Journal of Structural Engineering

Controlled rocking systems have been used in numerous structures around the world as a seismic force-resisting system. In a controlled rocking wall system, the wall is allowed to uplift from the foundation during seismic events, thus reducing the wall’s lateral stiffness and minimizing its corresponding seismic force demands. This rocking mechanism is often controlled using posttensioning (PT) tendons, resulting in negligible residual deformations compared to conventional walls (i.e., with fixed bases). For these reasons, promising strides have been taken to apply the concept of controlled rocking systems to masonry walls; however, several issues have been encountered when using PT tendons due to the brittle nature of the masonry material in compression. To address this, the current study aims to reduce damage and improve the performance of controlled rocking masonry walls (CRMWs) by omitting PT, instead relying on gravity loads and energy dissipation to control the seismic response. Three strategies to achieve this improved performance are proposed and investigated. The first strategy involves using externally mounted, replaceable energy dissipation devices; the second strategy introduces a steel base for the rocking wall; and the third strategy considers confinement plates in the rocking toe region of the wall. To assess these strategies, the study develops and validates a numerical model to capture the performance of previously tested CRMWs. The model is then used to develop and experimentally validate an index for masonry walls to quantify their damage based on numerical results. Next, a suite of 20 CRMWs is designed, 5 of which incorporate PT tendons while the remaining 15 walls omit PT and incorporate one or more of the proposed strategies to reduce damage. Numerical models of all of the archetype walls are subjected to reversed cyclic loading protocols, and the amount of damage incurred is compared across each archetype wall. The results demonstrate that the proposed modeling technique and damage index are effective at capturing the response and quantifying damage in CRMWs and that the proposed strategies result in a lower damage alternative to posttensioned CRMWs (PT-CRMWs).

A steel tube–reinforced concrete (ST-RC) column is composed of the inner concrete-filled steel tube (CFST) component and peripheral reinforced concrete (RC) component. In this study, the confinement interaction mechanism of axially loaded steel tube–reinforced concrete columns (ST-RC) was evaluated experimentally and analytically. Eleven column specimens were tested, including five ST-RC, three CFST, and three RC columns. The test results found that the confinement interaction between core CFST and outer RC components integrates both advantages while remarkably altering the section equilibrium and confinement mechanism compared with conventional confined concrete. Specifically, the following two aspects need to be considered. First, since the core CFST component is subjected to the secondary confinement provided by outer stirrups, the capacity of an ST-RC column is 1.07–1.21 times greater than that of the simple superposition of CFST and RC components (CFST+RC). Second, for the outer RC component, because the filled-in concrete is confined by the steel tube, the outer stirrups confinement cannot be effectively activated due to the weakened dilation of concrete. Such strain-lagging leads to a steeper falling branch of the load–axial strain curve of the ST-RC column under compression than that of CFST+RC. Finally, based on two modified constitutive models considering the confinement interaction mechanism in the ST-RC column, a well-defined analytical model for predicting the structural performance of axially loaded ST-RC columns was established.

This paper presents an experimental study on the multidirectional cyclic lateral-load response of post-tensioned self-centering (SC) cross-laminated timber (CLT) shear walls. SC-CLT shear wall damage states are introduced and qualitatively defined in terms of the repairs needed to restore the lateral-load response of the SC-CLT wall. A comparison between SC-CLT wall damage states under unidirectional (in-plane) and multidirectional (in-plane and out-of-plane) lateral loading is presented. The experimental results show that the initiation of SC-CLT wall damage occurs at smaller story drifts under multidirectional loading compared to unidirectional loading. Engineering demand parameters (EDPs) are used to quantify the SC-CLT wall damage states. Uncertainty in the EDP value when a damage state occurs is considered and quantified. Using the experimental results, component (i.e., a CLT wall panel corner) and system (i.e., an entire SC-CLT wall) fragility functions are developed and presented.

