Practice Periodical on Structural Design and Construction

Forum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing speculation, on a civil engineering topic of general interest and relevance to the readership of the journal. The views expressed in this Forum article do not necessarily reflect the views of ASCE or the Editorial Board of the journal.

Predicting the seismic response of masonry-infilled (MI) RC frames holds immense importance due to the significant influence of masonry on the structural performance. Despite numerous studies delving into the seismic behavior of these frames, their complex interaction of masonry infills and RC frame presents ongoing challenges for researchers, designers, and standards committees. Although numerous studies have been conducted to investigate the seismic behavior of masonry-infilled reinforced concrete frames, its complex behavior poses a challenge to researchers, designers, and the specification-making committees. In recent years, several national codes have been revised to include the estimation of the stiffness of reinforced and nonreinforced masonry walls and have provided guidelines for the modeling and analysis of structures considering MI. This article aims to provide a comprehensive review of how infilled masonry walls impact the seismic performance of RC frames, drawing comparisons with codal provisions. The focus lies on scrutinizing experimental, numerical, and analytical studies that explore in-plane and out-of-plane behaviors. Factors like masonry strength, stiffness, area of openings, stiffness degradation, energy dissipation capacity, and damage patterns are thoroughly examined. Key findings with critical implications are highlighted, shedding light on potential future research directions in this crucial field.

Seismic vibrations naturally induce significant horizontal displacements, resulting in collisions between neighboring buildings when there is insufficient spacing. Pounding, which occurs primarily in tall buildings, leads to severe damage due to these impacts. To mitigate structure collisions and reduce the risk of pounding, several approaches have been proposed. These include maintaining adequate separation distances, enhancing structural stiffness, employing supplementary elements, incorporating different dampers, and implementing bumpers. These measures aim to regulate lateral displacement and dissipate energy within the contact zones during impacts. This research paper aims to examine the impact of rubber bumpers in enhancing energy dissipation during collisions. Through experimental testing and numerical simulations, an impact scenario is recreated, and the damping ratio is calculated based on energy dissipation. The study proposes a novel formula for determining the damping ratio specifically tailored for bumpers attached at the base level of structures. This study focuses on defining a new equation to determine the damping ratio of bumpers used in impact scenarios. An iterative procedure is employed, considering parameters such as bumper dimensions, stiffness, and coefficient of restitution. The equation is solved to calculate impact force and energy dissipation. Numerical analysis results are validated against experimental data. Parametric studies are conducted to evaluate the formula’s accuracy by analyzing hysteresis loops obtained from impact tests. The research aims to provide a reliable and effective equation for accurately determining the damping ratio of bumpers in real-world impact situations. The study concludes by selecting the best calibration of hysteresis loops from numerical analyses and experimental tests as the optimal parameter values for demonstrating the equation. To investigate the equation’s impact, two 5-story buildings are modeled, with one of them equipped with a base isolation system and rubber bumpers to assess the influence of the bumpers during earthquakes. The research findings indicated that reducing the number of bumpers and increasing their thickness leads to decreased energy dissipation. Therefore, the suggestion is to increase the number of rubber bumpers and decrease their thickness for improved performance.

Abstract

The interface bond strength between carbon fiber-reinforced polymer (CFRP) layers and concrete is a crucial metric for determining the mechanical properties of CFRP-reinforced concrete. This bond strength is essential for evaluating CFRP-reinforced concrete’s performance and ensuring the materials’ structural integrity. A database was established using the experimental data in the literature to evaluate the interface bond strength. This database comprised 360 groups of different conditions test results of CFRP-reinforced concrete, which were used to create a prediction model using an artificial neural network. The database was randomly divided into two data sets: 310 groups were used for training the neural network model and 50 for simulated prediction. A three-layer artificial neural network model was trained using the backpropagation algorithm, which is widely used in artificial neural networks. The model’s input layer considered seven parameters, including the type of CFRP layer, surface form, CFRP layer thickness, anchorage length, failure mode, concrete compressive strength, and normalized concrete cover thickness. These parameters were selected based on their known influence on the interface bond strength between the CFRP layers and concrete. The output layer of the model represented the interface bond strength between the CFRP layers and concrete. The model’s results indicated that the backpropagation (BP) neural network model had strong capability of prediction and generalization. The predicting error was minimal, a crucial aspect of the model’s accuracy. Further, this approach allows for integrating many factors that influence the interface bond strength between the CFRP layers and concrete, providing accurate predictions of the bond strength. It can be used as a valuable tool for evaluating the performance of CFRP-reinforced concrete.

