Energy and emergy based cost–benefit evaluation of building envelopes relative to geographical location and climate

This paper presents an environmental evaluation of building envelopes, made of three different technologies: a traditional air-cavity wall, a plus-insulated wall (with an external cork covering), and a ventilated wall (with external brick panels fixed on extruded frames). An environmental accounting method, namely Emergy Evaluation (EE), was performed for assessing environmental resource use (energy and material flows), both directly and indirectly, for the construction of a façade (1000 m²). Then, energy use during the building lifetime was assessed as a constant inflow to the building depending on the thermal skills of building envelopes, besides thermal efficiency of air-conditioning system. In particular, this energy inflow is needed for maintaining constant indoor climate conditions (18 °C) and has to balance heat dissipation through envelopes (heat loss in winter and heat gain in summer). Outcomes were compared with an Energy Analysis (EA) based on an embodied energy accounting. Finally, costs for manufacturing walls (with enhanced performance) and benefits (energy saving) were compared in a unique balance, through both EA and EE. Moreover, outcomes were obtained for three scenarios corresponding to three geographic locations (Berlin in northern Europe, Barcelona on the Mediterranean coast and Palermo in the south of Italy). Results highlighted that performances of building envelopes depend on technologies relative to external climate conditions. Different environmental accounting methods, such as EE and EA, provided outcomes with some difference that are not contradictory to each other but complementary.     

Multifaceted public outreach and cost–benefit analysis for its effectiveness validation

A heavily trafficked 4.5km highway stretch on Interstate 15 east of Los Angeles was rebuilt using two extended closures, each spanning nine days with 24/7 operations. Before and during the closures, a multifaceted, extensive, dynamic public outreach programme was implemented to gain public support for the project and to minimize inconvenience to the public. That outreach programme is described, its overall effectiveness in terms of total net benefit and traffic inconvenience during lane closures is assessed, and changes in public perception of the accelerated construction strategy resulting from the outreach programme is examined. Pre‐ and post‐construction surveys performed using the project website mirrored the findings of the traffic measurement study, indicating that the outreach programme effectively reduced traffic demand. The results of two web‐based surveys with a combined total of approximately 400 respondents indicated a dramatic change in public perception of the accelerated construction strategy. The survey results showed that strong initial objection to the accelerated project eventually became supportive of future, accelerated projects. The cost–benefit analysis showed that the additional cost of the outreach programme was outweighed by the savings achieved from reduced road user delay costs.     

Structural fire performance of earthquake-resistant composite steel–concrete frames

Seismic and fire design of a building structure may be two very demanding tasks, especially if included in a performance based design philosophy. For the time being, the necessary harmonization on the regulations concerning these two design fields is almost missing, thus preventing the effective possibility of an integrated design. Besides, while many countries have already moved towards the use of performance-based codes for seismic design, the application of such methodologies for the fire design of structures is still limited in scope. Within this framework, the development of suitable procedures introducing structural fire performance issues for a comprehensive design methodology is needed.In this paper, a numerical investigation for the assessment of the structural fire performance of earthquake resistant composite steel–concrete frames is presented. With reference to a case study defined in the framework of a European Research Project, a great effort was devoted to the identification of the key structural parameters allowing for a possible correlation between the predictable performances under seismic and fire loadings, when these two are considered as independent actions.At the conceptual design level, the most suitable structural solution with respect to both design actions was chosen, including composite beams and circular steel concrete-filled columns. The frame was designed in order to resist severe seismic action according to the ductile design approach provided by Eurocode 8; the parameters affecting members’ sizing were outlined in this phase. Afterwards, the seismic performance of the designed frame was investigated by means of non-linear static analyses; once the seismic performance objectives were met, in order to evaluate the structural fire performance of the whole frame a set of criteria was defined. To this purpose, thermo-mechanical analyses under different boundary conditions were developed and in order to identify the possible mechanisms leading to structural failure, the state of stress at the critical cross-sections at different times of fire exposure was investigated. Another point of main concern was represented by the assessment of the influence of different restraining conditions on the achieved fire resistance rating and kind of structural failure.Moreover, the proposed methodology allowed making an estimate of the amount of axial restraint provided to the heated beams by the surrounding structure; in this view, the importance of choosing column elements in function of their flexural stiffness was revealed, in order to correlate it with the predictable performances under both seismic and fire loadings.     