Coupled cross-laminated timber (CLT) walls with steel link beams are a type of high-capacity lateral load resisting system for multistory buildings. In this study, a 6.6 m tall coupled CLT wall specimen with three steel link beams and mixed-angle screwed hold-downs was tested to $\pm 4.5\%$ drift to evaluate its cyclic performance. The system achieved peak strengths of $+590$ and $-592\mathrm{kN}$, while also exhibiting relatively high displacement ductility factors of 7.6 and 6.9 in the positive and negative directions, respectively. Failure of the system was characterized by combined bending and withdrawal of the mixed-angle screws in the hold-downs, yielding and eventual inelastic buckling of the steel link beams, CLT toe crushing, and local CLT delamination. In comparison with similar cantilever CLT shear walls, the coupled wall system exhibited 45% greater peak strength, dissipated approximately 50% more energy, and experienced less degradation of its energy dissipation capacity on repeated load cycles (when subjected to the same loading protocol). Following the initial test, the steel link beams, screw hold-downs, and damaged CLT regions were repaired, then the wall specimen was retested with the same loading protocol. The repaired wall behaved similarly to the original test and exhibited slightly higher energy dissipation and peak strength but more rapid strength deterioration under cyclic loading. The retesting provided evidence that it may be feasible to repair the coupled wall system after an earthquake because the damage was localized, and the main CLT wall elements were effectively protected from damage.

Hot-dip galvanized steel structures are well-established and state of the art for public and industrial buildings. They can achieve a corrosion protection period in the magnitude of the lifetime of the structures ($\ge 100\mathrm{years}$). The application of this corrosion protection system would also have great potential in bridge construction. Economic efficiency and sustainability in bridge construction are, in addition to the cost of new building, determined by the incurred maintenance costs. A prior research project had demonstrated hardly any losses on the fatigue strength compared with the nongalvanized steel components. Large bridge structures must be designed with assembly joints. Welded field joints of hot-dip galvanized components require a complex pretreatment and posttreatment of the corrosion protection. Nevertheless, onsite applied corrosion protection cannot reach the protection durability of a hot-dip galvanizing. This technological restriction can be avoided by the use of hot-dip galvanized bolted connections. Slip-resistant pretensioned connections with pretensioned bolts have been proven successful in steel bridge construction. Major scientific investigations are not yet available for the use of slip-resistant connections for hot-dip galvanized joints. Technical and scientific foundations for the application of hot-dip galvanized bolted connections in cyclically loaded steel and composite bridge constructions, based on the European standard for steel constructions are investigated within the scope of this research project. Construction and design recommendations are provided.

Perfobond rib shear connectors (known as PBL shear connectors) are structures widely used to transfer loads between concrete and steel structural elements. The performance of PBL shear connectors under monotonic loads has been extensively reported; however, their shear resistance under cyclic loads is not well investigated. A total of 13 PBL shear connector specimens were designed to explore their performance under cyclic displacement. The crack patterns and hysteretic load-slip responses of the specimens were observed. The cyclic displacement changed the crack development and accelerated the deterioration of the cohesive strength and shear-friction force. Cyclic loading weakened the transverse expansion of the damaged concrete dowel and reduced the contribution from the transverse reinforcement. On the basis of the test results, a theoretical method for estimating the peak shear resistance of a PBL shear connector under cyclic loading is proposed. The proposed model exhibits good accuracy in comparison with the test results.

