Journal of Structural Engineering

This paper presents numerical and experimental investigations of the in-plane strength and design of pin-ended circular arches having a sinusoidal corrugated web under combined in-plane loads. Finite-element models are developed that account for the effects of the corrugated web, initial geometric global and local imperfections of the arch and its web and flanges, residual stresses, the included angle and curvature of the arch, and different combined load cases. These are validated by test results and used together with the experiments to investigate the failure modes and strengths of such arches. It is found that an I-section arch with a corrugated web may fail in a global mode or in a web shear buckling mode. There are two types of global failure modes for arches under combined loads. In most cases, corrugated arches may fail in an elastoplastic buckling mode. However, when wind load plays an important role in the combined loads, corrugated arches may fail in a plastic yielding mode. An interaction design equation is proposed for predicting the global in-plane strength of steel arches with a sinusoidal corrugated web under combined axial and bending actions. The design equation provides lower bound predictions for the strengths of corrugated arches. General procedures are also proposed for the practical strength design of steel I-section arches with a sinusoidal corrugated web.

New high-strength structural steel, named H-SA700, is utilized to achieve a structural system that enables continuous use after very large earthquakes. Columns are built up of H-SA700 plates using bolts only, and bolted connections are adopted extensively for easier replacement or reuse of structural components. An analytical study is performed to predict three distinctive local buckling modes of the column and estimate its elastic flexural stiffness, yield strength, and maximum strength subjected to combined flexure and compression. Cyclic loading behavior of the column is examined through five half-scale specimens, which vary with axial force, bolt pitch, and loading direction (about major or minor axis). The columns achieve a very large elastic rotation, approximately 0.02 rad at the axial force ratio of 0.2, and a maximum bending strength surpassing the plastic moment of the reduced section accounting for bolt holes without fracture. The proposed equations predict the local buckling modes well and present a reasonably conservative estimation on the column strength subjected to combined flexure and compression.

Impact dampers have been considered as energy dissipating mechanisms for many years, and many types have been introduced. The latest member of the impact damper family is called the linear particle chain (LPC) impact damper, which is considered as an extension to the commonly known single unit and multi-unit impact dampers. It consists of a linear arrangement of two sizes of freely moving masses, constrained by two stops, and located on a primary system to be controlled. In this work, the results of an experimental study of the performance of the LPC impact damper are presented. The first prototype of the LPC impact damper is designed, fabricated, and experimentally tested. The experiments are conducted to examine the efficiency of the LPC impact damper in damping the free vibrations of a simple structure. The damping performance of the LPC impact damper is compared with those of a single unit and multi-unit impact dampers. The experimental results clearly show the significant effect of the LPC impact damper in attenuating the structure’s vibration. The investigations indicate that the damping performance of the LPC impact damper depends on the mass ratio of the impacting masses, the damper clearance, and the damper chain length.

This paper investigates variability in bobbing and jumping actions, including variations within a population of eight test subjects (intersubject variability) and variability on a cycle-by-cycle basis for each individual (intrasubject variability). A motion-capture system and a force plate were employed to characterize the peak ground reaction force, frequency of the activity, range of body movement, and dynamic loading factors for at least first three harmonics. In addition, contact ratios were also measured for jumping activity. It is confirmed that most parameters are frequency dependent and vary significantly between individuals. Moreover, the study provides a rare insight into intrasubject variations, revealing that it is more difficult to perform bobbing in a consistent way. The paper demonstrates that the vibration response of a structure is sensitive to cycle-by-cycle variations in the forcing parameters, with highest sensitivity to variations in the activity frequency. In addition, this paper investigates whether accurate monitoring of the ground reaction force is possible by recording the kinematics of a single point on the human body. It is concluded that monitoring the C7th vertebrae at the base of the neck is appropriate for recording frequency content of up to 4 Hz for bobbing and 5 Hz for jumping. The results from this study are expected to contribute to the development of stochastic models of human actions on assembly structures. The proposed simplified measurements of the forcing function have potential to be used for monitoring groups and crowds of people on structures that host sports and music events and characterizing human-structure and human-human interaction effects.

