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The performance of beam-column joints in reinforced concrete (RC) framed structures have long been recognized as a significant factor that affects the overall response of structure subjected to cyclic loads. The reversal of forces in beam-column joints during earthquakes may cause distress and often failure, when not designed and detailed properly. The present work aims to study the seismic performance of exterior beam column joint with non-conventional reinforcement detailing. Four one third scaled beam-column joint sub assemblages were tested under reverse cyclic loading applied at beam end. The specimens have been looked after into two groups based on the joint reinforcement detailing. The first group of two specimens (Group-I) comprises of joint assemblages having joint detailing as detailed in construction code of practice in India i.e. IS 456:2000. The second group (Group-II) consists of two specimens, one of the specimens having additional cross bracing reinforcements for the joint detailed as per IS 456:2000 and another specimen having diagonal bars in form of development length. Here comparison between conventional and non-conventional type reinforcement has been done to study its effect on strengthening of joint. The experimental results and findings indicate that additional cross bracing reinforcements improves the seismic performance.

Chemical scrubbing and biofiltration are well-established technologies for treating contaminated pollutants generated at wastewater treatment plants (WWTPs). Nevertheless, the growing need to reduce the ecological footprint of abatement technologies without affecting process efficiency is prioritizing biological alternatives. This study deals with the challenge of designing a structure for converting a chemical scrubber currently operating at a WWTP with a capacity of 6400 population equivalent (PE) into a modular bioreactor without any actual modification of the scrubber´s structure. The inside of the reactor was divided into three levels or platforms for holding the biomaterial, and the corresponding parts were manufactured in PVC, with the exceptions of the screws and cross bracing. The study of the parts’ stress and strain limits revealed that the slats and half-rings should be reinforced with ribs, and the optimal rib height was studied on a case-by-case basis. It was also concluded that the base legs could hold the weight of 80 cm height biomaterial bed onto each of the three platforms. Based on previous studies, the converted biofilter with an inlet flow rate of 1150 m3/h could render simultaneous removal efficiencies greater than 90 % for H2S and NH3. Regarding the viability study, the annual savings from the elimination of chemical consumption were around 9.7 % of the total investment cost. One of the main strengths of replacing the scrubber with a biofilter was the improvement in sustainable performance and health and safety, reducing both risk and the budget for prevention.

Elevated water tanks are the structures of greater importance which are considered as the main lifeline elements. Many displeasing experiences have taken place earlier due to the damage and collapse of elevated water tanks due to the occurrence of earthquakes. The reason behind the damage is lack of providing proper supporting system to the water tank to withstand the dynamic loads and also due to improper selection of staging. The main objective of the present study is to evaluate the seismic response of elevated rectangular water tank with different staging patterns and different water level conditions (full, half and empty). Four types of bracing systems of elevated water tank such as normal bracing, diagonal bracing, V bracing, and cross bracing are considered for the analysis with various water level conditions. A total of 12 combinations were analysed and base shear, base moment and roof displacement for the fixed models were calculated with SAP2000 v 20.0.0 software using Response Spectrum Method (RSM) and results are presented.

Regression tree, random forest, bagging and gradient boosting regression-based modelling techniques were used to estimate the time period of precast concrete frame structures with vertical irregularity and cross-bracing using 756 Etabs models. This paper thoroughly explored the efficacy of random forest, regression tree, bagging, gradient boosting-based modelling using RStudio. The time period has been the output parameter while the number of cross-bracing, column size, beam size, soft storey, irregularity coefficient and height of the building has been assigned as input parameters. The accuracy of machine learning techniques has been checked by reference to the formulas published in the literature. A comparison of results indicates that the gradient boosting-based regression approach performed well as compared to random forest regression, bagging and regression tree.

The design of slender structures is often associated with a number of assumptions made by engineers in checking on the stability of the structure. Not seldom, these assumptions are rather uncertain. In the present paper the effects of the stiffness of different members on the bracing stiffness of timber structures is studied. Both full-scale laboratory testing and FE-modelling are employed here in the investigation. In particular, two different bracing approaches are analysed, those of (1) cross bracing (wind trusses) and (2) diaphragm action (through use of steel sheeting) in the plane of the roof. In addition, the effects of the connections and the number of fasteners used in the structure are evaluated. The stiffness of the connections is obtained by means of an FE-updating approach, i.e. that the relevant parts included in the FE-model are calibrated to ensure that the FE-results match the laboratory results. The findings obtained indicated, (1) that the connections can have a significant effect on the stiffness of the bracing systems, (2) that the cross bracings close to the mid-span of the structure are less effective than those close to the supports, (3) that the lateral stiffness obtained using a diaphragm approach is closely related to the number of fasteners between the steel sheet and the timber parts in the roof that are employed, and (4) that the two different bracing approaches used provide about the same lateral stiffness of the roof. Finally, it should be emphasized that FE-models can markedly overestimate the stiffness of timber structures. If the connections are not modelled accurately, the engineers involved are advised to seek safe sided assumptions regarding them.