Near–surface sensors for condition monitoring of cover-zone concrete

With more demands being made on reinforced concrete, 100-year guarantees of durability will become a necessity. Lifetime calculations, and prediction of the residual service-life of structures, require quantitative information on cover-zone properties and threshold values for corrosion initiation. It is clear that there exists a need to determine quantitatively those near-surface characteristics of concrete which promote the ingress of gases and/or liquids containing dissolved contaminants. In addition, in-situ monitoring of the temporal change in such properties could assist in making realistic predictions as to the in-service performance of the structure; likely deterioration rates for a particular exposure condition or compliance with the specified design life. This paper details covercrete sensor arrangements; format of data presentation and information that can be obtained from embedded sensors. Such sensors could, ultimately, form part of a high-level monitoring strategy and should be considered at the design stage.     

Tests on cyclic performance of FRP–concrete–steel double-skin tubular columns

Eight FRP–concrete–steel double-skin tubular columns were tested under constant axial load and cyclically increasing flexural loading. The main parameters in the tests are axial load level and number of fibre reinforced polymer (FRP) layers. The influence of those parameters on the strength, ductility, stiffness, and energy dissipation was investigated. It was found that, in general, FRP–concrete–steel double-skin tubular columns exhibit high levels of energy dissipation prior to the rupture of the longitudinal FRP, but experience a sudden drop in the lateral load capacity after that. The ductility of the specimens can be improved to some extent due to the existence of the axial compressive load in current tests.     

Feasibility of cost‐benefit analysis for particulate matter air pollution control in Japan

In the present study, we identified cost benefit analysis (CBA) procedures and data availability to determine the programme feasibility of conducting an ex post CBA for particulate matter of a ten micron nominal diameter (PM‐10) air pollution control in Japan. This paper describes Freeman's benefits methodology to use for the benefits portion of the CBA, and the paper shows the US Environmental Protection Agency's (EPA) costs methodology supplemented by Dixon et al.'s procedures to use for the costs portion of the analysis. The findings included (1) developing a procedure for estimating benefits based on Freeman, (2) developing a procedure for estimating costs based on EPA and Dixon et al., (3) determining that pre‐control data and post‐control data on PM‐10 costs and benefits are available from government agencies in Tokyo, and (4) determining that concentration response functions for health impacts are available from EPA. In conclusion it is feasible to conduct a CBA for Japan, based on the availability of data for an analysis of the urban metropolis of Tokyo.     

Influence of test specimen on experimental characterization of timber–concrete composite joints

Load-carrying capacity of timber–concrete composite joints is usually evaluated using shear tests, which still lack specific standards. Regulations EN 26891 [1] and ASTM D 5652 [2] are usually used, both for timber joints, or EUROCODE 4 [3] for steel–concrete composite joints. Questions about test execution and arrangement of specimens are frequent and recurrent [4], [5], [6]. Steel–concrete composite structures already have a standard shear test for joints (push-out), described in Johnson and Anderson [7]. These authors also discussed the many differences in the results of shear tests because of differences in test methods before EUROCODE 4 [3] standardization.This paper presents some questions about the arrangement of test specimens for shear tests in timber–concrete joints. An experimental program was performed for this reason. The aim of the work was to compare shear test results using two different series of specimens most utilized in a review of the literature: the push-out type with concrete center and timber sides and the push-out type with timber center and concrete sides. 8.0, 10.0 and 12.5 mm diameter corrugated bars were used as connectors. Eucalyptus grandis Brazilian hardwood timber glulam was used. Two-component epoxy adhesive was used to glue the connectors into the timber. Average cylinder compressive strength of the concrete was 25 MPa (28 days old). Reinforcement was 6.0 mm diameter 500 MPa-yield-stress corrugated bars.The results showed that test specimen arrangement influenced the strength and deformation characteristics of timber–concrete composite joints. The specimen with the best shear strength was the concrete–wood–concrete type, similar to those used in steel–concrete composite structures. Since the arrangement of test specimen is an important factor in joint tests, it is recommended that further efforts be made towards standardization.     

