Four-story Building Research Articles

The behavior of cross-laminated timber and reinforced concrete floors in a multi-story building

The behavior of cross-laminated timber (CLT) and reinforced concrete (RC) floors in a multi-story building is investigated in this paper. The load-bearing capacity, fire resistance, and sound insulation characteristics of the floors are the main focus of this research. In order to achieve this goal, a four-story building having RC floors is modeled, analyzed, and designed using the StruSoft FEM-Design software (FEM) following the Eurocodes and Swedish national annex. The building is considered to be in the city of Gävle in Sweden. Then, the RC floors of the building are replaced with the CLT floors, and the same process is done utilizing FEM. The utilization ratios (the ratios of the applied loads to the load-bearing capacities), vertical deflections, weights of the RC and CLT floors, and reaction forces of the buildings are evaluated and compared. The results show that the RC floors meet the deflection requirements well which contributes to the focus on their utilization ratios. The designed RC floors are acceptable from the vertical deflection and utilization ratio perspectives. However, the CLT floors cannot meet the vertical deflection requirements, and thus, need strengthening. The CLT floors are strengthened with supporting timber beams and columns which result in acceptable vertical deflections and utilization ratios. Fire resistance and sound insulation conditions of the RC and CLT floors are assessed by calculations based on the requirements of the Swedish National Board of Housing, Building, and Planning regulations (BBR) as well. The RC floors have the ability to be soundproof and have no difficulties in meeting the fire resistance requirements R60 of BBR. A cross-section is proposed for the CLT floors which can meet the fire resistance requirement R60 and sound insulation requirement C of BBR. The maximum reaction forces of the buildings and total weights of the floors are larger in the case of RC than CLT.

Fire Risk Analysis in Large Multi-Compartment Structures Using a Hybrid Multiscale Approach

This paper proposes a hybrid multiscale approach to evaluate the fire performance of large multicompartment structures. A probabilistic network model is at the core of the proposed approach, whose inputs, namely the mean durations of the fire phases and fire transmission through the barriers between compartments (e.g., walls or ventilation ducts), are determined beforehand by a zone model, which is detailed in a companion paper and a one-dimensional computational fluid dynamics code. Next, a proof of concept is developed by applying the hybrid approach to different fire scenarios in a full-scale generic military corvette and a four-story office building. The simulation results highlight the strengths and limitations of the proposed approach. Regarding the latter, a field model is used to evaluate how the hybrid approach performs depending on the interaction between the entire building system and its ventilation and the fire. Finally, a statistical study is carried out to produce fire vulnerability and risk maps, ranking the fire compartments according to their vulnerability or propensity to generate serious fires.

A computationally efficient framework for the simulation of the nonlinear seismic performance of infilled RC frame buildings

This study proposes a novel approach for the computationally efficient numerical modeling of the nonlinear seismic response of entire buildings with infilled RC frames. The proposed modeling framework can be particularly helpful for buildings with multiple stories and complex layouts, for which the current methods can be cumbersome to implement, or inaccurate. This framework combines the force-vs.-displacement response for every bay of the building to obtain the envelop curves for every floor along the two main perpendicular horizontal directions. These curves are used to calibrate a box-type model of the building. The proposed methodology is employed to simulate the response of a two-bay, three-story frame tested on a shake table, and an instrumented four-story school building in Nepal, damaged by the 2015 Gorkha earthquake. The comparison of the numerical results with the test and field data indicates that the proposed approach can accurately capture the important features of the seismic response of the actual structures and their dynamic properties.