Practical Applications

This research develops an accurate method to predict the bond strength between CFRP layers and concrete using artificial neural networks. A strong bond is crucial for the structural integrity of concrete reinforced with CFRP. The neural network model considers factors like the type and thickness of CFRP used, how the concrete surface is prepared, and the concrete’s strength. Engineers can use this neural network tool to evaluate how well CFRP will reinforce specific concrete mixtures and structures before construction. This allows structures to be designed and built with optimal, cost-effective use of CFRP to reinforce concrete in applications like bridges and buildings. The neural network approach integrates many technological and material factors into one predictive model, providing a useful evaluation method for the construction industry.

Detecting cracks can be challenging, especially on rough surfaces such as masonry. This research paper focuses on the detection of surface cracks on masonry surfaces using deep-learning techniques. This study compared the performance of various networks trained using deep-learning techniques for semantic segmentation of cracks on masonry surfaces. For the semantic segmentation of cracks, the segmentation models U-Net, feature pyramid network (FPN), DeepLabV3+, and PSPNet were integrated with several convolutional neural networks (CNNs) acting as the network’s backbone. Two loss functions, binary cross entropy and binary focal loss, were used in the study. Comparisons among networks using different metrics were performed to find the most promising approaches. Over the training and validation masonry data sets, a total of 23 networks were examined. The results of this study show that three networks can also accurately detect finer surface cracks on masonry surfaces. Based on performance metrics [dice coefficient, intersection over union (IoU), and F1 score], the three best networks were FPN(#2a) (86.9%, 74.9%, 59.3%), FPN(#2c) (85.6%, 75.4%, 56.3%), DeepLabV3+(#1a) (83.1%, 72.0%, 54.4%), respectively. Trained networks have demonstrated proficient performance on existing masonry culverts. This study can significantly aid the detection of cracks in the masonry substructure of old railway bridges.

The possibility of detuning resulting from liquid depth fluctuation and low damping characteristics for being deep tanks hinder the utilization of overhead water tanks (OWTs) as tuned sloshing dampers (TSDs). This paper proposes a slender TSD (STSD) that can effectively serve as OWT as well. Unlike conventional TSDs, in an STSD, the liquid depth is allowed to fluctuate within any practically feasible range maintaining the condition $h/D\ge 1$, where $h$ is the liquid depth and $D$ is the tank dimension along excitation. For $h/D\ge 1$, the frequency and the lumped mass representative of the fundamental sloshing mode become independent of $h$. To improve damping, STSDs are provided with equally spaced horizontal ring baffles. It is shown that the effective damping ratio of the STSD with equally spaced horizontal ring baffles also becomes practically constant for $h/D\ge 1$. Thus, a consistent damper performance is possible despite liquid depth fluctuation. The mathematical model of the damper system is described followed by the design of OWT cum STSD for a real-life apartment building. Significant seismic vibration control of the building by the damper is demonstrated through a numerical study that shows consistent performance by the STSD despite 66.7% liquid depth fluctuation in the tank. The performance of the STSD is found to be comparable with conventional TSD.

