Pier Elements Research Articles

A COMPOSITE MODELLING APPROACH FOR THE RETROFITTING AND REHABILITATION OF AN HISTORICAL COASTAL ASSET

The Pont del Petroli pier is a coastal structure located in the coastal town of Badalona, north of Barcelona, in Spain. The pier was built in the 60s to allow mooring of petroleum tankers, but fallen in disuse in 1990. Restored between 2003 and 2009, the pier is now regarded as a historical and social asset of the Catalan coast. In January 2020 the storm Gloria (Amores et al., 2020), characterized by extreme wave conditions (recorded offshore significant wave heights in excess of 8.5 m) and lasting for nearly two days, caused flooding events, casualties and severe damages to several structures in Spain. The pier head platform was damaged, four supporting piles failed and part of footbridge beam was washed away. There is no recorded wave climate that hit the pier so strong during its 50-year life. To reproduce the conditions that led to the failure of the pier a compositemodelling has been carried out at Universitat Politènica de Catalunya (UPC). The outcomes of the work provide further insight and information on the interaction between waves and the key pier elements (platform, footbridge, piles, pile caps) and aided the design for the structural retrofitting, including the study of four different alternatives for the pier head platform and the footbridge attached to it.

3D Numerical Assessment of Rammed Aggregate Pier Performance under Dynamic Loading in Liquefiable Soils

Ground improvement (GI) techniques have shown promise in effective liquefaction mitigation, but the physical mechanisms governing their three-dimensional (3D) response during dynamic loading are not yet fully understood. To evaluate the 3D performance of one GI technique, the rammed aggregate pier (RAP), in-situ site characterization, full-scale field test data, and calibrated baseline constitutive soil model parameters are combined to model the 3D fully coupled hydromechanical response of natural (unreinforced) and improved (reinforced) soil profiles. To the authors’ knowledge, this contribution represents the first 3D model of a columnar-reinforced soil profile being calibrated using full-scale field testing. The field observations from the comprehensive ground improvement testing (GIT) program in New Zealand and insights from two-dimensional (2D) finite-difference analyses using constitutive model parameters calibrated against the field measurements were used. The developed 3D models were subjected to dynamic loads simulating the excitation generated by a vibroseis truck at one of the in-situ test sites of the GIT program, as well as unidirectional and bidirectional earthquake ground motions from the Canterbury Earthquake Sequence events. The 3D simulations showed that the improved soil profiles experienced reduced excess pore pressures and reduced dynamically induced shear strains compared to the natural, unreinforced soil models. The developed 3D finite-element predictions were compared and validated vis-à-vis the field observations of the GIT program. Compared to 2D analyses, 3D analyses provide a more accurate description of actual field conditions, and, for instance, it was observed that multidirectional shaking has a significant effect on liquefaction triggering, particularly for natural soil profiles. Finally, it was shown that soil densification around the installed pier elements and the lateral earth pressure increase within the densified soil and are the primary ground improvement mechanisms contributing to the reduction of dynamically induced shear deformations and excess pore pressure generation during earthquake shaking. It was also found that the permeability and shear stiffness of the installed RAP piers did not have a significant influence on the pore pressure response and shear strains developed along the centerline of the improved area.

Measuring Displacement of Tall Concrete Columns during Construction

Multiple-span, segmental concrete bridges built by balanced cantilever construction demand precise geometric control so that adjoining tips align at the time the closure segment is cast. When this type of bridge superstructure is cast monolithically on tall piers, moment redistribution, as well as creep, shrinkage, and temperature effects, can cause excessive demand on the exterior end spans and piers of the structure. To compensate, designers often use horizontal forces (jacking) to induce a counteractive moment in the pier columns. However, designers often do not make the effort to ensure that the intended displacement is realized at the needed structural elements. A methodology for measuring deflections of tall pier elements with tiltmeters during construction is presented in this paper for the Jeremiah Morrow Replacement Bridge, Interstate 71, Lebanon, Ohio. Fast-sampling data collection systems and postprocessing algorithms, including thermal effect removal, are detailed. In addition to the deflections from unbalanced cantilever moment during the casting cycle, fast-sampling data for the first horizontal jacking event are discussed and compared with the data collected through traditional laser survey techniques. The data were valuable information. They allowed the designer to fine-tune the geometry setup during the segment casting cycles, and they provided real-time displacement readings that permitted field decisions about the final force application during the jacking event.

