Steel Gusset Plates Research Articles

Instability of steel gusset plates in compression

As a result of the structural failure of the I-35W Bridge in Minneapolis in 2007, the Federal Highway Administration (FHWA) issued guidelines for the load rating of gusset plates and recommended that the capacity of these plates on non-redundant steel truss bridges be verified. The purpose of this study is to examine the buckling behaviour of steel gusset plates in greater detail, accounting for parameters that were not explicitly included in the guidelines, such as initial deformations of the gusset plate, stiffness of the framing members, load distribution from the framing members to the plate and load eccentricity. For this purpose, a finite-element model of a gusset plate was developed and verified against experimental measurements. Results show that, for in-plane compressive loads with no moment and no eccentricity, the FHWA guidelines for load rating are conservative and safe for initial out-of-plane deformations up to one plate thickness.

Numerical study of stainless steel gusset plate connections

Despite fundamental differences between the mechanical behaviour of stainless steel and carbon steel, design provisions for stainless steel connections in current standards essentially follow the rules for carbon steel with some limited modifications. For the common case of angle section members connected by one leg to a gusset plate, the design rules for net section capacity from EN 1993-1-8 for carbon steel have been adopted for stainless steel connections in EN 1993-1-4 and the SCI/Euro Inox Design Manual without any modification. In this paper, an investigation into net section rupture of stainless steel single angles connected by one leg to a gusset plate with a single row of bolts is investigated. Numerical models for austenitic stainless steel have been developed and validated against existing test results. These models are then used to perform parametric studies. Finally, based on the obtained results, revised design equations for determining the net section capacity of stainless steel angles are proposed and their reliability demonstrated by means of statistical analysis.

Experimental study of low yield point steel gusset plate connections

Concentrically braced frames have been used widely in the seismic-resistant design of steel building structures. During earthquake excitation, the braces of the concentrically braced frame are subjected to recursive tensile and compressive forces. The compressive strength of the brace is usually less than its tensile strength because of the buckling of the brace, and this may degenerate the seismic resistance capacity of the braced frame. In this reported research, an alternative design concept that adopts the weak gusset plate-strong brace is examined. The gusset plate is designed to yield prior to the buckling of the brace. Low yield point (LYP) steel is selected for the gusset plate. The LYP steel possesses low yield strength and high elongation capacity. A series of experimental studies was carried out to examine the LYP steel gusset plates under cyclic loads. It is found that adding slot-type restrainers (STR) to the LYP steel gusset plate greatly enhances the seismic resistance of the gusset plate. The proposed LYP steel gusset plate with an STR is able to provide similar strengths under tensile and compressive loads. The energy dissipation capacity of the gusset plate is also increased substantially. Based on this study, suggestions are made for the design of LYP gusset plates.

Investigation of Cold Rolled Steel Gusset Plates under Cycling Load When Varying the Unsupported Length–Thickness Ratio

AbstractThis article is an investigation of buckling of cold-rolled gusset plates subjected to cyclic axial load for various unsupported length-to-thickness ratios (L/e). A total of twelve specimens were tested and their respective time-to-failure (in terms of the number of cycles) were measured. Using the data obtained, the dependence of time-to-failure on the ratio L/e was investigated. The dependence of time-to-failure on the L/e ratio is important and can be rationalized via an equation through analyses and test results. Such an equation will especially be helpful in design and can be used, along with other requirements, for the selection of an appropriate size for a gusset plate. The paper draws conclusions based on the limited test results and discusses the importance of L/e and cyclic loads in design of gusset plates in bridges.

Experimental Investigation on Slip-In Connection for Cold-Formed Steel Double Channel Sections

The application of cold-formed steel in light steel framing design can become a popular choice of Industrialized Building System, by moving huge amount of construction work to the factory and leaving the construction site cleaner and safer. However the joints behaviour for primary structures, particularly the partial strength semi-rigid beam-to-column connection has not been studied in depth. This paper presents the isolated joint test on slip-in connection using 6 mm hot-rolled steel gusset plate. Two cold-formed lipped channel sections were placed back-to-back to form beam and column members. Three specimens with the depth of beam ranging from 150 mm to 250 mm were tested. From the experimental results, it is observed that the ratio of moment resistance of joint to the moment resistance of the connected beam increases in the range of 0.46 to 0.70. The rotational capacities of the joints exceed 30 mRad. The rotational stiffness achieves 511 kNm/rad to 1671 kNm/rad. It is concluded that the proposed connections could be classified as partial strength connection.