This study focuses on the design procedure and development of the unbonded fiber-reinforced elastomeric isolator (UFREI) and its application to prevalent masonry building practices in developing countries. The proposed design procedure caters to the development of rectangular UFREIs with or without modifications, considering an improved shear behavior formulation. Afterward, the proposed design procedure is used to design the isolation system for a pre-existing base-isolated masonry building located in the Tawang district in the northeastern state of Arunachal Pradesh in India. Three different configurations of the above building [i.e., fixed base, isolated using square UFREIs, and isolated using modified rectangular UFREIs (MR-UFREI)] are considered for a comparative response analysis under a set of probable ground motions during a service period of 100 years. The building is modeled in SAP2000, where it is subjected to nonlinear time-history analysis under the considered set of ground motions. The masonry walls are modeled as nonlinear layered shell elements, and concrete floors as rigid diaphragms. An improved shear formulation of UFREI is used to model the isolation system as a combination of a multilinear elastic spring and a dashpot. Major response parameters, i.e., floor accelerations, isolator displacement, interstory drift ratio, etc., are investigated, and a significant improvement is witnessed throughout with the use of the MR-UFREI isolation system. The stress–strain distribution and concentrations in the masonry structure and isolation system are also investigated. These distributions are further used to quantify the fatigue losses to the elastomer layers used in the isolation system during the design period, which is found to be minimal.

Panelized fabrication of light-frame wood buildings has higher productivity than the traditional stick-built method. However, the roof production process is inefficient due to the structural system and construction method. This study proposes a novel roof system to improve the productivity of the panelized construction process for light-frame wood residential building fabrication. This unique system uses a holistic approach to design several roof components considering structural requirements, manufacturing efficiency, and on-site installation factors. This paper presents a case study of the gable roof of a two-story building to demonstrate the implementation of this novel system. The two main components of the novel roof system are the ceiling frame and roof panels. Ceiling frame analysis showed that three different fabrication options are possible in the current off-site setting. Twenty-four nail-connection specimens were tested under shear and uplift loading to determine the load–slip response of nail connections used in structural composite wood such as oriented strand board (OSB) and laminated strand lumber (LSL). The roof panel design requirement was determined based on the nail connection test and finite-element analysis. The results showed that ceiling frames for a gable-type roof can be produced economically using a floor panel production line, and roof panel fabrication is possible using the current wall panel production line.

In civil structures, a lot of attention is paid to lightweight design, i.e., reduction in self-weight by design without compromising safety, integrity, and performance of a structure. The cost-effectiveness of lightweight design is another important consideration, as it can help to reduce the overall cost of a project. Thanks to the development of steel aluminum foam sandwich panels, a new lightweight design option is now available that offers a number of benefits, including reduced self-weight, improved energy efficiency, and increased durability. In this study, efforts were made to replace the stiffened plate by the sandwich panel with the aim of weight reduction. For this task, three different sandwich panels were selected, a sandwich panel made with face-plates S355, S690, and S1100. In this study, an arbitrary Huisman equipment was chosen which is made of S355 stiffened plate. This structure is redesigned with sandwiches S355, S690, and S1100. Static and buckling analysis was performed on the new design, as well as cost analysis, to evaluate the economic viability of sandwich panels. The findings of the study show that sandwich panels can be used to save significant amounts of weight, while still meeting other design requirements. Weight reduction of up to 30% can be achieved with the use of sandwich panels. The use of sandwich panels can increase the cost of the structure, but this increase can be offset by the savings in weight.

Abstract

Environmental considerations are an important aspect of construction activities, such as the impact of construction vibrations at project sites and in nearby properties. There are limited studies to investigate the impact of vibration from ground improvement construction and how underground utilities can be protected from vibration damage. This research is aimed at developing empirical formulations that can be used to predict ground particle velocities near buried structures. This will allow engineers to minimize potential vibratory damage to buried structures. In this study, ground vibrations are produced by the installation of rockfill columns, a ground improvement technique to stabilize riverbanks. Installation of rockfill columns was done near a buried aqueduct. So, there is a concern that this aqueduct can be damaged by ground vibrations. Finite-element analysis was done to provide information on ground vibrations caused by the installation of rockfill columns. The finite-element models were calibrated with particle velocities measured at the construction site. Results showed that the particle velocities obtained in the numerical models correlated well with the measured particle velocities and those reported in the literature (although from different sources of vibrations). Empirical relationships are proposed between ground vibrations and their impacts on nearby buried structures.

