Truss Connections Research Articles

Structural Behaviour of Precast Lightweight Foamed Concrete Sandwich Panel (PLFP) with Double Shear Truss Connectors under Axial Load: Preliminary Result

This report provides experimental data on the development of PLFP for building construction. An innovative concept was used in the design of this system and the use of lightweight foamed concrete was discussed. Preliminary result of PLFP with double shear truss connectors was analysed and presented. PLFP was tested to determine its ultimate load carrying capacity under axial loading. Ultimate load carrying capacity, load deflection profile, surface strains and crack pattern were recorded and analysed. Test results were compared with calculated values based on classical formulas that developed by previous researchers and experimental data from previous researchers on its compositeness in between wythes. Results shown that PLFP with double shear truss connectors achieved higher compositeness in between wythes and have adequate ultimate load carrying capacity.

Development of Precast Lightweight Foamed Concrete Sandwich Panel (PLFP) with Double Shear Truss Connector: An Overview

Urbanization in many cities needs to adopt modern and innovative techniques in the construction industry to balance the supply and demand in housing issues. To address the issue, there is a need to look for alternative solutions and provide affordable quality housing. Therefore, innovative construction method such as Industrialized Building System (IBS) needs to be adopted to move away from conventional building construction technique in order to meet the demand. Precast Sandwich panel is one of the alternative IBS that could meet and fulfil this target. Previous research had shown that this panel had a potential to provide possible solution to housing problems especially in low and medium cost housing sector. This paper presents findings from previous research in this field especially on the panel's materials properties, structural behaviours and empirical expression to determine its ultimate load carrying capacity. It is hoped the overview on this topic could be used as guidance for future research on developing a lightweight sandwich panel system in low to medium rise building.

7th International Workshop on Connections in Steel Structures 2012 – Connections VII

The International Workshop on Connections in Steel Structures (Connections I), jointly organized by the European Convention for Constructional Steelwork (ECCS) and the American Institute of Steel Construction (AISC) has been held since 1987. It started in Paris (Cachan), and was followed by Connections II in 1991 (Pittsburgh, Pennsylvania), Connections III in 1995 (Trento), Connections IV in 2000 (Roanoke, Virginia), Connections V in 2004 (Amsterdam) and Connections VI in 2008 (Chicago). The success of the “Connections“ series has been confi rmed by the number of outstanding scientists and engineers, mainly from Europe and the USA, but also from other areas, who, over the years, have contributed to the workshops with their papers, knowledge and professional experience. All that is included in the series of Proceedings volumes, summarizing 289 scientifi c papers, all of a very high quality. The recommendations issued at the end of each workshop are regarded as valuable references in codifi cation and practice in Europe, the USA and elsewhere. The 7th Workshop took place from 30 May to 2 June 2012 in the historic city of Timisoara, Romania. Hosts were the “Politehnica” University and the Romanian Academy, under the supervision of ECCS and AISC. This time, 44 papers were presented authored by 112 outstanding specialists in structural connectins coming from Europe and USA, but also from Canada, Brazil, Chile, China and Australia. Six topics were covered by these contributions: 1) Structural design, design codes 2) Methods of analysis 3) Connections for seismic eff ects 4) Connections for structures with hollow sections 5) Bolting and special connection topics 6) Bracing and truss connections

Experimental Evaluation of Connections in Hybrid Precast Concrete Bridge Truss Girders

An innovative, corrosion-free, precast, prestressed concrete truss girder has been developed for short- and medium-span, slab-on-girder bridges. The girder consists of top and bottom concrete flanges connected by precast vertical and diagonal members and made of fiber-reinforced polymer (FRP) tubes filled with concrete. The verticals and diagonals are connected, respectively, to the concrete flanges by means of glass FRP dowels and stud reinforcement made of corrosion-resistant steel or FRP material. The flanges are pretensioned with carbon FRP tendons. The deck slab is reinforced with corrosion-resistant steel bars in the bottom transverse layer and with glass FRP bars in the bottom longitudinal and the top layers. The girders may be posttensioned with external carbon FRP tendons to balance the slab weight and to provide continuity in multispan bridges. The new system has the advantages of light weight and enhanced durability. The light weight reduces the initial cost and allows for longer spans. The improved durability reduces the maintenance cost and extends the structure's life span. This paper describes the general details of the system and presents an experimental evaluation of its critical components, namely, the FRP tubes and the truss connections. Two types of FRP tubes and four types of connections were investigated. The results are presented of tests of eight connection specimens under static loading and four specimens under fatigue. The tests showed excellent performance of the connections when filament-wound tubes and continuous double-headed studs were used.

