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This paper presents a careful finite element investigation into interfacial stresses in reinforced concrete (RC) beams strengthened with a bonded soffit plate, with the aims of assessing the accuracy of existing approximate closed-form analytical solutions based on simplifying assumptions and highlighting aspects which are omitted by them. Finite element modelling issues are first discussed, with particular attention on stress singularities in such beams and appropriate finite element meshes for the accurate determination of interfacial stresses. Finite element stresses are then carefully examined and compared with the predictions from a closed-form solution recently derived by the authors. The finite element results show that stresses vary strongly across the adhesive layer, with the stresses along the adhesive-to-concrete (AC) interface being very different from those along the plate-to-adhesive (PA) interface. In particular, near the end of the plate, the interfacial normal stress is tensile along the AC interface but compressive along the PA interface, offering a plausible explanation for the fact that PA interfacial failure in tests has rarely been if at all reported. The closed-form solution, being based on the assumption of uniform stresses in the thickness direction in the adhesive layer, is incapable of predicting such complex stresses, but nevertheless provides a reasonably close prediction of stresses along the middle-thickness section of the adhesive layer, particularly when the adhesive layer is not very thin. This and other similar closed-form solutions are therefore believed to still form a useful basis on which design rules against debonding failures can be built, with appropriate tuning using experimental data. Finally, the effect of spew fillets on interfacial stresses is examined. [Copyright &y& Elsevier]

This study deals with the control of cracking at interior supports of continuous pre-cast pre-stressed concrete (PCS) girder bridges. Since PCS-girder bridges are constructed by placing in-situ concrete decks on the PCS-girders at time intervals, the differences in material properties and age at loading between the deck and girder lead to time-dependent material behaviors. In addition, the continuous deck by providing a negative moment connection at interior supports, also causes the transverse cracking of the concrete deck at interior supports. In that way, cracking at interior supports is predicted with the analytical model introduced in the companion paper. Based on the ACI model, the ultimate shrinkage strain is expressed as a function of concrete slump and the relative humidity while the other remaining factors such as unit weight of cement and air content are assumed, in accordance with the typical values in mixed concrete. Finally, field recommendations in terms of concrete slump and relative humidity are suggested to minimize early transverse cracking of concrete decks at interior supports. [Copyright &y& Elsevier]

This paper deals with the analysis of uncertainties associated with the behavior of bridges constructed with pre-cast pre-stressed girders and a continuous deck. To analyze the long-term behavior of bridges, an analytical model which can simulate the effects of creep, the shrinkage of concrete, and the cracking of concrete slabs in the negative moment regions is introduced. Based on the equilibrium of forces and the compatibility of strains with time, the prediction of stresses and strains in the constitutive materials at any time is achieved. To consider the different material properties across the sectional depth, the layer approach in which a section is divided into imaginary concrete and steel layers is adopted. An element stiffness matrix is constructed according to the assumed displacement field formulation, and the creep and shrinkage effects of concrete are considered in accordance with the first-order recursive algorithm based on the expansion of the compliance function. Correlation studies between analytical and experimental results are conducted with the objective of establishing the validity of the proposed model. Also, many parameters related to the continuity of spans are analyzed to minimize deck cracking at the interior supports. [Copyright &y& Elsevier]

The AASHTO Guide for Design of Pavement Structures uses a structural number as one of the major inputs for flexible pavement thickness design. Previous studies have shown that the layer coefficients, which are a component of the structural number, have variability. The use of these values without a strong consideration of their variability can influence the overall determination of the structural number, hence, the thickness of the pavement. This paper proposes to use convex models as a tool for addressing the variability and uncertainty in the structural number determination. The convex models provide a completely non-probabilistic representation of uncertainty. The uncertainty is treated as unknown-but-bounded. The approach is illustrated by an example. [Copyright &y& Elsevier]

A method employing ion chromatography for identifying and quantifying ions present in the aqueous phase of concrete after surface treatment with corrosion inhibitors is reported in this paper. With this technique, a broad range of ions including ethanolamine, nitrite and monofluorophosphate, present in the inhibitors tested, could be identified in solution. When ethanolamine and nitrite were applied to the surface of concrete, they were readily detected in samples into which they had penetrated. In the case of monofluorophosphate-treated concrete, only the hydrolysis products, fluoride and phosphate were detected and not the monofluorophosphate ion itself. Furthermore, concentrations of other important ions, such as chloride, were also quantifiable by this technique. One of the main advantages of ion chromatography for this type of application is its ability to analyse a wide range of ions in a given sample. [Copyright &y& Elsevier]

The aim of this paper is to analyse the static and dynamic behaviour of RC beams strengthened by CFRP-sheets after damage by cracking. An experimental program has been developed considering RC beam models with or without strengthening by CFRP-sheets on the tensile zone subjected both to static and dynamic tests. The tests on the RC beam models were repeated under different conditions to evaluate the structural responses during the life of RC beams. The experimental results by static tests are compared with the data obtained by theoretical model. The static behaviour of RC beams strengthened by CFRP-sheets is described up to failure. Finally, theoretical estimates variations in frequency values are compared with the data obtained by experimental dynamic tests. [Copyright &y& Elsevier]

A detailed knowledge of the present condition of bridges is essential for the planning of maintenance and rehabilitation. Mobile ground penetrating radar (GPR) systems are efficient tools for obtaining information such as depth of rebar, asphalt pavement thickness and concrete damage beneath the pavement. Non-destructive testing, quasi-continuous results and efficient data acquisition are the main advantages of mobile GPR systems. In this paper, benefits and limitations of mobile GPR systems are discussed using examples from EMPA''s recent work. The emphasis is on the investigation of pavement thicknesses and depths of rebar on concrete bridges. [Copyright &y& Elsevier]