During bridge construction, many loads affect its behavior and can be critical to its future performance. The screed machine and the fresh concrete loads acting on the overhang portion of the deck slab are very significant since they cause unbalanced eccentric loads, resulting in deflection of the overhang and rotation of the exterior girders. Moreover, as the concrete has not hardened yet, the deck slab formwork deflects, causing a non-uniform slab thickness, transversely. Other issues, such as a reduction in steel rebar cover, poor rideability, and local buckling in the girders, can occur from this. Many temporary bracing systems are currently used to prevent the rotation of the exterior girder due to construction loads, such as transverse and diagonal ties, timber blocks, and temporary cross bracing at the exterior panels. However, recent studies show that these bracing systems are not effective enough, and more efficient methods will be needed to solve this problem. The goal of this research is to find the most significant geometrical parameters that affect the rotation of the exterior girders under construction loads. Six parameters were considered in this study: the girder’s section properties, the unbraced length, the overhang width, the number of girders, the girder spacing and the diaphragm’s section properties. SAP2000 software was used to develop the Finite Element models to carry out the parametric study. The rotation of the exterior girders was recorded at the middle of the span at three locations (the top flange, the center of the web and the bottom flange). The results showed that the most significant variables to the rotation of the exterior girder were the girder’s section properties, the unbraced length, and the overhang width. Based on these three parameters a regression model is developed to predict the rotation value with an average error of 9.7%.

This paper presents a theoretical finite element study on effect of different strengthening techniques on structural behavior of the reinforced concrete frames subjected to earthquake motion. In the study, diagonal cross bracing, masonry infill wall, externally CFRP laminates, and reinforced concrete jacketing for columns are considered as different strengthening techniques of one story reinforced concrete bare frame. Time history analysis for the frame subjected to EL-Centro (1940 N-S) earthquake ground motion is carried out using ETABS software. The obtained results from the time history analysis including axial and shear stresses, lateral displacement, acceleration and base shear with time are illustrated and discussed with/ or without the strengthening techniques. The study illustrates the influence and enhancement of each technique on the performance of one story bare frame subjected to EL-Centro earthquake motion.

In this work we examine a plane metamaterial subjected to a generic biaxial macrostress, obtained by coupling a periodic mesh of rods with a periodic mesh of extremely flexible cables. In particular, we couple a square mesh of rods with diagonal cables with the aim of enhancing the stability performance of the obtained metamaterial. By introducing appropriate restrictions on the feasible critical modes, the study can be framed into the context of the Eulerian stability analysis and then, by means of Floquet-Bloch theory, a closed form solution for the stability domain is determined. Finally, on the basis of the previous stability analysis the optimal design problem is addressed.

The aim of this study was assessing the seismic performance of three types of mid-span connections in the cross bracing systems including: the mid-span connection with cover plates, the flanged connections and the braced ductile shear panel (BDSP). For this purpose, the linear buckling and post-buckling behavior of the cross braces with the aforementioned connections having nonlinear geometries and materials were numerically analyzed. The results were compared to the results of the common connection. According to the results, use of the cross braces with mid-span connection together with cover plates and flanged connections due to creating continuity in the mid-span connection, cause coordinated buckling of the discontinuous diagonal members (or so-called second mode buckling) and thereby improved compression performance of the cross braces. In addition, use of the ductile shear panel in the mid-span connection led to more energy dissipation by cross braces and prevented buckling of the diagonal bracing members.

Multi spine composite concrete-deck steel-box girder bridges became a very popular choice in highway bridges due to their high torsional and wraping stiffness as well as for economic and aesthetic reasons. This study presents an experimental investigation on both elastic and ultimate behavior of composite box girder bridges in order to study the effect of internal cross bracing between box girders along with the curvature effect at different loading stages. Three composite concrete deck-steel simply-supported twin-box bridge models, two curved and one straight, were fabricated, and tested. First, the response of each model was monitored under free-vibration excitation, then an eccentric loading was applied and the corresponding deflections were recorded in the elastic range. Finally, the bridge models were tested up to collapse. The structural behavior of the three bridge models was compared at the three loading stages. It was noticed that the presence of an external cross bracing system between the steel boxes had an insignificant effect on the developed deflection and the fundamental natural frequency in the elastic range of loading. On the other hand, these external bracings assisted in decreasing the developed deflection approaching failure and in increasing the load carrying capacity by about 8.9%. In addition, the external bracing ensured a better distribution of the stresses under ultimate loading conditions. Moreover, the experimental findings were verified numerically using finite element modeling. A good agreement was noticed to exist between the experimental findings and the numerical results.

