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U ovom završnom radu dimenzionira se okvirni nosač hale. U uvodu je objašnjeno što je to okvirni nosač, te kako definiramo lokalne koordinatne sustave pojedinih dijelova nosača. Na uvodnom primjeru objašnjena je metoda presjeka pomoću koje se dobiju unutarnje sile. Unutarnje sile okvirnog nosača izračunate su za slučajeve, a to su opterećenje uslijed vlastite težine, opterećenja uslijed djelovanja snijega i opterećenje vjetra iz vani te iz unutra na konstrukciju. Nakon proračuna unutarnjih sila crtaju se dijagrami unutarnjih sila i momenata, dimenzioniranje je provedeno za najnepovoljniju kombinaciju opterećenja. Nakon odabira profila vrši se prikaz raspodjele normalnih i posmičnih naprezanja po visini poprečnog presjeka. Provjera izračunatih vrijednosti je napravljena koristeći programski paket 2D Frame Analysis., In this work paper we are designing the portal frame of a hall. The introduction explains what a portal frame is and how do we define the local coordinate systems of each individual part of the frame. The introductory example explains the section method by which internal forces are obtained. The internal forces of the portal frame were calculated for the following cases, the load due to its own weight, the load due to the snow and the wind load from the outside and the inside of the structure. After the calculation of internal forces, diagram s of internal forces and moments are drawn, design is performed for the most unfavorable load combination. After selecting the profile, the distribution of normal and shear stresses according to the height of the cross section is shown. The verification of the calculated values was done using the 2D Frame Analysis software package.

The steel structure of light-weight buildings with portal frame has the following features: the column net is not limited by the building modulus, and the layout is relatively flexible; it is convenient for prefabrication, installation and construction, and disassembly; the explosion relief area is large, and it is easy to meet the explosion relief requirements of petrochemical units; The advantages of green environmental protection and resource recycling have been widely used in petrochemical project construction, but its design is not reasonable and waste often occurs. The reasonable design and optimization of light-weight buildings with gabled frames is a systematic and complex whole project; This paper analyzes and discusses the rationality and the possibility of optimization of a certain design from the aspects of the determination of the structural type, the importance grade, the load value, the span and the column distance, the purlin calculation, the longitudinal support arrangement, the connection node and so on, so as to make the structural design of the house more reasonable and save the investment.

U ovom završnom radu dan je proračun konstrukcije sastavljene od okvirnog nosača i štapova za zadano opterećenje. U uvodu je prikazano što je to okvirni nosač, te kako se definiraju lokalni i globalni koordinatni sustavi. U uvodnom primjeru prikazano je št o je to rešetkasti nosač te je riješen primjer istog. Napravljen je proračun unutarnjih sila za okvirni nosač bez štapova, zatim za okvirni nosač sa štapovima za zadano opterećenje. Zatim je odrađen isti proračun ali sa zamijenjenim osloncima. Nakon proračuna unutarnjih sila nacrtani su dijagrami unutarnjih sila i momenata. Dalje je napravljeno dimenzioniranje okvirnog nosača sa i bez štapova kao i samih štapova., In this work paper, a calculation of structure composed of a portal frame and bars for a given load will be described. The introduction shows what a portal frame is, and how local and global coordinate systems are defined. In the introductory example is shown what lattice girder is and how the example of lattice girder is solved. The calculation of the internal forces was made for portal frame without bars, and then for the portal frame with bars for a given load. Then the same calculation is done but with the supports replaced. After the calculation of internal forces, diagrams of internal forces and moments are drawn. Further more, the sizing of the portal frame with and without bars is performed, as well as the sizing of the bars themselves and the selection of profiles.

Optimisation of cold-formed steel (CFS) structures can be challenging due to the complex behaviour of thin-walled CFS sections affected by different buckling modes. In this paper, a coupled framework is presented for element and structural level optimisation of CFS portal frames, under serviceability limit state (SLS) and ultimate limit state (ULS) conditions, using Genetic Algorithm. First, CFS lipped-channel beam sections are optimised with respect to their flexural capacity determined in accordance with the effective width method specified in Eurocode 3 (EC3). The relative dimensions of the cross-section are considered as the main design variables, while the EC3 plate dimensions and slenderness limits and a number of manufacturing and end-use constraints are taken into account in the optimisation process. The results show that the optimum CFS sections exhibit significantly higher (up to 84%) ultimate capacity compared to the standard lipped channel sections with the same plate width and thickness. The structural level optimisation is then carried out to obtain the optimal design solution for a long-span CFS portal frame with knee braces under SLS and ULS conditions. Compared to conventional optimisation using standard cross-sections, it is shown that the proposed coupled framework leads to more cost-effective solutions (up to 20% less structural material) by using the more efficient CFS cross-sectional shapes optimised for generic applications. The results also indicate that optimising the frame geometry and knee brace configuration can noticeably improve the structural performance and reduce the required structural weight, especially when both ULS and SLS conditions are considered.

