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This paper investigated the analytical solution of the bond strength between ribbed steel bar and engineered cementitious composites (ECC). In this method, ECC cover was regarded as a thick‐walled cylinder subjected to the uniform internal pressure which consisted of an elastic uncracked outer ring and a partially cracked inner ring. For the uncracked outer ring, it can be solved by the elastic mechanics theory. To solve the partially cracked inner ring, two key problems that had to be investigated were the crack width and the tensile stress–crack width relationship of ECC. According to the steady‐state cracking mode, the hoop deformation of ECC was expressed by the equal distribution and then the crack width can be determined. Besides, the fictitious crack model in fracture mechanic was introduced to describe the crack propagation process. Then a trilinear model was applied to reflect the tensile stress–crack width relationship of ECC materials, which considered the combined action of aggregate bridging and fiber bridging on the crack surface. Finally, the comparison between the calculation results and experimental results was carried out to prove the validity of the analytic method of bond strength proposed in this paper. Results indicated that the analytical solution and the experimental data fitted in well with each other. Then parameter analyses were conducted based on the analytical method proposed in this paper. [ABSTRACT FROM AUTHOR]

Investigation on the behaviour of hybrid beams is presented. Hybrid beam stands for an element with hybrid cross sections. This means sections that consist of steel and concrete parts, connected together with composite dowels, and both are considered for shear flow analysis. In practice, a more general solution may be used for bridges in the form of a beam in which the span sections are hybrid and the support sections are concrete. For the first time in the world, it was decided to introduce a girder in bridge construction, in which a concrete web with a thickness of only 20 cm was formed, directly connected to the steel web, so that a hybrid cross-section is created in accordance with the new European design regulations currently being developed (1994-1-102). The solution is new itself and requires also a new approach for internal forces determination. In this paper a parametric analysis of different hybrid beams with span range from 20 to 40 m and with different reinforcment ratio is performed to get knowledge on the influence of (1) concrete cracking and (2) rheology of concrete on the redistribution of internal forces. Results are analysed and conclusions are presented. As a final step, a general method for computer aided modelling of hybrid beams (hybrid beam concept) is proposed, which is based on the uncracked analysis. Such an analysis is designer-friendly and while appropriate benchmarked (as in this paper) can spare a lot of time needed for detailed iterative cracked analysis. [ABSTRACT FROM AUTHOR]

This paper deals with an approximate solution of Saint-Venant torsion problem of orthotropic bar with solid cross section. The boundary collocation is used to get the approximate analytical solution of the torsion problem. Examples illustrate the applications of the presented numerical solution. [ABSTRACT FROM AUTHOR]

The unrestrained torsional analysis of bars is an important theme in elasticity theory, first solved by Saint-Venant using semi-inverse methods. It has been considered and solved by several others using analytical methods and numerical procedures due to the importance in the design of machine parts under torsional moments. In this paper, the Saint Venant torsion problem is solved for rectangular prismatic bars using Galerkin-Kantorovich variational method (GKVM). The work presents a detailed theoretical framework of the problem, deriving using first principles considerations the stress compatibility equation in terms of the Prandtl stress function ϕ(x, y). The derived domain equation which is required to be satisfied over the rectangular cross-sectional domain is a partial differential equation of the Poisson type. GKVM is adopted as the solution method for finding the solution to the domain equation. The unknown Prandtl stress function ϕ(x, y) is assumed, following Kantorovich method to be a product of an unknown function for f(x) sought to minimize the Galerkin-Kantorovich variational functional (integral) (GKVF) and a known function (y2 - n2) which satisfies the boundary conditions at all boundary points in the y-direction, that is, at y = ±b. The resulting GKVF is a simplified functional whose integral is a second order inhomogeneous ordinary differential equation (ODE) in f(x). The integrand is solved to find f(x) leading in a full determination of the Prandtl stress function. The expression for stresses, torsional moments and torsional parameters are then found and they satisfy the boundary conditions and the domain equation. The results for the torsional moments and torsional parameters are identical to previous results obtained using double finite sine transform method (DFSTM), and analytical methods. The merit of GKVM is that it has led to the exact solution of the unrestrained torsion problems. [ABSTRACT FROM AUTHOR]

