Cross Bracing Research Articles

Gradient boosting-based regression modelling for estimating the time period of the irregular precast concrete structural system with cross bracing

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.

EVALUATION OF SCAFFOLD ACCIDENTS DURING BUILDING MAINTENANCE WORKS

The impact of construction related accidents to the individual, the construction sector and the economy is huge. In Malaysia about 6000 workers’ related accidents are reported annually. Scaffold accidents are one of the major causes of injury and death on Malaysian construction sites. This research investigated the scaffolding accidents during maintenance work in the Malaysian construction industry. This study provides answers to two questions: 1) what are the causes of scaffolding accidents during maintenance work? and 2) what are the possible measures to reduce scaffolding accidents during maintenance work? Primary data were collected through survey interview techniques involving 10 maintenance construction stakeholders. The research revealed that the scaffold accidents that occurred during maintenance works are due to lack of a fall protection system, lack of proper baseplate, user behavior, lack of proper guardrail and weather conditions. To reduce scaffolding accidents during maintenance works adequate poor cross bracing, safety netting, jack base, pin lock and adequate inspection of the scaffolding during operations are required. Implicit in the findings of this research is that scaffold accidents are due to behavioral issues of the sites operative and contractors’ organizations as whole. The findings provide feedback and feed for-ward information and knowledge to construction site operatives.

Performance Evaluation of Elevated Storage Reservoir with Hybrid Staging

Elevated water tanks are essential Civil Engineering framework which are known as compulsory community services urban areas. A number of elevated water tanks suffered collapse and damage to their staging in deep earthquakes, consequently their safety performance is a crucial concern throughout effective earthquake. Because of storage of clean water, it is utilized for important needs such as drinking purpose and for other domestic purpose. Within the existing work, four support patterns viz. easy brace, cross brace, rectangular brace as well as radial brace connected with various staging heights (fifteen m, twenty m, and twenty-five m) are analysed for seismic zone II, III and IV for empty tank and loaded tank. Probably the most affordable as well as secure, Intze style tank of thousand kilolitre capacity considered. When it comes to the evaluation of Intze container, 72 designs are constructed with STAAD.ProV8i Software, by which 36 models are analysed for empty tank and additional 36 models are analysed for loaded tank. Each and every seismic zone has 12 models as well as every brace has three distinct staging rises. For the safety, stability and serviceability, different parameters are obtained for different brace pattern

Experimental Study on the Effect of Cross Bracing on the Behaviour of Composite Bridges

In this paper the results of an experimental program were presented to show the effect of cross bracing on the behavior of composite bridges. Two types of models were prepared in the laboratories of the American University in Cairo Egypt. These models were chosen to be one tenth scale of the model of the Federal Highway Administration (FHWA). Deflections and strains were measured for each model according to the set of bracing and comparisons were made to show the effect of bracing.

A feasibility study of the installation of a modular bioreactor inside a chemical scrubber at a wastewater treatment plant

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.

Seismic Analysis of Open Ground Storey Structure with Shear Wall and Cross Bracings

Seismic Analysis of Open Ground Storey Structure with Shear Wall and Cross Bracings

Seismic resistant structures with steel braces combined with resilient connections

The resilient slip friction joint (RSFJ) has recently been introduced to the construction industry. This resilient damper provides a self-centring and low damage behaviour in addition to life safety. One application of this technology is the tension-only brace where the diagonal cross braces integrated with the RSFJs are used to resist lateral loads. This system is well suited for new and existing buildings (especially with long spans) when compared with the conventional tension/compression braces. This paper introduces the RSFJ tension-only system and highlights the enhanced seismic performance of this system compared to the conventional tension-only systems. A preliminary design procedure is proposed and applied to a four-storey case study structure. The results confirmed that this system could provide a high level of structural ductility while providing a low-damage behaviour.

Seismic resistant structures with steel braces combined with resilient connections

The resilient slip friction joint (RSFJ) has recently been introduced to the construction industry. This resilient damper provides a self-centring and low damage behaviour in addition to life safety. One application of this technology is the tension-only brace where the diagonal cross braces integrated with the RSFJs are used to resist lateral loads. This system is well suited for new and existing buildings (especially with long spans) when compared with the conventional tension/compression braces. This paper introduces the RSFJ tension-only system and highlights the enhanced seismic performance of this system compared to the conventional tension-only systems. A preliminary design procedure is proposed and applied to a four-storey case study structure. The results confirmed that this system could provide a high level of structural ductility while providing a low-damage behaviour.

