Structures Congress 2022

The complexity of impact energy dissipation in laminated glass structures and the required model sophistication increases the computational demand of traditional computation (e.g., finite element analysis). Unlike hard computing, soft computing bypass these difficulties to offer a robust low-demand alternative. Therefore, in this study, the behavior of various laminated glass systems/configurations were investigated to anticipate the fracture patterns upon impact using genetic algorithms. Herein, recent laminated glass systems were examined, along with various laminated glass fracture models, all incorporated to develop the genes’ objective (fitness) function for evolution in a localized “near crack-tip” domain. Moreover, the influence of various interlayer materials was considered, including polyvinyl butyral (PVB), ethyl vinyl acetate (EVA), and thermoplastic polyurethane (TPU). Subsequently, a model was proposed allowing for an efficient crack path and critical impact scenario identification. Finally, the accuracy of the proposed fracture analysis and optimization scheme for laminated glass impact were evaluated against available results in the literature. Additionally, the adequacy of this approach in predicting laminated glazing responses to impact and blast loads for the various assemblies and parameters is discussed.

In recent years, the use of machine learning (ML) has been expanded to several engineering fields with applications in structural engineering. Deep neural network (DNN) models have been implemented to predict structural response of systems under conventional loading. Some of those DNN models are based on data sets of images, test data, and/or finite element models built for a specific environment; the accuracy of these models relies on the size of the data set that can vary from hundreds to thousands of data points. Since DNN models rely on data, their use in blast analysis and/or design is limited to the availability of data, which most of the time is scarce or restricted. This paper introduces the implementation of an ML/DNN model for the prediction of close-in blast loads based on experimental data from multiple blast test programs managed and executed by Stone Security Engineering, P.C. The blast tests were conducted at the Stone-OBL Open-Air Blast Test Facility (outside of Bend, Oregon) with multiple threat sizes and standoffs from the Stone-OBL rigid reaction structure. The current intent of this ML/DNN model is to provide a prediction tool to blast engineers to easily estimate loads from close-in range scenarios in upcoming blast test programs, thus reducing cost and time and optimizing the level of calibration tests that might be needed. This paper shows the accuracy of the model based on test data and compared with computational fluid dynamics (CFD) runs. Example cases are presented to illustrate ML/DNN model output.

The danger of malevolent vehicle penetration attempts at the perimeter of protected facilities is an increasing threat across the world. Passive, unanchored inertial vehicle barriers rely on their mass and friction with the ground surface to dissipate the energy of an impacting vehicle. Both vehicle and barrier characteristics factor into the design, implementation, and success of such systems. Although research has been done on these topics, there is a lack of unity across these methods and presently no such tool capable of succinctly applying them to the design of inertial barrier systems to mitigate the effects of vehicle impacts. This work presents research on the theory and methodology essential to compute the impact of errant vehicle collisions and provides insight into new opportunities to streamline this process. An inertial vehicle barrier calculator has been developed to estimate the penetration distances of threat vehicles given key parameters on the nature of the threat and the corresponding perimeter system. Finite-element analysis and existing crash test data validate the tool’s capabilities and verify its accuracy for several representative cases.

This article discusses development of crash rated barriers intended to mitigate attacks by heavy goods trucks. High-fidelity, physics-based (HFPB) simulations to screen performance of various barrier designs will be presented. The performance of barriers will be analyzed when impacted by a heavy goods truck traveling at different speeds. Judicious use of computational modeling can result in shorter design cycles and might require physical testing for limited cases, thus resulting in more cost efficient designs. Lessons learned from the study presented in this paper can be applied to other barrier types.

The use of blast resistant glazed facades in buildings are increasingly common. A variety of standards and reference guides exist that can be used for the design of these blast resistant glazing systems. These include documents produced by the American Society of Civil Engineers (ASCE), Unified Facilities Criteria (UFC), US Army Corps of Engineers Protective Design Center (USACE PDC), General Services Administration (GSA), and the Federal Emergency Management Agency (FEMA). While much attention in these guides is focused on static and dynamic design methods for glazing and mullions, comparatively little attention is devoted to determination of reactions on supporting elements and the design of connections and anchorages. Consequently, designers may find that guidance on reaction determination and connection safety factors or load and resistance factors is lacking. This paper will survey existing design methods to gain insight into industry standard practices for reaction calculation and safety factors. Comparisons will also be drawn to published test data to examine correlation and relationships with standard practices.

