Lateral Load Behavior Research Articles

Lateral load behavior of RC buildings exposed to fire: case study

ABSTRACT Fire damaged reinforced concrete buildings are often made usable by performing non-structural and cosmetic repairs. These types of repairs do not guarantee the safety of such buildings under the effect of future lateral loads, such as earthquakes. In this paper, an evaluation of the lateral load response of an RC fire damaged – building in Libya is presented. The building was used as a courtyard for the public and the fire visibly damaged some of its columns and beams. Material tests were conducted in situ and in the laboratory to evaluate the material strength of the building after the fire. Then, lateral load carrying capacity of the building before and after the fire was evaluated. Analysis results show that up to one-hour fire duration the building does not lose a considerable amount of its lateral strength; however, at about two and half hours fire duration, it lost about 30 percent of its lateral load carrying capacity. Lastly, analytically predicted residual strength material properties are in good agreement with material test results.

Numerical investigation of the lateral load behavior of core and coupled rocking walls

During last few decades, the researchers have developed new structural systems which have no or minor damage after being hit by severe events like earthquake. Development of self-centering wall having alternative energy dissipation mechanisms was one of these achievements. A wide variety of rocking wall systems, such as jointed walls, hybrid walls, precast walls with end columns (PreWEC), and PreWEC core wall systems, are proposed and studied. This paper describes an analytical investigation of the lateral load behavior of two new types of hybrid rocking wall systems. Core rocking wall is achieved by merging four single hybrid rocking walls and coupled rocking wall is accomplished by coupling two rocking walls using embedded reinforced concrete beams. The concept of coupling hybrid rocking walls using embedded reinforced coupling beam is emerged from previous coupled conventional shear walls studies. As single rocking wall system, in coupled and core rocking wall, post-tensioning tendons are used as a mean to provide self-centering force, and mild steel bars are used to dissipate energy. The nonlinear behavior of the wall is due to the gap opening at the base joint. Three-dimensional finite element model of each system was developed. The stress distribution, crack propagation, and critical sections of these systems are investigated. The effect of spalling concrete cover in the toe region due to rocking action is explained. In addition, the reduction in stiffness and lateral load resisting capacity of the systems due to cracks is monitored. Finally, the lateral load behavior of single rocking walls is compared to that of core and coupled rocking wall systems.

Nonlinear Numerical Evaluation of Dry Precast Beam Column Connection with Embedded Bolts

Precast dry connected frame systems are faster to construct with less erection efforts. These frame systems are considered non-emulate frame systems. The lateral load behaviour of these connections needs to be evaluated to ensure the desired performance. The performance of these dry connections with embedded bolts proposed was studied by finite elemental analysis. The nonlinear FEM analysis results obtained by considering appropriate elements, and material definition parameters, including failure and interactions, were validated with the experimental results available in the literature. The rigidity of the joints was evaluated using the beamline method. The beamline plot unveils that the joints can be classified as rigid joints. The results reveal that the joints under study have satisfactory stiffness degradation, energy dissipation characteristics, and failure modes like monolithic connection. The numerical procedure developed provide an efficient solution for performance evaluation and seismic design of these precast joints

Earthquake response of GFRP-reinforced concrete squat walls with aspect ratios of 1.14 and 0.68

This paper investigates the effect of aspect ratio (αs) and web reinforcement amount on the behavior of squat concrete walls entirely reinforced with glass fiber-reinforced polymer (GFRP) bars and spirals. Pseudo-static, reversed-cyclic lateral load behavior of six large-scale wall specimens—three with an aspect ratio of 1.14 and three with 0.68, detailed with different amounts of web reinforcement—are compared. The specimens were designed and detailed according to CSA S806-12, CSA A23.3-14, and ACI 318-19, where applicable, which resulted in wall segments with 150 mm thickness, 1400 mm length, and either 1600 mm or 950 mm height (for αs = 1.14 and 0.68, respectively). The results show that: 1) GFRP-reinforced concrete squat walls are able to achieve their peak lateral strength with a stable hysteretic response, characterized by negligible shear pinching and no strength degradation up failure; 2) the relative effectiveness of horizontal and vertical web reinforcements in resisting shear is a function of the wall aspect ratio; 3) increasing the web reinforcement amount (horizontal/vertical) substantially decrease the shear crack widths as well as the shear-induced deformations; 4) the fundamental period of GFRP-reinforced concrete squat walls can reach 2-to-3 times its original value prior to failure; and 5) until the development of new design provisions, the strut-and-tie calculations in CSA S806-12 and ACI 318-19 can be applied to GFRP-reinforced concrete squat walls.

