Intermediate Support Research Articles

Finite element modeling of plastic hinges based on ductility demand‐capacity method using nonlinear material for dynamic analysis

AbstractThe article discusses modeling plastic hinges in reinforced concrete intermediate supports using finite elements methods. The ductility demand‐capacity method was used to determine the geometrical parameters of cross‐section plasticization zones, their ability to move and rotate, as well as their ductility. Due to the varied geometry and stiffness of the supports and their nonlinear behavior under dynamic load, this method was concluded to be imperfect. Therefore, an improved algorithm was proposed by determining the main parameters of plastic hinges depending on the degree of concrete degradation according to Lubliner's assumptions. The new algorithm has been implemented in the form of mathematical equations. It was subsequently used, at the structure design stage, to perform numerical calculations based on the finite element method.

Thermal‐induced Buckling analysis of microbeams with intermediate support under thermal load based on modified couple stress theory

AbstractThis study investigates the buckling of microbeams with variable cross‐sections and middle supports in a thermal environment. Based on classical theories and modified couple stress, the size‐dependent behavior of the microbeam is modeled, and the intermediate support is simulated elastically. A temperature‐dependent relationship will also be assumed for the material properties of the microbeam. The governing equations will be derived using Hamilton's principle based on the modified Couple stress theory and the nonlinear thermal field. Using an analytical approach, buckling loads and deformation of microbeams will be determined. The accuracy of the answers will be investigated to demonstrate the effectiveness of the method used and the correctness of the results obtained. A comparison will be made between the obtained results and the results available in the scientific literature to prove the accuracy of the formulation and the method used. A parametric study will then be conducted to determine the effect of boundary conditions, the flexibility of the middle support, temperature distribution, and geometric characteristics on the buckling loads of microbeams.

Dynamics of size-dependent multilayered shear deformable microbeams with axially functionally graded core and non-uniform mass supported by an intermediate elastic support

The current study investigates the coupled dynamics of a size-dependent third-order shear deformable multilayered microbeam with an axially functionally graded core, a non-uniform mass distribution (mass imperfection) and an intermediate elastic support. A power-law function is used to model the material properties in the longitudinal direction of the core. The equations of motion are obtained by formulating the energies of the system while employing the modified couple stress theory to include miniature size effects within the multilayered microbeam structure. Hamilton's principle and the modal decomposition method are utilised to derive and solve the coupled motion equations. The equations of motion are first verified against a former work on a simplified microbeam system, while the numerical results are validated by comparison to those of a simplified functionally graded in axial direction obtained by finite element macrobeam simulation. It was concluded that increasing either the power term constant of the material grading or the value of the localized mass imperfection (when xm*=0.3) causes the first and second transverse and axial natural frequencies of the three-layered microbeam to decrease, whereas increasing the length-scale parameter causes the natural frequencies of transverse modes to increase, demonstrating the size-dependent effects of the three-layered microbeam.

A Survey on the Perception of Young People about Empty Houses in Gunsan and their Utilization Plan

The vacancy rate in Gunsan is 16.3%, which is already a serious level. In order to investigate the perception of vacant house maintenance in the region, a survey & interview were conducted with university students and administrative staff and related company managers. As a result of the survey, respondents said that ‘there are some vacant houses, but they are not being maintained’. Most wanted to change them into rental housing for the low-income class and a single-parent families. It was difficult to maintain empty houses due to difficulties in securing a budget, lack of will of owners to participate, loss of contact, and differences of opinion on how to utilize empty houses. In order to provide the reliable information, reliable management of vacant house information sites, disclosure of the latest data, and specialized operation management for small regions are necessary. For these things, an intermediate support organization in the private sector, an expert organization, and a dedicated administrative organization must be involved along with the master plan, and economic support is required.