Structural health monitoring (SHM) relies on data acquired from sensorial systems installed on site, and is nowadays being used more often not only for asset management, but also in critical structures when there is the need to detect damage in an early stage, before it impairs structural performance and safety. Early detection of damage in critical structures relies on the acquisition of continuous streams of information and on reliable techniques capable of analyzing it in real time, without generating false alerts. In this context, the combination of data fusion strategies, capable of converting large amounts of data into small pieces of information, with pattern recognition algorithms, which are able to analyze this information in real time, is addressed in the present paper with the objective of developing an original strategy capable of (1) removing the effects of regular actions imposed to structures without the need to measure them and of (2) compressing entire SHM data sets of arbitrary dimensions into a sensitive single-valued damage index. These capabilities are achieved by combining principal component analysis, the broke-stick rule, clustering methods, symbolic data objects, and symbolic distances. The proposed strategy was tested and validated with a numerical model of a cable-stayed bridge, using experimental data as input. From this analysis it was observed that, under the noise levels measured on site, the proposed strategy is able to automatically detect damage as small as 1% of stiffness reduction in a single stay cable. This sensitivity evidenced by the proposed strategy can be considered particularly high because it was obtained from a small amount of inexpensive sensors with a static character and because it was associated with a false detection incidence of only 0.1%.

The cyclic behavior of six full-scale reinforced concrete (RC) beams with a deficient lap splice strengthened with ultra-high-performance fiber-reinforced concrete (UHPFRC) is experimentally investigated. The experimental program is based on the findings of previous test series carried out in the same research program that demonstrated the ability of UHPFRC to eliminate bond failure in deficient lap splices of beams and wall-type bridge columns. The objective of this experimental work is to determine the efficiency of this strengthening technique on wide flexural elements (beams, slabs, walls, or wall columns) subjected to reverse cyclic loading. Specimen reinforcement consists of two pairs of deformed bars spliced at midspan on both tension and compression faces. The strengthening technique consists of replacing normal concrete around lapped bars in the splice region by UHPFRC, which allows for keeping the original member geometry. One type of fiber, three fiber contents, two bar diameters, and two bar arrangements are considered. For isolating the UHPFRC contribution, the splice regions are free of any confinement. The beam specimens are tested at four points, bending with a constant-moment region along the splice length. The result indicates that UHPFRC with a fiber content of 2 or 3% can significantly increase the bond strength of splice bars without confinement. The levels of ductility reached for the highest fiber content meet the requirements for high ductility demand, such as in seismic design. The results demonstrate that an appropriate casting method combined with a self-compacting UHPFRC with an appropriate fiber content ensure the efficiency of the strengthening technique for providing for the continuity of lapped bars and for enabling a high ductility capacity under monotonic or cyclic loading. The results also confirm the applicability of the method for strengthening lap-spliced regions of wide elements—such as slabs, shear walls, and wall-bridge piers—without having to provide any confinement.

Short columns in buildings are generally the members with high stiffness and governed by brittle shear failure. Therefore, lateral load displacement curves for short columns have significant influence on the seismic assessment. In this study, a trilinear relationship is proposed to simulate the seismic behavior of short columns failed in shear with the height-to-depth ratio of less than 2. The turning points of the proposed curve are defined as shear cracking, shear strength and collapse point, and straight lines connecting these points. Shear cracking is an apparent turning point in stiffness from shear cracking of concrete to reaching the shear strength of the short column. As cracks propagate, concrete struts are formed in the cracks and the crushing strength of the struts is subsequently reached. The proposed trilinear relationship of short columns is based on these observations from experimental results and can greatly simplify the analytical model. At last, a comparison with experimental results to verify and to check the applicability of the proposed model is reported.