While the effects of axial compression on beams have long been known, the effect of tensile axial loads on one-sided transversely cracked beams is less known. The crack namely shifts the position of the resultant of the axial normal stresses deeper into the uncracked part of the cross-section, and the crack tends to open, causing a transverse displacement. Therefore, this paper focuses on empirical modeling of the considered phenomenon for slender prismatic beams in order to establish a suitable 1D computational model based on detailed 3D FE mesh results. This goal can be achieved through the already established simplified model, where the crack is represented by an internal hinge endowed with a rotational spring. Several analyses of various beams differing in geometry, crack locations, and boundary conditions were executed by implementing 3D FE meshes to establish the appropriate model's bending governing differential equation. After that, the corresponding parameter definitions were calibrated from the database of 3D FE models. By redefining the model's input parameters, a suitable solution is achieved, offering a good balance between the results' accuracy and the required computational effort. The functionality of the newly obtained solutions was verified through some comparative case studies that supplement the derivations. [ABSTRACT FROM AUTHOR]

This paper studies the chatter stability of composite cutter bar milling system in rotating coordinate frame. The main contribution of this paper is establishing a continuous distributed chatter analysis model for a composite cutter bar milling system in rotating coordinate frame. The stability of the milling system with a rotary symmetric dynamic cutter bar is predicted using the semi‐discrete time domain method. The effects such as internal damping, external damping, and symmetrical and asymmetric laminates on the stability of the milling system were analysed, and the results were compared between rotating and fixed coordinate frames. The results are consistent for symmetrical cutter bars in both the rotating and fixed coordinate frames. A new chatter instability zone appears at high rotating speeds due to the material internal damping of the rotating composite cutter bar. [ABSTRACT FROM AUTHOR]

This paper presents two types of new deployable mechanisms based on the motion characteristics of the four-bar slider–crank mechanism (FBSCM): the prism mechanism with constant cross-section and the round deployable mechanism. A new basic planar deployable unit based on the path-generating characteristics of the FBSCM is proposed. The method of building a deployable mast unit with one DOF from the new planar deployable mechanism is given. The prism mechanism with constant cross-section of one DOF is constructed, and the magnification ratio is analyzed. Moreover, the deployable unit with a negative Poisson's ratio for building the round deployable mechanism based on the properties of functional output of the FBSCM is proposed. The structure of the round deployable mechanism is described, and the parameter model with multilevel deployment is calculated and validated with cases given; the DOF of the round deployable mechanism is one. Last, the static analysis of the round deployable mechanism is studied by simulation; by locking 6 guide rails, the structure is found to have a balanced bearing capacity, and the bearing performance is improved compared with locking only one guide rail. [ABSTRACT FROM AUTHOR]

It is necessary to generate the yield position away from the column face to minimize damage to the beam-column joint during a large earthquake in a reinforced concrete building. The same efficacy can be realized using partially high strengthened rebar. The number of longitudinal bars can be calculated for a bending moment smaller than the column face, reducing their number compared to the conventional bar-arrangement method. This paper describes reinforced concrete an interior beamcolumn subassemblage tests using this rebar as the longitudinal bars of beams and a column. The beam yield hinge was formed at a position apart from the column face, and the damage to the beam-column joint was less than the conventional bar-arrangement method. Additionally, the good performance was obtained if the bending strength of the column was large, even if the shear capacity margin of the beam-column joint was small. The column-beam flexural strength ratio and shear capacity margin at the beam-column joint need to be set with consideration of their relationship. [ABSTRACT FROM AUTHOR]

The compression load of straight bars, for which the cross-sections are smaller compared to their length, causes a phenomenon of bending along the longitudinal axis. Upon reaching a certain level, called the critical level of the stresses, the bending deformations begin to increase beyond the bearing limit of the bar. It yields instantly, due to an unstable elastic deformation state, although the material's resistance limit has not been exceeded. The irreversibility of the phenomenon is dangerous especially for the railway tracks and is not fully mastered by calculation methods. They can eventually establish the level of the critical demand, which has values specific to each rail configuration. It is accepted that for loads lower than this level, buckling of the respective rail does not occur. The longitudinal tension in the railway tracks occurs due to the expansion caused by their heating under the action of the sun's rays, but also due to the friction between the rails and the train wheels. This paper proposes the realization of a study model of the buckling of the railway tracks. This model is represented by an assembly, built in the SOLIDWORKS application for which a Buckling simulation was made. The imposition of two distinct temperatures on the rails and crossties is the source of the model's request. The increase in the temperature of the component parts of the assembly causes their expansion, so implicitly the appearance of some longitudinal deforming forces, specific to the buckling phenomenon. [ABSTRACT FROM AUTHOR]

