Journal of Structural Engineering

Cross-laminated timber (CLT) panels, when used as shear walls or diaphragms, are commonly connected with multiple ($n$) dowel-type fasteners in a row. For such connections, it is frequently observed that the load-carrying capacity of multiple fasteners is less than the sum of the individual fastener capacities, a phenomenon referred to as the group effect. The research presented in this paper investigated the group effect in self-tapping screw (STS) shear connections between CLT panels. Different joint types (surface splines with STS in shear, and half-lap and butt joints with STS in either shear or withdrawal) were evaluated in a total of 175 quasi-static monotonic and reversed cyclic tests, with the number of STS in one row varied between 2 and 32. The results showed that the group effect for the joint capacity (strength) can be expressed as $n_{\mathrm{eff}}=0.9n$ for all joints under static loading, where $n_{\mathrm{eff}}$ is the effective number of fasteners. In case of cyclic loading, a more pronounced group effect was observed that can be expressed as $n_{\mathrm{eff}}=n^{0.9}$. These reductions are significantly less conservative than the current Canadian design provisions for lag screws. For the reduction in stiffness and ductility, $n_{\mathrm{eff}}=n^{0.8}$ and $n_{\mathrm{eff}}=n^{0.9}$ can be used for all joints under static and cyclic loading, respectively. Finally, the capacity, ductility, and stiffness for joints under cyclic loading where the STS acted in withdrawal were on average 10% lower compared with the static values.

A review of the literature shows that current research on corrosion-affected reinforced concrete structures focuses more on strength deterioration than on serviceability deterioration. For corrosion-induced concrete cracking, little research has been based on fracture mechanics criteria and stochastic processes. In this paper, a new methodology is proposed for predicting the time to corrosion-induced concrete cracking based on fracture mechanics criteria. A stochastic model with a nonstationary lognormal process was developed for corrosion-induced concrete cracking, and the first-passage probability method was employed to predict the time-dependent probability of its occurrence. The merit of using a nonstationary lognormal process for corrosion-induced concrete cracking is that it eliminates unrealistic negative values of the normal distribution for inherently positive values of physical parameters. It was found that the diameter of reinforcing steel $D$, corrosion rate $i_{\mathrm{corr}}$, and effective modulus of elasticity $E_{ef}$ have the most influence on the probability of corrosion-induced concrete cracking. The methodology presented in the paper can serve as a tool for structural engineers and asset managers in making decisions with regard to the serviceability of corrosion-affected concrete structures.

One important application of fiber-reinforced polymer (FRP) composites is providing confinement for concrete columns. Utilization of prestressed FRP sheets can relieve stress hysteresis through active confinement. And most investigations focus on small size concrete columns, but it is unclear whether the models that developed from small-scale cylinders are appropriate for large-scale columns due to the size effect. This paper evaluated the axial compressive behavior of large-scale circular concrete columns confined by lateral prestressed carbon fiber-reinforced polymer (CFRP) strips. A total of 10 large-scale columns were tested, and the size of the specimen was 800 mm in diameter and 2,500 mm high. These specimens included one unconfined column, seven columns actively confined by prestressed CFRP strips, and two columns passively confined by externally bonded CFRP strips. Including different strengthening methods, the influences of various prestress levels and different strip spacing were considered in this experiment. The test results indicated that, considering reinforcement effectiveness, axial load-bearing capacity and ductility of large-scale columns confined with prestressed CFRP strips were improved significantly. A polynomial stress-strain model is proposed based on the experimental results, and this model could be used to estimate the axial compressive behavior of large-scale concrete columns confined by prestressed CFRP strips.