The dynamic analysis of a pneumatic beam structure, termed the Tensairity girder, is experimentally, numerically, and analytically studied. The structural concept of Tensairity relies on the combination of an airbeam with conventional struts, which leads in a light-weight structure of significant load-bearing capacity. By focusing on the analysis of the dynamic response of this structure, the objective of this work is to determine the pressure-dependent modal characteristics of the pneumatic beam and to couple these with the associated material properties. Based on the results of a modal identification procedure, relying on hammer and white noise excitation tests, a finite-element (FE) model is updated to reflect the actual system response. This procedure reveals the membrane’s shear modulus as the material property that more heavily relies upon the pressure level of the Tensairity girder. The experimental and numerical investigations indicate that the dynamic behavior of the beam can be expressed as a superposition of pressure dependent and pressure independent modes. The obtained insight allows for a better exploitation of the Tensairity in a new range of applications involving dynamic loading.

Analyzing the behavior of a masonry structure is a complex issue due to the complicated nature of masonry. Moreover, random spatial variation of masonry properties due to workmanship quality makes the prediction of its behavior even harder. This paper studies the effect of random spatial variability of mortar joint properties on the lateral strength of masonry walls under in-plane loads. Tensile strength of mortar joints is considered a random variable whose variation represents different quality of workmanship. Using a 3D nonlinear FE model, the influence of the random spatial variability of bed joint and head joint properties on the performance of unreinforced masonry walls is investigated. Results show the considerable effect of random spatial variability of bed joint properties on the performance of masonry walls under in-plane loads, while similar variation in head joint properties has a negligible effect on the wall response. The influence of correlation in bed joint properties on the wall strength is evaluated through a parametric analysis. Findings reveal that increasing the correlation of bed joint properties has a harmful effect on the lateral strength of unreinforced masonry walls with fair and poor workmanship quality.

Reinforced concrete or masonry cores commonly exist in multistory light wood frame buildings (LWFBs) as elevator shafts and stairwells. These cores are often not accounted for in structural design as part of the lateral load resisting system in combination with the light wood frame subsystem due to the uncertainty regarding material compatibility. In this paper, the interaction between the wood frame and masonry walls in a hybrid lateral load resisting wall system was investigated using a two-dimensional numerical model. Two two-story hybrid wood-masonry walls as well as individual wall subsystems and connections were tested experimentally under reversed cyclic loading to provide confidence in the ability of the numerical model to predict the lateral load response of the hybrid wall systems. From the experimental results it was noted that the bolted connections first failed when the load was applied to the wood frame in the hybrid system, while masonry walls first failed when the load was applied to the masonry wall. The results show that as displacement increases, the load shared by the wood subsystem was reduced due to progressive softening of wood shear wall specimens. When the load was applied to the wood frame subsystem the connections did contribute to the energy dissipation of the whole hybrid wall system. When the load was applied to the stiffer masonry wall, the energy dissipation by the connections can be ignored.

A number of construction techniques have been proposed to improve the seismic performance of infilled RC frames by increasing the strength and stiffness of the infill and/or the frame. The increase of the seismic capacity of infilled frames with these techniques can improve substantially their seismic performance as long as the demand does not exceed the capacity, but it can eventually lead to brittle failures once the capacity is exceeded. This study assesses numerically a new construction technique that introduces flexibility to the system to ensure its ductile behavior and minimal damage by splitting the infill in subportions and allowing the sliding along the horizontal joints connecting these subportions. A numerical model, validated with data from tests on the components of the proposed structural system and able to capture the interaction between them, has been developed to provide insight into the load-transfer mechanism that develops, and to optimize the proposed detailing. A parametric study investigates the sensitivity of the system to the design parameters, infill’s geometry, and material properties, so that design recommendations can be made.

For improving the seismic resiliency of coupled shear wall systems, a type of replaceable steel coupling beam was developed, which consists of a central “fuse” shear link connecting to steel beam segments at its two ends. Inelastic deformation is concentrated in the shear link during a severe earthquake, and the damaged links can be replaced easily as specialized link-to-beam connections are adopted. This paper presents a series of quasi-static tests conducted to examine the seismic behavior and replaceability of the replaceable coupling beams. A total of four large-scale specimens were designed and tested, where different types of beam-to-link connections were adopted, including end plate, splice plate, bolted web, and adhesive web. All specimens fully developed the shear strength of the fuse links and showed large inelastic rotation capacity of no less than 0.06 rad, except for the specimen with the adhesive web connection, which failed at an early stage. The specimen with the end plate connection had inelastic deformation concentrated in the shear link, showing very stable hysteresis behavior. Slippage of high-strength bolts was observed at the splice plate and bolted web connections, which led to increased deformation and “pinching” in hysteresis loops of coupling beams. Interestingly, at a coupling beam rotation exceeding 0.01 rad, a large axial force developed in the steel coupling beams, the maximum value of which reached approximately a quarter to half of the axial yield strength of the shear link. In addition, on-site replacement of shear links was demonstrated after the coupling beam specimens experienced 0.02-rad rotation. The end plate connection was replaced within the shortest time, whereas the bolted web connection was able to accommodate the largest residual deformation.