Practical Applications

Limiting ground vibration on structures near construction sites is a challenging task. Even though most guidelines use peak particle velocity (PPV) as the limiting parameter, there is no consensus as to which limiting values to use. Ideally, project-specific values could be estimated with predicting equations. Estimation of the vibratory impact from the installation of rockfill columns in the ground and their impact on buried structures is limited in the literature. This is due to the lack of data to validate prediction methods. As is shown in this paper, numerical results in this research reasonably agree with field PPVs reported in the literature. Therefore, empirically based predictions for the installation of rockfill columns, for the removal of steel casings, and for the vibratory impact of ground vibrations on buried structures for 5%, 50%, and 95% exceedances are proposed in this study. It is recommended that the proposed empirically based predictors be used as a preliminary evaluation tool, preceding numerical simulations to predict expected ground vibration in terms of PPV. It is understood that when the field data are obtained in the near field but prediction is for far field, the predictions tend to be conservative. On the other hand, prediction for the near-field response based on data from the far field is inappropriate and should be used with caution. In the field, well-planned instrumentation and monitoring would help protect buried structures from potential damage from ground vibrations, which was done in the case study presented in this paper.

The present study explores a cost-effective method for using activated ground granulated blast furnace slag (GGBFS) and silica fume (SF) as cement substitutes. Instead of activating them with expensive alkali solutions, the present study employs industrial-grade powdered sodium aluminate (SA) and hydrated lime (HL) as activators, reducing expenses by about 94.5% compared to their corresponding analytical-grade counterparts. Herein, the exclusivity is depicted using less pure chemicals rather than relying on reagents with 99% purity. Two mixing techniques are compared: one involves directly introducing powdered SA and HL, while the other premixes SA with water before adding it to a dry powder mixture of GGBFS, SF, and HL. Microstructural analysis reveals that the initial strength results from various hydrate phases, including calcium–sodium–aluminate–silicate hydrate. The latter strength is attributed to the coexistence of calcium–silicate hydrate, calcium–aluminate–silicate hydrate, and sodium–aluminate–silicate hydrate, with contributions from calcite and hydrotalcite. The SF content significantly influenced the formation of these gel phases. Thermogravimetric analysis (TGA) reveals phase transitions and bound water related to hydration products. The optimal mix comprises 10% SF, 90% GGBFS, 9.26% HL, and 13.25% SA, with a water-to-solid ratio of 0.45. This approach yields a compressive strength of 35.1 MPa after 28 days and 41.33 MPa after 120 days, hence being suitable for structural construction.

Deterioration of RC structures with the passage of time due to aggressive environment leads to reduction of strength, stiffness, and reliability of the structure. Generally, for assessing reliability or failure probability of aging structures that are time-dependent, one must consider the uncertainty in the structural degradation in association with nonstationarity in the load distribution process. In this paper, an approximate approach has been used for evaluating the effects of structural degradation and live-load variations on time-dependent failure probability of aging structures. In order to assess the time-dependent failure probability, the service life of the structure is considered to be 50 years. Due to heavy computational requirements that need a long and tedious completion process, soft computing, e.g., artificial neural networks (ANNs), have been used, which act as a physical system for rapid prediction of the structural reliability with reasonable accuracy. The predicted outputs obtained from the neural network model were validated with the actual outputs and were found to yield good results, making it suitable for estimating long-term time-variant behavior of aged structures under a significant loading process.

Using the steel strongback braced (SB) system to seismically strengthen and retrofit reinforced concrete moment frames (RCMFs), this research aims to enhance the effectiveness of RCMFs. In this study, RCMFs of 5-, 10-, and 15-stories were designed according to the first and fourth editions of the Iran Earthquake Standard 2800. The RCMFs designed for the first edition are strengthened and reinforced using the strongback braced system. The studied structures were analyzed under incremental static loading and time history analysis. The findings indicate that the yield force and maximum base shear of structures designed using the fourth edition have increased by a range of 1.28–1.42 compared with those designed with the first edition. This underscores the imperative to enhance the structural integrity of buildings constructed according to the first edition. Meanwhile, the results of retrofitted structures with strongback braces show the same or better performance than newly designed structures. This indicates that this retrofitting system has a favorable effect on uniform drift control. A reduction of 33%–44% in story drift was observed when the SB system is added to the first edition’s structure.