Cyclic Lateral Loading Behavior of Composite Plate Shear Walls/Concrete Filled

AbstractPlanar composite plate shear walls/concrete filled (C-PSW/CF) consist of two steel web plates and two flange (or closure) plates making up a long hollow box section that is filled with conc...

Centrifuge Modeling of Monotonic and Cyclic Lateral Behavior of Monopiles in Sand

AbstractThis paper presents a program of centrifuge model tests (100g) on the monotonic and cyclic lateral loading behavior of monopiles. The diameter and burial depth of the model pile were 59 and...

Performance of prefabricated RC column with replaceable Column-Base connection under cyclic lateral loads

A new prefabricated RC column with replaceable column-base connection was proposed for moment-resisting frames. The column-base connection was assembled with replaceable steel fuses and padding blocks, which can be easily replaced after an earthquake, to accommodate inelastic deformation. Eight full-scale column specimens were tested to evaluate the effectiveness of various parameters on the seismic performance under lateral loads. The experimental results showed that the column-base connections exhibited stable hysteretic behavior in terms of strength, stiffness and energy dissipation. The lateral load capacity increased with increase in cross-sectional area of steel fuses (1200–1520 mm2) and axial load ratio (0.14–0.24). The seismic performance before and after the replacement of the damaged components was found to be almost identical which indicated that the replaceable column-base connection is feasible and effective. An idealized moment-rotation theoretical model and a simplified 2D nonlinear theoretical model were further developed to predict the flexural response of the proposed columns. Comparison of theoretical model responses with the experiment results showed satisfactory results in predicting the lateral load behavior. Both the models provide a reference for the design procedure and practical applications of the replaceable column-base connection.

Lateral Load Behavior of Inclined Micropiles Installed in Soil and Rock Layers

Abstract In this paper, the lateral load-carrying behavior of inclined micropiles installed in various soil–rock layer conditions was investigated based on the results from the model load tests and...

Non-linear performance analysis of free headed piles in consolidating soil subjected to lateral loads

The analysis of laterally loaded pile is complex due to its site specific behaviour. Whereas most of the analytical methods provides only a generalized solution to it. Behaviour of piles in clay depends on site specific factors like subsoil condition, type of super-structure and the load transfer from it, construction duration and ground improvement process. The present study deals with the assessment of lateral load behaviour of pile based on the results of conventional and instrumented field load tests. The pile was designed based on the results of laboratory and field geotechnical investigations. The diameter and depth of bored cast in-situ pile were fixed as 600 mm and 16 m from the natural ground level respectively. The deflection profile obtained using inclinometer for various lateral loads on piles tested during different phases of site development were analyzed. The pile bending moment, shear force and soil reaction profile were established from the inclinometer data. The results obtained from the experimental data were found to be comparable with that of analytical method. The non-linear lateral load-displacement curves obtained from the load test conducted at different period of consolidation induced by site development process were analyzed. The curves thus obtained were transferred into a non-dimensional kh/khmax versus shear strain curve for the formation of equation explicit to the specific site. A site specific equation was proposed for the estimation of lateral load-displacement curve with respect to degree of consolidation of the surrounding soil subjected to surcharge load induced by the site development process.

