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Reinforced concrete elements without transverse reinforcement are vulnerable to shear failure. This premature failure mode prevents structures from developing their full flexural load bearing capacity. It is brittle in nature and occurs with the unstable propagation of cracks and limited preventive signs of distress. Moreover, the associated resistance is difficult to predict with accuracy. This uncertainty can lead to safety risks or inefficient structures. In this research, a novel approach was adopted to study the fundamental behaviour of reinforced concrete subjected to shear and to enhance the shear performance. Innovative specimen geometries and advanced monitoring techniques were used to investigate the interaction between internal resisting mechanisms on specimens with a span-to-depth ratio of 2.5 and a longitudinal reinforcement ratio below 1.3%. Novel configurations were developed through the targeted removal of material, with single or multiple voids denoted respectively Void and Truss. The behaviour of the specimens was enhanced by isolating the internal arch action and increasing the efficiency of the inclined struts. Contrary to common beliefs, it was shown that the targeted removal of material and reduction of internal redundancy can lead to a net increase in the overall resistance and ductility of reinforced concrete structures. Compared to the prismatic reference beams, the shear resistance of the Void and Truss specimens increased by +53% to +122% and the displacements at ultimate loads were 4 to 6 times greater. The isolation of a preferential load-path allowed for greater assurance and control of the resisting mechanism. Consequently, a brittle premature failure due to a critical shear crack was avoided, inducing a ductile failure mode through yielding of the longitudinal steel. Engaging the inherent plasticity of the system led to increased overall resistance and enhanced ductility. These conditions were associated with more reliable and consistent failure loads. The finding of this study can lead to enhanced design and assessment approaches, for the development of safer and more efficient structures.

Wood-frame residential roof failures due to extreme wind events are among the most common and expensive types of damage. Following extreme wind events, forensic damage investigations observe the final state of failed structures, and research must work backwards to identify the likely points of failure initiation under the expected wind loads. Based on previous studies, hip roofs are commonly understood to be more resilient during extreme wind in relation to gable roofs. Two predominant modes of residential roof failure have been studied in the literature; sheathing loss and failure of the roof-to-wall connection (RTWC). Hip roofs have specifically been proven more resilient to damage through these two modes. However, inspection of damage survey data from several recent tornadoes has identified that failures may have occurred in hip roofs at the roof framing members and their connections, rather than in the RTWC. Under wind uplift, the vertical load path through typical light-frame wood structures is still not well-defined, especially considering the possibility of failure of the framing members and connections. To prove the concept of partial failures within the frame of a hip roof, while conserving experimental resources, a finite element modelling technique is required. In the present work, a modelling method is developed to analyze the internal load effects and strength behaviour of the components of a wood-frame roof under wind uplift. Due to the uncertainties in construction of connections, lack of experimental data required for validation, and variability of the parameters affecting joint stiffness, the current study proposes a method which takes an envelope of the extreme member and joint forces under uplift, and compares them with unfactored strength values to produce conservative demand-to-capacity (D/C) ratios. Two-dimensional truss models are developed and validated against data from the literature to prove the modelling method before the D/C analysis is done for a truss under uplift. This method allows for performance, in terms of relative D/C ratios, of the structural components to be compared and the “weak-links” to be identified. Then, comparing the results for the framing members and connections to the known wind resistance of RTWCs provides a point of comparison for the observed framing failures. The results show that toe-nailed RTWCs are likely to be the weak-link, however the D/C ratios of certain truss connections confirm that their failure may be possible in certain configurations, or when the RTWCs are strengthened using hurricane ties.

In practice, infilled frame is a common structure but the contribution of infill walls is typically ignored in previous research on progressive collapse. To this end, numerical models based on solid-element are employed to investigate the behavior of reinforced concrete (RC) frames with concrete masonry infill walls under a middle column removal scenario (CRS). The numerical models of bare and infilled frames are initially validated through previous experimental results. Then the numerical models are used to illustrate the effects of infill walls on the load transfer mechanisms of the frames under a CRS and the interaction between infill walls and frame members. Thereafter, the size effect of the frame models is discussed and the numerical models are further extended to study the effects of pertinent geometric parameters on the progressive collapse behavior, including the height of partial-height infill walls, the opening position and area of wall panels as well as the number of stories. The results indicate that the load transfer mechanism of a two-story infilled frame in a middle CRS is the frame action provided by frame members and the truss mechanism provided by the interaction of infill walls and surrounding frame members, in which the latter remarkably enhances the initial structural stiffness and peak resistance. For the multi-story infilled frame with opening in which the geometric and mechanical properties are identical in each story, the load transfer mechanism is basically independent of the number of stories, whereas for the frame with full-height infill walls, the composite effect of multi-story walls is evident, increasing the peak structural resistance. Therefore, if each full-height infill wall is simplified into equivalent strut models in structural analysis, the results are underpredicted but on the safe side.

