Bent Frame Research Articles

Nonlinear Seismic Performance Evaluation of Flexural Slotted Connection Using Endurance Time Method

The equivalent statistical methods, spectral analysis, and time history analysis are usually offered in the steel structure design regulations. Among these methods, the third one is more accurate; however, it requires more time to align the accelerometers due to a large number of analyses. In the endurance time (ET) method, incremental acceleration functions gradually and uniformly increases over time while their linear and nonlinear response spectra are proportional to the mean of the real seismic spectrum. These functions are used as input functions to analyze the nonlinear time history of structures, and the performance of structures is evaluated based on the maximum length of time they can meet specified performance goals. A three-story steel bending frame with (slotted web) SW and (web unslotted flange) WUF connection is examined through the performance time method in performance-based design. This article aimed at evaluating the seismic performance of these connections in the bending frame through endurance time analysis to predict the structural response in the probabilistic evaluation of the seismic performance of the structures. It is found that the endurance time analysis is justified with the seismic performance of the connections with low computational cost and proper accuracy. The results of comparing both SW and WUF connections indicated that the SW connection prevents the connection welding area from being failed due to transferring the plastic joint into the beam and in an area away from the column face and causes less damage compared to the WUF connection.

Upgrading Seismic Behaviors of R/C Frames with Shaped Memory Alloys Based Braces

Intelligent systems in structural engineering are systems that are capable of automatically adapting structural behavior in response to instantaneous loads, thereby ensuring the safety of extended structural life and performance. One of the new technologies that makes it possible to achieve these goals is the production and development of smart materials. Examples of these smart materials used in structural engineering include piezo-ceramics, magnetorheological fluids, electrorheological fluids, and form-memory alloys. Shaped Memory Alloys (SMAs) are new materials that have been used in various fields of science and engineering in recent decades. In recent years, these materials attracted the attention of researchers in the field of building and earthquake engineering due to their properties such as high damping capacity, low permanent displacement and structural fatigue resistance. One of the application areas of these materials is that they are used as a brace in the structures, so the research results have shown the acceptable performance and operability of such structural systems. In this study, shape memory bracelets and steel bracelets installed as structural brackets were used as a lateral load system in the seismic improvement of concrete bending frames and factors such as residual displacement and base shear in these two load-bearing systems are compared.  The model under studying is a 6-story frame that has been subjected to time history analysis. SeismoStruct software was used to analyze the model.

Seismic behaviour of structural systems with separated gravity and lateral resisting systems

An innovative composite structural system with separated gravity and lateral resisting systems (SGLR system) was proposed to overcome the shortcomings of existing prefabricated structural systems. Two representative frame specimens with a scale ratio of 0.5 were tested under vertical floor loads and lateral cyclic loads to investigate the mechanical behaviour of the SGLR system. The slab crack patterns, failure modes, load–displacement curves, strength and stiffness degradations, energy dissipation capacity, deformation characteristics and strain development were analysed. The experimental results showed that the bent frame specimen (SGLR-1) exhibited good and stable seismic performance and the shear wall–bent frame (SGLR-2) with higher stiffness and capacity demonstrated obvious degradation due to buckling and fracture of steel plates at the bottom of shear walls. From test observations, flexural deformation was the dominated deformation pattern of the SGLR system under lateral loads. On the basis of test data, seismic performance assessment indicated that the SGLR system had larger safety margin than the conventional composite rigid frame (RF) system with the same design criteria of inter-storey drift ratios. The internal force analysis of the SGLR system showed that the base shear distribution in shear walls and columns varied with the increase of overall drift ratio. Moreover, it was revealed from the experimental analysis that the semi-rigidity of connections was significant and had conspicuous influence on both gravity and lateral force transfer mechanisms of the SGLR system.

Vulnerability analysis of aqueduct structure based on boundary method

The damage forms of aqueduct under earthquake are mainly reflected in column of bent and rubber bearing. Taking a typical aqueduct as an example, the uncertainty of structural materials of aqueduct is considered by Latin hypercube sampling method; the uncertainty of ground motion is considered by stratified sampling method; the aqueduct sample and seismic wave are randomly combined to carry out time history analysis to obtain structural response; the limit damage states of column of bent and rubber bearing are defined respectively; the vulnerability curves of components are established by classical vulnerability analysis method. The system vulnerability curve of aqueduct structure is obtained by boundary method. The results show that the rubber bearing of aqueduct is more vulnerable to damage than bent frame. The failure probability interval obtained by the second-order limit method is smaller than that obtained by the first-order limit method, and the second-order limit method is more reasonable to evaluate the seismic performance of aqueduct structure.