Cyclic behavior of c-shaped composite plate shear walls – Concrete filled

A Composite Plate Shear Wall/Concrete Filled (C-PSW/CF) is a special lateral-force resisting system consisting a sandwiched panel of two steel plates with concrete infill in between them, ideally suited for core-wall structures in high-rise construction. The steel plates are connected to each other using tie bars that are embedded in the concrete infill and, in some instances, steel-headed stud anchors. This research project was conducted to investigate the cyclic lateral load behavior of these walls, in terms of strength, and drift capacity. The testing program includes two large-scale C-shaped concrete filled composite plate shear core walls subjected to flexure and axial loads together. Their dimensions were the same, but different axial loads were applied up to 19% of axial loading capacity. The composite behavior and the plastic hinge development were investigated and compared to results from plastic moment calculations. This provides valuable results on the expected behavior of one composite cross-section that is frequently used in full core wall. This is done to support the development of design guidelines for high-rise core-wall steel buildings having C-PSW/CF as the primary lateral force resisting system.

Simulation of the in-plane structural behavior of unreinforced masonry walls and buildings using DEM

In this study, a novel computational modeling strategy is proposed to estimate the lateral load capacity and behavior of unreinforced masonry (URM) structures. All commonly noted failure mechanisms are captured via the proposed modeling strategy using the discrete element method (DEM) in three-dimensions (3D). Masonry walls are represented as a system of elastic discrete blocks, where the nodal velocities are evaluated by integrating the equations of motion using the central difference method. Then, the mechanical interactions among adjacent blocks are examined utilizing the relative contact displacements and employed in the contact stress calculation. Through this research, a new stress-displacement contact constitutive model is considered and implemented in the commercial software 3DEC, which includes softening stress-displacement behavior for tension, shear, and compression along with the fracture energy concept. The results of the discontinuum models are validated on small- and large-scale experimental studies available in the literature with good agreement. Furthermore, important inferences are made regarding the effect of block size, the number of contact points, and contact stiffness values for robust and accurate simulations of masonry walls.

Numerical modeling of confined brick masonry structures with parametric analysis and energy absorption calculation

The objective of this paper is to propose a new modeling methodology for numerical analysis of full-scale confined brick masonry structures. Two modeling strategies are used within a single structure, where the in-plane walls are modeled using “simplified micro-modeling” approach and out-of-plane walls are modeled using “macro-modeling” approach. The lateral load capacity is associated with the in-plane shear resistance of masonry elements, therefore more detailed analysis is required for in-plane walls to achieve a comprehensive understanding of the damage mechanism and load transfer. The investigation of the in-plane shear behavior of confined brick masonry structures is of significant importance. Additionally, the proposed hybrid model is validated by comparing the results of experimental studies of confined brick masonry structure. A parametric study is then conducted to investigate the effect of brick and mortar properties on the structural response metrics (e.g. base shear coefficient, effective stiffness, response modification factor, the three performance levels (i.e. Immediate Occupancy, Life Safety and Collapse Prevention limits) and the energy absorption properties). It is observed that these structural response metrics, changed considerably by varying the material properties. Apart from that, the damage behavior and damage pattern are also assessed for the better understanding of effect of these parameters on the response of the structure. The proposed hybrid-modeling approach gives sufficient accuracy in predicting the lateral load behavior as well as the damage mechanism of confined brick masonry structure, subjected to lateral loading.

Lateral load behavior of connections in Assam-type wooden houses in the Himalayan region of India

Traditional Assam-type wooden houses have performed well in the seismically active north-eastern Himalayan region of India. Such performance is attributed to various timber connections, unique infill-frame connections, timber elements, and light-weight materials. Connections govern the overall performance of any timber frame structure under lateral loading. Therefore, it is essential to study the behavior of each connection of Assam-type houses under relevant loading conditions to gain an insight on their lateral load behavior. The behavior of seven different connections generally provided in Assam-type houses was evaluated in the present study using quasi-static cyclic tests and pull-out tests. Most of the primary connections showed promising performance in terms of high deformability and ductile behavior. The primary connections of the timber frame hardly suffered any significant damage under the lateral loading. The performance was much superior when compared to the behavior of connections in other vernacular houses. The experimental results will help in better understanding of the lateral load behavior of such houses as well as in developing and calibrating the numerical models for predicting the seismic response of not only traditional Assam-type houses but also other timber-framed houses.

