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This study aimed to enhance the structural performance of a drift joint with a slotted-in steel plate using laminated timber made from small- to medium-diameter timbers. An analysis was conducted to compare and evaluate the structural performance and seismic behavior of laminated timber portal frames reinforced with fiber-reinforced plastic (FRP) laminates, such as glass fiber cloth (GFC), glass fiber reinforced plastic sheet (GS), and carbon-reinforced plastic sheet (CS), under low amplitude cyclic lateral loads, in comparison to unreinforced portal frames (UR). The reinforced portal frame, strengthened by FRP laminates, exhibited higher resistance to strength and stiffness strength degradation due to cyclic loading-induced degradation at low drift angles compared to the unreinforced frame affected by heterogeneous timber. The reinforced portal frame, particularly the GFC and GS, exhibited energy dissipation rates 32% and 17% higher than UR, respectively, making them the most effective in vibration damping. FRP laminates mitigated fiber direction cleavage from drift pin holes. The average maximum moment and average yield moment of the reinforced portal frame increased by 18% and 21%, respectively, due to the alleviation of joint failure. Finally, CS significantly affected the maximum moment, while GFC significantly influenced the yield moment. [ABSTRACT FROM AUTHOR]

The joints of cold-formed steel (CFS) portal frames with box sections are primarily formed either through stiffened welded connections or by bolted end plates, which typically involve costly full penetration butt welds. In New Zealand, CFS portal frames with nested tapered box beam (NTBB) sections are popular, and the joints of these portal frames are also formed through a bolted end plate system. In literature, it was found that welds in these joints are prone to cracking in the heat-affected zone (HAZ) under bearing opening moments (tension). Therefore, this paper focuses on proposing an alternative connection system (bolted-side plate) for eaves joints without any weld, aiming to reduce the overall cost of construction and increase construction speed. The performance (strength and stiffness) of these joints is mainly dependent on the geometric details of the bolted-side plate, which is limited in Australia/New Zealand standards (AS/NZ 4600). Herein, a non-linear finite element (FE) model was developed for the NTBB portal frame and validated against the experimental test results from the literature. Firstly, the validated FE model was used to investigate the feasibility of using bolted-side plates for NTBB portal frames and found that the bolted-side plate can increase the ultimate capacity of NTBB portal frame by 9%. A parametric study was then conducted by considering different geometric details of the bolted-side plates under both closing (gravity) and opening (wind uplift) moments. Finally, unified design equations for the moment capacity of bolted-side plates were proposed based on the results of the parametric study, and their accuracy was assessed through reliability analysis. [ABSTRACT FROM AUTHOR]

Article highlights A novel type of loading strut is applied in the cable supported portal frame structure. The screw is rotated in the middle of the strut to elongate the strut, so the strand prestress is applied. The strut is found to be simple to operate and could indirectly tension the steel strand to achieve loading.

Experiments on stainless steel frames were carried out within this research. In total, 5 portal frames made of austenitic stainless steel SHS/RHS were tested. The paper thoroughly describes the performance of the loading tests including the layout of auxiliary elements and measuring devices. The technical drawing of the experiment layout with a description is presented as well as several photos. The load‐bearing capacities of the frames are summarised in a table. The research aims for a global structure behaviour examination with a particular focus on stainless steel structures. Their behaviour is highly influenced by nonlinear material stress‐strain response. Material nonlinearity leads to loss of stiffness, which results in greater deflections. And greater deflections generate greater second‐order effects. Worldwide research show this particularity needs to be taken into consideration when conducting a global analysis of the structure. [ABSTRACT FROM AUTHOR]