Modeling statically indeterminate reinforced concrete slabs and beams under fire conditions

AbstractEN 1992‐1‐2 generally limits the redistribution of bending moments from the intermediate supports to the span for continuous reinforced concrete slabs and beams in fire conditions to 15%. While higher redistributions are allowed if sufficient rotation capacity is provided, EN 1992‐1‐2 does not indicate how to assess the rotation capacity. However, plastic hinges caused by the rotation demand under fire conditions are highly relevant when predicting the global response and structural safety of a structure (partially) exposed to fire. Rotation capacity is specifically necessary at support regions subjected to negative bending and fire, where concrete in compression undergoes thermal degradation while the tension chord remains close to ambient temperature. This article presents a comprehensive model for the behavior of statically indeterminate members in fire conditions, enabling to estimate whether sufficient rotation capacity is provided. Material properties specified by EN 1992‐1‐2 are applied combined with complementary considerations concerning (i) the biaxial compressive strength of concrete, (ii) strain hardening and limitations of the ultimate strain of reinforcement, as well as (iii) tension stiffening. Tension stiffening detrimentally influences the ductility of the tension chord, limiting the rotation capacity. When comparing predictions obtained by the model to experimental results given in the literature, the correlation is good for the investigated one‐way continuous slabs and beams. However, considerable uncertainty exists regarding the type of concrete aggregate used. Moreover, uncertainties concerning the behavior of concrete under compression and fire conditions are highly relevant for modeling the region of supports with rotational restraint.

Vibrations of Timoshenko Double-Beam Systems with Arbitrary Intermediate Supports and Axial Loads

Vibrations of Timoshenko Double-Beam Systems with Arbitrary Intermediate Supports and Axial Loads

Vibration of an axially loaded heterogeneous fixed–fixed beam with an intermediate roller support

The present paper investigates how an axial load can change the natural frequencies of heterogeneous fixed–fixed beams with an intermediate roller support. The problem is treated as a three-point boundary value problem (eigenvalue problem) that is paired with homogeneous boundary conditions. The Green functions are determined for the unloaded and pre-loaded beams as well—in the later case, both for compression and tension. With these, the eigenvalue problems can be transformed into eigenvalue problems governed by a homogeneous Fredholm integral equations. It is then replaced by an algebraic eigenvalue problem, that is solved numerically with an effective solution algorithm which is based on the boundary element method.

BUCKLING OF BEAMS WITH A BOUNDARY ELEMENT TECHNIQUE

The present work is devoted to the buckling study of non-homogeneous fixed- fixed beams with intermediate spring support. The stability issue of these beams leads to three-point boundary value problems. If the Green functions of these boundary value problems are known, the differential equations of the stability problems that contain the critical load sought can be turned into eigenvalue problems given by homogeneous Fredholm integral equations. The kernel function of these equations can be calculated from the associated Green functions. The eigenvalue issues can be reduced to algebraic eigenvalue problems, which are subsequently solvable numerically with the use of an efficient algorithm from the boundary element method. Within this article, the critical load findings of these beams are compared to those obtained using commercial finite element software, and the results are in excellent correlation.

Full-scale experimental study on continuous UHPC slabs of steel-UHPC composite deck system

The heavy self-weight and the cracking of normal strength concrete (NSC) deck slabs hindered the application of steel-concrete composite girders in long-span bridges. These problems can be solved by using ultra-high performance concrete (UHPC) deck slabs instead of the NSC deck slabs. Based on Yellow River Bridge of Zhanhua-Linzi Highway, a steel-UHPC composite cable-stayed bridge with span length of 442 m, full-scale tests on seven continuous UHPC (NSC) deck slabs were conducted. The studied parameters were sagging-to-hogging reinforcement ratio, concrete type, yield strength of steel bars and wet joints. The static properties of continuous UHPC (NSC) deck slabs were investigated in detail, including failure modes, load-deflection response, cracking behavior, strain development and moment redistribution. Discussions were made on the effect of different parameters according to the experimental data. Results showed that the use of UHPC can avoid shear failure, which was the case for the continuous NSC slab. Reducing the sagging-to-hogging reinforcement ratio from 1.00 to 0.63, the failure mode changed due to the altered formation order of plastic hinges. The ultimate capacity was decreased while the ductility and moment redistribution were improved by decreasing the yield strength of steel bars. The existence of wet joints significantly weakened the deck slabs. Strengthening the wet joints with steel plates can effectively compensate for this effect and even achieve better mechanical properties compared with integrally cast slabs. Furthermore, placing a comb-shaped wet joint at the intermediate support of continuous slab will result in a certain decrease of ultimate capacity and stiffness, which is acceptable for the transverse direction with relatively small internal forces. It is suggested that wet joints should be avoided at the supports of continuous deck slabs along the longitudinal direction.