Outrigger and belt truss have been successfully applied in reducing the lateral displacement of tall buildings under wind and earthquake conditions. Limited number of researches that have considered the inelastic seismic behavior of tall buildings with braced core-outrigger system, have just examined outrigger efficiency in reduction of drift or core moment and have not studied its efficiency in preventing “collapse” of tall buildings under severe earthquakes. This paper presents the results of an analytical study on the capability and effective level of outrigger in preventing collapse of tall buildings with braced core system during two sets of far and near field earthquakes. Results of NLTHA showed that tall buildings with braced core consisting of stronger braces, designed in accordance with UBC97, will collapse under severe near-field records as a result of failure of their columns. Similar buildings with either optimized braces, designed according to AISC341-16, or RC shear wall core could survive same earthquakes. Various levels were examined for the outrigger location along building height to prevent their collapse. By performing the incremental dynamic analysis on the studied structural models, the achieved enhancement due to the outrigger addition was investigated. A new damage measure was proposed to be used in IDA that can describe the point of structural collapse, more precisely. It was observed that in order to successfully prevent the collapse of studied structures under severe near-field records, two outriggers must be used, one at the second story and the other at about 0.14 height of structure.

This study presents a method for form-finding and analysis of hyperelastic tensegrity structures based on a special strut finite element and unconstrained nonlinear programming. The strut element can function as a hyperelastic truss element with an initial cut in its undeformed length or as a strut element that shows constant force irrespectively of its nodal displacements. For the hyperelastic strut element, the invariants of the Right Cauchy-Green deformation tensor are written in terms of the element’s nodal displacements and the cut in the element’s undeformed length. The structure’s total potential energy is expressed as function of its nodal displacements and the cuts in the elements’ undeformed lengths. The minimization of this function is a nonlinear programming problem where the displacements are the unknowns. The form-finding procedure is performed by a static analysis where the stiffness matrix maybe singular along the path to equilibrium without causing convergence problems. The mathematical model includes the element’s cross-sectional deformation while the element moves in space, fully modelling its three-dimensional character. The constraint for incompressibility is satisfied exactly, eliminating the need for a penalty or augmented Lagrangian method.

With the development of urban rail transit, long-span steel truss cable-stayed bridges have become increasingly favored. Therefore, train-induced bridge-borne vibration and noise are occurring more often. The damping pad floating slab (DPFS) has been widely used as an effective vibration damping track structure; however, there is a lack of research on the vibration mechanism and effects of the DPFS for long-span steel truss cable-stayed bridges. This study focuses on the steel truss cable-stayed bridge in urban rail transit. First, the theoretical model of the train-track-bridge coupling interaction is established in the frequency-domain (the track structure is DPFS, and the interaction of multiple wheels is considered). Using this model, the wheel–rail dynamic force, force transmission rate of the track, and the force transmitted to the bridge are calculated. Then, the vibration prediction model of the long-span steel truss cable-stayed bridge is established using the plate-beam finite element (FE) method and statistical energy method. The force transmitted to the bridge is applied to the vibration prediction model to obtain the vibration transmission characteristics of the typical plate of the bridge. The prediction model is verified by comparing the obtained results with the field test of a long-span steel truss cable-stayed bridge, and the damping mechanism of DPFS track is discussed. Finally, the force transmitted to the bridge is calculated based on the embedded-sleeper (ES) track structure (the ES has no vibration damping facilities). The values of the overall vibration level are calculated from the prediction models using ES and DPFS, and the vibration reduction effect of DPFS is studied by comparison with the ES.

A simplified method based on the theory of statically indeterminate structures of infinite degree is proposed to analyse the response of cable truss bridges under lateral loads. The bridge consists of two major cables anchored at their ends and a series of pin-ended hangers attached to the cables supporting a lightweight deck whose stiffness can be neglected. Assuming the hangers can be replaced by a continuous inextensible diaphragm, it will be shown that under the action of lateral loads, the diaphragm exerts on the cables a restitution force that can be assimilated to a reaction density. Writing the equations of static equilibrium of the cables under these conditions leads to a Fredholm integral equation whose solution is actually the unknown reaction density. The solution of the equation obtained through numerical integration was found to be in good agreement with the finite element method across different configurations of lateral loads. The method was subsequently used to carry a parametric study on the effects of some important parameters such as the initial pre-stress adjustment in the deck cable, and self-weight on the stability of the bridge to lateral loads. The method is robust yet simple to use; a detailed example of its implementation is given as the Appendix.

Incorrect prediction of dynamic properties of tall buildings can lead to discomfort for humans. It is therefore important to understand the dynamic characteristics such as natural frequency, mode s ...

This study pertains to the design and structural testing of trusses assembled with culms and slats of the bamboo species Guadua angustifolia (GA). The trusses were constructed using a novel design of steel clamps to accomplish the connections between the top and bottom chord culms and the diagonal and vertical slat elements. The clamps offer a better alternative to the conventional joining methods that typically lead to longitudinal splitting of the culms, since the clamps counteract the formation of longitudinal splitting and accommodate themselves to the geometric irregularities of the culms and slats. The experimental program included the monotonic static tests of pilot Howe truss prototypes with variations in the clamp joints. Next, four replicates of the proposed design (3 m long and 0.4 m high weighing 265.4 N) were tested under monotonic static load. The trusses were simply supported at the ends and loaded at three central joints. The stiffness of the trusses up to 9869 N (1.5 times the service load for floor use) was 631.3 N/mm (COV 3.6%), and no failure was shown at the proof load of 13,754 N. This pilot study demonstrates that these trusses are a good candidate to substitute the traditional materials to support the floors and roofs in low-cost, prefabricated housing projects. However, more experimental studies have to be accomplished to fully validate this application.