Behavior of steel fiber–reinforced high-strength concrete at medium strain rate

Impact compression experiments for the steel fiber–reinforced high-strength concrete (SFRHSC) at medium strain rate were conducted using the split Hopkinson press bar (SHPB) testing method. The volume fractions of steel fibers of SFRHSC were between 0 and 3%. The experimental results showed that, when the strain rate increased from threshold value to 90 s^-1, the maximum stress of SFRHSC increased about 30%, the elastic modulus of SFRHSC increased about 50%, and the increase in the peak strain of SFRHSC was 2-3 times of that in the matrix specimen. The strength and toughness of the matrix were improved remarkably because of the superposition effect of the aggregate high-strength matrix and steel fiber high-strength matrix. As a result, under impact loading, cracks developed in the SFRHSC specimen, but the overall shape of the specimen remained virtually unchanged. However, under similar impact loading, the matrix specimens were almost broken into small pieces.     

Ultimate load behaviour of webs in steel–concrete composite plate girders

The paper is concerned with the tension field action in webs of steel–concrete composite plate girders. A three-dimensional finite element model has been used to carry out nonlinear analyses on composite plate girders. The results obtained from the finite element analyses are compared with those from experiments. It is observed from the comparative study that the proposed nonlinear finite element model is capable of predicting the ultimate load behaviour of steel–concrete composite plate girders to an acceptable accuracy. Results are presented to explain the development of the tension field action in the webs and to illustrate a measure of the contribution by the concrete slab acting compositely with the girder to the changes in tension field compared to a plain steel girder.     

Twist behavior of high-strength concrete hollow beams–Formation of plastic hinges along the length

Torsion tests on high strength concrete hollow beams have revealed some ductile behavior. However, this ductile behavior only occurs for a narrow interval of the torsional reinforcement ratio. Tests have shown that a torsion plastic hinge can be formed. Furthermore, this torsion plastic hinge is concentrated in a small length of the longitudinal axis of the beams. In this paper, the authors show that plastic models are possible for beams under torsion. A torsion plastic hinge at the failure cross section can be assumed. This paper also shows that torsional ductility becomes more difficult as the concrete strength increases.     

Numerical investigation of inelastic buckling of steel–concrete composite beams prestressed with external tendons

The ultimate resistance of a continuous composite beam is governed by either distortional lateral buckling or local buckling, or an interactive mode of the two which is sharply different from the torsional buckling mode in a bare steel beam. A finite element model is developed and based on the proposed FE model, inelastic finite element analysis of composite beams in negative bending is investigated, considering the initial geometric imperfection and the residual stress patterns and the FE results are found agree well with the test results. Parametrical analysis is carried out on the prestressed composite beams with external tendons in negative bending. Factors that influence load carrying performance and buckling moment resistance of prestressed composite beams are analyzed, such as initial geometric imperfection, residual stress in steel beams, force ratio, which is defined as the extent of prestressing force and negative reinforcement in the beams, as well as the slenderness ratios of web, flange, and beams. By varying cross-section parameters, 25 groups of composite beams under negative uniform bending with initial geometric imperfection, residual stress as well as different force ratios, 200 beams in total are studied by means of the FE method. The computed buckling moment ratios are drawn against the modified slenderness proposed by the authors and compared with the Chinese Codified steel column design curve. It is demonstrated that the tentative design method based on the Chinese Codified design curve can be used in assessment of buckling strength of composite beams in a term of the modified slenderness defined.     