The main girders of the I-section steel-concrete composite twin girder bridge is usually connected together by frame cross bracing. When the cross girder is connected with the main girders by welding, the flat plates for stiffening can be used to strengthen the connection to ensure the effective transfer of connection forces between the two. In this paper, the finite element simulation method is used to study the influence of flat plates. The results show that, compared with the twin girder structure without flat plates for stiffening, when the same load acts on the cross girder: the stress peak value of the cross girder of the twin girder structure with flat plates is obviously reduced, and the stress peak value of the main girders is increased; the bending stress of the web of T-shaped connection stiffeners diffuses faster from the welding part to the end; the peak value of the axial stress on the web of T-shaped connection stiffeners decreases obviously, and the position of the peak value changes from the side near the cross girder to the side near the web of main girder. The above results show that it is necessary to set the flat plates for stiffening in the twin girder bridge to ensure the transfer of forces between the main girders and cross girder.

Investigation of previous and recent earthquake damage have shown that the buildings are subjected to severe destruction or collapse during the earthquake ground motion. Among the probable structural damages, seismically induced pounding has been usually witnessed in most of the earthquakes. During the earthquake, Building vibrates out phase due there different dynamics characteristics. Such buildings are usually separated by expansion joint which is insufficient to accommodate the lateral movements of the buildings during the earthquake. Seismic pounding can be prevented by providing safe separation distances; sometimes availability of required safe separation gap is not possible in metropolitan cities due to high land value and limited availability of land. If building separation is found to be deficient to prevent pounding, then there should be some easy and cost-effective methods to prevent structural pounding between adjacent buildings. This study covers the effect of structural pounding on conventional beam column system adjacent to flat slab system .In order to observe pounding effect, Time history analysis is carried out by taking 1944 Elcentro earthquake data which is to be known as above average earthquake. This study also covers the prevention techniques of pounding by using retrofitting’s like introducing X cross bracings, Eccen forward and backward cross bracing, V cross bracing systems with proper placement are proposed as possible mitigation techniques for pounding between adjacent structures

Professional engineers in Pre-engineered buildings (PEB) generally adopt two dimensional (2-D) modeling of frame i.e. plane frame modeling in transverse direction and profess for optimal design using elastic method. In practice, 2-D modeling of main frame is done for transverse frame while in longitudinal direction truss analogy is adopted mainly for analysis of bracing. In 2-D analysis majority of cases only major axis moment is considered and the minor axis moment (having sometimes significant effect on design) is generally ignored. This minor axis moment can be of less magnitude if the bracings are of X type designed as compression as well as tensile members. However in practice these bracings are designed as tension only members, leading to significant effect of minor axis moments. It is also reported that if the ratio of deflections at knee joint in direction of ridge from second order analysis (Δ2) versus first order (Δ1), is 1.5 or more, second order analysis is must, however most of the cases in practice this factor is ignored. This study is aimed to check and quantify the effect due to minor axis moment, i.e. My, in braced frames at knee joint. In absence of second order analysis, as mandated by codes, an approximate practical approach is presented for assessment of the minor axis moment, My, in terms of major axis frame moment, Mz. It is observed that the ratio of building height to width is significant in determining ratio My/Mz. Keywords: 2-D analysis, 3-D analysis, Cross bracing, Minor axis Moments,, Pre-engineered buildings, PEB,.

The phenomenon of dynamic instability of steel beams under harmonic axial loading is analysed, in particular to identify those elements in equilibrium under static axial loads, i.e. loaded below the Euler load, but that could fail under dynamic conditions, possibly compromising the entire structural stability. In the literature, the general problem of dynamic instability was comprehensively presented by Bolotin, who defined instability regions. Bolotin's method was extended herein and more accurate instability regions derived. In some conditions, depending on the ratio between the frequency of the exciting load and the beam transversal natural frequency, an elastic beam could sustain a dynamic axial load greater than the Euler load. The influence of geometric and material non-linearity on the shape of the instability regions has been evaluated herein through time series analyses. Then, response spectrum analyses were conducted to highlight possible effects of dynamic instability due to seismic loading. Two building typologies were considered: multi-storey buildings with cross bracing and existing industrial buildings. The results show that in the case of elements of the bracing system of new-designed multi-storey buildings, the dynamic instability is generally not an issue due to the high frequency of the single elements compared to the frequency of the fundamental mode of vibrations of the whole building. In the case of existing industrial buildings not designed to sustain seismic actions, some slender elements, with frequency of vibration compatible with the fundamental frequencies of the building, may undergo dynamic instability with possible detrimental effects in the whole building response.