Nonlinear finite element analysis of CFT-to-bracing connections subjected to axial compressive forces

The Abaqus finite element program together with nonlinear material constitutive models for concrete-filled tube (CFT) and steel gusset plate is used to analyze the behaviors of the gusset plate type CFT-to-Bracing connections subjected to axial compressive forces. It is found that the failure of CFT-to-Bracing connections occurs below the connecting area. Local bulged shapes of the steel tube might take place in the areas close to the gusset plate and the fixed end under the failure stage. The ultimate strengths of the CFT columns slightly increase with the increasing of the load ratio and the thickness of the gusset plate. The introduction of the cutouts on the gusset plates slightly increases the ultimate strength of the CFT column and causes more local bulged shapes on the steel tubes below the connection area under the failure stage.

A timber cantilevered view walkway in Vitoria, Spain

This paper describes the structural project for a timber cantilevered walkway truss recently built in Vitoria-Gasteiz, Spain, as a part of a nature education centre. This study analyses the structural aspects of this walkway, designed as a cantilevered truss with a span of 19·2 m and a backspan of around 10 m between the two lines of columns of the structure. The structure has been built mainly using laminated veneered lumber (LVL) for the struts and chords and steel bars for the diagonals. The critical sections, at the two lines of columns, have been built using frames made of steel and reinforced concrete. Due to the critical tension force that appears at the foundation, permanent anchors were used for transferring this force to the ground. Wind loading has also led to anchoring the two pairs of concrete columns. The joints in the timber trusses were designed using dowels with steel gusset plates and toothed plates. The singular structure of this construction makes it similar in size to the German Pavilion recently built in Hannover, which is considered to be the biggest timber cantilevered roof in Europe. Although the structural problem solved in this construction is not exactly the same (the snow load is not critical whereas in this example the live load is the key factor), some important general remarks can be learnt from this case study.

Evolutionary structural optimization of steel gusset plates

Evolutionary structural optimization is applied to determine the optimum shape of steel gusset plates subjected to axial forces. A number of different gusset plates used in various types of connections is considered for this purpose. The evolutionary structural optimization approach is employed to find the optimum shapes of a gusset plate used in these connections. The first example considers a gusset plate having two holes which are utilized in the connection of double angle carrying a tensile force. Within this example the effect of certain parameters in the evolutionary structural optimization process such as material removal ratio, mesh size and modeling of holes on the final shape is investigated. The gusset plates having three, four and five holes are also designed for optimal shape. Furthermore design examples include two rows of multiple holes as well as staggered holes and connections with multiple members. The final shapes obtained in the single member bolted connections are generally similar to those used in practice. However, they are lighter. Those shapes obtained for the multiple member connections and welded double angle connections are unpredictable. Although the shapes obtained in all the examples are lighter than the ones used in practice, they might be more expensive to produce. It is shown that the evolutionary structural optimization method has a potential in determining the optimum shape of gusset plates.

Gusset plate connections under monotonic and cyclic loading

A numerical investigation of the monotonic and cyclic behaviour of steel gusset plate connections is conducted using a nonlinear finite element model. Successive versions of the model, which include the effects of framing member stiffness, nonlinear material behaviour, initial imperfections, and bolt slip, are formulated and validated by comparison with test results. A parametric study is then conducted to examine the effects of the load sequence and the interaction between the gusset plate and the brace member under cyclic loading. This investigation demonstrates that the cyclic behaviour of gusset plate connections can be modelled accurately using a simplified finite element model. Gusset plate – brace member subassemblies, wherein the gusset plate is designed as the weak element in compression rather than the brace member, are shown to have stable behaviour under cyclic loading and better energy absorption characteristics than similar subassemblies with the brace member designed as the weak element in compression.Key words: steel, connections, gusset plates, cyclic loading, concentric bracing, buckling.

