Horizontal Stiffeners Research Articles

Analysis of collision performance of anticollision box made of steel–polyurethane sandwich plates

A finite element collision system model was established by using ANSYS/LS-DYNA for a new type of bridge anticollision device with stiffeners made of steel–polyurethane sandwich plates. The model is composed of the anticollision box, the bridge pier, and the ship. In this paper, a numerical dynamic calculation method was used to calculate the impact force of the box and the pier column, the collision depth of the ship, and the energy absorbed by various parts of the system in the most unfavorable frontal collision condition. Then, the influence of the different types and numbers of stiffening ribs on the anticollision performance of the system was analyzed, so as to properly arrange the stiffeners inside the box. The result shows that this kind of anticollision box can effectively protect the pier. When a frontal collision occurs, it can absorb >70% of the impact energy, while the pier only bears <10% of the impact energy. Among the various components of the anticollision box, the outer steel plate of the sandwich plate absorbs the most energy, and the inner steel plate absorbs the second most. The effect of setting the horizontal stiffeners on the impact force, impact depth, and absorption energy of each part of the system is larger than that of the vertical stiffeners, and the effect of improving the rigidity of the anticollision box is also better.

Experimental study on cyclic behavior of stiffened perforated steel shear panels

The use of steel shear walls in buildings has recently received much attention as a system resisting against lateral loads imposed by earthquakes. An opening in the steel shear wall may cause adverse effects on seismic behavior such as a decrease in strength, initial stiffness and energy dissipation capacity of the shear wall. Proper stiffeners can be installed around the openings to overcome these drawbacks. Seven steel shear panels with and without circular openings in the center of the panels with a diameter to width ratio of 20% and 35% with horizontal and vertical stiffeners recommended in the AISC 341-16 Regulation as well as diamond-shaped stiffener were tested under cyclic loading. The seismic parameters of the specimens, including strength, initial stiffness, ductility and energy dissipation, were determined using hysteresis diagrams obtained from experiments. Horizontal and vertical stiffeners improved the seismic performance of the shear panel appropriately. The specimens with diamond-shaped stiffeners showed an appropriate seismic performance before rupture on the plate in the vicinity of the lower corner of stiffener on the welded area during high loading cycles. Accordingly, the use of diamond-shaped stiffeners around the opening is not recommended in structural systems with high ductility demand.

Finite element study of the stiffening effects on torsional capacity of perforated stainless steel slender semi-elliptical hollow section members

A finite element study was carried out to investigate the effects of stiffened perforation on the torsional capacity of perforated slender lean duplex stainless steel semi-elliptical hollow section members. Four different stiffener arrangements viz. horizontal, vertical, square frame and ring, were considered for single circular perforation on flat element of the member. Effects of their geometric parameters i.e. width, thickness, anchorage length etc. on single circular perforated member torsional capacity were studied. Of the geometric parameters investigated, stiffener thickness was observed to provide considerable stiffening effect on the torsional capacity. For members with perforation on the curve element, horizontal and ring stiffeners were considered. Horizontal and vertical stiffener could only provide partial recovery, even at higher stiffener thickness. On the other hand, full recovery of torsional capacity was found to achieve with ring and square frame stiffeners with thickness higher than six times the member thickness.

Failure modes of end-plate connections with outer flange stiffeners: an experimental and numerical study

This paper presents the experimental and numerical results of six full-scale beam-to-column connections with bolted end plates in two groups. The effects of vertical and horizontal stiffeners on the static behaviour of the semi-rigid beam-to-column bolted connections were investigated. In addition, the aim of this research was to analyse the influence of end-plate connections that utilize the IPE profile with stiffeners welded on the behaviour of steel connections, to provide the necessary data for improving Eurocode 3, efficient use of residue IPE profiles and back to the consumption cycle. Furthermore, finite-element and experimental models of semi-rigid vertical and horizontal stiffened bolted connections were tested and compared. The main parameters observed are the evolution of the resistance, the stiffness, the rotation capacity, the ductility of a joint, failure mode and the energy dissipation.