Corrugated steel culverts are sometimes used as an alternative to portal frame bridges for small and medium crossings under railway lines. From a static point of view, the corrugated steel culverts ...

International audience; A new type of U-shaped steel-concrete beams (USCB) using L-angle shear connectors was recently proposed as an alternative solution for long-span structures. In a specific portal frame configuration used in a recent building, the USCB is connected to concrete-filled steel tubular columns by welded steel-concrete joints. The behaviour of these joints plays a crucial role in the global structural stability of the frame as much as that of the whole building. Due to the composite steel-concrete action within the joint, its design is not explicit nor available in design provisions. This paper has the objective to investigate the behaviour of this complex joint and propose a design model of the joint for practical engineers. An experimental campaign of two full-scale tests was carried out in order to determine the moment resisting capacity, the deformation capacity, the cracking patterns, and the failure mode of the joint. A finite element model of the test was also developed and validated against the experimental results to investigate more closely the load transfer mechanism and the propagation of plastification in the components of the joint. The stress map obtained from the FE model was afterwards used to define the geometry of the design model of the joint. This model was proposed based on the strut-and-tie method for the concrete part and the shear panel model for the steel part of the joint. The interesting feature of the design model is the inclusion of the load transfer mechanism of the forces between the steel and the concrete parts of the joint. Finally, a parametric study on the influence of steel detailing inside the joint using the FE model was carried out. It was found out that the initial solution can be simplified and optimised. © 2020 Elsevier Ltd

Majority of construction industries are aiming to go for taller and lighter buildings which may result in flexible and slender structures. Hence serviceability and safety become a critical issue during the occurrence of heavy winds and high magnitude earthquakes. Therefore, considerable techniques are adopted to minimize the vibrations caused by these natural responses of the structures. One of the techniques used prominently for tall structures is Tuned Mass Damper (TMD). TMD’s have been very effective in controlling structural vibrations. This study proposes a detailed analysis of a 2D frame structure with a TMD system placed at different levels of the structure in order to evaluate the behaviour of structure for given earthquake ground motions. The results obtained indicate installation of simple frames can decrease the response of the structure during an earthquake and location of TMD is also discussed in detail.

Previous studies on stressed skin effect of industrial steel buildings showed discrepancies between the ECCS formulae and experimental results. To clarify the discrepancies full-scale experimental test program was planned and executed by the Budapest University of Technology and Economics, Department of Structural Engineering. The aims of the full-scale tests were to refine the stressed skin design method and to adjust it to the nonstandard cladding structural system applied by an industrial partner. During execution of the full-scale experiments the shear flexibility of those industrially applied nonstandard diaphragms were examined, where the application of seam fasteners were rejected. Next to the building section a loading frame was built, so that tension and compression force could be applied to each frame, in order to examine the in-plane shear flexibility of the whole nonstandard diaphragm assembly, including the shear flexibility of the portal frame. In the test series four purlin and two trapezoidal sheeting height configurations were combined in more than 100 tests. This paper, denoted as Part I shows the test setup and introduces the results derived from the ECCS formulae, underlining the importance of extending the applicability of the current design formulae to nonstandard cases, which are often applied in industrial practice all over Europe. A companion paper (Part II) presents the comparative results between the various cladding configurations, also the main conclusions regarding the stiffening effect of the applied diaphragm configurations, and reports the effect of change in section size to shear flexibility. Besides this in Part II the effect of different structural components in regards to shear flexibility is underlined.

This paper presents quantitative investigations on the collapse behavior of steel portal frames exposed to standard fires. The complete collapse process is divided into safe, alert, dangerous and collapse stages. These four stages are to warn firefighters to make timely reactions to stay, ready to evacuate, and must evacuate, respectively. Numerical models are established and validated against fire tests on a full-scale steel portal frame. Based on the key displacements of the heated columns and rafters, the four stages are quantitatively determined in terms of visible phenomena and warning times. It is found that one should be ready to evacuate when the heated rafter shows large deflections, and must evacuate when the heated column moves back to its initial position. The 1 h, 2 h, 3 h fire rating of protected steel portal frames can be used to estimate the ready-evacuate, must-evacuate and collapse warning time, respectively. The findings from this preliminary study aim to provide references for firefighters to make wise decisions to evacuate timely and safety from the fire scene.