Time domain probabilistic seismic risk analysis using ground motion prediction equations of Fourier amplitude spectra

Modeling of Fourier amplitude spectra (FAS) of seismic motions has gained much attention in engineering seismology. In the past few years, several ground motion prediction equations (GMPEs) and inter-frequency correlation structure of FAS have been established. Due to many preferable characteristics of FAS, probabilistic seismic hazard/risk analysis is rapidly changing from ergodic, spectrum acceleration Sa(T0)-based approach to non-ergodic, site-specific, FAS-based approach. This paper presents time domain intrusive framework for probabilistic seismic risk analysis using GMPE of FAS. Methodology for time domain stochastic ground motion modeling based on GMPEs of FAS is presented in some detail. The simulated uncertain motions are modeled as a random process and represented by polynomial chaos Karhunen-Loève expansion. The random process excitations are further propagated into the uncertain structural system using Galerkin stochastic finite element method (SFEM). Probabilistic evolution of structural response is solved, and such solution is used to develop seismic risk for any damage state. The presented framework is illustrated through seismic risk analysis of a four-story building subjected to possible earthquakes from two strike slip faults. The influences of the epistemic uncertainties in source stress drop Δσ and site attenuation κ0 on seismic risk are investigated. The need for non-ergodic seismic risk analysis with source-specific and site specific characterizations is emphasized.

A neural network-based multivariate seismic classifier for simultaneous post-earthquake fragility estimation and damage classification

A scalar intensity measure (IM) could be insufficient to represent the earthquake intensity and variety in fragility estimation. Introducing multiple IMs to conventional regression of fragility functions can be computationally demanding and require priori assumptions of functional forms. In this study, multivariate seismic classifiers with multiple IMs as inputs are developed based on artificial neural networks (ANNs) to address the above disadvantages of traditional regression approaches. Case studies of a four-story code-conforming benchmark building indicate that fragility estimates from multi-IM ANN classifiers lead to higher accuracy (5.0% to 7.7%) in system-level and element-level damage classification than the single-IM traditional fragility curves. Further studies of IM combinations show that the ANN performance can be improved by more IMs correlated with structural responses while compromised by redundant irrelevant IMs. The optimal IM set should be determined by correlation ranking and ANN predictive performance together. Moreover, the ANN configuration of the case-study building is optimized with five readily available IMs as inputs, which enable a near real-time (within 0.3 ms) prediction of future earthquake damage while maintain high predictive performance. Overall, the multivariate ANN seismic classifier can be a promising tool for simultaneous seismic fragility estimation and damage assessment.

Multistage Optimization toward a Nearly Net Zero Energy Building Due to Climate Change

Climate change is one of the major problems of the planet. The atmosphere is overloaded with carbon dioxide caused by fossil fuels that are burned for energy. Almost 40 percent of the total energy worldwide is used by the building sector, which comes from non-renewable sources and contributes up to 30% of annual greenhouse gas emissions globally. The building sector in Iran accounts for 33.8% of Iran’s total energy usage. Within the building sector, the energy consumption of Iranian educational buildings is 2.5 times higher than educational buildings in developed countries. One of the most effective ways of reducing global energy consumption and greenhouse gas emissions is retrofitting existing buildings. This study aims to investigate whether a particular energy-optimized design under the present climate conditions would respond effectively to future climate change. This can help designers make a better decision on an optimal model, which can remain optimal over the years based on climate change. For methodological purposes, multistage optimization was used to retrofit an existing educational building. Specifically, the non-dominated sorting genetic algorithm (NSGA-II) was chosen to minimize the cooling and heating load, as well as consider investment costs for present and future weather files, using the jEPlus tool. Furthermore, the TOPSIS method was used to identify the best set of retrofit measures. For this purpose, a four-story educational building in Tehran was modeled on Design Builder software v7.0.0.116 as a case study to provide a better understanding for researchers of how to effectively retrofit a building to achieve a nearly zero energy building considering climate change. The results show that the optimized solution for the present weather file does not remain the optimized solution in 2080. Moreover, it is shown that to have an optimized building in regard to future weather files, the model should be designed for the future weather conditions. This study shows that if the building becomes optimized using the present weather file the total energy consumption will be reduced by 65.14% and 86.18% if using the future weather file. These two figures are obtained by implementing active and passive measures and show the priority of using the future weather file for designers. Using PV panels also, this building is capable of becoming a nearly net zero building, which would produce about 90% of its own energy demands.

