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Open Construction & Building Technology Journal
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This is an Open Access Journal

Open Access journal
ISSN (Online) 1874-8368
Published by Bentham Open

[69 journals]

Energy Dissipation in Frame Structures using Sliding Lever Mechanism
Technique
- Abstract: Aim:The aim of this study was to investigate the seismic energy dissipation mechanism of a novel and newly proposed sliding lever damping energy dissipation through dynamic shake table testing.Background:Typical energy dissipation systems consist of brace members and installed dampers, which are directly connected to structural members such as beams, columns and joint regions. This can cause additional load concentrations and may require retrofitting or strengthening of existing structures. In order to avoid the load demand on the main structural system, a new energy dissipation technique based on a sliding lever mechanism is proposed and tested through dynamic testing.Objective:The objective of this study was to test a new sliding lever damping energy dissipation through dynamic shake table testing within the scope of steel frame structures.Methods:In order to investigate the proposed energy dissipation configuration, a 1/3 reduced scaled, three-story and one bay steel frame model has been fabricated and tested in a uni-directional shaking with increasing excitation and, without and with the new technique. For the sliding lever energy dissipation configuration, a non-structural frame (, carrying no gravity loads) has been constructed and provided with an installed ramp-damper assembly. The shaking responses in the form of acceleration and displacement histories have been obtained during the experimental program and compared in order to check the efficiency of the proposed configuration.Results:The results showed a reduction of 55% to 6% in stories deflections and 36% to 12% in acceleration with the newly proposed sliding lever mechanism energy dissipation technique. The top story peak displacements for the damped frame case decreased by 36.55% in case of 0.1 g, 37.95% in case of 0.2g, 31.89% in case of 0.3g, 38.05% in case of 0.4g, 29.37% in case of 0.5g and 12.06% in case of 0.6g shaking excitation.Conclusion:It has been confirmed from the current experimental studies that the new configuration was quite effective in reducing the overall displacement and acceleration response. The reduction in the structural response parameters was very significant during low excitation shaking, whereas, with the increase in shaking intensities, the responses varied with much less difference.
Static Performances of Timber- and Bamboo-Concrete Composite Beams: A
Critical Review of Experimental Results
- Abstract: The use of composite beams made with traditional concrete and bio-based materials (such as timber and bamboo) is a valuable solution to reduce the environmental impact of the building sector. Timber-Concrete Composite (TCC) beams have been used for decades in structural applications such as new buildings, refurbishment of old timber structures, and bridges. Recently, different researchers suggested composite beams based on engineered bamboo, commonly named Bamboo-Concrete Composite (BCC) beams. This study presents a systematic comparison of structural performances and connection behavior of TCC and BCC beams under short-term static load. TCCs beams are compared to BCC ones using similar shear connectors. The most important aspects of the two composite systems are compared: mechanical behavior of connectors and structural behaviors of full-scale composite beams (, failure modes, connection stiffness, connection shear strength, ultimate load-carrying capacity, maximum deflection and composite efficiency). This comprehensive review indicates that BCC beams have similar or even better structural performances compared with TCC.
Investigation of Steel Frames Equipped with Steel Eccentric Braces and
Steel-Concrete Buckling-Restrained Braces Having Moment Link
- Abstract: Background:Different bracing systems of steel Eccentric Braces (EBs) and steel-concrete Buckling-Restrained Braces (BRBs) can be used in steel frames in order to make the frames stronger in resisting lateral loads. These steel frames with EBs or BRBs are generally called Eccentrically Braced Frames (EBFs) or Buckling-Restrained Braced Frames (BRBFs), respectively.Objective:This study aims to investigate steel frames with bracing systems of steel EBs and steel-concrete BRBs having moment link.Methods:The EBFs and BRBFs are nonlinearly analysed employing the finite element software ABAQUS. Experimental tests of the EBF and BRB are utilised for the validation of their modelling. The modelling is validated by comparing the modelling results with experimental tests results. Then, an EBF and a BRBF are designed having moment link. The extreme earthquake records of Tabas, Chi-Chi, and Northridge are selected for the dynamic analyses of the EBF and BRBF. The validated modelling method is applied to analyse the designed EBF and BRBF under the selected earthquake records.Results:The achieved results from the analyses are lateral displacements, base shears, and energy dissipations of the EBF and BRBF and moment link rotations. These results are compared and discussed.Conclusion: It is concluded that the hierarchy of the lateral displacements of the analysed EBF and BRBF, having moment link, is related to the Tabas, Chi-Chi, and Northridge records because the lateral displacements of the frames are directly proportional to the peak ground accelerations of the records, and there is the same hierarchy for the records in terms of their peak ground accelerations. Lower lateral displacements are witnessed for the BRBF than the EBF subjected to the Tabas and Chi-Chi records. However, larger lateral displacement is observed for the BRBF than the EBF under the Northridge record. The same procedure as the lateral displacements is also revealed for the effectiveness of the BRBF with regard to its link rotations compared with the EBF. Moreover, the BRBF improves the base shear capacities and energy dissipations of the frame compared with the EBF. Consequently, the BRBF is generally demonstrated to be superior to the EBF from the structural performance point of view. Thus, the BRBF can be used more efficiently in structures subjected to large lateral loads compared with the EBF.