Bending rigidity of yarns using beam method on a two-support configuration

This paper reports a simple, quick and reasonably accurate approach for measuring the bending rigidity of yarns. The beam method has been adapted and applied using a bending frame that has a fixed support and a simple support. The yarns are left to bend under the effect of their own weight. The accuracy and the precision of that bending frame are assessed over the time using an isotropic material and then compared against the ring-loop method and the KES-FB-2 pure bending tester. The findings show that the precision of this bending frame is acceptable. However, this bending frame gives at least 1.6 times greater values of bending rigidity than the KES-FB-2 pure bending tester, though the relationship between these two methods is linear and significant. Moreover, the spun yarns appear to have high levels of variability of the bending rigidity. This study is important as it overcomes the challenges faced while using other methods to measure the bending rigidity of yarn. It also provides a comprehensive account of the variation in this property. Further, it gives an indication of the highly non-uniform structure of spun yarns and the impact of yarn defects on the bending properties of yarns.

Nonlinear dynamic analysis of dielectric elastomer minimum energy structures

This paper presents a theoretical study of nonlinear dynamic behavior of a dielectric elastomer minimum energy structure (DEMES). While planar Dielectric Elastomer Actuators (DEA) solely poses material nonlinearity in their model, geometrical nonlinearity imposes additional challenge to model DEMES. Considering dielectric elastomer and bending frame, respectively, as a hyper-elastic film and an elastic beam, Euler–Lagrange equation is employed to derive the equation of motion of actuator subject to a harmonic voltage. Fixed point analysis of the equation of motion demonstrates supercritical pitchfork bifurcation with respect to film pre-stretch as bifurcation parameter. It is shown by simulation results that the system possesses harmonic resonances as well as superharmonic and subharmonic resonance. Investigating Poincare map of the time response indicates that by changing excitation frequency and amplitude the response transforms from periodic to quasiperiodic and eventually aperiodic form.

Study on the Seismic Performance of Bent Columns in Vertical Bent Frame Structures

A novel reinforced concrete (RC) vertical bent frame structure system consisting of a RC frame structure and RC bent structure has been proposed for the development of large-scale thermal power plants. To better understand the seismic performance of RC bent columns in vertical bent frame structures, a 1/5-scale representative component selected from a common vertical bent frame structure was tested by quasi-static testing (QST). The failure mode hysteretic characteristics, ductility, energy dissipation capacities of RC bent columns were investigated. Based on the experimental results, finite element models for the bent frame columns and vertical bent frame structures were developed and the nonlinear dynamic analyses were carried out. The results of finite element analysis indicate that the axial pressure ratio has significant effects on the seismic behaviour of RC bent columns. The relationship of drift angle for bent frame column under frequent earthquake and infrequent earthquake are investigated. The limitation values of axial compression ratios and the inter-storey drift angle for RC bent columns in vertical bent frame structures are suggested.

Base shear determination using response-spectrum modal analysis of multi-degree-of-freedom systems with soil–structure interaction

Building codes and design guidelines, e.g. FEMA (NEHRP recommended seismic provisions for new buildings and other structures, FEMA P-1050, Washington, 2015) and ASCE (Minimum design loads for buildings and other structures ASCE/SEI 7-10/2010, Reston, 2010), describe the problem of multi-degree-of-freedom systems with soil-structure interaction (SSI). These systems are modeled like those having a fundamental degree of freedom on a foundation with lateral and rotational interactions and the other vibration modes isolated and supported on a fixed foundation. This model oversimplifies the problem, neglecting the effects of having all modes coupled in the foundation with SSI. A simple, easily programmable, SSI model in which all vibration modes are coupled an attached to an infinitely rigid shallow foundation subjected to soil excitation is introduced here. Initially, the total response of the coupled system is calculated. Then, using traditional procedures to combine modal responses, a simplified alternative methodology to find the total response of this coupled system is proposed. The new methodology is verified against a robust numerical technique, i.e. boundary elements method, using a wide variety of cases that combine several types of soils, building heights and two structural typologies: bending frames and shear walls. Finally, it is clear from the parametric study that current methodologies, based only on the interaction of the fundamental mode of vibration of the structure, in some cases has a significant influence on the total base shear of buildings, particularly in tall buildings founded in soft soils.

Using Risk-based Robustness Index for Seismic Improvement of Structures

Nowadays, there are numerous indexes and parameters to review the seismic performance of improved structures. Response modification factor, fragility curves, ratio of different input energies to the structure affected by earthquake, maximum displacement and etcetera. are among these parameters, and most of these parameters are reviewed non-probabilistically. On one hand, since robustness index according to risk shapes probabilistically by reviewing uncertainty parameters of critical events and considering all existing parameters, it can be a beneficial index for reviewing the performance of improved structures. In this article, at first the robustness index is introduced according to risk analysis and one of its unique features is using percentage and amount of progressive collapse in it. After the considered robustness index, it has been used in reviewing the performance of a 4-story building of steel bending frame improved in two separate modes of concentrically brace frame and buckling restrained brace and a method has been suggested to obtain all effective parameters in intended robustness index. Ultimately, by reviewing this index for primary structure and improved structures, their behaviors have been compared and its results have been reported.