Cold-formed steel haunched portal frames are popular structures in industrial and housing applications. They are mostly used as sheds, garages, and shelters, and are common in rural areas. Cold-formed steel portal frames with spans of up to 30 m are now being constructed in Australia. As they are relatively new to the market, current design recommendations are fairly limited. In the specific frame system analyzed herein, the column is partially restrained against twist rotation at an intermediate point where the knee brace joining the column and rafter is connected. An experimental program was carried out on a series of portal frame systems composed of back-to-back channels for the columns and rafters. It was found that changing the knee brace and knee brace-to-column connection bracket significantly affected the buckling capacity of the column, however this was not captured in design calculations. In order to correctly predict frame behavior and ultimate loads for design purposes, the column buckling capacity must be accurately calculated. This paper presents an energy method approach to calculate the buckling load of a column with an intermediate elastic torsional restraint. Various end conditions of the column are considered including column base semi-rigidity, as well as multiple loading conditions. Displacement functions are determined based on measured experimental data. The Southwell and Meck plot methods to determine column buckling loads are discussed. The column buckling loads determined from the plot methods and calculated by the energy analysis are compared to the experimental column buckling loads. It is shown that the energy method outlined herein predicts the buckling load within 6% for columns with an intermediate elastic torsional restraint.

This paper presents experimental investigations on the collapse behavior of a full-scale 36 m × 12 m steel portal frame exposed to natural fires. Extensive thermal and structural responses of the frame are measured and presented. The frame collapses after 15-min fire exposure with a critical temperature of about 1100 °C in the heated column. The measured gas temperature history has a short growth period of 3 min, and reaches its peak temperature of 1100 °C within 8 min (400 °C higher than standard fire). It is found that a two-zone model can be assumed with uniform temperature distribution in the lower and upper half region, respectively. The temperature gap of these two zones reaches 200 °C. The gas temperature at top region decreases due to the deformation-induced opening of roof and fire walls. The surface facing the environment has higher gas temperatures than that inside the fire compartment (more than 200 °C). The temperature of rafters beyond the fire compartment reaches 700 °C due to the spread hot smoke. Outward bending of the external unexposed column and pulling out of corner column base are observed, which should be prevented in practical design to mitigate fire spread to adjacent buildings and ensure life safety of fire fighters. Numerical simulation is conducted and compared to experimental results which can be used for calibrating numerical models.

Semi-rigidness of the joint connections is one of the main characteristics of timber structures. The pin-joint assumption for the semi-rigid joint connections might be not conservative in the timber structural design. In this paper, structural analysis was conducted on a semi-rigid timber portal frame; the formulas were derived in terms of the internal force and the lateral stiffness, and the influence of the semi-rigid connections was discussed. Moreover, experimental tests were performed on three full-scale timber portal frames and five bolted timber connections to study the lateral performance of the frames and the moment resistance of the connections. For consistency, the connections from the portal frames and the connections for bending tests were of the same configuration. Finally, a calculation flowchart of the lateral performance on a semi-rigid frame was presented to verify the derived formulas and to show a framework of the lateral structural design process.

This paper presents experimental and numerical investigations on the collapse behavior of a 12 m × 6 m steel portal frame exposed to fire. A real fire test is conducted with a 4 m × 6 m fire compartment at the corner of the frame. Extensive thermal and structural responses of the frame are measured and presented. The experimental results show that the fire compartment collapses after 20-min heating with a critical column temperature of 850 °C. It is found that the measured gas temperatures are higher than the ISO fire, but lower than the parametric fire specified in EN 1991-1-2, indicating the underestimation of the thermal exposure for standard fires and unrealistic estimation for parametric fires. For steel temperatures, the prediction from parametric fires is in a reasonable agreement with the measurements by predicting a similar maximum temperature at a delayed time. The prediction from standard fires significantly underestimated the steel temperatures by up to 300 °C. The significant non-uniform gas temperature distribution along the frame height shows a two-zone model with a temperature gap of 200 °C. The maximum temperature of the members beyond the fire compartment exceeds 500 °C due to the spread of hot smoke. A numerical model is established and validated against experimental results. A potential outward collapse mode of the frame is predicted. It is suggested that a more realistic description of fire scenarios is still needed for a performance-based structural fire design, based on a better consideration of ventilation conditions and thermal properties of boundary enclosure.