This paper presents a proposal for the codification of an efficient design approach based on the direct strength method (DSM) for cold-formed steel equal-leg angle columns with short-to-intermediate lengths, i.e., those buckling in flexural-torsional modes. Initially, the available experimental failure load data consisting of fixed-ended and pin-ended (cylindrical hinges) columns with several geometries (cross-section dimensions and lengths) and tested by various researchers are collected. These are used to show that the currently codified DSM design provisions are not able to handle adequately short-to-intermediate angle columns and that a specific DSM-based design approach is needed to estimate the failure loads of such columns. Then, the paper presents a brief overview of the structural reasoning behind the proposed DSM-based design approach. Next, the quality (accuracy and reliability) of the failure load estimates obtained with this design approach is assessed through the comparison with the aforementioned experimental failure load data and also a fairly large number of numerical failure loads previously obtained by the authors. This merit assessment includes the determination of the load-resistance factor design (LRFD) resistance factors concerning the failure-to-predicted load ratios. It is shown that the value recommended for compression members by the North American specification, ${\varphi }_c=0.85$, can also be adopted for short-to-intermediate angle columns designed with this DSM-based approach. Finally, the paper presents and discusses a few numerical examples that illustrate the application of the proposed design approach and provide evidence of its user-friendliness and advantages/benefits when compared with the currently codified one.

The traditional Assam-type wooden house is one of the very few housing systems in India that has performed exceptionally well during past earthquakes. Due to the high seismicity of the northeastern region of India, local people have developed a unique earthquake resistant housing typology using locally available materials. The houses have a number of features, such as the light mass of the walls and roof, good wall-to-wall connection, and flexible joints that contribute to their earthquake safety. In spite of these exceptionally good features, these houses have not received due attention and their behavior has not been studied so far. In this study, full-scale frames of a single-story Assam-type house were tested under slow cyclic and monotonic lateral loads. Results showed excellent behavior in terms of lateral drift and ductility capacity without any significant drop in lateral load capacity even under large lateral drift. Failure was primarily due to the separation of secondary stud members at connections and flexural failure of vertical posts at a very high lateral drift levels during monotonic loading. However, the connections of the main posts with the foundation and with the top beam remained intact during the tests. Simplified analytical models were developed for lateral load analysis of the Assam-type housing frames and their lateral load behavior was validated with the experimental results. Finally, a simple empirical equation was developed for estimation of lateral load capacity of such frames from regression analysis of the experimental data.

Reinforced masonry shear walls with boundary elements have been introduced recently as a seismic force–resisting system as alternative to traditional reinforced masonry shear walls with rectangular cross sections. The introduction of the boundary elements enhances the wall’s in-plane performance because of the confinement action of the horizontal steel ties within the boundary elements that increase the compressive strain capacity and thus improve the overall wall displacement ductility. However, the performance of such reinforced masonry shear wall system has not yet been well investigated experimentally or analytically under out-of-plane loading (e.g., blast loads). Therefore, this study evaluated the contribution of boundary elements to the wall out-of-plane performance in terms of enhanced ultimate resistance load and displacement capacities. Three reinforced masonry shear walls with boundary elements, with different reinforcement ratios and distributions, were tested under quasi-static loading to evaluate the wall displacement response, mode of failure, damage state, ductility capacity, and energy absorption. Furthermore, a numerical model was developed and used to generate additional results of walls with similar in-plane or out-of-plane load resistance to those tested experimentally, but with rectangular cross sections, to allow for a performance comparison. The results showed that reinforced masonry shear walls with boundary elements achieved higher ductility capacity and energy absorption levels compared to their counterparts with rectangular cross sections. This study presents key experimental and numerical data that will facilitate quantifying several aspects pertaining to the out-of-plane performance of reinforced masonry shear walls with boundary elements within the next editions of relevant North American codes and standards.

A KK-type tube–gusset plate joint is a typical joint configuration used widely in the tubular structures of transmission towers. The mechanical characteristics of KK-joints, compared with K-joints, are more complex owing to the multiplanar effects in the actual structure. Based on material experiments and tubular K-joint ultimate load capacity experiments of Q690 high-strength steel, a parameter analysis is conducted on KK-type tube–gusset plate connections. Additionally, geometric parameters, axial load of the chord, and other factors that influence the ultimate bearing capacity of multiplanar KK-joints are studied in detail. The analysis indicates that the axial compression load of the chord, chord wall thickness, chord diameter, and loading ratio of the bracing members significantly affect the ultimate load capacity of KK-joints. According to the experimental and finite-element (FE) analysis results, a formula is developed to predict the ultimate load capacity of KK-joints using the virtual work principle.

