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.

Lateral Performance for Wood-Frame Shear Walls–A Critical Review

Wood is a green material in line with the sustainable development strategy.From the excellent performance of engineering wood products,modern wood structures represented by light wood structures have gained more development opportunities.As an indispensable part of light wood structure systems,the wood-frame shear wall plays a vital role in the bearing capacity and earthquake resistance of light wood structure systems.This paper is focused on a review of the lateral performance of wood-frame shear walls and classifies the influencing factors in relevant experimental research into three categories,including internal factors such as shear wall structure,external factors such as test scheme,and other factors of material production and test process.Finally,the research prospects in this field were introduced based on the summary of the research status.This work can be a reference for further research on the lateral performance of wood-frame shear walls.

Properties and Applications of Bamboo Fiber—A Current-State-of-the Art

Fibers are used in many forms in engineering applications–one of the most common being used as reinforcement.Due to its renewable short natural growth cycle and abundance of bamboo resources,bamboo fiber has attracted attention over other natural fibers.Bamboo fiber has a complex natural structure but offers excellent mechanical properties,which are utilized in the textile,papermaking,construction,and composites industry.However,bam-boo fibers can easily absorb moisture and are prone to corrosion limiting their use in engineering applications.Therefore,a better understanding of bamboo fiber is particularly important.This paper reviews all existing research on the mechanical characterization of bamboo fiber with an emphasis on the extraction and treatment techniques,and their effect on relevant properties.The chemical composition of bamboo fibers has also been thoroughly investigated and presented herein.Current applications and future opportunities for bamboo fibers in various fields have been presented with a focus on research needs.This work can serve as a reference for future research on bamboo fiber.

Review on Connections for Original Bamboo Structures

Bamboo is a green construction material in line with sustainable development strategies.The use of raw bamboo in architecture has existed since ancient times.In the long development years of original bamboo buildings,many areas in the world gradually formed unique bamboo buildings,which have become an important local cultural feature.For building structures,joints are the key to ensure structural load transfer.Because of hollow and thin-walled material property of bamboo,the connection in raw bamboo buildings has always been a major difficulty and problem in the application of bamboo,which seriously hinders the development of original bamboo structures.In order to promote the use of raw bamboo,two traditional connection methods in raw bamboo structures are described in this paper firstly,with the advantages and disadvantages of the two methods pointed out.Also,research progress on four categories of raw bamboo building joints is described namely,bolt joints,steel member joints,filler reinforced joints and other types of joints.This work can provide a reference for future research and engineering applications.

Review on Bond Properties between Wood and Fiber Reinforced Polymer

Retrofitting of existing ancient and modern timber structures has been an important project recently.And it triggers a need of excellent strengthening methods,so does the strengthening of newly built architecture.Traditional strengthening methods have shortcomings such as high costing and destroying the aesthetic of the structure,many of which can be overcome by means of using fiber reinforced polymer(FRP)composites.However,the behavior of FRP-towood systems has yet to be thoroughly researched compared with their FRP-toconcrete or FRP-to-steel counterparts.As FRP retrofitting and strengthening timber structures has a promising future,better understanding of their failure modes will enable more precise designs balancing safety and cost.Three of the most common FRP-to-wood systems in the literature are discussed in this paper,namely,the externally bonded reinforcement(EBR),the near-surface mounted(NSM)and the glued-in rods(GiR)techniques.Debonding of the FRP from the substrate is one of the most common failure modes,which exhibits the significance of the interface bond between FRP laminates and wood.Hence,bond properties and behavior of FRP-to-wood composite systems are described,parameters influencing the composite action are summarized in this paper,previous works on the bond interface of FRP and timber element are reviewed and future topics are also suggested.This work can provide a reference for future research and engineering applications.