Overlapping Decentralized Control Strategies of Building Structure Vibration Based on Fault-Tolerant Control under Seismic Excitation

The vibration control system of a building structure under a strong earthquake can be regarded as a large complex system composed of a series of overlapping subsystems. In this paper, the overlapping decentralized control of building structure vibration under seismic excitation is studied. Combining the overlapping decentralized control method, H∞ control algorithm, and passive fault-tolerant control method, a passive fault-tolerant overlapping decentralized control method based on the H∞ control algorithm is proposed. In this paper, the design of robust H∞ finite frequency passive fault-tolerant static output feedback controller for each subsystem is studied. The fault matrix of the subcontroller is expressed by a polyhedron with finite vertices. In order to reduce the influence of external disturbance on the controlled output, the finite frequency H∞ control is adopted and the Hamiltonian matrix is avoided. In this paper, the passive fault-tolerant overlapping decentralized control method based on H∞ control algorithm is applied to the vibration control system of the four-story building structure excited by the Hachinohe seismic wave. One drive is set on each layer of the structure, and a total of four drives are set. Select the driver fault factor of 0.5 or 1 and the frequency band [0.3, 8] Hz. The overlapping decentralized control scheme and 16 fault-tolerant fault matrices are designed, and the numerical comparison results are given. The results show that both overlapping decentralized control strategy and multioverlapping decentralized control strategy have achieved good control results. Due to the different number of subsystems and overlapping information, the overlapping decentralized control scheme increases the flexibility of controller setting and reduces the computational cost.

Development of seismic resilience index methodology for RC structures via functionality curve

Seismic resilience index (SRI) approach describes the post-seismic recovery phase of a single building by incorporating the time dimension. In recent decades, numerous quantitative frameworks have been developed to quantify earthquake resilience. The seismic resilience of existing reinforced concrete (RC) structures in Malaysia under far-field (FF) and near-field (NF) earthquake scenarios is examined in this research methodology using a seismic resilience index (SRI) and functionality curve. SRI is implemented to a four-story RC school building and a five-story RC hospital structure damaged by the 2015 Ranau earthquake. In addition, a total of 25 existing RC structures have been selected as target case studies for evaluating the SRI and presenting the results graphically using the Geographical Information System (GIS) platform. These buildings are primarily divided into three clusters: low, mid, and high rise. Non-linear dynamic analysis (NL-DA) is utilized in this approach to analyze the case studies and the selected buildings using the Finite Element platform (FE). Moreover, a group of seismic records encompassing of far-field and near-field are selected for simulation process using non-linear time history analysis (NL-THA). Eventually, Incremental Dynamic Analysis, fragility and vulnerability assessment, functionality assessment, time of recovery (TREC), loss of resilience (LOR), robustness (R) and SRI indicator are all part of this approach.•SRI helps decision-makers create or suggest repair or retrofitting solutions with acceptable recovery time and cost.•The consequences of failures for people's lives, properties, as well as the economy, will be mitigated.•Improve the sustainability and serviceability of structures to ensure seismic safety and meet Sustainable Development Goal 11.

DISASTER RESILIENCE IN BUILDING CONSTRUCTION THROUGH CONCRETE CASTING METHODS: IMPLICATIONS FOR THE USE OF STRONG COLUMNS AND WEAK BEAMS

<div><p class="Els-history-head">The difficulty in obtaining the construction of a strong-beam-weak column building will be encountered during the concrete casting work because in the implementation the beam may be cast using a higher quality concrete than that used for column casting. This has the potential to result in the construction of strong weak-beam columns which should be avoided in earthquake-resistant structures. This study aims to find the most effective concrete casting method that results in the construction of strong-weak beam-columns as intended above. Observations were made on the construction work of a four-story concrete construction building. Analysis by comparing all foundry works whose implementation uses ready mixed concrete made from one vendor, with those using different vendors for each casting of different building structural components. The data used are in the form of compressive strength test results for column casting samples and beam casting samples. From these data, a graph of the compressive strength sample of beam casting is made, then it is compared with the graph of the compressive strength sample of column casting. The results of the study concluded that using different vendors for casting different components of the building has a greater chance of producing a weak beam-strong column structure.</p></div>

Comparison of Strengthening Solutions with Optimized Passive Energy Dissipation Systems in Symmetric Buildings