Theoretical and numerical analysis and design of stiffened steel plate shear walls having unequal subpanels

SummaryFollowing the adequate seismic behavior, the steel plate shear walls have gained popularity among the designers worldwide, and many buildings have been designed employing such walls as their lateral load‐carrying system. Despite the fact that the steel shear walls using unstiffened thin plates outnumber the ones benefitting from stiffeners, it should be kept in mind that application of stiffeners prevents the buckling induced by lateral loads such earthquake or wind. On the other hand, the stiffeners enhance the stiffness and shear strength of the plate. Accordingly, this paper deals with an analytical and numerical investigation into the steel plates stiffened by unequaled vertical and horizontal stiffeners. The results obtained for the analyses led to the development of the analytical relations to compute the shear strength, stiffness, and displacement. To validate the proposed relations, analytical outputs were compared with those obtained from the numerical investigation indicating great accuracy of the proposed analytical relations. Moreover, in this paper, the design process of the stiffened steel plate shear walls has been presented based on the interaction between the plate and frame. The results indicate the addition of stiffeners to the steel plate, improves its shear strength by 6 to 15%.

A comparison of structural performance enhancement of horizontally and vertically stiffened tubular steel wind turbine towers

Stiffeners can be utilised to enhance the strength of thin-walled wind turbine towers in engineering practise, thus, structural performance of wind turbine towers by means of different stiffening schemes should be compared to explore the optimal structural enhancement method. In this paper two alternative stiffening methods, employing horizontal or vertical stiffeners, for steel tubular wind turbine towers have been studied. In particular, two groups of three wind turbine towers of 50m, 150m and 250m in height, stiffened by horizontal rings and vertical strips respectively, were analysed by using FEM software of ABAQUS. For each height level tower, the mass of the stiffening rings is equal to that of vertical stiffeners each other. The maximum von Mises stresses and horizontal sways of these towers with vertical stiffeners is compared with the corresponding ring-stiffened towers. A linear buckling analysis is conducted to study the buckling modes and critical buckling loads of the three height levels of tower. The buckling modes and eigenvalues of the 50m, 150m and 250m vertically stiffened towers were also compared with those of the horizontally stiffened towers. The numbers and central angles of the vertical stiffeners are considered as design variables to study the effect of vertical stiffeners on the structural performance of wind turbine towers. Following an extensive parametric study, these strengthening techniques were compared with each other and it is obtained that the use of vertical stiffeners is a more efficient approach to enhance the stability and strength of intermediate and high towers than the use of horizontal rings.

Seismic Performance of Steel Box Bridge Piers with Earthquake‐Resilient Function

A novel steel box bridge pier with replaceable energy dissipation wall plates at the base was proposed. After moderate earthquakes, the damaged energy dissipation wall plates and constraining steel plates on the two sides could be rapidly replaced, while the entire energy‐dissipated column at the base can also be replaced after rare earthquakes. In this way, the seismic capacity of the new type of steel box bridge pier could be restored after earthquakes. For the purpose of discussing the seismic performance of this novel steel box‐shaped bridge pier, the pseudostatic test and numerical simulation were performed. The results showed that the failure of the specimens in the pseudostatic tests occurred predominantly in the energy dissipation zone at the base. After replacing the damaged energy‐dissipated column at the base, the seismic behavior of the proposed steel bridge pier can be recovered rapidly. Axial compression ratio is an important factor influencing the seismic behavior of the novel steel box bridge pier. The strength of the energy dissipation wall plates influences the novel steel box‐shaped bridge pier’s bearing capacity and deformation capacity. Spacing between the horizontal stiffening ribs had little impact on the bearing capacity and deformation capacity of the proposed steel bridge pier. The larger the thickness of the energy dissipation wall plate, the higher the bearing capacity and deformation capacity of the steel box bridge pier. Finally, an empirical equation for the design of this novel steel bridge pier under cyclic loading was proposed.