Secondary fragments generated by the breakup of structural and non-structural elements during blast loading can pose a significant hazard to building occupants. Ungrouted and nonreinforced concrete masonry unit (URN CMU) walls can generate significant secondary fragments. Full-scale and quarter-scale CMU walls were exposed to blast loading, and their responses were recorded. A computationally efficient, energy-based, engineering-level methodology is developed to calculate the secondary fragment velocities of URN CMU walls. Measured fragment velocities from the experiments are compared with calculations from the analytical methodology, and strong correlation is observed. The analytical method is discussed, and comparisons between the analytical calculations and the observed results are presented.

When developing the safety and security measures for a school building, design professionals might consider utilizing federally recommended design process to mitigate risks, such as Crime Prevention through Environmental Design (CPTED) that focuses on changes to the physical and social environment that will reinforce positive behavior through proper design and effective use of the built environment, reducing fear and crime while improving the quality of life. Such approach considers an array of strategies rather than focusing on limited mitigations such as structural hardening or installing electronic security devises. A risk-based methodology is presented as a tool to develop credible threats at the school site, and justify the selection of appropriate ballistic mitigation strategies. This article will highlight the inherent ballistic rating, if any, for a typical public school building. Furthermore, cost effective mitigation strategies will be highlighted.

This paper presents a simplified approach to assess the safety of main cable and suspenders of long-span suspension bridges under blast loads, whereby a two-layer solution is adopted to solve the blast-bridge interaction problem: (1) blast aspect is modelled as nodal load by simulating the area of blast pressure contour on the deck surface; and (2) bridge is simulated as a 3D fishbone skeleton FE model. The detailed implicit dynamic analysis is performed under small to large sized blasts detonated at different locations to evaluate the redundancy of main cable and suspenders in a parametric manner. The analysis results show the sufficient and insufficient redundancy of main cable and suspenders under small to medium sized blasts, respectively, whereas a large sized blast can lead to the progressive collapse of entire bridge. At last, the first-order reliability analysis method is also applied to assess the safety of main cable and suspenders under large sized blasts, which concludes that a minimum safety factor of 3 is indispensable for main cable to achieve the target reliability index of 3.5, whereas the shorter suspenders carrying large axial stresses are more vulnerable to the blasts than longer ones and suffer the largest blast damage.

Understanding the behavior of structural steel in terms of fabrication and fashioning is an important factor in the design of steel structures. The search for structural steel with capabilities of acceptable responses in seismic regions alongside cost efficiency has led to the investigation of the behavior of high strength steels (HSS), which have a yield strength of 55 ksi (ASTM A572) or higher, as classified by US standards, while their inelastic capacity is less than that of conventional steel. The present research investigates the rotation capacity and flexural strength of hybrid high strength web-tapered I-shaped steel girders using an experimentally verified nonlinear finite element modeling technique. The academic multipurpose software package ANSYS19.2 was used to develop a finite element model, and a mesh convergence study was performed to ensure the accuracy of the results. Geometrical imperfections were applied to conduct a linear eigenvalue analysis and to capture buckling mode shapes to perform a nonlinear analysis. The residual stress was associated in the finite element model for different welding configurations. The numerical model was verified with previous experimental data, and close agreements were achieved. A total of 450 models were used to perform a parametric study with various flange and web slenderness as well as lateral bracing configurations to capture local, overall, and local-overall buckling modes. As results, some equations for direct design of non-prismatic hybrid high strength steel girders were proposed.

AFRP bars have experienced premature rupture under concentric loads due to their anisotropic properties, limiting their usage in compression members. A limited number of studies have been conducted on the reliability of implementing energy dissipaters to prevent the rupture of AFRP longitudinal bars in compression. However, the research to date has failed to emphasize the influence of rocking connection and size of replaceable fuse on the performance of the column. This research explored the strategy of designing the AFRP-reinforced concrete (AFRP-RC) column to remain elastic while incorporating external replaceable fuses as sacrificial elements to dissipate energy and reduce damage. A three-dimensional finite element model was developed and validated. An extensive parametric analysis was performed on 100 numerical models with a typical column size. Enhanced performance of the AFRP-RC controlled rocking system in terms of ductility, energy dissipation, damage index, and work index was found. Key design parameters of replaceable fuses that influence the cyclic performance of the column were identified. A set of equations are proposed to assist in designing the controlled rocking columns with replaceable fuses.