The Effects of Stress Singularity on Welded Gusset Plates Loaded in Tension

In spite of the extensive study of gusset plates under monotonic tension loading over the years, the stress singularity (unbounded stress) effect caused by the boundary condition at the corners of the fixed edges of the plates has seldom been considered by researchers and structural design engineers. Since the development of the tensioned stress concentration resulting in fracturing of gusset plates can be expedited by the stress singularity effect, the effects of stress singularity on steel gusset plates should not be neglected. The stress concentration of welded gusset plates caused by the stress singularity effect is investigated using the finite element method in this study. Numerical investigations of the interaction between the stress singularity effect on the gusset plates and the Whitmore effective section of the gusset plates are also conducted. Based on the investigation results, optimal configurations and modified Whitmore effective widths for gusset plates loaded in tension are presented and discussed. Later in this paper a practical design example is given which considers both the optimal configuration and the modified Whitmore effective section of the gusset plate.

Limit analysis of gusset plates in steel single-member welded connections

On the basis of the assumption of perfect plasticity, upper and lower bounds for the yield strength of a steel gusset plate with a single tie rod welded to the gusset plate have been derived. The analysis is kept as simple as possible and in accordance with generally accepted theories. The yield criterion of von Mises has been applied. For the lower bound in particular, a simple analytical expression is found, which is in fair agreement with tests.

Fully Overlapping Nailed Joints with Steel Gussets in Timber Structures

This paper presents an experimental investigation into the translational behavior of timber joints formed with steel gusset plates and connected by fully overlapping nails. Over 1,200 joints have been tested and their load-displacement characteristics studied, incorporating all of the factors that have influence on the strength and stiffness behavior of the joints. Using an empirical approach, a load-displacement model enveloping all displacement states up to failure is developed. The model incorporating characteristic properties is compared with the behavior of equivalent joints designed in accordance with Eurocode 5 rules. The comparison gives variable results and raises questions over the validity of the function being proposed in the code to allow for the effect of nail row spacing on joint strength.

Behavior of thin gusset plates in compression

The use of cold-formed steel members for roof and floor truss applications is gaining widespread acceptance in the United States. However, there is little technical information regarding the behavior and design of thin gusset plates in compression. Thus, a study was initiated at the University of Missouri-Rolla aimed at investigating the behavior of thin steel gusset plates in compression. Key parameters that were considered in the experimental study were the thickness of the gusset plate, the width and length of the gusset plates, the fastener location, and the fastener pattern. Both a plate model and a column model were investigated for computing the strength of a thin plate in compression. Based on the findings of this study, design recommendations are proposed.

Brace-Beam-Column Connections for Concentrically Braced Frames with Concrete Filled Tube Columns

Composite concrete filled tube (CFT) columns are advantageous for use in seismic resistant braced frame construction since these CFT columns are relatively inexpensive, stiff and strong. However, to utilize the composite behavior of the columns, the vertical component of brace force must be transferred through the beam-brace-column connection and distributed to both the concrete and steel in the column. Beam-brace-column connection details are critical for development of this composite action. This paper describes analytical and experimental studies carried out to better understand the transfer and distribution of force to the joint. A range of beam-brace-column gusset plate connections were considered. It is shown that the majority of force transferred from the steel into the concrete occurs by bearing rather than by friction. Steel gusset plates with horizontal ribs, or gusset plates with holes, allow more force transfer and have more composite action than plain gusset plates. Slip deformations between the steel and concrete are likely to be too small to mobilize the strength of shear studs in these connections.