The construction industry is a big contributor to greenhouse gas emissions, which has a negative environmental impact. Several studies have highlighted the possibility of using timber to reduce the environmental impact of construction. Most of these studies have focused on residential buildings, but little attention has been devoted to industrial buildings. In this paper, an attempt is made to compare the environmental impact of using timber, steel, and reinforced concrete in industrial buildings using life cycle assessment. The system boundary was set to cradle-to-gate with transportation to construction site due to the limitation of data, and only the quantities of the main structural system are considered. Portal frames with variable spans were designed using the three materials to meet similar load carrying capacity. Reinforced concrete was used in the foundation of all frames. The results of the comparative study show that timber has, by a good margin, better environmental impact than reinforced concrete and steel, due to the carbon stored in the wood. The results also show that reinforced concrete and steel alternatives have similar environmental impacts. The findings of this study agree with the findings of other studies on residential buildings. [ABSTRACT FROM AUTHOR]

Portal frame systems are widely used as coverage system in industrial projects. Selecting the proper portal frame system for a certain project depends on many technical, financial and logistical factors such as estimated cost, construction duration, availability of materials, equipment and skilled labor, besides environmental factors such as recycling and durability. The aim of this research is to create a Decision Support System (DSS) to decide the optimal portal frame system considering all these factors. The proposed (DSS) depends on integrating the Value Engineering (VE) concept with the Analytical Hierarchy Process (AHP) technique to identify the optimum system. The considered systems in this research are conventional portal made of hot rolled section, pre-engineered built-up portal frame, trussed frames and portal Frame truss. The developed (DSS) was tuned for the current Egyptian market conditions in 2019 and successfully verified using four selected projects with different height to span ratio.

In this paper, a piezoelectric energy harvesting application on a portal frame of two-degrees-of-freedom considering a quadratic coupling between the coordinates with two-to-one internal resonance is considered. The piezoelectric material is considered as a linear device using a voltage and a charge mathematical model. The equations of motion of the system were obtained by applying the energy method of Lagrange, and the method of multiple scales is applied to find an analytical approximated solution of the equations of motion. Numerical results showed that the voltage model and a charge model have good agreement in relation to the behavior and amplitudes of displacement of the system. [ABSTRACT FROM AUTHOR]

With the development of society, portal frame has been increasingly used in industrial buildings because of light weight, high degree of industrialization, and high economic efficiency. Some existing portal frames need to be reinforced and improved due to the expansion of production and the functional change. As a safe, reliable, and convenient reinforcement method, the external prestressing reinforcement technology is often used to reinforce the portal frame. In this paper, a new type of assembled anchoring joint was designed to connect the steel strand to the steel beam of a portal frame without damaging the original structure. The static loading test was performed by adjusting length of the strut. And the changes of strain and mid-span deflection were investigated. The Midas Gen FEM simulation was used to investigate stress characteristics of the reinforced portal frame, including strain, bending moment, shear force, etc. The experimental results and simulation results were compared to verify effectiveness of the designed joint. The results indicated the new prestressed anchoring joints had the advantages of simple structure, effectiveness, and force transfer path of the joints was clear. Therefore, the new prestressed anchoring joint can be applied to the external prestressing reinforcement of the portal frame. [ABSTRACT FROM AUTHOR]

Metal magnetic memory (MMM) testing is a nondestructive approach for evaluating the stress concentration and early damage of ferromagnetic components. However, research on the MMM testing of large steel structures has been limited. Thus, this study investigates the suitability of MMM technology for monitoring the damage in steel structures exposed to complex stresses. The normal components of magnetic signals Hp(y) on the beams and columns of a portal frame are obtained through pseudo-static testing. The signal increment ΔHp(y) and its absolute value |ΔHp(y)| under different loads are analyzed. The relationship between the equivalent stress and magnetic signal is investigated through numerical simulation. The results show that the ΔHp(y) curves are similar during the elastic stage but change abruptly during the plastic phase. Moreover, the differences in the magnetic signal directions caused by the varying detection directions cannot be ignored. In the elastic stage, with the increase in the load, |ΔHp(y)| curves initially increase and then decrease. The formation of the ΔHp(y) curve is similar to the distribution of the equivalent stress. The mutation of ΔHp(y) can determine whether a specimen is entering the plastic phase, and can warn against structural failure. The magnetic signal distribution qualitatively reflects the stress distribution. [ABSTRACT FROM AUTHOR]