Construction of the Gerald Desmond Bridge Replacement Project (GDBRP) in Long Beach, California, has recently been completed. The new bridge is located at the Port of Long Beach and consists of approximately 2.6 km of bridge structure. The approach spans are made up of conventional cast-in-place box girders, while the main span over the Back Channel includes California’s first major vehicular cable-stayed bridge. This signature structure has a 304.8 m main span and 152.4 m back spans. Now that it has been built, the new bridge is the second-tallest cable-stayed bridge in the US, and has the highest vertical clearance of any cable-stayed bridge in the country. The replacement bridge is founded on a total of 352 cast-in-drilled-hole piles that range in size from 1.8 to 2.4 m in diameter. More than 100 reinforced concrete columns of varying heights support the superstructure, with the two towers supporting the main span featuring a hollow 156.9 meter-tall monopole design. The signature cable-stayed bridge span consists of a pair of 1.8 m deep steel edge girders with a box shape cross-section. Framing into the edge girders are variable-depth steel floorbeams with four lines of longitudinal stringers spanning between them. This floorsystem supports the full-depth precast concrete deck panels. The cross-section of the bridge has an out-to-out width of approximately 47.5 m to accommodate three lanes in each direction and emergency lanes on both sides (3.0 m shoulders). Seismic demands on the main span are dissipated with passive dampers at the towers and end bents. The superstructure of the low-level approach spans was built using conventional falsework; however, the high-level approaches were built using a movable scaffolding system (MSS). This project is the first time in the State of California that an MSS was used to build bridge superstructure elements. The MSS had a self-weight of 1.41 million kg. With the load from the concrete, the MSS bore approximately 3.2 million kg, supported by brackets mounted onto the columns. The main-span superstructure was stick-built with help from stiffleg derrick cranes on the deck, and two 178.3 m tall tower cranes, which were the tallest tower cranes currently in use at the time on any infrastructure project in the US. This paper will provide a general overview of the project from the program manager/construction manager perspective, and describe some of its key design and construction innovations and challenges. In addition, design-build lessons learned during the construction phase will be summarized.

Full-depth precast and prestressed concrete slab panels offer an efficient alternative to traditional cast-in-place concrete bridge construction. Although utilizing the precast system makes the process of constructing much easier and faster, over time, damage at the longitudinal joints connecting the panels affects the bridge integrity and can reduce the load-carrying capacity of the structure. This study investigates the performance of a precast and prestressed box-beam bridge that has been in service for more than 50 years. A series of load tests were conducted on the bridge to evaluate the bridge’s structural response. Moreover, a finite element model was developed to study the bridge behavior considering possible damages in the longitudinal deck joints. A comparison between load testing results and the finite element model showed that the longitudinal joints were significantly damaged, resulting in a reduction of the bridge load-carrying capacity. A novel bridge monitoring approach was also proposed for joint damage detection in these types of bridges.

This paper presents a machine learning approach coupled with image visibility optimization techniques to enable more efficient visual bridge inspection when relying solely on remote-controlled drones. This approach involved convolutional neural network (CNN) considered a representative machine learning algorithm and image analysis of optimized high-resolution imagery collected with drones. To evaluate the efficiency of this approach, remote-controlled drones were utilized to detect and measure the damage of two timber bridges located in Minnesota. Visual inspections on each of the bridges were initially performed in 2019 with two drones (DJI Phantom 4 and DJI Matrice 210), which resulted in a total of 66,572 extracted images. Then, the CNN was trained with a large number of extracted images containing varying damage types (i.e., cracking, weathering, and spalling) and attempted to classify the damage in an effective fashion. The visibility of the images that were classified per damage type through the CNN training was optimized by fine-tuning different properties of its images to take a measurement of damage specific to critical sections for each bridge. Included in the image properties were brightness, contrast, and sharpness. Through the analysis of extracted images from both timber bridges, the integrated CNN coupled with an image visibility optimization approach demonstrated the capability of improving the visibility of the damage and the accuracy of damage measurement.

The Manulife Place Plus 15 Pedestrian Bridge serves as an important connection in the urban core of downtown Calgary in Canada, integrating the project to the rest of the Plus 15 network and serving as an opportunity to bring a different bridge design aesthetic to the city. Due to the elimination of all architectural cladding and mullion supports, the bridge connections and details have been designed to showcase structural clarity while responding to site constraints and architectural requirements. The unique construction sequence undertaken also influenced the design of the connections, resulting in a bridge that successfully combines form with function.