The main structure of Tai’an Tourism Distribution Center is a steel frame structure system. On its west side, there is a large span cantilever structure with a maximum cantilever length of 22 meters, which adopts a space steel truss structure. The cantilever structure has great visual impact and excellent ornamental value, but it also has irregular items such as irregular torsion, irregular vertical lateral stiffness, and sudden change of floor bearing capacity. The overall stress of the structure is complex, and the design and construction of seismic performance are highly required. The seismic performance of the structure is calculated and analyzed by performance-based seismic design method, and the cantilever structure is modeled and analyzed by 3D3S, a space steel structure design software. The results show that cross support is more reasonable for cantilever structure. In view of the difficulties in the design analysis, this paper also proposes effective strengthening measures to ensure the safety of the structure, and makes technical reserves for later construction of the project, which is also of certain reference significance for similar projects.

The ever-increasing need for housing generated the search for new and innovative building methods to increase speed and efficiency and enhance quality. One method is the use of light thin steel profiles as load-bearing elements having different solutions for interior and exterior cladding. Due to the increase in CFS construction in low-rise residential structures in the modern construction industry, there is an increased demand for performance inelastic analysis of CFS walls. In this study, the nonlinear behavior of cold-formed steel frames with various bracing arrangements including cross, chevron and k-shape straps was evaluated under cyclic and monotonic loading and using nonlinear finite element analysis methods. In total, 68 frames with different bracing arrangements and different ratios of dimensions were studied. Also, seismic parameters including resistance reduction factor, ductility and force reduction factor due to ductility were evaluated for all samples. On the other hand, the seismic response modification factor was calculated for these systems. It was concluded that the highest response modification factor would be obtained for walls with bilateral cross bracing systems with a value of 3.14. In all samples, on increasing the distance of straps from each other, shear strength increased and shear strength of the wall with bilateral bracing system was 60 % greater than that with lateral bracing system.

This paper studies distortion-induced fatigue cracks in a 1960s-era welded plate girder bridge that developed cracks in the web-gap region shortly after completion of a comprehensive seismic retrofit. Finite-element analysis (FEA) and field testing were conducted to investigate the cause of cracking and then to recommend appropriate repair measures for the bridge. The field test results validated the high-stress concentrations in the web-gap region of the bridge that led to fatigue cracking after only a limited number of cycles. FEA results indicated that the high-stress concentrations were principally a result of replacing K-type diaphragms with stiffer cross diaphragms as part of the seismic retrofit. Two conventional repair measures in addition to two innovative repair measures were evaluated. The proposed innovative repair measures focused on ease of installation compared with more conventional options and were found to reduce the distortion-induced stresses well below the constant amplitude f...

In order to analyze the mechanical properties of UHVDC transmission tower joint accurately, a multi-scale finite element model of the transmission tower is established with the interface between solid element model and beam element model. The model is applied to the nonlinear analysis of a key joint in a test condition .The results show that the tower destruction is caused by buckling behavior of the cross bracing member and the multi-scale model can simulate the force state of gusset-plate and the connected members realistically, which is superior to traditional large scale models. The analysis coincides with the experiment well and provides references for the transmission tower design.

Seismic pounding between adjacent buildings can cause severe damage to the structures under earthquakes, when owing to their different dynamic characteristics. During earthquake, the buildings vibrate out of phase and at rest separation is deficient to accommodate their relative motions. Such buildings are usually separated by expansion joint which is insufficient to provide the lateral movements of the buildings during earthquakes. It can be prevented by providing safe separation distances, sometimes getting of required safe separations is not possible in metropolitan areas due to high land value and limited availability of land space. If building separations is found to be deficient to prevent pounding, then there should be some secure and cost effective methods to prevent structural pounding between adjacent buildings. There are many buildings which are constructed very nearly to one another in Metropolitan cities, because everyone wants to construct up to their property line due to high cost of land. This study covers the prevention techniques of pounding between adjacent buildings due to earthquakes. Constructing new RC walls, cross bracing system and combined RC wall & bracing, with proper placement are proposed as possible prevention techniques for pounding between adjacent buildings

This paper introduces the design of a new combination of friction/hysteretic damper installed in the middle of cross bracing for dissipating seismic energy. Due to its relative simplicity and easy application, with no need for any special material or technology, this high-performance system has gained more attention than any other energy dissipation devices. Choosing appropriate slip load and maximum sliding movement values in this system, in comparison with its counterpart i.e. circular ring yielding dissipator, this combined system may inherit the advantages of both friction and steel yielding damper. In weak-to-moderate ground motions, it dissipates energy by friction and in strong ground motions, it absorbs energy by yielding These circular damper systems can be used to rehabilitate existing buildings whose slender braces are only designed based on resistance of tension forces. Also because of failure localization in this simple-type system, a distorted and damaged damper can be promptly replaced with a new one after a strong earthquake.

