Low-rise Buildings Research Articles

Performance-based seismic design of low-rise steel moment-resisting frames targeting collapse fragility curve

The aim of this study is to develop a performance-based seismic design method targeting a desirable collapse fragility curve. This direct fragility-based design method is developed and validated for low-rise steel moment-resisting frames. To this end, a relationship is first defined between target fragility curve and design displacement. To this end, 4-story buildings are designed with the design drift ratios of 1.5 % to 4 % and the seismic fragility analysis is performed via the Monte Carlo simulation. The mentioned relationship is derived by plotting the median collapse spectral acceleration versus the design drift ratio. With regard to have this relationship, a modified version of performance-based plastic design method is then proposed. The direct fragility-based design method has been proposed for the low-rise buildings located in Log Angeles. However, its efficiency is also validated for two other regions of Vancouver, Canada and San Francisco, U.S. It can be found from the results that the fragility curve of designed buildings is very close to the target fragility curves. Therefore, the direct fragility-based design method is capable of achieving a target fragility curve and can be considered as an effective design method for low-rise steel moment-resisting frames.

Diurnal variation in an amplified canopy urban heat island during heat wave periods in the megacity of Beijing: roles of mountain–valley breeze and urban morphology

Abstract. Against the background of global warming and rapid urbanization, heat waves (HWs) have become increasingly prevalent, amplifying canopy urban heat island intensity (CUHII). The megacity of Beijing, characterized by rapid urbanization, frequent high-temperature events, and exceptionally complex terrain, presents a unique case to study the synergies between HWs and canopy urban heat islands (CUHIs). However, research exploring the formation mechanisms of the amplified CUHII (ΔCUHII) during HW periods in the megacity of Beijing from the perspectives of mountain–valley breeze and urban morphology remains scarce. This study found that compared to non-heat-wave (NHW) periods, the average daily CUHII during HW periods significantly increased by 59.33 %. On the urban scale, the wind direction reversal of the mountain–valley breeze might contribute to the north–south asymmetry in the ΔCUHII. On the street scale, wind speed was inversely proportional to the ΔCUHII. In addition, the ΔCUHII was closely related to urban morphology, particularly the three-dimensional indicators of buildings. During the mountain breeze phase, high-rise buildings with lower sky view factors (SVFs) had a more pronounced effect on amplifying CUHII compared to low-rise buildings with higher SVFs. Conversely, during the valley breeze phase, high-rise buildings exerted a dual influence on amplifying CUHII. Our findings provide scientific insights into the driving mechanisms of urban overheating and contribute to mitigating the escalating risks associated with urban excess warming.

A comparative analysis of an RC low-rise building with the seismic codes of countries lying in the Himalayas: China, India, Nepal, and Pakistan

The Himalayan region is one of the most seismically active areas in the world due to its tectonic setting. This vulnerability poses significant risks to buildings, resulting in substantial loss of life, property, and infrastructure. This study investigates the seismic performance of a reinforced concrete (RC) low-rise building using the seismic codes of countries situated along the Himalayan belt: China, India, Nepal, and Pakistan. These countries, despite sharing a common geological seismic threat, have developed a distinct code and standards for construction. This inconsistency concerns the effectiveness and suitability of seismic design practices in this region, hence prompting a comparative study. This study begins by reviewing the development of seismic codes in these countries. Subsequently, a prototype RC low-rise building was modeled and analyzed using finite element software, employing the linear static method of analysis according to each country's seismic codes. This study focused on key seismic responses, including the fundamental period, base shear, displacement, and story drift. The analysis revealed significant differences in seismic responses among the codes. Notably, the Chinese seismic code resulted in the highest values for the parameters studied, followed by the Nepalese, Pakistani, and Indian codes. The comparison revealed that the base shear from the Chinese code was the highest, being 3.10 times greater than the Indian code, 1.66 times greater than the Nepalese code, and 1.86 times greater than the Pakistani code. Similar ratios for displacements and story drifts were found in the study.