The Structural Performance of Precast Lightweight Foam Concrete Sandwich Panel with Single and Double Shear Truss Connectors Subjected to Axial Load

The progressive research upon the issue on renewal technology that can improve the construction industry has initiated the study of Precast Lightweight Foam Concrete Sandwich Panel (PLFP) as an alternative to Industrialize Building System (IBS). This paper reports the analysis of structural behavior of PLFP with double shear connectors under axial load. The PLFP panel consists of two wythes which enclosed a layer of polystyrene layer. Six (6 mm) rebar was used as the vertical and horizontal reinforcement and 9 mm steel bar bent at 450 was used as the connector. Full scaled panel was tested under axial load till failure. It was found that PLFP panel with double shear truss connector has higher ultimate strength capacity compared to PLFP with single shear connectors ehen tested under axial load.

Testing of Precast Lightweight Foamed Concrete Sandwich Panel with Single and Double Symmetrical Shear Truss Connectors under Eccentric Loading

This paper reports the structural behavior of precast lightweight foamed concrete sandwich panel, PLFP, subjected to eccentric loading. An experiment was conducted to investigate the structural performance of PLFP under this load. Two PLFP panels, PE-1 and PE-2 were cast with 2000 mm in heights, 750 mm in width and 100 mm in thickness. The thickness of the wall is actually a combination of three layers. Skin layers were cast from lightweight foamed concrete while the core layer is made of polystyrene. The skin layers were connected to each other by 9 mm steel shear truss connector which were embedded through the layers. Panel PE-1 was strengthened with single diagonal shear truss connectors made of 6 mm steel rebar while panel PE-2 was strengthened with symmetrical diagonal shear truss connectors of similar steel diameter. Both panels were tested under eccentric load till failure. The results showed that panel with symmetrical double truss connectors, PE-2, is able to sustain higher load compared to panel with single shear truss connector. The load-deflection profiles indicate that both panels achieved certain degree of composite action especially during the later stage of loading where the wythes tend to move in the same direction until they reached failure. The load-strain curves for both panels highlight the inconsistent distribution of surface strain along the height of panels. The overall trend of the strain curves show that they are under compression.

A Strategy of Numerical Analysis of Space Truss Connections with Stamped Bar Ends

This paper describes a strategy for numerical simulation using the Finite Elements Method to analyze connections in steel space trusses composed of circular section bars with stamped ends. This type of space truss is widely used in Brazil and the bar ends are stamped to compose the connection. This is an inexpensive solution, but poses several structural problems, thus requiring studies to establish criteria and limits for its use. The most important variables of connections and structural behavior, such as eccentricities, section variation at the bar ends, and physical and geometrical nonlinearity were introduced into the numerical model. The interaction between the bars (relative displacement and sliding in the nodal region) was simulated by means of contact elements. The numerical analysis involved modeling of a complete joining of the structure with shell elements, which were inserted at different points of the space truss. The results were satisfactory, enabling us to evaluate how the behavior of the connections affects the strength and collapse mode of the space trusses.

Modelling and identification of delamination in double-layer beams by the virtual distortion method

The problem of modelling and identification of delamination in double-layer beams has been undertaken within the framework of the virtual distortion method. For delamination modelling, a concept of the contact layer has been proposed, assuming simple but effective truss connections. The laminate layers have been modelled with Bernoulli beams. Good correspondence of the delamination model with experiments has been observed despite disregarding the friction between layers. An algorithm for off-line identification of delamination, solving an inverse problem with the use of gradient optimization, has been proposed. For double cantilever beam examples, two co-existing delamination zones have been successfully detected. An idea of on-line identification of delamination has been put forward, too.