The large building complex making up the Emile Cohl Art School integrates innovative, lightweight structures with both the existing historic columns and the riveted lattice girders which support the saw-tooth roof of the former Renault factory, built in 1899. The roof above the central hall is a multi-span suspension structure. Two steel ribbons, supported by fan-shaped steel struts and anchored on both ends, give an undulating shape to the roof. Wooden box elements span the entire 12 m between the steel ribbons. The rectangular sections are made of a planar Kerto® wooden assembly, fixed onto the curved steel ribbons thanks to custom-fabricated intermediate wooden connections. This is a highly efficient way to cover the hall—using only one type of repeating surface element and minimizing the assembly procedure while giving the roof an elegant wave shape. The steel structure rests on a concrete portal frame, a new element which helps to stiffen the old existing roof structure, including the weak, o...

This paper presents a novel conceptual design framework which takes into account the direct wind loads and pressure loads acting on a structure due to the passing of a tornado. Furthermore, for the first time, the potential damage due to debris impact has been incorporated enabling a holistic assessment of structural loading to be considered. The model is built on a recently developed wind and pressure field model that captures the main features of tornadoes, which is used to generate a large number of tornado wind and pressure field realisations from which values of particular load effects can be determined. A cumulative distribution function of load effect is thus derived, which can be combined with tornado climatology probabilities to determine load effects at a particular risk level. This use of this framework is illustrated through two examples – the direct wind and pressure loads on a low-rise portal frame structure, and the debris loads on a medium rise rectangular structure.

This study aims to investigate the seismic performance of an innovative cold-formed steel (CFS) moment-resisting frame experimentally and analytically. A half-scale CFS moment-resisting portal frame was tested under static monotonic loading until failure. The frame consisted of two box-shaped columns (face-to-face channels connected with inside plates), a back-to-back lipped channel beam section and fully moment-resisting CFS bolted connections. During experimental tests, damage mostly concentrated at the top and bottom of the CFS columns due to the web crippling of the channels close to the connections, while no fracture or obvious slippage was observed at the connection zones. A detailed Finite Element (FE) model was developed using ABAQUS by taking into account the material non-linearity and geometrical imperfections. The lateral load-displacement behaviour, ultimate strength and failure modes predicted by the model were in very good agreement with the experimental results. The validated FE model was then used to assess the effects of key design parameters on the lateral load capacity, ultimate displacement, energy dissipation, ductility, and ductility reduction factor of the frame. It is shown that the proposed system can provide good seismic performance subjected to the appropriate design of the main structural elements. Increasing the axial load ratio of the columns by 50% resulted in 26%, 62%, and 50% decrease in the ultimate lateral load, energy dissipation capacity, and ductility ratio of the CFS frame, respectively. However, the energy dissipation capacity and the ductility ratio of the proposed system increased significantly by decreasing the width-to-thickness ratio of the columns.

This paper is devoted to identify the effect of soil-structure interaction on the dynamic response of,a portal frame railway bridge. The study aims to validate the accuracy of numerical models in e ...

Given the increasingly notable segmentation of underground space by existing subway tunnels, it is difficult to effectively and adequately develop and utilize underground space in busy parts of a city. This study presents a combined construction technology that has been developed for use in underground spaces; it includes a deformation buffer layer, a special grouting technique, jump excavation by compartment, back-pressure portal frame technology, a reinforcement technique, and the technology of a steel portioning drum or plate. These technologies have been successfully used in practical engineering. The combined construction technology presented in this paper provides a new method of solving key technical problems in underground spaces in effectively used cross-subway tunnels. As this technology has achieved significant economic and social benefits, it has valuable future applications. Keywords: Operating subway tunnel, Underground space, Construction, Combined technology

This paper describes the results of the numerical studies of the cold formed profiles joint assembled in a back-to-back pair compared with experimental tests results. The results are presented for eaves connection and apex connection. The entire study has been performed using KB600-5 and KB450-3,5 thin-walled steel profiles joints. The system is primarily of tow galvanized cold-formed steel profiles so called KB, which are joined by means of steel plates, placed in-between them. Connecting of this assembly is realized by using M20 bolts, witch work with to contact planes in shear. A comparative analysis of the experimental and numerical results was made.

The actual codes on design procedures to assess the structural reliability in case of fire allows for a whole scope of methodologies to be used. At one end of the spectrum, the codes allow to simply combine design rules with member analysis using tabulated data or simplified calculation models. On the other extreme end of the spectrum, complex performance-based design approaches are proposed, the results of which are unique and highly dependent on the system’s boundary conditions. Between those two extreme options, there are several other methodologies including the possibility to use probabilistic approaches. In this paper, reliability assessment of structures is based on the force-based method including temperature effects as well. This method is developed for single-bay portal frame and is based on the combined failure probability of five critical sections. All data needed to generate a probability density functions of the thermal actions on the structure is collected and described. Heat transfer equations of unprotected steel are used to calculate the profile temperature and reduction of mechanical characteristics during and after the fire. Coupling of the probabilistic-based thermal actions to the force-based method enables to create numerous simulations (Monte Carlo technique), and thus enable the system during and after a fire. This analysis is done for different load levels (self-weight), portal frame geometries and for several fire scenarios. Last, the post-fire behaviour of structural carbon steel single-bay portal frames is carefully investigated.