Shake-table tests of a full-scale 3-story reinforced concrete frame building were performed at the E-Defense facility (Miki City, Japan) as part of the Tokyo Metropolitan Resilience Project. Building data were collected before and after each shake-table experiment, using light detection and ranging (lidar) scanning technology. Three-dimensional point clouds were generated and processed to investigate the damage features that can be extracted, which are important for postdisaster structural assessment purposes. To this end, this paper discusses aspects pertaining to lidar data processing and registration, calculation of residual displacements and interstory drifts, and concrete cracking and spalling identification and measurement. Most notably, this paper deals with very large data sets, processed to extract structural response information at both global and local scales. Limited multiscale work has been done in the past, and the different sets of challenges that arise have typically been addressed separately. Evidently, this gap needs to be filled before lidar can be effectively used in the field for structural assessment applications. A series of examples in which lidar data are processed and analyzed to assess specific structural components is illustrated, showing that point cloud data can indeed be processed to obtain measurements of global residual drifts or of the extent of visible damage (e.g., crack width and spalling). Although preliminary in nature, the results presented in this paper indicate that collecting postdisaster data using terrestrial lidar scanners has the potential to contribute improving how buildings are assessed in the aftermath of seismic events.

Diaphragms transfer the forces exerted by lateral loads to vertical elements through an in-plane shear action. Cross-laminated timber (CLT) has garnered considerable interest as a diaphragm material, particularly for midrise nonresidential construction. This article discusses the findings of tests performed on two full-scale $6.1\mathrm{m}(20\mathrm{ft})\times 6.1\mathrm{m}(20\mathrm{ft})$ cantilever CLT diaphragms composed of three-ply CLT panels. The diaphragms were subjected to in-plane shear loads with a cyclic loading protocol. Two different layouts of CLT panels were considered for this study (simple span and two-span continuous panels). The displacement, force, or strain responses of various components of the diaphragms were measured and analyzed. The peak capacity of the diaphragms was governed by the fasteners used and exceeded the LRFD capacity by a factor close to two. Test results showed the primary energy dissipation mechanism for the diaphragms was via the slip of diaphragm components parallel and perpendicular to the direction of load and rotation of CLT panels, nearly all of which could be attributed to fastener deformations. Observation of strain data revealed deep-beam-like behavior of the diaphragms where the resistance to coupled tensile and compressive forces was primarily contributed by the outer portion of the edge panels, with little to no contribution from the inside panels. In the compression zone, a near-uniform compressive strain pattern was observed at the top and bottom ply, aligned along the major axis of the CLT panels. In the tension zone, the tensile strain was observed only in the top ply aligned along the major axis (where tension straps were installed), and compressive strain was observed in the bottom ply. The results of the strain data were used to suggest a design procedure for the tension and compression chords.

This study was part of a larger project investigating the feasibility of using ponderosa pine (Pinus ponderosa, PP) harvested from forest restoration programs in the Northwestern United States for low-rise modular buildings. The panels have a standard width of 1.2 m to consider dimensions available from local manufacturers. To use these panels as walls or floors, they must be joined using in-plane connections. The stiffness and capacity of these connection systems under reversal lateral loading affect the behavior of the multipanel wall systems. Such multipanel systems are proposed for use in modular construction, with the goal of finding suitable market outlets for PP cross-laminated timber (CLT). In-plane connections within the multipanel system here play the role of the intramodular connection, while intermodular connections connect different multipanel systems to form a structure. Butt joints with 45° screws and a bolted point-type connection system were selected as intramodular and intermodular connections, respectively, due to their suitability for prefabrication and ease of installation. The aim of the study was to determine the mechanical characteristics of these two types of connections in PP CLT. Ten intramodular connections under monotonic and cyclic loading in shear and tension, and 12 intermodular connections in monotonic and cyclic in two different configurations were tested. The resulting force-displacement curves were used to extract the mechanical characteristics of the connections, which were then compared to the performance of the same type of connections in CLT panels made from other wood species. The intramodular connection showed high ductility in shear and low to medium ductility in tension, while the intermodular connection had lower initial stiffness compared to tests of commercial CLT in all tested directions except compression.