Stabilised compressed soil blocks (SCSBs) in building fabrics are susceptible to deterioration if their choice conflicts with the required functionality. Various investigators to determine the weatherability potential of these materials have applied different assessment procedures, observed to be fraught with limitations. Such procedures have produced results that often conflict with real life situations. The current inadequately defined weatherability performance measurements require more qualitative descriptions of the field conditions. The underlying premise in this paper is to review the practicality or otherwise of the various testing techniques. The paper highlights some generalised framework essential for SCSBs weatherability assessment method that are rational, explicit enough and applicable to specific and almost all intended uses under a broad range of environmental concerns. [Copyright &y& Elsevier]

Investigations were undertaken to produce low heat sulfate resistant cement by activation of granulated slag obtained from the blast furnace process of iron making and phosphate industries with the calcium sulfate hemihydrate. Experimental data showed that cement gives fast setting characteristics in addition to high strength development. The setting time of cement was regulated with a small addition of set retarder without adversely affecting the strength development of cement. It is noted that beta hemihydrate plaster gives better strength results than the anhydrite activated cement. The results also confirm that granulated blast furnace slag can be replaced with phosphatic slag up to 10% by mass without loosing strength. DTA and X-ray diffraction analysis have been used to identify the hydration products formed in the hydrated cement. The heat of hydration data of cement is reported in the paper. [Copyright &y& Elsevier]

This paper shows that both the aggressivity of an acidic environment and acidic resistance of cement based materials are of a complex nature. Both depend on several conditioning factors. Therefore, the evaluation of the aggressivity of the environment only on the concentration of the aggressive species is entirely unsatisfactory and incorrect. On the other hand, even the evaluation of the acidic resistance on the cement used is inadequate. Therefore, further factors should be taken into consideration, conditions like the action of the aggressive medium on cement based material and the processing factors, e.g. w/c used, curing mode and others, conditioning the resistance of cement based materials. The various possibilies of protecting cement-based materials are considered. These are based on the optimal choice of the composition of the mixture, its consolidation and curing, aimed at ensuring maximal density and minimal permeability of the hardened material. A further possibility represents the application of surface coatings. The most effective way seems to be the preparation of materials on binders of new generation ensuring the compatibility with the acidic environment. [Copyright &y& Elsevier]

Strengthening with epoxy bonded steel plate is one of the most widely used techniques for flexural upgrading of reinforced concrete (RC) beams. However, debonding failure at the plate cut-off zone and or in the vicinity of flexure and shear cracks leads to catastrophic failure of the upgraded beams. This particular failure depends on several factors such as the distance of plate curtailment from the support, plate thickness and the provision of end anchors. Since the conventional beam theory cannot predict the debonding failure of such beams, a finite element model capable of predicting the overall behavior of strengthened beams including different failure modes accurately is developed. This paper presents the formulation of finite elements and material models and simulation results of some RC beams tested for flexural strengthening with epoxy bonded steel plates. [Copyright &y& Elsevier]

This article proposes a modelling of the ‘3 points bending test’ on compressed earth blocks (CEB) which will give their compressive strength. This test is already used in situ for CEB quality control. Conventional bending modelling gives the tensile stress at failure using three of the principal assumptions of the Strength of Materials theory, which are in fact not respected here. This is why it is proposed in this paper to model the arch behaviour in compression, which is of primary importance for aspect ratios less than three. Considering a proposed lattice, a behaviour at failure is obtained, close to that of a CEB during a 3 points bending test. The compressive stress at failure is obtained by using this lattice. The validation of the model is given using experimental data. Then the model gives information on the CEB structure such as isotropy, dry density gradient within the CEB, and effect of friction with the experimental direct compression test device, leading to confinement of the sample. [Copyright &y& Elsevier]

Granular materials are widely used in construction. The cost and environmental impact of supplying natural aggregates forces the construction industry to look for alternative materials for engineering applications. Recycled construction waste may be considered suitable for many of these applications. By nature these materials are perceived to be weaker than natural aggregates. The work described in this paper was undertaken to examine the shear strength of waste materials and to consider their possible utilisation when combined with soil reinforcement. Three possible waste materials were considered: building debris, crushed concrete and quarry waste. These materials were tested in a direct shear apparatus with and without reinforcement. Waste materials found at construction sites are generally in poor condition. For example, they may be contaminated with mud, dust etc. Therefore, the tests were carried out under various testing conditions: dry, wet and smeared with clay slurry. The performance of the waste materials was compared to that of traditionally used aggregate, in this case crushed basalt. Results indicated that the recycled materials yielded significantly lower shear strength when compared with the crushed rock. The results also showed a significant reduction in shear strength when the materials were smeared with clay slurry. However, the presence of soil reinforcement resulted in a significant increase in the shearing resistance of the granular materials; in some cases an increase of up to 50%. [Copyright &y& Elsevier]