Conventional reinforced concrete shear walls are vulnerable to strong earthquakes with significant residual deformations, which substantially affect structural service and can even lead to structural collapse. Superelastic shape memory alloys (SMAs) are advanced materials that can realize strain recovery upon unloading. If SMAs can be used as reinforcing bars in structures, they can undergo large deformation without permanent deformation. This study presents a complementary and synergistic material system that integrates SMA with damage-tolerant engineered cementitious composites (ECCs) to minimize residual displacement and mitigate concrete damage. This study explored the seismic performance of shear walls using SMA and ECC in the plastic hinge region. Reverse cyclic loading tests were performed on four specimens to demonstrate the feasibility of this method. The specimens included a conventional steel-reinforced concrete shear wall (SW-R-C), steel-reinforced ECC shear wall (SW-R-ECC), SMA-reinforced concrete shear wall (SW-SMA-C), and SMA-reinforced ECC shear wall (SW-SMA-ECC). The results show that the SW-SMA-C specimen exhibited remarkable self-centering capability of more than 85% even after a large deformation, compared to SW-R-C. Furthermore, reduced damage and better ductility were observed in the SW-SMA-ECC specimen in addition to reduced residual displacement. The proposed approach indicated that SMA combined with ECC is more effective in mitigating plastic hinge damage and minimizing residual displacements, which could improve the seismic performance of shear walls. [ABSTRACT FROM AUTHOR]

Strongly weathered phyllite is a metamorphic soft rock widely distributed in the central and western regions of China. Due to its inadequate engineering properties, the direct use of this material as a roadbed filler is not feasible and requires improvement. In this paper, calcium acetate Ca(CH 3 COO) 2 , magnesium acetate Mg(CH 3 COO) 2 and calcium chloride CaCl 2 are prepared to improve the filler by microbially induced carbonate precipitation (MICP). The effects of different calcium and magnesium sources on porosity, water absorption, uniaxial compressive strength, crack propagation time and failure patterns are investigated. The results show that CaCl 2 and Ca(CH 3 COO) 2 exhibit the most significant enhancement effect in reducing porosity and water absorption, increasing the uniaxial compressive strength by over 30%, delaying the time of failure occurrence and reducing the number of tensile cracks significantly. X-ray diffraction (XRD), scanning electron microscopy (SEM) and pore size distribution analyses reveal disparities among the rock samples. CaCl 2 and Ca(CH 3 COO) 2 have greater efficacy than Mg(CH 3 COO) 2 in terms of improvement, as they generate relatively many carbonate precipitates to bind the phyllite filler and reduce the size and quantity of pores. To avoid the corrosion of Cl- ions when adding reinforcement bars in actual engineering, Ca(CH 3 COO) 2 is an ideal calcium source for improving the strongly weathered phyllite filler. • The physical and mechanical properties of strongly weathered phyllite filler can be improved after modification. • The physical properties and strength of modified sample have a relationship with carbonate content and crystal morphology. • Calcium acetate is suggested for use as the calcium source to improve the strongly weathered phyllite filler. [ABSTRACT FROM AUTHOR]

