Search Results (16)

This study investigates the causes of soft-storey and weak-storey formations in low- and mid-rise RC (Reinforced Concrete) buildings in Türkiye. In the first phase of the study, 96 model buildings were designated for the examination of soft-storey irregularity when the ground floors are used for commercial purposes and the upper floors for residential use. The ground floor heights that would cause soft-storey irregularity in each of the selected buildings were determined according to the formulas given in the Türkiye Building Earthquake Code (TBEC) and the American Society of Civil Engineers Standard (ASCE). It was found that the ground floor heights obtained according to ASCE are usable in practice, whereas those obtained according to the TBEC, particularly for buildings over three storeys, are excessively high for practical use. This indicates that, even if the buildings in Türkiye are designed with very high ground floor heights, they do not have soft-storey irregularities, according to the TBEC, but soft-storey formation may occur in these buildings due to the high ground floor height as a result of the effects of earthquakes. Instead of the soft-storey irregularity coefficient limit value (n_ki > 2) found in the TBEC, this study proposes a new limit value to prevent the design of buildings with very high ground floors. In the second phase of the study, for the purpose of examining weak-storey irregularity, 105 model buildings differing in their infill wall layout, number of spans, span length, and number of storeys were selected. The weak-storey irregularity coefficients of each of these models were determined according to the TBEC. The results of the study revealed that buildings with no infill walls in one direction or with infill walls in only one of the exterior axes in one direction have a high risk of having weak storeys. Full article

Masonry has been widely used for the construction of residential buildings in Serbia and the majority of European countries. Confined masonry (CM) is a contemporary masonry technology that consists of load-bearing masonry walls enclosed in lightly reinforced horizontal and vertical reinforced concrete (RC) confining elements. CM has been widely used for the construction of low-rise and mid-rise residential buildings in Serbia and the region (Yugoslavia) since the 1960s. The design case study of a typical multi-family residential building located in Niš, Serbia (the third-largest urban center in the country), is discussed in this paper. This building was initially designed as a five-story CM structure in accordance with the 1981 Yugoslav seismic design code PTN-S, which was enforced in Serbia until 2019, when the Eurocode was adopted for official seismic design codes. Due to architectural constraints, the original design solution involving the CM system was not compliant with the code; hence, an alternative design using an RC-frame system with masonry infills was adopted. A comparison of two different design solutions provides insight into the different requirements of seismic design codes that have been used in the region. It is important to observe that seismic forces for RC structures determined in accordance with the PTN-S code are considerably lower compared to the ones determined according to EC 8-1, with the ratio ranging from 0.37 to 0.69. The seismic shear force according to Eurocode 8 is 1.46 times higher than the force that was used for seismic design according to the PTN-S code in the case of RC-frame structures. The results of an analysis of CM structures show that the seismic shear force in accordance with Eurocode 8 is almost 2.6 times higher than the force that was used for seismic design in accordance with the PTN-S code. The findings of this study are believed to be useful for understanding the difference in seismic design solutions for previous seismic design codes (which were used in the region for more than 40 years) and the present codes (Eurocodes). Full article

This study presents the performance-based seismic assessment of low-rise reinforced concrete archetype buildings, considering repair costs for ordinary moment-resistant frames (OMF) and dual systems consisting of OMF plus special shear walls (SSW). Historically, the OMF systems, conceived for residential purposes in Ecuador resulting from informal construction, have reported poor responses under seismic forces. This study analyzes damage levels through fragility curves as a function of the maximum global drift reached through incremental dynamic analysis. For this, two archetypes with OMF and two with a similar configuration, including structural walls, are modeled to define a loss function and annual collapse probabilities. As a result, it is noted that systems with structural walls significantly reduce repair costs by between 75 and 90% of the total cost of the building, and prevent collapse. Systems with ordinary moment frames report total losses, implying their use should be limited in areas of high seismicity. Full article

Nuclear safety-related structures are crucial for ensuring the safety of nuclear facilities and preventing the leakage of radioactive materials, with the primary structural component being low-rise reinforced concrete (LRC) walls. These walls are required to carry combined in-plane axial and horizontal loads, making the accurate prediction of their lateral load-carrying capacity particularly important. In this study, six LRC walls with aspect ratios between 0.33 and 1 were tested and a model for the prediction of the lateral load-carrying capacity of LRC walls was established based on the observed failure mode and plastic limit theory. The parameter in the model was calibrated using the obtained results in this test along with a database containing 131 walls in the literature. Compared to the equations in the American standard ACI 349 and the French standard RCC-CW, the proposed equation is most suitable for assessing the lateral load-carrying capacity of LRC walls in nuclear safety-related structures. The calculated values of the proposed equation exhibit a ratio closest to 1 when compared to experimental values and possess the minimum degree of variation. The computational results reveal that the proposed equations in this study exhibit superior precision and stability. Full article