Rancang Bangun Alat Deteksi Penyimpangan Deformasi Bending di PT. X

PT. X is an automotive manufacturing that produce kind of any vehicle on Indonesia. Bending process is one of process system in PT. X. As the biggest manufacturing which have so many consument in Indonesia, on time delivery is an important things that have to kept costumer smile achievement. From the main factor before if any proces that related delay delivery have to fastly contermeasure and standardization guarantee for reoccurance problem. With using 6 step Kaizen methode and focus to bending frame assy process and frame assy robot process that give the biggest impact to delivery, so as this reason the author make a target for both process can be guaranted as process delivery.

METHOD OF CREATION OF THE DESIGN SCHEME OF BENT FRAMES WITH THE METHOD OF FINITE ELEMENTS

The method of creation of calculation schemes of flattened frames with the help of the finite element method is developed. The algorithm for calculation of bending frames in the software complex LIRA-CAD is presented.

Investigating the effect of column removal on progressive collapse of buildings designed by buckling restrained braced and bending frames

Investigating the effect of column removal on progressive collapse of buildings designed by buckling restrained braced and bending frames

Characterization of a bent Laue double-crystal beam-expanding monochromator.

A bent Laue double-crystal monochromator system has been designed for vertically expanding the X-ray beam at the Canadian Light Source's BioMedical Imaging and Therapy beamlines. Expansion by a factor of 12 has been achieved without deteriorating the transverse coherence of the beam, allowing phase-based imaging techniques to be performed with high flux and a large field of view. However, preliminary studies revealed a lack of uniformity in the beam, presumed to be caused by imperfect bending of the silicon crystal wafers used in the system. Results from finite-element analysis of the system predicted that the second crystal would be most severely affected and has been shown experimentally. It has been determined that the majority of the distortion occurs in the second crystal and is likely caused by an imperfection in the surface of the bending frame. Measurements were then taken to characterize the bending of the crystal using both mechanical and diffraction techniques. In particular, two techniques commonly used to map dislocations in crystal structures have been adapted to map local curvature of the bent crystals. One of these, a variation of Berg-Berrett topography, has been used to quantify the diffraction effects caused by the distortion of the crystal wafer. This technique produces a global mapping of the deviation of the diffraction angle relative to a perfect cylinder. This information is critical for improving bending and measuring tolerances of imperfections by correlating this mapping to areas of missing intensity in the beam.

Investigating the Effect of Viscous Damper on Seismic Behavior of Steel Dual Frames with Divergent Bracing Affected by Near and Far Fields Earthquake to Fault

Current study is sought to study the effect of linear and nonlinear liquid viscous dampers on steel frames having dual systems of bending frame and divergent bracing. These frames were first designed according to regulations of Iran’s 2800 standard and tenth chapter of national regulations of construction (planning and performing steel construction) through equivalent static method then frames were modelled again in non-linear analysis software and time history non-linear analyses were done on them with installing viscous dampers on these frames using recorded near and far faults. In this study the effect of viscous dampers will be investigated on seismic behaviour of mentioned frames and results will be proposed in form of maximum graphs of relative displacements, stories lateral displacements, base shear maximum, waste energy graphs and dampers’ force-displacements. All non-linear analyses have been done in PERFORM-3D software.

Preparation and Study of a Type of Magneto-Rheological Materials Used in Vibration Control of Space Grid Structure

A type of Magneto-Rheological Materials (MRMs) was prepared. The off-state viscosity and the shear stress of the MRMs were characterized and studied by an advanced rotational rheometer system. A kind of Self-Decoupling Magneto-rheological (SDMR) damper was established based on these MRMs. An intellectual isolation system for grid structures was obtained by integrating SDMR damper and isolation device. The seismic whiplash effect of the top bent frame column and space grid roof of the hydropower plant could be reduced. Furthermore, the half stable increment method was proposed as the semi-active strategy. The results indicated that the SDMR dampers used at the grid roof supports setting plate rubber bearings can significantly improve the vibration performance and energy dissipation structure roof isolation system in different seismic intensity. In addition, these SDMR dampers can effectively reduce the lateral slippage of the plate rubber, so as to avoid failure or damage of the isolation system because of the transfinite horizontal displacements. Compared with the conventional damper only in case of multiple earthquakes, the damping force and adjustable multiple of this SDMR damper have better adaptability, and this SDMR damper provides a higher safety factor.