This paper presents the results of an experimental program designed to evaluate the out-of-plane shear strength of masonry wall system; and to evaluate of the influence of the area of externally bonded FRP composites on the shear strength of the system. Eighteen compact masonry wall panels (3′×2′×8″, 900×600×200 mm) were tested for static out-of-plane loads. Nine panels were reinforced by one layer of WEB ‘S-Glass’ fiber-reinforcing system attached to the tension side of the wall, while the remaining nine were reinforced with two layers of composite overlay on the tension side. The influence of the overlay''s embedded length (the distance between the support and the overlay''s end) on the shear strength was also investigated. The variables evaluated included three layout configurations and two reinforcement ratios. Three different distances between the overlay end and the adjacent support were tested, 0, d/4 (d is the block unit thickness) and d/2. Both one and two layers of WEB fibers were used and three specimens were evaluated for each variable. An MTS machine was used to test each panel under four-point load conditions. The failure loads, mid-span deflection, fiber-end slippage and failure modes were recorded. Based on the results of the experimental program, it appears that the out-of-plane shear strength of the concrete masonry wall systems is constant over the range of variables tested. The measured shear strength of the masonry wall specimens evaluated in this program indicates that the code defined shear strengths may not be as conservative as assumed. [Copyright &y& Elsevier]

Soil, rock and oil-well grouting require enormous amounts of cement and are therefore good examples of areas where high volumes of fly ash could replace cement partially to produce low-cost, environmentally friendly and durable grouts. This paper presents the results of the particle size distribution, three rheological properties (flow time, bleeding and setting time), and five mechanical and strain properties (compressive strength, shear bond strength, modulus of elasticity, Poisson''s ratio and drying shrinkage) of high-volume fly-ash (HVFA) grouts (cement replacement by fly ash of over 55% by weight), with and without superplasticizer (SP) and/or anti-washout agent (AWA). Rheological properties are reported for eight water–cementitious materials (cement+fly ash) ratios (W/CM), ranging from 0.4 to 1.3, whereas mechanical and strain properties of hardened grouts are given at W/CM of 0.5, 0.55 and 0.65. The effects of SP and AWA on the flow time of low-W/CM grouts and the stability of high-W/CM grouts were investigated. The results indicate that the addition of fly ash in cement grouts reduces the flow time, improves stability, reduces drying shrinkage, and attains similar compressive and shear bond strengths as pure cement grouts at later ages. Moreover, when SP is used for low-W/CM grouts, the latter destabilizes, and in those cases AWA should be used. [Copyright &y& Elsevier]

The results of an ongoing test program to evaluate the performance of polymer-modified cement-based mortars for repairing surfaces of concrete structures up to a depth of 75 mm (3 inches) damaged due to exposure to cold climates are presented. Twenty-five selected commercially available polymer-modified products, seven containing styrene butadiene rubber (SBR) and 18 containing acrylics were evaluated. They were compared with those of a pure cement-based mortar containing 8% silica fume by weight of the cement, with a water/cementitious materials (cement+silica fume) ratio (W/CM) of 0.31. All of the mortars were subjected to thermal compatibility with base concrete, drying shrinkage, permeability, abrasion-erosion resistance, bond strength, compressive strength and freezing and thawing cycling tests. The thermal compatibility with the base concrete at temperatures from −50 to +50 °C was used as a pre-selection test. This paper also presents the satisfactory performance of the three best selected polymer-modified cement-based mortars (included in the 25 mortars), after 6 years in service on two operating spillways of a dam in a severe cold climate. [Copyright &y& Elsevier]

One of the concerns with the conventional metal anchors that are used to tie the brick veneer to the backup portion of enclosure walls (e.g. masonry block) is the potential for corrosion. Corrosion reduces the load carrying capacity of such ties and this could lead to brittle failure especially in the event of an earthquake. In this paper, the forces in lateral ties in a typical brick veneer wall system are evaluated when the building is subjected to some earthquake records. Distribution of tie forces resulting from the dynamic analysis of a finite element model of the brick veneer-masonry block wall system are determined and compared to the conventional assumption. The performance of a corrosion resistant stainless steel helical tie is compared with that of conventional masonry ties. The potential advantages of this relatively new type of masonry tie are discussed with respect to its use in seismic regions. [Copyright &y& Elsevier]

The fire which spread over the top six floors of the 54 m tall building of the Open University in Novi Sad, caused severe damage to the load-bearing reinforced (RC) concrete structure and the steel facade structure. This paper presents the recorded data on the damage and the assessment of the structure after the fire. All the damage is described and the most characteristic ones are illustrated with photographs. The damages caused by the fire have been classified according to the criteria of the manner and degree to which they are manifested. The authors separate and describe the defects, which occurred as a result of errors made during the construction of the building. The results of the subsequent testing of the quality of the built-in materials are also presented in the paper. It has been concluded that the damage of the elements of the load-bearing RC structure from the 8th to the 12th floor has been so severe that the stability and bearing capacity of this part of the structure has been jeopardized, but with appropriate repair measures it can be restored to its previous condition. [Copyright &y& Elsevier]

This paper considers the compressive strength of masonry composed of mortar and clay bricks. By collecting data from published experimental results, the main objective is to assess the uncertainty in several models proposed either in the literature or herein for the prediction of masonry compressive strength. Furthermore, where possible, models suggested in representative design codes are also examined in the same manner. It is found that existing models give highly uncertain values of the compressive strength, whereas code values are uncertain as well as perhaps over-conservative. Using the collected experimental results new models are proposed based on regression analyses involving the mortar and brick compressive strengths and several other parameters relating to the geometry of the brick units, mortar joints or the wall. A decision aid is also introduced, which may be used for establishing which of the proposed models is most suitable. Additionally, incorporation of a model uncertainty factor is also achieved. [Copyright &y& Elsevier]