The construction of a bridge deck often introduces significant loads acting on the bridge girder system. These loads generally come from the construction equipment, the weight of fresh concrete, and the construction personnel, sometimes resulting in excessive rotation of the exterior girder during deck construction. To limit the girder rotation, temporary bracing systems are commonly used in the United States during bridge construction. The traditional temporary bracing system uses block-tie systems to resist the torsional forces in the girders; however, this system often loses its effectiveness due to the tightening issues of ties and the improper shimming of timber blocks. In this study, a new temporary bracing system—pipe-tie system—is developed to limit the girder rotation during deck construction. This system utilizes diagonally placed steel pipes and ties between girders to resist the torsional forces and limit the rotation of girders. To optimize the sizes of steel pipes and ties, and the spacing between the bracings, finite element analyses are conducted to evaluate the performance of the pipe-tie system under different scenarios during deck construction. Recommendations regarding the size of pipe and ties and the ratio of the bracing system spacing to girder depth are given based on the results from the parametric analysis in this study. This study provides a guideline for designers and engineers to implement the pipe-tie system for rotation prevention during deck construction.

An analytical model was proposed in this research, where the nonlinear material behaviors of stainless steel and concrete were adopted. The proposed analytical model was carried out by the computer software MATLAB to run the iterations and satisfy the equilibrium of the internal forces in the post-tensioned composite sections. Experimental and numerical results from the literature were presented to calibrate the proposed model. The validations include capacities, deflections, strains in the extreme fibers of the composite sections, and the incremental PT force in the tendons. The difference in the behavior of post-tensioned composite beams with various structural steel grades (carbon steel and stainless steel) was explored. The external PT force enhanced both the beam stiffness and capacity of the composite beams. The stainless steel with grade 1.4512 obtained the highest improvement in the beam capacity of 27.2% after adding the external PT, whereas grade 1.4362 obtained the lowest increase in capacity of 15.1%. The contribution of the external PT force to improve the behavior of composite beams with stainless steel was enhanced by using stainless steel with lower-yielding and ultimate strengths. However, the post-tensioned composite beam with conventional carbon steel showed higher stiffness and capacity over that one with stainless steel.

Deck anchors for cable-stayed bridges provide the connection between steel girders and stay cables, and typically consist of a welded assembly of ring plates, an anchor pipe, fin plates, stiffeners, and a gusset plate. The design of steel deck anchors involves many integrated design problems, including complex geometry and esthetics, structural analysis and design, and fabrication and erection. These design topics are largely discussed within the context of the shark fin deck anchor design of the Lewis and Clark Bridge, but also from a broader perspective with comparisons to other deck anchor designs. For this bridge, overall deck anchor geometry was driven by cable alignment, clearances, and integration with girder webs. A method for calculating work points was developed to ensure compatibility of the plane of the gusset and orientation of the anchor pipe with the sag of the cable. Smooth transitions between connected plates were shaped to reduce stress concentrations, improve fatigue performance, and unify the appearance of the steel assembly. With the varying stay sizes and stay inclination angles of the 104 stay cables along the bridge, a parametric design approach was employed. This approach helped optimize plate sizes and dimensions and provided a gradual evolution of form from one anchor to the next. Structural validation of the anchors was done by a combination of hand/spreadsheet calculations and nonlinear finite element models. Many practical considerations such as weld details and inspection, shipping height limitations, and clearances for strand installation equipment had an appreciable effect on the anchor form.

Full-scale cyclic tests were conducted to examine the seismic performance of a novel beam-column connection equipped with superelastic shape memory alloy (SMA) plates and SMA Belleville spring washers. The proposed connection employed a set of dog-bone SMA plates connecting the beam flanges to provide the self-centering capability and energy dissipation capacity of the connection. The SMA Belleville spring washers were used to minimize the axial deformation of the high strength bolts used in the connection and to provide additional energy dissipation and self-centering abilities. Tension coupon tests of the SMA plates with varied dimensions were conducted to examine the fundamental mechanical properties of the SMA plates. The cyclic behavior of the SMA Belleville spring washers was also examined experimentally. Test results showed that the connection exhibited flag-shaped hysteretic responses with negligible residual deformation in a wide drift spectrum, and the skeleton curve with multi-stage characteristics was observed. The applied load-drift responses of the connection indicated that the SMA plates have developed significant inelastic deformations, which were able to offer self-centering capacity and energy dissipation concurrently.