In steel buildings, circular hollow sections (CHS) present several advantages such as uniform behaviour in all directions, the possibility of obtaining composite behaviour by concrete infill, hence high strength, stability and good fire resistance. Moreover, their aesthetic appeal has great potential for influencing the choice of the decision makers (architect, building owner). However, CHS profiles are not widely adopted in current practice due to the complexity and high cost of their joint details. Their joints are manufactured with a vast amount of welds and local stiffeners, which results in high fabrication costs and energy consumption, and low structural reliability under extreme loads. As a possible remedy to the complex hollow section joint fabrication, this article highlights the opportunities provided by the laser cutting technology (LCT). LCT, unleashed from the constraints of traditional cutting techniques (such as large heat-affected zones, high maintenance need, slow-to-moderate speed, low precision and low cut-edge quality) can enable a simplified fabrication of hollow section joints, bringing substantial savings to the steel fabrication costs and material waste. This paper summarizes the problems in the joint fabrication of tubular structures, and presents a comprehensive literature review containing design guidelines regarding hollow section joints, use of different materials (high strength steel, stainless steel), and configurations (external diaphragm, steel-concrete composite, passing through, truss joints). It presents the LCT process parameters in relation with different steels (carbon, high strength, stainless steel), structural integrity of laser-cut profiles (issues related to heat-affected zone, static and fatigue properties, effect of surface conditions, cut geometry and welding), available structural cutting possibilities (for bolt holes, beam perforations, open and hollow section profiles), cut tolerances as well as their effect on welding, and LCT’s cost and environmental impact. Finally, the current outcomes of an ongoing European research project have been presented which study the hollow section joint fabrication making use of LCT.

Bolted ball-cylinder joint (BBC joint) is an innovative joint system applied in non-purlin spatial truss structures. According to the theoretical analysis, the fitting formulae of the uniaxial compression bearing capacity of the BBC joint were proposed in this paper. Experiments on 5 BBC joints were introduced briefly at first. The finite element (FE) models were established using ABAQUS and verified by the experimental results. The numerical and experimental results agreed well with each other in failure modes and load-displacement curves. Subsequently, parametric study was conducted to investigate the effects of the dimensions of hollow cylinder, rectangular tube and ribbed stiffener on the bearing capacity of the joint. Finally, the formulae to estimate the uniaxial compression bearing capacity of the BBC joint were obtained by means of regression analysis. And the increasing coefficients of bearing capacity were obtained on the basis of parametric study. The calculation results were verified against the experimental and numerical results. It is indicated that the practical calculation formulae can estimate the uniaxial compression bearing capacity accurately.

The composite box girder bridge with corrugated steel webs and trusses is a recently proposed enhanced composite box girder bridge structure. The shear-lag effect of this kind of structure is studied in detail in this research. Two 8.744 m-long test beams with and without concrete filled in the bottom steel tubes were constructed and tested. The non-uniform distribution of cross-sectional stress in the top concrete slab was captured. The filling of concrete inside the bottom steel tubes is shown not to have a great influence on the shear-lag effect. Numerical parametric studies were carried out to study the influence of various factors on the shear-lag effect of this kind of structure. The numerical results indicate that the magnitude of the shear-lag effect increases with the width-to-span ratio and the suspension ratio. Analytical equations were derived to calculate the shear-lag coefficient for composite box girders with corrugated steel webs and trusses based on the energy variational principle. The experimental and numerical validation indicates that the proposed equations can be well applied in engineering practice.

The behavior of prestressing tendons essentially affects the seismic responses of self-centering structures via providing restoring forces and controlling residual deformations. Conventionally, truss elements are chosen to model prestressing tendons when investigating the dynamic behavior of self-centering connections. However, truss elements fail to capture the piecewise configuration of prestressing tendons and underestimate the axial forces when self-centering connections are subject to large rotations. In order to analyze this error, two mathematical models are proposed for typical beam-to-column connections and column-to-base connections, respectively. To circumvent the drawbacks of truss elements, sliding cable elements based on rotated engineering strain are derived to modelling prestressing tendons in self-centering connections. Finally, numerical examples are presented to validate the effectiveness and accuracy of the proposed modelling method.

Deployable mesh reflector antennas are widely used for space applications and the form-finding analysis plays an important role to reach the high surface accuracy. In this paper, an optimized algorithm extends the traditional force density method for the form-finding analysis of an asymmetric offset antenna. The optimization problem is solved by minimizing the RMS error with respect to the ideal paraboloid. First, the algorithm is implemented considering rigid ring truss support. Then, the effect of the elastic deformation of truss support is taken into account. The minimum distance between each free node of the front net and the ideal surface is used for the calculation of the RMS error. Finally, a numerical example is carried out to demonstrate the validity of the proposed method.

This paper discusses a novel configuration of rebar truss stiffened cold-formed U-shaped steel-concrete composite beams (RCUCB). The open steel U-section is stiffened by a rebar truss. The interface between concrete slab and lower part (including steel U-section, encased concrete, and reinforcement) is enhanced with uniformly distributed inverted U-shaped rebars. The reinforcement is installed at the bottom of the lower part to control the concrete longitudinal deformation. A flexural experiment on ten specimens was conducted considering reinforcement ratio, steel ratio, beam depth, and shear stud spacing (at the bottom of steel U-section). Typical flexural failure mode was observed and the rebar truss and inverted U-shaped rebar were found to provide significant integrity for the RCUCB. Thus, the RCUCB can achieve plastic bending capacity and excellent deformability. The mid-span deflection, plastification factor, and ductility factor of the RCUCB are up to L0/20, 2.08, and 24, respectively. An effective slab width of b + L0/3 may be chosen according to the strain distribution. The bending capacity calculated according to EC4 and JGJ 138-2016 agrees generally well with the test result. Finally, design details pertaining to the width to thickness ratio of bottom steel soffit, the height to thickness ratio of steel web, the transverse reinforcement ratio of concrete slab, and bottom longitudinal reinforcement are suggested accordingly.