Strength deterioration of reinforced concrete beam–column joints subjected to cyclic loading

This paper proposes a method to predict the ductile capacity of reinforced concrete beam–column joints failing in shear after the development of plastic hinges at both ends of the adjacent beams. After the plastic hinges occur at both ends of the beams, the longitudinal axial strain at the center of the beam section in the plastic hinge region is expected to increase abruptly because the neutral axis continues to move toward the extreme compressive fiber and the residual strains of the longitudinal bars continue to increase with each cycle of additional inelastic loading cycles. An increase in the axial strain of the beam section after flexural yielding contributes to a widening of the cracks in the beam–column joints, thus leading to a reduction in the shear strength of the beam–column joints. The proposed method includes the effect of longitudinal axial strain of a beam in the plastic hinge region of the beam on the joint longitudinal strain and the strength deterioration of the joint. In order to verify the shear strength and the corresponding deformability of the proposed method, test results of RC beam–column assembly were compared. Comparisons between the observed and calculated shear strengths and their corresponding deformability of the tested assemblies showed reasonable agreement.     

Flexural behavior of strengthened steel–concrete composite beams by various plating methods

The effect of pre-intermediate separation on the flexural behavior of strengthened steel–concrete composite beams by either adhesively bonded carbon fiber reinforced polymers (CFRP) sheet or welded/bonded steel plate was studied. In the case of strengthened by CFRP sheet, two different attachment patterns, namely, CFRP sheet wrapped around the flange of the I-beam and CFRP sheet wrapped around the flange along with a part of the web, were examined by testing four different strengthened steel–concrete composite beams under four point bending (4PB). Two of these beams were strengthened by fully bonded CFRP sheet with the two different patterns, while, the others are similar but have pre-intermediate debonding area of 50 mm length × flange width at the bottom surface of the lower flange. In the case of strengthened by steel plate, three different attachment patterns of steel plate to the soffit of the beams, namely, discontinuously welded, end welded, and bonded/welded steel plates, were also tested under 4PB.The experimental results showed that, there is no growth of the intermediate debonding before the yield of the lower flange occurred for all strengthened beams by CFRP sheet. After yielding, the beams with pre-debonding area showed lower flexural capacity than those with fully bonding due to the rapid growth of the intermediate debonding. On the other hand, there is a difference in the yield load between the three different patterns of the welded steel plates with a marginal difference in the elastic stiffness.     

Lightweight steel–concrete–steel sandwich system with J-hook connectors

This paper investigates a new concept for designing composite structures comprising a lightweight concrete core sandwiched in between two steel plates which are interconnected by J-hook connectors. Specifically, lightweight concrete (density less than 1450 kg/m³) and novel J-hook connectors have been developed for this purpose. The hook connectors are capable of resisting tension and shear, and their uses are not restricted by the core thickness. Push-out tests confirms that the shear transfer capability of J-hook connector is superior to the conventional headed stud connector in achieving composite action between steel plate and concrete core. Twelve sandwich beam specimens have been tested to evaluate the flexural and shear performance subjected to static point load. Parameters investigated include degree of partial composite, concrete with and without fibres and concrete strength. Using Eurocodes as a basis of design, theoretical model is developed to predict the flexural and shear capacity considering partial composite and enable construction of sandwich structures with J-hook connectors. Compared with test results, the predicted capacity is generally conservative if brittle failure of connectors can be avoided. Test evidence also shows that inclusion of 1% volume fraction of fibres in the concrete core significantly increases the beam flexural capacity as well as its post-peak ductility.     