This paper presents innovative uses of cross-laminated timber (CLT) as part of the gravity and lateral force resisting systems for two school projects in Vancouver, the Sir Matthew Begbie and Bayview Elementary Schools. Natural Resources Canada Green Construction through Wood (GCWood) program supported the project construction and coordination costs associated with innovative mass timber construction. The two-storey school buildings will provide classrooms, teaching areas, gymnasium, as well as a learning center with exposed CLT walls, floors, and roof throughout; CLT walls are used for both gravity and lateral resistance in the building. At the upper storeys, hybrid steel-CLT storey-depth beams avoid intrusive drop beams below the floor. Long windows are framed with CLT panels acting as lintels. Both projects include long-span floor systems for which both deflection and vibration requirements fell outside the feasible range for CLT panels commercially available in North America; therefore, a ribbed CLT-glulam composite floor is utilized. In this paper, the innovative use of CLT includes long span composite CLT-glulam floor and roof systems, balloon-framed shear walls, and the use of concentrically and eccentrically loaded CLT lintels are discussed, focusing on the Sir Matthew Begbie Elementary School.

Cross-laminated timber (CLT), an engineered wood product categorized as “mass timber,” is gaining popularity in residential and non-residential applications. The prospect of building larger timber structures creates structural challenges, amongst them being that lateral forces created by high winds and strong earthquakes are higher and create higher demands of “hold-downs.” These demands are multiple: high strength to resist loads, high stiffness to minimize deflections during wind events, as well as deformation compatibility to facilitate the desired rocking-motion of the shear walls during an earthquake. Herein, recent research on several innovative hold-down solutions will be provided: internal-perforated-steel-plates fastened with self-drilling dowels; hyperelastic rubber pads with steel rods; and solutions with self-tapping screws. All systems are capacity-protected in the non-dissipative components: strength, stiffness, and ductility is governed by the energy-dissipative shear wall components. The results from component-level and full-scale CLT shear wall tests are presented. The findings provide design guidance to practicing engineers and will inform future revisions of the Canadian Standard for Engineering Design in Wood.

An experimental study with six bolted single-brace eccentric gusset plate connection specimens is presented in this paper. Using Abaqus FEA, numerical models are created and are validated on the tested specimens. Then, a numerical parametric study follows, showing the influence of eight geometrical and material parameters on the ultimate and critical load of the connection. Finally, the results are compared with the predictions of existing analytical models. It is shown that both the placement and the number of bolts in the connection have almost no effect on the compressive resistance. Furthermore, it is proven that parts of the gusset plate outside the so-called Whitmore section actually contribute to the compressive resistance of the connection, although they may not develop a full plastic hinge. For the tested connection geometry, the best and safe analytical prediction is given by a model which assumes the formation of two plastic hinges, a second-order effect, and reduction of the plate bending resistance due to the present axial force.

The $130M Arbour, a 10-storey, 16,000 m², exposed tall wood structure located on George Brown College’s waterfront campus in Toronto, Canada, will serve as an educational hub for the college, housing the Tall Wood Research Institute, a childcare center, and teaching and social spaces. The innovative large-span beamless structural floor system is comprised of cross-laminated timber (CLT) concrete composite slab bands with perpendicular CLT infill panels, all supported on glulam columns. This long-span flat plate system allows for flexibility in architectural programming and unobstructed mechanical distribution; its performance was validated by full-scale laboratory tests. The project, currently under construction, received external funding through the National Resources Canada Green Constriction Wood Program, alongside other partners, to facilitate mass timber innovation specific to this project. This catalyzed a full-scale structural testing regime at the University of Northern British Columbia, investigating timber concrete composite “slab bands,” to determine their performance and develop a low-cost composite connector.

This study examined the business resilience practices of engineering construction companies in Thailand as their strategy for survival and pandemic recovery. It also looked into the profile of the key informants and investigated their experiences on their business resilience practices. It also looked into the support strategies of engineering associations in Thailand for their members to enable them to survive during the COVID-19 pandemic. It was conducted in Thailand, and it applied the case study research design. Findings show that some dimensions of business resilience are being practiced by engineering firms. The Thai engineering associations revealed that their members are shifting to digitalization, and they offered them technical webinars. It can be concluded that the selected Thai engineering construction firms practice business resilience. It is recommended that the engineering construction companies in Thailand should adopt the innovative business resilience strategies proposed in this study.

Human actions have, and continue to, cause changes to our climate. The built environment sector is disproportionately responsible for present greenhouse gas emissions, and thus structural engineers have a unique opportunity to reduce the quantity of future greenhouse gas emissions. Emission reductions can be realized through building less, refurbishing more, appropriate lean design, completing life cycle assessments at early stages, designing with low-carbon materials, and applying circular economy principles to new designs and material life cycles. However, the construction industry is risk-averse, and engineers often defer to previous familiar historic design methods, which do not reduce greenhouse gas emissions. This paper proposes applying knowledge from the field of Behavioral Economics to the structural engineers’ quotidian design workflow to allow engineers to realize emission reductions. Recently implemented changes to the workflow at Schlaich Bergermann Partner (sbp) are discussed, in addition to planned actions within sbp and the industry at large.