The Pearl River Delta of China, which is considerably affected by typhoons, has many super high-rise buildings. Based on data recorded by the authors and other scholars over the last 10 years, the wind-induced responses and modal parameters of super-tall buildings in this area during typhoons are summarized and investigated in this study. Furthermore, wind tunnel experiments were conducted involving a typical super high-rise building to explore its wind resistance performance, and the test results were compared with measurement results. The results indicate that the building response was positively correlated with the typhoon strength and building height overall, but lower rectangular buildings without aerodynamic optimization measures could experience more noticeable vibrations. The dominant wind direction in the Pearl River Delta is the east and adjacent directions, and the maximum building vibrations mainly occur along the north–south direction, that is, cross-wind vibrations. The fundamental sway frequency measurement results of the buildings are generally greater than the finite-element modeling (FEM) results, and the fundamental frequency is positively correlated with the reciprocal of the building height. A stratification phenomenon is observed according to the variation in frequency with acceleration, and the damping ratios in the low-acceleration range are scattered, whereas both the fundamental sway frequencies and damping ratios exhibit obvious regularity over time and are correlated with the wind speed. The wind tunnel test results are suitably consistent with full-scale measurements. The narrow side of super-tall buildings with rectangular or quasirectangular plane configurations in the Pearl River Delta should be prevented from facing the east and adjacent directions.

T-shaped reinforced concrete (T-RC) beams are widely used in high-rise buildings due to their advantages of reduced concrete usage, low sectional stress, and decreased weight of the structure. However, the calculation method of residual flexural stiffness of T-RC beams has limited existing research. To address this knowledge gap, a comprehensive experimental investigation was conducted, comprising fire tests, dynamic tests, and static load tests on 10 T-RC beams. The aim was to analyze the effects of fire time and load ratio on the residual flexural stiffness of composite beams. The experimental results showed that the residual flexural stiffness of T-RC beams decreased with increasing fire time and load ratio. However, the impact of fire time was more significant than the load ratio. A refined finite element model of T-RC beams under high temperature and after high temperature was established by modifying the frequency data of the dynamic test and considering the impact of cracks. The model accurately predicted the temperature field and deflection change of T-RC beams under fire. Furthermore, a method for calculating the residual flexural stiffness of T-RC beams considering the effect of fire was proposed and validated against the measured values. The proposed method demonstrated a low error rate of less than 10%.

In this study, a stochastic tropical cyclone (TC) intensity model based on a deterministic fast physics-based TC intensity model is developed for potential applications in the TC hazard assessment. To account for the effect of randomness, an error term is introduced to the ordinary differential equation for the TC intensity. The error term is assumed to be the summation of a mean part and a white noise. The geographically weighted summary statistics method is adopted to estimate the geographically varying mean and white noise intensity of the error term using the 1,010 historical tropical cyclone records from the western North Pacific. The effects of the mean and random parts of the error term on the model’s performance are investigated in terms of the individual samples and the probabilistic characteristics of TC intensity evolution. The results show that, by introducing the error term, the difference of the 25-, 50-, and 100-year recurrence interval values between the model and observation can be largely reduced from the level of 10% to less than 4%, validating the adequacy of the proposed model in the TC hazard assessment.

A limited amount of data exists on the cyclic behavior of concrete-filled steel deck diaphragms, and the few historical testing programs that have been conducted used specimens that may not be representative of modern floor assemblies typical in North America. As part of a larger research project, the Steel Diaphragm Innovation Initiative, an experimental program was conducted to fill critical knowledge gaps related to the behavior and design of concrete-filled steel deck diaphragms leading to a better understanding of the seismic performance of steel buildings utilizing these types of diaphragms. The experimental program included eight diaphragm specimens that were approximately 4 m by 5 m, tested in a cantilever test setup wherein one edge is restrained against translation while the opposing edge is subjected to an in-plane cyclic displacement history. Parameters that were varied included deck height (51 mm and 76 mm), concrete cover over the deck (51 mm to 115 mm), concrete type (normal weight and lightweight), configuration of perimeter headed shear studs, and the presence and amount of reinforcing steel. Specimen behavior was quantified including initial stiffness, peak shear strength, ductility, and energy dissipation and qualitatively connected to observed cracking and deformations. The results of this experimental program, combined with tests from the literature were used to develop proposed expressions for peak shear strength and initial stiffness. The proposed expressions reasonably capture the experimental results and are suitable for design.

