Fiber alignment angles effect on the tensile performance of laminated bamboo lumber

For better application of laminated bamboo lumber (LBL) in construction industry, the tensile performance of LBL was studied by conducting tension test on LBL specimens with seven different fiber alignment angles, each alignment angle containing 30 specimens. All the specimens only experienced the elastic stage before brittle failure with four failure types. With increasing alignment angle, the tensile strength, tensile modulus, and ultimate tension strain decreased rapidly from 0° to 30°, while they almost remained constant after the angle of 45°. Hankinson’s formula (n = 1.75) can be used to predict the tensile strength of LBL. An empirical equation was proposed to predict the tensile modulus of LBL. The Poisson’s ratio increased and peaked at 15° before declining. Based on the stress–strain coordinate transformation, the relation between shear properties and the alignment angle of LBL was studied; the calculated shear strength decreased with increasing alignment angle, and an empirical equation was proposed, which could be used to obtain the shear strength of LBL for engineering use

Experimental and numerical study on eccentric compression properties of laminated bamboo columns with a chamfered section

The eccentric compression behavior of laminated bamboo lumber (LBL) columns with a chamfered section was investigated using eccentricity of 30 mm, 60 mm, 90 mm and 120 mm. The effect of eccentricity ratio on the ultimate bearing capacity, ultimate strain and failure mode was analyzed through eccentric compression tests. The failure modes of LBL columns with different eccentricities were basically same, which belonged to brittle tension failure. With the increase in eccentricity ratio, the ultimate bearing capacity and ultimate strain gradually decreased. The cross-section strain of the specimen was linearly distributed along the height direction, which conformed to the plane section assumption. The lateral deflection curves had similar characteristics under different load levels and could be expressed by sine half-wave curves. Based on the Hill failure criterion, a 3D finite element model was developed to calculate the ultimate bearing capacity of LBL columns with different dimensions under eccentric compression. According to the simulation results and test results, a general empirical formula was proposed considering both the influence of slenderness ratio and eccentricity ratio. The reliability of the proposed formula was verified by comparing the calculated results with the results in the existing literature

Size Effect on the Compressive Strength of Laminated Bamboo Lumber

The size effect on the axial compressive performance of laminated bamboo lumber is studied through compression tests on three groups of short columns with different heights and section sizes. The failure modes, bearing capacity, strain distribution, and deformation capacity were analyzed. Based on the test results, three groups of stress-strain models of laminated bamboo lumber with different sizes are presented. The simulated results were in good agreement with the test results. The slope method and the parameter method were used to calculate the size effect coefficient and the results showed that the linear regression parameter analysis method is more efficient for analyzing the size effect. It is concluded that the size effect coefficients of compressive strength, ultimate load, elastic modulus, ductility, and compressibility are 0.043 (1/23.26), 0.6676 (1/1.52), 0.064 (1/15.63), 0.0529 (1/18.90), and 0.133 (1/7.52), respectively

On dynamic control of structural vibrations research activities conducted within the covicocepad project

This paper provides an overview on the latest research and development (R&D) activities carried out under the project entitled Comparison of Vibration Control in Civil Engineering Using Passive and Active Dampers (COVICOCEPAD) which was executed within the framework of the Eurocores project, as a part of the sixth European program. The general interest of the paper relies upon the variety of presented highlights relevant to structural control research streams currently under development in a number of European universities, addressing the use of tuned liquid dampers (TLD), base isolation devices, magneto-rheological (MR) dampers and a hybrid technique using both devices together. The paper also provides details of a few new testing equipments which are in use of the relevant laboratories. Finally, research projects in the field of structural control at the involved research institutes are reviewed.info:eu-repo/semantics/publishedVersio

Research and Application Progress of Straw

Straw is a general term for the stem and leaf parts of mature crops, and is a multi-purpose renewable biomass energy resource in the agricultural ecosystem. The prospect of comprehensive utilization of straw has become broad with the development of agricultural production, the advancement of science and technology, and the improvement of the level of agricultural mechanization. The comprehensive utilization of straw plays an important role in enhancing the sustainable development ability of agricultural economy and improving the current situation of comprehensive utilization of agricultural resources in my country. This paper briefly combs the development history of straw and the prospect and current situation of comprehensive utilization, and expounds the separation technology of straw components, straw man-made panels, straw concrete, straw returning technology and oyster mushroom cultivation. It focuses on the description of the component separation technology of straw and the manufacturing process of straw-based panels. The different separation methods and separation effects of cellulose, hemicellulose and lignin were introduced in detail, and the static yield strength (MOR), internal bonding strength (IB) and water absorption thickness of several common straw-based panels were compared and studied (TS). Finally, it summarizes the benefit analysis of the comprehensive utilization of straw by scholars from the perspective of economics, and summarizes the corresponding measures based on their own views