Teaching structural engineering is a core part of education in every undergraduate civil engineering program. The content in these kinds of lectures is demanding advanced analytical thinking and abstract perception. Previous research showed the little level of using modern technology in structural engineering lectures to promote independent student learning, while the use of digital tools with spatial representation can enhance motivation. In this paper, the authors present the conception, workflow, and deployment of two mixed reality (MR) applications for verification of typical, yet geometrically complex, structural members: a reinforced concrete corbel and a steel frame. This paper reports the development, implementation, and evaluation of such MR applications in the context of structural engineering lectures. Participants were able to test the MR applications on their devices or watch pre-recorded videos. Their feedback indicated a great interest and potential in using such MR applications in teaching structural engineering.

Alkali-silica reaction (ASR) has been recognized as a potential cause of concrete degradation in the world since the 1940s. In Pakistan, mega hydropower structures like dams, weirs constructed from aggregates extracted from a local river bed, exhibited different levels of alkali-silica reactivity over an extended service period. The concrete expansion potential due to such aggregates has been categorized as slow-reactive. Apart from hydropower structures, ASR existence has been identified in the concrete structural elements of a textile mill building which used aggregates extracted from the nearby river bed. The original structure of the textile mill was erected in the 80s with addition of a textile “sizing and wrapping” hall constructed in the 90s. In the years to follow, intensive spalling was observed in the structural members of the subject hall, enough to threaten the overall stability of the building. Limitations such as incomplete building data posed hurdles during the detailed structural investigation. The paper lists observations made while assessing the extent of damage and its effect on the building hall structure. Core testing and petrographic tests were carried out as per the ASTM standards for strength degradation analysis followed by its root cause identification. Results confirmed significant structural strength reduction due to the presence of ASR, which necessitated the formulation of an immediate re-strengthening solution. The paper also discusses the possible tracks of rehabilitative measures likely to be adopted for structural stabilization and to seize further concrete expansion.

On May 23, 2020, a severe fire in a processing and storage steel structure located at Pier 45, Fisherman’s Wharf, in San Francisco, California, resulted in complete collapse of the single-story building. Accordingly, a post-fire forensic investigation was conducted to collect pre-fire and trans-fire event data, information regarding design of the structural system, and site observations of fire severity and structural failure. The collected information and engineering judgment was used to hypothesize a simplistic sequence of events leading to the fire-induced collapse of the building. To verify the hypothesized sequence of events, two distinct approaches were used to estimate gas temperature-time relations in a representative portion of the building, namely, standard fire exposure and zone-based compartment model. The generated gas temperature-time relations were utilized to predict temperature evolution in the column cross-sections using SAFIR software and then estimate failure time based on a critical temperature criterion. Material tests on steel coupons extracted from fire damaged members and thermo-mechanical modeling are planned in the future to further validate the hypothesized collapse mechanism.

Among different types of man-made and nature-made disasters, fire constitutes a significant threat to both people and structures. This study provides fire incident data including the origin and cause, as well as the extent and severity of real fire incidents that occurred in around 60 wood–frame residential buildings in the province of Ontario, Canada. Analysis of the data showed that most of the fires in the residential building were electrical fires; however, the causes for many of the fires were reported as “undetermined.” The primary places of origin of the fires were found to be the garages and kitchens. Sunday was the day of the week with the highest number of fire incidents. It was observed that floor joists and roof framings were the most vulnerable structural elements, and poor fire performance of I-joists often resulted in total loss. To protect floor framings from fire, it is recommended that the exceptions to the provisions of section R302.13 of the 2015/2018 IRC be eliminated so that all types and sizes of floor framings be covered with gypsum boards. Similar provisions shall be added to Part 9 of NBC as well as OBC and other Canadian provincial building codes. It is also recommended that I-joist floor systems and roof framings be sealed with a fire-protective coating after installation.