Small-Scale Modeling of Metal-Plate-Connected Wood Truss Joints

Abstract The objective of this research was to develop 1/3-scale models of full-size (prototype) metal-plate-connected wood truss joints and a complete truss using similitude theory. To verify material properties, we compared moduli of elasticity of prototype and 1/3-scale model boards. Although the variation in stiffness of the model was greater than that of the prototype, the average properties of the model and prototype were similar. The resulting average design stiffness of 1/3-scale tension splice joints was within 1 % of the prototype joint stiffness, while the ultimate load was 7 % lower than the prototype. Stiffness and strength of model heel joints were within 22 % and 17 %, respectively, of the stiffness and strength of their prototypes. Finally, ten complete model trusses were fabricated and tested; their average stiffness and strength were 780 N/mm and 17.3 kN, respectively, after scaling up by similitude. Modeling full-size truss connection behavior up to the design load, and possibly to failure, with small-scale models and similitude theory may be feasible.

Structural behaviour of eccentrically loaded precast sandwich panels

Results of an experimental investigation to study the ultimate strength behaviour of precast concrete sandwich panels (PCSP) with steel truss shear connectors are reported. Six full-scale sandwich panels with variable slenderness ratio were cast and tested under eccentric loads. Deflection characteristics, variations of strains across the insulation layer, strains in shear connectors, crack appearance and propagation under increasing load were recorded and analysed. The role of the shear truss connectors in transferring load from the outer wythe (layer) to the inner and ensuring composite behaviour was also observed. Results obtained showed that all panels behaved in a fully composite manner under eccentric load till failure. The ultimate strength of the PCSPs was found to decrease non-linearly with the increase in the slenderness ratio. Because of the complex behaviour of PCSP due to its material non-linearity and the interaction between its various components, finite element analysis (FEA) was conducted. Comparison with test results indicated that the FEA closely estimate the wall strength and formulae based on reinforced concrete principles underestimate the wall strength.

Experimentally analyzed stability and ductility behaviour of a space-truss roof system

A space-truss roof-system [1], was experimentally analysed to determinate the behaviour of this system until collapse. The main aim of the investigation to find what is the stability and ductility behaviour of this system under eccentric and concentric force and to investigate an adequate moment-rotation function to model the behaviour of the truss connections as semi-rigid joints in the numerical model. A symmetrical space-truss section was examined. This system contains thin-walled hollow squared sections as truss bars, and every bar has uniform length. In every joint eight bars are connected by high-strength pre-stressed bolts. Inductive transducers measured the deflections of joints, and strain gauges measured the strains in the investigated bars. Four strain gauges were in the mainly tension members and eight strain gauges were in the mainly compression members, each end of the bars. This paper deals with the detailed investigation of this roof system during the “elastic” range and the collapse.

Flexural Analysis of Prestressed Concrete Sandwich Panels with Truss Connectors

A closed form elastic continuum approach was modified to account for discrete truss connectors to estimate service load deflections and bending stresses of non-loadbearing semi-composite sandwich panels. Predictions of maximum deflections and bending stresses were compared to finite element results and experimental data. Close agreement was found between the two analytical approaches, and both methods produced conservative predictions as compared to experimental data. Sensitivity analyses indicate the presence of unidentified additional shear transfer mechanisms in actual panels that are not fully represented in the elastic models. However, the theory holds promise for design and for understanding the behavior of semi-composite sandwich panels.

Early Wooden Truss Connections vs. Wood Shrinkage: From Mortise-and-Tenon Joints to Bolted Connections

Early Wooden Truss Connections vs. Wood Shrinkage: From Mortise-and-Tenon Joints to Bolted Connections

Flexural Behavior of Composite Precast Concrete Sandwich Panels With Continuous Truss Connectors

Two series of composite precast concrete sandwich panel (PCSP) systems containing various connector reinforcement and construction details were tested in flexure. Panels of one series utilized details similar to certain commercially produced panels, while the second series panels contained modified details to better evaluate interface shear transfer behavior. Results of static testing indicated that a high degree of composite stiffness and composite flexural capacity can be attained with truss girder connectors oriented longitudinally in the panels. Test results also showed that construction details can have a significant impact on the distribution of shear in elements crossing the interface. Results of fatigue testing indicated relatively minor stiffness loss over 55,000 loading cycles.