The Influence of the Rate of Increase of Ground Vibration Accelerations
During Earthquakes on the Value of the Observed Macroseismic Effect
- Abstract: Aims:It is known that along with the traditionally considered amplitudes and durations of ground vibrations, the rate of increase in the intensity of ground vibrations in time can also affect the level of macroseismic effects caused by earthquakes. According to the previously obtained correlations, the differences between the observed macroseismic effects during earthquakes with slow and fast increases in the amplitude level of oscillations can reach one point of the macroseismic scale. The purpose of this study is to obtain, on the basis of a significantly (almost 9 times) larger than before, the volume of initial data (in combination with a more effective method of analysis) new and more accurate quantitative estimates of the studied dependences, as well as their possible interpretation.Background:This work continues the research that began in 1985-1989. A representative statistical material was used, including 1250 accelerograms of earthquakes that occurred in different regions of the world, with magnitudes = 2.5-7.7, distances of 5-230 km and independent estimates of macroseismic intensities = 3-10 points by the or .Objective:Correlations between the absolute and relative rates of increase of ground vibration accelerations during earthquakes with different magnitudes and distances, on the one hand, and macroseismic effects caused by these vibrations, on the other, are considered.Methods:The study was carried out in the form of a direct statistical comparison of the parameters describing the form of ground vibrations during earthquakes with the characteristics of variations in macroseismic effects caused by these vibrations. A sample was formed and analyzed, including 1250 accelerograms of sensible and strong earthquakes recorded in various regions of the world and having independent estimates of the macroseismic intensity of shaking at instrumental registration sites.Results:It is shown that the macroseismic intensity of shaking can depend on the relative rate of increase of acceleration amplitudes in the general wavetrain of ground vibrations. An increase in the macroseismic intensity of shaking was observed with an increase in the relative rate of increase of the amplitudes and, conversely, it decreases with a slowdown in the rate of increase of the acceleration intensity. Similar constructions, made according to the data of the Time-Frequency Signal Analysis (TFSA) of 50 accelerograms of earthquakes with = 3.3-6.2, a distance of 7-139 km and a macroseismic intensity of 4-7 points, showed the same dependence, but clearer and with large coefficients of regression and correlation. The difference between earthquakes with “fast” and “slow” accelerations in the intensity can reach one point.Conclusion:The results of this study indicate that the rate of increase in the acceleration of ground vibrations during earthquakes can in a certain way affect the macroseismic effects. Earthquakes with slowly increasing amplitudes of ground vibration accelerations form average less macroseismic effects than those with rapidly growing accelerations.Variations in the shaking intensity, at the same time, are quite significant and can be compared with variations associated with differences in soil-geomorphological conditions, focal mechanisms, general seismotectonic conditions and other factors that are traditionally taken into account in detailed assessments of seismic hazard. Therefore, this factor should also be taken into account when conducting such studies.
Experimental Investigation of Shear Strength for Steel Fibre Reinforced
Concrete Beams
- Abstract: Aims:The aim of this paper is to investigate the influence of the volume fraction of fibres, the depth of the beam and the shear span-to-depth ratio on the shear strength of steel fibre reinforced concrete beams.Background:Concrete is a material widely used in structures, as it has high compressive strength and stiffness with low cost manufacturing. However, it presents low tensile strength and ductility. Therefore, through years various materials have been embedded inside it to improve its properties, one of which is steel fibres. Steel fibre reinforced concrete presents improved flexural, tensile, shear and torsional strength and post-cracking ductility.Objective:A better understanding of the shear performance of SFRC could lead to improved behaviour and higher safety of structures subject to high shear forces. Therefore, the influence of steel fibres on shear strength of reinforced concrete beams without transverse reinforcement is experimentally investigated.Methods:Eighteen concrete beams were constructed for this purpose and tested under monotonic four-point bending, six of which were made of plain concrete and twelve of SFRC. Two different aspect ratios of beams, steel fibres volume fractions and shear span-to-depth ratios were selected.Results:During the experimental tests, the ultimate loading, deformation at the mid-span, propagation of cracks and failure mode were detected. From the tests, it was shown that SFRC beams with high volume fractions of fibres exhibited an increased shear capacity.Conclusion:The addition of steel fibres resulted in a slight increase of the compressive strength and a significant increase in the tensile strength of concrete and shear resistance capacity of the beam. Moreover, these beams exhibit a more ductile behaviour. Empirical relations predicting the shear strength capacity of fibre reinforced concrete beams were revised and applied successfully to verify the experimental results obtained in this study.