Numerical investigation on the lateral loading behaviour of tetrapod piled jacket foundations in medium dense sand

Recently tetrapod piled jacket (TPJ) foundations are considered as a promising solution for offshore wind turbines in waters with depths ranging from 20 m to 50 m. This paper presents a numerical study into the monotonic lateral loading behaviour of TPJ foundations in medium sand, in terms of overall load-displacement responses of TPJ foundations and internal force within individual corner piles as well as pile-soil interaction. The results of previous centrifuge model tests are used to provide high-quality verification for the development of a 3D finite element model established by ABAQUS. A series of parametric studies is then carried out to look into more detailed response of TPJ foundations subjected to lateral loads, including the influence of spacing and slenderness ratio of piles, loading height as well as soil friction angle. The numerical results show that there are two various deformation models of TPJ foundations during lateral loading. One is shearing dominated deformation model under smaller loads, while another one is overturning dominated model under larger loads. Moreover, the lateral soil-pile interaction is found to be greatly influenced by enhancing/weakening effects of the axial forces of individual piles. The cause of this phenomenon is primarily due to the change in soil stress induced by pile vertical movement and radial deformation. To quantify this effect on pile-soil interaction of TPJ foundation, an enhancement factor Γs, defined as the ratio of the soil resistance on downwind piles to that on upwind piles, is proposed. Consequently, the relationship between Γs, depth of influence zone zc and four parameters are carefully investigated. For simplicity, the Γs is assumed constant and independent with pile lateral deflection as well as soil depths, based on which the values for Γs and zc are recommended for practical design uses. It is highlighted in the present study that these values should be chosen based on the specific loading conditions to provide much safer and more robust design for TPJ foundations.

Empirical Models for Lateral Stiffness and Strength of Masonry-Infilled RC Frames Considering the Influence of Openings

Lateral load behavior of reinforced concrete (RC) frames infilled with fly-ash brick masonry having various sizes of central openings was investigated experimentally. Results showed that the infilled frames with openings exhibited significantly different lateral load behavior than the corresponding infilled frames without openings. The drift limit states corresponding to commencement of major events during the lateral loading (initiation of major cracks in frame members, peak load, and 80% of postpeak load) were found to improve significantly due to the presence of openings when designed in accordance with current earthquake standards. The presence of openings in masonry infills modifies two of the most important design parameters, lateral stiffness and strength, for which nonlinear prediction models were developed by carrying out statistical analyses of the experimental results. Empirical models were used to estimate the stiffness and strength of frames tested in past studies and were found to be more accurate and consistent compared with several existing predictive relations. A normalized lateral load–drift relationship for different performance levels of such frames was also propounded based on the observed damage events. The empirical equations can be used very conveniently to simulate the variations of stiffness and strength (global response) of the infilled frames with openings under lateral loads.

Laboratory Study of Lateral Load Capacity and Behaviour of Short Piles in Clayey Soil.

This research is an experimental study investigating the lateral loading capacity of piles in clayey soil. Important factors considered in this study included pile diameter, embedded length of pile, effective unit weight, and degree of saturation of soil, which were studied for their effects on the lateral loading capacity of short driven piles. The experimental study involved testing six specimens in the laboratory, each made of galvanized iron of 21.7 and 27 mm diameter and L/d (embedded length/diameter) ratios of 10, 14, and 18. The specimens were subjected to lateral loadings while embedded in clayey soil with effective unit weights of 13, 15, and 15.6 kN/m3 and degrees of saturation of 30, 41 and 97%, to simulate true pile behaviour. The obtained pile responses were then plotted as force-displacement diagrams. The varying parameters were thus diameter and embedded depth of pile, effective unit weight, and degree of soil saturation. The results of this experimental study on the behaviours of the piles under the influence of lateral loading in the clay were also compared with the predicted lateral capacity of the piles based on work by other researchers. Moisture content and degree of saturation were found to have the greatest effects on pile behaviour. This study thus aids understanding of the behaviours of short piles embedded in clayey soil under lateral loading to allow designers to take practical steps and choose an appropriate method when designing a pile.

