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The study investigates the enhancements in the load carrying capacity, crack resistance and energy absorption properties provided by the addition of hemp fibres in an earthen material. Notched earthen samples reinforced with two fibre contents (2% and 3% in weight) and three fibre lengths (10, 20, and 30 mm) were manufactured and tested under static and impact bending to investigate and compare the influence of the reinforcement on the fracture resistance of the soil material at low and high strain rates. The results of the experimental analyses show that the incorporation of fibres greatly improves the peak load, the post-crack strength, the ductility and the energy dissipation of soil under both static and impact bending. The mechanical response of both unreinforced and reinforced samples is significantly affected by the rate of loading, with samples exhibiting higher values of strength and absorbed energy under impact than under static bending. For both static and impact loading, the post-crack response of the material at large deformations is clearly improved by increasing the fibre content and, at the same fibre content, by increasing the fibre length.

Adobe buildings are located in many countries and are often constructed with fiber reinforced bricks, which are composite materials made of soil, water, and natural or artificial fibers. This study presents experimental findings for straw fiber reinforced adobe bricks typically used in Sardinia (Italy) and produced according to traditional worldwide handcrafted manufacturing procedures. A large number of compression and three-point bending tests were carried out on cubic and prismatic specimens, respectively. The identification of significant scatter in experimental data sets due to handcrafted manufacturing motivated the estimation of mechanical parameters at different percentile levels, in order to provide their characteristic and median values. The geometry of straw fibers was statistically characterized in terms of mean, standard deviation and probability distribution of their diameter and length. The mechanical characterization in compression included the estimation of fracture energy. Bending test data were processed to estimate Young?????????s modulus in tension, highlighting the bimodularity of the earthen composite material. Finally, both elastic?????????perfectly plastic and nonlinear stress?????????strain models are proposed for design/assessment purposes.

The study investigated the improvements in strength and crack resistance induced by the introduction of wool fibres in an earthen material. Earthen samples reinforced by wool fibres of various fibre lengths at different fibre weight fractions were tested under flexural loading to examine the structural response of the material in terms of first-crack resistance, post-cracking residual strength and energy absorption capability. It was found that the fibrous reinforcement greatly improved the residual strength, the ductility and the energy absorption of the reinforced material as compared to the unreinforced soil. The results of the study also showed that fibre length had a notable influence on the post-fracture response of the material at large deformation regimes.

In this paper, the dynamic behaviour of cement mortars reinforced with both glass and basalt fibres is studied. The influence of the addition of both types of fibre on energy absorption and tensile strength at high strain-rate was investigated, and the performance of the two types of fibre-reinforced mortar was compared. For this aim, basalt and glass fibres with same diameter and length were used. Static tests in compression, in tension and in bending were first performed. Dynamic tests by means of a Modified Hopkinson Bar were then carried out in order to investigate how glass and basalt fibres affected energy absorption and tensile strength of the fibre reinforced mortar at high strain-rate. The Dynamic Increase Factor (DIF) was finally evaluated. The experimental results show that DIF is not significantly affected by the addition of basalt and glass fibres, while energy absorption at high strain rate is significantly increased by the addition of glass fibres and only slightly increased by the addition of basalt fibres.

In this paper we study the problem of preparing adobe bricks for earth construction as little erodable as possible. We have therefore tested earthen specimens stabilised with both vegetal fibres and a compound of natural polymers, and we have compared their behaviour to that one of specimens stabilised only with fibres. We have studied how the stabilization with these natural polymers modifies porosity and bulk density, and how it improves both the behaviour under the water action and the compression strength. This kind of stabilization appears to give the earth a very good behaviour under the water action; moreover we have found out that the compression strength has been significantly increased, too.

The dynamic behaviour of earthen materials reinforced with natural fibres is little studied although earth buildings are often built in seismic areas. In this paper the dynamic behaviour of an earthen material reinforced with hemp fibres under different impact loadings has been experimentally investigated. The dynamic response of the material in 3-point bending was investigated through an instrumented dropweight device, while the response in tension and in compression was investigated through a modified Hopkinson bar device. Typical impact response curves for tension, compression and bending impact tests have been obtained. The favourable effect of fibres in dissipating fracture energy under impact loads has been observed in all these types of test.

In this paper, the dynamic behaviour of cement mortars reinforced with glass fibers was studied. The influence of the addition of glass fibers on energy absorption and tensile strength at high strain-rate was investigated. Static tests in compression, in tension and in bending were first performed. Dynamic tests by means of a Modified Hopkinson Bar were then carried out in order to investigate how glass fibers affected energy absorption and tensile strength at high strain-rate of the fiber reinforced mortar. The Dynamic Increase Factor (DIF) was finally evaluated.

The failure modes of K-joints of Concrete Filled Steel Tubular (CFST) truss structures were investigated through laboratory tests. CFST K-joint specimens consisted of a tubular chord filled with concrete and two braces inclined at the same angle with respect to the chord. Their size was chosen of the same scale as that of joints of real tubular structures currently used in bridges. The results were compared with those obtained by testing K-joint specimens of Circular Hollow Section (CHS) truss structures with the same size. Contrary to CHS K-joints, where a chord face failure mode occurred, in CFST K-joints no failure mode with inward deformation of the chord section can occur. Hence, punching shear failure was shown to be the typical failure mode of CFST K-joints, if no brace failure mode occurred before. Resistance of CFST K-joints to punching shear was then compared with the resistance values calculated through the Eurocode 3 and the AWS code formulae on CHS K-joints. The values provided by the former formula were quite close to (although always lower than) the actual resistance to punching shear of CFST K-joints. Finally, the favourable effect on joint resistance due to additional studs welded to the interior surface of the chord tube of CFST K-joint was also investigated.

This study examines the improvements provided by the insertion of hemp fibres with different weight fractions and lengths in an earthen material. The structural response of the materials was investigated by means of static and impact bending tests carried out on notched samples. The main focus of the analyses was in the characterization of the structural properties of the materials in terms of fracture resistance, post-cracking performance and energy absorption capability. The results of the study show that hemp fibres improve significantly the mechanical and fracture properties of the earthen material under both static and dynamic bending. It was also found that the structural properties of unreinforced and reinforced earthen materials are highly sensitive to the stress-rate, with higher strength and fracture resistance under impact loading than under static loading.

Specimen reinforced with glass and basalt fibers were prepared using Standard Portland cement (CEM I, 52.5 R as prescribed by EN 197-1) and standard sand, in accordance with EN 196-1. From this cementitious mixture, a reference cement mortar without fibers was first prepared. Compressive strength, modulus of elasticity, and mod of fracture were determined for all specimens. Static and dynamic properties were investigated using Instron testing machine and split Hopkinson pressure bar, respectively. Content of the glass fibers in the mortar does not influence the fracture stress at static loading conditions in a clearly observed way. Moreover at dynamic range 5% content of the fiber results in a significant drop of fracture stress. Analysis of the basalt fibers influence on the fracture stress shows that optimal content of this reinforcement is equal to 3% for both static and dynamic loading conditions. Further increase of the fiber share gives the opposite effect, i.e. drop of the fracture stress.