During construction of the single story, reinforced masonry Electrical Building No. 2 (EB2) of the Scott Candler Water Treatment Plant (WTP), owned and operated by DeKalb County, Georgia, a design change was made which impacted its structural integrity. Several pile supports were removed due to conflicts with underground utilities and were replaced by a steel angle supporting the slab edge off an adjacent sub-surface concrete basin wall. Soon after construction in 2002, signs of foundation settlement were initially observed. This grew progressively worse over time until there was a dramatic structural failure as one corner of the concrete base slab displaced downward up to 2 in. In 2018, Arcadis assembled a multi-disciplinary team comprised of structural, geotechnical, electrical, and process mechanical engineers to assess the long-term stability and viability of EB2 and determine a permanent solution. The investigation and resulting repair consisted of the following steps: Step One: Document Review; Step Two: Identifying the Problem; Step Three: Diagnosing the Cause of the Problem; Step Four: Locating the Source of the Problem; Step Five: Emergency Repairs; Step Six: Long Term Repair.

Experimental investigations on full-scale (9.6 m) and half-scale (4.8 m) cross-laminated timber (CLT)-concrete-composite (TCC) slab bands are presented. The out-of-plane shear and ultimate flexural capacities of these TCC floors utilizing several types of shear connectors were determined. The TCC system was comprised of a 245 mm thick, 7-ply CLT with 150 mm concrete topping joined with shear connectors. The efficiency of three types of shear connectors: self-tapping screws, steel kerf plates, and proprietary glued-in Holz-Beton-Verbund (HBV) connectors was evaluated. Six series of floor systems, one control series of raw CLT floors (without concrete topping) and five TCC series, were tested for a total of 6-half scale control slabs, 18-half scale, and 6-full scale TCC slabs were tested under four-point bending. The results from this research were utilized to make project-specific design decisions for “The Arbour,” a 10-storey mass timber building for George Brown College, located in Toronto, Canada.

Tessellations are patterns of repeating 2D geometric shapes that form an arrangement without gaps or overlaps. Although commonly used for their visual appeal in architecture, tessellations have only recently received attention for their applicability to structures as tessellated structural-architectural (TeSA) systems. Because TeSA systems are composed of repeating discrete pieces (tiles), tessellated structural members have several potential benefits including automated fabrication and construction, localization and repairability of structural damage, tunable structural behavior, and esthetic value. This paper presents experiments in which small-scale (approximately 20 mm wide × 75 mm tall × 300 mm long) TeSA beams were fabricated from 3D printed tessellated tiles and then loaded to failure. Load-displacement response and failure mode are presented for six beam specimens, each having a different tessellated pattern. Stiffness, strength, and failure mode are compared between the different patterns. The results provide insights into how to design tessellated structures to achieve a desired structural response. While the notion of tessellated structures is still in its nascency, this paper introduces the concept, demonstrates and discusses its potential, and makes some critical observations about structural behavior and design.

This paper introduces a new modular shear wall system designed for replaceability and resilience after extreme loading as well as architectural appeal. The walls are called tessellated structural-architectural (TeSA) walls because they consist of interlocking tiles (modules) with repetitive shapes (tessellations) and are intended to satisfy both structural and architectural demands. In TeSA systems, tile discontinuities may be able to contain damage within discrete units. This can facilitate quicker structural repair and reoccupation, and reduction of ensuing financial losses from service interruptions. Tiles of TeSA systems can be interlocking in one or two directions and can incorporate self-centering post-tensioning. This study focuses on documenting and quantifying damage in TeSA shear walls with tiles interlocking in one direction based on (1) laboratory tests performed on walls and (2) finite element modeling of TeSA walls. The considered TeSA walls consisted of reinforced concrete tiles and had self-centering post-tensioning. The interlocking tiles did not need mechanical connections to adjacent tiles. Wall damage was quantified in terms of the number of damaged tiles as observed through testing and obtained through analyses. Finite element analyses of the TeSA shear wall were performed in open-source analysis software (OpenSees). Static pushover analyses were performed to obtain force-displacement relationship and ensuing damage. A framework for calculating probability of damage at salient drifts is presented considering uncertainties in tile-interface properties, modeling approach, and applied loading. The 1-D interlocking TeSA wall had a 9% probability of no damage and 91% probability of slight damage at the drift of 0.87%. The framework can be used to generate fragility functions for the TeSA wall.