Portal frame systems are widely used as coverage system in industrial projects. Selecting the proper portal frame system for a certain project depends on many technical, financial and logistical factors such as estimated cost, construction duration, availability of materials, equipment and skilled labor, besides environmental factors such as recycling and durability. The aim of this research is to create a Decision Support System (DSS) to decide the optimal portal frame system considering all these factors. The proposed (DSS) depends on integrating the Value Engineering (VE) concept with the Analytical Hierarchy Process (AHP) technique to identify the optimum system. The considered systems in this research are conventional portal made of hot rolled section, pre-engineered built-up portal frame, trussed frames and portal Frame truss. The developed (DSS) was tuned for the current Egyptian market conditions in 2019 and successfully verified using four selected projects with different height to span ratio. [ABSTRACT FROM AUTHOR]

Effect of soil‐structure interaction on the dynamics of portal frame railway bridges Critical resonance phenomena on railway bridges caused by high‐speed trains lead to large deformations, accelerations and stresses on the structure, which are significantly influenced by the natural frequencies of the structure and only limited by damping. Particularly portal frame structures with short spans are expected to have a strong soil‐structure interaction because they are integrated into the subsoil, which leads to a high geometric damping due to wave propagation in the ground. In the present study the influence of soil‐structure interaction on the dynamics of frame‐type railway bridges is assessed by numerical simulations, based on natural frequencies, natural vibration modes and equivalent damping coefficients. The basis are simple plane finite element (FE) models, which consist of the frame structure and the surrounding soil. From the free vibration response induced by a pulse load in the center of the beam or column, the fundamental frequency in vertical or horizontal direction is determined. The decay of this response is used to identify effective damping. To obtain a more comprehensive insight into the dynamics of these structures, the geometry of the frame model and the soil parameters are varied in a parameter study. [ABSTRACT FROM AUTHOR]

Many offshore jackets have no braces between the top of jacket and the bottom of topsides deck. This can be either due to the installation requirement and/or an effort to reduce wave loads. This kind of jacket bay is a portal frame. For the design of portal frame columns, the current offshore standards point to the unbraced frame alignment chart solution from onshore standards such as the American Institute of Steel Construction (AISC). In this paper, we will show that the AISC alignment chart unbraced frame K-factor solution is conservative for offshore applications, and perhaps too conservative. This is because the traditional alignment chart assumes that the entire structure is a moment frame. In offshore applications, the unbraced frame is almost always combined with braced frames from above and/or below. In this paper, we will derive a K-factor solution that is suitable for a braced/unbraced frame combination. This solution is validated with structural buckling finite element method (FEM) analyses of typical offshore frames. Design implications from using the traditional alignment chart versus current new K-factor solution are also discussed. [ABSTRACT FROM AUTHOR]

In this study, an analytical model is presented to determine the random response of point-driven portal and multi-bay planar frame structures. Coupling effects between bending and longitudinal deformations are taken into account, with the Timoshenko-Ehrenfest beam theory being applied to model the bending deformations. With the excitation taken as band-limited white noise, expressions are derived for the mean square displacements and velocities in terms of the autocorrelation and cross-correlation components. The influence of modal cross-correlations on the overall response is shown to be dependent on the number of bays. For a lightly damped single-bay frame, the natural frequencies are generally well separated and the modal cross-correlations are small. In this situation, the velocity response displays a near symmetric distribution about the center point of the frame. Moreover, narrow zones of intensified response begin emerging as the number of responding modes increases. For frames having two or more bays, the contribution of modal cross-correlations is larger due to the increased occurrence of clusters of natural frequencies. In such cases, modal cross-correlations introduce asymmetry into the overall response distribution of the frame. Additionally, the drive-point velocity of the multi-bay frame can be severely underestimated if modal cross-correlations are ignored. The study also investigates the influence of increased damping on the response characteristics. • An analytical model is developed to analyse the random vibrations of a Timoshenko-Ehrenfest multi-bay planar frame structure. • Expressions for the mean square velocities are derived in terms of the modal autocorrelation and cross correlation components. • The significance of modal cross-correlations increases as the number of bays increases causing dramatic changes in the spatial distribution of the response. • Localized zones of highly intensified response levels are located at symmetric positions on the frame. • Finite element simulations in Ansys® APDL are used to verify all results. [ABSTRACT FROM AUTHOR]