In this paper, improvement of bond strength for epoxy-coated rebars is studied. Although the epoxy-coated rebar is well accepted as an alternative corrosion prevention method in engineering practice, it still suffers from its poor bond performance, which requires modification of design parameters such as development length and splice length. Following our previous study [Proceedings of the Third Structure Engineering Conference (1996) 651–659], it is proposed to mix the river sand in the epoxy to improve the bond strength of epoxy-coated rebar. Specimens of several sizes of river sand and sand/epoxy weight ratios were studied. The single-rebar pullout test was performed to examine the bond strength. The open circuit potential method and the linear DC polarization method were conducted for corrosion rate measurements to ensure for keeping the merit of epoxy-coated rebar, i.e. the ability of corrosion. Experimental results show that the proposed method is very promising. [Copyright &y& Elsevier]

The morphological, thermal and fundamental rheological characteristics of ethylene vinyl acetate (EVA) copolymer modified bitumens are studied in this paper. Nine plastomeric EVA polymer modified bitumens (PMBs) have been produced by laboratory mixing bitumen from three sources with an EVA copolymer at three polymer contents. The morphology, thermal properties and rheological characteristics of the EVA PMBs have been analysed using fluorescent microscopy, differential scanning calorometry and dynamic mechanical analysis using a dynamic shear rheometer, respectively. The results of the investigation indicate that EVA polymer modification increases binder stiffness and elasticity at high service temperatures and low loading frequencies with the degree of modification being a function of bitumen source, bitumen–polymer compatibility and polymer concentration. Filler type modification is evident at low temperatures, temperatures above the melting temperature of the semi-crystalline EVA copolymer and for those modified binders that do not exhibit a dominant polymer network. [Copyright &y& Elsevier]

Deterioration of antenna tower foundations is fast becoming an issue of critical importance. A great effort has been carried out to develop the international standards for design and construction of antenna towers and antenna-supporting structures. Comparatively little attention has been directed toward the design against failure of buried tower components. In this paper a case study is introduced for the investigation of 51 defective foundations of self-supported and guyed antenna towers. Factors affecting the durability of tower anchorages and foundations are discussed. These include corrosion of tower parts in direct contact with soil, inadequate reinforcement detailing of tower foundations, and lack of maintenance of concrete footings. Repair methods of tower foundations are introduced along with tower shoring systems used to maintain the structural capacity during the repair process. Furthermore, precautions necessary for preventing failure due to corrosion of buried tower components and deterioration of anchor blocks and foundations are also discussed. An innovative system of surface anchor blocks for guyed towers is evaluated and compared to the conventional anchoring systems. [Copyright &y& Elsevier]

The technique of bonding fibre reinforced polymer (FRP) composites to the tension face or sides of reinforced concrete (RC) beams has become very popular for strengthening or retrofitting purposes. A distinct characteristic of such strengthened RC beams is that they very often fail due to various premature debonding failures. This paper presents a fracture mechanics based finite element analysis of debonding failures. Numerical results for an experimental beam are presented. Initial findings show that the method can successfully simulate the concrete cover separation failure mode in FRP strengthened RC beams. [Copyright &y& Elsevier]

The method of strengthening concrete structures with FRP composites has existed for over a decade; the most common way to strengthen structures is in bending, but also wrapping of columns is quite common. There are also needs for strengthening concrete structures in shear, for example concrete beams, slabs, columns, etc. A typical structure can be a parking garage. However, strengthening concrete structures for shear is not as common as for bending and confinement. This paper presents examples to strengthen concrete beams for shear. First traditional strengthening methods are presented briefly, then the use of CFRP (Carbon Fibre reinforced Polymers) composites for shear strengthening is presented. Tests on beams strengthened in shear with CFRP sheets are presented and a short presentation on how to design for shear strengthening with CFRP is given. Furthermore, a field application of a parking slab strengthened for shear with CFRP unidirectional fabric is presented. The laboratory tests show the importance of considering the principal directions of the shear crack in relation to the unidirectional fibre. The field application shows that it is easy to strengthen existing structures for shear with CFRP fabrics. [Copyright &y& Elsevier]

Many studies have been undertaken on shear strengthening of reinforced concrete (RC) beams by externally bonding fibre-reinforced polymer (FRP) composites. These studies have established clearly that such strengthened beams fail in shear mainly in one of two modes: FRP rupture; and FRP debonding, and have led to preliminary design proposals. This paper is concerned with the development of a simple, accurate and rational design proposal for the shear capacity of FRP-strengthened beams which fail by FRP debonding. Existing strength proposals are reviewed and their deficiencies highlighted. A new strength model is then developed. The model is validated against experimental data collected from the existing literature. Finally, a new design proposal is presented. [Copyright &y& Elsevier]

This paper presents an experimental and analytical investigation for evaluating the ultimate response of unreinforced and reinforced concrete slabs repaired and retrofitted with fiber reinforced polymer (FRP) composite strips. A uniformly distributed pressure was applied to several two-way large-scale slab specimens using a high-pressure water bag. Both carbon/epoxy and E-glass/epoxy composite systems were used in this study. In predicting the behavior of the repaired slabs, the finite element method was used. Comparison between the experimental and the analytical results indicated the validity of the computational models in capturing the experimentally determined results for both the control and the rehabilitated slabs. For repair applications, test results indicated that both FRP systems were effective in appreciably increasing the strength of the repaired slabs to approximately five times that of the as-built slabs. For retrofitting applications, use of FRP systems resulted in appreciable upgrade of the structural capacity of the as-built slabs up to 500% for unreinforced specimens and 200% for steel reinforced specimens. [Copyright &y& Elsevier]