This paper proposes a modified Lemke algorithm to determine the non-holonomic response of rigid plastic skeletal structures subjected to extreme dynamic loading. The basic formulation for the dynamic rigid-plastic response has a mathematical form of linear complementarity problem (LCP), and, equivalently, a pair of dual quadratic programs (QP). Previous attempts using the Wolfe type LCP solver exhibited very pronounced sensitivity with semidefinite LCPs, which appear in this class of dynamics. Therefore, the current study offers a numerically robust Lemke algorithm, which is considerably adapted to deal effectively with the presence of unrestricted variables and the semidefinite characteristics of structural matrices. In addition, degeneracy in the LCP solution of rigid plastic structures is efficiently handled by using the Lexicographic Minimum Ratio test. To validate the formulation and the algorithm developed, bench tests are conducted, which involve a simply supported beam and a portal frame subjected to a uniformly distributed rectangular pulse loading.

This paper presents experimental and numerical investigations on the collapse modes of single span steel portal frames exposed to fire. A fire test on a scaled-down single span steel portal frame is conducted and measurements of deformation and collapse mode of the test frame are used to validate the numerical model for simulating the behavior of the single span steel portal frames subjected to fire. Four collapse modes of the portal frames, column lateral collapse, column buckling collapse, overall inward collapse and overall outward collapse, are revealed through parametric studies with the validated numerical model. The effects of heating conditions, stiffness of column base, temperature gradient, fire protection, load ratio, span-height ratio and column spacing on collapse modes of single span steel portal frames in fire are obtained. It is found that heating conditions, stiffness of column base and load ratio have a great impact on the portal frame collapse modes while temperature gradient and fire protection mainly affect the column collapse modes. The findings of this study lay the foundation for early-warning of fire-induced collapse of single span steel portal frames.

Cold-formed steel components exist in a variety of structural systems including wall, floor, and roofing systems. A common feature of these cross sections is that they are often open and singly symmetric or point symmetric. While design requirements for these cross-sections account for the relevant effects resulting from their lack of symmetry, structural analysis programs do not always consider these effects. Engineers will use structural analysis programs to calculate the appropriate load sharing among members in the structural system. Accounting for the appropriate stiffness of each member and the related deformations is a vital component to determining the final distribution of bending moment, forces, and displacements. Many common structural analysis programs treat all sections as doubly symmetric without warping. Removing this assumption causes non-symmetric cross sections to exhibit nonplanar displacements and complicates the stability limits. The analysis of two structural systems composed of non-symmetric members was completed with varying member modeling assumptions utilizing multiple finite element software programs. A single channel portal frame was investigated that was subjected to simulated gravity load and wind loading with varying bracing support. Additionally, a roofing system with Z-section or channel purlins and channel bracing was investigated. The finite element analysis results were compared among the various modeling assumptions and existing experiments where available. It was observed that good agreement between the doubly symmetric and the more complex analyses was obtained in some instances, particularly when the members were loaded to low levels and highly constrained. However when loading is closer to the elastic limits and members can more freely move out-of-plane, the inclusion of non-symmetric section properties becomes a critical factor in determining an accurate response for both internal forces and displacements. The variations between these different analysis methods were found to be difficult to predict due to the cumulative effect of the competing mechanical behaviors that could result in either conservative or unconservative responses when ignoring non-symmetric behavior.