User-Centered Design of Architectural Models Adapted to Monolithic Structure Technology

Monolithic Structure Technology (MST) is a new construction process patented in Morocco, offering significant advantages in terms of durability, resilience, and energy efficiency. This technology enables the mass production of low-rise green buildings thanks to the design of a monolithic metal formwork with a high reuse rate for the bonding of the structure working mainly in compression. Unlike conventional approaches to construction, the architectural design and load-bearing structure are studied simultaneously from the formwork design phase, as the structure mobilizes its form to guarantee stability. The design of architectural models adapted to MST is therefore of paramount importance if we are to exploit the full potential of this innovative technology. In this context, we developed the most suitable designs for MST based on a user-centered approach by directly involving the presumed future operators through a structured questionnaire to identify their preferences.115 respondents were interviewed, and the results were analyzed and used to design 10 different models. We then complemented the design process with a neuro-architectural approach to optimize design factors (facades, levels and rooms, shape and openings, roof type, interior layout, green spaces, and materials). The 10 designed models were then used for a closed card sorting study, followed by another semi-structured interview. User preferences were synthesized and the optimum design for the Moroccan countryside was selected.

Machine learning – based approach for predicting pushover curves of low-rise reinforced concrete frame buildings

Reinforced Concrete (RC) frame buildings are prevalent worldwide due to their seismic performance and the broad availability of materials. Pushover analysis is regarded as one way to assess the seismic performance of these buildings, which is simple to interpret. The only downside of this method is that it requires developing nonlinear models, which can be time-consuming and computationally expensive. Recently, Machine Learning (ML) has emerged as an alternative to approximate the pushover response of RC frame buildings. However, there are still improvements in several areas, such as including relevant and easily obtainable parameters in structural design (e.g. reinforcement ratios), considering a wide range of building configurations, and comparing different ML techniques. This paper presents the development of two models based on Random Forest (RF) and Artificial Neural Network (ANN) to predict the pushover response of low-rise RC frame buildings, supported by a user-friendly graphical interface. First, a dataset of over 138000 Pushover analyses was performed on flexure-controlled RC frames ranging from two to five stories using OpenSeesPy, subsequently used to develop predictive ML models. These models are designed to offer a trilinear approximation of a building's Pushover curve, and they require input information that is available from the customary building design. The pushover predictions obtained with RF and ANN take 0.12 % and 3.05 % of the computing time compared to the OpensSeesPy nonlinear model. The proposed models demonstrate a high level of accuracy, with a coefficient of determination (R²) of over 0.88 and 0.81 in testing datasets for RF and ANN models, underscoring their potential to significantly streamline the seismic performance assessment process by providing quick Pushover curve estimations.

Aerodynamic and codification study of low-rise buildings: Part II – Partially elevated structures

This study constitutes part II of an extensive study where the aerodynamics of elevated buildings is investigated using large-scale wind tunnel testing. Part II focuses on the case of elevated buildings with partially enclosed spaces beneath the elevated floor. For this purpose, four 1:10 scaled models of elevated single-story gable-roof buildings were selected, three of which were partially elevated with enclosed regions covering areas ranging from 19% to 54% of the model footprint. The tests aimed to examine the effect of the enclosed regions below the floor on the distribution of the localized peak pressure coefficients on the walls, floor, and roof surfaces of the models. Furthermore, the study evaluates the ASCE 7–22 provisions and the proposed provisions, presented by the authors in Part I, for estimating external wind pressure coefficients acting on the floor, roof, and walls of elevated buildings. The results indicate that enclosed regions below the floor significantly alter the aerodynamics of elevated low-rise buildings and could increase the wind-induced loads on the roof and walls of such structures, with the increase in some cases exceeding 80%. Furthermore, the results align well with the proposed modifications by the authors in Part I to the ASCE 7 provisions for estimating the external pressure coefficients for the various zones of low-rise buildings, addressing the underestimation issues previously identified within the current ASCE standard.