Many developments have been carried out in order to try to quantify the effects produced by damage and the vibration based methods of damage diagnostics are proved to be promising. I n the present study, a two storey one bay steel por tal frame with cross bracing is considered as an undamaged case. The damage is intr oduced to the frame by removing the bracing at vari ous levels. The modal parameters of the undamaged and damaged frames were extracted by using FEM software ANSYS 14.5 and val idated through experimental results performed using mini shake tab le. The Frequency response function (FRF) plot is d rawn from the experimental results. Further the damage is introduced to the fr ame by reducing the young’s modulus, reducing the csectional area and increasing the temperature due to fire in bracing a nd at each floor is also studied by using ANSYS 14. 5 by performing the modal analysis. The results show that the natural frequen cies for the damaged structure decreases and the am plitude increases.

Single angle cross bracings are customarily used in tower structures. According to the joint detailing, there exists not only force eccentricity but also rotational restraint at member ends. In addition, interaction occurs at the member buckling within a bracing panel, as well as within the two portions of a member. All these render the stability calculation rather complicate. In the current codes for tower design, simplified formulae of equivalent slenderness are given so as the member stability can be calculated as axially compressed struts. But these formulae are somewhat crude, giving unbalanced reliability. In this study, basing on the theory of elastic stability, and considering member buckling interaction in close coordination with joint detailing, formulae with better accuracy and reliability are put forward. One of the features of the proposed approach is the distinction between the cross-bracings connected to single angle leg post and those connected to a doubly symmetric leg post. The second feature lies in the refined formulae for specific interaction cases. The suggested formulae correlate well with available test data. Moreover, examination of test results reveals that it is unnecessary to specify lower buckling strength for cross-bracing bars connected by one bolt, provided that there is no in-plane eccentricity at the joint.

Fatigue-crack formation in the web-gap region of multi-girder steel bridges has been a common occurrence due to differential deflections between girders resulting in diaphragm forces that subject the web-gap to out-of-plane distortion. However, bridge design specifications do not directly deal with distortion induced stresses. The objective of this paper is to examine the behavior of web-gap distortion of a skewed multi-girder steel bridge through field testing and finite element studies. The field test involved measurements of strains for eight load cases by using strain gages placed in the web-gap region and in the cross bracing adjacent to the web-gap. The results of the field test were used as a basis for the verification of developed finite element models. Critical spots in the web-gap were examined utilizing the finite element analysis. Retrofit methods that include the provision of a connection plate between the stiffener and the girder top flange, loosening of the bolts connecting the cross-bracing to the stiffener, and supplementing a stiffener plate opposite to the original stiffener side were investigated. The results indicated that the connection plate addition and loosening of bolts alternatives were effective in reducing induced strains and stresses in the web-gap region. The finite element study on the impact of web-gap height variation indicated an inverse relationship between web-gap height and induced strains and stresses with the shortest web-gap height resulting in the highest strains due to increased bending by diaphragm forces in the web. Influence surfaces for strains, diaphragm force and relative out-of-plane displacement provide insight into the behavior of web-gap distortion, and can be used to provide quick estimate of the effect of truck load positioning. Expressions developed that relate vertical stresses and relative out-of-plane displacements combined with measurements of out-of-plane displacements by transducers can be utilized for prediction of induced stresses at other critical web-gap regions of the bridge and at critical locations in the web gaps of similar bridges.

Improving freight axle load is the most effective method to improve railway freight capability; based on the imported technologies of railway freight bogie, the 27 t axle load side-frame cross-bracing bogie and sub-frame radial bogie are developed in China. In order to analyze and compare dynamic interactions of the two newly developed heavy-haul freight bogies, we establish a vehicle–track coupling dynamic model and use numerical calculation methods for computer simulation. The dynamic performances of the two bogies are simulated separately at various conditions. The results show that at the dipped joint and straight line running conditions, the wheel–rail dynamic interactions of both bogies are basically the same, but at the curve negotiation condition, the wear and the lateral force of the side-frame cross-bracing bogie are much higher than that of the sub-frame radial bogie, and the advantages become more obvious when the curve radius is smaller. The results also indicate that the sub-frame radial bogie has better low-wheel–rail interaction characteristics.

The goal of this study is to design and evaluate simple and rapid seismic retrofit devices for relatively small rehabilitation projects for steel structures. These designs are consistent with the tenets of sustainable design and will result in a more resilient building stock as well as minimizing environmental and economical effects and social consequences during the rehabilitation project. To achieve these goals, a unique approach to designing supplemental systems by using tension-only elements is proposed, one that eliminates undesirable global and local buckling. The first generation of these devices, a bracing system consisting of cables and a central energy dissipating device [couples resisting (CORE) damper], is presented in this paper. Both analytical studies with advanced and simplified models and proof-of-concept testing demonstrated stable, highly efficient performance of the system under seismic loads. Preliminary applications of the CORE damper system to the retrofitting of a braced steel fram...

