – the details of which are then layered with additional information; eg, hard and soft performance criteria and so on. Solutions can be interrogated and demonstrated through an interactive virtual environment, in which multi‐option scenarios can be evaluated against specific user‐defined criteria. Findings have identified several core benefits, including the ability to: justify decisions corroborated with detailed data; evaluate options against each other; interrogate objects at a much greater detail than before; and see the effects of changes in a “real‐time” environment.