Aiming at the problem of displacement of collapse direction caused by the impact of the high-rise reinforced concrete chimney in the process of blasting demolition, combined with the monitoring methods such as high-speed photography observation, piezoelectric ceramic sensor, and blasting vibration monitor, the impact process of the 180 m high chimney was comprehensively analyzed. The results show that the chimney will experience multiple ‘weight loss’ and ‘overweight’ effects during the sit-down process, inducing compressive stress waves in the chimney. When the sit-down displacement is large, the broken reinforced concrete at the bottom can play a significant buffering effect, and the ‘overweight’ effect gradually weakens until the sit-down stops. The stress of the inner and outer sides of the chimney wall is obviously different in the process of collapsing and touching the ground. The waveform of the monitoring point of the piezoelectric ceramic sensor is divided into three stages, which specifically characterizes the evolution process of the explosion load and the impact of the chimney. The vibration induced by explosive explosion is mainly high-frequency vibration above 50 Hz, the vibration induced by chimney collapse is mainly low-frequency vibration below 10 Hz, and the vibration characteristics are obviously different. In the process of blasting demolition and collapse of high-rise reinforced concrete chimney, due to the impact of sitting down, the wall of the support tube is subjected to uneven force, resulting in the deviation of the collapse direction. In practical engineering, the control measures of chimney impact, blasting vibration, and collapse touchdown vibration should be fully strengthened to ensure the safety of the protection target around the blasting demolition object. Full article

This research investigates the convenience of structural identification tools to detect the rocking motion tendency, using as input the structural response to ambient vibrations. The rocking ratio and rocking spectrum are proposed as original tools to highlight the rocking motion and its frequency content. The proposed procedure allows the detection and quantification of rocking using only building vertical motion records in both cases of ambient vibration and earthquake. First, three-dimensional finite element models of reinforced concrete buildings are adopted to simulate the structural response to white noise vibration. Different low- and high-rise buildings are studied, having framed structure and frame–wall system, regular and irregular structure, shallow foundation and underground floors. The structural response obtained numerically is analyzed using different signal processing tools to obtain the dynamic features of buildings, and the rocking motion tendency is identified by comparison with a reference fixed base condition. Then, the reliability of the proposed methodology to detect rocking motion attitude, using only the structural motion, is verified and quantified using the proposed tools. Finally, the same approach is applied to real structural motion records of a high-rise reinforced concrete building. Full article

The direct modeling of masonry infill walls on many buildings, based on damage recorded by various past earthquakes, has become increasingly necessary in order to identify the seismic behavior of these elements, which constitute an important part of reinforced concrete buildings. In this paper, several 3D models were analyzed by the nonlinear static (pushover) method, when ignoring, and when considering, masonry infill walls. The finite element software SAP analyzed the proposed models. These models represent low and mid-rise reinforced concrete buildings infilled with double-leaf hollow bricks. The properties of materials used in Algeria, either in the frame elements or the infill elements, were used. The results obtained were compared according to two parameters, the natural time period of the building and the pushover curve, by varying the values of the dead load and the concrete compressive strength. The results were discussed according to the suggested parameters. The results showed that indirect modeling of such walls, either by taking assumptions embedded in the seismic behavior factor or by means of the macro-modal, can lead to a poor appreciation of the seismic behavior of such buildings. Consequently, direct modeling of walls by the infill of the real void showed acceptable results to some extent. This contributes greatly towards understanding the seismic behavior of this type of building. Full article