The objective of this paper is to study the size effect in eccentrically loaded stocky reinforced concrete (RC) columns from both experimental and numerical perspectives. An experimental campaign was carried out on eccentrically loaded RC columns of full-scale to facilitate a more accurate understanding of the influence of eccentricity on the failure behavior and size effect. A total of 30 geometrically similar RC columns sized from $200\times 200\times 900\mathrm{mm}$ to $800\times 800\times \mathrm{3,600}\mathrm{mm}$ was tested with the eccentricities of $0.1h_0$, $0.25h_0$, $0.4h_0$, $0.6h_0$, and $0.9h_0$ ($h_0$ denotes the effective cross-sectional height). A brittle-ductile transition behavior according to the initial eccentricity was found from the test observations, and a comparison of the present test results and the SEL proposed by Bažant was made. Meanwhile, a mesoscale numerical method for the simulation of failure behavior of RC columns was proposed. Good agreement between the present simulation results and the test observations of the RC columns without transversal reinforcement illustrates the reliability and accuracy of the numerical approach. The verified mesoscale approach was then extended to study the failure behavior of RC columns having transversal reinforcement, and the confinement effect was also discussed.

Cross-laminated timber (CLT) is a relatively new type of massive timber system that has shown to possess excellent mechanical properties and structural behavior in building construction. When post-tensioned with high-strength tendons, CLT panels perform well under cyclic loadings because of two key characteristics: their rocking behavior and self-centering capacity. Although post-tensioned rocking CLT panels can carry heavy gravity loads, resist lateral loads, and self-center after a seismic event, they are heavy and form a pinched hysteresis, thereby limiting energy dissipation. Conversely, conventional light-frame wood shear walls (LiFS) provide a large amount of energy dissipation from fastener slip and, as their name implies, are lightweight, thereby reducing inertial forces during earthquakes. The combination of these different lateral behaviors can help improve the performance of buildings during strong ground shaking, but issues of deformation compatibility exist. This study presents the results of a numerical study to examine the behavior of post-tensioned CLT walls under cyclic loadings. A well-known 10-parameter model was applied to simulate the performance of a CLT-LiFS hybrid system. The post-tensioned CLT wall model was designed on the basis of a modified monolithic beam analogy that was originally developed for precast concrete-jointed ductile connections. Several tests on post-tensioned CLT panels and hybrid walls were implemented at the Large Scale Structural Lab at the University of Alabama to validate the numerical model, and the results showed very good agreement with the numerical model. Finally, incremental dynamic analysis on system level models was compared with conventional light-frame wood system models.

Steady-state solutions represent a significant subset of dynamics of a nonlinear system. Herein, they are concerned for a taut cable damped by a nonlinear damper near one cable end, for the purpose of maximizing cable damping. Periodic vibrations of the cable-damper system are efficiently analyzed using the multiharmonic balance method. Furthermore, a continuation method is employed to predict system responses to a range of excitation frequencies near the cable eigenfrequencies. Control effect is then evaluated and optimized based on the frequency response functions, and optimal damper parameters are determined meanwhile. The proposed procedure is implemented for studying two common structural dampers in cable vibration control, i.e., nonlinear viscous damper and friction damper. In both cases, alternating time/frequency domain strategy is integrated for evaluating the nonlinear force and pertinent stiffness, and analytical formulations are obtained, ensuring that strong nonlinear behavior such as stick-slip motion is captured with affordable computational effort. Thanks to the efficiency of this methodology, extensive parametric studies are possible in determining the optimal damping effect and associated damper parameters for varied damper locations and cable modes. Numerical results confirm that nonlinear damper is advantageous over linear damper in terms of maximum attainable damping because nonlinearity can induce energy transfer from lower modes to more higher modes. This advantage becomes more apparent when the damper is closer to the cable end and targeted to suppress lower-mode cable vibrations because wherein, more higher modes are able to be excited. The damper nonlinearity is also found optimizable for specific damper location and cable mode. Those findings, among others, are of practical significance for cable damper design.