The aim of this study is to compare the seismic response of reinforced concrete (RC) symmetric buildings, with a varied number of stories, strengthening with three types of passive energy dissipation systems, as tuned mass dampers, viscous dampers, and friction dampers. The paper presents an overview of design optimization with the object of minimizing certain functions: (i) the maximum displacement at the top of the structures, (ii) the base shear loads, and (iii) the maximum interstory drift. The objective functions were evaluated in three residents’ buildings (a four-story building, a nine-story building, and a sixteen-story building) subjected to seven (real and artificial) seismic recorded accelerograms. For this purpose, 94 nonlinear dynamic analyses were carried out. The effects of each strengthening solution are presented, and from this innovative comparison (optimal design, three different passive energy systems, three different story numbers), further useful results were observed. The outcomes of the study show the effectiveness of a tuned mass damper (TMD) system, and how it might be better for tall and flexible structures than for stiffer structures. However, the response of the pendulum tuned mass damper (TMD) configuration is better than the conventional one because it acts in all directions. The viscous dampers (VDs) provide a significant reduction for mid-rise buildings, while friction dampers (FDs) boost the performance of all structures under seismic action, especially in terms of displacement, and they are more suitable for low-rise buildings.

Probabilistic integrated framework and models compatible with the reliability methods for seismic resilience assessment of structures

An integrated probabilistic framework is proposed with a set of probabilistic models that are compatible with the reliability methods used in resilience-based design (RBD). Previous seismic resilience estimation frameworks primarily have used conditional probabilities and total probability integration to compute the expected seismic resilience index while considering the effects of only a few types of uncertainty. However, a high level of uncertainty is associated with seismic resilience estimation. This study presents a probabilistic framework and models that can consider the effect of unlimited uncertainties when calculating the probability distribution of the seismic resilience index for generating resilience curves. These curves reveal the probability of a building resilience index falling below a specific value and can be used in RBD for a building by considering its resilience. Probabilistic models that are compatible with the reliability methods are proposed for the ground motion intensity, building response, building damage, loss of functionality, recovery, and resilience of a building. The proposed models have been validated using information from HAZUS and were implemented in Rt software. The proposed framework and software are demonstrated through generation of a resilience curve for a typical four-story concrete moment-resisting frame building and the results are compared with outputs of conventional methods.

Image Motion Extraction of Structures Using Computer Vision Techniques: A Comparative Study.

Vibrational measurements play an important role for structural health monitoring, e.g., modal extraction and damage diagnosis. Moreover, conditions of civil structures can be mostly assessed by displacement responses. However, installing displacement transducers between the ground and floors in real-world buildings is unrealistic due to lack of reference points and structural scales and complexity. Alternatively, structural displacements can be acquired using computer vision-based motion extraction techniques. These extracted motions not only provide vibrational responses but are also useful for identifying the modal properties. In this study, three methods, including the optical flow with the Lucas–Kanade method, the digital image correlation (DIC) with bilinear interpolation, and the in-plane phase-based motion magnification using the Riesz pyramid, are introduced and experimentally verified using a four-story steel-frame building with a commercially available camera. First, the three displacement acquiring methods are introduced in detail. Next, the displacements are experimentally obtained from these methods and compared to those sensed from linear variable displacement transducers. Moreover, these displacement responses are converted into modal properties by system identification. As seen in the experimental results, the DIC method has the lowest average root mean squared error (RMSE) of 1.2371 mm among these three methods. Although the phase-based motion magnification method has a larger RMSE of 1.4132 mm due to variations in edge detection, this method is capable of providing full-field mode shapes over the building.