Stress Analysis of the Circular Pier Anti-collision Box Made of Sandwich Plate with Stiffening Rib

The pier anti-collision box made of steel-polyurethane sandwich plate with stiffening ribs can withstand greater impact force. In order to ascertain the influence of stiffening ribs to anti-collision box, the static equivalent method is adopted to numerically calculate the stress and impact depth of the anti-collision box in the conditions of no stiffening rib and the different forms and amount of stiffening ribs. The results show that it can reduce the stress and deformation of anti-collision box to set vertical or horizontal stiffening rib separately, and the effect of the former is much better than the latter, but the decrease degree of vertical stress is different from horizontal stress. The stiffening rib in the box should not be too many; especially horizontal rib and vertical rib should be considered mainly. The anti-collision box with horizontal rib and vertical rib is mainly to reduce collision deformation; however, it can reduce little than the box with only vertical rib in the aspect of stress.

Experimental evaluation, FEM and condensed stiffness matrices of 2D external welded haunched joints

In recent years, several researchers have been working hard to improve the knowledge with respect to steel joints behaviour. Special effort has been made for obtaining the stiffness of the different components of the joints, with the aim of introducing this stiffness in the component method in accordance with the EC3. Nevertheless, the component method has important limitations and therefore it is necessary to develop new methods for obtaining the stiffness of joints.In the present work, an alternative method of evaluating the stiffness of 2D external welded haunched joints is presented. The authors show the results of 4 tests and their corresponding finite element models. Four different typologies of joints have been tested, in regards to the stiffening of the column web. The four configurations of joints are the following:Joint 1: with three horizontal stiffeners in the column web.Joint 2: with two horizontal stiffeners and an inclined stiffener in the column web.Joint 3: with two horizontal stiffeners in the column web.Joint 4: without web stiffeners.In all cases, the specimens have been subjected to a point load at the end of the beam, and rotations and displacements have been measured.Additionally, finite element models of the joints have been developed, and they have been properly calibrated with the results obtained in the tests. The condensed stiffness matrices of the joints have been extracted, and they have been tested by means of introducing such matrices into the global analysis of 4 frames, and comparing the obtained results with those ones extracted from the corresponding finite element models. The use of the condensed matrix of the joints presents very good results, and takes into account all the interactions between the different degrees of freedom of the joint.

An experimental and numerical investigation of reduced beam section connections with horizontal and vertical web stiffeners

Following the 1994 Northridge earthquake, reduced beam section (RBS) was presented as a novel connection detail in the steel moment-resisting frames. Proposed detail aims to debilitate the beam at a limited interval from the connection so that less moment and force are assigned to the connection. Cutting of the beam flange, especially in the narrow sections such as IPE, leads to an increase in the potential for the web local buckling, beam lateral-torsional buckling, and reduction in the beam strength. The hysteresis curve of IPE profiles, particularly in medium and large sections, is highly declining after the buckling. In this paper, a simple method was presented to amend the efficiency of IPE beams with an arched cutting in the flange, using horizontal and vertical stiffeners of the beam web. The experimental results and those of finite element in IPE beams revealed that the simultaneous application of horizontal and vertical stiffeners of the beam web largely prevented the declining of the beam hysteresis curve and left a full effect on its behavior. Therefore, the use of these types of connections in seismic areas with high relative risks is recommended.

Flexural performances of fiber face-sheets/corrugated core sandwich composite structures reinforced by horizontal stiffeners

The light-weight and high-strength design concept enables sandwich composite structures (SCS) to maximize specific strength and specific energy-absorption (SEA). To this end, a horizontal stiffener is designed to reinforce the flexural performances of corrugated core SCS for the first time. To explore preferable reinforcement parameters, several stiffeners with different thicknesses, positions and numbers are designed and studied. The flexural responses of SCS are predicted by finite element simulation. The predicted load responses, damage and deformation of face-sheets and core are consistent with experimental observations. From predicted results, the SCS undergoes several stages including elastic deformation, fracture of face-sheet, initial and stable deformation of core. The core with a stiffener obviously exhibits higher SEA than that without a stiffener. Complex reinforcement mechanisms and coupling deformation between pure core and stiffener are revealed. It is found that the stiffener improves not only the EA of pure core but also the EA of face-sheets, which explains the coupling EA. Structural parameters including thickness, position and number have great effects on flexural performances of SCS. Notably, the lightest SCS with 0.25 mm thickness improves the SEA about 23.83%. The SCS with three stiffeners presents an increase in EA of 92.33% but followed by a great increase in mass. Design recommendations are finally concluded through comprehensive evaluations.