An advanced polymer/continuous fibre composite (APC) and concrete system is an example in which two very dissimilar materials can be joined to form a composite structure. In the current investigation a duplex beam will be analysed where the high-compressive strength concrete is placed above, and the high strength and stiffness fibre/polymer composite is placed below the neutral axis; in this form the two materials will be used to their best advantage. When this structural duplex Tee beam is under load, two failure criteria of the system have been identified. These are the failure of the shear bond between the APC permanent shuttering and the concrete, and failure by buckling of the composite web of the beam. The experimental test results show that the shear bond is not critical. Buckling occurs in the specified panels at 20% of the ultimate load. On increasing the load, the beam continues to perform conventionally and fails in the concrete by crushing. In addition, the paper shows that the performance of the APCs are not impaired by long-term creep and fatigue loading whilst the concrete element shows a typical reduction in stiffness for these types of loading regimes. [Copyright &y& Elsevier]

Concrete beams reinforced with fiber reinforced polymer (FRP) bars exhibit large deflections and crack widths as compared to concrete beams reinforced with steel due to the low modulus of elasticity of FRP. Current design methods for predicting deflections at service load and crack widths developed in concrete structures reinforced with steel bars may not be used for concrete structures reinforced with FRP bars. Thus, the ACI 440 Committee has provided design guidelines for concrete beams reinforced with FRP bars. Verification of the ACI 440 methods for predicting deflections and crack widths for glass fiber reinforced polymer reinforced concrete beams are presented in this paper. In addition, improvement to the crack width equation was suggested to account for 2 layers of reinforcement. This study shows that ACI 440.1R-01 can be effectively used to predict deflections in concrete beams reinforced with FRP bars and crack width in beams with one-layer FRP bars. However, when FRP bars are placed in two layers, ACI 440.1R-01 can be used after some parameters are modified. Six full concrete beams reinforced with different GFRP reinforcement ratios were load tested and the measured deflections and crack widths were analyzed and compared with those predicted by the proposed models. The experimental results compared well with those proposed by the model. [Copyright &y& Elsevier]

This paper reports results of a study conducted to evaluate the effect of four types of coarse aggregates, namely calcareous, dolomitic, quartzitic limestone, and steel slag, on the compressive and tensile strength, and elastic modulus of high strength concrete. The highest and lowest compressive strength was obtained in the concrete specimens prepared with steel slag and calcareous limestone aggregates, respectively. Similarly, the split tensile strength of steel slag aggregate concrete was the highest, followed by that of dolomitic and quartzitic limestone aggregate concretes. The lowest split tensile strength was noted in the calcareous limestone aggregate concrete. The type of coarse aggregate also influences the modulus of elasticity of concrete. Weaker aggregates tend to produce a more ductile concrete than stronger aggregates do. [Copyright &y& Elsevier]

The effects of highly reactive aggregate, fused silica, and slowly reactive aggregate, Thames Valley sand, on the mechanical properties of concrete were investigated in this paper. The mechanical properties studied over a period of 12 months were the compressive strength, direct tensile strength, tensile splitting strength, flexural tensile strength (modulus of rupture), static modulus of elasticity and water absorption. The effects of both reactive aggregates on the mechanical properties of concrete were compared with that of sound concrete mix. The results presented in this investigation show that the effect of the reactive aggregates on the mechanical properties varies, depending on the type of reactive aggregate. From this study it appears that the direct tensile and static modulus of elasticity were the best indicators of reactivity. [Copyright &y& Elsevier]

When exposed to various thermal conditions, installed roofing membrane experiences dimensional change, which creates induced, loads on the membrane material. These loads can cause a number of undesirable effects such as the membrane separating away from the parapet wall, seam components splitting, membrane tear at the vicinity of fasteners and membrane slag causing blistering. This paper deals with two kinds of thermally-induced loads, namely, reversible thermal expansion/contraction and irreversible stress releasing. The mechanisms for each type of induced load have been explored in detail on two membrane types of different internal structure. Thermal conditions are configured in the experiments to simulate typical Canadian summer and winter temperatures on a black roofing membrane surface. This study also explores the role of the membrane''s length and pre-loading on the induced loads. Based on limited data, some practical recommendations are given, such as regarding the influence of the induced loads in the membrane and on the performance integrity of the roofing assembly constructions when subjected to various exposure conditions. [Copyright &y& Elsevier]

This paper reports on the second phase of a research program started at the American University of Beirut (AUB) to study the effects of used engine oil on concrete properties and concrete behavior. In the first phase, the effect of used engine oil on properties of fresh and hardened concrete was investigated. Results indicated that used engine oil acted as an air-entraining agent by improving the slump and fluidity of the concrete mix, and enhancing the air content of fresh concrete. Reductions in the strength properties of hardened concrete due to the incorporation of oil were not as significant as when a commercial chemical air-entraining admixture was used. Results of the first phase of the AUB study instigated further investigation reported in this paper. The objective was to evaluate the effect of used engine oil on structural behavior of reinforced concrete elements. Six full-scale beam specimens were tested in three sets. The difference between the three sets was the mode of failure of the beams: flexure; shear; or bond. The two companion beams in each set were identical except for the use of engine oil in one of them. The beams were tested in positive bending. Results showed that regardless of the mode of failure, used engine oil did not have any significant effect on the ultimate load or load-deflection behavior of the beams. [Copyright &y& Elsevier]