Seismic performance and fragility analysis of infilled steel frame structures using a new multi-strut model

Whether UnReinforced Masonry (URM) infills should be employed as structural members in frame structures is a debatable subject in performance-based earthquake engineering. This paper presents a detailed assessment of the seismic response of infilled moment-resisting steel frames. A recently proposed multi-strut model is applied here to consider both the local and global effects of URM infills. The capability of the employed model in predicting the local and global effects of URM panels has previously been verified by the authors of this study. Two structures, a four-story building and a two-story building, were designed using seismic design codes, and one of the outer frames of each structure was selected for the numerical models. Based on the conventional layouts of URM panels in buildings, three different configurations are considered: the bare frame (model in which the URM panels are isolated from the surrounding frame), the infilled frame, and the soft-first story frame. Fifteen ground motion records have been used to perform nonlinear Incremental Dynamic Analyses (IDA), which were then employed to derive the fragility curves of the studied structures for the Immediate Occupancy (IO), Life Safety (LS), and Collapse Prevention (CP) limit states. The results show that in lower limit states, the masonry infill leads to some beneficial effects. However, at more severe limit states, these beneficial effects diminish and at some point, revert to adverse effects. This is evident in the CP limit state, wherein the masonry infill weakens the seismic performance of the structure.

Study of effect of shear wall in the seismic response of the existing buildings

In Iraq, it has been observed that an increase in seismic activity, and that most existing buildings are not seismically designed and that can suffer serious damage or collapse, thus causing loss of life. In this paper, a numerical simulation of the experimental laboratory sample on the subject of non-seismically designed buildings and methods of strengthening them was performed using a seismic strengthening technique using an infill RC wall in order to maintain the risk of earthquakes. This study was carried out through the work of verifying the numerical and practical model by matching the results of laboratory work with the results of numerical analysis using the analysis finite element analysis method (FEAM) by Abaqus CAE 2019 software and then using the model to study the effect of openings in the infill RC walls and the extent of its impact on the response of the building. The practical model is a full four-story building tested laboratory in Elsa, Italy using pseudo dynamic test (PSD). The experimental model is a sample of not seismically design buildings (gravity design only) and ways to improve them by adding new RC walls with different contact details to the existing building. The goal of the experimental test was to study the effectiveness of adding RC infill walls with two types (North and South) infill RC walls, including designing it and the contribution of two types of dowels that connect the new infill walls to the existing RC building. In other words, it’s a way of strengthening by converting selected bays into RC walls with two types of reinforcement and connection between new infill RC walls and existing builders called (north and south) frames. The results of analytical modeling show that the percentage of differences in X- Direction of top story displacement between Abaqus software and Experimental tested at ELSA results are 2.47% in positive and 3.12% for negative X direction, which refer to a very good similarity and accurate building simulation.

A multi-hazard-based design approach for LRB isolation systemagainst explosion and earthquake

Base isolation system is originally known as one of the most efficient earthquake-resistance control systems. Isolated strategic structures may also experience terrorist attacks during their lifetime. In this paper, a design method is proposed for lead rubber bearing (LRB) isolation system under multi-hazard of explosion and seismic. This method is based on transforming the design problem into an optimization problem. The seismic response of structure has been defined as objective function while the constraints have been applied on its blast response. To validate the effectiveness of the proposed design method, LRB is designed for controlling a four-story steel moment-resisting building. For comparison objectives, this control system has been also designed under seismic hazard without paying attention to its blast performance. The results show that the earthquake-based optimally designed LRB has effective performance under seismic hazard whereas its blast performance is not as good as its seismic performance. Therefore, this control system cannot be considered as a well-designed control system for multi-hazard. The multi-hazard-based optimally designed LRB shows excellent performance under both blast and seismic loadings, so the proposed design method can be introduced as an effective design approach for LRB under multi-hazard of explosion and seismic.

Forced-Vibration Tests of a Reinforced Concrete Four-Story Building Structure

AbstractA set of acceleration records obtained at specific points of an actual reinforced concrete, four-story building structure subjected to forced vibrations are presented and documented in this...

Estimating optimum parameters of a new SMA damper under different earthquake ground motions