Responses of two-degree-of-freedom sliding base systems subjected to harmonic ground motions were studied. This study continues the previous work on this topic and focuses on explaining the inherent mechanism of the sliding base system and derivation of the theoretical solutions for important responses. Unlike fixed base structures, several resonant frequencies were observed after sliding occurred. These resonances are induced by the changing of the vibration center at the moment when the relative displacement is located farthest from the new vibration center. In general, the maximum pseudo-acceleration decreases as the mass ratio increases. For the sliding-sliding case, the maximum pseudo-acceleration reaches an upper limit, which is independent of the amplitude of the ground acceleration. Explicit expressions were derived for this upper limit. The amplitude of the sliding displacement is a suitable response quantity to represent the extent of sliding. As the ground acceleration increases, the sliding displacement amplitude tends toward the vibration amplitude of the ground displacement.

A physics-based macroscopic global seismic damage model is developed for lattice shell structures excited by strong earthquakes. Global seismic damage is generated from so-called modal damage that is defined as the loss ratio of potential energy stored in structures before and after earthquakes, with the combination rule based on the assumption of in-series independencies among modal damages involved. The minimum number of lower modes required in the combination is determined by the suggested procedures using the maximum nodal displacement as a key response quantity. The issue of modal match arises from the modal shift phenomenon that commonly exists in aseismic lattice shells is solved by the linear modal assurance criteria (LMAC) approach. The case study indicates that the predictions result from the model exhibit a desirable correlation with the maximum nodal displacement time history response and a good tendency in damage evolution as more modes are involved. The global damage curves can comply with a typical six-segment positive S-type damage evolution curve. The model can be regarded as an extension to the final softening model proposed by DiPasquale and Cakmak.

This paper reveals the great potential of using combined superelastic shape memory alloy (SMA) bolts and steel angles for self-centering connections with variable performance targets. Eight full-scale specimens were tested, and the main parameters included SMA bolt prestrain, bolt length, angle thickness, and layout of bolts and angles. The specimens showed desired yielding sequences and deformation modes. The inelastic deformation was accommodated by the SMA bolts and angles with no damage to the column and beam. The specimens also exhibited very good self-centering abilities at 2% drift, beyond which the self-centering abilities were dependent on the considered parameters. A ductility capacity of at least 4% was provided by all the specimens. The maximum equivalent viscous damping ranged between 11 and 15%, indicating moderate energy dissipation. Following the test program, a design framework for such connections was proposed, and a calculation example was provided to further illustrate the proposed design procedures. The design framework was also validated through comparing the design predictions against the test results in terms of residual connection rotation.

Reinforcing bar couplers are used in prefabricated bridge elements and bridge systems for accelerated bridge construction. Grouted splice sleeve connectors are used in bridge substructures because of the enhanced construction tolerances they offer. This paper presents a simplified modeling strategy for seismic assessment of precast bridge columns connected to precast footings using grouted splice sleeve connectors. A computational model was developed and validated using three half-scale bridge subassemblies tested to failure. Cyclic quasi-static loading was applied to two precast subassemblies and one cast-in-place specimen. The connectors were located in the footing, for the first precast alternative, and in the column end for the second precast alternative along with debonding of reinforcing bars in the footing. Force-based beam-column elements with fiber sections were used to construct the computational model based on plastic hinge weighted integration; the model included low-cycle fatigue and bond-slip. The proposed model was validated with the experiments through both local and global response comparisons. The results from the proposed computational model were found to be in good agreement with the experiments.