A novel shear strength model for partially encased composite (PEC) beams based on strain compatibility

Steel and concrete composite beam has been widely applied in large-span or heavily-loaded structures; however, the large shear force at the beam supports may cause web crippling or local damage. To address this problem, partially encased composite (PEC) beams, in which steel web is encased in concrete or reinforced concrete, are proposed to enhance the load-carrying capacity, anti-crippling, and anti-fire performances. In engineering practice, the vertical shear usually governs the final failure at intermediate supports; hence, accurate shear strength prediction is essential for PEC beams in practical design. Although some existing test results and shear equations exist for shear-critical PEC beams, the shear mechanism is still unclear because two shear force transferring mechanisms are coupled by the structural steel and web concrete. Therefore, it is essential to explore the contributions of the different mechanisms and how they work together as a composite structure. In this paper, the shear strength equations in current design codes and the shear strength models proposed by other researchers were reviewed and evaluated using a database consisted of the existing test results of 27 large-scale PEC beams. After identifying the shortcomings of these equations and models, this paper proposed a novel shear strength model, in which the shear contributions of the structural steel and web concrete were determined by von Mises yielding law and composite truss analogy, and the interaction between these two parts was evaluated by the strain compatibility. Finally, a comparison with the database was reported to verify the applicability of the proposed model. The results indicated that the proposed model could predict the shear strength of PEC beams with sufficient accuracy, and the strain compatibility could reasonably decouple the shear contributions of different anti-shear mechanisms.

Transverse free vibration of nanobeams with intermediate support using nonlocal strain gradient theory

In the present study, the transverse free vibration of intermediately supported nanobeams is investigated in the framework of size-dependent nonlocal strain gradient theory. Unlike the classical elasticity theory, nonlocal strain gradient theory considers the micro/nano scale effects in mechanical analysis of size-dependent structures. The potential and kinetic energies have been derived for the nanobeam model and the Ritz method has been used to determine the natural frequencies of intermediately supported nanobeams. A cantilever nanobeam model with intermediate support is considered in the analysis. By changing the position of the intermediate support, dimensionless vibration frequencies of the nanobeam model have been obtained. Obtained results from the present nonlocal strain gradient theory showed that hardening or softening material responses have been observed according to the classical elasticity theory depending on the magnitude of the material length scale parameter and nonlocal scale parameter. This mechanical behavior can provide an advantage to designers while modeling the micro/nanostructures. Present results can be used for the design of nano-sensors, nanotube-based resonators, and oscillators.

Curtain of Glass – Textured by Stone

The new World Trade Center site was rebuilt after 9/11 comprising seven mayor skyscrapers around the memorial site and the 9/11 museum. Between WTC 2 and WTC 3, Santiago Calatrava’s Oculus Station spans its wings in the NY air while finally, the complex is completed by the “The Ronald O. Perelman Performing Arts Center”. This building sets a one-in-a-kind visual appearance to the area. Its four-sided, 42 m tall, even facade is made from 4736 equal-sized insulated glass panes. More specifically, the architectural vision is to create a marble stone front covered with glass which results in a stone-glass laminate as a part of an insulated glass unit. The marble shows a distinguished white face with crisp black veining. Each of the four elevations of the building impresses with a perfect symmetry and veins touching at the vertical center line. So, the design team at Josef Gartner was challenged to set-up a logistics chain from quarry in Portugal where the stone panels were cut and catalogued to glass production of laminated glass in France and IGUs in Germany and assembly of curtain wall mega-panels at Gartner in Germany up to the site in Lower Manhattan. Our in-house logistics concept, customized for this project, guarantees that each individual piece of stone finds its correct and unique spot defined by the architect on the 7,000 m2 surface – a large-scale game of “Matching Pairs”. The steel base building provides a cantilevering roof that holds 128 hot-rolled steel mullions. Each 36 m in length with one intermediate lateral support only. This allows the visitor to experience a clear and unobstructed view along the transom-free facade elements that carry the translucent stone-wall. During the day, it appears white from the outside and shines with an amber-glow during the night when the interior space is illuminated. We show the use of a novel stone-glass product that is exposed to a variety of requirements. The logistics chain is described from quarry to site making sure that the architectural and economical demand is met along the whole process. Finally, the team connects all branches in facade design using stone, aluminum, glass and architectural exposed structural steel assembled in one landmark project.