Seismic Response of Open Ground Story Reinforced Concrete Buildings, Considering with Soil-Structure Interaction

This study investigates the seismic behavior of open-ground story (OGS) reinforced concrete buildings with soil-structure interaction (SSI) using SAP2000. The study mainly focused on mid-rise (8-storey) and low-rise (4-storey) OGS buildings, incorporating different masonry infill materials such as brick, concrete blocks, and autoclaved aerated concrete (AAC) blocks. Selected ground motions from the Bhuj, El Centro, and Chi-Chi earthquakes were utilized to simulate varying seismic intensities and frequency content. Critical parameters such as top-story displacement and inter-story drift are analyzed to assess the structural safety and serviceability of RC buildings. The results demonstrate that both OGS coupled with SSI and masonry infill type significantly affect the displacement and drift, with mid-rise buildings showing more pronounced impacts. Furthermore, ground motion characteristics are critical in producing different response patterns. The study highlights the importance of considering SSI, infill materials, and ground motion characteristics in the design of OGS buildings to enhance earthquake resilience and reduce seismic damage.

Study of FRP on Preloaded Beam as A Method of Retrofitting - A Review

Over the past two decades, fiber-reinforced polymers have gained prominence in structural engineering due to their unique properties, offering an alternative to traditional materials like steel and concrete. FRPs consist of high-strength fibers embedded in a polymer matrix, resulting in superior strength-to-weight ratios, excellent corrosion resistance, and fatigue durability. These materials are widely used in aerospace, automotive, and infrastructure applications. Key types of FRPs include carbon fiber reinforced polymer, glass fiber reinforced polymer, aramid fiber reinforced polymer, and basalt fiber reinforced polymer, each offering specific advantages. CFRP is recognized for its high tensile strength, while GFRP is widely chosen for its affordability and adequate performance in less demanding structural applications. This review paper focuses on retrofitting predamaged reinforced concrete beams using carbon fiber-reinforced polymer and glass fiber-reinforced polymer sheets. It examines how preloading, fiber material, and fiber arrangement affect the structural performance of these beams, particularly in terms of flexural strength, ductility, stiffness, and failure mechanisms. Going through several papers the studies showed that CFRP and GFRP significantly enhance load-bearing capacity, energy absorption, and delay failure due to deboning. Key factors such as preload levels and fiber configuration were compared by go thronging several paper. The paper highlights real-world applications, where CFRP is commonly used in bridge rehabilitation and GFRP is favored for less demanding tasks, such as retrofitting low-rise building beams, both playing a critical role in extending the service life of structures while reducing costs.

The site-city interaction effect uncertainty on structural responses and its application to fragility analysis of buildings in Shanghai CBD

Seismic fragility analysis is a crucial tool for assessing the seismic performance of buildings. In areas with dense clusters of tall buildings, the significant site-city interaction (SCI) effect alters wave propagation mechanisms, influencing the seismic fragility of structures. However, a significant increase in computational workload results from the need for detailed modeling of sites and building clusters for the SCI analysis. To address this challenge, this work first investigates the minimum number of earthquake waves required to characterize SCI-induced response changes. The Central Business District of Shanghai is analyzed. A table for the recommended minimum number for a given accuracy requirement and prediction reliability is provided. Moreover, a seismic fragility analysis method considering the SCI effect is proposed for low-rise buildings. The case study indicates that, buildings with similar height will exhibit various fragility changes after considering SCI. For the complete damage state, the mean intensity value of the fragility curve can be 14.4 % smaller than that without SCI. In addition, this approach provides significant computational workload reduction. For the case study, the computational workload of the proposed method is roughly 1/50 of that using traditional IDA method.

Assessment of Fine-Scale Urban Heat Health Risk and Its Potential Driving Factors Based on Local Climate Zones in Shenzhen, China

Cities are facing increased heat-related health risks (HHRs) due to the combined effects of global warming and rapid urbanization. However, few studies have focused on HHR assessment based on fine-scale information. Moreover, most studies only analyze spatial HHR patterns and do not explore the potential driving factors. In this study, we estimated the potential HHRs based on the “hazard–exposure–vulnerability” framework by using multisource data, including the modified thermal–humidity index (MTHI), population density, and land cover. Then, the variations in the HHRs among different local climate zones (LCZs) at the fine spatial scale were analyzed in detail. Finally, we compared the different contributions of the LCZs and types of land cover to the HHRs and their three components by using multiple linear regression models. The results indicate that the spatial pattern of the HHRs was different from those of the individual components, and high-hazard regions do not mean high HHRs. There were huge variations in the HHRs among the different LCZs. The built-up LCZs typically had much higher HHRs than the natural ones, with compact LCZs facing the most severe risk. LCZ 6 (open low-rise buildings) had a relatively low HHR and should be paid more attention in future urban planning. Compared to the LCZs, the land covers better explained the variations in the HHR. In contrast, the LCZs better predicted the land surface temperatures. However, both the LCZs and land covers made only slight contributions to the heat exposure and vulnerability. Furthermore, the manmade buildings and impervious surface areas contributed much more to the HHR than the natural land covers. Therefore, the arrangement of the warming LCZs and land cover types is worthy of further investigation from the perspective of HHR mitigation.