A simple gravimetric method for determination of moisture diffusivity which is able to give a moisture diffusivity vs. moisture relation point-wise is presented in this paper. The method can be employed in determining moisture diffusivity of anisotropic materials also in the case if one spatial dimension of the specimen is significantly smaller than the other two, which is the case of the most of lining materials, for instance. Practical application of the method is demonstrated for two fiber containing plate building materials produced in the Czech Republic, Dekalux and Dekalit P. Experimental results show that while for lighter Dekalit P, an order of magnitude difference in the moisture diffusivities κ for the two basic orientations, i.e. along and through the plate, is observed, for the heavier Dekalux the differences in κ are within the error bar of the experimental method. The method is tested by its application to rod samples, and a comparison with two commonly used methods is done with both mentioned lining materials and also with an extruded porcelain mixture which can be considered as a well homogeneous material. The results of this comparison show a reasonable agreement, taking into account the approximate character of the method. [Copyright &y& Elsevier]

Roundwood timber from forest thinnings is a plentiful and inexpensive resource in many parts of the world, generally destined for low grade applications such as pulping, board production or fuel. In recent years, there has been interest in developing higher grade uses for such material. One such application has been the construction of the KIND centre, a 350-m2 single storey residential centre completed in 2001, in which roundwood timber framing is used for the structural frame. The paper describes the structure, its design and construction. The paper outlines the societal, environmental and economic benefits of using locally grown roundwood timber thinnings, as well as the technical merits of the material and difficulties to be faced in its use. It describes how the design philosophy evolved to maximise the use of skills available within rural communities. The paper sets out a process of design validation followed when in using a novel engineering material, including the use of physical testing and re-evaluation of conventional performance criteria. The paper is amply illustrated to show the high quality internal useable space achieved, which has maintained the essence of the rustic and rural setting in its outer appearance. [Copyright &y& Elsevier]

In this paper, bond degradation due to the desalination process of chloride-contaminated reinforced concrete is investigated. Four different constant voltages were applied to study the effect of the current on the desalination. Two constant current densities were applied for comparison. Two different electrolytes, NaOH and Ca(OH)2, were used to examine the effect of electrolyte on the bond characteristics. Pullout specimens were cast and tested, using a single rebar pullout test. Three bond parameters of the bond strength, the critical debonding shear load per unit embedded rebar length and the shear stiffness per unit embedded rebar length were obtained to evaluate the bond quality after desalination. It is found that the bond characteristics decrease dramatically as the duration and/or the voltage of desalination increase. Using Ca(OH)2 solution as the electrolyte, less bond loss is observed than using NaOH solution. A micro-hardness experiment shows that softening of concrete near the rebar becomes more apparent as the desalination duration and/or desalination voltage increase. A chemical titration experiment indicates that the accumulation of potassium and sodium ions increases as the desalination duration and/or desalination voltage increase. A pH value measurement shows that the desalination current increases the pH value of concrete near the rebar. More than two-thirds of chloride ions migrate out of the rebar–concrete interface in two weeks of desalination with desalination voltage greater than 10 V. Bond strength decreases approximately 40–60%. [Copyright &y& Elsevier]

This paper describes the application of various types of dry boards that are normally used as non-load bearing building components, as a structural component in an innovative lightweight composite structural flooring panel system known as the Bondek II/Cemboard Composite Flooring Panel (BCCFP) system. The composite panel system consists of profiled steel sheeting attached to a top layer dry board by simple mechanical connectors. In the proposed system, dry board plays a dual role, firstly in providing a flat floor surface covering the corrugated profiled steel sheeting, and secondly, it helps in enhancing the stiffness and strength of the composite system. The role of dry boards in the BCCFP system and the performance of the system using various types and thickness of dry boards are investigated. In addition, the effect of varying the spacing of screws on the panel performance is also studied. From test results, it was found that the application of dry boards in the BCCFP system could increase the flexural stiffness of the composite panel by between 12.8% to as high as 26.3% compared to that of the steel sheeting alone for the various tested samples. The stiffness value of a typical practical configuration of the BCCFP system comprising of 1.0 mm thick Bondek II attached to 16 mm Cemboard with screw spacing of 100 mm was found to be 166 kNm2/m with a percentage interaction value of 21.3%. The introduction of a layer of dry board to the bare steel sheeting alone has been shown able to increase by 12.2% the moment capacity value from 8.2 kNm/m of the steel sheeting alone to 12.2 kNm/m of the typical BCCFP system mentioned above. It can be concluded that the dry boards, which are normally used in non-load bearing applications, are having great potential to be used as components in load bearing structural system. Some interesting applications of the system in real buildings are also highlighted in this paper. [Copyright &y& Elsevier]

There is a current trend all over the world to investigate the utilization of processed and unprocessed industrial by-products and domestic wastes as raw materials in cement and concrete. This has a positive environmental impact due to the ever-increasing cost of waste disposal and stricter environmental regulations. Historically, reference books on concrete technology and cement chemistry indicate that the leakage of oil into the cement in older grinding units resulted in concrete with greater resistance to freezing and thawing. This effect is similar to adding an air-entraining chemical admixture to the concrete. Such information is not backed by any research study reported in the literature. The objective of the research reported in this paper was to investigate the effects of used engine oil on properties of fresh and hardened concrete. The main variables included the type and dosage of an air-entraining agent (commercial type, used engine oil, or new engine oil), mixing time, and the water/cement ratio of the concrete. Results showed that used engine oil increased the slump and percentage of entrained air of the fresh concrete mix, and did not adversely affect the strength properties of hardened concrete. [Copyright &y& Elsevier]

The introduction of polymers and advanced polymer composites in the civil infrastructure has been a very rapid process in comparison to other civil engineering materials when they were in their infancy. Advanced polymer composite materials have hitherto been utilised predominately in the aerospace and marine industries, but for the last three decades there has been a growing awareness amongst civil/structural engineers of the importance of the unique mechanical and in-service properties of these materials together with their customised fabrication technologies. These extraordinary properties have enabled the design engineers to have greater confidence in the materials’ potential and consequently to use them in the renewal of civil infrastructure ranging from the strengthening of reinforced concrete, steel and cast iron, and the seismic retrofitting of bridges and columns for the use in replacement bridge decks and in the new bridge and building structures. This paper will outline the developing stages of this exciting material and will indicate future prospects for it. [Copyright &y& Elsevier]