Experimental study on lateral pile–soil interaction of offshore tetrapod piled jacket foundations in sand

Recently, tetrapod piled jacket (TPJ) foundations have shown considerable promise in offshore developments, due to the increases in power capacity and water depth for offshore wind turbines. This paper presents a set of centrifuge tests to look into the lateral loading behaviour of TPJ foundations in sand, with the overall load–displacement responses of the foundation as well as the soil resistance and internal forces on or within individual piles being examined carefully. Test results show that the back-row piles are more likely to be pulled out when the TPJ foundation is loaded laterally along the diagonal direction compared to when loaded along the orthogonal direction. The lateral soil resistance per unit length on the back-row pile(s) is approximately 60% of that on the front-row one(s) in the orthogonal loading case, and only about 40% in the diagonal loading case. Moreover, although the TPJ foundation is in its form a special case of pile groups, it is highlighted in the present study that the former case exhibits distinct loading behaviour from the latter case due to the typically large overturning moment encountered by the foundations for offshore wind turbines. Finally, the p-multipliers of the piles are demonstrated to be dependent on pile deflections, but independent on soil depths, and as a result, a modified pm model is proposed to provide guidance for the design of TPJ foundations in sand.

Confined and unreinforced masonry structures in seismic areas: Validation of macro models and cost analysis

Modern structural design requires consideration of sustainability parts from a life cycle perception, but also the initial design phase in which seismic actions have a substantial influence on the design of the structure. In recent times, the seismic assessment of masonry buildings by means of macro-element modeling methodologies has become popular, by application of performance-based evaluation techniques using nonlinear lateral load procedures (Pushover). This study addresses the endorsement of these methodologies by referring to two full-scale brick masonry structures subjected to a lateral loading conditions. The lateral load response of tested unreinforced masonry (URM) and confined masonry (CM) structures is compared with the response of the numerical models. The considered numerical models have good agreement for satisfactorily predicting the response of the experimental test and hence are capable of being used in a performance-based evaluation. Then, pointing to the characteristic housing of northern Pakistan and its typical design with a reinforced concrete (RC) building, the validated numerical models are used to estimate the hazard-resistant potentials of the URM and CM options for one, two and three story options, particularly in relation with maximum lateral load capacity. The load deformation response of both the typologies was also compared for the mentioned three story levels. It was observed that by confining the masonry its ductility capacity increases considerably, hence making it more suitable to be used in earthquake prone regions. Masonry structures are also compared regarding the construction costs compared to the RC typology. With regard to the dwellings studied, the projected lateral load behavior for masonry structures indicate the ability to withstand lateral loads adequately. These structures also allow a significant reduction in costs (up to 28%) compared to RC, hence appearing as challenging alternatives.

Lateral-bearing behaviour of vibratory driven monopiles in different model test set-ups

This paper presents a comparison between two different but dependent model test set-ups to investigate the vibratory pile penetration and lateral loading behaviour in sand. Relevant considerations ...

Centrifuge modelling of lateral loading behaviour of a “semi-rigid” Mono-pile in soft clay

Mono-pile foundations have been widely used for offshore wind turbines principally due to their convenient construction and cost-effective nature. So far, little attention has been paid to large diameter “semi-rigid” piles that have distinct behaviours from flexible or ideally rigid piles. This paper presents a series of centrifuge model tests to study the deforming and bearing characteristics of a 5.9 dia. semi-rigid pile under lateral loadings in kaolin clay. For monotonic loading, a modified p–y curve analysis model considering rotational soil flow near the rotation centre of pile was proposed, highlighting the limitation of classic plane-strain based plasticity models to evaluate the ultimate lateral pile-soil resistance. For cyclic loading, a strong correlation between the degree of soil degradation and cyclic load amplitude was identified. Besides, a degradation factor model, accounting for various cyclic stress levels and soil depths, was proposed, which can be used to assess the accumulative displacement of semi-rigid piles under cyclic loadings in soft clay.