Experimental investigation and nonlinear FE analysis of historical masonry buildings – A case study

A comprehensive investigation into the seismic behaviour of a masonry vault belonging to an historical building located in the city of Yazd, was performed. Evaluation of load carrying capacity of this type of structures usually needs to characterize the mechanical properties of the elements. For this reason, at first, the mechanical properties of constitutive materials including, bricks, adobes, mortars, pier elements of adobe and a vault element of brick were determined using standard experimental tests. The specimens, as far as possible, were obtained from the original case study materials. Experimental investigation on the properties of pier and vault elements made of adobe and brick, respectively, was conducted using the concept of homogenization. The outcomes provided a comparative study on the characteristics of historical building materials. The results of samples tested, reconfirmed the very low tensile bond strength to be expected of masonry elements, emphasizing the inability of these types of materials to resist a tensile force. Finally, the mechanical properties of pier and vault testing samples were implemented in a nonlinear finite element (FE) analysis of the building, under lateral loading, through macro-modelling concepts. The results have provided a basic understanding of the lateral performance and failure mode of unreinforced historical buildings.

Accurate modeling of the cyclic response of structural components constructed of steel with yield plateau

A time-independent constitutive model for structural steels with a yield plateau is presented. The model is based on the basic principles of time-independent plasticity. The model couples the nonlinear kinematic hardening concept with a memory surface in the plastic strain space, and a pseudo memory surface in the deviatoric stress space. A brief description of the constitutive model, which is capable of capturing the response of the material for monotonic, proportional and non-proportional cyclic loading paths are given. The performance of the proposed constitutive model is verified at the structural component level, by means of finite element simulations of large-scale structural columns or bridge pier elements under constant axial load and uni-directional quasi-static cyclic loading.

Performance Monitoring of a Rammed Aggregate Pier Foundation Supporting a Mechanically Stabilized Earth Wall

The use of rammed aggregate pier (RAP) foundations for support of retaining walls and earth fill embankments has increased in recent years to become a geotechnical solution for rapid construction of earth structures in soft ground conditions. A nominal 6-m mechanically stabilized earth wall was constructed over piers installed in relatively compressible soil to investigate the performance of RAP foundation elements in terms of stress-deformation and settlement behaviors for such applications. Geotechnical instrumentation consisting of total earth pressure cells, settlement plates, and vibrating wire piezometers was installed within the pier elements and at the foundation surface for short- and long-term monitoring of pier response. Monitoring data indicate: (1) mobilization and concentration of vertical stress on pier elements and matrix soil; and (2) load transfer response for the boundary condition associated with support of geogrid-reinforced earth fill. The practical implications of the experimental research findings are briefly discussed.

중실원형단면 조립식 교각의 내진 성능 평가

건설여건의 변화에 따라 교량구조물의 급속시공에 대한 요구가 늘어나고 있다. 이 논문에서는 하부구조에서 교각의 프리캐스트화를 위한 준정적 실험을 수행하였다. 프리캐스트 프리스트레스트 콘크리트 교각 설계의 가장 주요한 항목이 내진성능의 확보에 있다. 7개의 프리캐스트 교각을 제작하였고 주요 실험변수는 긴장재의 양, 프리스트레스트의 크기, 이음부의 위치 및 수로 설정하였다. 실험결과 축방향으로 도입되는 프리스트레스에 의해 작은 횡변위하에서는 일부 손상이 발생하여도 변형의 복원력을 발휘하였지만 소성힌 지구간의 손상이 많은 경우에는 이러한 복원력이 효과를 발휘하지 못하는 것을 확인하였다. 실험을 통해 관찰된 손상의 형태로부터 판단할 때 조립식 교각의 이음부 설계는 기초부와 교각부 사이의 이음부에 대해서 실시되어야한다. 축방향 긴장재의 양은 RC 교각과 강재비를 일치시키는 것은 지나친 설계가 될 수 있고 주어진 하중조건에 대한 P-M 상관도를 만족시키는 수준에서 결정되어야 한다. 변위연성도 평가를 볼 때 프리캐스트 교각에서 횡철근비는 현재의 철근 콘크리트 교각과 동일한 수준에서 확보되어야 요구연성도를 만족할 수 있다. 에너지 소산능력은 강재비가 증가함에 따라 향상되었고 이음부의 수가 많은 경우가 다소 뛰어난 능력을 발휘하였다. Fast bridge construction has been increasingly needed according to the changed construction environment. This paper deals with quasi-static tests on precast piers for bridge substructures. One of the most crucial aspect of the design of precast prestressed concrete bridge piers is the seismic performance. Seven precast pier elements were fabricated. The amount of prestressing bars, the prestressing force, and the location and number of the joint between segments were the main test parameters. Test results showed that the introduced axial prestress made the restoration of the deformation under small lateral displacement and minor damage. However, there was no effect of the prestress when the plastic hinge region was damaged severely due to large lateral displacement. Judging from the observed damage, the design of the joints in precast piers should be done for the first joint between the foundation and the pier segment. The amount of the necessary prestressing steel may be designed to satisfy the P-M diagram according to the service loads, not by having the same steel ratio as normal RC bridge piers. In order to satisfy the current required displacement ductility, it is necessary to have the same amount of the transverse reinforcements as RC piers. As the steel ratio increases, the energy absorption capacity increases. The number of joints showed a little influence on the energy absorption capacity.