Buckling of compression members may lead to progressive collapses of space grid structures. On the basis of the sleeved compression member, a buckling-monitoring member is introduced to raise the alert of and control buckling of the compression member by sensing the contact between the core and sleeve. Simplified theoretical analyses are conducted indicating that the contact opportunity between the core and sleeve is affected by three factors, namely protrusion length of the core above sleeve, slenderness ratio of the core and gap between the core and sleeve. Finite element analyses are performed with the finite element models calibrated identifying that the buckling-monitoring member has an improved resistance to buckling and the failure of buckling-monitoring member is attributed to local buckling of the core segment near the end. Parametric studies are performed to investigate the effects of the three factors on the improvement of ultimate and post-ultimate bearing capacities of the sleeved compression members for design suggestions of the buckling-monitoring members. Short protrusion length of the core above sleeve is proposed and the post-ultimate bearing capacities of the buckling-monitoring members are improved significantly. The buckling-monitoring member is applied in a space truss with the ultimate bearing capacity of the space truss monitored, which is considered as a positive supplement of the structural health monitoring system.

Most studies on the seismic performances of shear-critical, reinforced concrete columns have considered only their behavior when lateral deformations were applied parallel to one of the column faces. To investigate the influence of more general directions of loading, ten full-scale RC intermediate short columns with square cross-sections were subjected to displacement histories oriented 30° or 45° to their column faces. The columns had a variety of height-to-depth ratios (3.1 or 3.7), axial-load ratios (13% or 30%), and volumetric transverse-reinforcement ratios (0.35% or 0.70%). The performance of these columns was documented in terms of their cracking patterns, shear strengths, effective stiffnesses, degrading stiffnesses, and inelastic shear deformations. Based on these experimental results, a new model was developed to predict the envelope of cyclic force–deformation response, including the shear force and corresponding shear deformation at shear cracking, peak strength, and loss of axial-load-carrying capacity. In this model, the concrete contribution to shear strength for an intermediate short column corresponds to the force at the onset of critical shear cracking. The transverse reinforcement contribution is estimated with a spatial truss model consisting of idealized longitudinal, transverse, and diagonal truss elements, accompanied with the assumption that the diagonal crack plane is parallel to the neutral surface. Verification of the proposed model with test data from this study and an earlier study indicated that the model was applicable to be used for the seismic evaluation and rehabilitation of existing structures.

Lattice towers are extensively built in Europe and worldwide to serve telecommunication or power transmission purposes. Their members are usually made of equal leg angle profiles that are bolted at their extremities. Such types of towers are mainly designed to EN 1993-3-1 and EN 50341-1, based on a first-order linear elastic structural analysis of a truss structure. In this paper, an assessment of the current design approach is performed, where the tower has been simulated with a full non-linear finite element software, considering relevant imperfections as well as geometrical and material non-linearities. The importance of the second order effects in the analysis is underlined while the existence of an instability mode not properly covered directly by the norms, and usually therefore not checked, is highlighted. Two analytical models for the prediction of the critical load of this buckling mode are proposed and validated numerically. Both proposed models are rather easy to apply and may fill the gap in the existing design recommendations for lattice towers.

There is an increasing need for automated design processes that can help guide structural design towards lower embodied carbon solutions. This research presents a two-material truss topology optimization algorithm that aims at reducing the Global Warming Potential (GWP) of the designed structure. The ground structure approach is used and a new set of design variables are defined such that both the cross-sectional area and the material composition of each truss element is determined. The framework is developed for several different objective and constraint functions. These include designing for a minimum compliance objective with either weight or GWP constraints, and minimizing the GWP with stress constraints. The framework is demonstrated on truss designs with a mix of glue-laminated timber (GLT) and steel elements for both 2D and 3D design examples.

This paper focused on a new type of double-skin composite wall in which concrete-filled steel tubes are used as boundary elements, and steel-bar space trusses are used to stabilize the faceplates. The new composite wall is architecturally attractive and has some perceived advantages in strength and construction. However, limited knowledge exists regarding its behavior under the combined cyclic in-plane lateral load and axial compression. This paper reports the test results of five experimental specimens subjected to the intended combined loading. Among the tested specimens, four developed the preferred flexure-dominated limit state, while one developed the undesired shear-dominated limit state. The specimens with the flexure-dominated limit states exhibited ductile behavior up to the drift of 0.036 rad with minor strength degradations. It was found that local buckles in the faceplates of the composite wall did not compromise wall lateral resistance. The effect of using supplementary steel headed studs to stabilize faceplates is also addressed in the paper. Aside from the experimental work, a simplified model was established to compute the wall plastic moment and lateral resistance of the wall with the flexure-dominated limit state. Predictions from the model were found to agree well with the test results, suggesting the model can be used for future design and analysis of the composite wall.