In this study, structural thin-layer sandwich walls (SWs) made of steel-fibre-reinforced concrete (SFRC) without conventional reinforcements were investigated. Other researchers have shown that SWs with thin wythes can be used as load bearing structures in low-rise buildings, thereby reducing the amount of concrete by 2–5 times if compared to conventional reinforced-concrete SWs. In most studies, relatively warm climatic regions are the focus, and thin-layer SWs with shear connectors to obtain a certain level of composite action are investigated. In almost no studies has sound insulation been evaluated. In this study, a numerical investigation of structural, thermal and sound insulation performances was carried out. The load-bearing capacities of composite and non-composite SWs are compared. Regions with the lowest five-day mean air temperature of −20 ${}^{\circ }$C were considered. The characteristics of the SW are compared to the requirements given in relevant European and Latvian standards. The minimum thermal insulation for family houses varies from 120 mm to 200 mm, depending on the material. To ensure sufficient sound insulation, the average thickness of the concrete wythes should be around 60 mm, preferably with a 15 mm difference between them. Structural analysis of the proposed wall panel was performed using non-linear finite element analysis software ATENA Science. The obtained load-bearing capacity exceeded the design loads of a single-story family house by around 100 times, regardless of the degree of composite action. Full article

This study evaluates the structural behavior of aerated autoclave concrete (AAC) blocks laterally loaded in the in-plane direction under quasi-static loading. The study started with the evaluation of the basic physical properties of the AAC blocks, including its structural properties (individually and as part of an assembly), followed by large-scale testing of two (half-scaled) walls constructed with commercially available AAC blocks. The first wall was unreinforced, similar to the commonly used construction technique for low-rise houses where AAC blocks are utilized. The second one was internally reinforced with short dowels connecting the foundation to the walls through their lower block rows and externally reinforced with carbon-fiber-reinforced polymer (CFRP) sheets through the entire wall height. The reinforcement scheme was conducted in such a way that does not delay construction time. Reinforcing the wall significantly increased the strength of the wall in the in-plane direction. The reinforced wall exhibited increased initial stiffness, higher ductility, and larger energy dissipation, in addition to a change in the failure mode. The unreinforced wall failure mode was dominated by blocks sliding, while the reinforced wall failure was dominated by compressive shear failure with wall uplifting. The findings of this study can be implemented to increase the lateral strength of unreinforced new houses and can also be extended to strengthen existing houses built with unreinforced AAC blocks. Full article

The flanged, barbell, and rectangular squat reinforced concrete (RC) walls are broadly used in low-rise commercial and highway under and overpasses. The shear strength of squat walls is the major design consideration because of their smaller aspect ratio. Most of the current design codes or available published literature provide separate sets of shear capacity equations for flanged, barbell, and rectangular walls. Also, a substantial scatter exists in the predicted shear capacity due to a large discrepancy in the test data. Thus, this study aims to develop a single gene expression programming (GEP) expression that can be used for predicting the shear strength of these three cross-sectional shapes based on a dataset of 646 experiments. A total of thirteen influencing parameters are identified to contrive this efficient empirical compared to several shear capacity equations. Owing to the larger database, the proposed model shows better performance based on the database analysis results and compared with 9 available empirical models. Full article

Most of the reinforced concrete buildings in Nepal are low-rise construction, as this type of construction is the most dominant structural form adopted to construct residential buildings in urban and semi-urban neighborhoods throughout the country. The low-rise residential constructions generally follow the guidelines recommended by the Nepal Building Code, especially the mandatory rules of thumb. Although low-rise buildings have brick infills and are randomly constructed, infill walls and soil–structure interaction effects are generally neglected in the design and assessment of such structures. To this end, bare frame models that are used to represent such structures are questionable, especially when seismic vulnerability analysis is concerned. To fulfil this gap, we performed seismic vulnerability analysis of low-rise residential RC buildings considering infill walls and soil–structure interaction effects. Considering four analysis cases, we outline comparative seismic vulnerability for various analysis cases in terms of fragility functions. The sum of observations highlights that the effects of infills, and soil–structure interaction are damage state sensitive for low-rise RC buildings. Meanwhile, the design considerations will be significantly affected since some performance parameters are more sensitive than the overall fragility. We also observed that the analytical fragility models fundamentally overestimate the actual seismic fragility in the case of low-rise RC buildings. Full article

Cross laminated timber (CLT) panels have been gaining increasing attention in the construction field as a diaphragm in mid- to high-rise building projects. Moreover, in the last few years, due to their seismic performances, low environmental impact, ease of construction, etc., many research studies have been conducted about their use as infill walls in hybrid construction solutions. With more than a half of the megacities in the world located in seismic regions, there is an urgent need of new retrofitting methods that can improve the seismic behavior of the buildings, upgrading, at the same time, the architectural aspects while minimizing the environmental impact and costs associated with the common retrofit solutions. In this work, the seismic, energetic, and architectural rehabilitation of tall reinforced concrete (RC) buildings using CLT panels are investigated. An existing 110 m tall RC frame building located in Huizhou (China) was chosen as a case study. The first objective was to investigate the performances of the building through the non-linear static analysis (push-over analysis) used to define structural weaknesses with respect to earthquake actions. The architectural solution proposed for the building is the result of the combination between structural and architectonic needs: internal spaces and existing facades were re-designed in order to improve not only the seismic performances but also energy efficiency, quality of the air, natural lighting, etc. A full explanation of the FEM modeling of the cross laminated timber panels is reported in the following. Non-linear FEM models of connections and different wall configurations were validated through a comparison with available lab tests, and finally, a real application on the existing 3D building was discussed. Full article