Fiber reinforced polymer (FRP) composites or advanced composite materials are very attractive for use in civil engineering applications due to their high strength-to-weight and stiffness-to-weight ratios, corrosion resistance, light weight and potentially high durability. Their application is of most importance in the renewal of constructed facilities infrastructure such as buildings, bridges, pipelines, etc. Recently, their use has increased in the rehabilitation of concrete structures, mainly due to their tailorable performance characteristics, ease of application and low life cycle costs. These characteristics and the success of structural rehabilitation measures have led to the development of new lightweight structural concepts utilizing all FRP systems or new FRP/concrete composite systems. This paper presents an overview of the research and development of applications of advanced composites to civil infrastructure renewal at the University of California, San Diego (UCSD). [Copyright &y& Elsevier]

This paper reports on the North American state-of-the-art in the use of FRP composites in concrete structures. For new construction, FRP bars have been used as the internal reinforcement in concrete members to replace conventional steel rebars for a host of reasons. The principles for design and construction have been established and proposed to industry by the American Concrete Institute (ACI). For repair and upgrade, strengthening of concrete members with externally bonded FRP laminates or near surface mounted (NSM) bars has received remarkable attention. The design and construction principles for use in practice are being finalized by ACI. On the application side, FRP materials have been used in some multi-million dollar projects for strengthening parking garages, multi-purpose convention centers, office buildings and silos. The drivers for this technology are several, but perhaps the most relevant one is the ease of installation. In the repair/upgrade arena (as well as new construction), perhaps one of the most important unresolved question remains that of durability (including fire resistance). Further research and validation is necessary to increase confidence in FRP technology for concrete construction. [Copyright &y& Elsevier]

A variety of debonding failure modes have been observed in tests on reinforced concrete (RC) beams strengthened by bonding fibre reinforced polymer (FRP) plates to their tension face. These can be broadly classified into two types: (a) those associated with high interfacial stresses near the ends of the bonded plate; and (b) those induced by a flexural or flexural-shear crack away from the plate ends. The first type of failures has been extensively studied, leading to many strength models. By contrast, the second type of failures has received much less attention and no strength model appears to have been developed for it. This paper is, therefore, concerned with the second type of failures induced by a flexural or flexural-shear crack, which is referred to as intermediate crack-induced debonding. The mechanism of this type of debonding failures is first examined briefly, highlighting the similarity between such debonding failures and those in simple shear tests of FRP-to-concrete bonded joints used for determining bond strengths. Based on this similarity, the recent Chen and Teng bond strength model is combined with a simple section analysis for predicting the strength of beams and slabs, which fail by intermediate crack-induced debonding. It is shown that through a simple modification of the Chen and Teng bond strength model, the proposed debonding strength model provides a good first approximation to the strengths of such beams. A design procedure for the flexural strengthening of beams incorporating the proposed debonding strength model is finally proposed. [Copyright &y& Elsevier]

External confinement by the wrapping of FRP sheets (or FRP jacketing) provides a very effective method for the retrofit of reinforced concrete (RC) columns subject to either static or seismic loads. For the reliable and cost-effective design of FRP jackets, an accurate stress–strain model is required for FRP-confined concrete. In this paper, a new design-oriented stress–strain model is proposed for concrete confined by FRP wraps with fibres only or predominantly in the hoop direction based on a careful interpretation of existing test data and observations. This model is simple, so it is suitable for direct use in design, but in the meantime, it captures all the main characteristics of the stress–strain behavior of concrete confined by different types of FRP. In addition, for unconfined concrete, this model reduces directly to idealized stress–strain curves in existing design codes. In the development of this model, a number of important issues including the actual hoop strains in FRP jackets at rupture, the sufficiency of FRP confinement for a significant strength enhancement, and the effect of jacket stiffness on the ultimate axial strain, were all carefully examined and appropriately resolved. The predictions of the model are shown to agree well with test data. [Copyright &y& Elsevier]

This paper presents a unique strengthening technique for existing concrete columns that use expansive materials to apply lateral pre-tensioning. The technique increases the capacity and ductility of a column as well as achieving better utilisation of the confining FRP (Fibre Reinforced Polymer) material. The confinement material properties and the confined cylinder performance are investigated experimentally. From the results, it is shown that it is possible to control the degree of applied pre-tension by controlling the amount of expansive material used. In addition, it is confirmed that jacketing columns by pre-tensioned FRP materials can increase the load bearing capacity up to 35% compared with no pre-tensioning and up to more than four times compared with unconfined concrete. The paper presents details of experimental work undertaken for the development of the confinement pressure with different confining materials (Carbon-CFRP, Glass-GFRP and Steel) and makes comparisons with predictive models. [Copyright &y& Elsevier]

Concrete-filled fiber reinforced polymer (FRP) circular tubes provide an effective structural system for a variety of applications such as piles, columns, overhead sign structures and utility poles. This paper discusses the behavior of concrete-filled Glass-FRP tubes ranging in diameter from 90 to 942 mm, using test results of eight beams, five columns and ten beam-column specimens. The effects of concrete fill, laminate structure of the tube, reinforcement ratio based on the wall thickness, as well as different failure modes are examined. Analytical models have been established and used in a parametric study to examine the effects of fiber orientation within the FRP tubes, thickness of the FRP tube, and the diameter of a central hole, which could be used to reduce the self-weight of the member. The benefits of concrete fill as well as the confinement effects have been demonstrated experimentally and analytically. [Copyright &y& Elsevier]