Lifetime cost optimization of structures by a combined condition–reliability approach

Cost optimization for the determination of the most effective maintenance strategy of deteriorating structures has recently been used by researchers and accepted by experts. The main reasons for this lie in strict requirements of budgetary efficiency and in reliability requirements for structures. Accessible data directly related to structural performance include the condition state, obtained from generally stipulated visual inspections, and the reliability state, derived from the inspection or monitoring programs combined with numerical computations. In this paper, a novel approach to cost models for condition and reliability profiles is described. Global cost optimization can be achieved by means of multi-objective optimization or by means of a Cost-Optimized Condition-Reliability Profile (COCRP) approach. Since the assessment of structures is under uncertainty, it is essential to embed the COCRP concept in a full probabilistic framework. Probabilistic COCRP computations can be performed, even for complex structures, within a reasonable time by using advanced Monte Carlo Methods such as Latin Hypercube Sampling. The proposed COCRP approach allows realistic and efficient treatment of structures that involve uncertainties and detects the parameters having the most significant effects on lifetime cost.     

Evaluation of prestress losses in prestressed concrete specimens subjected to freeze–thaw cycles

Prestressed concrete structures are considered to be reliable and durable. However, their long-term performance when subjected to frost attack is still unclear. In this work, experiments were carried out to evaluate the prestress losses in post-tensioned prestressed concrete specimens subjected to freeze–thaw cycles (FTCs). Two cases were considered: in one case, a series of specimens were prepared and tested in a freeze–thaw chamber; in the second case, the same series of specimens were tested in an indoor environment (outside the chamber). The difference between the prestress losses of the specimens inside the freeze–thaw chamber and those outside the chamber equalled the prestress losses due to FTCs. When using mathematical models to predict the prestress losses due to the FTCs, it was found that they were relatively small when the concrete was slightly damaged. However, they increased rapidly when the FTCs were repeated. The eccentricity of the prestress wires led to larger prestress losses when subjected to FTCs. Moreover, the same cross section and eccentricity resulted in similar prestress losses due to the FTCs, and the relatively high-strength concrete could withstand more FTCs.     

Sand–concrete interface response: The role of surface texture and confinement conditions

Sand–concrete interface direct shear tests were used to investigate the effects of surface roughness, surface waviness, mean sand diameter and relative density on interface strength and behavior under different confinement conditions. Extreme concrete surface textures, including smooth, rough and rough–wavy textures, were reproduced. Surface plowing was assessed via image analysis, laser scanning and extended multifocal micrographs. The experimental results showed that smooth concrete surfaces exhibited high values of interfacial–to–internal friction angle ratios, ranging 88–90%, due to the angular shape of sand particles. The rough concrete surfaces generated higher interface strength than smooth concrete surfaces; however, the interface strength was still inferior to the surrounding sand strength. Surface plowing, which identified a mixed shear plane at the sand–concrete interface, was developed as particles were detached from the surface, thus inhibiting the interface friction angle from reaching the sand friction angle. Higher sand–concrete interface strength was achieved as surface waviness increased, and interface friction angles greater than the surrounding sand friction angle were reached. Under a constant normal stiffness condition, significantly high interface strength is achieved due to the increase of the current normal stress, which was directly influenced by the initial normal stress, stiffness, surface roughness, mean sand diameter and relative density; surface waviness did not have a marked effect on the normal stress variation. Based on these results, multiple regressions were proposed to estimate the sand–concrete interface strength by the interfacial–to–internal friction angle ratio and the effect of the constant normal stiffness condition.     

Behavior and strength of steel reinforced concrete beam–column joints with single-side force inputs

Five large-scale beam–column subassemblies were fabricated and tested under cyclic loading to investigate the behavior of SRC Type I exterior and Type II corner beam–column joints. In addition, the applicability of strength superposition method on joint shear strength was assessed. It was found that: (1) the strength superposition method was able to estimate the SRC beam–column joint shear strength with reasonable accuracy; (2) the anchorage position of beam longitudinal bars has an obvious influence on the joint shear strength and crack pattern; (3) increased depth of cross-sectional steel leads to a higher shear strength for the beam–column joint; and (4) a combination of corner stirrups and shaped steel cross-sections was able to provide sufficient lateral support to longitudinal steel bars and adequate confinement to the concrete in the joint to replace the need for closed hoops.