Structural Evaluation and Rehabilitation Design of Puente Blanco in Quebradillas 
 
Lismarie Vargas Andino  
Master in Civil Engineering 
Héctor J. Cruzado, PhD, PE 
Department of Civil & Environmental Engineering and Land Surveying 
Polytechnic University of Puerto Rico 
Abstract ¾ Puente Blanco is an arch bridge located 
in the municipality of Quebradillas, Puerto Rico. 
This reinforced concrete structure, which dates from 
1922, was initially designed and built as a railroad 
bridge but was later renovated to be used by 
automobiles. Over the years, the structure has 
suffered severe damage due to exposure to coastal 
environment and lack of maintenance, causing the 
bridge to be closed to automobiles. Using a 
structural engineering program, a model of the 
bridge was developed to evaluate its design under  
current standards. Using the results, a rehabilitation Figure 1 
that included reinforcement replacement and carbon Aerial view of bridge and surrounding area (Source: Google 
fiber application was designed. The estimated cost Maps)  
of implementing the design is $3,771,651.24. If this The objective of this project is to present a 
rehabilitation is not implemented, the historic bridge design to structurally rehabilitate Puente Blanco, 
is at risk of collapsing. therefore preserving the historic structure. To 
Key terms – historic bridge, steel reinforcement accomplish this, the present condition of the bridge 
replacement was inspected, and a computer model was developed 
to evaluate the structure using current standards. 
INTRODUCTION This paper continues with the historical 
Puente Blanco is a spandrel concrete arch bridge background of the bridge. Then, the findings of 
which construction was completed in 1922 in inspecting the bridge and field testing some of the 
Quebradillas, Puerto Rico. It is the only one of its elements are presented. This is followed by the 
class on the island. The original purpose of the analysis of the structure using a computer program, 
bridge was to resist the load of railroad traffic [1]. the design of the structural rehabilitation, and the 
The bridge crosses La Mala Creek and is currently cost estimate of implementing this design. Finally, 
part of Panorámica Street, located near the north the conclusions are presented. 
coast of Puerto Rico (figure 1). Nowadays, the 
bridge is closed to automobile traffic due to the poor HISTORICAL BACKGROUND 
condition of the structural elements because of lack  Puente Blanco was originally built as part of the 
of maintenance and exposure to the coastal railroad in Puerto Rico owned by the American 
environment. If no action is taken, the bridge could Railroad Company. At its location, there had been a 
eventually collapse. steel bridge that had spanned that section since 1907, 
but this had to be replaced because it was in poor 
condition. Puente Blanco was designed by Etienne 
Totti, a native of the municipality of Yauco, who 
served as chief engineer for the American Railroad 
Company. Construction of the arch bridge was The strength of the concrete structures was 
completed in 1922 with a cost of $18,000. It limited by 1910 design specifications to 2,000 psi. 
supported the 84-ton weight of two locomotives The reinforcement of this era had a yield of 30 to 35 
crossing the bridge [1]. The original architecture of ksi for mild steel and 50 to 60 ksi for hard steel [1]. 
the bridge [2] is shown in figure 2. The reinforcement in the columns is composed of 
four 1-inch diameter vertical bars and 1/4-inch hoops 
every 12 inches, as shown in the original plans. The 
reinforcing steel bars in the structure consist of 
twisted iron, better known as a twisted square bar 
[3]. 
In 1984, Puente Blanco was listed in the 
National Register of Historic Places. In 1985, the 
bridge was renovated to widen the roadway to 23 
feet for vehicular use by placing an 11-inch slab on 
top of ten beams (figure 4). In 2008, the Department 
of Transportation and Public Works (DTOP) closed 
the bridge to vehicular traffic [4]. 
 