Construction projects involve numerous tasks that can be mentally and physically challenging. Previous research has investigated construction worker perceptions and awareness of safety hazards and the safety information that should be obtained before working on a construction site. However, further study is needed to investigate how the conditions of a construction site, work operation, and work task affect construction worker safety as a result of the mental workload experience by workers during task performance. The present study aims to clarify and confirm the extent to which task-related characteristics, referred to as constituents, have an influence on the mental workload that a construction worker experiences when conducting tasks. The concept of mental energy is used as a means to quantify mental workload. The study also aims to determine the extent to which the amount of physical energy present on the site impacts the mental workload workers experience when performing tasks. To meet these aims, the researchers conducted an online survey to collect insights on the topic from construction professionals in the United States. The study revealed that task constituents such as interruptions, distractions, and complexity of the task have a high level of impact on mental workload. Similarly, certain physical energy types (e.g., gravity, motion, and heat) have a high level of impact on mental workload. The contributions of this research to practice are the determination and confirmation of the level of impact of task constituents and physical energy on the mental workload of construction workers. The study findings show that worker mental workload is impacted by the task constituents and physical energy and, as a result, suggest that there are practical implications associated with the constituents and physical energy present on construction sites. Construction practitioners can utilize the results to assess potential worker safety performance based on task characteristics and understand the safety behaviors of construction workers.

The long-period transition period ($T_L$) is an important parameter in both seismological theory and seismic design. Current estimates of the parameter used for design are based on seismological model data from 2006, and presumably are for nonsubduction earthquakes. ASCE 7-16, which contains standards for seismic design, provides mapped estimates for $T_L$ based on the maximum considered seismic ground shaking. To expand the data considered for $T_L$, this study used the NGA-Sub flatfile obtained from the NGA Subduction Portal at the B. John Garrick Institute for the Risk Sciences. For each record, $T_L$ was interpreted as the period at which spectral displacement is a maximum, an interpretation which becomes evident upon close examination of the two-point design response spectra in modern codes. The rationale for this interpretation is the very definition of $T_L$ in ASCE 7-16. As performance-based design for multiple hazard levels has evolved and continues to gain acceptance by the engineering community, there is a need for a method to estimate $T_L$ for multiple levels of ground shaking at a given site. The primary purposes of this study were to develop estimates for $T_L$ for subduction zones and to facilitate the estimation of $T_L$ for lower-magnitude, more-frequent subduction events in subduction zones for performance-based seismic design, as opposed to using a single mapped value for a particular region. In this study, other methods for estimating $T_L$ also were explored. The long-period transition parameter, $T_L$, for subduction zones was found to vary with moment magnitude as the primary influence. A model in tabular form, similar to that used to develop maps in ASCE 7, was developed for subduction zones.

Abstract

Calculating impact forces in asymmetrical lateral structures has been a complex challenge that spans decades in engineering. Traditional models often fall short due to the inherent complexity of asymmetrical members and the need for significant computational resources or a vast pool of training data. This paper develops an approximate formula for accurately calculating the impact force of asymmetrical lateral-impact members under lateral impact. Existing methods for assessing impact forces have been limited in their application due to the inherent complexity of asymmetrical members and the significant computational resources or extensive training data they often require. Our approach employs the residuals margin method, and Laplace transforms to derive an efficient and accurate formula for impact force calculation. The paper rigorously validates this Formula through experimental testing, demonstrating high precision with an error margin of less than 5%. Further validation against diverse impact data from multiple studies on different materials and loadings under static and dynamic conditions confirmed the Formula’s consistency. Despite simplifying assumptions, this research contributes a novel and computationally efficient approach for calculating impact forces. The formula offers engineers a practical tool while advancing a fundamental understanding of asymmetric impact dynamics. Rigid experimentation verified its significant accuracy, establishing the formula as a valuable structural impact analysis and design resource.