• An innovative re-centering SMA-ECC based prefabricated beam-column joint with excellent ductility was proposed. • A semi-mechanical sleeve connecter was designed for SMA bar and steel bar connection. • Low reciprocating cyclic loading tests were carried out to investigate the seismic behavior and re-centering mechanism of the joint. • The SMA-ECC prefabricated beam-column joint can undergo large displacement with superior self-centering and energy dissipation capacities. To enhance the seismic performance of prefabricated concrete frame joints, an innovative prefabricated beam-column joint with shape memory alloy (SMA) and engineered cementitious composite (ECC) materials was proposed in this paper. Four 1/2-scale test specimens, including one SMA–ECC prefabricated beam-column joint and three comparison joints (namely particularly reinforced concrete cast in situ joint, ordinary concrete prefabricated joint, and ECC-reinforced prefabricated joint) were designed and fabricated. A new type of semi-mechanical sleeve connector was designed to link the SMA bar with the longitudinal reinforcement of the precast beam. Through the low-cycle reciprocating loading tests on the specimens, the failure mechanism, bearing capacity, and self-centering performance of each frame joint were studied. The results show that post-pouring ECC in the plastic hinge zone of beam-column joints can significantly improve the cracking failure form and the ductility of the joints. Though the initial stiffness and energy dissipation capacity of the structure are slightly reduced when SMA and ECC are applied to the prefabricated beam-column joints. Nevertheless, the new composite materials can significantly enhance the ductility and self-centering capacity, reduce the residual deformation and the stiffness degradation rate of the structure. The SMA–ECC reinforced prefabricated beam-column joint can achieve better functional self-resilience ability after earthquake. [ABSTRACT FROM AUTHOR]

A theoretical method for analyzing the initial yield of a typical bending-dominant peri-odic lattice (BDPL) is established. Based on the principle of strain energy equivalence, the macroscopic effective stiffnesses of lattices are calculated. An empirical formula is employed to consider the contributions of both the axial force and bending moment. The initial yield surface of BDPL can be figured out by comparing the effective stress of each strut to the yield strength of the matrix material. The method is applicable to various BDPLs, which we believe is a helpful extension to the method for lattices comprising axial-tension bars in the literature. [ABSTRACT FROM AUTHOR]

Loop connection for precast Reinforced Concrete (RC) structural components using U-bars is advocated by researchers on the grounds of simple mechanism and strength. However, the system is difficult to materialize on-site in the lieu of which Ubars may be replaced with steel wire ropes, which offer a more suitable system in terms of convenience during the installation process. However, the literature is not rich on design requirements and methodology for loop connection. Thus, a theoretical study was undertaken to formulate the design methodology for the loop connection formed using steel wire ropes. The behavior of loop connection is governed by tension and shear, influenced by characteristics of wire ropes, grout, and vertical transverse bar. A design example is illustrated for the loop connection between precast wall-columns and the corresponding validation is demonstrated through numerical analysis and performance comparison with monolithic system and U-bar connection. The advantage of this research lies in the application of the systematic design approach with emphasis on all the influencing parameters of steel wire loop connection for precast components. It is expected that practicing engineers find the proposed design methodology useful in designing the loop connection for precast components. [ABSTRACT FROM AUTHOR]

• A self-centering SMA-ECC beam-column joint with low damage and energy dissipation capacities was proposed. • Low reciprocating cyclic loading tests were carried out on the two proposed SMA-ECC beam-column joints and three comparative members including RC, R-ECC and SMA-C joints. • The failure phenomenon, bearing capacity, energy dissipation capacity, displacement, ductility, residual deformation, and self-centering performance of the different frame joints were investigated. • SMA-ECC composite materials exhibit good supplement, significantly improving the ductility and self-centering capability of the joints and delaying stiffness degradation. • The finite element model of SMA-ECC joints was established, and the influence of SMA and ECC on the seismic behavior of the joints was investigated by parametric analysis. This paper presents a preliminary experimental investigation of a self-centering beam-column joint reinforced with superelastic Ni-Ti SMA bars and ECC materials. As an alternative to the longitudinal bars in the beam plastic hinge, SMA is used to reduce the residual deformations and dissipate energy, whereas the ECC materials used in the critical region of the joints can improve the ductility of the structural member. Five 1/2 scale frame joints were designed and manufactured. The failure phenomenon, bearing capacity, energy dissipation capacity, displacement ductility, residual deformation, and self-centering performance of the joints were comparatively analyzed through a low cyclic loading experiment. A finite element model of SMA-ECC joints was established, and the influence of the SMA and ECC on the seismic behavior of the joints was investigated. The study results show that SMA bars can dramatically enhance their self-centering capability, enabling self-retrofitting damage. The ECC material is helpful for optimizing the development of the plastic hinge at the end of the beam and improving the ductility and energy dissipation capacity of the structure. The SMA-ECC composite materials exhibit good supplement to significantly improve the ductility, energy dissipation, and self-centering capabilities and delay the stiffness degradation of the structure under extreme events. [ABSTRACT FROM AUTHOR]