This paper presents a review on combining NDT techniques, such as rebound hammer and ultrasonic pulse velocity, for assessing concrete compressive strength. These methods, though being favorably not invasive and easy to be extended to a larger number of elements, are affected by many contingency factors. The SonReb technique suggests combining the two methods to partially offset their low reliability if considered separately. For years, this concept was introduced in order to improve the evaluation compared with the use of one NDT. In order to combine the ultrasonic pulse velocity and rebound hammer, many empirical, multiparametric models were proposed in the literature as linear, power, exponential, or polynomial. However, the variety of these models emphasizes that they can give a correct strength prediction only for the particular cases that they are derived for. Therefore, to assess concrete on site, the strength should be predicted using a calibration procedure due to the variability of existing concrete mixes. This paper presents a brief outline of the key aspects of strength assessment, including the different approaches used to build the SonReb model and a calibration procedure for assessing concrete strength. A comparison study between the different approaches is proposed, and a performance analysis using Monte Carlo simulations is discussed. Finally, the estimation capacity of the existing model identification approaches is investigated, and the effect of the “trade-off” is analyzed for different random sampling with varying the number of cores.

CLT-concrete composite floor systems are a solution for timber buildings with a long-span floor. It yields a reduction of carbon footprint and even eco-friendly structure at the end of its service life. This study will evaluate the structural performance of notched connectors in the CLT-concrete composite floor, comprised of the serviceability stiffness, maximum load, and behavior at failure. The parameters of the test plan are the loaded edge length, the notch depth, the concrete thickness, and the screw length. Other secondary variables are also assessed, such as different loading sequences, speed of test, and timber moisture content. Experimental results prove that the performance of the connector depends significantly but not linearly on the notch depth and the length of the loaded edge. The connector with a deeper notch and a shorter heel will be stiffer and more robust, but it also tends to have a brittle rupture. The test results also help validate a solution for deconstructable connector systems. A nonlinear finite element model of the connector is built and validated versus the experimental results. It yields reasonably good predictions in terms of resistance and can capture the load-slip relationship.

Performance-based earthquake engineering (PBEE) has emerged as a powerful method of analysis and design philosophy in earthquake engineering. Structures are generally assumed to be fixed at their bases in the process of analysis and design under dynamic loading. Response of structures under earthquakes is strongly influenced by the soil-structure system. In soil-structure interaction (SSI) problems, the ability to predict the coupled behaviour of the soil and the structure is essential and requires combined soil and structure models. In the context of PBEE, this paper combines structural behaviour and seismic response analysis of SSI systems. Related to SSI analysis, several issues are studied, such as relative importance of soil parameters, and relative foundation/soil stiffness ratio, in regards to a specified aspect of the system response (e.g. response parameters). A simplified approach is proposed to consider SSI effects on the nonlinear seismic response of a reinforced concrete structure using the nonlinear replacement oscillator method. This oscillator is characterised by an effective ductility along with the known effective period and damping of the system for the elastic condition. The N2 method is used to determine the nonlinear response and extended to include SSI in the design. It is confirmed that the response of the structure depends not only on its dynamic characteristics and on the seismic excitation characteristics but also on the external environment surrounding the base of the structure, i.e. the interaction between the structure, the foundation and the soil. The proposed approach is validated and compared with time history analysis and two other recognised methods.

This paper applies the Sobol’s variance-based global sensitivity analysis to determine the contribution of input parameters to the structural lateral displacement considering damping and taking into account soil structure interaction (SSI) process. This method includes the main effect, the total effect and provides specific parametric interaction for each input. The considered input parameters are soil Poisson’s ratio, soil density, shear wave velocity, soil damping and structural damping. The N2-SSI simplified procedure is used to estimate the lateral displacement and damping of SSI model of RC structure. This simplified nonlinear method allows the assessment of the seismic performance considering the SSI. The results of the sensitivity analysis indicate that soil damping and structural damping greatly affect on the overall damping and can vary according to soil type. Whereas, the maximum lateral displacement is most sensitive to shear wave velocity and soil damping for very soft and soft soils, and it is sensitive to shear wave velocity and structural damping for hard and rock soils. This study reveals the importance of considering more than one output in the sensitivity study for the same input parameters. A same parameter can be considered as deterministic if it has a small influence on the output and it can be considered as probabilistic if it has significant influence on another output.

Inspection-based maintenance strategies can provide an efficient alternative for ageing civil engineering components subjected to ageing and degradation. The technical and/or economic efficiency of such strategies depends on many factors, such as the mechanisms involved in the loss of performance; the availability, cost and efficiency of inspection techniques; the relation between what can be measured through inspections and the level of performance of the structure; the level of required serviceability of the structure; and the direct and indirect economic losses due to a reduction in the performance of a structure. On this basis, it is studied here, using Monte Carlo simulations, the benefits and limitations of an inspection-based maintenance strategy. The quality of the inspection technique is analysed in terms of its sensitivity to defects in their initial stage of development, and on its discriminant ability (detection of a real defect, while avoiding false alarms). This study is carried out with ageing characteristics, inspection models and cost assumptions that can cover a wide field of ageing assets. The influence of several factors is highlighted to see how they influence optimal strategies; a focus is given on the quality of inspections and on the allowable probability of failure.