Practical Applications

This research presents an analytical formula for calculating impact forces on structures like buildings, bridges, and vehicles experiencing asymmetrical lateral impacts. Such impacts commonly occur due to falling debris, vehicle collisions, seismic pounding, and derailed train strikes. However, existing design formulas often oversimplify impact mechanics or require complex simulations. The proposed method provides engineers with a simple spreadsheet-compatible equation relating impact force directly to tangible mechanical quantities like momentum. This enables rapid impact load assessments essential for performance-based design against accidental hazards. The formula was validated through laboratory impact tests on reinforced concrete slabs, demonstrating precision within 5% of measured forces. Additional validations against published experimental and simulation data on different construction materials confirmed accuracy. The proposed formula equips structural engineers and safety analysts with a practical impact analysis tool by offering a computationally efficient approach with proven reliability. It facilitates assessing design performance for asymmetrical impact load scenarios, helping improve resilience for critical facilities subjected to hazardous lateral impacts.

Bridges are among the most important structures for human civilization. Bridge safety is therefore an ongoing concern of engineers. Scouring of river beds due to blocking of downstream current by the bridge pier is one of the main causes of bridge failure. A bridge pier with a slot facilitates the passage of water downstream and thereby creates less vorticity, which in turn results in the reduction of scour formation. The introduction of a slot in any compression member like a column (or a bridge pier in the present case) is likely to be questioned for its structural safety. Thus, the present work investigated the comprehensive structural behavior of bridge piers with slots in them. Such bridge piers were structurally evolved in the present work based on the basic design philosophy, and were numerically modeled in ABAQUS 2019. Multiple sizes of slots are investigated considering a wider scenario. Different performance measures like natural frequency, Von Mises stress, and strain were evaluated to explore the fundamental structural behavior. The Von Mises stress [considering the pier as a three-dimensional (3D) continuum] was taken into account for the typical design check between capacity and demand at the material level. Although the introduction of slots raises the concern for structural performance of the bridge pier, it was taken into account that there is an insignificant degradation (in terms of Von Mises stress measure as well as Cauchy’s stresses) in the structural performance of the slotted pier in comparison to the pier without slot. Reinforcement was proposed for the slotted pier considering induced stress pattern under reasonable loading scenario. Mode shapes of the slotted pier system were evaluated to understand its dynamic structural behavior. In addition, the overall capacity of the slotted pier system was evaluated on the basis of critical buckling load and axial load-carrying capacity against each of the different slot sizes in the pier, which may help to determine the trade-off between hydraulic requirements versus scouring and structural capacity/safety.

This article uses shake table tests to examine how tunnelling affects framed construction response on different foundations. Accelerometers on different floors were mounted to examine the outcome of a utility tunnel with the help of two scaled prototype steel buildings. Three popular foundation types, i.e., isolated, mat, and pile foundation along with two scaled prototype steel building frame heights were tested. To account for the development of the ovalling effect of tunnel, both the frame models were vibrated orthogonally to the axis of tunnel by considering two ground motions, i.e., El Centro N-S (north-south) and MDR N-S as an input motion. The investigation showed that the ovalling effect of circular tunnel largely affects building displacement when it is just below the central axis. The result is the same for all foundations. As the building frame and tunnel distance increased, the circular tunnel ovalling effect decreased. Buildings built over isolated foundations are most damaged, whereas those built on pile foundations are least affected. The results obtained from the tests demonstrate that higher rise prototype sized steel buildings are more affected than low-rise frames.