A Review of Basic Mechanical Behavior of Laminated Bamboo Lumber

Over the past decade,the physical and mechanical performances of laminated bamboo lumber(LBL)–a bamboo-based structural material,have been extensively studied using experimental,analytical,and numerical approaches.This paper presents a review of existing knowledge in the literature about the mechanical properties of LBL.The paper involved the review of the response of LBL to different types of loading such as tension,bending,compres-sion,and shear.Based on results of the literature reviewed,the strength of LBL parallel to grain was 90–124 MPa with MOE of 10700 MPa in tension,29.55–72.60 MPa,and MOE of 8396–11022 MPa in compression,63.87–128.4 MPa,and MOE of 8320–10912 MPa in bending,and 7.15–17.5 MPa in shear.The average strength of LBL was similar and in some cases exceeded the average values of bamboo-or wood-based materials,while the variability of its mechanical parameters was lower.The variability in strength values of LBL was affected by bamboo species,density and thickness of bamboo strips,growth portion,type of treatment,strips arrange-ments,and type of adhesive which in turn calls for classification of LBL by strength grades,degree of hardness,the capability of impregnation and penetration,as well as by areas of application in construction.The study pro-vided and discussed concluding observations,the current research gap,and future research directions on the mechanical properties of LBL.

Nodes Effect on the Bending Performance of Laminated Bamboo Lumber Unit

This research studied the ultimate bearing capacity of laminated bamboo lumber(LBL)unit and thereby calculated the maximum bending moment.The load-displacement chart for all specimens was obtained.Then the flexural capacity of members with and without bamboo nodes in the middle section was coMPared.The bending experiment phenomenon of LBL unit was concluded.Different failure modes of bending components were analysed and concluded.Finally,the bending behaviour of LBL units is coMPared with other bamboo and timber products.It is shown that the average ultimate load of BS members is 866.1 N,the average flexural strength is 101 MPa,the average modulus of elasticity is 8.3 GPa,and the average maximum displacement is 17.02 mm.The average ultimate load of BNS members is 1008.1 N,the average flexural strength is 118.02 MPa,the average modulus of elasticity is 9.9 GPa,and the average maximum displacement is 18.26 mm.Laminated bamboo lumber(LBL)unit without bamboo nodes(BNS)has relatively higher flexural strength coMPared with LBL unit with bamboo nodes(BS).The presence of bamboo nodes reduces the strength of the entire structure.Three failure modes were concluded for BS members,and two failure modes were observed for BNS members during the experimental process.According to a coMParison between the LBL unit and other products,the flexural strength and bending modulus of elasticity of the LBL unit are similar as bamboo scrimber and raw bamboo components,which is much higher than timber components.

Slenderness Ratio Effect on the Eccentric Compression Performance of Chamfered Laminated Bamboo Lumber Columns

Eccentric compression tests on 15 chamfered laminated bamboo lumber(LBL)columns with a height ranging from 600 to 3000 mm were conducted in order to study the eccentric mechanical performance.The failure of all specimens was caused by the crack of bamboo fiber in the tensile region.When the ultimate strength was reached,except specimens with a height of 600 mm,all other specimens could bear large deformation,showing good ductility.The lateral displacements of the specimens under eccentric compression were approximately para-bolic in the direction of column height.The ultimate bending moment of LBL columns with different slenderness ratios under compression with the same initial eccentricity was a fixed value.The relationship between ultimate capacity,axial displacement,lateral displacement,and slenderness ratio was analyzed based on test results.It was found that the plane section assumption could be used to express the stress and strain distribution of chamfered LBL columns under eccentric compression.A method for calculating the ultimate bearing capacity was proposed using a constitutive model based on the Ramberg-Osgood relation and the empirical formula for calculating the ultimate capacity was given on the basis of the former research as well as the test results in this paper.

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 efect of a stress/strain level in the columns has not been well defined because of the lack of well-defined strategies of modeing 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 exist-ing building regimes and highlights the possible future scopes to improve the use of FRP confined concrete in civil applications.

A Review on Strengthening of Timber Beams Using Fiber Reinforced Polymers

Fiber reinforced polymer(FRP)has been used in the construction industry because of its advantages such as high strength,light weight,corrosion resistance,low density and high elasticity.This paper presents a review of bonding techniques adopted to strengthen timber beams using FRP to achieve larger spans.Different methods of bonding between FRP and timber beams have been summarized with a focus on the influencing factors and their effects as well as relevant bond-slip models proposed for fundamental understanding.Experimental investigations to evaluate the flexural performance of timber beams strengthened by FRP bars,sheets and wraps have also been critically reviewed to identify key influencing parameters.Limited research available on the shear performance of FRP reinforced timber beams have been analyzed to determine the influencing factors of the shear performance in timber-FRP beams.The paper finally presents an overall summary of the current-state-of-the-art and proposes some future research directions in the field.