Steel braces are widely used in seismic retrofit of buildings. However, their tendency of buckling under compression impairs their efficacy. In this paper, characteristics of a cross bracing with rigid intersection, including its bearing capacity, hysteretic property and fracture ductility are investigated. With the analysis results, performance-based design requirements of a steel cross bracing are proposed based on its width-thickness ratio and effective slenderness ratio.

Thomas Leslie explains that the wind-induced collapse of the Tay Bridge in Scotland in 1879 illustrated the vulnerability of tall metal frames to lateral forces. Built Like Bridges: Iron, Steel, and Rivets in the Nineteenth-century Skyscraper recounts the revolution in structural methods that followed, culminating in the mid-1890s with the invention of the riveted all-steel skeleton frame and the elimination of thick masonry shear walls. The first generation of wind-braced skyscraper metal frames relied on bridgelike systems of cross bracing or shiplike systems of knee bracing, but these structures intruded into rentable spaces. The second generation of frames better exploited the material properties of steel, making stiff connections between girders and columns that, when multiplied throughout the building, could collectively resist lateral forces without such intrusions. Steel—which had replaced cast iron as a structural material by 1895—excelled in this role because it could be rolled into efficient, workable shapes and riveted to form tight connections.

Three nonseismically detailed interior reinforced concrete beam-column joints, namely, one eccentric and two concentric joints, strengthened with proposed fiber-reinforced polymer FRP wrapping configurations using glass fiber-reinforced polymer and carbon fiber-reinforced polymer strips and sheets, were tested under constant axial compression load and reversed cyclic loading which simulated low to moderate earthquake forces. Seismic performance of the strengthened beam-column joints in terms of their hysteresis response, stiffness, and energy dissipation capacity is evaluated and compared to those of the original and unstrengthened beam-column joints. Results indicate that applying strips at 45º on a flushed eccentric joint core and as cross bracing on the beam and confinement round the column is very effective. All specimens failed with gradual strength deterioration, bond degradation, and debonding of FRP sheets was observed near the joint core. The proposed strengthening schemes were found to be efficient and economical for mass repair or upgrading of nonseismically detailed structures. Accepted version

The use of horizontally curved composite multiple-box girder bridges in modern highway systems is quite suitable in resisting torsional and warping effects induced by highway curvatures. Bridge users react adversely to vibrations of a bridge and especially where torsional modes dominate. In this paper, continuous curved composite multiple-box girder bridges are analyzed, using the finite-element method, to evaluate their natural frequencies and mode shapes. Experimental tests are conducted on two continuous twin-box girder bridge models of different curvatures to verify and substantiate the finite-element model. Empirical expressions are deduced from these results to evaluate the fundamental frequency for such bridges. The parameters considered herein are the span length, number of lanes, number of boxes, span-to-radius of curvature ratio, span-to-depth ratio, end-diaphragm thickness, number of cross bracings, and number of spans.

The present paper describes a practical method for analysing and estimating the remaining fatigue life of a ‘cut-short’ web stiffener detail widely used in highway steel box girder bridges constructed in Ontario, Canada between 1960 and the early 1980s. The paper also discusses the design used to repair steel box bridges fabricated with this stiffener detail. Since 2000, over 20 bridges in southern Ontario have been retrofitted using these details. Steel box girder bridges with composite concrete decks were commonly fabricated in Ontario with a ‘cut-short’ welded stiffener detail that was used to connect intermediate vertical cross bracing to the girder webs. The bracing members, consisting of single angles, were attached to the ends of the stiffeners with fillet welds. The vertical web stiffener would usually be terminated above the girder bottom flange with a 20 – 50 mm web gap. Often, the fillet welds attaching the stiffener and the web would terminate short of the stiffener end, resulting in an even l...

Local and overall instabilities of the steel beam occur in the hogging-moment region in a continuous composite beam and these forms of buckling have been recognised to be highly interactive. The overall mode of buckling in composite steel-concrete tee-beams in regions of negative bending is what is herein termed restrained-distortional buckling (RDB). In negative bending the slab restrains the tension region of the steel and the neutral axis is not located at the mid-height of the web. The neutral axis is shifted towards the top flange, and in negative bending the steel region is subjected to predominantly compressive loading. In addition, the web usually carries proportionally higher shear loads than in ordinary steel beams. The lateral-distortional buckling resistance of the steel portion in continuous composite beams is therefore dependent on the extent to which the web can provide a restraining action to the unstable compression flange. This form of buckling is usually prevented in bridge girders by the cross bracing and the common view amongst engineers is that such bracing is excessive and uneconomical. Although buckling of plain steel beams in both the elastic and inelastic ranges of structural response has been studied extensively and a great deal of research work has been devoted to the understanding of their buckling modes, and codes of practice for the design of structural steelwork contain relevant clauses that presently are considered to be quite accurate, buckling of the steel component in composite beams still represents a grey area in structural engineering research and is much less well documented. The bubble augmented spline finite strip method of analysis, developed by the authors, is thus employed herein to study extensively the issue of RDB in composite tee-beams in hogging bending regions. The numerical investigations demonstrate that RDB mode is a governing mode for steel I-sections with one flange fully restrained, variations of the web slenderness parameter have a most pronounced influence on the elastic buckling capacity of composite T-section beams and the deformations can be reasonably large in the proximity of the internal supports and near the concentrated forces.