Analytical investigation and the design of the compressive strength of steel gusset plate connections

A parametric study of the inelastic compressive behaviour and strength of gusset plate connections is presented in this paper. The study is performed by the commercial finite element program ABAQUS. Based on the parametric study, general design guidelines are proposed. To increase the buckling strength of gusset plate connections efficiently and improve the energy absorption behaviour of the connections under cyclic loading, adding the centerline stiffener along the splice member as close to the beam and column boundaries as possible and/or adding free edge stiffeners are recommended. In addition, welded connection between the splice member and the gusset plate is recommended. The splice member with higher bending rigidity such as tee-sections and channel sections should always be used. Shaping the gusset plate according to 30° load dispersion angle may be recommended to reduce the size of the connection between the gusset plate and the beam and column boundaries provided that the splice member is sufficiently extended beyond the bending line. Finally, a design method accompanied by some design charts for rectangular type gusset plates subject to compression is proposed based on an inelastic plate buckling equation.

Failure In-the-Row Model for Bolted Timber Connections

Forces in heavy timber members are often transferred at connections into steel gusset plates via laterally loaded bolts, which are arranged in rows parallel to member axes. Elastic analysis predicts an unequal sharing for force between bolts, with the first or last bolt within a transferring the highest fraction of the member force. The capacity of a connection is taken to be inversely proportional to the force carried by the most heavily loaded bolt. Experiments confirm that there is a reduced effective capacity per bolt with any increase in the number that are placed in a row. This so-called row effect on strength, however, is often much less stringent than elastic analysis suggests. The discrepancy is because individual bolts within a exhibit some ductility in their response, prior to global failure of a connection. Global failure of a connection can appear to be either brittle or ductile, depending upon designer-selected parameters such as bolt slenderness, number of bolts, and bolt spacing. It is demonstrated here that, by allowing for a limited amount of nonlinear deformation at bolts, accurate predictions can be made of the effect on the strength of multiple-bolt connections. A hybrid elastoplastic analysis reliably predicts the capacity for a of bolts and whether the global failure at a connection will appear to be brittle or ductile.

An analysis of the cyclic behaviour of steel gusset plate connections

An analysis of the cyclic behaviour of steel gusset plate connections

Impact energy absorbing effect by the buckling of impact limiter's case of radioactive material transport cask

The energy-absorbing characteristic of impact limiters affects the cask design so significantly that it should be evaluated as accurate as possible. The objective of this study is to find the influence of the impact limiter's steel case and gusset plates which enclose the shock absorbing cellular material on the impact energy absorption. The influence of impact limiter's steel case and gusset plate stiffeners on the impact energy absorption behavior under horizontal drop impact was evaluated for a radioactive isotope transport cask. Though the impact limiters mitigate the impact damage of the cask, the impact limiter's steel case and gusset plate stiffeners increase the impact force so significantly that should be designed as soft as possible. The impact analysis without considering impact limiter's steel case and gusset plates stiffener gives non-conservative results, so the stiffness of the steel case and gusset plates should be considered in impact analysis.

Fire performance of gusset connections in glue‐laminated timber

AbstractThis paper describes a comprehensive experimental investigation of the fire performance of nailed gusset connections between large glue‐laminated timber members. Both plywood and steel gusset plates were investigated with a range of loaded and unloaded test methods. The principal conclusions are that unprotected gussets have poor fire performance, but that a layer of solid wood or gypsum plasterboard will provide at least one hour of fire protection to typical joints.

Methods for the limit state design of triangular steel gusset plates

This paper compares the design methods of Salmon et al. [2], the draft British Steel Code[3] and the author, with 15 experimental results by Salmon et al.[2] and 50 experimental results by the author. The draft British Steel Code[3] method is shown to be based on the wrong assumptions, is unsafe and inaccurate. The Salmon et al.[2] method based on the correct mode of failure is conservative and not very accurate. The ratio of u experimental/P u theory = 1.92 with a coefficient of variation of 0.64 for 22 experimental results for non slender gussets. Other experimental results for slender gussets are compared graphically. A method developed by the author is less conservative and more accurate. The ratio of P u experiment/P u theory = 1.45 with a coefficient of variation of 0.14 for 22 experimental results for non-slender gussets. Other experimental results for slender gussets are compared graphically. An alternative approximate method by the author for gussets where the slenderness ratio of the free edge is less than 185 is shown to be of comparable accuracy. The gusset plate aspect ratio H/L required to produce optimum weight design is shown to be approximately one.