Environmental, economic, and eco-efficiency assessment of residential heating systems for low-rise buildings

Transitioning from fossil fuels to renewable heating is essential for rapidly reducing greenhouse gas emissions. Besides greenhouse gas emissions, other environmental and economic impacts are crucial for successfully implementing renewable heating systems. This study evaluates 13 residential heating systems' environmental, economic, and eco-efficiency performance for a typical German two-story dwelling. The life cycle assessment method is employed to quantify the environmental impacts. Assuming a sustainable supply of biomass-based fuels, biomass heating systems exhibit the lowest environmental impacts, whereas gas heating systems are associated with high environmental impacts. Among heat pump systems, the water-source heat pump demonstrates the lowest environmental impact. Additionally, integrating a PV system into heat pump systems reduces the environmental impacts across all heat pumps. The evaluation indicates that the air-source heat pump is the most economical system, while the pellet boiler with solar thermal support and the heat pump with ice storage incur the highest costs. However, the cost differences among the heating systems are relatively small, making it challenging to establish a clear ranking based solely on economic evaluation. An eco-efficiency assessment, which combines environmental and economic aspects into a single indicator, reveals that the most eco-efficient systems are the air-source heat pump, both with and without a PV system, and the wood gasifier heating system. In contrast, the ice-storage heat pump and the pellet heating with solar thermal support show the lowest eco-efficiency.

Optimization and analysis of hysteretic energy dissipators in reinforced concrete frame structures of five, 10 and 15 stories

Frame structures are especially affected by earthquakes, due to their low lateral resistance. The use of energy dissipators may be a suitable solution for these structures; however, the effectiveness of these devices is questionable in low-rise buildings. We therefore analyze the behavior of these devices in frame buildings with varying numbers of stories (five, 10 and 15 stories). The use of hysteretic dissipators is found to considerably reduce the displacements of the bare structures, in addition to significantly improving their resistance, although the absolute accelerations are not reduced. Taller, more slender structures require less rigid dissipators with lower yield forces than shorter, more rigid structures. The effectiveness of the dissipators is also demonstrated by increasing the number of stories of the structures. The effectiveness of the dissipators increases as the rigidity of the structure decreases, as observed for the highest frame structures considered in this research, or as also occurs with the characteristics of the seismic records, such as their impulsivity. A high level of rigidity of the structures (as in low-rise structures or those with a significant number of stiffening elements, such as walls or braces) may have a significant impact on the behavior of the dissipators, due to the low displacement of the bare structures, which reduces their effectiveness. Finally, given the complexity of the different designs for dissipators in the scientific literature, this research offers a new, simple way to design dissipators based on the structural characteristics of the bare frames. To carry out this research, a nonlinear static analysis (push-over) and dynamic analysis are carried out using two different characteristic records, as part of a search for the optimal characteristics of the devices and to analyze how each of them affects the structural behavior in buildings with different numbers of stories.

Flexural Behaviour and Environmental Impact of African Fan Palm Reinforced Concrete Beams under Symmetrical Loading Conditions