Existing experimental results show that carefully designed RC column-to-steel beam (RCS) joints have high seismic resistance comparable to those of traditional steel or RC frames with seismic details. However, such high seismic performance requires complicated and expensive strengthening details, which causes difficulties in fabrication and construction. This study investigated simpler strengthening methods, targeting moderate seismic capacity. Four interior RCS joint specimens were tested under cyclic lateral loading. The major test parameters were the strengthening details of the beam–column joint such as face bearing plates, transverse beams, and headed studs. The test specimens with the proposed methods exhibited good deformation capacity exceeding 4.0% story drift ratio after yielding of the beams and beam–column connection. However, the peak load did not reach the nominal strength based on the beam plastic moment due to early joint damage. The failure modes and test strengths were compared with the predictions of ASCE design guidelines. On the basis of the results, design recommendations for the simplified connection details were proposed.

A demountable shear connector for use in composite floors with precast hollow-core slab units is proposed. The proposed shear connector consists of a steel square hollow tube welded on a steel plate that is bolted on the steel section’s top flange using four high-strength bolts. Concrete is cast only around the connector, allowing for an easy separation of the precast slab units from the steel sections during the deconstruction phase, with operations required only from the top of the composite floor. The shape of the hollow tube promotes a ductile elastic-plastic behavior under the longitudinal shear flow in a composite beam. Ten push tests using a horizontal testing arrangement were carried out to assess the structural performance of the novel shear connector. The experimental results show that the shear connector has a stiffness comparable to that of a welded shear stud, strength that can be adjusted to achieve the desired degree of shear connection in a composite beam, and slip capacity that is much higher than the requirements of the current codes of practice. A finite-element model was also calibrated against the tests and found capable of accurately reproducing the experimental behavior. The finite-element model was then used to conduct a number of parametric studies to safely generalize the experimental results. Based on the experimental and numerical results, a design model is proposed to predict the strength of the demountable shear connector based on either the yielding of the steel tube or the failure of the precast slab.

The slenderness ratio is one of the main influencing factors for columns. It is interesting to study how this factor influences the mechanical properties of parallel bamboo strand lumber (PBSL) columns. Based on this background, 27 column tests have been carried out and analyzed. Bending failure always occurred for the test specimens regardless of their length, even though two failure models can be classified by crack layers based on the test results for the PBSL columns. The strain values are more scattered for the short specimens. The ultimate strain values for two directions for compression surfaces are always the biggest ones among the four surfaces. Three stages can be identified for the failure process irrespective of column length. The paper proposes equations representing the relationship between the slenderness ratio and mechanical property parameters based on the test results.

The risk of large-amplitude vibrations of bridge hangers due to galloping instabilities has posed a challenge to the engineering and research communities. Galloping vibrations can lead to serviceability problems and reduce fatigue life. A number of aeroelastic models have been developed to predict the unstable behavior and to design counteracting measures, i.e., shape modifications and structural damping addition. All the proposed procedures generally consider that the parameters are assigned according to deterministic values. A framework is proposed for the deterministic and probabilistic assessment of the minimum structural damping required to prevent galloping of bridge hangers based on the output of a two-degree-of-freedom sectional quasi-steady aeroelastic model. All the variables required to define the hanger dynamics, the sheath aerodynamics, and the local wind climate are considered. Because of the large uncertainties and of the nonlinear nature of the problem, the distribution of the minimum structural damping required to prevent galloping is obtained by Monte Carlo simulations. An application of the method to the proposed Messina Straits crossing bridge is presented. Starting from wind tunnel measurements of the aerodynamic coefficients of a real plain high-density polyethylene (HDPE) cable sheath, the random nature of the aerodynamics is shown, which is ascribed to the cable irregularities (surface roughness, section distortion, and axis curvature). Then the statistical variation of the parameters of the model is considered, based on real data derived from wind tunnel tests and from the wind climate measured at the site. The distributions of the parameters defining the hanger dynamics are assigned according to typical values. Using a normal and a log-normal model of capacity, the probability of failure is calculated. The results are discussed and compared with conventional approaches based on the definition of the deterministic variables. Finally, using a deterministic model of capacity, a simplified closed-form equation for the evaluation of the structural damping needed to prevent galloping in a probabilistic-based performance approach is proposed.