Process optimization using metaheuristic algorithms is rapidly gaining interest from engineering practitioners and researchers. This study uses the cuckoo search algorithm (CSA) to find the optimum parameters of a novel smart damper under seismic excitations. For this purpose, seismic responses of four-story and nine-story building configurations under seven pairs of ground motions have been considered. The smart damper is a shear polyurethane friction (SPF) passive control device, made up of shape memory alloy (SMA) plates, friction devices, and polyurethane springs. The damper was installed using braced frame shear links of Y-shaped inverted type, in the form of a vertical link beam placed in the eccentrically braced frames. Because the shear mode of failure is common in such a configuration, the SPF damper is expected to reduce the residual inter-story drifts of the building subjected to strong earthquake loading. Numerical optimization and time-domain simulations were carried out using the MATLAB and OpenSees software programs, respectively. The targeted optimization criteria include the peak values of inter-story drift, residual drift, and floor acceleration; and the design parameters consist of SMA cross-sectional area, friction force, and the polyurethane stiffness of the SPF-SMA system. The results of this study demonstrate the suitability of CSA for the determination of optimum parameters of the SPF-SMA system for the buildings and ground motions considered. Future studies will investigate the generalizability of the proposed method to other building configurations and ground motions.

Experimental dynamic characterization of friction brace dampers and application to the seismic retrofit of RC buildings

Previous earthquakes have caused extensive damage to reinforced concrete (RC) structures with insufficient lateral force resistance or energy dissipation capacity. There is a need to retrofit vulnerable existing RC buildings, particularly those not originally designed for seismic effects or designed to an outdated seismic specification. This study investigates the use of friction dampers as displacement-dependent energy dissipation devices to retrofit RC moment frame structures. First, an experimental program was conducted to characterize the dynamic behavior of friction brace dampers with several different materials, finding that a sintered metal compound provided a stable friction coefficient of 0.4. A strength-based equivalent linearization design procedure was then developed based on the required friction slip force and considering the cracked state of the existing RC structure. A four-story RC school building was then designed using the proposed retrofit design method, validated using nonlinear response history analysis and compared to a previous retrofit scheme that employed buckling-restrained braces (BRBs) and a stiffness-based equivalent linearization design method. The analysis results suggest that the proposed retrofit design method and friction brace dampers are effective in reducing the maximum story drift.

A Park-Ang damage index-based framework for post-mainshock structural safety assessment

Following an earthquake event, the safety of continued occupancy in terms of whether a mainshock-damaged building could withstand upcoming strong aftershocks is a key question for stakeholders. To answer this question, the residual collapse capacity of mainshock-damaged buildings should be evaluated, and in this way, an accurate assessment of the structural damage inflicted during a mainshock-aftershock sequence is of great importance. Recent studies have shown that energy-based damage measures, which calculate the dissipated energy due to cyclic-plastic deformations, can more accurately reflect the secondary damage induced by aftershocks than deformation-based damage measures. Park-Ang damage index is a combined seismic damage measure that integrates the damage caused by excessive deformations with the damage caused by the cumulative hysteretic energy dissipation. This study presents a framework for assessing the post-mainshock structural safety, in which the quantification of the damage accumulated during a mainshock and the determination of the remaining capacity to sustain strong aftershocks are made based on the Park-Ang damage index. First, residual collapse capacity diagrams are produced by performing incremental dynamic analysis under a suite of selected sequential ground motions. Next, an average diagram is made to find the maximum safe damage index, so that values above this threshold would represent the buildings that are deemed to be unsafe. The proposed framework is applied to a reference four-story steel moment-frame building to investigate its collapse potential and evaluates its structural safety in a hypothetical earthquake scenario. The results of the case study indicate that the proposed framework can effectively help structural engineers to decide on whether a mainshock-damaged building is safe to reoccupy and communicate the final decision in a simple diagram to stakeholders.

Evaluation and Repair of Construction Damage to an Old Factory Building

This paper describes the performance based seismic rehabilitation of an old four-story RC frame building which is being remodeled to be reused as an office building in the creative industrial park. The building is part of the city’s adaptive reuse and redevelopment program. It was designed and constructed in the 1980’s and, therefore, does not meet current design and detailing standards. To make matters worse, two of the first floor columns were badly damaged during renovation and were in danger of collapsing at any time. This paper presents the effects of the accident, failure mechanism, as well as the actions taken to repair the building. The damaged columns are strengthened by a reinforced concrete jacket. The beams closer to damaged columns are retrofitted by externally bonded CFRP. Structural redesign made it feasible to rehabilitate and strengthen the structure sufficient to meet seismic criteria that were judged to be compatible with the site conditions.