Most current assessment methods for determining the capacity of perforated unreinforced masonry (URM walls) loaded in-plane are based on the assumption of infinitely rigid spandrel elements. Based on observations of damage following past earthquakes, this assumption has been proven to be invalid for certain perforated wall geometries. The reported study was conducted with the primary aim of investigating global and local response of perforated URM walls, with an emphasis placed on defining the influence of the spandrel geometry on the system level response of perforated URM walls responding in-plane. Pseudostatic cyclic testing of six replicated URM full-scale pier-spandrel substructures was conducted to investigate the variables that control spandrel failure modes and the influence of spandrel failure on the lateral capacity of multistory URM walls. Testing showed that the behavior of the spandrel has a significant effect on the failure mode of the piers and hence the strength, stiffness, and energy-dissipation capacity of the system.

Component-based connection models provide a natural framework for modeling the complex behaviors of connections under extreme loads by capturing both the individual behaviors of the connection components, such as the bolt, shear plate, and beam web, and the complex interactions between those components. Component-based models also provide automatic coupling between the in-plane flexural and axial connection behaviors, a feature that is essential for modeling the behavior of connections under column removal. This paper presents a new component-based model for single-plate shear connections that includes the effects of pretension in the bolts and provides the capability to model standard and slotted holes. The component-based models are exercised under component-level deformations calculated from the connection demands via a practical rigid-body displacement model, so that the results of the presented modeling approach remain hand-calculable. Validation cases are presented for connections subjected to both seismic and column removal loading. These validation cases show that the component-based model is capable of predicting the response of single-plate shear connections for both seismic and column removal loads.

This paper presents a new design methodology for equal-width rectangular hollow section (RHS) X-joints failing by sidewall buckling. In the new approach, a slenderness parameter is defined based on the elastic local buckling stress of the sidewall, idealized as an infinitely long plate under patch loading. A Rayleigh-Ritz approximation is thereby used to obtain a closed-form solution. The proposed design equation is verified against experimental results over a wide range of wall slenderness values obtained from the literature and complemented by a brief experimental program carried out by the authors. It is demonstrated that the new design equation yields excellent results against the experimental data. Finally, a reliability analysis is performed within the framework of both the Eurocode and the AISI standards to ensure that the proposed design equation possesses the required level of safety. The newly proposed equation strongly outperforms the current Comité International pour le Développement et l’Etude de la Construction Tubulaire (CIDECT) design rule for sidewall buckling and also further extends the range of applicability to a wall slenderness ratio of up to 50.

A new composite floor system was developed to reduce floor-to-floor height and to improve structural capacity and fire resistance as compared with existing encased composite floor systems. The proposed system is composed of asymmetric steel beams with web openings, a biaxial hollow concrete slab, and glass fiber-reinforced plastic (GFRP) plates. The shear resistance of the typical composite beams is commonly determined based on the shear strength of the steel web alone. However, for the proposed system, because the steel web has several circular openings, the concrete contribution to the shear resistance should be included in the design equation. In this paper, tests and finite-element analyses were conducted to evaluate the contribution of the shear-resisting components in the proposed system. An asymmetric steel beam with web openings, inner concrete panels, and a biaxial hollow concrete slab within the effective width for shear were considered as shear-resisting components. Each component fully resisted the applied shear force, exceeding the expected value until failure, and the design equation suggested was suitable for predicting the shear strength of the proposed system.

This paper summarizes the results of experimental investigations on steel composite beams with simple connections at elevated temperatures. In the United States, three different types of simple connections are most commonly used in building construction with steel composite beams: (1) double-angle connections; (2) single-angle connections; and (3) shear-tab connections. A testing program was conducted to examine the structural behavior of all three of these connections at elevated temperatures. Each specimen consisted of a steel composite beam attached to a loading frame with simple connections. The specimens were subjected to controlled heating and cooling curves while the loading frames were fire protected and designed to remain in the elastic range. The shear-tab connections showed the largest connection rotation, but they fractured during the cooling phase of the tests. The prying of the angles in the double-angle and single-angle connection during the tests provided ductility to prevent fracture during the cooling phase of the experiments. The double-angle connections demonstrated the least connection rotation and excellent performance during the tests.