Figure 4 
 Bridge in its present condition 
Figure 2 
Original condition of the bridge 
FIELD INSPECTION AND TESTING 
A copy of the original bridge plan was obtained, From March through May 2022, visits were 
from an old magazine article (figure 3) [3]. It shows made to the bridge to inspect it and collect data. The 
the structural details of the arch, the dimensions of surroundings of the bridge are of mixed use, as there 
the columns, the connections of the reinforcing bars are recreational, commercial, and residential areas. 
to the arch, and a cross-section of the bridge. The During the inspection visits, it was observed that, 
arch bridge is 117 feet long and 26 feet deep.  although the bridge continues to be closed to 
automobiles, it is used for recreational purposes by 
hikers and cyclists. 
Measurements were taken of some elements of 
the bridge structure to subsequently make as-built 
drawings of the structure. The dimensions shown in 
Figure 5 were not found in the plans, they were 
measured on site. 
 
Figure 3 
Structural blueprints 
  
Figure 5 Figure 6 
Interior of bridge View of north side of the bridge 
It was noticed that the north side of the bridge, 
which is closest to the coast, is more deteriorated 
than the south side. The north side of the bridge has 
advanced stages of rebar corrosion, concrete 
cracking, and concrete spalling (figure 6). 
Meanwhile, the elements on the south side are not as 
deteriorated (figure 7). 
 
Figure 7 
View of south side of the bridge 
As an example of the conditions found in the 
north side of the bridge, figure 8 shows contrast of 
the current condition of one of the columns with a 
red line indicating its original 16-in depth. It is 
estimated that this column has lost approximately 20 
percent of its gross sectional area. 
 
Figure 8 
Example of north side column 
Figure 9 shows the present condition underneath 
the bridge. It can be seen that some of the rebar of 
the arch has been exposed due to corrosion on the 
north side of the bridge. 
 
Figure 10 
Windsor probe test 
STRUCTURAL ANALYSIS 
For the structural analysis, a model was made 
using the computer program ETABS, as shown in 
figure 11, with the main objective of comparing 
results and determining the appropriate use that 
could extend the useful life of the bridge. The 
 following data was used in this analysis: 
Figure 9 
The inferior side of the arch • Load combination and load factors in 
accordance with AASHTO [7]. 
In accordance with the Handbook of • Live load of 85 psf, in accordance to the bridge 
Nondestructive Testing of Concrete, the bridge was being used by pedestrians and cyclists [7]. 
subjected to nondestructive testing for compressive • Spectrum data for seismic analysis according to 
strength [5]. A Windsor probe test was conducted on ATC Hazards by Location website.  
the bridge in accordance with ASTM C803 [6]. This • Soil type D - Stiff Soil (assumed). 
is a special gun that inserts the probe into the • Dimensions of the beam, column, and arch 
concrete and the depth of penetration can be elements according to their original condition. 
approximately related to the strength of the actual • Compressive strength of concrete of 3,000 psi in 
concrete. Three nondestructive tests were taken on a the beams constructed for the 1985 renovation 
column on the north side (figure 10). This test (assumed). 
required that the concrete not be plastered to obtain • Compressive strength of concrete of 5,500 psi in 
accurate results. The tests suggest that the concrete original columns and beams. 
has a compressive strength of 5,500 psi. • Strength of Twisted Reinforcing Bars a yield 
 strength of 50 ksi [8]. 
REHABILITATION DESIGN 
This section recommends strategies to repair the 
concrete focusing on restoring its structural strength, 
appearance, and durability. 
Replacement of Reinforcement 
The results of the structural analysis require 
increasing the ductility in the columns. To solve this, 
 
Figure 11 the installation of six No. 8 bars on the columns, as 
Computer model of the bridge shown in figures 13 and 14. 
For the beams that connect the north and south 
Figure 12 shows that, as a result of the analysis, side columns, where loss of reinforcement was 
it was identified that the columns on the axes marked observed, four no. 8 with stirrups at 12 inches are 
with a blue circle, require 4.75 in2 of additional required. Meanwhile, for damage beams that 
reinforcement. Similarly, columns on axes not connect columns on the same side (north or south) of 
marked with blue circle, require 1.92 in2 of the bridge, the installation of four No. 6 rods with 
additional reinforcement. hoops every 6'' is recommended. 
 