A novel method is presented for determining the effective length factors (K factors) for solid round steel leg (vertical) members in all-welded guyed communication towers with cross-bracing. Deflections due to an arbitrary load were used to determine the restraining moments and rotational stiffness of the legs. Using the closed-form solution for buckling of a column with rotational restraint at both ends, K factors were computed. From the study it is found that the K factors varied from 0.61 to 1.00, depending on the relative sizes of the leg and bracing members. An expression for estimating the effective length factors for solid round steel leg members of all-welded guyed lattice towers with cross-bracing is developed.Key words: cross-bracing, effective length factor (K factor), finite element analysis, guyed lattice tower, solid round steel leg member, welded tower.

While constructing multistorey buildings with reinforced concrete framed structures it is a common practice to provide parking space for vehicles at the ground floor level. This floor will generally consist of open frames without any infilled walls and is called an open-storey. From a post disaster damage survey carried out, it was noticed that during the January 26, 2001 Bhuj (Gujarat, India) earthquake, a large number of reinforced concrete framed buildings with open-storey at ground floor level, suffered extensive damage and in some cases catastrophic collapse. This has brought into sharp focus the need to carry out systematic studies on the seismic vulnerability of such buildings. Determination of vulnerability requires realistic structural response estimations taking into account the stochasticity in the loading and the system parameters. The stochastic finite element method can be effectively used to model the random fields while carrying out such studies. This paper presents the details of stochastic finite element analysis of a five-storey three-bay reinforced concrete framed structure with open-storey subjected to standard seismic excitation. In the present study, only the stochasticity in the system parameters is considered. The stochastic finite element method used for carrying out the analysis is based on perturbation technique. Each random field representing the stochastic geometry/material property is discretised into correlated random variables using spatial averaging technique. The uncertainties in geometry and material properties are modelled using the first two moments of the corresponding parameters. In evaluating the stochastic response, the cross-sectional area and Young\' modulus are considered as independent random fields. To study the influence of correlation length of random fields, different correlation lengths are considered for random field discretisation. The spatial expectations and covariances for displacement response at any time instant are obtained as the output. The effect of open-storey is modelled by suitably considering the stiffness of infilled walls in the upper storey using cross bracing. In order to account for changes in soil conditions during strong motion earthquakes, both fixed and hinged supports are considered. The results of the stochastic finite element based seismic analysis of reinforced concrete framed structures reported in this paper demonstrate the importance of considering the effect of open-storey with appropriate support conditions to estimate the realistic response of buildings subjected to earthquakes.

The optimal design of elastic perfectly plastic steel frames with or without suitable protection devices and subjected to static as well as seismic loadings is studied. Two minimum volume problem formulations are proposed, on the grounds of the so-called statical approach, accounting for three different resistance limits: the purely elastic limit, the (elastic) shakedown limit and the instantaneous collapse limit. The adopted load combinations are characterized by the presence of fixed loads, of quasi-static perfect cyclic loads and dynamic (seismic) loads. The linear elastic effects of the dynamic actions are studied by utilizing a modal technique. The proposed treatment is referred to the most recent Italian code related to the structural analysis and design. The solution of the optimization problem is reached by using an appropriate linearization iterative technique specialized to the proposed formulations. Flexural frames and cross-braced frames are studied, and the related minimum volume structures are reached for assigned features of the base isolation device. The Bree diagrams of the obtained optimal designs are also determined in order to characterize their structural behaviour.

The failure analysis of the composite transmission tower made of new and better material, E-Glass with vinylester, is presented in this paper. The conventional fastener method to join the cross members to the leg members was in place of a slip joint that was developed by Goldsworthy Engineering. The lamina of the leg member and the cross bracing were tested and compared with several other failure criteria, including the Tsai-Wu Theory, the Tsai-Hill Theory, the Hoffman Theory, the Fischer Criterion, the Cowin Criterion, the Yeh-Stratton Criterion, and the Quadric Surfaces Criterion. Besides, the full-scale tower tests were performed at Electrical and Power Research Institute. From the results of the simple failure analysis of the composite transmission tower with those failure criteria, it shows that building a transmission tower from a composite material, E-Glass and vinylester, is feasible.