This paper presents the results of an experimental program involving a series of seven full scale composite steel-concrete beam-column joints part of the “New Performance System” (NPS®). The NPS® is a novel steel-concrete composite moment resisting frame that utilizes steel wrapped reinforced concrete (RC) columns and steel-concrete composite beams, reinforced with steel truss elements made with bottom plates to double as partial formwork. Prior to this project, no experimental evidence was available to provide insight into the performance of the NPS®. In addition to the four interior and the three exterior NPS® specimens, two moderately ductile reinforced concrete (one interior and one exterior) beam-column joints, designed per Eurocode requirements and intended to serve as reference, were tested in the experimental program. The specimens were tested under quasi-static reversed cyclic horizontal loading, with a constant axial load applied to the column. The variables considered were the moment continuity solution through the beams and joint region, the level of shear reinforcement provided within the joint panel zone, and the presence/absence of additional shear reinforcement in the beam end-regions. The experimental results demonstrated that, if properly designed, the NPS® can achieve adequate strength, stiffness, ductility and energy dissipation, meeting modern seismic performance objectives. The analysis of the experimental results further demonstrated that, if properly detailed, the NPS® can meet or surpass the performance of a traditional Eurocode compliant RC specimen, designed to achieve moderate ductility.

Structural performance of both new and existing building structures under seismic actions can be assessed with a wide range of nonlinear static procedures and time history dynamic analysis available in literature. Most of these procedures, such as time history dynamic analysis, are complex as they require sophisticated finite element modelling. Reinforced concrete (RC) frames with masonry infill, for example, pose great challenge in modelling both the composite material behaviour and their interactions. With significant effort directed towards sustainable infrastructure development, a simplified nonlinear analytical procedure for evaluation of RC infill frames subjected to incremental horizontal loading is developed that can be used easily in integrated structural performance and sustainability evaluation. The method, developed on the premise of truss analogy and utilising the pushover analysis, assumes that all structural members of the RC frame are truss elements with homogeneous material properties derived on the basis of a pure axially loaded system and the infill masonry is converted into strut elements. Stiffness modification through evaluation of nonlinear stress-strain states is employed to generate the overall force-deformation behaviour of the structural system. Experimental data available in literature is used to validate the procedure.

Steel truss bridges are a critical part of the North American rail bridge inventory, with many being over a century old. Current assessment techniques are often based on visual inspections, which do not provide quantitative data to assess critical areas of the bridge with damage or deterioration. Distributed fibre optic strain sensors may be able to provide quantitative data to assess the effects of damaged members, different connection types, or deterioration. As a first step towards developing this technology for truss bridge assessment, a model truss bridge with three types of joint conditions and two types of simulated deterioration was monitored using two types of distributed fibre optic strain sensors while under static and cyclic loading. Although the impact of the changing joint conditions was clearly evident from displacement measurements, it was only possible to explain the difference in displacement measurements with the aid of the distributed strain data. At model scale, member continuity and joint movement played a significant role in the truss behaviour, which was evident from the strain data. Localized deterioration was detectable using dynamic distributed strain measurements although proximity to the deterioration and choice of sensing fibre influenced the accuracy of the measurements. Based on the results of the lab scale testing, distributed strain monitoring shows promise for steel railway truss bridge assessments although field trials of the monitoring technology are a required next step.

This paper introduces a new type of hybrid truss system composed of glue laminated bamboo (glubam) for web and upper chord members and steel pipes for lower chords. Several experiments of physical and mechanical properties were carried out on the glubam material for structural design and construction according to timber specifications and codes. A full-scale space truss model with different configurations was constructed and tested under gravity loads. Different failure modes, such as buckling of web chords, shear fracture of bolted connecting joints and yield of bottom steel pipes, were discussed. Analyses of the structural behavior under static load are compared with the experimental results, showing a good agreement. The experimental results validate that the space truss system is of excellent load carrying capacity. If yielding of the lower chord steel pipes can be realized, the system can also have a large plastic deformation under the ultimate loading condition. A prototype structure was successfully designed and constructed as a rain-shed canopy of an office building.

A numerical model was developed using the finite element method (FEM) software OpenSees to simulate the shear behavior of bolted side-plated (BSP) reinforced concrete (RC) beams. The multi-layer shell elements, truss elements, flat shell elements, and coupled zero-length elements were employed to model the concrete, reinforcement, steel plates, and bolt connection. Good agreement between the numerical results and the testing in literature indicates that the proposed FEM model can simulate the shear behavior of BSP beams. A parametric study was then conducted to reveal the variation of the shear performance with different factors, including the depth, thickness and yield strength of the bolted steel plates, the diameter, horizontal spacing, and number of rows of the anchor bolts, as well as the shear span ratio. By incorporating the piecewise transverse slip profile and improving the hypotheses in the shear-compression failure model of BSP beams, a semi-empirical design formula was derived based on the force equilibrium of the beam segment outside the main diagonal crack, thus the shear capacity of BSP beams can be evaluated. The accuracy of this theoretical model was then validated by comparing the prediction with the experimental and numerical results.

Lattice structures are quite sensitive to the lateral wind loading and prone to the nonlinear behavior and lateral buckling. However, research on the design sensitivity analysis for lattice structures accounting for the geometric nonlinearity is rarely reported in the literature. An approach is proposed in this paper for the design sensitivity analysis for the nodal displacements, element stresses and critical load factor of linear and nonlinear lattice structures. For this, a design sensitivity formula of the global internal force vector with respect to design variables is first derived. A three-bar planar truss is then used to verify the proposed sensitivity analysis formula for the global internal force and the corresponding displacements and stresses. The ability of the proposed approach in estimating the critical load factor and computing its design sensibility is also proposed and compared with those results reported in the literature for a 3D roof structure. Good agreements between the results of the proposed approach with theoretical counterparts and those reported in the literature demonstrate that the proposed approach is effective and accurate. Finally, a real 3D lattice structure is adopted to investigate the application and effectiveness of the proposed approach for the design sensitivity analysis on the structure under wind actions. Results of design sensitivity for the lattice structure under wind actions show that the proposed approach could be used to estimate the design sensitivities effectively for both linear and nonlinear structural systems.