Weldment Design for RHS Truss Connections. I: Applications

Recent International Institute of Welding/Eurocode 3 (IIW/EC3) recommendations for welding rectangular hollow‐section (RHS) truss connections are shown to be too simplistic since they do not consider the special aspects of a weld connector at a gapped or overlapped truss connection. Furthermore, these weldment recommendations are generally conservative and not consistent with the design approach of national welding and structural codes in that weld size requirements are related to the full strength of members with no consideration of actual member forces. This paper reviews codified formulas for the design of individual fillet weldments in steel made by arc welding. Next, design recommendations pertinent to fillet weldments in rectangular hollow‐section truss connections are reviewed and shown to result in quite different weld proportions. The paper concludes with design examples and thereby offers preferred design approaches. A companion paper deals with experimental work used to verify the effective weld length concept for flexible rectangular hollow‐section connections necessary for the weldment design examples.

Durability of Truss Connections In A Naturally Ventilated Swine Barn

ABSTRACT This study investigated the effect of a four-year exposure in a naturally ventilated building (NVB) environment on the lateral load capacity and stiffness of truss connections. Untreated and creosote brush treated joints exposed in the NVB were compared with matched specimens that had been stored under laboratory conditions. It was found that there was no statistical difference (P=0.05) in ultimate strength and axial stiffness between joints exposed in the bam and joints exposed in the laboratory considering either the steel gussets or plywood gussets. Other observations indicated that this bam was not a worst case concerning harshness of the environment local to the exposed joints.

Analysis of Wood Truss Connection Failure

On November 26, 1985, during the early morning hours, the roof structure at a recently completed shopping center in Longmont, Colorado collapsed following several days of snow and freezing rain. Fortunately, the structure was unoccupied. Photographs taken after the collapse are shown in Figures 1 and 2. Representatives from the architect and structural engineer on site immediately after the collapse conducted density measurements and determined the weight of snow to be on the order of 10.5 to 14 psf. The specified design snow load was 40 psf. Our office was contacted and arrived at the site on December 3, 1985. With a large portion of the snow melted we had to rely on the density measurements conducted by the previous investigators. However, with all of the collapsed trusses in the original failed position, we were able to obtain dimensions of the failed members. Our investigation included

Local buckling of braces in tubular K-joints

The local buckling of compression braces is one of the recognized failure modes yet to be studied in three-member truss connections of circular tubular members. A series of tests was performed to examine the brace local buckling behavior. The test results demonstrate that the brace local buckling is influenced not only by the wall thickness of the braces but also by the stiffness of the joints. Simple prediction equations for both the resistance and the deformation capacity of the joints failing in this mode are presented on the basis of these test results. It is shown that joint deformation can have beneficial effects on the overall ductility of trusses, when diameter-to-thickness ratios of braces are limited within the range of this test.

Interaction of shear and tension in welded truss connections

In many truss joints consisting of double-angle web members welded to stems of inverted lower chord tee sections, adequate fillet weld lengths may be provided without the need for gusset plates. In such cases where a joint may also be subjected to high combinations of shear and tension, the possibility of overstressing of a tee stem exists. In the investigation of this problem, four analytical techniques, including two proposed herein, and experimental results of 30 full-scale specimen tests, 22 of which were conducted during the investigation presented herein, are presented and evaluated. Analytical and experimental results indicate that the interaction of shear and normal stresses is an important consideration in the design of such joints and that an interaction check is required.Of the many parameters investigated as part of the experimental investigation, the two that most significantly influence the magnitude of tension force that a lower chord can simultaneously carry are the magnitude of applied shear force averaged over the available web shear area and the joint configuration itself. The inclination of a diagonal web member as well as intentional joint eccentricities have little effect on the strength of these joints, although joint ductility appears to be affected by eccentricities.Although all four analytical techniques have similar overall accuracies of prediction, a method based on applying a von Mises criterion at ultimate to determine an equivalent shear area in a tee chord is recommended as being the most suitable. Based on this method, as verified and validated by comparison with extensive experimental results of tests on full-scale specimens, a simplified design curve and associated equations are developed and proposed for design office use. Key words: connection, interaction, shear, tension, welded, truss.

Developments in the design of welded HSS truss joints with RHS chords

Recent developments in design proposals for rectangular hollow section truss joints are reviewed for statically loaded, single chord, planar truss connections having one compression bracing member and one tension bracing member welded to the chord face, with either a small gap or an overlap at the connection. After comparison with the results of many joint tests, undertaken both in isolation and in complete trusses in other countries, a relatively simple procedure for the design of such joints is advocated. The design method is presented in a format compatible with the Canadian Standards Association Limit States Design Code for Steel Structures.