The objective of this paper is to provide highlights of the most important references related to the development of current guide specifications for the design of straight and curved box-girder bridges. Subjects discussed in this review include (1) different box-girder bridge configurations; (2) construction issues; (3) deck design; (4) load distribution; (5) deflection and camber; (6) cross-bracing requirements; (7) end diaphragms; (8) thermal effects; (9) vibration characteristics; (10) impact factors; (11) seismic response; (12) ultimate load-carrying capacity; (13) buckling of individual components forming the box cross section; (14) fatigue; and (15) curvature limitations provided by the codes for treating a curved bridge as a straight one. The literature survey presented herein encompasses (1) the construction phase; (2) load distribution; (3) dynamic response; and (4) ultimate load response of box-girder bridges.

The characteristic deformations and stiffnesses of multistorey frameworks with cross-bracing are established in this paper. Formulae for the shear stiffness of cross-bracing of different geometrical arrangements are presented. The sandwich model is introduced for the full-height buckling analysis. Simple closed-form solutions are derived and a design diagram and tables are given for the calculation of the critical load. Multistorey, multibay frameworks subjected to concentrated top load or uniformly distributed load on the beams are considered, both on pinned and on fixed supports. The results of a detailed accuracy analysis show that the sandwich model is suitable for the stability analysis and the error of the formulae is less than 10%. A worked example is presented to illustrate how the formulae are used for the actual calculation. The geometrical and stiffness characteristics of the example are based on one of the bracing frames of the Cardington steel building constructed in the Building Research Establishment's large building test facility. The technique and formulae presented in this paper are directly applicable to either individual frameworks with cross-bracing or multistorey buildings braced by such frameworks (and shear walls), including the reinforced concrete buildings to be constructed and tested in the Building Research Establishment's large building test facility at Cardington.

Cross-bracing in which the bolted steel angle members are alternately in compression and tension is widely used in latticed tower structures. Within each set of cross-bracing, the tie is generally assumed to restrain the strut at the cross-over joint. A series of 13 tests on cross-bracing systems is described, with slenderness ratios in the range of 102 to 160. Other variables include the inclination of the main legs and bracing, the number of bolts in each end connection, and the size of the main leg relative to the bracing. The measured behavior is compared with the results of a flexibility-based analysis and the formulas from the American and European transmission tower design manuals. The behavior is complex, but the importance of end eccentricity and number of bolts in the connection of the bracing to the main legs is apparent in these results. A secant-based design formulation is shown to provide accurate predictions of the strength of the cross-bracing.

This paper will study the feasibility of building a transmission tower from a composite material, E-glass and Vinylester. The tower was fabricated using a fabrication process called pultrusion. Also instead of using the conventional fastener method to join the cross members to the leg members, the design team utilized a slip joint that was developed by Goldsworthy Engineering The lamina of the leg member and the cross bracing were tested and compared with two analytical failure criteria, Yeh-Stratton Criterion and Quadratic (strain space) Criterion. In addition to ply failure analysis a full scale tower tests were performed at Electrical and Power Research Institute.

When a sway force acts on a cross-bracing system, one of the braces goes into a tension state while the other goes into a compression state. The tension brace helps to stiffen the compression brace through a bolted intersecting point. This paper presents an energy method for determining the improved buckling capacity of such a compression brace. The braces considered consist of equal-leg angle members that intersect orthogonally. The present problem is more difficult to solve when compared to earlier studies made on rods and tubular brace members, because angle members may buckle in a complicated flexural torsional mode rather than in a simple flexural mode.

There are numerous structural lateral systems used in high-rise building design such as shear frames, frames with shear core, framed tubes, tube and tube, super frames etc. Generally, the structural systems of tall buildings are considered to be two types. One is interior and the other one is exterior type. A system is categorized as an interior structure when the major parts of the lateral load resisting system are located within the interior of the building. Likewise, if the major parts of the lateral load resisting system are located at the building perimeter, the system is categorized as an exterior structure. In this study it is intended to model an advanced structural system which can be applied to buildings taller than the existing tallest building in the world. In this innovative concept, several parallel shear walls have been arranged in both directions and connected with beams and R.C. floor slabs. The shear walls are continuous down to the base to which they are rigidly attached to form vertical cantilevers. Their high in plane stiffness and strength make them well suited for bracing buildings up to about 278 stories. Fewer widely spaced gravity columns are arranged in the core area of the building to carry floor loads. Because of the absence of core bracing and of a large number of heavy interior columns, the net leasable area for such a building increases. Static and Dynamic analysis (Time History Analysis) has been carried out. The drift by static analysis is 1884 mm which is below the allowable limit of 2001.6mm (If considered H/500, where H is the height of the structure [9]). Also it is found by research that, when this structural arrangement is applied to around 830 meter tall structure with aspect ratio 9.8:1, no additional structural supporting system (like Outriggers, Perimeter Belts, Cross Bracing, Tuned Mass Dampers etc.) is required. This shear walls arrangement is applicable for the tall buildings of any height to avoid additional supports to resist the lateral forces while taking advantage of the creative approach of this unique concept.