Over the past two decades, buckling-restrained braces (BRBs) have demonstrated their versatility in various non-traditional seismic applications including non-lifting rocking walls, high-rise outriggers, and mega-frame structures. Another use of BRBs is to substitute traditional diagonally reinforced concrete coupling beams with pairs of crossing BRBs (BRB coupling beams). This would be done because BRB coupling beams provide more predicable seismic performance, simple detailing, and it is feasible to replace these components after a seismic event. A feasibility assessment of BRB coupling beams was completed on the recently completed reinforced concrete corewall structure, the Grand Hyatt San Francisco International Airport Hotel. Structural analysis was performed to assess the performance of the building with BRB coupling beams compared to that of the same building with traditional diagonally reinforced concrete coupling beams. Specifically, the BRBs’ impact on building drift, torsion, and force distribution were examined. From this analysis, realistic demands on the BRBs and their connections were determined, allowing for a study on the detailing associated with these BRB coupling beams, particularly, how they can be detailed to facilitate replacement after a seismic event. By using BRBs arranged in a crossing configuration in lieu of conventional coupling beams, there is potential to control distribution of plasticity and ultimately capacity protect the most critical elements from extensive damage.

The ultimate moment capacity of individual footings subject to axial and uniaxial moments for footings of rectangular geometry has been well established and forms the governing equation for determining foundation moment capacity in ASCE 41 and prior FEMA publications related to seismic retrofit and rehabilitation of existing buildings. However, there is no comprehensive study for determining ultimate moment capacity for isolated footings of other plan shapes and bi-directional seismic overturning moments. This paper provides a simple, easy to follow general method for establishing the ultimate moment capacity for shallow foundations where soil resistance is represented by a rectangular pressure distribution under the footing. The concepts and results from this study have been extended to show equivalence between the derived closed form solution for foundation moment capacity and the maximum soil pressure for foundations modeled as beams on nonyielding compression only springs from a finite element analysis program.

As engineers, we all know that tornadoes are violent but rare wind events. Beginning with ASCE 7-22, limited tornado design appears in the code. But is there more to tornado design than “Basic Wind Speed” and “Exposure?” Let’s look at the historic records of US tornadoes, from the standpoint of probabilistic design, to see what we can learn about these devastating storms, common to much of our country. Just as earthquake damage involves more than acceleration and soil type, tornadoes have different sizes, duration, velocities, and these characteristics affect damage and risk to human life. We will address topics based on recorded tornado data: (1) How do tornadoes function? (2) Is the diameter of severe tornadoes larger or smaller than minor tornadoes? (3) Historically, how common are devastating tornadoes? (4) How can we build more tornado resistant structures for a reasonable economic cost? (5) What is the best method of protecting human life in tornadoes?

The state-of-the-practice engineering report on Design of Modular Structures for Industrial Facilities soon to be issued by the ASCE Energy Division’s Task Committee on Onshore Modularization for Heavy Industrial Applications will provide guiding principles that help practicing engineers design modules in petrochemical and other industrial facilities. Topics related to design and engineering of onshore modules that are addressed in this report include overview of onshore module types, philosophy, modularization study, detailed engineering, transportation and logistics, construction, and case histories. The report will also provide references to and highlights from building codes, industry standards, and common professional practices for onshore heavy industrial modularization.

Usage of onshore process plant modules includes transportation from a fabrication yard to a jobsite via a combination of water and land routes. Large modules (larger than 1,000 m) are normally transported over land using self-propelled modular transporters (SPMTs) in order to spread the module’s weight uniformly over a large area of the transportation path. SPMTs utilize hydraulic cylinders to lift and lower modules, and to achieve uniform wheel loads that transfer the module’s weight to the road. A suitable analysis is needed to consider this uniform wheel loading and to check against the hydraulic cylinder’s permissible stroke, spine beam permissible stresses, and deflections within the module. This paper describes a balancing approach for a SPMT analysis that is used by several companies. The discussion describes the method itself and includes how hydraulic-type reactions are modeled. One key element is specifically examined, the rigidity of the module and the resulting effect from SPMT-imposed support. The results of field measurements are presented in support of the approach.

Cavity permeability influences the rate of pressure equalization and load sharing between the two glazed walls of a double skin curtain wall. It is also known to affect weathertightness in these non-structural systems. However, in testing the weathertightness of curtain wall systems, manufacturers and regulators usually use testing sequences that do not replicate realistic wind events or co-occurring wind and rain events, which are some of the factors leading to water penetration and mist formation within the cavity of double skin systems. A full-scale wind testing study was carried out on a novel closed cavity double skin glazed curtain wall unit at 22.4 m/s, 31.3 m/s, and 40.2 m/s wind speeds with wind directions varying between 0° and 360° in 15° increments. This study finds the strong dependence between permeability and load sharing, water penetration, and dynamic properties. It also shows the limit of current code guidance in predicting load sharing at higher permeability.