In the seismic analysis, the boundary condition of a container crane is a complex problem when dealing with the contact between the crane's toes and the ground surface or wharf deck. In operation, the wheels of container cranes move on rails freely but are usually anchored when at rest. Therefore, the wheels could be lifted up and derailed due to seismic excitation. The boundary condition of a container crane has not been fully addressed in past research. It has mostly been simplified as pin supports without considering the possibilities of uplift and derailment of the crane legs. Hence, there is a need to conduct a study focusing on the effects of derailment and uplift on a container crane's seismic response. This paper investigates the seismic response of a container crane via a shake table testing of a 1/20 scale crane constructed according to the similitude law, with a simulation of the boundary condition of the scale crane as a pin and a friction boundary. A white noise test was conducted to determine the natural frequencies of the scale crane, then the seismic response of the container crane was determined via three input ground motions. The three input ground motions were designed by matching real earthquakes to the Korean design elastic response spectrum and scaling down for the shake table testing. Under these seismic excitations, the responses of the container crane were considered in terms of uplift, derailment, portal movement, and bending moments. The shake table testing shows that the maximum difference in the natural frequencies of the crane for the portal sway mode, between the friction boundary and pin support, was 2.1%. Due to the effects of derailment and uplift of the landside legs, the bending moments in the crane's seaside legs with a friction boundary were 109% higher than those with a pinned boundary. In addition, a residual deformation was observed in the portal frame after the vibration had stopped when the scale crane was assigned a friction boundary.

The work presented in this paper investigates the strength of moment-resisiting apex brackets of cold-formed steel portal frames. The results of two previously reported full-scale portal frame tests, where the frames failed through buckling of the apex bracket, were used to validate a finite element model that included material nonlinearity, geometric imperfections, and bolt bearing behaviour. From portal frame test results as well as the finite element results, the importance of appropriate detailing for the apex brackets for strength is demonstrated. A simplified finite element model of the apex bracket is then presented, again validated against previously reported experimental tests. The effects of geometrical parameters of the brackets, bolt-group configuration, and yield stress of brackets were investigated through a parametric study comprising 648 models. From the results of this parametric study, design equations are proposed that can be used by practicing engineers to predict the strength of apex brackets used for cold-formed steel portal frames.

This study employs a detailed 3-D numerical modeling to investigate the fire-resistance behavior of the damaged steel portal frame with reduced beam section (RBS) connections. Ignoring the material damage parameters, and the detrimental influence of residual stresses and geometrical imperfections in the previous numerical researches has given an unrealistic response in the subsequent fire analyses. Damages were induced by the cyclic loading protocol and considering damage parameters. Then, mechanical-thermal analysis was carried out by adopting a standard fire scenario, as per ISO-834. The analysis results indicate the necessity of considering damage parameters to improve the reliability of the approach. It is revealed that fire develops thermal stresses in the bottom flange of the RBS beam. These stresses lead to severe deformation in the RBS zone, thus influencing its vital performance. Damages induced by cyclic loading drastically reduce the fire-resistance period of the frame. Once the maximum drift exceeds three times the yield limit, the steel frame is practically not capable of resisting fire. Applying extra fire load to the frame with residual lateral displacement, when the maximum lateral displacement is greater than the yield limit, the frame can only sustain the stability for less than 2 min, which will also diminish by increasing the axial column load. Through conducting a subsequent case study, it was found that the fire-resistance time of the frame is increased by decreasing the DoI of the structure at equal cyclic loadings.

In this study, the seismic performance of a 2D portal frame subjected to the recorded seismic ground motions of the Northridge 1994 earthquake was evaluated by the force analogy method (FAM) with different element types. To increase the accuracy of FAM, Timoshenko (TS) elements were employed instead of the classical Euler Bernoulli (EB) elements, to revert the shear deformations that are neglected in EB elements. To perform evaluation, the same material and section properties were considered and the same portal frame was analyzed with different element lengths, from 0.5 to 7.0 m in 0.5 m steps.

The seismic response of buildings not specifically designed to resist earthquake actions can be generally improved by allowing the structure to dissipate an appropriate amount of energy. The use of passive devices for improving the seismic performance of precast concrete structures is investigated herein. In industrial and commercial precast concrete buildings, these devices can be successfully applied at the beam-to-column connections of hinged portal-frames, in order to increase the connection degree of fixity and the dissipated energy during a seismic event. The specific aspects and efficiency of passive dissipation devices based on rotational friction with and without the addition of a re-centring device is analyzed herein. Such devices may be applied both to existing and new buildings; indeed, they are able to mitigate the inter-storey drift demand, to limit the damage at the column base and to reduce residual drifts. A design procedure is developed in the paper for portal-frames implementing the investigated devices. A case study representing a single-storey precast concrete portal-frame is selected. The design procedure is applied to the case study, considering various devices configurations. The structural performance is assessed by means of non-linear time history analyses.