When designing steel members with nonsymmetric cross sections, it is essential to consider twisting effects when performing stability checks via second-order analysis according to the ANSI/AISC 360-22. Existing line-element formulations for nonsymmetric sections are mostly derived based on thin-walled assumptions, leading to an overestimation of member strength due to the inaccurate prediction of member behavior, especially when the cross sections have moderate wall thickness. This paper proposes an efficient line-element method for second-order analysis of steel members with nonsymmetric thick-walled sections considering the warping degree of freedom (DOF) and the twisting effects along with the transverse shear deformations. Additionally, a two-dimensional (2D) finite-element cross section analysis method employing the constant strain triangle (CST) element is developed to calculate the section properties for arbitrary cross sections, including the Wagner and the shear coefficients. The proposed method is implemented in the educational structural analysis software MASTAN2 and verified through two sets of examples.

The design axial resistance for circular hollow section (CHS) XX joints is typically calculated as the product of the CHS X joint resistance and a multiplanar factor. A simple function has been used as the multiplanar factor, which is independent of the joint geometry parameters. In this study, it is first shown that the geometry-independent multiplanar factor does not properly reflect the true behavior of CHS XX joints, resulting in an overly conservative design for joints with large braces. Therefore, an analytical ring model is developed that more accurately captures the effect of the two important nondimensional geometric parameters, namely the brace-to-chord diameter ratio ($\beta$) and chord diameter-to-thickness ratio ($2\gamma$). Subsequently, extensive test-validated numerical parametric analyses are performed, including a wide range of geometric and loading parameters, to propose an improved design resistance based on the developed analytical ring model. The formulated design resistance showed a better accuracy compared to the current code design resistance.

One of the obstacles to the recent trend toward taller timber buildings is the limited load-carrying capacity of softwood columns. With the aim of promoting the structural use of European beechwood (Fagus sylvatica L.) in high-performance applications, the buckling behavior of beech glued-laminated timber (GLT) columns reinforced with glued-in steel bars was investigated experimentally and numerically. Axial compression experiments were carried out on full-scale stocky and slender columns, and a finite-element model was developed and validated against the experimental data. The influence of geometric and material parameters on the load-carrying capacity of the steel-reinforced beech GLT columns was studied in parametric analyses. The experimental and numerical data demonstrate the high potential of this new structural product for high-strength columns in demanding residential, office, and industrial applications. The load-carrying capacity mainly depends on the cross section size, the column slenderness, the position and diameter of the reinforcement bars, and the initial deformed shape of the column. An eccentric layout with steel bars in the corners of the cross section is very effective in increasing the load-carrying capacity. Four corner steel bars of 20 mm diameter, 50 mm edge distance, and grade ST900/1100 were found to increase the load-carrying capacity of a 200-mm-wide square GL48h column by almost 40% across the slenderness ratios relevant to structural applications. The glued-in steel reinforcement is also expected to be able to provide an alternative load path for structural robustness, by enabling the columns to carry tensile forces. A design method for corner-reinforced beech GLT columns under axial compression was developed based on the empirical and numerical data.

While the use of cross-laminated timber (CLT) panels for building construction has increased over the last several decades, current standards and existing literature provide limited information regarding the design of CLT diaphragms or the prediction of their deflections when subjected to wind and strong earthquake motions. This paper presents the design and assessment of a CLT diaphragm that was part of a full-scale two-story structure subjected to shake-table testing. An analytical model is proposed for diaphragm deflection accounting for in-plane shear and bending stiffness, as well as the stiffness of various connections. Moreover, a refined numerical modeling strategy is proposed in order to consider phenomena such as panel-to-panel gap closure. Results indicate that the analytical model yields conservative results both in terms of deflections and forces when compared to the numerical model that simulates similar sources of strength and stiffness. The analytical model is suitable for the design of symmetric diaphragms with regular shapes, whereas the numerical model can also be used to model asymmetric diaphragms with irregular shapes.

