---
title: How Modular and Strip Seal Expansion Joints Work Together on Large Bridge Projects
description: D.S. Brown supplied Steelflex® D 240 and D 320 Modular Expansion Joint Systems for the Beaver River Bridge Replacement Project.
image: https://blog.dsbrown.com/hubfs/Bridge-rendering-1.jpg
---
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# D.S. Brown Blog
## [How Modular and Strip Seal Expansion Joints Work Together on Large Bridge Projects](https://blog.dsbrown.com/how-modular-and-strip-seal-expansion-joints-work-together-on-large-bridge-projects)
Nov 12, 2026, 1:38:34 PM / by [Ben Jacobus](https://blog.dsbrown.com/author/ben-jacobus)
### **Steelflex® Expansion Joint Systems on the Beaver River Bridge (I‑76)**
Large, high‑traffic bridges require expansion joint systems that can safely manage movement, protect the structure, and perform reliably for decades. On major infrastructure projects, engineers often specify **multiple expansion joint types**—each selected based on movement demands, location, and long‑term performance goals.
The [**Beaver River Bridge Replacement Project**](https://dsbrown.com/wp-content/uploads/2026/06/B_Beaver-River-Bridge_Project-Highlight_v007-1.pdf) on the Pennsylvania Turnpike (I‑76) is a clear example. D.S. Brown supplied [**Steelflex® D‑240 and D‑320 Modular Expansion Joint Systems**](https://dsbrown.com/product/steelflex-modular-expansion-joint-systems/) along with **[Steelflex® SSPA Strip Seal Expansion Joint Systems](https://dsbrown.com/product/steelflex-strip-seal-expansion-joint-systems/)**, allowing the design team to match joint performance to real‑world structural demands across the bridge.
#### **What Are Modular Expansion Joint Systems?**
**Modular expansion joints** are multi‑ seal systems designed to accommodate **large structural movements** while maintaining a smooth riding surface and protecting the bridge substructure.
**Key Characteristics**
- One or more center beams support tire loads, transferring traffic loads to the structure
- Multiple seals open and close to manage the bridge movements
- Elastomeric seals prevent water and debris intrusion
- Engineered for high traffic volumes and long spans
#### **How Steelflex® Modular Expansion Joints Work**
Steelflex® modular systems work by:
1. Distributing structural movement evenly across multiple seals instead of concentrating in a single gap.
2. Control springs, integrated with support bars, space the center beams allowing for controlled longitudinal movement while maintaining a comfortable riding surface.
3. Multiple support bars distribute the heavy loading while the connection to the center beam is designed to prevent fatigue during cyclical loading and impacts.
Because movement demand increases with span length and structural continuity, modular expansion joint systems are typically specified when total joint movement exceeds 4 inches.
On the Beaver River Bridge project, [Steelflex® D‑240 and D‑320 Modular Expansion Joint Systems](https://dsbrown.com/product/steelflex-modular-expansion-joint-systems/) were selected to handle locations with **significant longitudinal movement requirements**—conditions common on long bridges carrying nearly 25,000 vehicles per day.
#### **What Is a Strip Seal Expansion Joint System?**
A **strip seal expansion joint** uses a single elastomeric gland locked into steel edge rails to accommodate **moderate movements**.
**Steelflex® SSPA Strip Seal System**
The [**Steelflex® Strip Seal SSPA Expansion Joint System**](https://dsbrown.com/product/steelflex-strip-seal-expansion-joint-systems/) is commonly used where:
- Movement demands are 4 inches or less
- Watertight performance is critical
- Durability and ease of maintenance are priorities
On the Beaver River Bridge, strip seal joints were used in locations where movement was within the capacity of a single‑seal system, complementing the modular joints elsewhere on the structure.
#### **Why Both Modular and Strip Seal Systems Were Used on the Same Bridge**
Large bridge projects rarely rely on one expansion joint type. Instead, engineers assign systems strategically based on structural behavior.
**Typical Application Strategy**
- **Modular expansion joints**: Used at high‑movement locations where large displacement capacity is required, typically exceeding 4 inches of movement.
- **Strip seal expansion joints**: Used at locations with lower movement demands, 4 inches of movement or less.
This mixed approach optimizes:
- Performance
- Lifecycle cost
- Constructability
- Long‑term maintenance
The Beaver River Bridge Replacement reflects this best practice approach in modern bridge design.
#### **When to Use Modular vs. Strip Seal Expansion Joints**
| **Condition** | **Recommended System** |
| --- | --- |
| Large movement demands (greater than 4”) | **Steelflex® Modular** |
| Moderate movement (4” or less) | **Steelflex® Strip Seal SSPA** |
| High traffic volume | Modular |
| Lower movement, watertight priority | Strip Sea[l](https://blog.dsbrown.com/how-modular-and-strip-seal-expansion-joints-work-together-on-large-bridge-projects#_msocom_10) |
#### **FAQ: Steelflex® Expansion Joint Systems**
**1. When should modular expansion joints be specified?**
Modular expansion joints are specified when expected bridge movement exceeds the capacity of strip seal systems, typically on long spans or continuous structural units.
**2\. Why use both modular and strip seal joints on one bridge?**
Different locations experience different movement demands. Using multiple joint types allows engineers to match system performance to each location’s requirements.
**3\. What advantages do Steelflex® modular joints provide?**
Steelflex® modular systems accommodate large movements through a series of evenly controlled gaps and distributes wheel loads across multiple beams, improving durability, ride quality, and long‑term performance.
**4\. What is the role of strip seal expansion joints?**
Strip seal systems provide reliable, watertight performance for locations with lower movement demands and are often used in combination with modular joints on large projects.
#### **Connect With a D.S. Brown Bridge Expansion Joint Specialist**
Selecting the right expansion joint system is a critical part of long‑term bridge performance. Movement capacity, traffic loading, constructability, and lifecycle costs all need to be evaluated together—often requiring more than one solution on large bridge projects.
D.S. Brown works directly with owners, designers, and contractors to help align **Steelflex® modular and strip seal expansion joint systems** with real‑world bridge conditions. For guidance on expansion joint selection or to discuss a current or upcoming bridge project, connect with a D.S. Brown bridge specialist:
**Ben Jacobus**
National Sales Manager, Bridge Products
**D.S. Brown**
Mobile: 1‑612‑860‑9383
[bjacobus@dsbrown.com](mailto:bjacobus@dsbrown.com)
www.dsbrown.com
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### Posts by Topic
- [bridges (11)](https://blog.dsbrown.com/tag/bridges)
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- [Maurer System™ Swivel Expansion Joint Assembly (2)](https://blog.dsbrown.com/tag/maurer-system-swivel-expansion-joint-assembly)
- [disc bearing assembly (2)](https://blog.dsbrown.com/tag/disc-bearing-assembly)
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