The collapse of the nave and dome of the Cathedral of Noto, S. Nicolo`, in a rainstorm in 1996 brought to light 18th century construction errors unique to this building. S. Nicolo` is the most prominent church in the city of Noto, a rich Baroque center in southeastern Sicily completely reconstructed after an earthquake in 1693. During the course of its construction and reconstruction between 1696 and 1950, S. Nicolo` was plagued by multiple earthquake failures and construction errors. This paper attempts to assemble the unwritten construction history of the church for the first time in English, and to address the question of how architects, engineers and builders responded to the problem of creating a seismically resistant building. [Copyright &y& Elsevier]

On 13th March 1996 the dome of the St. Nicolo` Cathedral of Noto fell due to a post-seismic structural collapse. In order to study the soil–structure interaction a comprehensive laboratory and in situ investigation has been carried out to obtain a soil profile. In this paper the dynamic characterisation results and normalised laws are proposed to consider shear modulus decay and damping ratio increase with strain level. The existing foundations of the cathedral were investigated by means of excavations and tests on the stones and the mortar. In this way the foundations were subjected to visual inspections to detect their size and their embedment level. Now, the soil–foundation interaction has been analysed by means of the finite element code SOFIA, considering at this stage the superstructure weight through the influence area approach. In particular, the effects of the designed remedial work of the foundation have been studied, comparing the two configurations before and after the foundation improvement. [Copyright &y& Elsevier]

Use of fiber reinforced plastic (FRP) composite materials for strengthening and repair of structural members has become an increasingly popular area of research and application in the last decade. However, the method is yet to become a mainstream application due to a number of economical and design related issues. From a structural mechanics point of view, an important concern regarding the effectiveness and safety of this method is the potential of brittle debonding failures. Such failures, unless adequately considered in the design process, may significantly decrease the effectiveness of the strengthening or repair application. In recent years, there has been a concentration of research efforts on characterization and modeling of debonding failures. This paper provides a review of the progress achieved in this area regarding applications to both reinforced concrete and steel members. [Copyright &y& Elsevier]

The purpose of this paper is to present fatigue and strength experimental qualifications performed for an all-composite bridge deck. This bridge deck, made up of fiber-reinforced polymer (FRP) was installed on the campus at University of Missouri at Rolla on July 29th, 2000. The materials used for the fabrication of this 30 foot (9.144 m) long by 9 foot (2.743 m) wide deck were 3 inches (76.2 mm) pultruded square hollow glass and carbon FRP tubes of varying lengths. These tubes were bonded using an epoxy adhesive and mechanically fastened together using screws in seven different layers to form the bridge deck with tubes running both longitudinal and transverse to the traffic direction. The cross-section of the deck was in the form of four identical I-beams running along the length of the bridge. Fatigue and failure tests were conducted on a 30 foot (9.144 m) long by 2 foot (609.6 mm) wide prototype deck sample, equivalent to a quarter portion of the bridge deck. The loads for these tests were computed so as to meet American Association of State Highway and Transportation Officials (AASHTO) H-20 truckload requirements based on strength and maximum deflection. The sample was fatigued to 2 million cycles under service loading and a nominal frequency of 4 Hz. Stiffness changes were monitored by periodically interrupting the run to perform a quasi-static test to service load. Results from these tests indicated no loss in stiffness up to 2 million cycles. Following the fatigue testing, the test sample was tested to failure and no loss in strength was observed. The testing program, specimen detail, experimental setup and instrumentation, testing procedure, and the results of these tests are discussed in detail. A finite-element model of the laboratory test was also developed. The results from the model showed good correlation to deflections and longitudinal strains measured during the tests. The design of the bridge deck has been discussed in detail. [Copyright &y& Elsevier]

In order to investigate the hygrothermal performance and durability of well-insulated cold zinc roofs, a total of four cold zinc roofs with a low U-factor [U<0.25 W/(m2·K)] were constructed in a test building at the KU Leuven, Belgium. This paper presents the hygrothermal performances measured in the four roofs during an exposure period of 28 months. The zinc roofs with a specific design and careful workmanship exhibited a satisfactory thermal performance. The moisture content in the wood deck generally stayed below 20% by weight. However, the moisture situation at the underside of zinc sheeting was bad in all four roofs studied. We found that the strong undercooling of the zinc sheeting was the main cause for the bad moisture situation observed. Even a combination of a low air exfiltration and a good roof cavity ventilation rate did not eliminate or reduce the condensation at the underside of zinc sheeting. [Copyright &y& Elsevier]

In a previous paper [Zheng et al., Hygrothermal Performance, Part I; Const Building Mater, Vol. 18, Issue 1, pp. 49–59], the hygrothermal performances of four well-insulated cold zinc roofs were evaluated. This paper investigates the corrosion behavior of the zinc sheeting used in the roofs. The main corrosion products identified are Zn5(CO3)2(OH)6 and ZnO. Little corrosion occurred at the upside of the zinc sheeting. However, serious pitting corrosion developed at the underside. The maximum pit depths measured in the collected samples with an area of 0.35 m2 were between 167 and 273 μm. The traditional measures to minimize condensation deposit, i.e. low air exfiltration and good roof cavity ventilation, clearly did not work effectively in reducing the underside corrosion of the zinc sheeting. The results show that new techniques and roofing systems should be developed and implemented. [Copyright &y& Elsevier]