Shear behavior of steel I-girder with stiffened corrugated web, Part I: Experimental study

The shear stability of steel webs near the support section for long-span composite girders with corrugated steel webs is one of the main control factors for structural safety, which should be paid special attention to. Generally, concrete is poured on the inner side of corrugated steel webs to improve its shear stability, but encased concrete increases the weight of the girder, raises the difficulty of the construction process, and reduces the efficiency of the prestressing application. This paper proposes a new type of stiffened corrugated steel webs at the support area by adopting vertical or/and horizontal stiffeners instead of encased concrete. In order to explore the shear performance of proposed stiffened corrugated steel webs, experimental and numerical investigations were carried out in the present paper and the companion paper [1], respectively. Four steel I-girders with corrugated webs considering different stiffener arrangements were designed and tested under shear loading. The failure modes, shear strength and stiffness, strain distributions were obtained and analyzed in detail. The test results show that all specimens failed due to interactive shear buckling of corrugated steel web; shear buckling occurred between horizontal stiffeners and bottom flange for horizontal stiffened corrugated steel webs, but extended to the entire height for vertical stiffened corrugated steel webs, the stiffeners distorted associated with the deformation of corrugated steel web. Shear strength of corrugated steel webs can be improved by vertical and horizontal stiffeners. The vertical stiffeners do not affect the “accordion effect” of corrugated steel webs, but the horizontal stiffeners increase the axial stiffness of corrugated steel web in local area and resist bending moment together with top and bottom flanges. The shear strain of stiffened corrugated steel web still distributes uniformly along the height of the web. All the experimental results are then employed in the companion paper for the validation of finite element method and the evaluation of existing analytical models for predicting shear strength of un-stiffened and stiffened corrugated steel webs.

Shear behavior of steel I-girder with stiffened corrugated web, Part II: Numerical study

Abstract The shear stability of steel webs near the support section for long-span composite girders with corrugated steel webs is one of the main control factors for structural safety, which should be paid special attention to. Generally, concrete is poured on the inner side of corrugated steel webs to improve its shear stability, but encased concrete increases the weight of the girder, raises the difficulty of the construction process, and reduces the efficiency of the prestressing application. This paper proposes a new type of stiffened corrugated steel webs at the support area by adopting vertical or/and horizontal stiffeners instead of encased concrete. In order to explore the shear performance of proposed stiffened corrugated steel webs, experimental and numerical investigations were carried out in the present paper and the companion paper [1] , respectively. Four steel I-girders with corrugated webs considering different stiffener arrangements were designed and tested under shear loading. The failure modes, shear strength and stiffness, strain distributions were obtained and analyzed in detail. The test results show that all specimens failed due to interactive shear buckling of corrugated steel web; shear buckling occurred between horizontal stiffeners and bottom flange for horizontal stiffened corrugated steel webs, but extended to the entire height for vertical stiffened corrugated steel webs, the stiffeners distorted associated with the deformation of corrugated steel web. Shear strength of corrugated steel webs can be improved by vertical and horizontal stiffeners. The vertical stiffeners do not affect the “accordion effect” of corrugated steel webs, but the horizontal stiffeners increase the axial stiffness of corrugated steel web in local area and resist bending moment together with top and bottom flanges. The shear strain of stiffened corrugated steel web still distributes uniformly along the height of the web. All the experimental results are then employed in the companion paper for the validation of finite element method and the evaluation of existing analytical models for predicting shear strength of un-stiffened and stiffened corrugated steel webs.

Experimental study of beams with stiffened large web openings

The use of beams with isolated openings in the webs is common in steel structures. However, the presence of large openings in the web generates specific mechanical behavior in comparison with that of solid web beams and leads quite often to the reinforcement of the opening by welding stiffeners. An experimental program based on thirteen steel beams with a single rectangular web opening is performed. It aims to evaluate the influence of the openings reinforced or not by stiffeners on the behavior of the beam loaded in shear and bending. The stiffeners are used to increase the resistance of the openings. Different solutions are compared using various positions and lengths of stiffeners in the longitudinal and vertical directions. The comparisons are based on the failure load, the stiffness and the strain distribution. The experimental results and observations show the efficiency and the limits of the different studied solutions of stiffening. It has been observed that long horizontal stiffeners were the best stiffening solution. Furthermore, the use of double or single sided stiffeners showed that in both cases, they improve significantly the ultimate carrying capacity of the beam as long as the anchorage length is sufficient. The results can be used as a basis to develop numerical and analytical models.