Seismic behavior of coupled column bridge RC piers: Experimental campaign

This paper focuses on presenting an experimental campaign devised at the Laboratory of Earthquake and Structural Engineering (LESE) of Faculty of Engineering of University of Porto (FEUP), and some of its earlier stage results. The scope of said campaign consists of exploring the seismic behavior of a double-column reinforced concrete bridge bent frame with a short-spanned beam, which was designed to be applied on the construction of the Portuguese High-Speed Railway Line.As is the norm on HSRL bridges due to restricting code deformation limits, this particular application presents high stiffness to horizontal transverse loads. It is, therefore, predictable, that seismic demand on this bridge bent frame will be met with a structural performance associated with high shear load not only on the piers, but in the short-spanned beam as well, which can be a limiting factor on the global ductility achieved by the structure.In order to study this situation, reduced scale specimens were built, sharing a design goal of maximizing the shear ductility in the short-spanned beam. As such, the design approach was similar to that used in coupling beams of shear walls, for which several recommendations exist in the literature. Additionally, a new test setup is also presented, which was prepared at the LESE laboratory to accommodate the challenges of testing a frame structure under constant axial load and cyclic horizontal imposed displacements, on the specific context of this experimental campaign. The obtained results confirmed that shear ductility in the beams is a critical factor for the design of this type of structure, independent of the reinforcement layout, and that shear dominated failure is likely to occur, for lateral drift levels under 3.00%. Nonetheless, it also showed that specimens that adopt an adequate beam reinforcement layout for improved cyclic shear performance exhibit more than double the cumulative ductility of those that do not. In contrast, the columns were observed to experience relatively low damage outside the interface surfaces with the heavy shear damaged beams.

Analyzing the Effect of International Standards Details of Reinforced Concrete Buildings on Ductility and Energy Absorption of Structure (A Case Study of Nakhjavan Palace Project)

As studies have been conducted on structures exposed to earthquake or other similar destructive events revealed, implementation problems during construction have led to slight, serious and irrevocable damage. Meanwhile, with respect to various sensitive and subtle details, implementing concrete structures have not been excluded from this principle or are involved with these problem’s consequences. The present study investigated the relation between ductility and energy absorption, especially when the imposed lateral load is alternative. Also, the issue of energy-taking and input energy dissipation in a structure implemented according to international standards details of reinforced was studied. Furthermore, by implementing damage index model based on hysteric energy theory, three index levels including elemental, stratified and general structure damage were presented and the importance of precisely implementing regulation details were interpreted. Moreover, ductility and energy absorption level in tall structures’ load revisiting systems as well as structures’ non-linear behavior causes were explained. Since this case study focused on bending frame system and shear wall and analyzed total deformation of structures constituting shear wall and rigid frame. The research findings can be useful to determine the effect of implementing international standards details of reinforced concrete buildings on ductility and energy absorption of structure.

Analysis of the effects of process parameters in residual stress measurements on Titanium plates by HDM/ESPI

Hole drilling (HDM) is the most widespread approach for measuring residual stress profile. Many improvements were introduced along the years. Recently, research papers investigated the feasibility of using optical systems to replace strain gage rosette as measurement tool of the strain field generated by the drilled hole. Generally, the accuracy of the measurement is influenced by the proper choice of the experimental and analysis parameters. In this paper the effects of the choice of a proper analysis area are shown. Furthermore the influence of the drilling rotation speed of the cutter used for drilling the hole is considered. Experimental tests were performed on a Ti6Al4V specimen loaded in a four point bending frame. Results obtained for different part of the analysis area and at different speeds ranging in 5000–50,000rpm were compared with the theoretical expected value.

Mechanical Behavior of Wedge Adjustment Bending Device of Cold Leveler

Roll bending plays an important role in elimination of non-uniform transverse internal stress and improvement quality of plate shape in leveling process. Taken the wedge adjustment bending device on a 11-roll cold leveler in a cross cut line as research object, in order to studying its bending characteristic, three-dimensional assembly model contained roll system, roller bending frame and upper beam has been built based on the finite element method. With the model, the necessity and function of the bending device has been verified. Different plate width, leveling force and roll bending value effects on working roll gap curve have been discussed. The result could serve as theoretical base for online set model and provide more precise parameters, accordingly maximize the potential ability of levelers.

Analytical and Experimental Studies on Behavior of Beam to Column Connections with Flange Plate under Monotonic Loading

Behavioral study of connections using moment - rotation curve for analyzing different types of connections and also the concept of strength, ductility and rigidity of steel connections are important. One of the most common connections in bending frames of steel structures is beam to column connections with flange plates. A correct perception about structural behavior of beam to column connections and also appropriate knowledge of their force transmission and their behavior in modeling and analysis of the steel structures are essential. In present study, beam to column steel connection with flange plate under monotonic loading, both analytical and experimental would be investigated. The obtained results showed that moment - rotation curves of experimental sample and finite element (F.E.) model are reasonably close to each other. As a result, F.E. method could be an appropriate tool to investigate the behavior of these connections which would significantly decrease number of trial and error approaches.