Design Of Portal Frames Research Articles

Comparative analysis approaches for steel portal frame design in industrial buildings

Purpose The purpose of this study is to further investigate the potential benefits brought about by the development of modern technology in the steel construction industry. Specifically, the study focuses on the optimization of tapered members for pre-engineered steel structures, aligning with Eurocode 3 standards. By emphasizing the effectiveness of material utilization in construction, this research aims to enhance the structural performance and safety of buildings. Moreover, it recognizes the pivotal role played by such advancements in promoting economic growth through the reduction of material waste, optimization of cost-efficiency and support for sustainable construction practices. Design/methodology/approach Structural performance at initial analysis and final analysis of the selected critical frame were carried out using Dlubal RSTAB 8.18. The structural frame stability and sway imperfections were checked based on MS EN1993-1-1:2005 (EC3). To assess the structural stability of the portal frame using MS EN 1993-1-1:2005 (EC3), cross-sectional resistance and member buckling resistance were verified based on Clause 6.2.4 – Compression, Clause 6.2.5 – Bending Moment, Clause 6.2.6 – Shear, Clause 6.2.8 – Bending and Shear, Clause 6.2.9 – Bending and Axial Force and Clause 6.3.4 – General Method for Lateral and Lateral Torsional Buckling of Structural Components. Findings In this study, the cross sections of the web-tapered rafter and column were classified under Class 4. These involved the consideration of elastic shear resistance and effective area on the critical steel sections. The application of the General Method on the verification of the resistance to lateral and lateral torsional buckling for structural components required the extraction of some parameters using structural analysis software. From the results, there was only 5.90% of mass difference compared with the previous case study. Originality/value By classifying the web-tapered cross sections of the rafter and column under Class 4, the study accounts for important factors such as elastic shear resistance and effective area on critical steel sections.

Numerical Modelling of Single‐span Portal Frames

AbstractPortal frames are a common form of structural system used to create efficient wide‐span enclosures. Over the past few decades, the design of portal frames has evolved in the direction of longer, lighter and taller structures, while cladding systems have become more substantial. Although this allows larger spaces, it can also result in heightened structural challenges, such as increased frame flexibility, a greater portion of the load being borne by the cladding and greater differential thermal movement. This has led to general concerns related to the effects of scale. To investigate these concerns, with a particular focus on the contribution of the cladding to the global strength and stiffness of the structure (also referred to as the stressed skin effect), and the resulting demands placed on secondary components, this study presents the development of a numerical model for the accurate representation of the structural response of full single‐span portal frames. The model is validated herein in two ways; (i) through validation of each individual frame component against relevant physical experiments, and (ii) through validation of the full model against full scale frame tests. Finally, a preliminary parametric investigation is presented.

Design Optimization of RC Frames using Particle Swarm Optimization Technique

Design of portal frames were carried out for different grades of steel with a well-defined objective function framed in order to minimize the cost of construction of reinfofced concrete portal frames for different spans using direct stiffness method. The design variables that are considered are the volume of steel used for reinforcement, volume of concrete for sectional members that is got from the width, depth of the required section. The constrains for the design of beams were done according to the Indian codal provisions. Separate coding was written in MATLAB to determine the optimal design of beams. The optimal design results obtained had a minimum usage of concrete and steel when compared to the normal one with a variation of 5% for the beam and 3% for the column. The reduction in cost is due to reduction in the cross-section as a result of the optimization technique. Nearly 100 designed samples using different cross-section areas were carried out and the final conclusions were derived and found to provide optimal values to certain extent which would be useful for the design engineers.

Assessment of Semi-Rigidity of Dowel Type Knee Joint between Timber Elements

Creation of a moment resisting connection between column and beam elements in knee joints is the core problem in portal frame design of structural timber. The main performance requirement for rigid joints is to avoid any rotation between the members connected. Withstanding this condition by using glued finger joints, the knee joint can be classified as a rigid one and the bending moment produced by external loads can be transferred safely. Nevertheless, the solution of knee joints with mechanical fasteners is an effective way to overcome transportation limitations. Knee joints with mechanical fasteners exhibit a relevant semi-rigidity when some rotational movement develops between beam and column members connected due to the embedment of the fasteners in the wood and their bending deformation. The aim of the current study is to examine the rotational stiffness of semi-rigid joints. The rotational stiffness of the connection was determined in terms of design moment capacity to radians of rotation. The calculation methods for design of semi-rigid structural timber connections developed during recent years were used for the calculation of the bearing capacity. L-shape connection models of softwood lumber assembled by normal strength dowels were tested under a stepwise static load. The analysis of the test data testifies that connections with dowels located around a single circle demonstrate an intensive development of rotational movement. For design purposes the semi-rigidity of these connections may be characterised by the rotational stiffness value Kφ = 10 Md/rad. Moment resisting joints of dowels located in double circles behave almost as rigid, and their stiffness may be characterised by rotational stiffness value Kφ = 65 Md/rad. It is found from comparison of embedment deformations that dowels located around external circle transfer more than four times bigger reactive shear force than dowels around inner circle.