Austenitic stainless steel is an attractive structural material due to its high ductility, appropriate toughness, significant strain hardening and good fire resistance. Also the laser welding technology for fabrication of structural stainless steel profiles has recently become increasingly popular. However, there is still only a limited amount of experimental data on laser-welded stainless steel members. And loading tests of whole structures made of these sections have still not been published. Therefore, loading tests were performed on two austenitic stainless steel frames made of laser-welded I-sections. The frames had pinned columns and were loaded both vertically and horizontally. The objective of the loading tests was to capture the effects of material nonlinearity on the global sway behaviour of the stainless steel frames. In fact, material nonlinearity leads to a gradual loss of stiffness, which results in higher deformations and thus a higher second-order effect. The resulting load-displacement diagrams of the experiment are tabulated, allowing their further use. A numerical model of the studied frames was developed and validated on the basis of the performed experiments. Based on the elastic buckling load factor and the modified elastic buckling load factor, a large influence of material nonlinearity on second-order effect has been demonstrated. • Detailed arrangement of the frame loading tests with load introduction description. • Scheme of measuring devices and auxiliary elements for the loaded frames. • Tabulated load-displacement diagrams suitable for numerical model validation. • Validation of the numerical model based on experiments. • Influence of material nonlinearity on second-order effect. [ABSTRACT FROM AUTHOR]

This paper presents a formulation and solution for the problem of transverse and longitudinal vibration of the portal frame with damping. The dissipation of vibration energy in the model is caused by simultaneous constructional, internal and external damping. The eigenvalues of the system for a selected and variable parameters were calculated. The effect of different type of damping on amplitude decay factor was presented. [ABSTRACT FROM AUTHOR]

The paper presents the results of concept design for modelling, designing and producing long span portal frames and constructing buildings with them. Ordinary portal frames of steel structure are not suitable in many cases for a variety of reasons. They are heavy and very fragile to transport, are not fire resistant, are present special difficulties in use because of possible corrosion and are always not satisfactory architecturally. Wood-steel assemblies such as flitch beams are also complicated because of possible condensed water on metal and fasteners. Constructions using GLULAM and CLT (especially in the last decade) show rising trend. Timber has very many good properties as a building material if we know or remind ourselves of the skills how to handle it. The biggest enemy of wood and the reason for decay is moisture. All structures and finishing materials need very careful and qualified design to avoid collection of water on surfaces and consequent increasing moisture content. This paper describes a method appropriate for the 21st century of how to design portal frames of GLULAM and CLT panels and construct of them without metallic fasteners. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Building service equipment, such as ventilators, air conditioners, and cooling tower are structure-borne sources that are capable of injecting vibration input power to the building structure. The vibration waves propagate through the building elements and can result in audible low frequency noise. This paper proposes the development of an analytical model of the dynamics of a building using a two-dimensional portal frame structure consisting of beam and truss elements. The structural response due to an injected force from a structure-borne source is studied and is compared with a three-dimensional model from the Finite Element Method. It is shown that the vibration pattern from the two-dimensional result follows the pattern of that from the three-dimensional model for vertical vibration. The two-dimensional model can thus be used for a simple modelling to understand the behavior of the building vibration. [ABSTRACT FROM AUTHOR]