Stiffness of Experimentally Tested Horizontally Loaded Walls and Timber-Framed Modular Building.

This paper presents an overview of representative up-to-date research and the authors' own experimental results from tests of wall elements and a horizontally loaded timber-framed modular building. The research has been conducted in connection with the development of timber-based structures in recent years. In the present research, wall elements and modules of timber-frame construction with life-size dimensions were used. So far, these types of structures have mainly been tested in laboratories-especially with regard to anchoring and cyclic loading. An experimental testing was carried out on a natural scale in two stages based on the standard procedure described in EN 594. In the first stage, wall panels were tested. In the second stage, tests were carried out on a complete four-storey building. Dowel fasteners were used to fix the sheathing to the load-bearing wall structures. Additionally, the sheathing was glued to the timber frame of the walls. The same type of wall element was used for the construction of the tested building. Horizontal loads were applied at the height of the top of the walls in both stages. The building loads were applied in a direction perpendicular to the longitudinal axis of the modules. Based on test data, the stiffnesses of the wall panels and the whole building were derived, as well as the type of interaction between the modules and the influence of the walls on the spatial work of the building. On the basis of the conducted studies, both the stiffness of the walls in different configurations and the stiffness of the complete building were determined, as well as the nature of the interaction of neighbouring modules and the influence of wall connections on the 3D working of the building. The results show that the stiffness of the building in the horizontal plane in the direction of the applied load is almost twice as high as the sum of the stiffnesses of the building walls in the same direction.

Diagnostics of the RC Roofing Structure of the 100-Year-Old Municipal Theatre Facility.

Reinforced concrete has been a widely used material for the construction of buildings for many decades. However, with the passage of time, the material characteristics and connection of structural elements gradually degrade. Development in measurement technology makes it possible to efficiently obtain data on the current state of the structure and material characteristics using non-destructive methods, with limited or no destructive testing. The paper presents the analysis of the condition of the reinforced concrete roof of a 100-year-old theatre building in terms of its further use after planned modernisation. The tests carried out in situ as well as the computational analysis of structure are described. Based on the test results, the current load-bearing capacity was assessed and the limit state conditions were checked. Limitations on the accuracy of the non-destructive test results in relation to the destructive test results were formulated. Options for the strengthening reinforced concrete beams with regard to structural and technological considerations were analysed.

The Effect of Steel and Basalt Fibers on the Shear Behavior of Double-Span Fiber Reinforced Concrete Beams.

This study investigates the effects of adding different types of fibers to concrete mixes on the shear behavior of double-span fiber-reinforced concrete beams with or without shear reinforcement. As a part of the experimental study, a total of twenty-seven natural-scale double-span beams were tested. The beams, made of concrete with steel or basalt fiber, with fiber dosages of 78.5 and 5 kg/m3, were tested under shear force. The three tested series consisted of three beams with dimensions of 120 × 300 × 4150 mm, with various numbers of stirrups and contents of fiber reinforcement. During the tests, the shear capacity of the elements was determined. The values of support reactions, deflection in the middle of the span of both beam spans, deformations on the surface of the concrete member in the middle of the span in the compressive and tensile zone, and cracking (crack development and crack width) were also measured. The beams were tested using a digital image correlation (DIC) technique. Test results show that shear capacity increases in beams made of concrete with steel (1.87) or basalt fibers (1.23). Moreover, the failure mode changes from shear (brittle) to flexure-shear (less brittle). The experimental shear capacity of beams was compared with the theoretical values predicted by different design codes, i.e., fib Model Code 2010 and RILEM TC 162-TDF 2003. The results show that all the design codes underestimate the contribution of fiber-reinforced concrete beams to shear resistance and greatly overestimate the contribution of shear reinforcement.

Study of the Mechanical and Physical Behavior of Gypsum Boards with Plastic Cable Waste Aggregates and Their Application to Construction Panels.

The objective of this study was to analyze the physico-mechanical properties of gypsum boards including plastic waste aggregates from cable recycling. The plastic cable waste is incorporated into the gypsum matrix without going through any type of selection and/or treatment, as it is obtained after the cable recycling process. In the experimental process, gypsum boards of different dimensions were manufactured and tested for their Young's modulus, shock-impact resistance, flexural strength, thermal conductivity, and thermal comfort. The results obtained show a significant increase in the elasticity of the boards with plastic waste (limited cracking), compliance with the minimum value of flexural strength, and a slight improvement in the thermal conductivity coefficient (lower energy demand) and surface comfort (reduced condensation and greater adherence). Therefore, the analyzed material could provide a suitable alternative to currently marketed gypsum boards, contributing to sustainable construction not only in new constructions, but also in building renovations.

Estimation of Cement Composites Fracture Parameters Using Deformation Criterion.

A simple deformation criterion based on Dugdale's cohesive zone model is presented. The criterion can be used for both the experimental determination of the critical stress intensity factor, KIc, and the critical tip opening displacement, CTODc. It can also be applied for the evaluation of the load capacity of structural elements. The criterion is presented in explicit and compact form, which allows straightforward calculations to be performed for the estimation of KIc and CTODc values from the experimental data obtained from samples with a U-shaped notch, rounded with an arbitrary radius. Thanks to the simple form of the approximate relationship between the maximal load level and the dimensionless notch tip opening displacement, the reverse procedure was obtained, i.e., the estimation of the value of the maximal force loading the structural element as a function of the known critical stress intensity factor.

The Properties of Composites with Recycled Cement Mortar Used as a Supplementary Cementitious Material.

The process of recycling concrete rubble is accompanied by the formation of a large amount of fine fraction, which cannot be reused as aggregate. The results of research on the possibility of using recycled cement mortar (RCM), obtained during concrete recycling, as a cementitious supplementary material, are presented. The experimental research was carried out on the basis of two variables determining the recycling process: X1-temperature (range of variation 288-712 °C) and X2-time (range of variation 30-90 min) of thermal treatment of concrete rubble. The experiment included 10 series of new composites made with RCMs subjected to different variants of thermal treatment, and two additional control series. The best treatment parameters were determined based on the assessment of selected physical and mechanical properties of the new cement composites, as well as the analysis of characteristics and microstructure of RCM. The test results showed that proper thermal treatment of concrete rubble makes it possible to obtain a high-quality fine fraction, which has the properties of an active addition and can be used as a partial replacement for cement in mortars and concretes.