The paper presents the results of investigation on reinforced beams adopting eco-friendly materials for sustainable concrete. The use of African fan palm is explored to mitigate the environmental impact aimed at reducing carbon emissions associated with the production and use of steel reinforcement. The beams were tested under a four -point loading system with the ends simply supported. The test comprised twenty-three beams that were reinforced with African fan palm bars whilst two beams were reinforced with mild steel bars to serve as control beams. The study investigated the flexural strength and deformation characteristics of the beams under monotonic loading. Two concrete strengths of 15.34N/mm2 or 22.37N/mm2 were adopted and proposed optimal tensile ratios for an under reinforced fan palm section. The parameters considered included the tension bars ratio (ρ), concrete compressive strength, span-to-effective-depth ratio and loading conditions. A linear elastic behaviour of both fan palm and steel reinforced concrete beams was observed to the point of first crack load beyond which the beam stiffness continued to reduce until failure. A comparison of the experimental results with results of theoretical analysis of the beams revealed that a 1.22% increase in the tensile ratio of steel in the control beams increased the cracking moment (Mcr) to 36%, while the fan palm beam of the same size and same concrete strength with a higher tensile ratio of 9.69% exhibited a lower Mcr of 11.86%. This shows a significant effect of reinforcing steel bars on concrete cracking compared to the fan palm. The averages of experimental to theoretical failure loads of fan palm to steel were compared with failure loads of 36.52kN to 20.19kN and 32kN to 19.78kN respectively. These results of the study based on the failure mode, and failure loads, highlights the suitability of using African fan palm as substitute reinforcing material for low rise buildings. Furthermore, the study also proposed minimum and maximum tensile ratio of 0.76% and 5.60% respectively for fan palm reinforced concrete beams based on the Indian Standard and modulus of elasticity of steel.

Coupling CFD model and FEM model to investigate the impact of debris flows on a low-rise building

This study integrates a hydrodynamic model with a structural analysis model to investigate the behavior of a reinforced concrete (RC) frame building under the influence of various hydrodynamic variables, such as debris flow materials, flow intensity, and flow direction. The impact force generated during the first phase of fluid-structure interaction is significantly larger around (20 ÷ 30) % than that in the steady phase, resulting in a substantially bigger maximum value of bending moment (Mmax) and displacement (δ) in every RC column. An increase in flow intensity and solid concentration leads to a larger impact load, resulting in higher values of Mmax and δ. Furthermore, the flow that passes through the porous exterior of the house poses a greater risk than the flow that affects the non-porous side of the house. By comparison with two Vietnamese standards of bending moment and displacement, all columns of the target building are susceptible to collapse in all scenarios when taking into account the bending moment. Nevertheless, in relation to the key threshold of displacement, the building is likely to remain secure.

Structural and non-structural fragility curves for low-rise mainshock-damaged buildings subjected to aftershocks

The seismic response of mainshock-damaged buildings under aftershocks is an important topic in terms of the lateral response of damaged structures. The majority of current seismic design standards just consider a single earthquake (mainshock/design earthquake) and they don’t take into account the influence of aftershocks on the seismic design process. The aftershocks could have significant effects on the seismic response of mainshock-damaged structures. This situation was reported in some of the previous earthquake events in which the aftershocks caused additional damage to the structures. In this study, the fragility curves for structural and non-structural Drift-Sensitive Components (DSCs) and Acceleration-Sensitive Components (ASCs) of two low-rise mainshock-damaged moment resisting steel and reinforcement concrete buildings under the effect of aftershocks with different intensities were presented. The intensity of the mainshocks was adjusted until the intact buildings experienced three levels of damage states including slight, moderate and extensive damage states. After that, the fragility curve of the structural and non-structural components of the mainshock-damaged buildings under the effect of aftershocks was evaluated by the Incremental Dynamic Analysis (IDA). The results show that the effect of aftershocks on the probability of damage to structural and non-structural components of mainshock-damaged structures is related to the level of the initial damage. For slightly and moderately mainshock-damaged buildings, the probability of exceedance of the damage under aftershocks is relatively similar to the intact buildings, however, the aftershocks significantly increase the probability of damage to the extensively mainshock-damaged buildings. Although extensive initial damage causes a significant increase in the probability of damage to non-structural DSCs, the damage probability of non-structural ASCs remains relatively as similar to intact buildings. Regarding the HAZUS manual, the results show that the probability of damage exceedance of the structural components is higher than non-structural ASCs, however, the opposite observation was reported from the previous earthquakes. Therefore, in this study, four levels of damage threshold for non-structural ASCs are proposed.

