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In the freeze-thaw zone, the pre-stressed concrete of bridge structure will be damaged by freezing-thawing, the bearing capacity of structure will decrease and the safety will be affected. The purpose of this paper is to establish the time-dependent resistance degradation model of structure in the freeze-thaw zone, and analysis the structural reliability and remaining service life in different freeze-thaw zones.

First, according to the theory of structural design, a calculation model of the resistance of pre-stressed concrete structures in f freeze-thaw zone is established. Second, the time-dependent resistance model was verified by the test beam bending failure test results done by the research group, which has been in service for 20 years in freeze-thaw zone. Third, using JC algorithm in MATLAB to calculate the index on the reliability of pre-stressed concrete structure in frozen thawed zones, forecasting the s remaining service life of structure.

First, the calculation model of the resistance of pre-stressed concrete structures in freeze-thaw zone is accurate and it has excellent applicability. Second, the structural resistance deterioration time in Wet-Warm-Frozen Zone is the earliest. Third, once the pre-stressed reinforcement rusts, the structural reliability index will reach limit value quickly. Finally, the remaining service life of structure meets the designed expectation value only in a few of freeze-thaw zones in China.

The research will provide a reference for the design on the durability of a pre-stressed concrete structure in the freeze-thaw zone. In order to verify the security of pre-stressed concrete structures in the freeze-thaw zone, engineers can use the model presented in this paper for durability checking, it has an important significance.

During service period, due to the overload or other non-load factors, cracks of the pre-stressed concrete beam are seriously affecting the safety of the bridge structure. The purpose of this paper is to quickly realize the bearing capacity and the loss of the section stiffness through fracture characteristics and make correct judgments.

Through the flexural failure test of two test beams: collecting data of fracture characteristics and section stiffness loss value. According to the fracture characteristic data, the flexural stiffness of the section is obtained by the nonlinear calculation method, and the results are verified by test data. Data regression method is used to establish the section flexural stiffness loss ratio calculation formula, nominal tensile strain at the bottom edge of the cross-section used as a variable factor, and the accuracy of this formula is verified by comparing the flexural failure test results of pre-stressed hollow plates.

The loss of the flexural stiffness of section shows the decrease trend of first-fast-then-slow and the structural stiffness is sensitive to the initial cracking of beam. The calculation formula on the loss ratio of the flexural stiffness of section established with the nominal tensile stress at the bottom edge of beam as a variable is accurate and feasible, it realizes the possibility of assessing the stiffness loss of pre-stressed concrete structure by adopting the statistic parameters on crack characteristics.

A method for quickly determine the stiffness loss of structures by using fracture characteristics is established, and using this method, engineers can quickly determine whether a bridge is a dangerous bridge, without loading test. So, this method not only ensures the safety of human life, but also saves money.

During service period, due to the overload or other non-load factors, diagonal cracks of the pre-stressed concrete beam are seriously affecting the safety of the bridge structure. The purpose of this paper is to quickly realize the shear bearing capacity and shear stiffness through maximum width of the diagonal cracks and make correct judgments.

Through the shear failure test of four test beams, collecting data of diagonal cracks and shear stiffness loss value. According to the deformation curve of the shear stiffness, and combined with the calculation formula of the maximum width of diagonal cracks, the formula for calculating the effective shear stiffness based on the maximum width of diagonal cracks is deduced, then the results are verified by test data. Data regression method is used to establish the effective shear stiffness loss ratio calculation formula, the maximum width of diagonal cracks used as a variable factor, and the accuracy of this formula is verified by comparing the shear failure test results of pre-stressed hollow plates.

With the increase in width of the diagonal crack, the loss rate of shear stiffness of the concrete beams is initially fast and then becomes slow. The calculation formulae for shear stiffness based on the maximum width of the diagonal cracks were deduced, and the feasibility and accuracy of the formulae were verified by analysis and calculation of shear test data.

A method for quickly determine the shear stiffness loss of structures by using maximum width of the diagonal cracks is established, and using this method, engineers can quickly determine effective shear stiffness loss ratio, without complex calculations. So this method not only ensures the safety of human life, but also saves money.

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.

Introduction The development of the pre‐stressed concrete form of construction for pressure vessels has made rapid strides in recent years. Vessels of this type possess obvious advantages for nuclear power stations, and those currently under construction in this country employ such vessels for the reactor containment. During the construction of one station — for which this Company was appointed Inspecting Authority — an unusual corrosion problem arose which may well be pertinent to other pre‐stressed concrete structures. The post‐tensioning method of pre‐stressing using tendons stretched through the concrete and anchored at the outer face of the vessel was employed. About nine months after installation of the tendons in the bottom caps of the two vessels, it was discovered that serious corrosion had occurred. The C.E.G.B. subsequently set up a Working Party on which all interested bodies were represented, in order to look into the causes and recommend preventative measures. Extensive investigations were made both on site and in the laboratory. The following briefly summarises the case and the investigations carried out.