An ultrasonic elliptical vibration tool utilizing the coupled resonant vibration modes is the key component in the elliptical vibration cutting/texturing process, which has been successfully applied to ultra-precision machining and surface texturing. In this paper, an analytical approach is proposed to analyze the resonant frequency and mode shapes of the ultrasonic elliptical vibration tool. A new design of ultrasonic elliptical vibration tool based on a portal frame structure is presented and analyzed using the proposed model. The model assumes Euler-Bernoulli beams and utilizes the transfer matrix technique to reduce the order of the system to only six variables. The model can be utilized to provide a systematic approach for an optimal design and be extended to dynamic analysis of the tool for study of machine-tool dynamics. Finite element simulation results as well as experimental data based on the prototype design are presented to verify the model. An application of the proposed tool is also demonstrated in machining micro/nano-structured surfaces for structural coloration.

The use of stainless steel structures has increased during the last decade due to their durability, aesthetics and mechanical properties such as ductility, considerable strain hardening and excellent fire resistance. However, the majority of conducted research works have only focused on single isolated stainless steel members and advances in the analysis of stainless steel frames are limited. EN1993-1-4 does not provide global plastic design rules for indeterminate stainless steel structures, such as frames, despite their proved high ductility. On the other hand, the lack of guidance on plastic design is an obstacle for the optimal design of stainless steel structures, leading to uneconomical design. This paper presents a preliminary study on non-sway stainless steel frames with stocky hollow cross-sections. The study of the behaviour of stainless steel frames is based on numerical parametric studies, considering the nonlinear material behaviour and different stainless steel types (austenitic and ferritic). The paper deals with the redistribution of internal forces and assesses the existing methods based on global plastic design for frames with stocky cross-sections, where alternative design approaches accounting for moment redistribution and strain hardening effects are analysed in addition to traditional plastic design method. Preliminary results demonstrate that including bending moment redistribution and strain hardening effects in capacity predictions is essential for an efficient design of stainless steel structures.

In current design rules the effect of a haunch on the sway in-plane stability of a steel portal frame only takes into account the influence of the haunch dimensions on the beam-to-column connection strength and stiffness. The effect of the haunch dimensions on the beam behavior, and thus on the frame behavior, is not included. The paper describes the effect of this phenomenon by regarding current design methods and comparing these with analytical solutions. The validity of the methods is covered by numerical simulations. For a vertical beam loading, the larger the span of the portal frame, the higher the compressive force in the beam becomes. In addition, the longer the span of the frame, the smaller the critical buckling load of the beam becomes. This decreases the stability of the overall frame significantly. In fact, the compressive force in the beam of a portal frame has a significant effect on the additional stiffness the haunch provides to the column. Due to the adjusted center line of the haunch causing an eccentricity, an additional first order moment is generated. This additional internal moment reduces the additional stiffness the haunch provides. For some spans this may even cause the additional stiffness of the haunch to be negligible. The research has given more insight, also on the effect of the shift of the compressive force in the beam, which depends on the geometry of the haunch. The study resulted in two simple correction factors for the current design rules, where these correction factors cover amplification factors for the original stiffness of the beam. The factors depend on the kind of loading (point load or equally distributed load) and on the haunch to rafter ratio (with regard to the length of the haunch as well as with regard to the height of the haunch).

In order to propose an alternative structural element to be used for wooden dwelling houses in rich forest area, we paid attentions to a portal frame structure which is composed of not glulam but built-up members whose raw materials are dried sawn timbers taken from plantation grown forest. For establishing design procedure of the structural element, we made two different types of portal frames and conducted, at first, basic dynamic test to estimate natural frequency and dumping factors by fixing small shake excitation machine on the portal frames, then static push-pull cyclic loading tests were conducted until failure. The natural frequency of both portal frames was almost same but the higher order frequencies were likely to be affected by the difference of shear reinforcement of built-up members by hardwood dowels. While on static properties, as both portal frames failed in brittle manner due to bending failure at column or tear off at connection plate made of compression wood, further improvement of connection system was required for obtaining more stable alternative elements to glulam.

© 2017, Springer-Verlag GmbH Germany. This paper focuses on discrete sizing optimization of frame structures using commercial profile catalogs. The optimization problem is formulated as a mixed-integer linear programming (MILP) problem by including the equations of structural analysis as constraints. The internal forces of the members are taken as continuous state variables. Binary variables are used for choosing the member profiles from a catalog. Both the displacement and stress constraints are formulated such that for each member limit values can be imposed at predefined locations along the member. A valuable feature of the formulation, lacking in most contemporary approaches, is that global optimality of the solution is guaranteed by solving the MILP using branch-and-bound techniques. The method is applied to three design problems: a portal frame, a two-story frame with three load cases and a multiple-bay multiple-story frame. Performance profiles are determined to compare the MILP reformulation method with a genetic algorithm. ispartof: Structural and Multidisciplinary Optimization vol:57 issue:2 pages:579-593 status: published