In-plane modal behavior of a single shallow flexible cable with an intermediate transverse elastic support

Cross-tie solution has been successfully applied in field to mitigate undesirable bridge stay cable vibrations, especially for cables on modern long-span cable-stayed bridges which typically have long length and relative thick cross section. In evaluating the effectiveness of the cross-tie solution and analyzing dynamic response of the formed cable network, the taut cable assumption has been used in most existing studies. Nevertheless, cable sag and bending stiffness could have non-negligible influence in networks consisting of long cables with relatively large diameter. Since a transverse cross-tie provides an elastic constraint to a vulnerable cable by connecting it with its neighbors, to fully comprehend the impact of cable sag and bending stiffness on the dynamic behavior of shallow-cable networks, it is imperative to scrutinize their effect on the behavior of a shallow cable with a transverse elastic constraint within the span. In the current study, by using the linear theory of shallow cables, an analytical model for the in-plane dynamics of a single flexible low-sag cable with an intermediate transverse elastic support is proposed. The impact of the intermediate support stiffness, location, cable bending stiffness, and sag on the in-plane modal response of the studied cable system are examined. Results show that the presence of an intermediate transverse elastic support breaks the symmetry and anti-symmetry of the original cable mode shapes, which renders the influence of sag extends to all cable modes. Further, the level of such a mode shape distortion would determine whether or not modal cross-over would occur. For any given intermediate support location, it is found that there always exists a specific level of intermediate support stiffness of which the cable sag corresponding to the occurrence of modal cross-over would be independent of cable bending stiffness. By reducing or increasing the intermediate support stiffness to be lower or higher than this specific level, the increase of cable bending stiffness would either delay modal cross-over to occur at a larger cable sag or advance its occurrence at a smaller cable sag. Reducing the intermediate support stiffness would render a local mode to evolve into a global mode, and the presence of cable bending stiffness and sag is found to allow this mode evolution to occur when a more flexible intermediate support is used.

ON THE OPTIMAL POSITION OF THE INTERMEDIATE SUPPORT OF THE COMPRESSED THREE-SPAN ROD AND ITS QUALITATIVE FEATURES

The optimization problem is considered, which consists in maximizing the main critical force of a three-span longitudinally compressed rod supported at the ends on absolutely rigid hinge supports due to the optimal choice of the position of one of the intermediate supports. It is known that in many cases this position is a node of the buckling form, which corresponds to the second critical force in the spectrum of the two-span rod formed by removing the moving support. A range of recent studies have described cases where the maximum critical force is reached at other positions. This, in particular, occurs at a finite stiffness of one or both end supports of the rod. The proposed work seeks the optimal position of the rigid intermediate support, provided that the second intermediate support has a finite stiffness and a fixed position. The compressive force is assumed to be constant along the length of the rod, bending stiffness can vary according to the length of the rod according to arbitrary way. It is established that under certain conditions the solution of this problem can be reduced to the solution of another, previously studied problem, which seeks the maximum critical force of a two-span rod by changing its length, at which some segment of the rod adds or removes at one end of the rod with the transfer of the corresponding hinged support at the end of the newly created rod. The paper founds and describes the characteristic qualitative features of the buckling forms, which correspond to the maximum of the main critical force, in particular the absence of deformation of the bending of the end span adjacent to the moving support. The limitations in which the approach proposed in the paper leads to the determination of the desired optimal position of the movable support are studied. The results are obtained mainly on the basis of the systematic use of qualitative methods and allow to obtain qualitative estimates for the localization of the moving support and the value of the corresponding critical force. An example illustrating the proposed approach and the reliability of the results of its application are considered.

PHYSICOMATHEMATICAL MODEL OF CALCULATING CONTINUOUS BEAMS WITH ELASTIC YIELDING SUPPORTS

In this work there has been studied the rod system operation dependence on the action ofexternal force effects. The system presents a multi-span continuous beam with elastic yieldingsupports. To identify the stress-strain state of the object under study, a precise analytical methodof forces is used. The method of five moments is used as the resolving (canonical) equations. Thefinal results are the parameters of the stress-strain state for a five-span continuous beam withvariable compliance coefficients on 5 intermediate supports and an absolutely rigid left extremesupport, deflections, bending moments, shear forces, and support reactions.Theoretical provisionsand practical results can be used in the design of load-bearing beam structures in buildings andvarious engineering structures.