Cement has historically been a major contributor to carbon dioxide emissions, and substituting cement in concrete with alternative cementitious materials will lead to a decrease in carbon footprints. A vast amount of literature focuses on the mechanical properties and performance of concrete partially replaced with different cementitious materials. However, the literature on the structural performance of concrete with different cementitious materials is very limited. Therefore, the main aim of the current experimental study is to evaluate the flexural and shear performance of reinforced concrete (RC) beams cast with various replacement percentages of ordinary Portland cement (OPC) with supplementary cementitious materials (SCM) such as ground granulated blast furnace slag (GGBS) and fly ash. A total of 33 RC beams were cast with 50% and 70% replacement of cement with GGBS and fly ash. In addition, the tensile and compressive strengths of the different mixes with GGBS and fly ash were also compared with the 100% OPC mix at 28 and 56 days. All beams were subjected to monotonic four-point bending tests and load-deflection response curves along with failure modes were presented. The experimental results showed that the average compressive and tensile strength of mixes with GGBS and fly ash replacement were comparable with OPC. The mixes with 50% replacement and higher usage of GGBS showed higher compressive strengths compared to mixes with 70% replacement. In addition, the flexural performance of beams with GGBS and fly ash were comparable to the specimen with 100% OPC. Even GGBS and fly ash replacement increased the stiffness and yield strength of the beam specimens by 36 and 16% compared to the control specimen. The specimens tested at 56 days with higher usage of fly ash and 50% replacement showed the highest flexural load as compared with other specimens. In the case of the shear specimens, the normalized ultimate shear capacity of RC beams is not significantly affected when OPC is replaced with 50% and 70% of GGBS and fly ash, respectively. Therefore, it can be concluded that the overall behavior of SCM beams was comparable to that of the control OPC beams. The ACI 318-19 design guidelines were also used to predict the flexural and shear capacity of RC beams cast with GGBS and fly ash. The aforementioned experiments indicate the viability and effectiveness of cement replacements in concrete with SCM, which in return, contribute to lower carbon footprints.

Factors such as carbon storage potential, short construction schedules, prefabrication, and aesthetics are making mass timber a sought-after structural solution. For mass timber, fire design requirements can both drive and impact design decisions. These decisions must understand code limitations for exposed timber, as well as the options for fire protection. This article primarily discusses how the last motivator, aesthetics, affects fire protection design and the carbon storage potential of mass timber. To meet code requirements for different construction types, designers can use noncombustible protection installed directly to the timber, additional sacrificial timber thickness for char design to expose the timber aesthetically, or a combination of both. Although considerable information exists for these design options, there is little guidance on how these decisions affect sustainability goals for carbon storage. This paper presents a study of mass timber structural floor systems in the residential (R-2) occupancy with sprinklers using parametric design analysis. It found that assumed carbon storage for timber elements significantly affects embodied carbon (EC) of floor structures in their entirety and therefore requires further discussion and possible standardization in industry. For designs using half of the possible timber carbon storage material availability, the lowest-EC designs come from maximizing char design and minimizing noncombustible protection. Further, the timber concrete composite (TCC) and timber floor with girders (TG) systems offer the lowest-EC options.

Mars colonization signifies the upcoming frontier in space exploration and construction. Leveraging materials native to Mars presents a sustainable strategy for building habitats. Sulfur concrete, which can be synthesized using Martian soil, surfaces as a promising material in this context. While concrete benefits from reinforcement, shipping it from Earth is prohibitively expensive. As a solution, this study explores bamboo bars as tensile reinforcements in sulfur concrete beams, examining two distinct beam sizes. The bamboo bars’ ultimate tensile strength and density stand at roughly 38% and 9.5% of A36 mild steel’s benchmarks, respectively. Intriguingly, bamboo-reinforced beams reported a 30% to 60% shear strength augmentation compared to their nonreinforced counterparts. The research also delved into the beam size effect, revealing that larger bamboo-reinforced beams boast an 87% enhancement in postcracking stiffness relative to their smaller counterparts.

The presented paper explores the potential of the MICADO method in modular structures using a parametric development approach. MICADO is an innovative building production system that uses autonomous production lines to fabricate components, which are then assembled on site. By combining frame-supported modulus systems with prefabricated panels for exterior walls, the MICADO approach allows for the simultaneous installation of components. The study examines how MICADO structures perform under earthquake and gravity loads, addressing practical challenges such as column spacing and roof detailing. It specifically looks at parameters that are still unknown due to its new structural type. An L-shaped architectural case study is employed to evaluate structural elements’ resistance and assess the lateral stability of buildings under earthquake load. The results of the study suggest that increasing the distance between columns from 300 to 450 mm is a feasible option though the demand strength of elements increased slightly. In the L-shaped plan, there are important elements such as the edge column that significantly affect the structural behavior. Ultimately, the MICADO structure and its components offer a range of design possibilities, including the creation of green spaces on the roof.