Assessment of dust concentrations and chemical composition among exposed workers during low-rise building construction

Assessment of dust concentrations and chemical composition among exposed workers during low-rise building construction

Older adults’ decisions regarding mobility to age in place in medium- and high-rise multi-storey residential buildings in urban settings: A case study of South East Queensland, Australia

Population ageing and urbanisation requires a more thorough understanding and monitoring of older adult residential mobility trends. Many older adults move to urban areas and previous studies have been carried out on ageing in place in traditional low-rise residential buildings. However, there is little in the literature about the important push and pull factors influencing older adult moves to medium- and high-rise multi-storey residential buildings in urban areas as they age. This case study research considered the housing migration model of push and pull factors used in elderly residential mobility and investigated the older adults' decision-making regarding mobility to age in place in medium- and high-rise multi-storey residential buildings in South East Queensland, Australia. The study revealed how the older adults expressed a desire to age in place in multi-storey residential buildings in urban areas and identified it as an important element of quality of life. Many older adults chose to move house to high density urban areas from low density urban areas between the ages of 65 and 84. The ‘pull’ factor to significantly influence the decisions of movers was a low maintenance property and lifestyle change from a large suburban home whereas the ‘push’ factor was upkeep difficulties of the house related to old age. This study makes empirical contributions to knowledge in ageing residential mobility trends in urban areas and concludes by providing policy recommendations for developing more effective housing, public spaces, transportation, and community activities and services for older adults, including highlighting a number of recommendations for future research.

Novel rod-sprung-mass model to investigate characteristics of building structural vibration induced by railways

Railway-induced vibrations in building structures require predictions to assess the serviceability. Fundamental properties such as the predominant modes of railway-induced vibrations are critical in structural design and mitigation approaches. However, the existing numerical models are customised to specific buildings. This renders these models unsuitable for broader mechanistic investigations. To address this, this study proposes a rod-sprung-mass (RSM) model to investigate the dynamic behaviour of structures under vertical ground excitations induced by railways. The columns were modelled as axial vibration rods, with each floor suspended on the rod as a sprung mass. The model was validated using a three-story steel frame structure and a five-story concrete structure. Subsequently, the dynamic characteristics of the structures and railway-induced responses were discussed. The structural vertical modes are attributed to the interaction between the columns and slabs, and the structural natural frequencies are outside the frequency range of the individual components. Parametric studies revealed that lower-order structural modes are generally predominant. Under such circumstances, the floor response tends to first decrease and subsequently increase with the floor height. As a result, low-rise buildings exhibit the maximum amplitude on the top floor, whereas the maximum amplitude is on the ground floor for high-rise buildings. Meanwhile, when structural high-order modes become predominant owing to a high-frequency input, the responses of the middle floors intensify, and the peak responses can be altered to the middle floors. This study emphasises the necessity of considering vertical global modes, whereas existing studies have focused mainly on mode shapes on particular floors. The RSM model is an efficient tool for structural design and vibration control.

The effect of window proportions in low-rise residential buildings on annual energy consumption in humid temperate climate (case study: Rasht city in Iran)

The effect of window proportions in low-rise residential buildings on annual energy consumption in humid temperate climate (case study: Rasht city in Iran)

Sustainability Assessment of Harvesting Rainwater and Air-Conditioning Condensate Water in Multi-Family Residential Buildings under Various Conditions in Israel—A Simulation Study

The environmental impacts and water savings of different configurations of non-potable domestic water use (toilet flushing and laundry), sourced from rainwater harvesting (RWH) and air-conditioning condensate water (ACWH), in multi-family buildings in Israel are examined. Two building types differing in specific roof areas, and three climatic sub-regions were modeled. RWH satisfied 23 and 46% of the water demand for toilet flushing and laundry in high-rise and low-rise buildings, respectively. Air conditioning is used almost daily during Israel’s hot and dry summers. Hence, the combined RWH-ACWH system saved 42 and 64% in high- and low-rise buildings, respectively. Displacing desalinated seawater, a significant water source in Israel, with alternative water sources lowered the environmental impacts with an increase in storage, up to a certain volume, beyond which impacts started rising. The same infrastructure is used during winter for RWH and for ACWH during summer; thus, combining the two exhibits significant water savings, with marginal extra costs while lowering the environmental impacts.