The free vibration analysis of carbon nanotubes-reinforced deep conical shells with an intermediate ring support under various boundary conditions

This article explores the free vibration characteristics of a conical shell strengthened with intermediate ring. The system is thought to be made up of a linearly elastic nanocomposite that is reinforced with carbon nanotubes (CNTs). To get the effective material characteristics, the modified rule of mixtures is employed. To account for shear deformations and rotational inertias occurring across the depth of the shell, the first-order model of shells is combined with Donnell’s classical kinematic constraints. Hamilton’s principle is applied to construct the generic motion equations and their related boundary and compatibility constraints. The resulting set of equations is solved analytically in the structure’s circumferential direction. Additionally, the generalized differential quadrature element (GDQE) algorithm is performed to discretize the radial motion equations. An eigenvalue issue is constructed with various edge conditions for the structure boundaries and compatibility conditions to investigate the vibration frequencies. After demonstrating the efficacy and accuracy of the current approach for applying functionally graded (FG) CNT reinforced composite (RC) cylindrical shells with intermediate circle support, several parametric investigations are conducted to determine the effect of the geometric and ingredient properties of FG-CNTRC conical shells.

Vibration attenuation of beam structure with intermediate support under harmonic excitation

The optimal position design of viscoelastic supports is studied for vibration attenuation of a beam under a harmonic excitation. By attaching the supports properly to the structure, the dynamic deflection of the steady-state response can be significantly suppressed. In this work, the derivative analysis of the dynamic deflection is first investigated with respect to the attachment location of a viscoelastic support. A closed-form formulation for the dynamic response sensitivity is gained readily by use of the discrete methodology. Then, a heuristic optimization algorithm is applied on the design sensitivity analysis to achieve the optimal solution of the supporting points to minimize the maximal steady-state displacement vibration of a beam structure. Finally, two typical examples are presented to demonstrate the validity and accuracy of the design sensitivity formulation developed. Numerical results show that the structural vibration deflections can be substantially reduced with optimization of the intermediate support positions.

Feasibility Analysis of Post-Tensioned Beam for Industrial Building: A Review

Abstract: In recent years, due to corrosion and the constant demand for increased traffic flow, there is an eagerly need for an efficient system that can be used to repair or strengthen bridges and structures with steel-concrete composite sections. There have been so many strengthening techniques used to prevent such serious structural problems. One of these most useful techniques, which has successfully proven effective in repairing and strengthening structural members, is to use the externally post-tensioned tendons technique. The various study has also provided a recently completed experimental program on scaled bridge composite steel and concrete beams strengthened with external post-tensioning tendons to explore the fundamental cyclic loading behavior. This article summarizes the design of Post-Tensioned Beam for industrial building and a comparative study between PT Beam and RCC Beam based on a literature survey. We are analyzing such structure in our research having a large span. Manual design of PT Beam for three different span lengths without any intermediate supports and manual design of RCC Beam. We are doing a comparative study of PT Beam and RCC Beam based on the results. This report is based on a study of PT Beam that will aid future research and advances in the construction industry. Keywords: Post-Tensioning Beam, RCC Beam, Industrial Building

SEILAPLAN

Cable-based technologies have been the backbone of forest management and harvesting on steep slopes for decades. The design of a cable road is a complex task. It essentially comprises the identification of the start and end points of a cable road, as well as the intermediate supports. With the aim of simplifying this design process, we developed a semi-automated cable road design tool (QGIS plugin SEILAPLAN) that is easy and intuitive to use. SEILAPLAN is based on mechanical assumptions for the structural analysis that are »close-to-reality«, contains an algorithm that checks all possible intermediate support combinations and automatically identifies the optimal solution, and integrates tools and geodata within a GIS application. We present its main components and present an example of application. The integration into a GIS program, the implemented cable mechanics, and the associated information for the construction of a cable road were highly appreciated by the users.

Selecting Intermediate Respiratory Support Following Extubation in the Pediatric Intensive Care Unit

Effect of HFNC Therapy vs CPAP After Extubation on Liberation From Respiratory Support in Critically Ill Children