Abstract: At present, design values in codes and regulations are mainly based on test results of small size specimens, which are different from large-scale members used in practical engineering, therefore size adjustment coefficients are needed to be established. The four-point bending test method was adopted to investigate four groups of different sizes of Larch Glulam beams in their flexural behavior. Experiment data such as ultimate bearing capacity, deflection, strains and others are obtained, and the failure pattern and failure mechanism of bending members are analyzed. The research results indicate that the bending modulus of elasticity of Larch Glulam beam is not affected by the size. Bending strength of the Larch Glulam beam show a declining trend as the size of specimens increases, however, the ultimate bending moment increases. In addition, by means of a two-parameter Weibull model, a so-called size effect coefficient has been calculated by the slope method, thus providing a basis for the design and application of Larch Glulam beams.
Abstract: In scores of experiments indicates that the super-retarding mortar, keeping plasticity long-term, can make cement setting and hardening at a slower speed through chemical additive. Based on large numbers of orthogonal tests and theoretical analyses, the super-retarding mortar which satisfies the demands of actual engineering was developed successfully in present paper. And it is consist of cement, sand, water and composite retarder blended in an appropriate rate. From 0°C to 40°C, setting time can be adjusted from 1 day to 22 days in the light of to the engineering requirements, and after condensation, it begins to harden gradually and ends with the compression strengthen over 30MPa. Experiments were employed to test the influences of accession amounts of composite retarder dosage on setting time and compression strengthen of super-retarding mortar. Besides, the retarding mechanism was studied, and the super-retarding mortar was applied to experimental models. The results show the super-retarding mortar can be applied to the actual engineering, and it can be treated as the theoretical reference for the actual project application of the new prestressed concrete system.
Abstract: In this paper, the mixture ratio experiment has been done about OGFC-13 asphalt mixture of the layer on S103(liuyang section) of Changsha, Hunan province The void fraction of asphalt mixture is determined by vacuum sealing method and volume method on the condition of different material and different gradation. Through the comparison and analysis of void fraction determined values by vacuum method and volume method, it can been found that the air porosity of OGFC-13 asphalt mixture has a good linear relationship with the 2.36mm pass rate. The linear relationship of void fraction determined value by vacuum method and volume method relates with materials and nominal diameter.
Abstract: As one of the key components of non-ballast slab track in high speed railway, cement asphalt emulsion mortar (CAM) has low compressive strength and low elastic modulus. This makes CAM possible to be served as supporting, height-adjusting, vibration-dissipating and deformation-fitting sandwich-layer between pre-stress slab and concrete roadbed. To study the fatigue behavior of the CAM, fatigue tests were conducted at room temperature and negative temperature, respectively. The permanent strain, elastic modulus and yield strength of fatigue-tested specimens were compared to the reference one. The results showed that the small permanent deformation lead to very little displacement differences among the slab track system. Secondly, the elastic modulus and yield strength of fatigue test specimens were both higher than that of reference one. Because the fatigue process might strengthen the CAM by compacting micro-cracks. Additionally, arising from the temperature sensitivity of asphalt, viscosity behavior of asphalt mortar at room temperature is changed to brittleness behavior at negative temperature.
Abstract: The structural use of wood has increased steadily in recent times, including a renewed interest in the use of timber as a bridge material. As the only environment-friendly and resource-saving building material, wood has been gradually uesd for short and medium span bridges in China. In 2014, The domestic largest single-span glued-laminated timber (glulam) deck arch bridge crossing a freeway was completed and put into operation in Zhangjiajie City, central China' Hunan province. In order to know the bearing capacity of superstructures and assess its working conditions, in-site static and dynamic testings has been carried out. Many measures including finite element simulation, field test and comparision between test results and calculated results have been employed to study responses of the bridge under static loads and dynamic loads as well. The researches indicate this glulam footbridge has performed well in service and appear to be cost effective when compared with the cost of installing traditional concrete and steel bridges.
Abstract: At present, the relevant researches of Glulam columns in China are mainly restricted to short columns. In order to study the mechanical properties of long columns under axial loading, an experimental study on five different slenderness ratios of Larch Glulam columns was carried out. With slenderness ratio changing, the variations of experimental data such as axial strain, lateral deflection at mid-height, ultimate bearing capacity, and peak strain were comparatively analyzed. The failure pattern and failure mechanism of long columns were discussed. The results indicate that the ultimate bearing capacity of Larch Glulam columns gradually decreases as the slenderness radio increases and the failure mode is gradually converted from strength failure to instability failure. The ultimate load reduction factor is obtained by regression analysis based on the experiment results of Larch Glulam short columns. The basis for design and application of Larch Glulam columns are provided.
Abstract: This paper presents the results of an experimental research aiming to investigate on the compressive behavior of full size clay brick masonry columns reinforced with Basalt Fiber Reinforced Cementitious Matrix (BFRCM) or with steel wires collaring. Uniaxial compressive tests were performed on eight retrofitted columns and four control specimens. Two masonry strength were considered by varying the mortar grade. Results are presented and discussed in terms of axial stress-strain relationships, failure modes and crack patterns of the specimens tested up to failure. For the limit of investigated variables, comparisons with unreinforced specimens show the ability of these alternative techniques in increasing ductility with limited strength enhancements, even if further investigations should be addressed on detail effectiveness and scale effect.
Abstract: The basic mechanical performance of glue laminated timber (GLT) reinforced with glass fiber reinforced plastic (GFRP) for structural materials was studied. The differences of mechanical performance of the GLT reinforced with GFRP and the common GLT were compared by the test, and the quantitative influence of reinforcement ratio and arrangement pattern of GFRP on the mechanical performance was investigated. The test results showed that the static bending strength of GLT increased with the increasing of GFRP reinforcement ratio, and the reasonable arrangement pattern of GFRP could improve the internal bonding strength of GLT. The influence of reinforcement ratio and arrangement pattern of GFRP on the elastic modulus was relatively small. Finally, a mathematical model of static bending strength for GLT reinforced with GFRP was proposed, which can consider the influence of reinforcement ratio and GFRP arrangement pattern
Abstract: In recent decades the growing need for strengthening and retrofitting existing structures has led to the development of innovative strengthening materials. Fibre reinforced composites have been shown to be an effective strengthening solution for flexural and shear strengthening and for confinement of axially/eccentrically loaded elements. Fibre Reinforced Cementitious Matrix (FRCM) composites, comprised of high-strength fibres and an inorganic matrix, are a newly-developed type of composite that has better resistance to high temperature and compatibility with the substrate than traditional fibre reinforced polymer (FRP) composites. This paper investigates the behaviour of FRCM composites comprised of a glass or carbon fibre net tested using single-lap direct-shear tests. Observations regarding the load response and failure mode of FRCM-concrete joints with different geometrical and mechanical characteristics are provided.
Abstract: This paper reports the results of an experimental campaign conducted on a set of eight composite beams made of prefabricated steel trusses encased in structural concrete. The test setup is organized in such a way to apply an evenly distributed load on the beam, so to simulate the actual loading condition in real buildings. This is also to avoid the formation of peculiar and unusual shear resisting mechanisms occurring in three or four-point bending tests. The experimental results are presented in terms of force-displacement graphs and also in terms of stress-strain diagrams in the steel members. The outcome of this study highlights that Composite Truss Beams (CTBs) have an effective performance in the shear resisting mechanism, showing a capacity higher than that estimated through the current capacity equations given by Codes.