Study on the influence of flat plates for stiffening on the force transmission of frame cross bracing

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.

High efficiency analysis model for corrugated steel plate shear walls in modular steel construction

Modular steel construction has become increasingly popular in recent years, owing to its superiority in construction speed and quality. Corrugated steel plates are commonly used as the surface enclosure and lateral force resisting component for the module unit. However, establishing precise finite element models considering all geometric characteristics of corrugated steel plate shear walls (CSPSWs) is complex, especially for walls that include openings. Consequently, it is necessary to develop a high efficiency analysis model (HEAM) for CSPSWs to perform the dynamic structural analysis. In this paper, the skeleton curve and hysteretic regulation of CSPSWs were proposed, and universal formulas were deduced to determine the hysteretic model of CSPSWs. In addition, equivalent cross braces were proposed to simulate the seismic performance of CSPSWs, and the design parameters of the equivalent cross braces were determined according to the equivalence of the load bearing capacity and mass. The accuracy and reasonability of the HEAM were validated against available cyclic test data on CSPSWs. Furthermore, the HEAM was verified at the structural level by comparing the dynamic response of the HEAM with the precise analysis model (PAM) for a six-story and a 20-story modular container structure, respectively. The comparisons demonstrated that the HEAM was capable of providing a conservative prediction of the dynamic response of CSPSWs under earthquake compared to the PAM. The HEAM developed in this study was helpful in improving the analysis efficiency of CSPSWs and can be adopted for the nonlinear seismic analysis of modular steel construction.

Finite element analysis of cold-formed thin-walled steel skeleton wall with rigid diagonal braces

In order to investigate the shear resistance of cold-formed thin-walled steel skeleton wall under monotonic load, the finite element analysis of six walls was carried out to obtain the shear capacity of different walls and reveal the wrecking mode of the wall. The results show that the arrangement of rigid cross brace and rigid diagonal brace in the wall can significantly improve the shear resistance of the wall, the vertical continuous splay layout with two spans has the largest lifting range.

Effect of Different Bracing Systems in Reinforced Concrete Frames under Cyclic Loading

Reinforced concrete (RC) framed structures are widely used as load transferring system in residential and commercial buildings. Even though the RC frames are designed for gravitational and seismic forces, but they are week under severe seismic events. The main disadvantage of the framed structures is inefficient bracing systems designed in it. This investigation is conducted mainly to study the effective bracing system in the RC framed structure to transfer the seismic force. This research aims to study the seismic performance of RC frames influenced by the various types of cross bracings under cyclic loading. The finite element analysis software package ABAQUS is used to investigate the braced RC frames analytically. The research scheme consists of three RC frames; the bare frame, the bare frame with single X-bracing (X frame), double X bracing (D-X frame) along the height. The structural parameters include, load-displacement hysteresis envelope, stiffness degradation and energy absorption were studied to analyze the performance of bracings. The results showed that the X frame and D-X frame noticeably increased the lateral strength, stiffness and energy dissipation properties compared to the bare RC frame. The results also indicated that the addition of X bracing along the height significantly enhanced the structural parameters of the RC frame.

Dynamic instability of axially loaded elements: General considerations and seismic loading

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.

Optimization Design Analysis of Large Span Cantilevered Cross Bracing Truss of Tai’an Tourism Distribution Center

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.

Retrofitting Steel Moment Frames by Using the Cable Bracing

In this paper, the behavior of retrofitted steel moment frames with bracing has been investigated. Braces include double-channel cross brace, cross braces with cable and brace with two cables passed through a cylindrical steel sheath at the location of the cables. Nonlinear analysis of frames has been carried out under cyclic loading with increasing amplitudes. Comparison of numerical analysis results with laboratory data shows the accuracy of finite element models. By determining the hysteresis and plasticity behavior of the frames, advantages and disadvantages of each of the retrofitting methods have been examined. The results have shown the use of double channels and cables to retrofit the frame increases the initial hardness and final load of the frame considerably compared to the moment frames and reduces its ductility. In frame with sheathed cable brace, the initial hardness was the same with the moment frames and the frame has been shown to have ductile behavior.