Ontology-Based Representation of Design Decision Hierarchies

The design of complex engineering systems requires that the problem is decomposed into subproblems of manageable size. From the perspective of decision-based design (DBD), typically this results in a set of hierarchical decisions. It is critically important for computational frameworks for engineering system design to be able to capture and document this hierarchical decision-making knowledge for reuse. Ontology is a formal knowledge modeling scheme that provides a means to structure engineering knowledge in a retrievable, computer-interpretable, and reusable manner. In our earlier work, we have created ontologies to represent individual design decisions (selection and compromise). Here, we extend the selection and compromise decision ontologies to an ontology for hierarchical decisions. This can be used to represent workflows with multiple decisions coupling together. The core of the proposed ontology includes the coupled decision support problem (DSP) construct, and two key classes, namely, Process that represents the basic hierarchy building blocks wherein the DSPs are embedded, and Interface to represent the DSP information flows that link different Processes to a hierarchy. The efficacy of the ontology is demonstrated using a portal frame design example. Advantages of this ontology are that it is decomposable and flexible enough to accommodate the dynamic evolution of a process along the design timeline.

Dual-steel portal frame design to withstand a fire exposure of 45 minutes

This paper presents the design of industrial portal frames with plain carbon steel (S275) and micro-alloyed Fire Resistant (FR) steel, coated with intumescent paint as fire protection for the structure. The coating improves the overall heat resistance of the metallic structure. The portal frames with different spans were calculated to observe their fire behavior. The structure was dimensioned by estimating the stresses to which each particular structural section was subjected and by selecting the most economic combination. The process was then repeated with the new dimensions to reach an optimal structural design. The key variables analyzed in this study are: five different spans, seven intumescent paint thicknesses, and eleven price ratios between the FR and the S275 steels, considering a fire exposure time of 45 minutes in all of the scenarios under study. The main conclusion was that the use of FR combined with S275 and the intumescent paint system was the most profitable option. In many cases, the better performance of this combination offered the most technically feasible option for the design of portal frame steel structures.

Stressed Skin Effect on the Elastic Buckling of Pitched Roof Portal Frames

The paper presents the influence of the diaphragm effect on the behavior of pitched roof portal frames, having Z purlins and corrugated sheeting as cladding. The paper highlights the stabilizing effect in terms of load multiplication factor—αcr on portal frames by taking into account the lateral constraints ensured by a typical cladding system—Z purlins with one layer of sheeting panels. The purpose of the paper is to make a comparison between the simplified design model of a portal frame, where the supports simulating the purlins are considered with infinite axial rigidity and a portal frame design model where the calculated stiffness of the cladding for the lateral supports is introduced manually. The obtained results highlight the importance of the diaphragm effect and refer to the variation of the load multiplication factor αcr for main structural elements. The fundamental objective of this research is to develop a relatively fast checking procedure, easy to use in the current design process, by including the diaphragm stiffness in the analysis of the pitched roof portal frames. To evaluate the benefits of stressed skin action, simplified and complex modeling techniques have been developed. Obtained results emphasize the impact of stressed skin action on structural performance of pitched roof portal frames.

Analysis of Dynamic Characteristics of Portal Frame with Variable Section

Combined with a portal frame design, by the use of finite element software ANSYS, the finite element model of single specimens of portal rigid frame and the overall portal rigid frame building are established. portal rigid frame’s beam and column is variable cross section. Through the modal analysis, comparative analysis of the frequency and vibration type of the radiolabeling specimens and finite element model of the whole, for the further development of variable cross-section portal rigid frame of earthquake and wind vibration analysis lay the foundation.

The Comparison of Portal Frame Design by Penalty Function Optimization and Traditional Method

The comparison of portal frame design by penalty function optimization and traditional method aim at 30m span portal frame with tapered members was made. It was found that the essence of optimization design was to research the reasonable distributing of sections, through the interaction between capacity and key section parameters the optimization design were realized. Now the idea of green and less energy is fashionable, then optimization design is very significant in practical engineering. According to engineering statistics the optimization design can reduce 15%~30% of material quantity. In this article the selection of parameters during optimization design was expounded.