Uneven exposure to e.g. solar radiation can cause temperature differences between various structural parts of a bridge, which leads to tensile stresses if the parts cannot move freely. In this study, thermal simulations and stress calculations on a model of a portal frame bridge are performed with the aim of evaluating the temperature difference between the bridge parts. Factorial design is used in a parametric study to determine the influence of different factors on the temperature difference and the largest reasonable temperature difference obtainable for the chosen weather data. The study shows that the quasi-permanent temperature difference between parts which is proposed by Eurocode 1 is overestimated, causing tensile stresses in the transverse direction to be exaggerated significantly. Using the design method proposed by Eurocode 1 is therefore likely to overestimate the required reinforcement in crack width limit design, which in turn would lead to unnecessary costs and environmental impacts. The results also indicate that the temperature distribution within the bridge is different from what is given in Eurocode load cases, and consequently, the largest tensile stresses appear in other areas of the bridge. A simplified temperature distribution is therefore investigated and shown to give similar results as the detailed thermal simulations.

Summary The steel plate shear wall (SPSW) is an effective lateral force resisting system in which unstiffened steel infill plates are connected to the horizontal and vertical boundary elements (VBEs) on all sides of the plates. The boundary elements must be designed to resist the tension field force of the infill panels. When the VBEs are made from a steel box section, the flange of each box VBE connected with the infill panels can be pulled out-of-plane by significant panel forces, called pull-out action. This study investigates capacity design methods for box VBEs in SPSWs. Simplified fixed beam and portal frame models aim to estimate the pull-out responses of the flange of the box sections with and without infill concrete, respectively. In this study, cyclic tests of three full-scale two-story SPSWs using box VBEs with or without the infill concrete are conducted. Inelastic pushover analyses of the finite element models are conducted. The tests and analytical results confirm that the proposed design methods, which aimed to prevent the full yield of the flange under the pull-out action, are applicable. Furthermore, the test and analytical results suggest that the initial yielding of the flange of box VBEs under the collective effects of the pull-out action on the flange, the gravity load, and the sway action on the SPSW represents a local yielding. A strict prohibition of the initial yielding on the flange under the aforementioned collective effects is not recommended for pursuing a cost-effective design. Copyright © 2017 John Wiley & Sons, Ltd.

In this study, a two-stage method is presented for identifying multiple damage scenarios. In the first stage, the damage locating vector (DLV) method using normalized cumulative energy (nce) is employed for damage localization in structures. In the second stage, the differential evolution algorithm (DE) is used for damage severity of the structures. In addition, in the second stage, a modification of an available objective function is made for handing the issue of symmetric structures. To verify the effectiveness of the present technique, numerical examples of a 72-bar space truss and a one-span steel portal frame are considered. In addition, the effect of noise on the performance of the identification results is also investigated. The numerical results show that the proposed combination gives good assessment of damage location and extent for multiple structural damage cases.

This paper describes some of the extensive outcomes of a structural load test on a full-scale bamboo-epoxy composite frame. A bundle of 30 small diameter thick-walled bamboo culms was bonded using an epoxy-fibre resin to form structural beam and column elements, which were connected at the beam/column joints using rebar and a novel composite glue to form a Portal frame. The frame was heavily instrumented with over 90 strain gauges to establish the locations of any delaminations or hinge formations during inelastic behaviour under load. The frame and the gauges were assembled in India and shipped to Ireland for testing. In Trinity College Dublin, the frame was supported by steel shoes bolted to a 3000 kN internal reaction rig, with additional passive lateral supports in case of out-of-plane instability during loading. This paper describes the load–displacement response under combined horizontal and vertical loading, together with an explanation of the frame’s non-linear behaviour using the evidence...

Made available in DSpace on 2018-12-11T16:46:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-09-01 In the few decades, the study of electro-mechanical systems which are capable to extract energy from an operating system in the environment has been of most importance. In this work, we present the extraction of energy from a simple portal frame structure excited by a harmonic force, where the energy harvesting is computed by using of a nonlinear piezoelectric material. The dynamical response of the system is examined, when there is 2:1 internal resonance between the symmetric and the sway mode, resulting the saturation phenomenon and vibration energy transfer between the symmetric (vertical) mode and the horizontal (sway) mode. An evaluation of the energy available for harvesting, in each of the considered modes, is computed. UTFPR - Federal University of Technology - Parana Faculty of Mechanical Engineering UNESP - Sao Paulo State University, CP 473 ITA - Aeronautics Technological Institute UFFS - Federal University of Fronteira Sul Faculty of Mechanical Engineering UNESP - Sao Paulo State University, CP 473