Presenting a Differential Equation Strengthened by the Cross Braces for Roof System

Plate girders structures is a major industry, much used in the systems covered by these beams, reduce deflection and decrease the maximum bending moment can be considered as a development methodology that way, by the cross beams or braced beams element perpendicular to the girders is provided. In this paper, the effect of stiffness and distance elements development (braced beams) are studied. Differential equation of degree four governing the behavior of the partial structures a quadratic relationship is determined by solving the following mathematical transformations and the fundamental equations are derived. The resulting equations are solved by a practical problem and the answer to the problem. The modeling results are compared with the SAP2000 program shows that highly accurate implementation and compliance. It is thus stiffness changing elements within the cross can be different amounts of stress, bending moment and improved cover and roof system and regulation forces to be calculated. In the proposed method by changing several parameters affecting. Calculate the amount of stress and reduced bending moments and an optional stress adjustment achieved. Other factors, including the backing, boundary conditions, a subsidiary of loading and shooting the junction depth of the main beam are effective in regulating stress.

Seismic Analysis of RC Elevated Rectangular Water Tank using Various Staging Patterns

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.

Shaking table investigations on the seismic performance of a steel frame with optimized passive energy dissipation devices

In this study, the seismic responses of two kinds of optimized metallic energy dissipation devices (EDDs) are investigated by conducting shaking table tests on two storey full-scale steel frame model. The dampers are installed in pairs between the beams and corresponding cross bracings on each storey of the model. Then the whole setup, with and without dampers are subjected to different seismic waves with Peak Ground Accelerations (PGAs) of 0.14g, 0.40g, 0.62g and 0.90g with various configurations. In this paper, the dynamic properties, seismic responses and damage details of these distinct setups are recorded, analyzed and compared between controlled and uncontrolled structures. Thus obtained result shows that the effect of these kinds of dampers on acceleration and displacement are quite significant. This study lays down a firm foundation for the reliability of these kinds of passive energy dissipation devices on the basis of deeper research investigations.

Retrofitting steel moment frames by using the cable bracing

In this paper, the behavior of retrofitted steel moment frames with bracing has been investigated. Braces include double-channel cross brace, cross braces with cable and brace with two cables passed through a cylindrical steel sheath at the location of the cables. Nonlinear analysis of frames has been carried out under cyclic loading with increasing amplitudes. Comparison of numerical analysis results with laboratory data shows the accuracy of finite element models. By determining the hysteresis and plasticity behavior of the frames, advantages and disadvantages of each of the retrofitting methods have been examined. The results have shown the use of double channels and cables to retrofit the frame increases the initial hardness and final load of the frame considerably compared to the moment frames and reduces its ductility. In frame with sheathed cable brace, the initial hardness was the same with the moment frames and the frame has been shown to have ductile behavior.

STRENGTHENING STRATEGY APPLIED FOR REINFORCED CONCRETE (RC) FRAME STRUCTURE USING STEEL BRACES AFTER LOMBOK EARTHQUAKE (CASE STUDY: PARKING-LOT OF MALL BALI GALERIA-MBG)

Lombok Earthquake 2018 was very rare and interesting phenomenon to be taken into consideration due to its behavior. The pattern of seismicity was up and down which gives panic and confusion, especially to the public who live in Lombok, Bali and Sumbawa. There were at least six earthquakes with magnitudes of 5.5 to 6.9 ML in a short interval between 29th July to August 25, 2018. The earthquake caused structural damages in Lombok as well as in Bali region. The case study has been taken to cover 4-storey RC frame of MBG building which located in Kuta, Bali. Damage occurs on columns, beams. Beams and pre-printed reinforced concrete plates and reinforced concrete columns in place. Analysis has been applied into existing structure and stress ratio analysis check has also been taken in order to find failures. Overstresses has been found at the columns and beams, therefore, the strengthening is needs. Strengthening strategy using braces of Wide Flange-IWF, typically a cross bracing (X) method has been taken into account in order to find out the structural behavior as well as the performance level of building. Braces has been invoked for both: transverse and longitudinal directions of buildings and most of the beams and columns were reinforced by using Fiber. This strengthening has been done very nicely and the parking-lot building has been tested and it can be used regularly as it is.