Composite box girders with corrugated steel webs and trusses is a new type of advanced bridge structure proposed recently. This kind of structure consists of a top concrete slab, corrugated steel webs and two bottom concrete-filled steel tubes connected by trusses. The resistance to torsion and overturning of this kind of structure is larger than that of composite bridges with a single concrete-filled steel tube. This kind of structure is able to satisfy the requirement of rapid construction, environment protection and cost effectiveness. Two composite box girder bridges with corrugated steel webs and trusses have been or are being constructed in China. This paper presents the design of these two bridges in detail, which will provide valuable engineering experience for the further promotion of this kind of new bridge structure. Experimental research has been carried out to study the flexural behavior and the flexural capacity of this kind of new bridge structure. The test results show that when the test beam is at the elastic stage, the cross-section can be viewed as a plane section if only the strains of the concrete top slab and the bottom steel tubes are considered. The test beam shows good ductility throughout the whole loading process.

Dynamic Message Signs (DMSs) are increasingly used in highways as an effective means to communicate time-sensitive information with motorists. To ensure the long-term performance of DMSs, it is critical to ensure that the truss structures that hold them can resist not only extreme loading events, but also fatigue induced by service loads. The existing studies, however, are primarily focused on the loads that DMS-support structures experience during their service life and neglect the potential contribution of stresses induced during the transportation of them from the fabrication site to the location of installation. As a result, the potential damage that this important category of structures may sustain during transportation had remained largely unknown. To investigate this aspect, a comprehensive field test and numerical study were conducted. For field investigation, one span of a four-chord, overhead sign-support structure was instrumented to perform a short-term structural health monitoring. In addition, detailed finite element simulations were conducted to obtain an in-depth understanding of the potential modes of damage under the excitations induced by the road profile. The outcome of this study is expected to contribute to evaluating the extent of fatigue and structural vulnerability of DMS-support structures during transportation.

In this study, laboratory testing and theoretical analysis were carried out to investigate the human-induced vibration issues for a relatively new structural form, i.e. the arch prestressed concrete truss (APT) girder system. Ambient vibration was performed on the APT girder to capture its natural frequencies, damping ratios, and mode shapes. The APT girder system possesses high frequency and low damping. Heel-drop and jumping impact excited by a single person and dual persons were considered to evaluate the vibration performance and peak acceleration distributions for the APT girder system. The mid-span of the APT girder was selected as the key location for the vibration evaluation. It is found that the additional tester contributes to the acceleration attenuation. A reasonable shape function for the APT girder was proposed. The validity for the fundamental natural frequency was verified. The theoretical accelerations determined by the modal decomposition method with the proposed shape function agree generally well with the test results.

In this paper, a 1:5 scaled tower model for a typical 220 kV single-circuit power transmission tower with hybrid slab foundation has been designed and tested. The scaled tower model was tested under the movement of horizontal ground surface stretching with normal working loading conditions. One of the main objectives of this research is to investigate the stability of the power transmission tower subjected to horizontal ground movement by using hybrid slab foundation. The deformations of the tested tower model and stresses and strains within the different structural members of the tower and the reinforced concrete slab of the foundation have been fully measured. A large mount comprehensive test data has been generated. The research clearly indicated that compared to the isolated tower leg’s foundation the proposed hybrid slab foundation has very good resistance, in terms of truss members’ deformations and stresses, to the ground movement. Science and technology projects of China's State Grid Company

This paper presents the design of an experimental setup with a reduced number of sensors for the structural health monitoring of the historical bridge of Posadas (Cordoba, Spain), designed by the eminent engineer Eduardo Torroja in 1957. The motivation of this study stems from the need for safeguarding this piece of cultural heritage. In particular, the singularity of this historical construction, a steel–concrete composite typology consisting of a concrete deck slab and inverted bowstring steel trusses, makes continuous in-service condition assessment essential for its maintenance. Nevertheless, the application of existing continuous monitoring systems to such large-scale structures entails considerable investments as well as complex signal processing algorithms. Whereby the optimization of the number of sensors and their location is of the utmost interest. In this line, this work presents the application of an Optimal Sensor Placement (OSP) methodology to tailor an experimental setup for a cost-efficient continuous monitoring of the E. Torroja’s bridge. Due to the fact that most OSP approaches are model-based, it is essential to count on a sufficiently accurate numerical model. To this aim, an extensive vibration-based operational modal analysis is first conducted with a large number of accelerometers. Afterward, a three-dimensional finite element model of the E. Torroja’s bridge is updated on the basis of the experimentally identified dynamic properties with a genetic optimization algorithm. Finally, an optimal sensor placement methodology is utilized to design an experimental setup with a limited number of sensors for long-term monitoring purposes. The results demonstrate that few sensors are needed to accurately assess the main resonant frequencies and mode shapes.