The Comparison of Portal Frame Design by Penalty Function Optimization and Traditional Method

The comparison of portal frame design by penalty function optimization and traditional method aim at 30m span portal frame with tapered members was made. It was found that the essence of optimization design was to research the reasonable distributing of sections, through the interaction between capacity and key section parameters the optimization design were realized. Now the idea of green and less energy is fashionable, then optimization design is very significant in practical engineering. According to engineering statistics the optimization design can reduce 15%~30% of material quantity. In this article the selection of parameters during optimization design was expounded.

Structural assessment of minor axis steel joints using photoelasticity and finite elements

Traditionally, the steel portal frame design assumes that beam-to-column joints are rigid or pinned. However, it is largely recognized that the great majority of joints do not exhibit such idealized behaviour transmitting bending moments with non-negligible rotations. These joints are called semi-rigid and their design should be performed according to their actual structural behaviour. When minor axis beam-to-column joints are considered, the adopted design process generally assumes a flexible response although this is not true for the great majority of structural joints. Minor axis joints present a distinct behaviour that differentiates them from major axis joints. In fact, the absence of transverse stiffeners implies that the column web must resist all the tensile and compressive forces arising from the beam flanges in bending, akin to a plate supported on its vertical sides. In order to evaluate this component’s behaviour, this paper presents a comparison between results obtained from a finite element model analysis and experiments. The experimental programme was based on the use of reflection photoelasticity techniques to determine the column web stress and strain distribution present in minor axis semi-rigid joints. This technique, although widely used for determining stress and strain distributions in other applications, was first used in this investigation to determine the semi-rigid joints structural response.

Design optimization of steel portal frames

A computer code written by the authors at the University of Coruña and aimed to produce optimum design of portal frames is presented in this paper. The PADO software provides the least weight design for the most common types of planar frames. The code incorporates the complete set of constraints considered in the Spanish code of practice for steel structures. The software has a graphical interface to provide a user-friendly communication. Some application examples are presented in this paper to make clear the capabilities of PADO code.

Improvements to portal frame design using stressed skin action of sandwich panels

When used as roof and wall claddings, sandwich panels can offer many advantages such as better appearance, thermal insulation and strength. They can also develop a significant stressed skin action that can be used to resist wind loads on portal frame buildings. However, this beneficial effect is generally ignored by Australian designers since roof claddings are crest-fixed. To utilise this effect, a suitable design methodology and associated strength parameters must be developed. This paper investigates the possibility of combining three dimensional computer modelling with the results of a detailed experimental program to produce economical and safe portal frame buildings with crest-fixed sandwich panels. A design method is presented along with guidelines for three dimensional computer modelling.

Survey of deflection limits for portal frames in Australia

The design of portal frames can often be governed by deflection limits and it is therefore important that any deflection limits be realistic. Most current codes of practice do not provide mandatory deflection limits, preferring instead to leave them to the judgement of the designer. The authors, through the Australian Institute of Steel Construction, have recently conducted a survey among practising engineers of deflection limits for industrial buildings. Although the results of the survey have been reported, 1 it is thought that the results will be of interest to international readers, and so the findings are presented in this paper. The results of the survey show some diversity of opinion among designers. Nevertheless, recommendations for deflection limits are made.

Plastic design of steel portal frames using a microcomputer

The greatest benefit to structural designers from the use of microcomputers will probably come from the time savings which can be obtained in the design processes which would previously have been performed manually. One example of this is industrial portal frame design using plastic theory. A program has been developed which aids the designer in this task. All of the fairly simple but very time-consuming calculations involved are done rapidly by the machine, while leaving complete control with the designer. The design process is similar in sequence and appearance to its manual equivalent and can therefore be performed with the minimum of learning by the engineer. The time savings are, nevertheless, very considerable. Whilst greater speed can be achieved in some cases by allowing automatic optimisation, the combination of computer and experienced designer working together is extremely efficient, and is the quicker when factors not easily incorporated into the optimisation process become important.

On Foulkes Mechanism in Portal Frame Design for Alternative Loads

Minimum-weight design of a portal frame for alternative loadings is discussed. A linear programming formulation is used. The concept of Foulkes mechanism as the necessary and sufficient condition for optimum is generalized for this class of problems.