Experimental Study on Seismic Behavior of New Steel Box Bridge Piers with Embedded Energy Dissipation Shells

An investigation was conducted to evaluate the seismic behavior of a new type of steel box-section bridge piers with embedded energy dissipation shell plates. In this study, two sets of the new steel box-section bridge piers were designed and pseudo-static tests were carried out on ten steel box bridge piers under constant axial force, with a horizontal cyclic load on top of the piers. The change regularities of the failure mode, the patterns of local buckling, the load–displacement hysteresis curve and its curve skeletons, and the load-strain hysteresis curves of the specimens were analyzed. The rules of horizontal stiffener spacing on embedded shell plates, the axial compression ratio, the embedded shell strength, and the layout of longitudinal ribs in the box-section wallboards were obtained to evaluate their influence on the seismic behavior of the new-type steel piers. The test results indicated that, after installing the embedded shells, the deformation ability of steel box-section bridge piers was enhanced and their ductility was improved. The effects of axial compression ratio and the space of transverse stiffeners in embedded shells on the seismic behavior of the new steel piers were significant. When the space of the horizontal stiffeners on the embedded shells and the axial compression ratio become smaller, the bearing capacity and ultimate displacement capability of the specimens would be greater, the descent segment of the curve skeleton would be more gradual, and the deformability and ductility of the new-type steel piers would be better. The effects of setting longitudinal stiffening ribs and enhanced embedded shell strength on the bearing capacity and ductility of the steel box bridge piers were relatively small. Based on the experimental results, calculation equations were established for stable bearing capacity and maximum deformation of the new-type steel piers, under the constant axial force and horizontal cyclic loading, in order to promote their seismic design.

Experimental study of rigid connection of drilled beam to CFT column with external stiffeners

This research is intended to investigate the behaviour of rigid connection of steel beam to CFT column with external T stiffeners. However, the investigations have shown that the stress concentration in the location of stiffener groove welds to the beam flange and column web causes abrupt fragile failure leading to ductility reduction of the connection. In the current study, beam section is reduced using the method of drilling beam flange so as to diminish the stress concentration and increase the ductility. This method is much easier to fabricate compared to RBS (cutting with CNC machine) and more applicable for existing buildings as well. In this research project two series of analytical models with constant and variable holes are investigated to evaluate the effects of different parameters of drilling on the local behavior of connections. Finite element method using ABAQUS software has been employed for analyses. In another part of this survey, two full scale samples are selected out of the analytical models, and experimentally investigated. According to the obtained results, drilling the beam flange results in decrease in stress concentration in the connection location of stiffener to the beam and column. In addition, it decreases the probability of failure in the expected modes 1 (shear failure of T-shaped horizontal stiffener) and 2 (tension failure of T-shaped vertical stiffener in connection to the column web) and increase the ductility of connection. Moreover, such connections can be used in the intermediate as well as special moment resisting frames.

Experimental and Numerical Analysis of Large-Scale Circular Concrete-Filled Steel Tubular Columns with Various Constructural Measures under High Axial Load Ratios

To investigate the effect of constructional measures (including horizontal and vertical stiffeners, rebar cages, embedded steel tubes, and cavity welded steel plates) under high axial load ratios on the seismic performance of concrete-filled steel tubular (CFST) columns, quasi-static tests for six large-scale CFST columns with various constructional measures are performed. All specimens are subjected to identical axial forces. The failure mode, hysteresis characteristics, bearing capacity, stiffness degradation, ductility, and energy dissipation of specimens are analyzed. The study shows that the horizontal stiffener delays the occurrence and severity of column base buckling, the vertical stiffener improves the bending resistance capacity and initial stiffness of the member, the rebar cage improves the ductility, and the embedded circular steel tube significantly improves the member’s bearing capacity, ductility, and energy dissipation. When an internal circular steel tube and cavity welded steel plate are applied in tandem, the section steel ratio increases by 4.42% and the bearing capacity improves by 42.72%. A finite element model is created to verify test results, and simulation results match the test results well.