Foundation piles that are made by concrete 3D printers constitute a new alternative way of founding buildings constructed using incremental technology. We are currently observing very rapid development of incremental technology for the construction industry. The systems that are used for 3D printing with the application of construction materials make it possible to form permanent formwork for strip foundations, construct load-bearing walls and partition walls, and prefabricate elements, such as stairs, lintels, and ceilings. 3D printing systems do not offer soil reinforcement by making piles. The paper presents the possibility of making concrete foundation piles in laboratory conditions using a concrete 3D printer. The paper shows the tools and procedure for pile pumping. An experiment for measuring pile bearing capacity is described and an example of a pile deployment model under a foundation is described. The results of the tests and analytical calculations have shown that the displacement piles demonstrate less settlement when compared to the analysed shallow foundation. The authors indicate that it is possible to replace the shallow foundation with a series of piles combined with a printed wall without locally widening it. This type of foundation can be used for the foundation of low-rise buildings, such as detached houses. Estimated calculations have shown that the possibility of making foundation piles by a 3D printer will reduce the cost of making foundations by shortening the time of execution of works and reducing the consumption of construction materials. Full article

Modular buildings offer faster construction process, provide better construction quality, allow reducing construction waste and are potentially flexible. Frames of modular units can be made of metal, timber, concrete or mixed materials but lightweight structures do not always allow erecting high-rise buildings and generally present a higher risk of overheating and/or overcooling. To reconcile these pros and cons, a typology of modular building called Slab was designed by a group of architects. The building is composed on the one hand of a permanent concrete structure named shelf-structure and on the other hand of several flexible removable timber modular units, also known as modules. The shelf-structure will host the common utility rooms and will serve as docking infrastructure for the housing modules. To provide high flexibility, the Slab building was designed to adapt to any orientation and location in Luxembourg. An energy concept and a HVAC systems design has been developed for the Slab building. Furthermore, a two-fold sustainability analysis was carried out. The first part of the analysis regards the determination of the minimum required wall thicknesses of the modules in accordance with Luxembourgish regulatory requirements, although the current regulation does not yet consider the Slab building typology. The second part, which is the subject of this paper, is thermal comfort assessment, more precisely, summertime overheating risk assessment of these modules, in compliance with Luxembourgish standard. In this regard, dynamic thermal simulations have been realized on two module variants; the first fulfills the passive house requirements, and the second—the current requirements for building permit application, which in principle corresponds to low energy house requirements. Simulations showed that with adequate solar shading and reinforced natural ventilation by window opening, overheating risk could be avoided for the normal residential use scenario for both module variants. Full article

On 25 April 2015, a strong earthquake of magnitude 7.8 struck central Nepal including the capital city, Kathmandu. Several powerful aftershocks of magnitude 6.7, 6.9 and 7.3 together with hundreds of aftershocks of local magnitude greater than 4 hit the same area until May 2015. This earthquake sequence resulted in considerable damage to the reinforced concrete buildings apart from brick and stone masonry constructions. High-rise buildings in Nepal are mainly confined in Kathmandu valley and their performance was found to be in the life safety to collapse prevention level during the Gorkha earthquake sequence. In this paper, seismic performance assessment of a reinforced concrete apartment building with brick infill masonry walls that sustained life safety performance level is presented. Rapid visual assessment performed after the 12 May aftershock (M_W 7.3) highlighted the need for detailed assessment, thus, we carried out nonlinear time history analysis using the recorded accelerograms. The building was first simulated for the recorded acceleration time history (PGA = 0.16 g) and the PGA was scaled up to 0.36 g to assess the behaviour of building in the case of the maximum considered earthquake occurrence. The sum of results and observations highlighted that the building sustained minor damage due to low PGA occurrence during the Gorkha earthquake and considerable damage would have occurred in the case of 0.36 g PGA. Full article