This research investigation explores the potential of the modular insulated concrete core-advanced and optimized panelized production system (MICADO) method in the realm of modular structures through parametric study. MICADO is a new advanced building production system that uses autonomous production lines to fabricate components, which are then assembled on site. The MICADO approach combines frame-supported modular systems with prefabricated panels for exterior walls, enabling simultaneous installation. The study addresses various constraints associated with executive issues, including the number of stories, the plan dimensions, and the effects of openings. It particularly focuses on analyzing the structural behavior of MICADO structures under seismic and gravity loads. To evaluate the resistance of structural elements and assess the lateral stability of buildings during seismic events, a case study involving a rectangular architectural configuration is employed. Through this analysis, valuable insights are gained into the performance of MICADO structures. The results show that the MICADO structure is capable of supporting a maximum of two stories and its length should be around 12 m, especially in areas with high seismic risk. Additionally, the openings in the MICADO structures have a significant impact on their structural behavior, as columns with higher stiffness are utilized adjacent to the openings. Moreover, the outcomes are significant for architects, engineers, and construction professionals involved in modular structure design and construction. They can use the gained insights to create robust and sustainable structures that promote safety in the built environment.

This paper presents an experimental study on the behavior of the load capacity of handcrafted studs symmetrically embedded in concrete reinforced with steel fiber. A total of eight blocks were subjected to pull-out tests. The main variables were stud head thickness (3.17, 4.76, 6.35, and 7.9 mm) and concrete type. The results showed no significant difference in the mean pull-out strength in both types of concrete mixtures: conventional and fibrous. Therefore, the effect of steel fiber addition tends to reduce the inclination plane of cracks, changing the mode of abrupt failure to more ductile. Moreover, in conventional concrete, the thickness $t_h=7.93\mathrm{mm}$ (0.20 $d_h$) lost about 15% of the pull-out strength compared to the thickness $t_h=3.17\mathrm{mm}$ (0.08 $d_h$); in contrast, it obtained a gain of 5% in concrete with the steel fiber. That is, a thickness of approximately 10% of the head diameter can adequately provide satisfactory results in embedment with or without the addition of the steel fiber for $f_c=35\mathrm{MPa}$. In addition, the literature models were more conservative. Also, a modified concrete capacity design method was proposed, considering the head thickness and the empirical factor for concrete breakout strength adjustment, $k=20$. The results were satisfactory, with an average of 1.00 and a coefficient of variation of only 6% in steel fiber concrete.

With computer solutions becoming more commonplace for structural designs, designers may lose some of the insight that comes from hand calculations. A typical Bernoulli–Euler beam design requires checking strength (bending/flexural and shear stress) and stiffness (deflections). For most design scenarios, shear does not govern, leaving the designer to check flexural strength and deflections. A new method is presented for beams commonly designed in practice and provides a simple check to determine which of these two criteria govern. This method is valid for (1) any cross section where the neutral axis is located at its mid-height, and (2) where closed-form solutions are known for the beam’s maximum bending moment and deflection. These include a large class of beam designs (e.g., steel and wood beams, where the equations for maximum bending moments and deflections are known). For this method, one only needs the beam’s elastic modulus (E); allowable bending strength (${\mathit{F}}_{\mathit{b}}$); length (L); and desired deflection limitation (e.g., $\mathrm{\Delta }=L/240$). Based on these parameters, a value of a transition beam depth, $d^{*}$, can be calculated. Then, if the actual beam depth, $d$ is $<d^{*}$, then deflection of the beam will govern (not flexure). If $d>d^{*}$, then flexure governs (not deflection). A simple check is also presented to see whether live load deflections govern a design, for the case in which the live load and total loads have different deflection criteria. Also, if factored loads, or the plastic section modulus, are used in design, simple adjustment factors are given for these situations.