Topology optimization of a novel fuselage structure in the conceptual design phase

PurposeIn recent years, innovative aircraft designs have been investigated by researchers to address the environmental and economic issues for the purpose of green aviation. To keep air transport competitive and safe, it is necessary to maximize design efficiencies of the aircrafts in terms of weight and cost. The purpose of this paper is to focus on the research which has led to the development of a novel lattice fuselage design of a forward-swept wing aircraft in the conceptual phase by topology optimization technique.Design/methodology/approachIn this paper, the fuselage structure is modelled with two different types of elements – 1D beam and 2D shell – for the validation purpose. Then, the finite element analysis coupled with topology optimization is performed to determine the structural layouts indicating the efficient distributed reinforcements. Following that, the optimal fuselage designs are obtained by comparison of the results of 1D and 2D models.FindingsThe topological results reveal the need for horizontal stiffeners to be concentrated near the upper and lower extremities of the fuselage cross section and a lattice pattern of criss-cross stiffeners should be well-placed along the sides of the fuselage and near the regions of window locations. The slight influence of windows on the optimal reinforcement layout is observed. To form clear criss-cross stiffeners, modelling the fuselage with 1D beam elements is suggested, whereas the less computational time is required for the optimization of the fuselage modelled using 2D shell elements.Originality/valueThe authors propose a novel lattice fuselage design in use of topology optimization technique as a powerful design tool. Two types of structural elements are examined to obtain the clear reinforcement detailing, which is also in agreement with the design of the DLR (German Aerospace Center) demonstrator. The optimal lattice layout of the stiffeners is distinctive to the conventional semi-monocoque fuselage design and this definitely provides valuable insights into the more efficient utilization of composite materials for novel aircraft designs.

Design of horizontal stiffeners for stiffened steel plate walls in compression

The compressive stress is remarkable in design of steel plate walls (SPWs) for high-rise buildings. Stiffeners are required to avoid the compressive buckling in service limit state. This paper first studies the elastic stability of horizontally stiffened steel plate walls (S-SPWs) in compression. The effect of stiffener torsional stiffness on elastic buckling stress is presented. Then the study extends to the elastic-plastic stability of imperfect S-SPWs. Comparing the elastic and elastic-plastic behaviour, the increased ultimate compressive strength is smaller than the increased elastic buckling stress due to the column type buckling behaviour of wide plate. Stiffener torsional stiffness can also increase the ultimate capacity. Formulas to predict the stiffness requirement on horizontal stiffeners are proposed based on the philosophy similar to the stiffness requirement on brace for columns in compression. With some minor modifications, the proposed formulas show good accuracy compared with numerical results.

Cyclic performance of cross restrained steel plate shear walls with transverse braces

This paper presents an investigation on the cyclic performance of cross restrained steel plate shear walls (SPSWs) with transverse braces. Transverse braces connecting to two columns are proposed to replace horizontal cross stiffeners on the infill steel plates. Effects of transverse braces on the performance of SPSWs are estimated through an experimental study and a finite element analysis. Two 1/3-scale two-story single-bay SPSW specimens, including one unstiffened SPSW and one cross restrained SPSW with transverse braces, are first tested under the quasi-static cyclic loading. Subsequently, finite element models for SPSWs are developed and verified by the test results. Cyclic performance of SPSW structures with different restrains for the infill steel plates are compared in terms of failure mode, loading capacity, energy dissipation capacity and stiffness degradation. Emphasis is given on the stress development and out-of-plane deformation of infill steel plates. The results show that use of transverse braces as the substitute of horizontal stiffeners enhances the loading capacity, energy dissipation capacity and ductility of SPSW structure. It is also effective to homogenize stress distribution and to restrain the out-of-plane deformation of infill steel plates, which finally decreases the additional bending moments applied to the columns. Compared with the unstiffened SPSWs, the maximum inward flexural deformation of columns in the cross restrained SPSWs with transverse braces is reduced by about 40.0%. It has demonstrated that the proposed cross restrainers combined with transverse braces are effective in improving the cyclic performance of SPSWs.