 
Figure 12 
Structural model results with pedestrian and cyclist loads 
 
 
Figure 15 
Column retrofit detail 
The structural detail in figure 15 shows the 
installation of hoops to the existing concrete. This 
type of installation will be required for all elements 
requiring rebar replacement. 
Inhibitor Application 
 For effective protection of Puente Blanco 
Figure 13 
Lateral section of column retrofit detail against the coastal environment, the application of 
high-tech corrosion inhibitors is recommended. This 
additive should be applied to the arches, beams, 
columns, and slabs. 
COST ESTIMATE 
Table 1 presents the cost estimate of performing 
the rehabilitation of the historic elements of the 
bridge as designed. As part of the work, removal of 
all loose concrete is required, so a partial demolition 
item is included. Also included is the new 
reinforcement to be replaced to support the loads 
presented. The highest figure in the cost estimate is 
the installation of the innovative carbon fiber 
system. It can be seen that all the work comes to 
about $3.8 million. 
 
Figure 14 
Column retrofit detail the lateral existing connection Table 1 
Bridge rehabilitation cost estimate 
Carbon Fiber Application DESCRIPTION TOTAL 
Construction management $265,200.00 
To retrofit the arches, girders, and columns, the Environmental control, $17,700.00 
installation of double carbon fiber is recommended, health, and safety 
as shown in figure 15. The addition of the fiber Preconstruction task $40,366.00 
Damage repairs $1,687,295.80 
system is designed to provide the necessary Design/design management $85,000.00 
additional reinforcement to the bridge. For its FRP Systems  $2,095,361.80 
application, weak concrete and other loose particles Miscellaneous $838,144.72 
must be removed and cracks must be repaired using TOTAL $3,771,651.24 
epoxy injections. 
 
CONCLUSIONS [7] R. M. Barker and J. A. Puckett, Design of Highway Bridges: 
An LRFD Approach. Hoboken: Wiley, 2013. 
Puente Blanco is a historic concrete structure [8] A. Newman, Structural Renovation of Buildings: Methods, 
with severe damage and at risk of collapsing. Details, and Design Examples. New York: McGraw-Hill, 
Although it has been closed to automobiles, the 2001. 
structure is still in use and appreciated by pedestrian 
and cyclists. If the preservation of this structure is 
desired, action must be taken sooner than later. 
Figure 16 shows a visual concept of the final design, 
contemplating the proposed use of the bridge after it 
has been rehabilitated and is once again safe for 
visitors. 
 
Figure 16 
Visual concept of the rehabilitated bridge 
REFERENCES 
[1] L. Pumarada O’Neill, “Los puentes históricos de Puerto 
Rico,” Centro de Investigación y Desarrollo, Universidad de 
Puerto Rico, Recinto de Mayagüez, 1991. 
[2] National Park Service, National Register of Historic Places 
Inventory — Nomination Form: Puente Blanco, 1984 
[Online]. Available: 
https://npgallery.nps.gov/AssetDetail/NRIS/84003126 
[3] “Engineering news record. A consolidation of engineering 
news and engineering record,” Journal of Civil Engineering 
and Contracting, vols. 93-103, Jul. 1924–Dec. 1929. 
[4] Cámara de Representantes de Puerto Rico, “Informe de la 
investigación ordenada por la resolución de la Cámara 209,” 
1998 [Online]. Available: 
http://www.tucamarapr.org/dnncamara/Documents/Measur
es/b8d8b6b4-4abd-4044-881e-510a00c0b815.pdf 
[5] ACI Committee 364, “Guide for evaluation of concrete 
structures prior to rehabilitation.” 
Detroit: American Concrete Institute, 1993. 
[6] Standard Test Method for Penetration Resistance of 
Hardened Concrete, ASTM-C803, 2018.