Assessing the Post-Earthquake Temporary Accommodation Risks in Iran Using
Fuzzy Delphi Method
- Abstract: Background:The process of temporary accommodation after an earthquake is one of the most important issues in crisis management.Objective:This research study attempts to identify and prioritize the key risks inherent with the post-earthquake temporary accommodation process in Sanandaj, Iran using the Fuzzy Delphi method.Methods:To achieve this goal, first, we examined the previous research on the issue of temporary accommodation after earthquakes and other disasters worldwide in order to determine the current important challenges. Then, the opinions of crisis management experts in 11 areas and 94 questions in the form of Fuzzy Delphi survey questionnaire with Five-point Likert measurement scale were used to rank these challenges. The Delphi panel participants, who responded to the Fuzzy Delphi questionnaire, consisted of 18 experts related to crisis management in executive organizations of Kurdistan province.Result:After performing the steps of the fuzzy Delphi method, a basket of important risks in the temporary accommodation process were identified qualitatively and quantitatively, and were prioritized in order of relevance and significance. The results showed that climatic challenges have the highest potential of post-earthquake temporary accommodation risk in the region among of the 11 major risk areas under examination.Conclusion:The study’s findings and recommendations can serve as a policy instrument and consultative toolkit for relevant stakeholders.
Effect of Variation in Moisture Content on Soil Deformation and
Differential Settlement of Frame Structures in Nairobi Area and its
Environs
- Abstract: Background: The stability of structures to a great extent depends on the foundation. The foundation of a building structure plays a key role in transferring the loading from the structure to the soil underneath. In foundation design, the effect of changes in soil moisture content to soil deformation and subsequent differential settlement during the lifespan of a structure is often ignored.Objective: This research establishes the relationship between soil moisture content and soil deformation for soils in the Nairobi area and its environs. Soil deformation in some foundation supports in a building leads to an unequal settlement resulting in differential settlement. The research further determines the influence of soil deformation on the differential settlement of a typical four-storey reinforced concrete frame structure.Methods: Seven soil samples collected from the Nairobi area and its environs were subjected to moisture content variation. Soil deformation was measured, and the laboratory test results were applied to determine the modulus of subgrade reaction constant for the elastic foundation. A four-storey reinforced concrete frame structure was modelled at varying foundation conditions. The resulting differential settlement for frame structure was evaluated. Two control cases were assessed. The structural behaviour depicted by changes in bending moments, shear forces, differential settlement, and member stresses for varying foundation cases was assessed. Staad Pro software was applied in structural modelling.Results: Increasing soil moisture content from 30% to 50% and 75% by keeping all other factors constant led to increased soil deformation ranging from 17.2% to 34% for the 7 soil samples tested. Structural modelling revealed that increasing soil moisture content at a group of four outer footings in a 16 footings’ building contributes to significant changes in shear forces, bending moments, compressive and tensile stresses, and supports the differential settlement. Differential settlement induced by soil deformation arising from an increase in soil moisture content from 30% to 75% increased by 49.1%.Conclusion: Increase in soil moisture content contributed to soil deformation, which led to a significant differential settlement in a line of foundation’s outer footings in a building. The moisture content-caused differential settlement, which contributed to remarkable changes in the amount and distribution pattern for shear forces, bending moments, compressive and tensile stresses, and node displacement when the soil moisture content was increased from 30% to 75%.An increase in soil moisture content to 50% and above at some footings of a building would lead to structural failure unless the building structure is specifically designed to withstand such differential settlement. Construction stakeholders should consider the differential settlement attributed to variation in soil moisture content during the structure’s lifespan and safety factors adequately at the design stage to avoid potential structural failure and even collapse.
Client-Driven Level 2 BIM Implementation: A Case Study from the UAE