Bamboo node effect on the tensile properties of side press-laminated bamboo lumber

At present, most of the existing studies on bamboo nodes focus on the raw bamboo. There is still a lack of researches on the nodes in side press-laminated bamboo lumber (LBL). However, after processing, bamboo nodes in the laminated bamboo lumber are different from the raw bamboo nodes in terms of performance. Therefore, this paper carried out tests to analyze the influence of bamboo node on the tensile properties parallel to grain of side press-laminated bamboo lumber. A total of 180 specimens were divided into six groups, and the number and position of the bamboo nodes at the specimen in each group were different. The effects of these factors on the strength, elastic modulus, and Poisson’s ratio of the side press-laminated bamboo lumber under tension parallel to grain were obtained. The tensile failure of side press-laminated bamboo lumber was a brittle fracture, and the typical failure mode can be classified into three types. The mean value for tensile strength was 127.18 MPa when there was no bamboo node, while the mean value was 89.99–107.37 MPa when there were one to three bamboo nodes. The number of bamboo nodes would significantly affect the tensile properties parallel to grain of side press-laminated bamboo lumber, whereas the position of bamboo nodes has an insubstantial impact. Comparisons with other research results were also carried out. A series of formulas were proposed based on the test results to reflect how the node influenced the mechanical properties of side press LBL under tensile conditions

R&D on control of vibrations under covicocepad during 2007-2008

This paper provides information on the latest R&D within COVICOCEPAD project approved in the framework of Eurocores program. It addresses the use of TLD, base isolation devices, MR dampers and a hybrid technique using both devices together. Some results are provided associated with calibration of a MR damper at FEUP, as well as its inclusion in a small scale laboratory set-up with proper equations of motion of the controlled smart structure. An application of semi-active control technique to a bridge is outlined. Further remarks and details on future tests to be performed in LNEC shaking table, within COVICOCEPAD project, are provided

Length effect on bending properties and evaluation of shear modulus of parallel bamboo strand lumber

One hundred sixty-two parallel bamboo strand lumber (PBSL) beams were tested for the bending properties under three-point bending with variable span. Two typical failure types were classified, type I was tension failure of the bamboo fiber located below the neutral axis at mid-span, while type II was shear failure which was mainly found in specimens with large depth-span ratio. The shear modulus G LR of PBSL was also calculated according to Timoshenko’s bending theory. To evaluate the shear modulus, 45° off-axis compression tests had been done. The results showed that the mean values of shear modulus for G LT, G TR, and G LR are 1254.5 MPa, 408.1 MPa, and 716.4 MPa, respectively. The bending test result was compared with the shear modulus measured by 45° off-axis compression test. It was found that the shear modulus measured by three-point bending test with variable span was significantly less than the shear modulus obtained by 45° off-axis compression test. The empirical equation of shear factor s corresponding to depth-span ratio h/l was proposed. The calculation results gained from the proposed formula are in good agreement with the 45° off-axis compression test results

A Review of Fibre Reinforced Polymer (FRP) Reinforced Concrete Composite Column Members Modelling and Analysis Techniques

The use of fibre-reinforced polymer (FRP) to confine concrete columns improves the strength and ductility of the columns by reducing passive lateral confinement pressure. Many numerical and analytical formulations have been proposed in the literature to describe the compressive behaviour of FRP confined concrete under both monotonic and cyclic loads. However, the effect of a stress/strain level in the columns has not been well defined because of the lack of well-defined strategies of modelling and oversimplification of the model. This paper reviews the existing FRP combinations and the available numerical and analytical methods to determine the effectiveness of the adopted method. An effort has been made to examine the usage of FRP materials in column applications in existing building regimes and highlights the possible future scopes to improve the use of FRP confined concrete in civil applications