Low-rise brick masonry buildings are considered the most vulnerable type of structures when they are subjected to seismic excitation. Base isolation is considered a widely adopted strategy to enhance the seismic performance of low-rise brick masonry buildings. Previously developed sliding-based isolation systems did not specifically determine the most adequate combination of isolation layer thickness and the recentering mechanism that will result in the best isolation performance. Accordingly, this study investigates the identification of the best-performing configuration of the previously developed base isolation system through extensive numerical studies and experimental verification. The critical parameters considered in this research are the suitable thickness of the isolation layer and the spacing of the recentering rebars. A finite element analysis was conducted on a $1:3$ reduced scale unconfined brick masonry wall model. The first set of models was having a constant isolation layer thickness of 63.5 mm and four different values of recentering rebars spacings (i.e., 152.4, 203.2, 254, and 304.8 mm). The second set of numerical models consists of varying isolation layer thicknesses such as 50, 63.5, and 76 mm, and a constant recentering rebars spacing of 152.4 mm. It was concluded that the suitable value of isolation layer thickness is 63.5 mm with recentering rebars located at a distance of 152.4 mm because it gives the maximum amount of seismic energy dissipation. Later on, the isolator was experimentally verified using a reduced scale unconfined brick masonry wall subjected to displacement controlled cyclic loading tests. Finally, a case study was conducted to verify the performance of the proposed isolator in a full-scale school building.

In the presence of softening section constitutive relations, classical beam theories predict erroneous strain singularities, and the corresponding force/flexibility-based (FB) beam-column element formulations result in strain localization and loss of response objectivity, i.e., divergence, rather than convergence, with progressive mesh refinements. To address this challenge, various FB element formulations have been proposed in the literature. One of these formulations is the so-called “gradient inelastic” (GI) FB formulation, which is a two-node element formulation that eliminates the strain localization and achieves response objectivity through strain gradient nonlocality relations. Although a single two-node GI element can effectively simulate an entire beam or column, simulating such a member via multiple two-node GI elements in series (e.g., to apply intermediate point loads, to more accurately capture geometric nonlinearities, or to represent cross-section variation) would not lead to accurate response predictions. This is because, in a model with multiple two-node GI elements in series, the nonlocality relations are not enforced at the intermediate/connection nodes between adjacent elements. Instead, end member boundary conditions (BCs) are enforced at those connection nodes because the two-node GI formulation has been designed to simulate an entire member. To tackle this shortcoming, this paper proposes an innovative multinode GI FB element formulation. To enforce the nonlocality relations at the connection nodes, two different sets of mathematically admissible section strain compatibility conditions (CCs) are adopted. The multinode formulations using both sets of CCs are evaluated through several simulation examples, including beams and columns subjected to various loads. The evaluations demonstrate the ability of both element formulations to produce objective softening responses, while one set of CCs is found to more closely predict the responses of previously tested RC beams under midspan loading.

Modeling disaster consequences and postdisaster recovery is a key enabler of holistic community disaster resilience planning and implementation. An important step toward the application of such models in practice consists in ensuring that model parameters can be reliably estimated, building trust in model outputs, as well as reducing output uncertainty. This study aims to tackle these issues first by constructing a regional housing recovery model and validating its results for a real event, the 2010 Kraljevo, Serbia earthquake, and second, by presenting how regional recovery models can be updated following a disaster using early-arriving damage inspection data to reduce output uncertainty. The model outputs are updated postevent using 600 building damage assessment reports, reducing the uncertainty in recovery time predictions. The results confirm the practical applicability of the proposed regional recovery model and postevent updating, while identifying its main shortcomings, such as the lack of consideration for the weather conditions affecting the recovery process and the need for better methods to estimate the community’s ability to mobilize its recovery resources.