The paper summarizes experiments conducted at the University of Sydney on bolted moment end-plate connections. The overall context of this work was to obtain full-range moment-rotation curves of the connections which can be used to validate analytical and numerical models. The full-range moment-rotation curve covers not only the elastic and inelastic ranges but also the postultimate and postfracture ranges. Thirteen specimens were tested, with failure modes being either end-plate bending failure or column web buckling failure. Results of all experiments are provided in detail, including the full-range moment-rotation curves, observations of the two failure modes and deformations of individual joint components. The ultimate resistance measurements of the bending tests were compared with those predicted by the relevant standards.

Auxiliary batteries and battery rack systems are widely used as a risk mitigation strategy in several critical facilities to supply power following loss of external power from the grid. Although these systems might fail during earthquakes, causing cascading catastrophic economic and life losses, they have received little attention in terms of investigating their seismic performance. However, after recent extreme events (e.g., the Fukushima nuclear disaster), such risk mitigation systems have been attracting more attention to ensure their functionality during extreme events. This paper investigates the seismic performance and modes of failure of battery rack systems that are currently used in several critical facilities. Shake table tests were performed at different ground motion levels, following the recommendations of the FEMA 461 guidelines. The results demonstrated that the design guidelines and fragility curves currently assigned to battery rack systems in the FEMA P-58 prestandards do not encompass all possible failure mechanisms. This paper not only enlarges the experimental database of the seismic performance of battery rack systems, but also facilitates the adoption of these systems within the next generation of performance-based seismic design standards.

This paper presents experimental and numerical investigations of cold-formed high-strength steel (CFHSS) tubular structural members under combined bending and bearing. A test program that contained 33 experiments was undertaken on square hollow sections (SHSs) and rectangular hollow sections (RHSs) with nominal yield strengths up to 900 MPa. The combined bending and bearing experiments were performed under the interior-one-flange bearing load case as per the North American Specification (NAS). Finite-element models were built and validated with the experiments; a parametric study was undertaken upon validation. The experimentally and numerically obtained results were compared with nominal resistances as per the NAS and European Code (EC3) to examine their applicability to CFHSS SHS/RHS members under combined bending and bearing. Overall, the comparisons reveal that the NAS provisions were generally conservative whereas the EC3 provisions were overly conservative. It is shown that the codified bending and bearing interaction formulas can be used for CFHSS SHS/RHS members, while more accurate predictions can be achieved using recently proposed bearing design rules.

In this paper a recently developed multimode pushover procedure is evaluated for nonregular in elevation systems. The procedure is applicable to asymmetric in plan buildings under the concurrent action of two horizontal seismic components, and its main advantage is that it does not require independent analysis in two orthogonal directions. Thus, the use of simplified directional combination formulas, which is not valid in the nonlinear range, is avoided. A preliminary evaluation of the proposed methodology led to quite satisfactory results. However, studies conducted to date are limited to regular buildings. Hence, in this study the procedure is applied to four asymmetric in plan and non-regular in elevation reinforced concrete buildings. The values of selected response quantities are compared to those resulting from a conventional pushover analysis variant and from nonlinear dynamic analysis. The whole evaluation study leads to useful conclusions.