Abstract: The mechanical properties of concrete were optimized using response surface methodology (RSM) and fuzzy logic. The aggregate portion of the concrete was replaced with recycled aggregate to address the environmental problems caused by building demolition wastes. The essential key factors that influenced the suitability of recycled aggregate in concrete applications are the compressive strength (CS), flexural strength (FS), and the split tensile strength (STS). The experiments were designed with nine combinations of two input factors (percentage of coarse and fine recycled aggregates) at different levels 30, 60, and 100%. Furthermore, optimization techniques were used to determine the strong correlations between the variables and the mechanical parameters. Such optimization techniques helped to identify the optimistic maximum strength for replacing 44% coarse and 65% fine recycled aggregate. Using RSM, the maximum strength results were found to be: CS at 7, 28, 56, and 90 days were 23.61, 35.04, 40.02, and 43.63 N/mm2, respectively, FS 3.6 N/mm2 and STS 2.0 N/mm2. The maximum strength parameters were found using fuzzy logic: CS at 7, 28, 56, and 90 days were 23.5, 35.8, 41, and 46.7 N/mm2, respectively, FS 4.13 N/mm2 and STS 1.97 N/mm2. Such optimization can be carried out to lower the material wastage, energy consumption, and expenses for the production.

Abstract: Wood fiber insulation boards, as many other wooden materials, are susceptible to smolder. This type of slow and flameless thermal degradation has three upmost important drawbacks. First, smoldering can develop unseen until damages are noticed; second, it does not need any external heat to keep progressing, thus behaving as a self-sustaining process; third, it may shift into flaming combustion. Although wooden insulation materials are very competitive as insulators, its use is not permitted in several countries beyond mid-rise buildings due to smoldering hazard. As measuring of physical parameters is difficult and expensive at high temperatures, the objective of this investigation was to develop a theoretical model that comprises most relevant physical phenomena in order to serve as a supportive tool for further development of fire-retardant substances. The constructed model presents the novelty that it can simulate the self-sustaining smoldering without needing any external radiation heat, but only the self-heating generated by its own exothermic reactions. The model was built based on a program of experimental testing that included thermo-gravimetric analyses and differential-scanning calorimetry, being able to predict particle degradation at different heating rates and oxygen concentrations with errors of about 7,5 %. The adequacy of the model was also compared at the structural scale against a non-standard cone calorimeter test with terminal switching off heat radiation to emulate self-sustaining smoldering, which was used as model validation showing fits of about 23 % in consideration of mass loss, mass-loss rate and temperature profile. A comprehensive sensitivity analysis comprising 60 distinct parameters permitted to thoroughly assess the influence of each model input parameter, which is being presented as a ranking from the most to the less influencing parameters that prevent or foster self-sustaining smoldering. Several unexpected conclusions raised, positioning species’ densities, capacities and reaction activation energies as the most important parameters. To the best knowledge of the authors, this is the first model that can simulate the self-sustaining smoldering of wooden insulation materials, so it is expected to contribute on further development of fire retardant compounds for wooden products.

Abstract Hybrid multistory buildings are every day more common in the construction industry. However, there is little understanding of the performance of the hybrid connections. In this research, the static and dynamic response of cross-laminated timber (CLT) composites combined with reinforced concrete (RC), hollow steel profiles and laminated strand lumber (LSL) has been investigated. In addition, the effects of posttensioning stresses as well as distinct types of connectors such as nails, self-tapping screws and self-tapping dowels has been accounted for. After experimental work, numerical modelling for simulating the static and dynamic behavior for these hybrid connections was also investigated. Results indicate that such massive timber composite connections behave reasonably similar to conventional timber connections, except in that inelastic deformations may increase up to 200%. In addition, it has been found that existing hysteretic models like the modified Stewart hysteretic model (MSTEW) fit for modelling purposes except that very asymmetric hysteretic behavior can be found for timber-concrete hybrid connections.

Abstract The effectiveness of seismic dampers to improve the lateral performance of timber structures may be heavily diminished if restrictive lateral drift limits as set by building codes, governs the design of the structure. This paper presents an innovative approach to improve the performance of seismic dampers installed in stiff wood-frame shear walls. U-Shape Flexural Plate dampers with a novel internal restraint system, were installed in a 4880x2475 mm wood-frame shear wall with an Eccentric Lever-Arm System which aimed at amplifying the displacements by transferring them from the shear wall to the dampers. Cyclic tests were conducted to four specimens. Initial test results showed that the presented amplifying system suffered concentrated losses of stiffness at some connections joints reducing its real efficiency. The loss of displacement transmission to dampers was retrofitted, and the results showed a great benefit in terms of resilience for the damped shear wall in contrast with unprotected ones. It was found that this approach provides a feasible solution to enhance the lateral performance of wood-frame structures.

Abstract The FEMA P-695 report presents a methodology for the rational quantification of seismic performance factors for use in seismic design. Despite the fact that the methodology is comprehensive and covers a wide range of possible applications, it only provides ground motion sets recorded from shallow crustal earthquakes. Therefore, this paper presents a new set of ground motions aimed at extending the scope of the FEMA P-695 methodology to zones prone to subduction earthquakes. To consider the effect of spectral shapes on collapse capacities, the spectral shape factors SSF were also computed. Four light-frame buildings were analyzed to study the impact of using the new ground motion set. Results showed a decrease in collapse capacities of 12.4%, an increase in peak floor accelerations of 31.7%, and an increase in the dissipated hysteretic energy of 15.7%. Additionally, the number of ground motions and the intensity levels of the set proved to be robust enough to provide the same reliability that can be obtained when employing a much larger ground motion set. The ground motions and the information provided in this paper have been designed to be fully consistent with the FEMA P-695 guidelines. However, their application can be extended to other analyses that evaluate the seismic performance of structural systems in subduction areas. A database that includes the proposed ground motion set is available online.