This study proposed a new-type on-site all-bolted connection that connects a truss to a column and connects a column to a column in modularized prefabricated multi-story and high-rise steel structures. The components in a module are welded together in the factory, and various modules are assembled together quickly using the proposed connection on site. The connection connects a truss to a column through cover plates that extend from the flanges as well as through the vertical connecting plates and the joint flitches. The stiffness of the connection undergoes step-like changes as the load changes. During an earthquake, the cover plates slip relative to the chord members of the truss, dissipating energy. This study conducted tests and finite element analysis on the seismic performance of two specimens of the proposed bolted connection in which slip occurs between the cover plate and chord members, and some seismic performance data associated with the connection, such as hysteretic performance, skeleton curve, ductility, rotational capacity, stiffness degradation and failure mode, are obtained. Some parameters that affect mechanical and seismic properties of the connection were studied, and the slipping rule of the contact surfaces of the bolted connection was obtained. A comparative analysis of the test results for the slipping connection and the non-slipping connection shows that the slipping connection exhibited improved ductility and energy dissipation capacity without significantly reducing the ultimate bearing capacity, and most of the energy was dissipated from the slip. The proposed connection can be used for structures in seismic regions.

This paper presents the results of a unidirectional shake-table test performed on a full-scale, single-storey unreinforced masonry building. The specimen represented a typical detached house of the Groningen region of the Netherlands, consisting of double-wythe clay-brick unreinforced masonry walls, without any specific seismic detailing. The building prototype included large openings and a reentrant corner, causing a discontinuity in one of the perimeter walls. The floor was made of timber beams and planks, resulting in a flexible diaphragm. The roof, characterized by a very steep pitch, consisted of a series of timber trusses connected by wood purlins and boards. The two facades perpendicular to the shaking direction were designed to represent two typical gable geometries. An incremental dynamic test was conducted up to the near-collapse state of the specimen, using input ground motions compatible with induced-seismicity scenarios for the examined region. This paper summarizes the main characteristics of the specimen and the shake-table experimental results, illustrating the dynamic response of the structure, the evolution of the damage mechanisms, and the attainment of significant limit states.

A novel lightweight hybrid fiber-reinforced polymer (FRP) – aluminum space truss structure that consists of two triangular deck-truss beams has been designed for rapid emergency bridging system. This paper reports a large-scale pure torsion test on a cantilever full-scale specimen to evaluate the detailed linear-elastic torsional behavior and the load-carrying mechanism of the hybrid twin-trackway spatial structure. Additionally, a structural computational finite element model (FEM) was constructed and validated against the experiments. To fully understand the load-carrying mechanism obtained from the experiments, numerical analyses were performed by equivalently converting the torsion reaction of the hybrid twin-trackway structure to the bending and torsion of its twin triangular deck-truss beams. The results indicate that the experimental structure exhibits a good and specific torsional response, which can be well described by FEM. The unidirectional pultruded FRP profiles are mainly subjected to axial forces and are thus appropriate for application to this unique twin-trackway space truss, unlike in the case of the alone single-trackway triangular beam under torsion. The vertical bending of the twin triangular deck-truss beams play a key role in the behavior of load-carrying of the entire bridge, unlike in the case of the conventional torsional calculation method for the separated box beam. In the initial design, the torsional calculation of such a novel bridge can be carried out using the flexural analytical and numerical models of the triangular deck-truss beam.

In this paper, the aerodynamic loads on simplified lattice structures are evaluated as the sum of the force on each individual member rather than using conventional methods accounting for the overall truss through solidity ratio and global shielding coefficients. Wind tunnel tests were conducted on a single cylinder to determine the aerodynamic force coefficients and the velocity profile in its wake. Aerodynamic forces were measured on 5 models of regular lattices made of round bars. An empirical local method was developed in order to calculate the wind forces on lattice tower based on the forces acting on each individual members and considering the shielding effect. The wind forces on the 5 truss models calculated with this method compare very well to the results from wind tunnel tests and the difference with experimental tests is similar or smaller to the one obtained with the various design documents. Because it accounts for the shielding effect on each member individually, the approach presented appears to be promising for the calculation of wind forces on complex lattice structures at various angles of attack.

This paper investigates the behavior of Warren-vertical CFT truss girders by conducting both experimental tests and finite element analyses. Experimental tests on three CFT truss girders are first conducted. The test parameter is the compressive strength of the concrete infill. Finite element models, which were developed and benchmarked previously by the authors, are then used to further investigate the behavior of CFT truss girders and the influence of parameters such as the brace-to-chord strength ratio, shear span-to-depth ratio, and concrete compressive strength. Results from the parametric studies indicate that CFT truss girders are flexure dominated if (i) the brace-to-chord strength ratio ≥0.8 and (ii) the shear span-to-depth ratio ≥4.8. Both the experimental tests and FEM analyses indicate that the concrete compressive strength has negligible effects on the failure mode of CFT truss girders. Based on results from the experimental tests and FEM analyses, design equations are also proposed for estimating the flexural strength of Warren-vertical CFT truss girders.

The shear lag effect is a commonly reported observation in tests on flanged reinforced concrete (RC) structural walls. This effect is conventionally ignored but more evidence has shown that calculation and analyses ignoring this effect could significantly overestimate flexure strength and stiffness. Existing research indicates that well distributed diagonal cracks exist in the flange of the flanged RC walls with the shear lag effect and the effect should be calculated based on shear stiffness of the cracked concrete. A truss model was proposed but the model can only consider the effect at the bottom sections of cantilever flanged walls loaded at the top which therefore precludes its application in the design of flanged RC structural walls. This paper presents an improved truss analogy for calculating the shear lag effect for flanged section at any height of RC walls with any lateral load distributions. Predictions of the proposed method are compared with available experimental data and finite element (FE) results. The method is then applied to improve the fibre beam-column element models to generate a new prediction model which was found to predict to be able to accurately predict the flexure stiffness of RC walls.