Admixtures are materials that are added to concrete at some stage in its production to give concrete new properties whether in fluid or plastic conditions. The admixtures used in the construction industry are broadly classified into Mineral and Chemical admixtures. In recent years, the use of mineral and chemical admixtures in producing high performance concrete has increased significantly. The chemical reaction of cement with admixtures differs from material to material. Calcium nitrite based corrosion inhibiting admixtures have gained popularity for protection of reinforced and pre‐stressed concrete structures but calcium nitrite is not commercialized indigenously in India due to manufacturing difficulties. Hence, the objective of the present investigation was to study a novel corrosion inhibiting admixture system and to compare its effectiveness with sodium nitrite.

Di‐sodium phthalate, sodium orthophosphate and sodium nitrite‐based corrosion inhibiting admixtures were selected for the present investigation. The critical quantities of corrosion inhibiting additives were determined by accelerated laboratory tests. The following types of tests were conducted to evaluate the efficiency of the corrosion inhibiting admixtures: compressive strength of 100 × 100 × 100 mm concrete cubes after 3,7,14 and 28 days of curing, linear polarization resistance measurements, electrochemical impedance spectroscopy measurements, an accelerated 12 V controlled potential test.

From the above tests, the inhibitor admixtured concrete not only improved in compressive strength but also increased its corrosion resistance properties. Of the inhibitors studied, di‐sodium phthalate showed superior corrosion resistance properties, compared to sodium nitrite.

Di‐sodium phthalate may be considered a better substitute for calcium nitrite‐based corrosion inhibiting admixtures for durable concrete structures. This fulfils the objective of the investigation.

Introduction The demolition industry has traditionally been regarded as the poor relation of the construction industry, characterised by the brute force of the demolition ball — a wholly unrealistic view in the latter part of the 20th century.

This paper aims to research steel wire corrosion pitting distribution characteristics and evolution, the shape, number and size of corrosion pits from one tied arch bridge were tested, analyzed and researched.

The probability distribution model of corrosion pits of different shapes was established, and the law of corrosion pit growth and evolution was researched. The relationship between the steel wire local corrosion parameters and the average degree of corrosion was explored.

The results revealed that the pits of steel wires can be divided into four categories of shapes: a deep ellipsoidal shape, a shallow ellipsoidal shape, a groove shape and a saddle shape. When developing to a certain degree, the small dark narrow type corrosion pit will turn into a large open pit of either a shallow ellipsoidal shape, a groove shape or a saddle shape.

The maximum depth of the corrosion pits was close to the Weibull distribution, and the maximum width and length of the wire corrosion pits were close to the logarithmic normal distribution, causing a large error when using a uniform corrosion model of steel wire mechanics.

The industrialized housing system (IHS) is regarded as an effective building philosophy based on off-site construction techniques to achieve rapid and cost-effective housing development. The purpose of this paper is to develop a multi-criteria decision-making support system (DMSS) model for the evaluation of housing systems to select the relevant decision factors and to identify the types and characteristics of suitable IHSs for application in a mass housing development.

A multi-criteria DMSS model with the analytical hierarchy process was designed. Based on the literature review and also the response of the ten experts’ interviews, 30 decision factors were identified for evaluation. In addition, 5 IHSs were considered as a case study for testing the model. Then, 30 professionals participated in a questionnaire survey conducted to evaluate the priority vector importance level of the decision factors and housing systems.

The result of the decision-making process showed that the top three decision factors are customer needs, supply chain and the construction industry. In addition, both precast concrete beam and slab blocks, as well as agro stone panels are identified as suitable housing systems. The systems have the characteristics of being lightweight, easy to produce and erect, and cost-effective, and they use local input resources and semi-skilled labor. The findings also revealed the potential and practicality of the model among multiple alternatives across multiple decision factors.

The study has faced the limitations of available professionals and experts who have rich experience in the application of IHSs. In addition, there were few types of alternative IHSs and limited practice of IHSs implementation in large-scale housing construction. These challenges caused limitations to the relevant data collection. In order to address these challenges, all the available experts from the different sectors of the construction industry with the experience of IHSs construction are invited to participate and the available alternative IHSs in the market are selected for evaluation.

The rational evaluation method used to determine the important decision factors and the general characteristics of the suitable housing systems can help housing developers and decision makers in developing countries to make informed and effective decisions.

The findings of the study help to address the challenge of lack of sufficient housing supply to the overwhelming housing demand that exists and identify the most important decision factors and suitable housing systems that can be applied for the rapid and decent large-scale housing developments at an affordable price.

This paper bridges the knowledge gaps that exist regarding the identification and evaluation of IHSs in Ethiopia. This study can help practitioners, housing developers, and decision makers to make informed and effective decisions regarding the evaluation and selection of IHSs.

Introduction In a recent paper in this journal, Campbell outlined some of the techniques and problems associated with the demolition of existing structures and touched upon the possibility of recycling the debris from this process. This reflects the growing awareness among the general public, local authorities and central Government that the recycling of waste materials, from all sources, is both necessary and desirable. Indeed, according to a recently published report from the Trade and Industry Committee of the House of Commons: ‘The benefits of recycling are obvious: rarely do environ‐mental and economic factors so unambiguously support the same goal’.