Modern Performance-Based Design (PBD) approach for seismic analysis of building structures is based on the evaluation of nonlinear response to earthquake-induced demand and assessment of performance based on the lateral displacements/drifts. One of the key challenges associated with the application of PBD for seismic evaluation of confined masonry (CM) structures is the development of an adequate numerical model for simulating nonlinear response at different seismic demands. In this paper, an Equivalent Truss Model (ETM) has been proposed for nonlinear analysis of CM structures. The model is based on a truss analogy concept, where a CM wall is idealized as a truss consisting of pin-ended elements. A masonry panel is modelled as a compression element (strut), while horizontal and vertical reinforced concrete (RC) confining elements are modelled either as struts or tension elements (ties). ETM is essentially a macro-model that simulates nonlinear behaviour of a CM wall through lumped nonlinearity of masonry struts, while RC confining elements show linear elastic behaviour. The proposed model has been validated using the results of experimental studies on CM walls subjected to in-plane reversed cyclic loading. The paper also presents a case study, in which ETM was applied for seismic evaluation of an existing three-storey CM apartment building located in an area of moderate seismic hazard in India using nonlinear static analysis. The damage states for PBD were established based on past research studies on CM structures. A comparison of the results of conventional force-based design and PBD analyses showed that ETM can be used in conjunction with the PBD approach to evaluate existing CM buildings and also optimize design solutions for new buildings, which were developed using a conventional, force-based seismic design approach.

In this study, a novel floor system with horizontal K-shaped braces was applied to long-span high-speed railway steel truss cable-stayed bridges to reduce the crossbeams’ out-plane bending moment which is significant in the traditional stringer-crossbeam floor system. Based on the new floor system of Beijiang Bridge, a 1:4 scaled floor system specimen was experimentally tested; subsequently, two detailed finite element (FE) models for comparison of the specimen were established to investigate the stress distributions, force transferring and deformation characteristics. Furthermore, the ratio formula of the longitudinal force transmitted by the K-braces to that by crossbeam was determined. The results of the comparative analysis of FE models indicate that the horizontal K-shaped brace can reduce 81.0% of the crossbeam’s maximum stress caused by the out-plane bending moment and alleviate the longitudinal deformations. The measured stresses of the model increased linearly with the applied load from 0.4 to 2.2 times the maximum tension force cases. The K-shaped brace mainly bears axial force; additionally, the out plane bending moment of the crossbeam is small. The longitudinal force transmission ratio is determined by the geometric parameters of the floor system structure, such as section area Ak of the K-shaped brace, and the distance between the side stringer and the lower chord Lc (rather than load type or value). The longitudinal force transmission ratio calculated by experimental and numerical stresses were in the ranges of 1.35 to 6.46 and 1.39 to 7.30, respectively. This indicates that the horizontal K-shaped brace transmits 57.45 to 86.60 % and 58.16 to 87.95 % of the longitudinal force, for experimental and normal stresses, respectively. The similar ratio ranges in both cases reveal that the K-shaped brace can effectively transfer longitudinal forces, reduce the out-plane moment of the crossbeam, and improve the mechanical characteristic of the floor system.

Bolted connections are preferred in prefabricated steel structures because of the convenience for construction and quality control. A prefabricated steel structural system with truss beams and bolted joints were proposed, and enlarged bolt holes were adopted in the joints for easier assembly and better energy dissipations. A series of 6 truss-to-column joint specimens, with oversized or slotted bolt holes, were tested under cyclic loads. The resistance, the hysteresis behaviour, the ductility, the energy dissipation capacity, and the slipping behaviour of the tested joints were analysed, and the influences of the bolt hole dimensions and shapes were evaluated. Finite element models were established and validated for further investigation of the joint performances. According to the results, the enlarged bolt holes would slightly decrease the slipping resistance, but would significantly improve the joint ductility and energy dissipation capacity. The slippages in the joints with oversized or slotted bolt holes could make 38%∼59% of the contributions to the energy dissipation capacity, proving that the slippages could be utilized in seismic design. Based on the investigations, the diameters of the oversized bolt holes are recommended to be 4 mm larger than the nominal bolt diameter, and a 0.3 mm-thick copper plate is recommended to be adopted between the connected plates to obtain stable slip behaviours. Simplified calculation methods for the slipping resistance and the yield resistance of the investigated joints were proposed and evaluated to have acceptable accuracy for resistance prediction and design.

Form-finding design is critical in determining whether a cable-mesh reflector antenna can meet electrical performance requirements. However, the current methods rarely consider the interactive effects between the cable network and the supporting truss in the form-finding process, which requires more iteration steps for good design results. This study presents a force density sensitivity form-finding design method for cable-mesh reflector antennas based on systematic equilibrium equations. The sensitivity matrix of the support truss vertex and the cable network free node is derived with respect to force density, and the form-finding process of the reflector antenna is transformed into a sequential quadratic programming problem that can be easily solved. The antenna meets the accuracy requirements, and has a more uniform distribution of internal cable net tension and a smaller truss deformation as a result of constraining the vertex deformation of the supporting truss and cable tension. For practical engineering problems, more accurate design results can be obtained quickly. The effectiveness of the proposed method is verified through numerical examples.